Researchers have developed a brand new catheter-based device that mixes two powerful optical techniques to image the damaging plaques that may construct up contained in the arteries that provide blood to the guts. By providing recent details about plaque, the device could help clinicians and researchers improve treatments for stopping heart attacks and strokes.
Atherosclerosis occurs when fats, cholesterol and other substances accumulate on the artery partitions, which might cause these vessels to grow to be thick and stiff. A heart attack or stroke may occur if an atherosclerotic plaque contained in the blood vessels ruptures or parts of it break off.
“Atherosclerosis, resulting in heart attacks and strokes, is the primary reason behind death in Western societies — exceeding all combined cancer types — and, subsequently, a significant public health issue,” said research team member leader Laura Marcu from University of California, Davis. “Higher clinical management made possible by advanced intravascular imaging tools will profit patients by providing more accurate information to assist cardiologists tailor treatment or by supporting the event of latest therapies.”
Within the Optica Publishing Group journal Biomedical Optics Express, researchers describe their recent flexible device, which mixes fluorescence lifetime imaging (FLIM) and polarization-sensitive optical coherence tomography (PSOCT) to capture wealthy information in regards to the composition, morphology and microstructure of atherosclerotic plaques. The work was a collaborative project with Brett Bouma and Martin Villiger, experts in OCT from the Wellman Center for Photomedicine at Massachusetts General Hospital.
“With further testing and development, our device may very well be used for longitudinal studies where intravascular imaging is obtained from the identical patients at different timepoints, providing an image of plaque evolution or response to therapeutic interventions,” said Julien Bec, first creator of the paper. “This can be very helpful to raised understand disease evolution, evaluate the efficacy of latest drugs and coverings and guide stenting procedures used to revive normal blood flow.”
Gaining an unprecedented view
Most of what scientists find out about how atherosclerosis forms and develops over time comes from histopathology studies of postmortem coronary specimens. Although the event of imaging systems comparable to intravascular ultrasound and intravascular OCT has made it possible to check plaques in living patients, there remains to be a necessity for improved methods and tools to analyze and characterize atherosclerosis.
To handle this need, the researchers launched into a multi-year research project to develop and validate multispectral FLIM as an intravascular imaging modality. FLIM can provide insights into features comparable to the composition of the extracellular matrix (the protein scaffolding between cells), the presence of inflammation and the degree of calcification inside an artery. In earlier work, they combined FLIM with intravascular ultrasound, and on this recent work they combined it with PSOCT. PSOCT provides high-resolution morphological information together with birefringence and depolarization measurements. When used together, FLIM and PSOCT provide an unprecedented amount of knowledge on plaque morphology, microstructure and biochemical composition.
“Birefringence provides information in regards to the plaque collagen, a key structural protein that helps with lesion stabilization, and depolarization is said to lipid content that contributes to plaque destabilization,” said Bec. “Holistically, this hybrid approach can provide probably the most detailed picture of plaque characteristics of all intravascular imaging modalities reported to this point.”
Getting two imaging modalities into one device
The event of multimodal intravascular imaging systems compatible with coronary catheterization is technologically difficult. It requires very thin — lower than 1 mm — flexible catheters that may operate in vessels with sharp twists and turns. A high imaging speed of around 100 frames/second can be crucial to limit cardiac motion artifacts and ensure proper imaging inside an artery.
To integrate FLIM and PSOCT right into a single device without compromising the performance of either imaging modality, the researchers used optical components previously developed by Marcu’s lab and other research groups. Key to achieving high PSOCT performance was a newly designed rotary collimator with high light throughput and a high return loss — the ratio of power reflected back toward the sunshine source in comparison with the ability incident on the device. The catheter system they developed has similar dimensions and suppleness because the intravascular imaging devices which might be currently in clinical use.
After testing the brand new system with artificial tissue to exhibit basic functionality on well characterised samples, the researchers also showed that it may very well be used to measure properties of a healthy coronary artery faraway from a pig. Finally, in vivo testing in swine hearts demonstrated that the hybrid catheter system’s performance was sufficient to support work toward clinical validation. These tests all showed that the FLIM-PSOCT catheter system could concurrently acquire co-registered FLIM data over 4 distinct spectral bands and PSOCT backscattered intensity, birefringence and depolarization information.
Next, the researchers plan to make use of the intravascular imaging system to image plaques in ex vivo human coronary arteries. By comparing the optical signals acquired using the system with plaque characteristics identified by expert pathologists, they will higher understand which features may be identified by FLIM-PSOCT and use this to develop prediction models. In addition they plan to maneuver forward with testing in support of clinical validation of the system in patients.
