Generalisation of continuous time random walk to anomalous diffusion MRI models with an age-related evaluation of human corpus callosum

•Several anomalous diffusion models including DKI are unified under the CTRW framework.•Simulation study shows anomalous diffusion indices are sensitive to white matter changes.•Anomalous diffusion indices correlate positively with aging in the human corpus callosum.•DKI is shown to be a degree two approximation of the sub-diffusion model.•Superior tissue contrast is achieved in kurtosis maps based on the sub-diffusion model.