Three-dimensional mapping system and method for cranial surgical pathways

Abstract

An apparatus and method are provided for mapping and displaying a three-dimensional surgical path within an image of a head structure derived from voxels of a head scan. An entry voxel and a target voxel are selected as path endpoints. A series of respective neighboring voxels are mapped between the entry voxel and the target voxel to define the path. Each voxel in the series, Vx i , y i , z i About Voxel Vx i , y i , z i Voxel Vx, excluding the neighboring voxels of the voxel immediately before i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i The voxels immediately following the endpoint voxel are selected. The selection is made by comparing selection weights determined based on their relative distance to the endpoint voxel and their relative distance from voxels within a predetermined distance representing at least a threshold density. The voxels of the path are then selectively highlighted in the display view to provide a visualization of the 3D surgical path.

Description

[Technical field]

[0001] The present application provides systems, devices, and methods for improving medical procedures. [Background technology]

[0002] Visualization of internal structures can be performed by mapping the propagation of activation waves. Fluorescence, computerized tomography (CT), ultrasound and magnetic resonance imaging (MRI), as well as other techniques, can be used to provide visualization and graphic rendering of internal structures.

[0003] Typically, visualizations and graphic renderings of internal body structures are constructed from 3D scanned image voxels, where a voxel is image data at selected coordinates of a particular slice of the scan. For example, a head CT scan may produce a series of image "slices" of a subject's head, each of which is made up of a voxel of image data representing a material type, such as bone, tissue, air, etc. The scan slices are sequentially combined to produce a 3D scanned image of the subject's head and its internal and external structures from the head scan.

[0004] The type of material represented by a voxel is conventionally determined by applying selected analysis criteria to the scan data, such as applying the well-known Hounsfield scale, and colors or grayscale weights can then be selected to correspond to the determined represented material in order to present a lifelike image of the scanned skull on a display device.

[0005] Through the use of modern computer processors, which may include both a computer processing unit (CPU) and a graphic processing unit (GPU), a user can operate a display device to view virtually any cross-sectional or perspective view of the 3D scanned image of the skull derived from the scan data. Such views can also be printed, including using 3D printing techniques, to produce actual 3D renderings, if desired.

[0006] Various medical conditions may require surgery within a subject's head. For example, an ENT (ear, nose, and throat) physician may diagnose a disease that requires surgery at a relatively remote site within a patient's sinuses.

[0007] To prepare for such surgery, it is desirable to provide a visualization and three dimensional (3D) map of a path to a surgical site, where a surgical tool can be inserted for non-invasive surgery at a remote surgical site within the head, where the path does not pass through bone, tissue, or other such barriers. Although there may be multiple such paths, it is preferable that a relatively short path is selected while maintaining as great a distance from bone as possible. Summary of the Invention [Means for solving the problem]

[0008] Systems, devices, and methods are provided for mapping and displaying a three-dimensional (3D) surgical path within a displayed image of a head structure derived from voxels of a subject's head scan.

[0009] In an exemplary method, the initial entry voxel Vx e , y e , z e and surgical site target voxel Vx t , y t , z tA set of voxels is selected as the endpoint of the 3D surgical path, starting from the entry voxel Vx e , y e , z e and the target voxel Vx t , y t , z t Each voxel in the series with its previous voxel Vx becomes a neighbor of both the previous and the next voxel in the series, defining a 3D surgical path. i , y i , z i About Voxel Vx i , y i , z i Voxel Vx, excluding the neighbors of the voxel immediately before i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i Select the voxel immediately following .

[0010] The selection includes determining a selection weight for each voxel in the group of neighboring voxels based on a selected criterion. The criterion for voxel selection is an endpoint voxel Vx e , y e , z e and Vx t , y t , z t voxel Vx based on a comparison of the determined selection weights, as well as a relative distance d from voxels within a predetermined distance p that represents at least a threshold density. i , y i , z i The voxels of the determined 3D surgical path are then selectively highlighted within a displayed view of the head structure to provide a visualization of the 3D surgical path.

[0011] The selection criteria for determining the selection weight of a voxel may include a penalty if a voxel that represents at least the threshold density is within a predetermined distance. The penalty may be based on the difference between the predetermined distance p and the distance d of the voxel from the nearest voxel that represents at least the threshold density. In one example, the threshold density is set as minus five hundred (-500) Hu and the predetermined distance p is 0.8 mm. In another example, the threshold density is set to be the density of bone.

[0012] The 3D surgical pathway is based on the entry voxel Vx e , y e , z e In such a case, it may be determined that each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entrance voxel Vx e , y e , z e and the relative proximity to the target voxel Vx t , y t , z t The determination can be based on selected criteria including the relative distance from

[0013] Alternatively, the 3D surgical path may be t , y t , z t In such a case, it may be determined that each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entrance voxel Vx e , y e , z e and the relative distance from the target voxel Vx t , y t , z t The determination can be based on selected criteria including relative proximity to

[0014] Selectively highlighting voxels of the 3D surgical path within the display view of the head structure may include applying a different emphasis to voxels of portions of the 3D surgical path that are obscured within the display view.

[0015] The method of claim 1 further comprises: using a display view of the 3D surgical pathway to align the distal end of the catheter with an initial entry voxel Vx e , y e , z e , and inserting the catheter into the subject's head along the 3D surgical path to position the distal end of the catheter at the surgical site target voxel Vx t, , y t , z t . . , and may further include positioning the device at a physical location corresponding to the

[0016] An exemplary apparatus for mapping and displaying a three-dimensional (3D) surgical path within a graphical representation of a head structure derived from voxels of a head scan of a subject includes a processor and associated data storage, a display, and a voxel selection device. The data storage is configured to store voxels of the head scan of the subject. The processor and associated display device are configured to provide cross-sectional and perspective views of the head structure of the subject based on the head scan. The voxel selection device allows a user to select an initial entry voxel Vx as an endpoint of the 3D surgical path. e , y e , z e and surgical site target voxel Vx t , y t , z t is configured to select

[0017] The processor divides a set of voxels into an entry voxel Vx e , y e , z e and the target voxel Vx t , y t , z tEach voxel in the series with its immediately preceding voxel Vx is further configured to be a neighbor of both the immediately preceding voxel and the immediately succeeding voxel in the series, and to map the voxel Vx to define a 3D surgical path. i , y i , z i For voxel Vx i , y i , z i Voxel Vx, excluding the neighbors of the voxel immediately before i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i The method is configured to select the voxel immediately following the

[0018] Select the endpoint voxel Vx e , y e , z e and Vx t , y t , z t determining a selection weight for each voxel in the group of neighboring voxels based on selected criteria including a relative distance to voxels Vx, and a relative distance from voxels within a predetermined distance representing at least a threshold density; and then determining a selection weight for each voxel in the group of neighboring voxels Vx based on a comparison of the determined selection weights. i , y i , z i This is done by selecting the voxel immediately following

[0019] The processor is further configured to selectively highlight voxels of the determined 3D surgical path in an image of the head structure on the display device to provide a visualization of the 3D surgical path.

