《Multi-Slice MRI of Rat Brain Perfusion During》.pdf

Multi-Slice MRI of Rat Brain Perfusion During Amphetamine Stimulation Using Arterial Spin Labeling Afonso C. Silva, Weiguo Zhang, Donald S. Williams, Alan P. Koretsky When a single coil is used to measure perfusion by arterial be used to quantitate perfusion. The Bloch equations can spin labeling, saturation of macromolecular protons occurs be modified to include the effects of perfusion so that any during the labeling period. Induced magnetization transfer sequence that alters arterial water magnetization can be contrast (MTC) effects decrease tissue water signal intensity, used to derive a measure of perfusion (5). reducing the sensitivity of the technique. In addition, MTC effects must be properly accountedfor in acquiringa control The longitudinal field gradient used during the label- image. This forces the image to a single slice centered be- ing period of an experiment to measure perfusion allows tween the labeling plane and the control plane. Inthis work, a selective labeling of arterial water spins as long as the two-coil system is presented as a way to avoid saturation of frequency offset of the FWirradiation is much larger than macromolecular spins during arterial spin labeling. The sys- the tissue water bandwidth. This condition is, indeed, tem consists of one small surface coil for labeling the arterial very easily fulfilled. For example, as shown in Fig. la, water spins, and a head coil for MRI, actively decoupledfrom the labeling plane for rat brain perfusion is located in the the labeling coil by using PINdiodes. It isshownthat no signal neck about 2 cm apart from the detection slice. When a loss occurs due to MTC effects when the two-coil system is used for MRI of rat brain perfusion, enabling three-dimen- longitudinal gradie