微泡造影剂在左心超声中的应用

左心超声造影在评估心功能,诊断心尖部血栓和心肌致密化不全,鉴别真、假室壁瘤等方面可提供重要的信息,其准确性和可重复性好。心肌超声造影采用"微泡爆破技术"实时观测心肌区域内微泡的充填,可间接反映心肌灌注状态。微泡介导的靶向造影剂还可为基因或药物的靶向治疗提供重要载体。该文介绍微泡造影剂在左心超声显像中的应用进展。     

靶向超声微泡构建的策略和选择

利用超声微泡表面固有的生物学特性或通过特殊处理将特定配体连接于超声微泡表面可构建成靶向超声微泡,靶向超声微泡经静脉注入后能靶向性聚集并较长时间滞留于靶组织或靶器官中,并通过对比超声产生分子水平成像.实验研究表明靶向对比超声技术可无创性的定量评价诸如血管内皮损伤/炎症、血栓形成、肿瘤血管新生等病变组织和器官.靶向超声微泡的构建作为靶向对比超声技术的核心和关键近年来的研究进展十分迅速.     

靶向微泡超声空化助溶法治疗下肢静脉血栓患者血栓斑块的疗效

血栓斑块形成和栓塞是许多急性疾病的关键因素,及时恰当的溶栓治疗常常能挽救患者生命,但由于大剂量纤溶剂会引起出血等并发症,静脉溶栓治疗的应用存在局限性.近年来超声造影技术在治疗领域不断地发展,将溶栓药物与微泡结合可实现靶向结合血栓.若再于体表加以超声作用,利用空化效应破坏微泡,可加速血栓斑块软化、溶解[1].本研究拟探讨靶向微泡超声空化助溶法治疗血栓的疗效,为临床提供一种无创、简单、可反复使用的治疗血栓的方法.     

血小板膜糖蛋白Ⅱb/Ⅲa受体靶向超声造影剂的制备及体外实验研究

目的:制备血小板膜糖蛋白(GP)Ⅱb/Ⅲa受体靶向超声造影剂,探讨其体外寻靶的作用。方法:将6-氨基肽与脂质体采用交连法合成GPⅡb/Ⅲa受体靶向微泡,观察其对血小板聚集形成的微血栓的黏附效应。体外实验分2组,将靶向微泡滴加于健康人新鲜血凝块上,光镜下观察微泡与血凝块的黏附情况。对照组采用普通造影剂。结果:体外实验:靶向微泡在血凝块外围形成凝聚带,并能延伸到血凝块内部,对照组均未见微泡与血凝块的结合。结论:血小板膜糖蛋白Ⅱb/Ⅲa受体特异性靶向微泡在体外对人新鲜血栓有趋附作用,且能特异结合。     

会议论文文摘（续）

超声微泡靶向递送aFGF对糖尿病心肌病的治疗作用及其机制研究 目的：观察超声微泡靶向递送酸性成纤维细胞生长因子（SonoVue．aFGF）对糖尿病心肌病（DCM）大鼠左室舒缩功能的保护作用并初步探讨其机制。方法：24只健康雄性SD大鼠通过腹腔注射链脲佐菌素建立DCM模型,再随机平均分成DCM组与aFGF治疗组。另选择正常对照组12只。aFGF治疗组经尾静脉注射SonoVue—aFGF溶液并同时给予心肌定点超声辐照。干预后4周对所有大鼠行心导管检查,     

超声联合微泡辅助溶栓的研究进展

动脉栓塞性疾病严重危害人类健康,目前临床常用的治疗方案为药物溶栓、球囊介入血管成形术及外科取栓术,但在适用患者的选择、治疗时间窗的把握、治疗后并发症的预防等方面尚需进一步提升。近年来随着对超声波作用机制的深入理解及靶向微泡的研发应用,超声联合微泡辅助溶栓领域备受关注。现就超声联合微泡辅助溶栓的机制、影响因素及其应用的研究进展做一全面综述。     

超声微泡造影剂在心血管疾病治疗领域的应用

超声微泡造影剂不仅可用于超声成像,提高心血管疾病的诊断水平,还可作为携带基因或药物的栽体,介导心血管疾病的治疗.在超声监测下,造影剂微泡携带基因或药物进行治疗的整个过程变得可视化,并可定点释放基因或药物,增强治疗的靶向性,减少全身不良反应.超声微泡造影剂在血栓性疾病、冠状动脉粥样硬化等心血管疾病中的应用一直是超声医学研究的热点.现对超声微泡造影剂携基因或药物治疗的原理,在心血管疾病中的研究现状及该技术尚存的问题和发展前景作一综述.     

