Molecular Breast Imaging using Synthetic Projections from High-Purity Germanium Detectors: A Simulation Study.

High-Purity Germanium (HPGe) gamma cameras are an emerging technology for Molecular Breast Imaging (MBI) due to their 2D lateral spatial resolution, depth-of-interaction (DOI) estimation, and superb energy resolution. In this simulation study, we investigate the potential imaging performance of an opposing view dual-head HPGe breast imaging system using a synthetic-projection technique, which utilizes DOI data with varying degrees of overlap in an iterative OSEM reconstruction algorithm to create 3D images from which new 2D projections are then created. The radiation transport simulator Monte Carlo N-Particle was employed to generate projections from 10-mm thick HPGe detectors using tungsten parallel-hole collimators with short and wide holes. Simulations modeling 140-keV emissions from various contrast-detail and breast-torso phantoms were conducted. Synthetic projections were generated along with conjugate-counting images from collected HPGe projections. Tumor contrast, SNR, and hot-spot detection measurements were used to compare images. Results show that the synthetic projections could resolve more low-contrast tumors compared to single-camera projections and conjugate-counting methods. MBI simulations also showed increased contrast and SNR in synthetic projections compared to individual projections. In conclusion, the HPGe imaging system employing a synthetic-projection technique may offer advantages over individual dual-camera projections or conjugate-counting methods in terms of contrast, SNR, and tumor detectability.