Patent ID: 6882702

Claim:
A method in a computer for optimizing a dosage of intensity modulated radiotherapy (IMRT) comprising: dividing a three dimensional (3D) volume into a grid of dose voxels, wherein each dose voxel receives a dose of radiation from at least one pencil beam having a pencil beam weight and a gantry angle; selecting a first set of dose voxels from said 3D volume positioned within at least one of a planning target volume (PTV), organs at risk (OAR), and normal tissue in a neighborhood of said PTV; choosing a dose matrix from said first set of dose voxels; constructing a beam weight vector of individual beam weights for each pencil beam at each gantry angle; calculating a transfer matrix representing a dose deposition to the dose voxels from each pencil beam with unit beam weight; inverting said transfer matrix; performing a matrix multiplication of said inverted transfer matrix and said dose matrix and populating said beam weight vector with the results of said matrix multiplication; and iteratively modifying a plurality of doses in said dose matrix within a given range, wherein said range has a specific probability distribution function of acceptable dose values, and repeating said matrix multiplication until the negative weights in said beam weight vector are substantially eliminated, resulting in an optimized set of doses.