Interventional guidance

Abstract

An example computer-implemented method includes determining a position of a probe relative to a patient's anatomy, where the probe includes an emitter adapted to deliver energy. The method also includes calculating a virtual space projection of an energy field for the emitter based on the position of the probe and at least one operating parameter for the emitter. The method also includes generating a guidance for performing an intervention with the probe based on the virtual space projection.

Description

Technical Field

[0001] The present technology generally relates to generating guidance for applying interventions to anatomical targets. Background Art

[0002] Various procedures have been developed to analyze, diagnose and / or treat electrophysiological conditions of various organ systems, including the cardiovascular system, central nervous system, or peripheral nervous system. For example, energy may be applied from a catheter or other probe device to ablate target tissue, such as through a corresponding ablation modality. The efficacy of a given treatment may be reduced if it adversely affects adjacent tissue or other anatomical features that may be sensitive to the treatment. Summary of the invention

[0003] The technology of the present disclosure generally relates to generating guides for surgical interventions.

[0004] In one aspect, the present disclosure provides a computer-implemented method comprising determining a position of a probe relative to a patient's anatomical structure, wherein the probe comprises a transmitter adapted to deliver energy. The method also comprises calculating a virtual space projection of an energy field for the transmitter based on the position of the probe and at least one operating parameter for the transmitter. The method also comprises generating guidance for performing intervention using the probe based on the virtual space projection. On the other hand, one or more non-transitory machine-readable media have instructions that, when executed by a processor, execute the method.

[0005] In yet another aspect, the present disclosure provides a system comprising an elongated probe comprising a transmitter adjacent to its distal end. The transmitter may be configured to deliver energy based on at least one operating parameter thereof. The system also includes a non-transitory memory configured to store data and machine-readable instructions, and one or more processors are adapted to access the memory and execute the instructions. The processor can therefore determine the position of the probe relative to the patient's anatomical structure based on position data and geometric structure data. The position data represents the spatial coordinates of the probe, and the geometric structure data spatially represents at least one target area of ​​the patient's anatomical structure. The processor can also determine the virtual space projection of the energy field for the transmitter relative to the patient's anatomical structure based on the position of the probe, the transmitter data, and at least one operating parameter for the transmitter. The transmitter data can describe the energy field characteristics of the transmitter. The processor can also generate guidance based on the virtual space projection.

[0006] The details of one or more aspects of the present disclosure are set forth in the following drawings and description. Other features, objectives, and advantages of the techniques described in the present disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram of an example system that may be implemented to provide interventional guidance.

[0008] Figure 2A , Figure 2B and Figure 2C is a schematic diagram showing a graphical visualization of interventional guidance for different operating parameters.

[0009] Figure 3A and Figure 3B is a schematic diagram showing an example of using an ablation catheter.

[0010] Figure 4 is a schematic diagram showing an example of a graphical representation of an output guide superimposed on a graphical representation of an anatomical structure.

[0011] Figure 5 is a schematic diagram showing another example of a graphical representation of an output guide superimposed on a graphical representation of an anatomical structure.

[0012] Fig. 6A , Figure 6B and Figure 6C is a graph showing examples of energy fields that may be generated for different configurations of ablation electrodes.

[0013] Fig. 7A , Figure 7B and Figure 7C is a graph showing examples of energy fields that may be generated for other configurations of ablation electrodes.

[0014] Figure 8 is a flow chart of an example method that may be implemented for evaluating the impact of one or more interventions. DETAILED DESCRIPTION

[0015] The present disclosure relates to generating guidance for applying intervention to anatomical targets. For example, intervention can include the delivery of energy, such as to change the conductivity of a target area of ​​tissue in a patient's body. The type of energy being delivered can vary depending on the target area and the desired therapeutic or sub-therapeutic effect. Examples of energy types that can be applied include electrical energy, thermal energy, ultrasonic energy, electromagnetic radiation (e.g., light energy, such as laser ablation), and electrical energy (e.g., irreversible electroporation). In the examples described herein, energy is delivered by a transmitter device that is configured to ablate target tissue residing in a region of interest, such as by performing radiofrequency ablation, cryoablation, laser ablation, or pulsed field ablation (PFA). For example, PFA is a non-thermal ablation modality that involves using a pulsed electric field to achieve cell death via an irreversible electroporation mechanism.

[0016] The systems and methods described herein can provide guidance to ensure that sufficient energy is accurately delivered to the target tissue to achieve the desired therapeutic effect (e.g., ablation) or sub-therapeutic effect. Additionally, the systems and methods described herein can provide guidance so that the delivery of energy can be adjusted (e.g., automatically or in response to user input) to reduce or prevent the delivery of energy to one or more non-target anatomical tissue regions. For example, the location and level of energy being delivered can be shaped to avoid non-target areas including one or more anatomical features (e.g., phrenic nerves, esophagus, and / or other structures) that are particularly susceptible to injury or particularly sensitive to injury during such treatment. Additionally, or alternatively, as part of a pre-treatment process, energy can be applied to tissue (e.g., by heating or cooling the tissue) to change the conductivity of such tissue to facilitate subsequent treatment of the tissue or adjacent tissue.

[0017] Figure 1 A system 10 configured to provide interventional guidance is illustrated. The system 10 includes a transmitter 12, which can be located near the distal end of a probe (such as a catheter, a guidewire, or a cannula). The transmitter 12 is configured to deliver energy based on at least one operating parameter, which can be changed according to the type of energy being delivered. The type of transmitter can also depend on the type of energy to be delivered. In one example, a cardiac catheter carrying the transmitter 12 can be inserted into the femoral vein (or other known entry point) and advanced to position the transmitter 12 at a desired position in the patient's body 14, such as a target area of ​​the heart. In other examples, the probe and transmitter 12 can be adapted to be inserted into the body 14 and advanced to one or more positions so that energy is delivered to one or more other anatomical targets, such as a part of the central nervous system, the peripheral nervous system, the digestive system, etc. Therefore, although many examples described herein relate to providing guidance for performing cardiac interventions, the systems and methods described herein are applicable to other anatomical features. The system 10 may use any number of one or more probes and transmitters 12 simultaneously, which may be independently moved to different locations within the patient's body 14 .

