Patent Publication Number: US-2022211293-A1

Title: Real-time display of tissue deformation by interactions with an intra-body probe

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/349,646 filed on May 14, 2019, which is a National Phase of PCT Patent Application No. PCT/M2017/057175 having International Filing Date of Nov. 16, 2017, which claims the benefit of priority under 35 USC § 119(e) of U.S. Provisional Patent Application Nos. 62/422,705, 62/422,708 and 62/422,713, all filed on Nov. 16, 2016. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention, in some embodiments thereof, relates to the field of medical procedures using intrabody probes navigable within intrabody spaces, and more particularly, to presentation of procedure data dynamically acquired during the course of a catheter procedure. 
     Graphical game engines currently available comprise suites of software-implemented capabilities supporting the dynamic display and updating of simulated three-dimensional scenes. Typically, game engines include API calls supporting the creation and modification of a variety of scene objects (chiefly terrain, various types of physical objects, camera viewpoints, and lighting), a visual rendering pipeline, and optionally further services assisting tasks such as coding, animating, and/or debugging. User inputs are accepted from various user interface devices (including pointer devices, keyboards, game controllers, motion sensors, touch screens and the like) and converted into events in the simulated environment. Well-known game engines include the Unreal® and Unity® graphical game engines (www(dot)unrealengine(dot)com; www(dot)unity3d(dot)com). The rendering pipelines of modern game engines typically include facilities for creating realistic-looking visualizations of scene elements, based on properties assigned to instantiations of data objects representing those scene elements. 
     Several medical procedures in cardiology and other medical fields comprise the use of catheters to reach tissue targeted for diagnosis and/or treatment while minimizing procedure invasiveness. Early imaging-based techniques (such as fluoroscopy) for navigation of the catheter and monitoring of treatments continue to be refined, and are now joined by techniques such as electromagnetic field-guided position sensing systems. Refinements to techniques for registration of previously imaged (for example, by CT and/or MRI) anatomical features of a patient to electromagnetic field-sensed catheter position are a subject of ongoing research and development, for example as described in International Patent Application No. IB2016/052687 to Schwartz et al. filed May 11, 2016; and International Patent Application No. IB2016/052692 to Schwartz et al. filed May 11, 2016. Intrabody sensing from catheter probes to determine information about, for example, tissue contact and/or lesion assessment, has also been described (e.g., International Patent Application No. PCT IB2016/052690 to Schwartz et al. filed May 11, 2016; and International Patent Application No. IB2016/052686 to Schwartz et al. filed May 11, 2016). 
     SUMMARY OF THE INVENTION 
     There is provided, in accordance with some embodiments of the present disclosure, a method of visually displaying effects of a medical procedure, comprising: receiving interaction data from an intrabody probe indicating touching contacts between the intrabody probe and a body tissue region, wherein the interaction data at least associate the contacts to contacted positions of the body tissue region; adjusting geometrical rendering data representing a shape of the body tissue region to obtain adjusted geometrical rendering data, wherein the adjusting is based on an indication in the interaction data of a change in the shape of the body tissue region due to the contacting; rendering the adjusted geometrical rendering data to a rendered image; and displaying the rendered image. 
     In some embodiments, the intrabody probe is a catheter probe. 
     In some embodiments, the geometrical rendering data are adjusted as a function of time relative to a time of occurrence of at least one of the indicated contacts. 
     In some embodiments, the receiving, the adjusting, and the displaying are performed iteratively for a sequence of contacts for which interaction data is received. 
     In some embodiments, the adjusting is at a frame rate of 10 frames per second or more. 
     In some embodiments, the rendering and the displaying are at a frame rate of 10 frames per second or more. 
     In some embodiments, the geometrical rendering data include a representation of 3-D surface positions and a representation of surface orientations; wherein the two representations each correspond to a same portion of the shape of the body tissue region; and wherein the adjusting comprises adjusting the surface orientation representation to change a geometrical appearance in the rendering. 
     In some embodiments, the representation of surface orientation is adjusted separately from the representation of 3-D surface positions. 
     In some embodiments, the extent and degree of the adjusting model a change in a thickness of the body tissue region. 
     In some embodiments, the interaction data describe an exchange of energy between the intrabody probe and the body tissue region by a mechanism other than contact pressure. 
     In some embodiments, the adjusting comprises updating the geometrical rendering data based on a history of interaction data describing the exchange of energy. 
     In some embodiments, the exchange of energy comprises operation of an ablation modality. 
     In some embodiments, the updating changes an indication of lesion extent in the geometrical rendering data based on the history of interaction data describing the exchange of energy by operation of the ablation modality. 
     In some embodiments, the updating comprises adjusting the geometrical rendering data to indicate a change in mechanical tissue properties, based on the history of interaction data describing the exchange of energy. 
     In some embodiments, the ablation energy exchanged between the intrabody probe and the body tissue region comprises at least one of the group consisting of: radio frequency ablation, cryoablation, microwave ablation, laser ablation, irreversible electroporation, substance injection ablation, and high-intensity focused ultrasound ablation. 
     In some embodiments, the updating comprises adjusting the geometrical rendering data to indicate a change in tissue thickness, based on the history of interaction data describing the exchange of energy. 
     In some embodiments, effects of the history of interaction data describing the exchange of energy are determined from modelling of thermal effects of the exchange of energy on the body tissue region. 
     In some embodiments, the modelling of thermal effects accounts for local tissue region properties affecting transfer of thermal energy between the intrabody probe and the body tissue region. 
     In some embodiments, the adjusting is as a function of time relative to a time of occurrence of at least one of the indicated contacts, and comprises adjusting the geometrical rendering data to indicate gradual development of a change in geometry of the body tissue region as a result of the contacts. 
     In some embodiments, the gradually developed change in geometry indicates a developing state of edema. 
     In some embodiments, the method comprises geometrically distorting the rendering of the geometrical rendering data into a swollen appearance, to an extent based on the indicated development of the state of edema. 
     In some embodiments, the contacts comprise mechanical contacts, and the gradual development of a change in geometry indicates swelling of the body tissue region in response to tissue irritation by the mechanical contacts. 
     In some embodiments, the contacts comprise an exchange of energy between the intrabody probe and the body tissue region by a mechanism other than contact pressure. 
     In some embodiments, the interaction data indicate a contact force between the intrabody probe and the body tissue region. 
     In some embodiments, the interaction data indicate a contact quality between the intrabody probe and the body tissue region. 
     In some embodiments, the interaction data indicate a geometrical distortion introduced by touching contact between the intrabody probe and the body tissue region. 
     In some embodiments, the adjusting comprises geometrically distorting the rendering of the geometrical rendering data at a region of touching contact to an extent based on the interaction data. 
     In some embodiments, the geometrically distorting the rendering of the geometrical rendering data includes geometrically distorting a portion of the geometrical rendering data which is not geometrically corresponding to the portion of the body tissue region from which the interaction data were obtained. 
     In some embodiments, the interaction data comprises a 2-D image including a cross-sectional view of the body tissue region, and the distorted portion of the geometrical rendering extends out of a plane in the geometrical rendering data corresponding to the plane of the cross-sectional view. 
     In some embodiments, the interaction data describes injection of a substance from the intrabody probe to the body tissue region, and the adjusting comprises changing a thickness of tissue in the body tissue region, corresponding to an effect of the injection of the substance. 
     In some embodiments, the rendering includes a view of the intrabody probe. In some embodiments, the rendering is rendered from a viewpoint at least partially defined by a measured position of the intrabody probe relative to a surface of the body tissue region. 
     In some embodiments, the measured position includes a measured orientation of the intrabody probe. 
     In some embodiments, the intrabody probe contacts a lumenal surface of the body tissue region. 
     In some embodiments, the intrabody probe contacts an external surface of an organ comprising the body tissue region. 
     In some embodiments, the body tissue region comprises a tissue of at least one organ of the group consisting of the heart, vasculature, stomach, intestines, liver and kidney. 
     In some embodiments, the method further comprises assigning material appearance properties across an extent of the geometrical rendering data, based on the interaction data; and wherein the displaying of the rendered image uses the assigned material appearance properties. 
     In some embodiments, the rendering comprises a rendering in cross-section of the body tissue region. 
     In some embodiments, the extent and degree of the adjusting simulate stretching of the body tissue region. 
     In some embodiments, the geometrical rendering data represent a shape of a body tissue region comprising a heart chamber; and wherein the adjusting comprises adjusting a size of the heart chamber, based on the current heart rate data. 
     In some embodiments, the adjusting a size of the heart chamber comprises adjusting a size of a lumen of the heart chamber, based on the current heart rate data. 
     In some embodiments, the adjusting a size of the heart chamber comprises adjusting a thickness of a wall of the heart chamber, based on the current heart rate data. 
     In some embodiments, the adjusting geometrical rendering data comprises adjusting a position of the intrabody probe in the geometrical rendering data relative to a wall of the heart chamber, based on the current heart rate data. 
     There is provided, in accordance with some embodiments of the present disclosure, a system for visually displaying effects of interactions between an intrabody probe and a body tissue region, the system comprising computer circuitry configured to: receive interaction data indicating the interactions, and associated to positions on a surface of the body tissue region; adjust geometrical rendering data representing a shape of the body tissue region to obtain adjusted geometric rendering data, wherein the adjusting is based on an indication in the interaction data of a change in the shape of the body tissue region; render the adjusted geometrical rendering data to a rendered image; and present the rendered image. 
     In some embodiments, the rendering is performed using a graphical game engine, and the interaction data include sensed positions of the intrabody probe. 
     In some embodiments, the interaction data include probe-sensed characteristics of tissue in the vicinity of the intrabody probe. 
     In some embodiments, the interaction data includes operational data describing operation of the intrabody probe to treat tissue. 
     There is provided, in accordance with some embodiments of the present disclosure, a method of visually displaying a medical procedure, comprising: receiving position data indicating the position of an intracardial probe within a heart; receiving heart rate data for the heart; adjusting geometrical rendering data representing a shape of the heart and a shape and position of the intracardial probe to obtain adjusted geometric rendering data; wherein the adjusting is based on the heart rate data to maintain an accuracy of positioning of the intracardial probe relative to the heart as average size of the heart changes as a function of a heart rate; rendering the adjusted geometrical rendering data to a rendered image; and displaying the rendered image. 
     Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. 
     As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” 
     Furthermore, some embodiments of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and/or system of some embodiments of the invention can involve performing and/or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and/or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware and/or by a combination thereof, e.g., using an operating system. 
     For example, hardware for performing selected tasks according to some embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to some exemplary embodiments of method and/or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well. 
     Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the invention. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Program code embodied on a computer readable medium and/or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     Computer program code for carrying out operations for some embodiments of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Some embodiments of the present invention may be described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example, and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced. 
       In the drawings: 
         FIG. 1A  is a schematic flowchart illustrating the calculation and display of an image of a scene comprising simulated tissue having a geometry and/or geometrical appearance dynamically linked to interactions of the tissue with a catheter probe, according to some embodiments of the present disclosure; 
         FIG. 1B  is a schematic flowchart illustrating the calculation and display of a geometry and/or geometrical appearance dynamically changing over time as a result of prior interaction of the tissue with a catheter probe, according to some embodiments of the present disclosure. 
         FIGS. 2A-2E  illustrate a 3-D rendered display for indicating lesioning status to a user, according to some exemplary embodiments of the present disclosure; 
         FIGS. 3A, 3D, 3G, and 3J  schematically represent a sequence of rendered views of a catheter probe passing through a tissue wall portion, according to some embodiments of the present disclosure; 
         FIGS. 3B, 3E, 3H, and 3K  schematically represent a graph of position versus time and measured contact versus time for the catheter probe of  FIGS. 3A, 3D, 3G, and 3J , according to some embodiments of the present disclosure; 
         FIGS. 3C, 3F, 3I, and 3L  schematically represent an ultrasound image at a cross-section of a heart at the atrial level, and corresponding to the sequence of  FIGS. 3A, 3D, 3G, and 3J , according to some embodiments of the present disclosure; 
         FIGS. 4A-4D  schematically represent aspects of geometrical deformation of a tissue region due to an internal change such as edema, according to some embodiments of the present disclosure; 
         FIGS. 5A-5B  schematically represent global geometrical deformation of a tissue structure, for example, due to hydration state and/or more global edema than the example of  FIGS. 4A-4D , according to some embodiments of the present disclosure; 
         FIG. 6  is a schematic representation of a system configured for display of interactions between a catheter probe and a body tissue region, and/or their effects, according to some embodiments of the present disclosure; 
         FIG. 7  schematically represents software components and data structures of an interaction analyzer of a system, according to some embodiments of the present disclosure; 
         FIG. 8  schematically represents components, inputs, and outputs of a graphical game engine operating to manage and render scene elements to images for presentation at motion frame-rate, according to some embodiments of the present disclosure; 
         FIGS. 9A-9B  schematically represent, respectively, different geometrical data representations of flat and indented surfaces, according to some embodiments of the present disclosure; 
         FIGS. 10A-10B  illustrate normal mapping superimposed on a tissue region in order to provide the geometrical appearance of a swelling, according to some embodiments of the present disclosure; 
         FIGS. 10C-10D  schematically represent aspects of geometrical deformation of a tissue region in touching contact with a catheter probe, according to some embodiments of the present disclosure; 
         FIG. 11A  schematically illustrates a rendered image rendered from a camera viewpoint looking at tissue region along an axis parallel to an intrabody probe; according to some embodiments of the present disclosure; and 
         FIG. 11B  schematically illustrates a field of view projected from camera viewpoint, including indication of axis, according to some embodiments of the present disclosure. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION 
     The present invention, in some embodiments thereof, relates to the field of medical procedures using intrabody probes navigable within intrabody spaces, and more particularly, to presentation of procedure data dynamically acquired during the course of a catheter procedure. 
     Overview 
     An aspect of some embodiments of the current invention relates to the motion frame-rate, real-time display of geometrical effects on a simulation scene comprising simulated tissue, wherein the geometrical effects comprise changes to a geometrical representation of one or more elements in the scene, and wherein the changes are made based on ongoing and/or intermittent measurements of interactions between a catheter probe and the actual tissue being simulated. 
     Herein, “geometrical effects” optionally comprise one or both of changes to the 3-D position of simulated elements, and changes to the geometrical appearance of simulated elements. Geometrical appearance, as distinct from 3-D position, comprises geometrical that can give a relatively raised, indented, smoothed, irregular, blurred, focused, closer, further, shaded, and/or unshaded appearance to a portion of a surface, without affecting 3-D coordinates of the surface itself. Geometrical appearance optionally comprises features implemented at least in part by computational methods-for example, normal mapping, depth mapping, and/or shadow mapping. 
     In some embodiments, a software environment specialized for interactive visual simulations (for example a 3-D graphical game engine such as the Unreal® and/or Unity® graphical game engines) is used as a basis for implementing a simulation of a scene comprising simulated tissue (herein, such a scene is referred to as a simulation scene). For rendering images by the game engine&#39;s graphics pipeline, geometrical rendering data are optionally supplemented with one or more material appearance properties (preferably a plurality of such properties) that describe how virtual materials such as simulated tissue interact with simulated optical laws and lighting conditions to generate images for display. The geometrical rendering data optionally comprises a geometrical representation of a scene including tissue. In some embodiments, the rendering is implemented, by a rendering pipeline of the graphical game engine. 
     It should be understood that one or more capabilities used by some embodiments of the present invention and described as implemented by a game engine are optionally provided by alternative implementations not packaged in a game engine distribution, including: use of customized software, firmware and/or hardware; and/or use of separately distributed software libraries. The term “game engine” as used herein should be understood to encompass computer-implemented collections of such typical game engine capabilities as may be used by some embodiments of the present invention (examples of which are described herein), whether or not they have been packaged into a game engine distribution. 
     As used herein, the term “rendering” refers to the process of generating an image from a 2-D or 3-D model or models by means of one or more computer programs. The model may contain object parameter definitions and/or data structures; for example, geometry, viewpoint, texture, lighting, and/or shading information as a description of the virtual model. The data contained in the model may be passed to a rendering program to be processed and output to a digital image or raster graphics image file. The processing comprises one or more processing stages referred to collectively as a “pipeline”, and carried out by the software and hardware of a rendering device. In some embodiments, the rendering device includes one or more of a general purpose CPU and graphics hardware specialized for use within a rendering pipeline. 
     In some embodiments, updating of the simulation scene during a procedure is at least partially based on data inputs from one or more data sources supplying data during the procedure (for example, sources of probe-tissue interaction data such as sensing data and/or treatment status data described in relation to  FIG. 6  and  FIG. 7 ). Graphical game engines typically receive inputs from game input devices such as pointer devices, keyboards, game controllers, body motion sensors, and the like. In some embodiments of the present invention, inputs optionally are from one or more additional or alternative inputs related to the performance of a catheter procedure—for example, catheter probe position data, data tracking the intrabody use of catheter probes (particularly but not exclusively use to deliver treatment; e.g. by delivering treatment energies), and/or measurement data, for example measurement data obtained from an intrabody probe (herein a catheter probe is used as an example of an intrabody probe, but it should be understood that another intrabody probe is optionally used in some embodiments; e.g., a capsule probe). 
     In typical applications of game engines, the simulated world (also referred to herein as a simulated scene) maintained by a game engine does not directly correspond to any simultaneous objective-world state. However, an object of some embodiments of the current invention is to simulate the reality of a clinical situation sufficiently to allow substantially seamless interaction with that reality via a presentation of the scene simulation. In some embodiments, this comprises maintaining and displaying a simulated scene having a useful level of correlation with the changing reality of the actual tissue environment (as reflected in data available to characterize it). 
     Optionally, usefulness derives from actions which are taken by an operator on the basis of information in the scene simulation presentation which reveals to a catheter operator the changing state of the tissue environment. Potentially, the useful level of correlation with the changing reality of the actual tissue environment allows an operator to realize the state of the tissue or a change in that state, optionally without adding to the scene annotations indicative of such state or state change. Optionally, usefulness derives from the presented scene simulation providing fidelity of representation sufficient that actions the operator takes based on the presented scene simulation produce effects as intended in the corresponding real-world environment. Optionally, the useful level of correlation with the changing reality of the actual tissue environment is a level of correlation sufficient to allow the operator to perform actions within the real-world environment based on the presented scene simulation. The presented scene simulation may include effects simulating results of the actions taken by the operator. 
     In some embodiments of the invention, a display of a user interface is updated at motion frame rate with rendered images of a simulation scene simulating an intrabody probe (for example, a probe at the end of a catheter) and its tissue environment. The updating optionally indicates changes to an actual intrabody probe and tissue environment which occur as an operator manipulates the actual intrabody probe (wherein the updating is based, e.g., on position data describing the position of the intrabody probe), and/or operates the intrabody probe for treatment and/or diagnostic measurement of the actual tissue environment (wherein the updating is based, e.g., on operational data describing operation of the intrabody probe to treat tissue and/or measure properties of the tissue). In some embodiments, changes are shown in the rendered images as if occurring within the actual material of the tissue environment. 
     For example, immediate and/or developing effects of ablation are shown by simulating appearance and/or geometrical changes in ablated tissue (in contrast, for example, to marks, icons, and/or symbols indicating ablation events). In some embodiments, tissue is deflected and/or an intrabody probe shape is distorted in rendered images of a simulation scene based on interaction data indicating touching contacts. These and other simulation scene changes (for example, other simulation scene changes as described herein) potentially provide an operator with a sense of presence in the actual tissue region accessed by an intrabody probe, and/or intuitive indications of changing status during a procedure underway. 
     In some embodiments, a smoothly updating, naturalistic appearance of a rendered view of a simulation scene is achieved even when available inputs indicating changes to the simulation scene are incomplete, slowly updating, irregular, and/or lagging (for example, as described in relation to  FIG. 1B ). Herein, “naturalistic” scene appearance means that the displayed scene gives an operator the impression of substantial materials (i.e., volume-occupying, as opposed to merely shell defining materials) and/or reactive materials existing in a fluidly navigable environment. The reactions of the materials in turn become a significant part of the information which an operator relies on to act within the actual environment that the scene simulates. A material moreover may be simulated as occupying volume per se (for example, as a wall having thickness), rather than merely as a boundary extending in space (for example, as a structure defining a surface, but having no well-defined thickness). 
     Optionally, appearances in rendered views of simulation scene objects are moreover “realistic” in some aspects. For example, tissues, in some embodiments, are provided with material appearances that mimic their appearance in life, and to this extent are “realistic”. In some embodiments of the invention, for example, geometrical deformation of tissue in a simulation scene is directly based on deformation measurements, for example, ultrasound images of septal wall deflection during transseptal puncture are optionally converted into movements in three dimensions of a simulated septal wall&#39;s deflection. 
     However, non-realistic material appearances and even objects are optionally or additionally provided to a naturalistic scene. Degree of tissue compression, for example, is optionally used as a visual proxy for probe-tissue contact force (force of touching contact), whether or not the real tissue is indeed compressed. 
     In some embodiments of the invention, motion due to normal heart pulsations is indicated in the simulation by pulses with corresponding timing; this potentially helps an operator understand the difference between a probe in intermittent wall-touching contact and continuous wall-touching contact. Optionally, however, the amplitude of the simulated pulses is reduced from the real state, to stabilize the visual environment an operator uses for navigation. Additionally or alternatively, some geometrical states (such as degree of vasodilation and/or vasoconstriction) are optionally exaggerated for clarity. 
     In some embodiments, the size of one or more heart chambers is adjusted based on current heart rate, and/or the size and/or movements of a probe relative to the heart chamber are scaled based on current heart rate. It has been observed that as heart rate increases, the maximum size of the heart between contractions correspondingly decreases. This decrease can also be observed in the sizes adopted by heart chamber at other phases of the heartbeat cycle. For example, in some embodiments, the average rendered size of the heart over the course of a heartbeat cycle is decreased as a function of measured heart rate increase. The average size change is optionally to either a beating or non-beating rendered representation of the heart. Optionally heart wall thickness correspondingly increases with decreasing chamber size. It is a potential advantage to incorporate these dynamic changes in anatomy into a display used by an operator to guide an intrabody probe, and/or to improve the accuracy and/or precision with which actions by and/or through the probe (e.g., contacts and/or treatment administration) are associated to positions on the heart wall. 
     In another example, visual rendering of blood is preferably suppressed, making visualization possible from within a vascular or cardiac lumen. Optionally, one or more normally invisible tissue properties such as temperature are encoded by visual conventions; appearing as, for example in the case of temperature: ice, flame, smoke, and/or steam. In some embodiments, guiding marks related to planning and/or procedure progress are optionally provided as part of the simulation scene&#39;s naturalistic rendering to images. 
     Among the services provided by some prominent graphical game engines are motion physics simulators (e.g., for modeling collisions, accelerations, elastic deformations, object destruction, and the like). In some embodiments, one or more these motion physics simulators is used to increase the naturalistic impression and/or realistic fidelity of a rendered simulation scene. In some embodiments, one or more of these motion physics simulators is used to increase the naturalistic impression of a scene. Additionally or alternatively, geometrical deformations are used to indicate aspects of a procedure where a probe contacts tissue. As for the case of material appearances, the geometrical deformations may be, but are not necessarily realistic. 
     A general potential benefit of naturalistic (optionally also realistic) presentation of a scene comprising simulated tissue is to reduce cognitive load on a catheter operator and/or team of operators working with an intra-body probe. Such procedures typically have multiple interacting factors and requirements affecting procedure outcome. These factors and requirements preferably are tracked simultaneously and/or may need to be accounted for with little time for consideration. Examples of these factors and requirements in a standard operating environment optionally include any one or more of the following:
         Positions of one or more probes are selected and verified with respect to a procedure plan.   Results of procedure actions are verified.   If planned actions and actual procedure actions begin to diverge, adjustments may be made on the fly.   Similarly, actual procedure results may not match planned results.   Some parts of the procedure optionally rely on discovering tissue states and locations, for example, based on sensing from the catheter probe.   Such discovery steps are preferably performed quickly and without undue repetition of catheter motions.   Particularly after plan and procedure diverge, relative timing of past procedure steps can be critical for deciding what current and/or following steps are optimal. For example, edema that gradually develops following lesioning (as in certain ablation procedures) can interfere with further lesioning, potentially leading to a need to adjust parameters and/or positions away from those first planned if there is a delay or error in an earlier phase of the procedure.   Similarly, the interpretation of sensing data is optionally dependent on the timing and/or results of previous actions. For example, a detected current impulse block in heart tissue may be correlated with the recent history of lesioning in an area to determine if the impulse block is more likely to be permanent (e.g., pre-existing, or in a well-lesioned area) or temporary (e.g., in a region where inactivation, for example, due to use of a lesioning modality, is potentially reversible).       

