BR1: a new ultrasonographic contrast agent based on sulfur hexafluoride-filled microbubbles

Effects of noradrenaline and adenosine triphosphate on the degree on contrast enhancement in a rabbit model of atherosclerosis during contrast-enhanced ultrasonography

The aim of the study is to assess the effects of vasoactive agents on the degree of contrast enhancement in experimental atherosclerotic plaque during contrast-enhanced ultrasonography (CEUS). Abdominal aortic atherosclerosis was induced in 25 New Zealand white rabbits by a combination of cholesterol-rich diet and balloon endothelial denudation. Standard ultrasonography and CEUS were performed at baseline and during intravenous infusion of noradrenaline or adenosine triphosphate (ATP). The degree of contrast enhancement of the plaque after injection of contrast material was quantified by calculating the enhanced intensity in the plaque. The infusion of noradrenaline induced significant increase in systolic blood pressure (84 ± 13 mm Hg vs. 112 ± 20 mm Hg, p = 0.011) and significant decrease in the enhanced intensity in the plaque (7.52 ± 1.32 dB vs. 5.88 ± 1.33 dB, p < 0.001) during CEUS. The infusion of ATP resulted in the significant decrease in systolic blood pressure (80 ± 13 mm Hg vs. 65 ± 11 mm Hg, p = 0.005) and increase in the enhanced intensity in the plaque (7.52 ± 1.32 dB vs. 8.84 ± 1.55 dB, p < 0.001) during CEUS. The degree of contrast enhancement within an experimental atherosclerotic plaque during CEUS can be influenced by vasoactive agents and hemodynamic status.

Contrast-enhanced voiding urosonography with intravesical administration of a second-generation ultrasound contrast agent for diagnosis of vesicoureteral reflux: prospective evaluation of contrast safety in 1,010 children

BACKGROUND AND OBJECTIVE

To evaluate the safety of intravesical administration of a second-generation ultrasound (US) contrast agent for the diagnosis of vesicoureteral reflux in children.

MATERIALS AND METHODS

One thousand and ten children (563 girls, 447 boys; mean age: 2.9 years, range: 15 days-17.6 years) with 2,043 pelvi-ureter-units underwent contrast-enhanced voiding urosonography (ce-VUS) to rule out vesicoureteral reflux. A second-generation US contrast agent (SonoVue®, Bracco, Milan) was administered intravesically through transurethral bladder catheterization at a dose of 0.5 ml/bladder filling. Possible adverse events were monitored during the examination and followed up for 7 days after ce-VUS by phone calls. Urine analysis and culture were performed 3-5 days before ce-VUS in all children and 24-48 h in any patient who reported with adverse events.

RESULTS

No case of serious adverse event was recorded. Minor events were reported in 37 children (3.66% of the study population). These included dysuria (n = 26, 2.57%), urinary retention (n = 2, 0.2%), abdominal pain (n = 2, 0.2%), anxiety (n = 1, 0.1%) and crying (n = 1, 0.1%) during micturition, blood and mucous discharge (n = 1, 0.1%), increased frequency of micturition (n = 1, 0.1%), vomiting (n = 1, 0.1%), perineal irritation (n = 1, 0.1%), and an episode of urinary tract infection 10 days after ce-VUS (n = 1, 0.1%). Of these adverse events, 91.9% were subacute in onset and 8.1% were delayed. All events were self-limited and none required hospitalization.

CONCLUSION

There were no serious adverse events. Only a few minor events were reported, most likely due to the catheterization process. Thus, ce-VUS with intravesical administration of the second-generation US contrast agent (SonoVue®) for vesicoureteral reflux detection or exclusion had a favorable safety profile in our study group.

Serum influence on in-vitro gene delivery using microbubble-assisted ultrasound

BACKGROUND

Plasmid DNA (pDNA) is attractive molecule for gene therapy. pDNA-targeted delivery by efficient and safe methods is required to enhance its intra-tissue bioavailability. Among non-viral methods, sonoporation has become a promising method for in-vitro and in-vivo pDNA delivery. The efficiency of non-viral delivery methods of pDNA is generally limited by the presence of serum.

PURPOSE

The aim of this study was to evaluate the influence of serum on in-vitro pDNA delivery using microbubble-assisted ultrasound.

