Determination of calibration curves for 131I in thyroid tumour metabolic radiotherapy and other radionuclides used in SPECT imaging

SPECT studies are sensitive but inaccurate means through which to analyze small volumes such as, for instance, remnant tissues after thyroidectomy. We studied the relation between known volumes (0.1–10 cm3) and volumes measured with SPECT studies and using solutions of four different isotopes: 99mTc, 117mSn, 111In, 131I. The curves we determined were tested on SPECT images of two patients treated with 131I. Our work suggests the possibility to evaluate the small remnant mass using calibration curves specific to the system of image acquisition. However, it is necessary to extend the study to a larger number of patients.