Multicontrast x-ray computed tomography imaging using Talbot-Lau interferometry without phase stepping

Abstract

PURPOSE: The purpose of this work is to demonstrate that multicontrast computed tomography (CT) imaging can be performed using a Talbot-Lau interferometer without phase stepping, thus allowing for an acquisition scheme like that used for standard absorption CT. METHODS: Rather than using phase stepping to extract refraction, small-angle scattering (SAS), and absorption signals, the two gratings of a Talbot-Lau interferometer were rotated slightly to generate a moiré pattern on the detector. A Fourier analysis of the moiré pattern was performed to obtain separate projection images of each of the three contrast signals, all from the same single-shot of x-ray exposure. After the signals were extracted from the detector data for all view angles, image reconstruction was performed to obtain absorption, refraction, and SAS CT images. A physical phantom was scanned to validate the proposed data acquisition method. The results were compared with a phantom scan using the standard phase stepping approach. RESULTS: The reconstruction of each contrast mechanism produced the expected results. Signal levels and contrasts match those obtained using the phase stepping technique. CONCLUSIONS: Absorption, refraction, and SAS CT imaging can be achieved using the Talbot-Lau interferometer without the additional overhead of long scan time and phase stepping.