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.

When extracellular gadolinium-based agents are used for infarct size measurement, imaging parameters and timing are important because the kinetics of both normal and irreversibly injured myocardium must be considered. Manganese-based agents are highly specific and less sensitive to timing for infarct size determination, but further studies are required to determine if they are feasible for human use.

Abnormal-delta8-tetrahydrocannabinol (ABN-delta8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.

Although both MP-2269 and gadophrin-2 feature an albumin-binding capacity, only gadophrin-2 displayed a persistent necrosis-specific contrast enhancement in the rat model of reperfused liver infarction. Therefore, the role of albumin binding in the mechanisms of NACAs should be reevaluated.