A Four-Grating Interferometer for X-Ray Multi-Contrast Imaging

Published

March 24, 2024

Author(s)

Daniel Josell, Houxun Miao, James Williams, Jr.

Abstract

Background: X-Ray multi-contrast imaging with gratings provides a practical method to detect the differential phase and dark-field contrast images in addition to the traditional X-ray absorption image in a laboratory or hospital environment. Systems have been developed for preclinical applications in areas including breast imaging, lung imaging, rheumatoid arthritis hand imaging and kidney stone imaging. Purpose: Prevailing X-ray interferometers for multi-contrast imaging include Talbot-Lau interferometers and universal moiré effect-based phase-grating interferometers. Talbot-Lau interferometers suffer from conflict between high interferometer sensitivity and large field of view (FOV) of the object being imaged. A small period analyzer grating is necessary, but technically challenging to produce at high X-ray energy level, to achieve simultaneous high sensitivity and large FOV within a compact imaging system. Phase-grating interferometers suffer from an intrinsic fringe period ranging from a few µm micrometers to a few hundred micrometers that cannot be resolved by medical X-ray detectors. The purpose of this work is to introduce a four-grating X-ray interferometer that allows simultaneous high sensitivity and large FOV, without the need for a small period analyzer grating. Methods: The four-grating interferometer consists of a source grating placed downstream of and close to the X-ray source, a pair of phase gratings separated by a fixed distance placed downstream of the source grating, and an analyzer grating placed upstream of and close to the X-ray detector. The imaging object is placed upstream of and close to the phase-grating pair. The distance between the source grating and the phase-grating pair is designed to be far larger than that between the phase-grating pair and the analyzer grating to promote simultaneous high sensitivity and large FOV. The method was evaluated by constructing a four-grating interferometer with an 8 µm period source grating, a pair of phase gratings of 2.4 µm period, and an 8 µm period analyzer grating. Results: The fringe visibility of the four-grating interferometer was measured to be ≈ 24 % at 40 kV and ≈ 18 % at 50 kV X-ray tube operating voltage. A quartz bead of 6 mm diameter was imaged to compare the theoretical and experimental phase contrast signal with good agreement. Kidney stone specimens were imaged to demonstrate the potential of such a system for classification of kidney stones. Conclusions: The proposed four-grating interferometer promotes a compact X-ray multi-contrast imaging system with simultaneous high sensitivity and large FOV. Relaxation of the requirement for a small period analyzer grating makes it particularly suitable for high X-ray energy applications such as abdomen and chest imaging.

Citation

Medical Physics

Pub Type

Journals

Download Paper

https://doi.org/10.1002/mp.17052

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Keywords

imaging, gratings, kidney stones

Citation

Josell, D. , Miao, H. and Williams, J. (2024), A Four-Grating Interferometer for X-Ray Multi-Contrast Imaging, Medical Physics, [online], https://doi.org/10.1002/mp.17052, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956357 (Accessed September 11, 2024)