Evaluation of Effective Half-life of 131I in Patients with Thyroid Cancer Undergoing Radioiodine Therapy

Background: The discharge time of the patients treated with radioiodine-131 is the main concern for Health Physics to control radiation hazard. In this study, we performed an external dose rate (EDR) measurement with survey meter, and assessed EDR reduction plan in patients with thyroid cancer undergoing radioiodine therapy to estimate effective half-life considering the impact of age, gender, BMI, hormone level and quantitative assessment of their scintigraphy.Patients and Methods: EDR of 220 volunteer patients were measured with a calibrated Geiger Muller on 2, 12, 24, and 48 hours after 131I administration. Hormone levels was checked. Planar whole body 131I imaging was also acquired one week later and regional of interest (ROI) analysis assessment is performed to achieve distribution pattern. The mean age of patients was 55 years. The administered activity range was 100 to 200 mCi. Recorded EDR values were fitted as curve to obtain effective half-life of 131I and remained activity in patient body.Results: The mean value of discharge EDR was 41 μSv/h in the range of 15-120 μSv/h. The calculated effective half-life varies between 6.6 to 162 hr. The mean value of effective half-life is 15.4 hr. This study is shown complex relation between effective life and other variables. Therefore, using predictive analytics statistical techniques accomplish goals to predict effective half-life of 131I.Conclusions: The Dosimetry results would be helpful for patient discharge instructions, reducing hospitalization time and direct and indirect costs besides patient financial benefits in health care. Moreover, independent of administrated activity, broad metastases and/or residual thyroidal tissue were two main factors resulted in higher biological half-life and higher remained activity in patient s body.

Evaluation of Effective Half-life of 131I in Patients with Thyroid Cancer Undergoing Radioiodine Therapy Keywords:

Effective half-life , Radioiodine therapy , Patient Discharge