Susceptibility contrast imaging of CO2-induced changes in the blood volume of the human brain.
OBJECTIVE
To investigate changes in the regional cerebral blood volume (rCBV) in human subjects during rest and hypercapnia by MR imaging, and to compare the results from contrast-enhanced and noncontrast-enhanced susceptibility-weighted imaging.


METHODS
Five healthy volunteers (aged 24-29 years) were studied during inhalation of atmospheric air and 7% CO2. A bolus injection of Gd-DTPA was given during the acquisition of a series of susceptibility-weighted, fast gradient echo images (TR/TE = 27/22 ms). The images were converted to delta R2* maps, and CBV was calculated pixelwise by fitting a gamma-variate function to the data. The tissue concentration vs time curves were deconvoluted using an input function obtained by arterial sampling.


RESULTS
The ratio of gray to white matter CBV (1.9-2.5) as well as the fractional increase in rCBV during hypercapnia (about 30%) was found to be in accordance with results obtained by other methods. Noncontrast functional MR (fMR) imaging showed signal increases in gray matter, but also inconsistent changes in some white matter regions.


CONCLUSIONS
In this experiment, contrast-enhanced imaging seemed to show a somewhat higher sensitivity towards changes in cerebral hemodynamics than noncontrast-enhanced imaging. The results of the deconvolution analysis suggested that perfusion calculation by conventional tracer kinetic methods may be impracticable because of nonlinear effects in contrast-enhanced MR imaging.
Rostrup
E
E
Danish Research Center of Magnetic Resonance, Hvidovre Hospital, University of Copenhagen, Denmark.
Larsson
H B
HB
Toft
P B
PB
Garde
K
K
Ring
P B
PB
Henriksen
O
O
D000280:Administration, Inhalation; D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply*; D002245:Carbon Dioxide / Q000008:administration & dosage; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology; D003287:Contrast Media; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009942:Organometallic Compounds; D004369:Pentetic Acid / Q000031:analogs & derivatives*; D012680:Sensitivity and Specificity
D003287:Contrast Media; D009942:Organometallic Compounds; D002245:Carbon Dioxide; D004369:Pentetic Acid; D019786:Gadolinium DTPA