Abstract: For determining flowing material within a body by NMR tomography, a disk-shaped area in the body is excited, whereafter one applies a flow phase gradient directed in the same sense as the selection gradient (1) and comprising two successive, inversely identical sections (3,4) whose values are varied for the successive excitations. The echo signals obtained, which originate substantially from moving material, are received at a reading gradient directed perpendicularly to the selection gradient. 2DFT reconstruction of a set of spin echo signals furnishes an image which contains the spatial coordinate of the reading gradient in one direction and the flow speed of the material flowing in a direction perpendicular to the excited area in the second direction.

Abstract: NMR tomography permits identification of flowing matter within a closed body, as there is a reduction in signal intensity as a consequence of a saturation of the magnetization in the area of a slice that has been excited for imaging, while freshly inflowing matter has not experienced this saturation and consequently provides a stronger signal. Special excitation sequences permit either virtually complete saturation of stationary tissue, and thus particularly strong emphasis of flowing matter, or excitation of stationary and flowing matter in different zones and with differing intensities, thereby enabling very precise quantitative and even directional flow measurements to be performed.