Evaluating the use of anti-scatter grids in adult knee radiography

IntroductionAnti-scatter grids efficiently reduce scatter radiation from reaching the imaging receptor, enhancing image quality; however, the patient radiation dose increases in the process. There is disagreement regarding the thickness thresholds for which anti-scatter grids are beneficial. This study aims to establish a thickness threshold for the use of anti-scatter grids to optimise adult knee radiography.MethodsThe study consisted of two phases. In Phase 1 phantom knee radiographs were acquired at varying thicknesses (10–16 cm) and tube voltages (60–80 kV). For each thickness and tube voltage, images with and without an anti-scatter grid were obtained. In Phase 2, two radiologists and three radiographers, evaluated the image quality of these images. Visual Grading Analysis (VGA) scores were analysed using Visual Grading Characteristics (VGC) based on the visualisation of five anatomic criteria.ResultsThe average DAP decreased by 72.1% and mAs by 73.1% when removing the anti-scatter grid. The VGC revealed that overall images taken with an anti-scatter grid have better image quality (AUC ≥0.5 for all comparisons). However, the anti-scatter grids could be removed for thicknesses 10, 12 and 14 cm in conjunction with using 80 kVp,.ConclusionAnti-scatter grids can be removed when imaging adult knees between 10 and 12 cm using any kVp setting since the radiation dose is reduced without significantly affecting image quality. For thicknesses >12 cm, the use of anti-scatter grids significantly improves image quality; however, the radiation dose to the patient is increased. The exception is at 14 cm used with 80 kVp, where changes in image quality were insignificant.Implications for practiceOptimisation by removing anti-scatter grids in adult knee radiography seems beneficial below 12 cm thickness with any kVp value. Since the average knee thickness ranges between 10 and 13 cm, anti-scatter grid can be removed for most patients. Nevertheless, further studies are recommended to test if this phantom-based threshold applies to human subjects.     

A Priori Subcell Limiting Approach for the FR/CPR Method on Unstructured Meshes

A priori subcell limiting approach is developed for high-order flux reconstruction/correction procedure via reconstruction (FR/CPR) methods on two-dimensional unstructured quadrilateral meshes. Firstly, a modified indicator based on modal energy coefficients is proposed to detect troubled cells, where discontinuities exist. Then, troubled cells are decomposed into nonuniform subcells and each subcell has one solution point. A second-order finite difference shock-capturing scheme based on nonuniform nonlinear weighted (NNW) interpolation is constructed to perform the calculation on troubled cells while smooth cells are calculated by the CPR method. Numerical investigations show that the proposed subcell limiting strategy on unstructured quadrilateral meshes is robust in shock-capturing.     

阈值改良 Amsler 表与 Humphrey 静态视野分析仪对青光眼视野检查的比较

对５０只正常眼和４７只青光眼进行阈值改良Ａｍｓｌｅｒ表与Ｈｕｍｐｈｒｅｙ静态分析仪视野检查比较，两种方法存在着相关关系，阳性检出率无区别，提示阈值改良Ａｍｓｌｅｒ表对青光眼早期视野损害有较高的检出率。     

A Study of Grid Artifacts Formation and Elimination in Computed Radiographic Images

Computed radiography (CR) has many advantages such as filmless operations, efficiency, and convenience. Furthermore, it is easier to integrate with the picture archiving and communication systems. Another important advantage is that CR images generally have a wider dynamic range than conventional screen film. Unfortunately, grid artifacts and moiré pattern artifacts may be present in CR images. These artifacts become a more serious problem when viewing CR images on a computer monitor when a clinic grade monitor is not available. Images produced using a grid with higher frequency or a Potter–Bucky grid (i.e., a moving grid, Bucky for short) can reduce occurrence but cannot guarantee elimination of these artifacts [CR & PACS (2000); Detrick F (2001), pp 7–8]. In this paper, the formation of the artifacts is studied. We show that the grid artifacts occur in a narrow band of frequency in the frequency domain. The frequency can be determined, accurately located, and thus removed from the frequency domain. When comparing the results obtained from the proposed method against the results obtained using previous computer methods, we show that our method can achieve better image quality.     

