Neutron treatment plan parameter optimization method and neutron treatment plan system

Abstract

The invention relates to the technical field of automatic parameter optimization, and particularly provides a neutron treatment plan parameter optimization method and a neutron treatment plan system. The neutron treatment plan parameter optimization method provided by the invention comprises geometric automatic optimization, physical automatic optimization, biological automatic optimization and prescription automatic optimization, and formulation of an optimal neutron treatment plan is completed through cascading of the four automatic optimizations. According to the method, the irradiation parameters meeting the prescription requirement can be automatically optimized and output based on numerous parameters such as neutron source distribution, relative positions of a target region and an organ at risk, central positions such as a plan, a neutron irradiation angle and a neutron irradiation distance, and the time for making the neutron irradiation plan for the first time is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of parameter automatic optimization, and particularly provides a neutron treatment plan parameter optimization method and a neutron treatment plan system. BACKGROUND

[0002] Boron Neutron Capture Therapy (BNCT) is an innovative binary targeted radiotherapy technology, which uses high-energy particles generated by the reaction of boron-10 isotope and neutrons to accurately kill tumor cells. Neutron treatment plan system software (hereinafter referred to as "TPSn") is the "intelligent brain" of BNCT, and its core is to output a neutron treatment plan that can be used for clinical implementation of patients. Compared with traditional radiotherapy, the physical process of neutron treatment is more complex, the dose composition is more diverse, and the biological effects of the target area and some important organs at risk are obvious, which greatly increases the difficulty of neutron treatment planning, and often results in situations where the target area is underdosed, the organs at risk are overdosed and need to be repeatedly adjusted.

[0003] Although the neutron treatment plan system can automatically adjust the implementable irradiation angle and irradiation distance according to the different positions of the tumor, the actual implementable irradiation angle and irradiation distance may still have hundreds of combinations. How to automatically optimize and calculate the best irradiation scheme from among the hundreds of combinations is a real problem that needs to be urgently solved by the current neutron treatment plan system software.

[0004] To this end, the present application provides a neutron treatment plan parameter optimization method and a neutron treatment plan system to solve the above problems. SUMMARY

[0005] In order to overcome the above-mentioned defects, the neutron treatment plan parameter optimization method and the neutron treatment plan system provided by the present application can determine the optimal irradiation angle, source-skin distance, isocenter position and irradiation time through a one-level or multi-level automatic optimization program, thereby saving the time for preparing the neutron treatment plan.

[0006] In a first aspect, the present application provides a neutron treatment plan parameter optimization method, the parameters including an irradiation angle, a source-skin distance and an isocenter position, and the method comprising: Step S11: obtaining known information, the known information at least including a tumor barycenter, a tumor target area, an organ at risk area, a skin external contour point set, a beam exit port center point, a beam exit port range, and a source-skin distance value set; Step S12: determining an initial irradiation angle based on the tumor barycenter and the skin external contour point set; Step S13: determining a motion range of an isocenter based on the beam exit port center point and the tumor barycenter; Step S14: determining a current isocenter position based on the motion range and the tumor center; Step S15: determining a current irradiation angle based on the current isocenter position and the beam's eye center; Step S16: traversing the set of source skin distance values to obtain a minimum source skin distance under which no interference occurs at the current irradiation angle, and determining the minimum source skin distance as a current source skin distance; Step S17: recording the current irradiation angle, the current source skin distance and the current isocenter position as a first level target irradiation parameter.

[0007] In some embodiments, the step S13 of determining the motion range of the isocenter based on the beam's eye center and the tumor center comprises: establishing a line connecting the beam's eye center and the tumor center, making a plane perpendicular to the line through the tumor center, and determining a region range corresponding to a cross section of the tumor target region clipped using the plane as the motion range of the isocenter.

[0008] In some embodiments, the step S14 of determining the current isocenter position based on the motion range and the tumor center comprises: Step 141: taking the position of the tumor center as a starting position of the isocenter; Step 142: adjusting the isocenter based on the motion range and determining a moved position of the isocenter; Step 143: counting a total number of pixels of the organ at risk corresponding to the moved position, the total number of pixels of the organ at risk being used to represent a projected area of the organ at risk within the beam's eye range; Step 144: judging whether the beam's eye range under the field direction view contains the tumor target region and does not contain the organ at risk region, if yes, taking the moved position as the current isocenter position, otherwise, performing step 145; Step 145: judging whether the moved position is beyond the motion range, if yes, performing step 146, otherwise, returning to perform step 142; Step 146: taking a moved position corresponding to a minimum value in the total number of pixels of the organ at risk as the current isocenter position.

[0009] In some embodiments, the step S17 is followed by: establishing a beam exit port neutron source distribution corresponding to each set of irradiation angle and source skin distance, the beam exit port neutron source distribution comprising a position distribution and an angle distribution, the position distribution comprising a plurality of position segments and a position segment intensity value corresponding to each position segment, the angle distribution comprising a plurality of angle segments and an angle segment intensity value corresponding to each angle segment, wherein each angle segment corresponds to the plurality of position segments; determining tumor and organ at risk average intensity corresponding to irradiation angle and isocenter position based on the beam exit port neutron source distribution, and automatically updating the first level target irradiation parameter to obtain a second level target irradiation parameter by comparing the increment of tumor and organ at risk average intensity under different irradiation angle and different isocenter position; wherein the tumor and organ at risk average intensity comprises a target region average intensity and an organ at risk average intensity, the target region average intensity and the organ at risk average intensity are determined according to intensity values of pixel points in the tumor target region and intensity values of pixel points in the organ at risk region respectively, and the intensity value of each pixel point is calculated based on the beam exit port neutron source distribution.

