Mapping cavity

Abstract

To map a cavity.SOLUTION: A method is provided, consisting of acquiring data representative of a volume of a cavity of an organ, presenting on a display an electroanatomical (EA) map of a surface, generated in response to the data, enclosing the volume, and receiving input from a user, the input including a selected section of the EA map. The method includes, in response to the user input, locking a portion of the volume to subsequent updates of the data when updating the EA map, the portion of the volume consisting of the selected section of the EA map.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to mapping, and more particularly to mapping cavities. [Background technology]

[0002] During a medical procedure on a cavity, such as a heart chamber, the cavity may be initially mapped and then remapped to observe changes to the heart chamber resulting from the procedure. It is important that both the initial and subsequent mappings be as efficient as possible. [Brief explanation of the drawings]

[0003] The present disclosure will be understood from the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] 1 illustrates a catheter-based electrophysiological mapping and ablation system according to an example of the present disclosure. [Figure 2] FIG. 1 is a flow diagram of steps performed to map the surface of a cavity in a patient's organ, according to an example of the present disclosure. [Figure 3A] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3B] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3C] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3D] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3E] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3F] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3G] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3H] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. [Figure 3I] FIG. 1 illustrates steps of a flow diagram according to an example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0004] Description of the Examples overview In procedures on a heart chamber, such as an ablation procedure, the chamber is typically first mapped to generate an electroanatomical (EA) map of the chamber. Mapping may be performed using a fast anatomical mapping (FAM) method, in which a processor registers and acquires the locations of voxels on the surface of the chamber with a catheter and generates an EA map from the locations. During or after voxel acquisition, errors in the surface may be corrected by "shaving" the surface to remove inaccurately acquired voxels. Shaving may be performed manually by a physician or a technician assisting the physician and / or automatically.

[0005] The cavity may typically be remapped after the procedure is performed. During remapping, shaved voxels may be reacquired, resulting in the need for repeated shaving. Repeated shaving can be time-consuming and involve many map changes and intermediate results. Both the required time and map changes reduce the efficiency of the procedure.

[0006] Examples of the present disclosure improve the efficiency of remapping. The first shaved voxels and voxels adjacent to the shaved voxels are marked, and the catheter is locked to prevent acquisition of the marked voxels during remapping. The processor then performs remapping when there are no locked voxels, so there is no need to repeat shaving.

[0007] System Description In the following description, similar elements will be identified by the same numerals and, where necessary, distinguished by adding a letter as a suffix to the numerals.

[0008] Reference is now made to FIG. 1 , which illustrates a catheter-based electrophysiology mapping and ablation system 10 according to one example of the present disclosure. The system 10 includes multiple catheters that are percutaneously inserted by a physician 24 through a patient's vascular system into a vascular structure or cavity, such as cavity 31, of the heart 12. Typically, a delivery sheath catheter 37 is inserted into the left or right atrium near a desired location in the heart 12. Multiple catheters can then be inserted into the delivery sheath catheter to reach the desired location. The multiple catheters may include catheters dedicated to sensing intracardiac electrogram (IEGM) signals, mapping catheters, ablation catheters, and / or catheters dedicated to both sensing and ablation. An exemplary catheter 14 configured for sensing IEGM signals and mapping is illustrated herein.

[0009] The catheter 14 is an exemplary focal catheter that includes at least one electrode 26 distributed on the catheter's distal tip 28. The catheter 14 additionally includes at least one position sensor 29 embedded at or near the distal tip 28 for tracking the position and orientation of the distal tip. In the disclosed example, the position sensor 29 is a magnetic-based position sensor that includes three magnetic coils for sensing three-dimensional (3D) position and orientation.

[0010] The magnetic-based position sensor 29 may operate in conjunction with a location pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predetermined working volume. The real-time position of the distal tip 28 of the catheter 14 may be tracked based on the magnetic fields generated by the location pad 25 and sensed by the magnetic-based position sensor 29. The real-time position includes the location of the position sensor and its orientation. For details of magnetic-based position sensing technology, see U.S. Patent Nos. 5,5391,199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; and 6,892,091.

