Medical ablation system

Abstract

In some examples, a medical system includes control circuitry configured to substantially control an ablation level delivered by a balloon based on a size of the blood vessel intended to receive the ablation. Control circuitry is configured to receive an indicated size of the blood vessel and determine an apt flow rate of a fluid based on the indicated size. The control circuitry is configured to compare a flow rate within the medical system with the apt flow rate determined, and adjust the flow rate through the medical system based on the comparison. In examples, the medical system includes a valve configured to control the flow rate of the fluid. The medical system may include a sensor configured to determine a flow parameter of the fluid. In examples, the medical system includes a catheter system including an elongate body supporting the balloon.

Description

MEDICAL ABLATION SYSTEM

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 518,452, filed 9 August 2023, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present technology is related to medical devices and systems, such as medical devices and systems for ablation and / or neuromodulation.BACKGROUND

[0003] Catheters have been proposed for use with various medical procedures. For example, a catheter can be configured to deliver neuromodulation therapy to a target tissue site to modify the activity of nerves at or near the target tissue site. The nerves can be, for example, sympathetic nerves. The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Chronic overactivation of the SNS is a maladaptive response that can drive the progression of many disease states. For example, excessive activation of the renal SNS has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of arrhythmias, hypertension, states of volume overload (e.g., heart failure), and progressive renal disease.SUMMARY

[0004] The present disclosure describes devices, systems, and techniques for medical ablation and / or neuromodulation. The medical system disclosed is configured to control an ablation level (e.g., an ablation power such as a cooling power and / or heating power) based on a size of a target blood vessel. Example medical devices and systems including an elongate body (e.g., a catheter body) and a balloon configured to be positioned within a target blood vessel of a patient to deliver a therapy to the patient. The therapy can include, for example, neuromodulation therapy, such as renal denervation or denervation of other nerves. The elongate body is configured to deliver a fluid to the balloon. The balloon is configured to expand (e.g., under the influence of the fluid) within the blood vessel to contact a vessel wall of the blood vessel. The balloon is configured to facilitate a heat transfer between the vesselwall and the fluid flowing through the balloon to modify a temperature at or near a target tissue site. For example, the balloon may facilitate a heat transfer from the vessel wall to the fluid to cool the target tissue site. As another example, the balloon may facilitate a heat transfer from the fluid to the vessel wall to heat the target tissue site.

[0005] The medical system includes control circuitry configured to receive input indicative of a size of a target blood vessel, referred to herein as an indicated size, and determine an apt flow rate (e.g., a desired fluid flow rate) indicative of a flow through a balloon based on the indicated size. For example, the indicated size might be a diameter of the target blood vessel. The input can be from a user, a sensor, or the like. In some example, the apt flow rate is indicative of a flow rate of a fluid through a catheter system expected to cause the catheter system to deliver a suitable ablation level (e.g., corresponding to a desired lesion size, such as, but not limited to, a depth relative to the vessel wall) for a vessel of the indicated size. In some examples, the control circuitry is configured to control a flow rate within the catheter system based on the apt flow rate. For example, the control circuitry may compare a flow rate within the catheter system with the apt flow rate, and adjust the flow rate through the catheter system (e.g., through the balloon) based on the comparison. Thus, the control circuitry may control the flow rate through the balloon based on the indicated size of the target blood vessel, such that the balloon provides a relatively consistent ablation level over a range of blood vessel sizes.

[0006] In examples, a medical system comprises: an elongate body configured to be positioned within a vessel of a patient, wherein the elongate body defines a lumen; a balloon defining an interior volume; a sensor configured to generate a signal indicative of a flow parameter of a fluid within a flow path, the flow path including the interior volume and the lumen; a valve in fluidic communication with the flow path, wherein the valve is configured to position to control the flow of the fluid; and control circuitry configured to: receive an indicated size representative of a size of the vessel of the patient, determine, based on the indicated size, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of the fluid causing the balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size, and adjust a position of the valve based on a comparison of the flow parameter indicated by the sensor and the apt flow rate.

[0007] In examples, a medical system comprises: a valve configured to position to control the flow of a fluid in a flow path; and control circuitry configured to: receive an indicated size representative of a size of a vessel of a patient, determine, based on the indicated size, an aptflow rate, wherein the apt flow rate is indicative of a flow rate of a fluid causing a balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size, and adjust a position of the valve based on a comparison of a flow parameter indicated by a sensor and the apt flow rate.

[0008] In examples, a method comprises: receiving, by control circuitry, an indicated size representative of a size of a vessel of a patient from an input device; determining, using the control circuitry, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of a fluid that causes a balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size; and adjusting, using the control circuitry, a position of a valve based on a comparison of a flow parameter indicated by a sensor and the apt flow rate, wherein the flow parameter is indicative of a flow rate of the fluid within a flow path, the flow path including an interior volume of the balloon and a lumen defined by an elongate body supporting the balloon, wherein the valve is in fluidic communication with the flow path, and wherein the valve is configured to control the flow of the fluid.

[0009] Further disclosed herein is a medical system that includes control circuitry configured to substantially control an ablation level delivered by a balloon based on a size of the blood vessel intended to receive the ablation, wherein the control circuitry is configured to receive an indicated size of the blood vessel and determine an apt flow rate of a fluid based on the indicated size, wherein the control circuitry is configured to compare a flow rate within the medical system with the apt flow rate determined, and adjust the flow rate through the medical system based on the comparison, and wherein, in examples, the medical system includes a valve configured to control the flow rate of the fluid, wherein the medical system may include a sensor configured to determine a flow parameter of the fluid, and wherein the medical system includes a catheter system including an elongate body supporting the balloon.

[0010] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic illustration of an example medical system including a catheter system.

[0012] FIG. 2 is a schematic illustration of the medical system of FIG. 1 within a blood vessel of a patient.

[0013] FIG. 3 is a schematic illustration of the medical system of FIG. 1 accessing a renal artery of a patient.

[0014] FIG. 4 is a schematic illustration of the medical system of FIG. 1 in a delivery configuration.

[0015] FIG. 5 is a schematic illustration of the medical system of FIG. 1 in an expanded configuration.

[0016] FIG. 6A is an example illustration depicting an example of an indicated size and an apt flow rate within the medical system of FIG. 1.

[0017] FIG. 6B is an example illustration depicting another example of an indicated size and an apt flow rate within the medical system of FIG. 1.

[0018] FIG. 7 is a flow diagram illustrating an example technique for controlling an flow rate using the medical system of FIG. 1.DETAILED DESCRIPTION

[0019] The present disclosure describes example medical systems that include an elongate body configured to be positioned within a blood vessel of a patient, at least one balloon carried by the elongate body, and control circuitry configured to control therapy delivery via the elongate body and the balloon based on a size of a target blood vessel. For example, the control circuitry can be configured to control a flow parameter (also referred to herein as a fluid flow parameter) of a fluid flowing through the elongate body and the balloon based on a size of a target blood vessel to try to achieve a particular ablation level (e.g., an ablation power such as a cooling power and / or heating power). The ablation level can correspond to the ablation level that may achieve a therapeutic outcome for the patient. For example, the ablation level can correspond to a particular lesion size or range of lesion sizes, where the lesion can be the tissue region that has been ablated. The lesion size can be, for example, characterized by a length of the lesion as measured in a direction along a longitudinal axis of the blood vessel and / or depth of the lesion measured in a direction orthogonal to the longitudinal axis of the blood vessel.

[0020] The medical system, as well as devices of the systems and methods of using the systems, can be used for any suitable medical procedure, such as neuromodulation (e.g., denervation), that include delivering a therapy (e.g., cryoablation or heat-based thermalablation) to a target tissue site via the balloon. The elongate body may be configured to be positioned (e.g., by a clinician) within a blood vessel or other anatomical lumen of a patient.

[0021] The medical system is configured to deliver a fluid to the balloon to expand (also referred to herein as inflate) the balloon within the blood vessel such that, for example, an exterior surface of the balloon contacts a vessel wall of the blood vessel. The medical system is configured to substantially circulate a fluid through an interior volume of the balloon to modify a temperature at or near the target tissue site. For example, the medical system may circulate a cryogenic fluid through the balloon to deliver a cryoablation to the target site. As another example, the medical system may circulate a heated thermal fluid through the balloon to deliver a thermal ablation to the target site.

[0022] The balloon is configured to deliver (e.g., circulate) the fluid relative to a blood vessel wall to modify a temperature at or of the target tissue site. The temperature modification can be used to provide a therapeutic outcome (e.g., cryotherapy or heat-based therapy) or can be used to help protect the vessel wall or other anatomical lumen wall. For example, to help achieve a therapeutic outcome, the medical system can be further configured to cool the fluid to, for example, freeze tissues at a target site. As another example, the medical system can be configured to heat the fluid, to, for example, create a lesion at the target tissue site. While blood vessels are primarily referred to throughout the disclosure, the devices, systems, and techniques described herein are also applicable to other target tissue sites. In addition, while a single balloon catheter is primarily referred to throughout the disclosure, medical systems described herein can include more than one balloon, such as two, three, four or more balloons.

[0023] In some ablation systems, an ablation power (e.g., a cooling power and / or a heating power) delivered by a balloon may be generally dependent on an inflated dimension of the balloon (e.g., a balloon diameter) and a flow rate of a fluid through the balloon, among other factors. In some examples, for example when the balloon is a compliant balloon and / or an ablation system is a relatively low pressure system, a vessel wall of a blood vessel in which the balloon is inflated may act to substantially constrain the expansion (e.g., a radial expansion) of the balloon. As a result, the inflated dimension of the balloon (e.g., the diameter) may generally conform to a dimension of the blood vessel (e.g., a vessel diameter) in which the balloon is inflated. In ablation systems which provide a substantially similar flow rate (e.g., at the same flow rate setting) through the balloon relatively regardless of vessel size, the ablation power delivered using the balloon may be inconsistent over blood vesselshaving different dimensions (e.g., different diameters). For example, when a flow rate through the balloon is selected independent of the target vessel size, an ablation power delivered by a balloon having a larger diameter (e.g., a balloon within a larger vessel) may be less than an ablation power delivered when the balloon has a smaller diameter (e.g., when the balloon is within a smaller vessel). This may impact the ablation depth achieved by the ablation procedure.

[0024] The medical systems disclosed herein are configured to control an ablation level (e.g., an ablation power such as a cooling power and / or heating power) based on a size of the blood vessel intended to receive the ablation, which is also referred to herein as a target blood vessel. The medical systems include control circuitry configured to receive an indicated size that is representative of a dimension (e.g., a diameter) of a target blood vessel. In some examples, the control circuitry receives input indicative of the dimension of the target blood vessel. The input can have any suitable form, and can include, for example user input, input from a sensor configured to generate a signal indicative of the dimension of the blood vessel, and / or from medical imaging. For example, a catheter can include one or more electrodes with which impedance can be measured, and the control circuitry can determine the indicated size based on a measured impedance. As another example, a catheter can include one or more structures (e.g., expandable baskets) that are configured to be positioned in apposition with a blood vessel wall and the control circuitry can determine the indicated size based on a physical configuration of the one or more structures, e.g., as described in U.S. Patent No. 10,610,292, which issued on April 7, 2020, and is entitled, “DEVICES, SYSTEMS, AND METHODS FOR MONITORING AND / OR CONTROLLING DEPLOYMENT OF A NEUROMODULATION ELEMENT WITHIN A BODY LUMEN AND RELATED TECHNOLOGY.” U.S. Patent No. 10,610,292 is herein incorporated by reference in its entirety.

[0025] The control circuitry is configured to determine an apt flow rate (e.g., a desired fluid flow rate) through a balloon based on the indicated size. For example, the control circuitry can determine, based on information stored in memory, the apt flow rate that is associated with the indicated size. The apt flow rate may be indicative of a flow rate of a fluid through the medical system (e.g., a balloon) that is expected to cause the medical system to deliver a suitable ablation level when, for example, the balloon is inflated within a vessel of the indicated size. In some examples, the control circuitry is configured to compare a flow rate within the medical system with the apt flow rate, and adjust the flow rate through themedical system (e.g., through the balloon) based on the comparison. Thus, the control circuitry may control the flow rate through the balloon based on the indicated size of the vessel in which the balloon is inflated, such that the balloon provides a relatively consistent ablation level over a range of blood vessel sizes.