[0010] In some embodiments, the determining tumor and organ at risk average intensity corresponding to irradiation angle and isocenter position based on the beam exit port neutron source distribution, and automatically updating the first level target irradiation parameter to obtain a second level target irradiation parameter by comparing the increment of tumor and organ at risk average intensity under different irradiation angle and different isocenter position comprises: Step S21: determining current irradiation angle, current source skin distance and current isocenter position based on the first level target irradiation parameter, calculating target region average intensity and organ at risk average intensity based on current irradiation angle, current source skin distance and the beam exit port neutron source distribution to obtain intensity current value; Step S22: obtaining a plurality of different irradiation angle and source skin distance combinations based on current irradiation angle, current source skin distance and interference relationship check, and calculating target region average intensity and organ at risk average intensity corresponding to each set of irradiation angle and source skin distance combination to obtain a plurality of first intensity change values; selecting a set of irradiation angle and source skin distance for updating current irradiation angle and current source skin distance based on the increment of each first intensity change value relative to the intensity current value; Step S23: judging whether the organ at risk region is in the field direction view, if yes, executing step S24, otherwise directly to S25; Step S24: obtaining a plurality of different isocenter positions based on the movement of current isocenter and the positional relationship of tumor target region, calculating target region average intensity and organ at risk average intensity corresponding to each isocenter position to obtain a plurality of second intensity change values; selecting an isocenter position for updating current isocenter position based on the increment of each second intensity change value relative to the intensity current value; Step S25: record the current irradiation angle, the current source skin distance and the current isocenter position as the second level target irradiation parameters.

[0011] In some embodiments, the calculation of the target region average intensity and the organ at risk average intensity comprises: establishing a line connecting the beam exit port center point and the isocenter, making a plane perpendicular to the line at the isocenter, denoted as the isocenter plane, using the isocenter plane to clip the tumor target region to obtain a first boundary contour line, selecting first target pixel points according to the relative position relationship between the pixel points in the range corresponding to the first boundary contour line and the beam exit port, calculating the intensity values of all the first target pixel points to obtain the intensity values of the pixel points in the tumor target region, and obtaining the target region average intensity by averaging. making a plane parallel to the isocenter plane at the organ at risk barycenter, using the plane parallel to the isocenter plane to clip the organ at risk region to obtain a second boundary contour line, selecting second target pixel points according to the relative position relationship between the pixel points in the range corresponding to the second boundary contour line and the beam exit port, calculating the intensity values of all the second target pixel points to obtain the intensity values of the pixel points in the organ at risk region, and obtaining the organ at risk average intensity by averaging.

[0012] In some embodiments, the calculation of the intensity value of each pixel point comprises: determining the position segmented intensity value of the pixel point according to the matching relationship between the distance of the pixel point to the beam exit port center point and the plurality of position segments; determining the angle segmented intensity value of the pixel point according to the matching relationship between the angle of the pixel point to the beam exit port center point and the plurality of angle segments; wherein the angle segmented intensity value of the pixel point is obtained by accumulating the angle segmented intensity values corresponding to the plurality of position segments, and the angle of the pixel point to the beam exit port center point refers to the angle formed between the line connecting the pixel point and the beam exit port center point and the axis of the beam exit port center point.

[0013] In some embodiments, the method further comprises the step of automatically updating the first level target irradiation parameters or the second level target irradiation parameters to obtain third level target irradiation parameters: Step S31: counting all ROIs in the range of the beam exit port in the field direction view, wherein each ROI is used to represent a tumor target region or an organ at risk region; Step S32: determining a current irradiation angle, a current source-skin distance and a current isocenter position based on the first level target irradiation parameters or the second level target irradiation parameters, calculating an intensity value of each pixel in each ROI based on the current irradiation angle, the current source-skin distance and the neutron source distribution in the beam exit port, and calculating a target region average biological intensity and an organ at risk average biological intensity based on a boron composition equivalent factor of each ROI and the intensity value of each pixel to obtain a biological intensity current value; Step S33: obtaining a plurality of different irradiation angle and source-skin distance combinations based on the current irradiation angle, the current source-skin distance and the interference relationship check, calculating a target region average biological intensity and an organ at risk average biological intensity corresponding to each of the irradiation angle and source-skin distance combinations to obtain a plurality of first biological intensity change values, and selecting an irradiation angle and source-skin distance combination based on an increment of each of the first biological intensity change values relative to the biological intensity current value to update the current irradiation angle and the current source-skin distance; Step S34: determining whether an organ at risk region is in a field direction view, and if yes, performing step S35, otherwise directly performing step S36; Step S35: obtaining a plurality of different isocenter positions based on a movement of the current isocenter and a position relationship of the tumor target region, calculating a target region average biological intensity and an organ at risk average biological intensity corresponding to each of the isocenter positions to obtain a plurality of second biological intensity change values, and selecting an isocenter position based on an increment of each of the second biological intensity change values relative to the biological intensity current value to update the current isocenter position; Step S36: recording the current irradiation angle, the current source-skin distance and the current isocenter position as third level target irradiation parameters.

[0014] In some embodiments, the parameters further include a target irradiation time, and the method further includes: Step S41: calculating a simulated dose of each ROI per unit time based on the third level target irradiation parameters; Step S42: calculating a ratio of a prescription limit of each ROI to a simulated dose of each ROI according to a preset prescription limit of each ROI, taking a minimum value in the ratio as a shortest simulated irradiation time, and multiplying the shortest simulated irradiation time by the simulated dose of each ROI per unit time to obtain an ideal dose of each ROI under the current irradiation angle; Step S43: determining whether an ideal dose of a ROI corresponding to a tumor target region has reached a prescription limit and an ideal dose of a ROI corresponding to each organ at risk has not reached a prescription limit, and if yes, performing step S44, otherwise determining the shortest simulated irradiation time as a target irradiation time; Step S44: determining an organ-at-risk target dose according to the ideal dose and the prescription limit of the ROI corresponding to each organ-at-risk, and determining the minimum value in the ratio of the organ-at-risk target dose to the prescription limit of the ROI corresponding to each organ-at-risk as the target irradiation time.

[0015] In a second aspect, a neutron treatment planning system is provided, comprising a processor and a storage device, the storage device being adapted to store a plurality of program codes, the program codes being adapted to be loaded and run by the processor to perform the neutron treatment planning parameter optimization method described in any one of the technical solutions of the above-mentioned neutron treatment planning parameter optimization method.