Stability and specificity of heterodimer formation for the coiled‐coil neck regions of the motor proteins Kif3A and Kif3B: the role of unstructured oppositely charged regions

Abstract: We investigated the folding, stability, and specificity of dimerization of the neck regions of the kinesin‐like proteins Kif3A (residues 356–416) and Kif3B (residues 351–411). We showed that the complementary charged regions found in the hinge regions (which directly follow the neck regions) of these proteins do not adopt any secondary structure in solution. We then explored the ability of the complementary charged regions to specify heterodimer formation for the neck region coiled‐coils found in Kif3A and Kif3B. Redox experiments demonstrated that oppositely charged regions specified the formation of a heterodimeric coiled‐coil. Denaturation studies with urea demonstrated that the negatively charged region of Kif3A dramatically destabilized its neck coiled‐coil (urea_1/2 value of 3.9 m compared with 6.7 m for the coiled‐coil alone). By comparison, the placement of a positively charged region C‐terminal to the neck coiled‐coil of Kif3B had little effect on stability (urea_1/2 value of 8.2 m compared with 8.8 m for the coiled‐coil alone). The pairing of complementary charged regions leads to specific heterodimer formation where the stability of the heterodimeric neck coiled‐coil with charged regions had similar stability (urea_1/2 value of 7.8 m ) to the most stable homodimer (Kif3B) with charged regions (urea_1/2 value of 8.0 m ) and dramatically more stable than the Kif3A homodimer with charged regions (urea_1/2, value of 3.9 m ). The heterodimeric coiled‐coil with charged extensions has essentially the same stability as the heterodimeric coiled‐coil on its own (urea_1/2 values of 7.8 and 8.1 m , respectively) suggesting that specificity of heterodimerization is driven by non‐specific attraction of the oppositely unstructured charged regions without affecting stability of the heterodimeric coiled‐coil.     

康柏西普及光凝治疗弥漫型糖尿病性黄斑水肿的效果

目的:比较单纯康柏西普玻璃体内注射、单纯黄斑格栅激光光凝及二者联合治疗对弥漫型糖尿病性黄斑水肿(DME)的效果。方法:回顾性研究。将2016年8月至2019年10月长治医学院附属和平医院弥漫型DME 74例(82眼)分为单纯康柏西普玻璃体内注射组(A组,31眼)、单纯黄斑格栅激光光凝组(B组,24眼)和康柏西普联合激光光凝组(C组,27眼)。治疗后随访6个月,观察比较治疗前后视力、黄斑中心区厚度、FFA及注射次数。结果:治疗后A组和C组BCVA及黄斑中心区厚度(CMT)均较治疗前改善(P<0.05);B组治疗后BCVA无改善;B组CMT治疗后1个月无改善,治疗后3及6个月CMT下降(P<0.05)。治疗后BCVA及CMT的改善程度A组和C组差异无统计学意义,但均优于B组(P<0.05)。治疗后6个月FFA改善率3组间差异无统计学意义。治疗后6个月内康柏西普平均注射次数C组少于A组(P=0.001)。结论:康柏西普玻璃体内注射联合黄斑格栅激光光凝与单纯康柏西普注射治疗弥漫型DME效果相近,均优于单纯黄斑格栅激光光凝;黄斑格栅激光光凝可减少康柏西普注射次数。     

区域性消毒供应中心的网格化集中式管理

目的探讨网格化集中式管理模式在区域性消毒供应中心的运用效果。方法采用互联网结合WiFi无线网络技术,移动PDA技术,二维条形码技术,建立闸北区区域性消毒供应中心网络系统,闸北区内28个基层医疗机构均是管理系统里的一个网格,采用网格化集中管理模式进行管理,并与常规集中式管理进行效果比较。结果网格化集中式管理模式下消毒供应工作流程中回收、去污、消毒、包装、灭菌、储存和运送质量检查合格率,医疗机构满意率显著高于常规集中式管理,各岗位每人每小时消毒灭菌包个数显著多于常规集中式管理(均P0.01)。结论网格化集中式管理模式应用于区域化消毒供应中心可提高基层医院消毒物品质量,提高工作效率,达到资源共享和质量追溯。     

