Monte Carlo simulation study of performance evaluation for sensitivity and scatter fraction in gamma camera scintigraphy with TlBr pixelated semiconductor detector with different parallel-hole collimator designs

Abstract

Thallium bromide (TlBr) semiconductor materials are widely used to detect gamma rays. They have excellent detection efficiency owing to their high stopping and effective atomic number. The purpose of this study was to compare image quality using TlBr and conventional detector materials according to parallel-hole collimator geometry in gamma camera scintigraphy. The Geant4 application for tomographic emission (GATE) simulation tool was used. Cadmium telluride (CdTe), cadmium zinc telluride (CZT), and TlBr semiconductor materials were used; the parallel-hole collimator lengths were designed as 0.4, 0.6, 0.8, and 1.0 cm. For qualitative analysis, images were acquired using a quadrant-bar phantom with different bar thicknesses. Quantitative analyses, such as sensitivity (cps/MBq) and scatter fraction using a point source with 99mTc of 1 mCi, were conducted. The sensitivity with TlBr material with collimator lengths of 0.4, 0.6, 0.8, and 1.0 cm was 2.38, 2.39, 2.39, and 2.36 times greater than with CdTe and CZT materials, and the scatter fraction with TlBr material was 1.26, 1.25, 1.24, and 1.31 times less than the scatter fraction with CdTe and CZT materials with the same collimator length, respectively. There was no significant difference in sensitivity and scatter fraction between CdTe and CZT materials. Thus, we confirmed that TlBr is a potential detector material with improved sensitivity and scatter fraction in gamma camera scintigraphy.