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 (MROEF) with T2*-based methods. The goal of this study was to correct its effect and obtain more accurate estimates of vCBV and MROEF. 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 MROEF 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 MROEF was compared with and without DeltaB correction, no significant differences (P = 0. 467) were observed. The ability to simultaneously obtain vCBV and MROEF noninvasively may have profound clinical implications for the studies of cerebrovascular disease.