Patent Publication Number: US-2022225924-A1

Title: Automatic mesh reshaping of an anatomical map to expose internal points of interest

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electroanatomical (EA) mapping, and particularly to automatic editing of cardiac EA maps. 
     BACKGROUND OF THE INVENTION 
     Software-based editing tools for assisting in the interpretation of a mapped cavity of an organ were previously proposed in the patent literature. For example, in the field of dentistry, U.S. Patent Application Publication No. 2006/0286501 describes using a computer to create a plan for repositioning an orthodontic patient&#39;s teeth. The computer receives an initial digital data set representing the patient&#39;s teeth at their initial positions and a final digital data set representing the teeth at their final positions. The computer then uses the data sets to generate treatment paths along which the teeth will move from the initial positions to the final positions. In some embodiments, the individual tooth models include data representing hidden tooth surfaces, such as roots imaged through x-ray, CT scan, or MRI techniques. Tooth roots and hidden surfaces also can be extrapolated from the visible surfaces of the patient&#39;s teeth. 
     As another example, U.S. Patent Application Publication No. 2017/0325891 describes methods directed at generating a three-dimensional surface representation of an anatomic structure such as a heart cavity. More specifically, the three-dimensional surface representation of the anatomic structure is constrained relative to one or more anchor portions corresponding to received input regarding the location of anatomic features of the anatomic structure. The resulting three-dimensional surface representation includes salient features of the anatomic structure and, therefore, can be useful as visualization tools during any of various different medical procedures, including, for example, cardiac ablation. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention that is described hereinafter provides a method including receiving or generating a volume map of at least a portion of a cavity of an organ of a body including a plurality of mapped locations, and a point cloud of locations in the cavity marked for treatment. The volume map is updated by removing a portion of the mapped locations, so that the locations marked for treatment fall on a surface of the volume map. Using the updated volume map, a map of at least a portion of the cavity is generated, the map including the locations marked for treatment. The map is displayed to a user. 
     In some embodiments, removing the portion of the mapped locations includes identifying one or more of the locations marked for treatment that fall in an interior of the volume map, and removing the portion so that the identified locations marked for treatment fall on the surface of the volume map. 
     In some embodiments, identifying a location marked for treatment that falls in the interior of the volume map includes determining that a vector, from the location marked for treatment to a respective projected location on the surface, is opposite to an outward-pointing normal to the surface at the projected location. 
     In an embodiment, the locations marked for treatment are locations on a cardiac wall tissue, and are marked for ablation. 
     In another embodiment, generating the map includes generating an electroanatomical (EA) map of at least a portion of the wall tissue. 
     In some embodiments, removing the portion of the mapped locations includes projecting the locations marked for treatment to respective locations on the surface of the volume map, and removing the portion of the volume map that includes a surface connecting the locations marked for treatment with the projected locations. 
     In some embodiments, removing the surface connecting the locations marked for treatment with the projected locations includes removing a surface defined as a surface between a first curve generated by interconnecting the locations marked for treatment, and a second curve generated by interconnecting the projected locations. 
     In other embodiments, removing the portion of the volume includes defining, between each location marked for treatment and a respective projected location on the surface, a respective distance embedded in the surface, and defining the removed portion based on the distance. 
     In an embodiment, defining the removed portion of volume map includes defining a sphere having a diameter corresponding to the distance. 
     In another embodiment, wherein displaying the map to the user includes presenting one or more icons at the locations marked for treatment. 
