A novel application of normoxic polymer gel dosimeters for near real-time dose measurement using cone-beam computed tomography

The aim of this study is to evaluate the feasibility of using cone-beam CT system as a near real-time measurement device in dose estimation with normoxic polymer gel dosimetry (MAC). Each vial was filled with MAC gel and irradiated with uniform doses of 0-10 Gy to generate dose response curves. After irradiation, a cone-beam CT was used to perform the 3D dose measurement. In this study, two groups of gel samples were irradiated and measured in two ways for comparison: near real-time measurement, in which the gel phantom was read right after the irradiation, and delayed measurement, in which the measurement was performed 30 min, 4 h and 1 day after the irradiation for the gel phantom to be exposed to oxygen. All groups were also performed with and without a full bowtie filter to estimate the influence of a full bowtie filter to dose response. The linear dose response curves with and without a full bowtie filter for the four different CT imaging times were within a range 0.044-0.049 Delta N-CT cGy(-1) and 0.061-0.063 Delta N-CT cGy(-1), respectively, with no significant difference at different imaging times. Nevertheless, dose response curves with the full bowtie filter were higher than those without, with p-value <0.05 for all the different imaging times tested. Normoxic polymer gel dosimetry combined with cone-beam CT provides a useful method for near real-time dose measurement. (C) 2010 Elsevier B.V. All rights reserved.