Deformable image registration model

Abstract

A deformable image registration model has a housing, an outer cylinder having a first diameter, a parallel eccentric inner cylinder having a second diameter less than the first diameter, a ball socket mount, and a target region. The target area is installed on the shell through the inner cylinder, the outer cylinder and the ball socket support. The inner cylinder is rotatably mounted within the outer cylinder, and the target region is rotatably mounted directly or indirectly within the inner cylinder. The outer barrel may be rotatably mounted within the housing, and the ball socket support may be rotatably mounted within the inner barrel. Alternatively, the outer barrel may be rotatably mounted within the ball socket, and the ball socket support may be rotatably mounted within the housing.

Description

Technical Field

[0001] The present invention relates to an imaging quality assurance (QA) model device, and in particular to an adjustable deformable image registration model for on-table adaptive radiotherapy including dose measurement and dose accumulation. Background Art

[0002] Patients undergoing radiation therapy can exhibit motion and deformation in many degrees of freedom due to weight loss, tumor shrinkage, inflammation, movement caused by breathing, or simply lying in a slightly different position during treatment. This poses a challenge to radiation therapy, namely how to deliver the radiation dose to the target area while minimizing damage to surrounding healthy tissue or organs.

[0003] Deformable Image Registration (DIR) is the process of finding correspondences between images that are not linked by simple translations or rotations. This can be applied to many types of imaging, such as CT imaging or magnetic resonance imaging (MRI), and used to validate and adaptively plan treatments. The ability to model and adjust treatment plans based on physiological changes, such as weight loss during treatment, will help clinicians reduce the treatment envelope, increase the dose to the tumor, and reduce the dose to healthy tissue. This enables more effective treatment of cancers that have a higher mortality rate due to their proximity to other sensitive or mobile organs, such as pancreatic cancer, liver cancer, and lung cancer.

[0004] Using DIR to verify and adjust treatment plans requires image quality assurance tools that can generate quantified motion (translation and rotation) and deformation. The present invention involves the design of a DIR model capable of six degrees of freedom motion and deformation to verify the accuracy of the DIR process in treatment planning. Summary of the invention

[0005] According to the present invention, a deformable image registration model comprises an outer shell, an outer cylinder with a first diameter, a parallel eccentric inner cylinder with a second diameter smaller than the first diameter, a ball and socket support, and a target area. The target area is mounted on the outer shell through the inner and outer cylinders and the ball and socket support. The inner cylinder is rotatably mounted in the outer cylinder, and the target area is directly or indirectly rotatably mounted in the inner cylinder.

[0006] In another embodiment, the outer cylinder rotates about a first axis, and the inner cylinder rotates about a second axis, wherein the second axis is parallel to the first axis and offset from the first axis by a first offset distance.

[0007] In another embodiment, the target zone is offset from the second axis by a second offset distance. The first and second offset distances may be equal in length.

[0008] In another embodiment, the target volume is a deformable target volume. The target volume may also include one or more radiation dose detectors.

[0009] In another embodiment, the outer barrel is rotatably mounted within the housing, and the ball and socket bearing is rotatably mounted within the inner barrel and positioned with its center of rotation offset from the second axis by a second offset distance.

[0010] In another embodiment, the outer cylinder is rotatably mounted within the ball and socket bearing, and the ball and socket bearing is rotatably mounted within the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to enable a clearer understanding of the present invention, preferred embodiments of the present invention will now be described in detail by way of example with reference to the accompanying drawings, in which:

[0012] FIG. 1 is an isometric view of a deformable image registration model according to the present invention.

[0013] FIG. 2 is a front view of the model of FIG. 1 .

[0014] FIG. 3 is a side view of the model of FIG. 1 .

[0015] FIG. 4 is a side cross-sectional view of the model of FIG. 1 along line AA in FIG. 2 .

[0016] FIG. 5 is a front cross-sectional view of the model of FIG. 1 taken along line BB shown in FIG. 3 .

[0017] FIG. 6 is a rear view of the model of FIG. 1 .

[0018] FIG. 7 is an exploded isometric view of the model of FIG. 1 .

[0019] 8 is an isometric view of another embodiment of a deformable image registration model according to the present invention.

