Table 2.
Comparative Overview of Diffusion MRI Models
| Acquisition | ||||||
|---|---|---|---|---|---|---|
| Modeling approach | DWI sampling | DWI weighting | Metrics | Seminal references | ||
| ADC | S = S 0 e −bD | Few DWIs; one b=0 and 1 DWI | Low | ADC | Eccles et al., 1988 | |
| DTI | S = S 0 e −b:D | Few DWIs; one shell, minimum six directions | Low | Combinations of λ1, λ2, λ3. e.g. FA, TR, WL, WP | Basser et al., 1994 | |
| DKI |
|
Moderate number of DWIs; two shells | Low and moderate only | DTI metrics and mean kurtosis, axial and radial kurtosis and KFA | Jensen et al., 2005; Tabesh et al., 2011; Glenn et al., 2015 | |
| MAP | Asymmetric simple harmonic oscillator reconstruction and estimation | Moderate to many DWIs; multishell acquisition | Low, moderate, and high | DTI metrics and non‐Gaussianity, zero‐displacement probabilities, propagator anisotropy, ODFs | Özarslan et al., 2013; Avram et al., 2016 | |
| DSI | Model‐free | Many DWIs; Cartesian grid | Low, moderate, and high | ODFs possible to generate zero‐displacement probabilities | Tuch et al., 2003 | |
| Q‐ball | Model‐free | Moderate no. of DWIs; single‐shell HARDI acquisition | High | ODFs possible to generate zero‐displacement probabilities | Tuch, 2004 | |
| CHARMED | Intra/extra‐axonal compartments modeled by restricted/hindered sheets and cylinders | Multishell acquisition | Low, moderate, and high | Restricted and hindered component fractions; cone of uncertainty | Assaf & Basser, 2005 | |
| Axcaliber | Similar to CHARMED, but with additional modeling of axon diameter | Multishell acquisition | Low, moderate, and high flexible | CHARMED metrics and axon diameter | Assaf et al., 2008 | |
| NODDI | Watson distributed cylinders and sticks | Moderate no. of DWIs: multishell acquisition | Low, moderate, and high (flexible) | Cellular fractions, orientation dispersion index | Zhang et al., 2012; Tariq et al., 2016 | |
| WMTI | Intra/extra‐axonal compartments modeled with the Gaussian part of the DKI model | Moderate no. of DWIs; two shells (same as DKI) | Low and moderate only | Axonal water fraction, intra‐axonal diffusivity, extra‐axonal radial/axial diffusivity, extra‐axonal tortuosity | Fieremans et al., 2011 | |
| CSD tractography | Constrained spherical deconvolution | Single‐shell HARDI acquisition | High | ODFs and tractograms | Tournier et al., 2004, 2012 | |
Note: For physical and biophysical dMRI models (column 1, light and dark gray shading, respectively), a summary of the modeling approach (column 2) and acquisition strategy (columns 3 and 4) is given as well as the primary scalar metrics (column 5). Abbreviations: ADC ‐ Apparent Diffusion Coefficient; DWI ‐ diffusion weighted image; DTI ‐ Diffusion Tensor Imaging; TR ‐ Trace; WL ‐ Westin's Linear Anisotropy; WP ‐ Westin's Planar Anisotropy; DKI ‐ Diffusion Kurtosis Imaging; KFA ‐ Kurtosis FA; MAP ‐ Mean Apparent Propagator; ODF ‐ Orientation Distribution Function; DSI ‐ Diffusion Spectrum Imaging; CHARMED ‐ Composite Hindered And Restricted Model of Diffusion; NODDI ‐ Neurite Orientation Dispersion and Density Imaging; WMTI ‐ White Matter Tract Integrity; CSD ‐ Constrained Spherical Deconvolution; HARDI ‐ High Angular Resolution Diffusion Imaging.