人体组织厚度对体外冲击波碎石焦点位置及声压影响的仿真研究

目的研究体外冲击波碎石（extracorporeal shock wave lithotropisy，ESWL）治疗中不同厚度人体组织对ESWL焦点区域声压及实际形成焦点位置的影响，为ESWL治疗计划的制定提供理论依据。方法以Reichenberger的ESWL水中实验为例，建立三维仿真模型，用时域有限差分（finite differencetime domain，FDTD）数值仿真法，数值仿真ESWL治疗中形成的焦点区域。结果高强度聚焦超声波在人体脂肪、肌肉层非线性传播过程中形成的实际焦点位置和焦点区域声压，随着人体脂肪及肌肉层厚度的变化而变化。结论ESWL治疗过程中由于人体组织厚度的不同，超声非线性传播而形成的焦距和最大声压不同，对于不同体态的患者，在ESWL治疗时应该采用不同的焦距设定方法。     

单脉冲和双脉冲液电式体外冲击波粉碎结石术的数值模拟

目的通过数值模拟研究体外冲击波粉碎结石术(extracorporeal shock wave lithotripsy,ESWL)中单脉冲与双脉冲两种不同情况下的压力场,并对两者结果进行比较和分析。方法利用2D轴对称Euler方程和混合网格改进的时空守恒元解元(space-time conservation element and solution element,CE/SE)数值格式,对ESWL中冲击波水下传播的压力场进行模拟。结果 CE/SE方法成功地追踪了冲击波波阵面传播情况,数值解较好地展示了ESWL焦点附近的冲击波聚焦特性:在焦点附近双脉冲产生的压力峰值约为单脉冲的两倍,越靠近焦点处双脉冲ESWL所得到的碎石效率相较于单脉冲时越高,且在焦点附近产生正压随后出现了绝对值极高的负压。结论采用液电双脉冲波源机型能够有效地提高碎石效率,并且冲击波聚焦时出现空化是不可避免的。上述结论为ESWL碎石机的设计制造及临床应用提供了可靠的数值模拟结果。     

改进的液电式体外冲击波聚焦粉碎结石术的数值模拟

目的 模拟Dornier HM3碎石机椭球反射体的边缘位置附加不同角度反射器时体外冲击波聚焦粉碎结石术（extracorporeal shock wave lithotripsy, ESWL）的压力场变化。方法 利用空间轴对称Euler方程和混合网格改进的CE/SE数值格式,对ESWL中附加反射器所改变的冲击波聚焦压力场进行模拟。结果 对不同角度附加反射器焦点附近的压力值进行比较发现,附加反射器使整个流场的正负压力峰值显著增大,与没有附加反射器的结果相比增大近50%;压力场中压力峰值随着附加反射器角度的增大而逐渐减弱,45°比0°峰值减少了约25%。结论 在碎石初始阶段,附加反射器带来的能量汇聚效应将结石粉碎成更细的小块,因而可以降低放电轰击频率而达到同样或者更高的碎石效率。数值模拟结果为ESWL碎石机的改进和临床应用提供了可靠的数值计算结果和有益的参考。     

ESWL实际焦点位置的理论和数值分析

从理论和数值模拟两个方面分析了ESWL中的非线性的动力学焦点和实际焦点的位置 ,给出三种典型的动力学焦点的数值结果 ,说明非线性动力学焦点和实际焦点一般不是几何焦点 ,指出正确确定实际焦点在ESWL技术中的重要性。     

低能量长间距ESWL治疗尿路结石1200例报告

目的探讨低能量长间距冲击波技术在体外冲击波碎石（ESWL）中的应用以及X线、B超双定位技术在ESWL中的优势。方法应用低能量长间距冲击波及X线、B超双定位技术进行ESWL1200例。结果总碎石成功率为99．5%，3个月结石排净率为83.%。结论低能量长间距冲击波技术碎石率高、组织损伤小、无严重并发症等优点。X线、B超双定位技术值得推广。     