[0026] The suitable ablation level on which that apt flow rate is based may be indicative of a desired heat transfer between the medical system and a vessel of the indicated size to, for example, achieve a desired therapeutic outcome. For example, the suitable ablation level may be indicative of a heat transfer between the medical system and the vessel of the indicated size expected to cause a thermal ablation over a particular ablation depth (relative to the vessel wall) of the indicated size. The suitable ablation level may be indicative of a heat transfer between the medical system and the vessel of the indicated size expected to cause tissues of the vessel of the indicated size to achieve a target temperature and / or a temperature within a targeted temperature range. In examples, the suitable ablation is indicative of a heat transfer between the medical system and the vessel of the indicated size over a particular time (e.g., an ablation power, such as a cooling power or a heating power). For example, in some examples, the suitable ablation level may be a power level (e.g., a wattage) indicative of heat transfer between the medical system and the vessel of the indicated size. The apt flow rate may thus be indicative of a flow rate through the medical system expected to cause the balloon to enable the heat transfer between the medical system and a vessel having substantially the indicated size when the apt flow rate is provided and the medical system (e.g. the balloon) is positioned within the vessel having substantially the indicated size.

[0027] Hence, the control circuitry is configured to control the flow rate to account for the size of a blood vessel in which the elongate body and the balloon are or will be positioned. For example, the medical system (e.g., control circuitry) may receive an input (e.g., from a clinician) indicative of the indicated size (e.g., a diameter) of a target blood vessel in which a procedure is to be performed. The control circuitry may determine an apt flow rate based on the indicated size, with the apt flow rate indicative of a flow rate through the balloon expected to cause delivery of a suitable ablation level to the blood vessel. Once positioned within the blood vessel, the control circuitry can control the flow rate through the medical system (e.g., through the balloon) based on the apt flow rate, such that the medical system substantially provides the suitable ablation level to the blood vessel. In this manner, the control circuitry may provide a relatively consistent ablation level to blood vessels over a range of blood vessel sizes and with little to no clinician knowledge required to control the fluid flow rate throughthe catheter system to achieve the desired therapeutic outcome. In some examples, the control circuitry is configured to at least partially inflate and / or deflate the inflated balloon (e.g., based on received user input) to, for example, enable a clinician to position or reposition the medical system (e.g., the elongated body) within the patient.

[0028] The medical system is configured to cause the balloon to receive fluid at a plurality of different flow rates, such that the medical system may be utilized in blood vessels of varying size. This may be advantageous in intravascular procedures in which delivery of treatment (e.g., renal neuromodulation) is required in multiple blood vessels having different vessel diameters. The medical system enables a clinician to control the flow rate through the balloon to accommodate the differing sizes of each of the multiple blood vessels, such that the medical system may be utilized in each of the blood vessels in a manner providing relatively consistent ablation levels and / or ablations over a relatively consistent ablation depth in each blood vessel. For example, the medical system may be navigated to deliver treatments to each of the multiple blood vessels without requiring a removal of the medical system from the vasculature of the patient and without requiring the use of multiple catheters having expanded balloon sizes.

[0029] For example, a clinician may navigate the catheter to a first target treatment site in a first target blood vessel of a patient. The clinician may provide a first input indicative of a first indicated size of the first target blood vessel (e.g., obtained through imaging or sensing), and the control circuitry can determine a first apt flow rate based on the first indicated size. The clinician may position the balloon at the first target treatment site and the control circuitry can control the system to deliver the therapy at the first target treatment site by at least causing fluid to flow through the medical system at a first flow rate that is based the first apt flow rate. The clinician may subsequently navigate the medical system through the vasculature to a second treatment site in a second target blood vessel or another location within the first target blood vessel. The clinician may provide a second input indicative of a second indicated size of a blood vessel at the second treatment site and the control circuitry can determine a second apt flow rate based on the second indicated size. The control circuitry can control the system to provide fluid through the system at a second flow rate that is based on the second apt flow rate.

[0030] The first apt flow rate and the second apt flow rate may be indicative of flow rates causing thermal ablation (cryoablation or heat-based thermal ablation) over a given ablation depth for both the blood vessel sizes at the first and second target treatment sites. In likemanner, the system may deliver treatments to additional target treatment sites in the same or other blood vessels using apt flow rates determined for the indicated sizes at these additional treatment sites, such that the medical system provides relatively consistent thermal ablation level and / or thermal ablations over a relatively consistent ablation depth in at each treatment site.

[0031] In some examples, the control circuitry receives a plurality of apt flow rates and corresponding vessel sizes and stores the information in memory. In some examples, the control circuitry is configured to determine an apt flow rate for an indicated vessel size using data obtained from, for example, previous ablation procedures, modeling and / or measurement of flow rates through the medical system (e.g., an elongated body of the medical system), modeling and / or measurement of heat transfer characteristics of a balloon experiencing a given flow rate, and / or other data indicative of a heat transfer between an inflated balloon and a vessel wall when the balloon is positioned within a vessel of the indicated size. For example, the first apt flow rate may be based on data indicative of previous ablation procedures, such as modeling and / or measurement of ablation level delivered to a vessel having a size commensurate with the first indicated size. The second apt flow rate may be based on data indicative of previous ablation procedures, such as modeling and / or measurement of ablation level delivered to a vessel having a size commensurate with the second indicated size. In some examples, the control circuitry is configured to determine the apt flow rate using a machine learning algorithm trained to provide the apt flow rate based on, for example, the indicated size of a blood vessel.

[0032] The control circuitry may be configured to define the apt flow rate in any suitable manner indicative of a flow of fluid through an interior volume of the balloon. For example, in some examples, the apt flow rate is defined at least in part or in whole by a pressure (e.g., a static pressure, dynamic pressure, and / or total pressure) expected at some location when a fluid flows through a flow path fluidically coupled to the balloon interior. In addition or instead of pressure, in some examples, the apt flow rate is defined at least in part or in whole by a value of a fluid flow rate (e.g., a mass flow rate and / or volume flow rate) through the flow path fluidically coupled to the balloon interior, and / or defined by another fluid parameter indicative of the flow of a fluid through the medical system. In some examples, an apt flow rate (e.g., the first apt flow rate and / or second apt flow rate) is based on the flow characteristics of the medical system utilized to deliver the ablation.

[0033] The control circuitry is configured to control the flow of fluid through the elongate body and / or the balloon based on the apt flow rate using any suitable technique. In some examples, the control circuitry is configured to receive a signal indicative of a flow rate of a fluid flowing through a catheter system (e.g., flowing through the balloon or a lumen of the elongate body), compare the signal to the apt flow rate, and adjust the flow rate of the fluid flowing through the catheter system based on the comparison. In some examples, the catheter system includes a sensor configured to generate the signal. The signal may be, for example, indicative of a flow parameter of a fluid flowing through the medical system (e.g., the catheter system). For example, the sensor may generate a signal indicative of a pressure (e.g., a static pressure, dynamic pressure, and / or total pressure) at a location in the flow path fluidically coupled to the balloon interior. The sensor may generate a signal indicative of a flow rate (e.g., a mass flow rate and / or volume flow rate) at some location in the flow path, and / or substantially defined by another flow parameter indicative of the flow of a fluid through the catheter system. The medical system may be configured such that the signal provided by the sensor is at least proportional to the flow rate of the fluid flowing through the interior volume of the balloon.

[0034] In some examples, the control circuitry is configured to use the signal indicative of the flow parameter (e.g., a pressure) and one or more flow characteristics of a catheter system to infer (e.g., estimate) a flow rate of the fluid. For example, the signal may be indicative of a sensed flow parameter at a particular location (e.g., an inlet lumen or another location) of a specific catheter, which can be a proxy of the fluid flow rate at another part of the catheter system. In some examples, the control circuitry is configured to infer the fluid flow rate using the sensed flow parameter and flow data (e.g., from bench testing) reflecting an expected fluid flow for the specific catheter when the sensed flow parameter is present. For example, the control circuitry may receive a signal indicative of a sensed pressure at a particular location (e.g., an inlet lumen or another location) in the specific catheter and infer the flow rate in the specific catheter using flow data reflecting an expected flow rate when a pressure substantially equivalent to the sensed pressure is present at the particular location in the specific catheter. In some examples, the control circuitry is configured to infer a flow rate using the signal indicative of the flow parameter and a path flow resistance expected as the fluid flows through a flow path defined by the medical system. For example, the control circuitry may receive the signal and infer a flow rate using an equation or other expression based on the signal and the flow resistance.

[0035] In some examples, the control circuitry is configured to define the path flow resistance (e.g., using from a look-up table or other flow data) based on the flow parameter indicated by the signal, a specific catheter system in use, and / or a position of the valve. In some examples, the control circuitry is configured to determine a representative flow resistance indicative of the path flow resistance based on the flow parameter indicated by the signal, the specific catheter system in use, a position of the valve, and / or other factors influencing the fluid flow through medical system 100. In other examples, the control circuitry is configured to infer the flow rate using other methods. The control circuitry may infer the flow rate of the fluid and compare the inferred flow rate to the apt flow rate to enable the catheter system to provide relatively consistent ablation levels to blood vessels over a range of blood vessel sizes.

[0036] In some examples, the control circuitry is configured to control a flow rate (e.g., a flow rate through the balloon) based on the comparison of the signal and the apt flow rate. In examples, the control circuitry is configured to control a position of a valve to control the flow rate. For example, in some examples, the catheter system includes a valve in fluidic communication with a flow path defined by the catheter system. The flow path may be, for example, defined by the catheter system from a fluid supply device, through one or more lumens of an elongate body such as a catheter, and through the interior volume of the balloon. In these examples, the control circuitry is configured to control a position of the valve to control the flow rate of a fluid through the flow path. In examples, the control circuitry is configured to compare the flow rate indicated by the sensor with the apt flow rate determined for an indicated size of a target blood vessel and adjust a position of the valve based on the comparison. Thus, the control circuitry can control the flow rate based on a target vessel size to provide a relatively consistent ablation level over a range of blood vessel sizes.

[0037] In some examples, the catheter system is configured to provide a flow path for a fluid (e.g., nitrous oxide, nitrous oxide, nitrogen, argon, or helium) through an interior volume of the balloon to cause a heat transfer (e.g., via the balloon) between the fluid and the vessel wall of the blood vessel. In some examples, the system includes a cryoablation system and the fluid is a refrigerant that changes phase from a liquid to a gaseous physical state inside the catheter system, e.g., inside the balloon, to enable the balloon to expand and assist a heat transfer from the vessel wall to the fluid. In some examples, the catheter system includes a distributor positioned within the flow path configured to cause the fluid to expand from a liquid to a gas as the fluid flows through the distributor. In examples, an elongate body (e.g., acatheter) of the catheter system at least partially defines the flow path. The elongate body may support (e.g., mechanically support) the distributor within the flow path such that the distributor receives the fluid as a liquid and issues the fluid as a gas into the interior volume of the balloon.

[0038] For example, the elongate body may define an inlet lumen configured to receive a supply of the fluid (e.g., a liquid) from a fluid delivery system, such as a fluid reservoir and / or fluid pump. The elongate body may be configured to provide the fluid to the interior volume of the balloon via the inlet lumen. In examples, the distributor receives the fluid from the inlet lumen as a liquid and issues the fluid to the interior volume of the balloon as a gas. The elongate body may define an outlet lumen configured to receive a discharge of the fluid (e.g., as a gas) from the balloon interior, such that the elongate body provides the fluid flow through the balloon interior. In some examples, the catheter system defines an inlet flow path (e.g., using inlet tubing) fluidically connecting the fluid delivery system and the inlet lumen, and / or defines an outlet flow path (e.g., using outlet tubing) fluidically connected to the outlet lumen. Thus, in examples, the inlet flow path, the inlet lumen, the interior volume of the balloon, the outlet lumen, and / or the outlet flow path may define a flow path for the fluid flow through the catheter system.

[0039] In some examples, the system includes at least one sensor configured to provide a signal indicative of a flow parameter (e.g., a pressure and / or a fluid flow rate) in at least one of the inlet flow path, the inlet lumen, the interior volume of the balloon, the outlet lumen, and / or the outlet flow path. In some examples, the sensor is configured to provide a signal indicative of the flow parameter as the fluid flows as a liquid through the inlet flow path or the inlet lumen. However, the sensor may be configured to provide a signal indicative of the flow parameter at any location in the flow path, and / or when the fluid is present as a liquid, a gas, and / or a mixture of a fluid and a gas.

