Haifeng Zeng1,2, Jiadi Xu1,2, Nirbhay N Yadav1,2, Michael T McMahon1,2, Bradley Harden3, Dominique Frueh3, and Peter C.M van Zijl1,2
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 2F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, United States, 3Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States
A two-step heteronuclear
enhancement approach to magnify 15N MRI signal through indirect
detection of water is described. Chemical Exchange Saturation Transfer (CEST)
works by continuously perturbation of the spin magnetization of the
exchangeable spins, and then through chemical exchange to accumulate this
perturbation on water proton for signal magnification. This perturbation is
mainly limited to saturation or excitation pulse on the exchangeable protons.
In this work, the signal of 15N is detected indirectly through the
water signal by first inverting selectively protons scalar-coupled to 15N
in the urea molecule, followed by chemical exchange of the amide proton to bulk
water.
