Encoding strategies for three‐direction phase‐contrast MR imaging of flow

Three encoding strategies for the measurement of flow velocities in arbitrary directions with phase‐contrast magnetic resonance imaging are presented; their noise and dynamic range performance are compared by means of theoretical analysis and computer simulation. A six‐point measurement strategy is shown to be quite inefficient in terms of velocity variance per unit time. A simple four‐point method exhibits equal dynamic range; its noise depends on flow direction but on average is equal to that of the six‐point method. An alternate, balanced four‐point method has noise that is direction independent and has, depending on implementation, possibly lower noise levels. Either four‐point method is more efficient and is preferred over the six‐point approach.