Verify the quality of the treatment plan

Abstract

A method for verifying the quality of a treatment plan is provided, where the treatment plan specifies a radiation distribution to deliver radiation to a planning target volume. The method is performed by a quality assurance device and includes the following steps: obtaining the treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system, the first dose being a predicted dose to be deposited in a patient using the treatment plan; initiating a calculation of a secondary dose using a secondary dose calculation algorithm, the secondary dose being the dose deposited by the treatment plan; repeatedly calculating a confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; and interrupting the calculation of the secondary dose when the confidence interval is better than at least one predefined criterion.

Description

Technical Field

[0001] The present disclosure relates to the field of radiotherapy and, in particular, to verifying the quality of a treatment plan for radiotherapy. Background Art

[0002] In radiotherapy, a target volume is irradiated by one or several therapy beams. Various types of therapy beams can be used, such as photon beams, electron beams, and ion beams. The target volume can represent a cancer tumor. The therapy beam penetrates the tissue and delivers an absorbed radiation dose to kill tumor cells.

[0003] A treatment planning system determines a treatment plan that defines how a radiation delivery system will deliver a dose. When determining the treatment plan, quality assurance can be used to ensure that the treatment plan has sufficient quality.

[0004] WO 2018 / 048575 A1 discloses a system and method for learning a model for radiotherapy treatment planning to predict a radiotherapy dose distribution. WO 2018 / 077709 A1 discloses a graphical user interface for iterative treatment planning. EP 3 103 541 A1 discloses improvements in dosimetry techniques for radiotherapy.

[0005] The quality assurance performed in the prior art is very time-consuming and can take several hours to complete. For example, if the treatment plan is determined based on the patient's geometry on the treatment day, this is actually not feasible. Summary of the Invention

[0006] One objective is to provide quality assurance for a treatment plan in a more time-saving manner.

[0007] According to a first aspect, there is provided a method for verifying the quality of a treatment plan, wherein the treatment plan specifies a distribution of radiation to provide radiation to a planned target volume. The method is performed by a quality assurance device and includes the steps of: obtaining the treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system, the first dose being a predicted dose to be deposited in a patient using the treatment plan; using a secondary dose calculation algorithm to initiate the calculation of a secondary dose, the secondary dose being the dose deposited by the treatment plan; repeatedly calculating a confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; and interrupting the calculation of the secondary dose when the confidence interval is better than at least one predefined criterion, in which case the treatment plan is considered to have passed the quality assurance.

[0008] Each voxel in the secondary dose can include an estimate of the current confidence interval of the voxel.

[0009] The defined geometric volume can be the planned target volume.

[0010] The defined geometric volume can be an organ at risk.

[0011] The defined geometric volume can cover the planning target volume and the organ at risk.

[0012] The step of calculating the confidence interval of the comparative statistical measurement can be based on the available confidence intervals of the voxels in the secondary dose and on the spread of the possible secondary doses.

[0013] The comparative statistical measurement can be based on calculating a similarity by accumulating the difference measurements between corresponding voxels in the first dose and the second dose.

[0014] The comparative statistical measurement can be based on calculating a similarity by finding the difference between a third value and a fourth value, where the third value is obtained by accumulating the dose values of the first dose in all voxels within the defined geometric volume, and the fourth value is obtained by accumulating the dose values of the second dose in all voxels of the defined geometric volume.

[0015] According to a second aspect, there is provided a quality assurance device for verifying the quality of a treatment plan, wherein the treatment plan specifies the distribution of radiation so as to deliver radiation to a planning target volume. The quality assurance device includes: a processor; and a memory storing instructions which, when executed by the processor, cause the quality assurance device to: obtain the treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system, the first dose being a predicted dose to be deposited in a patient using the treatment plan; initiate the calculation of a secondary dose using a secondary dose calculation algorithm, the secondary dose being the dose deposited by the treatment plan; repeatedly calculate the confidence interval of a comparative statistical measurement by comparing the first dose and the secondary dose within a defined geometric volume; and interrupt the calculation of the secondary dose when the confidence interval is better than at least one predefined criterion, in which case the treatment plan is considered to have passed quality assurance.

