Gamma analysis method, device, and storage medium

Abstract

The present application relates to the medical field, and particularly relates to a gamma analysis method, device and storage medium.The gamma analysis method comprises the following steps: in radiotherapy plan verification, a spatial anisotropy gamma analysis is adopted; and the sensitivity and specificity of the gamma analysis are adjusted through spatial anisotropy gamma analysis parameters.The present application adopts the spatial anisotropy gamma analysis in the radiotherapy plan verification, selects corresponding spatial anisotropy parameters according to the characteristics of the radiotherapy technology and equipment to adjust the sensitivity and specificity of the optimized gamma analysis, and thus effectively solves the problem that the specificity and sensitivity of the conventional isotropic gamma analysis are insufficient in specific cases when the conventional isotropic gamma analysis is used in the radiotherapy plan verification.

Description

Technical Field

[0001] This invention relates to the medical field, and in particular to a gamma analysis method, apparatus, and storage medium. Background Technology

[0002] To ensure that deviations during radiotherapy execution and the accuracy of the dose algorithm in the Treatment Planning System (TPS) are within acceptable limits, radiotherapy plans typically need to be validated. Validation involves transferring the radiotherapy plan to a phantom for calculation and comparing the dose calculated in the TPS with the dose measured using various measuring devices within the phantom to ensure that the dose obtained from the executed plan is acceptable. The gamma index, proposed by Low et al. in 1998, is a widely accepted clinical analytical indicator. The gamma index quantifies the difference between measured and calculated dose distributions point-by-point, based on the difference in dose and distance to agreement (DTA).

[0003] In particle therapy, a common method is to use a detector matrix with a certain area, such as IBA's MatrixxPT, to measure the two-dimensional dose distribution in water (solid water) at a certain depth, and then perform gamma analysis on the corresponding 2D dose distribution calculated by TPS. However, due to errors in the range of the detected rays and / or the accuracy of the planned calculation grid, as well as errors in the calibration of the equivalent water depth along the ionization chamber matrix along the ray direction, 2D gamma analysis suffers from false positives, i.e., insufficient specificity. To address this issue, Ricci et al. introduced 3D gamma analysis to replace the traditional 2D gamma analysis process during the plan validation, and 43.1% of the failed cases met the pass criteria after applying 3D gamma analysis.

[0004] However, while traditional 3D gamma analysis can tolerate minor depth errors, correcting some erroneous results and improving specificity, it may also lead to the failure to detect some errors that should be detected, thus reducing the sensitivity of the gamma analysis method. For example, Li et al. found that under the 3mm DTA standard, 3D gamma analysis of doses measured by a 3D measurement matrix composed of 24 ionization chambers could not even detect the huge carbon ion beam spot size error in the TPS modeling data. Summary of the Invention

[0005] This invention provides a gamma analysis method, device, and storage medium to at least partially solve the problems of low specificity and sensitivity of the aforementioned gamma analysis methods in radiotherapy planning verification and gamma analysis.

[0006] In a first aspect, the present invention provides a gamma analysis method, the gamma analysis method comprising:

[0007] In the validation of radiotherapy plans, spatially anisotropic gamma analysis was used;

[0008] The sensitivity and specificity of gamma analysis were validated by adjusting the radiotherapy plan using spatial anisotropy gamma analysis.

[0009] Optionally, the spatially anisotropic gamma analysis includes:

[0010] Different distance consistency standards are applied to different spatial dimensions;

[0011] Gamma analysis was performed based on the distance consistency criteria of the different spatial dimensions.

[0012] Optionally, the step of performing gamma analysis based on the distance consistency criteria of the different spatial dimensions includes:

[0013] Based on the distance consistency criteria across different spatial dimensions, the gamma values ​​of a point in the measured dose distribution and a point in the calculated dose distribution are determined.

[0014] According to the gamma value Perform gamma analysis.

[0015] Optionally, based on the distance consistency criteria of the different spatial dimensions, the gamma value of a point in the measured dose distribution and a point in the calculated dose distribution is determined using the following formula.

