Skin dosimetry of thyroid radioiodine with MOSkin detector: A phantom study

• Published in: 2011 IEEE Nuclear Science Symposium Conference Record pp. 258 - 260
• Main Authors: Chuamsaamarkkee, K., Fuduli, I., Cutajar, D., Lian, C., Harvey, S., Rosenfeld, A. B.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-10-2011
• Subjects: Current measurement; Logic gates; Photonics
• ISBN: 1467301183; 9781467301183
• ISSN: 1082-3654; 2577-0829
• DOI: 10.1109/NSSMIC.2011.6154492

Radioiodine treatment is administered radioactive iodine to treat the thyroid cancer or to ablate a thyroid remnant. However, due to the risk of radiation, there is a possibility that the patient will experience side effects. Skin dose is an important parameter for quantifying patient dose. The aim of this study is to use a MOSFET detector for real time skin dosimetry. At the Centre for Medical Radiation Physics (CMRP), University of Wollongong, a new type of MOSFET detector called MOSkin is being developed to measure the skin dose, with real-time read out. This paper discusses the pre-clinical characterization the MOSkin and phantom study with radioiodine. In this study, the MOSkin is operated in active mode during irradiation, with +5 V gate bias supplied by a Lithium battery. The Electrical characterization, temperature response, dose linearity response, energy response, and sensitivity versus gate bias for MOSkin were investigated. For the detector characterization, the MOSkin had temperature instability Vth of 0.2 mV/°C under used readout current. The MOSkin energy response was like any MOSFET detector, the dose depending on photon energy. However for a photon energy of more than 250 keV the MOSkin had a flat response that allowed calibration of the MOSkin on a 6 MV LINAC. The sensitivity of the MOSkin was 1.72 mV/cGy and 2.54 mV/cGy under gate biases of +5 V and +15 V respectively. Sensitivity was constant and within 1% when MOSkin irradiated up to 10 Gy. A phantom study was performed with radioiodine 1-131 of activity 80 MBq. The absorbed skin doses for anterior neck and posterior neck were 63.95 and 2.92 cGy respectively. In conclusion, the unique design of the MOSkin appears to show great promise as a skin dosimetry device, with the added advantage of being small in size and having real-time dosimetry capabilities for radionuclide treatment in nuclear medicine.