[0018] The system 10 may include an invasive control system 16 configured to control the operation of the transmitter 12. For example, the control system 16 includes hardware and / or software configured to set one or more operating parameters and / or source energy in order to control the energy to be delivered by the transmitter 12. The transmitter is thus configured to deliver the corresponding energy (e.g., electrical energy, thermal energy, ultrasonic energy, electromagnetic energy, etc.) based on the invasive control. The catheter or probe can be moved manually, robotically assisted, or fully robotically to control the position at which the transmitter 12 is positioned.

[0019] For the example of electrical energy, the parameters may include energy level (e.g., current and voltage), pulse width, duty cycle, device shape, and repetition rate. For the example of laser intervention that provides electromagnetic radiation (e.g., coherent light or laser), the parameters may include energy level, duration, wavelength, and repetition rate. For the example of radio frequency (RF) ablation intervention, the parameters may include the number of electrodes to be activated, device shape, energy level (e.g., current and voltage), duration, and repetition rate. For the example of pulsed field ablation (PFA) intervention, the parameters may specify the number of electrodes, energy level (e.g., current and voltage), waveform composition, device shape, number and duration of pulses and pulse trains. These parameters may control whether the PFA intervention is permanent or reversible. Other parameters may be used and configured depending on the type and configuration of the transmitter 12 and the desired results. The control system may modify the parameters during the delivery of the corresponding intervention, or the control system 16 may change one or more parameters during the application of the intervention. The device shape also provides a variable parameter that can be changed during the intervention because the shape can be deformed and / or deflected during use, such as in response to contact with tissue.

[0020] The control system 16 can set parameters and apply the intervention based on automatic, manual (e.g., user input), or a combination of automatic and manual (e.g., semi-automatic control). One or more sensors (e.g., on a transmitter or catheter (not shown)) can also transmit (feedback) sensor information back to the control system 16. The sensor information can describe the sensed condition of the transmitter 12 and / or the tissue to which the intervention is being applied. The control system 16 can also be coupled to the mapping system 20, such as to receive instructions such as commands (e.g., to set operating parameters) or to trigger the control system 16 to apply the intervention. The control system 16 can also provide intervention data to the mapping system 20, such as describing the parameters used to apply the intervention and a timestamp describing when the corresponding intervention was applied.

[0021] The system 10 may also include one or more sensors 22. For example, the sensor 22 may include one or more electrodes adapted to measure electrophysiological signals from the body 14, such as cardiac electrophysiological signals of the heart. The sensor 22 may be carried by a probe (e.g., a catheter) and configured (e.g., as a contact electrode or a non-contact electrode) to measure cardiac electrophysiological signals of the heart. Such electrodes may be used to map the epicardial or endocardial cardiac surface. Additionally, or alternatively, the sensor 22 may include a distributed arrangement of multiple body surface electrodes (e.g., about 50, 100, 250 or more sensors) configured to be positioned on the outer surface of the patient's body 14. In one example, the arrangement of the sensors 22 (constituting body surface electrodes) is completely distributed around the chest, such as can be mounted to a wearable garment (e.g., a vest), wherein each of the electrodes has a known position in a given coordinate system. For example, the body surface electrodes can be implemented as a non-invasive type of sensor device, such as disclosed in U.S. Patent Publication No. 2013 / 0281814 entitled "Multi-Layered Sensor Apparatus". Other configurations and numbers of body surface electrodes 22 can be utilized in other examples. A signal measurement system 24 can be coupled to the sensor 22 and configured to receive electrophysiological signals from the sensor. The signal measurement system can also include hardware and / or software configured to perform signal processing (e.g., amplification, filtering, etc.) and provide corresponding physiological data 26 representing the electrophysiological signals measured over time.

[0022] In some examples, in addition to measuring electrophysiological signals, one or more sensors 22 are configured to measure one or more other conditions, including physiological conditions (e.g., respiration), environmental conditions (e.g., temperature and / or pressure), and / or contact between the probe / transmitter 12 and tissue (e.g., based on measured force or impedance). In one example, other sensors 22 may include a temperature sensor configured to measure tissue temperature (e.g., esophageal temperature). Sensors 22 may be integrated with probe / transmitter 12, such as as part of an electrode structure of an ablation catheter, or one or more such sensors may be separate from the probe / transmitter. Other condition measurements may be stored as part of data 26 along with a timestamp or other information to enable further processing and analysis using the electrophysiological data.

[0023] As another example, the system 10 includes a navigation system 28 configured to locate the spatial position of the transmitter 12 (or the catheter to which the transmitter is coupled). For example, the navigation system provides position data 30 representing the position of the transmitter 12. In some examples, the position data 30 provides the spatial coordinates of one or more sensors (e.g., electromagnetic coil sensors, shown as sensor 22) with known fixed positions relative to the transmitter 12, which are used to derive the spatial coordinates of the transmitter 12. The position data 30 can be stored in a memory of the navigation system 28 and / or in a memory of the mapping system 20. The position data 30 can represent the three-dimensional spatial position (e.g., spatial coordinates) and orientation of the transmitter 12. Alternatively, the position data 30 can represent the position of a position sensor or other known position on a probe carrying the transmitter, and the spatial position of the transmitter and / or other sensors can be easily derived from the position data 30. In an example where the transmitter 12 and one or more sensors 22 are integrated in a single device (e.g., an ablation catheter), the same position data 30 can represent the spatial position of both. In examples where the sensor 22 and the transmitter 12 are implemented in independently movable structures, separate position data 30 may be generated to represent the respective spatial positions.

[0024] The position data 30 may be provided in a coordinate system of the patient's body 14 or in a coordinate system of the navigation system 28. For example, the spatial position of the transmitter 12 (described by or derived from the position data 30) may be registered relative to the anatomical geometry of the patient's body 14. The registration may be repeated in response to detecting a change in the position data, such as when an electrode carrying the transmitter moves within the patient's body. In some examples, the navigation system 28 may also generate the position data 30 to include the position of one or more non-invasive sensors 22, such as the one or more non-invasive sensors may be distributed across the outer surface of the patient's body (e.g., on the thorax). For example, the transmitter 12 and the sensor 22 may be sensorized (e.g., including a navigation sensor mounted at a known location) to enable the navigation system 28 to track the corresponding position and orientation in real time.