[0011] The system 10 includes one or more electrode patches 38 positioned for skin contact on the patient 23 to establish a position reference for the location pads 25 and impedance-based tracking of the electrodes 26. For impedance-based tracking, current is directed to the electrodes 26 and sensed at the electrode skin patches 38, allowing the position of each electrode to be triangulated via the electrode patches 38. For details of impedance-based position tracking technology, see U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0012] Recorder 11 displays electrograms 21 captured by body surface ECG electrodes 18 and intracardiac electrograms (IEGMs) that may be captured by electrodes 26 on catheter 14. Recorder 11 may include pacing capability for pacing the cardiac rhythm and / or may be electrically connected to a stand-alone pacer.

[0013] System 10 may include an ablation energy generator 50 adapted to deliver ablation energy to one or more of electrodes 26. The energy generated by ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, including unipolar or bipolar high-voltage DC pulses, such as may be used to effect irreversible electroporation (IRE), or a combination thereof.

[0014] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between the catheters, electrophysiology equipment, a power source, and a workstation 55 that controls the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, location pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for implementing real-time calculations of catheter position and performing ECG calculations.

[0015] The workstation 55 includes a processor 22 having memory, a memory or storage device having appropriate operating software stored therein, and user interface functionality. The workstation 55 may optionally provide multiple functions, including (1) modeling the endocardial anatomical structure in three dimensions (3D) and rendering a model or anatomical map 20 for display on the display device 27, (2) displaying activation sequences (or other data) compiled from recorded electrograms 21 in a representative visual representation or image superimposed on the rendered anatomical map 20 on the display device 27, (3) displaying the real-time position and orientation of the distal tip 28 within the cardiac chamber, and (4) displaying sites of interest, such as locations where ablation energy has been applied, on the display device 27. The display device 27 has a screen 27S. One commercially available product embodying elements of system 10 is available as the CARTO™ 3 system, available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0016] Figure 2 is a flow diagram 100 of steps performed in mapping the surface of a cavity 31 of an organ 12 of a patient 23, and Figures 3A-3I illustrate steps according to one example of the present disclosure. In the following description, organ 12 is assumed to include heart 12, also referred to herein as heart 12, and cavity 31 is assumed to include cavity 31, also referred to herein as cavity 31; one skilled in the art can adjust the description mutatis mutandis for other cavities and / or organs of patient 23.

[0017] FIG. 3A schematically illustrates an initial map 150 of the surface of cavity 31, also referred to herein as surface 150. In generating the mapping, cavity 31 is assumed to be within a cube-like volume 170 composed of rectangular prism voxels, as shown in FIG. 3B, which is within a reference frame defined by location pads 25. Cube-like volume 170 is depicted on Cartesian x, y, and z axes. In one example, the voxels of cube-like volume 170 are x, y, and z cubes with 0.8 mm edges, although in other examples, the voxels may have different edge values ​​and / or may not be cubic. Cavity 31 is assumed to be composed of cavity x, y, and z voxels 172, which are a subset of the voxels of cube-like volume 170.

[0018] To generate the initial map 150, in a data collection step 104, the physician 24 inserts the distal tip 28 into the cavity 31 and moves the distal tip within the cavity. While the distal tip is within the cavity, the processor 22 records multiple positions of the position sensor 29 and the orientation of the sensor at each position. The dimensions of the distal tip 28 are known and provided to the processor 22. From the distal tip dimensions and the recorded position and orientation of the sensor 29, the processor 22 identifies and acquires a set of voxels of a volume 170, also referred to herein as data voxels, that correspond to the volume occupied by the distal tip. It will be understood that the acquired set of data voxels is a subset of the cavity voxels 172.

[0019] Once the processor 22 acquires a set of voxels corresponding to multiple locations of the distal tip, the processor analyzes the voxels to find a three-dimensional (3D) net of line segments connecting the voxels surrounding the acquired voxels. The net includes a set of line segments connecting data voxels (referred to herein as surface voxels) outside the acquired voxels. In one example, the surface voxels and the set of line segments connecting the surface voxels can be found using a ball pivot algorithm that forms the surface voxels and line segments into a set of connected triangles. In the disclosed example, the physician 24 may be able to set the resolution of the generated net by changing the diameter of the ball, essentially changing the size of the triangles in the net.

[0020] The generated 3D net encloses all acquired data voxels except for the surface voxels that are connected by the net.

