The interaction between magnetization transfer and blood-oxygen-level-dependent effects.
Low-power off-resonance spin-echo magnetization transfer (MT) imaging experiments with a long repetition time (TR) were performed on rat brain for a range of arterial PCO2 levels. The measured magnetization transfer ratio decreased with increased arterial PCO2 levels. When performing blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI)-type data analysis in which signal intensities were normalized to the normocapnic state, the CO2-based BOLD effect was much stronger with than without saturation. This increased effect is a consequence of the fact that the MT effect reduces the signal intensity in tissue more than in blood, thereby amplifying the contribution of the intravascular BOLD signal change to the overall BOLD effect. The results offer a potential approach to measure absolute cerebral blood volume in vivo and to amplify the BOLD effects for fMRI studies.
Zhou
Jinyuan
J
Division of MRI Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195, USA. jzhou@mri.jhu.edu
Payen
Jean-Francois
JF
van Zijl
Peter C M
PC
D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000166:cytology / Q000378:metabolism*; D001931:Brain Mapping / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation / Q000502:physiology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D010100:Oxygen / Q000097:blood*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002245:Carbon Dioxide; D010100:Oxygen