METHODS

The effects of a range of serum concentrations (0-50%) on efficiency of in-vitro pDNA delivery by sonoporation were determined on human glioblastoma cells. Furthermore, the influence of the serum on cell viability, membrane permeabilization, microbubble destruction, and pDNA topology were also assessed.

RESULTS

In-vitro results showed that a low serum concentration (i.e. ≤1%) induced a significant increase in transfection level through an increase in cell viability. However, a high serum concentration (i.e. ≥5%) resulted in a significant decrease in cell transfection, which was not associated with a decrease in membrane permeabilization or loss in cell viability. This decrease in transfection level was in fact positively correlated to changes in pDNA topology.

CONCLUSION

Serum influences the efficiency of in-vitro pDNA delivery by sonoporation through change in pDNA topology.

Microbubble-mediated ultrasound enhances the lethal effect of gentamicin on planktonic Escherichia coli

Previous research has found that low-intensity ultrasound enhanced the lethal effect of gentamicin on planktonic E. coli. We aimed to further investigate whether microbubble-mediated low-intensity ultrasound could further enhance the antimicrobial efficacy of gentamicin. The planktonic E. coli (ATCC 25922) was distributed to four different interventions: control (GCON), microbubble only (GMB), ultrasound only (GUS), and microbubble-mediated ultrasound (GMUS). Ultrasound was applied with 100 mW/cm(2) (average intensity) and 46.5 KHz, which presented no bactericidal activity. After 12 h, plate counting was used to estimate the number of bacteria, and bacterial micromorphology was observed with transmission electron microscope. The results showed that the viable counts of E. coli in GMUS were decreased by 1.01 to 1.42 log10 CFU/mL compared with GUS (P < 0.01). The minimal inhibitory concentration (MIC) of gentamicin against E. coli was 1 μ g/mL in the GMUS and GUS groups, lower than that in the GCON and GMB groups (2 μ g/mL). Transmission electron microscopy (TEM) images exhibited more destruction and higher thickness of bacterial cell membranes in the GMUS than those in other groups. The reason might be the increased permeability of cell membranes for gentamicin caused by acoustic cavitation.

Prospects for enhancement of targeted radionuclide therapy of cancer using ultrasound

Ultrasound-mediated drug delivery is a promising means of enhancing delivery, distribution and effectiveness of drugs within tumours. In this review, prospects for exploiting ultrasound to improve the tumour delivery and distribution of radiolabelled antibodies for radioimmunotherapy and to overcome barriers imposed by tumour microenvironment are discussed.

Increasing the sonoporation efficiency of targeted polydisperse microbubble populations using chirp excitation

The therapeutic use of microbubbles for targeted drug or gene delivery is a highly active area of research. Phospholipid- encapsulated microbubbles typically have a polydisperse size distribution over the 1 to 10 μm range and can be functionalized for molecular targeting and loaded with drugcarrying liposomes. Sonoporation through the generation of shear stress on the cell membrane by microbubble oscillations is one mechanism that results in pore formation in the cell membrane and can improve drug delivery. A microbubble oscillating at its resonant frequency would generate maximum shear stress on a membrane. However, because of the polydisperse nature of phospholipid microbubbles, a range of resonant frequencies would exist in a single population. In this study, the use of linear chirp excitations was compared with equivalent duration and acoustic pressure tone excitations when measuring the sonoporation efficiency of targeted microbubbles on human colorectal cancer cells. A 3 to 7 MHz chirp had the greatest sonoporation efficiency of 26.9 ± 5.6%, compared with 16.4 ± 1.1% for the 1.32 to 3.08 MHz chirp. The equivalent 2.2- and 5-MHz tone excitations have efficiencies of 12.8 ± 2.1% and 15.6 ± 1.1%, respectively, which were all above the efficiency of 4.1 ± 3.1% from the control exposure.

Double contrast-enhanced ultrasonography in preoperative Borrmann classification of advanced gastric carcinoma: comparison with histopathology

The purpose of this study was to investigate the accuracy of double contrast-enhanced ultrasonography (DCEUS) for assessing the Borrmann classification of advanced gastric carcinoma (AGC) preoperatively. Three hundred twenty nine patients with proved AGC were enrolled. DCEUS (intravenous microbubbles combined with combined with oral contrast-enhanced ultrasound) was performed preoperatively. The diagnostic accuracy of DCEUS in determining Borrmann classification was compared with postoperative pathological findings. The reliability of DCEUS was analyzed. The accuracy of DCEUS in determining the Borrmann classification of AGC was 91.49%. The intra- and inter-observer reproducibility was both almost perfect for assessing the Borrmann classification of AGC by DCEUS. DCEUS could be considered as an accurate, non-invasive, and reliable diagnostic method for preoperative Borrmann classification of advanced gastric carcinoma.

