Improved fluid injector maximum flow rate performance based on estimated downstream pressure

Abstract

Embodiments disclosed herein provide for a diagnostic contrast injector. The injector includes a pump and a controller electrically coupled to the pump. The controller is configured to control the pump to push fluid from a fluid reservoir through tubing to achieve a target flow rate and a target volume of fluid. While the pump is pushing the fluid, a first indication of pressure is received at a first location proximal the pump. A second indication of pressure is also received at a second location downstream of the first location. A third pressure is received at a third location downstream of the second location based on a pressure differential between the first location and the second location. The controller restricts pushing of fluid by the pump based on the third pressure.

Description

IMPROVED FLUID INJECTOR MAXIMUM FLOW RATE PERFORMANCE BASED ON ESTIMATED DOWNSTREAM PRESSUREBACKGROUND

[0001] Flow rate performance is one of the key injection performance specifications of diagnostic contrast injectors, such as CT (computed tomography) contrast injectors, angiography contrast injectors, and MR contrast injectors. The flow rate requirement is determined by application type. For example, in CT application contrast is typically injected to veins in the arm (e.g., antecubital vein) so the max flow rate is limited by what the vein system can handle, and most CT diagnostic contrast injectors on the market are specified as being capable of providing flow rates in the range of 0.1-10 ml / s. In use, however, the flow rate delivered by an injector may be further limited by the maximum allowed pressure. That is, injectors are commonly set or otherwise provided with a maximum system pressure. When the target flow rate is high, or vascular access device (VAD) size is challenging, the maximum system pressure may be a limiting factor to the injector’s maximum flow rate performance. The injector system pressure is typically estimated from pump motor current / speed or measured by in-line pressure sensors. The maximum allowable pressure is used in order to protect the system and disposable components from being subjected to too high of a pressure.SUMMARY

[0002] Embodiments disclosed herein provide for a diagnostic contrast injector. The injector includes a pump having an inlet and an outlet. A housing is also included and is configured to fluidly couple a fluid reservoir to the inlet of the pump and to fluidly couple a length of tubing to the outlet of the pump. The injector further includes a controller electrically coupled to the pump. The controller is configured to control the pump to push fluid from the fluid reservoir through the length of tubing to achieve a target flow rate and a target volume of fluid. While the pump is pushing the fluid from the fluid reservoir through the length of tubing, a first indication of pressure is received at a first location proximal the pump. A second indication of pressure is also receivedat a second location downstream of the first location. A third pressure is received at a third location downstream of the second location based on a pressure differential between the first location and the second location. In response to a requirement for higher pump pressure, increase the pump pressure up to a maximum pump pressure, wherein the maximum pump pressure is defined as one which results in the estimated third pressure reaching a maximum system pressure.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 is an example of a diagnostic contrast injector system that can be operated according to a method of the invention; and

[0004] Figures 2A-2C are block diagrams of examples of controllers for a diagnostic contrast injector according to the present invention.DETAILED DESCRIPTION

[0005] The subject matter described herein provides for a method of operating a diagnostic contrast injector that allows for increased flow rate performance while complying to maximum system pressure limit. One application of the invention is a computed tomography (CT) contrast injection system. A second application is an angiography contrast injection system, a third application is an MR contrast injection system, a fourth application is contrast enhanced mammography (CEM). Additionally, the invention is applied to other fluid injection systems that require flow rate performance and pressure control. For simplicity, a fluid injector with contrast media will serve as the example embodiment but any fluid injector could equally apply with minor variations. If a diagnostic contrast injector cannot reach target flow rate due to maximum system pressure limit, the contrast enhancement to a diagnostic imaging procedure may not be satisfactory which can lead to poor image quality, disrupted lab workflow, increased patient contrast dosage from repeated procedures, and user and / or patient unsatisfaction. The subject matter described herein addresses this and enables a diagnostic contrast injector to provide flow rates that are higher than those provided by existing diagnostic contrast injectors with the same maximum system pressure limit.

[0006] In embodiments of the invention, the diagnostic contrast injector system which is operated according to a method of the invention includes a fluid container, a pressurizing mechanism such as a syringe or peristaltic pump, tubing to conduct fluid from the fluid container and the pressurizing mechanism to a VAD, and a controlling unit that may, for example, have a user interface, a computer, and software program(s) to set, carry out, and monitor the system performance prior to and during an injection procedure, or which may have a microcontroller, single board computer, or FPGA to carry out and monitor the system performance prior to and during an injection procedure.