     In some embodiments of the current invention, immediate visual presentation of material appearance helps to control the complexity these factors can create. Potentially, a naturalistic display of information is more immediately understood by the clinical personnel, and/or intuitively draws attention to clinically relevant state updates. For example, instead of the operator team having to consider and/or calculate whether a previously lesioned tissue region was lesioned long enough ago to have converted to edematous tissue: in some embodiments, the edema is directly displayed as edematous tissue. Where a continuous lesion is planned, likely gaps in lesion extent can be directly seen in their overall context in the scene simulation, helping to guide the decision as to whether and/or how the procedure should be adapted to compensate. 
     A naturalistic presentation of catheter procedure information also contrasts, for example, with the presentation of this information using graphs and/or symbols. Familiarization with more abstract symbols, measures and graphs potentially requires prolonged training. An extra level of symbolic abstraction also potentially slows recognition by the physician of important changes in the state of the catheter interface or the tissue. 
     In some embodiments of the invention, a substantially continuous stream of input data describing a tissue region and/or probe interactions with it is used as a basis for correspondingly continuous updating of a scene simulating the tissue region. Optionally, the input data comprise only partial and/or indirect description of the tissue region. For example, spatially partial input data (such as from a cross-sectional image) is used in some embodiments to infer spatial changes over a larger region (such as a three-dimensional space extending outside the cross-sectional image). In another example, sensed pressure data from a catheter probe is optionally converted into corresponding movements in three-dimensional space of pressed-against tissue in the simulation scene. In some embodiments, effects on tissue by energy delivered from a lesioning probe are optionally simulated in a scene based on a model of energy dispersion in the tissue (e.g., thermal modeling, optionally thermal modeling incorporating information from anatomical data), and knowing a few parameters about how the energy was delivered (e.g., how long, with what energy, where, and/or with what efficacy). 
     In some embodiments, sensed input data is used as a basis for updating the state of the scene-representation of the probe itself. For example, sensed input data is used to adjust the position of the probe&#39;s scene representation, and/or to control the parameters of a viewpoint used in creating a rendered image of the simulation scene, wherein the viewpoint is defined by a position of the probe. In some embodiments, sensed input data (e.g., indicating tissue contact force and/or quality) is used as a basis for changing the shape of a simulated probe. The shape may be adjusted based, for example, on a mechanical model of the actual probe and/or a catheter or other device that carries the probe (e.g., a mechanical model which models the flexibility and geometry of the actual probe and/or associated carrying device). For example, some probes such as lasso electrode probes comprise a flexible portion that can be bent in response to the forces of touching contact. In another example, an otherwise stiff probe may be carried on a flexible member such as a catheter used to manipulate the probe. In some embodiments, sensed input data indicates forces applied to the actual probe, and the simulated probe is modified in response to the indicated forces according to the parameters of the mechanical model. The modification may also take into account other data, for example, a position of the probe itself, geometry of the chamber in which the probe is positioned, and/or a position of an aperture via which a probe is passed into a heart chamber or other body lumen. Potentially, the modeling allows a changing simulated probe shape to indicate changes to the actual intrabody probe in use, without requiring direct measurement of the actual intrabody probe&#39;s shape (e.g., by imaging). 
     Additionally or alternatively, in some embodiments, correlation between a simulation scene and the actual tissue region it represents is maintained at least in part by treating occasional inputs as describing events that (in the real world) trigger and/or entail certain predictable consequences to follow. In the simulation scene, the input optionally acts as a trigger for software routines that simulate those consequences. In some embodiments, longer-term effects of lesioning are optionally simulated by a physiological simulation. For example, a simulation converts estimated lesion damage into parameters for a script describing the gradual onset of tissue edema as it appears in rendered views of the simulation scene. 
     In some embodiments, moreover, partial and/or occasional inputs optionally guide calibration of the simulation scene maintained by the game engine so that it better-corresponds to the state of the actual tissue region. For example, sensing of tissue state or position directly using the probe as a sensing modality (additionally or optionally by another sensing modality, such as ECG, monitoring of patient hydration, or an intermittently acquired image) is optionally used to update a model state, potentially restoring and/or improving a degree of synchronization between the actual tissue region and the simulation scene. 
     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. 
     Methods and Systems for Visual Modeling of Probe-Tissue Interactions and Their Effects 
     Reference is now made to  FIG. 1A , which is a schematic flowchart illustrating the calculation and display of an image of a simulation scene, the simulation scene comprising simulated tissue having a geometry and/or geometrical appearance dynamically linked to interactions of the tissue with a catheter probe  11  (shown, for example, in  FIGS. 3A, and 6 ), according to some embodiments of the present disclosure. In overview, a cycle of activities of the method includes, in some embodiments:
         Receiving interaction data between probe  11  and tissue (at block  110 ).   Calculating geometrical effects altering a scene, the geometrical effects being indicated by the interaction data (at block  112 ).   Rendering the altered scene for visual presentation (block  114 ).       

