Investigating the effect of incorporating backscatter photons in molecular breast imaging

Molecular breast imaging (MBI) is an imaging modality used as an adjuvant to mammography in women with dense breast tissue. In order to be useful for population screening, the radiation dose from MBI must be on par with the dose obtained from x-ray mammography. In an effort to reduce radiation dose while maintaining acceptable image quality, we are investigating the use of incorporating backscattered photons in order to improve image quality. Because backscattered photons simply undergo a 180° scatter prior to detection, they yield the same spatial information as primary photons, but with reduced energy (90.4 keV for Tc-99m).We have performed Monte Carlo simulations of a Tc-99m source with a pixelated CZT based gamma camera to investigate the feasibility of backscatter imaging in an effort to reduce patient dose while maintaining image quality. Aspects of image quality was quantified through a comparison of the count sensitivity spatial resolution and contrast to noise ratio with and without backscatter photons using a clinical MBI system. Using a triple energy window scatter correction results in an increase in count sensitivity by up to 10%, minimal degradation in spatial resolution and an increase in contrast to noise ratio by up to 8%.