Diffusion tensor cardiovascular magnetic resonance with a spiral trajectory: An in vivo comparison of echo planar and spiral stimulated echo sequences.

PURPOSE: Diffusion tensor cardiovascular MR (DT-CMR) using stimulated echo acquisition mode (STEAM) with echo-planar-imaging (EPI) readouts is a low signal-to-noise-ratio (SNR) technique and therefore typically has a low spatial resolution. Spiral trajectories are more efficient than EPI, and could increase the SNR. The purpose of this study was to compare the performance of a novel STEAM spiral DT-CMR sequence with an equivalent established EPI technique.

METHODS: A STEAM DT-CMR sequence was implemented with a spiral readout and a reduced field of view. An in vivo comparison of DT-CMR parameters and data quality between EPI and spiral was performed in 11 healthy volunteers imaged in peak systole and diastasis at 3 T. The SNR was compared in a phantom and in vivo.

RESULTS: There was a greater than 49% increase in the SNR in vivo and in the phantom measurements (in vivo septum, systole: SNREPI  = 8.0 ± 2.2, SNRspiral  = 12.0 ± 2.7; diastasis: SNREPI  = 8.1 ± 1.6, SNRspiral  = 12.0 ± 3.7). There were no significant differences in helix angle gradient (HAG) (systole: HAGEPI  = -0.79 ± 0.07 °/%; HAGspiral  = -0.74 ± 0.16 °/%; P = 0.11; diastasis: HAGEPI  = -0.63 ± 0.05 °/%; HAGspiral  = -0.56 ± 0.14 °/%; P = 0.20), mean diffusivity (MD) in systole (MDEPI  = 0.99 ± 0.06 × 10-3 mm2 /s, MDspiral  = 1.00 ± 0.09 × 10-3 mm2 /s, P = 0.23) and secondary eigenvector angulation (E2A) (systole: E2AEPI  = 61 ± 10 °; E2Aspiral  = 63 ± 10 °; P = 0.77; diastasis: E2AEPI  = 18 ± 11 °; E2Aspiral  = 15 ± 8 °; P = 0.20) between the sequences. There was a small difference (≈ 20%) in fractional anisotropy (FA) (systole: FAEPI  = 0.49 ± 0.03, FAspiral  = 0.41 ± 0.04; P < 0.01; diastasis: FAEPI  = 0.66 ± 0.05, FAspiral  = 0.55 ± 0.03; P < 0.01) and mean diffusivity in diastasis (10%; MDEPI  = 1.00 ± 0.12 × 10-3 mm2 /s, MDspiral  = 1.10 ± 0.09 × 10-3 mm2 /s, P = 0.02).

CONCLUSION: This is the first study to demonstrate DT-CMR STEAM using a spiral trajectory. The SNR was increased by using a spiral rather than the more established EPI readout, and the DT-CMR parameters were largely similar between the two sequences. Magn Reson Med 80:648-654, 2018. © 2017 International Society for Magnetic Resonance in Medicine.