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Cerebral blood flow measurement using fMRI and PET: a cross-validation study.

Chen JJ, Wieckowska M, Meyer E, Pike GB - Int J Biomed Imaging (2008)

Bottom Line: The CBF changes were compared using 3 types of region-of-interest (ROI) masks.FAIR measurements of CBF changes were found to be slightly lower than those measured with PET (average DeltaCBF of 21.5 +/- 8.2% for FAIR versus 28.2 +/- 12.8% for PET at maximum stimulation intensity).Finally, a t-test comparison of the slopes of the linear fits of PET versus ASL DeltaCBF for all 3 ROI types indicated no significant difference from unity (P > .05).

View Article: PubMed Central - PubMed

Affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, PQ, Canada H3A 2B4. jean.chen@mail.mcgill.ca

ABSTRACT
An important aspect of functional magnetic resonance imaging (fMRI) is the study of brain hemodynamics, and MR arterial spin labeling (ASL) perfusion imaging has gained wide acceptance as a robust and noninvasive technique. However, the cerebral blood flow (CBF) measurements obtained with ASL fMRI have not been fully validated, particularly during global CBF modulations. We present a comparison of cerebral blood flow changes (DeltaCBF) measured using a flow-sensitive alternating inversion recovery (FAIR) ASL perfusion method to those obtained using H(2) (15)O PET, which is the current gold standard for in vivo imaging of CBF. To study regional and global CBF changes, a group of 10 healthy volunteers were imaged under identical experimental conditions during presentation of 5 levels of visual stimulation and one level of hypercapnia. The CBF changes were compared using 3 types of region-of-interest (ROI) masks. FAIR measurements of CBF changes were found to be slightly lower than those measured with PET (average DeltaCBF of 21.5 +/- 8.2% for FAIR versus 28.2 +/- 12.8% for PET at maximum stimulation intensity). Nonetheless, there was a strong correlation between measurements of the two modalities. Finally, a t-test comparison of the slopes of the linear fits of PET versus ASL DeltaCBF for all 3 ROI types indicated no significant difference from unity (P > .05).

No MeSH data available.


Related in: MedlinePlus

Sample ROIs (shown in red) defined for onesubject. The V1 ROI was obtained by retinotopic mapping, the t-map ROI included common voxels fromthresholded and resampled FAIR and PET t-maps,and the grey matter (GM) ROI was defined by Bayesian classification of theanatomical structures.
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fig3: Sample ROIs (shown in red) defined for onesubject. The V1 ROI was obtained by retinotopic mapping, the t-map ROI included common voxels fromthresholded and resampled FAIR and PET t-maps,and the grey matter (GM) ROI was defined by Bayesian classification of theanatomical structures.

Mentions: The threeROIs used for the ΔCBF comparisons were defined on a subject basis,as described in Methods and Materials, and an example is shown in Figure 3. Forall subjects, the V1 ROIs were the smallest, containing only between 0.101ccand 0.187cc, due to the stringent retinotopic mapping criteria. V1 wascorrectly identified by the ROIs, but due to the small mask size, thecorresponding ΔCBF measurements are prone to variationsintroduced by misregistration and motion. On the other hand, the t-map ROIs contained between 0.202cc and0.407cc. To obtain the t-map ROI's at P = .05, the fMRI t-maps were thresholded at 5.42, and the PET maps at 4.45. A lowerstandard deviation was seen in the responses detected in these ROIs, and theFAIR t-maps contained nostatistically significant voxels for 2 of the 10 subjects. The largest were theGM ROIs, covering 1.489-0.625 cc for the same group of subjects. Someautomatically classified GM voxels were excluded by the certainty-levelthreshold, but the final GM ROIs were still significantly larger than the V1ROIs. As previously mentioned, larger ROI masks may include nonactivatedvoxels, leading to reduced levels of measured ΔCBF. Nonetheless, the GM masks provide aneffective means of comparing CBF measurement across modalities, especially forthe hypercapnia condition.


