Accuracy of axial length measurements from immersion B-scan ultrasonography in highly myopic eyes

AIM:To evaluate the accuracy of axial length(AL)measurements obtained from immersion B-scan ultrasonography(immersion B-scan)for intraocular lens(IOL)power calculation in patients with high myopia and cataracts.METHODS:Immersion B-scan,contact A-scan ultrasonography(contact A-scan),and the IOLMaster were used to preoperatively measure the AL in 102 eyes from 102 patients who underwent phacoemulsification and IOL implantation.Patients were divided into two groups according to the AL:one containing patients with22 mm≤AL【26 mm(group A)and the other containing patients with AL≥26 mm(group B).The mean error(ME)was calculated from the difference between the AL measurement methods predicted refractive error and the actual postoperative refractive error.RESULTS:Ingroup A,ALs measured byimmersion Bscan(23.48±1.15)didn’t differ significantly from those measured by the IOLMaster(23.52±1.17)or from those by contact A-scan(23.38±1.20).In the same group,the standard deviation(SD)of the mean error(ME)of immersion B-scan(-0.090±0.397 D)didn’t differ significantly from those of IOLMaster(-0.095±0.411 D)and contact A-scan(-0.099±0.425 D).In group B,ALs measured by immersion B-scan(27.97±2.21 mm)didn’t differ significantly from those of the IOLMaster(27.86±2.18 mm),but longer than those measured by Contact A-scan(27.75±2.23 mm,P=0.009).In the same group,the standard deviation(SD)of the mean error(ME)of immersion B-scan(-0.635±0.157 D)didn’t differ significantly from those of the IOLMaster(-0.679±0.359 D),but differed significantly from those of contact A-scan(-0.953±1.713 D,P=0.028).CONCLUSION:ImmersionB-scanexhibitsmeasurement accuracy comparable to that of the IOLMaster,and is thus a good alternative in measuring AL in eyes with high myopia when the IOLMaster can’t be used,and it is more accurate than the contact A-scan.

Precise measurement method of optical fiber length based on timestamp technique

A measurement method of optical fiber length using timestamp technique is demonstrated. Based on IEEE1588 precise clock synchronization protocol, the principle that time delay asymmetry on two path results in synchronization time deviation is used, and the difference between two-path delays could be deduced by measuring the synchronization time deviation reversely. Then the length of optical fiber on one path could be calculated if that on the other path is known Due to the fact that the path of Sync and Delay_Req message is symmetric, the optical pulse dispersion and the asymmetry of photoelectric detector performance on two paths are averaged by exchanging two optical fibers. The time difference between master and slave clocks is eliminated by sharing the same time base. At last, the lengths of two single-mode optical fibers are measured with the uncertainty of 0. 578 m for 3 227. 722 m and 0. 758 m for 25 491. 522 m, respectively. Thus this method has high precision and long range.

Significance of Axial Length Monitoring in Children with Congenital Cataract and Update of Measurement Methods

Congenital cataract is the main cause of blindness in children, with significantly varying treatment effects. The development of axial length is an important factor that affects the prognosis of these children.However,when compared with the eyes of normal children,the mechanism of growth of the axial length is so complicated that the reported findings differ significantly in terms of the measuring apparatus,assessment methods,and statistical outcome,making the rule of axial length development still unclear. In this paper, we first review the process of axial length development in normal healthy children and compare different hypotheses about certain factors that could affect the development of axial length. The results of some current research about the characteristics of axial length development in congenital cataract children are then reviewed. Lastly, the advantages and disadvantages of current axial length measurements methods are compared and analyzed.The purpose of this review is to improve our understanding of the complexity and importance of axial length development and to suggest better use of axial length monitoring measurements in congenital cataract children for pediatric ophthalmologists,with the hope of offering assistance that will enhance long-term therapeutic effects for these children.

