  Cone beam computed tomography (CBCT) for breast imaging has potential to
replace conventional mammograms. However, concerns over dose and image quality
prevent CBBCT systems from the clinical trial phase to next stage. The time of
flight (TOF) method was recently shown to reduce the x-ray scattering effects
by 95% and improve the image CNR by 110% for large volume objects. The
advancements in x-ray sources like in compact Free Electron Lasers (FEL) and
advancements in detector technology show potential for the TOF method to be
feasible in CBCT when imaging large objects. In this study, we investigate the
efficacy of this TOF CBCT in improving the breast cancer imaging. The GATE
software was used to simulate the cone beam CT imaging of an 8 cm diameter
cylindrical water phantom using a modeled 20 keV quasi-energetic FEL source and
various detector temporal resolutions ranging from 1 to 1000 ps. An
inhomogeneous breast phantom of similar size was also imaged using the same
system setup. Results show that a detector temporal resolution of 10 ps
improved the image contrast-to-noise ratio (CNR) by 57% and reduced the
scatter-to-primary ratio (SPR) by 8.63 for a small cylindrical phantom. For the
breast phantom, the image CNR was enhanced by 12% and the SPR was reduced by
1.35 at 5 ps temporal resolution.
