Patent Number: 
Section: claims

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; andd. 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.