We report on a non-interferometric technique enabling dark-field imaging by using incoherent illumination and two achromatic optical elements. The simultaneous retrieval of absorption and differential phase images in the hard X-ray regime is also provided. We show that three projection images are sufficient to separate three signals: absorption, differential phase, and scattering. The method is highly efficient, also in terms of the dose delivered to the sample, flexible, robust against environmental vibrations, and scalable. It can be easily implemented in laboratories and translated into commercial systems, lending itself to a wide range of applications.

/pdf/hard-x-ray-dark-field-imaging-with-incoherent-sample-51dh43xr67.pdf

Hard X-ray dark-field imaging with incoherent sample illumination

Microcalcifications can be indicative in the diagnosis of early breast cancer. Here we report a non-invasive diagnostic method that may potentially distinguish between different types of microcalcifications using X-ray phase-contrast imaging. Our approach exploits the complementary nature of the absorption and small-angle scattering signals of microcalcifications, obtained simultaneously with an X-ray grating interferometer on a conventional X-ray tube. We demonstrate that the new approach has 100% sensitivity and specificity when applied to phantom data, and we provide evidence of the solidity of the technique by showing its discrimination power when applied to fixed biopsies, to non-fixed tissue specimens and to fresh, whole-breast samples. The proposed method might be further developed to improve early breast cancer diagnosis and has the potential to increase the diagnostic accuracy and reduce the number of uncomfortable breast biopsies, or, in case of widespread microcalcifications, to select the biopsy site before intervention.

/pdf/non-invasive-classification-of-microcalcifications-with-3f6iyclenh.pdf

Non-invasive classification of microcalcifications with phase-contrast X-ray mammography.

X-ray imaging is a standard tool for the non-destructive inspection of the internal structure of samples. It finds application in a vast diversity of fields: medicine, biology, many engineering disciplines, palaeontology and earth sciences are just few examples. The fundamental principle underpinning the image formation have remained the same for over a century: the X-rays traversing the sample are subjected to different amount of absorption in different parts of the sample. By means of phase-sensitive techniques it is possible to generate contrast also in relation to the phase shifts imparted by the sample and to extend the capabilities of X-ray imaging to those details that lack enough absorption contrast to be visualised in conventional radiography. A general overview of X-ray phase contrast imaging techniques is presented in this review, along with more recent advances in this fast evolving field and some examples of applications.

/pdf/x-ray-phase-contrast-imaging-12a2d7dtk3.pdf

X-ray phase-contrast imaging

We present a theoretical and experimental analysis of the angular sensitivity of edge illumination X-ray phase-contrast imaging in its implementation with conventional X-ray sources (sometimes referred to as the “coded-aperture” method). We study how the polychromaticity and finite source dimensions encountered in laboratory-based setups affect the detected signal. We also show that the sensitivity is independent of the period of the masks. Experimental images are presented and analyzed, proving that, despite the simple setup, high angular resolutions of a few hundred nanoradians can be obtained.

/pdf/sensitivity-of-laboratory-based-implementations-of-edge-w0h481vagu.pdf

Sensitivity of laboratory based implementations of edge illumination X-ray phase-contrast imaging

Purpose:
The purpose of this work is to investigate the feasibility of grating-based, differential phase-contrast, full-field digital mammography (FFDM) in terms of the requirements for field-of-view (FOV), mechanical stability, and scan time.
Methods:
A rigid, actuator-free Talbot interferometric unit was designed and integrated into a state-of-the-art x-ray slit-scanning mammography system, namely, the Philips MicroDose L30 FFDM system. A dedicated phase-acquisition and phase retrieval method was developed and implemented that exploits the redundancy of the data acquisition inherent to the slit-scanning approach to image generation of the system. No modifications to the scan arm motion control were implemented.
Results:
The authors achieve a FOV of 160 × 196 mm consisting of two disjoint areas measuring 77 × 196 mm with a gap of 6 mm between them. Typical scanning times vary between 10 and 15 s and dose levels are lower than typical FFDM doses for conventional scans with identical acquisition parameters due to the presence of the source-grating G
0. Only minor to moderate artifacts are observed in the three reconstructed images, indicating that mechanical vibrations induced by other system components do not prevent the use of the platform for phase contrast
imaging.
Conclusions:
To the best of our knowledge, this is the first attempt to integrate x-ray gratings hardware into a clinical mammography unit. The results demonstrate that a scanning differential phase contrast FFDM system that meets the requirements of FOV, stability, scan time, and dose can be build.

https://aapm.onlinelibrary.wiley.com/doi/pdf/10.1118/1.4914420

Slit-scanning differential x-ray phase-contrast mammography: Proof-of-concept experimental studies

Purpose: The edge illumination (EI) x-ray phase contrast imaging (XPCi) method has been recently further developed to perform tomographic and, thus, volumetric imaging. In this paper, the first tomographic EI XPCi images acquired with a conventional x-ray source at dose levels below that used for preclinical small animal imaging are presented. Methods: Two test objects, a biological sample and a custom-built phantom, were imaged with a laboratory-based EI XPCi setup in tomography mode. Tomographic maps that show the phase shift and attenuating properties of the object were reconstructed, and analyzed in terms of signal-to-noise ratio and quantitative accuracy. Dose measurements using thermoluminescence devices were performed. Results: The obtained images demonstrate that phase based imaging methods can provide superior results compared to attenuation based modalities for weakly attenuating samples also in 3D. Moreover, and, most importantly, they demonstrate the feasibility of low-dose imaging. In addition, the experimental results can be considered quantitative within the constraints imposed by polychromaticity. Conclusions: The results, together with the method's dose efficiency and compatibility with conventional x-ray sources, indicate that tomographic EI XPCi can become an important tool for the routine imaging of biomedical samples.

https://aapm.onlinelibrary.wiley.com/doi/epdf/10.1118/1.4884297

B. Johnson

Papers

Low-dose phase contrast tomography with conventional x-ray sources