[0040] In some examples, the medical system includes at least one valve configured to control the flow rate of the fluid through the flow path. For example, the at least one valve can be located within the system and configured such that changing a position of the at least one valve changes a flow area within the flow path. The medical system may be configured such that the fluid flowing through the flow area defined by the valve is a liquid, a gas, or a mixture of a liquid and a gas. In examples, the valve is configured to control a flow area within one of the inlet flow path or the inlet lumen, such that, for example, the fluid is substantially a liquid when the fluid flows through the flow area defined by the valve. In some examples, the valveis configured to control a flow area within one of the outlet lumen or the outlet flow path, such that, for example, the fluid is substantially a gas when the fluid flows through the flow area defined by the valve. However, the valve may be configured to control the flow area at any location in the flow path, and / or when the fluid is present as a liquid, a gas, and / or a mixture of a fluid and a gas.

[0041] The medical system described herein can be used to provide any suitable type of therapy, such as neuromodulation therapy or other ablation therapy. Neuromodulation therapy can include, for example, denervation therapy. Neuromodulation (e.g., renal neuromodulation) is the partial or complete incapacitation or other effective disruption of nerves (e.g., nerves terminating in the kidneys or in structures closely associated with the kidneys). Neuromodulation can include inhibiting, reducing, and / or blocking neural communication along neural fibers (e.g., efferent and / or afferent neural fibers). Such incapacitation can be long-term (e.g., permanent or for periods of months, years, or decades) or short-term (e.g., for periods of minutes, hours, days, or weeks). Neuromodulation may be expected to contribute to the systemic reduction of sympathetic tone or drive and / or to benefit at least some specific organs and / or other bodily structures innervated by sympathetic nerves. Accordingly, neuromodulation may be expected to be useful in treating clinical conditions associated with systemic sympathetic overactivity or hyperactivity, particularly conditions associated with central sympathetic overstimulation.

[0042] Conditions such as arrhythmias, hypertension, states of volume overload (e.g., heart failure), and progressive renal disease due to excessive activation of the sympathetic nervous system (SNS), may be mitigated by modulating the activity of overactive nerves (neuromodulating), for example, by denervating or reducing the activity of the overactive nerves. For example, renal neuromodulation may be expected to efficaciously treat hypertension, heart failure, acute myocardial infarction, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic and end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, polycystic kidney disease, polycystic ovary syndrome, osteoporosis, erectile dysfunction, and sudden death, among other conditions. In examples described herein, the neuromodulation is thermally- induced (by cryoablation or heating tissue) alone or in addition to being electrically induced, chemically-induced, or induced in another suitable manner or combination of manners at one or more suitable target sites during a treatment procedure.

[0043] Some sympathetic nerves, such as sympathetic nerves (renal nerves) of the kidneys, are positioned proximate to blood vessels, such that these overactive nerves may be chemically, thermally, or electrically denervated by ablating sympathetic nerve tissue in or near the blood vessels (e.g., renal blood vessels).

[0044] In neuromodulation, one or more therapeutic elements may be introduced near one or more target nerves. In renal neuromodulation, for example, the one or more therapeutic elements may be introduced near renal nerves located between an aorta and a kidney of a patient. The target site can be within or otherwise proximate to a renal lumen (e.g., a renal artery, a renal vein, a ureter, a renal pelvis, a major renal calyx, a minor renal calyx, or another suitable structure), and the treated tissue can include tissue at least proximate to a wall of the renal lumen. For example, with regard to a renal artery, a treatment procedure can include modulating nerves in the renal plexus, which lay intimately within or adjacent to the adventitia of the renal artery. In some examples, the one or more therapeutic elements may be carried by or attached to a catheter, and the catheter may be introduced intravascularly, e.g., into a renal artery via a brachial artery, femoral artery, or radial artery approach. In other examples, the one or more therapeutic elements may be introduced extravascularly, e.g., using a laparoscopic technique.

[0045] Although the present technology is herein described in many instances with reference to renal nerves and vessels, the present technology also has application to neuromodulation at other anatomical sites (e.g., spinal neuromodulation, cardiac neuromodulation, brain neuromodulation, sacral neuromodulation, urinary neuromodulation, and / or neuromodulation techniques directed to other portions of a body) and their associated nerves and that such devices and systems can be configured (e.g., have suitable shape and dimensions) for such sites. For example, a catheter may be configured to deliver neuromodulation therapy (e.g., thermal energy) to a particular anatomical lumen or a particular tissue (e.g., a renal artery, external iliac artery, internal iliac artery, internal pudendal artery, celiac artery, mesenteric artery, superior mesenteric artery, inferior mesenteric artery, hepatic artery, splenic artery, gastric artery, left gastric artery, pancreatic artery, uterine artery, ovarian artery, testicular artery, and / or their associated arterial branches, accessories, veins, and / or other hollow anatomical structures).

[0046] As used herein, the terms “distal” and proximal” define a position or direction with respect to the treating clinician or clinician's control device (e.g., a handle assembly). “Distal” or “distally” can refer to a position distant from or in a direction away from the clinician orclinician's control device. “Proximal” and “proximally” can refer to a position near or in a direction toward the clinician or clinician's control device.

[0047] FIG. 1 is a partially schematic perspective view illustrating a medical system 100 configured in accordance with examples of the present disclosure. FIG. 2 is a schematic illustration of a portion of medical system 100 within a blood vessel 102 of a patient 106 (FIG. 3), the blood vessel 102 having a vessel wall 104. FIG. 3 illustrates medical system 100 being navigated through vasculature of patient 106 to a target treatment site within blood vessel 102. In the examples of FIGS. 2 and 3, blood vessel 102 is a renal artery and vessel wall 104 is a renal artery wall. However, in other examples, medical system 100 is be configured to deliver treatments to other blood vessels, anatomical lumens, and / or other tissues, such as an external iliac artery, internal iliac artery, internal pudendal artery, celiac artery, mesenteric artery, superior mesenteric artery, inferior mesenteric artery, hepatic artery, splenic artery, gastric artery, left gastric artery, pancreatic artery, uterine artery, ovarian artery, testicular artery, and / or their associated arterial branches, accessories, veins, and / or other hollow anatomical structures of a patient.

[0048] Medical system 100 includes a catheter system 108 defining an elongate body 110 configured to be positioned (e.g., by a clinician) within blood vessel 102 of patient 106.Catheter system 108 includes one or more expandable elements such as balloon 112 (“balloon 112”) configured to expand (e.g., by inflation) when elongate body 110 is positioned within blood vessel 102. Balloon 112 may be configured to expand to, for example, establish contact with vessel wall 104, assist in occluding blood vessel 102 during a procedure, assist in maintaining elongate body 110 within blood vessel 102, assist in displacing and / or maintaining a displacement between elongate body 110 and vessel wall 104, and / or for other reasons. Elongate body 110 defines a longitudinal axis L. Balloon 112 may be configured to expand radially outwards relative to longitudinal axis L (e.g., substantially perpendicular to longitudinal axis L) when balloon 112 is inflated within blood vessel 102 of patient 106. In some examples, catheter system 108 includes a distributor 114 configured to issue a fluid into an interior volume 116 defined by balloon 112 to deliver a therapy to tissue to, for example, conduct a neuromodulation or another procedure on vessel wall 104 and / or other tissues associated with blood vessel 102. While the therapy is primarily referred to as ablation (e.g., thermal ablation, such as cryoablation or heat-based ablation), the therapy can be in the form of any suitable modality in other examples.

[0049] Medical system 100 is configured to deliver a fluid to interior volume 116 of balloon 112 to inflate balloon 112 within blood vessel 102. Balloon 112 is configured such that the inflation causes an exterior surface (e.g., balloon exterior surface 168 (FIGS. 4 and 5) of balloon 112 to contact vessel wall 104. In examples, balloon 112 is a compliant balloon configured to substantially conform to vessel wall 104 when balloon 112 inflates to establish contact with vessel wall 104. In examples, balloon 112 and / or medical system 100 may be configured such that an expansion of balloon 112 during the inflation is substantially constrained by vessel wall 104. For example, blood vessel 102 (e.g., in the absence of medical system 100) may define a dimension such as a vessel diameter DV. Balloon 112 and / or medical system 100 may be configured such that, when balloon 112 inflates and contacts vessel wall 104, balloon 112 establishes a dimension such as balloon diameter DB which is substantially limited by vessel diameter DV.

[0050] Balloon 112 and / or medical system 100 may be configured such that the expansion of balloon 112 remains constrained by vessel wall 104 over a range of pressures of the fluid within interior volume 116, such that balloon 112 substantially retains a balloon diameter DB which is generally the same as vessel diameter DV as a pressure of the fluid within interior volume 116 varies. For example, balloon 112 may be configured to expand substantially in a distal direction D or a proximal direction P when a pressure increases within interior volume 116 and balloon 112 is constrained from radial expansion by vessel wall 104. In some examples, medical system 100 is configured to provide a relatively low pressure fluid (e.g., a relatively low pressure gas) to interior volume 116 to cause the expansion of balloon 112. For example the fluid may be a gas having a pressure of from about 1 atmospheres to about 5 atmospheres. Hence, in examples, balloon 112 is configured such that an inflated dimension of balloon 112 (e.g., balloon diameter DB) generally conforms to a dimension of blood vessel 102 (e.g., vessel diameter DV) when balloon 112 is inflated within blood vessel 102.

[0051] Medical system 100 is configured to circulate the fluid through interior volume 116 to modify a temperature at or near a target tissue site. For example, balloon 112 may be configured to cause a heat transfer between the fluid within interior volume 116 and vessel wall 104, such as a heat transfer through a body of balloon 112 (e.g., balloon body 166 (FIGS. 4 and 5)). In examples, medical system 100 is configured to provide a cryogenic fluid to balloon 112 to deliver a cryoablation to the target site. In some examples, medical system 100 is configured to provide a heated thermal fluid through balloon 112 to deliver a heat-based thermal ablation to the target site. The temperature modification can be used to provide atherapeutic outcome (e.g., neuromodulation or other lesion generation) or can be used to help protect the vessel wall or other anatomical lumen wall. For example, the temperature modification can be used to cool the tissue prior to, during, or after delivery of other neuromodulation therapy, such as radiofrequency (RF) or ultrasound therapy that causes the tissue to heat up. As another example, the temperature modification can be used to heat the tissue between cycles of cryoablation, e.g., to help generate a lesion deeper into a wall of vessel 104 and maintain the integrity of the tissue at the direct interface between balloon 112 and vessel wall 104.

[0052] In some examples, balloon 112 is configured to help position catheter system 108 within blood vessel 102 during a procedure. For example, catheter system 108 may be configured such that inflation of balloon 112 helps retain elongate body 110 in a position (e.g., approximately centered in blood vessel 102) relative to vessel wall 104, helps maintain a displacement between elongate body 110 and vessel wall 104, and / or assists in other ways. In some examples, elongate body 110 supports (e.g., mechanically supports) balloon 112. Elongate body 110 may also support (e.g., mechanically support) distributor 114. For example, elongate body 110 may support distributor 114 within interior volume 116 of balloon 112.

[0053] Medical system 100 is configured to provide a flow path for a fluid through interior volume 116 to cause the heat transfer (e.g., via balloon 112) between the fluid and vessel wall 104. For example, catheter system 108 may be configured such that the fluid may flow into a fluid inlet 118 (e.g., flow Fl), through an inlet lumen defined by elongate body 110, through interior volume 116, then through an outlet lumen defined by elongate body 110, and subsequently discharge through a fluid outlet 120 (e.g., flow F2). Medical system 100 includes a valve 122 configured to control a flow rate of the fluid flowing through the flow path. In examples, at least some portion of valve 122 is fluidically coupled to the flow path defined by medical system 100.

[0054] Valve 122 is configured to position to control the flow rate of the fluid flowing through the flow path. That is, an element of valve 122 (e.g., restricting element 180) can be moved (e.g., relative to valve body 178) to control a fluid flow rate through the flow path that includes interior volume 116 of balloon 112. In examples, valve 122 is configured to position to control a flow area (e.g., flow area A (FIG. 4, FIG. 5)) within the flow path defined by medical system 100. For example, valve 122 may be configured to establish a first position (also referred to herein as a first state) establishing a first flow area, and configured toestablish (e.g., transition to) a second position (also referred to herein as a second state) establishing a second flow area different from the first flow area. Valve 122 may be configured such that (for a given inlet pressure of fluid), the first flow area allows a first flow rate of fluid through the flow path and the second flow area allow a second flow rate of fluid different that the first flow rate. Hence, medical system 100 is configured such a flow rate of the fluid through the flow path defined by medical system 100 may be controlled by the position of valve 122. In examples, valve 122 is configured to vary and / or establish flow area FA either continuously or discretely over a range between and including a fully shut position of valve 122 and a fully open position of valve 122 in order to vary and / or establish the fluid flow rate over a corresponding range. In examples, valve 122 is a proportional control valve.

