Unsteady Fluid Dynamics of Several Mechanical Prosthetic Heart Valves Using a Two Component Laser Doppler Anemometer System

Abstract: Five typical mechanical heart valves (Starr-Edwards, Björk-Shiley convexo-concave (c-c), Björk-Shiley monostrut, Bicer-Val, and St. Jude Medical) were tested in the mitral position under the pulsatile flow condition. The test program included measurements of velocity and turbulent stresses at 5 downstream locations. The study was carried out using a sophisticated cardiac simulator in conjunction with a highly sensitive 2 component laser Doppler anemometer (LDA) system. The continuous monitoring of parametric time histories revealed useful details about the complex flow and helped to establish the locations and times of the peak parameter values. Based upon the nondimensional presentation of data, the following general conclusions can be made. First, all the 5 valve designs created elevated turbulent stresses during the accelerating and peak flow phases, presenting the possibility of thromboembolism and perhaps hemolysis. Second, the difference in valve configuration seemed to affect the flow characteristics; third, the bileaflet design of the St. Jude valve appeared to create a lower turbulence stress level.     

Ballistocardiogram of avian eggs determined by an electromagnetic induction coil

As an avian embryo grows within a eggshell, the whole egg is moved by embryonic activity and also by the embryonic heartbeat. A technical interest in detecting minute biological movements has prompted the development of techniques and systems to measure the cardiogenic ballistic movement of the egg or ballistocardiogram. (BCG). In this context, there is interest in using an electromagnetic induction coil (solenoid) as another simple sensor to measure the BCG and examining its possibility for BCG measurement. A small permanent magnet is attached tightly to the surface of an incubated egg, and then the egg with the magnet is placed in a solenoid. Preliminary model analysis is made to design a setup of the egg, magnet and solenoid coupling system. Then, simultaneous measurement with a laser displacement measuring system, developed previously, is made for chicken eggs, indicating that the solenoid detects the minute cardiogenic ballistic movements and that the BCG determined is a measure of the velocity of egg movements.     

Endoscopic sphincterotomy for common bile duct stones: Impact of recent technical advances

Technical improvements, such as mechanical lithotripsy, stenting or nasobiliary drainage, and wire-guided cannulation, have reduced the risk of complications in endoscopic sphincterotomy. To determine the extent of this reduction in risk, we assessed the medical records of 1352 patients with common bile duct stones in whom the procedure was conducted. Complications examined were: acute cholangitis and pancreatitis. Stone clearance was achieved in 1256 patients (92.8%), with an overall morbidity rate of 7.7% and a mortality rate of 0.15%. One hundred and forty-two patients had stones with a diameter greater than 20mm; 97 of these patients did not undergo lithotripsy. Cholangitis occurred in 10 of these 97 patients (10.3%), whereas, in the 45 patients who underwent lithotripsy, there were no cases of cholangitis (P=0.02). Stone removal was not immediately accomplished or attempted in 396 patients. In 82 of these patients in whom a stent or a nasobiliary drain was placed in the common bile duct, the incidence of cholangitis was 1.2%, significantly less (P=0.045) than the incidence of 6.4% in the other 314 patients given no stenting or nasobiliary drain. To overcome difficult cannulation, precut sphincterotomy was conducted in 134 patients and wireguided sphincterotomy, a recently introduced procedure, was conducted in 55 patients. When the precutting technique was used, the incidence of acute pancreatitis was significantly higher (8/134; 6.0%) than that in the patients in whom the standard procedure was conducted, i.e., neither the precut technique nor wire-guided ES was used (23/1218; 1.9%) (P=0.008). There were no cases of pancreatitis in the 55 patients in whom wire-guided sphincterotomy was performed, although the difference was not statistically significant because of the small number of patients (P=0.06). Based on these findings, we conclude that improved technologies have led to a significant reduction of complications in endoscopic sphincterotomy.     

