Calculation of Blood Dose in Patients Treated With 131I Using MIRD, Imaging, and Blood Sampling Methods

Abstract

Radioiodine therapy is known as the most effective treatment of differentiated thyroid carcinoma (DTC) to ablate remnant thyroid tissue after surgery. In patients with DTC treated with radioiodine, internal radiation dosimetry of radioiodine is useful for radiation risk assessment. The aim of this study is to describe a method to estimate the absorbed dose to the blood using medical internal radiation dosimetry methods.In this study, 23 patients with DTC with different administrated activities, 3.7, 4.62, and 5.55 GBq after thyroidectomy, were randomly selected. Blood dosimetry of treated patients was performed with external whole body counting using a dual-head gamma camera imaging device and also with blood sample activity measurements using a dose calibrator. Absorbed dose to the blood was measured at 2, 6, 12, 24, 48, and 96 hours after the administration of radioiodine with the 2 methods.Based on the results of whole body counting and blood sample activity dose rate measurements, 96 hours after administration of 3.7, 4.62, and 5.55 GBq of radioiodine, absorbed doses to patients’ blood were 0.65 ± 0.20, 0.67 ± 0.18, 0.79 ± 0.51 Gy, respectively. Increasing radioiodine activity from 3.7 to 5.55 GBq increased blood dose significantly, while there was no significant difference in blood dose between radioiodine dosages of 3.7 and 4.62 GBq.Our results revealed a significant correlation between the blood absorbed dose and blood sample activity and between the blood absorbed dose and whole body counts 24 to 48 hours after the administration of radioiodine.

Patient Preparation and Radiation Protection Guidance for Adult Patients Undergoing Radioiodine Treatment for Thyroid Cancer in the UK

“…Time spent in close proximity to the patient and potential for contaminated clinical waste must be considered; for some patients, extended stays in hospital may be required so that radiation doses and clinical waste can be controlled within a hospital environment under guidance of the RPA/RWA. For injections following discharge from RAI treatment, using estimates of radioactivity in the blood following RAI administration [39] it has been shown that the level of radioactivity in sharps waste is unlikely to exceed the 40 KBq limit and therefore such waste can be disposed of via typical clinical waste routes such as via the general practitioner surgery. Written guidance should be provided to patients on best practice for handling waste.…”

Correlation analysis of I-131 SPECT/CT uptake parameters with the success ablation treatment of thyroid remnant in patients with low-intermediate-risk differentiated thyroid cancer

“…I-131 dosimetry should be calculated from a series of SPECT images generated time-activity curves. Therefore, the complicated operation process [21], imaging method [5] and calculation model may be limited in clinical application [22]. In this study, the actual activity of the therapeutic dose of I-131 in thyroid remnant tissue was quantified as %ID, and the operation process was performed by thyroid SPECT/CT scanning from whole-body iodine planar images after therapeutic dose I-131 administration.…”

Autosomal dominant polycystic kidney disease: a potential mistake in the interpretation of radioiodine whole-body scintigraphy

“…Many potential errors in radionuclide scintigraphy could occur and reporting should be done with caution [3] , [4] . Because of the harmful effects of radioiodine [8] , [9] , recognition of potential false-positive 131 I scintigraphy is critical to avoid renewal therapeutic doses of radioactive iodine.…”