超声微泡造影剂在疾病诊断与治疗中的研究进展

超声微泡造影剂在疾病诊断与治疗中的作用日渐明显.超声微泡造影剂可用于对心脏、肝脏、肿瘤等的声学造影诊断,具有靶向性的超声微泡造影剂对组织、血栓及肿瘤的靶向显影应用前景广阔.目前的研究表明,超声微泡造影剂在治疗中也显示出巨大潜力,可作为一种有效的基因或药物运载工具.而低功率超声辐射微泡治疗肿瘤研究亦有望取得突破性进展.     

超声微泡及其在分子影像诊断和靶向治疗中的应用

超声微泡是一种超声造影剂,利用超声微泡声学特征和靶向功能可提高超声分子诊断的灵敏性和特异性,利用其药物载体和释放功能可进行靶向药物治疗。现对超声微泡及其在分子影像诊断和靶向治疗中的应用进展作一综述。     

靶向超声微泡在肿瘤诊断与治疗方面的研究进展

靶向超声微泡属于"超声分子影像学"的范畴.通过在微泡上偶联肿瘤特异性抗体等方法可以使微泡具有靶向功能,这能大大提高对肿瘤诊断的准确性,同时还可以携带药物与基因用于肿瘤的治疗.随着靶向超声微泡技术的发展,靶向超声微泡必将为超声显像与临床治疗提供一种有效的方法.     

靶向超声微泡造影剂诊断与治疗炎性肠病的研究进展

炎性肠病(IBD)是一种慢性肠道性疾病,病程迁延,严重影响患者的生活质量。随着超声分子影像学的发展,靶向超声微泡造影剂除可应用于IBD的诊断外,还可作为一种载体,实现所携带药物、抗体等的靶向释放,起到对IBD靶向治疗作用,在IBD的诊断和治疗领域展现出很好的应用前景。     

靶向超声造影在乳腺癌诊断与治疗中的研究进展

乳腺癌是女性常见恶性肿瘤之一,发病机制尚未明确,早期诊断和治疗可以改善患者预后。随着超声分子影像技术的发展,靶向超声造影为乳腺癌的诊断及治疗提供了新的技术手段。本文对靶向超声造影在乳腺癌诊断和治疗中的应用进展做一综述。     

血栓靶向脂膜超声造影剂的制备与初步评价

目的制备血栓靶向脂膜超声造影剂,并对其配体结合率进行初步评价。方法通过生物素-抗生物素蛋白桥连法,制备携带血栓靶向配体的脂膜超声造影剂,非靶向脂膜微泡为对照;采用流式细胞仪初步评价靶向微泡配体结合率及其影响因素。结果靶向微泡荧光检测为阳性,对照组为阴性;流式细胞仪分析结果显示该血栓靶向微泡配体结合率达82.96%,对照组仅为0.92%、0.89%。结论采用生物素-抗生物素蛋白桥连接法,可以成功制备血栓靶向脂膜超声造影剂。微泡纯化过程中离心速度与离心时间对配体结合率的影响具有显著意义。     

超声介导携RGDS靶向超声造影剂对体外血栓的助溶研究

目的探讨携RGDS的脂膜氟烷超声造影剂（亲血栓靶向超声造影剂）对体外血栓的助溶效果。方法健康人体新鲜静脉血块60份，分为3组，分别加入亲血栓靶向超声造影剂、非靶向超声造影剂和生理盐水进行超声消融；采用超声治疗仪，选择1．2W／cm^2，距离3cm，治疗时间15min。称量溶栓前后血块的质量，组间比较采用t检验。电镜扫描经消融后的血块表面结构。结果经超声介导造影剂助溶前后的血块质量组间比较差异均有统计学意义（P〈0．01）。电镜扫描显示，生理盐水组血块经消融后表面结构无明显改变，靶向超声造影剂组可见大量均匀分布的空洞和裂隙，非靶向超声造影剂组仅见少量分布的小型凹陷及微小裂隙。结论治疗超声介导下的超声造影剂具有助溶作用，血栓靶向超声造影剂较非靶向超声造影剂具有更强的助溶效果。     

靶向血栓高分子超声造影剂的制备及其体外寻靶实验

目的制备靶向血栓高分子超声造影剂,并对其理化性质及体外寻靶能力进行研究。方法以高分子材料端羧基聚乳酸/羟基乙酸(PLGA-COOH)为载体,采用双乳化法制备PLGA微球;并用碳二亚胺法将该微球与血栓靶向短肽片段精氨酸-甘氨酸-天冬氨酸-丝氨酸(RGDS)共价结合制备靶向血栓高分子超声造影剂(RGDS-PL-GA);检测该造影剂的理化特性并通过体外寻靶实验,评价其对血栓的亲和性。结果采用本法成功制备了RGDS-PLGA,其形态规则,呈大小均匀的球形,平均粒径为(1.21±0.27)μm,RGDS携带率25.69%。体外实验显示RGDS-PLGA可以牢固结合到血栓表面。结论采用双乳化法及碳二亚胺法可以成功制备靶向血栓高分子超声造影剂,该造影剂粒径小,对血栓具有很强的靶向性及稳定性,有望在分子水平为血栓的诊断提供新方法。     

