TY - JOUR
T1 - In vivo determination of absolute cerebral blood volume using hemoglobin as a natural contrast agent
T2 - An MRI study using altered arterial carbon dioxide tension
AU - Ulatowski, John A.
AU - Oja, Joni M.E.
AU - Suarez, Jose I.
AU - Kauppinen, Risto A.
AU - Traystman, Richard J.
AU - Van Zijl, Peter C.M.
PY - 1999
Y1 - 1999
N2 - 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.
AB - 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.
KW - BOLD
KW - Carbon dioxide
KW - Cerebral blood volume
KW - MRI
KW - Spin-echo
KW - Transverse relaxation rate R
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U2 - 10.1097/00004647-199907000-00012
DO - 10.1097/00004647-199907000-00012
M3 - Article
C2 - 10413037
AN - SCOPUS:0033503669
SN - 0271-678X
VL - 19
SP - 809
EP - 817
JO - Journal of Cerebral Blood Flow and Metabolism
JF - Journal of Cerebral Blood Flow and Metabolism
IS - 7
ER -