[0007] Figure 1 shows an example embodiment of the invention showing the parts of the fluid flow path relevant to describing the invention.

[0008] In general, a fluid contrast injector uses one of the two main pump techniques (syringe pump and peristaltic pump, and in fact it is generally distinguished between syringe injectors and syringe-less injectors, respectively) to pressurize a liquid (e.g. contrast medium, saline, etc.) and relies on the pressure gradient to push liquid through a VAD into a patient’s blood vessel.Through this process, the flow rate performance is determined by the following factors:Fluid viscosity, which is further determined by contrast type and concentration, possible contrast / saline co-inj ection ratio and temperature,Injector system pressure,Pressure drop between pressurized chamber and the inlet of VAD, which is further determined by fluid pathway designs such as connecting tubing inner diameter (ID), length, wall thickness, material, additional components along fluid pathway (e.g., check valve, anti-dripping connector, Luer fitting, etc.),VAD type (e.g. short cannula, midline catheter, PICC, CVC) and specifications, especially pressure rating, flow rate rating, ID, length, and material,Tubing characteristics between pressurized chamber and VAD (e.g., length, inner diameter, valves and connectors along the tubing, etc.), and Patient blood vessel conditions.

[0009] The injector maximum flow rate performance can be defined by any specific injection case that requires maximum injector system pressure. For example, a specific injection case can contain following elements: a. Isovue® 370 contrast medium; b. Contrast medium at room temperature (20°C±l°C); c. Use 22G short IV catheter with ID between 0.546 mm - 0.648 mm and length of 2.54 cm (1.00 inch); d. Standard injector tubing (e.g., 150 cm (60 inch) patient line); e. 325 psi (2241 kPa) maximum system pressure.

[0010] This invention is independent of pump technology the injection system uses. The term “pressurized chamber” or “pump” herein may be used to refer to various pump mechanisms that pressurize fluid at pump. The diagnostic contrast injector uses a pressurized chamber, for example a syringe or peristaltic pump to push fluid, particularly contrast media and / or saline for CT imaging, downstream through tubing into a patient via a VAD, e.g. short IV catheter, midline catheter, PICC, CVC, or other device. Both 18Gand 20GIV (intravenous) catheters are common VADs used in CT imaging procedure for adult patients. 22G and 24G IV catheters are typically used for elder patients, pediatric patients, or patients with poor vascular conditions. Other diagnostic contrast applications where viscous contrast media and / or high flow rates meet with pressure limits that impact performance would be addressed by the disclosed invention in the same manner as the technological problem addressed here in the example of CT imaging.

[0011] By way of example, the subject matter described herein includes a method of optimizing diagnostic contrast injector maximum flow rate performance by being able to reach maximum rated VAD pressure based on obtaining two pressure indications near and / or downstream of the injector pump and real-time calculations to estimate a third pressure further downstream, closer to the VAD and controlling the pump based on that third pressure. The invention further encompasses a method of improving diagnostic contrast injector maximum flow rate performance by being able to deliver pressure at the inlet of the VAD that is closer to the VAD maximum rated pressure. The improved ability is based on estimating in-line pressure closer to the inlet of the VAD and controlling injector pump pressure to allow estimated in-line pressure to be equal or less than VAD maximum rated pressure.

[0012] In accordance with our invention, we understand that VAD manufacturers are required to recommend a maximum injector system pressure limit according to ISO 10555-1 standard. We have observed that VAD manufacturers tend to recommend the VAD maximum rated pressure asthe maximum injector system pressure limit. This recommendation is usually followed by users and user facility policies. The injector system pressure is usually defined at the injector pump or immediately distal of the injector pump which can be a few meters away from the VAD, separated by tubing and additional components. Therefore the actual pressure at the VAD will be substantially lower than the maximum rated V D pressure due to pressure drop through the tubing and components. For example, for viscous contrast media such as lomeron® 400 or Isovue® 370 with a high injection flow rate (8-9 ml / s), the pressure drop on a standard 150cm long patient line can easily be 75-100 psi so the pressure delivered at the inlet of the VAD will be much lower than the maximum rated pressure of the VAD. This results in limited and wasted injector flow rate performance ability, and can inhibit achieving target flow rates with viscous contrast media and high injection flow rate protocols.

