Medical image processing apparatus and medical image processing method

Abstract

To improve the visibility of a rendering image by deciding the positions of a view point and a light source in accordance with the structure of an object in volume data.SOLUTION: A medical image processing device according to this embodiment includes an obtaining unit and a rendering unit. The obtaining unit obtains volume data. The rendering unit decides the positions of a plurality of view points and the positions of a plurality of light sources on the basis of a distance between each view point position and each light source position, and the surface of object in the volume data or the anatomical feature thereof. The rendering unit executes rendering on the volume data on the basis of the decided plurality of view point positions and plurality of light source positions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The embodiments described in this specification relate to a medical image processing apparatus and a medical image processing method.

Background Art

[0002] Many known image rendering techniques that give an image of a scene derived from volumetric data allow movement of the position of the viewpoint from which the scene is rendered in its perspective, for example automatically or at the user's command. The rendered scene can be updated in real time as the viewpoint moves. Such a change in viewpoint can be particularly useful in medical imaging applications, and such a change in viewpoint can allow the user to view anatomical features or lesions of interest from different perspectives. For example, the user may be able to view anatomical features or lesions of interest from the clinically most useful perspective.

[0003] In one known image rendering technique, virtual light sources are also used and an image of the scene is rendered based on illumination by the one or more virtual light sources. In such a technique, movement of the virtual light sources can be provided, for example automatically or at the user's command. The rendered scene can be updated in real time as the virtual light sources move.

[0004] In the movement of a viewpoint or a virtual light source, it is known to move the viewpoint or the light source with reference to a volume to be rendered or a point within the volume. For example, many known systems provide a simple trajectory of the viewpoint or the virtual light source centered on the center of the volume or the center of the clip box. However, it is rare that visible substances are uniformly distributed in the volume to be rendered. Therefore, for a user viewing the rendered image, as the viewpoint moves, for example, the viewpoint such as a virtual camera may appear to approach or move away from an object of interest such as an anatomical feature or a pathology of the object of interest. Even if the clip box is used to define the center of rotation around which the viewpoint moves, a similar effect may still occur.

[0005] A similar effect to that described in the previous paragraph can also occur with respect to the virtual light source. When the light source moves around the volume, generally it will not apply, but unless the visible substances are uniformly distributed with respect to the center of rotation, the distance between the light source and the visible substances will change. For a point light or other light whose illumination intensity decreases with distance, when the light source moves, it can cause a significant change in the brightness of the rendered image.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the visibility of the rendered image by determining the positions of the viewpoint and the light source according to the structure of the object in the volume data. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. The problems corresponding to the respective effects of each configuration shown in the embodiments described later can also be positioned as other problems.

MEANS FOR SOLVING THE PROBLEMS

[0007] The medical image processing apparatus according to this embodiment includes an acquisition unit and a rendering unit. The acquisition unit acquires volume data. The rendering unit determines a plurality of viewpoint positions and a plurality of light source positions based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data. The rendering unit renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Modes for Carrying Out the Invention

[0009] One embodiment provides a medical image processing apparatus comprising a processing circuit configured to obtain volumetric image data for rendering, determine positions of a plurality of viewpoints or positions of light based on a distance or other spatial relationship between the viewpoint or light and a surface or other selected feature within the image data, and render the volumetric data based on the positions of the plurality of viewpoints or positions of light.

[0010] One embodiment provides a method comprising receiving volumetric image data for rendering, determining positions of a plurality of viewpoints or positions of light based on a distance or other spatial relationship between the viewpoint or light and a surface or other selected feature within the image data, and rendering the volumetric data based on the positions of the plurality of viewpoints or positions of light.

[0011] A data processing apparatus (medical image processing apparatus) 20 according to an embodiment is schematically shown in FIG. 1. In the present embodiment, the data processing apparatus 20 is configured to process medical imaging data. In other embodiments, the data processing apparatus 20 may be configured to process other suitable image data.

[0012] The data processing apparatus 20 includes a computing device 22 which is a personal computer (PC) or a workstation in this example. The computing device 22 is connected to a display screen 26 or other display device, and one or more input devices 28 such as a computer keyboard and a mouse.

[0013] The computing device 22 is configured to obtain an image data set from a data storage unit 30. The image data set is generated by processing data acquired by a scanner 24 and stored in the data storage unit 30.

[0014] Scanner 24 is configured to generate medical imaging data, and the medical imaging data may include two-dimensional, three-dimensional, or four-dimensional data in any imaging diagnostic method. For example, scanner 24 may include a magnetic resonance (MR or MRI) scanner, a computed tomography (CT) scanner, a cone beam CT scanner, an X-ray scanner, an ultrasonic scanner, a positron emission tomography (PET) scanner, or a single photon emission computed tomography (SPECT) scanner. The medical imaging data may include additional conditional data that may include, for example, non-imaging data, or may be associated with the additional conditional data.

[0015] Computing device 22 may receive medical image data and / or further conditional data from one or more additional data storage units (not shown) instead of, or in addition to, data storage unit 30. For example, computing device 22 may receive medical image data from one or more remote data storage units (not shown) that may form part of a Picture Archiving and Communication System (PACS) or other information system.

[0016] Computing device 22 provides processing resources for automatically or semi-automatically processing image data. Computing device 22 includes a processing device 32.

