Continuous arterial spin labeling using a local magnetic field gradient coil

Trampel, Robert; Mildner, Toralf; Goerke, Ute; Schaefer, Andreas; Driesel, Wolfgang; Norris, David G.

doi:10.1002/mrm.10228

Cited by 41 publications

(51 citation statements)

References 15 publications

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“…Indeed the substrate for mounting the coil elements was a football helmet. The design has been used successfully for human blood-oxygen level dependent (BOLD) FMRI at 4 T (10,11) and to image human brain perfusion employing continuous arterial spin labeling (12)(13)(14). However, the trade-in was a large z-gradient of the RF field B 1 .…”

Section: Introductionmentioning

confidence: 99%

Reengineered helmet coil for human brain studies at 3 Tesla

Driesel

Merkle

Hetzer

et al. 2005

Concepts Magn. Reson.

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ABSTRACT:We describe the further development of a circularly polarized helmet coil for magnetic resonance imaging (MRI) of the human brain at 3 T. The coil is used in transmit and receive (transceive) mode, a useful alternative over commercially available quadrature headcoils with scanners where phased arrays are unavailable. The coil is simple to build. Its structure is based on an assembly of two coplanar dual-loop coils of the split-circle design, which are arranged in crossed fashion. Both coils circumscribe dome-like the human head. Because of the symmetry of the assembly, a high degree of circularly polarized radiofrequency (RF) is obtained within the brain. Bench and in situ measurements of the RF magnetic field, B 1 , indicated good axial homogeneity and a moderate gradient along the symmetry axis. Compared to a commercial birdcage coil, the signal-to-noise ratio was increased up to a factor of 1.7 as a result of its superior filling factor. Initial applications in healthy volunteers included anatomical MRI and functional imaging with a cognitive paradigm.

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Section: Introductionmentioning

confidence: 99%

Reengineered helmet coil for human brain studies at 3 Tesla

Driesel

Merkle

Hetzer

et al. 2005

Concepts Magn. Reson.

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“…Functional perfusion imaging with whole-brain coverage, which is more appropriate for typical cognitive studies, might indeed benefit from a TCL approach. This could be achieved for example by use of a separate labeling gradient as suggested elsewhere (Trampel et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Towards quantification of blood-flow changes during cognitive task activation using perfusion-based fMRI

et al. 2005

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Multi-slice perfusion-based functional magnetic resonance imaging (pfMRI) is demonstrated with a color -word Stroop task as an established cognitive paradigm. Continuous arterial spin labeling (CASL) of the blood in the left common carotid artery was applied for all repetitions of the functional run in a quasi-continuous fashion, i.e., it was interrupted only during image acquisition. For comparison, blood oxygen level dependent (BOLD) contrast was detected using conventional gradient-recalled echo (GE) echo planar imaging (EPI). Positive activations in BOLD imaging appeared in p-fMRI as negative signal changes corresponding to an enhanced transport of inverted water spins into the region of interest, i.e., increased cerebral blood flow (CBF). Regional differences between the localization of activations and the sensitivity of p-fMRI and BOLD-fMRI were observed as, for example, in the inferior frontal sulcus and in the intraparietal sulcus. Quantification of CBF changes during cognitive task activation was performed on a multi-subject basis and yielded CBF increases of the order of 20 -30%. D 2005 Elsevier Inc. All rights reserved.Keywords: Arterial spin labeling; Cerebral blood flow; Functional perfusion imaging; Quantification; fMRI; Cognitive task activation IntroductionIn the last decade, perfusion imaging using magnetic resonance imaging (MRI) techniques with water as an endogenous tracer has been a topic of growing research. From early on, the perfusion contrast created by magnetically labeling of the blood or the tissue was also employed for mapping task-related brain activity (Edelman et al., 1994;Kwong et al., 1992). However, due to its higher sensitivity, the blood oxygen level dependent (BOLD) contrast became the standard tool for functional MRI (fMRI). Despite this fact, interest in perfusion-based fMRI (p-fMRI) remained high.Expected improvements in the localization of activation due to the capillary/tissue origin of the perfusion contrast, and in the quantification of functional signal changes were the attracting arguments (Buxton et al., 1998;Siewert et al., 1996;Yang et al., 1998;Ye et al., 1997). Techniques were developed to increase the number of slices, to reduce the transit-time sensitivity, and to improve the time resolution in p-fMRI (Alsop and Detre, 1998;Calamante et al., 1999;Pekar et al., 1996;Zhang et al., 1995). It was shown that p-fMRI has some additional advantages for multisubject studies or at low task frequencies (Wang et al., 2003). However, except for a single-slice study employing a workingmemory task , all published studies were limited to primary cortical areas, such as the visual or the motor cortex.The aim of the present work was to detect more subtle functional changes of cerebral blood flow (CBF) related to a cognitive task in different areas of the human brain. For this purpose, a continuous arterial spin labeling (CASL) approach with separate labeling and imaging coils was employed (Zaharchuk et al., 1999). With this technique, all blood entering the brain through one c...