[0025] Useful examples of navigation systems 28 include the STEALTH STATION navigation system (commercially available from Medtronic), the CARTO XP EP navigation system (commercially available from Biosense-Webster), and the ENSITE NAVX visualization and navigation technology (commercially available from St. Jude Medical); however, other navigation systems may be used to provide navigation data representing the spatial position of the transmitter 12 and associated probe. Another example of a navigation system that can be used to locate the position of an invasive electrode is disclosed in U.S. Patent No. 10,323,922, entitled “LOCALIZATION AND TRACKING OF AN OBJECT,” issued on June 18, 2019 and on August 29, 2014. For example, a probe (e.g., a catheter) may include a transmitter 12 having one or more transmitter elements (e.g., electrodes, cryoballoons, fiber lasers, etc.) disposed at known locations of the probe. The probe may be used to locate each such transmitter relative to the heart or other anatomical structure, and navigation system 28 may provide corresponding position data 30 representing the three-dimensional coordinates of the transmitter.

[0026] The system 10 includes a computing device having one or more processors configured to access a memory storing data and instructions. The processor can access and execute instructions corresponding to the functions and methods implemented by the mapping system 20. Therefore, the mapping system 20 includes instructions that can be executed by one or more processors of the computing device to perform the functions described herein.

[0027] exist Figure 1 In an example of , the mapping system 20 includes a position calculator 40 that is programmed to determine the position of the probe relative to the patient's anatomy based on the position data 30 and the geometry data 42. As described above, the position data 30 represents the three-dimensional spatial coordinates of the probe carrying the transmitter or the transmitter itself. The spatial coordinates can be provided in the coordinate system of the navigation system or have been registered relative to the patient's body 14. The geometry data 42 can be generated (e.g., by a geometry determination code not shown) to spatially represent at least one area of ​​the patient's anatomy to which the transmitter is to apply energy.

[0028] For example, the geometry data 42 may be anatomical geometry derived from imaging data acquired by a medical imaging modality, such as single-plane x-ray or multi-plane x-ray, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, positron emission tomography (PET), single photon emission computed tomography (SPECT), etc. Through appropriate image processing (including extraction and segmentation), the location of the sensor 22 and one or more surfaces of interest may be identified in a corresponding coordinate system of the acquired image (e.g., in the coordinate space of the body 14). For example, the segmented image data may be converted into a two-dimensional or three-dimensional graphical representation of a volume of interest including the patient. Appropriate anatomical landmarks or other landmarks may be identified in the geometry data 42 to facilitate spatial registration of the position data 30 and the sensor. The identification of such landmarks may be done manually (e.g., by a person via image editing software) or automatically (e.g., via image processing techniques). In one example, an anatomical model may be constructed based on imaging data acquired for a patient (e.g., by a medical imaging modality) to provide spatial coordinates or a model to describe the surface of interest and any sensor 22 on or in the body when imaging. In some examples, the geometry data may also include an impedance map and / or a conductivity map for the patient's anatomy, such as may be determined based on image analysis and / or electrical measurements across the patient's body.

[0029] The position calculator 40 may include a registration method that is programmed to spatially register the position data with the geometry data. For example, the registration method is programmed to transfer the position data 30 and the geometry data 42 into a common coordinate space (e.g., a spatial domain), which may be the coordinate space of the position data 30, the geometry data 42, or another common three-dimensional coordinate space. As a result, the position calculator 40 may provide the position (spatial coordinates) of the probe / transmitter 12 relative to the patient's anatomy described by the geometry data.

[0030] The mapping system 20 also includes a field projection calculator 44 that is programmed to determine a virtual space projection of the energy field of the transmitter 12 relative to the patient's anatomy based on the position of the probe (e.g., determined by the position calculator 40), the transmitter data 46, and at least one operating parameter for the transmitter. In some examples, the virtual space projection may also vary depending on characteristics of the tissue (such as tissue impedance or conductivity, thickness, etc.). The transmitter data 46 describes the field characteristics of the transmitter 12, which may vary depending on the operating parameters and configuration of the transmitter 12. One or more of the operating parameters and configuration of the transmitter may be selected in response to user input, such as interacting with a user input device 48 (e.g., a mouse, keyboard, touch screen interface, gesture interface, etc.) and providing user instructions to a user interface 50. The user interface 50 may be programmed to access control functions of the method implemented by the mapping system 20, such as through a set of defined application programming interfaces (APIs). The field projection calculator 40 thus determines a virtual space projection as a three-dimensional volume representing the energy field, which may change based on emitter operating parameters, relative emitter position (e.g., distance from tissue), emitter shape / configuration, and properties of surrounding tissue (e.g., conductivity and / or impedance). When any one or more of such parameters change during an intervention, such as in response to user input or emitter contact with tissue, the resulting virtual space projection may likewise change.

[0031] For example, the transmitter data 46 can store a field model that describes the three-dimensional energy field delivered by the transmitter 12 for a set or one or more operating parameters. The field model can include a mathematical model of the virtual space projection of the energy field of the transmitter 12 used by the field projection calculator to determine. In one example, the virtual space projection can be represented in three-dimensional space as a volume including the boundary of the reversible electroporation threshold (calculated in field strength, V / cm) and / or the irreversible electroporation threshold (calculated in field strength, V / cm). The parameters of the field strength will receive input from the PFA system (or input via a user interface), including the number of electrodes energized, voltage, current and pulse wave parameters. In another example, the virtual space projection can be represented in three-dimensional space as a volume including the boundary, and can be registered to the spatial domain of the transmitter such as determined by the position calculator 40. The three-dimensional configuration can be changed according to the operating parameters. In some examples, in the case where the virtual space projection overlaps with the tissue in a manner that will affect the shape or level of the energy in the field represented by the virtual space projection, the field projection calculator 44 can be programmed to adjust the virtual space projection accordingly. As described above, for a given multi-electrode configuration, the number of active electrodes and the operating parameters of each active electrode can be specified in response to user input and used to calculate the virtual field projection by the field projection calculator 44. When the shape or configuration of the emitter changes, such as in response to deflection / deformation of contacting tissue, such deflection / deformation can be detected (e.g., as a parameter change), which is reflected in the calculated virtual field projection.