[0017] The processing device 32 includes an acquisition processing circuit 34 configured to acquire image data (volume data) representing a volume of interest from any one of the scanner 24, the data storage unit 30, a further data storage unit, or other suitable sources. The acquisition processing circuit 34 corresponds to an acquisition unit. The acquisition unit, for example, acquires volume data. The acquisition processing circuit 34 is also configured to perform image data processing on the acquired data in order to identify, for example, a surface or other features represented by the acquired data. For example, the acquisition processing circuit 34 can use any suitable and known segmentation technique to identify a surface or other features of interest represented by the data, such as the surface of a patient or other subject represented by the data and / or anatomical features and / or pathologies of interest.

[0018] The processing device 32 also includes a rendering circuit 36 configured to render an image from the acquired image data. The rendering circuit 36 corresponds to a rendering unit. The rendering circuit 36 can use any suitable image rendering technique and can render an image such that the rendering is performed from the perspective of a selected viewpoint, which may include a virtual camera for example. The rendering circuit 36 may generate one or more simulated light sources automatically or in response to a user command, and the rendering may be performed based on the simulated illumination by the light source.

[0019] The processing device 32 also includes an interface circuit 38 configured to obtain user or other input and / or output a rendered image frame or other rendered data from the rendering circuit 36, for example, to a display screen 26 for display. In some embodiments, the interface circuit 38 is configured to obtain user input used to determine a viewpoint position and / or the position of one or more virtual light sources and changes in their positions.

[0020] In this embodiment, circuits 34, 36, and 38 are each implemented in computing device 22 by a computer program having computer-readable instructions executable to perform the method of the embodiment. However, in other embodiments, various circuits may be implemented as one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs).

[0021] The computing device 22 also includes a hard drive, an operating system including RAM, ROM, a data bus, various device drivers, and other components of a PC including a hardware device such as a graphics card. Such components are not shown in FIG. 1 for clarity.

[0022] The data processing device 20 of FIG. 1 is configured to execute the methods shown and / or described below.

[0023] In one embodiment, the rendering circuit 36 is configured to determine a plurality of positions of viewpoints and / or positions of one or more virtual light sources based on the distance between the viewpoint or light source and a surface or other selected feature in the image data, and to render volumetric data to obtain an image based on the plurality of viewpoint positions or light positions. For example, the rendering unit determines a plurality of viewpoint positions and a plurality of light source positions based on the distance between each viewpoint position and each light source position and the surface or anatomical feature of the object in the volume data. Further, the rendering unit performs rendering on the volume data for each determined viewpoint position and each determined light source position to generate respective images.

[0024] FIG. 2 is a schematic diagram showing a path 54 of a viewpoint 50 with respect to a surface 52 of an object of interest 56 within an imaging volume according to an embodiment.

[0025] The acquisition processing circuit 34 receives volumetric imaging data, which is CT data in the present embodiment, from the data storage unit 30, and then identifies features of interest such as, for example, anatomical features or pathologies of the object of interest, and performs segmentation processing to determine boundaries of such features that can be considered to represent the positions of the surfaces of the features of interest. In some embodiments, for example, any suitable segmentation method can be used by the acquisition processing circuit 34 based on the intensity values of the voxel array forming the volumetric imaging data. In the example of FIG. 2, the acquisition processing circuit 34 uses, for example, threshold processing regarding the intensity values of the voxels to identify the voxels representing the object of interest 56, and then determines the position of the surface 52 of the object 56 from the identified voxels, thereby determining the position of the surface 52 of the object of interest 56.

[0026] Also, the image data is provided to the rendering circuit 36 by the acquisition processing circuit 34. The rendering circuit 36 performs rendering processing to generate a volume, specifically, one or more images representing the object of interest 56 or a part of the object. For example, the rendering of the volume data by the rendering unit is based on the viewing direction and the direction of light. The rendering process is executed from the perspective of the viewpoint 50. Any suitable rendering technique may be used to generate an image representing the view of the scene represented by the volumetric data. Based on ray casting from one or more virtual light sources to the volume, a volumetric array is calculated as a result of irradiance values representing the irradiance at an array of points within the volume, and an image is determined from the light received at the viewpoint based on the irradiance as a function of position and the path of light from points within the volume. Examples include global illumination techniques and other advanced image rendering techniques. However, the embodiments are not limited to such techniques, and any suitable rendering method may be used.

[0027] The position of the viewpoint 50 may be set by the user or automatically set. The viewpoint 50 may move, and additional images may be rendered at different viewpoint positions as a result. The movement of the viewpoint 50 may be started by a user command or automatically started. In this embodiment, accordingly, the viewpoint is characterized by moving along the path 54.

[0028] The position of the viewpoint 50 along the path 54 is determined by the rendering circuit 36, and the rendering circuit 36 renders an image of the volume from the perspective of the viewpoint for each position along the path 54. Thus, in this example, when the viewpoint 50 orbits along the path 54, the user will see a continuous image of the object of interest 56. Thereby, the user can view the object from successive different perspectives.

[0029] This embodiment is characterized in that the position of the viewpoint along the path 54 is determined by the rendering circuit 36 based on the distance between the viewpoint 50 and the surface 52 of the object of interest 56 determined by the acquisition processing circuit 34. In the example of FIG. 2, when the viewpoint moves around the object 56, the rendering circuit 36 determines the path 54 and the position of the viewpoint so as to maintain a constant distance between the viewpoint 50 and the surface 52. In other words, the rendering unit determines a plurality of viewpoint positions and a plurality of light source positions such that a constant distance is maintained between the surface of the object or other selected features in the volume data, the viewpoint position, and the light source position.

