Technetium using

Technetium-99m ("Tcm) is a radionuclide that finds many applications in nuclear medicine. Virtually all technetium used in nuclear medicine labs is prepared synthetically from other radioactive materials. "Tcm is produced by the (3 decay of "Mo as illustrated in the reaction below. "Mo is produced through fission of 235U or via the capture of a neutron by "Mo. 

Scheme 3 Basic organometallic compounds of technetium useful as starting materials for further syntheses...

Holm E, Gafvert T, Lindahl P, and Roos P (2000) In situ sorption of technetium using activated carbon. Applied Radiation and Isotopes 53 153. 

Neidhart, B., Bachmann, K, Kramer, S., Link, I. Selective separation of fission technetium using solid chlorides. Radiochem. Radioanal. Lett. 12, 59-69 (1972)... 

The isotope molybdenum-99 is produced in large quantity as the precursor to technetium-99y, a radionucleide used in numerous medical imaging procedures such as those of bone and the heart (see Medical imaging technology). The molybdenum-99 is either recovered from the fission of uranium or made from lighter Mo isotopes by neutron capture. Typically, a Mo-99 cow consists of MoO adsorbed on a lead-shielded alumina column. The TcO formed upon the decay of Mo-99 by P-decay, = 66 h, has less affinity for the column and is eluted or milked and either used directly or appropriately chemically derivatized for the particular diagnostic test (100). 

Each has been recovered and used in various quantities. Rhodium, palladium, and technetium have also been recovered for potential catalytic or precious metal appHcations (34,35). 

Certain neutral technetium complexes can be used to image cerebral perfusion (Fig. 4). Those in Figure 4a and 4b have been approved for clinical use. Two other complexes (Fig. 4c and 4d) were tested in early clinical trials, but were not developed further. An effective cerebral perfusion agent must first cross the blood brain barrier and then be retained for the period necessary for image acquisition. Tc-bicisate is retained owing to a stereospecific hydrolysis in brain tissue of one of the ester groups to form the anionic complex TcO(ECD) , which does not cross the barrier. This mechanism of retention is termed metaboHc trapping. 

Several hydrophilic, anionic technetium complexes can be used to perform imaging studies of the kidneys. Tc-Mertiatide (Fig. 5a) is rapidly excreted by active tubular secretion, the rate of which is a measure of kidney function. Tc-succimer (Fig. 5b), on the other hand, accumulates in kidney tissue thus providing an image of kidney morphology. 

Many kits contain the indicated biologically active ingredient in a lyophilized form with stannous chloride. A Tc-labeled radiopharmaceutical, which can be used for six hours, is formed when mixed with Tc pertechnetate. Preparation of the agent is at room temperature, unless otherwise stated. Technetium-99m. Available Tc kits are Hsted below. 

Technetium-9 9m sestamibi is used in myocardial perfusion imaging for the evaluation of ischemic heart disease. It is prepared from a lyophilized kit containing tetrakis(2-methoxy isobutyl isonittile) copper(I) tetrafluoroborate stored under nitrogen. Upon reconstitution with up to 5.6 GBq (150 mCi) of 99mTc pertechnetate, the product is formed by boiling for 10 minutes. 

Technetium-99m oxidronate is a bone imaging agent used to demonstrate areas of altered osteogenesis. It is rapidly cleared from the blood and taken up in areas of bone that are undergoing osteogenesis. The kit is a vial containing a lyophilized powder where sodium oxidronate is the active... 

Technetium-99m gluceptate is used in brain and kidney imaging. Sodium gluceptate is the active ingredient. The product is formed by the addition... 

Technetium-99m disofenin is used for hepatobiliary imaging. Disofenin (2,6-diisopropylphenylcarbamoyhnethyliminodiacetic acid) is the active ingredient. Product formation is accompHshed by addition of up to 3.7 GBq (100 mCi) of Tc pertechnetate. 

Technetium-99m albumin coUoid is cleared by the reticuloendothehal (RE) cells and is used for visualization of the RE system of the Hver, spleen, and bone marrow. The product is formed by the addition of up to 2.8 GBq (75 mCi) of Tc pertechnetate. 

Technetium-99m pyrophosphate is used for bone imaging. The compound appears to have an affinity for the hydroxyapatite crystals within bone, and is formed by addition of up to 7.4 GBq (200 mCi) pertechnetate. 

Technetium-99m mertiatide (A/-[Ai-[A/-[(benzoylthio)acetyl]glycyl]glycine) is a renal imaging agent. It is excreted by the kidneys via active tubular secretion and glomerular filtration. The kit vial is reconstituted by using 740—3700 MBq (20—100 mCi) of Tc pertechnetate and boiling for 10 minutes. 

Technetium-99m mebrofenin is an iminodiacetic acid derivative used as a hepatobiliary agent. The kit is suppHed as a single vial containing lyopbilized mebrofenin. The reconstituted kit has 18-hour usage, owing to the preservative, propylparaben. 

Technetium-99m exametazime [(RR,3 3)-4,8-diaza-3,6,6,9-tetramethylundecane-2,10-dionebisoxime] is used as an adjunct in the detection of altered regional cerebral perfusion in stroke. The kit for the preparation of the radiopharmaceutical is suppHed as a single dose vial. 

Technetium-99m tetrafosmin ( Tc-(V)02 (l,2-bis(bis(2-ethoxyethyl)phosphino)ethane) (see Fig. 3d)) is a myocardial perfusion agent. It is used as an adjunct in the diagnosis and localization of myocardial ischemia and/or infarction. 

Technetium-99m bicisate is a brain imaging agent that is used for localization of stroke. The lyopbilized kit contains ethyl cysteine dimer as the active ingredient. 

Technetium-99m coordination compounds are used very widely as noniavasive imaging tools (35) (see Imaging technology Radioactive tracers). Different coordination species concentrate ia different organs. Several of the [Tc O(chelate)2] types have been used. In fact, the large majority of nuclear medicine scans ia the United States are of technetium-99m complexes. Moreover, chiral transition-metal complexes have been used to probe nucleic acid stmcture (see Nucleic acids). For example, the two chiral isomers of tris(1,10-phenanthroline)mthenium (IT) [24162-09-2] (14) iateract differentiy with DNA. These compounds are enantioselective and provide an addition tool for DNA stmctural iaterpretation (36). 

The -y-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these "y-rays. 

Technetium-99m (the m signifies a metastable, or moderately stable, species) is generated in nuclear reactors and shipped to hospitals for use in medical imaging. The radioisotope has a half-life of 6.01 h. If a 165-mg sample of technetium-99m is shipped from a nuclear reactor to a hospital 125 kilometers away in a truck that averages 50.0 kmh. what mass of technetium-99m will remain when it arrives at the hospital ... 

Holman BL, Carvalho PA, Mendelson J, er al Brain perfusion is abnormal in cocaine-dependent polydrug users a study using technetium-99m-HMPAO and ASPECT. J Nucl Med 32 1206-1210, 1991... 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

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