Cavitation enhances coagulated size during pulsed high-intensity focussed ultrasound ablation in an isolated liver perfusion system

Purpose: To investigate whether cavitation enhances the degree of coagulation during pulsed high-intensity focussed ultrasound (HIFU) in an isolated liver perfusion system.

Methods: Isolated liver was treated by pulsed HIFU or continuous-wave HIFU with different portal vein flow rates. The cavitation emission during exposure was recorded, and real-time ultrasound images were used to observe changes in the grey scale. The coagulation size was measured and calculated.

Results: HIFU treatment led to complete coagulation necrosis and total cell destruction in the target regions. Compared to exposure at a duty cycle (DC) of 100%, the mean volumes of lesions induced by 6?s exposure at DCs of 50% and 10% were significantly larger (P?01) but were smaller at a DC of 5%. The necrosis volume was negatively related to the perfusion rate in the pulsed HIFU at a DC of 50% for exposure durations of 4 and 6?s, while the perfusion flow rate did not affect the necrosis volume for exposure durations of 1, 2 and 3?s. For increased perfusion flow rates, there was no significant decrease in the cavitation activity for the pulsed-HIFU (P?>?.05). For continuous-wave HIFU exposure, there was a significant decrease in the necrosis volume and cavitation activity for exposure times of 1, 2, 3, 4, and 6?s with increasing portal perfusion rates.

Conclusion: Perfusion flow rates negatively influence cavitation activity and coagulation volume. Ablation is significantly enhanced during pulsed HIFU exposure compared with continuous-wave HIFU.     

Gel Phantom Study with High-Intensity Focused Ultrasound: Influence of Metallic Stent Containing Either Air or Fluid

We aimed to investigate whether a cylindrical structure containing either air or fluid and with or without a metallic stent affects the volume and density of cavitation produced by high-intensity focused ultrasound via a gel phantom study. Sixteen tissue-mimicking phantoms based on a polyacrylamide gel mixed with bovine serum albumin with a cylindrical hole 1 cm in diameter and 7.5 cm in length were divided into four groups of four phantoms with air in the holes (group 1), four phantoms with fluid in the holes (group 2), four phantoms with air-containing metallic stents (group 3) and four phantoms with fluid-containing metallic stents (group 4). A pulsed high-intensity focused ultrasound beam (50% duty cycle, 40-Hz pulse repetition frequency) at 75 W of acoustic power was directed perpendicularly to the longitudinal axis of the hole, with its focus at the posterior wall of the hole. The size of the cavitation on the x-, y-, and z-axes was measured, and the volumes of cavitation and coagulation were calculated using the formula for the volume of an elliptical cone. The density of cavitation was measured in the tissue phantom anterior to the hole with a 1 × 1-cm square region of interest. For statistical analysis, the Kruskal–Wallis test and Mann–Whitney U-test were used. The phantoms with air-containing holes (groups 1 and 3) developed larger and denser cavitations anterior to the focus, without unnecessary coagulation posterior to the focus, compared with the phantoms with fluid-containing holes (groups 2 and 4), regardless of the presence of stents. All of the axes and volumes of the anterior cavitations were significantly larger than those of the posterior cavitations in groups 1 and 3 (all p-values <0.05). The results of this study might be applied to maximize cavitation to enhance drug delivery into tumors.     

肺结核空洞的CT表现及病理基础

目的笔者对肺结核空洞进行CT形态学分型,分析其病理基础。探讨空洞分型在肺结核的诊断、分型及治疗中的意义。方法收集伴有空洞的肺结核病人76例,按洞壁性质将空洞分为薄壁空洞、干酪空洞和纤维空洞,所有病人均有完整的CT资料。结果①肺结核空洞的CT表现:按空洞的形态将肺结核空洞分为浸润空洞和纤维空洞两型,本组病例包括浸润空洞51例,纤维空洞25例。②肺结核空洞的动态变化:比较治疗前后结核空洞的变化,发现浸润空洞治疗后多明显好转,纤维空洞无明显变化。③肺结核空洞的病理观察:本组有9例手术切除病例,薄壁空洞和干酪空洞多与CT分类的浸润空洞吻合,纤维空洞与CT分类的纤维空洞吻合。结论肺结核空洞的CT表现有助于确定结核病的活动性、评价预后、治疗效果以及鉴别诊断。     

