Phantom Study for Volume-of-Interest Breast Imaging using Differential Phase Contrast Cone Beam CT (DPC-CBCT)

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.