IN-VIVO F-19 MR-IMAGING - RELAXATION ENHANCEMENT WITH GD-DTPA

The lack of a naturally occurring background signal from fluorine in m agnetic resonance (MR) imaging makes fluorinated compounds potentially attractive candidates for tissue-specific MR contrast agents. Problem s associated with the in vivo use of fluorinated compounds are toxicit y, which limits the amount of agent that can be used; multiple resonan ce lines; and an excessively long T1, which leads to long sequence TRs and consequently long imaging times. Many fluorinated agents also pos sess complex MR spectra that result in chemical shift artifacts if not corrected. The authors demonstrate the use of an extracellular fluori nated agent with a single MR peak for selective imaging of a brain abs cess in an animal model and show that the image signal per unit of acq uisition time can be enhanced through the use of a T1 relaxation agent , gadolinium diethylenetriamine-pentaacetic acid (DTPA). Trifluorometh ylsulfonate was administered at a fluorine-19 dose of 4 mmol/kg, and f luorine images of the induced abscess were acquired before and after t he injection of a standard dose of Gd-DTPA (0.1 mmol/kg); non-section- selected projection images were used. Typical imaging times were less than 5 minutes. The signal enhancement factor achieved was approximate ly four (4.0 +/- 0.8) with use of a 500/12 (TR msec/TE msec) spin-echo sequence.