Asia Oceania Journal of Nuclear Medicine and Biology

Asia Oceania Journal of Nuclear Medicine and Biology

Continuous monitoring of radiation emissions from 131I thyroid cancer ablation subjects: development of a novel radiation detector system and measurement of effective retention half-time in 250 subjects

Document Type : Original Article

Authors
Dale L Bailey 1, 2
Afsaneh Lahooti 2, 3
Kathy P Willowson 1, 4
Brian H C Shin 5
Carl Munoz-Ferrada 5
1 Department of Nuclear Medicine, Royal North Shore Hospital, Sydney, Australia
2 Faculty of Medicine & Health, University of Sydney, Sydney, Australia
3 Nanoscale Organization and Dynamics Group, School of Science, Western Sydney University, Sydney, Australia
4 Institute of Medical Physics, Faculty of Science, University of Sydney, Sydney, Australia
5 Globalsonics Research Pty Ltd, Sydney, Australia
10.22038/aojnmb.2025.88612.1638
Abstract
Objectives(s): To report methodology that has been developed to provide real-time monitoring of radiation emissions from subjects treated with radionuclide therapies and summarise the radioiodine retention profiles of 250 subjects treated for differentiated thyroid cancer with 131I.
Methods: A small ceiling-mounted radiation detector for continuously monitoring the exposure rate in the radiation isolation rooms has been developed. Measurements were made every minute after administration of 1-6 GBq of 131I over the one to three days typical inpatient admission. The data are saved in text format and have been fitted with a mono-exponential curve to measure retention half time.
Results: The average effective retention half time (t½ (Eff)) for all subjects was 11.9±3.2 hrs (range: 5.0–23.1 hrs; n=250). Over 90% of the subjects had their serum TSH levels increased by injection of recombinant human TSH prior to treatment. Average retention half-time was found to be less in subjects lower than 55 year of age (t½ (Eff)=11.5 hrs) compared to those 55 or older (t½ (Eff)=14.4 hrs) (P=0.0007).
Conclusions: Despite the subjects, being free to move around the isolation room during admission and thus changing the source-detector geometry markedly, the system has been able to characterise their retention profiles after radioiodine treatment. These real-time measurements have applications in planning therapy and monitoring the subjects during their admission to the hospital and can be used for “live” updates for all staff as well as providing insights into the fate of radioiodine in the body.
Keywords
Radiation exposure
Iodine-131
Thyroid ablation
Retention
Detector
Subjects
  1. Nguyen NC, Anigati EM, Desai NB, Öz OK. Radioactive iodine therapy in differentiated thyroid cancer: An update on dose recommendations and risk of secondary primary malignancies. Sem Nucl Med. 2024; 54: 488-496.
  2. Remy H, Borget I, Leboulleux S, Guilabert N, Lavielle F, Garsi J, et al. 131I effective half-life and dosimetry in thyroid cancer patients. J Nucl Med. 2008; 49(9): 1445-50.
  3. Barbosa N, Niño F, Vallejo-Ortega MT, Naranjo M, Granados CE. Comparison of whole-body dosimetry measurements in 131I therapy using Ceiling-Mounted Geiger–Müller detectors and γ-camera scans: An agreement analysis. Cancer Biother Radiopharm. 2023; 38: 445-449.
  4. Kääriä L, Lapela M, Seppänen M, Högerman M, Ruohola J, Ålgars A, et al. Determination of effective half-life of 131I in thyroid cancer patients using remote dose-rate meter. EJNMMI Physics. 2024; 11(1): 101.
  5. Amin MB, Greene FL, Edge SB, Compton CC, Gershenwald JE, Brookland RK, et al. The eighth edition AJCC cancer staging manual: Continuing to build a bridge from a population-based to a more "personalized" approach to cancer staging. CA Cancer J Clin. 2017; 67(2): 93-99.
  6. Hertz S, Roberts A. Radioactive iodine in the study of thyroid physiology; the use of radioactive iodine therapy in hyper thyroidism. J Am Med Assoc. 1946; 131: 81-86.
  7. Fahey FH, Grant FD. Celebrating eighty years of radionuclide therapy and the work of Saul Hertz. J App Clin Med Phys. 2021; 22: 4-10.
  8. Menzel C, Kranert WT, Döbert N, Diehl M, Fietz T, Hamscho N, et al. rhTSH stimulation before radioiodine therapy in thyroid cancer reduces the effective half-life of (131)I. J Nucl Med. 2003; 44(7): 1065-8.
  9. Klain M, Nappi C, De Risi M, Piscopo L, Volpe F, Manganelli M, et al. Whole-Body radioiodine effective half-life in patients with differentiated thyroid cancer. Diagnostics (Basel). 2021; 11(10):1740.
  10. Chuah KW, Azman MT, Letchumanan M, Khoo AC. Assessment of radiation exposure measurements using the Ceiling-Mounted Geiger Müller (GM) detector and handheld survey meter in high dose radioactive 131I (RAI) therapy facility. Health and Technology. 2025; 1-6.
Asia Oceania Journal of Nuclear Medicine and Biology
Volume 14, Issue 1
January 2026
Pages 1-9