[0030] Any suitable technique can be used to calculate the desired position of the viewpoint. In the embodiment of FIG. 1, the acquisition processing circuit 34 uses a signed distance field (SDF) to represent the visible material surface 52. The SDF is, for example, a field that indicates the distance from the surface of the object by varying the positive and negative signs inside and outside the object in the volume data.

[0031] Thereafter, the rendering circuit 36 selects the position of the viewpoint 50, such as the position of a virtual camera, and determines the movement of the viewpoint 50 so that the viewpoint crosses the SDF field while maintaining a constant distance to the surface (or to satisfy any other desired requirements or constraints that define the movement of the viewpoint). By maintaining a fixed distance from the surface or other desired features, a more realistic or distinct impression can be given to the user. For example, the user can observe the surface or other features of interest without being disturbed by other unwanted effects that occur when the viewpoint approaches or moves away from the surface or feature of interest as the viewpoint moves.

[0032] In this embodiment, a signed distance field (SDF) is used to represent a scalar volume that takes on the value of the Euclidean distance from each pixel or voxel to the one or more surfaces or other selected features or surfaces that are closest. Voxels or other data points representing positions inside the object have negative distances, and such voxels or other data points are given negative SDF values. Voxels or other data points representing positions outside the object have positive distances, and such voxels or other data points are given positive SDF values.

[0033] The SDF representation of surface geometry has fixed complexity random access, and surface features such as, for example, spatial variations of the surface and the distance from any point in the space to the surface can be determined by reading and processing the SDF value at any point, for example, in O(1) (constant time computational complexity).

[0034] In an alternative embodiment, other methods can be used to model the surface and determine the distance from points in the volume to the surface, such as, for example, a mesh or a spatially partitioned mesh, but they may require more complex calculations.

[0035] In the embodiment of FIG. 1, after performing a segmentation process to determine a surface or other feature of interest represented by volumetric data, the acquisition processing circuit 34 calculates the SDF values of the volume, for example, for each voxel in the volumetric data set. That is, the SDF is generated by the acquisition unit based on the volume data. The SDF values in the example of FIG. 2 represent the distance to the surface 52 of each voxel.

[0036] The calculated SDF values are stored, for example, in a lookup table and / or a database. Thereafter, the rendering circuit 36 can look up the SDF values at any one or more specific positions within the volume and use the SDF values to determine the position of the viewpoint 50, for example, to maintain the viewpoint at a certain distance from the surface 52 or to satisfy other desirable rules or constraints. In other words, the rendering unit is generated based on the volume data and determines a plurality of viewpoint positions and a plurality of light source positions based on a signed distance field (SDF) that indicates the distance from the surface with different positive and negative signs inside and outside the object. If the position of the viewpoint or the light source is determined at a resolution higher or lower than the spatial resolution of the stored SDF values, or if the position of the viewpoint or the light source is outside the region where the stored SDF values are available, in order to obtain the SDF value at a specific position, the SDF value can be interpolated or extrapolated or recalculated as necessary.

[0037] In the embodiment of FIG. 1, the viewpoint position, such as the virtual camera position, for example, defines a coordinate frame in which an instruction to move the viewpoint in a specific direction, such as left, right, up, down, etc., can be implemented as a function of position by moving along the tangent vector of the SDF field, and an instruction to move the viewpoint inside or outside with respect to the surface or other feature of interest can be implemented by moving in the gradient direction of the SDF field. In this way, the movement based on separate calculations of translation and rotational movement for each movement of the viewpoint can be replaced with a single interactive model based on the SDF value. Any other operation based on the SDF value can be performed as necessary to determine the movement of the viewpoint.

[0038] For example, the use of an SDF field such as a lookup table containing pre-calculated SDF values provides a particularly simple way to determine how to move the viewpoint automatically or in response to user input while maintaining a fixed distance from the surface or other feature of interest or any other desirable spatial relationship with the surface or other feature of interest.

[0039] A modification of the embodiment of FIG. 1 is characterized in that, similar to the viewpoint position, the view direction of the viewpoint, such as the orientation of the virtual camera, is also determined based on the spatial relationship to the surface or other selected features of interest. The processing according to such a modification is schematically shown in the flowchart of FIG. 3. For example, the rendering unit determines the direction of light from the light source position and the view direction from the viewpoint position for each viewpoint position and each light source position.

[0040] In the first stage 60 of the processing, the desired movement of the viewpoint 50 is determined automatically or by the user's command. For example, as discussed, the desired movement may be to maintain a certain distance between the viewpoint 50 and the closest point on the surface 52 (the closest point changes as the viewpoint 50 moves).

[0041] The position and range of the object of interest 56 and the surface 52 are determined using the segmentation process described above in connection with FIGS. 1 and 2. As described above in connection with FIGS. 1 and 2, the SDF value is calculated based on the determined position of the surface 52 for positions throughout the volume, and the calculated SDF values are stored in a lookup table along with the corresponding positions within the volume.

