携IgG单抗靶向超声造影剂的构建及其靶向效能的体外评价

Objective To construct targeted ultrasound contrast agent carried goat anti-mouse IgG antibody (UCA-IgG) and evaluate the effectiveness of its targeted adhesion using parallel plate flow chamber. Methods The ultrasound contrast agent targeted to mouse IgG was designed by conjugating monoclonal antibodies against mouse lgG to the lipid monolayer shell of the agent using biotin-streptavidin. The binding of IgG antibodies to the ultrasound contrast agent were identified by fluorescence in vitro. The attachment and detachment of UCA-IgG to mouse IgG immobilized on a culture dish were assessed in a parallel-plate flow chamber. While the plate lacked mouse IgG,or blocked with large number of goat anti-mouse IgG were served as two control groups. Results UCA-IgG issued a bright green fluorescence, while the contral lipid ultrasound contrast agent didn't show fluorescence. The number of UCA-IgG bound to mouse IgG of experimental group was greater than two control groups,increased with increasing coverslips surface antibody concentrations (P<0. 05),and there was significant positive correlation between the number of UCA-IgG bound to mouse IgG and time of combination (P<0.05). The adhesion rate of experimental group increased with shear stress before 0. 5×10-5 N/cm2 (P<0.05) and then decreased (P<0. 05). There was limited adherence of control groups to the UCA-IgG. The stess of half-maximal detachment was increased with increasing coverslips surface antibody concentrations (P<0.05). Conclusions UCA-IgG could adhere to mouse IgG in the physical conditions. It may provide strong supports for studying other targeted ultrasound contrast agent preliminary and fatherly in vitro.     

靶向超声造影评价裸鼠肾癌新生血管的实验研究

目的 探讨以血管内皮生长因子受体2 (VEGFR2)为靶点的靶向超声造影评价裸鼠肾癌新生血管的应用价值.方法 建立人肾透明细胞癌皮下移植瘤裸鼠模型,制备携VEGFR2抗体的靶向造影剂(MBV),每只裸鼠分别随机注射普通造影剂(MBC)和MBV并行超声造影检查,比较两种造影剂的视频强度,并对肿瘤组织行VEGFR2免疫组化检测.结果 超声造影示MBV组视频强度(6.50±1.43)Db,MBC组视频强度(2.59±0.99)Db,两者差异有统计学意义(P<0.01),且MBV组持续强化时间较MBC组长,免疫组化结果证实肿瘤血管内皮VEGFR2高表达.结论 以VEGFR2为靶点的靶向造影剂可特异性增强肾癌显影,对评估肿瘤新生血管有重要价值.

Abstract：

Objective To investigate the value of contrast enhanced ultrasound(CEUS) with microbubbles targeted to vascular endothelial growth factor receptor type 2 (VEGFR2) for imaging tumor angiogenesis in murine tumor models.Methods Established human renal cell carcinomas(RCC) subcutaneous xenograft tumor model in nude mice,microbubbles targeted to VEGFR2(MBV) was prepared,control microbubbles(MBC) and MBV were injected respectively in each mouse,the intensity of each microbubble was compared,the expressions of VEGFR2 in tumors were tested by immunohistochemistry.Results CEUS imaging showed the intensity of MBV and MBC was (6.50±1.43)dB,(2.59±0.99)dB,respectively.There was significantly higher intensity when using MBV compared with MBC (P<0.01).The time to wash out was longer in MBV contrast group compared with MBC group.Immunohistochemistry showed VEGFR2 was highly expressed in novel vessel walls.Conclusions Contrast microbubbles targeted to VEGFR2 can specially enhance the images of RCC and has tremendous significance in the assessment of angiogenesis.     