应用激光技术治疗痔—附1376例报告

本文较详细地介绍了应用激光技术即用CO_2及Nd:YAG激光手术刀治疗各种类型痔的临床观察。我院自1988年应用CO_2及Nd,YAG(以下简称激光手术刀)的技术治疗各种痔1376例均取得满意的治疗效果,治愈率达100％,并对有关问题进行探讨。     

ELECTROHYDRAULIC LITHOTRIPSY: AN EFFECTIVE AND ECONOMICAL MODALITY OF ENDOSCOPIC URETERIC LITHOTRIPSY

Background : Electrohydraulic lithotripsy (EHL) has been available for endoscopic treatment of urinary calculi since 1960, but the large probe size and concerns regarding safety had previously restricted its use to the treatment of bladder calculi. However, recent refinements have made it particularly suitable for the treatment of ureteric calculi. Methods : The authors report their initial experience using EHL in conjunction with mini-ureteroscopy in the treatment of 94 ureteric calculi in 89 patients. The size of the calculi ranged from 3 to 19 mm in diameter, with a mean of 8.2 mm. The mean operating time was 29 min, ranging from 10 to 120 min. Results : A complete fragmentation rate of 91.5% of the calculi was achieved. There were no major complications and a low incidence of minor complications: haematuria (2.2%), urinary tract infection (3.4%) and postoperative ureteric colic (2.2%). There were four cases of minor ureteric perforations (4.5%); all were successfully treated using conservative measures. Conclusions : It is concluded that EHL is a safe and effective method of treating ureteric calculi.     

输尿管镜治疗输尿管结石185例

目的探讨输尿管镜气压弹道碎石治疗输尿管结石的效果。方法2004年2月～2005年3月，我们对185例输尿管结石（其中伴肾绞痛96例）采用输尿管镜取石或气压弹道碎石进行总结和分析。结果失败12例，其中6例改开放手术，6例术后3d行体外冲击波碎石。一次碎石成功率93．5％（173／185），其中上段结石为75．0％（24／32），中段为95．8％（46／48），下段为98．1％（103／105）。肾绞痛者成功率为100％（96／96）。术中输尿管损伤率2．9％（5／173），其中3例（1．7％）中转开放手术。术后肾绞痛1例。全组随访6～12个月，平均10．2月，无复发。结论输尿管镜气压弹道碎石安全有效，并发症少，是治疗输尿管中下段结石的首选方法，尤其对肾绞痛者疗效更好。     

Nd:YAG激光虹膜周边切除术治疗闭角型青光眼的临床研究

目的探讨Nd：YAG激光虹膜周边切除术治疗闭角型青光眼的疗效。 方法26例30只眼闭角型青光眼分为AB两组，A组为中周部高能量组（首次击射能量为7．4mJ），B组为极周边部低能量组（首次击射能量为5．3mJ），行Nd：YAG激光虹膜周边切除术。 结果两组患者均穿孔成功，A组并发症较B组明显减少，且一次穿孔率达100％。 结论Nd：YAG激光虹膜周边切除术治疗闭角型青光眼疗效可靠，并发症少，值得推广应用。     

肾盂切开气压弹道碎石治疗鹿角形肾结石(附46例报告)

目的 探讨肾盂切开气压弹道碎石治疗鹿角形肾结石的疗效。方法 对46例鹿角形肾结石采用肾盂切开气压弹道碎石，将结石分解成数块，再逐一取出。双侧肾结石采用一次分侧手术取石。结果 46例鹿角形肾结石均较顺利取出，无黏膜撕脱、出血等并发症。25例肾功不全者均显著改善。结论肾盂切开结合气压弹道碎石是治疗鹿角形肾结石较好方法；双侧肾结石多有梗阻致肾功能受损，应双侧一次取石，有利于双肾功能恢复。     

钬激光腔内治疗泌尿系结石(附126例报告)

目的：探讨泌尿系结石腔内钬激光治疗效果及安全性。方法：总结钬激光结合腔内泌尿外科技术治疗126例泌尿系结石的临床资料。结果：5例肾结石和11例膀胱结石，均一次碎石成功，109例输尿管结石，单次碎石率为96.3%(105/109)，复杂结石1例数次行输尿管腔镜下碎石。平均结石排净时间2.8周，平均手术时间30min，平均术后住院2d。术中除1例输尿管穿孔外，无其他并发症。结论：钬激光结合腔内泌尿外科技术治疗泌尿系结石，是一种较新的、安全的、有效的方法。     

Thermal analysis of the bone surface induced by laser radiation

High energy laser has emerged to be an important surgical tool in medical technology. However, the application of laser energy to drill or cut a bone is still in an experimental state. In order to estimate the adequacy of laser heating of bone surface and at the same time minimize the damage to the bone tissue, we developed a mathematical model of the temperature distribution in bone due to laser irradiation. The thermal analysis shows that the temperature distribution depends on several parameters, including the density, the specific heat, and the thermal conductivity of the osseous tissue.