In vivo fluorine‐19 MR imaging: Relaxation enhancement with Gd‐DTPA

Abstract

The lack of a naturally occurring background signal from fluorine in magnetic resonance (MR) imaging makes fluorinated compounds potentially attractive candidates for tissue-specific MR contrast agents. Problems associated with the in vivo use of fluorinated compounds are toxicity, which limits the amount of agent that can be used; multiple resonance lines; and an excessively long T1, which leads to long sequence TRs and consequently long imaging times. Many fluorinated agents also possess complex MR spectra that result in chemical shift artifacts if not corrected. The authors demonstrate the use of an extracellular fluorinated agent with a single MR peak for selective imaging of a brain abscess in an animal model and show that the image signal per unit of acquisition time can be enhanced through the use of a T1 relaxation agent, gadolinium diethylenetriamine-pentaacetic acid (DTPA). Trifluoromethylsulfonate was administered at a fluorine-19 dose of 4 mmol/kg, and fluorine images of the induced abscess were acquired before and after the 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 approximately four (4.0 +/- 0.8) with use of a 500/12 (TR msec/TE msec) spin-echo sequence.

Fluorine electron double resonance imaging for 19F MRI in low magnetic fields

“…The relative sensitivity of 19 F is 0.84 times that of 1 H at a constant magnetic field. The small difference between the gyromagnetic ratios of 1 H and 19 F offers the advantage that the same 1 H imaging NMR hardware may readily be adapted for 19 F imaging as well. But the very low natural concentration (ϳ4 M) of 19 F metabolites in biological samples demands the use of exogenous 19 F compounds as "tracers" for imaging applications.…”

“…Among the other nuclei studied, 19 F is an attractive alternative for in vivo imaging because it is a spin 1/2 nucleus with high gyromagnetic ratio (␥ ϭ 40.05 MHz/T), second only to that of 1 H, and 100% natural abundance (1)(2)(3). The relative sensitivity of 19 F is 0.84 times that of 1 H at a constant magnetic field.…”

“…Among the other nuclei studied, 19 F is an attractive alternative for in vivo imaging because it is a spin 1/2 nucleus with high gyromagnetic ratio (␥ ϭ 40.05 MHz/T), second only to that of 1 H, and 100% natural abundance (1)(2)(3). The relative sensitivity of 19 F is 0.84 times that of 1 H at a constant magnetic field. The small difference between the gyromagnetic ratios of 1 H and 19 F offers the advantage that the same 1 H imaging NMR hardware may readily be adapted for 19 F imaging as well.…”

“…The small difference between the gyromagnetic ratios of 1 H and 19 F offers the advantage that the same 1 H imaging NMR hardware may readily be adapted for 19 F imaging as well. But the very low natural concentration (ϳ4 M) of 19 F metabolites in biological samples demands the use of exogenous 19 F compounds as "tracers" for imaging applications. However, in such "tracer" studies the low natural occurrence produces negligible competing background signal and hence alleviates the implementation of special techniques for background suppression.…”

“…The feasibility of 19 F imaging was first demonstrated nearly 25 years ago (4). Since then, 19 F imaging has been used to study biological processes including metabolism (5), tumor growth (6,7), cerebral blood flow (8), drug distribution (9 -11), enzyme activities (12), blood oxygenation (13)(14)(15), perfusion (16), etc.…”