Complementary X-ray tomography techniques for histology-validated 3D imaging of soft and hard tissues using plaque-containing blood vessels as examples

Abstract

A key problem in X-ray computed tomography is choosing photon energies for postmortem specimens containing both soft and hard tissues. Increasing X-ray energy reduces image artifacts from highly absorbing hard tissues including plaque, but it simultaneously decreases contrast in soft tissues including the endothelium. Therefore, identifying the lumen within plaque-containing vessels is challenging. Destructive histology, the gold standard for tissue evaluation, reaches submicron resolution in two dimensions, whereas slice thickness limits spatial resolution in the third. We present a protocol to systematically analyze heterogeneous tissues containing weakly and highly absorbing components in the original wet state, postmortem. Taking the example of atherosclerotic human coronary arteries, the successively acquired 3D data of benchtop and synchrotron radiation-based tomography are validated by histology. The entire protocol requires ∼20 working days, enables differentiation between plaque, muscle and fat tissues without using contrast agents and permits blood flow simulations in vessels with plaque-induced constrictions.

X-ray microscopy of soft and hard human tissues

“…Figure 1 demonstrates that this is not necessarily the case. The three-dimensional representation of the 7.5 mm-long part of the diseased human coronary artery originates from synchrotron radiation-based µCT in absorption contrast mode (HZG, DESY, Hamburg, Germany) [7]. The region available for blood flow and thus accessible by contrast agent is marked in yellow, while the total cross-section of the lumen is indicated in red.…”

“…The distribution of the average wall shear stress can be derived from flow simulations based on SRµCT data [7]. For this purpose, the lumen has not only to be extracted from the raw data (segmentation) but also converted to a mesh representation [7].…”

“…For this purpose, the lumen has not only to be extracted from the raw data (segmentation) but also converted to a mesh representation [7]. For the present diseased artery the average wall shear stress varies from approximately 5 Pa to values well above 13 Pa [7]. …”

“…Recently, it has been demonstrated that the combination of images from different modalities applying sophisticated registration tools allows for conclusions about otherwise inaccessible anatomical features. The acquired knowledge is essential for improved patient treatments in fields such as neurodegenerative and cardiovascular diseases [7] as well as oral health [8]. The question arises to what extent the assessment developed for specific modality combinations selected for the heterogeneous tissue of interest can be applied for other combinations that may be better suited for different heterogeneous material or tissue.…”

Implementation of a double-grating interferometer for phase-contrast computed tomography in a conventional system nanotom® m

“…In the hard X-ray regime, phase contrast is often preferred over conventional absorption contrast for soft tissue imaging 3,4 and visualizing weak X-ray absorbing species in the direct neighborhood of stronger absorbing components, 5 in particular, for three-dimensional imaging of a cartilage which is involved in the degenerative changes of a joint, [6][7][8][9][10] providing imaging data of morphological features with unprecedented contrast. Disorders associated with cartilage degeneration, such as debilitating joint diseases, are one of the leading causes of disability worldwide.…”