A dual-detector x-ray <i>μ</i> -CT system for simultaneous spectral and phase contrast imaging

X-ray phase contrast imaging (XPCI) and x-ray spectral imaging (XSI) are being increasingly used in advanced biomedical imaging applications, as they offer significant advantages for structural and compositional analysis over conventional attenuation imaging. In this work, we present a dual-detector imaging system capable of simultaneous XPCI and XSI, implemented at the SYRMEP beamline of the Elettra synchrotron. XPCI was performed using the beam tracking technique by introducing an absorbing mask into the beamline's standard polychromatic-beam configuration, which involves a lens-coupled detector used at the 10 μm pixel size. XSI was achieved by inserting a Laue crystal in the beam to diffract X-rays around a selected energy and detecting them with a photon-counting detector with a 60 μm pixel pitch. Notably, the XSI setup remains fully compatible with the standard polychromatic-beam configuration. The system was tested on a heterogeneous phantom containing silver dilutions, chalk, a toothpick, plastic microspheres, and nylon wires as well as on a biological specimen consisting of an osteochondral sample loaded with a cationic iodinated contrast agent. A dedicated processing pipeline was developed to integrate the data from both imaging branches. The combined use of XPCI and XSI provided absorption, phase, and dark-field images. Spectral absorption images, processed via a material decomposition algorithm, yielded quantitative maps of the contrast agent, calcium, and water. The results demonstrate the system's ability to deliver complementary morphological and compositional information with high spatial resolution and quantitative accuracy.