Synthesis and biodistribution of nitrido technetium-99m radiopharmaceuticals with dithiophosphinate ligands: a class of brain imaging agents.

The symmetrical complexes [99mTc][TcN(R2PS2)2] [R = CH3, CH2CH3, CH2CH2CH3, CH2(CH3)2], and the unsymmetrical complex [99mTc][TcN(Me2PS2)(Et2PS2)] have been prepared, at tracer level, through a two-step procedure involving the preliminary formation of a prereduced technetium nitrido intermediate followed by substitution reaction onto this species by the appropriate dithiophosphinate ligand [R2PS2]Na. The chemical identity of the resulting complexes have been established by comparison with the corresponding 99Tc-analogs prepared, at macroscopic level, by reacting the complex [99TcNCl4] [n-Bu4N] (n-Bu = n-butyl) with an excess of ligand in methanol, and characterized by elemental analyses and spectroscopic techniques. The complexes are neutral and lipophilic, and possess a square pyramidal geometry, with an apical Tc identical to N group and two dithiophosphinate ligands spanning the four positions on the basal plane through the four sulfur atoms of the > PS2 group. In vitro studies showed that these radiopharmaceuticals are stable in solution and that their chemical identity was not altered after incubation with rat blood. Biodistribution studies have been carried out in rats and primates. The results demonstrate that these compounds are significantly retained into the brain of these animals for a prolonged time. Planar gamma camera images have been obtained in monkeys showing a good visualization of the cerebral region. However, the existence of persistent blood activity yields a brain/blood ratio lower than that observed with other 99mTc-based brain perfusion imaging agents.

[Biodistribution of new polynitroxides using electron paramagnetic resonance]. / Biodistribution de nouveaux polynitroxydes par résonance paramagnétique électronique.

The most important paramagnetic contrast agents used in Nuclear Magnetic Resonance Imaging are limited to a few metal complexes such Gd-DTPA or stable free radicals such as nitroxides simply functionalized. We studied the biodistribution of new polynitroxides agents by Electronic Paramagnetic Resonance in Sprague Dawley rats. Three of the six different polynitroxides agents studied, showed an interesting and selective localisation in the lungs, heart and liver.

[Unidimensional imaging. A simple method for evaluating the efficacy of a contrast agent in magnetic resonance imaging. Application of new nitroxides]. / L'imagerie unidimensionnelle. Une méthode simple pour évaluer l'efficacité d'un agent de contraste en imagerie par résonance magnétique. Application à de nouveaux nitroxydes.

We present an experimental set-up of one-dimension imaging which permits on a conventional NMR spectrometer, to measure the difference in relaxation time T1 of two organ samples, one normal and the other injected with a contrast agent. Using that technique and M.R.I. two new nitroxides reveal a substantial contrast effect for kidneys and heart.

Synthesis and biodistribution of labelled p-iodo phentermine (IP), N,N,-dimethyl-p-iodo phentermine (IDMP) and N-isopropyl-p-iodo phentermine (IIP) in rats.

p-Iodo-phentermine (IP) and two of its derivatives, N,N,-dimethyl-p-iodo-phentermine (IDMP) and N-isopropyl-p-iodo-phentermine (IIP) were synthesized and radiolabelled with iodine by isotopic exchange. They were evaluated as potential brain imaging agents and compared to IAMP biodistribution in rats did not show any superiority to IAMP.