TLD ARRAY FOR PRECISE DOSE MEASUREMENTS IN STEREOTAXIC RADIATION TECHNIQUES

We developed a new TLD array for precise dose measurement and verifica tion of the spatial dose distribution in small radiation targets. It c onsists of a hemicylindrical, tissue-equivalent rod made of polystyren e with 17 parallel moulds for an exact positioning of each TLD. The sp atial resolution of the TLD array was evaluated using the Leskell sphe rical phantom. Dose planning was performed with KULA 4.4 under stereot actic conditions on axial CT images. In the Leksell gamma unit the TLD array was irradiated with a maximal dose of 10 Gy with an unplugged 1 4 mm collimator. The doses delivered to the TLDs were rechecked by dio de detector and film dosimetry and compared to the computer-generated dose profile. We found excellent agreement of our measured values, eve n at the critical penumbra decline. For the 14 mm and 18 mm collimator and for the 11 mm collimator combination we compared the measured and calculated data at full width at half maximum. This TLD array may be useful for phantom or tissue model studies on the spatial dose distrib ution in confined radiation targets as used in stereotactic radiothera py.