Table 2.

Comparative overview of diffusion MRI models. For physical and biophysical dMRI models (column 1, light and dark grey shading respectively) a summary of the modeling approach (column 2) and acquisition strategy (columns 3 and 4) are given as well as the primary scalar metrics (column 5).

	Modeling approach	Acquisition		Metrics	Seminal References
		DWI sampling	DWI weighting
ADC	S = S0e−bD	Few DWIs; 1 b=0 and 1 DWI	low	ADC	81
DTI	S = S0e−b:D	Few DWIs; 1 shell, minimum 6 directions,	low	combinations of I1, I2, I3. E.G. FA, TR, WL, WP, etc.	76
DKI	$S=S_0{e}^{-bD+\frac{1}{6}{b}^2{D}^{2}K}$	Moderate # of DWIs; 2 shells	low and moderate only	DTI metrics and mean kurtosis, axial and radial kurtosis and KFA	77, 78, 86
MAP	Asymmetric Simple Harmonic Oscillator Reconstruction and Estimation	Moderate to many DWIs: Multi shell acquisition	low, moderate and high	DTI metrics and non-Gaussianity, zero-displacement probabilities, propagator anisotropy, ODFs	90, 91
DSI	Model-free	Many DWIs; cartesiangrid	low, moderate and high	ODFs possible to generate zero displacement probabilities	84
Q-ball	Model-free	Moderate # of DWIs: Single shell HARDI acquisition	high	ODFs possible to generate zero displacement probabilities	85
CHARMED	Intra/extra-axonal compartments modeled by restricted/hindered sheets and cylinders	Multi shell acquisition	low, moderate and high	restricted and hindered component fractions; cone of uncertainty	96
Axcaliber	similar to CHARMED, but with additional modeling of axon diameter	Multi shell acquisition	low, moderate and high	CHARMED metrics and axon diameter	97
NODDI	Watson Distributed cylinders and sticks	Moderate # of DWIs: Multi shell acquisition	low, moderate and high (flexible)	Cellular fractions, orientation dispersion index	103, 104
WMTI	intra/extra-axonal compartments modeled with the Gaussian part of the DKI model	Moderate # of DWIs; 2 shells (same as DKI)	low and moderate only	axonal water fraction, intra-axonal diffusivity, extra-axonal radial/axial diffusivity, extra-axonal tortuosity	102
CSD Tractography	Constrained Spherical Deconvolution	Single shell HARDI acquisition	high	ODFs and tractograms	94, 95