Platform for intensity modulated radiation therapy
View Patent ↗In certain embodiments novel sparse orthogonal collimators (SOCs) for use in radiotherapy are provided. In certain embodiments the SOCs comprise 2 layer 4 bank orthogonal collimators with 2-8 leaves in each of the 4 banks. Instead of using the limited heuristic approach to create jaw-only IMRT, a novel fluence map optimization method is provided based on wavelet decomposition and this method is used for IMRT. An algorithm to simplify the fluence maps with minimal and predictable dose quality compromise is also provided.
1. A method of generating a radiation treatment plan using a radiotherapy device comprising a sparse orthogonal collimator comprising a first bank of individually longitudinally movable elongate leaves, and a second bank of individually longitudinally movable elongate leaves the second bank being disposed in an opposed relationship to the first bank, a third bank of individually longitudinally movable elongate leaves, and a fourth bank of individually longitudinally movable elongate leaves the fourth bank being disposed in an opposed relationship to said third bank, and said first bank and said second bank being oriented orthogonal to said third bank and fourth bank, and said first bank, second bank, third bank, and fourth bank each individually contain from two to four leaves, said method comprising:
providing a fluence map for said radiation treatment plan; and
generating using a computer a time sequence of sparse orthogonal collimator leaf settings from said fluence maps, wherein said generating comprises:
representing a desired fluence map using discrete Haar wavelet coefficients; and
optimizing Haar fluence using a direct aperture regularization approach centered on dose domain optimization wherein sparsity is used to limit total number of Haar coefficients and thus total number of apertures while maintaining dosimetric quality; and
generating and writing instruction files to implement said time sequence of sparse orthogonal collimator leaf settings to a tangible medium accessible for execution by the radiotherapy device.
2. The method of claim 1 , wherein said representing a desired fluence map comprises representing a fluence map, fmat using discrete Haar wavelet coefficients, αc, such that:
H c T α c H c =ƒ mat , (1)
where H c is the classical Haar transform matrix, but changing the differential Haar transform, H c , to a scaling function, which is a modified Haar transform, H m that uses a coefficient set, α m where for a 2 n ×2 n fluence matrix, the coefficient matrix α m has dimensions (2 n +1−1)×(2 n +1−1), and H m has dimensions (2 n +1−1)×2 n .
3. The method according to claim 1 , wherein said optimizing comprises:
minimize ½∥ W ( AH v α v −d 0 )∥ 2 2 +λ∥α v ∥ 1
subject to α v ≥0, (4)
where
α v =vec(α m ) is the optimization variable;
H v is the Haar transform matrix for the coefficient vector;
W is a weighting factor for the structures of interest;
A is the fluence to dose transformation matrix; and
d 0 is the desired dose.
4. The method of claim 3 , wherein d 0 is set to the prescription dose for the planning target volume (PTV) and zero for the organs at risk (OARs).
5. The method of claim 3 , wherein the fluence to dose transformation matrix is calculated using a convolution/superposition code using a 6 MV x-ray polyenergetic kernel.
6. The method of claim 3 , wherein said instruction files contain a treatment plan comprising sparse orthogonal collimator leaf positions and optionally one or more of the following: machine gantry and couch positions, beam intensities, imager positions at a given time or plan delivery point.
7. The method of claim 6 , wherein said treatment plan comprises couch positions and gantry angles for a non-coplanar beam treatment.