Direct Measurement of Cellular Oxygen Consumption
Increased 17O MRS/I sensitivity at 9.4 T and 16.4 T
Researchers at the Center for Magnetic Resonance Research, at the University of Minnesota, have successfully applied high field and ultra-high field 17O magnetic resonance spectroscopy (MRS) to visualize the cerebral metabolic rate of oxygen consumption via the detection of natural abundance H217O. The research investigates in vivo assessment of oxidative metabolism. Altered oxidative metabolism is associated with brain function and neurological disease.
Comprehension of metabolic change from normal to diseased tissue has been held back due to the lack of robust and straightforward imaging mechanisms to investigate cellular oxidative metabolism. The research team has developed a viable method that uses 17O magnetic resonance spectroscopy/imaging (MRS/I) to provide the specificity needed. The direct detection of the dynamics of metabolic H217O production allows measurement and quantification of the cellular oxygen consumption rate in a non-destructive, in vivo analysis.
In vivo 17O MRS approaches for the measurement of the cerebral metabolic oxygen consumption (CMRO2) rate and the myocardial oxygen consumption rate in animals and humans provide the opportunity for research into brain function and neurological disease.
The study employed high field 9.4 Tesla and ultra-high field (UHF) 16.4 Tesla large bore magnetic resonance imaging (MRI) instruments to measure and compare 17O sensitivity in a phantom solution and in rat brain at two high field strengths. The aim was to quantify the possible signal-to-noise ratio gain for in vivo 17O MRS/I applications.
The Ultra-high Field Advantage
The results demonstrate a 2.5-2.9-fold signal-to-noise ratio gain at 16.4 T, compared to 9.4 T in both phantom and rat brain analysis. A smaller measurement variance (2-4-fold reduction) was obtained at 16.4 T compared to 9.4 T, indicating an improved signal stability. The improvements at ultra-high field strength indicate a significant advantage. More reliable imaging of CMRO2 is expected from the direct detection of small dynamic changes of metabolically generated H217O signal during a brief 17O2 inhalation at ultra-high magnetic fields.
The significant signal-to-noise ratio improvements achievable at 16.4 T could benefit the 3D CMRO2 imaging based on the 17O MRS/I methods, paving the way to improved spatial and temporal resolution in detecting an altered oxidative metabolism associated with brain function and neurological disease.
Read the full paper here.
Zhu XH, Chen W. In vivo oxygen-17 NMR for imaging brain oxygen metabolism at high field. Prog Nucl Magn Reson Spectrosc. 2011 Nov;59(4):319-35. doi: 10.1016/j.pnmrs.2011.04.002. Epub 2011 Apr 23. PMID: 22027341; PMCID: PMC3202696.
Lu M, Zhang Y, Ugurbil K, Chen W, Zhu XH. In vitro and in vivo studies of 17O NMR sensitivity at 9.4 and 16.4 T. Magn Reson Med. 2013 Jun;69(6):1523-7. doi: 10.1002/mrm.24386. Epub 2012 Jul 6. PMID: 22777729; PMCID: PMC3470764.