Robust intravascular optical coherence elastography driven by acoustic radiation pressure

Abstract

High strain spots in the vessel wall indicate the presence of vulnerable plaques. The majority of acute cardiovascular events are preceded by rupture of such a plaque in a coronary artery. Intracoronary optical coherence tomography (OCT) can be extended, in principle, to an elastography technique, mapping the strain in the vascular wall. However, the susceptibility of OCT to frame-to-frame decorrelation, caused by tissue and catheter motion, inhibits reliable tissue displacement tracking and has to date obstructed the development of OCT-based intravascular elastography. We introduce a new technique for intravascular optical coherence elastography, which is robust against motion artifacts. Using acoustic radiation force, we apply a pressure to deform the tissue synchronously with the line scan rate of the OCT instrument. Radial tissue displacement can be tracked based on the correlation between adjacent lines, instead of subsequent frames in conventional elastography. The viability of the method is demonstrated with a simulation study. The root mean square (rms) error of the displacement estimate is 0.55 µm, and the rms error of the strain is 0.6%. It is shown that high-strain spots in the vessel wall, such as observed at the sites of vulnerable atherosclerotic lesions, can be detected with the technique. Experiments to realize this new elastographic method are presented. Simultaneous optical and ultrasonic pulse-echo tracking demonstrate that the material can be put in a high-frequency oscillatory motion with an amplitude of several micrometers, more than sufficient for accurate tracking with OCT. The resulting data are used to optimize the acoustic pushing sequence and geometry.

Optical coherence elastography for tissue characterization: a review

“…Some of the early developments of OCE techniques are focused on the application in artery [49, 51, 144-146]. Such work mainly concerns on the computational approaches for the tissue velocity and strain estimation based on the OCT structural images.…”

“…Among these, a multi-resolution vibrational framework is proposed for robust estimation of the velocity and strain field from the arterial wall, which is demonstrated with both numerical simulation and experiment on ex vivo normal human aorta segment [49]. In the further development of intravascular OCE, the loading of the tissue deformation is synchronized with the A-line scanning of OCT and the displacement quantification is performed between the adjacent A-lines, which avoids the mechanical imaging artifacts caused by the OCT frame-to-frame decorrelation [146]. Numerical simulations demonstrate the feasibility of this method in detecting the high-strain spot from vulnerable atherosclerotic lesions [146].…”

“…In the further development of intravascular OCE, the loading of the tissue deformation is synchronized with the A-line scanning of OCT and the displacement quantification is performed between the adjacent A-lines, which avoids the mechanical imaging artifacts caused by the OCT frame-to-frame decorrelation [146]. Numerical simulations demonstrate the feasibility of this method in detecting the high-strain spot from vulnerable atherosclerotic lesions [146]. These studies lay the foundation for the future strain analysis of the in vivo intravascular OCT images of the coronary arteries, which is highly desired for the advancement of intravascular OCE technique.…”

Optical coherence elastography: current status and future applications

“…To measure the radial displacement of vascular tissue, van Soest et al 74,75 developed a catheter-based OCT alternatingline elastography (OCTALE) technique. It employs the correlation between the overlapping point-spread functions of adjacent A-scans, instead of subsequent B-mode imaging.…”

Tissue-mimicking bladder wall phantoms for evaluating acoustic radiation force-optical coherence elastography systems

“…Only one report in published literature demonstrated ARF-OCE in strain mapping of the vascular wall for plaques. 15 The development of any novel imaging system requires the use of some tissue-mimicking model or phantoms for initial testing and system optimization. The major advantages of using quality control phantoms for establishing novel imaging methods include reproducibility and uniformity in evaluation of system performance.…”