Accuracy of Quadratic Versus Linear Interpolation in Noninvasive Electrocardiographic Imaging (ECGI)

Electrocardiographic Imaging (ECGI) is a cardiac functional imaging modality, noninvasively reconstructing epicardial potentials, electrograms and isochrones (activation maps) from multi-channel body surface potential recordings. The procedure involves solving Laplace’s equation in the source-free volume conductor between torso and epicardial surfaces, using Boundary Element Method (BEM). Previously, linear interpolation (LI) on three-noded triangular surface elements was used in the BEM formulation. Here, we use quadratic interpolation (QI) for potentials over six-noded linear triangles. The performance of LI and QI in ECGI is evaluated through direct comparison with measured data from an isolated canine heart suspended in a human-torso-shaped electrolyte tank. QI enhances the accuracy and resolution of ECGI reconstructions for two different inverse methods, Tikhonov regularization and Generalized Minimal Residual (GMRes) method, with the QI-GMRes combination providing the highest accuracy and resolution. QI reduces the average relative error (RE) between reconstructed and measured epicardial potentials by 25%. It preserves the amplitude (average RE reduced by 48%) and morphology of electrograms better (average correlation coefficient for QI ∼ 0.97, LI ∼ 0.92). We also applied QI to ECGI reconstructions in human subjects during cardiac pacing, where QI locates ventricular pacing sites with higher accuracy (≤ 10 mm) than LI (≤ 18 mm).     

Real-time automatic extraction of lumen region and boundary from endoscopic images

A new approach to the automatic extraction of the lumen region and its boundary for gastrointestinal (GI) endoscopic images is presented. First, a quasi region of interest, the darker regions of the image, is segmented using a region splitting scheme termed progressive thresholding. The centre of mass of this segmented region acts as a seed for further processing. Then the lumen region is obtained using a region growing technique called the integrated neighbourhood search (INS). A new quad structure based technique is introduced to enhance the INS speed significantly. A back projection algorithm is suggested to optimise the search for pixels belonging to the lumen region and boundary. A boundary-thinning algorithm is also proposed to remove the redundant pixels from the lumen boundary and to generate a connected single pixel width boundary. The proposed approach does not need a priori knowledge about the image characteristics. The experimental results indicate that the proposed technique enhances the speed of conventional INS by 45.5% to 28.6% based on the lumen size varying from 22,709 pixels to 4947 pixels. The main advantage of the proposed technique is its high-speed response that facilitates real-time analysis of endoscopic images.     

下颌颏部骨折内固定的三维有限元模型及边界约束的建立

通过Pro／E和ANSYS建立下颌骨颏部骨折内固定的三维有限元模型，并模拟了各种功能状态下的边界约束。使用计算机图像处理软件对CT扫描图像进行预处理，然后采用自编程序获取下颌骨解剖结构的三维坐标数据，用ANSYS建立下颌骨的三维有限元模型。采用数值化建模软件Pro／E建立小型接骨板-螺钉固定体系统的实体模型。模拟下颌骨颏部正中骨折坚强内固定治疗，建立该内固定治疗的有限元模型。通过改变各组咀嚼肌力的大小，进行了三种咬合状态的边界约束。获得了形态逼真、相似性好的下颌颏部骨折内固定后的三维有限元模型，并模拟了各功能状态下的边界约束，为后期的生物力学分析奠定了基础。     

Fast measurement of the CO2 partial pressure in gases and fluids

A CO₂-electrode system consisting of a membrane covered pH electrode, an electronic antilog modul and a special electronic analog circuit is described. Since the electrode output signal is a logarithmic function of the CO₂ partial pressure the output signal of the antilog module is proportional to the CO₂ partial pressure. The time course of the electrode signal has been analyzed after a step change of . This step response may be approximated by a sum of three exponential functions. Knowing the dynamic behaviour, the transfer function is formulated mathematically and a special analog circuit is constructed with a frequency response inverse to the frequency response of the electrode. Using this device the response time (T ₉₅) of the electrode system is diminished from 11,5 s to 750 ms after a step change of in gas (Luttmann, et al., 1974). If the time for the hydration of CO₂ is decreased by the addition of carbonic anhydrase the response time of the electrode is diminished to 6.5 s. Using the analog circuit yields a response time of 200 ms.Further studies were made to analyze the transient response in fluids at various flow velocities and various mountings. In order to analyze the influence of the fluid boundary layer on the surface of the electrode a photometric method has been developed (Luttmann and Mückenhoff, 1975), which allows to estimate the time course of the CO₂ partial pressure independently of and simultaneously with the electrode measurement.The experimental data are compared with a theory based on theoretical considerations of Schuler and Kreuzer (1967) and Crank (1956).List of Symbols A _i gain factor of thei-th compartment - A _i gain factor of the simulation network - C _i capacity - D diffusion coefficient - d electrode diameter - fraction of CO₂ - F _c (j) frequency response of the linearizing network - F _g (j) frequency response of the boundary layer - F _M (j) frequency response of the measuring system - F _M frequency response of the simulation network - I _i impedance transformer - j Gauss number (j ²=–1) - (j) frequency function of the CO₂ partial pressure - (t) time function of the CO₂ partial pressure - R _i electrical resistance - T _i time constant of the electrode - T _i time constant of the simulation network - T ₉₅ time for reaching 95% of the total difference - V voltage gain factor - v velocity of the streaming fluid - x coordinate - x(t) time function - X(j) corresponding frequency function - dilution factor - inverse time constant - thickness of boundary layer - ^* kinematic viscosity - thickness of diffusion layer - radian frequency Supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 114 (Bionach)     

