A comparison of multi-ADC and DTI fit metrics of diffusion MRI data acquired with Stejskal-Tanner and asymmetric bipolar gradients at identical echo time.

Asymmetric-Bipolar (AS) gradients have been proposed in diffusion MRI (dMRI) experiments as alternative to Stejskal-Tanner (ST) gradients to achieve flow and motion-compensation. However, it remains unclear whether the gradient shape affects commonly derived metrics. Data at multiple diffusion-weightings was acquired on 4 subjects with ST and flow-compensated gradients, then fit with a multi-ADC model and DTI. Results showed that some metrics, as free water signal fraction and fractional anisotropy were comparable between AS and ST, whereas diffusion coefficients and perfusion fraction were remarkably different. Great care is suggested when comparing studies using different waveforms despite other identical acquisition parameters.