Arterial spin labeling using time varying gradients

#The present application relates to a technique for imaging fluid flow noninvasively using MRI with radio frequency arterial spin labeling and, more particularly, to a labeling technique that permits extension of this technique to a multislice or volume examination.

#Magnetic Resonance Imaging (MRI) is an imaging technique used primarily in medical settings to produce high quality images of the inside of the human body. MRI is based on principles of nuclear magnetic resonance (NMR), a spectroscopic technique used to obtain microscopic chemical and physical information about molecules.

#MR (magnetic resonance) techniques may be used to study fluid flow, such as, for example, blood flow and blood perfusion in tissue. One of many possible applications is to study blood perfusion in the human brain.

#In the drawings, which are incorporated herein by reference, and in which like elements have been given like reference characters,

#FIG. 1a schematically illustrates a conventional single-slice MR blood flow mapping study;

#FIG. 1b schematically illustrates how a conventional magnetization transfer compensation scheme fails to compensate for magnetization transfer effects when used in a multislice MR study;

#One embodiment of the present invention is described below in relation to FIGS. 2-11. Although the embodiment of FIGS. 2-11 refers to measuring perfusion of blood in the brain, the present invention is not so limited. The invention may also be applied to any MR study of fluid flow or perfusion, whether in live tissue, or under other conditions. Furthermore, the present invention may be used for angiographic studies and other medical and scientific applications, as deemed appropriate by one skilled in the art.

#The embodiment of the invention illustrated in FIGS. 2-11 involves proton magnetic resonance imaging of perfusion using water as a freely diffusable tracer. Application of the invention to the measurement of cerebral blood flow (CBF) is detailed in relation to FIGS. 10 and 11.

#Although terms “flow” and “perfusion” may sometimes be used interchangeably, perfusion as used herein refers to a diffusable exchange between a fluid and a substance, such as, for example, human tissue. The term “flow” as used herein, generally refers to flow of liquid in vessels, such as, for example, flow of blood in arteries.