[0016]

[0017] In the formula, Δd i A standard for consistent distances across different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution Euclidean distances in different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution The dose deviation; i is the three-dimensional space x, y or z dimension, where the x-dimensional direction is parallel to the measurement ray, and the y and z-dimensional directions are two directions perpendicular to the measurement ray.

[0018] Optionally, based on the aforementioned consistency criteria for distances in different spatial dimensions, the gamma value of a point in the measured dose distribution and a point in the calculated dose distribution are determined using the following formula.

[0019]

[0020] In the formula, Δd i A standard for consistent distances across different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution Euclidean distances in different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution The dose deviation; i is the two-dimensional space x or y dimension, where the x-dimensional direction is parallel to the measurement ray and the y-dimensional direction is perpendicular to the measurement ray.

[0021] Optionally, based on the gamma value Gamma analysis is performed using the following formula:

[0022]

[0023] Optionally, the gamma analysis method further includes:

[0024] Based on the potential error sources in each spatial dimension of the detector matrix, different spatial dimension distance consistency criteria are selected, including:

[0025] The detector matrix determines the x-space dimension distance consistency standard based on the range error of the detected rays, the error caused by the accuracy of the planned computational grid, and / or the error of the equivalent water depth calibration along the ray direction of the flat plate ionization chamber.

[0026] Based on the positioning error of the detector matrix, determine the distance consistency criteria for the y and / or z spatial dimensions;

[0027] In a second aspect, the present invention provides an electronic device, the electronic device comprising: a memory, a controller, and a computer program stored in the memory and executable on the processor;

[0028] When the computer program is executed by the controller, it implements the steps of the gamma analysis method as described in any of the preceding claims.

[0029] Thirdly, the present invention provides a computer-readable storage medium storing a gamma analysis program, which, when executed by a controller, implements the steps of the gamma analysis method as described in any of the preceding claims.

[0030] This invention employs spatially anisotropic gamma analysis in radiotherapy planning validation, thereby appropriately selecting spatially anisotropic gamma analysis parameters based on the characteristics of radiotherapy technology and validation equipment. This allows for the adjustment and optimization of the sensitivity and specificity of gamma analysis, effectively addressing the problem that conventional gamma analysis is insufficient in specific situations during radiotherapy planning validation. Attached Figure Description

[0031] Figure 1 This is a flowchart of the gamma analysis method according to an embodiment of the present invention;

[0032] Figure 2 This is a graph showing the analysis results of gamma pass rate according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] This invention provides a gamma analysis method, such as... Figure 1 As shown, the gamma analysis method includes:

[0036] S101, in the validation of radiotherapy plans, spatial anisotropic gamma analysis was used;

[0037] S102, through the spatial anisotropy gamma analysis obtained in S101 by selecting the corresponding spatial anisotropy gamma analysis based on the characteristics of radiotherapy technology and related planning verification equipment, the sensitivity and specificity of gamma analysis in radiotherapy planning verification are adjusted and optimized.

[0038] Traditional formulas for calculating gamma values ​​are as shown in formula (1) and formula (2).

[0039]

[0040]

[0041] In the formula, To measure the gamma value at a point in a plane.

[0042] Formula (1) means that a point in the measured dose distribution is the same as any point in the calculated dose distribution. The mathematical symbol "arbitrary" is used to calculate the gamma value, and the minimum value is taken as the gamma value of that point in the measurement distribution.

[0043] Formula (2) Calculation The gamma value of a point in the measured dose distribution and the gamma value of a point in the calculated dose distribution are compared. The subscript m represents the measured dose distribution and c represents the calculated dose distribution. To measure the Euclidean distance between a point in the dose distribution and a point in the dose distribution; The dose deviation between a point in the measured dose distribution and a point in the calculated dose distribution; Δdm For distance consistency criteria; ΔD m This represents the allowable value for dose deviation.

[0044] Gamma analysis can be divided into two-dimensional gamma analysis and three-dimensional gamma analysis. The difference lies in the scope of gamma value calculation: whether the retrieval range is a two-dimensional dose calculation plane or a three-dimensional dose calculation space, as well as the calculation of the r-value.