脉冲高强度聚焦超声联合微泡非热损伤兔肝VX2移植瘤的病理观察

目的探讨脉冲高强度聚焦超声(HIFU)联合微泡非热损伤兔肝VX2移植瘤的病理变化。方法将36只荷瘤兔随机分为假照组、P-HIFU组和P-HIFU UCA组进行HIFU辐照,观察辐照后组织的病理学变化。结果假照组、P-HIFU组和P-HIFU UCA组TTC染色后,肉眼下各组肿瘤组织被均匀红染,而组织学检查显示P-HIFU组和P-HIFU UCA组肿瘤细胞有损伤征象,胞浆内有大小不等空泡。结论脉冲高强度聚焦超声(HIFU)以及联合微泡均可对兔肝VX2移植瘤通过非热损伤达到治疗目的。     

Hydrodynamic characteristics of bileaflet mechanical heart valves in an artificial heart: cavitation and closing velocity

The aim of this study was to investigate the possibility of using the bileaflet valves in an electrohydraulic total artificial heart (EHTAH). Three kinds of bileaflet valves, namely the ATS valve (ATS Medical Inc., Minneapolis, MN, USA), the St. Jude valve (St. Jude Medical Inc., St. Paul, MN, USA), and the Sorin Bicarbon valve (Sorin Biomedica, Vercelli, Italy), were mounted in the mitral position on an inclined 45 degrees plane in an EHTAH. The pressure waves near the valve surface, the valve-closing velocity, and a high-speed camera were employed to investigate the mechanism for bileaflet valve cavitation. The cavitation bubbles in the bileaflet valves were concentrated along the leaflet tip. The cavitation intensity increased with an increase in the valve-closing velocity. It was established that squeeze flow holds the key to bileaflet valve cavitation. At lower heart rates, the delay time of the asynchronous closure motion between the two leaflets of the Sorin Bicarbon valve was greater than that of the other bileaflet valves. At higher heart rates, no significant difference was observed among the bileaflet valves.     

超声介导微泡破裂增强体外基因转染的方法学研究

目的 对超声促进基因转染的方法进行系统的优化研究,初步确定超声介导微泡破裂(UMMD)增强体外基因转染的最优参数.方法 选用 Ishikawa、Hela 和 MCF-7 3种细胞系为研究对象,用1 MHz超声仪.超声强度为1.0W/cm2,系统研究不同参数下的细胞活力及两种DNA质粒[红色荧光蛋白质粒(DsRed)和荧光索酶质粒(pCMV-LUC)的基因转染情况,优化UMMD的转染条件(质粒浓度、占空比及辐照时间),分析SonoVue微泡对基因转染的增强作用.结果 基因转染率随着质粒浓度的增加而增高,当质粒浓度达到30 μg/孔时转染率最高,两种DNA质粒的最佳转染浓度相同.与10%占空比的超声辐照相比,20%占空比的转染率显著提高(P＜0.01).辐照3 min时基因表达率最高,但存活率无明显下降(89.03±2.01)%,为最佳辐照时间.无超声辐照时,单独应用质粒或微泡十质粒的样本几乎不表达红色荧光蛋白.与单纯超声辐照相比,超声辐照联合SonoVue微泡可显著提高基因转染效率(P＜0.01).结论 UMMD的转染参数影响转染效率和细胞活力,优化的参数有利于促进基因转染.     

Is Alcohol Use Associated With Cavitary Disease in Tuberculosis?

