Characterization and Applications of MOSFET Dosimeters in Radiotherapy

Abstract

AIM AND OBJECTIVES: The aim of the study was to investigate the dosimetric characteristics of the commercial available Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeter of three types such as Standard Sensitivity MOSFET, High Sensitivity MOSFET and microMOSFET in external beam therapy and brachytherapy. Additional objectives were to investigate the feasibility of using these dosimeters for in-vivo dosimetry in clinical radiotherapy applications and also to develop Complementary Metal Oxide Semiconductor (CMOS) based new dosimeter and to evaluate its dosimetric characteristics for clinical practice. MATERIALS AND METHODS: Standard sensitivity MOSFET dosimeters of sensitivity 1mV/cGy were used along with quotmobile Dose verification softwarequot to acquire data for characteristics of MV beam, imaging of MV beam Image Guided Radiotherapy (IGRT), in-vivo dose measurements in total body irradiation and patient specific Quality Assurance measurements in Intensity Modulated Radiotherapy (IMRT). High sensitivity MOSFET dosimeter of sensitivity 3 mV/cGy was used to perform kV beam imaging measurements in IGRT. MicroMOSFET dosimeter of sensitivity I1mV/cGy was used to perform dosimetric characteristics of therapeutic electron beams and for brachytherapy measurements. RESULTS: The response of Standard Sensitivity MOSFET dosimeter was found to be linear for wide ranges of dose (10 cGy to 400 cGy) for therapeutic photon beams. The linear model fit for the relationship between MOSFET response and dose with values of R ? is newline1. The energy and dose rate dependency of this dosimeter was found to be lt1% for Co60 beam, 6 MV and 15 MV x-ray beams. CONCLUSION: The high precision, accuracy, immediate readout has made these MOSFET dosimeters a valuable dosimeter in routine clinical measurements. The study of dosimetric characteristics of MOSFET dosimeters has found that it is suitable for in vivo dose measurements during image guidance with MV and kV X-ray beams.