A two-step heteronuclear enhancement approach was combined with chemical exchange saturation transfer (CEST) to magnify 15N MRI signal of molecules through indirect detection via water protons. Previous CEST studies have been limited to radiofrequency (rf) saturation transfer or excitation transfer employing protons. Here, the signal of 15N is detected indirectly through the water signal by first inverting selectively protons that are scalar-coupled to 15N in the urea molecule, followed by chemical exchange of the amide proton to bulk water. In addition to providing a small sensitivity enhancement, this approach can be used to monitor the exchange rates and thus the pH sensitivity of the participating 15N-bound protons.
ASJC Scopus subject areas
- Colloid and Surface Chemistry