A dual echo approach to removing motion artefacts in fMRI time series

In fMRI, subject motion can severely affect data quality. This is a particular problem when movement is correlated with the experimental paradigm as this potentially causes artefactual activation. A method is presented that uses linear regression, to utilise the time course of an image acquired at very short echo time (TE) as a voxel‐wise regressor for a second image in the same echo train, that is acquired with high BOLD sensitivity. The value of this approach is demonstrated using task‐locked motion combined with visual stimulation. Results obtained at both 1.5 and 3 T show improvements in functional activation maps for individual subjects. The method is straightforward to implement, does not require extra scan time and can easily be embedded in a multi‐echo acquisition framework. Copyright © 2009 John Wiley & Sons, Ltd.     

后路半椎体切除矫治先天性脊柱侧后凸的临床疗效分析

目的：探讨后路半椎体切除矫治先天性脊柱侧后凸的临床疗效。方法选取该院收治的先天性脊柱侧后凸患者50例,全部患者均行后路半椎体切除矫治术治疗,比较术前、术后,X线片中测量的侧凸Cobb角、后凸Cobb角,分析后路半椎体切除矫治术治疗的临床效果。结果全部50例患者,术后侧凸Cobb角（10.4±2.3）o,明显小于术前侧凸Cobb角（52.5±6.6）o,比较差异有统计学意义（P<0.05）;术后后凸Cobb角（8.3±1.6）o,明显小于术前后凸Cobb角（31.9±5.2）o,比较差异有统计学意义（P<0.05）。结论后路半椎体切除矫治先天性脊柱侧后凸具有明显的手术效果,患者术后侧、后凸Cobb角均得到了较好的矫正,临床效果明显,值得临床上推广应用。     

Computer‐Based Analysis of Dynamic QT Changes: Toward High Precision and Individual Rate Correction

Background: New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes. Methods: The EClysis software processes digitally‐recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means ± SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R‐R measured on beat level, an individual correction for the R‐R dependence can be performed. Results: EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T‐wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R‐R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction. Conclusions: The EClysis system provides a precise and reproducible method to analyze ECGs. A.N.E. 2002;7(4):289–301     

Penalization,bias reduction,and default priors in logistic and related categorical and survival regressions

Penalization is a very general method of stabilizing or regularizing estimates, which has both frequentist and Bayesian rationales. We consider some questions that arise when considering alternative penalties for logistic regression and related models. The most widely programmed penalty appears to be the Firth small‐sample bias‐reduction method (albeit with small differences among implementations and the results they provide), which corresponds to using the log density of the Jeffreys invariant prior distribution as a penalty function. The latter representation raises some serious contextual objections to the Firth reduction, which also apply to alternative penalties based on t‐distributions (including Cauchy priors). Taking simplicity of implementation and interpretation as our chief criteria, we propose that the log‐F(1,1) prior provides a better default penalty than other proposals. Penalization based on more general log‐F priors is trivial to implement and facilitates mean‐squared error reduction and sensitivity analyses of penalty strength by varying the number of prior degrees of freedom. We caution however against penalization of intercepts, which are unduly sensitive to covariate coding and design idiosyncrasies. Copyright © 2015 John Wiley & Sons, Ltd.     