BACKGROUND: Alcohol mediates detrimental alterations in the immune response to Mycobacterium tuberculosis. The association between quantity and frequency of alcohol use and the prevalence of cavitary disease in tuberculosis (TB) has not been analyzed. To investigate the relationship of alcohol use and the prevalence of cavitary disease in a 6-year population-based data set of individuals with TB. METHODS: We assessed quantity and frequency of alcohol use (daily alcohol use, years of alcohol use, and lifetime alcohol use) with a standardized questionnaire. The study group consisted of 1,250 patients analyzed for cavitary disease (HIV sero-negative subjects that were 18 years or older). Significant covariates for cavitary disease were entered into multiple logistic regression models. RESULTS: Although daily alcohol use, years of alcohol use, and alcohol use 30 days or 6 months before symptom onset were significant predictors of cavitary disease in univariate analysis, no independent associations were found between alcohol use and cavitary disease in the multivariate analysis. Only diabetes mellitus was independently associated with cavitary disease at any level or frequency of alcohol use. CONCLUSION: Alcohol use is not independently associated with increased prevalence of cavitary disease in adult patients with TB.     

高强度聚焦超声在肝癌治疗中的应用

高强度聚焦超声是一种肝癌局部治疗的新技术,因其与手术治疗和局部治疗(如射频消融、肝动脉栓塞化疗、酒精注射等)方法相比,具有无创伤、精确度高、肿瘤组织坏死确切及术后并发症少等诸多优势,得到了临床上广泛的认可,作为一种重要的肝癌治疗手段正逐步普及于临床。本文就高强度聚焦超声治疗肝癌的机制、操作方法、疗效评判标准、具体治疗方法及术后护理等予以综述,并对其所存在的问题及解决方法加以探讨。     

Impulsive-Motion Model for Computing the Closing Motion of Mechanical Heart-Valve Leaflets

The speed of mechanical heart-valve leaflets is known to be an important quantity for predicting cavitation, yet no simple computational means exists for predicting the leaflet speed. In this study, a model for simulating the motion of heart-valve leaflets in rigid test systems is presented. The input for the simulations is the ventricular pressure trace, readily measured in heart-valve tests. The model is based upon an impulsive-motion approximation, wherein the motion within the system is produced by rapid acceleration at the boundary, e.g., by a moving piston. A set of quasisteady, linear equations for the pressure field that are decoupled from the leaflet equation of motion is derived. The pressure field and leaflet moment are computed without the need to treat moving boundaries. Model predictions of closing time compared favorably with those measured in a 1994 cavitation study. Computed values of leaflet tip speed were also compared with those of a previous study, at the same value of average pressure slope. The model values were in agreement with measured speeds, given the limitations of using the average pressure slope as a metric for comparison. © 2003 Biomedical Engineering Society. PAC2003: 8719Hh, 8719St, 8768+z, 8710+e     

Three-Dimensional Fluid-Structure Interaction Simulation of Bileaflet Mechanical Heart Valve Flow Dynamics

The wall shear stress induced by the leaflet motion during the valve-closing phase has been implicated with thrombus initiation with prosthetic valves. Detailed flow dynamic analysis in the vicinity of the leaflets and the housing during the valve-closure phase is of interest in understanding this relationship. A three-dimensional unsteady flow analysis past bileaflet valve prosthesis in the mitral position is presented incorporating a fluid-structure interaction algorithm for leaflet motion during the valve-closing phase. Arbitrary Lagrangian-Eulerian method is employed for incorporating the leaflet motion. The forces exerted by the fluid on the leaflets are computed and applied to the leaflet equation of motion to predict the leaflet position. Relatively large velocities are computed in the valve clearance region between the valve housing and the leaflet edge with the resulting relatively large wall shear stresses at the leaflet edge during the impact-rebound duration. Negative pressure transients are computed on the surface of the leaflets on the atrial side of the valve, with larger magnitudes at the leaflet edge during the closing and rebound as well. Vortical flow development is observed on the inflow (atrial) side during the valve impact-rebound phase in a location central to the leaflet and away from the clearance region where cavitation bubbles have been visualized in previously reported experimental studies.