     There is additionally provided, in accordance with another embodiment of the present invention, a system including a memory and a processor. The memory is configured to store a plurality of mapped locations acquired in a cavity of an organ of a body, and a point cloud of locations in the cavity marked for treatment. The processor is configured to (i) receive or generate a volume map of at least a portion of the cavity including the plurality of mapped locations, (ii) update the volume map by removing a portion of the mapped locations, so that the locations marked for treatment fall on a surface of the volume map, (iii) using the updated volume map, generate a map of at least a portion of the cavity, including the locations marked for treatment, and (iv) display the map to a user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
         FIG. 1  is a schematic, pictorial illustration of a system for electroanatomical (EA) mapping, in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a volume-rendered semi-transparent EA map of a left atrium showing locations marked for ablation and respective projected locations on a surface of the EA map, in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  is a flow chart that schematically illustrates a method for exposing locations of a cardiac cavity marked for ablation, in accordance with an exemplary embodiment of the present invention; and 
         FIGS. 4A and 4B  are volume-rendered non-transparent maps of a cardiac cavity showing respectively a surface that hides icons of locations for ablation, and the mesh reshaped surface with the icons exposed at locations marked for ablation, in accordance with exemplary embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Overview 
     A cavity of an organ of a patient, such as a cardiac cavity, also called hereinafter cardiac chamber, can be mapped (e.g., electroanatomically mapped) using a mapping catheter having one or more suitable sensors, such as electrodes, fitted at its distal end for mapping within the organ. Using location signals generated by the various sensors, a processor may calculate the sensor locations within the organ (e.g., the locations of sensing electrodes inside the cardiac cavity). Using the calculated locations, the processor may further derive an anatomical map of the cavity surface. In case of a cardiac cavity (e.g., cardiac chamber), the processor may derive an electroanatomical (EA) map of the cavity surface. In some embodiments, such an EA map also graphically indicates arrhythmogenic locations over the cavity wall tissue that should be ablated for treatment of arrhythmia. 
     Typically, therefore, before a cardiac ablation procedure, the cardiac chamber is mapped, to (i) obtain a volume representation of the cardiac chamber anatomy, and (ii) acquire a point cloud of locations in the cardiac chamber to be marked for ablation. At least some of the locations marked for ablation are typically located along a curve. For example, in a fast anatomical mapping (FAM) of a cardiac chamber, point locations for ablation on an inner surface of the cavity are drawn using acquired EA data. Subsequently, a physician may ablate the locations along the curve to block an aberrant electrophysiological signal, as in the case of isolating a pulmonary vein ostium in a left atrium. 
     However, erroneous catheter locations may also be acquired and automatically added to a FAM-constructed cavity surface during FAM reconstruction. Examples of such undesired data points include cavity wall locations distorted by being pushed outward by the catheter, as well as incorrect wall locations due to respiration-induced movement. 
     The accumulation of such undesired locations affects the accuracy of the reconstructed EA map. To address these inaccuracies, during or after acquisition, a physician, or a specialist helping the physician, may manually edit the surface that is generated from the acquired points to correct for the errors. This manual editing typically involves erasing locations and/or removing (“shaving”) entire portions from the computed surface. However, this manual editing is a time-consuming process. 
     Moreover, in some cases erroneous catheter locations may obstruct or hide markings that point to wall tissue locations selected for treatment, such as cardiac wall tissue locations selected for ablation. Typically, while locations for ablation are marked (e.g., overlaid) on the map as icons (e.g., “visitags”), some of the icons may become invisible because they appear inside the chamber, rather than on its outer surface, due to the above, or other, mapping errors. 
     Embodiments of the present invention use an underlying assumption that the mapped locations marked for treatment (e.g., ablation) are correct, and that any obstruction of such marks by other locations on the cavity wall is due to erroneous mapping of the wall tissue. Such mapping errors cause locations marked for treatment to erroneously appear inside the chamber. This results in icons (e.g., visitag icons) pointing at these locations being hidden in a typical, non-transparent view of the map of the cavity of the organ. 
     To overcome such errors, a processor corrects the mapping of the cavity so that the locations marked for treatment fall on the cavity wall. In an embodiment, the processor receives or generates an EA map of at least a portion of a volume of a cardiac cavity, and a point cloud of locations marked for treatment (e.g., ablation). The processor identifies that one or more of the locations marked for treatment fall in an interior of the volume, and in response updates the volume by removing a portion of the mapped locations, so that the locations marked for treatment fall on a surface of the volume of the chamber map. Using the updated EA mapping data, the processor generates a map of at least a portion of the cavity, comprising the locations marked for treatment, and displays the map to user. 
