Optimal flushing agents for integrated optical and acoustic imaging systems

Abstract

An increasing number of integrated optical and acoustic intravascular imaging systems have been developed and hold great promise for accurately diagnosing vulnerable plaques and guiding atherosclerosis treatment. However, in any intravascular environment, the vascular lumen is filled with blood, a high-scattering source for optical and high-frequency ultrasound signals. Blood must be flushed away to provide clearer images. To our knowledge, no research has been performed to find the ideal flushing agent for combined optical and acoustic imaging techniques. We selected three solutions as potential flushing agents for their image-enhancing effects: mannitol, dextran, and iohexol. Testing of these flushing agents was performed in a closed-loop circulation model and in vivo on rabbits. We found that a high concentration of dextran was the most useful for simultaneous intravascular ultrasound and optical coherence tomography imaging.

Measurement of tissue optical properties in the context of tissue optical clearing

“…There are many OCAs which are used for OC of blood, such as dextrans, iohexol (x-ray contrast, i.e., Omnipaque™), mannitol, glucose, glycerol, PG, PEG, hemoglobin, and some others. 17,53,[191][192][193][194][195][196][197][198] The mechanisms of the improvement of light transport in tissue and blood depend on the particular OCA and mode of application. 17,53,161,183,[199][200][201][202][203][204][205][206][207][208][209][210][211] The RI matching between RBC and blood plasma is one of the major mechanisms of the OC of blood, however, cell aggregation and deformation induced by an OCA or the displacing of blood at OCA flushing may also lead to decreasing of light scattering in blood.…”

Integrated intravascular ultrasound and optical coherence tomography technology: a promising tool to identify vulnerable plaques [INVITED PAPER]

“…This doesn’t pose a problem for ex vivo experiments [24, 26, 31, 33] summarized in the next section, since blood was usually drained from cadaver samples before imaging. Prior to in vivo imaging, an optical flushing agent is needed to be selected [34], so as to acquire clear IVUS and OCT images simultaneously, without inducing a great amount of toxicity. Since X-ray contrast agents (such as iohexol and iodixanol) are often used in patients in both IVUS and OCT procedures [35, 36], they were predicted as effective IVUS-OCT flushing agents and were commonly used in in vivo IVUS-OCT experiments [24–26].…”

“…Since X-ray contrast agents (such as iohexol and iodixanol) are often used in patients in both IVUS and OCT procedures [35, 36], they were predicted as effective IVUS-OCT flushing agents and were commonly used in in vivo IVUS-OCT experiments [24–26]. However, alternative flushing agents, which have less side-effects than X-ray contrast agents and better OCT or IVUS clearing effects [34, 37–41], can be used in vivo experiments in future. Potential alternative flushing agents include mannitol, dextran, glucose solution and propylene glycol [42].…”

“…Potential alternative flushing agents include mannitol, dextran, glucose solution and propylene glycol [42]. A high concentration of dextran was demonstrated to be useful for simultaneous IVUS-OCT imaging and could replace unsafe contrast agents [34]. …”

A Review of Intravascular Ultrasound-based Multimodal Intravascular Imaging

“…Moreover, similar to other optical intravascular imaging techniques, another important drawback of OCT is that it requires the temporal clearance of high-scattering luminal blood by using flushing agents such as iohexal and iodixanol, which may cause life-threatening reactions during or after the imaging procedures. 30,31 …”