CBF changes during brain activation: fMRI vs. PET

doi:10.1016/j.neuroimage.2004.01.017

NeuroImage

Volume 22, Issue 1, May 2004, Pages 443-446

https://doi.org/10.1016/j.neuroimage.2004.01.017 Get rights and content

Abstract

The changes in regional cerebral blood flow (rCBF) associated with the changes in neuronal activity are routinely measured both by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) techniques. However, direct comparison has not been performed to determine similarities and differences of PET and fMRI techniques in determining the rCBF response to brain activation. In the present study, a quantitative comparison of the functional rCBF maps obtained by PET and fMRI are made by performing an activation study in a single group of subjects under precisely controlled conditions and using identical visual stimuli. Twelve healthy volunteers participated in the activation study using the visual checkerboard stimulation with flip frequency at 8 Hz. By selecting the conjunctive pixels which activated on both PET and fMRI maps, the change in rCBF measured by fMRI was 36.95 ± 2.54%, whereas the value measured by PET was 38.79 ± 2.63%. Our results have demonstrated that there is no statistically significant difference (P = 0.22) in the measurements of rCBF change between MRI and PET methods.

Introduction

Positron emission tomography (PET) and magnetic resonance image (MRI) have been developed to be practical tools to measure cerebral blood flow (CBF) in vivo. PET technique has been validated with the standard tracer technique (Raichle et al., 1983) and is considered to be the “gold standard” in CBF measurements in humans. With advantages such as providing higher spatial resolution and repeatability, MRI is gaining popularity in generating CBF maps.

Two distinct MRI methods are currently used in obtaining CBF images: contrast-agent dynamical perfusion and arterial spin labeling (ASL) techniques Rosen et al., 1990, Detre et al., 1992. These two MRI methods have been compared with the PET technique in determining CBF values at resting state for both healthy volunteers and patients Carroll et al., 2002, Lin et al., 2001, Liu et al., 2001, Østergaard et al., 1998, Ye et al., 2000. Their previous results have showed that, at resting state, CBF values measured by MRI were not statistically different from the values measured by PET.

CBF-based PET and functional MRI (fMRI) techniques have been used in brain activation studies. Due to its simplicity and cost efficiency, ASL-based MRI technique has played a dominated role in fMRI field as compared to the contrast-agent dynamic perfusion MRI method. Although the resting-state CBF images obtained by both PET and MRI were compared in previous studies as mentioned above, no single study has compared the CBF brain activation maps generated by PET and fMRI techniques. By using an activation study under precisely controlled conditions in a single group of subjects and using identical visual stimuli, we have compared quantitatively the functional CBF maps obtained by PET and ASL-based fMRI.

Section snippets

Methods

Experiments were performed using a whole body 1.9-T GE/Elscint Prestige MRI scanner (GE/Elscint, Haifa, Israel) and a Siemens/CTI-HR+ whole body PET scanner (Siemens/CTI, Knoxville, TN, USA) at the Research Imaging Center, University of Texas Health Science Center at San Antonio (UTHSCSA). Twelve healthy subjects, six females and six males, aged 20–50 years, participated in this study. Subjects were recruited from local community and gave informed written consent. The protocol of this study was

Results

fMRI and PET maps of rCBF change during visual stimulation, averaged throughout 10 subjects, are shown in Fig. 1 (fMRI, left; PET, right). A highly focal statistically significant activation (P < 0.05), due to relative CBF change, can be seen in the visual cortex.

CBF comparisons with the conjunct ROI showed that the relative average CBF change in fMRI is 36.95 ± 2.54%, whereas in PET is 38.79 ± 2.63% (Fig. 2a). There was no statistically significant difference between fMRI and PET measurements

Discussions and conclusion

A direct comparison study of the relative changes in CBF response to visual stimulation measured by fMRI and PET was performed. Based on conjunction ROIs, the results have demonstrated that there is a reasonable agreement in the functional CBF maps generated by MRI and PET techniques. Both the percentage change of CBF and extent of activation area using two image modalities were examined, and their values agree well with each other. No statistically significant difference was found between MRI

Acknowledgements

JHG was supported by grants from NIH (RR17198 and AG19844), Office of National Drug Control Policy, USA (DABK39-03-C-0047), and National Natural Science Foundation of China (30128005). LHT was supported by a Hong Kong Research Grants Council Central Allocation Vote research grant (HKU 3/02C).

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View full text

CBF changes during brain activation: fMRI vs. PET

Abstract

Introduction

Section snippets

Methods

Results

Discussions and conclusion

Acknowledgements

Absolute quantification of cerebral blood flow with magnetic resonance, reproducibility of the method, and comparison with H215O positron emission tomography

J. Cereb. Blood Flow Metab.

Perfusion imaging

Med. Reson. Med.

Brain blood flow measured with intravenous H215O. I. Theory and error analysis

J. Nucl. Med.

The theory and application of the exchange of inert gas at the lungs and tissues

Pharmacol. Rev.

Quantification of relative cerebral blood flow change by flow-sensitive alternating inversion recovery (FAIR) technique: application to functional mapping

Magn. Reson. Med.

Global spatial normalization of human brain using convex hulls

J. Nucl. Med.

Quantitative measurements of cerebral blood flow in patients with unilateral carotid artery occlusion: a PET and MR study

J. Magn. Reson. Imaging

Absolute quantification of cerebral blood flow with magnetic resonance, reproducibility of the method, and comparison with H₂¹⁵O positron emission tomography

Brain blood flow measured with intravenous H₂¹⁵O. I. Theory and error analysis