Whole-heart Coverage Quantitative First-pass Spiral Perfusion in Cardiac Magnetic Resonance Imaging

First-pass adenosine stress cardiac magnetic resonance (CMR) perfusion imaging is a promising modality for evaluating coronary artery disease (CAD) and is capable of providing comprehensive assessment of ischemia, function, and scarring. Measuring the extent of ischemic myocardium accurately has important implications in determining patients that may benefit from revascularization. The absolute quantification of perfusion reserve (PR) by CMR with whole heart coverage may more accurately reflect the extent of ischemia as compared to the relative assessment provided by SPECT. However, current CMR perfusion techniques are limited by spatial coverage and dark-rim artifacts (DRA) which may be mistaken for true perfusion abnormalities resulting in false positive studies.

Spiral imaging trajectories are robust to motion, have high signal-to-noise ratios and are superior data acquisition efficiency compared to standard Cartesian trajectories. These advantages could help to reduce DRA artifacts which are known to be exacerbated by low spatio-temporal resolution. Recent studies have demonstrated excellent image quality and high diagnostic accuracy of first-pass adenosine stress perfusion imaging using an optimized spiral pulse sequence. However, this sequence was only capable of imaging 3 short-axis slices at heart rates up to 110 BPM without absolute quantification. Considering that greater than 10 million stress tests are performed in the US alone, improvements in the accuracy of non-invasive assessments of CAD could significantly reduce health care costs resulting from incorrect diagnoses. Therefore, we hypothesize that whole-heart absolute quantification of perfusion using spiral trajectories can provide high quality images to detect small perfusion abnormalities and accurately assess the extent of ischemia. This hypothesis will be tested by the following specific aims:

Specific Aim #1 is to develop a 2D multi-slice spiral perfusion pulse sequence with whole heart coverage. (a) Design a spiral pulse sequence to achieve whole heart coverage. (b) Characterize the performance of different spiral trajectories and k-t sampling patterns for parallel imaging and compressed sensing reconstruction. (c) Perform retrospective reconstructions to validate the spiral trajectories and k-t sampling patterns. (d) Apply the sequence in clinical subjects.

Specific Aim #2 is to develop a reduced field-of-view (FOV) whole-heart coverage single-shot excitation spiral perfusion pulse sequence with outer volume suppression (OVS). (a) Design a 2D OVS pulse and validate its performance in phantom experiments. (b) Incorporate 2D OVS into the single-shot excitation spiral pulse sequence. (c) Compare the rFOV single-shot excitation perfusion sequence with normal FOV single-shot perfusion sequence in clinical patients.

Specific Aim #3 is to develop a quantitative spiral perfusion sequence with validation in phantoms and clinical patients. (a) Design a quantitative dual-contrast spiral perfusion sequence to quantify myocardial blood flow. (b) Validate the sequence in gadolinium phantoms and healthy volunteers. (c) Quantify absolute myocardial perfusion in patients with suspected CAD at both rest and stress.