A linear crack length measurement method for railway bridges based on calibration points fitting

For the linear crack skeleton of railway bridges with irregular strike,it is difficult to accurately express the crack contour feature by using a single smoothing fitting algorithm.In order to improve the measurement accuracy,a polynomial curve fitting was proposed,which used the calibration point of crack contour as the boundary point,and then put them all together to produce a continuous contour curve to achieve the crack length measurement.The method was tested by measuring the linar cracks with different shapes.It is shown that this proposed algorithm can not only solve the jagged problem generated in the crack skeleton extraction process,but also improve the crack length measurement accuracy.The relative deviation is less than 0.15,and the measurement accuracy is over 98.05%,which provides a more effective means for the crack length measurement in railway bridges.

Injection transient study using a two-frequency bunch length measurement system at the SSRF

The bunch length can be measured by comparison of two frequency components of a synchrotron beam signal.An online bunch length measurement system has been implemented based on this method.Working frequencies of 3 GHz and 500 MHz were selected,and the raw data was acquired by digital oscilloscope and was resampled and analyzed using the MATLAB software platform at bunch-by-bunch rate.The constructed system was employed to study the bunch length synchronous oscillation phenomenon during injection.The beam experiments demonstrated a time resolution of less than 0.5 ps.

Automatic Detection and Measurement of Fetal Biparietal Diameter and Femur Length —Feasibility on a Portable Ultrasound Device

An automatic method able to recognize a presented section through the biparietal plane of the fetal head and a section through the fetal femur in ultrasound images is developed. Once the correct anatomical section for measurement is identified by the machine, the placement of the measurement calipers is automatically determined by fitting an active contour model to the structure of interest. The fetal biparietal diameter (BPD) and femur length (FL) are then measured automatically. The validation data set contained 167 and 197 B-mode images for BPD and FL measurements, respectively. The images were acquired using 4 different ultrasound scanners, which resulted in varied image quality and gain settings. The mean gestational age (GA) of the fetuses was 19.4 weeks, range 16 to 41 weeks. A measurement success rate of 90% was achieved for both BPD and FL. The correlation coefficients between the manual and automatic measurements were 0.995 (BPD) and 0.967 (FL), mean errors were 0.5 mm (BPD) and -1.7 mm (FL) and error range with 95% confidence interval (CI) were ﹣3.8 - 4.8 mm (BPD) and ﹣11.4 - 8.1 mm (FL). The automatic measurement results were consistent in both high and low gain settings. The intraclass correlation coefficients between manual and automatic measurements were 0.995 (95% CI;0.981 - 0.999) for BPD in high gain, 1.0 (95% CI;0.998 - 1.0) for BPD in low gain, 0.998 (95% CI;0.991 - 0.999) for FL in high gain and 0.999 (95% CI;0.996 - 1.0) for FL in low gain settings. The method was implemented on a prototype, portable ultrasound machine designed to be used in low- and middle-income countries (LMIC). The overall performance of the method supports our hypothesis that automated methods can be used and are beneficial in a clinical setting.

Variations of OCT measurements corrected for the magnification effect according to axial length and refractive error in children

Purpose:The aim of this paper was to examine the distribution of macular,retinal nerve fiber layer(RNFL)thickness and optic disc parameters of myopic and hyperopic eyes in comparison withemmetropic control eyes and to investigate their variation according to axial length(AL)andspherical equivalent(SE)in healthy children.Methods:This study included 293 pairs of eyes of 293children(145 boys and 148 girks),ranging in age from 6 to 17 years,Subjects were dividedaccording to SE in control(emmetropia,99 children),myopia(100 children)and hyperopia(94children)groups and according to axial AL in 68 short(<22.00 mm,68),medium(from≥22.00 mmto 25.00 mm,189)and long eyes(>25.00 mm,36).Macular parameters,RNFL thickness and opticdisc morphology were assessed by the Cirrus^(TM) HD-OCT.AL was measured using the IOL-Mastersystem.Littmann's formula was used for calculating the corrected AL-related ocular magnification.Results Mean age(±SD)was 10.84±3.05 years;mean(±SD)SE was+0.14±0.51 D(range from8.75 to+8.25 D)and mean AL(±SD)was 23.12±1.49.Average RNFL thickness,averagemacular thickness and macular volume decreased as AL and myopia increased.No correlationsbetween AL/SE and optic disc parameters were found after correcting for magnification effect.Conclusions:AL and refractive error affect measurements of macular and RNFL thickness inhealthy children.To make a correct interpretation of ocT measurements,ocular magnificationeffect should be taken into account by clinicians or OCT manufacturers.