[0045] In particle therapy, a common method is to use a two-dimensional detector matrix with a certain area, such as IBA's Matrixx PT, to measure the two-dimensional dose distribution in water (solid water) at a certain depth, and then perform gamma analysis on the 2D dose distribution of the corresponding plane calculated by TPS.

[0046] In particle radiotherapy QA, traditional 2D gamma analysis may produce false positives, indicating poor specificity. For example, the setup of the measurement equipment (such as the IBA's DigiPhant tank, which requires an equivalent water depth calibration procedure in the direction parallel to the beam each time) and the dose grid size of the TPS in the depth direction can introduce depth errors. Furthermore, due to the specificity of the particle dose distribution—its finite range and large dose gradient in the beam direction—the TPS modulates the beam intensity not only laterally (e.g., in photon planning systems) but also in the depth direction. Because of the large dose gradient in the depth direction, small errors caused by particle range uncertainty can lead to significant dose errors, resulting in plan validation failure.

[0047] However, compared to 2D gamma analysis, while traditional 3D gamma analysis can tolerate small depth errors, correcting some erroneous results and improving specificity, it does not consider the differences between the depth and lateral directions of the particle projection. The larger dose variation space in the depth direction can improve gamma analysis results, potentially causing some errors that should be detected to go undetected, thus reducing the sensitivity of the gamma analysis method.

[0048] Through research, this application found that the above problems are partly due to the assumption in gamma analysis that the permissible distance consistency standard is the same in all directional dimensions (Equation 2), while the dose change gradients in each direction are different. For example, in particle radiotherapy, if the measured dose of Matrixx PT is analyzed using a standard of 3% / 3mm, then the permissible distance deviation in each direction in space is 3mm.

[0049] Based on the aforementioned findings, this application employs spatially anisotropic gamma analysis in radiotherapy planning validation. By adjusting the sensitivity and specificity of gamma analysis through spatially anisotropic gamma analysis, it effectively addresses the problem of insufficient specificity and sensitivity of gamma analysis methods in specific situations during radiotherapy planning validation and gamma analysis.

[0050] In some embodiments, the spatially anisotropic gamma analysis includes:

[0051] Different distance consistency standards are applied to different spatial dimensions;

[0052] Gamma analysis was performed based on the distance consistency criteria of the different spatial dimensions.

[0053] This embodiment allows for the use of different distance consistency criteria in different directions within space, thereby enabling the appropriate selection of spatially anisotropic gamma analysis parameters based on the characteristics of the radiotherapy technique and validation equipment, and adjusting and optimizing the sensitivity and specificity of gamma analysis. This embodiment can more accurately assess the clinical impact of deviations between planned and executed radiotherapy doses in the depth direction, such as in proton and heavy ion therapy.

[0054] In some embodiments, different spatial dimension distance consistency standards can be selected based on the source of error in the dose measured by the detector matrix.

[0055] Specifically, during analysis, different allowable distance error values ​​can be selected for different directions based on the different sources of error. The x-dimensional distance consistency standard can be determined based on the range error of the rays detected by the detector matrix, the error caused by the accuracy of the planned computational grid, and / or the error in the equivalent water depth calibration of the flat-plate ionization chamber along the ray direction; and / or, based on the placement error of the detector matrix, the y- and / or z-dimensional distance consistency standards. For example, in a scenario where a detector matrix is ​​used for planning QA in proton radiotherapy, possible errors in the direction parallel to the ray include the range error of the ray itself, the error caused by insufficient accuracy of the planned computational grid, and the error in the equivalent water depth calibration of the detector matrix along the ray direction. Error sources in the direction perpendicular to the ray include the placement error of the flat-plate ionization chamber. If applied to other situations, the distance consistency standard needs to be determined based on the error sources measured in different spatial dimensions.

[0056] In other words, there are several considerations when applying this distance consistency standard in practice:

[0057] 1. The sources of error differ in different directions. For example, the positioning error of the equipment. For the direction of parallel rays, the error of the entire equipment, including the two-dimensional detector and the water tank or solid water, is at the millimeter level and has little impact on the gamma analysis results. However, for the direction of perpendicular rays, a millimeter-level error will cause an overall dose shift, which may lead to the failure of gamma analysis.