[0032] In some examples, the emitter data 46 includes a library of emitter models for a plurality of different emitters, which may include different configurations of common types of emitters or different types of emitters (e.g., RF ablation electrodes, cryoballoons, PFA electrodes). For examples where the emitter 12 is implemented as an RF electrode and / or a PFA electrode, the available electrode models may include configurations for a single electrode (corresponding to a single point) or a range of electrode arrangements (such as arrangements along a straight axis or a curved axis) or a three-dimensional electrode configuration (e.g., representing a volumetric arrangement of electrodes such as on a basket, sphere, or other 3D shape). Corresponding emitter models may be generated for one or more manufacturer's product lines to facilitate selection of the correct configuration that matches the emitter 12 being used. For example, a user may select a given manufacturer and model of an emitter from a drop-down user interface, and the field projection calculator 44 may access the corresponding emitter data for the selected emitter for use in calculating the virtual field projection of the emitter 12.

[0033] The mapping system 20 also includes a guidance generator 52, which is configured to generate guidance based on the virtual space projection. For example, the guidance generator is programmed to spatially align the virtual space projection with the patient's anatomical structure based on the determined position of the transmitter, and provide the spatially aligned features as guidance data to the output generator. The output generator 54 can be programmed to provide output data 56, which includes graphic text and other information graphically reproduced on a display 58. The display 58 may include a screen, wearable augmented reality glasses, a head-up display, etc. The display 58 is configured to display a graphical visualization based on the output data 56, such as a reproduction including a graphical map 60, which presents a graphical representation of a virtual field projection superimposed relative to a graphical representation of the patient's anatomical structure. In some examples, the graphical map 60 includes a graphical representation of a virtual field projection superimposed relative to a graphical representation of an electroanatomical map (such as a potential map of the surface of the heart). The electroanatomical map can be generated based on electrophysiological signals measured invasively, non-invasively, or a combination of invasive and non-invasive electrophysiological signal measurements from the body surface. In one example, the mapping system 20 includes code programmed to reconstruct the electrophysiological signals onto the heart surface based on the electrophysiological data and the geometric data, such as by solving an inverse problem. For example, the mapping system 20 can be programmed to calculate the reconstructed electrophysiological signals according to any of the methods described in U.S. Pat. No. 6,772,004 or U.S. Pat. No. 7,983,743.

[0034] Portions of the anatomy within the visualization provided by the graphical map 60 may be updated based on the position data 30, such as to maintain the emitter within the visualization. It should be understood that at this stage of the workflow, the operating parameters used by the field projection calculator 44 are used for the following purposes: calculating the virtual space projection of the energy field and generating corresponding guidance without controlling the emitter to deliver actual energy. Thus, the guidance gives the user a high-level preview of how the energy (if applied based on the current operating parameters) may affect the tissue. The output generator 54 may further generate output data 56 to include information (e.g., text and / or graphics) based on other data representing one or more other conditions measured by the sensor 22 (such as described herein, for example, temperature, pressure, contact, etc.). The other sensed conditions can therefore be presented on the display 60 (e.g., in the same or different display window) along with the graphical representation of the virtual field projection to provide additional guidance to the process (including before, during, and after the delivery of energy). In one example, the guide generator 52 and / or the output generator 54 are programmed to cooperate to project information captured or derived from one or more such other sensors 22 (e.g., data 26) onto the virtual space projection. In another example, the output generator 54 and / or the position calculator 40 can be programmed to determine the location of the electrodes or other sensors 22 based on the data 26 and 30 to display a representation of the catheter geometry projected onto a graphical representation of the patient's anatomy, such as showing which electrodes are in contact with tissue.

[0035] In some examples, the mapping system 20 includes a target selector 62. The target selector 62 can be programmed to define one or more target and / or non-target areas within the patient's body. For example, one or more anatomical features to be avoided can be determined, such as by a default set of rules, or manually specified in response to a user's selection in an image or graphic map through an input device 48. The target area or non-target area can be an anatomical landmark or other identified area of ​​a tissue (e.g., phrenic nerve, pulmonary vein, and / or other structure) that is considered susceptible to injury or sensitive to injury during such treatment. The guide generator 52 can be further programmed to provide an output guide as a graphical visualization, which includes a virtual space projection, a graphical representation of each non-target area, and a graphical representation of one or more target areas within the patient's body. For example, the guide generator 52 can be programmed to generate an output to indicate whether the at least one non-target area resides within the three-dimensional volume of the virtual space projection. The output generator 54 can provide the output as a notification in the output data 56, such as a graphical representation, a textual representation, and / or an audible sound that can be presented on a display. The indicated non-target areas may be color coded or otherwise graphically distinguished from other anatomical structures.

[0036] In another example, the target area can be identified via one or more physiological stimulation mechanisms. For example, a pacing stimulus can be applied to an indwelling electrode to stimulate a nerve of interest, such as the phrenic nerve. If stimulation at a certain threshold (in volts) generates a physiological pacing response, the distance to the target to be avoided can be estimated and projected onto an electroanatomical map as an anatomical structure.

[0037] For another example, when the transmitter includes one or more RF ablation electrodes or PFA electrodes, the energy field can represent an electric field. In such examples, the shape of the electric field and the relative penetration depth of the current density can be programmed into the transmitter model through a set of operating parameters. For example, if the shape of the electric field and the relative penetration depth of the current density into the tissue are strong enough, the field may damage non-target tissue (e.g., neural tissue, such as the phrenic nerve). Therefore, the guidance generator 52 can be programmed to suggest or specify one or more operating parameters to avoid potential damage to non-target areas, such as by identifying one or more operating parameters (e.g., power, duration of energy delivery, which electrodes should be active, etc.). In some examples, the guidance generator 52 can provide a warning and / or specify the distance between the field projection or probe and any defined non-target that should be avoided. If the field projection or probe is within a threshold distance from the non-target, a warning can be generated. The threshold distance can be a default value or can be user-programmable in response to user input. Additionally, the user may manually adjust (e.g., tune in response to user input) one or more parameters of the transmitter in response to determining that the at least one non-target area resides within the three-dimensional volume of the virtual space projection. In another example, the guidance generator 52 may be enabled to automatically adjust (e.g., tune) one or more operating parameters of the transmitter (e.g., in response to user input) so that the target area resides within the three-dimensional volume of the virtual space projection and at least one non-target area resides outside the three-dimensional volume of the virtual space projection.

