Capabilities and limitations of Phase Contrast Imaging techniques with X-rays and neutrons

[摘要] Phase Contrast Imaging (PCI) was studied with the goal of understanding its relevance and its requirements. Current literature does not provide insight on the effect of a relaxation in coherence requirements on the PCI capabilities of an imaging system. This problem is all the more important since coherent X-ray and Neutron sources are mostly unavailable. We develop a model for PCI contribution to imaging for partially incoherent systems, and develop a methodology to identify a minimum and an optimum coherence length 4min and opt. We propose a figure-of-merit KPcI that quantifies the PCI capabilities of an imaging system. Our calculations show that X-ray PCI systems based on free space propagation using microfocus X-ray tubes have little PCI capabilities. We develop a model to explain the edge enhancement observed with those systems; our results suggest that scatter reduction is the process responsible for the observed edge enhancement. We performed experiments that show good agreement with the model. Coded Source Imaging (CSI) is proposed as a tool to produce highly coherent sources. The general theory of CSI is developed. We propose two possible systems: Fluorescent Coded Sources (FCS) and the AEB Encoded X-ray tube.

[发布机构] Massachusetts Institute of Technology