     In another embodiment, to remove a portion of the mapped locations, the processor projects the locations marked for treatment onto a modeled surface of the cavity. The processor then joins the locations marked for treatment by a first spline, and joins the projected locations by a second spline. A “ball rolling” algorithm is then used: A “ball,” having a variable radius found by connecting respective locations marked for treatment and projected locations, is “rolled” along the two splines, and anatomical locations in the chamber volume and surface are removed from the cloud. The chamber surface is then reconstructed using the updated data set to reveal the original locations marked for treatment (e.g., to make their icons visible in an external view of the model). In general, a shape other than ball can be used, such as of an ellipsoid having a variable width and diameter. 
     By exposing hidden landmarks (e.g., icons) of locations marked for treatment, the disclosed technique may assist the physician to improve the quality of complicated diagnostic tasks performed during diagnostic catheterizations, such as marking (e.g., by visitag icons) tissue locations mapped for ablation. Another advantage of the disclosed technique is reducing the editing time of portions of the EA map, e.g., when done manually for this purpose. 
     System Description 
       FIG. 1  is a schematic, pictorial illustration of a system  21  for electroanatomical (EA) mapping, in accordance with an embodiment of the present invention.  FIG. 1  depicts a physician  27  using a Pentaray® EA mapping catheter  29  to perform an EA mapping of a heart  23  of a patient  25 . Catheter  29  comprises, at its distal end, one or more arms  20 , which may be mechanically flexible, each of which is coupled with one or more electrodes  22 . During the mapping procedure, electrodes  22  acquire and/or inject unipolar and/or bipolar signals from and/or to the tissue of heart  23 . 
     A processor  28  in a console  30  receives these signals via an electrical interface  35 , and uses information contained in these signals to construct an EA map  40  that processor  28  stores in a memory  33 . During and/or following the procedure, processor  28  may display EA map  40  on a display  26 . User controls  32  of a user interface  100  enable physician  27  to communicate with processor  28  and command editing and/or highlighting portions of EA map  40 . Controls  32  may include, for example, a trackball and control knobs, as well as a keyboard. Other elements of user interface  100  may include touch screen functionality of display  26 . 
     During the procedure, a tracking system is used to track the respective locations of sensing electrodes  22 , such that each of the signals may be associated with the location at which the signal was acquired. For example, the Active Catheter Location (ACL) system, made by Biosense-Webster (Irvine Calif.), which is described in U.S. Pat. No. 8,456,182, whose disclosure is incorporated herein by reference, may be used. In the ACL system, a processor estimates the respective locations of the electrodes based on impedances measured between each of the sensing electrodes  22 , and a plurality of surface electrodes  24 , that are coupled to the skin of patient  25 . For example, three surface electrodes  24  may be coupled to the patient&#39;s chest, and another three surface electrodes may be coupled to the patient&#39;s back. (For ease of illustration, only one surface electrode is shown in  FIG. 1 .) Electric currents are passed between electrodes  22  inside heart  23  of the patient and surface electrodes  24 . Processor  28  calculates an estimated location of all electrodes  22  within the patient&#39;s heart based on the ratios between the resulting current amplitudes measured at surface electrodes  24  (or between the impedances implied by these amplitudes) and the known locations of electrodes  24  on the patient&#39;s body. The processor may thus associate any given impedance signal received from electrodes  22  with the location at which the signal was acquired. 
     The example illustration shown in  FIG. 1  is chosen purely for the sake of conceptual clarity. Other tracking methods can be used, such as those based on measuring voltage signals. Other types of sensing catheters, such as the Lasso® Catheter (produced by Biosense Webster) or a basket catheter may equivalently be employed. Contact sensors may be fitted at the distal end of EA mapping catheter  29 . As noted above, other types of electrodes, such as those used for ablation, may be utilized in a similar way and fitted to electrodes  22  for acquiring the needed location data. Thus, an ablation electrode used for collecting location data is regarded, in this case, as a sensing electrode. In an optional embodiment, processor  28  is further configured to indicate the quality of physical contact between each of the electrodes  22  and an inner surface of the cardiac chamber during measurement. 