[0020] The processor is configured such that the selected criteria used by the processor to determine the selection weight of the voxel includes a penalty if a voxel that represents at least the threshold density is within a predetermined distance. The processor may be configured to determine the penalty based on a difference between the predetermined distance and the distance of the voxel from a nearest voxel that represents at least the threshold density. In one example, the threshold density is set as minus five hundred (-500) Hu and the predetermined distance is 0.8 mm.14. In another example, the threshold density is set to be the density of bone.

[0021] The processor determines whether the 3D surgical path is an entry voxel Vx e , y e , z e In such a case, it may be determined that each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entrance voxel Vx e , y e , z e and the relative proximity to the target voxel Vx t , y t , z t The distance is determined based on selected criteria including the relative distance from

[0022] Alternatively, the processor may further include a 3D surgical path for detecting a target voxel Vx t , y t , z t In such a case, it may be determined that each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entrance voxel Vx e , y e , z e and the relative distance from the target voxel Vx t , y t , z t The determination is based on selected criteria including the relative proximity to

[0023] The processor may also be configured such that selectively highlighting voxels of the 3D surgical path within the display view of the head structure includes applying a different highlighting of voxels of portions of the 3D surgical path that are hidden within the display view.

[0024] An exemplary apparatus may further include a catheter having a distal end from which a surgical tool may be actuated, and an associated catheter position sensing device coupled to the processor. The position sensing device is configured to provide a signal that enables the processor to track a position of the distal end of the catheter when the distal end of the catheter is inserted into the subject's head. In this case, the processor is configured to control a display device to display a corresponding visualization of the catheter movement, such that a user can use a display view of the 3D surgical path to track the distal end of the catheter relative to the initial entry voxel Vx e , y e , z e , and inserting the catheter into the subject's head along the 3D surgical path to position the distal end of the catheter at the surgical site target voxel Vx t, , y t , z t , and can be positioned at a physical location corresponding to the [Brief description of the drawings]

[0025] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which: [Figure 1A] FIG. 2 is a diagram of a voxel and its neighboring voxels in a 3D image derived from a scan. [Figure 1B] 1B is a graphic representation of an exemplary notation representing the corresponding voxels of FIG. 1A. [Diagram 2] FIG. 1 is a diagram of an example system in which one or more features of the subject matter of the present disclosure may be implemented. [Diagram 3] 1 is a graphical depiction of selected display views illustrating a surgical path between endpoints derived in a conventional manner. [Figure 4] 4 is a graphic depiction of a display view corresponding to the display view of FIG. 3 showing a surgical path between endpoints derived in accordance with an example of the teachings of the present invention. [Diagram 5] 5 is a flow chart for deriving a surgical path between the endpoints shown in FIG. 4 in accordance with the teachings of the present invention. [Figure 6A] 6B is a graphical depiction of a first case of the relative position of a immediately preceding voxel FIG. 6A relative to a voxel FIG. 6B from which a subsequent voxel is to be determined. [Figure 6B] 6B is a graphical depiction of a first case of the relative position of a immediately preceding voxel FIG. 6A relative to a voxel FIG. 6B from which a subsequent voxel is to be determined. [Figure 7A] 7B is a graphical depiction of a second case of the relative position of the immediately preceding voxel FIG. 7A relative to the voxel FIG. 7B from which the subsequent voxel is to be determined. [Figure 7B] 7B is a graphical depiction of a second case of the relative position of the immediately preceding voxel FIG. 7A relative to the voxel FIG. 7B from which the subsequent voxel is to be determined. [Figure 8A] 8B is a graphical depiction of a third case of the relative position of the immediately preceding voxel FIG. 8A relative to the voxel FIG. 8B from which the subsequent voxel is to be determined. [Figure 8B] 8B is a graphical depiction of a third case of the relative position of the immediately preceding voxel FIG. 8A relative to the voxel FIG. 8B from which the subsequent voxel is to be determined. [Figure 9] 4 is a graphical depiction of a display view corresponding to the display view of FIG. 3 showing a surgical path between endpoints derived in accordance with another example of the present teachings. [Figure 10] 10 is a flow chart for deriving a surgical path between the endpoints shown in FIG. 9 in accordance with the teachings of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] According to an implementation of the disclosed subject matter, image data in the form of voxels from a scan of a subject's head is used to derive a visualization and three-dimensional (3D) map of a path to a desired location, such as an internal head location, where a surgical procedure is to be performed.

[0027] For reference herein, a voxel may be represented by the notation Vx,y,z, where z indicates a particular slice in a series of image slices derived from a scan, and x and y are coordinates in the z slice. The order of the subscripts x, y, and z in the Vx,y,z notation is used as an example and is not intended to be limiting. For example, Vz,y,x may be a form of notation.

[0028] A voxel Vx,y,z can be considered as a cube generally surrounded by 26 other voxels, with voxel Vx,y,z being at the center of a 3×3 cubic array of voxels, as shown in Figure 1 A. Exceptions are where x or y represent the coordinates of the edge of slice z, or where z is the first or last slice in a series of image slices.

[0029] The 26 surrounding voxels of a voxel Vx, y, z are referred to herein as "neighboring voxels." The 26 neighboring voxels of a voxel Vx, y, z are as follows, as shown in FIG. 1B: The six "adjacent neighboring" voxels, namely, voxels Vx+1, y, z, Vx-1, y, z, Vx, y+1, z, Vx, y-1, z, Vx, y, z-1, and Vx, y, z+1, The 12 "2D diagonal neighboring" voxels, namely, voxels Vx+1,y+1,z, Vx+1,y-1,z, Vx-1,y+1,z, Vx-1,y-1,z, Vx,y+1,z+1, Vx,y-1,z+1, Vx+1,y,z+1, Vx-1,y,z+1, Vx,y+1,z-1, Vx,y-1,z-1, Vx+1,y,z+1, Vx,y+1,z-1, Vx,y-1,z-1, Vx+1,y,z-1, and Vx-1,y,z-1; Eight "3D diagonal neighboring" voxels, namely voxel Vx+1, y+1, z+1, It will be appreciated that the vectors consist of Vx-1, y+1, z+1, Vx+1, y-1, z+1, Vx-1, y-1, z+1, Vx+1, y+1, z-1, Vx-1, y+1, z-1, Vx+1, y-1, z-1, Vx+1, y-1, z-1, and Vx-1, y-1, z-1.

