Investigation of the MAGAS normoxic polymer gel dosimeter with Pyrex glass walls for clinical radiotherapy dosimetry

Depth doses for a 6 MV photon beam have been measured with the Methacrylic Acid Gelatin with AScorbic acid (MAGAS) polymer gel dosimeter contained in a cylindrical Pyrex glass phantom and Pyrex glass tubes and compared with depth doses calculated using Monte Carlo EGS4 code and ionisation chamber measurements in water. Differences between the polymer gel, Monte Carlo and ionisation chamber depth doses were up to 4%. Measurements were performed with an ionisation chamber under different thicknesses of Pyrex glass to determine correction factors for the Pyrex glass phantom wall material in the polymer gel measurement of depth dose. With radiological depth scaling and correction factors applied, the extent of agreement with ionisation chamber measurements in water was within 3%. The R 2 -dose response of the polymer gel in glass vials was linear up to 25 Gy. The MAGAS polymer gel dosimeter has shown potential as a clinical radiotherapy tool for the evaluation of depth dose. Further investigation is required to fully develop its capabilities and to reduce differences with measurements made with other dosimetry systems.