Table 2.
Summary of different multi-compartment models.
| Parameter of interest | Recommended methods | Assumptions | Acquisition | Reference |
|---|---|---|---|---|
| Axon diameter | CHARMED | Single diameter, no exchange between intra- and extracellular compartments, axons are assumed as straight cylinders | PGSE with variable diffusion time | (Assaf and Basser, 2005, Assaf et al., 2004) |
| AxCaliber | Gamma distribution for axon diameters | PGSE | (Assaf et al., 2008, Barazany et al., 2009) | |
| ActiveAx | Single diameter | PGSE | (Alexander et al., 2010) | |
| MMWMD | Single diameter | PGSE | (Dyrby et al., 2013) | |
| ActiveAx-D | Axon diameter index, dictionary-based fitting | PGSE | (Sepehrband et al., 2016b) | |
| Axon diameter mapping | Watson ODF, single diameter | PGSE | (Zhang et al., 2011) | |
| Diffusivity and signal fraction | Ball + Stick | Same intra and extracellular diffusivity | PGSE, clinical | (Behrens et al., 2003) |
| Stick + Tensor | Different intra- and extracellular diffusivity | PGSE | (Kroenke et al., 2004, Jespersen et al., 2007, Fieremans et al., 2011, Hui et al., 2015) | |
| NODDI | Watson ODF, fixing intracellular diffusivities, tortuosity constraint | PGSE, clinical | (Zhang et al., 2012) | |
| NODDIDA | Watson ODF, variable diffusivities, no tortuosity constraint | PGSE | (Jelescu et al., 2016) | |
| TEDDI | Variable TE | PGSE | (Veraart et al., 2018) | |
| Standard Model | Variable diffusivities, no tortuosity constraint | PGSE | (Novikov et al., 2018) | |
| LEMONADE | Rotation invariant mapping | PGSE | (Novikov et al., 2016) | |
| LEMONADE(t) | Time dependency is considered | PGSE | (Lee et al., 2018a) | |
| B-tensor encoding | (Fieremans et al., 2018, Reisert et al., 2018, Coelho et al., 2019, Lampinen et al., 2017, Lampinen et al., 2018, Lampinen et al., 2020) | |||
| Sphere size, diffusivity and signal fraction | Ball + Stick + sphere | No exchange | PGSE | (Palombo et al., 2020) |
Acronyms: CHARMED – composite hindered and restricted model of diffusion, PGSE – pulsed gradient spin echo, MMWMD – minimal model of white matter diffusion, ODF – orientation distribution function, NODDI – neurite orientation dispersion and density imaging, NODDIDA – NODDI with diffusivity assessment, TEDDI – TE dependent diffusion imaging, TE – echo time, LEMONADE – linearly estimated moments provide orientations of neurites and their diffusivities exactly.