BOLD Based Functional MRI at 4 Tesla Includes a Capillary Bed Contribution: Echo‐Planar Imaging Correlates with Previous Optical Imaging Using Intrinsic Signals

Ravi S. Menon, Seiji Ogawa, Xiaoping Hu, John P. Strupp, Peter Anderson, Kamil Ugurbil

Research output: Contribution to journalArticlepeer-review

329 Scopus citations

Abstract

We show that the EPI time course in functional MR imaging at 4 Tesla displays a multiphasic response in response to photic stimulation. Focal areas of gray matter display an initial negative change in signal intensity that reaches a maximum of 1 % about 2 s after the onset of photic stimulation. This component then changes sign, reaching a positive maximum about 5 s after the onset of the stimulus. Other areas, including those where draining veins are visible, show only a positive signal change, reaching a maximum of about 6% after the onset of the visual stimulus. These time constants are in very good agreement with published data obtained with intrinsic optical mapping techniques, where a deoxygenation phase has been shown to occur in functionally specific cortical columns, followed by an increase in blood volume which is more distributed in nature. Thus, we believe there is strong evidence that a sensitivity to capillary oxygenation state is present in high S/N functional MR images obtained with EPI at 4 T.

Original languageEnglish (US)
Pages (from-to)453-459
Number of pages7
JournalMagnetic resonance in medicine
Volume33
Issue number3
DOIs
StatePublished - Mar 1995

Keywords

  • cerebral blood flow
  • functional MR
  • hemoglobin
  • oxygen

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