Quantitative Bayesian model-based analysis of amide proton transfer MRI
Journal
Magnetic Resonance in Medicine
Journal Volume
70
Journal Issue
2
Pages
556-567
Date Issued
2013
Author(s)
Abstract
Amide Proton Transfer (APT) reports on contrast derived from the exchange of protons between amide groups and water. Commonly, APT contrast is quantified by asymmetry analysis, providing an ensemble contrast of both amide proton concentration and exchange rate. An alternative is to sample the off-resonant spectrum and fit an exchange model, permitting the APT effect to be quantified, correcting automatically for confounding effects of spillover, field inhomogeneity, and magnetization transfer. Additionally, it should permit amide concentration and exchange rate to be independently quantified. Here, a Bayesian method is applied to this problem allowing pertinent prior information to be specified. A three-pool model was used incorporating water protons, amide protons, and magnetization transfer effect. The method is demonstrated in simulations, creatine phantoms with varying pH and in vivo (n = 7). The Bayesian model-based approach was able to quantify the APT effect accurately (root-mean-square error < 2%) even when subject to confounding field variation and magnetization transfer effect, unlike traditional asymmetry analysis. The in vivo results gave approximate APT concentration (relative to water) and exchange rate values of 3 × 10-3 and 15 s -1. A degree of correlation was observed between these parameter making the latter difficult to quantify with absolute accuracy, suggesting that more optimal sampling strategies might be required. ? 2012 Wiley Periodicals, Inc.
Subjects
Bayesian networks
Chemical analysis
Finance
Mean square error
Proton transfer
Saturation magnetization
Amide proton transfers
Bayesian model-based analysis
Chemical exchange saturation transfer
Degree of correlations
Field inhomogeneity
Magnetization transfer
Resonant spectrum
Root mean square errors
Amides
amide
creatine
proton
water
adult
amide proton transfer magnetic resonance imaging
article
Bayes theorem
controlled study
human
human experiment
in vivo study
magnetism
measurement accuracy
normal human
nuclear magnetic resonance imaging
nuclear magnetic resonance scanner
pH
phantom
proton transport
quantitative analysis
simulation
SDGs
Type
journal article