Enhancement patterns of gastric carcinoma on contrast-enhanced ultrasonography: relationship with clinicopathological features

The aim of this study was to assess the relationship between the enhancement patterns and clinicopathological features of gastric cancer using intravenous contrast-enhanced ultrasonography (CEUS). In this Ethics Committee-approved prospective study, five hundred fifty two patients with gastric cancer who gave informed consent were examined preoperatively with CEUS. The enhancement pattern of each tumor was analyzed visually. Gross and histopathological findings on the postoperative specimens were compared with the preoperative CEUS findings. The most common CEUS pattern in differentiated gastric cancer was homogeneous enhancement, whereas heterogeneous enhancement was the most common pattern in undifferentiated gastric cancer. The proportion of heterogeneous enhancement was significantly different between the two histological subtypes (Chi- square = 146.735, P<0.001). The sensitivity and specificity of early heterogeneous enhancement on CEUS in diagnosing undifferentiated gastric cancer were 78.84% and 72.59% respectively. Gastric cancers with heterogeneous enhancement were more often Borrmann III and IV macroscopic types than those with homogeneous enhancement (66.56% vs. 30.80%, P<0.001), more commonly T3 and T4 depth of invasion than those with homogeneous enhancement (71.52% vs. 59.60%, P<0.05), more often showed lymphatic invasion than those with homogeneous enhancement (84.44% vs. 76.40%, P<0.05), and were less likely to receive curative gastrectomy than those with homogeneous enhancement (74.83% vs. 86.40%, P<0.005). The intra- and inter-observer reproducibility were both almost perfect for assessing enhancement patterns, with Kappa values of 0.916 (P<0.001) for intra-observer and 0.842 (P<0.001) for inter-observer reproducibility. CEUS provided detailed information about tumor vascularity and contrast enhancement patterns in gastric cancer. CEUS is promising as a new and useful method to predict the histological type of gastric cancer.

Contrast-enhanced ultrasound in the characterization of hepatocellular carcinomas treated by ablation: comparison with contrast-enhanced magnetic resonance imaging

The purpose of this study was to evaluate the clinical utility of low-mechanical-index contrast-enhanced ultrasound (CEUS) in assessing the response to percutaneous microwave ablation in patients with hepatocellular carcinoma by comparing the results with those of contrast-enhanced magnetic resonance imaging (CEMRI). Between August 2005 and July 2011, 182 patients with 231 lesions treated by microwave ablation were included in the study. One month after microwave ablation, CEUS and CEMRI were performed to evaluate therapeutic responses. The difference in diagnostic accuracy between the two methods was analyzed to evaluate the value of contrast-enhanced ultrasound after microwave ablation. The final diagnosis was based on computed tomography and MRI typical findings of therapeutic response of hepatocellular carcinoma, proven serum tumor marker levels and additional follow-up. The sensitivity of CEUS and CEMRI in evaluating the therapeutic effect of hepatocellular carcinoma was 86.5% and 84.6%; the specificity, 98.3% and 98.9%; and the accuracy, 95.7% and 95.7%.There was no significant statistical disparity between CEUS and CEMRI (p > 0.05).The sensitivity, specificity and accuracy were 98.1, 97.2 and 97.8% when CEUS was used in combination with CEMRI to evaluate the therapeutic response of hepatocellular carcinoma to microwave ablation. CEUS examination was proven to be a tolerable and easy modality for assessment of the therapeutic effect of microwave ablation and can provide results comparable to those obtained with CEMRI. Combining the results of these two examinations may reduce false-positive and false-negative diagnoses.

