微泡造影剂的声学特性及相关新技术

声学造影剂的历史可上溯至１９６８年［１］,之后为研制出能增强灰阶信号及多普勒信号的造影剂以应用于心脏及非心脏领域,医技人员作出了巨大的努力。理想的声学造影剂应具有以下特性：①无毒性,无副作用;②能经外周静脉注射;③能通过肺及全身毛细血管床;④性能稳定,持续时间足够长;⑤不影响全身或某一系统的血流动力学,不影响全身血流状态;③通过简单的方法即能控制造影剂的体内存留时间［２］。直到近１０年才逐渐有造影剂能达到上述要求并逐步应用于临床。 目前造影剂根据剂型及成分的不同,可分为：①自由气体;②包裹气体;…     

超声微泡造影剂的临床应用及研究进展

随着超声造影和微泡制备技术的不断发展，超声不仅作为一种临床诊断工具，而且更扩展了治疗领域。新型超声造影刑的临床应用是近年来超声医学研究的热点，具有广阔的应用前景。现就超声微泡造影剂的应用及研究进展综述如下。     

超声微泡造影剂的临床应用及研究进展

随着超声造影和微泡制备技术的不断发展,超声不仅作为一种临床诊断工具,而且更扩展了治疗领域.新型超声造影剂的临床应用是近年来超声医学研究的热点,具有广阔的应用前景.现就超声微泡造影剂的应用及研究进展综述如下.     

微泡介导下诊断超声开放人血脑屏障的可行性实验研究

目的:探讨微泡介导下诊断超声波开放人血脑屏障的可行性。材料和方法:①用青年人颞骨代替兔顶骨,制作模拟超声波经人颅骨的动物模型;②经兔耳缘静脉匀速注射微泡(0.5ml/kg)时,诊断超声波经人颅骨连续辐照兔脑10min。立即用伊文思蓝(Evens blue,EB)示踪法评价靶区血脑屏障的开放情况,并观察有无神经细胞的损伤。结果:微泡介导下诊断超声波经青年人颅骨能够促EB跨兔血脑屏障进入脑组织,且不导致神经细胞的损伤。结论:微泡介导下诊断超声波经青年人颅骨能够安全、有效地开放兔血脑屏障,表明微泡介导下诊断超声开放人血脑屏障具有可行性,而且相对安全。     

谐波成像技术与微泡造影剂的发展现状

近十年来，经周围静脉使用的超声微泡造影剂的研制取得了快速的发展，而微泡造影剂与谐波技术的联合应用更为超声成像带来新的进展。     

大鼠脑缺血后高血糖对血脑屏障通透性的影响

采用＾３Ｈ标记的α－氨基异丁酸（＾３Ｈ－ＡＩＢ）做为血脑屏障（ＢＢＢ）通透性指示剂，定量观察了高血糖大鼠脑缺血后ＢＢＢ的变化。结果发现，在大鼠４血管阻断脑缺血２０ｍｉｎ，高血糖组ＢＢＢ通透性明显高于正常血糖组及非脑缺血对照组；正常血糖组与对照组间无明显差异。提示高血糖能够加重ＢＢＢ损害，ＢＢＢ的损害可能是高血糖加重脑缺血性损害及脑水肿的重要病理生理机制之一。     

超声微泡造影剂携带基因和药物靶向治疗的研究进展

超声微泡造影剂携带基因和药物的靶向治疗是当前医学领域中的研究热点。超声微泡造影剂到达靶组织后,在超声能量作用下,因"空化效应",能有效穿透血管内皮屏障,定向释放内部包裹的基因或药物,使局部浓度大大增高,达到靶向治疗目的。本文就其在抗肿瘤、溶栓和炎症方面的研究进展做一简要综述。     

七氟醚对成年大鼠血脑屏障通透性的影响

为观察不同浓度七氟醚对大鼠血脑屏障（blood-brain barrier,BBB）通透性的影响,将30只成年大鼠随机分为对照组、七氟醚1MAC（肺泡气最低有效浓度,minimal alveolar concentration）及1.5MAC组（各维持呼气末浓度在2.2％及3.3％,1h）。实验结束前静脉注射伊文思蓝 （EB）溶液,取脑做EB染色观察、镧醛灌注后电镜观察及HE染色光镜观察。结果显示吸入1MAC和1.5MAC的七氟醚均未均未增加大鼠BBB对大分子（EB－白蛋白）和小分子（镧离子）的通透性,对中枢神经系统形态也无明显影响。     

反复下体负压致意识丧失对大鼠血脑屏障通透性的影响

为阐明多次发生＋Ｇｚ致意识丧失对脑的影响及其机制，观察了反复下体负压（ＬＢＮＰ）致意识丧失对大鼠血脑屏障（ＢＢＢ）通透性的影响。雄性ＳＤ大鼠，麻醉后置于－４．０ｋＰａ的下体负压舱内，至脑电波消失２ｍｉｎ后恢复常压。分别于一次和三次ＬＢＮＰ作用后１ｈ利用硝酸镧示踪法观察ＢＢＢ通透性的变化。一次ＬＢＮＰ致意识丧失组大鼠脑皮层组织变化不明显；三次ＬＢＮＰ致意识丧失组大鼠脑皮层组织中大部分毛细血管内皮细胞     

Is viscosity important in the production of blood-brain barrier disruption by intracarotid contrast media?

