Measuring the actual I-131 thyroid uptake curve with a collar detector system: a feasibility study

Abstract

Radionuclide therapy using I-131 is commonly used for the treatment of benign thyroid diseases. The therapeutic dose to be administered is calculated based on the type of disease, the volume of the thyroid, and the measured uptake percentage. This methodology assumes a similar biological half-life of iodine, whereas in reality a large variation in biological half-life is observed. More knowledge about the actual biological half-life of iodine for individual patients will improve the quantification of the delivered radiation dose during radioiodine therapy and could aid the evaluation of the success of the therapy. In this feasibility study we used a novel measurement device [Collar Therapy Indicator (CoTI)] to measure the uptake curve of patients undergoing I-131 radioiodine therapy. The CoTI device is a light-weight wearable device that contains two independent gamma radiation detectors that are placed in a collar. By comparing results of thyroid uptake measurements with results obtained with a gamma camera, the precision of the system is demonstrated. Additionally, for three patients the uptake curve is measured during 48 h of admission in the hospital. The presented results demonstrate the feasibility of the new measurement device to measure the uptake curve during radioiodine therapy.

Real-time quantitation of thyroidal radioiodine uptake in thyroid disease with monitoring by a collar detection device

“…In that initial study, the repeated measurements by a phantom (for I-123) showed a mean sensitivity of 2.2 × 102 (± 15) cps/MBq with a good precision of 7% 4 . The coefficient of determination between the COTI measured values and the standard gamma probe was 0.87, confirming the excellent correlation between the two methods 4 . For I-131, there was an uncertainty of 3%, and a correction factor above 2000 counts per second was recommended.…”

“…Previous work on COTI has involved demonstrations of the technique's feasibility and comparability with the standard uptake probe. In the study by Brinks et al, reproducibility, linearity, and accuracy measurements using both I-123 and I-131 radiotracer were performed 4 . In that initial study, the repeated measurements by a phantom (for I-123) showed a mean sensitivity of 2.2 × 102 (± 15) cps/MBq with a good precision of 7% 4 .…”

“…In the study by Brinks et al, reproducibility, linearity, and accuracy measurements using both I-123 and I-131 radiotracer were performed 4 . In that initial study, the repeated measurements by a phantom (for I-123) showed a mean sensitivity of 2.2 × 102 (± 15) cps/MBq with a good precision of 7% 4 . The coefficient of determination between the COTI measured values and the standard gamma probe was 0.87, confirming the excellent correlation between the two methods 4 .…”

“…The Collar Therapy Indicator (COTI) is a radiation detection device embedded in a cloth collar secured around the patient’s neck and connected to a recording and data transmission box. In previously published experience, the data can be collected either at multiple time points, reflecting local thyroidal residual tissue RAI exposure and correlating well with conventional methods 4 .…”

A method to measure the absorbed dose of the thyroid during I‐131 therapy, using a collar detector system and a SPECT acquisition

“…The device is described in detail in Ref. Acquisitions are initiated by the patient by pressing a large button on a second device, which is wirelessly connected to both the acquisition unit and the Internet. The latter option allows for remote monitoring of the measurements.…”