携RGDS的靶向超声造影剂的制备及鉴定

目的制备血栓靶向脂膜超声造影剂,并对其理化特性及靶向作用进行鉴定.方法将脂膜超声造影剂通过酰胺键共价键键合的方式与血栓靶向短肽片段(RGDS)进行结合.制备产物通过流式细胞仪进行携带率和稳定性的检测;对内源性凝血途径产生的血栓进行寻靶特性研究.结果流式细胞仪显示携带RGDS的脂膜超声造影剂其波长发生了明显变化,携带率达到82%;激光共聚焦显微镜显示携带RGDS的脂膜超声造影剂对离体血栓具有很强的靶向性和稳定性.结论采用共价键键合的化学修饰方法成功制备了亲血栓靶向脂膜超声造影剂.     

液态氟碳纳米粒在超声分子靶向成像及治疗中的研究进展

随着超声分子影像学技术的发展,液态氟碳纳米粒作为构建超声分子探针的新型材料,在超声分子靶向成像及治疗的研究中表现出良好的应用前景,是一种非常具有潜力的超声分子探针,有望实现超声分子影像技术对疾病的精准诊断及治疗。本文对液态氟碳纳米粒在超声分子靶向成像及治疗中的研究进展进行综述。     

Enhanced targeting of ultrasound contrast agents using acoustic radiation force

Contrast-enhanced ultrasound has shown significant promise as a molecular imaging modality. However, one potential drawback is the difficulty that ultrasound contrast agents (UCA) may have in achieving adhesion to target molecules on the vascular endothelium. Microbubble UCA exhibit a lateral migration toward the vessel axis in laminar flow, preventing UCA contact with the endothelium. In the current study, we have investigated low-amplitude acoustic radiation as a mechanism to move circulating UCA toward targeted endothelium. Intravital microscopy was used to assess the retention of microbubble UCA targeted to P-selectin in the mouse cremaster microcirculation and femoral vessels. Acoustic treatment enhanced UCA retention to P-selectin four-fold in cremaster venules and in the femoral vein and 20-fold in the femoral artery. These results suggest acoustic treatment as a mechanism for enabling ultrasound-based molecular imaging in blood vessels with hemodynamic and anatomical conditions otherwise adversarial for UCA retention.     

肝灰阶超声造影剂量与效果关系的实验研究

目的 探讨不同超声造影剂剂量对肝灰阶超声造影效果的影响及其变化规律。方法 分别对5只新西兰大白兔在8个剂量水平(剂量范围：0．02～0．16ml／kg)团注超声造影剂，应用低机械指数灰阶超声造影和时间强度曲线定量分析门静脉和肝实质造影增强效果。结果 门静脉和肝实质开始增强时间随造影剂剂量的增加而缩短，均呈指数递减形式；造影剂剂量与门静脉、肝实质峰值增强时间无明确相关性(r=-0．35，0．22)；在0．02～0．10ml／kg范围内，造影剂剂量与门静脉、肝实质峰值信号强度呈直线相关关系(r=0．89，0．92)；门静脉和肝实质的平均渡越时间和曲线下面积均随造影剂剂量的递增而增加，呈指数递增形式。结论 超声造影剂剂量影响肝造影增强各参数。确定剂量和效果的关系及认识其规律是进行超声造影和定量研究的前提条件。0．10ml／kg是兔理想的造影剂量。     

Influence of scanning frequency and ultrasonic contrast agent on reproducibility of left ventricular measurements in the mouse.

BACKGROUND: Mice are now widely used as models of cardiovascular disease. Their small size and fast heart rates are technically challenging to echocardiography. This study examined the influence of different scanning frequencies and ultrasonic contrast agent (UCA) on the accuracy and reproducibility of measurements of left ventricular (LV) structure and function. METHODS: Normal mouse hearts (C57BL6) were imaged at 3 different scanning frequencies before and after intravenous injection of the UCA, Optison. Coronary artery ligation mice and sham-operated controls were scanned at 10-22 MHz with and without UCA. RESULTS: Scanning frequency had no significant effect on intraobserver or interobserver variation of LV measurements in normal mice under baseline conditions. Use of UCA significantly reduced estimated ejection fraction at 10-22 MHz compared with baseline (baseline 50.8 +/- 7.6% vs UCA 39.7 +/- 7.6%; P = .03) and significantly increased values for LV cavity dimensions (eg, LV area diastole 20.74 +/- 1.20 vs 23.23 +/- 0.98 mm 2 ; P = .002). UCA significantly reduced intraobserver and interobserver variation in LV ejection fraction. CONCLUSIONS: Scanning frequency had no significant effect on reproducibility of LV measurements in the mouse but UCA significantly reduced interobserver variation. Use of UCA could reduce the number of mice required in any given experiment to observe a statistically significant change in LV function.     

