Comparison of 24 h neck uptake using camera based and standard uptake probe based methods undertaken with 25μCi of ¹³¹I capsule in patients with benign thyroid conditions

To make a quantitative comparison of thyroid uptake values calculated using camera based and thyroid uptake probe based methodologies in patients with benign thyroid disorders (mostly patients of hyperthyroidism) after administration of 25uCi ¹³¹I capsule. Patients undergoing 25 μCi ¹³¹I thyroid uptake and scan in our centre for various indications were included for the study. These patients mostly belonged to hyperthyroidism group who underwent the procedure before being considered for ¹³¹I therapy for thyrotoxicosis. Based upon the patient profile, the patients were categorized into two groups: (a) Patients with hyperthyroidism and (b) Patients with non-thyrotoxic group. 25 μCi capsule was administered and 24 h thyroid uptake by thyroid probe was undertaken by standardized institutional protocol. Uptake was calculated by the equation background subtracted neck counts/background subtracted standard counts. Gamma camera with high energy collimator was used to calculate neck uptake for calculation of uptake by gamma camera based methods. Standard capsule was scanned and counts were calculated by drawing ROI around the capsule image. Similarly neck counts were obtained by drawing ROI around thyroid image. Background subtraction was done by drawing ROI near thyroid image. Data of these two different groups were compared with paired t-test. Result: A total of 50 patients were included in this study (32 hyperthyroid and 18 non-thyrotoxic). The difference in % uptake observed by these two methods does not vary significantly in both the groups. For group (a) the uptake value varied from 40.13% to 98.6% while for group (b) the uptake value varied from 1.48% to 34.29%. In Group (a) P value from t-test is 0.418 and for group (b) P value is 0.444. Camera based uptake can be used as an alternative method for thyroid uptake using probe based method, by which this could be useful to centres who do not possess thyroid uptake probe. In a routine setting this could reduce patients inconvenience and save scan time as the quantitative value can be obtained by single neck scan. (author)