Time-efficient simultaneous fat and water cardiac cine imaging using spiral MRI.

Background: Cardiac cine imaging is routinely used in patient with suspected or known cardiac dysfunction. Water and fat (W/F) separated cardiovascular magnetic resonance (CMR) will be helpful to distinguish adipose tissue, blood and myocardium. Inclusion of a multi-echo acquisition in the conventional balanced steady-state free precession (bSSFP) cine sequence can introduce artifacts and reduce temporal resolution. Spiral MRI is known for its signal-to-noise ratio (SNR) efficiency and has the potential to improve temporal efficiency for W/F separated cine imaging. The present work implements a spoiled gradient echo sequence (SPGR) with spiral trajectory to obtain W/F separated cine images simultaneously.

Methods: Three different sequences were performed for comparison, a Cartesian 2-TE bSSFP sequence, a Cartesian 3-TE bSSFP sequence, and the proposed spiral SPGR sequence. Five volunteers were recruited for the scans on a 1.5T scanner with spatial resolution 1.7×1.7×8.0mm over a 400×400mm FOV. In addition to qualitative comparisons, a quantitative measurement is performed in terms of the contrast to noise ratio (CNR).

Results: The proposed method to obtain W/F separated cine images provides better temporal efficiency and fewer artifacts compared to conventional Cartesian bSSFP sequences. The 2-TE bSSFP features the highest artifact level including susceptibility artifacts and fat/water swaps. The proposed method reduces scan time by approximately 50% with similar spatial and temporal resolution with lower specific absorption rate (SAR). The contrast between the blood pool and myocardium is higher when using the spiral readout (p≤0.05). The results suggest that the presented sequence has potential to facilitate simultaneous imaging for water and fat components in a cine scan while shortening exam time and lowering SAR.