Performance of 18-fluoro-2-deoxyglucose positron emission tomography for esophageal cancer screening

AIM To evaluate the performance of 18-fluoro-2-deoxyglucose positron emission tomography(FDG-PET) for esophageal cancer(EC) screening.METHODS We retrospectively analyzed the data of consecutive asymptomatic individuals who underwent FDG-PET and esophagogastroduodenoscopy(EGD) simultaneously for cancer screening at our institution from February 2004 to March 2013. In total, 14790 FDG-PET and EGD procedures performed for 8468 individuals were included in this study, and the performance of FDGPET for EC screening was assessed by comparing the results of FDG-PET and EGD, considering the latter as the reference.RESULTS Thirty-two EC lesions were detected in 28 individuals(31 squamous cell carcinomas and 1 adenocarcinoma). The median tumor size was 12.5 mm, and the depths of the lesions were as follows: Tis(n = 12), T1a(n = 15), and T1b(n = 5). Among the 14790 FDG-PET procedures, 51 examinations(0.3%) showed positive findings in the esophagus; only 1 was a true-positive finding. The screen sensitivity, specificity, positive predictive value, and negative predictive value of FDGPET for ECs were 3.6%(95%CI: 0.1-18.3), 99.7%(95%CI: 99.6-99.7), 2.0%(95%CI: 0.0-10.4), and 99.8%(95%CI: 99.7-99.9), respectively. Of the 50 FDG-PET false-positive cases, 31 were observed in the lower esophagus, and gastroesophageal reflux disease was observed in 17 of these 31 cases.CONCLUSION This study is the first to clarify the FDG-PET performance for EC screening. Based on the low screen sensitivity, FDG-PET is considered to be difficult to use as a screening modality for ECs.

Parametric sensitivity analysis of precipitation and temperature based on multi-uncertainty quantification methods in the Weather Research and Forecasting model

Sensitivity analysis(SA) has been widely used to screen out a small number of sensitive parameters for model outputs from all adjustable parameters in weather and climate models, helping to improve model predictions by tuning the parameters. However, most parametric SA studies have focused on a single SA method and a single model output evaluation function, which makes the screened sensitive parameters less comprehensive. In addition, qualitative SA methods are often used because simulations using complex weather and climate models are time-consuming. Unlike previous SA studies, this research has systematically evaluated the sensitivity of parameters that affect precipitation and temperature simulations in the Weather Research and Forecasting(WRF) model using both qualitative and quantitative global SA methods. In the SA studies, multiple model output evaluation functions were used to conduct various SA experiments for precipitation and temperature. The results showed that five parameters(P3, P5, P7, P10, and P16) had the greatest effect on precipitation simulation results and that two parameters(P7 and P10) had the greatest effect for temperature. Using quantitative SA, the two-way interactive effect between P7 and P10 was also found to be important, especially for precipitation. The microphysics scheme had more sensitive parameters for precipitation, and P10(the multiplier for saturated soil water content) was the most sensitive parameter for both precipitation and temperature. From the ensemble simulations, preliminary results indicated that the precipitation and temperature simulation accuracies could be improved by tuning the respective sensitive parameter values, especially for simulations of moderate and heavy rain.