Test-retest reproducibility of a rapid method to measure brain oxygen metabolism

Abstract

Cerebral metabolic rate of oxygen (CMRO2) is an important index of tissue viability and brain function, but this parameter cannot yet be measured routinely on clinical scanners. Recently, a noninvasive technique was proposed which estimates global CMRO2 by concomitantly measuring oxygen-extraction-fraction using T2-relaxation-under-spin-tagging MRI and pulse oximetry, and cerebral-blood-flow using phase-contrast MRI. This study sought to establish a standard acquisition procedure for this technique and to evaluate its test-retest reproducibility in healthy subjects. Each subject was examined in five sessions and each session included two measurements. Intrasession, intersession, and intersubject coefficients of variation for CMRO2 were found to be 3.84 ± 1.44% (N = 7, mean ± standard deviation), 6.59 ± 1.56%, and 8.80% respectively. These reproducibility values were comparable or slightly superior to 15O positron emission tomography (PET) results reported in the literature. It was also found that oxygen-extraction-fraction and cerebral-blood-flow tended to co-vary across sessions (P = 0.002) and subjects (P = 0.01), and their coefficients of variation were greater than that of CMRO2. The simplicity and reliability features may afford this global CMRO2 technique great potential for immediate clinical applications. Copyright © 2012 Wiley Periodicals, Inc.