[0013] The maximum pressure in a diagnostic contrast injector system is at the pressure chamber, e.g. the syringe pump 106 shown in the example embodiment described along with and in Figure 1 (there can be additional pumps, e.g. for saline). In addition to the fluid pathway shown in Figure 1, other example embodiments of the invention include syringe pumps to pressurize contrast fluid and saline solution, respectively, but the fluid pathway leads to a disposable VAD in any case. Alternatively, other pump mechanisms may be used, including peristaltic pumps, to pressurize contrast fluid and / or saline solution. One example is a multi-use injector setup which can be described in relation to Figure 1 , although Figure 1 is not limited to a multi-use setup. For contrast fluid filled from a fluid reservoir 102 (and similarly for saline or other solution which could be in a second fluid reservoir and second pump), the pressurized fluid is connected by day set tubing 110 (or just proximal tubing) which extends downstream, or distally 120, from the syringe pump 106 (or a line of tubing from each of two syringe pumps, e.g. contrast and saline pumps) would having tubing extending distally from them and connecting to a connection point 108 which can be a T or a Y connector. Day set tubing 110 (or just the proximal tubing) then often continues to a point 112 downstream of the syringe pump 106 which connects the day set tubing 110 to a patient set tubing 114 (or just distal tubing), for example by use of a standard connector (e.g., Luer connector) or a proprietary connector. An anti-dripping valve may be used at the distal side of the day set tubing 110 and the connector used at connection point 112 is generally a swabable connector. The patient set tubing 114 (or just distal tubing) extends from the point 112 to a VAD 116 downstream which connects to a patient 118, and then fluid is injected via the VAD 116 intothe patient 118. Typical diagnostic contrast injectors work with a given system maximum pressure and attempt to deliver target volume and flow rate according to the clinical application-dependent protocol. The most distal point of the fluid pathway, the inlet of the VAD 116 (for patient and VAD-device safety) has a rated pressure which healthcare facility policies generally set as the system pressure. In the injector’s fluid pathway, the highest pressure in the system occurs at the pump compressive chamber, or at the syringe pump 106, or peristaltic pump or other pressurizing mechanism, at the most proximal 122 point (e.g., syringe pump 106) of the system. The pressure in the fluid pathway gradually decreases as fluid travels distally from the syringe pump 106 to the inlet of the VAD 116. The actual pressure at the VAD 116 will be lower than the syringe pump 106 pressure due to pressure losses of fluid which has viscosity and is flowing at a flow rate through the tubing with a given inner diameter.

[0014] As a second example, a single-use injector can be used with the invention. The difference between a single-use injector and a multi-use injector is essentially that the day set tubing and patient set tubing are replaced with a single-use patient set tubing which is used for one patient only. In the example single-user set, patient set tubing connects to fluid containing pumps (contrast and saline, for example) and then continues with or without some intervening connectors all the way to a V D. The remaining aspects follow the remaining description of the previous examples given above.

[0015] The present invention is useful for both multi-use and single-use injectors and the invention can be described by referring simply to the injector example described in relation to Figure 1, but the same description of the invention applies to a multi-use injector example and a single-use injector example. Where proximal tubing is referred to, day set tubing or the proximal portion of patient set tubing would be implicated but the relevant considerations have to do with the relationship of the first and second pressure indications having some length between them, and the third pressure estimation occurring downstream of the first two pressure indications.

[0016] Additional fluid pathway beyond that shown in Figure 1 would be present to complete typical contrast injection workflow (e.g., filling tubing allows fluid to be filled from bottle / bag to syringe) but can be neglected for maximum flow rate performance analysis in a CT application. Regarding diagnostic contrast injector maximum flow rate performance, two pressure related constraints need to be understood in order to identify approaches to further improve maximumflow rate: component pressure rating and pressure measurement / estimation accuracy. For safety concerns, the maximum pressure applied to any component along fluid pathway shall not exceed the pressure rating of the component. Since pressure gradually drops from proximal side of the fluid pathway (syringe pump(s) 106 in Figure 1) to the distal side of the fluid pathway (VAD 116 in Figure 1), the component pressure rating usually drops accordingly. For example, some injector disposables (syringe and tubing) are rated for 400 psi, while VADs are typically rated 300 psi or 325 psi. In order to minimize user error (e.g., a user choosing 325 psi maximum injection system pressure for a 300 psi VAD), many healthcare systems set the user selectable maximum injection system pressure up to 300 psi in their IV (intravenous) injection guidelines. In addition, pressure measurement accuracy also plays an important role here. Larger pressure measurement tolerance means further decreased peak pressure in operation. Most syringe-based contrast injectors use motor current and motor speed to estimate chamber pressure in the syringe. While calibration for each system during production can decrease pressure estimation tolerance to approximate ±25 psi, this method is disposable dependent: any syringe inner diameter and wiper tolerance change (e.g., change in the syringe mold) can change frictions between syringe and wiper which causes cascade effect on pressure estimation accuracy.