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“…Thus, the difference between the labeled and the control images will return the perfusion territory supplied only by those labeled arteries. To date, this strategy has been implemented according to three different approaches: (1) using a dedicated labeling RF coil positioned over the arteries of interest (14)(15)(16)19,30,31); (2) employing selective inversion of spatially confined areas where the arteries of interest are located (5,17,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29); and (3) using multidimensional RF pulses to directly label the artery of interest (18). Each approach will be described and critically discussed in the following sections.…”

Section: General Principles Of Mapping Vascular Territories With Aslmentioning

confidence: 99%

“…The same principles as described above were applied by Zaharchuk et al (15) and by the group of David Norris (16,19) to measure the vascular territories of the CCAs with the use of a separate labeling RF coil placed directly over a single individual artery, as illustrated in Fig. 2a.…”

Section: Use Of a Separate Labeling Rf Coilmentioning

confidence: 99%

“…MRI of cerebral vascular territories require selective labeling of blood in the artery (ies) of interest, and thus arterial spin labeling (ASL) techniques have been used with exclusivity to map the vascular territories of major cerebral arteries (5,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Ideally, techniques dedicated to map cerebral perfusion territories should allow a flexible selection of which arterial territory to demarcate, and to do so within the short time constraints available for clinical exams, providing images of the whole brain with high SNR and devoid of artifacts resulting from labeling the arteries of interest.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of cerebral perfusion territories using arterial spin labelling

2007

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The ability to assess the perfusion territories of major cerebral arteries can be a valuable asset to the diagnosis of a number of cerebrovascular diseases. Recently, several arterial spin labeling (ASL) techniques have been proposed to obtain the cerebral perfusion territories of individual arteries according to three different approaches: (1) using a dedicated labeling RF coil; (2) applying selective inversion of spatially confined areas; or (3) employing multi-dimensional RF pulses. Methods that use a separate labeling RF coil have high SNR, low RF power deposition and unrestricted 3-dimensional coverage, but are mostly limited to separation of the left and right circulation, and do require extra hardware, which may limit their implementation in clinical systems. Alternatively, methods that utilize selective inversion have higher flexibility of implementation and higher arterial selectivity, but suffer from imaging artifacts resulting from interference between the labeling slab and the volume of interest. The goal of the present review is to provide the reader with a critical survey of the different ASL approaches proposed to date to obtain cerebral perfusion territories, by discussing the relative advantages and disadvantages of each technique, so as to serve as a guiding resource towards future refinements of this promising methodology.

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Continuous arterial spin labeling using a local magnetic field gradient coil

Cited by 41 publications

References 15 publications

Reengineered helmet coil for human brain studies at 3 Tesla

Reengineered helmet coil for human brain studies at 3 Tesla

Towards quantification of blood-flow changes during cognitive task activation using perfusion-based fMRI

Measurement of cerebral perfusion territories using arterial spin labelling

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