[0055] In the example shown in FIG. 1, medical system 100 includes a fluid delivery system 124 configured to provide the fluid to catheter system 108. Fluid delivery system 124 may include, for example, at least one of a fluid container defining a reservoir configured to hold a volume of the fluid or a pump configured to move the fluid. In some examples, medical system 100 includes an inlet conduit 126 defining an inlet flow path fluidically coupled to fluid delivery system 124 and fluid inlet 118. Medical system 100 may include an outlet conduit 128 defining an outlet flow path fluidically coupled to fluid outlet 120. Hence, in examples, two or more of fluid delivery system 124, inlet conduit 126, the inlet lumen of elongate body 110 (e.g., inlet lumen 170 (FIG. 4, FIG. 5)), interior volume 116, the outlet lumen of elongate body 110 (e.g., outlet lumen 172 (FIG. 4, FIG. 5)), and / or outlet conduit 128 define a flow path for the fluid flow through catheter system 108.

[0056] A state of valve 122 controls a flow rate of the fluid within any of inlet conduit 126, the inlet lumen of elongate body 110, interior volume 116, the outlet lumen of elongate body 110, and / or outlet conduit 128. In examples, valve 122 is configured such that altering a flow rate in any one of inlet conduit 126, the inlet lumen of elongate body 110, interior volume 116, the outlet lumen of elongate body 110, and / or outlet conduit 128 alters an amount of the flow of fluid through at least one other of inlet conduit 126, the inlet lumen of elongate body 110, interior volume 116, the outlet lumen of elongate body 110, and / or outlet conduit 128. In some examples, valve 122 is configured such that altering the flow rate alters an amount of the flow of fluid through each of inlet conduit 126, the inlet lumen of elongate body 110, interior volume 116, the outlet lumen of elongate body 110, and outlet conduit 128.

[0057] In some examples, medical system 100 includes a regulating valve 130 in fluidic communication with at least one of the outlet flow path of outlet conduit 128 or the outletlumen of elongate body 110. Regulating valve 130 may be configured to, for example, control a pressure of the fluid within some portion of the flow path defined by medical system 100, such as a pressure (e.g., a back pressure) in one or more of the outlet flow path of outlet conduit 128, the outlet lumen of elongate body 110, and / or interior volume 116. In some examples, medical system 100 may include an evacuating pump (e.g., a vacuum pump) (not shown) in fluidic communication with at least one of the outlet flow path of fluid outlet 120 or the outlet lumen of elongate body 110 to, for example, control a pressure of the fluid within some portion of the flow path and / or evacuate the fluid from catheter system 108. In some examples, fluid delivery system 124 includes one or more additional components, such as a conditioning assembly (e.g., a cooling assembly) (not shown) configured to control a temperature of the fluid and / or a pressure of the fluid within fluid delivery system 124 and / or another portion of medical system 100. In some examples, control circuitry 132 is configured to control a pressure within interior volume 116 using, for example, regulating valve 130, the evacuating pump, and / or other components of medical system 100.

[0058] In some examples, such as in some cryoablation examples, medical system 100 is configured to expand the fluid from a liquid to gas to assist balloon 112 in facilitating a heat transfer from vessel wall 104 to the fluid within interior volume 116 of balloon 112. In examples, distributor 114 is configured to cause the fluid to expand from a liquid to a gas as the fluid flows through distributor 114. Distributor 114 may be positioned within (e.g., fluidically coupled to) the flow path defined by medical system 100. For example, distributor 114 may be positioned within interior volume 116, as shown in FIG. 1. Elongate body 110 may support distributor 114 such that distributor 114 receives the fluid as a liquid (e.g., from the inlet lumen of elongate body 110) and issues the fluid as a gas into interior volume 116. In examples, medical system 100 is configured to provide the fluid as a liquid via fluid delivery system 124 and inlet conduit 126 and discharge the fluid as a gas via outlet conduit 128 and, in some examples, regulating valve 130. In some examples, valve 122 is configured to control the flow of the fluid as a liquid to control the flow rate of the fluid through medical system 100 (e.g., as a liquid issuing from fluid delivery system 124 of flowing through inlet conduit 126). However, valve 122 may be configured to control the flow of the fluid as a liquid, a gas, and / or a mixture of a fluid and a gas to control the flow rate of the fluid through medical system 100. In other examples in which medical system 100 is configured for cryoablation, balloon 112 is inflated via the cryogenic fluid in liquid form.

[0059] Medical system 100 includes control circuitry 132 configured to control a flow rate of the fluid through medical system 100 (e.g., through the defined flow path) based on an indicated size of a blood vessel of a patient. The indicated size may be obtained through, for example, imaging of a target vessel such as blood vessel 102, via sensing one or more parameters indicative of the vessel size, and / or through other methods. For example, the indicated size of blood vessel 102 may be similar to and / or substantially equivalent to vessel diameter DV (FIG. 2) or another dimension defined by blood vessel 102. Control circuitry 132 may be configured to receive the indicated size via an input device 134. Input device 134 may be, for example, a user input device configured to receive the indicated size from a user (e.g., a clinician), circuitry of an imaging system configured to detect the indicated size, circuitry configured to provide the indicated size (e.g., from prior records), circuitry configured to receive input from a sensor, and / or other systems and / or devices.

[0060] In some examples, input device 134 has a suitable configuration sufficient to receive an input from a user. For example, input device 134 can include a button or keypad, a touch screen, a speaker configured to receive voice commands from a user, and / or a display, such as a liquid crystal (LCD), light-emitting diode (LED), or organic light-emitting diode (OLED). In some examples, user interface 134 may include or be configured to be used in combination with a mobile phone, smartphone, tablet computer, personal computer, desktop computer, personal digital assistant, router, modem, remote server or cloud computing device, and / or related device. In some examples, user interface 134 is configured to display information, such as a one or more indicated sizes, setpoints, apt flow rates, and / or flow parameters (e.g., the current indicated size and / or apt flow rate being used by control circuitry 132 and / or one or more predetermined indicated sizes and / or setpoints from which the user can select to input an indicated size of blood vessel 102.

[0061] Control circuitry 132 configured to determine an apt flow rate (e.g., a desired flow rate) through balloon 112 based on the indicated size. The apt flow rate may be indicative of a flow rate of a fluid through medical system 100 (e.g., balloon 112) expected to cause medical system 100 (e.g., catheter system 108) to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel of the indicated size (e.g., blood vessel 102) when balloon 112 is inflated within the vessel of the indicated size. In some examples, control circuitry 132 is configured to compare a flow rate of a fluid flowing within medical system 100 with the apt flow rate determined, and adjust the flow rate based on the comparison. Hence, controlcircuitry 132 is configured to control the flow rate (e.g., in elongate body 110 and / or through balloon 112) to account for the size of a target blood vessel (e.g., blood vessel 102).

[0062] Control circuitry 132 may be configured to determine an apt flow rate for an indicated size using stored data, such as, but not limited to, data obtained from, for example, previous ablation procedures, modeling and / or measurement of fluid flow through the catheter system, modeling and / or measurement of heat transfer characteristics of a balloon experiencing a given fluid flow, and / or other data indicative of a heat transfer between an inflated balloon such as balloon 112 and a vessel wall such as vessel wall 104. Although not shown in FIG. 1, medical system 100 can include a memory that stores a plurality of vessel sizes and corresponding apt flow rates. In some examples, the memory can also store a plurality of vessel sizes and corresponding apt flow rates for each ablation level of a plurality of ablation levels. The ablation level can, for example, correspond to a depth of a lesion formed by the neuromodulation therapy.

[0063] In the example shown in FIG. 1, medical system 100 includes a sensor 136 configured to generate a signal indicative of a flow parameter (e.g., a pressure, a fluid flow rate, or other flow parameter) of a fluid within the flow path defined by medical system 100. Sensor 136 may be configured such that the signal is indicative of (e.g., proportional to) a flow rate of fluid flowing through interior volume 116 of balloon 112. Sensor 136 may be configured to sense the flow parameter at any location within the flow path defined by medical system 100, including inlet conduit 126, an inlet lumen defined by elongate body 110, interior volume 116, an outlet lumen defined by elongate body 110, outlet conduit 128, and / or another portion of the flow path. Sensor 136 may be configured to sense the flow parameter at a location where the fluid is expected to be a liquid, a gas, or a mixture of a liquid and a gas. In examples, sensor 136 is configured to sense the flow parameter when the fluid is a liquid flowing through inlet conduit 126.

[0064] In some examples, control circuitry 132 is configured to control the flow rate based on the comparison of the signal from sensor 136 and the apt flow rate determined for the indicated size of the vessel of the patient (e.g., vessel diameter DV). For example, control circuitry 132 may be configured to control valve 122 (e.g., a position of a movable element of valve 122) to control the flow rate. Hence, control circuitry 132 may be configured to control the flow rate through balloon 112 based on the apt flow rate determined to, for example, to provide a relatively consistent ablation level over a range of blood vessel sizes. In examples, control circuitry 132 is configured to controls the flow rate through balloon 112 based on theapt flow rate to provide a relatively consistent ablation depth over the range of blood vessel sizes.

[0065] Elongate body 110 defines a distal portion 110A (“distal body portion 110A”) and a proximal portion HOB (“proximal body portion HOB”). Balloon 112 and / or distributor 114 are positioned on distal body portion 110A in the example shown in FIG. 1. In examples, catheter system 108 is configured to assume a relatively low profile delivery configuration in which at least one of distal body portion 110A and / or balloon 112 defines a dimension DS (e.g., a diameter), which can be measured in a direction perpendicular to longitudinal axis L. The dimension DS may define a displacement sufficient to allow the passage of at least distal body portion 110A and balloon 112 through vasculature of patient 106 to reach a target treatment site within patient 106. In some examples, distal body portion 110A is configured to locate balloon 112 and / or distributor 114 at an intraluminal (e.g., intravascular) location. In examples, catheter system 108 is configured such that, in the delivery configuration, the dimension DS measures 2, 3, 4, 5, 6, or 7 French or another suitable size. Balloon 112 is configured to expand from the delivery configuration to an expanded configuration (FIG. 2) to, for example, facilitate a heat transfer between vessel wall 104 and a fluid flowing through the flow path defined by medical system 100. Balloon 112 may be configured to establish inner volume 116 in the expanded configuration such that balloon 112 may establish contact with vessel wall 104 for a plurality (e.g., a range) of vessel diameters that might be expected for a vessel such as vessel 104.

[0066] In some examples, medical system 100 (e.g., catheter system 108) includes a therapeutic element (not shown) configured to transmit energy or another therapy (e.g., a chemical) to vessel wall 104 to provide a therapeutic outcome. The therapeutic element may be configured to transmit ultrasound energy, microwave energy, RF energy, or another type of energy. Elongate body 110 and / or balloon 112 may support (e.g., mechanically support) the therapeutic element. In examples, medical system 100 is configured to control a power and / or wavelength of the energy transmitted from the therapeutic element to, for example, control a temperature of the tissues at the target site receiving the energy.

[0067] In some examples, medical system 100 (e.g., proximal body portion 110B) includes a handle portion 146, which is configured to remain outside vasculature of a patient when distal body portion 110A is within vasculature of the patient. Handle portion 146 may be configured to allow a clinician to navigate at least distal body portion 110A through the vasculature, allow inflation and / or deflation of balloon 112, allow and / or control a flow offluid through balloon 112, and / or enable other functions of medical system 100 which may assist in the delivery of a treatment (e.g., a neuromodulation) to patient 106. At least some portion of catheter system 108 (e.g., distal body portion 110A) may be substantially flexible, such that catheter system 108 may flex and / or bend enroute to positioning distributor 114 substantially at a target location within a blood vessel of a patient. Hence, although illustrated as substantially linear in FIG. 1, catheter system 108 (or portions thereof) may be configured to assume linear, curved, and / or curvilinear shapes. Correspondingly, longitudinal axis L (and / or portions thereof) defined by catheter system 108 may be linear, curved, and / or curvilinear.

[0068] In examples, medical system 100 includes a console 148 including a console housing 150. Console 148 includes fluid delivery system 124, valve 122, some portion of inlet conduit 126, some portion of outlet conduit 128, regulating valve 130, at least some portion of control circuitry 132, input device 134, and / or other components of medical system 100. In some examples, console 148 includes fluid delivery system 124, valve 122, inlet conduit 126, outlet conduit 128, regulating valve 130, control circuitry 132, and / or input device 134 at least partially within (e.g., at least partially surrounded by) console housing 150.

