RESUMO
Three carbohydrate derivatives, MAG(3)-Gl, MAG(3)-Ga, MAG(3)-NG, were synthesized and radiolabeled in high yields. These substances were injected in health Swiss mice and their biodistribution were evaluated. Among them, (99m)Tc-MAG(3)-Ga displayed higher accumulation in hepatic tissue, due to the presence of specific receptors in the liver for this carbohydrate. Thus, the use of (99m)Tc-MAG(3)-Ga to assess hepatic function can be considered.
Assuntos
Carboidratos/química , Tecnécio Tc 99m Mertiatida/química , Animais , Carboidratos/síntese química , Carboidratos/farmacocinética , Glicina/análogos & derivados , Glicina/química , Glicina/farmacocinética , Marcação por Isótopo , Fígado/metabolismo , Camundongos , Tecnécio Tc 99m Mertiatida/farmacocinética , Distribuição TecidualRESUMO
OBJECTIVE: The objective of this work was to determine the minimum administered activity of (99m)Tc-mercaptoacetyltriglycine (MAG3) needed both to estimate effective renal plasma flow (ERPF) with adequate precision and to obtain good image quality. METHODS: Three groups of 10 patients each were injected with 45, 71, or 132 MBq of MAG3. Renograms and perfusion and clearance images were obtained. The age, sex, and weight of the patients; the labeling yield; the mean count and counting rate 2 min after injection; the kidney-to-background and cortex-to-background ratios; the uptake time from the renograms; the percentage of the injected activity 2 min after injection in the left and right kidneys (A2(LK) and A2(RK), respectively); and the ERPF for both kidneys were obtained and analyzed. Discriminant analysis of image quality was used to select the variables that most affected image quality. The selected variables were studied among activity groups to optimize the amount of activity administered in these studies. RESULTS: Precision in ERPF assessment did not significantly differ among administered activity levels (P = 0.824). The SDs of the ERPF were +/-1.5 for 132 MBq, +/-1.7 for 71 MBq, and +/-2.0 for 45 MBq. The labeling yield, the ratios of counts in the left and right kidneys to the background and in the left and right cortices to the background, and A2(LK) and A2(RK) were the only variables that provided a significant discriminant function for image quality. The only variable that significantly differed with the variation in administered activity was the ratio of counts in the right kidney to the background (P = 0.026), most likely because of the labeling yield. CONCLUSION: A 45-MBq activity is sufficient to guarantee good image quality and adequate precision in ERPF determination from the time-activity curve, provided the labeling yield is kept high.
Assuntos
Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Rim/diagnóstico por imagem , Rim/metabolismo , Renografia por Radioisótopo/métodos , Tecnécio Tc 99m Mertiatida/administração & dosagem , Tecnécio Tc 99m Mertiatida/farmacocinética , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Taxa de Depuração Metabólica , Pessoa de Meia-Idade , Compostos Radiofarmacêuticos/administração & dosagem , Compostos Radiofarmacêuticos/farmacocinética , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Background. Technetium-99m-mercaptoacetyltriglycine (99-mTc-MAG3) is a radiopharmaceutical for tubular function and can be prepared with 99-mtechnetium and the ligand Bz-MAG3 (Instituto Nacional de Investigaciones Nucleares, Mexico City). No radiopharmacokinetic parameters have been found for the healty adult Mexican population with 99mTc-MAG3, prepared with the nationally produced or imported Bz-MAG3 kit. Methods. The radiopharmacokinetic parametrs and the clearance of 99mTc-Mag3 in seven healthy Mexican volunteers were determined by the single-and multi-sample methods. Computer programs were used for the calculations. Results. Using several plasma samples from 0.43 min and the BIEXP program, it was show that 99mTc-MAG3 follows a two-compartment model of distribution, with an apparent volumen in the central compartment Vdcc = 6.7 + 1.0 1, T½Ó = 0.07 + 0.02 h-1, T½ ß = 0.49 + 0.15 h-1, mean residence time MRT = 0.60 + 0.17 h and clearance = 208 57 (ml/min)/1.73 m². In comparison, the clearance value with a single sample drawn 43 min post-injection and calculated with Tauxe's formula was 193 ñ 59 (ml/min)/m². Conclusions. The 15 ml difference between the two methods is neither statistically different (p= 0.11) nor important for routine clinical studies. The single-sample method is recommendad because it is reliable and can be done at the same time that dynamic renal scan is aquiered. Estimated absorbed radiation dose was calvulated for several organs