[0038] In an example where the transmitter is configured to perform reversible PFA, the guide generator 52 can be programmed to generate field projections to represent tissue regions that will exhibit reversible electroporation, stimulation regions of the tissue, or both tissue regions that will exhibit reversible electroporation and stimulation regions. The stimulation region is typically larger than the reversible region. For example, the guide generator 52 can be programmed to assign weights (e.g., in response to user input) to specify the importance of the stimulation and reversible regions, which can be used to adjust and / or increase the delivery parameters of the energy field.

[0039] In another example, the user may also move the probe and the emitter to different locations, and the position calculator 40, the field projection calculator 44, and the guidance generator 52 will update the corresponding calculations, resulting in the generation of updated guidance and providing the guidance to the user. For example, the field projection calculator 40 will update the three-dimensional volume of the virtual space projection based on the position of the emitter (e.g., the relative position determined by the position calculator) and / or the adjusted operating parameters of the emitter.

[0040] After the user is satisfied with the guidance provided showing the virtual field projection on the graphical representation of the patient's anatomy, the user can set (e.g., lock) one or more operating parameters through the transmitter control function 64. Alternatively, the current (e.g., most recent) operating parameters can be automatically selected for the current procedure until or unless the operating parameters are modified by the user in response to user input. The transmitter control function 64 is configured to provide instructions to the control system 16 (e.g., via a wired or wireless communication link) that specify the operating parameters for controlling the transmitter 12 to deliver energy to the target area within the patient's body. For example, the guidance generator 52 can also be programmed to provide a set of operating parameters for supplying the virtual field projection to the control function, such as automatically or in response to user input to trigger energy delivery.

[0041] As mentioned, one or more sensors 22 can measure electrophysiological signals that are stored as physiological data 26. In one example, the physiological data 26 includes electrophysiological measurements in a first time interval before the delivery of energy and in a second time interval after the delivery of energy. The sensors can also measure other conditions, such as those described herein. The output generator 54 can be programmed to provide output data 56 (in response to user input or automatically) to include a graphical representation of the physiological data 26 for the first time interval and the second time interval. In one example, the graphical representation of the physiological data 26 for the first time interval and the second time interval can be provided as a comparative electrogram waveform. In another example, the graphical representation of the physiological data 26 for the first time interval and the second time interval can be provided as a comparative electroanatomical map of the electrophysiological signals that have been reconstructed onto the surface of the heart. As a result, the graphical representation can provide a side-by-side comparison of physiological signal measurements (e.g., electrophysiological measurements and / or other physiological data) before and after the delivery of energy, whereby the user can confirm whether the desired therapeutic effect has been achieved.

[0042] In yet another example, the field projection calculator may be programmed to calculate multiple virtual space projections for different values ​​of the operating parameters of the transmitter. The guide generator 52 and the output generator 54 may generate corresponding output guides, such as a graphical representation of the virtual field projection superimposed on the graphical representation of the patient's anatomical structure for each of the different operating parameter values. The corresponding graphical outputs may be simultaneously reproduced in a separate window of the display 58 for comparison. A given graphical representation of the virtual field projection may be selected from those graphical representations that have been generated, such as automatically or in response to a user input selection. In response, for the graphical representation of the selected virtual field projection, the corresponding operating parameter of the transmitter 12 may be set to a corresponding value based on the selected given virtual space projection. In response, the transmitter controller 64 may instruct the control system 16 to deliver energy from the transmitter based on the setting. The user may also be given the opportunity to confirm (or reject) the instruction for causing the transmitter to deliver the requested energy, such as in response to user input made through the input device 48 or through a button or other control device on the control system 16. As a result of using the systems and methods, improved treatment strategies can be determined and desired therapeutic effects (eg, tissue ablation) can be achieved more effectively and with less harm.

[0043] Figure 2A , Figure 2B and Figure 2C A representation of a probe (e.g., catheter) 100 having a transmitter located near the distal end of the probe is depicted. In these examples, the transmitter includes a plurality of electrodes 102 and 104 that show different examples of virtual field projections 106, 108, and 110 of energy fields (e.g., electric fields) based on corresponding transmitter operating parameters. Any number and distribution of electrodes may be used.

[0044] For example, Figure 2A , Figure 2B and Figure 2C A field (e.g., a 3D volume) is shown as a result of an increase in size due to an increase in electrical power (e.g., voltage and / or current) applied to respective electrodes 102 and 104. As described herein, the same or different power levels may be used for each of the electrodes, such as in response to user input, based on which the field projection calculator 44 determines respective virtual field projections 106, 108, and 110. In the case of pulsed field ablation, such field distributions may also be altered if the number of pulsed fields or one or more pulse wave parameters of the pulses are being modulated.

[0045] Figure 2A , Figure 2B and Figure 2CAlso shown are target tissue regions 112 and non-target tissue regions 114 located near the distal end of the probe 100, respectively. Additionally, each of the fields includes two discrete power levels, such as may be represented based on volts per centimeter (V / cm) determined for each of the corresponding virtual field projections 106, 108, and 110. Figure 2A and Figure 2B In the example of , at least a portion of the target area 112 resides within the corresponding virtual field projections 106 and 108, but the non-target area 114 resides outside the volume of the virtual field projections 106 and 108. Figure 2C , at least a portion of target region 112 and non-target region 114 both reside within virtual field projection 110. Thus, guidance generator 52 may provide output guidance (e.g., one or more graphical visualizations, such as a graphical map) to indicate that using operating parameters associated with virtual field projection 110 may have less desirable results than using operating parameters associated with virtual field projections 106 and 108. Figure 2A , Figure 2B and Figure 2C The examples show the use of a single catheter, but in other examples, two or more catheters may be used simultaneously for energy delivery to generate a composite field projection representing the combined field, which can be updated in real time between the energy delivery catheters.

[0046] In some examples, the probe 100 may also include one or more sensors (e.g., electrodes or other types of sensors) to detect contact with tissue. In one example, the sensor may measure contact impedance, and the measured contact impedance may be included in a graphical output combined with (e.g., superimposed on) a virtual field projection, such as to visualize which electrodes are in contact with tissue. In another example, the sensor may include one or more temperature sensors, and the sensed temperature may be included in a graphical output combined with (e.g., superimposed on) a virtual field projection, such as to visualize the temperature increase caused by subtherapeutic RF energy delivery. As described herein, by displaying sensor information (e.g., contact impedance and / or temperature) in conjunction with a field projection, the user is given additional understanding of the procedure and expected results, which can reduce time and improve treatment accuracy.

