ASSESSMENT OF SURFACE DOSE ON THE ART PHANTOM USING THREE-DIMENSIONAL CONFORMAL BREAST RADIOTHERAPY
The assessment of surface dose is essential in radiotherapy to avoid deterministic effect or to reduce the severity of side effects from radiation treatment. In this study, the surface dose for breast cancer radiotherapy was measured using two types of dosimeter; Thermoluminescent Dosimeter (TLD) and Optically Stimulated Luminescent Dosimeter (OSLD). The study was performed on the left breast of female Alderson Radiation Therapy (ART) phantom. The treatment planning was carried out on the ART phantom to determine the homogeneity of dose distribution within the target organ is complied with the tolerance limits of 95% to 107% as recommended by the International Commission on Radiation Units and Measurements (ICRU)’s Report No. 50. From the treatment planning result, the phantom then was irradiated with 267 cGy dose per fraction for two beam fields; medial tangential and lateral tangential fields using a 6 MV photon beam produced from three-dimensional (3D) conformal radiotherapy. Result shows that the OSLD provides 25.7% and 23.5% higher surface dose compared to TLD for medial tangential and lateral tangential fields, respectively. This condition may be due to higher effective point of measurement and angular dependence of the OSLD compared to TLD. As a conclusion, suitable dosimeter should be selected to ensure accurate estimation of surface dose could be made thus reduction of skin reaction to patient could be achieved.