Determinação dos fatores de recuperação do 111In e do 99mTc na quantificação de atividade com imagens SPECT / Determination of 111In and 99mTc recovery in the quantification of activity with SPECT imaging

OBJETIVO: Determinar, experimentalmente, os coeficientes de recuperação do 111In e do 99mTc usando imagens SPECT. MATERIAIS E MÉTODOS: Quatro diferentes concentrações de 111In e de 99mTc foram usadas para quantificar a atividade em esferas de diferentes tamanhos. As imagens foram obtidas com um equipamento híbrido SPECT/CT, com dois detectores. A reconstrução das imagens foi realizada usando o método iterativo ordered subset expectation maximization (OSEM). A correção de atenuação foi realizada com o uso de um mapa de atenuação e a correção de espalhamento foi realizada usando a técnica das janelas de energia. RESULTADOS: Os resultados mostraram que o efeito do volume parcial foi observado de forma mais significativa para as esferas com volume < 6 ml. Para o 111In, os resultados mostram uma dependência com relação às concentrações usadas nas esferas e ao nível de background usado. Para o 99mTc, pôde-se observar uma tendência à subestimação dos resultados quando os níveis mais altos de background foram utilizados. CONCLUSÃO: É necessário usar os fatores de correção para compensar o efeito do volume parcial em objetos com volume < 6 ml para ambos os radionuclídeos. A subtração das contagens espúrias presentes nas imagens SPECT foi o fator que mais influenciou na quantificação da atividade nessas esferas.

OBJECTIVE: To experimentally determine the 99mTc and 111In activity recovery coefficients in SPECT imaging. MATERIALS AND METHODS: Four different 99mTc and 111In concentrations were utilized for quantifying activity in spheres of four different sizes. Images were obtained with a hybrid dual-head SPECT-CT imaging system. The ordered subset expectation maximization (OSEM) iterative method was utilized for images reconstruction. An attenuation map was utilized for attenuation correction, and the multiple energy window technique for scattering correction. RESULTS: Results for spheres < 6 ml in volume were significantly affected by the partial volume effect. For 111In quantification, results show a dependence on sphere concentrations and background levels. For 99mTc quantification, there was a tendency towards values underestimation with higher background levels. CONCLUSION: Correction factors must be utilized for compensating the partial volume effect on objects with < 6 ml in volume for both radionuclides. Background subtraction to compensate spurious count present on SPECT images has a significant influence on the quantification of activity, especially for the smaller objects.

Efeitos da braquiterapia intra-arterial com samário-153 sobre a neoproliferação intimal / Effects of intra-arterial brachytherapy with Samarium- 153 over intimal neoproliferation

Estudos experimentais e em humanos o balão de angioplastia pode levar à estenose pela migração e proliferação das células musculares lisas e a síntese de matriz extracelular. Estudos têm mostrado a ação da braquiterapia contra esses mecanismos. Nós desenhamos este estudo para avaliar a inibição do tecido de proliferação pelo Samário-153(153Sm). Quarenta e três coelhos hipercolesterolêmicos foram submetidos à lesão de ambas artérias ilíacas e separados em três grupos: com a dose de 15 Gy (n=14), com 60 Gy (n=36) e controle (n=36). A análise histológica morfométrica mostrou significante redução da neo-íntima com 15 Gy, quando comparado com os outros grupos. A dose de 60 Gy teve modificações estruturais e tissulares sugestivas de radiolesão.As previous demonstrated by experimental and human models, balloon dilation during angioplasty could lead to injury and stenosis due to smooth muscle cell migration and proliferation as well as extracellular matrix synthesis. Brachytherapy has been usefull against these factors. We pourposed was this study to evaluate neointimal tissue proliferation inhibition by Samarium-153 (153 Sm). Forty-three hypercholesterolemic rabbits underwent balloon injury in their both iliac arteries. They were separated into three groups: throught 15 Gy irradiation doses (n=14), 60 Gy (n=36) and control group (n= 36). Histopathologic and morphometric analysis showed a significant neointimal reduction with 15 Gy, comparing to others groups to control and 60 Gy dosis. The 60 y doses determined structure and tissue changes as the ones of radiation lesion...

Biodistribution study of the anaesthetic sodium phenobarbital labelled with technetium-99m in Swiss mice infected with Schistosoma mansoni Sambon, 1907

Technetium-99 (99m Tc) 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 99m Tc 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 99m Tc, as sodium pertechnetate. The radioactivity labelling (per cent) was determined by paper ascending chromatography performed with acetone (solvent). The 99m Tc-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, poral, 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 worms. We concluded that the worm shiff was due to an action on the lost of the sodium phenobarbital.