In Vivo Quantitative Imaging of Coronary Blood Flow by Intracoronary Doppler OCT

Objective: This work aims to develop a novel approach for in vivo quantitative imaging of coronary blood flow using intracoronary Doppler OCT. Methods: A 200 kHz swept-source OCT system with an endoscopic catheter probe was used to acquire both structural and Doppler OCT images. In the Doppler measurement, raw OCT phase signal was processed with timing variation and motion compensation to reduce the phase noise. Furthermore, the Doppler measurement angle was inferred by pullback image data and used to correct the measurement error due to oblique imaging caused by non-coaxial alignment of the imaging catheter. To validate our system, the flow rate measurement was performed using an ex vivo phantom and in vivo experiments were conducted in living swine coronary arteries. Results: After oblique imaging compensation, the measurement error was reduced from 3.0±11.4% to 0.7±8.1%. A minor systematic difference of 4.2±8.7% was found between preset (0 – 240 ml/min) and calculated flow rate for all the measurements. The feasibility of imaging coronary flow in vivo was successfully demonstrated in a living swine. Conclusion: The experimental results show that Doppler OCT can be an accurate approach for quantitative assessment of the intracoronary flow in vivo. Significance: To our knowledge, this is the first in vivo catheter-based Doppler OCT coronary blood flow measurement.

I. Introduction

Atherosclerotic cardio–vascular disease (CVD) remains a leading cause of vascular diseases in recent years worldwide [1]. Atherosclerosis results in the narrowing of the blood vessel and may further cause adverse cardiac events. Various imaging methods have been applied to reveal morphological features of the diseased vessels, such as the plaque type, lumen area, and fiber cap thickness, to assist in the determination of treatment plans [2]. However, in many cases, anatomic characteristics may not fully quantify the overall severity of lesion. Instead, physiological function may be critical in the diagnosis of culprit lesions that were associated with clinical outcome. The blood flow is an important function parameter indicating whether the blood supply capacity of the diseased vessel is decreased [3]. Equally in patients with coronary microvascular diseases, the resistance of microcirculation can be evaluated by measuring the flow rate and thus aiding to achieve a certain diagnosis of coronary vascular function [4]. However, traditional imaging modalities are not satisfactory for such applications. For example, angiography has limited resolution and intravascular imaging methods such as intravascular ultrasound is inaccessible for small blood vessels that require ultrathin imaging catheters [5].