Effects of the apparent transverse relaxation time on cerebral blood flow measurements obtained by arterial spin labeling

Lawrence, Keith St.; Wang, Danny J.J.

doi:10.1002/mrm.20364

Cited by 71 publications

(80 citation statements)

References 37 publications

(75 reference statements)

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“…The higher perfusion values in FAIR-TrueFISP may be due the longer data readout (ϳ300 msec at 1.5T) as compared to EPI, resulting in higher inflow effects of vascular blood. Additionally, FAIR-EPI may show lower perfusion values due to the longer TE with increased T2* relaxation effects, which were recently reported to result in reduced cerebral blood perfusion values measured by ASL techniques (29). The perfusion values for WM areas differed significantly with both imaging modalities.…”

Section: Discussionmentioning

confidence: 93%

FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

Boss

Martirosian

Klose

et al. 2007

Magnetic Resonance Imaging

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Purpose:To estimate cerebral blood perfusion in areas of strong magnetic susceptibility changes with high spatial and temporal resolution using a flow-sensitive alternating inversion recovery (FAIR) arterial spin labeling (ASL) method. Materials and Methods:We implemented an ASL method that is capable of imaging perfusion in areas of high magnetic susceptibility changes by combining a FAIR spin preparation with a true fast imaging in steady precession (TrueFISP) data acquisition strategy. A TrueFISP readout sequence was applied especially in regions with magnetic field inhomogeneities and compared with corresponding FAIR measurements obtained with a standard echo-planar imaging (EPI) readout. Quantitative perfusion images were obtained at 1.5 Tesla (1.5T) from eight healthy volunteers (24 -42 years old) and one patient (23 years old). FAIRTrueFISP perfusion images were compared with FAIR echoplanar images. T1 maps, which are necessary for quantitative perfusion estimation, were obtained with inversion recovery (IR) TrueFISP and IR EPI. Additionally, high-resolution perfusion measurements were performed on four volunteers at 3T. Results:The two ASL perfusion imaging modalities yielded comparable diagnostic image quality in brain areas with low susceptibility differences at 1.5T. Cerebral perfusion of gray matter (GM) areas was 105.7 Ϯ 5.2 mL/100 g/minute for FAIR-TrueFISP and 88.8 Ϯ 14.6 mL/100 g/minute for FAIR-EPI at 1.5T, and 70.4 Ϯ 7.1 mL/100 g/minute for FAIR-TrueFISP and 63.5 Ϯ 6.9 mL/100 g/minute for FAIR-EPI at 3.0T. Higher perfusion values at 1.5T were due to more pronounced partial-volume effects from fast moving spins at lower spatial resolution. The FAIR-TrueFISP sequence showed no significant distortions and markedly reduced signal void artifacts in areas of high susceptibility changes (e.g., near brain-bone transitions and close to metallic clips) compared to FAIR-EPI. At 3T, highly resolved FAIR-TrueFISP perfusion images were acquired with an in-plane resolution of up to 1.3 mm.Conclusion: FAIR-TrueFISP allows for assessment of cerebral perfusion in areas of critically high susceptibility changes with conventional ASL methods.

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Section: Discussionmentioning

confidence: 93%

FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

Boss

Martirosian

Klose

et al. 2007

Magnetic Resonance Imaging

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“…As p-CASL and PASL use gradient echo readout instead of spin echo readout, T 2a was replaced by T 2 * a (T 2 * of arterial blood, 50 ms; St Lawrence and Wang, 2005;Uludag et al, 2009;Dai et al, 2008). For single TI PASL, a similar model was used.…”

Section: Quantificationmentioning

confidence: 99%

Intra- and Multicenter Reproducibility of Pulsed, Continuous and Pseudo-Continuous Arterial Spin Labeling Methods for Measuring Cerebral Perfusion