[0042] In the next stage 62 of the processing, the rendering circuit 36 uses the current session of the viewpoint 50 (or the starting position of another selected viewpoint 50), the selected requirement of maintaining a certain distance from the viewpoint 50 to the surface 52, and the SDF lookup table to determine a series of points that satisfy the requirement. In the current example, to determine the points within the volume representing the contour line at a certain distance from the current viewpoint position to the surface 52, the circuit 36 uses the lookup table.

[0043] In the next stage 64 of the process, the rendering circuit 36 determines the consecutive positions taken by the viewpoint 50 and the time for the viewpoint to move to the next position, thereby determining the movement of the viewpoint 50. The determined consecutive points form the path 54. In some embodiments, the consecutive positions are positions read from a look-up table and correspond to SDF values that meet selected requirements (e.g., a requirement of a constant distance to a surface or any other selected requirement). In other embodiments, the consecutive positions may be determined using interpolation, extrapolation, or other calculations based on positions read from a look-up table and SDF values.

[0044] The time for the viewpoint 50 to move to the next position along the path 54 can be determined using, for example, values of speed or velocity parameters that are set based on user input, automatically determined, and / or pre-determined. In various embodiments, the speed or velocity parameter may represent the movement speed of the viewpoint in a linear direction, such as in the Cartesian coordinate system of the volume represented by the imaging direction. In other embodiments or operation modes, the speed or velocity parameter represents an angular velocity.

[0045] Returning to the flowchart, in the next stage 66, desirable requirements for the view direction of the viewpoint 50, such as the orientation of a virtual camera, are determined automatically or by a user's command.

[0046] In this embodiment, the desirable requirement is for the viewpoint 50 to face the closest point on the surface 52 of the object 56. Thus, as the viewpoint 50 moves around the object 56 along the path 54, the view direction of the viewpoint 50 will change so as to ensure that the viewpoint 50 always faces the closest point on the surface 52 during the movement.

[0047] In an alternative embodiment, any other desirable requirements for the viewing direction of viewpoint 50 may be selected or predetermined. For example, in some embodiments, depending on the angle that the viewing direction makes with the surface, there may be additional requirements to vary the viewing direction such that, for example, it points straight at the surface or at a selected or desired oblique angle to the surface. Such embodiments may be appropriate when viewing a curved structure, for example, when the virtual camera is located inside a cylindrical or other curved structure.

[0048] In the next stage 68, the rendering circuit 36 uses the successive positions of viewpoint 50 determined in stage 64, the selected requirements for the viewing direction of viewpoint 50 such that the viewpoint points at the nearest point on surface 52, and the SDF lookup table to determine the SD gradient values to be used when calculating the required viewing direction of the viewpoint at each determined position of viewpoint 50 along path 54. The SDF gradient values are generated, for example, by calculating the gradient using the SDF at each point in the SDF.

[0049] In the next stage 69, the rendering circuit 36 uses the SDF values to determine the required viewing direction at each position of viewpoint 50 along path 54. In the requirement that the viewpoint points at the nearest point on the surface, the viewing direction corresponds to the direction along the gradient line of the SDF value field, and the rendering circuit 36 can perform a gradient calculation based on the SDF value and the surrounding values at the viewpoint position to determine the viewing direction at each position of viewpoint 50 along path 54. In some embodiments, the SDF gradient values are pre-calculated and the lookup table stores the SDF gradient values together with the SDF values.

[0050] Following stage 69, the rendering circuit 36 performs a rendering process to generate successive images from the perspective of viewpoint 50 in the viewing direction determined in relation to each determined position of viewpoint 50.

[0051] The generated image may be stored and / or displayed. The image may be displayed, for example, as an animation and / or a series of still images. In the case of an animation, as the animation progresses, the change in the image corresponds to the value of the speed or velocity parameter described above. In some embodiments, the speed or velocity may be set by the user, and the animation may be accelerated or decelerated according to the user's command. Additionally, or alternatively, the series of still images may be displayed in a step-through process in order, and may proceed automatically or according to the user's command from one image to the next.

[0052] As described above, in some embodiments, depending on the rendering process used, the rendering circuit 36 may automatically or according to the user's command generate one or more simulated light sources, and the rendering of the image may be performed based on the simulated illumination by the light source.

[0053] In some embodiments, it is characterized in that the position of the virtual light source can also be determined based on the distance between the light source and the surface 52 or other selected features in the image data.

[0054] In such embodiments, the position of the virtual light source may change at least partially according to the position of the viewpoint 50 from which the image rendering process is performed. For example, while the virtual light source is at any desired position, if the viewpoint 50 is on one side of the object being viewed, the virtual light source will typically be located on at least the same side as the viewpoint of the object so that the surface of the object being viewed is illuminated.

[0055] If there is relative movement between the viewpoint 50 and the object 56 being viewed, for example, if the viewpoint 50 moves around the object 56, the virtual light source will also typically move to ensure that the surface of the object being viewed is properly illuminated.

[0056] According to an embodiment, the same or similar processing performed to determine the position of the viewpoint 50 with respect to the surface or other feature of interest according to the embodiments of FIGS. 1 to 3 is used to determine the position and / or orientation of the virtual light source with respect to the surface or other feature of interest.

[0057] For example, in one embodiment shown in FIG. 4, the system of FIG. 1 is used to determine the position of the virtual light source 70 as the virtual light source 70 moves around the object 56. The virtual light source 70 in this embodiment is determined to take successive positions such that the virtual light source 70 tracks a path 74 around the object 56.