[0021] The processor 22 uses interpolation to fill the net triangles to calculate a 3D surface and presents the calculated surface to the physician 24 on the device 27. The presented surface corresponds to the calculated surface of the cavity 31.

[0022] In a "shaving" step 108, physician 24 uses tools on device 27 to edit the surface generated in step 104. Typically, the generated surface will have errors that are apparent to the physician, caused by, for example, the beating of heart 12, the breathing of patient 23, and / or tenting of the walls of cavity 31 when the distal tip contacts the wall. The tools used to modify the surface allow physician 24 to identify to processor 22 areas of the surface that appear to be inaccurate. For each identified inaccurate surface area, processor 22 registers the 3D locations of the surface voxels associated with that area, recalculates the net assuming the registered surface voxels do not exist, and presents a recalculated 3D surface based on the recalculated net to physician 24 on device 27.

[0023] Figure 3C shows a first recalculated surface 154, where the physician 24 modifies the initial surface 150 within region 158 and the processor 22 recalculates the surface as described above. Figure 3D shows a second recalculated surface 174, where the physician 24 modifies the initial surface 150 within region 178 and the processor 22 recalculates the surface as described above.

[0024] Examples of the present disclosure assume that at some point after the performance of steps 104 and 108, the initial mapping of cavity 31 performed in step 104 is repeated in a subsequent mapping operation.

[0025] Prior to subsequent mapping, in an identification step 112, processor 22 records the 3D locations of surface voxels associated with the modified initial surface, i.e., surface voxels associated with region 158 and surface voxels associated with region 178, and identifies a set of cavity voxels that are proximate to the recorded surface voxels. As described below, identified cavity voxels that are proximate to the recorded surface voxels are "locked" so that processor 22 does not record the locations of the locked voxels during subsequent mapping.

[0026] Examples of the present disclosure provide two alternative methods for identifying voxels adjacent to a recorded surface voxel: a morphological closure method and an extrusion method. Both methods are described below. The morphological closure method is described with reference to FIG. 3C, and the extrusion method is described with reference to FIG. 3D.

[0027] Morphological closure method In the morphological closure method, processor 22 applies a dilation and erosion algorithm to each of the recorded surface voxels. The algorithm allows the processor to close gaps between surface voxels separated from each other by a predetermined distance. After applying the algorithm and identifying the gap voxels that form the gap, processor 22 checks for closed subvolumes, or voids, within the volume containing the set of surface voxels and the identified gap voxels. The processor identifies the voxels within each void as filled voxels.

[0028] In the disclosed example, the processor uses a cube with an edge length of 5 voxels as the kernel for the dilation and erosion algorithm, resulting in a kernel containing a cube of 125 voxels. In the dilation portion of the algorithm, the processor dilates all recorded surface voxels, generating, for each given surface voxel, a set of 124 dilated voxels that surround the given voxel.

[0029] The erosion portion of the algorithm uses a kernel to check whether the dilated voxels generated by the dilation are retained. To check for retention, the processor applies the kernel to all voxels generated by the dilation and rejects a given one of these dilated voxels unless the kernel is completely filled by other dilated voxels or surface voxels.

[0030] Upon completion of the algorithm, there will be a result set of voxels, some of which, but not necessarily all, may close gaps between surface voxels. The voxels in the result set are also referred to herein as gap voxels.

[0031] As a first example of the application of the algorithm, for a single surface voxel, only the single surface voxel comprises the result set after the implementation of the algorithm. As a second example of the algorithm, for two surface voxels separated by a single voxel, the two surface voxels and the separating voxel comprise the result set after the implementation of the algorithm.

[0032] After applying the dilation and erosion algorithms to all recorded surface voxels, the processor analyzes the resulting set of voxels, i.e., gap voxels, for closed three-dimensional voids within the set. In a disclosed embodiment, the analysis may be performed by applying a flood-filling algorithm to the combined set of surface voxels and gap voxels within the cube-like volume 170 and recording which voxels other than those in the combined set are not filled. It will be understood that the unfilled voxels correspond to gap voxels within the combined set of voxels, and these voxels are referred to herein as gap voxels.

[0033] To complete the identification step 112 for the morphological closing method, the processor 22 saves the locations of the surface voxels recorded in step 108 and the locations of the gap and void voxels discovered in step 112 .