[0016] The one or more technical solutions of the present application have at least one or more of the following beneficial effects: the geometric automatic optimization process in the neutron irradiation scheme proposed by the present application can automatically output a better isocenter position, irradiation angle and source skin distance; based on the neutron source distribution (angle distribution and position distribution) and the three-dimensional spatial position of the tumor, on the basis of geometric automatic optimization, the physical automatic optimization of the neutron irradiation scheme is completed by comparing the average intensity increments of the tumor and the organ-at-risk under different irradiation angles and different isocenter ranges, and a better isocenter position, irradiation angle and source skin distance are automatically output; based on the field direction view, the boron CBE of the target region and the organ-at-risk, the set blood boron concentration and combined with the planning isocenter spatial adjustment (the isocenter needs to be located in the tumor region), on the basis of physical automatic optimization, the biological automatic optimization of the neutron irradiation scheme is completed by comparing the average biological intensity increments of the tumor and the organ-at-risk under different irradiation angles and different isocenter ranges, a better planning isocenter, irradiation angle and source skin distance are automatically output, and dose calculation is performed; based on the prescription limit of the target region and the organ-at-risk (upper and lower limits of the target region, upper limit of the organ-at-risk), on the basis of biological automatic optimization, the prescription automatic optimization of the neutron irradiation scheme is completed by the dose result per unit time and the simulated irradiation time of each ROI, and the optimal neutron treatment plan that meets the clinical implementation is finally obtained. The scheme of the present application applied to neutron treatment planning can improve the selection efficiency of the optimal neutron irradiation parameters and save the time for the first preparation of the neutron irradiation plan. BRIEF DESCRIPTION OF DRAWINGS

[0017] The disclosure of the present application will become more apparent with reference to the drawings. Those skilled in the art will readily understand that these drawings are merely for illustrative purposes and are not intended to limit the scope of protection of the present application. Among them: Figure 1 is a flowchart of a process for obtaining a first-level target irradiation parameter based on a geometric automatic optimization process provided by the embodiments of the present application; Figure 2Is the embodiment of the application provides a flowchart of the implementation manner of determining isocenter position based on motion range and tumor barycenter; Figure 3 Is the flowchart of the embodiment of the application for obtaining the second level target irradiation parameter based on physical automatic optimization process; Figure 4 Is the flowchart of the embodiment of the application for calculating the average intensity of the target region and the average intensity of the organ at risk; Figure 5 Is the flowchart of the embodiment of the application for obtaining the third level target irradiation parameter based on biological automatic optimization process; Figure 6 Is the flowchart of the embodiment of the application for obtaining the fourth level target irradiation parameter based on prescription automatic optimization process. DETAILED DESCRIPTION

[0018] Some embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0019] In the description of the present application, "module" and "processor" can include hardware, software or a combination of both. A module can include hardware circuit, various suitable sensors, communication port, memory, and can also include software part such as program code, and can be a combination of software and hardware. The processor can be a central processor, microprocessor, image processor, digital signal processor or any other suitable processor. The processor has data and / or signal processing functions. The processor can be implemented in software, hardware or a combination of both. The term "A and / or B" means all possible combinations of A and B, such as only A, only B or A and B. The term "at least one of A or B" or "at least one of A and B" has similar meaning as "A and / or B", which can include only A, only B or A and B. The singular form of the term "one", "this" can also include plural forms.

[0020] It should be understood that the terms "first", "second" and the like in the present application are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0021] After analyzing and summarizing the existing neutron therapy device and the complete process of neutron therapy, although the tumor conditions of the treatment objects are different, the source term of the beam port of the treatment head and the spatial distribution of the intermediate photon spectrum are relatively fixed in the actual irradiation process, the size of the treatment head is basically fixed, the boron concentration and the T / N ratio (i.e. the ratio of the boron concentration of the tumor to the normal tissue) are basically fixed, and the parameters that can be changed include a few parameters such as the isocenter (which determines the irradiation direction to a certain extent), the irradiation angle, and the source skin distance. The neutron therapy plan parameter automatic optimization method proposed in the present application overcomes the difficulty of quickly preparing a neutron therapy plan caused by various positioning restrictions. First, the present application proposes four automatic optimization processes: geometric automatic optimization (first level), physical automatic optimization (second level), biological automatic optimization (third level), and prescription automatic optimization (fourth level). Second, the neutron therapy plan parameter optimization method of the present application can be realized through the cascade of one or more of the four automatic optimization processes, and then the neutron therapy plan scheme that maximizes the satisfaction of the prescription requirements can be output, which can greatly save the time for preparing a neutron therapy plan and reduce the use threshold of a neutron therapy physicist.

[0022] Referring to Figure 1 The neutron therapy plan parameter optimization method proposed in the present application can be realized based on the geometric automatic optimization (first level) process of the present application, as shown in FIG. 1. Figure 1 The process of obtaining the first level target irradiation parameter based on the geometric automatic optimization process mainly includes the following steps S11 to S17: Step S11: acquiring known information, the known information at least including a tumor center, a tumor target region, a critical organ region, a skin external contour point set, a beam port center point, a beam port range, and a source skin distance value set; In this embodiment, the known information can be parameter information directly input by a user, or parameter information calculated based on known parameters or a CT image of the irradiated object. For example, the beam port range can be determined according to the known diameter of the treatment head beam port, and the tumor center and the tumor target region can be determined based on the CT image.

[0023] Step S12: determining an initial irradiation angle based on the tumor center and the skin external contour point set; In this embodiment, the closest incidence point of the tumor and the skin can be obtained based on the tumor center and the skin external contour point set, and the initial irradiation angle can be constructed based on the tumor center and the incidence point.

[0024] Further, in this embodiment, the irradiation angle can be decomposed into a corresponding deflection angle B1 (0 to 180 degrees), a horizontal roll angle C1 (±90 degrees), and a pitch angle D1 (±90 degrees) according to the treatment bed coordinate system.

[0025] Step S13: Determine the range of motion of the isocenter based on the center point of the outlet and the center of gravity of the tumor; In this embodiment, this step specifically involves: establishing a line connecting the center point of the outlet to the center of gravity of the tumor; drawing a plane perpendicular to the line through the center of gravity of the tumor; and determining the range of motion of the isocenter point as the area corresponding to the cross-section obtained by cutting the tumor target area using the plane.