[0069] In examples, fluid delivery system 124 includes a supply container 152 configured to hold the fluid supplied to catheter system 108. The supply container 152 can be a single-use cartridge or a larger container that contains a sufficient volume of fluid to perform multiple procedures. In examples, supply container 152 may be a refillable container (e.g., a refillable cylinder). Fluid delivery system 124 and / or supply container 152 may be configured to retain the fluid at a desired pressure and / or a desired temperature. For example, in one example, fluid delivery system 124 may be configured to hold nitrous oxide within supply container 152. Fluid delivery system 124 may be configured to hold the nitrous oxide at a pressure of 750 psi or greater (5.17 MPa or greater) to maintain the nitrous oxide in a substantially liquid state at ambient temperatures. In other embodiments, the fluid may include carbon dioxide, a hydrofluorocarbon (“HFC”), and / or other suitable compressed or condensed refrigerant.

[0070] In examples, control circuitry 132 is configured to receive the signal from sensor 136 via a communication link 138. Control circuitry 132 may be configured to issue and / or receive signals to and / or from valve 122 via a communication link 140. Control circuitry 132 may be configured to receive a signal indicative of an indicated size of a vessel from input device 134 via communication link 142. In some examples, control circuitry 132 may be configured to issue and / or receive signals to and / or from regulating valve 130 via acommunication link 144. Communication link 138, 140, 142, 144 may be hard-line and / or wireless communications links. In some examples, communication link 138, 140, 142, 144 may comprise some portion of control circuitry 132. In some examples, communication link 138, 140, 142, 144 may comprise a wired connection, a wireless Internet connection, a direct wireless connection such as wireless LAN, Bluetooth™, Wi-Fi™, and / or an infrared connection.

[0071] Control circuitry 132, as well as other processors, processing circuitry, controllers, control circuitry, and the like, described herein, may include any combination of integrated circuitry, discrete logic circuity, analog circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), or field- programmable gate arrays (FPGAs). In some examples, control circuitry 132 includes multiple components, such as any combination of one or more microprocessors, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry, and / or analog circuitry.

[0072] Although not shown in FIG. 1, medical system 100 can also include a memory configured to store program instructions, such as software, which may include one or more program modules, which are executable by control circuitry 132. When executed by control circuitry 132, such program instructions may cause control circuitry 132 to provide the functionality ascribed to control circuitry 132 herein. The program instructions may be embodied in software and / or firmware. The memory can include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), ferroelectric RAM (FRAM), flash memory, or any other digital media.

[0073] FIG. 2 schematic illustrates a portion of medical system 100 (e.g., distal body portion 110A, balloon 112, and distributor 114) within blood vessel 102 defined by vessel wall 104 of patient 106. Catheter system 108 is configured to enable inflation of balloon 112 to cause catheter system 108 to transition from the delivery configuration (FIG. 1) to an expanded configuration when distal body portion 110A is positioned within blood vessel 102. In examples, catheter system 108 is configured to expand balloon 112 such that balloon 112 defines the dimension DB in an expanded configuration. The dimension DB defined in the expanded configuration may be greater than the dimension DS defined in the delivery configuration (FIG. 1). In examples, balloon 112 is configured to define the dimension DS,the dimension DB, and / or another dimension (e.g., a dimension substantially perpendicular to longitudinal axis L) based on a pressure PI of the fluid within interior volume 116.

[0074] In examples, medical system 100 (e.g., catheter system 108) is configured such that balloon 112 can expand to contact vessel wall 104. For example, balloon 112 may expand such that an exterior surface 168 of balloon 112 (“balloon exterior surface 168”) contacts vessel wall 104. Distal body portion 110A may support balloon 112 such that, when balloon 112 defines the dimension DB, catheter system 108 defines a displacement DP substantially between balloon exterior surface 168 and longitudinal axis L, distributor 114, and / or a therapeutic element of medical system 100. In examples, catheter system 108 is configured to substantially center (e.g., center or nearly center to the extent permitted by vessel symmetry) longitudinal axis L, distributor 114 and / or another element of medical system 100 within blood vessel 102 when balloon 112 expands to contact vessel wall 104.

[0075] Balloon 112 facilitates heat transfer between a fluid within interior volume 116 and vessel wall 104 to induce one or more desired effects (e.g., neuromodulation and / or ablation effects) on localized regions of blood vessel 102 and regions adjacent to blood vessel 102. For example, when blood vessel 102 defines a renal artery associated with a kidney 156, distributor 114 may induce one or more desired neuromodulating effects to a portion of Renal Plexus (RP) 158 lying within or adjacent to the adventitia of the renal artery. The heat transfer, whether cooling or heating of tissue, can create a lesion within tissue in or proximate to vessel wall 104.

[0076] FIG. 3 illustrates a portion of medical system 100 positioned within vasculature of a patient 106 to place balloon 112 and / or distributor 114 within blood vessel 102. FIG. 3 is described with primary reference to a renal artery, however similar devices, systems, and techniques may be adapted for accessing other anatomical lumens or tissues within patient 106.

[0077] Catheter system 108 (e.g., elongate body 110) may provide access to the renal plexus (RP) through an intravascular path (P), such as a percutaneous access site in the femoral (illustrated), brachial, radial, or axillary artery to a target treatment site within blood vessel 102. By manipulating proximal body portion 110B of elongate body 110 from outside the intravascular path (P), a clinician may advance at least distal body portion 110A through the sometimes-tortuous intravascular path (P) and remotely manipulate distal body portion 110A. In examples, distal body portion 110A may be remotely manipulated by a clinician using handle portion 146.

[0078] In the example illustrated in FIG. 3, balloon 112 is delivered intravascularly to the treatment site using a guidewire 160 in an OTW technique. Catheter system 108 (e.g., elongate body 110) may define a passageway for receiving guidewire 160 for delivery of elongate body 110 (e.g., distal body portion 110A) using either an OTW or a RX technique. At the treatment site, guidewire 160 can be at least partially withdrawn or removed, and balloon 112 may be expanded from the delivery configuration (FIG. 1) to an expanded configuration (FIG. 2). Balloon 112 may substantially position balloon 112 relative to blood vessel 102 for delivering energy to blood vessel 102 and / or other anatomical lumens or tissues within patient 106. In other examples, balloon 112 and / or distributor 114 may be delivered to the treatment site within a different guide device, such as guide sheath (not shown in FIG. 3), with or without using guidewire 160. In examples in which medical system 100 includes a guide sheath, when balloon 112 and / or distributor 114 are at the target treatment site, the guide sheath may be at least partially withdrawn or retracted and balloon 112 may be transformed into an expanded configuration. In still other examples, elongate body 110 may be steerable itself such that balloon 112 and / or distributor 114 may be delivered to the treatment site without the aid of guidewire 160 and / or a guide sheath.

[0079] FIG. 4 is a schematic illustration of medical system 100 with catheter system 108 in a relatively low profile delivery configuration within blood vessel 102, with catheter system 108 defining a dimension DS. FIG. 5 is a schematic illustration of medical system 100 within catheter system 108 in an expanded configuration within blood vessel 102, with catheter system 108 defining a dimension DB. Dimension DB is greater than dimension DS. In examples, as shown in FIG. 5, catheter system 108 is configured to cause balloon 112 to contact vessel wall 104 in the expanded configuration. Dimension DS and / or the dimension DB may be a cross-sectional dimension of catheter system 108 (e.g., balloon 112), the crosssection being taken perpendicular to longitudinal axis L of elongate body 110. In examples, dimension DS and dimension DB define a displacement in a direction substantially perpendicular to longitudinal axis L. In examples, longitudinal axis L extends through catheter system 108 through a distal end 162 of elongate body 110 (“body distal end 162”). Longitudinal axis L may extend through at least some portion of distal body portion 110A and / or proximal body portion HOB. Distal end 162 may be substantially distal or substantially proximal to balloon 112 when balloon 112 is in either of the delivery configuration or expanded condition.

[0080] Medical system 100 (e.g., control circuitry 132) is configured to receive an indicated size of blood vessel 102 and determine an apt flow rate (e.g., a desired flow rate) indicative of a flow rate through catheter system 108 (e.g., balloon 112). The apt flow rate may be a fluid flow rate expected to cause medical system 100 to provide a suitable ablation level to blood vessel 102. The suitable ablation level may be indicative of a desired heat transfer between medical system 100 (e.g., balloon 112) and blood vessel 102 to achieve a desired therapeutic outcome, such as a cryoablation or thermal ablation of a target tissue site of blood vessel 102, creation of a lesion of a desired size from the heat transfer, or the like. In examples, the suitable ablation level is indicative of a heat transfer between medical system 100 and blood vessel 102 expected to cause a thermal ablation relative to an ablation depth AD defined by blood vessel 102. For example, the heat transfer may be expected to cause thermal ablation in vessel wall 104 to at least the ablation depth AD or limit thermal ablation in vessel wall 104 to less than the ablation depth AD. In some examples, the suitable ablation level is indicative of a heat transfer expected to cause tissues of blood vessel 102 to achieve a target temperature and / or a temperature within a targeted temperature range. In examples, the suitable ablation level may be a power level (e.g., a wattage) indicative of heat transfer between balloon 112 and vessel wall 104. The apt flow rate may thus be indicative of a fluid flow rate through medical system 100 expected to cause balloon 112 to deliver the suitable ablation level to blood vessel 102 via balloon 112 when balloon contacts vessel wall 104.

[0081] For example, blood vessel 102 may be a first blood vessel with vessel diameter DV equal to a first vessel diameter. Balloon 112 may be configured such that balloon diameter DB is equal to a first balloon diameter constrained by and / or substantially equal to the first vessel diameter when balloon 112 is in the expanded configuration of FIG. 5 within the first blood vessel. Medical system 100 may be configured such that a first mass flow rate through catheter system 108 (e.g., through balloon 112) causes balloon 112 to provide a suitable ablation level to vessel wall 104 when balloon 112 establishes the first balloon diameter. For example, medical system 100 may be configured such that the first mass flow rate causes balloon 112 to provide a temperature within a range of target temperatures substantially at the ablation depth AD when balloon 112 establishes balloon diameter DB equal to the first balloon diameter, balloon exterior surface 168 contacts vessel wall 104, and catheter system 108 receives a flow of fluid at the first mass flow rate.

[0082] In another example, blood vessel 102 may be a second blood vessel with vessel diameter DV equal to a second vessel diameter greater than the first vessel diameter, such thatballoon 112 establishes balloon diameter DB is equal to a second balloon diameter greater than the first balloon diameter when balloon 112 is in the expanded configuration of FIG. 5 within the second blood vessel. Medical system 100 may be configured such that a second mass flow rate through catheter system 108 (e.g., through balloon 112) causes balloon 112 to provide the suitable ablation level to vessel wall 104 when balloon 112 establishes the second balloon diameter. In examples, the second mass flow rate necessary to provide the suitable ablation level when balloon 112 establishes the second balloon diameter is greater than the first mass rate necessary to provide the suitable ablation level when balloon 112 establishes the first balloon diameter. For example, medical system 100 may be configured such that the second mass flow rate causes balloon 112 to provide the temperature within the range of target temperatures substantially at the ablation depth AD when balloon 112 establishes balloon diameter DB equal to the second balloon diameter, balloon exterior surface 168 contacts vessel wall 104, and catheter system 108 receives a flow of fluid at the second mass flow rate.

[0083] Control circuitry 132 is configured to control the flow rate through catheter system 108 such that balloon 112 delivers the suitable ablation level over a range of blood vessel sizes (e.g., vessel diameters). Control circuitry 132 is configured to receive the indicated size of a blood vessel (e.g., the first vessel diameter or the second vessel diameter) and determine an apt flow rate for the indicated size. Control circuitry 132 is configured to provide a flow of fluid to catheter system 108 at the apt flow rate, such that balloon 112 provides the suitable ablation level when balloon 112 when balloon 112 is in the expanded configuration of FIG. 5 within the vessel having the indicated size.

