Table 1.
The scale of DTI and the brain: neuron sizes and quantities, and water diffusion times and distances.
| Quantity | Measurement | Reference |
|---|---|---|
| axon packing density (pyramidal tract) |
Error! | [11] |
| axon packing density (corpus callosum) |
338,000/mm2 | [11] |
|
| ||
| axon diameter (pyramidal tract) | 26 μm | [11] |
| axon diameters in central nervous system |
0.2 to 20 μm | [85] |
| neuron cell body diameter | 50 μm or more | [85] |
|
| ||
| voxel size in diffusion MRI | 2.5×2.5×2.5 mm | |
| typical diffusion time in DTI | 30–100ms | [42, 34] |
| mean water diffusion distance | 1-15 μm (in 50-100 ms) |
[42] |
|
| ||
| number of neurons in human brain |
100 billion (1011) | [85] |
| synaptic connections per axon | up to 1,000 | [85] |