HIFU联合氟碳乳剂损伤兔肝脏的实验研究

目的　探讨氟碳乳剂对高强度聚焦超声 (HIFU )损伤效率的影响。方法　使用同一聚焦超声换能器 ,辐照深度、功率一致条件下 ,静脉注射等量氟碳乳剂 (实验组 )或生理盐水 (对照组 )后 ,用 HIFU辐照兔肝脏 ,测量凝固性坏死体积 ,计算能效因子。结果　静脉注射生理盐水后 HIFU辐照兔肝脏所产生的凝固性坏死体积和灰度值小于注射实验组 ,能效因子和辐照时间大于实验组。结论　氟碳乳剂增强了 HIFU的损伤效率 ,使损伤后靶区的灰度值明显提高 ,有利于深部肿瘤的治疗和 HIFU治疗的实时监控。     

HIFU治疗中的空化效应及其应用

超声空化效应是高强度聚焦超声（HIFU）治疗中的重要生物学效应之一，在形成凝固性坏死与提高治疗效率等方面起着关键性作用。因而在HIFU治疗中是否有空化效应参与，什么条件下发生，对热效应有怎样的影响，如何评价它的利弊及怎样去控制和利用它是研究者关注的问题，本文就这些问题进行综述。     

经静脉注射脂质包裹液态氟碳纳米粒增效高强度聚焦超声治疗肿瘤的初步研究

目的观察经静脉注射脂质包裹液态氟碳纳米粒对高强度聚焦超声(HIFU)治疗肿瘤的增效作用,并探讨其增效机制。方法首先制备脂质包裹的液态氟碳纳米粒。然后选取建模成功后3周的荷VX2肝癌移植瘤的新西兰大白兔36只,随机等分为3组,用HIFU对兔肝肿瘤进行辐照。A组为对照组,即辐照前经兔耳缘静脉注射生理盐水,B组在辐照前注射液态氟碳纳米粒,30 s后用HIFU辐照,C组在辐照前24 h注射液态氟碳纳米粒。观察各组辐照区域视频灰度变化及肿瘤凝固性坏死情况。结果 B组和C组均见到辐照区域明显灰度变化,A组仅部分见到灰度变化,B、C组辐照前后灰度变化面积和变化值与A组有显著差异(P0.05);3组兔肝肿瘤内均观察到明显的凝固性坏死,B、C组坏死的范围明显大于A组(P0.05)。结论经静脉注射脂质包裹的液态氟碳纳米粒能够增强HIFU的疗效,此效应可能与纳米粒改变组织声环境、增加聚焦超声的空化作用有关,但具体作用机制有待进一步探讨。     

超声造影剂增强HIFU消融兔肝组织的电镜观察

目的探讨高强度聚焦超声(HIFU)联合超声造影剂消融后兔肝细胞超微结构变化。方法30只动物分为两组,A组单纯HIFU辐照,B组辐照前注射超声造影剂。辐照后1h、6d、14d电镜观察。结果辐照后两组靶区细胞坏死,辐照后早期A组靶区可见细胞轮廓。辐照后6d两组靶区细胞崩解,边缘见纤维包裹带,靶区周围细胞浊肿,B组较A组严重,B组靶区周围凋亡小体多于A组。结论超声造影剂增强HIFU消融作用,进一步破坏组织超微结构。     

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。     

HIFU联合HL-1损伤正常兔肝脏组织的体内实验研究

目的　探讨一种脂质体 (HIFU L iposomes- 1,HL - 1)增强兔肝高强度聚焦超声 (high intensity focused ultrasound,HIFU )能量沉积和灰阶超声实时监控的效果。方法　将兔随机分为 A,B两组 ,A组右肝为实验侧 (HL - 1侧 ) ,左肝为生理盐水侧 ,B组相反。输入生理盐水后以一定参数行 A组左肝或 B组右肝 HIFU损伤 ;然后输入 HL - 1以相同参数行对侧组织 HIFU损伤 ;记录 HIFU靶区 B超灰度值。实验后 2 4h解剖 ,测量凝固性坏死组织大小、计算能效因子 (energy efficiency factor,EEF)并行组织病理检查。结果　灰度增强出现率在 A、 B两组的 HL - 1侧均有所增加 ,但差异无显著性 (P>0 .0 5 ) ;A,B两组 HL - 1侧的 EEF均明显低于对照侧 (P<0 .0 1) ;损伤组织大体观及病理检查两组两侧均为典型的凝固性坏死。结论　 HL - 1联合 HIFU能导致靶区组织发生凝固性坏死 ,并有增强正常兔肝脏组织 HIFU能量沉积的作用 ,灰阶超声对靶区组织凝固性坏死的实时监控作用有待进一步研究。     

