Near-field speckle-scanning-based x-ray tomography

Abstract

We previously demonstrated near-field speckle scanning based x-ray imaging to be an easy-toimplement phase sensing method capable of providing both high sensitivity and high resolution. Yet, this performance combination could only be achieved at the cost of a significant number of sample exposures and of extensive data acquisition time, thus tempering its implementation for tomography applications. Here, we show ways of drastically lowering the number of exposures for the speckle scanning method to become attractive for computed tomography imaging. As the method presented can cope with a high divergence beam, it is also expected to attract the attention of the laboratory sources community.

State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

“…Moreover, still several dozens of diffuser positions are needed for a successful reconstruction. Recently, a stepping scheme has been proposed that uses the concept of 2D XSS, but with a sparse sampling for the sample scan [156]. The acquisition of the reference patterns without the specimen in the beam is performed with a 2D raster scan of the diffuser as for classic 2D XSS, while sample images are taken only at every n-th point of the diffuser scanning grid of the reference scan.…”

“…This significantly reduces the scan time and dose to the sample. However, a four-fold reduction of the sensitivity has been reported for the 5 × 5-step sparse scanning scheme compared to a conventional 25 × 25-step 2D XSS scan [156].…”

“…Three approaches for this purpose have been proposed, namely the speckle-vector tracking technique (XSVT) [157], the mixed XSVT approaches [135,156] and the unified modulated pattern analysis (UMPA) [134]. They all rely on taking sample and reference scans at several different diffuser positions, as shown in Figure 6a.…”

“…Recently, also a mixed XSS-XSVT approach has been proposed [156]. The acquisition of the sample interference patterns follows the normal XSVT scheme, and sample images are taken at several random diffuser positions building up a sample vector for each pixel to be reconstructed; see Figure 6h.…”

“…It has been shown that absorption speckle allows the use of high-energy X-rays, for which the contrast of a conventional near-field speckle pattern created by a piece of sandpaper is usually low [136]. On the other hand, recently, near-field speckle-based imaging was demonstrated also using conventional phase speckle with high-energy X-rays from a filtered synchrotron bending magnet beam with a mean energy of 65 keV and 25% bandwidth of the detected spectrum [156]. A speckle pattern of high visibility was achieved in this setup by stacking several sheets of sandpaper.…”