CONFORMAL THERAPY USING MAXIMUM-ENTROPY OPTIMIZATION

Conformal therapy offers considerable advantages over conventional rad iotherapy treatment, because it has the potential for matching almost exactly the delivered dose distribution to the prescribed dose distrib ution. Associated (inverse) treatment planning methods address a const rained linear optimization problem. In this article, a method based on maximizing the total entropy of the beam profiles is developed. Maxim um entropy optimization constrains the computed dose to be within well -defined tolerances of the prescribed dose, and has advantages of robu stness, fast convergence, and high accuracy. For the work reported her e, it is assessed using clinically prescribed irregular target dose vo lumes based on magnetic resonance imaging and computed tomography imag es. Results are shown for a two-dimensional, homogeneous absorption, p rimary dose computation model, to illustrate the feasibility of the ap proach; however, the method may be extended to accommodate a more gene ral three-dimensional model, including inhomogeneities and scatter dos e contributions. Optimization of beam offset for a regular angular dis placement of beams is also considered, with particular regard to impli cations on total beam energy, entropy, and computation time. (C) 1995 John Wiley and Sons, Inc.