P4F-2 Ultrasonic Elastography and Plane Strain Inverse Algorithms for Polymer Gel Dosimetry

In radiation therapy, 3D-dosimetry is needed for quality assurance of complicated irradiation geometries. Here, a preliminary evaluation of a combined system for dosimetry based on radiation sensitive gels, ultrasonic elastography and a plane strain inverse algorithm is presented. A block of gel was irradiated along one of its axes producing a stiff rod-like region. Good stiffness contrast between this region and the homogeneous background was found, generating the correct absolute dose in the rod-area. Noise in the background and boundary condition artifacts, prevented the accuracy and precision needed in dosimetry, but improvements of the experimental setup and the assumptions in the inverse computation remain possible. The promising result suggests that a system based on measuring stiffness contrast in radiation sensitive gels may be used in the future for the measurement of dose- distributions.