Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine
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The use of high-permittivity materials has been shown to be an effective method for increasing transmit and receive sensitivity in areas of low-signal intensity in the brain at high field. Results in this article show that the use of these materials does not increase the intercoil coupling for a phased array receive coil, does not have any detrimental effects on the B(0) homogeneity within the brain, and does not affect the specific absorption rate distribution within the head. Areas of the brain close to the pads exhibit significant increases (>100%) in transmit field efficiency, but areas further away show a less pronounced (~10%) decrease due to the homogenization of the transmit field and the loss introduced by the dielectric pads.
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With the increasing number of transgenic mouse models of human brain diseases, there is a need for a sensitive method that allows assessing quantitative whole brain perfusion within a reasonable scan time. Arterial spin labeling (ASL), an MRI technique that permits the noninvasive quantification of cerebral blood flow, has been used to assess rodents brain perfusion. ⋯ Pseudo-continuous ASL was experimentally optimized and compared with a standard flow-sensitive alternating inversion recovery sequence for sensitivity, robustness, absolute quantification, and multislice imaging capability. A sensitivity gain up to 40% and clear advantages for multislice imaging are obtained with pseudo-continuous ASL.