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. 2015 Oct;74(4):945-52.
doi: 10.1002/mrm.25463. Epub 2014 Sep 26.

Quantitative mapping of cerebral metabolic rate of oxygen (CMRO2 ) using quantitative susceptibility mapping (QSM)

Jingwei Zhang  1   2 , Tian Liu  3 , Ajay Gupta  2 , Pascal Spincemaille  2 , Thanh D Nguyen  2 , Yi Wang  1   2
Affiliations

Quantitative mapping of cerebral metabolic rate of oxygen (CMRO2 ) using quantitative susceptibility mapping (QSM)

Jingwei Zhang et al. Magn Reson Med. 2015 Oct.

Abstract

Purpose: To quantitatively map cerebral metabolic rate of oxygen ( CMRO2) and oxygen extraction fraction ( OEF) in human brains using quantitative susceptibility mapping (QSM) and arterial spin labeling-measured cerebral blood flow (CBF) before and after caffeine vasoconstriction.

Methods: Using the multiecho, three-dimensional gradient echo sequence and an oral bolus of 200 mg caffeine, whole brain CMRO2 and OEF were mapped at 3-mm isotropic resolution on 13 healthy subjects. The QSM-based CMRO2 was compared with an R2*-based CMRO2 to analyze the regional consistency within cortical gray matter (CGM) with the scaling in the R2* method set to provide same total CMRO2 as the QSM method for each subject.

Results: Compared to precaffeine, susceptibility increased (5.1 ± 1.1 ppb; P < 0.01) and CBF decreased (-23.6 ± 6.7 ml/100 g/min; P < 0.01) at 25-min postcaffeine in CGM. This corresponded to a CMRO2 of 153.0 ± 26.4 μmol/100 g/min with an OEF of 33.9 ± 9.6% and 54.5 ± 13.2% (P < 0.01) pre- and postcaffeine, respectively, at CGM, and a CMRO2 of 58.0 ± 26.6 μmol/100 g/min at white matter. CMRO2 from both QSM- and R2*-based methods showed good regional consistency (P > 0.05), but quantitation of R2*-based CMRO2 required an additional scaling factor.

Conclusion: QSM can be used with perfusion measurements pre- and postcaffeine vascoconstriction to map CMRO2 and OEF.

Keywords: OEF; QSM; quantitative CMRO2.

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Figures

Figure 1
Figure 1
Example of GM and WM masks on a mid-brain slice. The GM mask is segmented into six regions corresponding to different vascular territories as shown. The masks cover the supratentorial brain parenchyma from the vertex to the superior aspect of the cerebellum.
Figure 2
Figure 2
An example of QSM and CBF maps acquired pre- and post-caffeine and the derived CMRO2 and OEF maps in a healthy subject (subject 12).
Figure 3
Figure 3
An example of volumetric pre- and post-caffeine OEF and CMRO2 maps using the QSM-based method, and T2 weighted images of a healthy subject (subject 7). The locations of the slices are marked on the scout images shown on the right.
Figure 4
Figure 4
Examples of QSM- and R2* -based CMRO2 maps of two representative subjects (subject 1 and 4). The locations of the slices are marked on the scout images.
See this image and copyright information in PMC

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