Detection of motion using B1 gradients.
An NMR method which makes use of a radiofrequency (RF) field gradient to detect diffusion, perfusion, or flow is demonstrated. The technique is analogous to the detection of motion using pulsed B0 gradients. The simplest form of the experiment is as follows: A spatially imhomogeneous RF field generated by a surface coil produces dispersal of magnetization in the Y Z plane. After a delay, the RF field is applied within reversed phase to restore polarization along +Z, which is then sampled using an observe pulse or pulse sequence. If molecular motion occurs during the delay period the amplitude of Z magnetization will be reduced. The lengths of the RF pulses and the delay period are varied so that the effects of relaxation, flow, and diffusion or perfusion can be distinguished. The present study demonstrates the use of this method to detect slow fluid flow. Advantages of this method include the availability of large RF gradients, and the avoidance of eddy currents. It is suggested that the method may have application to the study of perfusion and flow in vivo.
Karczmar
G S
GS
Magnetic Resonance Unit, Veterans Administration Medical Center, San Francisco, California.
Twieg
D B
DB
Lawry
T J
TJ
Matson
G B
GB
Weiner
M W
MW
D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009038:Motion; D010477:Perfusion; D012212:Rheology