[0017] In a first example, the pressure drop between any two points along the tubing can be calculated based on the following Equation 1 , assuming laminar flow in tubing, where Ap is the pressure drop along the tubing, Q is the flow rate of the fluid in the tubing, p is the fluid viscosity, L is the length of the tubing along which pressure drop is being calculated, and D is the inner diameter of the tubing:Equation 1

[0018] Say, the pressure at or near syringe pump 106 is p 126, the pressure at or near the in-line pressure sensor 124 is p2128, the pressure at or near the inlet of VAD 116 is p3130, the length of tubing between the location of126 at or near the syringe pump 106 and p2128 at or near pressure sensor 124 is L15the length of tubing between p2128 at or near pressure sensor 124 and p3130 at or near the inlet of the VAD 116 is L2, the inner diameter of the tubing 110 between pump 106 and pressure sensor 124 is D , the inner diameter of the tubing 114 (which may be the same as tubing 110 or different) between pressure sensor 124 and the inlet of the VAD 116 is D2,the flow rate at any given or steady state is Qo, and the fluid viscosity is defined as / r0- According to Equation 2, the pressure drop between p 126 at or near the pump 106 and p2128 at or near pressure sensor 124 is Equation 2

[0019] The pressure drop between the location of p2128 at or near pressure sensor 124 and p3130 at or near the inlet of VAD 116 is. 128QOUOL2„Ap23 = P2 - P3 = — —4 — Equation 3

[0020] Assume the same pressure sensing accuracies of p 126, p2128 and p3130, then in Equation 2 the value Ap12represents the injection performance ability benefit of redefining system pressure from syringe pump 106 to p2128 at or near pressure sensor 124, and Ap23in Equation 3 represents the injection performance ability benefit of redefining system pressure from pressure sensor 124 to p3130 at or near the inlet of VAD 116.

[0021] While measuring pressure at the inlet of VAD 116 can provide best injection performance ability, the location of the inlet of VAD 116 is on the patient side of the tubing and it would be more costly to measure pressure at this location without complicating workflow. However, it is contemplated and possible to create a fluid pathway from the inlet of VAD 116 back to pressure sensor 124 or locate a disposable pressure sensor at or near the VAD 116 to allow for pressure sensor measurement at the inlet of VAD 116. In embodiments of the invention, a pressure sensor 124 may be located in or at the distal 120 end of the tubing 110 which would be day-set tubing in a multi-use injection setup, or a position in patient set tubing 114 at the proximal 122 end of patient set tubing 114. In a single-use injection setup, pressure sensor 124 may be located at a point along the tubing (which tubing would encompass tubing 110 and tubing 114 and have distal 120 and proximal 122 portions of tubing) at a position distal 120 of the syringe pump 106 but proximal 122 enough to be part of the capital injector and not disposable itself, e.g. at a point like connection 112. A reasonably accurate prediction of pressure at the inlet of VAD 116 from pressure measurement at pressure sensor 124 is possible.

[0022] Consider Equation 2, the pressure drop between the syringe pump 106 and pressure sensor 124 can be determined by flow rate, fluid viscosity, tubing length and inner diameter. At any steady state condition, every parameter except fluid viscosity (unless fluid viscosity is given, which may occur) is known so that fluid viscosity can be calculated according to pressure drop measurement. Then the pressure drop between p2128 at or near pressure sensor 124 and and p3130 at or near the inlet of VAD 116 can be calculated according to Equation 3 because fluid viscosity does not change from the syringe pump 106 to the inlet of VAD 116. With the ability to estimate p3230, the injector system can gradually increase p 226 until p3230 approaches the VAD pressure rating, and the maximum flow rate can be increased accordingly.

