Jingwei Zhang BEng, Abstract Co-Author: Nothing to Disclose

Tian Liu PhD, Abstract Co-Author: Nothing to Disclose

Ajay Gupta MD, Abstract Co-Author: Nothing to Disclose

Pascal Spincemaille PhD, Abstract Co-Author: Nothing to Disclose

Thanh D. Nguyen PhD, Abstract Co-Author: Nothing to Disclose

Yi Wang PhD, Presenter: Nothing to Disclose

The cerebral metabolic rate of oxygen (CMRO2) and the oxygen extraction fraction (OEF) are important markers of neuronal function, particularly for managing ischemic stroke. In MRI, changes in local R2* or phase induced by the deoxyhemoglobin (dHb) magnetic field have been used to estimate CMRO2. However, R2* and phase images are contaminated by blooming artifacts and highly dependent on imaging parameters. Quantitative susceptibility mapping (QSM) by deconvolving MRI signal has been developed recently and can be used to accurately quantify dHb. The purpose of this study is to demonstrate the feasibility of using QSM to map CMRO2 in the healthy human brains when combined with cerebral perfusion measurements. 

Healthy volunteers (n=13) were recruited in this IRB approved MRI study using 3D gradient echo (GRE) and 3D arterial spin labeling (ASL) sequences on a 3T MRI system. dHb and Ferritin contributions to voxel susceptibility measured by QSM are resolved by performing two iso-CMRO2 measurements before and 25 minutes after an oral bolus of 200 mg caffeine. Pre- and post-caffeine QSM and CBF maps were used to generate CMRO2 and OEF maps maps using mass conservation and the assumption of iso-CMRO2 pre- and post-caffeine.

A statistically significant decrease in both susceptibility (-4.6 ± 1.8 ppb, p<0.01) and CBF (-23.1 ± 6.4 ml/100g/min, p<0.01) were measured in the cortical grey matter (GM) at 25 min post-caffeine compared to the pre-caffeine values. Consistent with the decrease in CBF after the caffeine challenge, OEF significantly increased from 22.5 ± 4.1% to 36.7 ± 5.3% (p<0.01) at 25 min post-caffeine. Mean CMRO2 in the cortical GM was 129 ± 21 μmol/100g/min.

QSM can be used in conjunction with cerebral perfusion measurements before and after a caffeine challenge to map CMRO2 and OEF in human brains.

CMRO2 and OEF maps generated from QSM and ASL have the potential to provide important markers of neuronal function in ischemic stroke and tumor.

Zhang, J, Liu, T, Gupta, A, Spincemaille, P, Nguyen, T, Wang, Y, Quantitative Mapping of Cerebral Metabolic Rate of Oxygen (CMRO2) Using Quantitative Susceptibility Mapping (QSM) and Quantitative Cerebral Perfusion.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14011086.html