超声靶向破坏微泡介导基因或药物抗血管再狭窄的研究进展

血管成形术是治疗狭窄或闭塞性血管疾病的主要方法之一,而术后的再狭窄影响其远期疗效,预防再狭窄一直是心血管疾病的重要课题.超声靶向破坏微泡技术使携带的基因或药物在靶组织定向释放,使局部浓度大大增高,从而达到靶向治疗目的,为抗再狭窄提供了新的方法.现对超声靶向破坏微泡介导基因或药物治疗的原理及在抗血管再狭窄中的研究现状及应用前景作一综述.     

超声微泡在治疗中的应用

近年来，有关超声造影剂靶向运载药物的研究日益增多。通过调整微泡本身的特性，可将药物或治疗性基因整合于微泡中，同时将高度特异的抗体或其他配体连接于微泡表面。经静脉注入携药的微泡后，用超声照射特定的部位，即可实现药物或治疗性基因的定向释放。本文着重介绍了超声微泡药物运载系统在基因治疗，溶栓治疗和抗肿瘤治疗方面的应用。     

超声微泡在治疗中的应用

近年来,有关超声造影剂靶向运载药物的研究日益增多.通过调整微泡本身的特性,可将药物或治疗性基因整合于微泡中,同时将高度特异的抗体或其他配体连接于微泡表面.经静脉注入携药的微泡后,用超声照射特定的部位,即可实现药物或治疗性基因的定向释放.本文着重介绍了超声微泡药物运载系统在基因治疗,溶栓治疗和抗肿瘤治疗方面的应用.     

Assessment of myocardial blood flow and volume using myocardial contrast echocardiography

The development of new microbubble agents and ultrasound imaging modalities now allows the assessment of myocardial perfusion with echocardiography. Microbubbles also can be administered intravenously as constant infusions, which allows their concentration in blood to reach steady state. If the relation between microbubble concentration and video intensity is within the linear range, then myocardial video intensity will reflect the concentration of microbubbles in that region, which at steady state is the myocardial blood volume. The ability to destroy microbubbles and measure their replenishment into the ultrasound beam provides an opportunity to evaluate microbubble (or red blood cell) velocity. The product of myocardial blood volume and red blood cell velocity represents myocardial blood flow.     

反义寡核苷酸并超声微泡造影剂转染联合超声照射逆转肝癌多药耐药

目的探讨体内、体外mdr1、mrp、lrp反义寡核苷酸(AODNs)并超声微泡造影剂转染联合低强度超声照射逆转肝癌多药耐药的可行性,寻找逆转肿瘤多药耐药有效和靶向的方法。方法利用超声微泡造影剂包载肿瘤耐药基因mdr1、mrp、lrp的AODNs进行转染,联合低强度超声照射,以肝癌细胞多药耐药细胞模型(HepG2／ADM) 为研究对象,通过逆转录聚合酶链反应、western blot和四甲基偶氮唑盐法,从体外细胞培养及动物实验,研究 AODNs并超声微泡造影剂转染联合超声照射逆转癌细胞多药耐药及降低肿瘤恶性表型和成瘤能力的作用。结果 HepG2／AMD细胞增殖被抑制,其mdr1和mrp的mRNA、蛋白质表达水平明显降低;裸鼠皮下移植瘤生长受抑制。结论体外、体内AODNs并超声微泡造影剂转染联合低强度超声照射能有效逆转人肝癌细胞HepG2／ADM的多药耐药, 该技术可能为肝癌临床治疗提供新的思路。     

Imaging of Myocardial Perfusion with SonoVue™ in Patients with a Prior Myocardial Infarction

Myocardial contrast echocardiography (MCE) is an evolving noninvasive imaging technique that can be used to assess regional myocardial perfusion. MCE relies upon the detection of nonlinear ultrasound signal from gas-filled microbubbles during their microvascular transit, resulting in tissue opacification. Provided that the relation between myocardial microbubble concentration and video intensity (VI) is within the linear range, VI measured from any myocardial region reflects the relative tissue concentration of microbubbles, which is influenced by three factors: (1) microbubble concentration in blood; (2) the myocardial blood volume fraction; and (3) microbubble destruction that occurs within the ultrasound beam. In this article, we discuss how these three factors may influence myocardial perfusion information provided by MCE and highlight the importance of image processing. In order to illustrate these concepts, we examine data obtained during perfusion imaging in patients with prior myocardial infarction using intermittent harmonic imaging at various ultrasound pulsing intervals (PIs) during bolus and continuous venous infusions of a second-generation microbubble agent (SonoVue™). Our results suggest that evaluation of resting perfusion is most accurate when both myocardial blood volume and blood velocity are assessed. This information is provided only with continuous infusions of microbubbles during imaging protocols that vary the ultrasound PI.     