Precise Optical Fiber Length Measurement System Based on Fresnel Reflection

In this study, a precise optical fiber length measurement system is proposed. The measurement technique is based on the measurement of relative Fresnel reflected light intensity in a test fiber. Time delayed optical reflected pulses are obtained from a single nanosecond pulse injected at the input due to the difference in lengths of the reference and test fibers. The lengths of the different optical fibers have been measured with this technique with high resolution and fast response time. The measured results show that, the proposed technique has a comparable performance with the well-known length measurement systems.

Beak Measurements of Octopus (Octopus variabilis) in Jiaozhou Bay and Their Use in Size and Biomass Estimation

Cephalopods play key roles in global marine ecosystems as both predators and preys.Regressive estimation of original size and weight of cephalopod from beak measurements is a powerful tool of interrogating the feeding ecology of predators at higher trophic levels.In this study,regressive relationships among beak measurements and body length and weight were determined for an octopus species(Octopus variabilis),an important endemic cephalopod species in the northwest Pacific Ocean.A total of 193 individuals(63 males and 130 females) were collected at a monthly interval from Jiaozhou Bay,China.Regressive relationships among 6 beak measurements(upper hood length,UHL;upper crest length,UCL;lower hood length,LHL;lower crest length,LCL;and upper and lower beak weights) and mantle length(ML),total length(TL) and body weight(W) were determined.Results showed that the relationships between beak size and TL and beak size and ML were linearly regressive,while those between beak size and W fitted a power function model.LHL and UCL were the most useful measurements for estimating the size and biomass of O.variabilis.The relationships among beak measurements and body length(either ML or TL) were not significantly different between two sexes;while those among several beak measurements(UHL,LHL and LBW) and body weight(W) were sexually different.Since male individuals of this species have a slightly greater body weight distribution than female individuals,the body weight was not an appropriate measurement for estimating size and biomass,especially when the sex of individuals in the stomachs of predators was unknown.These relationships provided essential information for future use in size and biomass estimation of O.variabilis,as well as the estimation of predator/prey size ratios in the diet of top predators.

A New High Accuracy Measurement Method forHot Deformation of Large Structures

This paper presents a new high accuracy measurement for hot deformation of large structure. Its princple and technological features, several key technologies and factors that affect measurement accuracy are discussed, the uncertainty of measurement is analyzed, and measures to ensure accuracy are given.

Use of Foot Measurements as Sonographic Parameter for Estimation of Fetal Age

Objectives: this research was conducted to describe the ultrasonic measurements of the foot full measurements (FFM) and their importance in the antenatal care (ANC). Material and methods: the Descriptive quantitative cross-sectional study conducted in the ultrasound department at Alshaekh Mohammed Ali Fadol hospital in Omdurman locality. The study included 400 healthy Sudanese pregnant women whom in the 1st (late), 2nd and 3rd trimesters (i.e., after 10 weeks gestational age) of different parity and ages (15 years old and above);they have regular menstrual cycle and well certain of their last menstrual period and calculated date of delivery. Ultrasonographic measurement of Full Foot Length1 (FFL1), Foot Full Length2 (FFL2), and Foot Full Width (FFW) of all pregnant women were done. Sonographically we measured fetal foot from 14 to 40 weeks of gestation. Results: the study revealed that the mean FFL1 was 58.7 ± 12.9 mm. The minimum measurement was 18.8 mm, and the maximum was 89.1 mm, while the mean value of FFL2 was 53.4 ± 11.4 mm, with minimum value 17.5 mm and maximum 81.7 mm, and the mean FFW was 23.7 ± 5.1 mm, with minimum value 7.0 mm and maximum 38.0 mm. Conclusion: a strongly significant relationships were observed between (FFL1, FFL2, FFW) and gestational age (p = 0.00). However there is no significant difference between the FFL1, FFL2, and correlations with sex of embryo, residence, occupation, parity, maternal height, socioeconomic status, bleeding during this pregnancy, chronic illness, and caesarian section, moreover there are significant correlations between the FFL1, FFL2 and the (maternal age, maternal weight, and body mass index), but in the measurement of the fetal FFW there were no significant correlations with (sex of embryo, maternal age, body mass index, residence, occupation, parity, socioeconomic status, bleeding during this pregnancy, chronic illness, and caesarian section). Also there are significant correlations between the FFW and the maternal weight and height.