[0034] In the disclosed example, regions corresponding to the locations of the saved voxels may be displayed on the recalculated surface 154 to the physician 24 using the device 27. Figure 3F schematically shows region 162 corresponding to the saved voxels from region 158.

[0035] Two-dimensional diagram of the morphological closure method As described above, in identification step 112, processor 22 analyzes the three-dimensional surface voxels recorded in step 108. Figure 3E provides a two-dimensional view of the analysis stage of step 112. The illustration assumes that processor 22 has acquired and recorded surface voxels 210 in step 108. Surface voxel 210 is assumed to be located within a section of a two-dimensional (2D) rectilinear grid 204 that is part of cube-like volume 170, with rectangles in the grid indicating possible other voxels 200, also referred to as empty voxels 200 of the grid.

[0036] In the 2D example of Figure 3E, it is assumed that the processor uses a square kernel 208 of 5x5 voxels when applying the dilation and erosion algorithm. Gap voxels 220 resulting from applying the kernel are shown in the figure. As shown, the algorithm generates gap voxels 220A and 220B between surface voxels 210A and 210B, and gap voxel 220C between surface voxels 210C and 210D. (Note that no gap voxel is generated between surface voxels 210E and 210F.)

[0037] Once the processor 22 has scanned all of the surface voxels 210 acquired in step 108, the processor applies a flood-filling algorithm to the grid 204. The algorithm detects voids 224 in the grid, and the processor records the locations of filled voxels 230 within the voids.

[0038] Extrusion Method 3G and 3H illustrate the extrusion method. FIG. 3G shows a surface 174 as presented on the screen 27S of the device 27, and FIG. 3H illustrates the process applied by the processor 22 in implementing the method. In contrast to the morphological method described above, in the extrusion method, a user, assumed herein to be the physician 24, uses a tool on the device 27 to draw a boundary 180 on the surface 174, typically enclosing an area 178. The boundary 180 forms a perimeter surrounding an enclosed area 184. The enclosed area may be any convenient shape selected by the physician 24; in the disclosed example shown in FIG. 3G, the boundary 180 and enclosed area 184 are circular.

[0039] 3H schematically illustrates plane 27P, which corresponds to the plane of screen 27S of device 27. Representations 180P and 184P of boundary 180 and enclosed region 184 are depicted on plane 27P. FIG. 3H also illustrates the planes of cube-like volume 170. A callout for one of the planes indicates surface voxels 210 present in the plane. At least some of the other planes of the cube-like volume typically also have surface voxels 210. In all planes, empty voxels 200 typically exist.

[0040] 3H, processor 22 extrudes enclosed region 184 along vector 190. Vector 190 is perpendicular to plane 27P, i.e., the plane of screen 27S of device 27, and points toward the screen. The extrusion of region 184 forms prism 194 having a prism base corresponding to region 184, and it will be understood that if boundary 180 is circular, prism 194 comprises a right circular cylinder.

[0041] The processor 22 registers all voxels within the prism 194 , namely the surface voxels 210 and the empty voxels 200 , and records them as filled voxels 230 .

[0042] To complete the extrusion method identification step 112, the processor 22 saves the locations of all fill voxels 230 within the prism 194.

[0043] In the disclosed embodiment, regions corresponding to the locations of the stored voxels can be displayed on surface 174 to physician 24 using device 27. Figure 3I schematically shows region 182 corresponding to the stored voxels from region 178 (Figure 3G).

[0044] Returning to flow diagram 100, in locking step 116, processor 22 assigns all voxels identified and saved in step 112 as locked voxels, i.e., voxels that will not be considered in calculating the cavity surface in subsequent scanning and mapping of cavity 31.

[0045] In a subsequent mapping step 120 at the end of the flow diagram, physician 24 remaps cavity 31 using distal tip 28 substantially as described above for data acquisition step 104. During remapping, the processor does not record the locations of any of the voxels locked in step 116, even if the acquired voxels are identified as corresponding to the volume occupied by distal tip 28.

[0046] The remapping generates a new surface that can be displayed to the physician 24 on the device 27. Because of the voxels that were locked in step 116, the new surface does not require shaving. [Example]

[0047] Example 1. A method comprising: obtaining data representative of the volume of an organ cavity (31); presenting on a display (27) an electroanatomical (EA) map (20) of a surface surrounding the volume generated in response to the data; receiving input from a user, the input including a selected section of the EA map; and locking a portion of the volume to subsequent updates of the data when updating the EA map in response to user input, the portion of the volume including a selected section of the EA map.