[0084] For example, control circuitry 132 may control the flow rate so catheter system 108 receives a fluid (e.g., a cryofluid) at the first flow rate in response to receiving a first indicated size indicative of the first vessel diameter of the first blood vessel, such that balloon 112 delivers the suitable ablation level to the first blood vessel. Control circuitry 132 may control the flow rate so catheter system 108 receives the fluid at the second flow rate in response to receiving a second indicated size indicative of the second vessel diameter of the second blood vessel, such that balloon 112 delivers the suitable ablation level to the second blood vessel. Hence, control circuitry 132 is configured to control the flow rate through catheter system 108 to cause balloon 112 to deliver a substantially consistent ablation level for a plurality of blood vessel sizes. Control circuitry 132 uses an indicated size of a blood vessel as a proxy for the balloon diameter DB that balloon 112 is likely to establish whenballoon 112 is inflated within the blood vessel and balloon exterior surface 168 contacts a wall of the blood vessel.

[0085] As an example, FIG. 6A illustrates an example relationship between an indicated size of a blood vessel and the apt flow rate provided to catheter system 108. In this example, control circuitry 132 is configured to receive one or more indicated vessel sizes such as DI, D2, D3, . . . , DN and determine one or more apt flow rates such as Ml, M2, M3, . . . , MN, respectively, to cause balloon 112 to provide a suitable ablation level. For example, balloon 112 may be configured such that apt flow rate Ml causes balloon 112 to substantially deliver the suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having indicated size DI, apt flow rate M2 causes balloon 112 to substantially deliver the suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having indicated size D2, apt flow rate M3 causes balloon 112 to substantially deliver the suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having indicated size D3, apt flow rate MN causes balloon 112 to substantially deliver the suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having indicated size DN, and so on. In examples, indicated size DI is a dimension within a range Rl, indicated size D2 is a dimension within a range R2, indicated size D3 is a dimension within a range R3, and / or indicated size DN is a dimension with a range RN.

[0086] In examples, the apt flow rates Ml, M2, M3, . . . , MN increase as the indicated sizes DI, D2, D3, . . . , DN increase. In some examples, the apt flow rates Ml, M2, M3, . . . , MN are described by a correlation Cl relating the apt flow rate to the indicated size. In some examples, the correlation Cl is continuous, such that correlation Cl describes a specific apt flow rate for any specific indicated size between and including indicated size DI and indicated size DN. The correlation Cl may be a discrete, such that such that correlation Cl describes a specific apt flow when the indicated size defines or is assigned (e.g., by control circuitry 132) a discrete value (e.g., one of DI, D2, D3, . . . , DN ). In some examples, the correlation Cl is defined by a coordinate data structure (e.g., a table) describing a plurality of ordered pairs describing a set of coordinates (e.g., a coordinate describing a specific apt flow rate and a coordinate describing a specific indicated size). The coordinate data structure, as well as other information associating indicated vessel sizes with respective apt flow rates can be stored by a memory of system 100 or a memory of another device in communication with control circuitry 132.

[0087] The correlation Cl may define any shape relative to indicated vessel sizes such as DI, D2, D3, . . . , DN. For example, although the correlation Cl in FIG. 6 A defines a shape having an increasing slope as the indicated vessel sizes increase (e.g., concave up), the correlation Cl may define shapes varying with respect to the indicated vessel sizes in other manners, such as other curved, linear, and / or curvilinear shapes. For examples, FIG. 6B illustrates the correlation Cl defining a shape having an decreasing slope as the indicated vessel sizes increase (e.g., concave down) and defining apt flow rates M4, M5, M6, . . . , ML which increase as the indicated sizes DI, D2, D3, . . . , DN increase.

[0088] In some examples, the correlation Cl is defined by a plurality of separate correlations defined over one or more intervals, such as an interval between DI and D2, an interval between D2 and D3, and / or another interval. The correlation Cl may define any curvature and / or slope over any interval, and may be a linear or a nonlinear function over one or more intervals. Control circuitry 132 may be configured to cause a flow rate through catheter system 108 to substantially achieve an apt flow rate (e.g., one of Ml, M2, M3, . . . , MN and / or M4, M5, M6, . . . , ML) in order to cause balloon 112 to provide a suitable ablation level within a vessel described by an indicated size (e.g., one of DI, D2, D3, . . . , DN).

[0089] The correlation Cl may be based on data obtained from, for example, previous ablation procedures, modeling and / or measurement of flow rates through medical system 100 (e.g., through elongated body 110, balloon 112, and / or other portions of medical system 100), modeling and / or measurement of heat transfer characteristics of balloon 112 experiencing a given flow rate, and / or other data indicative of a heat transfer between balloon 112 and a vessel wall when balloon 112 is positioned within a vessel of the indicated size.

[0090] Although FIG. 6A and FIG. 6B illustrates the correlation Cl as a two-dimensional correlation determining apt flow rates apt flow rates Ml, M2, M3, . . . , MN and / or M4, M5, M6, . . . , ML based solely on the indicated sizes DI, D2, D3, . . . , DN, the correlation Cl may determine apt flow rates Ml, M2, M3, . . . , MN and / or M4, M5, M6, . . . , ML using additional variables and / or factors in other examples. For example, the correlation Cl, may be defined in a space having any number of dimensions and defined by any number of variables and / or factors in addition to indicated sizes DI, D2, D3, . . . , DN. Further, although in examples control circuitry 132 defines indicated sizes DI, D2, D3, . . . , DN using imagery or other methods, control circuitry 132 may define indicated sizes DI, D2, D3, . . . , DN using a correlation defined in a space having any number of dimensions and defined by any numberof variables. For example, if vessel wall 104 defines a tapered or other shape wherein an indicated size varies over a length of vessel 102, then more than one measurement might be needed to characterize the necessary flow rate (e.g., the apt flow rate) to ensure appropriate contact between balloon 112 and vessel wall 104.

[0091] Balloon 112 is configured such that a fluid in balloon interior 116 (e.g., a fluid supplied by fluid delivery system 124) establishes an inflation pressure PI within balloon interior 116. In examples, balloon interior volume 116 is bound at least in part by an interior surface 164 (“balloon interior surface 164”) defined by a body 166 of balloon 112 (“balloon body 166”). Balloon body 166 may define balloon exterior surface 168 substantially opposite balloon interior surface 164. In examples, balloon body 166 is configured to cause a heat transfer between the fluid within interior volume 116 and vessel wall 104 when balloon exterior surface 168 contacts vessel wall 104. In examples, the heat transfer between the fluid within interior volume 116 and vessel wall 104 occurs via balloon interior surface 164, balloon body 166, and balloon exterior surface 168.

[0092] Balloon 112 is configured to inflate from the delivery configuration of FIG. 4 to the expanded configuration of FIG. 5 in response to an increase in the inflation pressure PI. Balloon 112 is configured to establish balloon diameter DB based on vessel diameter DV in the expanded configuration. In examples, balloon 112 is configured such that, in the expanded configuration of FIG. 5, balloon diameter DB is within a percentage range of vessel diameter DV. For example, balloon diameter DB may be at least 70 percent and less than 130 percent of vessel diameter DV, such as at least 80 percent and less than 120 percent of vessel diameter DV, at least 90 percent and less than 110 percent of vessel diameter DV in some examples, and / or substantially equal to vessel diameter DV. As used herein, vessel diameter DV may be equivalent to the indicated size of a blood vessel.

[0093] In some examples, control circuitry 132 is configured to control the delivery of a fluid to interior volume 116 of balloon 112 to cause balloon 112 to substantially establish the expanded configuration within blood vessel 102. Control circuitry 132 may be configured to provide the fluid at the apt flow rate or another flow rate different from the apt flow rate to cause balloon 112 to substantially establish the expanded configuration within blood vessel 102. Balloon 112 has any suitable configuration. In examples, balloon 112 is configured to such that an imaging system (e.g., an imaging system extracorporeal to patient 106) can capture an image of balloon 112 when balloon 112 is within patient 106. In examples, balloon 112 (e.g., balloon body 166) comprises silicone. In some examples, balloon 112 is a dippedballoon fabricated using a dip molding process. Balloon 112 (e.g., balloon body 166) may be constructed of any compliant, semi-compliant or non-compliant material, typically a plastic such as polyurethane, nylon, polyethylene, PE.

[0094] Control circuitry 132 is configured to control the delivery of a fluid to interior volume 116 of balloon 112 using any suitable technique and control elements. In some examples, control circuitry 132 is configured to cause valve 122 to transition to and / or establish a position (or “state”) correlated with the apt flow rate associated with an indicated size of a vessel. Medical system 100 may be configured such that, when valve 122 transitions to and / or establishes the position correlated with the apt flow rate, a fluid flows from fluid delivery system 124 and through catheter system 108 at a rate causing medical system 100 to experience a flow rate substantially equivalent to the apt flow rate. In some examples, in addition to or instead of causing valve 122 to achieve a position correlated with the apt flow rate, control circuitry 132 may receive a signal from sensor 136 indicative of a rate of flow of the fluid from fluid delivery system 124 through catheter system 108, and adjust valve 122 until the signal from sensor 136 indicates that medical system 100 is experiencing a flow rate substantially equivalent to the apt flow rate.

[0095] For example, control circuitry 132 may receive an indicated size of blood vessel 102 from input device 134. Control circuitry 132 may determine an apt flow rate to cause catheter system 108 to deliver a suitable ablation level for blood vessel 102 based on the indicated size. With catheter system 108 positioned within blood vessel 102, control circuitry 132 may adjust (e.g., position) valve 122 such that fluid delivery system 124 substantially delivers the apt flow rate through the flow path defined by catheter system 108 (e.g., a flow path including interior volume 116). In examples, control circuitry 132 receives a flow signal indicative of a flow of the fluid within the flow path from sensor 136 and adjusts valve 122 (e.g. using an actuator 182) based on a comparison of the flow parameter indicated by sensor 136 and the apt flow rate determined for the indicated vessel size. In examples, medical system 100 is configured to provide and / or otherwise communicate the flow signal provided by sensor 136 to one or more other devices of medical system 100.

[0096] In examples, the flow signal provided by sensor 136 is indicative of a pressure (e.g., a static pressure, dynamic pressure, and / or total pressure) at a location in the flow path defined by catheter system 108. For example, sensor 136 may include a collector 137 (e.g., a transducer) configured to provide a flow signal indicative of a pressure within inlet lumen 170 and / or inlet conduit 126, and / or another portion of catheter system 108. Control circuitry 132may be configured to substantially infer the flow rate through the flow path using the pressure and flow data (e.g., from bench testing) reflecting an expected fluid flow for catheter system 108 when a given pressure (e.g., within inlet lumen 170 and / or inlet conduit 126) is indicated by sensor 136 (e.g., via collector 137). Control circuitry 132 may be configured to compare the inferred flow rate to the apt flow rate and adjust a position of valve 122 based on the comparison. For example, when sensor 136 provides a flow signal indicative of a pressure (e.g., a pressure within inlet lumen 170 and / or inlet conduit 126), control circuitry 132 may adjust valve 122 in an opening direction or a closing direction until the pressure indicates the flow rate of the fluid through the flow path is substantially equivalent (e.g., within a defined range of) the apt flow determined for the indicated vessel size.

[0097] In examples, the flow signal provided by sensor 136 is indicative of a flow rate (e.g., a mass flow rate and / or volumetric flowrate) at a location in the flow path defined by catheter system 108. For example, collector 137 may be configured to provide a flow signal indicative of a flow rate within inlet lumen 170 and / or inlet conduit 126, and / or another portion of catheter system 108. Control circuitry 132 may be configured to substantially infer the flow rate through the using the flow signal and / or flow data (e.g., from bench testing) reflecting an expected fluid flow for catheter system 108 when a given flow rate (e.g., within inlet lumen 170 and / or inlet conduit 126) is indicated by sensor 136 (e.g., via collector 137). Control circuitry 132 may be configured to compare the inferred flow rate to the apt flow rate and adjust a position of valve 122 based on the comparison. For example, when sensor 136 provides a flow signal indicative of a flow rate (e.g., a flow rate within inlet lumen 170 and / or inlet conduit 126), control circuitry 132 may adjust valve 122 in an opening direction or a closing direction until the flow rate indicates a flow of the fluid through the flow path substantially equivalent to (e.g., within a defined range of) the apt flow determined for the indicated vessel size.

[0098] In some examples, the flow signal provided by sensor 136 is indicative of a position (or state) of valve 122 (e.g., for a given pressure of the fluid within fluid delivery system 124). For example, control circuitry 132 may be configured to receive a valve position signal indicative of a valve position of valve 122 from a valve position indicator 139. Control circuitry 132 may be configured to substantially infer the flow rate through the flow path of catheter system 108 using the valve position signal and flow data (e.g., from bench testing) reflecting an expected fluid flow for catheter system 108 when a given valve position of valve 122 is indicated by sensor 136. Control circuitry 132 may be configured to adjust a position ofvalve 122 (e.g., in in an opening direction or a closing direction) such that the inferred flow rate through the flow path is substantially equivalent (e.g., within a defined range of) the apt flow determined for the indicated vessel size.

