A system for intensity modulated dose plan verification based on an experimental pencil beam kernel obtained by deconvolution

Abstract

The number of intensity modulated radiation therapy !IMRT" procedures is continuously growing worldwide and it is necessary to develop tools for patient specific quality assurance !QA" that avoid using machine time that could be employed in treating additional patients. One way of achieving this goal is to perform a multileaf collimator quality assurance periodically in the linear accelerator and check the treatment planning system !TPS" calculation by employing an independent calculation system. Within the work frame of the pencil beam kernel approach, a new system was developed for obtaining an experimental kernel. This new technique is based on a deconvolution procedure using the Hankel transform. The resulting kernel is obtained in a way completely independent of those employed in commercial treatment planning systems, usually calculated by Monte Carlo simulations. Also provided are comparisons between calculated and measured doses with radiographic film, linear array of diodes, and ionization chamber. Measurements taken in polystyrene and water for clinical IMRT plans demonstrate that this method can calculate IMRT dose distributions, as well as treatment times, with great accuracy. Apart from other applications, it can be used as a double-check algorithm for IMRT QA.