99mTc-Pertechnetate

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. 

The effective (whole body) dose equivalent for pertechnetate " Tc is 0.013 mSv/MBq (International Commission on Radiological Protection 1987). The effective dose in adults (70 kg) resulting from 75 MBq of intravenously injected Tc-pertechnetate for thyroid scintigraphy is approximately 1 mSv. The absorbed radiation dose to the thyroid (without a blocking agent) resulting from an intravenous injection of 75 MBq of 99mTc-pertechnetate corresponds to 1.7 mCy. 

System I Separation of Tc-pertechnetate in organic solvent methyl ethyl ketone (MEK) Tc-diphosphonates and hydrolized Tc activity remain at the start free 99mTc-pertechnetate is measured at the solvent front. 

Technetium is usually supplied in the form of heptavalent pertechnetate. Consequently, the syntheses of technetium complexes is necessarily accompanied by the reduction of pertechnetate. When concentrated hydrochloric acid is employed as a reductant, tetrachlorooxotechnetate(V) complexes can easily be obtained. A further reduction procedure is required to obtain hexachlorotech-netate(IV). Using these complexes, a number of technetium complexes have been synthesized by ligand substitution. The importance of preparative substitution reactions also increases in the light of the design and preparation of radiopharmaceuticals labelled with 99mTc and 188Re. 

MIRD/dose estimate report //8. Summary of current radiation dose estimates to normal humans from 99mTc as sodium pertechnetate. J. Nucl. Med. 1976, 17, 74-77. 

FIGURE 4.2 Mean gastric emptying curves from radiolabeled formulations of cholestyramine, sucralfate, and Carbopol (n = 10 mean S.E.M.). The cholestyramine formulation was labeled with "mTc-sodium pertechnetate, the sucralfate formulation with 99mTc-diethylenetriaminepentaacetic acid, and Carbopol with "mTc-tin colloid. (From Jackson, S.L., Bush, D., and Perkins, A.C., Int. J. Pharm., 212, 55, 2001. With permission). 

Sodium pertechnetate, Na Tc04 from the generator is the starting material for all radiopharmaceuticals based on 99mTc xhe generator eluate, Tc04, is introduced into... 

Methods Recommended by the Manufacturer. Thin-layer chromatography (TLC) on silica gel reversed phase plates (migration distance 10-15 cm) and acidified methanol-saline is used as solvent for the analysis of three components, namely the " Tc-MAG3 complex (R =0.4-0.5) reduced, hydrolized technetium at the start and unbound 99mTc-Na-pertechnetate at the solvent front. The radiochemical purity of the " Tc-MAG3 complex should not be less than 90%. 

System I In saline (20%) unbound Tc-Na-pertechnetate is identified at the solvent front (Rf=l). The sum of activities of reduced, hydrolized technetium and the 99mTc-iDA complex is measured at the start (Rf=0). 

System I Gelman ITLC-SG fiberglass plates and MAM as solvent Rednced, hydro-lized Tc-technetium is measnred at the start (A) Tc-depreotide and free 99mTc-Na-pertechnetate as well as the " Tc complexes (glnceptate and edetate) move with the solvent front. 

Alterations in background by contamination with other frequently used radioisotopes Since fluorescent thyroid scans are often performed to evaluate further the findings initially obtained from a pertechnetate or sodium iodide scan, the effect of these radioisotopes on quantitation and imaging of iodine distribution was evaluated by x-ray fluorescence. Figure 9 shows the 99mTc spectrum with the source shutter of the instrument closed. 

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