Experimental investigation of the penetration of ultrasound nanobubbles in a gastric cancer xenograft

Nanobubbles as a type of ultrasound contrast agent have attracted much interest in recent years due to their many advantages, such as strong penetrating power and high stability. However, there is still insufficient morphological evidence concerning gas-filled nanobubbles in tumor tissue spaces and tumor angiogenesis. We used a gastric cancer xenograft as an example to study this question. Nanobubbles with a particle size of 435.2 ± 60.53 nm were prepared and compared with SonoVue® microbubbles in vitro and in vivo, and they exhibited a superior contrast imaging effect. After excluding the impact of the nanobubbles in blood vessels through saline flush, we used an ultrasound burst and frozen sectioning to investigate the distribution of nanobubbles in the gastric cancer xenografts and confirmed this by transmission electron microscopy. Preliminary results showed that the nanobubbles were able to pass through the gaps between the endothelial cells in the tumor vascular system to enter the tissue space. These findings could provide morphological evidence for extravascular ultrasound imaging of tumors and serve as a foundation for the application of nanobubbles in extravascular tumor-targeted ultrasonic diagnostics and therapy.

Ultrasound contrast materials in cardiovascular medicine: from perfusion assessment to molecular imaging

Ultrasound imaging is widely used in cardiovascular diagnostics. Contrast agents expand the range of tasks that ultrasound can perform. In the clinic in the USA, endocardial border delineation and left ventricle opacification have been an approved indication for more than a decade. However, myocardial perfusion contrast ultrasound studies are still at the clinical trials stage. Blood pool contrast and perfusion in other tissues might be an easier indication to achieve: general blood pool ultrasound contrast is in wider use in Europe, Canada, Japan, and China. Targeted (molecular) contrast microbubbles will be the next generation of ultrasound imaging probes, capable of specific delineation of the areas of disease by adherence to molecular targets. The shell of targeted microbubbles (currently in the preclinical research and early stage clinical trials) is decorated with the ligands (antibodies, peptides or mimetics, hormones, and carbohydrates) that ensure firm binding to the molecular markers of disease.

Evaluation of the vascular architecture of focal liver lesions using micro flow imaging

OBJECTIVES

To identify the vascular architecture of focal liver lesions using micro flow imaging and compare it with characteristics on contrast harmonic imaging during the arterial phase.

METHODS

Micro flow imaging and contrast harmonic imaging were performed in 118 patients with various focal liver lesions: hepatocellular carcinoma (n = 70), metastasis(n = 19), intrahepatic cholangiocarcinoma (n = 3), lymphoma (n = 1), hemangioma (n = 17), and focal nodular hyperplasia (n = 8). The vascular architecture of the lesions on micro flow imaging was evaluated by 2 investigators independently to reveal 6 patterns (types IVI). Enhancement characteristics on contrast harmonic imaging were also evaluated.

RESULTS

Inter-reader agreement for delineating the vascular architecture was higher on contrast harmonic imaging (κ= 0.856) than micro flow imaging (κ= 0.613). On micro flow imaging, the vascular patterns of hepatocellular carcinomas were types I (28.6%), II (65.7%), and III (5.7%). On contrast harmonic imaging, 44 of 70 (62.9%) hepatocellular carcinomas showed chaotic vessels, of which 40 were type II and 4 were type II. The vascular patterns of metastases were types IV (78.9%), I (10.5%), and II (10.5%). Typical rim enhancement was identified in 57.9% of metastases on contrast harmonic imaging, and all were type IV. The vascular patterns of focal nodular hyperplasia were types VI (87.5%) and I (12.5%). Typical spoked wheel arteries were identified on contrast harmonic imaging in 2 focal nodular hyperplasia cases. The vascular patterns of hemangiomas were types V (94.1%) and II (5.9%). Typical peripheral nodular enhancement was identified in 88.2% of hemangiomas on contrast harmonic imaging, and all were type V. The χ(2) test revealed that differences in vascular architecture between the lesions were significant on micro flow imaging (P < .001).

CONCLUSIONS

Micro flow imaging permitted detailed delineation of the vascular architecture of focal liver lesions. Hepatocellular carcinoma, metastasis, focal nodular hyperplasia, and hemangioma showed characteristic vascular architecture.

