Myocardial arterial spin labeling perfusion imaging with improved sensitivity

Abstract

BackgroundMyocardial arterial spin labeling (ASL) is a noninvasive MRI based technique that is capable of measuring myocardial blood flow (MBF) in humans. It suffers from poor sensitivity to MBF due to high physiological noise (PN). This study aims to determine if the sensitivity of myocardial ASL to MBF can be improved by reducing image acquisition time, via parallel imaging.MethodsMyocardial ASL scans were performed in 7 healthy subjects at rest using flow-sensitive alternating inversion recovery (FAIR) tagging and balanced steady state free precession (SSFP) imaging. Sensitivity encoding (SENSE) with a reduction factor of 2 was used to shorten each image acquisition from roughly 300 ms per heartbeat to roughly 150 ms per heartbeat. A paired Student’s t-test was performed to compare measurements of myocardial blood flow (MBF) and physiological noise (PN) from the reference and accelerated methods.ResultsThe measured PN (mean ± standard deviation) was 0.20 ± 0.08 ml/g/min for the reference method and 0.08 ± 0.05 ml/g/min for the accelerated method, corresponding to a 60% reduction. PN measured from the accelerated method was found to be significantly lower than that of the reference method (p = 0.0059). There was no significant difference between MBF measured from the accelerated and reference ASL methods (p = 0.7297).ConclusionsIn this study, significant PN reduction was achieved by shortening the acquisition window using parallel imaging with no significant impact on the measured MBF. This indicates an improvement in sensitivity to MBF and may also enable the imaging of subjects with higher heart rates and imaging during systole.

Assessment of segmental myocardial blood flow and myocardial perfusion reserve by adenosine‐stress myocardial arterial spin labeling perfusion imaging

“…First‐pass MRI and PET perfusion imaging may be used for comparison but were not available in this healthy volunteer cohort, but will be required in the future to validate ASL‐derived estimates of both MBF and MPR. Current implementations of myocardial ASL suffer from greater noise and lower spatial resolution than state‐of‐the‐art first‐pass MRI, but these are not fundamental limitations of the ASL approach and are currently under investigation . Another limitation of the current study is that we only used a single midventricular short‐axis slice for imaging.…”

“…Breath‐holds and cardiac triggering were used to minimize respiratory and cardiac motion, respectively. Single‐gated myocardial ASL perfusion imaging was performed using FAIR with balanced steady state free precession (bSSFP) image acquisition …”

“…MBF was calculated in the same way as previously described . All data processing was performed in MatLab (MathWorks, Natick, MA).…”

A look-locker acquisition scheme for quantitative myocardial perfusion imaging with FAIR arterial spin labeling in humans at 3 tesla

“…The ordering scheme of the sequence within this thirteen heart beat breath‐hold (SS‐GS or GS‐SS) was varied. Sequence parameters were based closely on those used successfully in MOLLI implementations and included a 35 ° excitation flip angle, image slice thickness of 8 mm, an initial TI of 115 ms (with the following values being 115 ms + RR, 115 ms + 2RR,…), TR/TE of 3 ms/1.5 ms, 320 mm field of view with 75% phase resolution and 6/8 partial Fourier, a 192 × 144 image matrix (interpolated to 384 × 288) and an acceleration factor of GRAPPA 2 . All inversion pulses and readouts occurred during the diastolic phase of the cardiac cycle.…”

Review of Journal of Cardiovascular Magnetic Resonance 2015

“…Recent advances reported in the journal have included improved flow mapping, [1–3] real-time imaging, [4] T1 mapping, [5–7] simulations, [8, 9] perfusion, [10–12] coronary imaging, [13] diffusion tensor imaging, [14–16] feature tracking, [17–20] and strain assessment. [21, 22] The full breadth of new developments is described in the papers in the section.…”