Pressure Gradient Measurement in the Coronary Artery: Towards Noninvasive Quantification of Fractional Flow Reserve

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Project Summary/Abstract Fractional Flow Reserve (FFR) is an invasive procedure evaluating the functional significance of an intermediate stenosis by measurement of pressure differences across that particular stenosis. Noninvasive techniques such as CT-FFR, using computational fluid dynamic methods with computed tomography (CT) images to calculate the FFR index, have shown to reduce the number of patients requiring invasive procedures. However, the use of ionizing radiation in CT prevents longitudinal monitoring of patients who were deferred from invasive tests and treatment. To address the problem, we propose a noninvasive pressure measurement technique in the coronary arteries using magnetic resonance imaging (MRI), which has no ionizing radiation. The method is based on velocity measured from phase-contrast MRI (PC-MRI) in conjunction with navier-stokes equations to derive pressure differences, which has been studied in various vessels such as the aorta, carotid, renal and intracranial arteries. To apply the technique in the coronary arteries, challenges such as cardiac and respiratory motion and high spatial and temporal resolution for PC-MRI acquisitions need to be addressed. In this study, we aim to address the challenges by using 1) ECG and Navigator-gating to minimize motion errors and 2) 2D interleaved multi-slice radial acquisition using a golden-angle sampling scheme to achieve high spatial and temporal resolution. The hypothesis is that the proposed PC-MRI technique could further improve the navier- stokes analysis and thus, the derived pressure difference index. The measured velocity values from proposed PC-MRI and derived pressure difference index will be compared to invasive flow and pressure to evaluate the feasibility of the proposed method and its correlation to clinical gold standard. This noninvasive technique could potentially obtain both the anatomical and functional information in one imaging session without added risks, patient discomfort and high surgical costs from invasive procedures or ionizing radiation from CT-FFR.