[0026] Step S14: Determine the current isocenter position based on the range of motion and the tumor's center of gravity; Step S15: Determine the current illumination angle based on the current isocenter position and the beam outlet center point; Similar to step S13 above, the current irradiation angle determined by the current isocenter point position Gi and the outlet center point can also be decomposed into the corresponding deflection angle Bi (0 to 180 degrees), roll angle Ci (±90 degrees), and pitch angle Di (±90 degrees) according to the treatment bed coordinate system.

[0027] Step S16: Traverse the set of source-skin distance values ​​to obtain the minimum source-skin distance that will not cause interference at the current illumination angle, and determine the minimum source-skin distance as the current source-skin distance; In this embodiment, "no interference at the current irradiation angle" means that there will be no interference with the treatment object, the treatment bed, and the auxiliary firmware at the current irradiation angle. For example, the source-skin distance value range in the source-skin distance value set is preferably 1 to 10 cm, and the corresponding source-skin distance values ​​in the source-skin distance value set are 1 cm, 2 cm, ..., 10 cm, a total of 10 values.

[0028] Step S17: Record the current illumination angle, the current source-to-skin distance, and the current isocenter position as the first-level target illumination parameters.

[0029] Based on step S14 above, a specific implementation of determining the current isocenter position based on the range of motion and the tumor centroid is as follows: Figure 2 As shown, the specific steps include 141 to 146: Step 141: Take the position of the tumor's centroid as the starting position of the isocenter point; Step 142: Adjust the isocenter point based on the range of motion and determine the position of the isocenter point after movement; For example, assuming that the total number of pixels in the motion range is N, the position of the isocenter can be understood as corresponding to the position of the pixel, assuming that the position of the tumor center of gravity is G, and the plane where the motion range is located is P. Adjusting the isocenter means moving the isocenter in the up, down, left and right directions on the plane P from the G point. The position of the isocenter after moving can be recorded as Gi, where i corresponds to any pixel in the N pixels, and 1≤i≤N.

[0030] Step 143: Count the total number of pixels corresponding to the position after moving, which is used to represent the projected area of the organ at risk in the beam exit range; For example, when the position of the isocenter is Gi, the total number of pixels corresponding to the position after moving is Si, where Si is the projected area of the organ at risk in the beam exit range, and 1≤i≤N.

[0031] Step 144: Determine whether the beam exit range in the beam's eye view contains the tumor target region and does not contain the organ at risk region. If yes, the position after moving is determined as the current isocenter position. Otherwise, step 145 is performed. The beam's eye view (BEV) is an imaging technique for observing patient anatomy from the perspective of the radiation source, used to determine the beam direction. It helps to evaluate the spatial relationship between the beam and the patient's treatment site by simulating the irradiation path of the radiation source.

[0032] Step 145: Determine whether the position after moving is beyond the motion range. If yes, step 146 is performed. Otherwise, return to step 142. Step 146: Determine the position after moving corresponding to the minimum value of the total number of pixels of the organ at risk as the current isocenter position.

[0033] In one specific embodiment, the neutron treatment planning parameter optimization method proposed in the present application can be implemented based on the cascade of the geometric automatic optimization (first level) process and the physical automatic optimization (second level) process of the present application. Specifically, after the above step S17, it can further include: Establishing a beam exit neutron source distribution corresponding to each set of irradiation angles and source skin distance, the beam exit neutron source distribution including a position distribution and an angle distribution, the position distribution including a plurality of position segments and a position segment intensity value corresponding to each position segment, and the angle distribution including a plurality of angle segments and an angle segment intensity value corresponding to each angle segment, wherein each angle segment corresponds to the plurality of position segments. The angle distribution covers a range of 90 degrees, the position distribution covers a range of 15 cm outside the beam port, the plurality of angle segments are U segments obtained by dividing the angle distribution from small to large, the intensity of each angle segment is denoted as Mj (1≤j≤U), the plurality of position segments are V segments obtained by dividing the position distribution from near to far, the intensity of each position segment is denoted as Nk (1≤k≤V), and each position segment contains U angle segments.

[0034] Based on the neutron source distribution in the beam port, tumor and organ at risk average intensities corresponding to irradiation angles and isocenter positions are determined, and the first-level target irradiation parameters are automatically updated by comparing the increments of the tumor and organ at risk average intensities under different irradiation angles and different isocenter ranges to obtain second-level target irradiation parameters. The tumor and organ at risk average intensities include target region average intensity and organ at risk average intensity, and the target region average intensity and the organ at risk average intensity are determined according to intensity values of pixel points in the tumor target region and intensity values of pixel points in the organ at risk region, respectively. The intensity value of each pixel point is calculated based on the neutron source distribution in the beam port.

[0035] In this embodiment, the calculation of the intensity value of each pixel point includes: According to the matching relationship between the distance of the pixel point to the isocenter and the plurality of position segments, the position segment intensity value of the pixel point is determined. According to the matching relationship between the angle of the pixel point to the isocenter and the plurality of angle segments, the angle segment intensity value of the pixel point is determined. The angle segment intensity value of the pixel point is obtained by accumulating the angle segment intensity values corresponding to the plurality of position segments, and the angle of the pixel point to the isocenter refers to the angle formed between the connecting line of the pixel point to the isocenter and the axis of the isocenter.

[0036] Referring to Figure 3 In the physical automatic optimization process proposed in this application, the specific implementation of determining the tumor and organ at risk average intensities corresponding to irradiation angles and isocenter positions based on the neutron source distribution in the beam port, and automatically updating the first-level target irradiation parameters by comparing the increments of the tumor and organ at risk average intensities under different irradiation angles and different isocenter ranges to obtain second-level target irradiation parameters includes the following steps S21 to S25: Step S21: Based on the first-level target irradiation parameters, the current irradiation angle, the current source skin distance, and the current isocenter position are determined, the target region average intensity and the organ at risk average intensity are calculated based on the current irradiation angle, the current source skin distance, and the neutron source distribution in the beam port to obtain the current intensity value. Step S22: obtaining a plurality of different combinations of irradiation angles and source-skin distances based on the current irradiation angle, the current source-skin distance and the interference relationship check, and calculating the target region average intensity and the organ at risk average intensity corresponding to each combination of irradiation angle and source-skin distance to obtain a plurality of first intensity change values; selecting a combination of irradiation angle and source-skin distance based on the increment of each first intensity change value relative to the intensity current value for updating the current irradiation angle and the current source-skin distance; The implementation of obtaining a plurality of different combinations of irradiation angles and source-skin distances based on the current irradiation angle, the current source-skin distance and the interference relationship check is as follows: updating the current irradiation angle according to a preset angle interval and automatically performing interference check on the current source-skin distance, if interference occurs, then the current source-skin distance is accumulated by a preset step until no interference occurs, and the irradiation angle and source-skin distance after each update are counted to obtain a plurality of different combinations of irradiation angles and source-skin distances. Illustratively, the current irradiation angle is updated according to an angle interval of 1 degree and an upper limit of update of ±10 degrees, and interference check is automatically performed in combination with the current source-skin distance, if interference occurs, then the source-skin distance is accumulated by a step of 0.5 cm until no interference occurs.

