Fluorine-19 fast recovery fast spin echo imaging for mapping 5-fluorouracil.

We investigated the effects of fast recovery (FR) to increase the sensitivity of fluorine-19 ((19)F) fast spin echo (FSE) in mapping 5-fluorouracil (5-FU) and its metabolites. We added an additional 90 degrees pulse (which flips back longitudinal magnetization at the end of the sequence) to the chemical shift selective (19)F FSE pulse sequence. In 5-FU solution, FR remarkably improved the signal-to-noise (S/N) ratio of (19)F 5-FU images, having higher effects with shorter repetition time and smaller echo train numbers. In animal studies, FR produced a conspicuous increase in (19)F signals in the urinary bladder. FR effects for (19)F signals in the liver were smaller than those in other organs but still substantial. Utilization of FR in (19)F FSE images promises more sensitive observation of (19)F metabolite maps of 5-FU and other (19)F-containing compounds that have relatively long relaxation times.