     Processor  28  typically comprises a general-purpose computer with software programmed to carry out the functions described herein. In particular, processor  28  runs a dedicated algorithm as disclosed herein, including in  FIG. 3 , that enables processor  28  to perform the disclosed steps, as further described below. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. 
     Automatic Mesh Reshaping of an Anatomical Map for Internal Points of Interest  FIG. 2  is a volume-rendered semi-transparent EA map  200  of a left atrium showing locations marked for ablation ( 202 ) and respective projected locations  204  on a surface of the EA map, in accordance with an embodiment of the present invention. 
       FIG. 2  shows a map for clarity and simplicity of presentation only. The disclosed process does not necessarily require generating such an initial map. Rather, acquisition data comprising locations is received in a processor, and the processor applies the disclosed steps to the mapped volume. 
     As seen, mapped locations marked for ablation  202  are each along a circumference of an ostium  222  of a pulmonary vein. The mapped location may define a contour (not shown) along which a subsequent ablation is performed to isolate an arrhythmia. 
     As noted above, errors in map  200  may cause icons of locations  202  to be hidden in a non-transparent view. 
     In one embodiment of the disclosed technique, the processor identifies only locations  202  marked for treatment that fall in an interior of the mapped volume by determining if a vector between each location  202  marked for treatment and its respective projected surface location  204  is opposing an outward-pointing normal to the surface of the cavity at the projected location. Subsequently, the processor projects locations  202  to surface locations  204 , in order to subsequently generate a map in which icons of locations  202  are visible, as described below. 
     In another embodiment, the processor projects all points marked for treatment, without attempting to identify which of the locations is internal. If a point is already on the surface, then the rolled ball diameter, or local volume to remove, will be zero or negligible. 
     While the shown cavity is of a left atrium, the description holds for cavities of other organs and for different treatments than ablation. 
       FIG. 3  is a flow chart that schematically illustrates a method for exposing locations of a cardiac cavity marked for ablation, in accordance with an embodiment of the present invention. The algorithm, according to the presented embodiment, carries out a process that begins with processor  28  receiving an EA map of at least a portion of a volume of a cardiac chamber, and a point cloud of locations marked for ablation, at a data receiving step  302 . At this stage some of the location marked for ablation may comprise hidden icons. 
     Next, processor  28  projects the locations marked for ablation to respective locations on a surface of the chamber map volume, at a data projection step  304 . 
     At a data connection step  306 , processor  28  joins locations marked for ablation by a first spline, and joins the respective projected locations found in step  304  by a second spline. 
     Next, at a point cloud updating step  308 , processor  28  generates an updated volume by automatically removing portions of the volume that comprise a surface connecting the locations marked for ablation with the projected locations. For example, the processor “rolls” a ball having a variable diameter (or “rolls” the aforementioned ellipsoid) along the two splines and removes from the chamber map volume the intersection between the chamber volume and the rolled ball, or ellipsoid. 
     At an EA map generation step  310 , using the updated mapped data, or chamber volume map, processor  28  generates an EA map, such as map  440  shown below in  FIG. 4B , of the portion of the cardiac cavity comprising visible icons that mark ablation locations. 
     Finally, at a map displaying step  312 , processor  28  presents the EA map to a user. 
     The example flow chart shown in  FIG. 3  is chosen purely for the sake of conceptual clarity. For example, in alternative embodiments, the cavity is of an organ other than a heart. 
     Reshaped Mesh of an Anatomical Map 
       FIGS. 4A and 4B  are volume-rendered non-transparent EA maps  400  and  440  of a cardiac cavity showing, respectively, a surface  405  that hides ( 402 ) icons of locations for ablation, and the mesh reshaped surface with the icons ( 404 ) exposed at locations marked for ablation, in accordance with embodiments of the present invention. 
     As seen in  FIG. 4A , almost all the icons marking locations  402  for ablation on two ostia of a pulmonary vein of a left atrium are hidden under surface  405 . In  FIG. 4B , on the other hand, the regenerated surface  410  exposes respective locations, as shown by icons  404 . 
     A physician may use map  440  to perform the required ablation. 
     It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.