[0030] Voxel Vx e , y e , z e From the initial entry site starting at voxel Vx t , y t , z t A surgical path to a surgical target site at is defined by a series of voxels, where voxels Vx e , y e , z e and voxel Vx t , y t , z t Each voxel between is a neighbor of both its immediately preceding voxel and its immediately succeeding voxel in the series that defines the path.

[0031] 2 is a diagram of an example mapping system 20 capable of implementing one or more example features of the subject matter of this disclosure. The mapping system 20 includes a data processing component 22 and a data storage component 24 configured to process and store 3D scan images, such as 3D scan images derived from image data of a scan of a head 26 of a patient 28, for an ENT (ear / nose / throat) physician 30 to perform a non-invasive surgical procedure at a selected site within the patient's head 26.

[0032] The mapping system 20 includes a monitor or other display device 32 for selectively displaying, for example, selected cross-sectional or perspective views from the 3D scanned image of the patient's head 26. The data processing component 22 may include one or more CPUs, GPUs, and / or other processors coupled to the data storage component 24 and the display device 32 to generate desired cross-sectional or perspective views on the display device 32 from the 3D scanned image, as derived from the scan data of the patient's head 26.

[0033] In a 3D-like perspective view displayed by display device 32, where the display device uses a Cartesian pixel representation, the voxels are appropriately mapped to pixels to provide a perspective view that appears to have three dimensions using conventional GPU techniques. However, if a holographic or other true 3D display device is used, the voxels may be directly mapped to 3D coordinate representation elements.

[0034] The data processing component 22 is further configured to control the display device to display the 3D surgical path between selected voxels within the display view by applying a predetermined attribute, e.g., a solid color, to the display voxels that define a particular 3D surgical path, which is referred to herein as highlighting the voxels of the 3D surgical path.

[0035] If in a particular view, a portion of the pathway is underneath a barrier voxel, such as bone or tissue, that portion of the pathway may be highlighted differently, such as with a different color, to indicate that the pathway portion is in fact hidden behind a barrier material, such as bone or tissue. In such a case, the ENT physician may wish to select a different view of the 3D scan image in which the previously hidden portion of the pathway is not behind the barrier material.

[0036] For example, for the view shown in FIG. st , y st , z st and voxel Vx t , y t , z t The portion of the determined path shown between appears to pass above the bone material. If a path portion that appears to pass above the bone material is determined to actually be in a passage below the bone material, then a different emphasis is preferably applied by processing component 22 such that the display view reflects the actual relative location of the portion of the path below the displayed bone material.

[0037] The mapping system 20 includes one or more peripheral devices, such as a trackball and / or touch pad 34, to allow a user to select a particular view of the 3D image data, for example, of a scan of the head 26, to be displayed on the display device 32. One or more of the peripheral devices, such as the device 34, are also configured to allow the user to select a particular voxel to serve as an endpoint of a path between them. Such peripheral devices may include, but are not limited to, a computer mouse device, a video game controller device, a joystick device, a laser pointing device, a voice command device, and a touch screen display control. Preferably, the one or more peripheral devices are used to allow a user, such as an ENT physician 30 or a surgical assistant, to pan through successive views of the 3D scan image as may be desired to select a target voxel for positioning a surgical tool to perform a surgical procedure.

[0038] The mapping system 20 may also include a device, such as a catheter 38, that includes a surgical tool or into which a surgical tool may be inserted for manipulation at a distal end of the catheter 38. The catheter 38 may include an ultrasound transducer configured to obtain biometric data, ultrasound slices, or the like. The distal end of the catheter 38 may include a probe that operates in conjunction with a location pad 39 that is positioned on a gurney 41 on which the patient 28 is positioned for the surgical procedure.

[0039] 2, a distal probe and location pad 39 of catheter 38 is equipped with position sensing equipment and is coupled to processing component 22 by respective cables 42, 43. In this example, processing component 22 is configured to use signals from the catheter probe and location pad 29 to track the position of the distal end of catheter 38 as it is inserted into the subject's head by ENT physician 30, and to display a visualization of the catheter movement on display device 32 in conjunction with a view of the displayed 3D scan image.

[0040] In this manner, the ENT physician 30 can use the display views to accurately determine the location of the voxels Vx in positioning a surgical tool for a surgical procedure. e , y e , z e From the initial entry site starting at voxel Vx t , y t , z t The determined 3D surgical path can be followed to a surgical site at the target site. Thus, while referring to the display view, the ENT physician 30 begins at a physical location in the subject's head corresponding to the initial entry site, inserts the distal end of the catheter 38 along the path, and positions the distal end of the catheter at a physical location corresponding to the target site by following the displayed path. At that point, a surgical tool is properly positioned for the surgical procedure if it is already disposed at the distal end of the catheter or if a surgical tool can be inserted through the catheter for operation at the target site.

[0041] As described above, the pathway for non-invasive head surgery includes the initial entry site, voxel Vx e , y e , z e and voxel Vx, the surgical target site as the endpoint. t , y t , z t The path is then defined by a set of voxels, where voxels Vx e , ye , z e and voxel Vx t , y t , z t Each voxel between is a neighbor of both its immediately preceding voxel and its immediately succeeding voxel in a series that defines a path.

[0042] Traditionally, starting at one of the endpoint voxels and ending when the other endpoint is reached, the next voxel in the path sequence is determined by selecting the "best" successor voxel from among 26 neighboring voxels, using what is known as the A* algorithm.

[0043] The A* algorithm is a well-known algorithm for finding paths in mapping CT scans. The main parameter set of the A* algorithm is in the formula F=G+H. The F, G, and H variables are attributed to each voxel and are calculated for each neighboring voxel in relation to the selection of the successor voxel in the voxel's path series. If a neighboring voxel is a barrier voxel representing bone or tissue, it is automatically excluded from consideration as the next voxel in the series.

[0044] F is the weight of the voxel. G is the distance between the voxel and the start endpoint voxel. H is the heuristic estimated distance from the voxel to the end endpoint voxel.