冲击波聚焦粉碎人体结石过程中的空化现象的数值模拟

利用数值方法对粉碎人体结石时冲击波会聚过程进行了模拟,其中善于水下的负夺聚焦演化过程数值结果与实验相准确地吻合。数值模拟证明,在碎石冲击波聚焦过程中出现空化是不可避免的,因而碎石过程中的空蚀不可忽视。     

经皮肾微造瘘取石术联合体外冲击波治疗复杂性肾结石

目的 探讨经皮肾微造瘘取石术（MPCNL）联合体外冲击波（ESWL）治疗复杂性肾结石的疗效．方法 对22例复杂性肾结石先行MPCNL取出主要结石．再行ESWL治疗残留结石，随后再次行MPCNL取出碎石．结果 22例中有18例完全取出结石，4例虽有部分细碎结石残留，但病人症状消除，复查肾功能良好，造影剂顺利通过，梗阻消除．结论 MPCNL联合ESWL是治疗复杂性肾结石的有效方法，影响疗效主要在于MPCNL技术的操作水平．     

低脉冲次数体外冲击波碎石治疗上尿路结石疗效报告

目的探讨低脉冲次数（1 000次以内）体外冲击波碎石（ESWL）治疗上尿路结石的疗效。方法从2003年6月至2010年6月接受体外电磁波碎石机治疗的患者中,根据结石分布部位共选出1 200例,其中碎石机改进前、后治疗的患者各600例,每组肾结石、上段、中段、下段输尿管结石150例。回顾性分析入选患者的临床资料,对比两组患者的疗效和并发症发生情况。结果改进前组486（81%）例患者获得随访,平均冲击次数（1 987±326）次,碎石时间（36±17）min,碎石成功477例（98.1%）;改进后组498（83%）例患者获得随访,平均冲击次数（683±186）次,碎石时间（21±6）min,碎石成功492例（98.8%）。碎石术后肾绞痛、输尿管石街、肉眼血尿的发生率两组间无显著差异。结论低脉冲次数ESWL治疗上尿路结石疗效肯定,与高脉冲次数碎石相比,减少了患者的治疗时间和机器的运行时间,减轻了操作者的劳动强度和冲击波、X线辐射对患者机体的损伤,是治疗最大直径小于等于2.0 cm上尿路结石的首选方法。     

遗传算法在256阵元相控阵高强度聚焦超声治疗系统多焦点控制中的应用

阐述了遗传算法优化多点超声聚焦的方法以及球面相控阵声场计算方法。对实验室研发的256阵元相控阵聚焦超声治疗系统作了简介。利用此遗传算法和声场计算方法，对轴上和离轴单焦点以及轴对称六焦点和非轴对称四焦点进行了256阵元相控阵的声场仿真，并观察了实验室研发的256阵元相控阵聚焦超声治疗系统作用于有机玻璃和透明仿体的实验结果。用遗传算法和声场计算方法的仿真和系统实验结果表明，此方法可在实际聚焦手术中准确地控制3维单焦点和3维多焦点。     

复杂肾结石手术治疗体会

随着体外冲击波碎石（ESWL）和经皮肾镜（PCNL）等微创碎石技术的发展,肾结石开放性手术明显减少,但对于复杂肾结石仍采用开放性手术治疗。本文回顾分析我科2009年1月～2009年12月采用开放手术治疗的47例复杂肾结石患者临床资料,效果满意,现报告如下。     

球面托槽和传统托槽作用下口腔黏膜的生物力学研究

目的 通过三维有限元分析探索在球面托槽以及传统托槽的作用下口腔黏膜的力学反应。 方法 建立上唇组织-中切牙-托槽的三维有限元模型。 根据中切牙不同排列情况设计 4 个模拟案例,分析滑动的上唇组织分别在球面托槽以及传统托槽作用下的应力、应变情况。 结果 牙齿平齐时,球面托槽对口腔黏膜的最大应力较传统托槽大;切牙发生近中扭转 15°、30°以及唇侧倾斜 15°时,传统托槽情况下口腔黏膜最大应力均大于球面托槽最大应力。 结论 具有圆滑外形的球面托槽比方形传统托槽更契合牙列不齐正畸患者口腔软组织的功能运动,建议改善方形托槽的外形设计以降低口腔黏膜组织的力学反应。     

Spherical aggregates of coxsackie B4 virus particles in mouse pancreas.

