Room: ePoster Forums
Purpose: To develop and evaluate the dosimetric characteristics of a low cost in-house developed Complementary Metal Oxide Semiconductor (CMOS) based dosimeter with therapeutic gamma rays.
Methods: The investigated dosimetric characteristics are: dose response for the dose range of 50 cGy to 800 cGy , the energy dependency for Co-60 gamma rays, 6 and 15 MV x-rays, field size dependency with 10x10cm2, the dose reproducibility to the dose of 100 cGy for 10 times and to the dose of 50 cGy for 3 days, PDD measurements insteps up to 7 mm where the build-up region occurs and insteps of 1 cm beyond the dose maximum region till 20 cm depth,, the dose variation at the off axis by moving the dosimeters in steps of 1 cm away from the central axis up to 8 cm.
Results: The response of CMOS for the dose range of 10cGy to 400cGy has shown the linear regression value R2 equal to 1 indicating the linear fit. The maximum percentage variation of +0.55% with 15 MV indicated the independency of energy. The maximum and minimum experimental uncertainty in output factors were 1.9% and 2.4% with ion chamber respectively. CMOS has a good reproducibility for repeated irradiations with an uncertainty of Â±0.7% (SD). The dose measured was consistent with repeated exposure for 3 days with Â±1.05 % (SD).
Conclusion: CMOS was constructed and desired dosimetric parameters were investigated and validated with an ionization dosimeter and standard sensitivity MOSFET dosimeter. The results have shown good linear response, stability during read out, good reproducibility, reusability and good self life comparable with the standard dosimeters. This cost effective dosimeter confirms that CMOS based dosimeter could be used in various radiotherapy applications. However a more detailed study has to be performed to establish it for clinical use.