北京佑安医院降低平均住院日的管理措施研究

目的探讨首都医科大学附属北京佑安医院实施平均住院日管理的效果。方法首都医科大学附属北京佑安医院在2022年1月起采取建立集中预约平台、成立住院服务中心、实时沟通机制、积极开展日间手术和微创手术、深入推进临床路径和单病种管理、优化多学科诊疗模式等多项措施综合管控平均住院日,比较2021年1—12月和2022年1—12月病案首页数据,对全院、重点科室、前20位疾病的平均住院日相关数据进行统计分析。结果采取多措并举后,2022年1—12月全院平均住院日、重点科室平均住院日和前20位疾病平均住院日均较2021年1—12月明显下降,2022年1—12月平均住院日由9.49 d降至8.50 d。结论多部门联动后优化措施可有效缩短平均住院日。

面向油品参数快速计量的高精度傅里叶近红外光谱仪

针对油品现场检测中实时性和准确度的需要,研制了一种面向油品参数快速计量的高精度傅里叶近红外光谱仪。该光谱仪采用相干长度扩增方法,可快速定位有效信号;通过驱动采集控制系统对傅里叶近红外检测光路进行100 nm等间隔的干涉调制,最终由傅里叶逆变换解析出的吸收光谱分辨力可达3.25 cm^(-1)。用该光谱仪对汽油样品进行质量检测的结果表明:该光谱仪可在短时间内对汽油中5种物质含量进行快速计量,其最大体积误差不超过0.7%,可以满足油品参数现场计量的需求,对市场中成品油质量的监管具有重要意义。

调频连续波激光多路并行相干精密长度测量方法

面向航空航天等大型复杂机电系统,长度测量的需求从单独的一维位移测量发展到多目标、灵活便于拓展的多路并行测量。调频连续波激光雷达长度测量技术具备抗干扰、精度高、无合作等优势。本文基于调频连续波激光雷达技术开展多路并行相干精密长度测量方法研究,针对传统长度测量系统存在光纤色散、辅助路光纤漂移导致长度测量精度降低问题,提出一种含有氰化氢气体吸收池的三光路马赫-曾德尔干涉测量系统,在此基础上,基于光开关结构实现精密长度多路并行测量。通过精密导轨长度测量实验结果表明,提出的方法在3.6 m长度范围内标准差不超过25μm,实现了四路并行长度测量。与商用激光干涉仪测量结果比较,多路测量结果的绝对误差不超过30μm。

流动式相对重力仪的研制与应用

地球重力场信息是进行地球物理研究的重要基础数据,对我国具有重要意义。作为陆上高精度重力测量的核心仪器,流动式相对重力仪因其技术门槛高,国内市场长期被国外产品所垄断。天津航海仪器研究所依托掌握的金属零长弹簧制备核心技术,成功研制出流动式相对重力仪,成为国内极少数掌握该项技术的单位,可全面满足包括陆上重力基线场在内的野外测量作业要求。由天津航海仪器研究所研制的流动式相对重力仪通过了国内最具权威用户组织中国地震局的入网测评,实测重复性标准差为3.1μGal,精度为3.5μGal,分辨力优于1μGal,整体性能达到国际先进水平。

眼轴长度与角膜曲率半径比值在儿童青少年近视评估中的效能

目的:评估眼轴长度与角膜曲率半径比值(AL/CR)在儿童青少年近视诊断中的价值。方法:收集2022-01/2023-12在北海市第二人民医院视光门诊初次就诊的儿童青少年2182例4364眼的屈光度及眼生物学参数,并进行分析。结果:受试者工作特征曲线(ROC曲线)分析显示,AL/CR诊断近视具有更高的曲线下面积(AUC=0.925,95%CI为0.917-0.933),且AL/CR=3.053时,Youden指数最大,随着AL/CR界值变小,近视诊断的灵敏度呈升高趋势,特异度则有所下降。与筛查性近视相比,AL/CR=3.053诊断近视的灵敏度偏低,但特异度较高,尤其在远视和近视前期者中表现更明显。结论:AL/CR对于近视诊断的准确性优于眼轴长度及平均角膜曲率,且具有更高的特异度;随着AL/CR界值变小,其诊断近视的灵敏度增加,但特异度下降。在远视和近视前期者中,AL/CR对于近视诊断的特异度高于筛查性近视。