载Fe3O4全氟溴辛烷纳米粒增强超声显像的实验研究

目的 探讨载磁性纳米材料Fe3O4颗粒的全氟溴辛烷纳米粒(Fe3O4-PFOB)增强超声显像的效果.方法 将Fe3O4-PFOB纳米粒与RAW264.7 巨噬细胞孵育30 min、1 h后,分别进行光镜及体外超声检查.12只健康SD大鼠随机分为2组,分别于注射Fe3O4-PFOB及空白PFOB纳米粒前后进行大鼠肝脏超声显像,并用DFY超声图像定量分析诊断仪评价显像效果.结果 Fe3O4-PFOB纳米粒与巨噬细胞孵育1 h后可见大量Fe3O4-PFOB纳米粒被巨噬细胞吞噬,巨噬细胞吞噬纳米粒后能够增强超声回声信号.体内显像中,与空白PFOB纳米粒相比,Fe3O4-PFOB能够更好地增强大鼠肝实质超声显像效果,而且其增强显影时间延长.结论 膜壳装载Fe3O4颗粒的Fe3O4-PFOB纳米粒能够有效增强超声显像效果,有望实现一种造影剂多种模态显像.

Abstract：

Objective To study the feasibility of the Fe3O4-loaded lipid perfluorooctylbromide nanoparticles (Fe3O4-PFOB) for enhanced ultrasound imaging.Methods The Fe3O4-PFOB nanoparticles,incubated with RAW264.7 macrophage cells,were monitored by microscope and ultrasound.Twelve SD rats were randomized into two groups,Fe3O4-PFOB group and PFOB group.Ultrasound imaging of rats' liver was performed before and after intravenous injection of the contrast agents.The liver echogenic intensity was quantified by DFY ultrasound quantified system analysis.Results Incubation of the Fe3O4-PFOB nanoparticles with macrophages resulted in the uptake of Fe3O4-PFOB by macrophages.Macrophages loaded with Fe3O4-PFOB exhibited enhanced echogenicity in vitro.In in vivo imaging,Fe3O4-PFOB produced better and prolonged ultrasound enhancement of rats' liver compared to PFOB nanoparticles.Conclusions Fe3O4-PFOB nanoparticles could enhance ultrasound imaging and may potentially serve as a multimodal probe for ultrasound,CT and MR imaging.     

基于总变差的医学影像配准

Recent biomedical ultrasound development taking advantage of unique properties of ultrasound contrast microbubbles on ultrasonic molecular imaging, drug delivery and therapy has opened up powerful emerging applications. The microbubbles work by resonating in an ultrasound field, rapidly contracting and expanding in response to the pressure changes of the sound wave. The intense radial oscillation makes them several thousand times more reflective than normal body tissues and emits significantly stronger acoustic signal. As well as being useful in itself, the oscillation resonance that microbubbles produce has several special properties that can be exploited to improve diagnoses. Just as with a musical instrument, multiple harmonic signals are produced. Ultrasound scanners can be designed and tuned to "listen" to these harmonics and produce strong preferential imaging of the microbubbles. The microbubbles are therefore can be used as sensitive acoustic biomarkers in molecular imaging when conjugated with certain proteins. Moreover, due to the large surface area, the microbubbles are wonderful candidates as gene and drug carriers. Selective ultrasound excitation can spatially-manipulate the microbubbles through the mechanism of acoustic radiation force and also destroy microbubbles to release the drug relatively easily. These effects can be useful both in molecular imaging and in localized drug delivery applications. In this seminar, besides background knowledge, I will present a sensitive targeted molecular imaging technique, by taking advantage of high frequency acoustic emission from ultrasound contrast agents, and also recent drug delivery investigations. Based on these preliminarly research, the function of next generation biomedical ultrasound is put forward for discussion: The possiblity of imaging, drug delivery and therapy in one.     