[0023] Pressure at a first point along the pressurized fluid flow path, whether estimated or measured as a first indication of pressure at a first location at or near the pump can be compared to pressure at a second point downstream of the first point. Pressure at the second point may be measured, and the injector will use the comparison or difference of the first and second pressures to estimate a third pressure at a third location downstream of the second location. In any given locations of the first and second pressure indication points, they will be separated by some length of tubing and both pressure indication points will generally be in the proximal region of the pressurized tubing since pressure measurements nearer the capital components of an injector (the pumps and controller) are more convenient. But pressure measurement could be made even much more distally and closer to the VAD, the furthest downstream point of the pressurized fluid pathway from the injector. The tubing used will have an inner diameter, and the injector will be controlling a flow rate. The invention then allows, whether in response to the target flow rate, or requiring higher pump pressure, or at any time, the injector to increase pump pressure up to a maximum pump pressure, wherein the maximum pump pressure is defined as one which results in the estimated third pressure reaching a maximum system pressure.

[0024] In this first example, using laminar flow equations results in there being a tolerance kept away from the actual VAD-rated or system pressure because turbulence effects will occur as fluid flows through the tubing, and connectors, and this will lead to a lower actual pressure at the inlet of the VAD than estimated by the third pressure. The laminar flow equations are simpler than turbulent flow theoretical calculations.

[0025] In a second example, adjustments for turbulence created by connections in the fluid tubing can be theoretically calculated according to further equations. Flow generally becomes turbulent when the Reynolds number (Re) exceeds a value, such as 2300. The equations required to model and predict pressure drop accounting for turbulent flow are complicated, and so most conventional diagnostic contrast injectors simply limit pump pressure to whatever VAD maximum pressure would be, thereby ensuring VAD pressure will not exceed the maximum. The Reynolds number can be calculated based on flow rate ( ?), fluid density (p), tubing inner diameter ( / )), and fluid viscosity (p): Equation 4

[0026] When flow becomes turbulent, calculating the pressure drop (Ap) over a length of tubing (A), with inner tubing wall roughness (e): Equation 5

[0027] Estimating pressure at the VAD or through the VAD to the patient can be calculated in theory using the following equation:

[0028] In conventional diagnostic contrast injectors without the benefit of the invention, for example, if the V D has a pressure limit of 300 psi, and pump pressure is set to not exceed 300 psi in a conventional diagnostic contrast injector, which is a common practice, then flow rate performance may be limited, especially for viscous contrast media and higher flow rates.

[0029] By use of embodiments of the invention, improved diagnostic contrast injector performance can be achieved across a broader range of contrast media and flow rate targets.

[0030] Further description of various embodiments can be made with reference to Figure 1 which again is an example of a diagnostic contrast injector system 100 showing an embodiment of the present invention. A fluid reservoir 102 holds contrast fluid (or other fluid such as saline) and a syringe pump 106 (or other pressurized chamber) pressurizes the contrast fluid to create distal 120 flow of the contrast fluid. Alternatively, other pump mechanisms may be used, including peristaltic pumps, to pressurize contrast fluid and / or saline solution. The pressurized fluid is connected at a first connection 108, by a mechanism such as a 3-way stopcock, or a dual one-way check valve, or a one-way check valve plus a pinch valve, or similar mechanism, to a day set tubing 110 which extends downstream, or distally 120, to a second connection 112 which connects the day set tubing 110 to a patient set tubing 114. In general, the different mechanisms for connections have various pros and cons: a one-way valve is simple and inexpensive, but prevents an air removal pathway from 106 to 102; a stopcock is more flexible for workflow but requires some time to change status, which creates performance concern for continuous pump operation; and a pinch valve requires high quality tubing but acts fast and doesn't create additional fluid constraint. The patient set tubing 114 connects to a pressure sensor mechanism 124 located near its proximal 122 end, which pressure sensor mechanism 124 is also connected to the day set tubing 110, then to a third connection which is the VAD 116 to which the patient set tubing 114 extends downstream or distally 120. The VAD 116 connects to a patient 118, and then fluid is injected via the VAD 116 into the patient 118. In this example embodiment, the diagnostic contrast diagnostic contrast injector 100’s maximum flow rate performance is limited by the third pressure estimation instead of pump pressure. The syringe pump 106 and fluid reservoir 102 are coupled by a housing 134. A controller 132 is electrically coupled to the syringe pump 106 and is also coupled to a first location for a first pressure indication 126 and a second location downstream of the first location for a second pressure indication 128. A first indication of pressure 126 at or near the syringe pump 106 is obtained by a controller 132 connected to the diagnostic contrast injector 100. Controller 132 may take various forms and may be a microcontroller unit, a single board computer, or an FPGA unit, to control fluid flow in real-time, or by other hardware and software on a computer (see description of Figure 2 below) various aspects of the controller may be part of or contained inside of the controller 132 or may be connected to it wirelessly or by a hardwired connection. The first indication of pressure 126 may be obtained by the controller 132 from motor current and speed which give an indication of pressure at the pressure chamber of the syringe pump 106. Forincreased accuracy of the first indication of pressure, a dedicated pressure sensor may be added at or near the pump and used to obtain the first indication of pressure 126 instead of motor current and speed. This pressure sensor may be located at or near or distal of the pump. In embodiments with more than one pump, a sensor may be associated with each. Or pressure may be obtained from each pumps motor and current.

