Soft tissue discrimination with contrast agents using micro-CT scanning

Abstract

The use of high resolution, three-dimensional visualization has been receiving growing interest within life sciences, with non-invasive imaging tools becoming more readily accessible. Although initially useful for visualizing mineralized tissues, recent developments are promising for studying soft tissues as well. Especially for micro-CT scanning, several X-ray contrast enhancers are performant in sufficiently contrasting soft tissue organ systems by a different attenuation strength of X-rays. Overall visualization of soft tissue organs has proven to be possible, although the tissue-specific capacities of these enhancers remain unclear. In this study, we tested several contrast agents for their usefulness to discriminate between tissue types and organs, using three model organisms (mouse, zebrafish and Xenopus). Specimens were stained with osmium tetroxide (OsO4), phosphomolybdic acid (PMA) and phosphotungstic acid (PTA), and were scanned using high resolution microtomography. The contrasting potentials between tissue types and organs are described based on volume renderings and virtual sections. In general, PTA and PMA appeared to allow better discrimination. Especially epithelial structures, cell-dense brain regions, liver, lung and blood could be easily distinguished. The PMA yielded the best results, allowing discrimination even at the level of cell layers. Our results show that those staining techniques combined with micro-CT imaging have good potential for use in future research in life sciences.

Feeding kinematics and morphology of the alligator gar (Atractosteus spatula, Lacépède, 1803)

“…During this time, the specimen and solution were set to mix on an orbital shaker, kept at room temperature, and covered with foil to prevent photoreaction. PMA is a contrast agent used to enhance μCT-scans (Descamps et al, 2014;Pauwels, Van Loo, Cornillie, Brabant, & Van Hoorebeke, 2013) allowing distinction between a variety of tissues including muscle, bone, ligament, and nervous tissue.…”

Development of a contrast‐enhanced micro computed tomography protocol for the oval squid ( Sepioteuthis lessoniana ) brain

“…In this study, the fastest stain progression was observed in I 2 E-stained specimens whereas the slowest staining progression was observed in PTA-stained specimens. This difference might occur because of the large molecular size of phosphotungstic acid (Keggin, 1934), leading to a slower movement of phosphotungstic acid than of the iodine ion (Descamps et al, 2014;Metscher, 2009b). The movement of the large-molecule contrast agent is slower than the smallmolecule agent.…”

“…We think that the reason the CR derived from longer staining duration did not affect the visibility of 2D scan images is because the subtle differences in contrast measurable by the computer software are not detectable by our vision. Regarding visibility of scanned images, the physicochemical property of the molecules in the contrast agent is important because it affects the osmotic speed and X-ray absorption rate (Descamps et al, 2014;Gignac et al, 2016;Keggin, 1934;Metscher, 2009aMetscher, , 2009bMizutani et al, 2008 Pauwels et al, 2013). The concentration also influences the osmotic pressures, such that the contrast agent with higher concentration is absorbed more quickly by soft tissues (Visckerton, Jarvis, & Jeffery, 2013).…”

Enhanced contrast in X‐ray microtomographic images of the membranous labyrinth using different X‐ray sources and scanning modes

“…Because most soft tissues are composed of a very similar set of molecules (largely water), they cannot readily be distinguished on an X-ray lCT scan (Richter et al 2009;Descamps et al 2014). Sometimes, PCI increases the CNR sufficiently in order to alleviate the need for soft tissue staining (Dullin et al 2017).…”