System, method and computer program for setermining a radiation therapy plan for a radiation therapy system

Patent metadata

Field	Value
Publication number	US-2023001236-A1
Application number	US-202017780507-A
Country	US
Kind code	A1
Filing date	Nov 25, 2020
Priority date	Dec 2, 2019
Publication date	Jan 5, 2023
Grant date	—

Abstract

The invention relates to a system for determining a radiation therapy plan for a radiation therapy system ( 100 ), comprising a multi-leaf collimator. The radiation therapy plan determination system ( 110 ) comprises a therapy system characteristics providing unit ( 111 ), wherein the characteristics comprise possible leaf positions and possible radiation fluence values, a planning objectives providing unit ( 112 ), wherein the planning objectives are indicative of a desired therapeutic radiation dose distribution, an optimization function providing unit ( 113 ), wherein the optimization function is indicative of a deviation of a radiation dose distribution from the planning objectives and of an uncertainty of the radiation dose distribution at edges of the possible apertures, and a therapy plan optimization unit ( 114 ) adapted to determine a sequence of possible apertures and possible radiation fluence values for which the optimization function is optimized. Thus, an optimal therapy plan can be provided for each individual patient.

First claim

1 . Radiation therapy plan determination system for determining a radiation therapy plan for a radiation therapy system comprising a multi-leaf collimator, wherein the MLC comprises a plurality of moveable leaves for shaping an aperture of the MLC such that a radiation beam is shaped by the aperture before being provided to a patient, wherein the radiation therapy plan determination system comprises:
a therapy system characteristics providing unit for providing characteristics of the radiation therapy system, wherein the characteristics comprise possible leaf positions defining possible apertures of the MLC and possible radiation fluence values that are providable by the radiation therapy system, a planning objectives providing unit for providing planning objectives, wherein the planning objectives are indicative of a desired therapeutic radiation dose distribution that should be provided to the patient, an optimization function providing unit for providing an optimization function being indicative of a deviation of a radiation dose distribution from the planning objectives, wherein the radiation dose distribution depends on a sequence of possible apertures defined by the possible leaf positions and possible radiation fluence values, and wherein the optimization function is further indicative of an uncertainty of the radiation dose distribution at edges of the possible apertures, a therapy plan optimization unit for determining an optimized therapy plan, wherein the therapy plan optimization unit is adapted to determine a sequence of possible apertures and possible radiation fluence values for which the optimization function is optimized, wherein the sequence of optimized possible apertures and optimized possible fluence values defines the optimized therapy plan.

2 . A radiation therapy plan determination system according to claim 1 , wherein the uncertainty of the radiation dose distribution is determined based on the possible leaf positions of the MLC defining the possible apertures and based on the possible radiation fluence values on which the radiation dose distribution depends.

3 . A radiation therapy plan determination system according to claim 2 , wherein the therapy plan optimization unit is adapted to determine the sequence of possible apertures and possible fluence values for which the optimization function is optimized such that a sequence of possible apertures and possible fluence values is preferred as optimized therapy plan that leads to a radiation dose distribution with less uncertainty.

4 . The radiation therapy plan determination system according to claim 1 , wherein the uncertainty for a radiation dose distribution is modelled based on an uncertainty function centered at at least one edges of each possible aperture, wherein the uncertainty function of an edge comprises a width corresponding to an anticipated uncertainty for the respective edge.

5 . The radiation therapy plan determination system according to claim 4 , wherein the uncertainty function of each edge is weighted with a possible fluence value that is associated with the possible aperture to which the edge belongs.

6 . The radiation therapy plan determination system according to claim 1 , wherein the uncertainty of a radiation dose distribution in the movement direction of the leaves of the leaf pairs of the MLC is determined using:
U=∫ (Σ i w i ( e i ( x−x l,i )+ e i ( x r,i −x ))) 2 dx,
wherein w i corresponds to the possible fluence value associated with a possible aperture, e i (x) refers to an uncertainty function defining the distribution of the uncertainty, and x l,i and x r,i refer to possible left and right leaf positions of a pair of leaves of the MLC, and x runs over the aperture size in x-direction defined as the movement direction of the leaves of the leaf pair.

7 . The radiation therapy plan determination system according to claim 4 , wherein the uncertainty function is a Gaussian type function.

8 . The radiation therapy plan determination system according to claim 7 , wherein the optimization function is defined as:
O=D+λU, wherein D refers to the deviation and λ is a weight for weighting the influence of the uncertainty U during the optimization of the optimization function O.

9 . The radiation therapy plan determination system according to claim 1 , wherein the radiation therapy system is configured to provide the radiation beam from a plurality of directions, wherein the therapy system characteristics providing unit is adapted to provide possible beam directions of the radiation therapy system as characteristics of the radiation therapy system, wherein the radiation dose distribution further depends on a sequence of possible radiation directions, and wherein the uncertainty is determined based on the uncertainty determined for each partial radiation dose distribution defined by a possible direction, a possible aperture and a possible fluence value being part of the sequence defining the radiation dose distribution.

10 . The radiation therapy plan determination system according to claim 9 , wherein each radiation direction of a possible sequence of radiation directions is associated with at least one possible aperture and at least one possible fluence value defining a radiation dose distribution for the radiation direction, wherein the uncertainty is determined based on a sum of the uncertainties of each partial radiation dose distribution associated with each possible direction of the sequence of possible directions.

11 . The radiation therapy plan determination system according to claim 1 , wherein the radiation therapy system is adapted to continuously change between possible beam directions, leaf positions and fluence values while generating the radiation beam, wherein the uncertainty for a radiation dose distribution resulting from a sequence of continuously changing possible beam directions, leaf positions and fluence values is estimated based on summing over uncertainties determined for partial radiation dose distributions determined for a plurality of directions of the continuously changing sequence of possible directions.

12 . The radiation therapy plan determination system according to claim 11 , wherein the uncertainty is further determined taking into account uncertainties resulting from a small arc approximation used for determining the radiation dose distribution from the sequence of continuously changing possible beam directions, leaf positions and fluence values.

13 . A radiation therapy system for providing a radiation therapy to a patient, wherein the radiation therapy system comprises:
a radiation beam generating unit adapted for generating a radiation beam with at least one possible fluence value, wherein the radiation beam generating unit is further adapted to provide the radiation beam to a patient, an MLC comprising a plurality of moveable leaves being movable to a plurality of possible leaf positions for shaping an aperture of the MLC such that the beam of radiation is shaped by the aperture before being provided to the patient, a radiation therapy plan determination system according to claim 1 for determining an optimized radiation therapy plan comprising a sequence of optimized possible leaf positions and optimized possible fluence values, and a radiation therapy controlling unit for controlling the radiation beam generating unit and the MLC such that the therapy plan is provided to the patient.

14 . Radiation therapy plan determination method for determining a radiation therapy plan for a radiation therapy system comprising a MLC, wherein the MLC comprises a plurality of

Assignees

• Koninklijke Philips Nv

Inventors

• Heese Harald Sepp
• Vik Torbjoern
• Weese Rolf Jürgen

Classifications

• A61N5/1036 Primary

  Leaf sequencing algorithms · CPC title

• A61N5/1045

  using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT · CPC title

• A61N5/1031

  using a specific method of dose optimization · CPC title