CAD: New Methods

1355491 - Quantification of Fractional Myocardial Blood Volume Throughout the Cardiac Cycle using Ferumoxytol-Enhanced Magnetic Resonance Multitasking

Wednesday, January 25, 2023

5:00 PM – 6:30 PM

Location: Silver Pearl 1

Presenting Author(s)

XL

Xinyi Li, BS

Graduate Student Researcher
University of California, Los Angeles
Los Angeles, California, United States

Primary Author(s)

XL

Xinyi Li, BS

Graduate Student Researcher
University of California, Los Angeles
Los Angeles, California, United States

Co-Author(s)

AP

Arutyun Pogosyan

Staff Research Associate
University of California, Los Angeles, United States
ZM

Zhengyang Ming

Graduate Student Researcher
University of California, Los Angeles, United States
HL

Hsu-Lei Lee, PhD

Postdoctoral scientist
Cedars-Sinai Medical Center, United States
John P. Finn, MD

Professor
University of California, Los Angeles
Los Angeles, California, United States
Anthony G. Christodoulou, PhD

Assistant Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Kim-Lien Nguyen, MD

Associate Professor
University of California, Los Angeles
Los Angeles, California, United States

Disclosure(s):

John P. Finn, MD: No relevant disclosure to display

Background: Fractional myocardial blood volume (fMBV) estimated from ferumoxytol-enhanced magnetic resonance imaging (FE-MRI) offers unique insight into myocardial tissue perfusion at rest without reliance on pharmacologic stress agents¹. This understanding of the hemodynamic response to myocardial hypoperfusion would be further enriched through additional knowledge on how fMBV varies throughout the cardiac cycle, a marker not previously addressed. The free-breathing, non-ECG, Multitasking T1 mapping technique can track cyclic changes due to its multidimensional capability². In this study, we aim to capitalize on Multitasking framework’s ability to continuously acquire T1 relaxometry data in order to demonstrate the feasibility of characterizing the cyclic changes in fMBV for healthy subjects and for patients with ischemic heart disease.

Methods:

We recruited volunteers and patients with ischemic heart disease to be scanned on a clinical 3.0T MRI scanner (Skyra®, Siemens Medical Solutions USA, Malvern, PA). Ferumoxytol was infused to a total dose of 4.0 mg/kg, building in increments of 0.0, 0.125, 2.0, and 4.0 mg/kg. One-minute, Multitasking and reference mid-ventricular short-axis T1 maps with the 5(3)3(3)3 Modified Look-Locker Inversion (MOLLI) recovery sequence were acquired at each dose. Multitasking T1 maps at mid-systole, end-systole, mid-diastole, and end-diastole were reconstructed². To generate pixel-wise fMBV maps, an in-house two-compartment water exchange model was applied to the registered multi-dose T1 maps¹. These pixel-wise fMBV maps were then segmented according to the American Heart Association 17-segment model.

Results:

Healthy female (n=3, age 29) volunteers and patients with ischemic heart disease (n=2, age 73) underwent FE-MRI without any adverse effects. MOLLI-fMBV maps had a global median fMBV value of 12.0% (IQR 4.8) and Multitasking-fMBV maps had a global median at end-diastole of 15.6% (IQR 5.5). Bland-Altman analysis of the MOLLI-fMBV relative to the Multitasking-fMBV showed no significant bias (p=.1308, Figure 1). Figure 2 summarizes the cyclic change in fMBV distribution in the mid-ventricular slice of healthy volunteers across the coronary vessel territories (left anterior descending artery [LAD], right coronary artery [RCA], left circumflex artery [LCX]). There is a significant (p< .05) reduction in fMBV from end-diastole to end-systole as the overall fractional intravascular distribution space decreases. This physiology is reflected in patients with ischemic heart disease where the largest change in fMBV is between end-diastole and end-systole, with blunted variation in regions that exhibited myocardial perfusion defects.

Conclusion:

We have found expected cardiac-phase-specific changes in fMBV both in volunteers and patients with ischemic heart disease, using ferumoxytol-enhanced Multitasking. Additional investigations in larger cohorts are needed to clarify precision and differences in this novel parameter across the spectrum of health and disease.