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Cerebral blood flow quantification using vessel-encoded arterial spin labeling.

Okell TW, Chappell MA, Kelly ME, Jezzard P - J. Cereb. Blood Flow Metab. (2013)

Bottom Line: Experimental results in healthy volunteers showed that there is no systematic bias in the CBF estimates produced by VEPCASL and that the signal-to-noise ratio of the two techniques is comparable.Although more complex acquisition and image processing is required and the potential for motion sensitivity is increased, VEPCASL provides comparable data to PCASL but with the added benefit of vessel-selective information.This could lead to more accurate CBF estimates in patients with a significant collateral flow.

View Article: PubMed Central - PubMed

Affiliation: Nuffield Department of Clinical Neurosciences, Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, Oxford, UK.

ABSTRACT
Arterial spin labeling (ASL) techniques are gaining popularity for visualizing and quantifying cerebral blood flow (CBF) in a range of patient groups. However, most ASL methods lack vessel-selective information, which is important for the assessment of collateral flow and the arterial supply to lesions. In this study, we explored the use of vessel-encoded pseudocontinuous ASL (VEPCASL) with multiple postlabeling delays to obtain individual quantitative CBF and bolus arrival time maps for each of the four main brain-feeding arteries and compared the results against those obtained with conventional pseudocontinuous ASL (PCASL) using matched scan time. Simulations showed that PCASL systematically underestimated CBF by up to 37% in voxels supplied by two arteries, whereas VEPCASL maintained CBF accuracy since each vascular component is treated separately. Experimental results in healthy volunteers showed that there is no systematic bias in the CBF estimates produced by VEPCASL and that the signal-to-noise ratio of the two techniques is comparable. Although more complex acquisition and image processing is required and the potential for motion sensitivity is increased, VEPCASL provides comparable data to PCASL but with the added benefit of vessel-selective information. This could lead to more accurate CBF estimates in patients with a significant collateral flow.

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Related in: MedlinePlus

Example vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL) data: (A) Images of one slice in one subject at each postlabeling delay. For VEPCASL, the arterial source of the signal is representing using color, as shown in the legend; (B) data (circles) and fits (lines) in the encircled voxel shown in panel A. Only VEPCASL data from the dominant internal carotid artery (ICA) components are shown here for clarity. Blood from the right ICA (RICA) arrives later than blood from the left ICA (LICA), causing underestimation of the total cerebral blood flow (CBF) for PCASL (66.5 mL/100 g per minute) compared with VEPCASL (75.7 mL/100 g per minute).
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fig4: Example vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL) data: (A) Images of one slice in one subject at each postlabeling delay. For VEPCASL, the arterial source of the signal is representing using color, as shown in the legend; (B) data (circles) and fits (lines) in the encircled voxel shown in panel A. Only VEPCASL data from the dominant internal carotid artery (ICA) components are shown here for clarity. Blood from the right ICA (RICA) arrives later than blood from the left ICA (LICA), causing underestimation of the total cerebral blood flow (CBF) for PCASL (66.5 mL/100 g per minute) compared with VEPCASL (75.7 mL/100 g per minute).

Mentions: Example perfusion images at each PLD are shown in Figure 4 for both PCASL and VEPCASL in the same subject. In this subject, the right anterior cerebral artery territory is supplied by both the RICA and the LICA. In the highlighted voxel, it can be seen that blood from the RICA is somewhat delayed relative to blood from the LICA, causing PCASL to underestimate the CBF here. However, in these healthy volunteers there were few such voxels showing significant differences in the BAT: for voxels within the brain masks only 2.0% had significant (P<0.01) perfusion from more than one artery and BAT differences greater than 0.5 second. This value decreases to 0.3% for BAT differences greater than 1 second.


Cerebral blood flow quantification using vessel-encoded arterial spin labeling.

Okell TW, Chappell MA, Kelly ME, Jezzard P - J. Cereb. Blood Flow Metab. (2013)

Example vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL) data: (A) Images of one slice in one subject at each postlabeling delay. For VEPCASL, the arterial source of the signal is representing using color, as shown in the legend; (B) data (circles) and fits (lines) in the encircled voxel shown in panel A. Only VEPCASL data from the dominant internal carotid artery (ICA) components are shown here for clarity. Blood from the right ICA (RICA) arrives later than blood from the left ICA (LICA), causing underestimation of the total cerebral blood flow (CBF) for PCASL (66.5 mL/100 g per minute) compared with VEPCASL (75.7 mL/100 g per minute).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824178&req=5

fig4: Example vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL) data: (A) Images of one slice in one subject at each postlabeling delay. For VEPCASL, the arterial source of the signal is representing using color, as shown in the legend; (B) data (circles) and fits (lines) in the encircled voxel shown in panel A. Only VEPCASL data from the dominant internal carotid artery (ICA) components are shown here for clarity. Blood from the right ICA (RICA) arrives later than blood from the left ICA (LICA), causing underestimation of the total cerebral blood flow (CBF) for PCASL (66.5 mL/100 g per minute) compared with VEPCASL (75.7 mL/100 g per minute).
Mentions: Example perfusion images at each PLD are shown in Figure 4 for both PCASL and VEPCASL in the same subject. In this subject, the right anterior cerebral artery territory is supplied by both the RICA and the LICA. In the highlighted voxel, it can be seen that blood from the RICA is somewhat delayed relative to blood from the LICA, causing PCASL to underestimate the CBF here. However, in these healthy volunteers there were few such voxels showing significant differences in the BAT: for voxels within the brain masks only 2.0% had significant (P<0.01) perfusion from more than one artery and BAT differences greater than 0.5 second. This value decreases to 0.3% for BAT differences greater than 1 second.

Bottom Line: Experimental results in healthy volunteers showed that there is no systematic bias in the CBF estimates produced by VEPCASL and that the signal-to-noise ratio of the two techniques is comparable.Although more complex acquisition and image processing is required and the potential for motion sensitivity is increased, VEPCASL provides comparable data to PCASL but with the added benefit of vessel-selective information.This could lead to more accurate CBF estimates in patients with a significant collateral flow.

View Article: PubMed Central - PubMed

Affiliation: Nuffield Department of Clinical Neurosciences, Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, Oxford, UK.

ABSTRACT
Arterial spin labeling (ASL) techniques are gaining popularity for visualizing and quantifying cerebral blood flow (CBF) in a range of patient groups. However, most ASL methods lack vessel-selective information, which is important for the assessment of collateral flow and the arterial supply to lesions. In this study, we explored the use of vessel-encoded pseudocontinuous ASL (VEPCASL) with multiple postlabeling delays to obtain individual quantitative CBF and bolus arrival time maps for each of the four main brain-feeding arteries and compared the results against those obtained with conventional pseudocontinuous ASL (PCASL) using matched scan time. Simulations showed that PCASL systematically underestimated CBF by up to 37% in voxels supplied by two arteries, whereas VEPCASL maintained CBF accuracy since each vascular component is treated separately. Experimental results in healthy volunteers showed that there is no systematic bias in the CBF estimates produced by VEPCASL and that the signal-to-noise ratio of the two techniques is comparable. Although more complex acquisition and image processing is required and the potential for motion sensitivity is increased, VEPCASL provides comparable data to PCASL but with the added benefit of vessel-selective information. This could lead to more accurate CBF estimates in patients with a significant collateral flow.

Show MeSH
Related in: MedlinePlus