Method and system for real-time DMLC-based target tracking with optimal motion compensating leaf adaptation
View Patent ↗A method of multileaf collimator (MLC) leaf positioning in tracking-based adaptive radiotherapy is provided. The method includes determining a radiotherapy beam pattern by transforming a treatment beam plan into radiotherapy beam coordinates, determining a dose discrepancy between the radiotherapy beam pattern and a deliverable MLC aperture, where the dose discrepancy includes a sum of an overdose cost and an underdose cost to a treatment volume, and minimizing the dose discrepancy, where the dose discrepancy minimization provides a determined deliverable MLC aperture for the radiotherapy beam.
1. A method of multileaf collimator (MLC) leaf positioning in tracking-based adaptive radiotherapy, comprising:
a. determining a radiotherapy beam pattern in real-time during a radiotherapy treatment beam delivery, wherein said radiotherapy beam pattern comprises transforming a treatment beam plan into radiotherapy beam coordinates;
b. determining a dose discrepancy between said radiotherapy beam pattern and a deliverable MLC aperture in said real-time during said radiotherapy treatment beam delivery, wherein said dose discrepancy comprises a sum of an overdose cost and an underdose cost to a treatment volume;
c minimizing said dose discrepancy in said real-time during said radiotherapy treatment beam delivery according to instantaneous target motion, wherein said dose discrepancy minimization provides a determined deliverable MLC aperture for said radiotherapy beam that configures said multileaf aperture to shape a radiotherapy beam that optimally accounts for changes in a patient's anatomy measured during said radiotherapy treatment beam delivery; and
d. collapsing a plan aperture f and an estimated anatomical motion T onto a beam-eye-view plane, wherein an ideal motion-compensated aperture is determined by composing said plane aperture f with said collapsed beam-eye-motion plane according to g=f°T, wherein said map is represented with a binary function over a region of interest (ROI), wherein said ROI: Ω→{0,1} so that
g
(
x
)
=
{
1
x
∈
transformed
plan
aperture
opening
;
0
else
,
wherein x=(x, y) denotes a beam element location in said BEV.
2. The method of claim 1 , wherein said radiotherapy beam coordinates are based on a projection of i) a translation of at least part of said radiotherapy beam pattern, ii) a rotation of at least part of said radiotherapy beam pattern, and iii) a deformation of at least part of said radiotherapy beam pattern, or i), ii) or iii).
3. The method of claim 1 , wherein said overdose cost comprises an integration of pixelwise overdose penalties, wherein said overdose penalties can be spatially variant.
4. The method of claim 1 , wherein said underdose cost comprises an integration of pixelwise underdose penalties, wherein said underdose penalties can be spatially variant.
5. The method of claim 1 , wherein at least one previously determined said dose discrepancy is used when determining a next said deliverable MLC aperture for said radiotherapy beam.
6. The method of claim 1 , wherein a determination of said overdose cost and a determination of said underdose cost are based on a tissue type and a radio-sensitivity of said tissue.