[0045] In addition to the F, G, and H parameters, two lists of voxels are maintained in the implementation of the algorithm: an open list and a closed list. The open list is a list that contains selectable voxels that have been evaluated, but has not had all possible successor voxels evaluated. It is a list of pending tasks.

[0046] The closed list is a list that contains the voxel that has been evaluated, and all possible successor voxels have been evaluated and added to the open list, if applicable.

[0047] The A* algorithm first calculates the starting endpoint voxel Vx e , y e , z e This is started by adding the following to the open list:

[0048] Repeat the following steps: Select the voxel in the open list that has the lowest cost (F). This is called the current voxel. b. Switch the current voxel to a closed list. c. For each of the 26 neighboring voxels of the current voxel, i. If a neighboring voxel is not selectable (tissue, bone, or other barrier voxel type) or is in a closed list, ignore it. ii. If the neighboring voxel is not in the open list, add the neighboring voxel to the open list. Make the current voxel a predecessor voxel of the neighboring voxel, and determine and record the F, G, and H costs of the neighboring voxel. iii. If the neighboring voxel is already in the open list, check if the path to the neighboring voxel is better, using the G-cost as a measure. A lower G-cost means this is a better path. If so, change the neighboring voxel's predecessor voxel to the current voxel and recalculate the G and F-costs of the node. If the open list remains auto-populated according to the cost F, it may need to resort to taking the change into account.

[0049] This process is performed on the target voxel Vx t , y t , z t is added to the closed list, in which case the process stops when a path is found. Alternatively, the process stops when the open list is empty, in which case there are no acceptable paths and the algorithm does not proceed to the target voxel Vx t , y t , z t It will stop if it can't find the

[0050] Target voxel Vx t , y t , z t If found, the target voxel Vx t , y t , z t Working backwards from each closed list voxel to its predecessor voxel, we find the starting voxel Vx e , y e , z e The sequence of voxels leading to reaching is saved as a path.

[0051] Because all 26 neighboring voxels are considered to select the next voxel in the sequence, the process is computationally complex and relatively time consuming and resource consuming.

[0052] Figure 3 shows the entrance site voxel Vx e , y e , z e Starting from the surgical site target voxel Vx t , y t , z t 1 shows a display view of a voxel path determined using a conventional A* algorithm from the entry site voxel Vx e , y e , z e and the target voxel Vx t , y t , z t , and are highlighted by the processing unit 22 so as to be displayed as a continuous line representing the determined path between

[0053] As shown in Figure 3, the conventionally determined path closely follows the nasal bone. Therefore, inserting the catheter 38 along the conventionally determined path increases the difficulty of manipulating the surgical tool at the target site.

[0054] According to an embodiment of the present invention, processing component 22 is configured to perform head path mapping to define a desired surgical path in a faster, less computationally complex manner that also provides better spacing from bone and / or other barrier voxels.

[0055] For example, FIG. 4 shows the same entry site voxel Vx e , y e , z e Starting from the same surgical site target voxel Vx t , y t , z t 4 shows a display view of a voxel path determined using the modified A* algorithm from the entry site voxel Vx e , y e , z e and the target voxel Vx t , y t , z t , and are highlighted by the processing unit 22 so as to be displayed as a continuous line representing the determined path between

[0056] In the exemplary implementation of the invention that generated the path shown in Figure 4, the formula F = G + H was still used and the F value remained F = G + H. However, the G value was the sum of the distance from the starting endpoint voxel to the current voxel and a penalty that was a function of the proximity of the voxel to voxels of at least a threshold density, such as voxels representing tissue or bone. The H value was the Euclidean distance from the current voxel to the ending endpoint voxel.

[0057] 4, the exemplary determined path traverses the nasal cavity at a significant distance from the illustrated bones, when possible. Thus, inserting the catheter 38 along the determined path reduces the difficulty of maneuvering surgical tools at the target site.

[0058] Entry site voxel Vx as the starting endpoint voxel e , y e , ze and the target region voxel Vx as the end endpoint voxel t , y t , z t Preferably, the process starts with an entry site voxel Vx as the end endpoint voxel. e , y e , z e and the target site voxel Vx as the starting endpoint voxel t , y t , z t It can be implemented with:

[0059] An example of a penalty P added when determining the G value is given by P equal to 0.0 mm or the maximum of the values ​​of (pd), where p is a predetermined distance for the desired minimum spacing from relatively dense material, and d is the distance between the current voxel and the nearest voxel that represents a density of at least the threshold density.

[0060] For example, the threshold density can be set to measure the distance to voxels having a Hounsfield value of at least minus five hundred (-500 HU), including voxels representing bone, tissue, and other barrier materials. If desired, the threshold can be set as the density of a particular material, such as the density of bone, tissue, or another type of barrier material.

[0061] For example, the predetermined distance p can be set as 0.8 mm. In such a case, if the current voxel is farther than 0.8 mm from the nearest voxel, a voxel with a relatively high density (i.e., at least one of the threshold densities), no penalty is added to the normal G value. Thus, the penalty is calculated in 3D space, finding the distance d from the current voxel to any relatively high density voxel in all directions within a sphere of radius p, which in this example is a sphere of radius 0.8 mm.

[0062] In implementing the modified A* algorithm, to reduce the computational complexity of the mapping method, the number of neighboring voxels evaluated for the current voxel automatically excludes the predecessor voxels of the current voxel, as well as all neighboring voxels that are also neighbors of the predecessor voxels of the current voxel. In this process, the number of voxels that qualify to be in the group of voxels considered as successors of the current voxel depends on whether the current voxel is adjacent, 2D diagonal, or 3D diagonal to its predecessor voxel.

[0063] If a predecessor voxel of a current voxel, such as the solid voxel shown in Figure 6A, is adjacent to the current voxel, such as the solid voxel shown in Figure 6B, then all voxels indicated by light shading are automatically excluded from the selection process of successors to the current voxel. Only the nine non-shaded voxels that are not neighbors of the predecessor voxel define the group of potential successors of the current voxel. In the illustrated neighboring case of Figures 6A and 6B, using the notation of Figure 1B where the current voxel is represented as Vx, y, x, the nine voxels that define the group of potential successor voxels of the current voxel are the "adjacent neighboring" voxel Vx, y, z+1, the "2D diagonal neighboring" voxels Vx, y+1, z+1, Vx, y-1, z+1, Vx+1, y, z+1, Vx-1, y, z+1, and the "3D diagonal neighboring" voxels Vx+1, y+1, z+1, Vx-1, y+1, z+1, Vx+1, y-1, z+1, Vx-1, y-1, z+1.