A high titer culture of Coxsackie B4 virus was used to induce pancreatitis in newborn mice. In animals sacrificed 1 or 2 days after intraperitoneal inoculation, we observed cytonecrosis consistent with picornaviral infection as well as necrosis indicative of pancreatitis. In addition, we observed aggregates of particles which seem to be Coxsackie B4 virus particles, some arranged in the typical picornaviral crystalloid lattice formation and others arranged into spherical masses approximately 102 nm in diameter. Depending upon the depth and orientation of section through the spherical aggregates, the particles were arranged into two patterns which were readily distinguishable. When the plane of section was through the center of the sphere, 10 particles circularly arranged around a dense particle core were observed. When the sphere was cut tangentially, the particles were arranged in a zig-zag pattern so that there were two concentric layers of at least 6 particles per layer, with no central core. Both crystalloid and spherical aggregates were observed free within acinocyte cytoplasm, and within autophagic vacuoles, cytosegresomes, and fine granular bodies of acinocytes, and within phagocytic vacuoles of macrophages. We conclude that the spherical aggregates represent a distinct crystalloid form of Coxsackie B4 virus during its replicative cycle, which may eventually develop into the more typical picornaviral crystalloid lattice configuration and that the spherical aggregates are located in foci of viral synthesis. Marked pathogenicity of Coxsackie B4 virus in the newborn mouse pancreas should be considered a factor in the observations noted.     

小光斑准分子激光治疗单纯近视的机理及应用

在准分子激光治疗近视的手术中,角膜修正量的精确描述和激光实现方法是重点和难点问题,它直接决定了手术的效果。本文针对单纯近视情况,提出了一种角膜修正量模型,给出了其数学形式,在此基础上,设计了一种用小光斑准分子激光实现该修正量的方法。基于这种激光修正角膜矫正近视的原理,我们研制的准分子激光眼科治疗仪实现了治疗近视。目前该治疗仪已经用于临床。39例单纯近视眼睛在接受用该治疗仪做的L ASIK手术后,眼屈光状况显著改善。术前平均球镜度为:- 5 .5 7±2 .95 D,平均裸眼视力为:0 .12±0 .0 7;术后一天平均球镜度为:- 0 .0 3±0 .5 7D,平均裸眼视力为:0 .90±0 .2 9;术后一个月平均球镜度为:- 0 .6 8±0 .98D,平均裸眼视力为:1.0±0 .2 6     

Acoustic backscatter and effective scatterer size estimates using a 2D CMUT transducer

Compared to conventional piezoelectric transducers, new capacitive microfabricated ultrasonic transducer (CMUT) technology is expected to offer a broader bandwidth, higher resolution and advanced 3D/4D imaging inherent in a 2D array. For ultrasound scatterer size imaging, a broader frequency range provides more information on frequency-dependent backscatter, and therefore, generally more accurate size estimates. Elevational compounding, which can significantly reduce the large statistical fluctuations associated with parametric imaging, becomes readily available with a 2D array. In this work, we show phantom and in vivo breast tumor scatterer size image results using a prototype 2D CMUT transducer (9 MHz center frequency) attached to a clinical scanner. A uniform phantom with two 1 cm diameter spherical inclusions of slightly smaller scatterer size was submerged in oil and scanned by both the 2D CMUT and a conventional piezoelectric linear array transducer. The attenuation and scatterer sizes of the sample were estimated using a reference phantom method. RF correlation analysis was performed using the data acquired by both transducers. The 2D CMUT results indicate that at a 2 cm depth (near the transmit focus for both transducers) the correlation coefficient reduced to less than 1/e for 0.2 mm lateral or 0.25 mm elevational separation between acoustic scanlines. For the conventional array this level of decorrelation requires a 0.3 mm lateral or 0.75 mm elevational translation. Angular and/or elevational compounding is used to reduce the variance of scatterer size estimates. The 2D array transducer acquired RF signals from 140 planes over a 2.8 cm elevational direction. If no elevational compounding is used, the fractional standard deviation of the size estimates is about 12% of the mean size estimate for both the spherical inclusion and the background. Elevational compounding of 11 adjacent planes reduces it to 7% for both media. Using an experimentally estimated attenuation of 0.6 dB cm(-1) MHz(-1), scatterer size estimates for an in vivo breast tumor also demonstrate improvements using elevational compounding with data from the 2D CMUT transducer.     