[0037] Illustratively, the intensity current value is E1 and F1, each first intensity change value is E2 and F2, the increment calculated for each first intensity change value is ΔE and ΔF, where ΔE=E2-E1 and ΔF=F2-F1, and according to the increment, a combination of irradiation angle and source-skin distance representing the highest target region average intensity increase can be selected for updating the current irradiation angle and source-skin distance, for example, a combination of irradiation angle and source-skin distance corresponding to the first intensity change value with the largest ΔE is preferentially selected for updating the current irradiation angle and source-skin distance, if there are multiple equal largest ΔE, then a combination of irradiation angle and source-skin distance corresponding to the first intensity change value with the largest ΔE and the smallest ΔF is selected for updating the current irradiation angle and source-skin distance.

[0038] Step S23: determining whether the organ at risk region is in the field direction view, if yes, performing step S24, otherwise directly performing step S25; Step S24: obtaining a plurality of different isocenter positions based on the movement of the current isocenter point and the position relationship of the tumor target region, calculating the target region average intensity and the organ at risk average intensity corresponding to each isocenter position to obtain a plurality of second intensity change values; selecting an isocenter position based on the increment of each second intensity change value relative to the intensity current value for updating the current isocenter position; The implementation of obtaining a plurality of different isocenter positions based on the movement of the current isocenter and the position relationship of the tumor target region is as follows: moving the current isocenter in the upward, downward, left, right, front and rear six directions within the tumor target region until the isocenter falls outside the tumor target region, and then stopping, and counting the isocenter position after each movement to obtain a plurality of different isocenter positions.

[0039] Exemplarily, the current intensity values are E1 and F1, each set of second intensity change values is E3 and F3, the increments calculated for each set of second intensity change values are ΔE and ΔF, where ΔE=E3-E1 and ΔF=F3-F1, and an isocenter position representing the highest average intensity increase of the target region can be selected according to the increments to update the current isocenter position. For example, the isocenter position corresponding to the set of second intensity change values with the maximum ΔE is preferentially selected to update the current isocenter position, and if there are multiple sets of second intensity change values with equal maximum ΔE, the isocenter position corresponding to the set of second intensity change values with the maximum ΔE and the minimum ΔF is selected to update the current isocenter position.

[0040] Step S25: recording the current irradiation angle, the current source skin distance and the current isocenter position as the second-level target irradiation parameters.

[0041] Further, in the physical automatic optimization process proposed in the present application, the calculation process of the target region average intensity and the organ at risk average intensity is as shown in Figure 4 Steps 201 and 202 are included: Step 201: establishing a line connecting the beam exit port center point and the isocenter, making a plane perpendicular to the line through the isocenter, denoted as the isocenter plane, and using the isocenter plane to clip the tumor target region to obtain a first boundary contour line, selecting first target pixel points according to the relative position relationship between the pixel points in the range corresponding to the first boundary contour line and the beam exit port, calculating the intensity values of all the first target pixel points to obtain the intensity values of the pixel points in the tumor target region, and obtaining the target region average intensity by taking the average. The implementation of selecting the first target pixel points according to the relative position relationship between the pixel points in the range corresponding to the first boundary contour line and the beam exit port is as follows: assuming that the total number of the pixel points in the range corresponding to the first boundary contour line is T, and the distance of each pixel point from the current isocenter is Hx, where 1≤x≤T, the first target pixel points are the remaining pixel points after eliminating the pixel points with Hx exceeding 15 cm outside the beam exit port.

[0042] Step 202: a plane parallel to the isocenter plane is made through the organ at risk, and a second intersection contour line is obtained by cutting the organ at risk region with the plane parallel to the isocenter plane; second target pixels are selected according to the relative position relationship between the pixel points in the range corresponding to the second intersection contour line and the beam exit port; intensity values of all the second target pixels are calculated to obtain intensity values of the pixel points in the organ at risk region; and the average intensity of the organ at risk is obtained by averaging.

[0043] The implementation of selecting the second target pixel according to the relative position relationship between the pixel points in the range corresponding to the second intersection contour line and the beam exit port is as follows: assuming that the total number of the pixel points in the range corresponding to the second intersection contour line is W, and the distance of each pixel point from the current isocenter point is Hy, where 1≤y≤W, the second target pixel is the pixel point remaining after the pixel points with a distance of more than 15 cm from the beam exit port are removed.

[0044] In one specific embodiment, the neutron treatment planning parameter optimization method proposed in the present application can be implemented based on the cascade of the geometric automatic optimization (first level) process, the physical automatic optimization (second level) process and the biological automatic optimization (third level) process of the present application. Specifically, after obtaining the second level target irradiation parameter based on the physical automatic optimization process, the method can further include the steps of obtaining the third level target irradiation parameter based on the biological automatic optimization process, as shown in the figure, and the specific steps are as follows: Figure 5 Step S31: all ROIs in the field of view of the beam exit port are counted, where each ROI is used to represent a tumor target region or an organ at risk region; Step S32: the current irradiation angle, the current source skin distance and the current isocenter point position are determined based on the first level target irradiation parameter or the second level target irradiation parameter; the intensity value of each pixel point in each ROI is calculated based on the current irradiation angle, the current source skin distance and the neutron source distribution in the beam exit port; and the target region average biological intensity and the organ at risk average biological intensity are calculated based on the boron component equivalent factor of each ROI and the intensity value of each pixel point to obtain the current biological intensity value; ​For example, all ROIs (including tumor target region and organ at risk region) located in the range of the beam exit port are recorded under statistical portal view, and Q is the total number of ROIs, each ROI is recorded as Li, 1≤i≤Q, the boron component equivalent factor (CBE factor) of each ROI is recorded as CBEi, 1≤i≤Q, the intensity value of each pixel point in each ROI is recorded as E, the average biological intensity of the target region is recorded as EB, and the average biological intensity of the organ at risk is recorded as FB; the intensity value E of each pixel point corresponding to the ROI of the tumor target region is multiplied by the CBE factor corresponding to the ROI of the tumor target region and accumulated to obtain the average biological intensity EB of the target region, and the intensity value F of each pixel point corresponding to the ROI of the organ at risk region is multiplied by the CBE factor corresponding to the ROI of the organ at risk region and accumulated to obtain the average biological intensity FB of the organ at risk.

