Dose distribution measurements by means of gel-layer dosimeters. Evaluation of algorithms for artifacts amendment.

MAURO CARRARA GRAZIA GAMBARINI STEFANO TOMATIS MAURO VALENTE

Michigan

Congreso; SORMA 2006; 2005

Abstract One of the major necessities that appear with the continuum development of conformal radiotherapies is a corresponding improvement of dosimetry techniques. Fricke gel-layer dosimetry, coupled with a suitably developed software, has proved to be a reliable technique for 3D absorbed dose distribution verification. The method is based on the measurement of optical transmittance of the gel-layers. The experimental assessment consists basically in a planar illumination source and a computer-controlled CCD camera for the acquisition of optical transmission images. Two possible sources of errors that may alter the right dose distribution evaluation are possible defects in the gel structures and an eventual non-uniform illumination source. Various algorithms for the post-processing detection and amendment of both kinds of artifacts were evaluated on a series of properly chosen gel-layers images. Dose profiles along the central axis of a phantom irradiated with different X-beam fields and evaluated with the proposed algorithms were then compared with measurements obtained by means of a ionization chamber. © 2006 Elsevier Science. All rights reserved Keywords: Dose distribution imaging; Fricke gel; Gel dosimetry; Optical imaging; edge-detecting algorithms