Thyroid Remnants Therapeutic Dose Determination Using a Small Field of Gamacamera; Pilot Study
Warsaw Medical Physics Meeting 2015
P. Solny1,2, P. Vlček1, J. Zimák1, L. Jonášová1;
The aim of this pilot study was to investigate and verify the possibilities of dosimetry for patients undergoing first Radioiodine therapy (RAIT) using a small single head mobile gamma camera.
Camera Solo mobile was used for the measurement of 131I accumulation in remnants of patients' thyroids and 131I accumulating nods (neck region). Vials with a known activity of 131I were used to calibrate the system. The patient-volunteers were around 3 months after thyreoablation due to thyroid carcinoma. The weight of the accumulating remnants or nods was established using ultrasound or roughly estimated using phantom measurements. Two types of collimators - MEGP (medium energy general purpose) and HEGP (high energy general purpose) were tested. Seven patients were examined using the MEGP collimator; HEGP was used for the five patients.
The absorbed doses within remnants or nodes vary from 40 Gy up to 800 Gy with an uncertainty from 25% up to 50% depending mainly on the mass of the remnants estimation. Based on the measurements the administered therapeutic activity is considered to be sufficient for most of the patients, a consequent follow-up will be done.
The dose assessment uncertainty could be significantly reduced by processes optimization. Based on the results appropriate grant for further investigation will be sought out.
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