Effect of complex wavelet transform filter on thyroid tumor classification in three-dimensional ultrasound

Ultrasonography has great potential in differentiating malignant thyroid nodules from the benign ones. However, visual interpretation is limited by interobserver variability, and further, the speckle distribution poses a challenge during the classification process. This article thus presents an automated system for tumor classification in three-dimensional contrast-enhanced ultrasonography data sets. The system first processes the contrast-enhanced ultrasonography images using complex wavelet transform-based filter to mitigate the effect of speckle noise. The higher order spectra features are then extracted and used as input for training and testing a fuzzy classifier. In the off-line training system, higher order spectra features are extracted from a set of images known as the training images. These higher order spectra features along with the clinically assigned ground truth are used to train the classifier and obtain an estimate of the classifier or training parameters. The ground truth tells the class label of the image (i.e. whether the image belongs to a benign or malignant nodule). During the online testing phase, the estimated classifier parameters are applied on the higher order spectra features that are extracted from the testing images to predict their class labels. The predicted class labels are compared with their corresponding original ground truth to evaluate the performance of the classifier. Without utilizing the complex wavelet transform filter, the fuzzy classifier demonstrated an accuracy of 91.6%, while utilizing the complex wavelet transform filter, the accuracy significantly boosted to 99.1%.

The effect of lipid monolayer in-plane rigidity on in vivo microbubble circulation persistence

The goal of this study was to increase in vivo microbubble circulation persistence for applications in medical imaging and targeted drug delivery. Our approach was to investigate the effect of lipid monolayer in-plane rigidity to reduce the rate of microbubble dissolution, while holding constant the microbubble size, concentration and surface architecture. We first estimated the impact of acyl chain length of the main diacyl phosphatidylcholine (PC) lipid and inter-lipid distance on the cohesive surface energy and, based on these results, we hypothesized that microbubble stability and in vivo ultrasound contrast persistence would increase monotonically with increasing acyl chain length. We therefore measured microbubble in vitro stability to dilution with and without ultrasound exposure, as well as in vivo ultrasound contrast persistence. All measurements showed a sharp rise in stability between DPPC (C16:0) and DSPC (C18:0), which correlates to the wrinkling transition, signaling the onset of significant surface shear and gas permeation resistance, observed in prior single-bubble dissolution studies. Further evidence for the effect of the wrinkling transition came from an in vitro and in vivo stability comparison of microbubbles coated with pure DPPC with those of lung surfactant extract. Microbubble stability against dilution without ultrasound and in vivo ultrasound contrast persistence showed a monotonic increase with acyl chain length from DSPC to DBPC (C22:0). However, we also observed that stability dropped precipitously for all measurements on further increasing lipid acyl chain length from DBPC to DLiPC (C24:0). This result suggests that hydrophobic mismatch between the main PC lipid and the lipopolymer emulsifier, DSPE-PEG5000, may drive a less stable surface microstructure. Overall, these results support our general hypothesis of the role of in-plane rigidity for increasing the lifetime of microbubble circulation.

Contrast imaging and gene delivery through the combined use of novel cationic liposomal microbubbles and ultrasound in rat carotid arteries

INTRODUCTION

Lipid-coated cationic microbubbles represent a new class of agents with both diagnostic and therapeutic applications. The main goal of this study was to evaluate the efficiency of gene transfer through the combined use of microbubbles and ultrasound in rat carotid arteries. Furthermore, we assessed whether the cationic liposomal microbubbles could allow long-term enhanced imaging, comparing with SonoVue(®).

MATERIAL AND METHODS

Normal rat carotid arteries were imaged after intravenous bolus injections of 0.5 ml/kg of two contrast agents (SonoVue(®) and the cationic liposomal microbubbles). Forty Sprague-Dawley rats were divided into 5 groups according to ultrasound parameters and were treated with or without microbubbles. All rats were sacrificed after being transfected for 2 days. The level of protein expression was determined by western blot analysis.

RESULTS

The enhancing time of self-made microbubbles was much longer than that of SonoVue(®) in rat carotid arteries (p < 0.05). The results of the western blot analysis revealed that the expression of SR-BI DNA in the carotid artery was highest in the SR-BI + US/CLM group (p < 0.05).

CONCLUSIONS

These results suggest that the novel cationic liposomal microbubbles enhance image quality over a longer period than does SonoVue(®). Additionally, the combination of ultrasound and this new type of microbubble can act synergistically to increase SR-BI DNA transfection.

Contrast-enhanced ultrasound combined with three-dimensional reconstruction in preoperative perforator flap planning

BACKGROUND

Along with technical advancements in perforator flap surgery, great interest has been recently focused on the accuracy of preoperative perforator location through the assessment of the donor-site vascular network. The goal of the present study was to investigate the usefulness of contrast-enhanced ultrasound combined with three-dimensional reconstruction in the planning of perforator flaps.

