The Use of Gamma Probe in Thyroid Uptake Studies

Evaluation of thyroid uptake, by administration of small activities of radioactive iodine (I or I), is a well-defined procedure. Nowadays, nuclear medicine departments are using scintillation cameras coupled to pinhole collimators to perform such studies. On the other hand, gamma probes, which are normally used in radioguided surgical procedures, can technically be used for measuring the thyroid uptake of radioiodine. In this context, the aim of this work is to evaluate the potential use of surgical gamma probe as an alternative method for thyroid uptake measurements. Primarily, studies of feasibility were performed to quantify the efficiency of gamma probe and to compare it with the scintillation camera one. Henceforth, measurements were carried out with a group of 12 patients undergoing 24 hours thyroid function study, after oral administration of I. Thyroid uptake was obtained by scintillation camera (AXIS Picker equipped with a pinhole collimator) according to the protocol of the Society of Nuclear Medicine. Immediately after the camera image acquisition, a gamma probe (Europrobe equipped with a high energy CsI(Tl) probe) was placed 10 cm from the neck, supported by an acrylic specially designed to hold it. Count-rates from one patients’ thigh were employed as background. For each patient, the maximum difference between the values obtained for thyroid uptake with both equipments was about 6%. The results indicate surgical gamma probe as simple and reliable method for thyroid function investigation, allowing the use of scintillation camera for other purposes.