     Illustrating examples of systems configured for carrying out this method, further reference is made to  FIG. 6 , which is a schematic representation of a system  1  configured to present interactions between a catheter probe  11  and a body tissue region  7 , and/or effects of these interactions. System  1  is optionally configured to present the interactions and/or their effects at user interface  55 . Reference is also made to  FIG. 7 , which schematically represents software components and data structures of an interaction analyzer  21  of system  1 , according to some embodiments of the present disclosure. 
     Receipt of Interaction Data 
     The flowchart of  FIG. 1A  begins; and at block  110 , in some embodiments, a system  1  (for example, the system  1  of  FIG. 6 ) configured for display of interactions between a catheter probe  11  and a body tissue region  7  and/or results of such interactions receives interaction data. The interaction data may include, for example, data acquired by a sensing modality, and/or operation data of a treatment modality. 
     The interaction data, in some embodiments, comprise data indicating and/or numerically describing characteristics of interactions between probe  11  and tissue region  7 ; including, for example, positions of the probe and/or of contacts between the probe and the tissue region, contact characteristics characterizing a contact between the probe and the tissue region, measurements taken by the probe (for example, measurements of the physiological state and/or dielectric properties of the tissue region), and/or actions of the probe (e.g., operations comprising delivery of treatment). Optionally, interaction data comprise imaging data obtained during probe-tissue interactions. 
     System  1  of  FIG. 6  indicates examples of sources of interaction data that are optionally provided in some embodiments of the present disclosure. Interaction data is optionally received in raw form, or in any suitable stage of intermediate processing to indicate a parameter and/or status of more direct applicability. With respect to  FIG. 6 , details for certain types of interaction data available in some embodiments of the invention (e.g., one type, all types, or any other combination of types) are now described for: position data, imaging data, dielectric tissue property sensing, general sensing (for example, of temperature and/or contact force), and treatment interactions. 
     Position data: In some embodiments (optionally), position data is sensed by use of an electromagnetic field navigation subsystem, comprising body surface electrodes  5 , field generator/measurer  10 , position analyzer  20 , and sensing electrodes  3  (for example, sensing electrodes  3  located on catheter probe  11 ). The electromagnetic field navigation subsystem operates by inducing at least one time-varying electromagnetic (EM) field  4  (for example, three crossing EM fields, each of a different frequency) across a region of body  2  including a body tissue region  7  that is targeted to be navigated by catheter  9  and catheter probe  11 . Typically, the time varying EM field is induced with a total inter-electrode voltage of one volt or less, at a frequency of between about 10 kHz and about 1 MHz. Voltages sensed at different positions by sensing electrodes  3  are characteristic of corresponding intrabody positions, allowing conversion by position analyzer  20 , for example of voltage measurements to position information (for example, after exploration of an intrabody region  7  using the probe  11 , and/or initially based on EM fields simulated with respect to a particular configuration of electrodes and anatomical data  31 ). 
     In some embodiments of the invention, position sensing at least partially comprises sensing of the relative position of a catheter probe  11  and a surface of tissue region  7 ; for example, by sensing of the dielectric environment of a sensing electrode  3  of catheter probe  11 . 
     Imaging data: Additionally or alternatively, in some embodiments, there is provided an imaging modality  6 , which may include, for example, an ultrasound modality and/or a fluoroscopy modality. Imaging modality  6  is configured to monitor body tissue region  7  during use of the catheter probe. Characteristics monitored by imaging modality  6  optionally comprise position information of the probe and/or of tissue affected by operation of the probe. In some embodiments, the imaging modality is in continuous, real-time (e.g., 5, 10, 15, 20, 30, 60 or more images per second) use during at least some phase of a procedure. Optionally, system  1  continuously processes changes in images produced by imaging modality  6  for immediate display (within a few milliseconds, for example, within 250 milliseconds) at user interface  55 . 
     Additionally or alternatively, in some embodiments, imaging modality  6  operates less frequently (for example, once every minute to every five minutes, or at another interval). An infrequently updating imaging modality  6  is optionally used for providing periodic “key frames” used to synchronize and/or verify display of simulated states of tissue region  7  and/or catheter  9 . Optionally, imaging information provides indirect information about elements in the scene simulation—for example, displacement of an organ boundary imaged with relatively high contrast optionally provides information about the displacement of a less clearly visualized organ in communication with the organ boundary. Also for example, data imaged in a tissue cross-section optionally provides information which can be extrapolated to regions outside of the cross-section. Optionally, an imaging modality is used only briefly during a procedure, for example, during a particular phase of a procedure such as a septal crossing. 
     Dielectric tissue property sensing: In some embodiments, dielectric property measurements (e.g., of impedance behavior of the electrical fields) providing indications of tissue state, and/or of tissue-probe contacts, are made by dielectric property analyzer  22 . The measurements, in some embodiments, use sensing electrodes  3  (or a subset thereof) to determine impedance behavior of electromagnetic fields generated in conjunction with field generator/measurer  10 , and optionally body surface electrodes  5 . Dielectric distance sensing has already been mentioned in connection with the discussion of position data. Additionally or alternatively, in some embodiments, dielectric property sensing is used to distinguish, for example, the state of tissue as healthy, fibrotic, edematous, charred or charring, and/or electrophysiologically active (or capable of being so, e.g., retaining cellular integrity after attempted ablation). In some embodiments, dielectric property sensing identifies and/or verifies tissue type(s) in a sensed region. Dielectric property sensing for such properties is described, for example, in International Patent Application Nos. PCT/IB2016/052690 and PCT/M2016/052686, the contents of which are incorporated by reference herein in their entirety. 
     General sensing: In some embodiments, other sensor information (sensed by optional other sensor(s)  14  on catheter probe  11 ) is used as interaction data. For example, a force sensor may provide information on contact between a catheter probe  11  and its environment. The information may include indication that the contact has happened, and optionally with what degree of force. 
     Additionally or alternatively, contact quality and/or contact force information is provided from sensing electrodes  3 , based on impedance measurements and/or sensing of dielectric properties. For example, where a surface of tissue region  7  and an electrode  3  of a catheter probe  11  are in contact, dielectric sensing optionally is used to provide an indication of contact quality (optionally as related to a corresponding contact force), for example as described in International Patent Application No. PCT/IB2016/052686, the contents of which are included by reference herein in their entirety. Contact quality may include dielectric and/or impedance sensing of the tissue environment of one or more electrodes, based on which force, pressure, area, and/or angle of contact between electrodes and the tissue environment is inferred, relatively and/or absolutely. 
     In some embodiments, other sensor(s)  14  comprise a temperature sensor, flow sensor, and/or another sensor configured to provide information about the environment of the catheter probe  11 . 
     Treatment interactions: In some embodiments, a treatment element  8  is provided on catheter probe  11 . The interaction data (for example, treatment status data  1102  of  FIG. 7 ) optionally comprises information about the operation of the treatment element and/or components controlling its effect (for example, power levels, activation events, timing settings, and/or substance amounts administered). 
     Treatment element  8  is optionally a probe for ablation treatment using an ablation modality; for example, one or more of the following ablation modalities: radio frequency ablation, cryoablation, microwave ablation, laser ablation, irreversible electroporation, substance injection ablation, and/or high-intensity focused ultrasound ablation. In some embodiments, treatment element  8  is also used as a sensing electrode  3  (for example, in RF ablation, a treatment delivery electrode may also be used to sense the effect of local dielectric properties on measured electrical field impedance). Optionally, treatment element  8  is operated in conjunction with a treatment controller  13 , configured to provide treatment element  8  with functions such as power, control (e.g., of signal frequency, phase, and/or timing), and/or monitoring. In some embodiments, the treatment element  8  is configured to deliver a treatment other than ablation (for example, temporary activation or inactivation of tissue activity) using heat, cold, electrical current, sound radiation and/or light radiation. 
     Optionally, treatment element  8  comprises an injection apparatus, used to inject a treatment substance, and/or a substance used in diagnosis such an imaging tracer. In some embodiments, the injected substance comprises ethyl alcohol, Botox, living cells, and/or growth factor. Optionally, the injected substance comprises a radiolabeled substance, an immunosubstance, and/or a radiopaque trace substance. Optionally, treatment element  8  comprises a tool for manipulating tissue (e.g., grasping, holding, sampling, cutting, attaching, and/or suturing). Data indicating operations of treatment element  8  (and/or the rest of a treatment delivery system, for example, including a treatment controller  13 ) are optionally available within system  1 , and in particular available to modules of interaction analyzer  21 , as treatment status data  1102  ( FIG. 7 ). It should be understood that treatment status data  1102  are not limited strictly to data about operations targeted to disease treatments as such, but optionally also include administration of substances and/or energy affecting a tissue region for a diagnostic purpose. 
     Interaction data relating to the interactions of a treatment element  8  with a target tissue region  7  include, for example, duration of operation, time of operation, nature and/or concentration of substances delivered, quantities of substances delivered, and/or power and/or frequencies of an exchange of energy between the treatment element  8  and tissue region  7  by a mechanism other than contact pressure (e.g., energy delivered for heating, energy removed for cooling, and/or energy delivered for disruption of structure). Optionally, operational settings are combined with information about the position and/or environment of treatment element  8  in order to derive interaction data. In some embodiments, such combination is performed by one or more of simulators  1110  of  FIG. 7 . 
     It should be understood that not every source of interaction data described in relation to  FIG. 6  is necessarily implemented in every embodiment of the invention. Preferably, there is provided in embodiments of the invention at least a position sensing modality (e.g., comprising position analyzer  20 ), and a treatment modality which is monitored through treatment status data (e.g., comprising treatment controller  13 ). In  FIG. 7 , data from sensing indicated as sensing data  1101  optionally includes data from one or a plurality of sensing modalities; for example, sensor electrodes  3 , other sensors  14 , and/or imaging modality  6 , described in relation to  FIG. 6 . 
     Moreover, it should be understood that computation-performing and/or control operation-performing modules are optionally implemented by any suitable combination of shared and/or dedicated processing units and/or controllers. For example, implementations of treatment controller  13 , position analyzer  20 , and/or interaction analyzer  21  optionally comprise one shared processing unit, or any other suitable number of shared and/or dedicated processing units. 
     Optionally, the flowchart continues with block  112 . In some embodiments, certain types of interaction data (such as inputs indicating onset of ablation treatment) branch additionally or alternatively to  FIG. 1B  (dotted line branch indicates optional branching). 
     Geometrical Effects and Rendering of Virtual Materials 
     At block  112  of  FIG. 1A , in some embodiments, geometrical effects which modify the apparent position of geometrical features in a rendered view of a simulation scene are optionally calculated for locations defined by a 3-D data structure representing geometry of the targeted body tissue region  7 . The operations of block  112  are carried out, in some embodiments, by interaction analyzer  21  (detailed for some embodiments in  FIG. 7 ). Optionally the geometrical effects of block  112  are calculated based on discrete events in the interaction data; for example, a single event such as a high-pressure contact triggering a tissue response like edema. Optionally, the geometrical effects of block  112  are calculated based on a history of interaction data; for example, a history of the delivery of ablation energy to a tissue region is used to estimate properties (for example, lesion extent) of an ablation lesion produced. The lesion properties are optionally estimated using a model of a thermal profile of the target tissue region and an estimate of temperatures/times at temperatures above which ablation occurs. 
     In further explanation of the distinction between adjustment of geometric points as such, and geometrical effects which affect the apparent position of geometrical points in a rendering, reference is now made to  FIGS. 9A-9B , which schematically represent, respectively, different geometrical data representations of flat and indented surfaces, according to some embodiments of the present disclosure. The grids shown in the two figures to indicate geometrical point positions are illustrative; alternatively or additionally, these could be, for example: any set of geometrical points defined in a 3-D space by mesh data; by polygon definitions; and/or by one or more parametrically defined shapes such as polyhedra, ellipsoids, cylinders, planar-shape extrusions, and/or parametric curves. 3-D flat geometry  901  and indented geometry  903  (indented at indentation  905 ) represent the use of 3-D positions of geometrical points to visually convey surface shapes. The indentation  905 , for example, is represented by displacing geometrically defined points falling within it by an appropriate distance out of the plane defined by other points of 3-D indented geometry  903 . 
     Additionally or alternatively, geometrical appearance is changed (e.g., from a flat appearance to an indented appearance) by assigning to the surface of each rendered region within indentation  905  a suitable orientation (for purposes of rendering), chosen to optically mimic the angle the surface would have if the 3-D flat geometry  901  comprised a geometrically indented region like that of 3-D indented geometry  903 ; but without necessarily changing the 3-D geometry to which it maps. By convention, the surface orientation is represented by the orientation of a vector normal to (sticking straight out of) the surface. 
     For example, normal maps  902 ,  904  indicate by shading a changing elevation angle of a normal to the surface throughout region  906  (white is 90° elevation of the normal, while successively darker values represent successively decreased elevation values). Though not shown in the figure, normal maps  902 ,  904  preferably include representation of azimuth, e.g., azimuth mapped from 0°-360° around concentric circumferences of indentation  905 . Surface orientation as represented by a normal map does not necessarily follow the geometrical surface orientation (for example,  FIG. 9A  shows a flat geometry  901  paired to a normal map  902  that represents an indentation). Though the resulting appearance change is not shown in  FIGS. 9A-9B ,  FIGS. 10A-1B  do provide an example of how a geometrical appearance can be changed (in that case to appear like a raised bump) by use of shading, without necessarily changing underlying geometrical positions. 
     To render the effects of a normal map, a rendering pipeline typically takes into account at least the relative angle of each surface normal and a light source in order to determine how much light is received at the camera. Then, for example (and other things being equal): when the relative angle is low, the surface is brighter; when the relative angle is high, the surface is darker. Optionally, the normal mapping algorithm also takes into account camera position and/or viewing angle-dependent surface reflection/scattering properties of the surface. 
     Normal mapping uses include, for example: to create the appearance of surface irregularities where the 3-D geometrical data has none, to exaggerate the 3-D appearance of shapes in the 3-D geometrical data, and/or to smooth transitions between polygons where the 3-D geometrical data describes abrupt changes (for example, between polygons in a mesh). In connection with some embodiments of the present invention, normal mapping (and a normal map, supplied as part of the geometrical rendering data  1121 ) has particular application for the showing of tissue deformations such as swelling (e.g., to indicate tissue damage) and indentation (e.g., to indicate probe-tissue contact). Embodiments optionally implemented with the use of normal mapping are described, for example, in relation to  FIGS. 10A-10B, 10C-10D, 4A-4D , and  5 A- 5 B. A distinction is drawn between the use of normal mapping techniques to define and/or highlight surface features having functional significance to an ongoing catheterization procedure, and the use of normal mapping techniques to provide general texture (such as bump mapping), and/or to mask display artifacts (such as masking of geometrical mesh artifacts using Gouraud shading or Phong shading). 
     Herein, 3-D structure rendered in a scene (in particular, 3-D data defining organ structure) is geometrically represented by geometrical rendering data  1121 . 3-D positions are one part of the geometrical rendering data. Data used to affect geometrical appearance such as by use of normal maps (apart from use to define fine-grain texture) are considered to comprise a second part of the geometrical rendering data  1121 . 
     In some embodiments, the geometrical rendering data  1121  comprise mesh data; for example as commonly used in defining structures for computerized visual rendering of 3-D structures. Geometrical rendering data  1121  specify positions (and usually also connections among positions, and/or positions joined by the extent of a common surface and/or material volume), corresponding to positions of surfaces of a target body tissue region to be visually rendered for presentation. Optionally, the geometry of positions interior to the surface is also defined and/or represented. For example, presentation optionally includes the use of transparency and/or cross-sectional views, whereby an interior portion of a tissue region is made visible. 
     Surfaces represented are optionally external (e.g., organ surfaces; not necessarily surfaces visible externally to the body) and/or internal (e.g., lumenal) surfaces of the target body tissue region. In some embodiments, geometrical rendering data  1121  are derived from anatomical data  31 ; for example, appropriately segmented 3-D medical image data. In some embodiments, anatomical data  31  include specification of tissue region thicknesses, for example, thicknesses of heart walls. Heart wall thickness is optionally obtained from, for example: atlas information (optionally for a population corresponding to the current patient), modified atlas information (for example, scaled according to anatomical landmark correspondence, heart rate, and/or point observations), and/or imaging of the patient (for example, one or more of CT, MRI, and/or nuclear imaging techniques). 
     Moreover, in some embodiments, the appearance of the raw geometrical rendering data  1121  that is finally presented by a user interface  55  is also determined in part by the assignment to the geometry of material appearance properties (MAPs); that is, properties affecting the appearance of materials represented in the rendered image. As the term is used herein, MAPs comprise any properties associated to positions (typically positions of a “virtual material”, as next described) in a virtual environment for visual rendering according to simulated optical laws, and which affect how a surface and/or its enclosed volume are visualized within a 3-D rendered space. For example, MAPs may define color, texture, transparency, translucency, scattering, reflectance properties, and the like. MAPs are usually but not only assigned to surface positions defined by the geometrical rendering data. MAPs are optionally assigned to volumes defined by surfaces specified by the geometrical rendering data  1121 . MAPs can also be assigned to the virtual environment (e.g., as lighting parameters) in such a way that they selectively affect material appearance at different positions. In some embodiments of the current invention, MAPs are used to in part define surface textures, for example by use of bump mapping (a type of normal mapping technique). 