[0047] Figure 3A and Figure 3B is a schematic diagram showing an example of using the ablation catheter 200 . Figure 3A and Figure 3B An example graphical visualization is illustrated in which a graphical rendering of a virtual space projection of a field is superimposed on a graphical representation of an ablation catheter 200 and a patient anatomy (eg, based on navigation and / or geometry data). Figure 3A and Figure 3B The visualization shown in is an example of an embodiment that can be used by the systems and methods described herein (e.g., Figure 1 and Figure 8 ) generated, and can refer to such descriptions for additional information.

[0048] exist Figure 3A and Figure 3B In an example of the present invention, ablation catheter 200 is configured to perform PFA ablation, such as for forming a lesion in tissue 202, such as at an orifice 204 adjacent to the left superior pulmonary vein. In one example, catheter 200 may be a pulmonary vein ablation catheter GOLD (PVAC GOLD) available from Medtronic plc. TM GOLD) ablation catheter. Figure 3A and Figure 3B In the example of the present invention, the catheter 200 includes a ring electrode structure 206 having a plurality of electrodes 208. In other examples, the catheter 200 can have other shapes and configurations. In some examples, the electrodes 208 can be configured to deliver energy. The field energy can be delivered by one or more electrodes that are in contact with the tissue. In other ablation modalities (e.g., PFA), energy can be delivered to the tissue in a non-contact manner. In addition, or as an alternative example, the catheter 200 can include one or more of the electrodes 208 and / or one or more other sensors (not shown, see e.g. Figure 1 Other sensors 22) are configured to measure one or more physiological conditions or device conditions, including one or more electrophysiological signals (e.g., unipolar or bipolar electrograms), environmental conditions (e.g., temperature and / or pressure), and / or contact between tissue and electrode 208 or another portion of the catheter. Such measured physiological conditions or device conditions can be used by the systems and methods described herein to map and / or verify ablation results.

[0049] As described herein, the navigation system can provide position data representing coordinates of the catheter 200. The systems and methods herein determine the position of the probe relative to the patient's anatomy based on the position data and the geometric structure data. A virtual space projection of the energy field of the electrode structure can be generated for the electrode 206 based on the position of the electrode relative to the patient's anatomy, the transmitter data, and the operating parameters for PFA ablation. In this example, the transmitter data can describe the energy field characteristics of the multi-electrode ring structure, which can be determined a priori, such as provided by the manufacturer, derived from empirical studies and / or field modeling software. Output guidance can be generated and reproduced on a display based on the virtual space projection, such as to provide a graphical map that is adapted to visualize a graphical representation of a 3D virtual field projection 210 overlaid on a graphical representation of the anatomical structure, such as around the electrode in Figure 3A. As described herein, a user can change the position of catheter 200 and / or tune operating parameters of catheter 200 (e.g., pulse interval, pulse width, number of pulses, and / or field strength), which will trigger an update to the graphical representation of the 3D virtual field projection 210. In some examples, a user can change the viewing angle in response to user input, such as to visualize virtual penetration of the field into tissue. Additionally, contact sensing or imaging modalities (e.g., fluoroscopy, intracardiac echo, etc.) can be used to confirm contact between the electrode and the target tissue.

[0050] like Figure 3B As shown in , once the user is satisfied with the position and distribution of the 3D field projection relative to the target tissue (and any non-target tissue), the user can trigger the control system (e.g., using a button, switch or other user interface component, such as a graphical user interface element, such as a portion of user interface 50) to cause energy delivery using operating parameters set by the user to ablate the tissue accordingly, shown at 212 as a lighter colored ring below electrode 206. For example, the guidance generator can provide a warning and / or specify a distance between the field projection or probe and any defined non-target that should be avoided. If the field projection or probe is within a threshold distance from the non-target, a warning can be generated. The threshold distance can be a default value or can be user-programmable in response to user input.

[0051] Figure 3B Also shown in the figure is an additional graphic display window 214 that can be reproduced with the visualization on one or more displays. For example, the graphic display window 214 can include a display of measured electrophysiological signals, such as measured by the electrode 208 or other sensor before, during, or after tissue ablation. The graphic display window 214 may include a graphical user interface for display control, such as to control animations and other display features. In some examples, the graphical user interface can also be configured to adjust one or more ablation parameters and / or deliver energy for ablation (e.g., in response to activating a GUI button).

[0052] Figure 4 2 is a schematic diagram showing an example of a graphical representation 250 of output guidance that may be provided during use of a cryoablation catheter 252, such as may be provided by output generator 54 (e.g., as output data) to display 58. For example, catheter 252 includes a cryoballoon 254 configured to apply thermal energy (e.g., cooling) to form a generated lesion in tissue 256 (e.g., at an orifice adjacent to the left upper pulmonary vein). For example, catheter 252 may use an Arctic Front 2000 selected from the group commercially available from Medtronic, Inc. TMA series of cardiac cryoablation catheters are implemented. As described herein, the systems and methods can generate output guidance on a display console, such as visualizing a graphical representation of a 3D virtual field projection 260 overlaid on a graphical representation of the anatomical structure based on the position of the cryoballoon 254 (e.g., determined by a position calculator from position data) and selected operating parameters (e.g., size, temperature, etc.). For example, a virtual space projection of the energy field for the cryoballoon 254 can be determined based on the position of the cryoballoon relative to the patient's anatomical structure, cryoemitter data, and operating parameters for cryoablation. In this example, the cryoemitter data can describe the cryoenergy field characteristics for the cryoballoon structure, which can be determined a priori, such as provided by the manufacturer, derived from empirical studies and / or field thermal modeling software. Additionally, contact sensing or imaging modalities (e.g., fluoroscopy, intracardiac echo, etc.) can be used to confirm contact between the electrode and the target tissue.

