Measurement of Dose outside a 6 MV Field Edge Using Optically Stimulated Luminescent Nano Dot Dosimeters

Abstract

The purpose of this study is(was) to investigate the shielding ratio of 1 ㎜Pb and the off axis ratio outside the field edge at depth of 1 ㎝ from a phantom surface for 6 MV photon beam. A dose of 180 cGy was delivered to a depth of 10 ㎝ for a 10×10 ㎠ and 15×15 ㎠ field in the SAD technique. The off axis ratio was calculated by measuring the dose of optically stimulated luminescent nanoDot dosimeters(OSLnDs) positioned at 2, 4 and 6 ㎝ from the field edge, and the center axis of field. And the shielding ratio of 1 ㎜Pb was calculated by measuring the dose of OSLnDs positioned at 2, 4 and 6 ㎝ from the field edge.. As a result, for a 10×10 ㎠ and 15×15 ㎠ field, the off axis ratios were acquired 0.008-0.023 and 0.011-0.028, respectively. Also the shielding ratios of 1 ㎜Pb were acquired 0.868-0.888 and 0.807-0.842, respectively. These results provide data to protect organs at risk outside the radiation treatment field.