[0064] If a predecessor voxel of a current voxel, such as the solid voxel shown in Figure 7A, is 3D diagonal to the current voxel, such as the solid voxel shown in Figure 7B, then all voxels that are indicated by light shading are automatically excluded from the selection process of successors to the current voxel. Only the 19 non-shaded voxels that are not neighbors of the predecessor voxel define the group of potential successors of the current voxel. In the illustrated 3D diagonal case of FIGS. 7A and 7B , using the notation of FIG. 1B where the current voxel is represented as Vx, y, x, the 19 voxels that define the group of potential successor voxels of the current voxel are the “adjacent neighbors” voxels Vx−1, y, z, Vx, y+1, z, and Vx, y, z+1, the “2D diagonal neighbors” voxels Vx+1, y+1, z, Vx−1, y+1, z, Vx−1, y−1, z, Vx, y+1, z+1, Vx, y-1, z+1, Vx+1, y, z+1, Vx-1, y, z+1, Vx, y+1, z-1, and Vx-1, y, z-1, as well as the "3D diagonal neighboring" voxels Vx+1, y+1, z+1, Vx-1, y+1, z+1, Vx+1, y-1, z+1, Vx-1, y-1, z+1, Vx+1, y+1, z-1, Vx-1, y+1, z-1, Vx-1, y+1, z-1, and Vx-1, y-1, z-1.

[0065] If a predecessor voxel of a current voxel, such as the solid voxel shown in FIG. 8A, is 2D diagonal to the current voxel, such as the solid voxel shown in FIG. 8B, all voxels indicated by light shading are automatically excluded from the selection process of successors to the current voxel. Only the 15 non-shaded voxels that are not neighbors of the predecessor voxel define the group of potential successors of the current voxel. In the illustrated 2D diagonal case of FIG. 8A and FIG. 8B, using the notation of FIG. 1B where the current voxel is represented as Vx, y, x, the 15 voxels that define the group of potential successors of the current voxel are the "adjacent neighbors" voxels Vx, y+1, z and Vx, y, z+1, the "2D diagonal neighbors" voxels Vx+1, y+1, z, Vx-1, y +1, z, Vx, y+1, z+1, Vx, y-1, z+1, Vx+1, y, z+1, Vx-1, y, z+1, and Vx, y+1, z-1, and "3D diagonal neighbors" Vx+1, y+1, z+1, Vx-1, y+1, z+1, Vx+1, y-1, z+1, Vx-1, y-1, z+1, Vx+1, y+1, z-1, and Vx-1, y+1, z-1.

[0066] For any given voxel, there are six options to reach adjacent neighbors. For any given voxel, there are eight options to reach 3D diagonal neighbors. For any given voxel, there are twelve options to reach 2D diagonal neighbors. Thus, according to the exemplary inventive method of selecting successive voxels, the average number of voxels considered in the successive selection is 14.8, or (6 * 9+8 * 19+12 * 15) / 26=14.8).

[0067] Generally, the process proceeds according to the steps of Figure 5. In a first step 501, an ENT physician selects entry and target endpoint voxels. In a second step 502, for each pathway voxel that has a previous pathway voxel, a successor pathway voxel is selected from among a group of neighboring voxels excluding the previous voxel's neighbors. In step 503, the successor voxel selection is based on relative proximity to the start endpoint and relative distance from the end endpoint, with a penalty of the voxel's proximity to voxels with at least a threshold density. In step 504, the mapped pathway is displayed to the ENT physician.

[0068] More specifically, a method is provided for mapping and displaying a three-dimensional (3D) surgical path within a displayed image of a head structure derived from voxels of a head scan of a subject, the method including selecting an initial entry voxel Vx as an endpoint of the path, and e , y e , z e and surgical site target voxel Vx t, , y t , z t Then, a set of voxels is selected from the entry voxel Vx e , y e , z e and the target voxel Vx t , y t , z t Each voxel in the series between Vx and Vx is a neighbor of both the previous and next voxel in the series, defining a 3D surgical path. i , y i , z i About Voxel Vx i , y i , z i Voxel Vx, excluding the neighbors of the voxel immediately before i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z iSelect the voxel immediately following the endpoint voxel Vx e , y e , z e and Vx t , y t , z t and determining a selection weight for each voxel in the group of neighboring voxels based on selected criteria including a relative distance from voxels Vx, ... i , y i , z i The voxels of the 3D surgical path are then highlighted in a displayed view of the head structure to provide a visualization of the 3D surgical path.

[0069] Further implementations of the present invention include selection of sub-targets based on the ENT physician's knowledge of the head structure. For example, "sub-target" voxels can be selected according to the ENT physician's knowledge of where the path must go, such as if it needs to cross narrow passageways, etc., with the selection also taking into account known cavities. FIG. 9 shows the same surgical site target voxel Vx of FIG. t , y t , z t Same entrance site voxel Vx e , y e , z e In addition, the sub-target voxel Vx st , y st , z st 9 shows a display view of a voxel path determined using the method of FIG. 9. The voxels in the determined path in FIG. 9 are sub-target voxels Vx st , y st , z st The entrance site voxel Vx e , y e , z e and the target voxel Vx t , y t , z t , and are highlighted by the processing unit 22 so as to be displayed as a continuous line representing the determined path between

[0070] In the exemplary implementation of the present invention that generated the pathway shown in FIG. 9, the process simply involved extracting the entry site voxels Vx using conventional methods. e , y e , z e and the target voxel Vx t , y t , z t This was completed six times faster than directly calculating the path between the two.

[0071] Specifically, the method includes determining whether a voxel representing bone is located at an initial entry voxel Vx e , y e , z e and surgical site target voxel Vx t , y t , z t It is much more efficient if the sub-target voxel Vx is within the shortest distance (Euclidean distance) between the st , y st , z st The voxel representing the bone is the initial entry voxel Vx e , y e , z e and the sub-target voxel Vx st , y st , z st so that the initial entry voxel Vx is not within the shortest line between e , y e , z e and surgical site target voxel Vx t , y t , z t can be advantageously selected between

[0072] 9, an exemplary determined path traverses the nasal cavity at a significant distance from the illustrated bones, when possible. Thus, inserting the catheter 38 along the determined path reduces the difficulty of maneuvering surgical tools at the target site.

