Optimization of Tc-99m-sestamibi/I-123 subtraction SPECT/CT protocol for parathyroid scintigraphy

Abstract

The purpose of this study was to optimize effective, but technically challenging Tc-99m-sestamibi/I-123 subtraction SPECT/CT protocol for parathyroid scintigraphy. An anthropomorphic parathyroid phantom was set up using a small sphere, a thyroid phantom and a thorax phantom with clinical range of activities of 1231 and Tc-99m. SPECT/CT acquisitions were performed using three collimators (Low Energy High Resolution (LEHR), Low Energy Ultra High Resolution (LEUHR) and Medium Energy Low Penetration (MELP)) and two energy window settings. Images were reconstructed with a combination of four different numbers of iterations and with or without scatter correction. Images were subjected to visual and quantitative evaluation. The effect of collimator, energy window selection and reconstruction parameters had a significant effect on visual appearance and adenoma contrast in parathyroid Tc-99m-sestamibi/I-123 subtraction SPECT/CT. Symmetrical energy windows and ultra-high resolution collimator yielded best results with some improvement with scatter correction.