Technical Note: Determination of individual thyroid clearance effective half-life with a common handheld electronic...

To determine the thyroid clearance effective half-life T with a common handheld electronic dosimeter (ED) in patients undergoing radioiodine treatment for hyperthyroidism.

Dose rates from 12 inpatients were measured daily with an ED and with a clinical uptake counter. The ED was attached to the patient with two different setups, one using a cervical collar and another employing a neck strap. Estimation of T was performed by linear regression analysis of the log of both the ED and the uptake counter measurements versus time. The latter provided the reference data.

Based on repeated neck strap dose rate measurements, individual Ts were determined with clinically required accuracy. The mean difference from the reference method equaled to -0.09 ± 0.35 days.

Determination of individual T is feasible with a common handheld ED using the simple and easy to instruct neck strap measurement setup. This simple method complements stationary uptake counter measurements and thus may improve the accuracy of radioiodine treatment planning by adding an individual T for dose calculation.