[0073] Generally, the process proceeds according to the steps of Figure 10. In a first step 1001, an ENT physician selects entry and target endpoint voxels. In a second step 1002, an ENT physician selects sub-target voxels between the endpoint voxels. In step 1003, subsequent voxel selection is made from one endpoint voxel to a sub-target voxel and then from the sub-target voxel to the other endpoint voxel. In step 1004, the mapped path is displayed to the ENT physician.

[0074] More specifically, a further method is provided for mapping and displaying a three-dimensional (3D) surgical path within a displayed image of a head structure derived from voxels of a head scan of a subject. e , y e , z e and surgical site target voxel Vx t , y t , z t where the voxels representing bones are the initial entry voxels Vx e , y e , z e and surgical site target voxel Vx t , y t , z t The sub-target voxel Vx is located within the shortest path between st , y st , z st Also, the initial entry voxel Vx e , y e , z e and surgical site target voxel Vx t , y t , z t Select between the sub-target voxel Vx st , y st , z st The set of voxels including the entry voxel Vx e , y e , z e and the target voxel Vx t , y t , z t, and each voxel between becomes a neighbor of both the previous and the next voxel in the sequence, defining a 3D surgical path.

[0075] Initial entrance voxel Vx e , y e , z e and the sub-target voxel Vx st , y st , z st For each voxel Vx in the series between i , y i , z i About Voxel Vx i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i Select the voxel immediately following the entry voxel Vx e , y e , z e and sub-target voxel Vx st , y st , z st determining a selection weight for each voxel in the group of neighboring voxels based on a selected criterion including a relative distance from voxel Vx i , y i , z i Select the voxel immediately following .

[0076] Sub-target voxel Vx st , y st , z st and the target voxel Vx t , y t , z t For each voxel Vx in the series between j , y j , z j About Voxel Vx j , y j , z j Among the group of neighboring voxels of voxel Vx j , y j , z jSelect the voxel immediately following the target voxel Vx st , y st , z st and target voxel Vx t , y t , z t determining a selection weight for each voxel in the group of neighboring voxels based on a selected criterion including a relative distance from voxel Vx j , y j , z j Select the voxel immediately following .

[0077] Within a displayed view of the head structure, the selected path voxels and the voxels of the 3D surgical path are selectively highlighted to provide visualization of the 3D surgical path.

[0078] The implementation using the sub-target can be combined with the use of the exemplary modified A* algorithm disclosed above. In such a case, For each voxel in the series Vx i , y i , z i About Voxel Vx i , y i , z i Voxel Vx, excluding the neighbors of the voxel immediately before i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i For each voxel Vx, the voxel immediately following is selected. i , y i , z i Determining the selection weights of the neighboring voxels of includes a penalty based on the relative distance from voxels within at least a predetermined distance representing a threshold density. j , y j , z j About Voxel Vx j , y j , z j Voxel Vx, excluding the neighbors of the voxel immediately beforej , y j , z j Among the group of neighboring voxels of voxel Vx j , y j , z j For each voxel Vx, the voxel immediately following is selected. j , y j , z j Determining the selection weights of the neighboring voxels of includes a penalty based on their relative distance from the voxel within at least a predetermined distance representing a threshold density.

[0079] Any of the functions and methods described herein can be implemented in a general purpose computer, processor, or processor core. Suitable processors include, by way of example, general purpose processors, special purpose processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGA) circuits, any other type of integrated circuit (IC), and / or state machines. Such processors can be manufactured by configuring a manufacturing process with the results of processed hardware description language (HDL) instructions and other intermediate data such as netlists (such instructions can be stored on a computer readable medium). The result of such processing can be a mask work that is then used in a semiconductor manufacturing process to manufacture a processor implementing features of the present disclosure.

[0080] Any of the functions and methods described herein can be implemented in a computer program, software, or firmware embodied in a non-transitory computer-readable storage medium and executed by a general-purpose computer or processor. Examples of non-transitory computer-readable storage media include read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs).

[0081] It should be understood that many variations are possible based on the disclosure herein. Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements, or in various combinations with or without the other features and elements.

[0082] [Embodiment] (1) A method for mapping and displaying a three-dimensional (3D) surgical pathway within a displayed image of a head structure derived from voxels of a head scan of a subject, the method comprising: As an endpoint of the 3D surgical path, an initial entrance voxel Vx e , y e , z e and surgical site target voxel Vx t, , y t , z t Selecting A series of voxels is denoted by the entry voxel Vx e , y e , z e and the target voxel Vx t , y t , z tsuch that each voxel between is a neighbor of both the immediately preceding and the immediately succeeding voxel in said series, defining said 3D surgical path; For each voxel in the series, Vx i , y i , z i About Voxel Vx i , y i , z i Voxel Vx, excluding the neighboring voxels of the immediately preceding voxel i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i selecting the immediately succeeding voxel of The endpoint voxel Vx e , y e , z e and Vx t , y t , z t determining a selection weight for each voxel in said group of neighboring voxels based on selected criteria including a relative distance to, and a relative distance from voxels within at least a predetermined distance representing a threshold density; Based on the comparison of the determined selection weights, voxel Vx i , y i , z i selecting the immediately succeeding voxel of Selectively highlighting the voxels of the 3D surgical path within a display view of the head structure to provide a visualization of the 3D surgical path. (2) The method of claim 1, wherein the selected criteria for determining the selection weight of a voxel includes at least a penalty if a voxel representing the threshold density is within the predetermined distance. (3) the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 3. The method of claim 2, wherein the predetermined distance is 0.8 mm. (4) The 3D surgical path is located at the entry voxel Vx e , y e , z e It is determined that the start occurs at Based on the selected criteria, each voxel Vx i , y i , z i The determining of the selection weight of each voxel in the group of neighboring voxels of the entry voxel Vx e , y e , z e and the relative proximity to the target voxel Vx t , y t , z t Includes the relative distance from 2. The method of claim 1, wherein the selected criteria for determining the selection weight of a voxel includes a penalty based on the difference between the predetermined distance and the distance of the voxel from at least the nearest voxel representing the threshold density. (5) the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 5. The method of claim 4, wherein the predetermined distance is 0.8 mm.