METHODS

The authors retrospectively analyzed the preoperative imaging vascular anatomy provided by contrast-enhanced ultrasound combined with three-dimensional reconstruction in 32 patients undergoing perforator flap reconstruction between 2009 and 2011. The static and dynamic features of any suitable perforator including number of branches, source vessel, running course, blood flow pattern and velocity (peak systolic velocity and resistance index), and its anatomical relationship were assessed preoperatively by the novel navigation imaging. Based on this information, the preferred perforator and the ideal donor site were selected for the flap harvesting. The accuracy of preoperative imaging data was checked during surgery.

RESULT

Contrast-enhanced ultrasound provided a continuous blood flow signal and a clear and reliable image of perforators, and three-dimensional reconstruction displayed their spatial anatomical relationship and their roots. Consistent with the surgical findings, perforators were identified accurately in all 32 cases with high specificity (100 percent) and sensitivity.

CONCLUSIONS

Contrast-enhanced ultrasound with three-dimensional image reconstruction provides valuable preoperative perforator navigation. It detects precisely the perforator's location, its course, and the quality of its blood flow and allows the choice of the preferred perforator and the ideal donor site. Preoperative location of perforators using contrast-enhanced ultrasound with three-dimensional image reconstruction improves flap planning and eases flap harvesting.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, IV.

Ultrasound-mediated stimulation of microbubbles after acute myocardial infarction and reperfusion ameliorates left-ventricular remodelling in mice via improvement of borderzone vascularization

AIMS

Post-infarction remodelling (PIR) determines left-ventricular (LV) function and prognosis after myocardial infarction. The aim of this study was to evaluate transthoracic ultrasound-mediated microbubble stimulation (UMS) as a novel gene- and cell-free therapeutic option after acute myocardial infarction and reperfusion (AMI/R) in mice.

METHODS AND RESULTS

For myocardial delivery of UMS, a novel therapeutic ultrasound-system (TIPS, Philips Medical) and commercially available microbubbles (BR1, Bracco Suisse SA) were utilized in a closed-chest mouse model. UMS was performed as myocardial post-conditioning (PC) on day four after 30 minutes of coronary occlusion and reperfusion. LV-morphology, as well as global and regional function were measured repeatedly with reconstructive 3-dimensional echocardiography applying an additional low-dose dobutamine protocol after two weeks. Scar size was quantified by means of histomorphometry. A total of 41 mice were investigated; 17 received PC with UMS. Mean ejection fraction (EF) prior UMS was similar in both groups 53%±10 (w/o UMS) and 53%±14 (UMS, p = 0.5), reflecting comparable myocardial mass at risk 17%±8 (w/o UMS), 16%±13 (UMS, p = 0.5). Two weeks after AMI/R, mice undergoing UMS demonstrated significantly better global LV-function (EF = 53%±7) as compared to the group without PC (EF = 39%±11, p<0.01). The fraction of akinetic myocardial mass was significantly lower among mice undergoing UMS after AMI/R [27%±10 (w/o UMS), 13%±8 (UMS), p<0.001)]. Our experiments showed a fast onset of transient, UMS-induced upregulation of vascular-endothelial and insulin-like growth factor (VEGF-a, IGF-1), as well as caveolin-3 (Cav-3). The mice undergoing PC with UMS after AMI/R showed a significantly lower scar size. In addition, the microvascular density was significantly higher in the borderzone of UMS-treated animals.

CONCLUSION

UMS following AMI/R ameliorates PIR in mice via up-regulation of VEGF-a, IGF-1 and Cav-3, and consecutive improvement of myocardial borderzone vascularization.

Modeling and optimization of an acoustic diode based on micro-bubble nonlinearity

The first acoustic diode (AD), which is composed by integrating a super lattice (SL) with a nonlinear medium (NLM), has recently been proposed to make a one-way street for the acoustic energy flux. This device prohibits the acoustic waves from one direction, but allows the transmission of the second harmonic wave (generated from the NLM) from the other direction. To improve its performance, it is crucial to transfer more acoustic energy from the stop-band of the acoustic filter (i.e., the SL) to its pass-band with the help of the NLM. In this work, a finite difference time domain model is developed to study the dynamic behaviors of the AD, in which a micro-bubble suspension takes the role of the NLM. Based on this model, the method of optimizing the nonlinearity-based AD is investigated by examining its performance with respect to several parameters, such as the periodicity number of the SL, the bubble size distribution, the bubble shell parameters, and the bubble concentration. It is also suggested that, instead of the rectification ratio, it might be more reasonable to characterize the performance of the AD with the energy attenuation coefficients (or transmission loss) for both incident directions.