[0031] A second indication of pressure 128 at or near the second connection 112, including being just distal 120 of the second connection 112, is obtained by the controller 132. This second indication of pressure may be proximal or distal of 112 or at it, so long as there is some length of tubing between the first and second indications of pressure. This second indication of pressure 128 may be obtained through use of a pressure sensing mechanism 124, which may be, for example, a Honeywell SR100PGTB which has ±1% span accuracy. The controller 132 requires receiving tubing length and inner diameter along with fluid flow rate, which are all known for a given diagnostic fluid injector setup, and the controller 132 can use Equation 2 to calculate fluid viscosity upon calculating the pressure drop between the first indication of pressure 126 and the second indication of pressure 128.

[0032] Once the fluid viscosity is known, using Equation 3, and another known length of tubing and inner diameter and flow rate are obtained by the controller 132, the pressure 130 at a point near the inlet of the VAD 116 can also be obtained. This estimated pressure 130 can be defined as the injector system pressure. Since this example uses laminar flow calculations, the actual pressure experienced by the VAD 116 will be lower than pressure 130, but closer than pump pressure 126. Though the actual pressure at the VAD 116 will still be lower than the syringe pump pressure 126 due to pressure losses of fluid 204 with viscosity flowing at a flow rate through the tubing with a given inner diameter, the real-time ability to confidently estimate the third pressure 130 at the VAD 116 allows for controlling the fluid flow through the diagnostic contrast injector 100 to achieve better performance than conventional systems. Additionally, it is within the invention to use a pressure sensor to determine pressure where other embodiments estimate the third pressure, at or near the VAD 116. A disposable pressure sensor may be used in the tubing 114 for this embodiment.

[0033] In accordance with the invention, then, our solution allows a fluid injector to be operated more effectively by obtaining two pressure measurements and accurately estimating a thirdpressure at or near the VAD to control pump pressure and not exceed VAD maximum rated pressure but allowing the pressure at the pump at least partially compensating pressure loss through fluid pathway to the VAD. This invention allows diagnostic contrast injectors to be operated in a more effective manner by allowing for higher pump pressure and ensuring optimal flow rates up to, for example, 10 ml / s, even with higher viscous fluids. Additionally, there are particular benefits to using higher viscosity contrast medium but more pressure is required to achieve optimal flow rates in diagnostic contrast injectors. In a clinical study (DOI: 10.1097 / RLI.0b013e31821c7ff4 ) there was a demonstrated clinical benefit of lomeron® 400, the highest concentration iodinated contrast on the market, compared to lower concentration contrast (Iodixanol-320). The main benefits include: significant benefit for coronary arterial enhancement compared with the iso- osmolar contrast medium iodixanol-320 when administered at identical flow rates and volumes for coronary DS-CTA, and finding that higher enhancement levels were associated with lower numbers of inadequately visualized segments. In this particular way, our invention allows obtaining the benefit of being able to effectively use higher viscosity fluids.

[0034] FIGS. 2A and 2B illustrate some example controllers 200-201 that are configured to perform the acts of the method of operating an injector system as described herein. The controller can be one of various forms, including a microcontroller 200 (FIG. 2A) including program memory, a clock, an interrupt, registers, flags, a port and an address counter operably connected to a CPU core, where the microcontroller 200 has been configured and / or programmed to carry out the operations of the controller described in the invention in a diagnostic contrast injector, or an FPGA 201 (FIG. 2B) including a sensor CMOS controller, an image capture controller, a head controller, a PCA algorithm, an external memory controller, and a communications controller where the FPGA 201 has been configured and / or programmed to carry out the operations of the controller described in the invention in a diagnostic contrast injector, or a single board computer (not shown) to control fluid flow in real time.