[0020] FIG. 9 is a front view of the model of FIG. 8 .

[0021] FIG. 10 is a side view of the model of FIG. 8 .

[0022] FIG. 11 is a side sectional view of the model of FIG. 8 taken along line CC shown in FIG. 9 .

[0023] FIG. 12 is a front cross-sectional view of the model of FIG. 8 taken along line DD shown in FIG. 10 .

[0024] FIG. 13 is a rear view of the model of FIG. 8 .

[0025] FIG. 14 is an exploded isometric view of the model of FIG. 8 .

[0026] FIG. 15 is another exploded isometric view of the model of FIG. 8 . DETAILED DESCRIPTION

[0027] According to the present invention, a deformable image registration model allows controlled adjustment of the position of an imaging target in an imaging model with six degrees of freedom. The deformable imaging target can also be used to simulate any type of motion or deformation of the target. The present invention can be used to test the accuracy of imaging equipment (such as computed tomography (CT) or magnetic resonance imaging (MRI) equipment) when tracking known motion and deformation of the target. This makes it possible to ensure the quality of imaging equipment used for pre-treatment adjustment of radiation therapy plans. The target can also include one or more radiation dose detectors to confirm the radiation dose delivery to the target according to the adjusted treatment plan.

[0028] As shown in Figures 1 to 7, the model 1 has a shell 2, two parallel eccentric cylinders 3 and 4, a ball and socket mount 5 and a target area 6. The shell 2 can have any desired shape or configuration, such as a cylinder, a truncated cylinder or an ellipse, or an anatomical shape, such as a torso, a skull, an abdomen or a chest. Preferably, the shell 2 is a truncated cylinder or an ellipse to provide a flat, stable base for the model 1. The parallel eccentric cylinder includes an outer cylinder 3 and an inner cylinder 4. The outer cylinder 3 is rotatably mounted in a complementary shaped opening in the shell 2 so as to rotate about a first axis and has a first diameter d1. The inner cylinder 4 has a second diameter (d2) smaller than the first diameter d1 and is rotatably mounted in a complementary shaped opening in the outer cylinder 3 so as to rotate about a second axis. The second axis is parallel to the first axis and is also offset from the first axis by an offset distance D1.

[0029] As shown in FIGS. 2 , 4 and 5 , the ball and socket mount 5 of the target 6 is mounted in the inner cylinder 4. The ball and socket mount 5 is positioned so that its center of rotation is offset from the second axis of the inner cylinder 4 by an offset distance D2. Therefore, when the inner cylinder 3 and / or the outer cylinder 4 rotate, the target 6 (in the ball and socket mount 5) moves relative to the outer shell 2. The ball and socket mount 5 allows the target 6 to rotate about three axes (pitch, roll and yaw). The target 6 can be any desired configuration or type of target, but preferably includes a cylindrical insert 7 that is deformable into the imaging target 6, which slides into the position of the rotation center of the ball and socket mount 5. This enables the target 6 to rotate along three axes (pitch, roll and yaw) without displacement of the target 6 (i.e., movement along the x, y or z axis). Alternatively, the target 6 can be offset from the rotation center of the ball and socket mount 2. Multiple inserts 7 of target 6 of various sizes can be used and replaced with each other to simulate changes in the overall size of the target 6, such as simulating a decrease or increase in the size of a tumor. Multiple inserts 7 may also include target volumes 6 having various imaging properties. Inserts 7 may also be used that include multiple target volumes 6 to simulate multiple radiation target volumes or organs at risk, or both. The term "target volume" is generally used to refer to radiation target volumes and organs at risk, but any particular target volume may be one of them as desired.

[0030] As shown in Figures 1, 2 and 7, the inner barrel 4 has an opening through which the ball and socket bearing 5 can be accessed for inserting or adjusting the position of the target area 6. Preferably, the ball and socket bearing 5 can rotate freely about an axis parallel to the second axis (roll axis) of the inner barrel 4. In a configuration where the insert 7 protrudes from the ball and socket bearing 5, thereby interfering with the free rotation of the ball and socket bearing 5 about two axes (pitch axis and yaw axis) orthogonal to the second axis, as shown in Figures 1 and 4, the rotation of the ball and socket bearing 5 about these axes is limited by the size of the insert 7 and the opening in the inner barrel 4.

