Relevance of a thyroid phantom in estimating thyroid radioiodine uptake values using a gamma camera

The objective of this work was to evaluate the necessity of a thyroid phantom in counting a standard capsule during estimation of iodine-131 thyroid uptake using gamma camera methods. For this, camera-based uptake was calculated taking a standard capsule within a thyroid phantom, as well as a standard capsule (without phantom) placed at 5, 10, and 15 cm from the face of the collimator. The values obtained in each setting were compared with the traditional standard thyroid probe-based method. Among these four sets of values, that with the phantom was the closest to the reference probe-based uptake values. Among those without the phantom, the camera-based uptake with the standard at 15 cm from the face of the collimator was closer to the standard probe method. However, as the image at 15 cm would give poor resolution, it would not be feasible to adopt this method for clinical routine. Thus, to conclude, for calculating camera-based uptake, a standard capsule in the phantom gives the best comparable values to the standard probe-based method, indicating the need for the phantom when adopting the gamma camera-based methodology.