[0053] Figure 5 is a schematic diagram showing an example of a graphical representation 300 that may be provided (e.g., provided by output generator 54 to display 58) during use of an ablation catheter represented at 302. For example, catheter 302 includes a tip element 304 configured to apply energy (e.g., RF energy or cooling energy) for forming a focal lesion in tissue 306 (such as at the ostium adjacent to the left upper pulmonary vein). For example, catheter 302 may use an RF Marinr commercially available from Medtronic, Inc. TM The catheter 302 can be implemented using a MC catheter in the MC catheter. For another example, the catheter 302 can be implemented using a Freezor catheter commercially available from Medtronic, Inc. TM This is achieved using a cardiac cryoablation catheter from a series of cardiac cryoablation catheters.

[0054] exist Figure 5 In an example of, a mapping catheter 308 is used in conjunction with the catheter 302, such as for measuring electrophysiological signals. As described herein, systems and methods can generate output guidance on a display console, such as to visualize a graphical representation of a 3D virtual field projection 310 overlaid on a graphical representation of an anatomical structure based on the position of the catheter tip 304 and selected operating parameters (e.g., tip diameter, tip length, temperature, etc.). For example, a virtual space projection of an energy field for the tip 304 can be determined based on the position of the catheter tip relative to the patient's anatomy, transmitter data, and operating parameters for ablation. In the example of RF ablation, the transmitter data can describe the RF field and thermal characteristics of the ablation electrode within the range of corresponding operating parameters. In the example of cryoablation, the transmitter data can describe the cryoenergy field characteristics of the tip structure. The transmitter data can be determined a priori, such as provided by the manufacturer, derived from empirical studies and / or field thermal modeling software. Figure 5 Also shown in FIG. 3 is a previously ablated target site 312 .

[0055] Figures 6-7 are diagrams showing examples of energy fields that can be provided for different configurations of ablation electrodes and operating parameters. As shown in Figures 6-7, the three-dimensional shape (e.g., volume) of the field projection changes depending on which electrodes are energized and the operating parameters. The information provided by such energy fields can be used to provide transmitter data 46, which is used to determine the virtual field projection described herein. As described herein, any changes in current, voltage, electrode selection, pulse wave parameters (e.g., pulse width, number of pulses, number of pulse trains) that can be modulated in response to user input selections can affect the virtual field projection. The virtual projection for a given set of ablation parameters can be projected as a graphical representation of the range of voltage isochrones (as V / cm) for each active electrode. Therefore, a threshold can be set to determine whether a given field projection will result in undesirable tissue damage (e.g., non-target tissue damage), and one or more corresponding parameters can be modulated and the projection dynamically adjusted accordingly to achieve ablation of the desired target area.

[0056] For example, Fig. 6A , Figure 6B and Figure 6C Different views of the electric field projections shown at 400, 402 and 404 are shown for a ring electrode having nine electrodes (shown as electrodes E1 to E9). Fig. 6A , Figure 6B and Figure 6C In the example of FIG. 4 , electrodes E5 and E6 are inactive and provide relatively uniform energy levels to electrodes E1 to E4 and electrodes E7 to E9. For such electrode configurations and operating parameters, view 400 shows a top view of an electric field projection. View 402 shows a depth distribution of the field projection, and view 404 shows a side view showing a width distribution of the field projection.

[0057] Fig. 7A , Figure 7B and Figure 7C Different views of the electric field projections shown at 450, 452 and 454 are shown for a ring electrode having nine electrodes (shown as electrodes E1 to E9). Fig. 7A , Figure 7B and Figure 7C In the example of , electrodes E1 to E4 and electrodes E6 to E9 are configured to deliver energy to electrode E5, which is operated in focal mode on the loop catheter. Given such electrode configuration and operating parameters, view 450 shows a top view of the electric field projection, view 402 shows the depth distribution of the field projection, and view 404 shows a side view showing the width distribution of the field projection.

[0058] Figure 8 An example of a method 500 that can be implemented by the system 10 to perform the functions described herein is depicted. Figure 8 The example method 500 is shown and described as being performed sequentially, but the example method 500 is not limited to the order shown, as some actions may occur in a different order, multiple times, and / or concurrently with the actions shown and described herein in other examples. Additionally, each step in the method 500 may be implemented as machine-readable instructions executed by a processor (such as by the mapping system 20). Figure 8 The description also refers to Figure 1 .

[0059] refer to Figure 8 , method 500 begins at 502, where a position of a probe / emitter 12 is determined relative to a patient anatomy 14 (e.g., by a position calculator 40). As described herein, the probe includes an emitter adapted to deliver energy. At 504, the method includes calculating (e.g., by a field projection calculator 44) a virtual space projection of an energy field for the emitter based on the position of the probe and at least one operating parameter for the emitter. The field projection can be calculated based on emitter data, such as describing a model, a lookup table, or other function or data structure programmed to generate a field projection.

[0060] At 506, the method includes generating (e.g., by the guidance generator 52) guidance for performing intervention with the probe based on the virtual space projection. As described herein, the guidance can be rendered (e.g., by the output generator) to include rendering of a graphical map 60 that visualizes a graphical representation of the virtual field projection superimposed with respect to a graphical representation of the patient's anatomy. In addition, the visualization can include one or more identified tissue regions, such as including one or more target regions and / or one or more non-target regions.

[0061] From 506, the method proceeds to 508 to determine whether the position of the probe and / or one or more operating parameters have been adjusted. In response to determining that the position of the probe and / or one or more operating parameters have been adjusted, the method returns to 502 to update (e.g., recalculate) the corresponding calculations at 502 to 506 for determining the field projection model and updated user-perceivable guidance. In an example where the position of the transmitter remains unchanged but one or more parameters are changed, the method can return to 504 for calculating updated field projections and guidance. If neither the position nor any parameters are adjusted, the method 500 can loop at 508. The method 500 can continue until terminated by the user at any time, such as after the guidance derived from the virtual projection is within the expected / desired parameters and one or more interventions are performed. The method 500 can also include other features shown and described herein.

[0062] It should be understood that the various aspects disclosed herein may be combined in combinations different from those specifically presented in the specification and drawings. It should also be understood that, depending on the example, certain actions or events of any of the processes or methods described herein may be performed in a different order, may be added, merged, or omitted entirely (e.g., not all described actions or events may be required to perform these techniques). In addition, although for clarity, certain aspects of the present disclosure are described as being performed by a single module or unit, it should be understood that the techniques of the present disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0063] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include a non-transitory computer-readable medium that corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer).

