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Quantification of oxygen metabolic rates in Human brain with dynamic 17 O MRI: Profile likelihood analysis
Author(s) -
Kurzhunov Dmitry,
Borowiak Robert,
Hass Helge,
Wagner Philipp,
Krafft Axel Joachim,
Timmer Jens,
Bock Michael
Publication year - 2017
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26476
Subject(s) - identifiability , magnetic resonance imaging , white matter , prior probability , nuclear medicine , positron emission tomography , nuclear magnetic resonance , chemistry , physics , mathematics , statistics , bayesian probability , medicine , radiology
Purpose Parameter identifiability and confidence intervals were determined using a profile likelihood (PL) analysis method in a quantification model of the cerebral metabolic rate of oxygen consumption (CMRO 2 ) with direct 17 O MRI. Methods Three‐dimensional dynamic 17 O MRI datasets of the human brain were acquired after inhalation of 17 O 2 gas with the help of a rebreathing system, and CMRO 2 was quantified with a pharmacokinetic model. To analyze the influence of the different model parameters on the identifiability of CMRO 2 , PLs were calculated for different settings of the model parameters. In particular, the 17 O enrichment fraction of the inhaled 17 O 2 gas, α , was investigated assuming a constant and a linearly varying model. Identifiability was analyzed for white and gray matter, and the dependency on different priors was studied. Results Prior knowledge about only one α ‐related parameter was sufficient to resolve the CMRO 2 nonidentifiability, and CMRO 2 rates (0.72–0.99 µmol/g tissue /min in white matter, 1.02–1.78 µmol/g tissue /min in gray matter) are in a good agreement with the results of 15 O positron emission tomography studies. Nonconstant α values significantly improved model fitting. Conclusion The profile likelihood analysis shows that CMRO 2 can be measured reliably in 17 O gas MRI experiment if the 17 O enrichment fraction is used as prior information for the model calculations. Magn Reson Med 78:1157–1167, 2017. © 2016 International Society for Magnetic Resonance in Medicine.