[0058] 2. In particle therapy, the repeatability of the energy delivered by the particle therapy equipment has a certain uncertainty. The range error caused by this uncertainty will also affect the allowable value setting in the x-direction. This is because the dose gradient is very volatile in some areas of this direction. If the allowable value is slightly larger, it will be easy to pass through the area with a large dose gradient, and errors will not be easy to detect.

[0059] 3. In particle therapy, when using a water tank similar to the Digiphant for a two-dimensional flat-panel ionization chamber produced by IBA, the equivalent water depth of the two-dimensional flat-panel detector needs to be calibrated. This calibration procedure has a certain degree of uncertainty, and this error needs to be taken into account when selecting a distance consistency standard for the spatial dimension parallel to the ray.

[0060] 4. Other factors affecting range accuracy, such as TPS debugging data and modeling errors, range calculation errors, and water model thickness errors.

[0061] In some embodiments, performing gamma analysis based on the consistency criteria of distances in different spatial dimensions may include:

[0062] Based on the distance consistency criteria across different spatial dimensions, the gamma values ​​of a point in the measured dose distribution and a point in the calculated dose distribution are determined.

[0063] According to the gamma value Perform gamma analysis.

[0064] Specifically, the gamma value can be determined using the following formula.

[0065]

[0066] In the formula, Δd i A standard for consistent distances across different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution Distance deviation in different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution The dose deviation; i is the x, y, or z spatial dimension, where the x spatial dimension direction is parallel to the measurement ray, and the y and z spatial dimension directions are two directions perpendicular to the measurement ray.

[0067] This embodiment allows for the use of different distance consistency standards in different directions in space through a new gamma value calculation formula (3). The sensitivity and specificity of gamma analysis can be adjusted by different distance consistency standards in each dimension, so as to more accurately assess the clinical impact caused by deviations between the planned and executed radiotherapy doses in the depth direction, such as in particle heavy ion therapy.

[0068] In traditional gamma analysis, the DTA standard used in the three dimensions is the same, which is Δdm. However, in our proposed improved method, this embodiment introduces a new formula for calculating the gamma value (3), where Δdm is used instead of Δdm. m,x Δd m,y Δd m,z Different values ​​can be taken for the DTA standard in different directions. By modifying this formula, the original spherical search area is transformed into an ellipsoid.

[0069] Of course, if it is a two-dimensional gamma analysis, formula (3) will become a two-dimensional form.

[0070]

[0071] A gamma analysis software was developed that can perform 2D gamma analysis and 3D gamma analysis. The software also allows different DTA standards to be set for different directions, i.e., spatial anisotropic gamma analysis.

[0072] Fifteen MatrixxPT particle field measurements were taken in relatively flat depth regions along the x-axis in water, along with one depth measurement (fall zone) with a large dose gradient. These 30 measurements were subjected to conventional 2D gamma analysis (3% / 3mm, 3% / 2mm), 3D gamma analysis ((3% / 3mm, 3% / 2mm)), and spatially anisotropic 3D gamma analysis, and the results were compared. The gamma transmittance analysis results are as follows: Figure 2 As shown. The gamma pass rate is defined as the proportion of points of interest in the measurement plate whose gamma value is less than 1. Generally, a pass rate of 95% is considered a pass.

[0073] In measurements of regions with gentle dose gradients, under the 3% / 3mm standard, two out of 15 data points in the 2D gamma analysis failed to achieve a 95% pass rate. However, when using 3D gamma analysis, all data points passed under the 3% / 3mm standard, but two data points also failed to meet the standard under the 3% / 2mm standard. In spatially anisotropic 3D gamma analysis, with DTAy and DTAz set to 3mm, and DTAx reaching 1.5mm, all data points achieved a pass rate exceeding 95% for measurements in flat regions, and the pass rate remained almost unchanged when DTAx was further relaxed. These results indicate that spatially anisotropic 3D gamma analysis with a 1.5mm DTAx provides relatively better specificity in regions with relatively gentle dose gradients, and a more relaxed DTAx does not necessarily lead to a greater improvement in specificity.