Influence of microbubble surface charge on capillary transit and myocardial contrast enhancement

OBJECTIVE: The goal of the study was to determine whether microbubble charge influences the microvascular retention of microbubble contrast agents. BACKGROUND: Interactions between serum proteins and lipid membranes are greater with anionic compared with neutral membranes. These interactions may influence the microvascular behavior of anionic lipid microbubbles. METHODS: Intravital microscopy of the cremaster muscle was performed in six wild-type mice and three C3-deficient mice during intravenous injection of lipid-shelled microbubbles with either a neutral or a negative charge. Both agents were prepared with and without a protective surface layer of polyethyleneglycol (PEG). Complement attachment to microbubbles was assessed by flow cytometry with flourescein isothiocyanate-conjugated anti-C3b monoclonal antibody. Myocardial contrast echocardiography was performed in six dogs to assess pulmonary and myocardial retention of microbubbles. RESULTS: Size-independent capillary retention of microbubbles, occurring for a few seconds to >10 min, was frequently observed with anionic, but rarely with neutral, microbubbles (4.3 +/- 0.3 vs. 0.4 +/- 0.1 mm(-3), p < 0.01). Anionic microbubble retention was reduced by 70% by surface PEG and was also markedly reduced in C3-deficient mice (1.4 +/- 0.1 mm(-3), p < 0.05 vs. wild-type). Flow cytometry demonstrated complement attachment to only anionic microbubbles. Contrast echocardiography indicated both pulmonary and myocardial retention of only anionic microbubbles, the latter evidenced by persistent opacification >10 min after bolus intravenous injection. CONCLUSIONS: Lipid microbubbles with a net negative charge can be retained within capillaries via complement-mediated attachment to endothelium. This property may be useful for the development of ultrasound contrast agents that can be imaged late after venous injection.     

Interactions Between Microbubbles and Ultrasound: In Vitro and In Vivo Observations

Objectives. We attempted to examine the interactions between ultrasound and microbubbles.Background. The interactions between microbubbles and ultrasound are poorly understood. We hypothesized that 1) ultrasound destroys microbubbles, and 2) this destruction can be minimized by limiting the exposure of microbubbles to ultrasound.Methods. We performed in vitro and in vivo experiments in which microbubbles were insonated at different frequencies, transmission powers and pulsing intervals. Video intensity decay was measured in vitro and confirmed by measurements of microbubble size and concentrations. Peak video intensity and mean microbubble myocardial transit rates were measured in vivo.Results. Imaging at lower frequencies and higher transmission powers resulted in more rapid video intensity decay (p = 0.01), and decreasing exposure of microbubbles to ultrasound minimized their destruction in vitro. Although these effects were also noted in vivo with venous injections of microbubbles, they were not seen with aortic root or direct coronary artery injections.Conclusions. Ultrasound results in microbubble destruction that is more evident at lower frequencies and higher acoustic powers. Reducing the exposure of microbubbles to ultrasound minimizes their destruction. This effect is most marked in vivo with venous rather than aortic or direct coronary injections of microbubbles. These findings could lead to effective strategies for myocardial perfusion imaging with venous injections of microbubbles.(J Am Coll Cardiol 1997;29:1081–8)© 1997 by the American College of Cardiology     

超声介导白蛋白微泡破裂法促进增强型绿色荧光蛋白C3基因在中国仓鼠卵巢细胞的表达

基因治疗的研究已取得不少进展，但要成功地应用于临床仍存在许多困难，安全、有效的基因载体及良好的靶向性就是其中最重要的难点之一。本研究超声介导白蛋白微泡破裂可以增加真核细胞膜对大分子（如DNA）通透性的原理，探讨一种新的转基因方法，以便安全有效和定向地转移目的基因。实验中选择绿色荧光蛋白C3基因为标记基因，以白蛋白微泡为载体，用超声介导微泡破裂的方法在体外进行中国仓鼠卵巢细胞的基因转化，同时以脂质体为对照，激光共聚焦显微镜和流式细胞计数仪分别定性和定量观察细胞转化效率。台盼蓝染色观察细胞的活性。体外试验发现0．8MHz,1.0W/cm^2、10％脉冲周期、60s超声介导10％白蛋白微泡破理解可以有效稳定转化增强的绿色荧光蛋白C3基因在中国仓鼠卵巢细胞表达，平均转化阳性率可达56．2％，活性实验证明对细胞无毒副作用，提示超声介导白蛋白微泡破理解法有应用于临床基因治疗的广阔前景。     

Optimization of ultrasound parameters for cardiac gene delivery of adenoviral or plasmid deoxyribonucleic acid by ultrasound-targeted microbubble destruction

