Michael A. Chappell1,2, Manus J. Donahue3,
Yee Kai Tee1, Peter Jezzard2, Stephen J. Payne1
1Institute of Biomedical Engineering,
University of Oxford, Oxford, United Kingdom; 2FMRIB Centre,
University of Oxford, Oxford, United Kingdom; 3School of Medicine,
Vanderbilt University, Nashville, TN, United States
Amide Proton Transfer contrast arises from the exchange of endogenous amide and water protons. The magnitude of the effect depends both on the amide proton concentration and exchange rate, but it is only the latter that relates to pH. In theory it is possible to quantify both concentration and exchange rate using a spectrum sampled at a number of saturation frequencies and model-based fitting. We investigated the feasibility of the approach for in vivo APT using a probabilistic algorithm and a 3-pool model. In 7 healthy subjects estimated exchange rate images were relatively homogenous with an estimated pH around 6.9.