Abstract
Purpose Diffusion tensor imaging (DTI) is commonly used in cardiac diffusion magnetic resonance imaging (dMRI). However, the tissue’s microstructure (cells, membranes, etc.) restricts the movement of the water molecules, making the spin displacements deviate from Gaussian behaviour. This effect may be observed with diffusion kurtosis imaging (DKI) using sufficiently high b-values (b > 450 s/mm2), which are presently outside the realm of routine cardiac dMRI due to the limited gradient strength of clinical scanners. The Connectom scanner with Gmax = 300 mT/m enables high b-values at echo times (TE) similar to DTI on standard clinical scanners, therefore facilitating cardiac DKI in humans.
Methods Cardiac-gated, second-order motion-compensated dMRI was performed with bmax = 1350 s/mm2 in 10 healthy volunteers on a 3T MRI scanner with Gmax = 300 mT/m. The signal was fitted to a cumulant expansion up to and including the kurtosis term and diffusion metrics such as fractional anisotropy (FA), mean diffusivity (MD), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) were calculated.
Results We demonstrate deviation of the signal from monoexponential decay for b-values > 450 s/mm2 (MK = 0.32 ± 0.03). Radial kurtosis (RK = 0.35 ± 0.04) was observed slightly larger than axial kurtosis (AK = 0.27 ± 0.02), and the difference is statistically significant (RK − AK = 0.08 ± 0.04, p = 2e − 4).
Conclusion This work demonstrates the feasibility of quantifying kurtosis effect in the human heart in vivo (at an echo time shorter than typical TEs reported for cardiac DTI), using high-performance gradient systems (which are 4-8 times stronger than on standard clinical scanners). Our work lays the foundation for exploring new biomarkers in cardiac dMRI beyond DTI.
Competing Interest Statement
FF was employed by the company Siemens Healthcare Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Footnotes
Funding Information This work was supported by Wellcome Trust Investigator Award; grant 219536/Z/19/Z and 096646/Z/11/Z, EPSRC; grant EP/M029778/1, Wellcome Trust Strategic Award; grant 104943/Z/14/Z, British Heart Foundation; grant PG/19/1/34076, Swedish Cancer Society; grant 22 0592 JIA