Gevers

Osch

Bokkers

et al. 2011

J Cereb Blood Flow Metab

133

126

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Intra-and multicenter reproducibility of currently used arterial spin labeling (ASL) methods were assessed at three imaging centers in the Netherlands, equipped with Philips 3TMR scanners. Six healthy participants were scanned twice at each site. The imaging protocol consisted of continuous ASL (CASL), pseudo-continuous ASL (p-CASL) with and without background suppression, pulsed ASL (PASL) with single and multiple inversion times (TIs), and selective ASL for segmentation. Reproducibility was expressed in terms of the coefficient of repeatability and the repeatability index. Voxelwise analysis of variance was performed, yielding brain maps that reflected regional variability. Intra-and multicenter reproducibility were comparable for all methods, except for single TI PASL, with better intracenter reproducibility (F-test of equality of two variances, P < 0.05). Pseudocontinuous ASL and multi TI PASL varied least between sites. Variability maps of all methods showed most variability near brain-feeding arteries within sessions and in gray matter between sessions. On the basis of the results of this study, one could consider the use of reference values in clinical routine, with whole-brain p-CASL perfusion varying < 20% over repeated measurements within the same individuals considered to be normal. Knowledge on regional variability allows for the use of perfusion-weighted images in the assessment of local cerebral pathology.

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“…Particularly, water permeability is an order of magnitude lower in the central nervous system than the systemic circulation, because the structure of the blood-brain barrier (BBB) only allows water molecules to be transported into brain tissue through the plasma membrane of endothelial cells instead of through cellular gaps (Paulson, 2002). With ASL methods, it is generally reasonable to ignore the effects of limited water exchange in the quantification of perfusion, provided that the relaxation rates in tissue and blood are similar (Parkes and Tofts, 2002;St Lawrence et al, 2000;St Lawrence and Wang, 2005). Nevertheless, analyzing ASL data with tracer kinetic models that include both tissue and vascular contributions may improve quantification in tissues, such as white matter, that have significantly different relaxation rates from blood (Li et al, 2005;Parkes and Tofts, 2002;St Lawrence et al, 2000;St Lawrence and Wang, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…A series of ASL perfusion scans with varying diffusion weightings were acquired to fit the fractions of ASL signals in the vascular and tissue compartments, which have fast and slow diffusion properties, respectively (Silva et al, 1997a). The single-pass approximation (SPA) model was used to determine the water exchange rate from the vascular and tissue fractions (St Lawrence et al, 2000;St Lawrence and Wang, 2005).…”

Section: Introductionmentioning

confidence: 99%

When Perfusion Meets Diffusion: in vivo Measurement of Water Permeability in Human Brain

Wang

Fernández‐Seara

Wang

et al. 2007

J Cereb Blood Flow Metab

118

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Quantification of water permeability can improve the accuracy of perfusion measurements obtained with arterial spin labeling (ASL) methods, and may provide clinically relevant information regarding the functional status of the microvasculature. The amount of labeled water in the vascular and tissue compartments in an ASL experiment can be estimated based on their distinct diffusion characteristics, and in turn, water permeability determined from the relative vascular and tissue contributions. In the present study, a hybrid magnetic resonance imaging technique was introduced by marrying a continuous ASL method with a twice-refocused spin-echo diffusion sequence. Series of diffusion-weighted ASL signals were acquired with systematically varied b values. The signals were modeled with fast and slow decaying components that were associated with the vascular and tissue compartments, respectively. The relative amount of labeled water in the tissue compartment increased from 61% to 74% and to 86% when the postlabeling delay time was increased from 0.8 to 1.2 and to 1.5 secs. With a b value of 50 secs/mm 2 , the capillary contribution (fast component) of the ASL signal could be effectively minimized. Using the single-pass approximation model, the water permeability of gray matter in the human brain was estimated based on the derived relative water fractions in the tissue and microvasculature. The potential for in vivo magnetic resonance mapping of water permeability was showed using two diffusion weighted ASL measurements with b = 0 and 50 secs/mm 2 in both healthy subjects and a case of brain tumor.

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Effects of the apparent transverse relaxation time on cerebral blood flow measurements obtained by arterial spin labeling

Cited by 71 publications

References 37 publications

FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

Intra- and Multicenter Reproducibility of Pulsed, Continuous and Pseudo-Continuous Arterial Spin Labeling Methods for Measuring Cerebral Perfusion

When Perfusion Meets Diffusion: in vivo Measurement of Water Permeability in Human Brain

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