检影验光在眼屈光检查中的应用

1、检影验光定义 通过检影镜观察影动,并用镜片消解影动,最终找到中和点(反转点、远点)的位置,从而判断被检者屈光不正的性质及程度,这种屈光检查称为检影验光。 2、检影验光优点 不仅对被检眼屈光不正的性质和程度有一个快速、准确的客观判断,还能对其屈光介质有无病变,如白内障等有一初步检查。此检查法成本低、技术含量高、检查准确、快速、适用范围广(如屈光度高、停电等客观条件不好或经济条件差的地区),另外对疑难病症的屈光检查提供了重要的依据。

联合应用正负柱镜检影法检测混合散光

目的 研究联合正、负柱镜检影方法在发现混合散光中临床应用。方法 189例 (340只眼 )混合散光患者随机分为实验组和对照组 ,根据散光度数的大小分为 3个区间 (<3 0 0D、3 0 0～6 0 0D ,>6 0 0D)。其中散光度数 <3 0 0D的 15 6只眼 (试验组 76只眼 ,对照组 80只眼 ) ;3 0 0D～6 0 0D者 132只眼 (试验组 6 8只眼 ,对照组 6 4只眼 ) ;>6 0 0D者 5 3只眼 (试验组 2 9只眼 ,对照组 2 4只眼 )。患者均于睫状肌麻痹后 ,通过正、负柱镜片组合进行检影 ,并用常规的球镜检影法或柱镜检影法作为对照。根据中和影的形态均匀程度、轴位判断的准确性和难易程度、检影时间和镜片组合的数目作综合评价 ,将检影结果分为 3级 ,Ⅰ级 :中和影均匀 ,轴位容易判断 ,检影时间 <5min ,镜片组合的数目 1或 2片 ;Ⅱ级 :中和影欠均匀 ,轴位判断不困难 ,检影时间 5～ 10min ,镜片组合的数目 2或 3片 ;Ⅲ级 :中和影欠均匀 ,易受到干扰 ,轴位判断困难 ,检影时间 >10min ,镜片组合的数目 >3片。结果 散光度数 <3 0 0D时 ,试验组与对照组的检测结果差异无显著意义 (χ2 =0 0 94 ,P =0 75 9)。散光度数为在 3 0 0～ 6 0 0D时 ,试验组与对照组检测结果的差异有显著意义 (χ2 =5 5 4 6 ,P =0 0 19)。散光度数 >6 0 0D时 。

Review of Shadow Detection and De-shadowing Methods in Remote Sensing

Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,mountain and urban materials.The shadow correction process consists of two steps:detection and de-shadowing.This paper reviews a range of techniques for both steps,focusing on urban regions(urban shadows),mountainous areas(topographic shadow),cloud shadows and composite shadows.Several issues including the problems and the advantages of those algorithms are discussed.In recent years,thresholding and recovery techniques have become important for shadow detection and de-shadowing,respectively.Research on shadow correction is still an important topic,particularly for urban regions(in high spatial resolution data) and mountainous forest(in high and medium spatial resolution data).Moreover,new algorithms are needed for shadow correction,especially given the advent of new satellite images.

^(18)F-DG PET/CT in detection of recurrence and metastasis ofcolorectal cancer

AIM: To evaluate the value of 18F-DG PET/CT in detecting recurrence and/or metastasis of colorectal cancer (CRC). METHODS: Combined visual analysis with semiquantitative analysis, the 18F-DG PET/CT whole- body imaging results and the corresponding clinical data of 68 postoperative CRC patients including 48 male and 20 female with average age of 58.1 were analyzed retrospectively. RESULTS: Recurrence and/or metastasis were confirmed in 56 patients in the clinical follow-up after the PET/CT imaging. The sensitivity of PET/CT diagnosis of CRC recurrence and/or metastasis was 94.6%, and the specificity was 83.3%. The positive predictive value (PPV) was 96.4% and the negative predictive value (NPV) was 76.9%. PET/CT imaging detected one or more occult malignant lesions in 8 cases where abdominal/pelvic CT and/or ultrasonography showed negative findings, and also detected more lesions than CT or ultrasonography did in 30.4% (17/56) cases. Recurrence and/or metastasis was detected in 91.7% (22/24) cases with elevated serum CEA levels by 18F-DG PET/CT imaging. CONCLUSION: 18F-DG PET/CT could detect the recurrence and/or metastasis of CRC with high sensitivity and specificity.

Retrieval and Analysis of Coal Fire Temperature in Wuda Coalfield, Inner Mongolia, China

Coal fire burning around the world is an environmental catastrophe characterized by the emission of noxious gases, particulate matter, and condensation by-products. In this study, coal fire temperature is retrieved based on Landsat 5 TM images and Generalized Single-Channel Algorithm (GSCA), in Wuda coalfield, Inner Mongolia, China. Then coal fire zones are extracted by Jenks′ natural breaks and threshold methods based on temperature images. Changes of coal fire zones are analyzed from 1989 to 2008. The results are summarized as follows: 1) The coal fire temperature retrieval method based on Landsat 5 TM and the GSCA model is effective and feasible, because the temperature error is relatively small (from –2.9℃ to +2.6℃) between the measured temperature and the retrieved temperature. 2) The accuracy is relatively high to extract coal fire zones through the Jenks′ natural breaks and threshold methods, because 83.56% of surveyed area is located in the coal fire zones extracted in 2005. 3) The coal fire area increased 9.81 × 10 5 m 2 from 1989 to 2005, and the annual growth is about 6.1 × 10 4 m 2 , with an annual increasing rate of 2.48%. The area of coal fire decreased by 8.1 × 10 5 m 2 from 2005 to 2008.

Sparse Kernel Locality Preserving Projection and Its Application in Nonlinear Process Fault Detection

Locality preserving projection (LPP) is a newly emerging fault detection method which can discover local manifold structure of a data set to be analyzed, but its linear assumption may lead to monitoring performance degradation for complicated nonlinear industrial processes. In this paper, an improved LPP method, referred to as sparse kernel locality preserving projection (SKLPP) is proposed for nonlinear process fault detection. Based on the LPP model, kernel trick is applied to construct nonlinear kernel model. Furthermore, for reducing the computational complexity of kernel model, feature samples selection technique is adopted to make the kernel LPP model sparse. Lastly, two monitoring statistics of SKLPP model are built to detect process faults. Simulations on a continuous stirred tank reactor (CSTR) system show that SKLPP is more effective than LPP in terms of fault detection performance.