An investigation comparing optical CT with MR scanning for polymer gel dosimetry

Radiation sensitive gels, including BANG and Fricke-gels, are at the forefront of research into improved dosimetry techniques. Despite being the only dosimeter that offers true 3D information about the dose-distribution, radiation sensitive gels have to-date made little impact in most clinics. This is due to the fact that the field is still new and rapidly developing, but also due to the high cost and high noise characteristics of the standard way of reading these gels-MR scanning. To circumvent these difficulties several groups are looking at an alternative low-cost approach to reading the gels, using laser based optical-CT scanning. In this paper we report on an optical CT scanning system recently developed in our lab, and a preliminary study which compares, for the same gel samples, MR with optical scanning. The comparison has two parts: (a) calibration methods and accuracy, and (b) noise and resolution in dosimetric images. We also outline a novel optical calibration method with primary advantages in terms of speed and robustness. The important feature of the study is that each scanning method was applied to the same gel samples.