Oscillatory Pressurization of an Animal Cell as a Poroelastic Spherical Body

The analytical solution of a spherical poroelastic body under an oscillatory hydrostatic pressurization is obtained. This solution is then parameterized and interpreted in terms of a spherical animal cell with the cytoskeleton serving as the solid phase. It is found that for a cell with free or nearly free membrane leakage (such as in the case of an osteocytic cell body), the induced pore fluid pressure amplitude near the center of the cell exceeds the amplitude of the applied pressure by 50% if the loading frequency falls near that of normal human gait (1 Hz). A parametric analysis shows that the leakage coefficient is proportional to the intrinsic permeability ratio between the boundary and the bulk matrix. The physiological implication of the solution is further interpreted and discussed through an anatomical analysis of two representative cellular entities under compression: a chondrocyte and an osteocytic cell body. Finally, through a comparison between the characteristic time of gait and the characteristic pore fluid pressure relaxation times of various fluid-saturated entities in the body (such as a tumor, the brain, the cortical bone, the trabecular bone, and the cartilage, etc.), it is found that the gait-induced pore fluid transport seems to be important only in deeply buried cells and the mineralized cartilage.     

Spherical lesion phantoms for testing the performance of elastography systems

A set of three cubic one-litre phantoms containing spherical simulated lesions was produced for use in comparing lesion detection performance of different elastography systems. The materials employed are known to be stable in heterogeneous configurations regarding geometry and elastic contrast identical with (storage modulus of lesion material) / (storage modulus of background material), and regarding ultrasound and NMR properties. The materials mimic soft tissues in terms of elastic, ultrasound and NMR properties. Each phantom has only one value of elastic contrast (3.3, 4.6 or 5.5) and contains arrays of 1.6 mm, 2 mm, 3 mm and 4 mm diameter spherical simulated lesions. All the spheres of a given diameter are arranged in a regular array with coplanar centres. Elastograms of an array made with ultrasound allow determination of the depth range over which lesions of that diameter and elastic contrast can be detected. Two phantoms are made from agar-plus-gelatin-based materials, and one is made from oil-in-gelatin dispersions. The methods for producing the phantoms are described in detail. Lesion detection performances for two ultrasound systems, both operating at about 7.5 MHz and focused at about 5 cm, were quantified with distinctions between the two systems demonstrated. Neither system was capable of detecting any of the 1.6 mm lesions. Phantoms such as these should be useful in research labs that are refining hardware and/or software for elastography.     

Tandem shock wave cavitation enhancement for extracorporeal lithotripsy

Extracorporeal shock wave lithotripsy (ESWL) has been successful for more than twenty years in treating patients with kidney stones. Hundreds of underwater shock waves are generated outside the patient's body and focused on the kidney stone. Stones fracture mainly due to spalling, cavitation and layer separation. Cavitation bubbles are produced in the vicinity of the stone by the tensile phase of each shock wave. Bubbles expand, stabilize and finally collapse violently, creating stone-damaging secondary shock waves and microjets. Bubble collapse can be intensified by sending a second shock wave a few hundred microseconds after the first. A novel method of generating two piezoelectrically generated shock waves with an adjustable time delay between 50 and 950 micros is described and tested. The objective is to enhance cavitation-induced damage to kidney stones during ESWL in order to reduce treatment time. In vitro kidney stone model fragmentation efficiency and pressure measurements were compared with those for a standard ESWL system. Results indicate that fragmentation efficiency was significantly enhanced at a shock wave delay of about 400 and 250 micros using rectangular and spherical stone phantoms, respectively. The system presented here could be installed in clinical devices at relatively low cost, without the need for a second shock wave generator.