The cross-section of an X-ray phase shift image is a thousand times greater than that of X-ray attenuation in soft tissue over the diagnostic energy range implying phase imaging can achieve a much higher signal-to-noise ratio and substantially lower radiation dose than attenuation-based X-ray imaging. Grating interferometry is a state of the art X-ray imaging approach, which can simultaneously acquire information of X-ray phase-contrast, dark-field, and linear attenuation. This imaging modality can reveal subtle texture of tissues. For example, the growth of tumors causes remarkable differences of small-angle scattering patterns from that of healthy tissues. It is clinically important that the structural variation in tumor modifies the refractive index; however, conventional grating interferometers often use flat gratings, with serious limitations in the field of view and the flux of photons. This invention provides novel and advantageous systems and methods for X-ray phase-contrast imaging (PCI), including the use of one or more period-varying or quasi-periodic gratings. This X-ray PCI system can include a phase grating that is period-varying or quasi-periodic and can be positioned between an object being imaged and a detector. A second grating, such as an absorption grating or an analyzer grating can also be present and disposed between the phase grating and the detector. The subject invention also provides second-order approximation models for X-ray phase retrieval, for example using paraxial Fresnel-Kirchhoff diffraction theory. An iterative method can be used to reconstruct a phase-contrast image andor a dark-field image. The models can be iteratively solved using the algebraic reconstruction technique (ART). State of the art compressive sensing techniques can be incorporated to achieve high quality image reconstruction.

Submission Date
Reference Number
R15-027
Inventor(s)
Contact
Natasha Sanford