Development of an X-ray spectral CT imaging system for cultural heritage

A novel prototype X-ray imaging system has been designed to fulfil the growing demand for non-invasive and increasingly advanced analysis in the field of Cultural Heritage. Within the international Medipix4 Collaboration, a hybrid-pixel photon counting detector based on the Timepix4 Application-Specific Integrated Circuit (ASIC) has been developed, aiming at realizing a system (fig.1) with photon counting and energy resolving capabilities, suitable for energy-resolved radiography and multi-energy computed tomography (MECT). Compared to the well-known energy-integrating detectors, these detection systems represent a cutting-edge advancement in spectral imaging. They can detect individual X-ray photons, determine their position with high spatial and temporal resolution, and most importantly measure their energy. Notably, they enable material characterization through selective energy thresholding, allowing the identification of element distribution throughout the object volume using a polychromatic X-ray tube. The Timepix4 chip features a 448×512 matrix bump-bonded to semiconductor pixelated sensors (55 μm pitch) of various materials and thicknesses, providing tailored applications. Initial calibration and characterization tests have been performed on an assembly equipped with a 100 μm Si sensor[2]. Additionally, a preliminary radiographic result (fig.2) was successfully obtained using a Gallium Arsenide (GaAs) sensor, demonstrating its imaging potential. The project also involves the use of a Cadmium Telluride (CdTe) sensor to exploit its higher detection efficiency, which can lead to better results in terms of image quality and material differentiation. These advancements can mark a significant step forward in non-invasive, high-resolution imaging for Cultural Heritage.