[0016] Each voxel in the secondary dose can include an estimate of the current confidence interval of the voxel.

[0017] The defined geometric volume can be the planning target volume.

[0018] The defined geometric volume can be an organ at risk.

[0019] The defined geometric volume can cover the planning target volume and the organ at risk.

[0020] According to a third aspect, there is provided a computer program for verifying the quality of a treatment plan, wherein the treatment plan specifies a distribution of radiation to deliver radiation to a planned target volume. The computer program includes computer program code which, when run on a quality assurance device, causes the quality assurance device to: obtain the treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system, the first dose being a predicted dose to be deposited in a patient using the treatment plan; initiate a calculation of a secondary dose using a secondary dose calculation algorithm, the secondary dose being the dose deposited by the treatment plan; repeatedly calculate a confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; and interrupt the calculation of the secondary dose when the confidence interval is better than at least one predefined criterion, in which case the treatment plan is considered to have passed quality assurance.

[0021] According to a fourth aspect, there is provided a computer program product comprising the computer program according to the third aspect and a computer-readable device having the computer program stored thereon.

[0022] In general, unless otherwise clearly defined herein, all terms used in the claims shall be construed according to their ordinary meaning in the technical field. Unless otherwise clearly stated, all references to "an element, apparatus, component, device, step, etc." shall be construed openly as referring to at least one instance of the element, apparatus, component, device, step, etc. Unless otherwise clearly stated, the steps of any method disclosed herein need not be performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Aspects and embodiments are now described by way of example with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic diagram illustrating an environment in which embodiments proposed herein can be applied;

[0025] Figures 2A-2B is a schematic diagram illustrating two embodiments of a quality assurance device;

[0026] Figure 3 is a flowchart illustrating a method for verifying the quality of a treatment plan;

[0027] Figure 4 is a schematic diagram illustrating Figure 1 components of a quality assurance device; and

[0028] Figure 5 shows an example of a computer program product including a computer-readable device. DETAILED DESCRIPTION

[0029] Aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. However, these aspects may be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of all aspects of the invention to those skilled in the art. The same numbers refer to the same elements throughout the description.

[0030] Figure 1 FIG. is a schematic diagram illustrating an environment in which embodiments presented herein can be applied. A treatment planning system 1 determines a radiation distribution for radiotherapy in the form of a treatment plan 12. The treatment plan 12 is provided to a quality assurance device 10, which evaluates the treatment plan 12 as described in more detail below. It should be noted that although the quality assurance device 10 is shown here as being external to the treatment planning system 1, the quality assurance device 10 can also be within the treatment planning system 1.

[0031] The result 13 of quality assurance is provided from the quality assurance device 10 to the treatment planning system 1. If the result 13 is positive, the treatment planning system 1 proceeds and provides the corresponding treatment plan 12 to the radiation delivery system 2. Based on the treatment plan 12, the radiation delivery system 2 generates a beam 7 for delivering radiation to the target volume 3 of the patient 8 while avoiding radiation to the organs at risk 5.

[0032] The manner in which the radiation delivery system 2 generates the beam and delivers the dose depends on the treatment modality (such as photons, electrons or ions), as is well known in the art itself. However, the common goal is to deliver a dose as close as possible to the prescribed dose to the target volume (i.e., the tumor) 3 while minimizing the dose to the organs at risk 5 such as the bladder, brain and rectum, depending on the location of the tumor.

[0033] Figures 2A-2B FIG. is a schematic diagram illustrating two embodiments of the quality assurance device 10. First, the embodiment of Figure 2A will be described.

[0034] An evaluator module 20 evaluates the treatment plan 12. This evaluation is based on evaluating the treatment plan 12 (from the treatment planning system) and the dose of this plan, herein represented as a first dose. The first dose is compared with a second dose 14 calculated by a dose calculator 22a. If the evaluation is positive, the evaluator 20 sends the result 13 to the treatment planning system, and the dose calculator ends its calculation of the secondary dose. Also, if the calculation of the secondary dose 14 has reached an end condition and the evaluator has not determined a positive evaluation, the result 13 is negative. In Figure 2A , the dose calculator 22a is a dose calculator within the quality assurance device 10.

