RESUMO
A standard protocol for performance evaluation of positron emission mammography (PEM) systems has not yet been established. In this work we propose a methodology based on the design of specific phantoms for this imaging modality with component dimensions in accordance with typical breast lesion sizes together with the adaptation of current international protocols designed for clinical and preclinical positron emission tomographs (PET) systems. This methodology was used to evaluate the performance of the Flex Solo II PEM scanner in terms of spatial resolution, uniformity and contrast lesion detectability, recovery coefficients and spill-over ratios. Positron range effects were studied with 18F and 68Ga, which have very different energy spectra. Our results indicate that in-plane spatial resolution of the system is around 3.0 mm and 4.4 mm for 18F and 68Ga, respectively. Lesion detectability tests with sphere diameters between 4 and 10 mm confirmed that the PEM system can resolve all the spheres (hot or cold). Percent contrast values for 18F lie between 6%-38% and 34%-51% for hot- and cold- spheres, respectively; the corresponding intervals for 68Ga are lower, 4%-25% and 32%-44%. Regarding uniformity quantification, the system shows percentage standard deviations within 4.9%-5.7%, while the percent background variability measurements ranged between 6.7% and 10.9% for both radionuclides. Recovery coefficients measured with hot rod diameters between 1.5 and 9 mm, have values between 0.2-1.05 and 0.17-0.69 for 18F and 68Ga, respectively. Spill-over ratios have large values (0.22 in average) for both radionuclides. Our results indicate that the phantoms and the methodology developed in this work can serve as the basis for establishing an image quality protocol for the systematic evaluation of PEM systems, with a potential extension for performance evaluation of dedicated breastPET scanners.
Assuntos
Elétrons , Mamografia/instrumentação , Imagens de Fantasmas , Desenho de Equipamento , Controle de Qualidade , Tomografia Computadorizada de EmissãoRESUMO
El objetivo del presente artículo es proveer un resumen ordenado de la bibliografía publicada en las últimas décadas, concerniente a la aparición o el agravamiento de las recesiones gingivales en relación a los tratamientos ortodóncicos. Diferentes estudios, en modelos animales, han demostrado que el movimiento ortodóncico hacia vestibular genera con bastante frecuencia dehiscencias óseas. En la mayoría de los casos, esto no se acompaña con la aparición de recesiones gingivales. Los estudios retrospectivos constituyen al momento la mejor evidencia disponible. Si bien se encuentran problemas metodológicos en los mismos, es posible establecer algunas conclusiones. El tratamiento ortodóncico puede contribuir a la aparición de recesiones gingivales o al agravamiento de las mismas. La prevalencia de las mismas es baja al terminar el tratamiento, pero se incrementa a medida que transcurren los años. Las piezas dentarias con mayor prevalencia son los incisivos inferiores, especialmente los centrales. El tratamiento con mayor asociación ha sido la vestibularización de los mismos, pero también se han encontrado asociaciones en pacientes de clase III cuando los incisivos son retrotraídos en un intento de camuflar su malposición. Son necesarios estudios prospectivos para evaluar esta asociación, en los cuales se midan variables como el biotipo gingival, o la presencia de crestas delgadas o dehiscencias óseas y se las relacione con diferentes movimientos y técnicas ortodóncicos a fin de establecer criterios de riesgo(AU)
The objective of this article is to provide an ordered summary of the literature published in recent decades, concerning the appearance or worsening of gingival recessions in relation to orthodontic treatments. Different studies, in animal models, have shown that the orthodontic movement toward the vestibular bone generates bone dehiscence quite frequently. In most cases, this is not accompanied by the appearance of gingival recessions. Retrospective studies are currently the best available evidence. Although methodological problems are found in them, it is possible to establish some conclusions. Orthodontic treatment can contribute to the appearance of gingival recessions or aggravation of them. The prevalence of them is low at the end of treatment, but increases as the years pass. The teeth with more prevalence are the lower incisors, especially the central ones. The treatment with greater association has been the proclination of them, but associations have also been found in class III Angle patients when the incisors are retruded in an attempt to camouflage their malposition. Prospective studies are needed to evaluate this association, in which variables such as the gingival biotype, or the presence of thin ridges or bone dehiscences are measured and related to different orthodontic movements and techniques in order to establish risk criteria (AU)
Assuntos
Ortodontia Corretiva/efeitos adversos , Técnicas de Movimentação Dentária , Retração Gengival , Estudos Prospectivos , Estudos Retrospectivos , Fatores de Risco , Progressão da DoençaRESUMO
BACKGROUND: Acute variceal bleeding in cirrhotic patients is an emergency with a high risk of rebleeding and death. Endoscopic procedures such as sclerotherapy or banding, combined or not with drugs such as octreotide could be considered. AIM: To assess the value of octreotide in the control of acute variceal bleeding. PATIENTS AND METHODS: Ninety-two patients were randomized into three groups: endoscopic therapy plus octreotide 50 microg/h bolus and continuous infusion for 5 days (n=36); octreotide (same dosage) (n=13) and endoscopic therapy only (banding and/or sclerotherapy) (n=43). RESULTS: Haemostasis at 24 hours was achieved in 97% of patients with combined treatment, 69% of patients receiving octreotide, and 93% of patients with endoscopic therapy (p=0.2). Three patients with combined treatment, four patients receiving octreotide and eight patients with endoscopic therapy, rebled during the first five days (p=0.15). The mean of blood units transfused was similar in the three groups. No differences were observed in hospital days and side effects. At 42 days of follow up, eight patients with endoscopic therapy, one patients with combined therapy and 2 patients receiving octreotide, died (p=NS). CONCLUSIONS: Octreotide is useful in the management of acute variceal bleeding. The absence of important side effects, renders it as a safe adjuvant treatment associated with endoscopic treatment.