Xizeng Wu PhD, Presenter: Nothing to Disclose

Hong Liu PhD, Abstract Co-Author: Nothing to Disclose

Biological tissues not only attenuate x-ray, but also change the x-ray wave’s phase. For tissues the x-ray phase-change are about one thousand times more sensitive than the x-ray attenuation. In order to image tissue phase-contrasts there is a pressing need for system-design guidelines. We present the experimental validation of a theory of phase-contrast imaging that we developed recently, and we propose a quantitative measure of phase-contrast visibility as the key figure of merit for the phase-contrast imaging system design.

We recently developed a new theory of phase-contrast x-ray imaging based the Wigner distribution formalism. Based on the theory we derived a quantitative measure of phase-contrast visibility called the relative phase-contrast factor (RPF). For experimental verification of the theory we performed experiments employing an x-ray tube with multiple focus spot sizes. The imaging experiments were performed with different system configurations by varying focal spot sizes of (10-50 micrometer), tube voltages (50-90 kVp), and different SID (1-3m) and magnification factors (1-4). In addition the focal spot intensity-distributions and the incident and exit x-ray spectra were measured for all the system configurations as well for use in RPF-calculations.

The mathematical formula of RPF is derived, which incorporates the effects of phase-contrast visibility of the body parts attenuation, spatial coherence of incident x-ray, x-ray spectrum and radiation dose to patients. The observed phase-contrast effects in phantom images acquired with different system configurations were correlated very well with the calculated RPF’s. The experiments validate the theory, and show that RPF is the key figure of merit for the phase-contrast imaging system design.

A new theory of phase-contrast x-ray imaging based the Wigner distribution is experimentally validated. The derived RPF is a quantitative measure of x-ray phase-contrast visibility, and it is the key figure of merit for the phase-contrast imaging system design.

Wu, X, Liu, H, Phase-Contrast Visibility in X-ray Imaging.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4411228.html