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Application of 19F chemical shift imaging in studies of mice with orally administered 5‐fluorouracil

In vivo quantitative metabolic mapping is an ideal tool for pharmacokinetic studies. Oral 5‐fluorouracil (5‐FU) and its metabolites in mice were imaged simultaneously by the 19F fast spin echo (FSE) sequence using interleaved frequency selection at 9.4T. However, 5‐FU images in the small intestine have never been obtained regardless of concentration. The reason for the discrepancy between image intensity and concentration was T2. At a pH above 6, a dramatic decrease in T2 of a 19F 5‐FU signal in an aqueous solution was found; T2 was shorter in the small intestine (14 ms) than in the stomach (52 ms). The 19F CSI sequence in FID sampling mode was employed for detecting short T2 signals. With a 13‐min resolution time, the detection of the 5‐FU signals in the region of the small intestine (0.6 mmol/kg) was successful with a 5 × 5 mm2 in‐plane resolution. Furthermore, two signals separated by 2 ppm were clearly distinguishable, but failed to be separately detectable with the 19F FSE sequence. For quantitative simultaneous monitoring of 5‐FU and its metabolites of varying T2, the 19F CSI sequence in FID sampling mode was found to be superior to the 19F FSE sequence. Magn Reson Med 46:864–869, 2001. © 2001 Wiley‐Liss, Inc.