[0074] In the drop zone results, for 2D gamma analysis, only 6 / 15 out of 3% / 3mm achieved a pass rate of over 95%, while for 3D gamma analysis, all data met the standard under the 3% / 3mm standard. In the spatial anisotropic gamma analysis, 3, 2, and 1 data points failed to meet the standard for DTAx selections of 1.5mm, 2mm, and 2.5mm, respectively.

[0075] Of course, since the technology for solving this problem is still under development and there is no true gold standard, the changes in sensitivity and specificity mentioned above are based on logical speculation and are predictable. The key point is to demonstrate the ability of spatial anisotropic gamma analysis technology to adjust the analysis results based on the sources and magnitudes of various errors in actual measurements, because most errors in measurements are quantifiable and limitable.

[0076] As can be seen from the above gamma analysis software, the embodiments of the present invention allow the use of different distance consistency standards in different directions in space. Different distance consistency standards are selected for each dimension according to technical characteristics and error sources to adjust the sensitivity and specificity of gamma analysis. This can more accurately assess the clinical impact caused by deviations between the planned and executed radiotherapy doses in the depth direction, such as in proton and heavy ion therapy.

[0077] Example 2

[0078] This invention provides a storage device, which includes: a memory, a controller, and a computer program stored in the memory and executable on the processor;

[0079] When the computer program is executed by the controller, it implements the steps of the gamma analysis method as described in any one of Embodiment 1.

[0080] Example 3

[0081] This invention provides a computer-readable storage medium storing a gamma analysis program. When the gamma analysis program is executed by a controller, it implements the steps of the gamma analysis method as described in any of the embodiments in Example 1.

[0082] In the specific implementation process of Examples 2 and 3, reference can be made to Example 1, and they have corresponding technical effects.

[0083] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A gamma analysis method, characterized in that, The gamma analysis method includes: In the validation of radiotherapy plans, different distance consistency standards are used for different spatial dimensions. Based on the distance consistency criteria in different spatial dimensions, the gamma values ​​of a point in the measured dose distribution and a point in the calculated dose distribution are determined. ; According to the gamma value Perform gamma analysis; The sensitivity and specificity of gamma analysis were verified by adjusting the radiotherapy plan through spatial anisotropy gamma analysis. The gamma value at a point in the measured dose distribution and the gamma value at a point in the calculated dose distribution are determined using the following formula. : In the formula, A standard for consistent distances across different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution Euclidean distances in different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution The dose deviation; the x-space dimension of the three-dimensional space is the direction parallel to the measurement ray, and the y and z-space dimensions of the three-dimensional space are two directions perpendicular to the measurement ray; Alternatively, the gamma value of a point in the measured dose distribution and a point in the calculated dose distribution can be determined using a distance consistency standard based on the different spatial dimensions. : In the formula, A standard for consistent distances across different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution Euclidean distances in different spatial dimensions; To measure a point in the dose distribution With a point in the calculated dose distribution The dose deviation; the x-space dimension of the two-dimensional space is parallel to the measuring ray, and the y-space dimension of the two-dimensional space is perpendicular to the measuring ray.

2. The gamma analysis method according to claim 1, characterized in that, According to the gamma value Gamma analysis is performed using the following formula: 。 3. The gamma analysis method according to any one of claims 1-2, characterized in that, The gamma analysis method further includes: Based on the error sources in different spatial dimensions of the detector matrix, distance consistency standards are selected for different spatial dimensions.

4. The gamma analysis method according to claim 3, characterized in that, Based on the error sources in different spatial dimensions of the detector matrix, distance consistency criteria are selected for different spatial dimensions, including: Based on at least one of the following: the potential range error of the rays detected by the detector matrix, the error caused by the planned computational grid accuracy, and the potential error in the calibration of the equivalent water depth of the detector matrix along the ray direction, determine the x-space dimension distance consistency criterion; and / or, Based on the potential positioning error of the detector matrix, determine the consistency criteria for the distance in the y and / or z spatial dimensions.

5. An electronic device, characterized in that, The electronic device includes: a memory, a controller, and a computer program stored in the memory and executable on a processor; When the computer program is executed by the controller, it implements the steps of the gamma analysis method as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a gamma analysis program, which, when executed by the controller, implements the steps of the gamma analysis method as described in any one of claims 1-4.

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