Cerebral oxygen extraction fraction and cerebral venous blood volume measurements using MRI: effects of magnetic field variation.
The presence of magnetic background field inhomogeneity (DeltaB) may confound quantitative measures of cerebral venous blood volume (vCBV) and cerebral oxygen extraction fraction (MR_OEF) with T2*-based methods. The goal of this study was to correct its effect and obtain more accurate estimates of vCBV and MR_OEF. A 3D high-resolution gradient echo sequence was employed to obtain DeltaB maps by two algorithms. The DeltaB maps were then used to recover the signal loss in images acquired by a 2D multiecho gradient echo / spin echo sequence. Finally, both quantitative estimates of MR_OEF and vCBV were obtained from the DeltaB- corrected 2D multiecho gradient echo / spin echo images. A total of 12 normal subjects were studied. An overestimated vCBV was observed in the brain (4.29 +/- 0.78%) prior to DeltaB correction, while the measured vCBV was substantially reduced after DeltaB correction. Whole brain vCBV of 2.97 +/- 0.44% and 2.68 +/- 0.47% were obtained by the two different DeltaB correction methods, in excellent agreement with the reported results in the literature. Furthermore, when MR_OEF was compared with and without DeltaB correction, no significant differences (P = 0.467) were observed. The ability to simultaneously obtain vCBV and MR_OEF noninvasively may have profound clinical implications for the studies of cerebrovascular disease.
An
Hongyu
H
Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
Lin
Weili
W
D000465:Algorithms; D001811:Blood Volume Determination / Q000379:methods*; D001921:Brain / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008962:Models, Theoretical; D010101:Oxygen Consumption / Q000502:physiology*; D019047:Phantoms, Imaging; D014680:Veins / Q000502:physiology