Summary A canine model was used to investigate the effects of intracarotid methylglucamine iothalamate (280 mgI/ml) at different viscosities on the normal blood-brain barrier. To alter viscosity, without changing physicochemical parameters, injections were made at either 23°C or 37°C. The degree of blood-brain barrier damage was assessed using Evans' Blue dye as a visual marker and by contrast enhancement measured by a computed tomographic (CT) scanner. It was found that methylglucamine iothalamate caused more blood-brain barrier damage at 23°C than at 37°C (p<0.1). Control studies at each temperature using intracarotid injections of physiological saline showed no temperature effect (p>0.1). The implications of these findings are discussed.     

Vascular volume and blood-brain barrier permeability measured by dynamic contrast enhanced MRI in hippocampus and cerebellum of patients with MCI and normal controls

PURPOSE: To measure the cerebrovascular volume and blood-brain barrier (BBB) permeability indices in hippocampus and cerebellum of patients with mild cognitive impairment (MCI) using dynamic contrast-enhanced MRI (DCE-MRI), and compare to that of normal controls. MATERIALS AND METHODS: A total of 11 MCI subjects and 11 healthy elderly controls participated in this prospective study. DCE-MRI was performed to measure the contrast enhancement kinetics. The early enhancement percentage (at 50 seconds after injection) was defined as the vascular volume index, and the ratio between the four to five-minute enhancement relative to the 50-second enhancement was defined as the BBB permeability index. RESULTS: The enhancement kinetics measured from hippocampus of MCI individuals demonstrated a lower magnitude and slower decay than healthy controls, suggesting that they had a smaller vascular volume (significant in the right side; P <0.001) and a higher BBB permeability (not reaching significance level). The vascular volume index was significantly correlated with naming ability (P 0.05). CONCLUSION: These results suggest that changes in cerebrovasculature may occur in hippocampus of MCI. DCE-MRI may provide a noninvasive means to measure the subtle BBB leakage associated with the cerebrovascular pathology commonly found in Alzheimer's disease.     

Pulse sequence and timing of contrast‐enhanced MRI for assessing blood–brain barrier disruption after transcranial focused ultrasound in the presence of hemorrhage

Purpose:

To optimize the timing of contrast‐enhanced magnetic resonance imaging (MRI) that best indicates blood–brain barrier (BBB) disruption induced by focused ultrasound (FUS) along with an ultrasound contrast agent (UCA) and to verify that the contrast‐enhanced spin‐echo MRI sequence can indicate the degree and location of BBB disruption in the presence of hemorrhage better than a gradient‐echo sequence.

Materials and Methods:

Sonication was applied to 12 rat brains with four different doses of UCA to cause variable degrees of hemorrhage. Two imaging sequences were performed to acquire T1‐weighted (T1W) images at two time‐points after the administration of a T1‐shortening contrast agent. The contrast enhancement at the sonicated regions was quantified and correlated against Evans blue (EB) staining.

Results:

The spin‐echo T1W images at 10 minutes post–contrast enhancement showed the best correlation with EB staining in both quantity of EB extravasation (r = 0.812; P < 0.01) and spatial distribution (r = 0.528, P < 0.01). This capability was more robust than the gradient‐echo sequence.

Conclusion:

Our results suggest that contrast‐enhanced T1W spin‐echo sequence acquired in the early phase post–contrast enhancement should be considered to monitor the degree and location of BBB disruption under the possibility of hemorrhage induced by FUS. J. Magn. Reson. Imaging 2010;31:1323–1330. © 2010 Wiley‐Liss, Inc.     

