Optical Evaluation of normoxic PAGAT polymer gel dosimeters used to measure SWDP on diagnostic CT scanners

Abstract

Slice-width dose profile (SWDP) is a measurement undertaken during acceptance testing of diagnostic CT scanners for determination of patient dose. Effective whole body dose from various diagnostic scanner protocols is determined from a SWDP measurement using a 100 mm calibrated ionization chamber. Normoxic polymer gel dosimeters in conjunction with magnetic resonance imaging (MRI) were previously used to measure SWDP and then calculate the computer tomography dose index (CTDI) during acceptance testing of a Philips ACQSIM CT scanner and compared with the conventional ionization chamber measurement for a range of imaging protocols. The resulting CTDI for both polymer gel dosimeter and ionization chamber was within 2%. Uniformity of dose and dose profile measured at the same time with the same polymer gel dosimeter were within the specifications of the equipment manufacturer. In this study PAGAT polymer gel dosimeters were used to evaluate the SWDP of a diagnostic CT scanner. The irradiated PAGAT gel dosimeter was successfully evaluated with a Vista (Modus Medical Devices Inc.) optical scanner. The use of normoxic polymer gel dosimeters with optical CT evaluation has been shown to be a suitable methodology for determining CTDI on diagnostic CT scanners.