[0048] Example 2. The method of Example 1, wherein acquiring data includes obtaining positions of a set of hollow voxels that make up the volume and analyzing the positions to determine outer voxels of the set, the outer voxels corresponding to a surface that encloses the volume, and locking a portion of the volume includes selecting a subset of the outer voxels in response to user input and not recording the positions of the subset when updating the EA map.

[0049] Example 3. The method of example 2, wherein locking the portion of the volume further comprises selecting a predetermined group of cavity voxels that are adjacent to the subset.

[0050] Example 4. The method of example 3, wherein selecting the predetermined group includes applying a dilation and erosion algorithm to the subset to produce a result set of hollow voxels.

[0051] Example 5. The method of example 4, wherein selecting the predetermined group includes analyzing the result set to determine one or more voids therein, the predetermined group including cavity voxels within the one or more voids.

[0052] Example 6. The method of example 3, wherein receiving input from a user includes the user drawing a boundary surrounding an enclosed two-dimensional (2D) region on the display of the EA map of the surface, the predetermined group including hollow voxels within a prism having a base as the closed 2D region.

[0053] Example 7 The method of Example 1, wherein the organ comprises a heart.

[0054] Example 8. An apparatus comprising: A display (27), and A processor (22), obtaining data representative of the volume of a cavity (31) of an organ; presenting on a display an electroanatomical (EA) map (20) of a surface surrounding the volume generated in response to the data; receiving input from a user, the input including a selected section of the EA map; and a processor configured to: in response to user input, when updating the EA map, lock a portion of a volume to subsequent updates of the data, the portion of the volume including a selected section of the EA map.

[0055] The foregoing embodiments are cited by way of example, and the present disclosure is not limited to what has been particularly shown and described in the foregoing specification. Rather, the scope of the present disclosure includes both combinations and subcombinations of the various features described in the foregoing specification, as well as variations and modifications thereof not disclosed in the prior art that would occur to one skilled in the art upon reading the foregoing description.

[0056] [Embodiment] (1) A method comprising: obtaining data representative of a volume of a cavity of an organ; presenting on a display an electroanatomical (EA) map of a surface surrounding the volume generated in response to the data; and receiving input from a user, the input including a selected section of the EA map; and locking a portion of the volume to subsequent updates of the data when updating the EA map in response to the user input, the portion of the volume including the selected section of the EA map. (2) The method of embodiment 1, wherein acquiring the data includes obtaining the positions of a set of hollow voxels that constitute the volume and analyzing the positions to determine outer voxels of the set, the outer voxels corresponding to the surface that surrounds the volume, and locking the portion of the volume includes selecting a subset of the outer voxels in response to the user input and not recording the positions of the subset when updating the EA map. (3) The method of embodiment 2, wherein locking the portion of the volume further comprises selecting a predetermined group of the hollow voxels that are adjacent to the subset. (4) The method of embodiment 3, wherein selecting the predetermined group includes applying a dilation and erosion algorithm to the subset to generate the resulting set of hollow voxels. (5) The method of embodiment 4, wherein selecting the predetermined group includes analyzing the result set to determine one or more voids therein, the predetermined group including the cavity voxels within the one or more voids.

[0057] (6) The method of embodiment 3, wherein receiving the input from the user includes the user drawing a boundary surrounding an enclosed two-dimensional (2D) region on the display of the EA map of the surface, and the predetermined group includes the hollow voxels within a prism having a base as the closed 2D region. (7) The method of embodiment 1, wherein the organ comprises a heart. (8) A device comprising: The display and 1. A processor, comprising: obtaining data representative of a volume of a cavity of an organ; presenting on the display an electroanatomical (EA) map of a surface surrounding the volume generated in response to the data; and receiving input from a user, the input including a selected section of the EA map; and a processor configured to, in response to the user input, when updating the EA map, lock a portion of the volume to subsequent updates of the data, the portion of the volume including the selected section of the EA map. (9) The apparatus of embodiment 8, wherein acquiring the data includes acquiring the positions of a set of hollow voxels that constitute the volume and analyzing the positions to determine outer voxels of the set, the outer voxels corresponding to the surface that surrounds the volume, and locking the portion of the volume includes selecting a subset of the outer voxels in response to the user input and not recording the positions of the subset when updating the EA map. (10) The apparatus of embodiment 9, wherein locking the portion of the volume further comprises selecting a predetermined group of the hollow voxels adjacent to the subset.