     Creating the visual rendering in some embodiments may include surfaces and/or volumes comprising “virtual material”; for example, a virtual material having a visual appearance of myocardial tissue, and used in the representation of a heart wall defined by two surfaces. A virtual material, in some embodiments, is subject to simulated optical rules approximating processes such as reflection, scattering, transparency, shading, and lighting. Not every optical rule used in visual rendering is a copy of a real-world physical process; the art of computer rendering includes numerous techniques (for achieving both realistic and deliberately unrealistic results) that apply simulated optical rules that have no direct physical equivalent. Normal mapping has already been mentioned as a technique which can be applied to change a texture and/or geometrical appearance. Another example of a simulated optical rule is ambient occlusion. Ambient occlusion is an efficiently calculable method of simulating the effect of ambient lighting, but the occlusion is defined as a mapped property of an object&#39;s surface, rather than as an effect of light emitted from positions in the environment. 
     A virtual material optionally also defines material properties that are not directly either geometrical or “of appearance”, for example, density, viscosity, thermal properties, and/or elastic properties. Insofar as these properties do in turn (in a given embodiment) affect the definition of MAPs (for example, via calculations of one or more simulators  1110 ), they are optionally treated as parts of material appearance properties data  1122 , without actually comprising MAPs in themselves. Additionally or alternatively, non-appearance properties, particularly those that affect how geometry changes (such as thickness, density, velocity, viscosity, and/or elasticity), are optionally considered part of the geometrical rendering data  1121  insofar as they affect geometrically apparent behaviors of the material (e.g., how the material changes in shape). 
     Calculation of Geometrical Effects from Interaction Data 
     In some embodiments of the invention, geometrical effects of tissue-probe interactions on a simulated tissue region are assigned based on the output of one or more simulators  1110  ( FIG. 7 ). 
     In some embodiments, sensing data  1101  and/or treatment status data  1102  (i.e., data describing the operation of a treatment modality) are used directly or indirectly as input to one or more simulators  1110  (e.g., simulators  1111 ,  1112 ,  1113 , and/or  1114 ) that make adjustments to a modeled appearance state  1120  of the tissue based on inputs received, and one or more simulated aspects of tissue physiology, geometry, and/or mechanics. The modeled appearance state  1120  includes the geometrical rendering data  1121  and material appearance properties data  1122  in a form suitable for being operated on by the simulators  1110 ; it may also be or comprise a renderable model state  1103  suitable for rendering for presentation, or else be convertible to a renderable model state  1103 . In some embodiments, modeled appearance state also includes data indicating the probe state  1123 . 
     Simulators  1110  also optionally receive as starting input anatomical data  31  and/or tissue state data  1104 . In addition to adjusting the modeled appearance state  1120 , simulators  1110  optionally maintain their own internal or mutually shared simulation states. In some embodiments, simulators  1110  use motion simulation services exposed by a graphical game engine that can produce geometrical changes to a scene based, for example, on simulated collisions among scene elements, gravity effects, velocity, momentum, and/or elasticity. 
     Operations of some exemplary simulators  1111 ,  1112 ,  1113 , and/or  1114  are described in the context of the examples of  FIGS. 2A-2E, 3A-3L, 4A-4D, 5A-5B, 10A-10B , and  10 C- 10 D. 
     In relation to  FIG. 7 , different input types providing probe-tissue interaction data as input to simulators  1110  are now described, including direct sensing input, physiologically interpreted sensing input, positionally interpreted sensing input, and treatment status input. In some embodiments, the inputs comprise direct and/or transformed use of one or more of the interaction data types described in relation to block  110 . 
     Direct sensing input: In some embodiments, adjustment of the simulation scene is implemented based directly on sensing data  1101 . For example, a pressure reading from a pressure sensor  14  is optionally mapped directly to a geometrical displacement according to the measured pressure. 
     Additionally or alternatively, in some embodiments, a more involved simulation is performed; wherein probe interaction with a virtual material representing tissue is, in at least one aspect, physically and/or physiologically simulated in order to produce a new modeled appearance state. 
     Physiologically interpreted sensing input: In some embodiments, the use of sensing data  1101  by a simulator is indirect after interpretation by one or more physiology trackers  1106 . Physiology tracker  1106 , in some embodiments, is a module which accepts sensing data  1101  and generates an assessment of current physiological state based on the sensing data  1101 . For example, in some embodiments, sensing data  1101  comprises dielectric measurements that physiology tracker  1106  is configured to convert into assessment of tissue state, for example fibrotic, healthy, or edematous; for example as described in International Patent Application No. PCT/IB2016/052690, the contents of which are included by reference herein in their entirety. Optionally or alternatively, electrical activity originating in tissue indicating a functional state (e.g., general capacity to support electrical activity, and/or feature of the activity itself) is measured and used as sensing input. 
     The output of the physiology tracker  1106  from one or more of these inputs is optionally in terms of one or more states such as tissue thickness (e.g., heart wall thickness), lesion depth, lesion volume, degree of lesion transmurality, characterization of tissue edema, characterization of functional activity and/or inactivation, a classification as to a potential for tissue charring, and/or a classification as to a potential for or occurrence of steam pop. “Steam pop” is a phenomenon occurring during ablation with an audible popping noise and/or spike in impedance, which is apparently due to sudden release of steam after excessive heating, associated with risk of perforation. 
     These outputs are optionally provided to a physiology simulator  1114  and/or an ablation physics simulator  1112 , configured to convert such states into MAPs, other virtual material properties, and/or geometrical effects that indicate the tissue state(s) calculated from the measurements. Optionally, the tissue state interpreted from the sensing input also affects mechanical properties used, for example, by a contact physics simulator  1111  and/or an injection simulator  1113 . It is a potential advantage to implement a physiological tracker  1106  as a distinct module that can be treated as a computational “service” to any appropriate simulator  1110 . However, it should be understood that physiological tracker  1106  is optionally implemented as part of one or more simulators  1110  producing changes to a modeled appearance state  1120 . In this case, the module configuration is more like that of direct sensing input, with the simulation of appearance integrated with physiological interpretation of the sensing data. 
     Positionally interpreted sensing input: In some embodiments, the use of sensing data  1101  by a simulator is indirect after interpretation by a probe position tracker  1107 . Probe position tracker  1107 , in some embodiments, is a module that accepts appropriate sensing data  1101  (e.g., electromagnetic field navigation data, acoustic tracking data, and/or imaging data) and converts it to a measurement of the position (e.g., a measurement of the location and/or a measurement of the orientation) of a probe such as catheter probe  11 , for example as described in International Patent Application No. PCT/1132016/052687. It optionally comprises position analyzer  20 . Optionally, position tracker  1107  implements processing to massage outputs of position analyzer  20  in view of the current state of the scene simulation—for example, to recalibrate sensed position data to positions compatible with the scene simulation. Optionally, position tracker  1107  integrates position data from a plurality of position inputs. 
     Optionally position determination includes determination of tissue contact force and/or quality, using a force sensor on the probe, and/or for example as described in International Patent Application No. PCT/IB2016/052686, the contents of which are included by reference herein in their entirety. Additionally or alternatively, on-line imaging data (e.g., ultrasound and/or angiographic images) are used, intermittently and/or continuously, to determine and/or verify probe position. 
     Probe position determinations are optionally used as inputs to any of simulators  1110 ; for example in order to assign particular positions to measurements of other tissue states/properties, and/or to help characterize changes induced by probe interactions with tissue (e.g. geometrical distortions of tissue introduced by touching contact with the probe, and/or simulated effects of treatment procedures). It is a potential advantage to implement probe position tracker  1107  as a distinct module that can be treated as a computational “service” to any appropriate simulator  1110 . However, it should be understood that probe position tracker  1107  is optionally implemented as part of one or more simulators  1110  producing changes to a modeled appearance state  1120  maintained by interaction analyzer  21 . 
     Treatment status input: In some embodiments, simulation is implemented based on treatment status data  1102 . Treatment status data  1102  include data indicating the operation and/or status of a treatment modality—for example, power, control parameters (e.g., of signal frequency, phase, and/or timing), and/or monitoring data. Optionally, treatment status data are applied directly to modeled appearance state  1120 ; for example, as an indentation or other deformation at a position of treatment modality activation. Additionally or alternatively, in some embodiments, at least one aspect of the tissue and/or tissue/probe interaction is physically and/or physiologically simulated in order to produce a new modeled appearance state  1120 , based on the treatment status data. 
     For example, in some embodiments, a physiology simulator  1114  receives input indicating that a probe-delivered treatment operation has occurred at some particular position (optionally along with parameters of the treatment operation). Physiology simulator  1114  is optionally configured to model the reaction of tissue to the treatment, instantaneously (for example, due directly to energy delivered by an ablation treatment), and/or over time (for example, as an edematous reaction develops in the minutes following an ablation treatment). In another example, an injection simulator  1113  receives treatment status data indicating that a material injection is occurring. Injection simulator  1113  is optionally configured to model an appropriate reaction of tissue to the injected substance (e.g., swelling to indicate the injected volume, and/or to indicate injury response to the injection). The reaction is optionally immediate, and/or includes a slow-developing component as the material diffuses from the injection site. Optionally, changes in geometry due to the addition of material volume to the tissue are also modeled. 
     Presentation of Visual Rendering 
     At block  114 , in some embodiments, a rendering of the modeled appearance state is created for presentation. 
     In some embodiments of the invention, geometrical effects on a simulated tissue region are assigned based on the output of one or more simulators  1110  ( FIG. 7 ). 
     In some embodiments, sensing data  1101  and/or treatment status data  1102  are used directly or indirectly as input to one or more simulators  1110  (e.g., simulators  1111 ,  1112 ,  1113 , and/or  1114 ) that make adjustments to a modeled appearance state  1120  of the tissue based on inputs received, and one or more simulated aspects of tissue physiology, geometry, and/or mechanics. Simulators  1110  also optionally receive as starting input anatomical data  31  and/or tissue state data  1104 . In addition to adjusting the modeled appearance state  1120 , simulators  1110  optionally maintain their own internal or mutually shared simulation states. In some embodiments, simulators  1110  use motion simulation services exposed by a graphical game engine that can produce geometrical changes to a scene based, for example, on simulated collisions among scene elements, gravity effects, velocity, momentum, and/or elasticity. 
     Operations of some exemplary simulators  1111 ,  1112 ,  1113 , and/or  1114  are described herein in the context of the examples of  FIGS. 2A-2E, 3A-3L, 4A-4D, and 5A-5B . 
     In some embodiments of the invention, a modeled appearance state  1120  is converted to a renderable model state  1103  and provided to a display module  1130  that converts (renders) the renderable model state into at least one image comprising a visually rendered representation of the intrabody region  7 . Optionally, modeled appearance state  1120  is directly represented as a renderable model state  1103  (this is a potential advantage for tighter integration of the simulation with a game engine driving its rendering and presentation). The at least one image is displayed by one or more graphical displays of a user interface  55 . User interface  55 , in some embodiments, comprises one or more displays, for example a computer monitor, virtual reality goggles, and/or 2-D or 3-D projection device. Preferably, user interface  55  also comprises one or more user input devices that can be used for tasks such as selecting operating modes, preferences, and/or display views. It is noted that insofar as catheter probe position sensing affects simulation and/or display, catheter probe manipulation also acts as a special form of user input device; but for purposes of the descriptions herein such catheter probe sensing inputs should be considered distinct from inputs provided through user interface  55 . 
     In some embodiments, the display module  1130  renders from one, two, three, or more viewpoints simultaneously. In some embodiments, rendering is performed (and the resulting images are displayed) at a frame rate sufficient to produce perceived motion (herein, such a frame rate is termed a motion frame rate)—for example, at least 10-15 frames per second; and optionally at least, for example, 15, 20, 30, 50, 60, or 100 frames per second (fps), or another greater or intermediate value. Within this range, lower frame rates (e.g. 10-20 fps) tend to give the appearance of “choppy” motion, with apparent motion growing increasingly fluid with rates up to at least 30-60 fps. More fluid motion is potentially less fatiguing and/or more precise for guiding actions based on events in the simulation scene. Still higher frame rates (above the nominal frequency of visual flicker fusion) add the potential advantage of increasingly convincing presentation of very rapid motion (e.g., reducing visual appearance of discrete-position motion “trails”). Trans-flicker fusion frequency frame rates are optionally preferred for immersive, virtual reality (VR) user interface implementations; higher frame rates potentially help mitigate VR motion sickness. 
     In some embodiments of the invention, display module  1130  includes a computer-implemented software module comprising the rendering pipeline  1230  of a 3-D graphics engine  1200  (software environment) such as is provided with graphical game engines such as the Unreal® or Unity® graphical game engine, or another game engine. Some general aspects of 3-D graphical game engines are discussed in relation to  FIG. 8 , herein. Optionally, the conversion of a modeled appearance state  1120  into a renderable model state  1103  comprises the creation and/or instantiation of computer data and/or code structures that are directly used by the rendering pipeline of the 3-D graphics engine  1200 . 
     Optionally, some functions of interaction analyzer  21  (for example, any of simulators  1110 ) are provided as functions (e.g. classes, hook implementations, etc.) making use of the application programming interface (API) of such a 3-D graphics engine  1200 . 
     Ending the presentation of  FIG. 1A : at block  116 , in some embodiments, flow optionally returns to block  110  to receive more interaction data, or else (if adaptive visual rendering is to be suspended), the flowchart ends. 
     Use of a Graphical Game Engine in Real-Time Anatomical Navigation 
     Continuing reference to  FIG. 7 , in some embodiments of the invention, geometrical effects on a simulated tissue region are assigned based on the output of one or more simulators  1110 . 
     In some embodiments, sensing data  1101  and/or treatment status data  1102  are used directly or indirectly as input to one or more simulators  1110  (e.g., simulators  1111 ,  1112 ,  1113 , and/or  1114 ) that make adjustments to a modeled appearance state  1120  of the tissue based on inputs received, and one or more simulated aspects of tissue physiology, geometry, and/or mechanics. Simulators  1110  also optionally receive as starting input anatomical data  31  and/or tissue state data  1104 . In addition to adjusting the modeled appearance state  1120 , simulators  1110  optionally maintain their own internal or mutually shared simulation states. In some embodiments, simulators  1110  use motion simulation services exposed by a graphical game engine that can produce geometrical changes to a scene based, for example, on simulated collisions among scene elements, gravity effects, velocity, momentum, and/or elasticity. 
     Operations of some exemplary simulators  1111 ,  1112 ,  1113 , and/or  1114  are described in the context of the examples of  FIGS. 2A-2E . 
     Reference is now made to  FIG. 8 , which schematically represents components, inputs, and outputs of a graphical game engine  1200  operating to manage and render scene elements  1220  to motion frame-rate images  1240 , according to some embodiments of the present disclosure. 
     In some embodiments of the invention, a graphical game engine  1200  is used not only to render images (for example as described in relation to block  114  of  FIG. 1A ), but also to provide more generally the data structure and code framework of the “scene” and how it changes in response to time and/or input. 
     In broad outline, a graphical game engine  1200  comprises a collection of computer software components exposing one or more application programming interfaces (APIs) for use in describing, instantiating (initializing and maintaining), continuously updating, rendering, and/or displaying of scene elements  1220 . Examples of graphical game engines include the Unreal® and Unity® graphical game engines. 
     The scene elements  1220  provided for the operations of graphical game engine  1200  optionally include, for example, descriptions of terrain  1221 , objects  1224 , cameras  1223 , and/or elements for lighting  1222 . In some embodiments of the present disclosure, definitions of scene elements  1220  are derived from geometrical rendering data  1121  and/or MAPs data  1122 . Definitions are optionally expressed in terms of geometrical-type scene data  1225  (e.g. model assets, shapes, and/or meshes), and/or appearance-type scene data  1226  (e.g., image assets, materials, shaders, and/or textures). In some embodiments, geometrical rendering data  1121  and MAPs data  1122  are initially produced already in a format that is directly used by graphical game engine  1200 . 
     In some embodiments, scene elements  1220  are provided with simulated dynamic behaviors by an iterated series of calculated scene adjustments  1210 . Scene adjustments  1210  are optionally implemented by a variety of software components for e.g., motion physics services  1212 , collision detection service  1213 , and/or scripts  1211 . These are examples; graphical game engines  1200  optionally implement additional services, e.g., “destructibility”. Scripts  1211  can be provided to simulate, for example, autonomous behaviors and/or the effects of triggered events. Scripts  1211  are optionally written in a general-purpose computer language taking advantage of APIs of the graphical gaming engine  1200 , and/or in a scripting language particular to an environment provided by the core graphical gaming engine  1200 . Graphical gaming engines optionally also accept integration with plugin software modules (plugins, not shown) that allow extending the functionality of the core graphical game engine  1200  in any of its functional aspects. For purposes of the descriptions provided herein, plugins that perform functions related to updating the scene state are also encompassed within the term “script”  1211 . In some embodiments, all or part of any of simulators  1110  is implemented as a script  1211 . 
     For purposes of descriptions herein, scripts  1211  (optionally including plugins) and scene elements  1220  are considered part of the graphical game engine  1200  as a functional unit. Optionally, for example where reference is made particularly to the off-the-shelf graphical game engine apart from specialized adaptations for uses described herein, the term “core graphical game engine” is used. 
     For interactivity, graphical game engines  1200  accept user input  1214  (optionally including, but not limited to, inputs from user interface  55  devices such as mouse, keyboard, touch screen, game controller, and/or hand motion detector; and for some embodiments of the current invention, optionally including data provided as input that indicate probe positions, treatment modality operation, etc.). 
     A typical graphical game engine also includes a rendering pipeline  1230  that may include one or more stages of 3-D rendering, effects application, and/or post-processing, yielding at least one stream of frame-rate images  1240 . In some embodiments, the stages of the rendering pipeline  1230  include modules that implement simulated optical algorithms—not necessarily directly based on real-world physical laws—generally selected to produce a rendered result that visually gives to elements in the rendered scene the appearance of material substances. 
     Table 1 includes some examples of how graphical game engine features and concepts are optionally used in some embodiments of the current invention: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Examples of Graphical Engine Feature/Concept Usage 
               