OBJECTIVES: This study was undertaken to optimize echocardiographic parameters for successful gene delivery to the heart and to extend the method from adenoviral to plasmid deoxyribonucleic acid (DNA). BACKGROUND: We have previously shown that ultrasound-targeted microbubble destruction can direct tissue expression of adenoviral transgenes to the heart. The optimal echocardiographic parameters for this technique have not been reported. METHODS: Adenoviral or plasmid DNA encoding the luciferase reporter gene was incorporated into liposome microbubbles and infused intravenously into anesthetized rats. We systematically evaluated the effects of ultrasound parameters known to influence microbubble destruction, including electrocardiogram (ECG) triggering, ultrasound frequency, mode of ultrasound, and mechanical index, on gene expression in rat myocardium four days after treatment. In addition, gene expression in heart, liver, and skeletal muscle were compared between adenoviral and plasmid DNA. RESULTS: Optimal ultrasound parameters for this technique include low-transmission frequency (1.3 MHz), maximal mechanical index, and ECG triggering to allow complete filling of the myocardial capillary bed by microbubbles. No difference was seen between ultraharmonics and power Doppler mode. Using adenoviral DNA, optimal ultrasound parameters yielded myocardial luciferase activity on the order of 104 relative light units/mg protein/min but with even higher liver activity. Plasmid DNA was expressed in rat myocardium at similar levels but without detectable liver expression. CONCLUSIONS: Ultrasound-targeted microbubble destruction can be used to deliver adenoviral or plasmid DNA to the myocardium. This technique holds great promise in applying the rapidly expanding repertoire of gene therapies being developed for cardiac disease.     

Microbubble contrast agents for echocardiography: rationale, composition, ultrasound interactions, and safety

Imaging the small blood vessels within the myocardium, which contains only a small fraction of the total coronary blood volume, is a significant challenge for ultrasound imaging. Recent advances in microbubble design and ultrasound technology have improved our ability to image the microcirculation. It is essential to understand the fundamentals of microbubble behavior in an ultrasound field and how it impacts technology and safety.     

A new strategy for septal ablation with transendocardial ethanol injection using a multifunctional intracardiac echocardiography catheter: A feasibility study in canines

Objectives : To evaluate the feasibility and safety of a novel multifunctional intracardiac echocardiography catheter for target septal ablation with transendocardial ethanol injection in canines. Background : Percutaneous transluminal septal myocardial ablation has been the primary catheter‐based strategy for the treatment of hypertrophic obstructive cardiomyopathy (HOCM). However, inherent limitations of the technique have reduced its therapeutic efficacy. Methods : A new catheter (10 F), integrated with a nitinol needle (29 G) and a 6.5–10‐MHz, 32‐element, side‐fire ultrasound imaging transducer, was delivered into the right ventricle in nine canines and the left ventricle in three canines. A 0.3‐ml microbubble and 0.5–1.5 ml absolute ethanol were sequentially injected into the interventricular septum. Electrocardiograph recordings were obtained during the whole procedure. Three hours after this operation, the heart was harvested for gross and histological examination. Results : In all canines, the catheter provided the structural support and helped guide proper needle position within the septum. The microbubble further allowed the confirmation of the needle location through focal echo‐density enhancement. Different amounts of ethanol infusion produced a dose‐related effect on myocardial ablation. Macroscopic examination showed that the target myocardium became pale with a distinct border between lesions and normal tissue. Hematoxylin and eosin staining further confirmed necrosis within the injection region. Conclusions : Transendocardial ethanol injection at the interventricular septum resulted in controlled myocardial infarction. In addition, the injection depth could be visually followed using this new system, which may provide a safer and more intuitive method for the treatment of HOCM or other cardiomyopathies. © 2011 Wiley‐Liss, Inc.     

Tumor radiation response enhancement by acoustical stimulation of the vasculature

We have discovered that ultrasound-mediated microbubble vascular disruption can enhance tumor responses to radiation in vivo. We demonstrate this effect using a human PC3 prostate cancer xenograft model. Results indicate a synergistic effect in vivo with combined single treatments of ultrasound-stimulated microbubble vascular perturbation and radiation inducing an over 10-fold greater cell kill with combined treatments. We further demonstrate with experiments in vivo that induction of ceramide-related endothelial cell apoptosis, leading to vascular disruption, is a causative mechanism. In vivo experiments with ultrasound and bubbles permit radiation doses to be decreased significantly for comparable effect. We envisage this unique combined ultrasound-based vascular perturbation and radiation treatment method being used to enhance the effects of radiation in a tumor, leading to greater tumor eradication.