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CN-121446055-B - FLASH radiotherapy plan optimization method and system

CN121446055BCN 121446055 BCN121446055 BCN 121446055BCN-121446055-B

Abstract

The invention discloses a FLASH radiotherapy plan optimization method and a FLASH radiotherapy plan optimization system. The method comprises the steps of defining a FLASH effect index in a FLASH radiotherapy system, indirectly quantifying the FLASH effect, providing a basic index for maximizing the FLASH effect, designing a FLASH biological database aiming at the characteristics of the X-ray and the FLASH effect, facilitating the accurate calculation of the equivalent photon dose of the FLASH effect, providing accurate data support for multi-target coordination, and ensuring the control of the tumor killing and the organ-at-risk dose and maximizing the FLASH effect by the design of the tumor target region weight, the organ-at-risk weight and the FLASH effect weight in the optimization process.

Inventors

  • HU JIABING
  • BAI YANG
  • ZHAN WEI
  • LIU XIANHONG

Assignees

  • 中玖闪光医疗科技有限公司

Dates

Publication Date
20260512
Application Date
20260107

Claims (13)

  1. 1. A method for optimizing a FLASH radiation treatment plan, comprising the steps of: acquiring initial planning parameters; setting a composite objective function according to the initial planning parameters, wherein the composite objective function is used for evaluating the combined action of tumor killing effect parameters, normal tissue organ injury control parameters and set FLASH effect indexes; The composite objective function specifically comprises: ; wherein TotalLoss represents a cost value; A weight representing the target volume; a deviation analysis function representing the equivalent dose of the tumor target area and the prescribed dose ensures tumor killing; representing the prescribed dose for the ith tumor target area; Representing the equivalent dose of the ith target; Representing weights of organs at risk; a deviation analysis function representing the equivalent dose of the organ at risk from a safety limit for reducing damage; represents a safety limit for the organ at risk, Represents the equivalent dose of the jth organ at risk; A weight representing a FLASH effect index; the FLASH effect index difference analysis function representing the organ or tissue is shown in the following form and is used for indirectly maximizing the FLASH effect, The Flash effect index representing the organ or tissue m, A FLASH effect index set by the organ or tissue m; calculating an actual FLASH effect index according to the initial planning parameters; The actual FLASH effect index is obtained based on the following formula: ; In the formula, Voxel dose, FED equivalent photon dose, n number of voxels; calculating an actual FLASH effect index according to the initial planning parameters; based on the composite objective function, the initial equipment parameters and the actual FLASH effect index are adjusted by a preset algorithm until the plan parameters meeting preset limiting conditions are obtained, and the optimization is completed.
  2. 2. A method for optimizing a FLASH radiation therapy plan according to claim 1, wherein the following steps are performed after the initial plan parameters and the actual FLASH effect indexes are adjusted by a preset algorithm based on a composite objective function according to preset limiting conditions: and generating a FLASH physical dose, a dose volume histogram of equivalent photons and FLASH effect index values and outputting the adjusted planning parameters.
  3. 3. A method of optimizing a FLASH radiation therapy plan as claimed in claim 1, wherein said planning parameters include setting some or all of a FLASH effect index, patient information, FLASH biological data information, initial equipment parameters, and preset constraints; The preset limiting conditions comprise one or all of a cost value convergence set value and preset iteration times.
  4. 4. A method of optimizing a FLASH radiation therapy plan as claimed in claim 1, wherein said steps of A FLASH effect index difference analysis function representing an organ or tissue, ; Wherein, the Is a transition function.
  5. 5. A method of optimizing a FLASH radiation therapy plan as claimed in claim 4, wherein said steps of The transition function is specifically: 。
  6. 6. a method of optimizing a FLASH radiation therapy plan according to claim 1, wherein said calculating an actual FLASH effect index from initial planning parameters comprises the steps of: according to the initial planning parameters, calculating the three-dimensional dose distribution of the whole organ or tissue of the patient, obtaining the accumulated absorbed physical dose of each voxel in the irradiated tissue, and forming the dose representing all voxels Is a three-dimensional dose matrix of (a), Voxel dose rate calculation based on three-dimensional dose matrix and illumination time Is a dose rate matrix of (a); calculating equivalent photon dose according to the three-dimensional dose matrix and the dose rate matrix; and calculating the actual FLASH effect index of the organ or the tissue according to the equivalent photon dose.
  7. 7. A method of optimizing a FLASH radiation therapy plan as claimed in claim 6, wherein said calculating an equivalent photon dose from a three-dimensional dose matrix and a dose rate matrix comprises the steps of: calculating equivalent photon dose by adopting one or more of a FLASH effect phenomenological formula, a neural network learning calculation model and a model constructed based on physical parameters; Calculating equivalent photon dose by using one or more combinations of radical recombination, oxygen depletion and immunoregulation FLASH effect hypothesis mechanism models; the physical parameters include dose, dose rate, pulse repetition frequency, pulse duration.
  8. 8. A method of optimizing a FLASH radiation therapy plan as claimed in claim 7, wherein said calculating an equivalent photon dose FED using one or more of a FLASH effect phenomenological formula, a neural network learning calculation model, and a model constructed based on physical parameters comprises the steps of: Based on voxel dose Voxel dose rate In the biological data information 、 Calculating FLASH effect retention factors according to the following formula : ; ; S (x) in the formula is used to smoothly map the input value to an output value between 0 and 1; ; wherein k1, k2, f are formula constants independent of dose rate and dose, To set the lowest dose rate at which tissue organogenesis FLASH effects occur, To set the lowest dose at which tissue organogenesis FLASH effects occur, The voxel dose rate is represented as a function of, Representing voxel dose.
  9. 9. A method of optimizing a FLASH radiation therapy plan as claimed in claim 6, wherein said FLASH effect index comprises a single value for a single organ, tissue or a unified value for a plurality of organs, tissues.
  10. 10. A method of optimizing a FLASH radiation therapy plan as claimed in claim 3, wherein said FLASH biological data information comprises all or part of tissue and organ oxygen diffusion parameters, radical generation parameters, and immunomodulation related parameters.
  11. 11. A method of optimizing a FLASH radiation therapy plan as claimed in claim 1, wherein said FLASH effect index is a value in the range of 0-1.
  12. 12. A FLASH radiation therapy plan optimization system for implementing a FLASH radiation therapy plan optimization method as claimed in any one of claims 1-11, comprising: The acquisition module is used for acquiring initial planning parameters; The calculation module is used for calculating an actual FLASH effect index according to the initial planning parameters; And the optimization module is used for adjusting the initial equipment parameters according to a preset algorithm based on the composite objective function and a preset limiting condition.
  13. 13. A FLASH radiation therapy plan optimization system in accordance with claim 12, further comprising a plan evaluation and output module; and the plan evaluation and output module is used for generating a FLASH physical dose, a dose volume histogram of equivalent photons and FLASH effect index value and outputting the adjusted plan parameters.

