Gamma camera based method for (131)I capsule counting: an alternate method to Uptake probe method.

The main objective of this study was to check the validity of using gamma camera as an alternate method to thyroid uptake probe, for counting 25uCi (0.925 MBq) and 50uCi (1.85 MBq) (131)I capsules before administration to thyroid patients. Methods: - 10 sets each of 25uCi (0.925 MBq) and 50uCi (1.85 MBq) (131)I capsules received from Board Of Radiation and Isotope Technology, Department Of Atomic Energy, India (BRIT, DAE) have been counted individually using thyroid uptake probe for 10 seconds following institutional protocol and also by keeping individual capsule of a set with 8cm gap between each of them .These capsules were also scanned by Scintillation gamma camera for 100 seconds. Capsules having counts within the range of mean ±2 Standard Deviation (SD) were accepted for patient administration. After analysing both the data, correlation coefficient between these two methods has been evaluated. Results: Scanned images were analysed by drawing Identical ROI around each set of 25uCi (0.925 MBq) and 50uCi (1.85 MBq) (131)I capsules. Capsules with counts within 2 Standard Deviation from mean were accepted for patient administration. Good correlation coefficient (r >0.95) was observed between these two counts set. Conclusion: Gamma camera based (131)I -capsule counting method is an easy and time saving method compared to probe based capsule counting method as we can scan a set of capsules in a single acquisition. It can provide uniformity information for a batch of (131)I -capsules and avoid the time consuming method of individual capsule counting with the thyroid uptake probe.