[0031] As shown in FIGS. 2 , 4 and 5 , the outer cylinder 3 and the inner cylinder 4 can be rotated to a position where the offset distances D1 and D2 face in opposite directions, so that the ball and socket support 5 and the target area 6 are located at the center of the model 1. This occurs when the offset distances D1 and D2 are equal. From this position, the target area 6 can be moved in a plane orthogonal to the first and second axes (i.e., in the x-axis and y-axis) by rotating the outer cylinder 3 and / or the inner cylinder 4. The rotation of the inner cylinder 4 in the outer cylinder 3 changes the distance between the rotation center of the ball and socket support 5 and the first axis of the outer cylinder 3. The rotation of the outer cylinder 3 in the shell 2 causes the rotation center of the ball and socket support 5 to move along a circular path relative to the shell 2. By combining the rotation of the outer cylinder 3 and the inner cylinder 4, the rotation center of the ball and socket support 5 and the target area 6 can be displaced to any position along the x-axis and y-axis within the area determined by the offset distances D1 and D2. The displacement in the z-axis (the same axis as the first and second axes of the outer cylinder 3 and the inner cylinder 4) can be achieved by sliding the outer cylinder 3 or the inner cylinder 4 or the insert 7 (if used) relative to other parts of the model 1 on which the outer cylinder 3 or the inner cylinder 4 is mounted. Alternatively, the model 1 can also be moved along the z-axis on the imaging table in the imaging device.

[0032] The movement of the outer cylinder 3 and the inner cylinder 4 can be manually controlled by a control knob 8 mounted on and accessible from the front portion 2a of the housing 2, as shown in Figures 2 and 3. The front portion 2a of the housing 2 may also have markings about the opening where the outer cylinder 3 is mounted to indicate the rotation angle of the outer cylinder 3 relative to the housing 2. Similarly, the front portion 3a of the outer cylinder 3 may have visual markings around the opening where the inner cylinder 4 is mounted to indicate the rotation angle of the inner cylinder 4 relative to the outer cylinder 3. Visual markings may also be provided on the rear of the model 1, such as on the inner cylinder 4 (as shown in Figure 6), or on the ball and socket mount 15 (as shown in Figures 13 and 15). Alternatively, or in addition to the visual markings, imaging structures (such as reference points 9) may be added to one or more of the housing 2, the outer cylinder 3, the inner cylinder 4, the ball and socket mount 5, the insert 7, or the target area 6 to facilitate measurement of their relative positions using relevant imaging equipment and to track adjustments more accurately than visual observation and manual measurement by imaging technicians.

[0033] Although the configuration of the model 1 has been described, in which the ball and socket bearing 5 is located within the inner barrel 4 (as shown in Figures 1-7), the model 1 can also be configured in the opposite manner, in which the outer barrel 4 is located within the ball and socket bearing 5 (as shown in Figures 8-15). The operation of this alternative configuration is similar to the configuration described above, but the relative positioning and mounting of the components are different. The target area 6 or the insert 7 containing the target area 6 is located or mounted in the inner barrel 14 instead of the ball and socket mounting 5, because in this configuration, the inner barrel 14 is the innermost of the three components. In either configuration, the target area 6 is mounted directly or indirectly within the inner barrel 4 or 14.

[0034] The inner cylinder 14 and the outer cylinder 13 are similar in structure and function to the inner cylinder 4 and the outer cylinder 3 described above. In both cases, they are parallel eccentric cylinders whose first and second axes are offset by an offset distance D1. However, as shown in Figures 11, 14 and 15, the inner cylinder 14 and the outer cylinder 13 preferably have hemispherical rear ends 14a and 13a to fit and facilitate rotation in the ball and socket bearing 5.