[0083] (6) The 3D surgical path is located at the target voxel Vx t , y t , z t It is determined that the start occurs at Based on the selected criteria, each voxel Vx i , y i , z i The determining of the selection weight of each voxel in the group of neighboring voxels of the entry voxel Vx e , y e , z eand the relative distance from the target voxel Vx t , y t , z t including the relative proximity to 2. The method of claim 1, wherein the selected criteria for determining the selection weight of a voxel includes a penalty based on the difference between the predetermined distance and the distance of the voxel from at least the nearest voxel representing the threshold density. (7) the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 7. The method of claim 6, wherein the predetermined distance is 0.8 mm. (8) The method of embodiment 1, wherein the threshold density is set to be the density of bone. (9) The method of embodiment 1, wherein selectively highlighting the voxels of the 3D surgical path within the display view of the head structure includes applying a different emphasis to voxels of portions of the 3D surgical path that are hidden within the display view. (10) Using the display view of the 3D surgical pathway, align the distal end of the catheter with the initial entry voxel Vx e , y e , z e , inserting the distal end of the catheter into the head of the subject along the 3D surgical path, starting at a physical location within the head of the subject corresponding to the surgical site target voxel Vx t, , y t , z t 2. The method of embodiment 1, further comprising:

[0084] (11) An apparatus for mapping and displaying a three-dimensional (3D) surgical path within a graphical representation of a head structure derived from voxels of a head scan of a subject, the apparatus comprising: a data storage device configured to store voxels of the head scan of the subject; a processor and associated display device configured to provide cross-sectional and perspective views of the subject's head structure based on the head scan; The user selects an initial entry voxel Vx as the endpoint of the 3D surgical path. e , y e , z e and surgical site target voxel Vx t , y t , z t a voxel selection device configured to select The processor divides a set of voxels into the entry voxels Vx e , y e , z e and the target voxel Vx t , y t , z t and configured to map such that each voxel between is a neighbor of both a previous and a next voxel in the series to define the 3D surgical path; For each voxel in the series, Vx i , y i , z i For voxel Vx i , y i , z i Voxel Vx, excluding the neighboring voxels of the immediately preceding voxel i , y i , z i Among the group of neighboring voxels of voxel Vx i , y i , z i The immediately succeeding voxel of The endpoint voxel Vx e , y e , z e and Vx t , y t , z t determining a selection weight for each voxel in said group of neighboring voxels based on selected criteria including a relative distance to, and a relative distance from voxels within at least a predetermined distance representing a threshold density; Based on the comparison of the determined selection weights, voxel Vx i , y i , z i and selecting the immediately succeeding voxel of The apparatus, wherein the processor is configured to selectively highlight the voxels of the 3D surgical path in an image of a head structure on the display device to provide a visualization of the 3D surgical path. (12) The apparatus of embodiment 11, wherein the processor is configured such that the selected criteria used by the processor to determine the selection weight of a voxel includes at least a penalty if a voxel representing the threshold density is within the predetermined distance. (13) The processor, the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 13. The apparatus of claim 12, wherein the predetermined distance is configured to be 0.8 mm. (14) The processor, The 3D surgical path is the entry voxel Vx e , y e , z e It is determined that the start occurs at For each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entry voxel Vx e , y e , z e and the relative proximity to the target voxel Vx t , y t , z t based on selected criteria including a relative distance from The apparatus of embodiment 11, wherein the selected criteria used by the processor to determine the selection weight of a voxel includes a penalty based on the difference between the predetermined distance and the distance of the voxel from at least the nearest voxel representing the threshold density. (15) The processor, the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 15. The apparatus of claim 14, wherein the predetermined distance is configured to be 0.8 mm.

[0085] (16) The processor, The 3D surgical path is the target voxel Vx t , y t , z t It is determined that the start occurs at For each voxel Vx i , y i , z i The selection weight of each voxel in the group of neighboring voxels of the entry voxel Vx e , y e , z e and the relative distance from the target voxel Vx t , y t , z t based on selected criteria including relative proximity to The apparatus of embodiment 11, wherein the selected criteria used by the processor to determine the selection weight of a voxel includes a penalty based on the difference between the predetermined distance and the distance of the voxel from at least the nearest voxel representing the threshold density. (17) The processor, the penalty is based on a difference between the predetermined distance and a distance of the voxel from a nearest voxel that represents at least the threshold density; the threshold density is set as minus five hundred (-500) Hu; 17. The apparatus of claim 16, wherein the predetermined distance is configured to be 0.8 mm. (18) The apparatus of claim 11, wherein the processor is configured to set the threshold density to be the density of bone. (19) The apparatus of embodiment 11, wherein the processor is configured such that the selectively highlighting the voxels of the 3D surgical path within the display view of the head structure includes applying a different highlighting of voxels of portions of the 3D surgical path that are obscured within the display view. (20) A catheter having a distal end, a surgical tool operable from the distal end; and an associated catheter position sensing device coupled to the processor, the position sensing device is configured to provide a signal that enables the processor to track the position of the distal end of the catheter when the distal end of the catheter is inserted into the subject's head; The processor is configured to control the display device to display a corresponding visualization of catheter movement, such that a user can use the displayed view of the 3D surgical path to align the distal end of the catheter with the initial entry voxel Vx e , y e , z e , inserting the distal end of the catheter into the head of the subject along the 3D surgical path, starting at a physical location within the head of the subject corresponding to the surgical site target voxel Vx t, , y t , z t An apparatus as described in embodiment 11, which enables positioning at a physical location corresponding to

Claims

1. 1. A method for mapping and displaying a three-dimensional (3D) surgical path within a displayed image of a head structure derived from voxels of a head scan of a subject, the method comprising: As the endpoint of the 3D surgical path, an initial entry voxel Vx ｅ , y ｅ , z ｅ and the surgical site target voxel Vxt, y ｔ , z ｔ Selecting A series of voxels is defined as the initial entry voxel Vx ｅ , y ｅ , z ｅ and the surgical site target voxel Vx ｔ , y ｔ , z ｔ such that each voxel between is a neighbor of both the immediately preceding and the immediately succeeding voxel in said series, defining said 3D surgical path; Each voxel in the series with the immediately preceding voxel Vx ｉ , y ｉ , z ｉ For voxel Vx ｉ , y ｉ , z ｉ voxel Vx, excluding the neighboring voxels of the immediately preceding voxel ｉ , y ｉ , z ｉ Among the group of neighboring voxels of voxel Vx ｉ , y ｉ , z ｉ selecting the immediately succeeding voxel of The endpoint voxel Vx ｅ , y ｅ , z ｅ and Vx ｔ , y ｔ , z ｔ determining a selection weight for each voxel in said group of neighboring voxels based on selected criteria including a relative distance to, and a relative distance from voxels within a predetermined distance having a CT value at least equal to a threshold CT value; Based on the comparison of the determined selection weights, voxel Vx ｉ , y ｉ , z ｉ selecting the immediately succeeding voxel of Selectively highlighting the voxels of the 3D surgical path within a display view of the head structure to provide a visualization of the 3D surgical path; The selection weights are: a penalty based on the difference between the predetermined distance and the distance from the nearest voxel having a CT value at least equal to the threshold CT value, plus the distance from the initial entry voxels Vx e , ye , z e to the voxels Vx i , y i , z i ; the Euclidean distance from said voxel Vx i , y i , z i to said surgical site target voxel Vx t , y t , z t ; A method which is the addition of

2. The threshold CT value is set as minus five hundred (−500) HU; The method of claim 1 , wherein the predetermined distance is 0.8 mm.

