Table 1. The difference between 2D PC MRI and 4D flow MRI.
| Variable | 2D PC MRI | 4D flow MRI |
|---|---|---|
| Introduced (year) | 1980s | 1990s |
| Velocity encoding | 1-directional | 3-directional |
| Analysis level | The direction oriented perpendicular to the imaging slice | Any level of a given vessel |
| Time-resolved | No | Yes |
| Scan time | Short | Long |
| Temporal resolution | Shorter | Around 40 ms |
| Spatial resolution | Lower | Isotropic high spatial resolution |
| Volume coverage | Small | Large |
| Hemodynamic parameters | Low velocity, flow direction (forward flow, reverse flow, regurgitation fraction), flow volume | In addition to the basic flow parameters,4D flow MRI also detects wall shear stress, turbulent kinetic energy, vorticity, pressure gradient, pulse wave velocity and flow component |
| Postprocessing time required | Short | Long |
MRI, magnetic resonance imaging.