Prognostic value of technetium-99m-labeled single-photon emission computerized tomography in the follow-up of patients after their first myocardial revascularization surgery

OBJECTIVE: To assess the prognostic value of Technetium-99m-labeled single-photon emission computerized tomography (SPECT) in the follow-up of patients who had undergone their first myocardial revascularization. METHODS: We carried out a retrospective study of 280 revascularized patients undergoing myocardial scintigraphy under stress (exercise or pharmacological stress with dipyridamole) and at rest according to a 2-day protocol. A set of clinical, stress electrocardiographic and scintigraphic variables was assessed. Cardiac events were classified as "major" (death, infarction, unstable angina) and "any" (major event or coronary angioplasty or new myocardial revascularization surgery). RESULTS: Thirty-six major events occurred as follows: 3 deaths, 11 infarctions, and 22 unstable anginas. In regard to any event, 22 angioplasties and 7 new surgeries occurred in addition to major events, resulting a total of 65 events. The sensitivity of scintigraphy in prognosticating a major event or any event was, respectively, 55% and 58%, showing a negative predictive value of 90% and 83%, respectively. Diabetes mellitus, inconclusive stress electrocardiography, and a scintigraphic visualization of left ventricular enlargement were significant variables for the occurrence of a major event. On multivariate analysis, abnormal myocardial scintigraphy was a predictor of any event. CONCLUSION: Myocardial perfusion tomography with Technetium-99m may be used to identify high-risk patients after their first myocardial revascularization surgery.

Biodistribution Study of the Anaesthetic Sodium Phenobarbital Labelled with Technetium-99m in Swiss Mice Infected with Schistosoma mansoni Sambon, 1907

Technetium-99m (99mTc) is a radionuclide that has negligible enviromnental impact, is easily available, inexpensive and can be used as a radioactive tracer in biological experiences. In order to know the mode of action of sodium phenobarbital in moving adult Schistosoma mansoni worms from mesenteric veins to the liver, we labelled sodium phenobarbital (PBBT) with 99mTc and a biodistribution study in infected and non-infected Swiss mice was performed. The PBBT was incubated with stannous chloride used as reducing agent and with 99mTc, as sodium pertechnetate. The radioactivity labelling (%) was determined by paper ascending chromatography perfomed with acetone (solvent). The 99mTc-PBBT was administered by intraperitoneal route to Swiss mice infected eight weeks before. The animals were perfused after diferent periods of time (0,1,2,3,4 hr) when blood, spleen, liver, portal vein, mesenteric veins, stomach, kidneys and adult worms were isolated. The radioactivity present in these samples was counted in a well counter and the percentage was determined. The radioactivity was mainly taken up by the blood, kidney, liver and spleen. No radioactivity was found on the adult worms. We concluded that the worm shift was due to an action on the host of the sodium phenobarbital

Relações do ramo externo do nervo laríngeo superior com a artéria tireóidea superior: estudo em 101 nervos

OBJETIVO: Construir um protocolo das relações anatômicas topográficas do ramo externo do nervo laríngeo superior (NLSE) com a artéria tireóidea superior, para minimizar as falhas das propostas descritas na literatura. MÉTODOS: Foram dissecadas bilateralmente as regiões cervicais de 57 cadáveres frescos, no Instituto Médico-Legal do Estado do Amazonas, com identificação fotográfica dos NLSE e respectivas relações com a artéria tireóidea superior. A partir dos dados obtidos elaborou-se classificação: Tipo1: NLSE não identificado; Tipo 2: NLSE cruza a artéria tireóidea superior a distância maior de 1,5cm do limite cranial do lobo da glândula tireóide; Tipo 3: NLSE cruza a artéria entre 1cm e 1,5cm do limite cranial do lobo da glândula tireóide; Tipo 4: NLSE cruza a artéria a menos de 1cm do limite cranial do lobo da glândula; Tipo 5: NLSE cruza, látero-medialmente, abaixo do limite cranial do lobo tireóideo. Como suplemento classificatório, os tipos 2, 3 e 4 receberam subclassificação: A - quando se encontrava parcial ou totalmente envolto no tecido conjuntivo superficial peri-muscular ou intra-muscular, no constritor inferior da faringe, em mais da metade de seu percurso, após cruzar a artéria tireóide superior; B - quando se encontrava fora destes tecidos. RESULTADOS: Tipo 1, 11,88%; Tipo 2, 13,86%; Tipo 3, 34,65%; Tipo 4, 38,61% e Tipo 5, 0,99%. CONCLUSÃO: Os NLSE mais próximos ao limite cranial (Tipos 3 e 4) percorriam, em sua maioria, o tecido frouxo peri-muscular ou intramuscular, no pólo superior da tireóide, o que neste estudo, desobrigam identificação sistemática do nervo nas tireoidectomias (p=0,075).