[0099] In examples, control circuitry 132 is configured to adjust valve 122 to cause a flowrate of fluid through catheter system 108 in response to an initiation signal. Medical system 100 may be configured to provide the initiation signal in response to an action by a clinician, such that the clinician may control the commencement of an ablation delivered by medical system 100. For example, control circuitry 132 may be configured to receive the initiation signal from input device 134 (e.g., prompted by a user). In some examples, in response to receiving the initiation signal, control circuitry 132 adjusts valve 122 to a valve position correlated with the apt flow rate and / or adjust valve 122 until the signal from sensor 136 indicates medical system 100 is substantially experiencing a flow rate substantially equivalent to the apt flow rate.

[0100] In examples, catheter system 108 (e.g., elongate body 110) defines an inlet lumen 170 and an outlet lumen 172 configured to provide at least a portion of the flow path through catheter system 108. Inlet lumen 170 and / or outlet lumen 172 are fluidically coupled to interior volume 116, such that a fluid may flow into interior volume 116 via inlet lumen 170, flow through some portion of interior volume 116, and flow out of interior volume 116 via outlet lumen 172. For example, inlet lumen 170 may be configured to provide a flow path for an inlet flow Fl (FIG. 5) from fluid inlet 118 to interior volume 116 (e.g., via distributor 114). Outlet lumen 172 is configured to provide a flow path for an outlet flow F2 from interior volume 116 to fluid outlet 120. In examples, medical system 100 includes a cryoablation system and the fluid is a refrigerant that changes phase from a liquid to a gaseous physical state inside balloon 112. In some examples, distributor 114 is configured to cause the fluid to expand from a liquid to a gas as the fluid flows through distributor 114. In some examples, medical system 100 is configured to such that inlet flow Fl is a liquid and / or a liquid-gas mixture. Medical system 100 may be configured to such that outlet flow F2 is substantially gaseous.

[0101] Inlet flow Fl may be some portion of or substantially all of a flow of the fluid provided by fluid delivery system 124. In examples, inlet conduit 126 defines an inlet flow path fluidically coupled to fluid delivery system 124 and fluid inlet 118 and / or outlet conduit 128 defines an outlet flow path fluidically coupled to fluid outlet 120. Hence, in examples, two or more of fluid delivery system 124, inlet conduit 126, inlet lumen 170, interior volume116, outlet lumen 172, and / or outlet conduit 128 define a flow path for the fluid flowing through catheter system 108. Medical system 100 is configured such that the fluid flowing through the flow path is fluidically isolated from blood vessel 102 when catheter system 108 (e.g., distal body portion 110A) is positioned within blood vessel 102.

[0102] In examples, valve 122 defines a flow area A configured to control a flow rate through the flow path defined by medical system 100. In examples, valve 122 is configured such that the fluid flows into a valve inlet 174 and at least partially through flow area A before discharging from an outlet 176 of valve 122 (“valve outlet 176”). Valve inlet 174 and / or valve outlet 176 may be defined by a body 178 of valve 122 (“valve body 178”). Valve 122 can have any suitable configuration configured to control a rate of fluid flow. In examples, valve 122 includes a restricting element 180 (e.g., a valve disc) configured to at least partially define the flow area A. Restricting element 180 may be configured to move relative to a portion of a valve body 178 (e.g., relative to a valve seat) to define the flow area A. In examples, valve 122 is configured such that a size (e.g., an area) of flow area A is a function of a position of restricting element 180 relative to valve body 178. Hence, control circuitry 132 can be configured to control a position of valve 122 (e.g., a position of restricting element 180 relative to valve body 178) to control the flow area A, and thus control the flow rate through medical system 100 (e.g., catheter system 108 and / or balloon 112) based on the position of valve 122. Valve 122 may be any type of valve sufficient to control a flow rate from valve inlet 174 to valve outlet 176, such as a proportional control valve, a globe valve, a poppet valve, a needle valve, a gate valve, a spool valve, or some other mechanism or combination of mechanisms sufficient to control the flow rate.

[0103] In examples, valve 122 includes an actuator 182 configured to position valve 122 (e.g., configured to position restricting element 180 relative to valve body 178). In examples, actuator 182 is configured to position and / or alter a position of valve 122 based on a valve signal received from control circuitry 132 via communication link 140 (e.g., an electrical, electronic, hydraulic, pneumatic, or other type of signal). Actuator 182 may be any type of actuator sufficient to position valve 122 (e.g., restricting element 180). Actuator 182 may be configured to position and / or alter a position of valve 122 in response to a received electrical or electronic communication (e.g., received via communication link 140). In some examples, actuator 182 is configured to position and / or alter a position of valve 122 based on a supply of a control fluid. For example, valve 122 may be a hydraulically or pneumatically operated valve. Valve 122 may include control circuitry configured to control components of valve 122in response to a received valve signal. The control circuitry may be some portion of control circuitry 132 or may be substantially separate from control circuitry 132. Valve 122 may be configured to provide communications to other devices in data communication with control circuitry 132.

[0104] An example technique for controlling a flow of a fluid through a balloon is illustrated in FIG. 7. Although the technique is described mainly with reference to medical system 100 of FIGS. 1-6, the technique may be applied to other medical systems in other examples and by control circuitry 132 alone or in combination with other control circuitry in other examples.

[0105] The technique includes receiving, by control circuitry 132 of a medical system 100, an indicated size representative of a size of a blood vessel 102 of a patient 106 (702). The indicated size may be representative of a dimension (e.g., a diameter) of blood vessel 102 or a target location within a blood vessel 102, from which control circuitry 132 can determine the associated vessel size. In examples, control circuitry 132 receives the indicated size via user input, input from a sensor configured to generate a signal indicative of the dimension of the blood vessel, and / or from medical imaging. In some examples, control circuitry 132 receives and / or determines the indicated size using a catheter system 108, such as using one or more electrodes configured to measure impedance that correlates with vessel size, and / or one or more structures (e.g., expandable baskets) configured to be positioned in apposition with a blood vessel wall. In some examples, control circuitry 132 receives the indicated size via input device 134, either alone or in combination with another device such as a mobile phone, smartphone, tablet computer, personal computer, desktop computer, personal digital assistant, router, modem, remote server or cloud computing device, and / or related device. In some examples, user interface 134 displays information, such as a one or more indicated sizes, setpoints, apt flow rates, and / or flow parameters.

[0106] The technique includes determining, using control circuitry 132, an apt flow rate using the indicated size (704). The apt flow rate may be indicative of a flow rate of a fluid through medical system 100 (e.g., a balloon 112) that is expected to cause delivery of a suitable ablation level when balloon 112 is inflated within blood vessel 102 having the indicated size. In examples, the suitable ablation level is indicative of a heat transfer expected to cause a thermal ablation over an ablation depth AD of blood vessel 102. In some examples, the suitable ablation level is indicative of a heat transfer expected to cause tissues of blood vessel 102 to achieve a target temperature and / or a temperature within a targeted temperaturerange. In some examples, the suitable ablation level is indicative of an ablation power, such as a cooling power or a heating power.

[0107] Control circuitry 132 may determine the apt flow rate for an indicated size using data obtained from, for example, previous ablation procedures, modeling and / or measurement of fluid flow through the catheter system, modeling and / or measurement of heat transfer characteristics of a balloon experiencing a given fluid flow, and / or other data indicative of a heat transfer between an inflated balloon such as balloon 112 and a vessel wall such as vessel wall 104. In examples, control circuitry 132 determines the apt flow rate using a memory storing a plurality of vessel sizes and corresponding apt flow rates. In some examples, the memory stores a plurality of vessel sizes and corresponding apt flow rates for each ablation level of a plurality of ablation levels .In some examples, control circuitry 132 determines the apt flow rate using a correlation Cl relating the apt flow rate to the indicated size.

[0108] The technique includes adjusting, using control circuitry 132, flow rate of a fluid flow within catheter system 108 based on the apt flow rate (706). For example, control circuitry 132 can control a position of a valve 122 based on a comparison of a flow parameter indicated by a sensor 136 and the apt flow rate. Sensor 136 may generate a signal indicative of a flow parameter of a fluid within a flow path defined by medical system 100 (e.g., catheter system 108). In examples, sensor 136 generates a signal is indicative of (e.g., proportional to) a flow rate of fluid flowing through an interior volume 116 of balloon 112. In examples, sensor 136 senses the flow parameter in an inlet conduit 126, an inlet lumen 170, interior volume 116, an outlet lumen 172, an outlet conduit 128, and / or another portion of the flow path. Sensor 136 may sense the flow parameter at a location where the fluid is expected to be a liquid, a gas, or a mixture of a liquid and a gas. In examples, sensor 136 senses the flow parameter when the fluid is a liquid flowing through inlet conduit 126.

[0109] Control circuitry 132 may adjust valve 122 to control the flow rate of the fluid flowing through the flow path. In examples, valve 122 controls the flow rate based on a position of valve 122. The flow path may include interior volume 116 of balloon 112. In examples, the flow path includes two or more of a fluid delivery system 124, inlet conduit 126, inlet lumen 170, interior volume 116, outlet lumen 172, and / or outlet conduit 128.

[0110] In examples, sensor 136 provides a flow signal indicative of a pressure (e.g., a static pressure, dynamic pressure, and / or total pressure) at a location in the flow path (e.g., using collector 137). In examples, sensor 136 provides a flow signal indicative of a flow rate (e.g., a mass flow rate and / or volumetric flowrate) at a location in the flow path (e.g., usingcollector 137). In examples, sensor 136 provides a flow signal indicative of a position of valve 122 (e.g., using valve position indicator 139). Control circuitry 132 may infer the flow rate through the flow path using the flow signal and flow data (e.g., from bench testing) reflecting an expected fluid flow for catheter system 108 when a flow signal is indicated by sensor 136. Control circuitry 132 may compare the inferred flow rate to the apt flow rate and adjust a position of valve 122 based on the comparison. For example, control circuitry 132 may adjust valve 122 in an opening direction or a closing direction until the flow signal indicates the flow rate of the fluid through the flow path is substantially equivalent (e.g., within a defined range of) the apt flow determined for the indicated vessel size.[OHl] In examples, control circuitry 132 adjusts valve 122 to cause a flow rate of fluid through catheter system 108 in response to an initiation signal. Medical system 100 may provide the initiation signal in response to an action by a clinician. In examples, control circuitry 132 receives the initiation signal from input device 134. In response to the initiation signal, control circuitry 132 may adjust valve 122 to a valve position correlated with the apt flow rate and / or adjust valve 122 until the signal from sensor 136 indicates medical system 100 is substantially experiencing a flow rate substantially equivalent to the apt flow rate.

[0112] In one or more examples, the functions described in this disclosure, e.g., attributed to control circuitry 132, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may be an article of manufacture including a non-transitory computer-readable storage medium encoded with instructions. Instructions embedded or encoded in an article of manufacture including a non-transitory computer- readable storage medium encoded, may cause one or more programmable processors, or other processors or control circuitry, to implement one or more of the techniques described herein, such as when instructions included or encoded in the non-transitory computer-readable storage medium are executed by the one or more processors. Example non-transitory computer-readable storage media may include RAM, ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), electronically erasable programmable ROM (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), ferroelectric RAM, a floppy disk, a cassette, magnetic media, optical media, or any other computer readable storage devices or tangible computer readable media.

[0113] In some examples, a computer-readable storage medium comprises non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache).

[0114] The functionality described herein may be provided within dedicated hardware and / or software modules. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0115] Various examples of the disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following examples.

[0116] Example 1. A medical system comprising: an elongate body configured to be positioned within a vessel of a patient, wherein the elongate body defines a lumen; a balloon defining an interior volume; a sensor configured to generate a signal indicative of a flow parameter of a fluid within a flow path, the flow path including the interior volume and the lumen; a valve in fluidic communication with the flow path, wherein the valve is configured to position to control the flow of the fluid; and control circuitry configured to: receive an indicated size representative of a size of the vessel of the patient, determine, based on the indicated size, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of the fluid causing the balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size, and control a position of the valve based on a comparison of the flow parameter indicated by the sensor and the apt flow rate.

[0117] Example 2. The medical system of Example 1, wherein the flow parameter includes a pressure of the fluid.