[0045] Step S33: based on the current irradiation angle, the current source skin distance, and the interference relationship check, a plurality of different irradiation angle and source skin distance combinations are obtained, and the average biological intensity of the target region and the average biological intensity of the organ at risk corresponding to each irradiation angle and source skin distance combination are calculated to obtain a plurality of first biological intensity change values; based on the increment of each first biological intensity change value relative to the current biological intensity value, a set of irradiation angle and source skin distance is selected for updating the current irradiation angle and the current source skin distance. Wherein, the implementation of obtaining a plurality of different irradiation angle and source skin distance combinations based on the current irradiation angle, the current source skin distance, and the interference relationship check can refer to the description of step S22 above.

[0046] Exemplarily, the current biological intensity value is EB1 and FB1, each first biological intensity change value is EB2 and FB2, and the increment calculated for each first biological intensity change value is △EB and △FB, where △EB=EB2-EB1 and △FB=FB2-FB1. According to the increment, a set of irradiation angle and source skin distance that represents the highest increase in the average biological intensity of the target region can be selected for updating the current irradiation angle and the current source skin distance. For example, the irradiation angle and source skin distance corresponding to the first biological intensity change value with the maximum △EB is preferentially selected for updating the current irradiation angle and the current source skin distance. If there are multiple sets of first biological intensity change values with equal maximum △EB, the irradiation angle and source skin distance corresponding to the first biological intensity change value with the maximum △EB and the minimum △FB is selected for updating the current irradiation angle and the current source skin distance.

[0047] Step S34: judge whether the organ at risk region is in the portal view, if yes, execute step S35, otherwise directly execute S36; Step S35: Based on the relationship between the movement of the current isocenter and the position of the tumor target area, obtain multiple different isocenter positions, calculate the average biological intensity of the target area and the average biological intensity of the organs at risk corresponding to each isocenter position to obtain multiple sets of second biological intensity change values; select an isocenter position based on the increment of each set of second biological intensity change values ​​relative to the current biological intensity value to update the current isocenter position; The method for obtaining multiple different isocenter positions based on the movement of the current isocenter and the positional relationship of the tumor target area can be referred to the description of step S24 above.

[0048] For example, the current biological intensity values ​​are EB1 and FB1, and the second set of biological intensity changes are EB3 and FB3. The increments calculated for each set of second biological intensity changes are ΔEB and ΔFB, where ΔEB = EB3 - EB1 and ΔFB = FB3 - FB1. Based on the increments, the isocenter positions representing the highest increase in average biological intensity of the target area can be selected to update the current isocenter positions. For example, the isocenter positions corresponding to the set of second biological intensity changes with the largest ΔEB are preferentially selected to update the current isocenter positions. If there are multiple equal maximum ΔEB values, the isocenter positions corresponding to the set of second biological intensity changes with the largest ΔEB and the smallest ΔFB are selected to update the current isocenter positions.

[0049] Step S36: Record the current illumination angle, current source-to-skin distance, and current isocenter position as the third-level target illumination parameters.

[0050] In one specific embodiment, the neutron therapy planning parameter optimization method proposed in this application can be implemented based on the cascade of four optimization processes: geometric automatic optimization (first level), physical automatic optimization (second level), biological automatic optimization (third level), and prescription automatic optimization. Specifically, after obtaining the third-level target irradiation parameters based on the biological automatic optimization process, it may further include... Figure 6 The steps in the automated prescription optimization process shown to obtain the fourth-level target irradiation parameters are as follows: Step S41: Calculate the simulated dose per unit time for each ROI based on the third target irradiation parameters; In this embodiment, the irradiation angle, source-skin distance, and isocenter point in the third target irradiation parameters can be used as input parameters. Based on the Monte Carlo neutron dose calculation in the prior art, the biological dose result per unit time for each pixel position can be obtained, that is, the simulated dose result for each ROI can be obtained.

[0051] Step S42: Calculate the ratio of the prescription limit of each ROI to the simulated dose of each ROI according to the preset prescription limit of each ROI, take the minimum value in the ratio as the shortest simulated irradiation time, and multiply the shortest simulated irradiation time by the simulated dose of each ROI in the unit time to obtain the ideal dose of each ROI under the current irradiation angle. For example, the prescription limit of each ROI (Li) is Vi, 1≤i≤Q, the ratio of the prescription limit of each ROI to the simulated dose of each ROI is calculated, the minimum ratio is taken as the shortest simulated irradiation time, and the shortest simulated irradiation time is multiplied by the simulated dose of each ROI in the unit time to obtain the ideal dose of each ROI under the current irradiation angle Ti (1≤i≤Q).

[0052] Step S43: Determine whether the ideal dose of the ROI corresponding to the tumor target area has reached the prescription limit and the ideal dose of the ROI corresponding to each critical organ has not reached the prescription limit, if yes, execute step S44, otherwise determine the shortest simulated irradiation time as the target irradiation time. For example, Vi of the ROI corresponding to the critical organ is not more than 1500 cGy, Vi of the ROI corresponding to the tumor target area is not less than 2000 cGy, the maximum value of Ti corresponding to each critical organ ROI calculated is 1000 cGy, and Ti of the ROI corresponding to the tumor target area is 2000 cGy, which indicates that there is room for improvement and optimization of the target area prescription dose. After the determination of this step, step S44 is executed.