MRA of the lower extremities in patients with pulmonary embolism using a blood pool contrast agent: initial experience

PURPOSE: To evaluate the feasibility of blood pool contrast-enhanced magnetic resonance angiography (MRA) to visualize the arterial and venous vessel tree and to detect deep venous thrombosis (DVT) of the lower extremities. MATERIALS AND METHODS: Nine consecutive patients with pulmonary embolism (mean age = 46 +/- 9) were randomized to various doses of NC100150 (between 0.75 and 6 mg of Fe/kg of body weight). A T1-weighted (T1W) 3D gradient recalled echo (GRE) sequence (TE = 2.0 msec, TR = 5.0 msec) was used. Two observers blinded to the dose of contrast agent assessed image quality, contrast attenuation, and appearance of thrombi. RESULTS: Qualitative assessment of overall MRA image quality and semiquantitative vessel scoring revealed good to excellent delineation of venous and arterial vessel segments independent of the dose of NC100150. However, quantitative region of interest analysis revealed a significantly higher signal-to-noise ratio (SNR) in the high-dose group than in the mid- and low-dose groups of NC100150 (P < 0.01). Between dose groups, the SNR was independent of vessel type (artery or vein) and vessel segment localization (proximal or distal). All seven venous thrombi (mean length = 7.2 +/- 0.95 cm) were characterized by a very low signal intensity (SI), which was only 16.6 +/- 7% of the SI in adjacent venous segments (P < 0.0001). CONCLUSION: High-quality MR angiograms of the lower extremities can be obtained using low concentrations of NC100150 in combination with a strong T1W 3D GRE sequence. The obvious delineation of venous thrombi suggests that this technique may be potentially used as a noninvasive "one-stop shopping" tool in the evaluation of thromboembolic disease.     

Evaluation of the therapeutic efficacy of high-intensity focused ultrasound ablation of hepatocellular carcinoma by three-dimensional sonography with a perflubutane-based contrast agent

Objective

We performed contrast-enhanced three-dimensional sonography (CE 3D US) with a perflubutane-based contrast agent to immediately evaluate the completeness of ablation of small hepatocellular carcinoma (HCC) lesions by extracorporeal high-intensity focused ultrasound (HIFU).

Subjects and methods

Twenty-one HCC lesions were treated by a single ultrasound-guided HIFU ablation session, and CE 3D US was performed before, immediately after, and 1 week, and 1 month after HIFU, and contrast-enhanced CT (CE CT) or contrast-enhanced MRI (CE MRI) was performed before HIFU, 1 week and 1 month after HIFU, and during the follow-up period.

Results

Immediately and 1 month after HIFU, 17 lesions were evaluated as adequately ablated by CE 3D US, and the other 4 lesions as residual tumors. One month after HIFU, 18 were evaluated as adequately ablated by CE CT or CE MRI, and the other 3 as residual tumors. The evaluation by CE 3D US immediately after HIFU and by CE CT or CE MRI 1 month after HIFU was concordant with 20 lesions. The kappa value for agreement between the findings of CE 3D US and other modalities by two blinded observers was 0.83. When the 1-month CE CT or CE MRI findings were used as the reference standard, the sensitivity, specificity, and accuracy of CE 3D US immediately after HIFU for the diagnosis of the adequate ablation were 100%, 75%, and 95%, respectively.

Conclusion

CE 3D US appears to be a useful method for immediate evaluation of therapeutic efficacy of HIFU ablation of HCC lesions.     

Contrast‐enhanced in vivo magnetic resonance microscopy of the mouse brain enabled by noninvasive opening of the blood‐brain barrier with ultrasound

The use of contrast agents for neuroimaging is limited by the blood‐brain barrier (BBB), which restricts entry into the brain. To administer imaging agents to the brain of rats, intracarotid infusions of hypertonic mannitol have been used to open the BBB. However, this technically challenging approach is invasive, opens only a limited region of the BBB, and is difficult to extend to mice. In this work, the BBB was opened in mice, using unfocused ultrasound combined with an injection of microbubbles. This technique has several notable features: it (a) can be performed transcranially in mice; (b) takes only 3 min and uses only commercially available components; (c) opens the BBB throughout the brain; (d) causes no observed histologic damage or changes in behavior (with peak‐negative acoustic pressures of 0.36 MPa); and (e) allows recovery of the BBB within 4 h. Using this technique, Gadopentetate Dimeglumine (Gd‐DTPA) was administered to the mouse brain parenchyma, thereby shortening T₁ and enabling the acquisition of high‐resolution (52 × 52 × 100 micrometers³) images in 51 min in vivo. By enabling the administration of both existing anatomic contrast agents and the newer molecular/sensing contrast agents, this technique may be useful for the study of mouse models of neurologic function and pathology with MRI. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

碘对比剂在下肢深静脉CT成像中的应用和技术要点

目前,CT扫描技术已成为诊断下肢深静脉血栓的重要影像手段。由于下肢静脉独特的解剖学特点,获得高质量静脉CT血管影像尚有一定难度,目前临床应用的间接静脉法、直接静脉法及双向法等多种CT检查技术亦均有其各自的局限性。因此,如何安全、合理使用碘对比剂,以提高下肢深静脉管腔内对比剂浓度的同时减少伪影,并通过降低碘对比剂的用量防止对比剂急性肾损害的发生,一直是临床上关注的热点问题。现就不同CT检查方法的技术要点以及碘对比剂用量、注射流率、浓度及温度等参数的应用策略予以综述。