Efficacy of radiopaque substances in optical clearing and their impact on red blood cell aggregation

P. Moldon, M. Maksimov, Yu. Surkov, A.Lugovtsov, P.Timoshina, Pengcheng Li, A.Priezzhev

Abstract: Objective: Numerous techniques are used, in particular, optical clearing to increase the image contrast and depth of penetration of visible and near-infrared radiation into the biological tissues to enhance the efficacy of diagnostic and therapeutic procedures. Typically, optical clearing agents (OCAs) are used for this purpose. When applied to the tissue surface, the mechanism of the OCA action is based on the reduction of the reflectance from the tissue surface and diffuse penetration of the OCA into the deep layers of tissues. As a result of the second process, the tissue becomes more optically homogeneous and transparent, which increases the depth and resolution of imaging techniques, for example, the digital capillaroscopy method for in vivo visualization of terminal capillaries in the nail bed area. One of the aims of this work was to study the efficacy of various OCAs which are already used in clinical practice as radiopaque substances in MRI or CT scans for improving the visualization of subsurface structures. Another goal of this work was to investigate the effect of these OCAs on the aggregation of rat’s red blood cells (RBCs) to study the possible mechanisms of OCAs affecting the blood flow after their administration into the bloodstream. Materials and methods: In vivo measurements were performed within the nail bed using optical coherence tomography (OCT). The OCAs: magnevist®, gadovist®, mixture of visipaque® and DMSO (90% and 10%, correspondingly), mixture of visipaque® and polypropylene glycol 400 (40% and 60%, correspondingly), accupaque®, and a solution consisting of visipaque® 54%, DMSO 10%, polypropylene glycol 36%) were verified. To study the effect of OCA on RBC aggregationtwo OCAs were chosen: magnevist® and gadovist®. Rat blood samples incubated with different concentrations of these OCAs were measured by the laser aggregometry technique. Results: It was shown that almost all chosen OCAs are effective in the optical clearing of nail beds. For example, after the application of gadovist® attenuation coefficient decreased by 16 ± 8% at the depth of 0 - 50 μm. According to the experimental data obtained by laser aggregometry technique, the RBC aggregation decreases with the increase of OCA concentration, similarly equally to the control sample. Discussion: We hypothesize that the observed optical clearing effect from the chosen OCAs is caused by pulling free water from the tissue under study. Analyzing the results obtained by laser aggregometry, we can conclude that magnevist® and gadovist® have no pronounced effect on RBC aggregation properties. Conclusion: The results of the study allows us to expand the scope of the application of radiopaque agents in the optical clearing of tissues, visualizing the capillaries and shedding some light on their interaction with RBCs in the bloodstream.


Series on Biomechanics, Vol.38, No.4(2024),53-58
DOI: 10.7546/SB.08.04.2024

Keywords: nail bed; optical clearing; radiopaque agents; Red blood cells (RBCs); red blood cells aggregation

DOI: 10.7546/SB.08.04.2024

Date published: 2024-12-11