Nonparametric 5D D-R2 distribution imaging with single-shot EPI at 21.1 T: Initial results for in vivo rat brain

•Multidimensional diffusion MRI was implemented at 21.1 T.•High anisotropic phantom and Sprague Dawley rats were used to investigate if the state-of-the-art multidimensional diffusion and relaxation approach can be translated to 21.1 T.•Data show diffusivity consistent with lower field studies and expected elevated R2.•Data show signs of increased susceptibility distortion from EPI readout anticipated for ultra-high field.•Study shows that it is feasible to implement combined diffusion and relaxation sequence but efforts to shorten echo time and mitigate distortions are needed.