Oral Abstract Session
SCMR 22nd Annual Scientific Sessions
Austin Robinson, MD
Fellow
University of Virginia
Yang Yang, PhD
Assistant Professor
Icahn School of Medicine at Mount Sinai
Christopher Kramer, MD
Ruth C. Heede Professor of Cardiovascular Medicine
University of Virginia Health System
Michael Salerno, MD
Associate Professor of Medicine (Cardiology), Radiology, and Biomedical Engineering
University of Virginia
Background:
A shortcoming of standard CMR myocardial perfusion imaging is limited spatial coverage of the left ventricle (3-4 slices) and limited spatial resolution (2-2.3 mm). Whole heart coverage enables quantification of ischemic burden, and high spatial resolution enables assessment of transmural perfusion gradients. We have previously described the development of spiral-based pulse sequences capable of 1.25 mm spatial resolution and whole heart coverage at 3T. The goal of the present study is to test their use with adenosine stress in subjects with coronary artery disease (CAD) and correlation with invasive coronary angiography.
Methods:
Subjects age 18 – 85 with risk factors for CAD undergoing invasive coronary angiography were recruited for rest and stress first-pass perfusion imaging. First-pass stress perfusion images were acquired on a 3T Siemens Scanner during adenosine infusion at 140 mcg/kg/min, and with 0.075 mmol/kg Dotarem bolus. The pulse sequence used was a variable density spiral trajectory dual sequence with 1.25 mm in-plane resolution. The spiral trajectory was designed as 4 interleaves with 4ms per interleave, 20% of trajectory fully sampled with ending density of 0.05x Nyquist. Other sequence parameters included: FOV 340 mm, TE 1.0 ms, TR 7 ms, SRT 90 ms, FA 26o, 6 slices with 10 mm thickness. The images were reconstructed by L1-SPIRiT using finite temporal difference as the sparsity transform. Pixelwise quantification of myocardial perfusion at stress and rest was performed by Fermi-function deconvolution using a custom MATLAB program. Endocardial to epicardial (E:E) ratios were calculated as the myocardial blood flow (MBF) in the endocardium of each segment divided by the MBF of the epicardium in the same segment.
Results:
A total of 7 subjects were enrolled, 5 of which had severe stenoses or chronic occlusions of major epicardial arteries and 2 who had non-obstructive CAD. Stress and rest myocardial perfusion images from a representative subject demonstrated stress-induced reductions in myocardial perfusion in the anterior, anteroseptal and inferoseptal segments (Figure 1). Quantification of MBF confirmed stress-induced reductions of perfusion in these territories (Figure 2). E:E ratios were 0.48, 0.29 and 0.64 in the anterior, anteroseptal, and inferoseptal segments, respectively, compared to 0.83, 0.81, and 0.77 in the inferior, inferolateral and anterolateral wall segments. Invasive angiography revealed subtotal occlusion of the left anterior descending artery (Figure 3). In patients with significant respiratory motion, there was evidence of blurring.
Conclusion:
Quantitative myocardial perfusion with whole heart coverage, at 1.25 mm spatial resolution at 3T is technically feasible with spiral pulse sequences. The technique enables detailed evaluation of endocardial-to-epicardial gradients in CAD. Further refinements of the reconstruction to compensate for respiratory motion, and evaluation in a larger cohort of patients are warranted.