[0035] Additionally, for illustration of further possibilities, including connections to a display and user input which may be found on a diagnostic contrast injector but which are not relevant to the present invention’s operation, FIG. 2C shows the controller 250 could include a central processing unit (“CPU”) 202 that is coupled to the system bus 204. The CPU 202 may be a general purpose CPU or microprocessor, graphics processing unit (“GPU”), and / or microcontroller. The presentembodiments are not restricted by the architecture of the CPU 202 so long as the CPU 202, whether directly or indirectly, supports the operations as described herein. The CPU 202 may execute the various logical instructions according to the present embodiments.

[0036] The controller 250 may also include random access memory (RAM) 208, which may be synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), or the like. The controller 250 may utilize RAM 208 to store the various data structures used by a software application. The controller 250 may also include read only memory (ROM) 206 which may be PROM, EPROM, EEPROM, optical storage, or the like. The ROM may store configuration information for booting the controller 200. The RAM 208 and the ROM 206 hold user and system data, and both the RAM 208 and the ROM 206 may be randomly accessed.

[0037] The controller 250 may also include an VO adapter 210, a communications adapter 214, a user interface adapter 216, and a display adapter 222. The VO adapter 210 and / or the user interface adapter 216 may, in certain embodiments, enable a user to interact with the controller 250. In a further embodiment, the display adapter 222 may display a graphical user interface (GUI) associated with a software or web-based application on a display device 224, such as a monitor or touch screen.

[0038] The VO adapter 210 may couple one or more data storage devices 212, such as one or more of a hard drive, a solid state storage device, a flash drive, a compact disc (CD) drive, a floppy disk drive, and a tape drive, to the controller 250. According to one embodiment, the data storage 212 may be a separate server coupled to the controller 250 through a network connection to the I / O adapter 210. The communications adapter 214 may be adapted to couple the controller 250 The user interface adapter 216 couples user input devices, such as a keyboard 220, a pointing device 218, and / or a touch screen (not shown) to the controller 250. The display adapter 222 may be driven by the CPU 202 to control the display on the display device 224. Any of the devices 202- 222 may be physical and / or logical.

[0039] The applications of the present disclosure are not limited to the architecture of controller 250. Rather the controller 250 is provided as an example of one type of computing device that may be adapted to perform the functions of the user interface device 210. For example, any suitable processor-based device may be utilized including, without limitation, personal dataassistants (PDAs), tablet computers, smartphones, computer game consoles, and multi-processor servers. Moreover, the systems and methods of the present disclosure may be implemented on application specific integrated circuits (ASIC), very large scale integrated (VLSI) circuits, or other circuitry. In fact, persons of ordinary skill in the art may utilize any number of suitable structures capable of executing logical operations according to the described embodiments. For example, the controller 250 may be virtualized for access by multiple users and / or applications.

[0040] If implemented in firmware and / or software, the functions described above may be stored as one or more instructions or code on a computer-readable medium, such as the one or more storage devices 212. Examples include non-volatile computer-readable media encoded with a data structure and computer-readable media encoded with a computer program. Computer-readable media includes physical computer storage media. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer- readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc includes compact discs (CD), laser discs, optical discs, digital versatile discs (DVD), floppy disks and blu-ray discs. Generally, disks reproduce data magnetically, and discs reproduce data optically. Combinations of the above should also be included within the scope of computer-readable media.

[0041] In addition to storage on computer- readable medium, instructions and / or data may be provided as signals on transmission media included in a communication apparatus. For example, a communication apparatus may include a transceiver having signals indicative of instructions and data. The instructions and data are configured to cause one or more processors to implement the functions outlined in the claims.

Claims

CLAIMSWhat is claimed is:

1. A diagnostic contrast injector comprising: a pump having an inlet and an outlet; a housing configured to fluidly couple a fluid reservoir to the inlet of the pump and to fluidly couple a length of tubing to the outlet of the pump; a controller electrically coupled to the pump, the controller configured to: control the pump to push fluid from the fluid reservoir through the length of tubing based on a target flow rate; receive a first indication of pressure at a first location proximal the pump while the pump is pushing the fluid from the fluid reservoir through the length of tubing; receive a second indication of pressure at a second location downstream of the first location while the pump is pushing the fluid from the fluid reservoir through the length of tubing; estimate a third pressure at a third location downstream of the second location based on a pressure differential between the first location and the second location; and restrict pushing of fluid by the pump based on the third pressure.

2. The diagnostic contrast injector of claim 1, wherein the controller is configured to calculate fluid viscosity based in part on the first and second indications of pressure and the calculated fluid viscosity is used to estimate the third pressure.

