Differential phase-contrast (DPC) technique is promising as the next breakthrough in the field of X-ray CT imaging.
Utilizing the long ignored X-ray phase information, Differential phase-contrast (DPC) technique has the potential of
providing us with projection images with higher contrast in a CT scan without increasing the X-ray dose. While
traditional absorption-based X-ray imaging is not very efficient at differentiating soft tissues, differential phase-contrast
(DPC) is promising as a new method to boast the quality of the CT reconstruction images in term of contrast noise ratio
(CNR) in soft tissue imaging. In order to validate and investigate the use of DPC technique in cone-beam CT imaging
scheme, a new bench-top micro-focus DPC-based cone-beam computed tomography DPC-CBCT system has been
designed and constructed in our lab for soft tissue imaging. The DPC-CBCT system consists of a micro-focus X-ray tube
(focal spot 8 μm), a high-resolution detector, a rotating phantom holder and two gratings, i.e. a phase grating and an
analysis. The detector system has a phosphor screen, an optical fiber coupling unit and a CMOS chip with an effective
pixel pitch of 22.5 microns. The optical elements are aligned to minimize unexpected moiré patterns, and system
parameters, including tube voltage (or equivalently X-ray spectrum), distances between gratings, source-to-object
distance and object-to-detector distance are chosen as practicable to be applied in a rotating system. The system is tested
with two simple phantoms for performance evaluation. 3-D volumetric phase-coefficients are reconstructed. The
performance of the system is compared with conventional absorption-based CT in term of contrast noise ratio (CNR)
under the condition of equal X-ray dose level.