[0058] The path 74 is configured to maintain a certain distance from the closest point on the surface 52 of the object 56. The position of the virtual light source 70 is calculated in the same way as calculating the position of the viewpoint 50 described above in connection with FIGS. 1 to 3, using the SDF value.

[0059] FIG. 4 also shows a path 75 that would be traced when the virtual light source 70 traces a circular path centered on a fixed point within the volume. From FIG. 4, it can be understood that when the virtual light source traces a fixed path, as the virtual light source 70 approaches or moves away from the surface 52, the surface 52 of the object 56 will appear brighter or darker. In contrast, ensuring that the virtual light source 70 traces a path 74 that maintains a certain distance from the surface can keep the illumination level of the surface constant, or normalized, or at least more uniform when the virtual light source moves relative to the object 56.

[0060] In embodiments where the light source has a directivity rather than an omnidirectional intensity with no intensity change at an angle, for example, using the SDF value, the direction of the light source may be calculated in the same or a similar way as calculating the viewing direction of the viewpoint 50 described above in relation to FIGS. 1 to 3. For example, in some embodiments, the light source may be controlled to face the nearest surface or other feature of interest. Alternatively, or in addition, in some embodiments, there may be additional requirements to vary the direction of the light source according to the angle that the light source makes with the surface, for example, to direct a light ray towards the surface or other feature and / or to direct the light of maximum intensity straight or at a selected or desired oblique angle.

[0061] In a further embodiment, each process for calculating the position of the viewpoint 50 described above is additionally or alternatively used to calculate the position of the virtual light source 70.

[0062] In some embodiments, both the virtual light source 70 and the viewpoint 50 move relative to the object so as to maintain their respective desired positions with respect to the surface 52 or other feature of interest. For example, in some embodiments, both the virtual light source 70 and the viewpoint 50 move along their respective paths so as to maintain their respective desired fixed distances from the surface 52 or other feature of interest.

[0063] In such embodiments, the virtual light source is farther from the surface or other feature of interest than the viewpoint and / or the movement of the virtual light source along the path may lag or precede the position of the viewpoint along the path. For example, in such embodiments, the movement is accelerated / decelerated so that the orbital period is constant. In such a configuration, two independent orbits of light and camera may be synchronized, for example.

[0064] In some embodiments, the calculation of the position of the virtual light source and the position of the viewpoint may be performed separately, for example, using the SDF value as described above. In other embodiments, the position of the virtual light source may be determined relative to the position of the viewpoint, and vice versa. For example, the position of the viewpoint such as path 54 may be determined using the SDF value as described above in connection with FIGS. 1 to 3, and the position of the virtual light source may be determined relative to the position of the viewpoint. For example, the virtual light source may be determined to be at a selected or predetermined distance and / or angle relative to the viewpoint position. Thus, as the viewpoint moves around the object along path 54, the virtual light source will also move around the object. Further constraints may apply, for example, the virtual light source may be determined to be at a fixed distance from the viewpoint but always away from the surface of the viewpoint. In this example, the fixed distance of the virtual light source from the viewpoint is, for example, perpendicular to the contour line representing a constant SDF value, or a fixed distance at another selected angle.

[0065] Depending on the shape of the object being viewed and the arrangement of the object's surface, the determined consecutive positions of the viewpoint (or virtual light source) may follow a path that extends in all three orthogonal directions in the Cartesian coordinate system of the volume, for example, the position may follow a 3D path. For example, similar to on the x - y plane (or other plane), the path may also extend in the z - direction (or other direction). In some embodiments, the rendering circuit 36 constrains the viewpoint position and / or the light source position to be on a selected two - dimensional plane within the volume. In such embodiments, the rendering circuit 36 is configured to determine the viewpoint position or the light position on the plane based on the projection of a constant gradient line of the SDF or other determined path onto the plane. For example, the rendering unit determines a plurality of viewpoint positions and a plurality of light source positions based on one or more constant gradient lines regarding the signed distance field. For example, a mode can be defined in which the SDF is defined as a fixed plane for each moving axis so that the camera can take a 3D path by SDF traversal and the movement does not move away from the plane.

[0066] An example of an embodiment restricted to the two-dimensional plane 84 where the viewpoint or virtual light source is selected is shown in FIG. 5. In this example, the object of interest is the pelvic and spinal region of a human subject, and the path of the viewpoint calculated to maintain a constant distance to the nearest point on the surface follows a three-dimensional path. The path is projected onto the selected two-dimensional plane 84, and the viewpoint is restricted to follow the path 82 corresponding to the projection on the plane 84. For example, the rendering unit sets at least one of the viewpoint position or the light source position on the two-dimensional plane to have different positive and negative signs inside and outside the object, and determines it based on the projection of a certain gradient line or other determined trajectory in the signed distance field (SDF) indicating the distance from the surface onto the two-dimensional plane.

[0067] In some embodiments, the object of interest may have a relatively complex structure, and the path of the viewpoint and / or virtual light source determined based on the distance to the surface of the object or other features of interest may be relatively complex, for example, having many corners or sudden direction changes. In some embodiments, a smoothing process is performed to smooth the calculated path of the viewpoint and / or virtual light source. For example, in some embodiments, an averaging window with a selected or predetermined width may be used to average the calculated location values to smooth the calculated path of the viewpoint and / or virtual light source. Other any suitable smoothing process may be used in alternative embodiments.