Microbubbles as a scattering contrast agent for grating-based x-ray dark-field imaging

In clinically established-absorption-based-biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.

Liver dysplasia: US molecular imaging with targeted contrast agent enables early assessment

PURPOSE

To investigate the ability of vascular endothelial growth factor receptor type 2 (VEGFR2)-targeted ultrasonographic (US) microbubbles for the assessment of liver dysplasia in transgenic mice.

MATERIALS AND METHODS

Animal experiments were approved by the governmental review committee. Nuclear factor-κB essential modulator knock-out mice with liver dysplasia and wild-type mice underwent liver imaging by using a clinical US system. Two types of contrast agents were investigated: nontargeted, commercially available, second-generation microbubbles (SonoVue) and clinically translatable PEGylated VEGFR2-targeted microbubbles (BR55). Microbubble kinetics was investigated over the course of 4 minutes. Targeted contrast material-enhanced US signal was quantified 5 minutes after injection. Competitive in vivo binding experiments with BR55 were performed in knock-out mice. Immunohistochemical and hematoxylin-eosin staining of liver sections was performed to validate the in vivo US results. Groups were compared by using the Mann-Whitney test.

RESULTS

Peak enhancement after injection of SonoVue and BR55 did not differ in healthy and dysplastic livers (SonoVue, P = .46; BR55, P = .43). Accordingly, immunohistochemical findings revealed comparable vessel densities in both groups. The specificity of BR55 to VEGFR2 was proved by in vivo competition (P = .0262). While the SonoVue signal decreased similarly in healthy and dysplastic livers during the 4 minutes, there was an accumulation of BR55 in dysplastic livers compared with healthy ones. Furthermore, targeted contrast-enhanced US signal indicated a significantly higher site-specific binding of BR55 in dysplastic than healthy livers (P = .005). Quantitative immunohistologic findings confirmed significantly higher VEGFR2 levels in dysplastic livers (P = .02).

CONCLUSION

BR55 enables the distinction of early stages of liver dysplasia from normal liver.

The destructive effects of high-intensity focused ultrasound on hydatid cysts enhanced by ultrasound contrast agent and superabsorbent polymer alone or in combination

Cystic echinococcosis, caused by the metacestode stage of Echincoccus granulosus, remains endemic in many regions around the world. The present work evaluated whether or not a superabsorbent polymer (SAP) and ultrasound contrast agent (UCA) alone or in combination could enhance damage efficacy of high-intensity focused ultrasound (HIFU) on hydatid cysts in vitro. HIFU of 100 W acoustic power, with the aid of 0.1 ml UCA and 0.1 g SAP alone or in combination, was used to ablate hydatid cysts in vitro. The comparison of ultrasound image for each layer of hydatid cyst before and after HIFU ablation was made immediately, and the protoscolices of the cysts were stained by eosin exclusion assay, and the structures of protoscolices were observed by light microscopy. To understand the destructive effects of HIFU, the pathological changes in cyst walls of hydatid cyst ablated with HIFU were examined. The results demonstrated that HIFU had some lethal effect on hydatid cysts: echo enhancement of ultrasound image, increase of mortality rate of protoscolices, serious structural damage of protoscolices, and complete destruction or even disappearance of laminated layer and germinal layer was observed in the group of HIFU combined with UCA and SAP alone or in combination. It was found that the destructive effect of HIFU aided with a combination of UCA and SAP to hydatid cysts was more effective than that of HIFU just aided with UCA or SAP alone. These results suggested that UCA and SAP might be used as a HIFU enhancing agent to improve the efficacy of HIFU ablation to hydatid cysts, which could be a possible therapeutic option for cystic echinococcosis.

Contrast-enhanced ultrasound (CEUS) follow-up after radiofrequency ablation or cryoablation of focal liver lesions: treated-area patterns and their changes over time

OBJECTIVES

To describe the early patterns of liver lesions successfully treated with radiofrequency ablation (RFA) or cryoablation (CA) and their changes over time.

METHODS

Twenty-two RFA-treated and 17 CA-treated patients underwent CEUS from week 1 to year 3 post-ablation. Patterns, margins and volumes of RF-induced and cryolesions were evaluated and compared over time.