[0035] As shown in Figures 11, 12, 14 and 15, the ball and socket bearing 15 is preferably a two-component ball and socket bearing, which operates in a similar manner to a gimbal, having an inner gimbal 15a and an outer gimbal 15b. The inner gimbal 15a has a third axis, about which the inner gimbal 15a rotates, and the third axis is perpendicular to the first axis and the second axis of the inner cylinder 14 and the outer cylinder 13. The outer gimbal 15b has a fourth axis, about which the outer gimbal 15b rotates, and the fourth axis is perpendicular to the third axis of the inner gimbal 15a and also perpendicular to the first and second axes of the inner cylinder 14 and the outer cylinder 13. As shown in Figure 12, the inner gimbal 15a has a generally annular shape, which is assembled in the outer gimbal 15b and accommodates the outer cylinder 13. Specifically, the inner gimbal 15a has the shape of a ball segment (or a spherical frustum) with a hemispherical cylindrical hole in the center. The outer universal joint 15b also has a generally annular shape to fit within the housing 12 and accommodate the inner universal joint 15a. Like the inner universal joint 15a, it has a ball segment shape, but has a ball segment-shaped hole in its center. Preferably, as shown in Figures 14 and 15, the inner universal joint 15a is formed of a single piece, while the outer universal joint 15b is formed of two pieces to facilitate assembly.

[0036] As best shown in Figures 14 and 15, the inner gimbal 15a has a post 16 that extends outwardly from the inner gimbal 15a and engages with the outer gimbal 15b to limit the movement of the inner gimbal 15a relative to the outer gimbal 15b to rotate about a third axis. Preferably, the length of the post 16 is no greater than the thickness of the outer gimbal 15b so as not to interfere with the movement of the outer gimbal 15b relative to the housing 12. Similarly, the outer gimbal 15b has a post 17 that extends outwardly from the outer gimbal 15b and engages with the outer housing 12 to limit the movement of the outer gimbal 15b relative to the housing 12 about a fourth axis. Preferably, the third and fourth axes are configured such that rotation of the inner gimbal 15a adjusts pitch, while rotation of the outer gimbal 15b adjusts yaw. When the model 11 uses visual markings to indicate the relative positions of various components, the inner cylinder 14 and the outer cylinder 13, as well as the column 17 and the hemispherical rear end 13a of the outer cylinder 13, can be marked with visual indicators to indicate the precise relative position of each component. In this case, the column 17 and the hemispherical rear end 13a are visible on the outside of the model 11, as shown in Figures 8, 13 and 15.

[0037] Model 1 can be configured for any desired imaging modality, such as X-ray, CT, PET or MRI. Model 1 and its components are preferably made of solid rigid materials for X-ray or CT imaging (kV or MV). Alternatively, model 1 or one or more of its components is configured for MRI or PET imaging and is made of rigid (MRI invisible) material, comprising one or more sealed containers containing fluid (MRI signal generating) materials. When model 1 includes a sealed fluid reservoir, it is preferably configured with a first and second volume portion, as described in U.S. Patent Nos. 10,180,484B2 or 10,310,048B2 in the name of the applicant. The first volume portion is the space defined by the side walls and end caps of the shell 2. The second volume portion is an expandable chamber or expandable bladder attached to the shell 2 and connected to the fluid of the first volume portion.

[0038] For MRI applications, the housing 2 is preferably made of acrylic acid because it has a magnetic susceptibility that closely matches human tissue, and the MRI signal generating material is an MRI contrast medium, such as an aqueous solution having a magnetic susceptibility that closely matches human tissue. The aqueous solution is doped with one or more suitable T1 and T2 relaxivity modifiers, adjusted to provide physiologically relevant T1 and T2 values, and to form a specific contrast between healthy tissue and tumors. Alternatively, the housing can be another plastic that matches the equivalent magnetic susceptibility of human tissue, and the MRI contrast agent can be an aqueous solution to which a viscosity modifier, mineral oil, silicone oil, vegetable oil, propylene glycol, or a gel that generates an MRI signal is added. Preferably, the relaxivity modifier is one or more of the following: copper (II) sulfate (CuSO4), manganese (II) chloride (MnCl2), gadolinium (III) chloride (GdCl3), or other salts and chelates of paramagnetic metals that are soluble or freely dispersed in the MRI contrast agent, superparamagnetic iron oxide nanoparticles (SPIONs) or micelles. Preferably, the model 1 is configured for multi-modality applications, including two or more of the following: MRI, CT (MV or kV), and PET imaging.