[0068] As described above in connection with FIG. 3, the view direction of the viewpoint, such as the orientation of the virtual camera, can also be determined based on the distance to the surface or other selected features of interest. In the embodiment described in connection with FIG. 3, the requirement selected as the view direction of the viewpoint 50 is the view direction such that the viewpoint points towards the nearest point on the surface 52.

[0069] In alternative embodiments, any other suitable requirements or constraints may be imposed on the view direction of the viewpoint. In some embodiments, the view direction may be calculated based on, for example, contour lines or gradient lines of the SDF field and / or based on local or global minima of the SDF field or other functions of the SDF field. The SDF field represents SDF values calculated as a function of positions within a volume represented by imaging data.

[0070] FIG. 6 is a schematic diagram showing an object of interest having a surface 90. The lines included in FIG. 6 are contour lines, and each line represents a constant value of the respective SDF. The SDF of positions outside the surface 90 has a positive value, and the SDF of positions inside the surface 90 has a negative value. The SDF in this example has local minima (local minimum values) at positions 94, 96, 98 and has a global minimum at position 92. Position 92 corresponds to the position of the global minimum.

[0071] In some embodiments, the view direction is determined to be along the gradient of the SDF (e.g., the steepest gradient at the position in question). This means that the view direction is towards the nearest object.

[0072] In other embodiments, the view direction is selected to be towards the global minimum of the SDF, which may represent, for example, the center of an object or the solid object with the largest area and the largest volume (e.g., towards point 92).

[0073] In some embodiments, the view direction is selected to be towards the nearest local minimum of the SDF (e.g., 94, 96 or 98). This may be more stable than looking along the gradient lines of the SDF because the direction of the gradient lines may change abruptly with the movement of the viewpoint depending on the complexity of the object surface.

[0074] In an embodiment where the viewing direction is determined to be the local SDF minimum value, the viewing direction may immediately change with the movement of the viewpoint. For example, in the embodiment of FIG. 6, when the local minimum closest to the viewpoint 50 switches from one of 94, 96, 98 to another of 94, 96, 98, the viewing direction immediately changes. In such an embodiment, additional constraints are applied to give the maximum rate of viewing direction change. In such an embodiment, the viewing direction will gradually change at a selected or predetermined maximum rate even if there is a sudden switch from one local minimum of the SDF to another local minimum of the SDF. For example, when the viewing direction and / or the direction of light switches from the direction towards the first point among a plurality of local minimum points in the signed distance field to the direction towards the second point, the rendering unit controls the change rate of the viewing direction and / or the direction of light.

[0075] In various embodiments, the viewing direction and / or the direction of the virtual light source (direction of light) is independent of the direction of movement of the viewpoint or the light source. The viewing direction or the direction of light may be determined based on the direction of movement of the viewpoint position or the light source position. The viewing direction or the direction of light may be along the gradient, for example, along the steepest gradient of the SDF. That is, the viewing direction and / or the direction of light may be along the gradient of the signed distance field. The viewing direction or the direction of light may be towards the nearest surface or other selected feature (anatomical feature) and / or towards a selected point. In some embodiments, the viewing direction or the direction of light may be towards the global (overall) minimum point or the local (local) minimum point of the SDF. The rendering of the volume data by the rendering unit is based on the viewing direction and the direction of light and at least one of the above descriptions in this paragraph.

[0076] As described above, in connection with FIG. 3, the movement speed or velocity of the viewpoint and / or the virtual light source can be controlled or varied as desired. In some embodiments, the movement speed of the viewpoint and / or the virtual light source is varied according to the shape of the path traced within a Cartesian coordinate system so as to maintain a constant or substantially constant angular velocity. For example, the rendering unit varies the movement speed of the viewpoint position and / or the light source position so as to maintain the angular velocity of the viewpoint position and / or the light source position.

[0077] One such embodiment is shown in FIG. 7. Here, the rendering circuit 36 divides the path traced by the viewpoint 50 into twelve equal-sized angular segments of a circle 100 defined with respect to a fixed point 102. The movement speed of the viewpoint along the path is varied for each segment such that the time for the viewpoint to cross the segment is substantially the same for each segment. Thus, for example, in the embodiment of FIG. 7, in order to ensure that the angular velocity by the viewpoint 50 when passing through each segment is substantially the same, the viewpoint 50 moves slowly when passing through segment 104a (for example, the two lower segments in FIG. 7, which is the region where the angular velocity is the largest: low-speed region), moves fast when passing through segment 104b (for example, the lower right segment in FIG. 7, which is the region where the angular velocity is the smallest: high-speed region), and moves at an intermediate or normal speed when passing through segment 104c (for example, the region excluding the two lower segments and the lower right segment in FIG. 7, which is smaller than the angular velocity in segment 104a and larger than the angular velocity in segment 104b: normal-speed region). Segment 104a corresponds to the low-speed region, segment 104b corresponds to the high-speed region, and segment 104c corresponds to the normal-speed region. For example, the rendering unit varies the movement speed of the viewpoint position and / or the light source position according to the distance between the viewpoint position or the light source position and the surface of the object or other selected features in the volume data.

[0078] Any other desirable control of the speed or angular velocity of the viewpoint and / or virtual light source may be provided in other embodiments. For example, the movement speed of the viewpoint or light may be varied in any desirable manner according to the distance to the surface or other selected features.