Description

FLASH radiotherapy plan optimization method and system Technical Field The invention relates to the technical field of radiotherapy, in particular to a FLASH radiotherapy plan optimization method and system. Background Radiotherapy is a technique of killing tumors by X-rays or other radiation, and the core goal is to "let tumor tissue receive enough dose (kill tumor) while leaving surrounding normal tissue receive as little dose as possible (reduce injury)". FLASH radiotherapy is an emerging radiotherapy technology in recent years, and the core principle is that ultra-high dose rate irradiation (generally >40Gy/s, which is 100-1000 times of the traditional radiotherapy dose rate) can trigger FLASH effect, which is verified in brain, chest and abdomen tissues of animal models such as mice, rats, dogs and the like, can obviously reduce radiation damage of normal tissues, but does not influence tumor killing effect. The damage caused by the physical dose of normal tissues is reduced. There is a variation in the extent of physical dose damage reduction of the FLASH effect, which is currently known to be related to two types of parameters: Pulse structure parameters including instantaneous dose rate (dose per unit time), pulse duration (duration of each radiation output), pulse repetition frequency (number of pulses output per minute), total irradiation time, etc.; biological factors include the type of organ being irradiated (e.g., lung is more sensitive to FLASH effects than skin), patient age (elderly patients may have weaker tissue repair, effects may be more pronounced), number of fractions, etc. The existing partial radiotherapy plans are only optimally designed for physical doses, and FLASH effects are not included in optimization consideration dimensions, so that the plans cannot accurately reflect the actual damage degree of radiation to biological tissues, and the requirements of FLASH radiotherapy technology on accurate evaluation of the biological effects are difficult to match. In addition, the technical scheme relates to equivalent biological dose optimization based on the FLASH effect, but the FLASH effect is not set as an independent constraint index, for example, in the optimization process of preferentially meeting the target area dose target, the system can reduce the dose rate from 100Gy/s to 50Gy/s, so that the actual dose rate is lower than the FLASH effect threshold value, the FLASH effect cannot be effectively exerted, and the system is not configured with a corresponding early warning mechanism. Finally, although the physical dose of the radiotherapy plan can reach the preset standard, the clinical advantage of the FLASH effect cannot be fully released, and the precise regulation and control capability of the FLASH effect of a single tissue organ is lacking. Essentially, no clear correlation mechanism between FLASH effect quantification indexes (such as effect intensity) and target area dosage indexes is established in the prior art, so that the cooperative optimization of the FLASH effect quantification indexes and the target area dosage indexes lacks theoretical support. Disclosure of Invention The invention solves the problem that a clear association mechanism between a FLASH effect quantification index (such as effect intensity) and a target area dose index is not established in the prior art, and provides a FLASH radiotherapy plan optimization method and a FLASH radiotherapy plan optimization system, so that the problems in the prior art can be expected to be solved. In order to solve the technical problems described above, an aspect of the present invention provides a method for optimizing a FLASH radiation treatment plan: a method for optimizing a FLASH radiation treatment plan, comprising the steps of: acquiring initial planning parameters; setting a composite objective function according to the initial planning parameters; calculating an actual FLASH effect index according to the initial planning parameters; setting a composite objective function comprising a cost value, wherein the cost value represents the deviation between the equivalent dose of a tumor target area and a organs at risk and the prescribed dose, and the FLASH effect index deviation; setting FLASH effect indexes, namely designating special or unified FLASH effect indexes according to tissues or organs possibly related to the input data, wherein the FLASH effect index values are defined as average values of ratios of equivalent photon doses of tissue or organ constituent voxels to physical doses corresponding to the equivalent photon doses; based on the composite objective function, the initial equipment parameters and the actual FLASH effect index are adjusted by a preset algorithm until the plan parameters meeting preset limiting conditions are obtained, and the optimization is completed. According to a further technical scheme, the method comprises the following steps of adjusting initial planning parameters a