Analysis of a Nuclear Magnetic Resonance Blood Flowmeter for Pulsatile Flow

Nuclear magnetic resonance (NMR) techniques have been applied to the measurement of steady or quasi-steady flow by using, principally, the tag-detect method. This paper describes a two-magnet NMR flowmeter that can be used to measure pulsatile flow. The pulsatile nature of the flow causes a pulsed magnetization of the fluid, which is detected by a flow-sensitive NMR detector. A parabolic velocity profile has been assumed. The results of theoretical computations closely approximate in vitro data from a 1.6-mm ID rigid tube with respect to the shape of the NMR signal and to the proportionality of the NMR signal amplitude to flow rate. Selected in vivo results are also presented.