Protection of plasmid DNA by a Ginkgo biloba extract from the effects of stannous chloride and the action on the labeling of blood elements with technetium-99m

Ginkgo biloba extract (EGb) is a phytotherapeutic agent used for the treatment of ischemic and neurological disorders. Because the action of this important extract is not fully known, assays using different biological systems need to be performed. Red blood cells (RBC) are labeled with technetium-99m (Tc-99m) and used in nuclear medicine. The labeling depends on a reducing agent, usually stannous chloride (SnCl2). We assessed the effect of different concentrations of EGb on the labeling of blood constituents with Tc-99m, as sodium pertechnetate (3.7 MBq), and on the mobility of a plasmid DNA treated with SnCl2 (1.2 µg/ml) at room temperature. Blood was incubated with EGb before the addition of SnCl2 and Tc-99m. Plasma (P) and RBC were separated and precipitated with trichloroacetic acid, and soluble (SF-P and SF-RBC) and insoluble (IF-P and IF-RBC) fractions were isolated. The plasmid was incubated with Egb, SnCl2 or EGb plus SnCl2 and agarose gel electrophoresis was performed. The gel was stained with ethidium bromide and the DNA bands were visualized by fluorescence in an ultraviolet transilluminator system. EGb decreased the labeling of RBC, IF-P and IF-RBC. The supercoiled form of the plasmid was modified by treatment with SnCl2 and protected by 40 mg/ml EGb. The effect of EGb on the tested systems may be due to its chelating action with the stannous ions and/or pertechnetate or to the capability to generate reactive oxygen species that could oxidize the stannous ion.

Biodistribution of 99m technetium- labeled creatinine in healthy rats

The distribution of creatinine, one of the toxic guanidine compounds, in various tissues has not been studied in detail by using radiolabeled creatinine. Our objective was to investigate the biodistribution of creatinine labeled with 99m technetium (99mTc) by the stannous (II) chloride method in healthy male Wistar rats. Quality controls were carried out by radio thin layer chromatography, high-performance liquid chromatography, and paper electrophoresis. The labeling yield was 85 ± 2% under optimum conditions (pH 7 and 100 µg stannous chloride). Rats (N = 12) were injected intravenously with 99mTc-creatinine and their blood and visceral organs were evaluated for 99mTc-creatinine uptake as percent of the injected dose per gram wet weight of each tissue (%ID/g). The lowest amount of uptake was detected in the brain and testis. When the rate of uptake was evaluated, only the kidney showed increasing rates of uptake of 99mTc-creatinine throughout the study. Kidneys showed the highest amount of uptake throughout the study (P < 0.001 compared to all other organs), followed by liver, spleen and lung tissue.

Alternative chromatographic system for the quality control of lipophilic technetium-99m radiopharmaceuticals such as [99mTc(MIBI)6]+

Knowledge of the radiochemical purity of radiopharmaceuticals is mandatory and can be evaluated by several methods and techniques. Planar chromatography is the technique normally employed in nuclear medicine since it is simple, rapid and usually of low cost. There is no standard system for the chromatographic technique, but price, separation efficiency and short time for execution must be considered. We have studied an alternative system using common chromatographic stationary phase and alcohol or alcohol:chloroform mixtures as the mobile phase, using the lipophilic radiopharmaceutical [99mTc(MIBI)6]+ as a model. Whatman 1 modified phase paper and absolute ethanol, Whatman 1 paper and methanol:chloroform (25:75), Whatman 3MM paper and ethanol:chloroform (25:75), and the more expensive ITLC-SG and 1-propanol:chloroform (10:90) were suitable systems for the direct determination of radiochemical purity of [99mTc(MIBI)6]+ since impurities such as99mTc-reduced-hydrolyzed (RH),99mTcO4- and [99mTc(cysteine)2]-complex were completely separated from the radiopharmaceutical, which moved toward the front of chromatographic systems while impurities were retained at the origin. The time required for analysis was 4 to 15 min, which is appropriate for nuclear medicine routines.