Tian XIA^1,2*, Junshan MA^1†, Xuelong ZHANG^2‡, Jinghai CHENG^1,2, Weijun PENG³, and Xufeng YAO^1,2

¹School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, P. R. China
²Shanghai Medical Instrumentation College, Shanghai, P. R. China
³Fudan University Shanghai Cancer Center, Shanghai, P. R. China

(Received January 7, 2014; Accepted February 27, 2014)

In clinical applications, the X-ray spectra from tungsten are continuous, and include both attenuation and phase effects for in-line X-ray imaging. A new approach for extracting the pure phase effect from the mixed images is presented. In this work, a normalized imaging formula independent of the light intensity is derived for the polychromatic case. Taking both photoelectric and Compton interactions into account, the attenuation effects at 70 and 50 kVp for borosilicate pyrex, air, and water are accurately calculated and shown to be stable across these substances. The attenuation effect at the interface can be greatly weakened by the subtraction of the attenuation effects of two normalized images, thus revealing details of the phase effect. The experimental results show that this approach is valid.

Key words: phase-contrast imaging, attenuation effect, phase effect, electron density

^*E-mail address: Bruce{_}xiatian@163.com
^†E-mail address: junshanma@163.com
^‡E-mail address: zhangxl@smic.edu.cn