低度屈光不正对中年干眼患者的影响

目的 探讨低度屈光不正对中年干眼患者眼部症状的影响,为干眼患者选择安全合理的治疗措施.方法 选取在我院眼科门诊就诊的年龄为40 ～ 60岁,屈光度为-3.00～ +3.00D的干眼患者191例(373眼),对所有入选病例进行干眼常规检查和干眼症状评分,同时对所有患者进行医学验光并按照初诊时屈光度分成3组:正视组:-0.50～ +0.25 D,不伴散光,64例125眼;近视组:-0.75～-3.00 D,68例131眼;远视组:+0.50～ +3.00 D,59例117眼.结合分组情况对患者进行相应的屈光矫正,并给予人工泪液及糖皮质激素眼液滴眼.治疗1个月后随访,对结果进行统计学分析.结果 3组患眼初诊时客观体征间差异均无统计学意义(均为P ＞0.05),但远视组患者的症状评分为(25.61±8.07)分,明显高于正视组的(15.43±5.27)分和近视组的(17.19±6.34)分(均为P＜0.05),而正视组和近视组之间差异无统计学意义(P＞0.05).远视组117眼中,戴镜矫正合并干眼治疗者63眼,仅接受干眼治疗者54眼,治疗1个月后戴镜矫正组症状评分与治疗前的差值为(8.89±1.74)分,明显高于未矫正组的(4.73±3.57)分,差异有统计学意义(P＜0.05).近视组是否戴镜矫正联合干眼治疗并未表现出统计学上的疗效差异.结论 对合并屈光不正的中年干眼患者,尤其是低度远视患者,给予恰当的屈光矫正可以明显改善干眼症状.     

射波刀治疗床修正值对六维颅骨追踪总体精度的影响

目的:探讨射波刀治疗床可修正值与六维颅骨(6D Skull)靶区追踪总体精度的关系.方法:通过影像引导将治疗床移至所需修正位置进行6D Skull球方模型定位精度测试,将测试结果与修正值为0相比较及分析.结果:治疗床3个平移方向修正值为0、3、6、10 mm,靶区追踪总体精度分别为0.23、0.32、0.53、0.55 mm;治疗床3个旋转方向修正值为(0.3、0.3、1°)、(0.6、0.6、2.)、(1、1、3°),靶区追踪总体精度分别为0.12、0.99、0.78 mm;治疗床3个平移方向和3个旋转方向修正值为(3、3、3 mm,0.3、0.3、1°)、(6、6、6mm,0.6、0.6、2°)、(10、10、10 mm,1、1、3°),靶区追踪总体精度分别为0.08、0.8、1.4 mm.结论:射波刀6D Skull靶区追踪总体精度随着治疗床3个平移方向或(和)3个旋转方向修正值的增加而增大,日常治疗摆位时应尽可能地减小治疗床的修正值.     

Experimental quantum coding against qubit loss error

The fundamental unit for quantum computing is the qubit, an isolated, controllable two-level system. However, for many proposed quantum computer architectures, especially photonic systems, the qubits can be lost or can leak out of the desired two-level systems, posing a significant obstacle for practical quantum computation. Here, we experimentally demonstrate, both in the quantum circuit model and in the one-way quantum computer model, the smallest nontrivial quantum codes to tackle this problem. In the experiment, we encode single-qubit input states into highly entangled multiparticle code words, and we test their ability to protect encoded quantum information from detected 1-qubit loss error. Our results prove in-principle the feasibility of overcoming the qubit loss error by quantum codes.     

生物力学影响的靶区位姿精度保持方法研究

目的:分析二次摆位中靶区位姿在生物力学影响下的器官肿瘤变形规律,控制机械臂位置来补偿此误差。方法:利用解剖学和生物力学相关知识,通过Mimics v17.0软件建立包含肿瘤的肺组织有限元模型,将建立的有限元模型导入ANSYS15.0,利用前人总结的生物力学特性参数仿真分析肺和肿瘤的变形误差。结果:得到在二次摆位中肺组织最大变形为21.24 mm,肿瘤最大变形为3.17 mm,并利用二次多项式拟合给出了误差模型,摆位验证后其误差变形均在此范围内,其中头脚方向变形最大。结论:基于自主设计的六自由度摆位医用机械臂提出一种通过前馈修正的位置控制方法,该方法在二次摆位过程中可以预先补偿肿瘤的位移误差,提高放疗精度和效率,减少对治疗靶区周围正常组织的损伤。 【关键词】靶区位姿;生物力学;变形误差;前馈修正