HIFU消融后兔肝细胞凋亡与增殖的研究

目的探讨高强度聚焦超声（HIFU）消融兔肝组织后细胞凋亡和增殖细胞核抗原（PCNA）表达的变化。 方法24只新西兰大白兔肝组织接受HIFU辐照，辐照后5min，1、3、6、9、14d分别处死4只动物，取出肝脏，HE染色观察组织病理改变，透射电镜观察细胞超微结构变化，原位末端标记法（TUNEL）检测细胞凋亡，免疫组织化学方法检测PCNA表达。 结果HE染色显示HIFu辐照后靶区边缘形成纤维包裹带，随时间逐渐加宽（P〈0．05）。电镜发现辐照后靶区周围组织有凋亡小体生成，TUNEL检测凋亡指数于辐照后3d最高。辐照后靶区周围组织出现PCNA阳性细胞，PCNA阳性细胞指数于辐照后6d达到峰值。 结论HIFU辐照后凝固坏死区域逐渐机化包裹，靶区周围组织出现凋亡细胞和PCNA阳性细胞，数量随时间变化，为进一步控制和增强HIFu消融作用提供实验基础。     

聚焦超声增强聚桂醇消融兔肝的实验研究

目的 研究聚焦超声同步辐照对聚桂醇消融正常兔肝脏的增效作用。方法 健康新西兰大白兔26只随机分为三组：聚焦超声组（FUS组,6只）、聚桂醇组（LAU组,10只）及聚焦超声+聚桂醇组（FUS+LAU组,10只）,分别给予聚焦超声辐照、聚桂醇及聚桂醇联合聚焦超声同步辐照处理。FUS焦点的平均声强（ISPTA）30.0W/cm2,工作占空比50%。48小时后观察处理区解剖及超声造影表现,测量血流充盈缺损区最大径。采用量筒法测定消融体积,消融灶HE染色后镜下观察组织学改变。采用Wilcoxon秩和检验比较LAU组与FUS+LAU组肝脏充盈缺损区最大径及消融体积的差异。结果 FUS组实验兔肝脏处理区未出现消融灶,LAU组与FUS+LAU组形成相似的黄白色消融灶。两组兔肝超声造影充盈缺损区平均最大径分别为(0.73±0.15)mm、(0.91±0.16)mm,差异有统计学意义(Z=-2.077,P=0.038);两组平均消融体积分别为(0.19±0.06)ml、(0.47±0.20)ml,差异有显著统计学意义(Z=-3.182,P=0.001),FUS+LAU组平均消融体积约为LAU组的2.5倍。两组消融灶HE染色均表现为典型的肝细胞坏死性改变。结论 聚焦超声同步辐照对聚桂醇消融正常兔肝有增效作用。     

MRI监控HIFU损伤活体兔肝组织的影像学观察

目的 观察HIFU损伤30只活体兔肝组织的MRI监控图像,探讨MRI图像变化及与实际损伤的关系.方法 采用不同剂量HIFU辐照活体兔肝组织,于术后即刻进行T1WI、T2WI、PDWI、增强T1WI扫描.观察并测量MRI显示损伤灶与实际损伤灶面积,同时取损伤组织HE染色病理检查.结果 所有30只损伤灶中,30只于T1WI中为边界清晰的高信号,与实际黄白色损伤面积比较无统计学差异(P>0.05).损伤灶于 T2WI(18只)和PDWI(3只)中为稍低信号.30只损伤灶于增强T1WI中无强化,其中17例无强化区面积大于实际损伤面积.结论 MRI能有效监控及评价HIFU辐照活体兔肝组织的效果.     

A Comparison of Acoustic Cavitation Detection Thresholds Measured with Piezo-electric and Fiber-optic Hydrophone Sensors

A Fabry-Perot interferometer fiber-optic hydrophone (FOH) was investigated for use as an acoustic cavitation detector and compared with a piezo-ceramic passive cavitation detector (PCD). Both detectors were used to measure negative pressure thresholds for broadband emissions in 3% agar and ex vivo bovine liver simultaneously. FOH-detected half- and fourth-harmonic emissions were also studied. Three thresholds were defined and investigated: (i) onset of cavitation; (ii) 100% probability of cavitation; and (iii) a time-integrated threshold where broadband signals integrated over a 3-s exposure duration, averaged over 5–10 repeat exposures, become statistically significantly greater than noise. The statistical sensitiviy of FOH broadband detection was low compared with that of the PCD (0.43/0.31 in agar/liver). FOH-detected fourth-harmonic data agreed best with PCD broadband (sensitivity: 0.95/0.94, specificity: 0.89/0.76 in agar/liver). The FOH has potential as a cavitation detector, particularly in applications where space is limited or during magnetic resonance-guided studies.     