超声造影评价不同狭窄程度颈动脉粥样斑块内的新生血管形成

Objective To evaluate contrast-enhanced ultrasound imaging of carotid atherosclerosis with different stenostic degree as a clinical tool to study intraplaque neovascularization.Methods Fifty-eight patients suspected of carotid stenosis with 73 plaques were studied by standard and contrast-enhanced ultrasound.Plaque echogenicity at standard ultrasound were evaluated.Contrast enhancement within the plaques was categorized as 0 - 4 degree and compared to the stenosis degree and the plaque echogenicity.The degree of stenosis was determined by intravenous digital subtraction angiography.Results In the group with stenosis less than 90% ,stenosis degree was not associated with the grade of contrast enhancement (P =0.358),while the grade of enhancement was significantly higher in the group with sever stenosis(＞90%).The grades of enhancement were significantly different between plaques with different echogenicity (P =0.000).Conclusions Contrast-enhanced real-time ultrasound imaging can demonstrate the enhancement of carotid plaques non-invasively,which is helpful for assessing intraplaque neovascularization and provide valuable information for plaque risk stratification     

实时组织弹性成像在评价肝肿瘤中的应用价值

Objective To explore the imaging features of liver tumors with real-time tissue elastography.Methods Eighty-five liver lesions in 67 cases were scanned with conventional ultrasonography and elastography using HI-Vision900 system and then assessed with grade scores.Results on ultrasound were compared with those on pathology.Results Majority of lesions with grade a-b on elastography were identified as benign on pathology, while most of masses with grade c-e on elastography were confirmed as malignant on pathology.The sensitivity, specificity and accuracy were 93.5%, 87.0% and 91.8% for elastography to detect malignant lesions,74.2% ,73.4% and 74.1% for conventional ultrasound.The Kappa value of two doctors on elastography in group Ⅰ (the depth of the lesion ≤10cm) was significantly higher than group Ⅱ (the depth of the lesion ＞10cm).Conclusions Real-time tissue elastography of liver tumors provides a new convenient,non-invasive diagnostic methods,contribute to identify the benign and malignant live tumors.     

实时组织弹性成像在评价肝肿瘤中的应用价值

Objective To explore the imaging features of liver tumors with real-time tissue elastography.Methods Eighty-five liver lesions in 67 cases were scanned with conventional ultrasonography and elastography using HI-Vision900 system and then assessed with grade scores.Results on ultrasound were compared with those on pathology.Results Majority of lesions with grade a-b on elastography were identified as benign on pathology, while most of masses with grade c-e on elastography were confirmed as malignant on pathology.The sensitivity, specificity and accuracy were 93.5%, 87.0% and 91.8% for elastography to detect malignant lesions,74.2% ,73.4% and 74.1% for conventional ultrasound.The Kappa value of two doctors on elastography in group Ⅰ (the depth of the lesion ≤10cm) was significantly higher than group Ⅱ (the depth of the lesion ＞10cm).Conclusions Real-time tissue elastography of liver tumors provides a new convenient,non-invasive diagnostic methods,contribute to identify the benign and malignant live tumors.     

超声造影剂在诊断超声辐射下对兔睾丸生精细胞的影响

Objective To study the impact of ultrasound contrast agent with different doses or imaging modes on rabbit spermatogenic cell in the diagnosis of radiation dose.Methods Thirty-three New Zealand white rabbits were randomly divided into 3 groups.In group Ⅰ ,three minutes gray scale ultrasound radiation was performed for three rabbits.In group Ⅱ, SonoVue was bolus injected from ear vein for eighteen rabbits.The rabbits in this group were divided into 6 sub-group according to different doses and different sampling times, the single injections of SonoVue with dosage of 0.1 ml/kg(A1, A2) or 1 ml/kg (C1 ,C2) and repeated injections with dosage of 0.1 ml/kg interval 15 min (B1 ,B2) were taken.In group Ⅲ ,twelve rabbits were bolus injected with SonoVue and then the agent bubbles were blasted when the SonoVue suffused the whole testis.The rabbits in this group were divided into 4 sub-groups according to different doses and different sampling times, and the dosages of SonoVue were 0.1 ml/kg(D1, D2) and 1 ml/kg(E1,E2).Testis were drew immediately or 24 hours later for the observation under light microscope and transmission electron microscope.Results Apoptotic cells in group Ⅲ were more than those in group Ⅰ and Ⅱ ( P ＜0.05) ,while no significant difference of the total number of apoptotic cells between group Ⅰ and Ⅱ ( P ＞0.05).The appearances of focal ultra-structural damage were observed by transmission electron microscope in group C1, such as intercellular space widening and mitochondria swelling, and no distinct damage were observed in the other groups.The appearances of intercellular space widening, mitochondria swelling and cellular edema were observed by transmission electron microscope in group Ⅲ, and spotty necrosisetc was also observed in group D1 and E1.Conclusions Large dose of contrast agent could cause germ cells slight instantaneous effects, while conventional dose had no effect.Contrast agent blasting may cause germ cells unrecoverable damage.     