[0039] In addition to multimodal imaging applications, the model 1 can also be configured for dosimetry, gel dosimetry, deformable dose accumulation, deformable image registration (DIR), deformable image fusion, targeting or gating applications. Preferably, in applications requiring dosimetry, the insert 7 contains one or more radiation dose detectors, such as ion chambers, diodes, OSLDs, scintillators, metal oxides, diamond detectors, thin film diode or chamber arrays, 3D gel or solid dosimeters. Preferably, the insert 7 contains a target area 6, which is a gel imaging target area or a gel filled target area for 3D imaging and dosimetry and is also deformable. Such a deformable dosimeter can be formed by adding radiation indicators (such as acrylamide and bisacrylamide monomers) to a deformable hydrogel, where radiation-induced polymerization can be determined by MRI, CT or optical methods. Other suitable indicators include radiochromic dyes, which can be added to deformable hydrogels, polyurethanes or silicone rubber materials, where the color change caused by radiation can be determined by optical methods. Alternatively, radiation-induced crosslinking of silicone rubber or polyurethane rubber doped with appropriate additives can be detected by MRI or CT imaging and used to measure the cumulative radiation dose. In a further alternative, an ion chamber or other radiation measurement device can be placed in a recess in the target area 6, which can serve as or receive an ion chamber holder.

[0040] The insert 7 may have a structure substantially similar to the deformable imaging model described in the applicant's U.S. patent application publication US2020 / 0400716A1 "Deformable Imaging Model for 4D Motion Tracking". In this deformable application, the insert 7 has a generally cylindrical shape with a continuous side wall and two opposing end caps. The side walls and the end caps define a sealed reservoir containing an MRI contrast agent and a deformable target area 6. Preferably, the deformable target area 6 is made of open-cell polyurethane foam, but other similar materials, such as open-cell polyvinyl alcohol foam, open-cell silicone foam, closed-cell foam, other foams or other viscoelastic materials, may also be used. Alternatively, a continuous material with viscoelasticity and intrinsic MRI signals, such as polyurethane rubber, silicone rubber or a thermoplastic elastomer (e.g., styrene-ethylene-butylene-styrene copolymer), can be used for viscoelastic hydrogels, based on natural or artificial gel-forming polymers, such as gelatin, agarose, polyvinyl alcohol, acrylamide-based polymers or combinations thereof, with or without a crosslinker, such as a metal ion salt, aldehyde, amine or acrylamide. Preferably, the deformable target region 6 is in free contact with the MRI contrast agent that fills the sealed container within the insert 7 and the gaps within the deformable target region 6 (if any). Alternatively, the deformable target region 6 may be encapsulated in a thin-walled barrier or coating of a deformable material, such as natural or artificial rubber, silicone, fluorosilicone rubber, or a similar inert elastomer. When a foam material is used, it is best to use a vacuum to remove air bubbles and impregnate the foam material with the MR contrast agent to minimize MR and CT imaging artifacts in the target region. The material is not limited to foams, but can also be polyurethane rubber, thermoplastic elastomers (such as styrene-ethylene-butylene-styrene copolymers), latex balloons, or hydrogels, with or without the addition of high-density, non-metallic, non-conductive powders that can improve CT contrast. The different proton or electron densities of these regions result in different imaging characteristics. In FIG1 , the target region 6 is shown as a single eccentric elliptical structure, but can have other locations and geometries, such as a sphere or the physiological shape of an organ or tumor.

[0041] Fiducial markers or fiducial points 9 can be positioned at any desired location within the model 1 for modeling verification, such as being attached to the target area 6 within the deformable insert 7, as shown in FIG1 . The fiducial points 9 can be additive or subtractive, positive or negative signal. Preferably, a spherical fiducial point 9 having a diameter of at least 3 mm is fixed to the target area 6 and positioned on three orthogonal axes. The fiducial points 9 provide verification for interpreting the position and motion of the target area 6, for example, in kV or MVCT imaging. When the fiducial points 9 are to be used for MVCT applications, they must be made of a material with a sufficiently high density to ensure visibility, such as an alumina or zirconia ceramic material. Alternatively, the fiducial points 9 can be made of another high-density non-metallic material that is visible on MV. In another alternative, if the target area 6 itself has a density that is visible on kV and MV imaging, the fiducial points 9 may not be necessary. For MR-only applications, the fiducial points may also be unnecessary.