            
           
           
               
               
            
               
                 FEATURE/ 
                   
               
               
                 CONCEPT 
                 EXAMPLES OF USE 
               
               
                   
               
               
                 Scene 
                 Overall visually renderable model of environment and 
               
               
                   
                 objects within it. Optionally equivalent to a renderable 
               
               
                   
                 model state 1103 and/or scene elements 1220. 
               
               
                 Terrain 
                 Optionally used to represent geometry of the anatomical 
               
               
                   
                 environment; e.g., geometrical rendering data 1121. For 
               
               
                   
                 example, the heart wall might be implemented as terrin 
               
               
                   
                 1221 (alternatively, anatomical features are implemented 
               
               
                   
                 as objects 1224; e.g., as mesh geometry objects, and/or 
               
               
                   
                 combinations of primitive objects such as cylinders, 
               
               
                   
                 boxes, and/or ellipsoids). 
               
               
                 Objects 1224 
                 Probe 11 is optionally represented as a “game” object, 
               
               
                   
                 and may optionally serve as a viewpoint anchor like 
               
               
                   
                 avatars and/or tools in certain 3-D games. Significant 
               
               
                   
                 features of the anatomical environment such as scars, 
               
               
                   
                 lesions, and/or regions of edema, are optionally 
               
               
                   
                 implemented as appropriately positioned objects, e.g., 
               
               
                   
                 embedded in an environment of surrounding tissue. 
               
               
                   
                 Guides and markers are optionally implemented as 
               
               
                   
                 game objects. 
               