[0079] For example, embodiments have been described in which the viewpoint and / or virtual light source move in a manner that meets selected requirements, such as maintaining a constant distance from the surface or other features of the object of interest. The movement may be continuous or stepwise, and may be automatic or under the user's command. For example, the rendering unit determines a series of viewpoint positions or a series of light source positions divided by a step size as a plurality of viewpoint positions or a plurality of light source positions, and selects the step size automatically or based on user input. In alternative embodiments, additional or alternative constraints are applied to the movement of the viewpoint and / or virtual light source.

[0080] For example, even if it is a user command, constraints may be applied to avoid the viewpoint and / or light source from entering or penetrating the surface or other selected features, and / or, even if the user commands the viewpoint and / or light source to approach closer than the minimum distance, constraints may be applied to maintain the desired minimum distance from the surface or other features. For example, the rendering unit determines a series of viewpoint positions or a series of light source positions as a plurality of viewpoint positions or a plurality of light source positions, and determines the series of viewpoint positions or the series of light source positions without entering or penetrating the surface or anatomical features of the object and / or while maintaining the minimum distance from the surface or anatomical features.

[0081] In some embodiments, the viewpoint and / or the light source may be located outside the boundary of the volume represented by the imaging data. At this time, the rendering unit determines at least one of a plurality of viewpoint positions or a plurality of light source positions to be outside the volume represented by the volume data. For example, the determined path 54 or 74 may pass outside the volume represented by the imaging data. In such embodiments, the acquisition processing circuit 34 extends the value of the SDF for positions outside the volume represented by the volumetric image data and uses the extended value when determining the viewpoint position and / or the light position. That is, the acquisition unit extends the value of the signed distance field (SDF) that indicates the distance from the surface of the object with different positive and negative signs inside and outside the object for positions outside the volume represented by the volume data. To extend the SDF, the value of the SDF for positions outside the volume may be obtained by at least one of resampling the SDF or using the SDF value on or near the boundary of the volume. To obtain the SDF value for positions outside the boundary, for example, an extrapolation process of extrapolating from the SDF value on or near the boundary may be used. That is, the acquisition unit extends the value of the signed distance field by at least one of resampling the signed distance field or using the value of the signed distance field on or near the boundary of the volume to extend the value of the signed distance field.

[0082] Although embodiments have been described in which the position, view direction, and orientation are set based on the distance to the closest surface, other arbitrary suitable constraints or requirements may be applied so that the position, view direction, and / or orientation are determined based on, for example, the distance to a selected anatomical feature or region or other spatial relationships rather than the closest surface.

[0083] According to an embodiment, an SDF-based camera model is provided that keeps the view within a given distance of the substances in the scene. The camera model may also determine the look-at direction of the camera.

[0084] According to an embodiment, a method for providing a view of a 3D object from a consistent distance using a signed distance field to a visible substance, when the distance is kept constant, provides a method for a camera model to cross the gradient lines of the SDF field. Zooming or forward movement may be defined as the gradient direction of the SDF field when the distance decreases. The minimum forward distance may be defined so as not to approach or enter the substance. The resampled SDF field may be used to provide an additional range outside the volume boundary. The range of the SDF field may be extended outside the volume boundary by interactively calculating SDF values outside the boundary based on the outer surface of the SDF field. At this time, the rendering unit uses the value of the extended SDF when determining the viewpoint position and / or the light source position. The look-at direction may be independent of the movement direction. The look-at direction may be determined based on the movement direction. The look-at direction may be the direction along the gradient of the SDF at the camera location (towards the nearest surface), or the direction towards the point crossed by the camera in a plurality of steps towards the local minimum value of the SDF, or the direction towards the (fixed) point of the global minimum value of the SDF. Movement (e.g., for each axis) may be limited to a single plane by evaluating the 2D gradient / tangent plane of the SDF field projected onto the plane.

[0085] Certain circuits are described herein, but in alternative embodiments, one or more functions of these circuits can be provided by one processing resource or other component, or the functions provided by one circuit can be provided by combining two or more processing resources or other components. Reference to one circuit includes the multiple components that provide the function of the circuit, regardless of whether such components are separated from each other. Reference to multiple circuits includes one component that provides the functions of those circuits.

[0086] Certain embodiments are described, but these embodiments are presented for illustrative purposes only and are not intended to limit the scope of the invention. In fact, the novel methods and systems described herein can be embodied in various other forms. Furthermore, various omissions, replacements, and changes in the forms of the methods and systems described herein may be made without departing from the gist of the invention. The claims of the appended patent claims and their equivalent scope are intended to cover forms and changes such as those that fall within the scope of the invention. For example, when the technical features in this embodiment are realized by a medical image processing method, the medical image processing method receives volume data, determines a plurality of viewpoint positions and a plurality of light source positions based on the distance between the viewpoint position and the light source position and the surface or anatomical features of the object in the volume data, and renders the volume data based on the determined plurality of viewpoint positions and a plurality of light source positions.

