Optimal diffusion weighting for in vivo cardiac diffusion tensor imaging

PurposeTo investigate the influence of the diffusion weighting on in vivo cardiac diffusion tensor imaging (cDTI) and obtain optimal parameters. MethodsTen subjects were scanned using stimulated echo acquisition mode echo planar imaging with six b-values, from 50 to 950 smm(-2), plus b=15 smm(-2) reference. The relationship between b-value and both signal loss and signal-to-noise ratio measures was investigated. Mean diffusivity, fractional anisotropy, and helical angle maps were calculated using all possible b-value pairs to investigate the effects of diffusion weighting on the main and reference data. ResultsSignal decay at low b-values was dominated by processes with high apparent diffusion coefficients, most likely microvascular perfusion. This effect could be avoided by diffusion weighting of the reference images. Parameter maps were improved with increased b-value until the diffusion-weighted signal approached the noise floor. For the protocol used in this study, b=750 smm(-2) combined with 150 smm(-2) diffusion weighting of the reference images proved optimal. ConclusionMean diffusivity, fractional anisotropy, and helical angle from cDTI are influenced by the b-value of the main and reference data. Using optimal values improves parameter maps and avoids microvascular perfusion effects. This optimized protocol should provide greater sensitivity to pathological changes in parameter maps. Magn Reson Med 74:420-430, 2015. (c) 2014 Wiley Periodicals, Inc.