Quantitative evaluation of focused ultrasound with a contrast agent on blood-brain barrier disruption

The use of an ultrasound contrast agent (UCA) with focused ultrasound sonication has the potential to disrupt the blood-brain barrier (BBB) noninvasively and reversibly at target locations. This study investigated the effects of UCA dose and ultrasound pressure on BBB disruption. Sonications were applied at 1 MHz with a burst length of 10 ms, a 1% duty cycle and a repetition frequency of 1 Hz. The duration of the sonication was 30 s. In in vivo experiments, 16 male Wistar rats were sonicated in the presence of UCA at four doses (0, 30, 60 and 90 microL/kg). BBB integrity was evaluated by injecting Evans blue (EB) into the femoral vein of anesthetized rats. The relationship between UCA dose and the region of EB extravasation was evaluated at ultrasound pressures of 0.9 and 1.2 MPa. The BBB disruption, as quantified by the amount of EB extravasation, was significantly greater in rats injected with UCA at a dose of 60 or 90 microL/kg than at a dose of 0 or 30 microL/kg. The amount of EB extravasation increased monotonically with the quantity of UCA injected into the femoral vein before sonication. Furthermore, the BBB disruption could be enhanced in the focal region relative to the surrounding region with a higher dose of UCA (60 or 90 microL/kg). This study demonstrates that BBB disruption can be both increased and localized to the focal region by injecting an appropriate quantity of UCA before performing focused ultrasound sonications.     

Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging

Quantitative assessment of regional myocardial function at rest and during stress with Doppler tissue imaging (DTI) plays an important role in daily routine echocardiography. However, reliable visual analysis is largely dependent on image quality and adequate border delineation, which still remains a challenge in a significant number of patients. In this respect, an ultrasound contrast agent (UCA) is often used to improve visualization in patients with suboptimal image quality. The knowledge of how DTI measurements will be affected by UCA present in the tissue is therefore of significant importance for an accurate interpretation of local myocardial motion. The aim of this paper was to investigate how signal contribution from UCA and nonlinear wave propagation influence the performance of the autocorrelation phase shift estimator used for DTI applications. Our results are based on model experiments with a clinical 2-D grayscale scanner and computational simulations of the DTI velocity estimator for synthetically-derived pulses, simulated bubble echoes and experimentally-sampled RF data of transmitted pulses and backscattered contrast echoes. The results show that destruction of UCA present in the tissue will give rise to an apparent bidirectional velocity bias of individual velocity estimates, but that spatial averaging of individual velocity measurements within a region-of-interest will result in a negative bias (away from the transducer) of the estimated mean or mean peak velocity. The UCA destruction will also have a significant impact on the measured integrated mean velocity over time, i.e., displacement. To achieve improved visualization with UCA during DTI-examinations, we either recommend that it is performed at low acoustic powers, mechanical index ≤0.3, thereby minimizing the effects from bubble rupture, or that each Doppler pulse package is preceded by a destruction burst similar to “Flash imaging” to clear the target area of contrast microbubbles. (E-mail: marcus.ressner@imt.liu.se)     

Correlation between inertial cavitation dose and endothelial cell damage in vivo

Previous in vivo studies have demonstrated that vascular endothelial damage can result when vessels containing gas-based microbubble ultrasound contrast agent (UCA) are exposed to MHz-frequency pulsed ultrasound (US) of sufficient pressure amplitudes, presumably as a result of inertial cavitation (IC). The hypothesis guiding this research was that IC is the primary mechanism by which the vascular endothelium (VE) is damaged when a vessel is exposed to pulsed 1-MHz frequency US in the presence of circulating UCA. The expectation was that a correlation should exist between the magnitude and duration of IC activity and the degree of VE damage. Rabbit auricular vessels were exposed in vivo to 1.17-MHz focused US of variable peak rarefaction pressure amplitude (1, 3, 6.5 or 9 MPa), using low duty factors (0.04% or 0.4%), pulse lengths of 500 or 5000 cycles, with varying treatment durations and with or without infusion of a shelled microbubble contrast agent. A broadband passive cavitation detection system was used to measure IC activity in vivo within the targeted segment of the blood vessel. The magnitude of the detected IC activity was quantified using a previously reported measure of IC dose. Endothelial damage was assessed via scanning electron microscopy image analysis. The results supported the hypothesis and demonstrate that the magnitude of the measured IC dose correlates with the degree of VE damage when UCA is present. These results have implications for therapeutic US-induced vascular occlusion.     