               
                 Assets 
                 Tissue, probe, guide, and/or other objects and/or their 
               
               
                   
                 appearances are optionally instantiated from assets 
               
               
                   
                 which represent available types of objects, their 
               
               
                   
                 behaviors and/or their appearances. Optionally includes 
               
               
                   
                 geometrical-type scene data 1225 (e.g., model assets, 
               
               
                   
                 shapes, and/or meshes), and/or appearance-type scene 
               
               
                   
                 data 1226, (e.g., images assets, material, shaders, 
               
               
                   
                 and/or textures). 
               
               
                 Cameras 1223 
                 Cameras optionally define flythrough viewpoint(s) of 
               
               
                   
                 the anatomy traversed by the catheter probe 11, and/or 
               
               
                   
                 overview viewpoint(s) (showing probe and tissue from 
               
               
                   
                 a remote viewpoint). Optionally, the position of 
               
               
                   
                 catheter probe 11 defines one or more camera 
               
               
                   
                 viewpoints by its position/or orientation. 
               
               
                 Lighting 1222 
                 In addition to providing general lighting of the tissue 
               
               
                   
                 being navigated, lighting 1222 is optionally defined to 
               
               
                   
                 provide highlighting, e.g., of regions pointed at by 
               
               
                   
                 probe 11, indications of environmental state by choice 
               
               
                   
                 of light color, light flashing, etc. Lighting is 
               
               
                   
                 optionally used to implement MAPs non-locally (that 
               
               
                   
                 is, a defined light source optionally is defined to 
               
               
                   
                 illuminate a view of simulated tissue to selectively 
               
               
                   
                 change its material appearance, while not being part 
               
               
                   
                 of the material properties of appearance of the 
               
               
                   
                 simulated tissue as such). 
               
               
                 Image Assets; 
                 MAPs that are also material properties of 
               
               
                 Materials, 
                 appearance, for example, defining the appearance of 
               
               
                 Shaders, and 
                 tissue as healthy muscle, edematous, fibrotic, heated, 
               
               
                 Textures 1126 
                 cooled, etc. 
               
               
                 Particle 
                 Type of object optionally used for providing effects 
               
               
                 Systems 
                 such as smoke/steam-like indications of ablation 
               
               
                   
                 heating, spray, transfer of energy, etc. 
               
               
                 Collision 
                 Optionally used for interactions between probe and 
               
               
                 Detection 
                 the geometry of the anatomical environment; 
               
               
                 1213 and 
                 optionally including deformation of the probe and/or 
               
               
                 Motion 
                 the anatomy. As implemented by core graphical game 
               
               
                 Physics 
                 engines, the term “physics” generally is limited 
               
               
                 Service 
                 to physics affecting movement/deformation of game 
               
               
                 1212 
                 objects such as collision, gravity, or destruction. 
               
               
                   
                 In some embodiments, simulators 1110 include 
               
               
                   
                 simulation of other “physics”, such as 
               
               
                   
                 temperature, physiological change, etc. 
               
               
                 Scripts 
                 Optionally used for animating and/or showing changes 
               
               
                 1211 
                 in dynamic features of the environment (lighting, 
               
               
                   
                 terrain), view (camera position) and/or game objects, 
               
               
                   
                 optionally gradually over a period of time: for example, 
               
               
                   
                 development of lesions, development of edema, 
               
               
                   
                 heating/cooling effects, and/or injection effects. 
               
               
                   
                 Optionally, scripts are used to implement 
               
               
                   
                 dynamic appearance, even though the underlying state 
               
               
                   
                 representation is constant (e.g., coruscating and/or 
               
               
                   
                 pulsing effects). 
               
               
                 User Input 
                 Optionally comprise inputs reflecting changes in probe 
               
               
                 1214 
                 position (e.g., output of probe position tracker 1107) 
               
               
                   
                 for guiding navigation through the scene, 
               
               
                   
                 and/or determining camera position. Some treatment 
               
               
                   
                 status data 1102 are optionally interpreted 
               
               
                   
                 as inputs reflecting operator interaction with the 
               
               
                   
                 scene. 
               
               
                 Multiplayer 
                 During a procedure, there is optionally a plurality of 
               
               
                   
                 different operators working simultaneously with a 
               
               
                   
                 system according to some embodiments of the current 
               
               
                   
                 invention. For example, while a primary physician 
               
               
                   
                 manipulates the intra-body probe, one or more additional 
               
               
                   
                 workers are optionally reviewing the simulated 
               
               
                   
                 environment to locate next target sites for the probe, 
               
               
                   
                 evaluate effects of previous ablations, etc. Optionally, 
               
               
                   
                 there is more than one probe in use at a time, each of 
               
               
                   
                 which is optionally treated as a different “player” 
               
               
                   
                 with its own associated camera views and/or interaction 
               
               
                   
                 capabilities. 
               
               
                   
               
            
           
         
       
     
