Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
Division of Cardiology, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA.
J Magn Reson Imaging. 2021 Jun;53(6):1699-1709. doi: 10.1002/jmri.27494. Epub 2020 Dec 31.
Fractional myocardial blood volume (fMBV) estimated using ferumoxytol-enhanced magnetic resonance imaging (MRI) (FE-MRI) has the potential to capture a hemodynamic response to myocardial hypoperfusion during contrast steady state without reliance on gadolinium chelates. Ferumoxytol has a long intravascular half-life and its use for steady-state MRI is off-label. The aim of this prospective study was to optimize and evaluate a two-compartment model for estimation of fMBV based on FE-MRI. Nine healthy swine and one swine with artificially induced single-vessel coronary stenosis underwent MRI on a 3.0 T clinical magnet. Myocardial longitudinal spin-lattice relaxation rate (R1) was measured using the 5(3)3(3)3 modified Look-Locker inversion recovery (MOLLI) sequence before and at contrast steady state following seven ferumoxytol infusions (0.125-4.0 mg/kg). fMBV and water exchange were estimated using a two-compartment model. Model-fitted fMBV was compared to simple fast-exchange fMBV approximation and percent change in pre- and postferumoxytol R1. Dose undersampling schemes were investigated to reduce acquisition duration. Variation in fMBV was assessed using one-way analysis of variance. Fast-exchange fMBV and ferumoxytol dose undersampling were evaluated using Bland-Altman analysis. Healthy normal swine showed a mean mid-ventricular fMBV of 7.2 ± 1.4% and water exchange rate of 11.3 ± 5.1 s . There was intersubject variation in fMBV (p < 0.05) without segmental variation (p = 0.387). fMBV derived from eight-dose and four-dose sampling schemes had no significant bias (mean difference = 0.07, p = 0.541, limits of agreement -1.04% [-1.45, -0.62%] to 1.18% [0.77, 1.59%]). Pixel-wise fMBV in one swine model with coronary artery stenosis showed elevated fMBV in ischemic segments (apical anterior: 11.90 ± 4.00%, apical septum: 16.10 ± 5.71%) relative to remote segments (apical inferior: 9.59 ± 3.35%, apical lateral: 9.38 ± 2.35%). A two-compartment model based on FE-MRI using the MOLLI sequence may enable estimation of fMBV in studies of ischemic heart disease. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.
使用铁氧体增强磁共振成像（FE-MRI）估计的心肌血容量分数（fMBV）有可能在不依赖钆螯合物的情况下捕获对比剂稳态期间心肌低灌注的血流动力学反应。铁氧体的血管内半衰期较长，其用于稳态 MRI 是超适应证的。本前瞻性研究的目的是优化和评估基于 FE-MRI 的双室模型，以估计 fMBV。九只健康猪和一只人工诱导的单血管冠状动脉狭窄猪在 3.0T 临床磁体上进行 MRI 检查。在七次铁氧体（0.125-4.0mg/kg）输注前后，使用 5(3)3(3)3 改良 Look-Locker 反转恢复（MOLLI）序列测量心肌纵向自旋晶格弛豫率（R1）。使用双室模型估计 fMBV 和水交换。比较模型拟合的 fMBV 与简单的快速交换 fMBV 近似值以及铁氧体前后 R1 的百分比变化。研究了剂量欠采样方案以减少采集时间。使用单向方差分析评估 fMBV 的变异性。使用 Bland-Altman 分析评估快速交换 fMBV 和铁氧体剂量欠采样。健康正常猪的中间心室 fMBV 平均值为 7.2±1.4%，水交换率为 11.3±5.1s。fMBV 存在个体间差异（p<0.05），但无节段性差异（p=0.387）。来自八剂量和四剂量采样方案的 fMBV 没有显著偏差（平均差异=0.07，p=0.541，一致性限-1.04%[-1.45，-0.62%]至 1.18%[0.77，1.59%]）。一只冠状动脉狭窄猪模型的像素级 fMBV 显示缺血节段的 fMBV 升高（心尖前壁：11.90±4.00%，心尖间隔：16.10±5.71%），而远节段的 fMBV 降低（心尖下壁：9.59±3.35%，心尖侧壁：9.38±2.35%）。基于 MOLLI 序列的 FE-MRI 双室模型可能能够在缺血性心脏病的研究中估计 fMBV。证据水平：2.技术功效阶段：2.
