Table 1.
Flow-related parameters
| Flow parameters | Short definition | Unit |
|---|---|---|
| Flow rate | The amount of blood passing through a plane per time unit (also known as through-plane volume per second) | mL/s |
| Flow volume | Volume of blood passing through a plane within a certain amount of time. Derived from the area under the curve of the flow rate graph (flow [ml/s] versus time [s]) | mL |
| Flow velocity vector | Magnitude and direction of blood flow through a plane (also known as through-plane propagation speed of blood) | m/s or cm/s |
| Flow jet angle | The angle between the direction of blood flow and the centerline of the vessel | ° (degrees) |
| Flow displacement | The degree of eccentric flow, defined as the distance between the center of the vessel and the center of velocity (often normalized to lumen diameter) | mm (or relative to lumen diameter) |
| Vorticity | Local in-plane rotation of a fluid particle around a common axis (comparable to the angular velocity of solid objects) | 1/s |
| Helicity | Alignment of vorticity with the main velocity vector | m/s2 |
| Wall shear stress | The tangential force caused by friction of blood as it flows along the vessel wall | Pascal or dyne/cm2 |
| Kinetic energy | The energy that is stored in movement of blood | Joules |
| Viscous energy loss | The energy that is lost due to frictional forces | Joules |
| Turbulent kinetic energy | The energy that is stored in turbulent flow of blood | Joules |
| Pulse wave velocity | The propagation speed of a pulse wave created by the systolic contraction of the left ventricle (a measure of arterial stiffness) | m/s |
| Pressure fields | Differences in distribution of local pressure within a vessel (gradients between local pressure fields are used to assess hemodynamic significance of obstructions) | mmHg or Pascal |