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Continuous Arterial Spin Labeling (continuous + arterial_spin_labeling)

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Medical Sciences100%

Selected Abstracts

Continuous arterial spin labeling using a train of adiabatic inversion pulses,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2005
Bradford A. Moffat PhD
Abstract Purpose To develop a simple and robust magnetic resonance imaging (MRI) pulse sequence for the quantitative measurement of blood flow in the brain and cerebral tumors that has practical implementation advantages over currently used continuous arterial spin labeling (CASL) schemes. Materials and Methods Presented here is a single-coil protocol that uses a train of hyperbolic secant inversion pulses to produce continuous arterial spin inversion for perfusion weighting of fast spin echo images. Flow maps of normal rat brains and those containing a 9L gliosarcoma orthotopic tumor model conditions were acquired with and without carbogen. Results The perfusion-weighted images have reduced magnetization transfer signal degradation as compared to the traditional single-coil CASL while avoiding the use of a more complex two-coil CASL technique. Blood flow measurements in tumor and normal brain tissue were consistent with those previously reported by other CASL techniques. Contralateral and normal brain showed increased blood flow with carbogen breathing, while tumor tissue lacked the same CO2 reactivity. Conclusion This variation of the CASL technique is a quantitative, robust, and practical single-coil method for measuring blood flow. This CASL method does not require specialized radiofrequency coils or amplifiers that are not routinely used for anatomic imaging of the brain, therefore allowing these flow measurements to be easily incorporated into traditional rodent neuroimaging protocols. J. Magn. Reson. Imaging 2005;21:290,296. © 2005 Wiley-Liss, Inc. [source]

Continuous arterial spin labeling at the human common carotid artery: the influence of transit times

NMR IN BIOMEDICINE, Issue 1 2005
Toralf Mildner
Abstract In evaluating the sensitivity of arterial spin labeling (CASL) and for quantification of perfusion, knowledge of the transit time from the labeling plane to the imaging slice is crucial. The purpose of the current study was to obtain estimates of transit times relevant under the specific experimental conditions of CASL in human subjects using a separate local labeling coil at the neck. Specifically, the post-label delay (PLD), i.e. the time between the end of the labeling period and the image acquisition, was varied either with or without additional application of crusher gradients to suppress intravascular signal contributions. The overall sensitivity change for varying the PLD between 1000 and 1700,ms was low. A tissue transit time from the neck to an axial supraventricular section through Broca's knee was obtained by fitting the PLD dependence to a two-compartment model. Averaging over subjects yielded 1930,±,110,ms for the tissue transit time, and 73,±,5,ml,min,1 100,g,1 for the cerebral blood flow. Small areas that exhibited a very high signal change upon labeling were indicative of regional variation in cerebral blood flow related to vascular anatomy. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Continuous arterial spin labeling using a train of adiabatic inversion pulses,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2005
Bradford A. Moffat PhD
Abstract Purpose To develop a simple and robust magnetic resonance imaging (MRI) pulse sequence for the quantitative measurement of blood flow in the brain and cerebral tumors that has practical implementation advantages over currently used continuous arterial spin labeling (CASL) schemes. Materials and Methods Presented here is a single-coil protocol that uses a train of hyperbolic secant inversion pulses to produce continuous arterial spin inversion for perfusion weighting of fast spin echo images. Flow maps of normal rat brains and those containing a 9L gliosarcoma orthotopic tumor model conditions were acquired with and without carbogen. Results The perfusion-weighted images have reduced magnetization transfer signal degradation as compared to the traditional single-coil CASL while avoiding the use of a more complex two-coil CASL technique. Blood flow measurements in tumor and normal brain tissue were consistent with those previously reported by other CASL techniques. Contralateral and normal brain showed increased blood flow with carbogen breathing, while tumor tissue lacked the same CO2 reactivity. Conclusion This variation of the CASL technique is a quantitative, robust, and practical single-coil method for measuring blood flow. This CASL method does not require specialized radiofrequency coils or amplifiers that are not routinely used for anatomic imaging of the brain, therefore allowing these flow measurements to be easily incorporated into traditional rodent neuroimaging protocols. J. Magn. Reson. Imaging 2005;21:290,296. © 2005 Wiley-Liss, Inc. [source]

Normal cerebral perfusion measurements using arterial spin labeling: Reproducibility, stability, and age and gender effects

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2004
Laura M. Parkes
Abstract Before meaningful conclusions can be drawn from clinical measures of cerebral blood perfusion, the precision of the measurement must be determined and set in the context of inter- and intrasubject sources of variability. This work establishes the reproducibility of perfusion measurements using the noninvasive MRI technique of continuous arterial spin labeling (CASL). Perfusion was measured in 34 healthy normal subjects. Intersubject variability was assessed, and age and gender contributions were estimated. Intersubject variation was found to be large, with up to 100% perfusion difference for subjects of the same age and gender. Repeated measurements in one subject showed that perfusion remains remarkably stable in the short term when compared with intersubject variation and the large capacity for perfusion change in the brain. A significant decrease in the ratio of gray-matter to white-matter perfusion was found with increasing age (0.79% per year (P < 0.0005)). This appears to be due mainly to a reduction in gray-matter perfusion, which was found to decrease by 0.45% per year (P = 0.04). Regional analysis suggested that the gray-matter age-related changes were predominantly localized in the frontal cortex. Whole-brain perfusion was 13% higher (P = 0.02) in females compared to males. Magn Reson Med 51:736,743, 2004. © 2004 Wiley-Liss, Inc. [source]

Functional perfusion imaging using continuous arterial spin labeling with separate labeling and imaging coils at 3 T

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2003
Toralf Mildner
Abstract Functional perfusion imaging with a separate labeling coil located above the common carotid artery was demonstrated in human volunteers at 3 T. A helmet resonator and a spin-echo echo-planar imaging (EPI) sequence were used for imaging, and a circular surface coil of 6 cm i.d. was employed for labeling. The subjects performed a finger-tapping task. Signal differences between the condition of finger tapping and the resting state were between ,0.5% and ,1.1 % among the subjects. The imaging protocol included a long post-label delay (PLD) to reduce transit time effects. Labeling was applied for all repetitions of the functional run to reduce the sampling interval. Magn Reson Med 49:791,795, 2003. © 2003 Wiley-Liss, Inc. [source]