Differential phase contrast (DPC) imaging is reported to be able to deliver higher contrast-to-noise ratio (CNR)
compared to attenuation-based x-ray imaging technologies. Due to the nature of attenuation contrast, the conventional
cone beam CT (CBCT) technology has limitations in characterizing breast lesions with sufficiently high contrast and
spatial resolution. As an alternative, the grating-based DPC-CBCT technology is potentially a powerful tool for breast
imaging. However, limited by current grating fabrication techniques, a full field-of-view (FOV) that covers the whole
breast is not practical at present. Previously by our group, a volume-of-interest (VOI) imaging method, which
incorporates DPC-CBCT into a dedicated attenuation-based CBCT imaging system, was presented. In the method, the
CBCT scan was performed to localize the suspicious volume and then a VOI scan by DPC-CBCT characterized the
suspicious volume with higher contrast and resolution. In this work, we investigated the performance of DPC-CBCT
VOI imaging by performing a phantom study using our bench-top DPC-CBCT system with a hospital-grade X-ray tube.
A cylinder water phantom with a size of over twice of the FOV of our DPC-CBCT system was designed. The phantom
contains four different materials and it was scanned at four different dose levels. In thick object scanning, phase
wrapping errors cause artifacts for DPC-CBCT VOI imaging. A low-pass filter was designed to reduce the artifacts. In
order to compare the DPC-CBCT VOI with attenuation-based CBCT, the scanning data were used to reconstruct both
phase coefficient image and attenuation coefficient image. The reconstructed images will be quantitatively and visually
evaluated with regards to contrast, noise level and artifacts.