Fig. 2.

15N spectrum and image of 15N-imidazole using the frequency converter interfaced to a clinical 3T MR scanner that was not equipped with multinuclear hardware. (A) 15N MR spectrum of doubly labeled 15N-imidazole, which is a planar 5-membered ring containing two nitrogens. Because hydrogen can bind in rapid exchange to either 15N atom, the two 15N atoms are in equivalent tautomeric forms and thus, appear as a single peak in the 15N MR spectrum. (B) Axial 15N image (color) of the 15N-imidazole phantom superimposed on its T1-weighted proton image (gray scale).