Abstract: In an NMR imaging system, an image plane is scanned and NMR signals are collected over a plurality of image lines. The experiment is repeated, with the timing of the excitation pulses changed. Images are formed by performing Fourier transformations of the signal values. A ratio image is then formed by performing a complex division of the two images on a pixel by pixel basis. The ratio values cancel phase error effects in the image data and the use of complex numbers maintains the proper pixel polarity.

Abstract: The effects of particle motion or flow within a sample may be measured by applying a motion-encoding gradient to the sample, along with spatial encoding gradients. The motion-encoding gradient applies two gradient fields of respective opposite sense to the spins of the sample so as to encode motion as a net phase component resulting from the two fields. Two image data sequences, one with motion encoding and one without, may be compared to measure the effects of motion, or a plurality of image data sequences may be taken, each with a different value motion-encoding gradient. A Fourier transformation performed on the sequence data in the latter case with respect to the variation in the motion-encoding gradient pulses will yield a plurality of images, each representing the amount of material which exhibits a different velocity.