     Independently Time-Evolving Probe-Tissue Interactions 
     Reference is now made to  FIG. 1B , which is a schematic flowchart illustrating the calculation and display of an rendered image of a simulation scene comprising a view of simulated tissue having a geometry and/or geometrical appearance of a tissue dynamically changing as a function of time to represent changes developing subsequent to a triggering interaction between the tissue and a catheter probe, according to some embodiments of the present disclosure. 
     In some embodiments of the invention, simulation of probe-tissue interactions includes simulation of tissue effects (e.g., injury response) developing substantially independently of continuing inputs from probe-tissue interaction data. In some embodiments, the flowchart of  FIG. 1B  branches off from certain input cases of the flowchart of  FIG. 1A , wherein geometrical effects develop at least partially concurrently with (and optionally unsynchronized to) geometrical effects which immediately track changes in inputs. In  FIG. 1B , initial interaction data is received (optionally entering the flowchart from block  110  of  FIG. 1A ). After this, the simulated geometry evolves according to the results of pre-set rules which operate substantially independently of further input for a time. A potential advantage of this approach is to allow continuously updated visualization of tissue changes, even when no new sensing data has been obtained to confirm them. 
     The flowchart optionally begins after a triggering probe-tissue interaction has occurred which is to be modeled as provoking changes to the scene which continue after the trigger time to. For example, an input indicating that ablation energy has been delivered triggers the operations of the flowchart. 
     Optionally, operations of the flowchart of  FIG. 1B  are implemented by a script  1211 . Additionally or alternatively, operations of the flowchart are implemented by a simulator  1110 , for example, physiology simulator  1114 . 
     At block  120 , in some embodiments, one or more geometries and/or geometrical appearances are set to an initial state (an existing state is optionally used as the initial state) and a simulation function is selected and assigned to change the geometries and/or geometrical appearances as a function of time according to parameters set from inputs describing the probe-tissue interaction. These inputs may be included in the interaction data received at block  110 . In some embodiments, the simulation function is configured to evolve according to the state of a timer. 
     For example, in some embodiments, a physiology simulator  1114  is configured to emulate effects of edema developing post-ablation, based on parameters such as the position, amount of energy delivery, and/or duration of energy delivery causing the ablation. Edema is optionally modeled to develop over the course of several minutes (for example, 2, 5, 10, 15, 20 or another number of minutes). Optionally, modeled changes in geometry and/or geometrical appearance simulate changes in muscle tone, e.g., vasodilation or vasoconstriction. The geometry and/or geometrical appearance is optionally modeled to show thickening and/or thinning, increase and/or decrease in surface height variation over a surface area, and/or another deformation, for example: dimpling, puckering, “goose-pimpling”, stretching, collapsing, expanding, distending, and/or shrinking. Lumenal structures optionally show change in cross-sectional shape (e.g., radius). 
     Optionally, one or more MAPs are changed in coordination with change in geometry and/or geometrical appearance. Adjusted MAPs optionally include, for example, those that can be modified to show increasing “redness” of the tissue with time to indicate swelling, “whiteness” or “greyness” to indicate loss of perfusion, color change to indicate change in temperature, etc. 
     As another example: in some embodiments, geometrical effects are applied to indicate contractile state (for example, of cardiac muscle, or gastrointestinal tract motion). Optionally, simulations of contraction are triggered by measurements of heartbeat and/or pulse phase, and/or of autonomic nervous system activity. The geometrical effects are preferably simulated to be in synchrony with what is expected to be actually occurring in the tissue that the simulation describes. However, the simulation is optionally different from reality in one or more respects; for example, amplitude is optionally adjusted. Larger-adjusted amplitude potentially emphasizes activity (e.g., vasoconstriction is exaggerated for clarity); smaller-adjusted amplitude potentially reduces distracting effects of activity (e.g., heart contraction is shown with reduced amplitude). 
     In some embodiments of the invention, dynamic adjustment of heart size in a rendered view of a simulated scene is based on heart rate. Optionally, this is implemented by dynamic adjustment of the geometrical rendering data representing the heart shape. In some embodiments, the adjusting comprises adjusting a static size of one or more heart chambers (e.g., a lumenal volume of the heart chambers, and/or a lumenal dimension of the heart chambers). In some embodiments, the adjusting comprises selecting a range of heart chamber sizes simulated cyclically over the course of each heartbeat cycle, e.g., between changing minimum and/or maximum sizes. 
     In some embodiments of the invention, the adjustment of heart chamber size to larger or smaller sizes is accompanied by corresponding inverse adjustment of heart wall sizes to smaller or greater thicknesses. 
     A potential advantage of these adjustments is to increase an accuracy and/or precision with which an intrabody probe (and in particular, an intracardial catheter probe) can be positioned, and/or with which the position of such a probe can be determined. In particular, positioning precision/accuracy with respect to one or more particular regions of heart wall tissue is potentially improved; for example, a nearest and/or a pointed-at region of heart wall tissue. A pointed at location is located along a longitudinal axis extending through the probe tip. 
     This in turn potentially increases certainty of achieving targeted effects of treatment administration (e.g., ablation), and/or of evaluating those treatment effects. Adjustment of a display to maintain an accuracy of positioning of the intracardial probe relative to the heart is implemented, in some embodiments, using one or more of the following methods. Optionally, positioning changes of a probe relative to a heart wall due to heart size changes are at least partially represented to an operator by simulating relative movements and/or scaling of a rendered representation of an intrabody probe in a display, while suppressing at least part of the size changes undergone by the actual heart chamber represented in the display. For example, if heart chamber beats are at least partially suppressed, then changing actual probe position relative to the beating heart chamber walls is optionally displayed by movements of the probe itself. Optionally, for example, if inter-pulse heart chamber size changes (e.g., due to heartbeat rate changes) are at least partially suppressed: scaling of detected intracardial probe movements is adjusted in a display so that relative positions of heart wall and probe remain synchronized between the actual tissue and probe pair, and a display of a simulated tissue and probe pair. 
     In some embodiments, the wave pattern to be simulated is determined at least in part from direct measurements of impulse wave propagation. In some embodiments, the wave pattern is simulated from a generic heart tissue or other tissue model. Optionally, the wave pattern is adapted according to knowledge about tissue state, for example, to indicate regions of weak and/or slow propagation attributed to states of fibrosis, perfusion state, and/or denervation. Optionally, moreover, the degree of impulse transmission is itself modulated in simulations managed by physiology simulator  1114 ; for example, to reflect transmission effects of treatment activities such as lesioning, tissue cooling, injections, etc. 
     At block  122 , in some embodiments, the current state of the geometry and/or geometrical appearance (optionally including changes to MAPs) is rendered to a visual representation of the tissue with which the interaction occurred. In some embodiments, the rendering makes use of 3-D graphics engine, for example as described in relation to display module  1130 , and/or in relation to  FIG. 8  and/or Table 1. 
     At block  124 , in some embodiments, the timer is incremented. 
     At block  126 , in some embodiments, a decision is made as to whether the loop is to continue (returning to block  120 ), or is terminated (stopping the flowchart). Time-evolving geometry and/or geometrical appearance optionally evolve, for example, cyclically (for example, repeating a movement pattern), transiently (disappearing at the end of a generation cycle, for example, in a simulation of cooling from a heated condition or re-warming from a cooled condition), and/or to a new steady-state appearance (for example, edema that develops to a fully developed state during a period after ablation, and then persists beyond the period during which the tissue is simulated). 
     It should be understood that sensing feedback is optionally integrated with the flowchart of  FIG. 1B  to create semi-open/semi-closed loop simulation: periods of open loop simulation producing results (e.g., geometrical effects) that are periodically verified, guided, and/or corrected according to sensed data. In some embodiments, for example, simulation of developing edema optionally proceeds independently as long as no further sensing data characterizing the edema state is available. However, if edema state is measured at some midpoint of the simulated edema time-course (for example, by use of dielectric measurements), then the simulation is optionally adjusted mid-course to reflect the sensed data. Adjustment is optionally immediate, and/or includes a period of interpolated adjustment (which potentially helps maintain the sense of presence in rendered views of the simulation scene). 
     Modes of Simulating Geometrical Effects 
     Cross-Sectional Perspective Views of Single-Lesion Progress 
     Reference is now made to  FIGS. 2A-2E , which illustrate a 3-D rendered display for indicating lesioning status to an operator, according to some exemplary embodiments of the present disclosure.  FIGS. 2A-2E  show a sequence of visual renderings of a single lesion over the course of the operation of an RF ablation probe to create it. This provides an example of how adjusted geometry and/or geometrical appearance can be used (optionally together with adjustment of MAPs) to convey to an operator a direct understanding of how use of an ablation probe is affecting target tissue. 
     In appearance,  FIGS. 2A-2E  comprise images (rendered in some embodiments in the rendering pipeline  1230  of a 3-D graphical game engine  1200 ) of an RF ablation probe  202  (corresponding, in some embodiments, to catheter probe  11 , wherein treatment element  8  is an ablation electrode, and treatment controller  13  operates to supply ablation energy to the RF ablation probe  202 ) and its position relative to tissue  205  targeted for ablation (e.g., part of body tissue region  7 ). Optionally, the rendering is in color, and/or otherwise using applied MAPs conveying the vital appearance (e.g., properties of roughness, specular reflection, etc.) of the tissue (black and white is shown herein for purposes of illustration). In some embodiments, RF ablation probe  202  is implemented as an object  1224  belonging to scene elements  1220  ( FIG. 8 ). Tissue  205  is optionally implemented as terrain  1221  or an object  1224  belonging to scene elements  1220 . 
       FIG. 2A , in some embodiments, shows the moment of initial contact between probe  202  and tissue  205 . Optionally, this view is triggered when contact is sensed by a sensor on the probe, such as a force sensor (an example of an “other sensor”  14 ) and/or dielectric sensing of contact (e.g., via dielectric property analyzer  22 ). The triggering, mediated in some embodiments by interaction analyzer  21  (and optionally taking advantage of a collision detection service  1213  of a game engine  1200 ), is optionally visually implemented as a jump from a wider angle view with the probe out of contact to a close-up of the probe contacting tissue. Optionally, transition from no-contact to contact (or vice versa) is shown by a short bridging animation. In some embodiments, continuous sensing of probe position and/or probe distance to the tissue wall (for example, by a position sensing subsystem comprising sensing electrodes  3 , body surface electrodes  5 , field generator/measurer  10 , and/or position analyzer  20  and/or position tracker  1107 ) allows any jump in a sensed transition between contact and non-contact to be smoothed out using actual position data. 
       FIG. 2B , in some embodiments, includes a visual indication of increased contact pressure between the tissue  205  and probe  202  comprising an indented region  204 . In  FIG. 2C  and then  FIG. 2D , the deeper indented region  204  shows that pressure has been increased still further. Optionally, the geometry and/or geometrical appearance modifications indicate sensed and/or calculated contact pressure; the appropriate transformation being calculated, for example, by contact physics simulator  1111  (which may in turn take advantage of motion physics services  1212  and/or collision detection service  1213  of game engine  1200 ). Although preferably modeled based on sensed contact quality and/or force data, distances of the indentation deformation need not be exactly corresponding to deflection distances in the real tissue. Rather, the visual degree of indentation shown is optionally considered as a proxy indicator for when the probe is out of contact, in poor contact, in a good position to ablate, and/or exerting excessive force on the tissue. Optionally, tissue  205  is shown in cross-section. 
     This has a potential advantage for allowing the indentation size to be clearly seen (as a deflection of the surface boundary  203 ). Optionally, the cross-sectional view also displays information about achieved lesion parameters such as lesion depth and/or lesion transmurality. Where cross-section is shown, transformation of geometrical position data is preferably used to show indentation changes. Geometrical appearance changes (e.g., by manipulation of normal mapping) are optionally used as well; but preferably not used alone, since the edge-on view of a cross-section highlights the spatial position of surface contours. 
     Additionally or alternatively, in some embodiments of the invention, transparency effects are applied to allow seeing into a targeted volume of tissue. For example, before ablation begins, a local region of tissue selected by the position of probe  202  is shown with increased transparency. Optionally, as portions of the tissue become lesioned, they are represented in simulated display as more opaque; creating an ablation “island” that directly shows the progress of lesioning. A potential advantage of the transparency approach is to allow representation of lesioning progress from any arbitrary 3-D point of view including the targeted tissue region. 
     In  FIG. 2C , in some embodiments, there has been a slight increase in sensed contact (shown by increased indentation of indented region  204 ), and ablation by delivery of RF energy to the tissue from probe  202  has begun. A superficial lesioned portion  208  of tissue  205  is now shown, for example, in a lighter shade (in color, lesioned portion  208  is optionally colored a light grey compared to darker red vital tissue). As lesioning proceeds (for example, to the intermediate state indicated in  FIG. 2D , and finally to the completed lesion  209  in  FIG. 2E ), lesioned portion  208  gradually increases in extent and/or degree of MAP change from the pre-lesioned state.  FIG. 2D  also indicates an increased pressure of contact by an indented region  204  in the tissue, while  FIG. 2E  shows pressure reduced. Optionally, the geometrical deformation changes as tissue ablation proceeds (even for a fixed pressure), for example to indicate changes in tissue elasticity and/or volume. 
     In some embodiments, this progression is based on inputs describing the operation of the treatment modality (ablation, in the illustrated example). For example, inputs describing power, duration, and/or contact quality are factored into a simulation (e.g., by an ablation physics simulator  1112 ) linked to how the tissue is displayed in its geometrical and/or material appearances. Optionally, operation of an ablation physics simulator  1112  includes thermal modeling (thermal simulation), based on local tissue region properties, for example, of local tissue type, thickness, thermal conductivity, and/or thermal exchange (e.g., between tissue and flowing blood). In some embodiments, at least part of the information providing local tissue type and/or thickness is obtained based on dielectric properties calculated from measurements of an alternating electromagnetic field obtained from a sensing electrode  3  at or near the position of the lesion  209 . 
     In some embodiments, calculated dielectric properties are used as indications of lesion state (e.g., size, transmurality, completeness and/or irreversibility), for example as described in International Patent Application No. PCT/IB32016/052690, the contents of which are incorporated by reference herein in their entirety. In in vitro studies, accuracy of transmurality has been found to be about ±1 mm. In prospective in vivo studies, 100% sensitivity and specificity in predicting lesion transmurality was found, while in humans, at least 90% specificity and sensitivity was found. Specificity is the percentage of actually well-ablated areas that were dielectrically identified as well-ablated; sensitivity is the percentage of actually partially ablated areas that were dielectrically identified as partially ablated. 
     Additionally or alternatively, the progression during lesioning is based on inputs describing sensed data reflecting one or more treatment effects, for example, measured temperature and/or changes in dielectric properties as tissue begins to break down. In general, probe-based temperature sensing, where available, is limited in resolution and/or depth, so that completely sensing-based adjustment may be difficult or impossible to obtain. However, sensed data may nevertheless be used as input to an ablation physics simulator  1112  that extrapolates lesion state through a 3-D block of tissue. Optionally, the extrapolated state is used as a corrective and/or calibrating input to an ablation physics simulator  1112 . 
     In some embodiments, one or more additional indications of house lesioning is proceeding are provided as part of the rendered image. For example, in  FIG. 2D , “steam”  207  is shown arising from the lesion point. Optionally, this is an indication that temperature has reached (and/or is maintained at) a certain threshold. The threshold may be, for example, a threshold at which lesioning occurs, a threshold above which a danger of effects such as steam pop or charring occurs, or another threshold. Different characteristics of the “steam” could be used, for example, conversion to black (or increasingly black) “smoke” in case of increased danger of excessive heating. In some embodiments of the invention, such steam- and/or smoke-like effects are implemented using a particle system facility provided by a graphical game engine. 
     Simulation of Tissue “Tenting” 
     Reference is now made to  FIGS. 3A, 3D, 3G, and 3J , which schematically represent a sequence of rendered views of a rendered catheter probe  11 A (representing a catheter probe  11 ) passing through a rendered tissue wall region  50 , according to some embodiments of the present disclosure. Reference is also made to  FIGS. 3B, 3E, 3H, and 3K , each of which schematically represents a graph of position versus time and measured contact versus time for the catheter probe  11  rendered as rendered catheter probe  11 A of  FIGS. 3A, 3D, 3G, and 3J , according to some embodiments of the present disclosure. Additionally, reference is made to  FIGS. 3C, 3F, 3I, and 3L , which schematically represent an ultrasound image at a cross-section of a heart at the atrial level, and corresponding to the sequence of  FIGS. 3A, 3D, 3G, and 3J , according to some embodiments of the present disclosure. 
     In some embodiments of the invention, the geometry of a three-dimensional simulation of a tissue wall region  50  is updated for displaying at a motion frame rate. The frame updating may be based on information received from one or more sensing modalities. The information may be received as catheter probe  11  interacts with a tissue wall. The two figure series of  FIGS. 3B, 3E, 3H, and 3K  and  FIGS. 3C, 3F, 3I, and 3L  represent different examples of sensed inputs related to tissue-catheter probe interactions, based on which (in any suitable combination) the tissue deformations of  FIGS. 3A, 3D, 3G, and 3J  are simulated. 
     The sensing modalities optionally comprise modalities that are non-imaging in nature (e.g., catheter probe position tracking data, and/or probe-sensed parameter time-course data), and/or comprise images giving incomplete view coverage of the simulated tissue region (for example, cross-sectional images). New sensing data is optionally acquired faster, slower, or at the same rate as the simulation appearance is updated. 
     Simulation and visualization updating is optionally in correspondence with states indicated by recently sensed data. For example when sampling is slow and/or intermittent, the current simulation state is optionally extrapolated from recent data according to one or more trends therein. Optionally, simulation updating is delayed from the acquisition of real-time data (for example, delayed to a buffer of at least two recent samples, and/or for example, by up to about 250 msec), which optionally allows smoothing interpolation between actually measured sensing data points in exchange for a certain amount of lag. 