Outlining the prostate boundary using the harmonics method

In a computerised ultrasound image guidance for automated prostatectomy system, it is necessary to identify a smooth, continuous contour for the prostate (boundary) from the ultrasound image. The radial bas-relief (RBR) method, which has been reported previously, can extract a skeletonised image from an ultrasound image automatically. After this process the prostate boundary is clearly revealed. However, analysis of the image is far from complete, as there are many spurious branches that create too much ambiguity for the system to define the actual boundary. There are also sections missing from the prostate boundary. Therefore further post-processing is required to describe and define the prostate boundary. In the paper, the harmonics method is used to describe the prostate boundary. The harmonics method uses Fourier information for noise removal and encodes a smooth boundary. The results of using the harmonics method after application of the RBR method on ultrasound images are presented. Factors that affect the performance are also highlighted and discussed.     

临床试验中多处理组比较期中分析方法研究

目的 :介绍临床试验中多处理组比较期中分析方法。方法 :在多处理组比较分析方法的基础上 ,将两处理组比较成组序贯期中分析方法进一步扩展用于多处理组比较期中分析。结果 :多处理组期中分析包括各组的总检验和处理组间的两两比较。结论 :多处理组期中分析的关键是每次期中分析时界值的确定     

Policing Epistemic Deviance: Albert von Schrenck-Notzing and Albert Moll1

Shortly after the death of Albert von Schrenck-Notzing (1862–1929), the doyen of early twentieth century German para psychology, his former colleague in hypnotism and sexology Albert Moll (1862–1939) published a treatise on the psychology and pathology of parapsychologists, with Schrenck-Notzing serving as a prototype of a scientist suffering from an ‘occult complex’. Moll’s analysis concluded that parapsychologists vouching for the reality of supernormal phenomena, such as telepathy, clairvoyance, telekinesis and materialisations, suffered from a morbid will to believe, which paralysed their critical faculties and made them cover obvious mediumistic fraud. Using Moll’s treatment of Schrenck-Notzing as an historical case study of boundary disputes in science and medicine, this essay traces the career of Schrenck-Notzing as a researcher in hypnotism, sexology and parapsychology; discusses the relationship between Moll and Schrenck-Notzing; and problematises the pathologisation and defamation strategies of deviant epistemologies by authors such as Moll.     

84例肾细胞癌患者MSCT检查的图像分析及相关生物学行为评价

目的分析肾细胞癌患者多层螺旋CT(MSCT)检查的图像及相关生物学行为。方法选取2015年6月~2018年11月我院肾细胞癌患者84例,患者均采取MSCT检查,并行手术治疗,在术中取肾细胞癌组织和相应癌旁正常肾组织标本,以免疫组织化学SP法检测患者肾细胞癌组织和癌旁正常肾组织中Ki-67、缺氧诱导因子-1α(HIF-1α)表达情况,并观察患者MSCT征象(瘤体大小、强化程度、有无坏死、液化、囊变,肿瘤边界清楚与否、有无血管受侵、有无邻近脏器侵犯或远处转移),分析肾细胞癌MSCT征象和Ki-67、HIF-1α表达情况相关性。结果本组术前应用MSCT扫描对肾细胞癌检出率及定性诊断率均为100%;Ki-67、HIF-1α在肾细胞癌组织中表达均高于癌旁正常肾组织(P<0.05);MSCT征象表现为瘤体大小>5cm、强化程度≥20HU、存在坏死、液化、囊变、肿瘤边界不清楚、有血管受侵、产生邻近脏器侵犯或远处转移者Ki-67、HIF-1α表达均高于瘤体大小≤5cm、强化程度<20HU、无坏死、液化、囊变、肿瘤边界清楚、无血管受侵、未产生邻近脏器侵犯或远处转移者(P均<0.05)。结论应用MSCT扫描可对肾细胞癌施行准确术前诊断,且肾细胞癌患者MSCT征象和Ki-67、HIF-1α表达有着密切相关性,能间接反映肿瘤生物学行为,为肾细胞癌诊断、治疗提供有力参考。     

Comparison of spherical and realistically shaped boundary element head models for transcranial magnetic stimulation navigation

Objective

MRI-guided real-time transcranial magnetic stimulation (TMS) navigators that apply electromagnetic modeling have improved the utility of TMS. However, their accuracy and speed depends on the assumed volume conductor geometry. Spherical models found in present navigators are computationally fast but may be inaccurate in some areas. Realistically shaped boundary-element models (BEMs) could increase accuracy at a moderate computational cost, but it is unknown which model features have the largest influence on accuracy. Thus, we compared different types of spherical models and BEMs.

Methods

Globally and locally fitted spherical models and different BEMs with either one or three compartments and with different skull-to-brain conductivity ratios (1/1–1/80) were compared against a reference BEM.

Results

The one-compartment BEM at inner skull surface was almost as accurate as the reference BEM. Skull/brain conductivity ratio in the range 1/10–1/80 had only a minor influence. BEMs were superior to spherical models especially in frontal and temporal areas (up to 20 mm localization and 40% intensity improvement); in motor cortex all models provided similar results.

Conclusions

One-compartment BEMs offer a good balance between accuracy and computational cost.

Significance

Realistically shaped BEMs may increase TMS navigation accuracy in several brain areas, such as in prefrontal regions often targeted in clinical applications.