3. The diagnostic contrast injector of claim 1, wherein the controller is configured to receive a fluid viscosity and the received fluid viscosity is used to estimate the third pressure.

4. The diagnostic contrast injector of claim 1, wherein the pump is a syringe pump.

5. The diagnostic contrast injector of claim 1, wherein the pump is a peristaltic pump.

6. The diagnostic contrast injector of claim 1, further comprising a second fluid reservoir, and a second pump electrically coupled to the controller, and the second pump andsecond fluid reservoir configured to push saline solution through at least a portion of the length of tubing.

7. The diagnostic contrast injector of claim 1, wherein the first indication of pressure is based on a current drawn by the pump.

8. The diagnostic contrast injector of claim 1, further comprising a first pressure sensor located along the tubing, wherein the first pressure sensor sends the second indication of pressure at the second location to the controller.

9. The diagnostic contrast injector of claim 7, further comprising a second pressure sensor located at or near the pump and proximal of the first pressure sensor, wherein the second pressure sensor sends the first indication of pressure at the first location to the controller.

10. The diagnostic contrast injector of claim 1, wherein the controller is configured to estimate the third pressure by considering flow as laminar.

11. The diagnostic contrast injector of claim 1 , wherein the controller is configured to estimate the third pressure considering both laminar flow and turbulent flow.

12. A method of operating a diagnostic contrast injector system having a pump and tubing to inject fluid into a patient, comprising: controlling the pump to push fluid from the fluid reservoir through the length of tubing to achieve a target flow rate and a target volume of fluid through the tubing and injected into a patient; obtaining a first indication of pressure at a first location at or near the pump; obtaining a second indication of pressure at a second location downstream of the first location; estimating a third pressure at a location downstream of the second location based on pressures measured / estimated between the first location and the second location; and in response to the target flow rate requiring higher pump pressure, increasing the pump pressure up to the estimated third pressure being the maximum system pressure.

13. The method of claim 12, wherein the tubing includes a day set tubing fluidly coupled in series with a patient set tubing, the day set tubing disposed proximal to the pump relative to the patient set tubing, and further wherein: the first indication of pressure is based on a current drawn by the pump and speed of the pump and the second indication of pressure is based on a reading from a pressure sensor located near the distal end of the day set tubing.

14. The method of claim 12, wherein the tubing includes a day set tubing fluidly coupled in series with a patient set tubing, the day set tubing disposed proximal to the pump relative to the patient set tubing, and further wherein: the first indication of pressure is based on a current drawn by the pump and speed of the pump and the second indication of pressure is based on a reading from a pressure sensor located near the proximal end of the patient set tubing.

15. The method of claim 12, wherein estimating the third pressure further includes estimating the third pressure proximate the inlet of the VAD based on received length and inner diameter of the day set tubing, and received length and inner diameter of the patient set tubing.

16. The method of claim 15, wherein estimating the third pressure further includes estimating the third pressure based on received fluid viscosity.

17. The method of claim 14, further including: calculating fluid viscosity based on the first and second indications of pressure; wherein estimating the third pressure further includes estimating the third pressure based on the calculated fluid viscosity.

18. The method of claim 13, wherein the tubing includes a day set tubing fluidly coupled in series with a patient set tubing, the day set tubing disposed proximal to the pump relative to the patient set tubing, and further wherein:the first indication of pressure is based on a reading from a first pressure sensor located near the pump and the second indication of pressure is based on a reading from a second pressure sensor located near the connection between the day set tubing and the patient set tubing.

19. A method of operating an injector system having a pump and tubing to inject fluid into a patient, comprising: controlling the pump to push fluid from the fluid reservoir through the length of tubing to achieve a target flow rate and a target volume of fluid through the tubing and injected into a patient; obtaining a first indication of pressure at a first location downstream of the pump; obtaining a second indication of pressure at a second location downstream of the first location; estimating a third pressure at a location downstream of the second location based on received length and inner diameter of the patient set tubing, and a pressure differential between the first location and the second location in the estimation; and in response to the estimated third pressure being above a threshold, reducing the flow rate for the fluid through the tubing.

20. The method of claim 19, wherein the tubing includes a day set tubing fluidly coupled in series with a patient set tubing, the day set tubing disposed proximal to the pump relative to the patient set tubing, and further wherein: the first indication of pressure is based on a reading from a first pressure sensor located near the pump and the second indication of pressure is based on a reading from a pressure sensor located near the connection between the day set tubing and the patient set tubing.

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