An overview of polymer gel dosimetry using x-ray CT

Abstract

The use of x-ray computed tomography (CT) for the imaging of irradiated polymer gels was first introduced at the 1st international conference on radiotherapy gel dosimetry, DOSGEL99, and in a subsequent paper [1,2]. These works showed dose dependent contrast in CT images of irradiated polyacrylamide (PAG) gel, quantified a CT dose response for PAG gel and thereby established the potential of CT as an alternative to MRI and optical CT for gel read-out. The advantages of CT readout are practical ones: accessibility of CT to clinical radiation therapy environments, ease and speed of image acquisition, and a CT dose response that is stable and relatively insensitive to environmental factors. However, significant drawbacks include a very low sensitivity of CT number (H) to dose (~1%) and the fact that the act of imaging with CT will impart additional dose to the gel. Recent work has focused on means of understanding and minimizing these drawbacks.