Relationship between cerebral blood flow changes during visual stimulation and baseline flow levels investigated with functional MRI

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 (ΔCBF) measured using a flow-sensitive alternating inversion recovery (FAIR) ASL perfusion method to those obtained usingH2O15PET, 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 (averageΔCBF of21.5±8.2% for FAIR versus28.2±12.8% for PET at maximum stimulation intensity). Nonetheless, there was a strong correlation between measurements of the two modalities. Finally, at-test comparison of the slopes of the linear fits of PET versus ASLΔCBF for all 3 ROI types indicated no significant difference from unity (P>.05).

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Interdependence of Regional and Global Cerebral Blood Flow during Visual Stimulation: An O-15-Butanol Positron Emission Tomography Study

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-200106000-00004 ◽

2001 ◽

Vol 21 (6) ◽

pp. 664-670 ◽

Cited By ~ 27

Author(s):

Lars J. Kemna ◽

Stefan Posse ◽

Lutz Tellmann ◽

Thomas Schmitz ◽

Hans Herzog

Keyword(s):

Positron Emission Tomography ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Visual Stimulation ◽

Emission Tomography ◽

Global Flow ◽

Positron Emission ◽

Global Cerebral Blood Flow ◽

Flow Changes ◽

O 15

The authors investigated the influence of variations in global cerebral blood flow (gCBF) on regional flow changes during visual stimulation. Global flow was varied using different end-expiratory CO2 values (Petco2) between 20 and 70 mm Hg. Visual stimulation was performed with a red LED-array flashing at 8 Hz. Blood flow was measured with O-15-butanol, continuous arterial blood sampling, and positron emission tomography (PET). Global flow changes surpassed the published values of O-15-H2O studies, better fitting the results of the inert gas technique (gCBF at 20, 40, and 70 mm Hg Petco2 ± SD was 31 ± 4, 48 ± 13, and 160 ± 50 mL 100 g−1 min−1, respectively). The relation between Petco2 and CBF in the current study was best described by an exponential rather than a linear function. At low Petco2, the activation-induced flow changes are moderately damped, whereas at high Petco2, they are nearly lost (ΔCBF (±SD): 52% ± 25%, 68% ± 22%, 16% ± 25% at Petco2 = 20, 40, 70 mm Hg, respectively).

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