Multi-Mesh-Scale Approximation of Thin Geophysical Mass Flows on Complex Topographies

This paper is devoted to a multi-mesh-scale approach for describing the dynamic behaviors of thin geophysical mass flows on complex topographies. Because the topographic surfaces are generally non-trivially curved, we introduce an appropriate local coordinate system for describing the flow behaviors in an efficient way. The complex surfaces are supposed to be composed of a finite number of triangle elements. Due to the unequal orientation of the triangular elements, the distinct flux directions add to the complexity of solving the Riemann problems at the boundaries of the triangular elements. Hence, a vertex-centered cell system is introduced for computing the evolution of the physical quantities, where the cell boundaries lie within the triangles and the conventional Riemann solvers can be applied. Consequently, there are two mesh scales: the element scale for the local topographic mapping and the vertex-centered cell scale for the evolution of the physical quantities. The final scheme is completed by employing the HLL-approach for computing the numerical flux at the interfaces. Three numerical examples and one application to a large-scale landslide are conducted to examine the performance of the proposed approach as well as to illustrate its capability in describing the shallow flows on complex topographies.     

Familiarity expands space and contracts time

When humans draw maps, or make judgments about travel‐time, their responses are rarely accurate and are often systematically distorted. Distortion effects on estimating time to arrival and the scale of sketch‐maps reveal the nature of mental representation of time and space. Inspired by data from rodent entorhinal grid cells, we predicted that familiarity to an environment would distort representations of the space by expanding the size of it. We also hypothesized that travel‐time estimation would be distorted in the same direction as space‐size, if time and space rely on the same cognitive map. We asked international students, who had lived at a college in London for 9 months, to sketch a south‐up map of their college district, estimate travel‐time to destinations within the area, and mark their everyday walking routes. We found that while estimates for sketched space were expanded with familiarity, estimates of the time to travel through the space were contracted with familiarity. Thus, we found dissociable responses to familiarity in representations of time and space. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.     

The Effect of Dose Grid Resolution on Dose Volume Histograms for Slender Organs at Risk during Pelvic Intensity-modulated Radiotherapy

PurposeThere are enduring uncertainties regarding the optimal dose grid resolution for use with pelvic intensity-modulated radiotherapy (IMRT) plans in which the adjacent organs at risk are slender and transect the field edge. Therefore, this study evaluated the effect of dose grid resolution on bladder wall dose-volume histogram (DVH) calculations for prostate IMRT plans.Materials and MethodsThe planning computed tomography scans and clinical plans from 15 prostate cancer patients were included in this analysis. For each study computed tomography, the entire inner and outer bladder surfaces were delineated. Nine versions of the clinical plan were created, varying interval between the dose grid calculation points uniformly in three dimensions, whereas all other plan parameters were kept constant. The dose grid increments tested were 1–10 mm. The plans were recalculated and the bladder wall DVH compared against the study benchmark (1 mm grid).ResultsAll the dose grid increments evaluated resulted in a systematic overestimation of the bladder wall volume receiving low doses and an underestimation of the volume receiving high doses. Grid increments <2.5 mm all resulted in mean volume differences less than 1 cm³ across the whole DVH. Grid increments >5.0 mm resulted in mean volume differences greater than 2 cm³. Individual patient analysis revealed that only the 1.5 mm increment resulted in maximum volume differences ≤1 cm³ for every patient across the full length of the DVH curve. Bladder wall thickness ranged from 1.7 to 4.4 mm and displayed no correlation with the magnitude of the dose grid effect.ConclusionsFor an accurate DVH calculation for bladder wall during IMRT planning for prostate cancer, a 1.5 mm dose grid increment is recommended. This finding was unaffected by a normal range in bladder wall thickness. It is suggested that the application of any new treatment planning technique or organ delineation method be accompanied with an evaluation of optimal dose grid resolution.