Evaluation of MR-derived cerebral oxygen metabolic index in experimental hyperoxic hypercapnia, hypoxia, and ischemia.

Abstract

BACKGROUND AND PURPOSE:

A noninvasive MRI method to measure cerebral oxygen metabolism has the potential to assess tissue viability during cerebral ischemia. The purposes of this study were to validate MR oxygenation measurements across a wide range of global cerebral oxygenation and to examine the spatiotemporal evolution of oxygen metabolism during focal middle cerebral artery occlusion in rats.

METHODS:

A group of rats (n=28) under normal, hyperoxic hypercapnia and hypoxia were studied to compare MR-measured cerebral oxygen saturation (O(2)Sat(MRv)) with blood gas oximetry measurements in the jugular vein (O(2)Sat(JV)) and superior sagittal sinus (O(2)Sat(SSS)). In a separate group of rats (n=31), MR-measured cerebral oxygen metabolic index (MR_COMI) was acquired at multiple time points during middle cerebral artery occlusion. Histogram analysis was performed on the normalized MR_COMI (rMR_COMI) to examine evolution of oxygen metabolism during acute ischemia.

RESULTS:

Highly linear relationships were obtained between O(2)Sat(MRv) and O(2)Sat(JV)/O(2)Sat(SSS) in rats under global cerebral oxygenation alterations. In the focal ischemia study, rMR_COMI values were significantly lower within the areas of eventual infarction than other regions. Moreover, the rMR_COMI values within the ischemic territory decreased with time, concomitant with an increase in the number of voxels with severely impaired oxygen metabolism.

CONCLUSIONS:

Accurate estimates of O(2)Sat(MRv) can be obtained across a broad and physiologically relevant range of cerebral oxygenation. Furthermore, this method demonstrates a dynamic alteration of cerebral oxygen metabolism during acute ischemia in rats.

• Authors: Hongyu An, Qingwei Liu, Yasheng Chen, Weili Lin
• Journal: Stroke (Stroke) Vol. 40 Issue 6 Pg. 2165-72 (Jun 2009) ISSN: 1524-4628 [Electronic] United States
• PMID: 19359642 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Topics

• Animals
• Brain Chemistry (physiology)
• Brain Ischemia (metabolism)
• Calibration
• Data Interpretation, Statistical
• Hydrogen-Ion Concentration
• Hypercapnia (metabolism)
• Hyperoxia (metabolism)
• Image Processing, Computer-Assisted
• Magnetic Resonance Imaging
• Magnetic Resonance Spectroscopy
• Male
• Middle Cerebral Artery (physiology)
• Oxygen Consumption (physiology)
• Rats
• Rats, Long-Evans