[0087] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0088] 20 Device (Data Processing Device, Medical Image Processing Device) 22 Computing Device 24 Scanner 26 Display (Display Screen) 28 Input Device 30 Data Storage Unit 32 Processing Device 34 Acquisition Processing Circuit 36 Rendering Circuit 38 Interface Circuit 50 Viewpoint 52 Surface 54 Path 56 Object of Interest 70 Virtual Light Source 74 Path around Object 75 Path 82 Path 84 Plane 90 Surface 92 Global Minimum 94 Local Minimum 96 Local Minimum 98 Local Minimum 100 Circle 104a Low-Speed Region 104b High-Speed Region 104c Normal-Speed Region

Claims

1. An acquisition unit that acquires volume data; Determining a plurality of viewpoint positions and a plurality of light source positions based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data; A rendering unit that renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions; Comprising: The rendering unit: Based on a signed distance field that is generated based on the volume data and indicates the distance from the surface with different positive and negative signs inside and outside the object, determining the plurality of viewpoint positions and the plurality of light source positions; The rendering unit determines the plurality of viewpoint positions and the plurality of light source positions based on one or more constant gradient lines regarding the signed distance field; A medical image processing apparatus.

2. The rendering unit executes rendering on the volume data for each of the determined viewpoint positions and the determined light source positions to generate respective images. The medical image processing apparatus according to Claim 1.

3. The rendering unit determines the plurality of viewpoint positions and the plurality of light source positions such that a constant distance is maintained between the surface or the anatomical features and the viewpoint positions and the light source positions. The medical image processing apparatus according to Claim 1 or 2.

4. An acquisition unit that acquires volume data; Determining a plurality of viewpoint positions and a plurality of light source positions based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data; A rendering unit that renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions; Comprising: The rendering unit determines, for each of the viewpoint positions and each of the light source positions, the direction of light from the light source position and the view direction from the viewpoint position; When the view direction and / or the direction of light switches from the direction towards a first point to the direction towards a second point among a plurality of local minimum points in a signed distance field that indicates the distance from the surface with different positive and negative signs inside and outside the object, the rendering unit controls the change rate of the view direction and / or the direction of light; A medical image processing apparatus.

5. The rendering of the volume data by the rendering unit is based on the view direction and the direction of light, and the view direction and / or the direction of light is independent of the moving direction of the viewpoint position or the moving direction of the light source position, the view direction or the direction of light is determined based on the moving direction of the viewpoint position or the moving direction of the light source position, the view direction and / or the direction of light is along the gradient of the signed distance field indicating the distance from the surface with different positive and negative signs inside and outside the object, the view direction and / or the direction of light is directed towards the surface or the anatomical feature closest to the viewpoint position or the light source position, the view direction or the direction of light is based on at least one of the following: being directed towards a global minimum point or a local minimum point in the signed distance field, The medical image processing apparatus according to claim 4.

6. The rendering unit determines a series of viewpoint positions or a series of light source positions as the plurality of viewpoint positions or the plurality of light source positions, and determines the series of viewpoint positions or the series of light source positions without penetrating or entering the surface or the anatomical feature, and / or maintaining the minimum distance from the surface or the anatomical feature, The medical image processing apparatus according to any one of claims 1 to 5.

7. The rendering unit determines a series of viewpoint positions or a series of light source positions divided by a step size as the plurality of viewpoint positions or the plurality of light source positions, and selects the step size automatically or based on user input, The medical image processing apparatus according to any one of claims 1 to 5.

8. The rendering unit changes the moving speed of the viewpoint position and / or the light source position according to the distance, The medical image processing apparatus according to any one of claims 1 to 7.

9. An acquisition unit that acquires volume data, determines a plurality of viewpoint positions and a plurality of light source positions based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical feature of the object in the volume data, a rendering unit that renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions, comprising The rendering unit changes the moving speed of the viewpoint position and / or the light source position so as to maintain the angular velocity of the viewpoint position and / or the light source position. Medical image processing apparatus.

10. An acquisition unit that acquires volume data; A plurality of viewpoint positions and a plurality of light source positions are determined based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data. A rendering unit that renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions. Comprising: During at least one rendering process, the rendering unit restricts the viewpoint position and / or the light source position to be on a selected two-dimensional plane. The rendering unit determines the viewpoint position or the light source position on the two-dimensional plane based on the projection of a constant gradient line or other determined trajectory in a signed distance field indicating the distance from the surface with different positive and negative signs inside and outside the object. Medical image processing apparatus.

11. An acquisition unit that acquires volume data; A plurality of viewpoint positions and a plurality of light source positions are determined based on the distance between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data. A rendering unit that renders the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions. Comprising: The rendering unit determines that at least one of the plurality of viewpoint positions or the plurality of light source positions is outside the volume represented by the volume data. The acquisition unit expands the value of the signed distance field indicating the distance from the surface with different positive and negative signs inside and outside the object for the position outside the volume represented by the volume data. The rendering unit uses the expanded value when determining the viewpoint position and / or the light source position. Medical image processing apparatus.

12. The acquisition unit expands the value of the signed distance field by at least one of resampling the signed distance field or using the value of the signed distance field on or near the boundary of the volume to expand the value of the signed distance field. The medical image processing apparatus according to claim 11.

13. Receiving volume data, Determining a plurality of viewpoint positions and a plurality of light source positions based on the distances between each of the viewpoint positions and each of the light source positions and the surface or anatomical features of the object in the volume data, Rendering the volume data based on the determined plurality of viewpoint positions and the plurality of light source positions, Changing the moving speed of the viewpoint position and / or the light source position so as to maintain the angular velocity of the viewpoint position and / or the light source position, A medical image processing method comprising the above.

Images