[0053] Step S44: Determine the critical organ target dose according to the ideal dose of the ROI corresponding to each critical organ and the prescription limit, and determine the target irradiation time according to the ratio of the critical organ target dose to the corresponding prescription limit.

[0054] For example, Vi of the ROI corresponding to the critical organ is not more than 1500 cGy, where cGy is the dose unit, and the maximum value of Ti corresponding to each critical organ ROI calculated is 1000 cGy, so the critical organ target dose can be determined as a value close to 1500, for example, the critical organ target dose is 1400 cGy. According to the ratio of the critical organ target dose to the prescription limit of the ROI corresponding to the critical organ, the proportion of the target area dose increase can be determined, and then the target irradiation time and / or the target irradiation dose acting on the target area can be determined according to the proportion of the target area dose increase. For example, the ratio is 1000 / 1400, the Ti corresponding to the tumor target area calculated is 2000 cGy, so the target irradiation dose is 2800 cGy, and the target irradiation time is the target irradiation dose divided by the simulated dose of the ROI in the unit time corresponding to the tumor target area.

[0055] It should be noted that although the above embodiments describe the steps in a specific order, those skilled in the art can understand that in order to achieve the effect of the present application, the different steps do not have to be executed in such an order, they can be executed simultaneously (in parallel) or in other orders, and these changes are within the protection scope of the present application.

[0056] Further, the present application also provides a neutron treatment planning system. In an embodiment of the neutron treatment planning system according to the present application, the system comprises a processor and a storage device, the storage device can be configured to store a program for executing the neutron treatment planning parameter optimization method of the above-mentioned method embodiments, and the processor can be configured to execute the program in the storage device, which includes but is not limited to the program for executing the neutron treatment planning parameter optimization method of the above-mentioned method embodiments. For the convenience of illustration, only the parts related to the embodiments of the present application are shown, and the specific technical details not disclosed are referred to the method part of the embodiments of the present application.

[0057] Those skilled in the art can understand that the program in the system can be adaptively split or combined in modules. Such splitting or combining of specific modules will not cause the technical solution to deviate from the principles of the present application, therefore, the technical solutions after splitting or combining will fall within the protection scope of the present application.

[0058] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without deviating from the principles of the present application, and the technical solutions after such changes or replacements will fall within the protection scope of the present application.

Claims

1. A method for optimizing neutron therapy planning parameters, characterized in that, The parameters include irradiation angles, source-skin distances, and isocenter positions, and the method comprises: Step S11: obtaining known information, the known information at least comprising a tumor barycenter, a tumor target volume, an organ at risk volume, a skin external contour point set, a beam exit port center point, a beam exit port range, a source-skin distance value set; Step S12: determining initial irradiation angles based on the tumor barycenter and the skin external contour point set; Step S13: determining a motion range of an isocenter based on the beam exit port center point and the tumor barycenter; Step S14: determining a current isocenter position based on the motion range and the tumor barycenter; Step S15: determining a current irradiation angle based on the current isocenter position and the beam exit port center point; Step S16: traversing the source-skin distance value set to obtain a minimum source-skin distance that does not cause interference under the current irradiation angle, and determining the minimum source-skin distance as a current source-skin distance; Step S17: recording the current irradiation angle, the current source-skin distance, and the current isocenter position as first-level target irradiation parameters.

2. The method of optimizing parameters for a neutron therapy plan according to claim 1, wherein, The step S13 of determining the motion range of the isocenter based on the beam exit port center point and the tumor barycenter comprises: establishing a line connecting the beam exit port center point and the tumor barycenter, making a plane perpendicular to the line through the tumor barycenter, and determining a range of an area corresponding to a cross section of the tumor target volume obtained by clipping the tumor target volume using the plane as the motion range of the isocenter.

3. The method of claim 1, wherein, The step S14 of determining the current isocenter position based on the motion range and the tumor barycenter comprises: Step 141: taking the position of the tumor barycenter as a starting position of the isocenter; Step 142: adjusting the isocenter based on the motion range and determining a moved position of the isocenter; Step 143: counting a total number of organ at risk pixels corresponding to the moved position, the total number of organ at risk pixels being used to represent a projection area of the organ at risk within the beam exit port range; Step 144: determining whether the beam exit port range contains the tumor target volume and does not contain the organ at risk volume in a field direction view, and if yes, determining the moved position as the current isocenter position, and if not, executing Step 145; Step 145: determining whether the moved position is beyond the motion range, and if yes, executing Step 146, and if not, returning to execute Step 142; Step 146: determining a moved position corresponding to a minimum value in the total number of organ at risk pixels as the current isocenter position.

4. The method of parameter optimization for a neutron therapy plan according to any one of claims 1-3, wherein, The step S17 further comprises: establishing a beam exit port neutron source distribution corresponding to each set of irradiation angles and source-skin distances, the beam exit port neutron source distribution comprising a position distribution and an angle distribution, the position distribution comprising a plurality of position segments and a position segment intensity value corresponding to each position segment, and the angle distribution comprising a plurality of angle segments and an angle segment intensity value corresponding to each angle segment, wherein each angle segment corresponds to the plurality of position segments. determine tumor and organ at risk average intensities corresponding to irradiation angles and isocenter positions based on the beam exit port neutron source distribution, and automatically update the first level target irradiation parameters by comparing increments of the tumor and organ at risk average intensities under different irradiation angles and different isocenter positions to obtain second level target irradiation parameters; wherein the tumor and organ at risk average intensities include target region average intensity and organ at risk average intensity; the target region average intensity and the organ at risk average intensity are determined according to intensity values of pixel points in the tumor target region and intensity values of pixel points in the organ at risk region respectively, and the intensity value of each pixel point is calculated based on the beam exit port neutron source distribution.

