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MRI may be used to measure fractional changes in cerebral oxygen metabolism via a metabolic model. One step commonly used in this measurement is calibration with image data acquired during hypercapnia, which is a state of increased CO2 content of the blood. In this study some commonly used hypercapnia-inducing stimuli were compared to assess their suitability for the calibration step. The following stimuli were investigated: (a) inspiration of a mixture of 4% CO2, 21% O2 and balance N2; (b) 30-s breath holding; and (c) inspiration of a mixture of 4% CO2 and 96% O2 (i.e., carbogen). Measurements of BOLD and cerebral blood flow made on nine subjects during the different hypercapnia-inducing stimuli showed that each stimulus leads to a different calibration of the model. We argue that of the aforementioned stimuli, inspiration of 4% CO2, 21% O2 and balance N2 should be preferred for the calibration as the other stimuli produce responses that violate assumptions of the metabolic model.

Original publication

DOI

10.1002/mrm.21862

Type

Journal article

Journal

Magn Reson Med

Publication Date

02/2009

Volume

61

Pages

391 - 398

Keywords

Adult, Algorithms, Brain, Calibration, Humans, Hypercapnia, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Male, Oximetry, Oxygen, Oxygen Consumption, Reproducibility of Results, Sensitivity and Specificity