超声造影剂在诊断超声辐射下对兔睾丸生精细胞的影响

Objective To study the impact of ultrasound contrast agent with different doses or imaging modes on rabbit spermatogenic cell in the diagnosis of radiation dose.Methods Thirty-three New Zealand white rabbits were randomly divided into 3 groups.In group Ⅰ ,three minutes gray scale ultrasound radiation was performed for three rabbits.In group Ⅱ, SonoVue was bolus injected from ear vein for eighteen rabbits.The rabbits in this group were divided into 6 sub-group according to different doses and different sampling times, the single injections of SonoVue with dosage of 0.1 ml/kg(A1, A2) or 1 ml/kg (C1 ,C2) and repeated injections with dosage of 0.1 ml/kg interval 15 min (B1 ,B2) were taken.In group Ⅲ ,twelve rabbits were bolus injected with SonoVue and then the agent bubbles were blasted when the SonoVue suffused the whole testis.The rabbits in this group were divided into 4 sub-groups according to different doses and different sampling times, and the dosages of SonoVue were 0.1 ml/kg(D1, D2) and 1 ml/kg(E1,E2).Testis were drew immediately or 24 hours later for the observation under light microscope and transmission electron microscope.Results Apoptotic cells in group Ⅲ were more than those in group Ⅰ and Ⅱ ( P ＜0.05) ,while no significant difference of the total number of apoptotic cells between group Ⅰ and Ⅱ ( P ＞0.05).The appearances of focal ultra-structural damage were observed by transmission electron microscope in group C1, such as intercellular space widening and mitochondria swelling, and no distinct damage were observed in the other groups.The appearances of intercellular space widening, mitochondria swelling and cellular edema were observed by transmission electron microscope in group Ⅲ, and spotty necrosisetc was also observed in group D1 and E1.Conclusions Large dose of contrast agent could cause germ cells slight instantaneous effects, while conventional dose had no effect.Contrast agent blasting may cause germ cells unrecoverable damage.     

超声辐照促纳米多聚体释放DNA的体内研究

目的 通过研究不同超声参数与绿色荧光蛋白表达之间的关系,探讨超声辐照促进绿色荧光蛋白基因(GFP)与雄激素受体抗体标记的PLGA纳米颗粒(NP-PLGA-GFP-AR)的体内降解与释放的作用.方法 建立人前列腺癌PC-3细胞裸鼠动物模型,将NP-PLGA-GFP-AR纳米粒注射于瘤内2 h后,对癌瘤使用不同强度和类型的超声进行局部辐照,通过激光共聚焦荧光显微镜观察GFP表达,从而评价转染效果.结果 粒径优选后的纳米粒能稳定转染GFP与雄激素受体抗体标记的DNA质粒,超声辐照组较非辐照组的GFP表达提前,占空比为50%的连续波超声较脉冲波超声对前列腺癌的转染效果好.结论 优化后的超声辐照可有效靶向增强体内DNA转染,局部超声辐照结合特异PLGA纳米粒能有效用于DNA靶向递送.