3. The 3D surgical path is the initial entry voxel Vx ｅ , y ｅ , z ｅ It is determined that the start occurs at Based on the selected criteria, each voxel Vx ｉ , y ｉ , z ｉ The determining of the selection weight of each voxel in the group of neighboring voxels of the initial entry voxel Vx ｅ , y ｅ , z ｅ and the relative proximity of the surgical site target voxel Vx ｔ , y ｔ , z ｔ The method of claim 1 , comprising a relative distance from

4. The 3D surgical path includes the surgical site target voxel Vx ｔ , y ｔ , z ｔ It is determined that the start occurs at Based on the selected criteria, each voxel Vx ｉ , y ｉ , z ｉ The determining of the selection weight of each voxel in the group of neighboring voxels of the initial entry voxel Vx ｅ , y ｅ , z ｅ and the relative distance from the surgical site target voxel Vx ｔ , y ｔ , z ｔ The method of claim 1 , further comprising a relative proximity to

5. The method of claim 1 , wherein the threshold CT number is set to a value corresponding to bone density.

6. The method of claim 1 , wherein the selectively highlighting the voxels of the 3D surgical path within the display view of the head structure includes applying a different highlighting of voxels of portions of the 3D surgical path that are hidden within the display view.

7. 1. An apparatus for mapping and displaying a three-dimensional (3D) surgical path within a graphical representation of a head structure derived from voxels of a head scan of a subject, the apparatus comprising: a data storage device configured to store voxels of the head scan of the subject; a processor and associated display device configured to provide cross-sectional and perspective views of the subject's head structure based on the head scan; The user selects an initial entry voxel Vx as an endpoint of the 3D surgical path. ｅ , y ｅ , z ｅ and surgical site target voxel Vx ｔ , y ｔ , z ｔ a voxel selection device configured to select The processor divides a set of voxels into the initial entry voxels Vx ｅ , y ｅ , z ｅ and the surgical site target voxel Vx ｔ , y ｔ , z ｔ and configured to map such that each voxel between is a neighbor of both a previous and a next voxel in the series to define the 3D surgical path; Each voxel in the series with the immediately preceding voxel Vx ｉ , y ｉ , z ｉ For voxel Vx ｉ , y ｉ , z ｉ voxel Vx, excluding the neighboring voxels of the immediately preceding voxel ｉ , y ｉ , z ｉ Among the group of neighboring voxels of voxel Vx ｉ , y ｉ , z ｉ The immediately succeeding voxel of The endpoint voxel Vx ｅ , y ｅ , z ｅ and Vx ｔ , y ｔ , z ｔ determining a selection weight for each voxel in said group of neighboring voxels based on selected criteria including a relative distance to, and a relative distance from voxels within a predetermined distance having a CT value at least equal to a threshold CT value; Based on the comparison of the determined selection weights, voxel Vx ｉ , y ｉ , z ｉ and selecting the immediately succeeding voxel of the processor is configured to selectively highlight the voxels of the 3D surgical path in an image of a head structure on the display device to provide a visualization of the 3D surgical path; The selection weights are: a penalty based on the difference between the predetermined distance and the distance from the nearest voxel having a CT value at least equal to the threshold CT value, plus the distance from the initial entry voxels Vx e , ye , z e to the voxels Vx i , y i , z i ; the Euclidean distance from said voxel Vx i , y i , z i to said surgical site target voxel Vx t , y t , z t ; A device that is an additive value of.

8. The processor, The threshold CT value is set as minus five hundred (−500) HU; The apparatus of claim 7 , wherein the predetermined distance is configured to be 0.8 mm.

9. The processor, The 3D surgical path is the initial entry voxel Vx ｅ , y ｅ , z ｅ It is determined that the start occurs at Each voxel Vx ｉ , y ｉ , z ｉ The selection weight of each voxel in the group of neighboring voxels of the initial entry voxel Vx ｅ , y ｅ , z ｅ and the relative proximity of the surgical site target voxel Vx ｔ , y ｔ , z ｔ The apparatus of claim 7 , configured to determine based on selected criteria including a relative distance from

10. The processor, The 3D surgical path includes the surgical site target voxel Vx ｔ , y ｔ , z ｔ It is determined that the start occurs at Each voxel Vx ｉ , y ｉ , z ｉ The selection weight of each voxel in the group of neighboring voxels of the initial entry voxel Vx ｅ , y ｅ , z ｅ and the relative distance from the surgical site target voxel Vx ｔ , y ｔ , z ｔ The apparatus of claim 7 , configured to determine based on selected criteria including relative proximity to

11. The apparatus of claim 7 , wherein the processor is configured to set the threshold CT number to a value corresponding to bone density.

12. 8. The apparatus of claim 7, wherein the processor is configured such that the selectively highlighting the voxels of the 3D surgical path within the display view of the head structure includes applying a different highlighting of voxels of portions of the 3D surgical path that are obscured within the display view.

13. a catheter having a distal end, a surgical tool operable from said distal end; and an associated catheter position sensing device coupled to the processor, the catheter position sensing device is configured to provide a signal that enables the processor to track a position of the distal end of the catheter when the distal end of the catheter is inserted into the subject's head; The processor is configured to control the display device to display a corresponding visualization of catheter movement, such that a user can use the displayed view of the 3D surgical path to align the distal end of the catheter with the initial entry voxel Vx ｅ , y ｅ , z ｅ t, y t , and inserting the distal end of the catheter into the head of the subject along the 3D surgical path, starting at a physical location within the head of the subject corresponding to ｔ , z ｔ 8. The apparatus of claim 7, wherein the device enables a user to position the device at a physical location corresponding to the physical location of the user.

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