[0035] Now look Figure 2B , in this embodiment, the dose calculator 22b is external to the quality assurance device 10.

[0036] Figure 3 is a flow chart of a method for verifying the quality of a treatment plan. As explained above, the treatment plan specifies the distribution of radiation so as to deliver radiation to a planned target volume. The method is performed by a quality assurance device.

[0037] In step 40 of obtaining a treatment plan, the quality assurance device obtains a treatment plan and a corresponding first dose. The first dose is defined by the treatment plan. The treatment plan has been calculated in a treatment planning system and can be obtained from the treatment planning system. The first dose is the predicted dose to be deposited in a patient using the treatment plan. The treatment plan is evaluated in terms of quality assurance.

[0038] In step 42 of initiating a calculation, the quality assurance device initiates the calculation of a secondary dose calculated by a dose calculator. The secondary dose is defined as the dose to be deposited by the treatment plan, and the dose can be calculated on a voxel-by-voxel basis. A secondary dose calculation algorithm is used to calculate the secondary dose. Each voxel in the secondary dose can include an estimate of the current confidence interval for the voxel. The secondary dose calculation algorithm is different from the dose calculation algorithm of the treatment plan for calculating the first dose. Otherwise, any comparison between the first dose and the second dose would be meaningless because they would be the same amount. For example, the first dose calculation algorithm can be based on an analytical model of the total dose deposited in tissue, while the second dose algorithm can be based on a Monte Carlo simulation of particle transport. It should be noted that the calculation of the secondary dose can continue in parallel with all other steps of the method until the calculation of the secondary dose is interrupted.

[0039] In step 44 of calculating a confidence interval, the quality assurance device repeatedly calculates the confidence interval of a comparison statistical measure by comparing the first dose and the second dose over a defined geometric volume.

[0040] The defined geometric volume can be any suitable geometric volume for making this comparison. For example, the defined geometric volume can be a planned target volume, an organ at risk, or a volume covering the planned target volume and the organ at risk. The defined geometric volume can also be the entire patient body.

[0041] The calculation of the confidence interval of the comparison statistical measure can be based on the available confidence intervals of the voxels in the secondary dose and on the spread of possible secondary doses, such as the dose spread according to Monte Carlo simulation in each voxel.

[0042] The comparison statistical measure can be based, for example, on the standard deviation of the second dose.

[0043] In one embodiment, the confidence interval is calculated as follows:

[0044] CI = [S(TP, D ID + σ ID (t)), S(TP, D ID - σ ID (t))], (1)

[0046] where CI represents the confidence interval, S is a similarity operation (e.g., as exemplified below), TP is the treatment plan, D ID is the second dose and σ ID (t) is the standard deviation of the second dose, which depends on the time since the secondary dose was successively calculated and evaluated. In words, the confidence interval is the interval between a first similarity and a second similarity. The first similarity is the similarity between the first dose (of the treatment plan) and the sum of the second dose and its standard deviation. The second similarity is the similarity between the first dose and the second dose minus its standard deviation.

[0047] In one embodiment, the similarity between two doses is calculated as follows:

[0048]

[0049] where S is the similarity, D1 is the first dose, D2 is the second dose, v is the defined geometric volume, and is a voxel. In words, the similarity can be calculated by accumulating the difference measurements between corresponding voxels in the first dose and the second dose.

[0050] In one embodiment, the similarity is calculated as follows:

[0051]

[0052] In words, the similarity can be based on finding the difference between a third value and a fourth value, where the third value is obtained by accumulating the dose values of the first dose over all voxels in the defined geometric volume, and the fourth value is obtained by accumulating the dose values of the second dose over all voxels in the defined geometric volume. Then, the difference is normalized by dividing the difference by the volume of the geometric volume.