Evaluation of Dose Distribution of Molecular Delivery After Blood-Brain Barrier Disruption by Focused Ultrasound with Treatment Planning

The permeability of the blood-brain barrier (BBB) can be enhanced by focused ultrasound (FUS) in localized regions with applications of ultrasound contrast agent (UCA). The purpose of this study was to evaluate the dose distribution of Evans blue (EB) in the targeted brain by sonication with treatment strategy. FUS exposure was applied with an ultrasound frequency of 1 MHz, a 5% duty cycle and a repetition frequency of 1 Hz. Single sonication with two doses of UCA and two sonications at the same location or an interval of 3 mm to induce BBB disruption for assessing dose distribution. The permeability of the BBB was measured quantitatively based on EB extravasation. Gadolinium deposition was monitored by contrast enhanced MR imaging for dose distribution of the focal plane. Hematoxylin and eosin staining was performed for histologic observation. No significant difference was found for EB in the focal regions between the single sonication with UCA at a dose of 300 μL/kg and repeated sonication with UCA at a lower dose of 150 μL/kg. There was a sharper dose distribution in the brain with repeated sonication at the same location, compared with the brain receiving two sonications at an interval of 3 mm. Compared with a single sonication with UCA at a dose of 150 μL/kg, the histologic evaluation of the sonicated regions indicated that more erythrocytes were seen in the brain treated with single sonication at a higher dose of 300 μL/kg or repeated sonication at a dose of 150 μL/kg. This study demonstrated that the dose distribution of molecular delivery could be regulated by sonication with treatment planning.     

Relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent and the level of VEGFR2 expression in an in vivo breast cancer model.

OBJECTIVE: The aim of this study was to characterize the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent (UCA) and VEGFR2 expression in tumor vasculature of breast cancer. METHODS: 67NR breast cancer tumors implanted in mice were evaluated in vivo with both VEGFR2-targeted and nontargeted UCAs, and a high-frequency ultrasound system. A bolus of the UCA was injected and allowed to circulate for 4 minutes to allow binding of targeted microbubbles. After that, 2 sets of images before and after a high-power ultrasonic destruction sequence were acquired. The average video intensity of predestruction and postdestruction images was measured and used as a relative measure of retention of the UCA in the tumor. Levels of VEGFR2 expression and tumor vascular density were quantified by immunohistochemical staining and compared with retention of the VEGFR2-targeted UCA. RESULTS: Retention of VEGFR2-targeted microbubbles in tumors was significantly higher than retention of nontargeted microbubbles (mean +/- SD, 47.75+/-9.85 versus 18.5+/-5.46 dB; P< .001). Retention of the VEGFR2-targeted UCA was found to correlate with the level of VEGFR2 expression in the studied tumors (r(2)=0.41). In contrast, retention of the nontargeted UCA was not correlated with the level of VEGFR2 expression (r(2)=0.08). Furthermore, retention of the VEGFR2-targeted UCA was not correlated with the level of tumor vascularity. CONCLUSIONS: The magnitude of the molecular ultrasonographic signal from a VEGFR2-targeted UCA retained by tissue correlates with VEGFR2 expression. These results validate the use of molecular ultrasonography for in vivo detection and quantification of VEGFR2 expression in this breast cancer model.     

光热型超声造影剂用于治疗肿瘤研究进展

随着分子影像学和纳米技术的发展,可用于光热治疗的多功能超声造影剂(UCA)逐渐涌现.受近红外光触发后,光热型UCA可清晰显示肿瘤病灶,并可监控靶向热消融肿瘤.将光热剂整合于造影剂结构中,不仅提高了光热剂的稳定性,同时可协同超声空化效应增效光热治疗.本文针对光热型UCA用于治疗肿瘤的研究进展进行综述.     

Scoping Review of Targeted Ultrasound Contrast Agents in the Detection of Angiogenesis

A systematic search was conducted to categorize targeted ultrasound contrast agents (UCAs) used in cancer-related angiogenesis detection. We identified 15 unique contrast agents from 2008 to March 2018. Most primary research articles studied UCAs targeted to vascular endothelial growth factor receptor or α_vβ₃-integrin. Breast cancer and colon cancer are the most common neoplastic processes in which these agents were studied. BR55 (Bracco Research SA, Geneva, Switzerland), a vascular endothelial growth factor receptor–targeting UCA, is the first targeted UCA that has completed phase 0 trials. Our review identifies a gap in the literature regarding the application of targeted UCAs in cancer models beyond breast and colon cancers and identifies other promising UCAs.