     The X-axes of graphs  310  of  FIGS. 3B, 3E, 3H, and 3K  represent relative time. The Y-axes overlappingly represent sensed catheter probe position advance above a baseline position  311  (dashed lines including points  312 ,  314 ,  316 , and  318 ), and a measure of sensed catheter probe-tissue contact (solid lines including points  313 ,  315 ,  317 , and  319 ). The measure of sensed catheter probe-tissue contact may include, for example, force and/or dielectrically measured contact quality. The position of contacted region  302  of the actual tissue wall portion represented by rendered tissue wall region  50  relative to catheter tip  301  is represented in the graphs by dotted line  309 . 
     In some embodiments of the invention, probe-tissue contacts causing and/or represented by geometrical tissue deformations within the body are measured using one or more sensing modalities (for example, sensing by a force sensor, by sensing of impedance properties, or another sensing modality) that are only partially indicative of the overall geometrical effects of the contact. In some embodiments, the one or more sensing modalities provide information as to the variation over time of a limited number of parameters communicated in the interaction data; for example, one, two, three, or more parameters. 
     For example, in some embodiments, sensing information that encodes position of probe  11  is available. The position of probe  11  may be indicated by the interactive information absolutely and/or relative to the tissue portion represented by rendered tissue region  50 . In some embodiments, the sensing information may be indicative of contact quality and/or contact force measured to exist between probe  11  and the tissue portion represented by rendered tissue region  50 . In some embodiments, these measurements are used to guide changes made to simulated tissue region  50  and rendered probe  11 A, and the model rendered in turn to a sequence of images that visually simulate geometrical effects associated with the sensed information. 
     In some embodiments, the simulated model comprises a mechanical model of a tissue wall, including, for example, properties of tissue wall thickness, elasticity, density, velocity, and/or viscosity suitable to the tissue being simulated. Simulation of deformations optionally comprises applying a force commensurate with sensed forces and/or positions. Preferably, simulated geometrical effects are generated to faithfully visualize those effects that are actually occurring. In such embodiments, a mechanical model of the tissue wall is preferably provided with parameter values yielding realistic-looking behavior in reaction to applied simulated force and/or displacement. Graphical game engines commonly expose services for the simulation of physical interactions of scene elements, providing a potential advantage for ease of implementation. 
     Optionally or additionally, simulated geometrical effects may convey to an operator information about the contact, even though actual geometrical distortions (e.g., geometrical distortions introduced by touching contact with a probe, which may comprise pressing on tissue by the probe) are potentially different than the simulation shows: e.g., smaller in size, and/or modeled to simply indicate stages in deformation, without quantitative fidelity. In such embodiments, a simulated mechanical model is optionally implemented with parameters giving model behaviors that are potentially different from the actual case. Optionally, the model is implemented more simply; for example, as a mapping of a range of geometrically distorted wall shapes to one or more corresponding ranges of sensed input values. 
     Additionally or alternatively, in some embodiments, image information at least partially describing geometrical changes is available to the operator. The image information may be spatially incomplete: for example, an ultrasound cross-section that illustrates deformation in a planar cross-section of the tissue wall portion that an intrabody probe is penetrating. In some embodiments, an imaging modality other than ultrasound is used, for example, X-ray fluoroscopy. Preferably, the imaging modality provides images at a rate sufficient to guide manipulation of the catheter probe  11 , but this can optionally be a rate below motion frame rate; for example, at least 2-5 Hz.  FIGS. 3C, 3F, 3I, and 3L  represent a time sequence of ultrasound images measured from an ultra sound probe located in the lumen of a left atrium  321  (about at the apex of ultrasound images  320 ), as a probe  11  crosses into the left atrium  321  from a right atrium  322 . In the case illustrated, rendered tissue wall region  50  and/or imaged tissue wall portion  50 B represent a tissue wall portion comprising an interatrial septum which is to be crossed by a catheter probe  11  at a contact region corresponding to contacted region  302 , for example the foramen ovale (which may be a weak spot in the interatrial septum, or even a residual opening between the two atria). Although the ultrasound images  320  do not simultaneously show in imaged tissue wall portion  50 B the whole three dimensional structure of the tissue wall portion represented by rendered tissue wall region  50 , they potentially do reveal partial information about how the wall is deforming. In some embodiments, the partial information is used in a simulation of tissue-wall interaction dynamics to show a live-updated 3-D view of the tissue wall. For example, a curve extending through the image plane along the visualized extent of the interatrial septum is optionally used as a guide, to which a simulated tissue wall geometrical distortion in that plane is fit; and moreover, may be used as a boundary condition to which out-of-plane tissue wall geometrical distortions are also constrained. 
     Turning now to the images in sequence,  FIG. 3A  represents a rendered view showing the tip  301  of rendered catheter probe  11 A approaching the contacted region  302  of rendered tissue wall region  50 . Rendered tissue wall region  50  is shown in cross section; however, it should be understood that in other examples (not drawn) it may be shown from any other appropriate view angle. Optionally or additionally, rendered tissue wall region  50  is shown opaque, transparent, or in any suitable combination of the two. 
     In  FIG. 3A , the rendered tissue wall region  50  is shown in what is optionally its default and/or resting state geometry: for example, a geometry determined from a segmentation of an earlier MRI and/or CT scan (it should be understood that contact-independent behaviors such as periodic heart contractions are optionally superimposed on a default geometry). In some embodiments, based on the data of  FIG. 3B , a simulator is configured to recognize that this non-interacting geometry default should be shown. For example, a contact sensing parameter value  313  optionally indicates that there is no contact force exerted. Additionally or alternatively, the distance between catheter probe position  312  and the expected (optionally, sensed) wall position trace at dotted line  309  indicates that there is not yet any contact. 
     Additionally or alternatively, the ultrasound image of  FIG. 3C  shows no deformation of rendered wall region  50  in the vicinity of target contacted region  302 , and/or shows a separation between rendered wall region  50  and rendered catheter probe  11 A. Use of 3-D rendering to augment ultrasound imaging of tissue wall deformation (for example, as shown in  FIG. 3C ) has the potential advantage of converting a relatively abstract-appearing (cross-sectional, black and white, visually noisy) display of ultrasound-imaged anatomical structures into a solid looking indication of how forces from a catheter are interacting with a heart wall, on the basis of which the penetration operation can be guided. 
     In the second set in the sequence ( FIGS. 3D-3F ), wall contact has begun, as shown ( FIG. 3D ) by the deformation of the rendered tissue wall region  50  in contact with catheter probe tip  301 . Optionally ( FIG. 3E ), this simulation is generated to track the rising value of sensed contact (e.g., at point  315 ). Additionally or alternatively, the simulation is generated to track the forward movement of the probe tip  301  to point  314 ; optionally, the simulation scene is generated to track the forward movement with respect to expected or measured wall position trace at dotted line  309 . Additionally or alternatively, deformation of the imaged tissue wall portion  50 B in an ultrasound image ( FIG. 3F ) is used as a constraint to guide how the rendered tissue wall region  50  is geometrically distorted in 3-D. Optionally, contact between imaged tissue wall portion  50 B and catheter probe  11  is determined and/or verified from the ultrasound image as well. 
     In the third set in the sequence, ( FIGS. 3G-3I ), deformation has reached a maximum before catheter probe  11  breaks through the rendered tissue wall region  50  at contacted region  302  (foramen ovale). In the fourth set in the sequence ( FIGS. 3J-3L ), rendered catheter probe  11 A is shown having broken through the rendered tissue wall region  50 . From the sensing data of  FIG. 3K , the breakthrough is optionally inferred by the sudden drop in sensed contact, optionally in concert with the continued advance of the catheter probe  11 . Additionally or alternatively, the breakthrough is inferred from the sudden increase in distance between the catheter probe  11  and the actual tissue wall (inferred, for example, from a sudden change in the dielectric environment of an electrode associated with probe tip  301 ). In the ultrasound image of  FIG. 3L , the breakthrough is optionally inferred from a relaxation of the geometrical distortion of imaged tissue wall portion  50 B, and/or by the observation of a portion of catheter probe  11  extending on the other side of the imaged tissue wall portion  50 B. 
     Contact Simulation—Example of Simulation 
     Reference is now made to  FIGS. 10C-10D , which schematically represent aspects of geometrical deformation of a rendered tissue region  50  in contact with a rendered catheter probe  11 A, according to some embodiments of the present disclosure. In some embodiments of the invention, displayed interactions of a rendered catheter probe  11 A with a rendered tissue wall region  50  include geometrical effects which look like deformations of the tissue wall that visually convey the forces of their interaction. 
     Full geometrical deformation, including mesh deformation, is described herein in relation to the examples of  FIGS. 2A-2E and 3A-3L . In  FIGS. 10C-10D , a different mode of indentation is shown, wherein relatively limited (and, potentially, computationally less expensive) geometrical deformation is simulated by the use of one or more rendering techniques such as normal mapping, depth mapping, shadow mapping, depth of field simulation, and the like. 
     In  FIG. 10C , rendered catheter probe  11 A is shown in a sequence of positions relative to the rendered surface  1010  of a rendered tissue region  50  (optionally, rendered surface  1010  is rendered with the use of any suitable MAPs to provide it with a tissue-like visual appearance). Apart from the obvious lateral displacement, each position  1011 ,  1012 ,  1013  is also vertically displaced with respect to the tissue surface. However the only visual indication that positions  1012   1013  actually contact the surface (while 1011 does not) is a slight successive truncation of the catheter probe tip  301 . 
     In  FIG. 10D , all the elements of  FIG. 10C  and their relative positions remain the same, but there is shown in addition the effects of manipulation of the surface normal map in region  1021  and indentation region  1022 , assuming a light source that is to the left and somewhat behind the plane of the drawing (normal mapping is described in relation to  FIGS. 9A-9B ). The normal map manipulations have been chosen to give the appearance of geometrical changes—specifically, to indicate indentations in rendered surface  1010 . In some embodiments of the invention, this geometrical appearance change is optionally triggered by any suitable input related to probe-tissue contact, for example, contact force measurements, dielectric contact quality measurements, and/or relative position measurements of tissue and probe. Optionally, the normal map is also adjusted to reflect contact angle, for example, stretched along a dimension of elongated contact. Since no change in the underlying 3-D object geometry is required in order to produce this effect, there is a potential advantage for computational efficiency and/or reduced complexity of implementation compared to manipulation of the full 3-D geometry. 
     The normal-mapped mode of representing geometrical deformation is of potential use to an operator for helping to gauge contact quality before lesioning, particularly in views having a substantial elevation angle above the contacted surface. Optionally, views using normal mapping-type indentation are presented alongside views where 3-D geometrical distortion is used (for example, in cross-section, as discussed in relation to  FIGS. 2A-2E ). Optionally, normal mapping is used to exaggerate 3-D geometrical deformation, for example, to potentially increase emphasis and/or clarity. 
     Physiological Simulation—Example of Simulation 
     Reference is now made to  FIGS. 4A-4D , which schematically represent aspects of geometrical deformation of a rendered tissue region  50  due to an internal change such as edema, according to some embodiments of the present disclosure. Reference is also made to  FIGS. 10A-10B , which illustrate normal mapping superimposed on a rendered tissue region  50  in order to provide the geometrical appearance of a swelling, according to some embodiments of the present disclosure. Further reference is made to  FIGS. 5A-5B , which schematically represent global geometrical deformation of a tissue structure, for example, due to hydration state and/or more global edema than the example of  FIGS. 4A-4D , according to some embodiments of the present disclosure. 
     In  FIG. 4A , lesion  401  represents a recently formed lesion, for example, an RF ablation lesion. Over the course of a few minutes after RF ablation, tissue potentially reacts with a swelling response. In some embodiments of the invention, the swelling response is simulated (for example, as a function of time according to the method of  FIG. 1B , and/or based on measurements such as dielectric measurements that provide edema data) by one or both of increasing thickness in a region  403  surrounding lesion  401  (thickness changes can also be seen in the changing thickness of region  411  between  FIGS. 4B-4D ; comparison also can be made to the baseline surface boundary  50 A), and a change in color and/or texture in region  402  (represented by the partial rings in the drawing). 
       FIGS. 10A-10B  illustrate how normal mapping can be used to potentially enhance the appearance of changes in a tissue, for example as a result of treatment and/or injury. Lesion  401  again indicates a recently formed lesion. In  FIG. 10A , a surface is rendered as combination image  1000  by combining baseline surface texture  1006 , with an injury response overlay  1002 . In the combination image  1000  (in the example shown, the method of combination is partial transparency overlaying; optionally, another method of combining within a rendering pipeline  1230  is chosen) the injury response is detectable, but not clearly delineated.  FIG. 10B  adds to this an overlay  1003  generated from a normal map (assuming a light source to the left of the page) that describes a swelling in the region of the injury response. By changing the geometrical appearance of the tissue (though not necessarily the 3-D tissue geometry data itself), the injured region is potentially emphasized in the resulting view. It is to be understood that the 3-D geometry swelling of  FIGS. 4A-4D  are optionally combined with the normal mapping of  FIGS. 10A-10B . 
     In  FIGS. 5A-5B , generalized tissue thickening is represented by the change in tissue dimension between baseline thickness  420 A and swollen thickness  420 B. The thickening is optionally derived from measurements and/or extrapolation, for example, according to one or more of the methods of  FIGS. 1A-1B . Optionally, other changes are also made to represent tissue changes. As can be seen from the cross-sectional borders  422 ,  423  of tissue region  50 , the 3-D geometry of rendered tissue region  50  is optionally smoothed out with increasing swelling. Additionally or alternatively, normal mapping across the extent of surfaces  421 A,  421 B is adjusted as a function of swelling: for example, simulated wrinkles used to texture surface  421 A are optionally smoothed and/or stretched, for example to indicate a tauter appearance as at texture surface  421 B. 
     Example of Probe-Determined Camera Perspective 
     Reference is now made to  FIG. 11A , which schematically illustrates a rendered image  1150  rendered from a camera viewpoint  1154  looking at rendered tissue region  50  along an axis  1156  parallel to a rendered catheter probe  11 A, according to some embodiments of the present disclosure. Reference is also made to  FIG. 11B , which schematically illustrates a field of view  1152  projected from camera viewpoint  1154 , including indication of axis  1156 , according to some embodiments of the present disclosure. Indentation region  1022  indicates a region of touching contact between probe  11  and rendered tissue region  50 .  FIG. 11A  and  FIG. 11B  comprise views looking onto the same simulation scene. 
     In some embodiments, a camera viewpoint  1154  is defined (e.g., as part of the definition of a camera  1223 ,  FIG. 8 ) to be positioned on or near the body of a catheter probe  11 , and looking along an axis  1156  which is substantially parallel to the rendered catheter probe  11 A (termed a “probe-mounted” view herein). Insofar as the system tracks (using measured position) the location and orientation of the actual catheter probe  11  which the rendered orientation of rendered catheter probe  11 A simulates, camera viewpoint  1154  also tracks (by adjustment to match the orientation of the rendered catheter probe  11 A) the orientation of the actual catheter probe  11 . 
     It may be noted that rendered catheter probe  11 A appears in rendered image  1150  in a position similar to the position of hand-held tools seen in some “first-person” games, wherein a tool is shown on the screen in a position as if held before otherwise unseen avatar whose eyes define the camera position. In some embodiments of the present invention, this viewpoint configuration provides a potential advantage for obtaining a clear view of the field of operation of the probe, e.g., when it contacts tissue. 
     Optionally, registration between the probe and the viewpoint may comprise any other suitable combination of position and orientation. For example, looking back along a catheter is potentially useful for obtaining a sense of what freedom exists in how the catheter probe can be presently positioned. Looking at the catheter itself from a more distant position potentially provides an improved sense of how the catheter relates to its overall surroundings. In some embodiments, viewpoint optionally shifts (automatically and/or under manual control) depending on what action is being performed; for example, a probe-mounted view like that of  FIG. 11A  is optionally used for selection of where a probe should be advanced to contact tissue, while a vantage point more distant from the probe may be selected to show details of how probe and tissue interact once contact is made (for example, as shown in the sequence of  FIGS. 3A, 3D, 3G, and 3J ). In some embodiments, the angular size of the field of view (area subtended within the frame of the rendered image) is selected to be larger or smaller. A larger angular size provides a potential relative advantage in helping an operator orient within a simulated environment, while a smaller angular size is optionally used to magnify details and/or reduce simulated optical distortion in the rendered view. 
     General 
     It is expected that during the life of a patent maturing from this application many relevant catheter probes will be developed; the scope of the term catheter probe is intended to include all such new technologies a priori. 
     As used herein with reference to quantity or value, the term “about” means “within ±10% of”. 
     The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean: “including but not limited to”. 
     The term “consisting of” means: “including and limited to”. 
     The term “consisting essentially of” means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure. 
     As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof. 
     The words “example” and “exemplary” are used herein to mean “serving as an example, instance or illustration”. Any embodiment described as an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. 
     The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features except insofar as such features conflict. 
     As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts. 
     As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition. 
     Throughout this application, embodiments of this invention may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as “from 1 to 6” should be considered to have specifically disclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”, “from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. 
     Whenever a numerical range is indicated herein (for example “10-15”, “10 to 15”, or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases “range/ranging/ranges between” a first indicate number and a second indicate number and “range/ranging/ranges from” a first indicate number “to”, “up to”, “until” or “through” (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. 
     It is the intent of the Applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is/are hereby incorporated herein by reference in its/their entirety. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.