3-D dose-volume compensation using nonlinear least-squares regression technique

A method for external beam dose-volume optimization is presented. The Gauss-Marquardt nonlinear least-squares regression technique is applied to compensator design and determination. The dose distribution (uniform or otherwise) desired throughout a volume is specified. Compensators optimized to produce the necessary variation of beam intensity across the surface of each beam are simultaneously determined for all the beams. Solutions for homogeneous dose, homogeneous target dose, and restricted dose to exterior target volume structures, and inhomogeneous target dose cases are presented. Dependence of the results on the number of parameters as well as the role of degree of desirability weighting is explained and illustrated via examples. Discussion of the significance and limitations of this optimization method is also presented.