Advancing Nuclear Breast Imaging with the use of High-Purity Germanium detectors

Nuclear Breast Imaging with specifically designed gamma cameras can improve breast cancer detection. One benefit of semiconductor-based imaging systems is their superior energy resolution (ER) compared to scintillator cameras, which results in better scatter rejection. In this work we conducted simulations to compare the imaging performance of High-Purity Germanium (HPGe) and Cadmium Zinc Telluride (CZT) systems with 1% and 3.8% ER at 140 keV, respectively. The objective was to investigate whether the better ER offered by HPGe would translate into improved imaging performance. Using the Monte Carlo N-Particle (MCNP5) simulation package, we modeled both 5 mm-thick CZT and 10 mm-thick HPGe detectors with the same parallel-hole collimator for the imaging of a breast/torso phantom with three spherical tumors. Simulated energy spectra were generated, and images were created for various energy windows around the 140 keV photopeak. Scatter and torso fractions were calculated along with tumor contrast. Simulations showed that utilizing a ±1.25% energy window with an HPGe system suppressed torso background and small-angle scattered photons better than a comparable CZT system using an -5%/+10% energy window. Higher contrast between tumor signal and background was observed with HPGe with increases in sensitivity for equivalent activity imaged. Thus, further improvements in ER may lead to better tumor detection capabilities with conventional parallel-hole collimation.