Cerebral blood flow measurement using fMRI and PET: a cross-validation study.

Chen JJ, Wieckowska M, Meyer E, Pike GB - Int J Biomed Imaging (2008)

Sample ROIs (shown in red) defined for onesubject. The V1 ROI was obtained by retinotopic mapping, the t-map ROI included common voxels fromthresholded and resampled FAIR and PET t-maps,and the grey matter (GM) ROI was defined by Bayesian classification of theanatomical structures.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553188&req=5

fig3: Sample ROIs (shown in red) defined for onesubject. The V1 ROI was obtained by retinotopic mapping, the t-map ROI included common voxels fromthresholded and resampled FAIR and PET t-maps,and the grey matter (GM) ROI was defined by Bayesian classification of theanatomical structures.
Mentions: The threeROIs used for the ΔCBF comparisons were defined on a subject basis,as described in Methods and Materials, and an example is shown in Figure 3. Forall subjects, the V1 ROIs were the smallest, containing only between 0.101ccand 0.187cc, due to the stringent retinotopic mapping criteria. V1 wascorrectly identified by the ROIs, but due to the small mask size, thecorresponding ΔCBF measurements are prone to variationsintroduced by misregistration and motion. On the other hand, the t-map ROIs contained between 0.202cc and0.407cc. To obtain the t-map ROI's at P = .05, the fMRI t-maps were thresholded at 5.42, and the PET maps at 4.45. A lowerstandard deviation was seen in the responses detected in these ROIs, and theFAIR t-maps contained nostatistically significant voxels for 2 of the 10 subjects. The largest were theGM ROIs, covering 1.489-0.625 cc for the same group of subjects. Someautomatically classified GM voxels were excluded by the certainty-levelthreshold, but the final GM ROIs were still significantly larger than the V1ROIs. As previously mentioned, larger ROI masks may include nonactivatedvoxels, leading to reduced levels of measured ΔCBF. Nonetheless, the GM masks provide aneffective means of comparing CBF measurement across modalities, especially forthe hypercapnia condition.

Bottom Line: The CBF changes were compared using 3 types of region-of-interest (ROI) masks.FAIR measurements of CBF changes were found to be slightly lower than those measured with PET (average DeltaCBF of 21.5 +/- 8.2% for FAIR versus 28.2 +/- 12.8% for PET at maximum stimulation intensity).Finally, a t-test comparison of the slopes of the linear fits of PET versus ASL DeltaCBF for all 3 ROI types indicated no significant difference from unity (P > .05).

View Article: PubMed Central - PubMed

Affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, PQ, Canada H3A 2B4. jean.chen@mail.mcgill.ca

ABSTRACT
An important aspect of functional magnetic resonance imaging (fMRI) is the study of brain hemodynamics, and MR arterial spin labeling (ASL) perfusion imaging has gained wide acceptance as a robust and noninvasive technique. However, the cerebral blood flow (CBF) measurements obtained with ASL fMRI have not been fully validated, particularly during global CBF modulations. We present a comparison of cerebral blood flow changes (DeltaCBF) measured using a flow-sensitive alternating inversion recovery (FAIR) ASL perfusion method to those obtained using H(2) (15)O PET, which is the current gold standard for in vivo imaging of CBF. To study regional and global CBF changes, a group of 10 healthy volunteers were imaged under identical experimental conditions during presentation of 5 levels of visual stimulation and one level of hypercapnia. The CBF changes were compared using 3 types of region-of-interest (ROI) masks. FAIR measurements of CBF changes were found to be slightly lower than those measured with PET (average DeltaCBF of 21.5 +/- 8.2% for FAIR versus 28.2 +/- 12.8% for PET at maximum stimulation intensity). Nonetheless, there was a strong correlation between measurements of the two modalities. Finally, a t-test comparison of the slopes of the linear fits of PET versus ASL DeltaCBF for all 3 ROI types indicated no significant difference from unity (P > .05).

No MeSH data available.


Related in: MedlinePlus