Abstract：

Objective To investigate the feasibility and the efficacy of ultrasound in promoting PLGA nanoparticle-mediated gene transfection in vivo.Methods Prostate cancer cell line PC-3 was used to generate xenografts in nude mice for gene transfection experiment in vivo.GFP plasmid was encapsulated in PLGA-based nanoparticles.Nanoparticles were injected into tumors locally.Two hours later,xenografts were exposed to ultrasound.Xenograft tissues were harvested in different time points to assess the efficiency of gene expression with regard to different parameters of ultrasound. Results PLGA nanoparticle-encapsulated GFP plasmids were readily transfected to PC-3 cells in vivo.A large number of GFP expressing cells were observed after exposed to ultrasound with 1.0 MHz 50% duty factor continuous wave.In comparison,ultrasound exposure with 40% duty factor pulse wave in vivo had low efficacy in terms of GFP expression.No animal death was noticed due to ultrasound exposure.Conclusions Ultrasound exposure can enhance the release of plasmid DNA content delivered by PLGA nanoparticles in vivo,local exposure to ultrasound wave would be used in conjunction with PLGA nanoparticle-mediated targeted delivery to the tissue or organ of interest.     

叶酸受体靶向液态氟碳纳米粒造影剂的制备及体外寻靶

目的 制备叶酸受体靶向的被脂质包裹的液态氟碳纳米粒造影剂,鉴定其基本性质,观察其体外靶向性能.方法 以氯仿将偶联叶酸的磷脂[DSPE-PEG(2000)]按照一定比例溶解在成膜材料中,用旋转蒸发仪去除有机溶剂成膜,加入磷酸盐缓冲液重新水合后,在悬液中逐滴加入适量液态氟碳,均质乳化后得到叶酸受体靶向的纳米粒造影剂.在人卵巢癌SKOV3细胞中验证该造影剂的靶向性能(靶向造影剂组),并与不带叶酸的普通造影剂组和游离叶酸干预组相比较.结果 叶酸受体靶向液态氟碳纳米粒造影剂外观与普通造影剂无明显差别.体外靶向实验发现此纳米粒造影剂聚集且牢固地黏附于SKOV3细胞,而普通造影剂组和游离叶酸干预组则未见明显特异性结合.结论 成功制备了偶联叶酸的被脂质包裹的液态氟碳纳米粒造影剂,该造影剂对高表达叶酸受体的SKOV3细胞具有较强的亲和力,有望成为卵巢癌靶向显影与治疗的理想分子探针.     

脂质超声造影剂携半乳糖化多聚赖氨酸靶向结合HepG2细胞的实验研究

目的 探讨连接以半乳糖化多聚赖氨酸作为配体的脂质微泡超声造影剂的细胞靶向能力,为体内靶向显影及治疗肝癌寻求新方法.方法 用还原胺化法将多聚赖氨酸进行半乳糖化,人工合成小分子量的靶向配体,在室温下与自制脂质微泡发生化学结合制备成靶向脂质微泡,于荧光显微镜下观察体外靶向效果.结果 半乳糖与多聚赖氨酸在摩尔比为1:100,室温下反应24 h时,能进行高效连接;靶向脂质微泡粒径平均为2.05弘m,大小均一;激光共聚焦荧光显微镜见HepG2肝癌细胞能与靶向造影剂特异性结合.结论 连接有以半乳糖化多聚赖氨酸为靶向配体的脂质微泡在HepG2肝癌细胞的内吞作用下能与之有效结合.     

纳米脂质微泡超声造影剂制备及其显影效果的实验研究

目的 制备一种纳米级脂质超声微泡造影剂,并将其与普通脂质微泡在正常兔肝的造影效果进行比较,以评价其造影效果.方法 经机械振荡法制备纳米脂质微泡,检测其形态、粒径、表面电位等物理特性.分别经兔耳缘静脉团注自制纳米脂质、普通脂质微泡造影剂(2.5 ml/kg),动态观察肝的实质回声增强情况,并用DFY型超声图像分析诊断仪对造影效果进行定量分析.结果 纳米脂质微泡平均粒径为415.8 nm,平均电位为-(13.7±1.6)mV.造影后观察:该纳米微泡能明显增强兔肝的二维灰阶显像,与普通脂质微泡比较,纳米微泡达峰时间较晚,峰值持续时间较短,增强持续时间较普通脂质微泡长,纳米微泡对肝的增强峰值强度略低于普通微泡.结论 自制纳米微泡形态好,粒径均一,显影效果理想,为肿瘤的靶向性研究提供了一个前期基础.     