Temporal and Spatial Detection of HIFU-Induced Inertial and Hot-Vapor Cavitation with a Diagnostic Ultrasound System

The onset and presence of inertial cavitation and near-boiling temperatures in high-intensity focused ultrasound (HIFU) therapy have been identified as important indicators of energy deposition for therapy guidance. Passive cavitation detection is commonly used to detect bubble emissions, where a fixed-focus single-element acoustic transducer is typically used as a passive cavitation detector (PCD). This technique is suboptimal for clinical applications, because most PCD transducers are tightly focused and afford limited spatial coverage of the HIFU focal region. A Terason 2000 Ultrasound System was used as a PCD array to expand the spatial detection region for cavitation by operating in passive mode, obtaining the radiofrequency signals corresponding to each scan line and filtering the contribution from scattering of the HIFU signal harmonics. This approach allows for spatially resolved detection of both inertial and stable cavitation throughout the focal region. Measurements with the PCD array during sonication with a 1.1-MHz HIFU source in tissue phantoms were compared with single-element PCD and thermocouple sensing. Stable cavitation signals at the harmonics and superharmonics increased in a threshold fashion for temperatures >90°C, an effect attributed to high vapor pressure in the cavities. Incorporation of these detection techniques in a diagnostic ultrasound platform could result in a powerful tool for improving HIFU guidance and treatment. (E-mail: cfarny@bwh.harvard.edu)     

An in vitro study of a phase-shift nanoemulsion: a potential nucleation agent for bubble-enhanced HIFU tumor ablation

Phase-shift nanoemulsions have the potential to nucleate bubbles and enhance high-intensity focused ultrasound (HIFU) cancer therapy. This emulsion consists of albumin-coated dodecafluoropentane (DDFP) droplets with a mean diameter of approximately 260 nm at 37°C. It is known that superheated perfluorocarbon droplets can be vaporized with microsecond long ultrasound pulses if the acoustic pressure exceeds a specific threshold. In addition, it is well documented that particles smaller than 400 nm can extravasate through leaky tumor vessels and accumulate in the tumor interstitial space. Thus, nanoemulsions may passively target solid tumors, thus localizing cavitation nuclei for bubble-enhanced HIFU-mediated heating. In this study, we investigate the acoustic droplet vaporization of a DDFP nanoemulsion in tissue-mimicking gels and demonstrate the ability to nucleate inertial cavitation (IC) and enhance HIFU-mediated heating. The nanoemulsion was dispersed throughout albumin-acrylamide gel phantoms and sonicated with microsecond-length HIFU pulses (f = 2 MHz). The pressure threshold needed to vaporize the nanoemulsion was measured as a function of degree of superheat, pulse length and nanoemulsion concentration. It was determined that the vaporization threshold was inversely proportional with degree of superheat and independent of pulse length and concentration within the range of values tested. It was also shown that the bubbles formed from vaporized nanoemulsions reduced the IC threshold in the gel phantoms. Finally, it was demonstrated that cavitation from vaporized nanoemulsions accelerated HIFU-mediated heating. The results from this study demonstrate that phase-shift nanoemulsions can be combined with HIFU to provide a high degree of spatial and temporal control of bubble-enhanced heating.     

Passive Cavitation Detection during Pulsed HIFU Exposures of Ex Vivo Tissues and In Vivo Mouse Pancreatic Tumors

Pulsed high-intensity focused ultrasound (pHIFU) has been shown to enhance vascular permeability, disrupt tumor barriers and enhance drug penetration into tumor tissue through acoustic cavitation. Monitoring of cavitation activity during pHIFU treatments and knowing the ultrasound pressure levels sufficient to reliably induce cavitation in a given tissue are therefore very important. Here, three metrics of cavitation activity induced by pHIFU and evaluated by confocal passive cavitation detection were introduced: cavitation probability, cavitation persistence and the level of the broadband acoustic emissions. These metrics were used to characterize cavitation activity in several ex vivo tissue types (bovine tongue and liver and porcine adipose tissue and kidney) and gel phantoms (polyacrylamide and agarose) at varying peak-rare factional focal pressures (1–12 MPa) during the following pHIFU protocol: frequency 1.1 MHz, pulse duration 1 ms and pulse repetition frequency 1 Hz. To evaluate the relevance of the measurements in ex vivo tissue, cavitation metrics were also investigated and compared in the ex vivo and in vivo murine pancreatic tumors that develop spontaneously in transgenic KrasLSL.G12 D/+; p53 R172 H/+; PdxCretg/+ (KPC) mice and closely re-capitulate human disease in their morphology. The cavitation threshold, defined at 50% cavitation probability, was found to vary broadly among the investigated tissues (within 2.5–10 MPa), depending mostly on the water-lipid ratio that characterizes the tissue composition. Cavitation persistence and the intensity of broadband emissions depended both on tissue structure and lipid concentration. Both the cavitation threshold and broadband noise emission level were similar between ex vivo and in vivo pancreatic tumor tissue. The largest difference between in vivo and ex vivo settings was found in the pattern of cavitation occurrence throughout pHIFU exposure: it was sporadic in vivo, but it decreased rapidly and stopped over the first few pulses ex vivo. Cavitation activity depended on the interplay between the destruction and circulation of cavitation nuclei, which are not only used up by HIFU treatment but also replenished or carried away by circulation in vivo. These findings are important for treatment planning and optimization in pHIFU-induced drug delivery, in particular for pancreatic tumors.     

