Motion-compensated spin-echo cardiac diffusion tensor imaging in multiple cardiac phases using an ultrahigh gradient...

Area of Science:

• Cardiovascular Imaging
• Diffusion Tensor Imaging
• Magnetic Resonance Imaging Physics

Background:

• Traditional cardiac diffusion tensor imaging (cDTI) relies on inefficient stimulated echo techniques for assessing cardiac microstructure.
• Ultrahigh gradient strength systems enable shorter motion-compensated diffusion encoding, potentially improving cDTI efficiency and robustness.
• This study investigates the comparative performance of high and ultrahigh gradient strengths in motion-compensated spin echo (MCSE) cDTI during systole and diastole.

Purpose of the Study:

• To compare the efficacy of high (G_H) versus ultrahigh (G_UH) gradient strengths in acquiring systolic and diastolic motion-compensated spin echo cardiac diffusion tensor imaging (MCSE cDTI).
• To evaluate image quality, specifically signal-to-noise ratio (SNR), and microstructural parameter accuracy between the two gradient strengths.
• To assess the ability of MCSE cDTI with different gradient strengths to detect dynamic changes in cardiac microstructure throughout the cardiac cycle.

Main Methods:

• Second-order MCSE sequences were developed and applied on a Siemens 3T Connectom scanner (300mT/m maximum gradient amplitude).
• Breath-hold cDTI data were acquired at peak systole and end diastole using maximum achievable ultrahigh gradient strength (G_UH, 116mT/m) and limited high gradient strength (G_H, 66mT/m).
• Imaging parameters included specific echo times (TE), voxel resolution (2.8×2.8x8mm³), b-values (b=500s/mm², b=150s/mm²), and 6 encoding directions.

Main Results:

• Both G_UH and G_H achieved high success rates for systolic acquisitions, with G_UH showing slightly better performance in diastolic acquisitions.
• Ultrahigh gradient strength (G_UH) resulted in significantly higher SNR compared to high gradient strength (G_H) in both diastolic and systolic phases.
• Differences in fractional anisotropy, transmural helix angle gradient (HAG), and sheetlet angle (|E2A|) were observed between systole and diastole, with some phase-specific differences being more apparent with G_UH or G_H.

Conclusions:

• Ultrahigh gradient strength systems provide superior SNR and more robust diastolic imaging for MCSE cDTI.
• While diastolic imaging reliability needs further improvement, G_UH enables the identification of dynamic cardiac microstructural changes.
• These findings support the broader clinical research application of multiphase MCSE cDTI with ultrahigh gradient strengths.