[0118] Example 3. The medical system of any of Example 1 or Example 2, wherein the fluid is a cryofluid and the suitable ablation level is a cryoablation level.

[0119] Example 4. The medical system of any of Examples 1-3, wherein the suitable ablation level is dependent on the flow rate of the fluid within the flow path.

[0120] Example 5. The medical system of any of Examples 1-4, wherein the flow path defines a path flow resistance as the fluid flows through the flow path, and wherein the control circuitry is configured to determine a representative flow resistance indicative of the path flow resistance.

[0121] Example 6. The medical system of Example 5, wherein the control circuitry is configured to determine the representative flow resistance based on the signal.

[0122] Example 7. The medical system of Example 5 or Example 6, wherein the control circuitry is configured to determine a flow rate of the fluid in the flow path based on the signal and the representative flow resistance.

[0123] Example 8. The medical system of any of Examples 5-7, wherein the flow parameter includes a pressure of the fluid within the flow path.

[0124] Example 9. The medical system of any of Examples 1-8, wherein the sensor is configured to generate the signal indicative of the flow parameter within the lumen.

[0125] Example 10. The medical system of any of Examples 1-9, wherein the medical system defines an inlet flow path fluidically coupling the valve and the lumen.

[0126] Example 11. The medical system of Example 10, wherein the sensor is configured to generate the signal indicative of the flow rate of the fluid within the inlet flow path.

[0127] Example 12. The medical system of any of Examples 1-11, further comprising a console supporting a fluid delivery system configured to supply the fluid to the valve, wherein the fluid delivery system includes at least one of a fluid container defining a reservoir configured to hold a volume of the fluid or a pump configured to move the fluid.

[0128] Example 13. The medical system of Example 12, wherein the console comprises a housing in which at least some portion of the control circuitry is positioned.

[0129] Example 14. The medical system of any of Examples 1-13, wherein the flow path is configured to cause the fluid to flow in a downstream direction from the valve to the interior volume, and wherein the sensor is configured to generate the signal indicative of the flow parameter downstream of the valve.

[0130] Example 15. The medical system of any of Examples 1-13, wherein the flow path is configured to cause the fluid to flow in a downstream direction from the valve to the interior volume, and wherein the sensor is configured to generate the signal indicative of the flow parameter upstream of the valve.

[0131] Example 16. The medical system of any of Examples 1-15, wherein the suitable ablation level is indicative of an ablation level causing ablation to an ablation depth in the vessel having the indicated size.

[0132] Example 17. The medical system of any of Examples 1-16, wherein the lumen comprises an inlet lumen, the medical system further comprising an outlet lumen, and wherein the flow path is defined through the inlet lumen and the outlet lumen.

[0133] Example 18. The medical system of any of Examples 1-17, wherein the balloon is a compliant balloon configured to achieve a balloon diameter substantially conforming to a diameter of the vessel of the patient when the elongate body is positioned within the vessel of the patient and the fluid flows within the flow path.

[0134] Example 19. The medical system of any of Examples 1-18, further comprising a distributor positioned within the flow path, wherein the distributor is configured to expand the fluid from a liquid to a gas, and wherein the distributor is configured to issue the gas to the interior volume of the balloon.

[0135] Example 20. The medical system of Example 19, wherein the distributor is mechanically supported by the elongate body within the interior volume of the balloon.

[0136] Example 21. The medical system of any of Examples 1-20, wherein the valve includes a restricting element configured to define a flow area through the valve, wherein the medical system is configured to control a flow rate of the fluid within the flow path using the flow area, and wherein the control circuitry is configured to cause the valve to position the restricting element to adjust the flow area.

[0137] Example 22. The medical system of any of Examples 1-21, wherein the balloon is mechanically connected to the elongate body.

[0138] Example 23. The medical system of any of Examples 1-22, wherein the medical system is configured to provide a continuous flow of the fluid through the flow path.

[0139] Example 24. The medical system of any of Examples 1-23, wherein the indicated size of the vessel of the patient comprises a cross-sectional dimension of the vessel of the patient.

[0140] Example 25. The medical system of any of Examples 1-24, wherein the control circuitry is configured to receive the indicated size by at least receiving user input indicative of the size of vessel.

[0141] Example 26. The medical system of any of Examples 1-25, wherein the control circuitry is configured to receive the indicated size by at least receiving a sensor input indicative of a size of the vessel of the patient.

[0142] Example 27. The medical system of any of Examples 1-26, wherein the control circuitry is configured to: receive a specified ablation depth from an input device, and determine, using the indicated size and the specified ablation depth, the apt flow rate, wherein the apt flow rate is indicative of the flow rate of the fluid that is expected to cause the balloon to ablate tissue comprising or adjacent a vessel wall of adjacent the vessel having the indicated size to the specified ablation depth when the balloon delivers the suitable ablation level.

[0143] Example 28. The medical system of any of Examples 1-27, wherein the control circuitry is configured to determine the apt flow rate using a machine learning algorithm, wherein the machine learning algorithm is configured to receive an input vector indicative of the indicated size and provide an output vector indicative of the apt flow rate in response to the input vector.

[0144] Example 29. The medical system of Example 28, wherein, prior to determining the apt flow rate, the machine learning algorithm was trained using one or more training data sets including a training input vector and a training output vector, wherein the training input vector is representative of a vessel size and the training output vector is representative of an ablation level delivered by the fluid to a vessel having the vessel size.

[0145] Example 30. The medical system of Example 29, wherein at least one of the one or more training data sets is indicative of one or more physiological characteristics of a cohort of patients.

[0146] Example 31. A medical system comprising: a valve configured to position to control a flow of a fluid in a flow path; and control circuitry configured to: receive an indicated size representative of a size of a vessel of a patient, determine, based on the indicated size, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of a fluid causing a balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size, and control a position of the valve based on a comparison of a flow parameter indicated by a sensor and the apt flow rate.

[0147] Example 32. The medical system of Example 31, further comprising: the balloon, wherein the balloon defines an interior volume; and an elongate body configured to bepositioned within a vessel of a patient, wherein the elongate body supports the balloon, and wherein the flow path includes a lumen defined by the elongate body and the interior volume.

[0148] Example 33. The medical system of Example 31 or Example 32, further comprising the sensor, wherein the sensor is configured to generate a signal indicative of the flow parameter, wherein the flow parameter is indicative of a flow rate of the fluid within the flow path.

[0149] Example 34. A method, comprising: receiving, by control circuitry, an indicated size representative of a size of a vessel of a patient from an input device; determining, using the control circuitry, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of a fluid that causes a balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size; and controlling, using the control circuitry, a position of a valve based on a comparison of a flow parameter indicated by a sensor and the apt flow rate, wherein the flow parameter is indicative of a flow rate of the fluid within a flow path, the flow path including an interior volume of the balloon and a lumen defined by an elongate body supporting the balloon, wherein the valve is in fluidic communication with the flow path, and wherein the valve is configured to control the flow of the fluid.

[0150] Example 35. The method of claim 34, further comprising generating a signal, by the sensor, wherein the signal is indicative of the flow parameter.

[0151] Example 36. The method of claim 34 or claim 35, further comprising determining, using the control circuitry, a representative flow resistance indicative of a path flow resistance of the flow path when the flow of the fluid flows through the flow path.

[0152] Example 37. The method of Example 36, further comprising determining, using the control circuitry, the representative flow resistance using the signal.

[0153] Example 38. The method of Example 37 or Example 36, further comprising determining, using the control circuitry, the flow rate of the fluid indicated by the sensor using the signal and the representative flow resistance.

[0154] Example 39. The method of any of Examples 34-38, further comprising: causing, using the medical system, the fluid to flow in a downstream direction from the valve to the interior volume; and generating, using the sensor, the flow parameter downstream of the valve.

[0155] Example 40. The method of any of Examples 34-39, further comprising: causing, using a medical system including the valve, the fluid to flow in a downstream direction fromthe valve to the interior volume; and generating, using the sensor, the flow parameter upstream of the valve.

[0156] Example 41. The method of any of Examples 34-40, further comprising: expanding, using a distributor positioned within the flow path, the fluid from a liquid to a gas; and issuing, using the distributor, the gas to the interior volume of the balloon.

[0157] Example 42. The method of any of Examples 34-41, further comprising: supporting, using the elongate body, the balloon; and providing, using the medical system, a continuous flow of the fluid through the flow path.

[0158] Example 43. The method of any of Examples 34-42, further comprising: receiving, by the control circuitry, a specified ablation depth from the input device, determining, by the control circuitry and using the indicated size and the specified ablation depth, the apt flow rate, wherein the apt flow rate is indicative of the rate flow of the fluid causing the balloon to ablate the vessel having the indicated size to the specified ablation depth when the balloon delivers the suitable ablation level.

[0159] Example 44. The method of any of Examples 34-43, further comprising determining, using the control circuitry, the apt flow rate using a machine learning algorithm configured to receive an input vector indicative of the indicated size of the vessel and provide an output vector indicative of the apt flow rate in response to the input vector.

Claims

CLAIMS1. A medical system comprising: an elongate body configured to be positioned within a vessel of a patient, wherein the elongate body defines a lumen; a balloon defining an interior volume; a sensor configured to generate a signal indicative of a flow parameter of a fluid within a flow path, the flow path including the interior volume and the lumen; a valve in fluidic communication with the flow path, wherein the valve is configured to position to control the flow of the fluid; and control circuitry configured to: receive an indicated size representative of a size of the vessel of the patient, determine, based on the indicated size, an apt flow rate, wherein the apt flow rate is indicative of a flow rate of the fluid causing the balloon to deliver a suitable ablation level to tissue comprising or adjacent a vessel wall of a vessel having the indicated size, and control a position of the valve based on a comparison of the flow parameter indicated by the sensor and the apt flow rate.

2. The medical system of claim 1, wherein the flow parameter includes a pressure of the fluid.

3. The medical system of claim 1 or claim 2, wherein the suitable ablation level is dependent on the flow rate of the fluid within the flow path.

4. The medical system of any of claims 1-3, further comprising a console supporting a fluid delivery system configured to supply the fluid to the valve, wherein the fluid delivery system includes at least one of a fluid container defining a reservoir configured to hold a volume of the fluid or a pump configured to move the fluid.

5. The medical system of any of claims 1-4, wherein the flow path is configured to cause the fluid to flow in a downstream direction from the valve to the interior volume, and whereinthe sensor is configured to generate the signal indicative of the flow parameter downstream of the valve.

6. The medical system of any of claims 1-5, wherein the suitable ablation level is indicative of an ablation level causing ablation to an ablation depth in the vessel having the indicated size.

7. The medical system of any of claims 1-6, wherein the balloon is a compliant balloon configured to achieve a balloon diameter substantially conforming to a diameter of the vessel of the patient when the elongate body is positioned within the vessel of the patient and the fluid flows within the flow path.

8. The medical system of any of claims 1-7, further comprising a distributor positioned within the flow path, wherein the distributor is configured to expand the fluid from a liquid to a gas, and wherein the distributor is configured to issue the gas to the interior volume of the balloon.

9. The medical system of any of claims 1-8, wherein the medical system is configured to provide a continuous flow of the fluid through the flow path.

10. The medical system of any of claims 1-9, wherein the indicated size of the vessel of the patient comprises a cross-sectional dimension of the vessel of the patient.

11. The medical system of any of claims 1-10, wherein the control circuitry is configured to: receive a specified ablation depth from an input device, and determine, using the indicated size and the specified ablation depth, the apt flow rate, wherein the apt flow rate is indicative of the flow rate of the fluid that is expected to cause the balloon to ablate tissue comprising or adjacent a vessel wall of adjacent the vessel having the indicated size to the specified ablation depth when the balloon delivers the suitable ablation level.

12. The medical system of any of claims 1-11, wherein the control circuitry is configuredto determine the apt flow rate using a machine learning algorithm, wherein the machine learning algorithm is configured to receive an input vector indicative of the indicated size and provide an output vector indicative of the apt flow rate in response to the input vector.

13. The medical system of claim 12, wherein, prior to determining the apt flow rate, the machine learning algorithm was trained using one or more training data sets including a training input vector and a training output vector, wherein the training input vector is representative of a vessel size and the training output vector is representative of an ablation level delivered by the fluid to a vessel having the vessel size.

14. The medical system of claim 13, wherein at least one of the one or more training data sets is indicative of one or more physiological characteristics of a cohort of patients15. The medical system of any of claims 1-14, wherein the control circuitry is configured to receive the indicated size by at least receiving a sensor input indicative of a size of the vessel of the patient.

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