[0042] A motion assembly (e.g., an MR-compatible motor system) may be connected to the insert 7 to drive the movement of the insert 7 relative to the housing 2 or to drive the deformation of the deformable target region 6, or both. Preferably, the motion assembly is an MR-compatible piezoelectric motor assembly, such as described in U.S. Pat. No. 10,090,781 B2 in the name of the present applicant. Alternatively, other types of motion assemblies may be used, such as pneumatic or hydraulic actuators.

[0043] The present invention has been described and illustrated by exemplary embodiments, however, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of the present invention as described in the following claims. Therefore, the present invention is not limited to the specific embodiments disclosed herein.

Claims

1. A deformable image registration model, characterized in that: The invention comprises a shell, an outer cylinder with a first diameter, a parallel eccentric inner cylinder with a second diameter smaller than the first diameter, a ball and socket support, and a target area mounted on the shell through the inner cylinder, the outer cylinder and the ball and socket support, wherein the inner cylinder is rotatably mounted in the outer cylinder, and the target area is directly or indirectly rotatably mounted in the inner cylinder.

2. The deformable image registration model according to claim 1, characterized in that: in, The outer cylinder rotates about a first axis and the inner cylinder rotates about a second axis, the second axis being parallel to the first axis and offset from the first axis by a first offset distance.

3. The deformable image registration model according to claim 2, characterized in that: The target area is offset from the second axis by a second offset distance.

4. The deformable image registration model according to claim 3, characterized in that: The first and second offset distances are equal in length.

5. The deformable image registration model according to claim 3, characterized in that: in, A target volume is one or more target volumes, each of which is independently configured to simulate a radiation target volume or organ at risk.

6. The deformable image registration model according to claim 3, characterized in that: The target area includes one or more radiation dose detectors.

7. The deformable image registration model according to claim 3, characterized in that: Rotating the inner cylinder or rotating the inner cylinder and the outer cylinder may cause the target area to be displaced in a plane orthogonal to the first and second axes.

8. The deformable image registration model according to claim 3, characterized in that: The outer cylinder or the inner cylinder is configured to slide along the first axis or the second axis respectively, and the target area is moved along an axis parallel to the first axis and the second axis.

9. The deformable image registration model according to claim 3, characterized in that: The target region is contained within the insert.

10. The deformable image registration model according to claim 9, characterized in that: Wherein the insert is configured to slide along an axis parallel to the first and second axes to move the target volume along an axis parallel to the first and second axes.

11. The deformable image registration model according to claim 3, characterized in that: in, A series of visual markings are located on one or more of the front end of the housing, the front end of the inner barrel, the front end of the outer barrel, and the ball and socket mount to facilitate measuring their relative positions.

12. The deformable image registration model according to claim 3, characterized in that: in, A plurality of imaging structures are positioned in one or more of the outer housing, inner cylinder, outer cylinder and ball and socket mount to facilitate measurement of their relative positions.

13. The deformable image registration model according to claim 3, characterized in that: The outer cylinder is rotatably mounted in the outer shell, and the ball and socket bearing is rotatably mounted in the inner cylinder and is positioned such that its rotation center is offset from the second axis by a second offset distance.

14. The deformable image registration model according to claim 13, characterized in that: The ball and socket support rotates at least around a third axis and a fourth axis, and the third axis and the fourth axis are both perpendicular to the first axis and the second axis.

15. The deformable image registration model according to claim 3, characterized in that: The outer cylinder is rotatably mounted in the ball and socket bearing, and the ball and socket bearing is rotatably mounted in the outer shell.

16. The deformable image registration model according to claim 15, characterized in that: The ball and socket support includes an inner universal mount and an outer universal mount.

17. The deformable image registration model according to claim 16, characterized in that: Wherein the inner universal joint rotates about a third axis perpendicular to the first and second axes, and the outer universal joint rotates about a fourth axis perpendicular to the first, second and third axes.

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