US-MRI图像配准融合技术在高强度聚焦超声消融子宫肌瘤中的应用价值

目的 探讨超声和MRI图像（US-MRI）配准融合技术在高强度聚焦超声（HIFU）消融子宫肌瘤中的价值。方法 评估78例子宫肌瘤患者的80组US-MRI图像的配准与融合效果;记录并分析用于指导不同配准融合操作的解剖标记部位和效果。结果 以子宫的边界为标志配准同一子宫平面,与配准前比较,图像清晰度评分显著增加（P=0.004）;以子宫肌瘤的边界为标志配准同一子宫肌瘤平面,与配准前比较,图像清晰度评分显著增加（P<0.001）;以耻骨边界为标志能配准同一耻骨平面;以骶岬为标志点能配准骶尾骨。结论 US-MRI配准技术可有效提高HIFU消融子宫肌瘤的可视化空间。     

The effect of endostatin and gemcitabine combined with HIFU on the animal xenograft model of human pancreatic cancer

Objective

To investigate the influence of the recombinant human endostatin and gemcitabine combined with HIFU on the mouse xenograft model of pancreatic cancer.

Methods

Use human pancreatic cancer cell line PANC-1 to set up the mouse xenograft model, then randomized into four arms. Each arm was treated with gemcitabine, endostatin, gemcitabine combined with endostatin and normal saline respectively. Observe the volume of the tumor, the serum VEGF level and MVD in the tumor tissue among the different arms. All mice were treated with HIFU, then pathological examination was done.

Results

The tumor volume, serum VEGF level and MVD in the combined-therapy arm are all lower than the monotherapy arms and the control arm. The coagulation necrosis occurred in tumors after HIFU treatment.

Conclusion

Endostatin and gemcitabine has better effect than gemcitabine or endostatin monotherapy on the animal xenograft model of human pancreatic cancer. HIFU combined with chemotherapy and/or targeted therapy may enhance the effect for pancreatic cancer.     

晚期胰体癌HIFU消融效果与CT靶皮距的相关性

目的探讨晚期胰体癌HIFU消融效果与CT靶皮距的相关性。方法将HIFU消融体积比>30%定为A组,即存在与HIFU相关的消融;≤30%定为B组,即不明确存在与HIFU相关的消融。根据上述分组,对20例晚期胰体癌肿物消融效果与CT靶皮距的相关性进行分析。结果 A组与B组之间CT靶皮距差异有统计学意义(P<0.05),且CT靶皮距每增加1cm,消融效果降低0.31倍;ROC曲线显示,当CT靶皮距为7.15cm时,其预测消融效果的敏感度为80.00%,特异度为70.00%,曲线下面积为0.81(P=0.02)。结合临床,将7cm作为CT靶皮距的分界值,预测消融效果的敏感度和特异度分别为77.80%和72.70%,OR值为9.33。结论晚期胰体癌HIFU消融效果与CT靶皮距呈负相关;CT靶皮距等于7cm可作为胰体癌HIFU治疗的适应证选择界值。     

基于超声图像处理的HIFU所致组织损伤自动检测方法:实验研究

目的 探讨基于超声图像处理的HIFU所致组织损伤的自动检测方法。方法 针对HIFU辐照后新鲜离体猪肉声像图中的ROI,通过搜索灰度极大区域自动定位图像中的所有亮斑,结合数学形态学、连通域标记和Canny边缘检测算法提取测试对象的边缘轮廓;根据亮斑中心至边缘轮廓的欧式距离去除边缘附近的亮斑噪声,获取HIFU损伤候选区;而后提取候选区特征参数,并结合支持向量机（SVM）识别HIFU损伤。结果 最大灰度值和矩形度两个特征参数的识别率分别为86.25%和93.33%。选用识别率更高的矩形度,可正确识别单处、多处HIFU损伤或无HIFU损伤的图像。结论 采用此法可直接分析HIFU辐照后超声声像图而自动检测HIFU损伤,无需依靠图像配准技术,可减少手动定位带来的误差。