[0053] In the conditional confidence interval good enough step 45, the quality assurance device determines whether the confidence interval calculated in step 44 is good enough. This can be determined by comparing the calculated confidence interval with at least one predefined criterion. The at least one criterion can be one or more thresholds. In one embodiment, the at least one predefined criterion is a single threshold. For example, the predefined criterion can be defined such that when the confidence interval is less than a certain percentage, the confidence interval is considered good enough. This comparison can be performed for each voxel of the defined geometric volume. In this case, all voxels need to be good enough to pass quality assurance.

[0054] If the confidence interval is good enough, the method proceeds to the QA passed step 46. Otherwise, the method proceeds to the conditional calculation complete step 47.

[0055] In the QA passed step 46, the quality assurance device interrupts the calculation of the secondary dose. In this step, the treatment plan is considered to have passed quality assurance.

[0056] In the conditional calculation complete step 47, the quality assurance device determines whether the calculation of the secondary dose is complete. If this is the case, the method proceeds to the QA not passed step 49 (because the confidence interval may not be good enough to have the method in step 47). If the calculation of the secondary dose is not complete, the method returns to the conditional confidence interval good enough step 45, which optionally occurs after an idle period (not shown).

[0057] In the QA not passed step 49, the quality assurance device determines that quality assurance has not passed because this step can only be executed when the confidence interval is not good enough and the calculation of the secondary dose is complete.

[0058] Using the embodiments presented herein, once the secondary dose indicates sufficient quality, quality assurance is affirmed and no more time needs to be spent on further dose calculations for quality assurance. Different from the prior art where each voxel needs to be good enough to pass quality assurance, this method is based on a comparison of the entire defined volume. This results in significantly faster quality assurance than the prior art. In particular, such quality assurance can be applied to, for example, online adaptive treatment planning, which can be used to determine a treatment plan based on the patient's geometry on the day of treatment, as the patient's geometry can vary significantly, for example due to bladder and stomach states.

[0059] Figure 4 is illustrated Figure 1Schematic diagram of components of the quality assurance device 10. The processor 60 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc. that can execute software instructions 67 stored in the memory 64, so the processor can be a computer program product. The processor 60 can alternatively be implemented using an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc. The processor 60 can be configured to execute the method described above with reference to FIG. 2.

[0060] The memory 64 can be any combination of random access memory (RAM) and / or read only memory (ROM). The memory 64 also includes a permanent storage device, for example it can be any one or combination of a magnetic memory, an optical memory, a solid state memory or even a remotely mounted memory.

[0061] A data memory 66 is also provided for reading and / or storing data during the execution of software instructions in the processor 60. The data memory 66 can be any combination of RAM and / or ROM.

[0062] The quality assurance device 10 further includes an I / O interface 62 for communicating with external and / or internal entities. Optionally, the I / O interface 62 also includes a user interface.

[0063] Other components of the quality assurance device 10 are omitted so as not to obscure the concepts presented herein.

[0064] Figure 5 An example of a computer program product 90 including a computer-readable device is shown. On this computer-readable device, a computer program 91 can be stored, and this computer program can cause the processor to execute the method according to the embodiments described herein. In this example, the computer program product is an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-ray disc. As explained above, the computer program product can also be embodied in the memory of a device, such as Figure 3 the computer program product 64. Although the computer program 91 is schematically shown herein as tracks on the illustrated optical disc, the computer program can be stored in any manner suitable for a computer program product, such as a removable solid state memory, for example a universal serial bus (USB) drive.

[0065] The various aspects of the present disclosure have been described above with reference to several embodiments. However, as will be readily appreciated by those skilled in the art, other embodiments beyond those disclosed above are equally possible within the scope of the invention as defined by the appended patent claims. Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, and the true scope and spirit are indicated by the following claims.

Claims

1. A method for checking the quality of a treatment plan (12), wherein, A treatment plan specifies a distribution of radiation so as to deliver radiation to a planning target volume (3), the method being performed by a quality assurance device (10) and comprising the following steps: Obtain (40) the treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system (1), the first dose being a predicted dose to be deposited in a patient using the treatment plan; Initiate (42) a continuous calculation of a secondary dose using a secondary dose calculation algorithm different from the dose calculation algorithm used for the first dose, the secondary dose being the dose deposited by the treatment plan; While the continuous calculation of the secondary dose persists, repeatedly calculate (44) a confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; and Interrupt (46) the calculation of the secondary dose when the current confidence interval is better than at least one predefined criterion, and in the case where the confidence interval is better than at least one predefined criterion, the treatment plan (12) is considered to have passed quality assurance.

