An interactive freehand ROI tool for thyroid uptake studies using gamma camera

Abstract

Thyroid Uptake is a procedure that requires an injection of radiotracer/radio-isotope into the patient’s blood stream. After injecting 2 millicuries of Technetium-99m pertechnetate radio-isotope, thyroid images are acquired. This uptake requires a special purpose camera called Gamma Camera. Thyroid uptake study provides both the functional, structural information. It is used for the diagnosis of various thyroid disorders. Thyroid uptake is calculated depending on the counts. Counts are nothing but the total number of intensity values present in the selected region of interest. LEAP (Low Energy All Purpose) collimator is used in the Gamma Camera which can handle only photons of lower energies. Technetium-99m pertechnetate is used having an emission energy of 140 keV. Thyroid uptake scan study using Gamma Camera has to be calibrated at each organization. In our super specialty hospital, it has been standardized that the uptake value greater than 2.5% is considered as Hyperthyroidism, and value between 0.5 and 2.5% is considered as Normal and the value less than 0.5% is considered as Hypothyroidism. An Interactive freehand ROI tool was developed in Matlab R2013a as an alternative to the software existing in the Department of Nuclear Medicine, SSSIHMS. This ROI throws light on understanding the image data and calculating the Glomerular Filtration Rate. The GFR is calculated using GATES formula. The tracer uptake is obtained from both left and right thyroid lobes by manually drawing a ROI separately. Developed tool was tested on 30 real time thyroid cases with expected thyroid disorders. The uptake value obtained from the developed tool are compared with the values of the existing software in SSSIHMS.