靶向CD147纳米微泡的制备及超声成像能力检测

目的 制备靶向CD147纳米微泡造影剂,并评价其理化性质、对肝细胞肝癌(肝癌)细胞的靶向能力及超声成像能力.方法 将PLGA-PEG、DSPE-PEG2000-COOH、全氟丙烷饱和水溶液混合,通过偶联反应与CD147抗体结合,制备靶向CD147纳米微泡.将靶向CD147及非靶向纳米微泡分别与MHCC-97H(肝癌细胞...     

携Gelsolin单抗靶向超声造影剂的制备及体外靶向实验

目的 制备一种以肿瘤淋巴转移相关特异性膜抗原蛋白——凝溶胶蛋白（Gelsolin）为靶点的纳米级高分子造影剂,并观察其体外寻靶及显影能力。方法 通过改良的双乳化法制备高分子PLGA-COOH造影剂,以碳二亚胺法将造影剂与Gelsolin单抗连接,制备出GSN-PLGA靶向超声造影剂。检测该造影剂的一般性质,评估Gelsolin单抗与造影剂表面连接情况,评价其体外寻靶能力并进行体外显影实验。结果 GSN-PLGA靶向超声造影剂平均粒径为（575.67±4.71）nm,表面电位（-11.46±1.19）mV,造影剂表面GSN单抗结合率达96.93%。体外摄取实验显示细胞表面高表达Gelsolin抗体的小鼠腹水型肝癌高淋巴转移细胞株（Hca-F细胞）可较多摄取GSN-PLGA靶向造影剂。体外显像实验显示靶向超声造影剂体外显影效果较好。结论 GSN-PLGA靶向超声造影剂可与高表达Gelsolin的Hca-F细胞特异性结合,且体外显影效果较好。     

携HMME-Gd液态氟碳纳米粒造影剂的制备及体外双模态成像研究

目的 制备携带血卟啉单甲醚-钆(HMME-Gd)的液态氟碳纳米粒(HMME-Gd-PFPNPs),观察体外US/MRI的成像效果。方法 以磷脂、胆固醇、HMME-Gd和全氟戊烷(PFP)为原料,用薄膜水化法和乳化法制备脂质体纳米粒HMME-Gd-PFPNPs。倒置光学显微镜、透射电子显微镜及激光共聚焦显微镜检测其基本表征;粒径分析仪分析粒径及表面电位;紫外分光光度计分析HMME-Gd的包封率;观察HMME-Gd-PFPNPs体外US/MRI成像的效果。结果 成功制备HMME-Gd-PFPNPs,光镜下为形态规则、大小均一的球形,电镜下为黑色的球形结构。HMME-Gd-PFPNPs平均粒径为(250.27 ± 11.9)nm,电位为(-26.17 ± 0.45)mV,HMME-Gd的包封率为(84.7 ± 0.35)%。在低强度聚焦超声辐照下,体外US成像信号显著增强,与LIFU激发强度成正相关。随HMME-Gd-PFPNPs浓度增加,体外MRI成像效果显著增强。结论 成功制备了携带HMME-Gd的液态氟碳纳米粒,可用于体外US/MRI双模态成像。     

纳米级超声造影剂的研究进展

随着超声分子成像技术和生物纳米技术的迅猛发展,近年来出现了多种纳米级超声造影剂,包括纳米级脂质体造影剂、纳米级氟烷乳剂和纳米级微泡造影剂。本文就纳米级超声造影剂的研究背景、研究现状、现存的问题及发展前景做一综述。     