5. The method of optimizing parameters for a neutron therapy plan of claim 4, wherein, The determination of the tumor and organ at risk average intensities corresponding to irradiation angles and isocenter positions based on the beam exit port neutron source distribution, and the automatic update of the first level target irradiation parameters by comparing increments of the tumor and organ at risk average intensities under different irradiation angles and different isocenter positions to obtain second level target irradiation parameters include: Step S21: determine a current irradiation angle, a current source-skin distance and a current isocenter position based on the first level target irradiation parameters, calculate target region average intensity and organ at risk average intensity based on the current irradiation angle, the current source-skin distance and the beam exit port neutron source distribution to obtain current intensity values; Step S22: obtain a plurality of different irradiation angle and source-skin distance combinations based on the current irradiation angle, the current source-skin distance and the interference relationship, and calculate target region average intensity and organ at risk average intensity corresponding to each of the irradiation angle and source-skin distance combinations to obtain a plurality of first intensity change values; select an irradiation angle and a source-skin distance based on increments of each of the first intensity change values relative to the current intensity values to update the current irradiation angle and the current source-skin distance; Step S23: determine whether the organ at risk region is in the field of view, if yes, execute Step S24, otherwise, directly execute Step S25; Step S24: obtain a plurality of different isocenter positions based on movement of the current isocenter and position relationship of the tumor target region, calculate target region average intensity and organ at risk average intensity corresponding to each of the isocenter positions to obtain a plurality of second intensity change values; select an isocenter position based on increments of each of the second intensity change values relative to the current intensity values to update the current isocenter position; Step S25: record the current irradiation angle, the current source-skin distance and the current isocenter position as the second level target irradiation parameters.

6. The method of optimizing parameters for a neutron therapy plan of claim 5, wherein, The calculation of the target region average intensity and the organ at risk average intensity includes: establish a line connecting a beam exit port center point and an isocenter, draw a plane perpendicular to the line through the isocenter, denoted as an isocenter plane, cut the tumor target region with the isocenter plane to obtain a first boundary contour line, select first target pixel points according to relative position relationship between pixel points in a range corresponding to the first boundary contour line and the beam exit port, calculate intensity values of all the first target pixel points to obtain intensity values of pixel points in the tumor target region, and obtain the target region average intensity by averaging. A plane parallel to the isocenter plane is made through the center of mass of the organ at risk, and a second intersecting contour line is obtained by cutting the organ at risk region with the plane parallel to the isocenter plane. A second target pixel point is selected according to the relative position relationship between the pixel point in the range corresponding to the second intersecting contour line and the beam exit port. The intensity value of all second target pixel points is calculated to obtain the intensity value of the pixel point in the organ at risk region, and the average intensity of the organ at risk is obtained by averaging.

7. The method of claim 4, wherein, The calculation of the intensity value of each pixel point comprises: determining the position segmented intensity value of the pixel point according to the matching relationship between the distance of the pixel point to the center point of the beam exit port and the plurality of position segments; determining the angle segmented intensity value of the pixel point according to the matching relationship between the angle of the pixel point to the center point of the beam exit port and the plurality of angle segments; wherein the angle segmented intensity value of the pixel point is obtained by accumulating the angle segmented intensity values corresponding to the plurality of position segments, and the angle of the pixel point to the center point of the beam exit port refers to the angle formed between the connecting line of the pixel point to the center point of the beam exit port and the axis of the center point of the beam exit port.

8. The method of claim 4, wherein, The method further comprises the step of automatically updating the first level target irradiation parameter or the second level target irradiation parameter to obtain a third level target irradiation parameter: Step S31: counting all ROIs in the range of the beam exit port in the field of view, wherein each ROI is used to represent a tumor target region or an organ at risk region; Step S32: determining the current irradiation angle, the current source skin distance and the current isocenter point position based on the first level target irradiation parameter or the second level target irradiation parameter, calculating the intensity value of each pixel point in each ROI based on the current irradiation angle, the current source skin distance and the neutron source distribution in the beam exit port; calculating the average biological intensity of the target region and the average biological intensity of the organ at risk based on the boron component equivalent factor of each ROI and the intensity value of each pixel point to obtain the current value of the biological intensity; Step S33: based on the current irradiation angle, the current source skin distance and the interference relationship, a plurality of different combinations of irradiation angle and source skin distance are obtained, and the average biological intensity of the target region and the average biological intensity of the organ at risk corresponding to each combination of irradiation angle and source skin distance are calculated to obtain a plurality of first biological intensity change values; based on the increment of each first biological intensity change value relative to the current value of the biological intensity, a combination of irradiation angle and source skin distance is selected for updating the current irradiation angle and the current source skin distance; Step S34: determining whether the organ at risk region is in the field of view, if yes, executing step S35, otherwise directly executing step S36; Step S35: based on the movement of the current isocenter point and the position relationship of the tumor target region, a plurality of different isocenter point positions are obtained, and the average biological intensity of the target region and the average biological intensity of the organ at risk corresponding to each isocenter point position are calculated to obtain a plurality of second biological intensity change values; based on the increment of each second biological intensity change value relative to the current value of the biological intensity, an isocenter point position is selected for updating the current isocenter point position; Step S36: recording the current irradiation angle, the current source skin distance and the current isocenter point position as the third level target irradiation parameter.

9. The method of optimizing parameters for a neutron therapy plan of claim 8, wherein, The parameters further include a target irradiation time, and the method further includes: Step S41: calculating a simulated dose of each ROI per unit time based on the third-level target irradiation parameters; Step S42: calculating a ratio of a prescription limit of each ROI to a simulated dose according to a preset prescription limit of each ROI, taking a minimum value in the ratio as a shortest simulated irradiation time, and multiplying the simulated dose of each ROI per unit time by the shortest simulated irradiation time to obtain an ideal dose of each ROI under a current irradiation angle; Step S43: judging whether an ideal dose of a ROI corresponding to a tumor target area has reached a prescription limit and an ideal dose of a ROI corresponding to each critical organ has not reached a prescription limit, and if yes, executing Step S44, otherwise, determining the shortest simulated irradiation time as the target irradiation time; Step S44: determining a critical organ target dose according to the ideal dose of the ROI corresponding to each critical organ and the prescription limit, and taking a minimum value in a ratio of the critical organ target dose to the prescription limit of the ROI corresponding to each critical organ as the target irradiation time.

10. A neutron therapy planning system comprising a processor and a storage device, the storage device being adapted to store a plurality of program codes, characterized in that, The program code is adapted to be loaded and run by the processor to execute the neutron treatment planning parameter optimization method of any one of claims 1 to 9.

Images