Abstract
BACKGROUND: Continuously monitored external dose-rate signals from remote dose-rate meters (DRMs) were analyzed to determine the effective half-life (T(eff)) of (131)I in differentiated thyroid cancer (DTC) patients. The aim is to gain novel understanding of the excretion of radioactive iodine (RAI) in DTC patients and to demonstrate that a remote DRM system can be reliably used for real-time monitoring of external dose-rates of DTC patients. METHODS: 110 DTC patients who received postoperative RAI therapy between September 2018 and February 2023 in Turku University Hospital were studied retrospectively. The external dose-rates of the patients were continuously monitored during their hospitalization with a remote DRM fixed in the ceiling of the isolation room. Generalized linear mixed model (GLMM) was used to analyse the association between logarithmical T(eff) and patient characteristics. RESULTS: The median T(eff) for all patients was 12.60 h (Q1: 10.35; Q3: 14.75 h). Longer T(eff)s were associated with higher BMI (p = 0.004), lower GFR (p < 0.001), and diabetes (p = 0.007). Our study also revealed that neither age nor subsequent RAI therapies have a significant impact on the whole body T(eff) (p = 0.522 and p = 0.414, respectively). CONCLUSION: Patients with higher BMI, decreased GFR, or diabetes have a longer whole-body T(eff) of (131)I. Ceiling-mounted remote DMRs can reliably be used to determine patient's T(eff). Since T(eff) values vary among patients, ceiling-mounted meters can be used to optimize the length of radiation isolation period at the hospital while improving patient comfort and staff efficiency.