The aim is to evaluate the usefulness of technetium pertechnetate (99mTc) thyroid uptake (TcTU) obtained from thyroid scintigraphy using quantitative Single Photon Emission Computed Tomography / Computed Tomography (SPECT/CT) in determining personalised dose of 131I radioactive iodine (RAI) therapy for hyperthyroidism. A study of 131 participants with hyperthyroidism referred for RAI therapy was performed. 66 participants were enrolled into the prospective (calculated dose) group whereas 65 participants were from retrospective control (fixed dose) group. Quantitative thyroid SPECT/CT was performed for the prospective group prior to receiving RAI. TcTU and thyroid gland volume obtained from the Quantitative thyroid SPECT/CT were incorporated into modified Marinelli formula for RAI dose. Outcome of RAI was determined at the end of 6 months follow-up. Descriptive analysis of demographics and regression analyses of variables were performed. Mean calculated RAI dose was 17.74 mCi (SD 6.27) with mean dose for successful RAI at 6 months was 16.42 mCi (SD 5.87). Success rate was 80.3 % in the calculated group, versus 60.0 % in the fixed dose group (p-value 0.013). Regression analysis showed thyroid gland volume as an independent factor in determining successful outcome (adjusted OR = 0.963 CI: 0.942, 0.985) with volume of <77.2 ml more likely to produce successful outcome; sensitivity and specificity of 69 % and 83 % respectively. Quantitative SPECT/CT is useful in determining personalised dose of 131I RAI therapy. It significantly improves treatment outcome for hyperthyroidism as compared to the conventional fixed dose method.
Hyperthyroidism