Human hand radiography using X-ray differential phase contrast combined with dark-field imaging

Abstract

Established X-ray-based imaging procedures such as conventional radiography and computed tomography (CT) rely on the interaction of photons when passing through tissue, including the Compton scattering and the photoelectric effect, which is influenced by the X-ray energy and the type of matter. The resulting mean attenuation of X-rays can be measured and depicted on images with different gray levels. X-ray phase contrast imaging (PCI) represents a relatively new imaging technique relying upon the refraction of Xrays. As such, PCI relies on a fundamentally different physical contrast mechanism compared with conventional, absorption-based X-ray imaging. In the energy range of diagnostic imaging (10–120 keV), refraction is the dominant effect over absorption, but more difficult to acquire. Previous studies have demonstrated that PCI can provide considerably higher contrast in soft tissue, giving rise to its application in fields where conventional radiography and CT are usually limited. Among a variety of techniques used to acquire phase contrast images, grating interferometry [1] has recently attracted great attention because of its compatibility with conventional X-ray tubes [2, 3], which is the key prerequisite for the clinical applicability. In addition, this technique provides a third contrast mode along with absorption and phase contrast, which is the dark-field contrast [4]. Similarly, dark-field imaging again exploits a physically different interaction mechanism and represents the intensity of the scattered X-rays within the area of a single detector pixel. Image pixels with high gray values indicate strong scattering. Recent studies have investigated the performance of phase contrast (PC) and dark-field contrast (DC) in the imaging of female breast tissue, indicating promising results for distinguishing microcalcifications and the malignant conversion or extension of the carcinoma into normal breast tissue [5, 6]. Yet, joint pathologies such as rheumatoid arthritis, crystal arthropathies, and connective tissue diseases (e.g., scleroderma), are also associated with soft tissue affection and occasional calcifications. Conventional radiography of the hand is a cornerstone imaging study for the detection and monitoring of joint diseases as subtle changes of joint space and bones (narrowing and erosions or osteophytes) and—if perceivable—of soft tissue (including calcifications and fibrosis) [7, 8], indicating disease activity and/or progress. While tissue evaluation with conventional radiography is based on morphological criteria Electronic supplementary material The online version of this article (doi:10.1007/s00256-013-1606-7) contains supplementary material, which is available to authorized users T. Thuring (*) : Z. Wang :C. David :M. Stampanoni Paul Scherrer Institut, WBBA/213, 5232, Villigen, Switzerland e-mail: thomas.thuering@psi.ch