The relationship between cerebral blood flow and volume in humans.
The purpose of this study was to establish the relationship between regional CBF and CBV at normal, resting cerebral metabolic rates. Eleven healthy volunteers were investigated with PET during baseline conditions, and during hyper- and hypocapnia. Values for rCBF and rCBV were obtained using 15O-labelled water and carbon monoxide, respectively. The mean value of rCBF using PET was 62 +/- 18 ml 100 g(-1) min(-1) during baseline conditions, with an average increase of 46% during hypercapnia, and a decrease of 29% during hypocapnia; baseline rCBV was 7.7 ml/100 g, with 27% increase during hypercapnia and no significant decrease during hypocapnia. A regionally uniform exponential relationship was confirmed between PaCO2 and rCBF as well as rCBV. It is shown that the theoretical implication of this is that the rCBV vs. rCBF relationship should be modelled by a power function; however, due to pronounced intersubject variability, the goodness of fit for linear and nonlinear models were not significantly different. The results of the study are applied to a numerical estimation of regional brain deoxy-haemoglobin content. Independently of the choice of model for the rCBV vs. rCBF relationship, a nonlinear deoxy-haemoglobin vs. rCBF relationship was predicted, and the implications for the BOLD response are discussed.
Rostrup
Egill
E
Danish Research Center for Magnetic Resonance, DK-2650, Copenhagen University Hospital, Hvidovre, Denmark.
Knudsen
Gitte M
GM
Law
Ian
I
Holm
Søren
S
Larsson
Henrik B W
HB
Paulson
Olaf B
OB
D000328:Adult; D001810:Blood Volume / Q000502:physiology*; D001921:Brain / Q000098:blood supply*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016857:Hypocapnia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D017711:Nonlinear Dynamics; D010101:Oxygen Consumption / Q000502:physiology; D049268:Positron-Emission Tomography; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology
D006454:Hemoglobins; C100003:deoxyhemoglobin