Abstract

Advances in X-ray computed tomography (CT) has enabled soft-tissue X-ray imaging with improved contrast and resolution. As a result, non-destructive X-ray 3D virtual histology is bridging the gap between radiology and histology. Formalin-fixed paraffin embedded (FFPE) blocks are the most abundant archival tissues, and the backbone of histology. Laboratory-based 3D X-ray virtual histology of FFPE blocks is a promising complementary technique to conventional 2D histology. However, there is no generic optimization and consensus on the optimal settings, and associated artifacts with FFPE blocks. Therefore, a comprehensive study on the technical aspects of X-ray 3D virtual histology of FFPE tissue blocks is needed to extract the wealth of information available from them. In this study, laboratory X-ray micro-CT is first optimized with respect to FFPE block positioning, X-ray imaging conditions and artifacts. Then propagation-based imaging (PBI) is discussed and Paganin phase-retrieval as well as Bronnikov-aided correction algorithms are demonstrated for the FFPE blocks. Afterwards, the utility of PBI and its validity domain with considerations of imaging system parameters and FFPE blocks dimensions is investigated based on transport of intensity equation. Then, high-resolution imaging of FFPE blocks based on local CT, and laminography is discussed. In the end, future perspectives are given by considering state-of-the-art micro-CT scanners using liquid-metal-jet sources, large-area detectors, and photon counting detectors. This article provides a starting point for anyone stepping into the world of X-ray 3D virtual histology on FFPE blocks, but also serves as a useful overview for those who might be more experienced in the field.