2. The method according to claim 1, wherein For each voxel, the secondary dose includes an estimate of the current confidence interval of the voxel.

3. The method according to claim 1 or 2, wherein The defined geometric volume is the planning target volume (3).

4. The method according to claim 1 or 2, wherein The defined geometric volume is an organ at risk (5).

5. The method according to claim 1 or 2, wherein The defined geometric volume covers the planning target volume (3) and the organ at risk (5).

6. The method according to any one of the preceding claims, wherein, The step of calculating (44) the confidence interval of the comparison statistical measure is based on the available confidence intervals of the voxels in the secondary dose and on the spread of possible secondary doses.

7. The method according to claim 6, wherein, The comparison statistical measure is based on calculating a similarity by accumulating difference measures between corresponding voxels (9) of the first dose and a second dose (14).

8. The method according to claim 6, wherein, The comparison statistical measure is based on calculating a similarity by finding the difference between a third value and a fourth value, wherein the third value is obtained by accumulating the dose values of the first dose in all voxels (9) within the defined geometric volume, and the fourth value is obtained by accumulating the dose values of the second dose in all voxels (9) of the defined geometric volume.

9. A quality assurance device (10) for verifying the quality of a treatment plan (12), wherein, A treatment plan specifies a distribution of radiation so as to deliver radiation to a planning target volume (3), the quality assurance device (10) comprising: A processor (60); and A memory (64) storing instructions (67) which, when executed by the processor, cause the quality assurance device (10) to: Obtain a treatment plan and a corresponding first dose, the treatment plan having been calculated in a treatment planning system (1), the first dose being a predicted dose to be deposited in a patient using the treatment plan; Initiate a continuous calculation of a secondary dose using a secondary dose calculation algorithm different from the dose calculation algorithm used for the first dose, the secondary dose being the dose deposited by the treatment plan; While the continuous calculation of the secondary dose persists, repeatedly calculate a confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; and When the current confidence interval is better than at least one predefined criterion, interrupt the calculation of the secondary dose. In the case where the confidence interval is better than at least one predefined criterion, the treatment plan (12) is considered to have passed quality assurance.

10. The quality assurance device (10) according to claim 9, wherein, For each voxel, the secondary dose includes an estimate of the current confidence interval for the voxel.

11. The quality assurance device (10) according to claim 9 or 10, wherein, The defined geometric volume is the planning target volume (3).

12. The quality assurance device (10) according to claim 9 or 10, wherein, The defined geometric volume is the organ at risk (5).

13. The quality assurance device (10) according to claim 9 or 10, wherein, The defined geometric volume covers the planning target volume (3) and the organ at risk (5).

14. A computer program product (64, 90) comprising a computer program (67, 91) for verifying the quality of a treatment plan (12) and a computer-readable device having the computer program stored thereon, wherein, The treatment plan specifies the distribution of radiation to deliver radiation to the planning target volume (3). The computer program includes computer program code that, when run on a quality assurance device (10), causes the quality assurance device (10) to: Obtain a treatment plan and a corresponding first dose. The treatment plan has been calculated in a treatment planning system (1), and the first dose is the predicted dose to be deposited in a patient using the treatment plan; Initiate a continuous calculation of a secondary dose using a secondary dose calculation algorithm different from the dose calculation algorithm used for the first dose. The secondary dose is the dose deposited by the treatment plan; While the continuous calculation of the secondary dose continues, repeatedly calculate the confidence interval of a comparison statistical measure by comparing the first dose and the secondary dose within a defined geometric volume; And When the current confidence interval is better than at least one predefined criterion, interrupt the calculation of the secondary dose. In the case where the confidence interval is better than at least one predefined criterion, the treatment plan (12) is considered to have passed quality assurance.

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