Abstract
.Purpose: We investigate an analyzer-less x-ray interferometer with a spatially modulated phase grating (MPG) that can deliver three modalities (attenuation image, phase image, and scatter images) in breast computed tomography (BCT). The system can provide three x-ray modalities while preserving the dose to the object and can achieve attenuation image sensitivity similar to that of a standard absorption-only BCT. The MPG system works with a source, a source-grating, a single phase grating, and a detector. No analyzer is necessary. Thus, there is an approximately 2x improvement in fluence at the detector for our system compared with the same source–detector distance Talbot–Lau x-ray interferometry (TLXI) because the TLXI has an analyzer after the object, which is not required for the MPG.Approach: We investigate the MPG BCT system in simulations and find a clinically feasible system geometry. First, the mechanism of MPG interferometry is conceptually shown via Sommerfeld–Rayleigh diffraction integral simulations. Next, we investigate source coherence requirements, fringe visibility, and phase sensitivity dependence on different system parameters and find clinically feasible system geometry.Results: The phase sensitivity of MPG interferometry is proportional to object–detector distance and inversely proportional to a period of broad fringes at the detector, which is determined by the grating spatial modulation period. In our simulations, the MPG interferometry can achieve about 27% fringe visibility with clinically realistic BCT geometry of a total source–detector distance of 950 mm and source–object distance of 500 mm.Conclusions: We simulated a promising analyzer-less x-ray interferometer, with a spatially sinusoidal MPG. Our system is expected to deliver the attenuation, phase and scatter image in a single acquisition without dose or fluence detriment, compared with conventional BCT.
Highlights
According to statistics from the Centers for Disease Control and Prevention, breast cancer is the most common cancer—one in eight American women will develop it sometime during the course of her life
In current clinical-based breast computed tomography (BCT) prototypes at the University of California at Davis (UC Davis)[4,5,6] and the Koning Corporation (University of Rochester),[7,8,9] the breasts are scanned by a cone-beam x-ray in pendant geometry in which patients lie in the prostrate position on a table with an opening that allows the breasts to pass through without compression
3.1.1 Parallel source, intensity carpet, and fringe analysis The intensity carpet is shown in Fig. 8 for 1 and 0.6 μm pitch of the modulated phase grating (MPG), respectively, for W 1⁄4 100 μm
Summary
According to statistics from the Centers for Disease Control and Prevention, breast cancer is the most common cancer—one in eight American women will develop it sometime during the course of her life. It is the second-highest cause of death among women in the United States. Absorption x-ray mammography is the prevalent technique for breast-cancer screening for women above age 40. In mammography, spatial overlap of soft tissues in 2D breast projections may increase the risk of false-positive and false-negative cases in screening and diagnosis. The UC Davis prototype provided a high spatial resolution using a complementary metal-oxide semiconductor flat-panel detector, which is able to reach 50-μm pixel size.[4,5,6] In January 2015, the Food and Drug Administration (FDA) approved the U Rochester BCT prototype for breast diagnostic imaging in the United States.[8,9] Other studies have investigated the feasibility, flat-panel detectors, and spectral optimization for BCT systems.[10,11,12]
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