The temperature dependence of relative permittivity and conductivity of ex-vivo pig liver, lung and heart at 2 450 MHz was studied. The relative permittivity and conductivity of three kinds of biological tissues were measured by the open-end coaxial line method. The dielectric model was fitted according to the principle of least square method. The results showed that the relative permittivity and conductivity of pig liver, pig lung and pig heart decreased with the increase of tissue temperature from 20 to 80 ℃. The relative permittivity and conductivity models of pig liver, pig lung and pig heart were established to reflect the law of dielectric properties of biological tissue changing with temperature and provide a reference for the parameters setting of thermal ablation temperature field.
The effect of relaxation time in hyperbolic heat transfer model on the temperature field of microwave ablation of atrial fibrillation was investigated. And the results were compared with those calculated by Pennes model. A three-dimensional model of microwave ablation of atrial fibrillation was constructed. The relaxation time (τ) was 0, 1, 5, 8, 10, 15 and 20 s, respectively. And the temperature field of myocardial tissue was obtained. The results showed that the highest temperature of the hyperbolic model was 21.8 ℃ lower than that of the Pennes model at the beginning of ablation. With the increase of ablation time, the highest temperature tended to be the same. The lesion dimensions appeared at 3, 4, 6, 7, 8, 9, and 10 s, respectively after ablation. Therefore, the influence of hyperbolic model on temperature will decrease with the increase of the ablation time. At the beginning of ablation, the relaxation time will hinder the speed of myocardial thermal diffusion. The larger the relaxation time is, the slower the speed of thermal diffusion is. This study provides a reference for the application of hyperbolic model in microwave ablation of atrial fibrillation.
Objective To make an individualized treatment plan for a newly diagnosed Barrett esophagus patient by means of evidence-based medicine. Methods After the clinical problems were put forward, both the systematic reviews and randomized controlled trials (RCTs) were collected from The Cochrane Library (Issue 3, 2009) and PubMed (1995 to 2010) and SCIE (1995 to 2010). The treatment protocol was made by combining the evidence and the preference of patient. Results A total of 21 RCTs and 6 systematic reviews (meta-analyses) were identified. A rational treatment plan was made upon a serious evaluation and patient’s preferences: improving the lifestyle and adopting the APC therapy combined with acid-suppressive drugs (Omeprazole, 40 mg, bid) for six weeks. Three months later, the endoscope reexamination showed the patient was much better. After another twelve-month follow-up, the plan proved to be optimal. Conclusion In accordance with the evidence-based methods, the rational treatment plan made for a diagnosed Barrett esophagus male can effectively relieve symptoms and improve quality of life.
Objective To establish the overall diagnostic accuracy of the measurements of vascular endothelial growth factor (VEGF) for malignant ascites. Methods After a systematic review of current studies, sensitivity, specificity, and other measures of the value of ascites concentrations of VEGF in the diagnosis of malignant ascites were pooled by using random effects models. Qualified studies on evaluation of VEGF in diagnosis of malignant ascites in English and Chinese published from January 1990 to December 2009 were retrieved from The Cochrane Library, Cochrane Central Register of Controlled Trials, MEDLINE, EMbase, China National Knowledge Infrastructure (CNKI) databases, WanFang Data, and VIP Information. Two reviewers independently assessed the methodological quality of each study with the tool of QUADAS. Statistical analyses were performed by employing Meta-Disc 1.4 software. Meta-analyses of the reported sensitivity and specificity of each study and Summary Receiver Operating Characteristic (SROC) curve were performed. Results Seven studies met the inclusion criteria for the analysis. After testing the heterogeneity of the included studies, a random effect model was selected to calculate the pool weighted sensitivity and specificity with 95% confidence interval: the sensitivity was 0.81 (95%CI 0.75 to 0.85), the specificity was 0.90 (95%CI 0.86 to 0.94), the DOR was 50.45 (95%CI 28.37 to 89.73), and the AUC of SROC was 0.9507 (SE=0.013 0). The subgroups were analyzed to identify the sources of heterogeneity according to race and agent sources. There was homogeneity among the three studies with agents from Ramp;D company (χ2=0.05, P=0.9750; I2=0.0%), and the AUC of SROC were 0.9675 (SE=0.016 7). Conclusion VEGF has a highly accurate sensitivity and specificity with a b ROC curve, which makes it a new marker to differentiate malignant ascites from the benign.