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Measurement of regional blood oxygenation and cerebral hemodynamics
Author(s) -
Hoppel Bernice E.,
Weisskoff Robert M.,
Thulborn Keith R.,
Moore John B.,
Kwong Kenneth K.,
Rosen Bruce R.
Publication year - 1993
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910300609
Subject(s) - hemodynamics , oxygenation , cerebrovascular circulation , blood oxygenation , medicine , cardiology , cerebral blood flow , functional magnetic resonance imaging , radiology
An echo planar linewidth mapping technique, Shufflebutt , has allowed temporal measurements of changes in linewidth caused by static inhomogeneities (ΔLWSI) and transverse relaxation rate (ΔR2) in models of hypoxia and hypercapnia. We demonstrate these changes are due to intravascular susceptibility differences(Δ X ) between the blood and tissue. Contrast agent injections at a /Δ X equivalent to that of deoxygenatetd blood showed a twofold difference between the contrast agent and physiological anoxia values. Hypercapnia decreased both Δ LWSI and Δ R2 consistent with an increase in blood oxygenation. We attribute these findings to constant oxygen extraction during an increase in blood flow, resulting in less deoxygenated venous blood and thus reduced Δ X . For in vivo perturbations we found that Δ R /Δ R 2′ ≈ 0.33, a ratio much different from that measured in whole blood phantoms (Δ R /Δ R 2′ ≈ 2). This demonstrates that signal changes in these studies are produced predominantly by dephasing of extravascular protons due to field inhomogeneities produced by intravascular deoxygenated hemoglobin (deoxyHb).