靶向性超声显影评价不同程度肝损伤的初步实验研究

目的 使用靶向超声分子显像对比分析大鼠不同程度急性肝损伤后峰值回声强度的改变与去唾液酸糖蛋白受体（ASGPR）的含量及血清学检查的关系.方法 根据腹腔灌注四氯化碳分析纯的不同剂量（10%、20%、30%、40%、50%）,将45只健康雄性SD大鼠随机分为相应5组（组Ⅰ~组Ⅴ）,每组9只,每组中再随机抽取4只取肝组织,分别检测ASGPR的含量;另5只仅常规麻醉,胸腹部备皮,经尾静脉团注靶向液态氟碳纳米脂质超声造影剂.从注射开始至0.5 h内连续观察并记录,0.5～1 h内每10 min观察并记录,1 h至造影剂消退每30 min观察并记录肝实质超声图像.DFY型超声图像定量分析诊断仪对各时间点采集到的超声图像进行分析.另选10只健康雄性SD大鼠作为靶向超声造影对照组,方法同前.结果 随着肝损伤程度的增加,肝组织内的ASGPR含量逐渐减少,且各组样本均数两两比较差异均有统计学意义（P〈0.05）.同时肝靶向超声造影后峰值回声强度逐渐降低,除对照组与组Ⅰ比较差异无统计学意义外,其余各组两两比较差异均有统计学意义（P〈0.05）,而达峰时间、峰值回声强度、造影前肝实质回声强度及清退后肝实质回声强度各组间比较差异均无统计学意义（P〉0.05）.结论 自制靶向肝实质细胞膜受体ASGPR的液态氟碳纳米超声造影剂的肝靶向性显影效果佳;不同程度肝损伤后的靶向超声显影结果改变与ASGPR结果改变一致,有利于超声显影定量评价肝脏功能.     

Investigation of vaporized submicron perfluorocarbon droplets as an ultrasound contrast agent

Acoustically activated submicron droplets of liquid perfluorocarbon are investigated as a new class of ultrasound contrast agent. In the liquid state, intravascular droplets can extravasate within tumours. Activation is then accomplished by using bursts of ultrasound to vaporize the droplets. We use acoustical and optical techniques to assess the characteristics of vaporized droplets and the resulting microbubbles in vitro, including size, conversion threshold, echogenicity and nonlinearity. Under exposure to single 5-50 cycle bursts of ultrasound at 7.5 MHz and mechanical index <1.0, droplets with mean diameter of 400 nm convert into microbubbles with mean diameter of 1.4 μm at 1 ms after vaporization, expanding to 5.6 μm by 1 s. The growth of microbubbles produced by vaporization causes a characteristic time-dependent increase in linear and nonlinear echogenicity, enabling selective detection with conventional bubble-specific imaging. These results suggest that submicron perfluorocarbon droplets, activated in situ, may be a candidate for an extravascular ultrasound contrast agent.     

Transmission electron microscopy of rabbit liver after high-intensity focused ultrasound ablation combined with ultrasound contrast agents

The purpose of this study was to observe sequential changes in rabbit liver under transmission electron microscopy after high-intensity focused ultrasound (HIFU) ablation. Thirty rabbits were randomly divided into 2 groups. The livers of rabbits in group A underwent single HIFU ablation; those in group B were given the ultrasound contrast agent Sonovue 0.2 mL/kg before HIFU exposure. Five rabbits from each of the 2 groups were killed at 0 h, 6 d, and 14 d after HIFU ablation. Tissue samples that included targeted and untargeted tissues were observed under transmission electron microscopy. Electron microscopy showed that most of the cell organs in targeted areas of groups A and B disappeared early after HIFU, but the basic cell structure was seen in group A. On the sixth day after HIFU ablation in the 2 groups, all cells in the targeted areas were disrupted and fibrous bands were detected in the rims of targeted areas. In surrounding areas, cell swelling in group B was more severe than in group A, and a greater number of apoptotic bodies were found in group B. The use of an ultrasound contrast agent can enhance the effects of HIFU ablation on the destruction of cell ultrastructure and can enlarge the region of HIFU ablation; this provides experimental evidence for control of HIFU effects.