附加速度与基线长约束的海上基线网平差

为削弱全球卫星导航系统(GNSS)测量误差对海底控制点测量的影响,对GNSS基线解算后的数据进行后处理,并根据海上作业环境提出一种基于速度和基线长等先验信息的约束卡尔曼滤波(KF)方法:充分利用海上多天线的观测模式,将接收机间的速度与距离关系作为约束引入到模型当中,以提高状态估计的精度;然后对GNSS差分定位中基线解算之后的数据进行网平差;最后与最小二乘法和传统卡尔曼滤波进行比较。实验结果证明,与前2种方法相比,提出方法的观测噪声平滑能力更为突出,所选3条基线的基线长偏差的标准差和均方根较RTKLIB软件动态基线解算后的数据分别下降了27%、48%和67%以上;由于水声换能器的三维坐标由GNSS天线坐标转化而来,所以网平差后的GNSS坐标能够提供更加精确的水声换能器坐标,进而提高海底控制点的量测精度。

基于数字化三维技术二次电缆长度自动统计方法

针对在二次电缆长度测量和统计过程中,接触式的方法过度依赖选择的测量仪器,统计人工性较强,导致总统计成本较高。提出基于数字化三维技术的二次电缆长度自动统计方法。采用数字化三维技术处理多条基本线缆,利用线束分支结构和线束主结构,组成二次电缆三维信息模型,分析挡块与二次电缆的几何关系,测量三维位移场,获得独立的二次电缆的动态长度,从二次电缆模型中选择三个参考点,经过拼接转换计算,统计出二次电缆整体长度。实验结果表明:设计的方法测量成本和检测误差成本均低于计划成本,与常规的人工统计方法相比,经济性更高。

钢桥面板顶板贯穿裂纹长度涡流检测及其影响因素

针对正交异性钢桥面板顶板贯穿型疲劳裂纹隐蔽性强、难以精确检测的问题,提出通过涡流检测方法对裂纹长度进行测量。首先,对试验获取的涡流检测信号进行分析,探究信号特征与裂纹长度之间的关系,据此拟合出裂纹长度的测量公式,并通过有限元模拟对其有效性进行验证;其次,研究线圈参数与扫查速度对检测效果的影响;最后,通过有限元模拟分析了水平裂纹相邻顶点间距、裂纹与线圈中心的偏移距离、裂纹与线圈扫查方向的夹角对检测结果的影响。结果表明:增加圆柱形线圈外径与内径之比并适当减小线圈内阻可提高检测灵敏度;裂纹长度的测量值随着线圈扫查速度的增大而减小;水平裂纹相邻顶点间距越大,越利于精确测量裂纹长度;随着裂纹与线圈中心偏移距离的增加,检测信号的变化幅值逐渐减小,裂纹长度测量值也随之下降;此外,线圈扫查方向与裂纹长度方向的夹角越大,越不利于检测。该钢桥面板疲劳裂纹长度涡流检测方法可实现高效、便捷、精准的无接触式检测,为钢桥的运营维护提供相关技术参考。

高分辨率光纤法珀传感器解调系统设计

光纤法珀传感器的腔长测量精度取决于解调系统的分辨率,现有的解调系统的分辨率多大于10 nm,难以实现10 nm以内腔长变化的测量。针对该问题,提出了以7 450像元数的线阵图像传感器为基础搭建解调系统,通过硬件设计与软件算法提高特征信号质量,完成腔长数据提取,实现了一种高分辨率光纤法珀传感器解调系统。实验结果表明,该系统在0~20μm的腔长测量范围内,实现了2.7 nm的光学分辨率,精度达到0.013 5%FS。