[0064] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, the term "processor" as used herein may refer to any of the aforementioned structures or any other physical structure suitable for implementing the described techniques. Additionally, these techniques may be fully implemented in one or more circuits or logic elements.

[0065] As used herein, the expression “based on” means “based, at least in part, on.” Thus, if X is based on Y, then X may vary depending on Y and any number of other factors.

[0066] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. One or more non-transitory machine-readable media having instructions that, when executed by a processor, perform a method comprising: determining a position of a probe relative to anatomy of a patient, the probe comprising an emitter adapted to deliver energy; calculating a virtual space projection of an energy field of the emitter based on the position of the probe and at least one operating parameter of the emitter; as well as Based on the virtual space projection, guidance for performing an intervention with the probe is generated.

2. The medium of claim 1, wherein the method further comprises setting the at least one operating parameter in response to user input, Wherein said calculating and said generating are repeated based on said setting of said at least one operating parameter.

3. The medium according to claim 1 or 2, wherein: The virtual space projection includes a three-dimensional volume representing an electric field that varies based on the at least one operating parameter, tissue properties of surrounding tissue, and a distance from the transmitter, The method further includes defining at least one non-target region within the patient anatomy, and Generating the guidance further includes generating a graphical visualization including the virtual space projection, a graphical representation of the at least one non-target region, and a graphical representation of the target region within the patient anatomy.

4. The medium according to claim 3, further comprising: adjusting the at least one operating parameter of the transmitter in response to determining that the at least one non-target area resides within the three-dimensional volume of the virtual space projection; as well as updating the three-dimensional volume of the virtual space projection based on the position of the probe and the adjusted at least one operating parameter of the transmitter; as well as The guidance is updated based on the updated three-dimensional volume for the virtual space projection.

5. A medium according to claim 1 or 4, wherein the at least one operating parameter of the transmitter is automatically adjusted so that the target area resides within the three-dimensional volume of the virtual space projection and the at least one non-target area resides outside the three-dimensional volume of the virtual space projection.

6. The medium of any one of claims 3 to 5, wherein the at least one non-target area is defined in response to user input.

7. The medium of any one of claims 3 to 6, wherein the guiding further comprises generating an output to indicate whether the at least one non-target area resides within the three-dimensional volume of the virtual space projection.

8. The medium of claim 1, wherein: The transmitter comprises a plurality of electrodes in a distributed spatial arrangement, Each electrode of the plurality of electrodes is configured to deliver energy based on a corresponding operating parameter, and The virtual space projection includes a three-dimensional volume representing a focused electric field emanating from each electrode of the plurality of electrodes based on the corresponding operating parameter.

9. A medium according to any preceding claim, wherein the virtual space projection of the energy field is calculated based on the type of energy that the transmitter is configured to deliver, and the transmitter is configured to deliver the energy using one of radiofrequency ablation, cryoablation, laser ablation, or pulsed field ablation.

10. The medium of any preceding claim, wherein the method further comprises controlling the energy delivered by the transmitter to the target area based on the guidance and the at least one operating parameter.

11. The medium of claim 10, wherein: The virtual space projection includes a three-dimensional volume, The method further comprises defining at least one target region within the patient anatomy, and Generating the guidance further includes generating a graphical visualization including the virtual space projection and a graphical representation of the at least one target region within the patient anatomy.

12. The medium of claim 10, further comprising: storing electrophysiological data representing electrophysiological signal measurements during a first time interval prior to the delivery of the energy and during a second time interval after the delivery of the energy; and Based on a comparison of the electrophysiological data measured before and after delivery of the energy, a desired therapeutic effect or a desired sub-therapeutic effect is confirmed.

13. A medium according to any preceding claim, wherein a plurality of virtual space projections are calculated for different values ​​of the at least one operating parameter of the transmitter and / or different positions of the probe, and the method further comprises: selecting, in response to user input, a given virtual space projection from the plurality of virtual space projections; as well as Based on the selected given virtual space projection, setting the at least one operating parameter to a corresponding value; as well as Based on the settings, energy delivery from the transmitter is controlled.

14. A system, comprising: an elongated probe comprising a transmitter adjacent a distal end of the elongated probe, the transmitter configured to deliver energy based on at least one operating parameter of the transmitter; a non-transitory memory configured to store data and machine-readable instructions; one or more processors adapted to access the memory and execute the instructions, the instructions being programmed to do at least one of: determining a position of the probe relative to anatomy of a patient based on position data representing spatial coordinates of the probe and geometry data spatially representing at least one target region of the anatomy of the patient; determining a virtual space projection of an energy field of the emitter relative to the patient anatomy based on the position of the probe, emitter data describing energy field characteristics of the emitter, and the at least one operating parameter of the emitter; as well as Guidance is generated based on the virtual space projection.

15. The system of claim 14, further comprising setting the at least one operating parameter in response to user input, Wherein the virtual space projection and the guidance are updated in response to the user input.

16. A system according to claim 14 or 15, wherein: The instructions are further programmed to define at least one non-target region within the patient anatomy, and The guiding further includes a graphical visualization including the virtual space projection, a graphical representation of the at least one non-target region, and a graphical representation of the target region within the patient anatomy.

17. The system of claim 16, wherein the instructions are further programmed to: In response to determining that the at least one non-target area resides within the volume of the virtual space projection, adjusting the at least one operating parameter of the transmitter; and updating the virtual space projection based on the position of the probe and the adjusted at least one operating parameter of the transmitter; and The guidance is updated based on the updated virtual space projection.

18. The system of claim 17, wherein the instructions are further programmed to automatically adjust the at least one operating parameter of the transmitter so that the target area resides within the volume of the virtual space projection and the at least one non-target area resides outside the volume of the virtual space projection.

19. The system of any one of claims 14 to 18, wherein the transmitter comprises a plurality of electrodes in a distributed spatial arrangement, each electrode of the plurality of electrodes being configured to deliver energy based on a respective operating parameter, and Wherein the virtual space projection includes a three-dimensional volume representing a focused electric field emanating from each electrode of the plurality of electrodes based on the corresponding operating parameter.

20. The system of any one of claims 14 to 19, wherein the instructions are further programmed to control the energy delivered by the transmitter to the target area based on the guidance and the at least one operating parameter.

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