[0058] (11) The apparatus of embodiment 10, wherein selecting the predetermined group includes applying a dilation and erosion algorithm to the subset to generate the resulting set of hollow voxels. (12) The apparatus of embodiment 11, wherein selecting the predetermined group includes analyzing the result set to determine one or more voids therein, the predetermined group including the cavity voxels within the one or more voids. (13) The device described in embodiment 10, wherein receiving the input from the user includes the user drawing a boundary surrounding an enclosed two-dimensional (2D) region on the display of the EA map of the surface, and the predetermined group includes the hollow voxels within a prism having a base as the closed 2D region. (14) The device of embodiment 8, wherein the organ comprises a heart.

Claims

1. 1. An apparatus comprising: The display and 1. A processor, comprising: obtaining data representative of a volume of a cavity of an organ; presenting on the display an electroanatomical (EA) map of a surface surrounding the volume generated in response to the data; and receiving input from a user, the input including a selected section of the EA map; and a processor configured to, in response to the user input, when updating the EA map, lock a portion of the volume to subsequent updates of the data, wherein the portion of the volume includes the selected section of the EA map.

2. 2. The apparatus of claim 1, wherein acquiring the data includes acquiring positions of a set of hollow voxels that constitute the volume and analyzing the positions to determine outer voxels of the set, the outer voxels corresponding to the surface that surrounds the volume, and locking the portion of the volume includes selecting a subset of the outer voxels in response to the user input and not recording the positions of the subset when updating the EA map.

3. The apparatus of claim 2 , wherein locking the portion of the volume further comprises selecting a predetermined group of the hollow voxels that are adjacent to the subset.

4. The apparatus of claim 3 , wherein selecting the predetermined group comprises applying a dilation and erosion algorithm to the subset to generate the resulting set of hollow voxels.

5. 5. The apparatus of claim 4, wherein selecting the predetermined group comprises analyzing the result set to determine one or more voids therein, the predetermined group including the cavity voxels within the one or more voids.

6. The apparatus of claim 3, wherein receiving the input from the user includes the user drawing a boundary surrounding an enclosed two-dimensional (2D) region on the display of the EA map of the surface, and the predetermined group includes the hollow voxels within a prism having a base as the closed 2D region.

7. The device according to any one of claims 1 to 6, wherein the organ comprises a heart.

8. 1. A method comprising: obtaining data representative of a volume of a cavity of an organ; presenting on a display an electroanatomical (EA) map of a surface surrounding the volume generated in response to the data; and receiving input from a user, the input including a selected section of the EA map; and locking a portion of the volume to subsequent updates of the data when updating the EA map in response to the user input, the portion of the volume including the selected section of the EA map.

9. 9. The method of claim 8, wherein acquiring the data includes acquiring positions of a set of hollow voxels that constitute the volume and analyzing the positions to determine outer voxels of the set, the outer voxels corresponding to the surface that encloses the volume, and locking the portion of the volume includes selecting a subset of the outer voxels in response to the user input and not recording the positions of the subset when updating the EA map.

10. The method of claim 9 , wherein locking the portion of the volume further comprises selecting a predetermined group of the hollow voxels that are adjacent to the subset.

11. The method of claim 10 , wherein selecting the predetermined group comprises applying a dilation and erosion algorithm to the subset to generate the resulting set of hollow voxels.

12. 12. The method of claim 11, wherein selecting the predetermined group comprises analyzing the result set to determine one or more voids therein, the predetermined group including the cavity voxels within the one or more voids.

13. 11. The method of claim 10, wherein receiving the input from the user includes the user drawing a boundary surrounding an enclosed two-dimensional (2D) region on the display of the EA map of the surface, and the predetermined group includes the hollow voxels within a prism having a base as the closed 2D region.

14. The method of any one of claims 8 to 13, wherein the organ comprises a heart.

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