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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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Comparison of cerebral blood flow (CBF) estimates from vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL): (A) Central slice of the CBF map for each subject in this study (in units of mL/100 g per minute) with VEPCASL images shown as separate components (in color) as well as summed across all feeding arteries, to aid comparison; (B) Correlation between the two methods for one subject for all voxels within a brain mask with the ideal equality line and line of best fit overlaid (note that PCASL tends to underestimate the CBF in voxels supplied by multiple arteries whose bolus arrival time (BAT) differences are greater than 0.5 second, plotted separately here); (C) Gradient of the line of best fit for each subject. Intercept values are too small to be shown here (<10−6 mL/100 g per minute).
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fig5: Comparison of cerebral blood flow (CBF) estimates from vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL): (A) Central slice of the CBF map for each subject in this study (in units of mL/100 g per minute) with VEPCASL images shown as separate components (in color) as well as summed across all feeding arteries, to aid comparison; (B) Correlation between the two methods for one subject for all voxels within a brain mask with the ideal equality line and line of best fit overlaid (note that PCASL tends to underestimate the CBF in voxels supplied by multiple arteries whose bolus arrival time (BAT) differences are greater than 0.5 second, plotted separately here); (C) Gradient of the line of best fit for each subject. Intercept values are too small to be shown here (<10−6 mL/100 g per minute).

Mentions: Figure 5A shows example VEPCASL and PCASL CBF maps in each subject, highlighting the good image quality obtained in all cases and the qualitative similarity between the two methods. An example of the correlation analysis performed in one subject is shown in Figure 5B, showing the high degree of correlation between the CBF estimates of the two methods and a line of best fit that is very close to the ideal line of equality. In voxels fed by multiple arteries with a BAT difference of greater than 0.5 second it can be seen that there is a tendency for PCASL to underestimate the CBF, as expected from the simulations above. These voxels are therefore excluded from the correlation analysis.


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

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

Comparison of cerebral blood flow (CBF) estimates from vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL): (A) Central slice of the CBF map for each subject in this study (in units of mL/100 g per minute) with VEPCASL images shown as separate components (in color) as well as summed across all feeding arteries, to aid comparison; (B) Correlation between the two methods for one subject for all voxels within a brain mask with the ideal equality line and line of best fit overlaid (note that PCASL tends to underestimate the CBF in voxels supplied by multiple arteries whose bolus arrival time (BAT) differences are greater than 0.5 second, plotted separately here); (C) Gradient of the line of best fit for each subject. Intercept values are too small to be shown here (<10−6 mL/100 g per minute).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Comparison of cerebral blood flow (CBF) estimates from vessel-encoded (VE) and standard pseudocontinuous arterial spin labeling (PCASL): (A) Central slice of the CBF map for each subject in this study (in units of mL/100 g per minute) with VEPCASL images shown as separate components (in color) as well as summed across all feeding arteries, to aid comparison; (B) Correlation between the two methods for one subject for all voxels within a brain mask with the ideal equality line and line of best fit overlaid (note that PCASL tends to underestimate the CBF in voxels supplied by multiple arteries whose bolus arrival time (BAT) differences are greater than 0.5 second, plotted separately here); (C) Gradient of the line of best fit for each subject. Intercept values are too small to be shown here (<10−6 mL/100 g per minute).
Mentions: Figure 5A shows example VEPCASL and PCASL CBF maps in each subject, highlighting the good image quality obtained in all cases and the qualitative similarity between the two methods. An example of the correlation analysis performed in one subject is shown in Figure 5B, showing the high degree of correlation between the CBF estimates of the two methods and a line of best fit that is very close to the ideal line of equality. In voxels fed by multiple arteries with a BAT difference of greater than 0.5 second it can be seen that there is a tendency for PCASL to underestimate the CBF, as expected from the simulations above. These voxels are therefore excluded from the correlation analysis.

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