In vivo determination of absolute cerebral blood volume using hemoglobin as a natural contrast agent: An MRI study using altered arterial carbon dioxide tension

John A. Ulatowski, Joni M.E. Oja, Jose I. Suarez, Risto A. Kauppinen, Richard J. Traystman, Peter C.M. Van Zijl

Research output: Contribution to journalArticle

Abstract

The ability of the magnetic resonance imaging transverse relaxation time, R2 = l/T2, to quantify cerebral blood volume (CBV) without the need for an exogenous contrast agent was studied in cats (n = 7) under pentobarbital anesthesia. This approach is possible because R2 is directly affected by changes ill CBF, CBV, CMRO2, and hematocrit (Hct), a phenomena better known as the blood-oxygenation-level-dependent (BOLD) effect. Changes in CBF and CBV were accomplished by altering the carbon dioxide pressure, PaCO2, over a range from 20 to 140 mm Hg. For each PaCO2 value, R2 in gray and white matter were determined using MRI, and the whole-brain oxygen extraction ratio was obtained from arteriovenous differences (sagittal sinus catheter). Assuming a constant CMRO2, the microvascular CBV was obtained from an exact fit to the BOLD theory for the spin-echo effect. The resulting CBV values at normal PaCO2 and normalized to a common total hemoglobin concentration of 6.88 mmol/L were 42 ± 18 μL/g (n = 7) and 29 ± 19 μL/g (n = 5) for gray and white matter, respectively, in good agreement with the range of literature values published using independent methodologies. The present study confirms the validity of the spin-echo BOLD theory and, in addition, shows that blood volume can be quantified from the magnetic resonance imaging spin relaxation rate R2 using a regulated carbon dioxide experiment.

Original languageEnglish (US)
Pages (from-to)809-817
Number of pages9
JournalJournal of Cerebral Blood Flow and Metabolism
Volume19
Issue number7
DOIs
StatePublished - Jan 1 1999

Keywords

  • BOLD
  • Carbon dioxide
  • Cerebral blood volume
  • MRI
  • Spin-echo
  • Transverse relaxation rate R

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine

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