RESULTS

After contrast enhancement, shortly after ablation, undefined margins with persistent enhancing small vessels penetrating >2 mm into the treated zone were significantly more frequent after CA (67 %) than RFA (22 %) (P < 0.02). During the arterial phase, a thin, enhancing marginal rim was seen during week 1 (T1) in around 28 % of RF lesions, while 75 % of cryolesions had thick enhancing rims (P < 0.02). The mean RF-induced lesion volume, maximum at T1 (44.1 ± 37.5 ml), shrank slowly over time, remaining clearly visible at 1 year (8.3 ± 7.4 ml). Cryolesions shrank faster (P = 0.009), from an average of 16.6 ± 7.1 ml at T1 to 1.7 ± 1.3 ml 1-year post-ablation.

CONCLUSION

RF-induced and cryolesions differ, particularly their margins and shrinkage rates. Knowing these differences allows avoidance of incomplete treatment or falsely diagnosed recurrence, especially after CA.

KEY POINTS

• Contrast-enhanced ultrasound (CEUS) provides new follow-up information following hepatic radiological inyervention. • CEUS provides good visualisation of vascular modifications after thermoablation. • RFA-induced lesions and cryoablated lesions differ. • Knowledge about RF and cryolesion patterns is essential for correct CEUS follow-up. • Cryolesions have thicker peripheral inflammatory reactions and shrink faster than RFA-induced lesions.

Non-invasive automated 3D thyroid lesion classification in ultrasound: a class of ThyroScan™ systems

Ultrasound-based thyroid nodule characterization into benign and malignant types is limited by subjective interpretations. This paper presents a Computer Aided Diagnostic (CAD) technique that would present more objective and accurate classification and further would offer the physician a valuable second opinion. In this paradigm, we first extracted the features that quantify the local changes in the texture characteristics of the ultrasound off-line training images from both benign and malignant nodules. These features include: Fractal Dimension (FD), Local Binary Pattern (LBP), Fourier Spectrum Descriptor (FS), and Laws Texture Energy (LTE). The resulting feature vectors were used to build seven different classifiers: Support Vector Machine (SVM), Decision Tree (DT), Sugeno Fuzzy, Gaussian Mixture Model (GMM), K-Nearest Neighbor (KNN), Radial Basis Probabilistic Neural Network (RBPNN), and Naive Bayes Classifier (NBC). Subsequently, the feature vector-classifier combination that results in the maximum classification accuracy was used to predict the class of a new on-line test thyroid ultrasound image. Two data sets with 3D Contrast-Enhanced Ultrasound (CEUS) and 3D High Resolution Ultrasound (HRUS) images of 20 nodules (10 benign and 10 malignant) were used. Fine needle aspiration biopsy and histology results were used to confirm malignancy. Our results show that a combination of texture features coupled with SVM or Fuzzy classifiers resulted in 100% accuracy for the HRUS dataset, while GMM classifier resulted in 98.1% accuracy for the CEUS dataset. Finally, for each dataset, we have proposed a novel integrated index called Thyroid Malignancy Index (TMI) using the combination of FD, LBP, LTE texture features, to diagnose benign or malignant nodules. This index can help clinicians to make a more objective differentiation of benign/malignant thyroid lesions. We have compared and benchmarked the system with existing methods.

The effect of contrast medium SonoVue® on the electric charge density of blood cells

The effect of contrast medium SonoVue® on the electric charge density of blood cells (erythrocytes and thrombocytes) was measured using a microelectrophoretic method. We examined the effect of adsorbed H⁺ and OH⁻ ions on the surface charge of erythrocytes or thrombocytes. Surface charge density values were determined from electrophoretic mobility measurements of blood cells performed at various pH levels. The interaction between solution ions and the erythrocyte's or thrombocyte's surface was described by a four-component equilibrium model. The agreement between the experimental and theoretical charge variation curves of the erythrocytes and thrombocytes was good at pH 2-9. The deviation observed at a higher pH may be caused by disregarding interactions between the functional groups of blood cells.

The phagocytosis of gas-filled microbubbles by human and murine antigen-presenting cells

This study was designed to evaluate the potential of gas-filled microbubbles (MB) to be internalized by antigen-presenting cells (APC). Fluorescently labeled MB were prepared, thus permitting to track binding to, and internalization in, APC. Both human and mouse cells, including monocytes and dendritic cells (DC), prove capable to phagocyte MB in vitro. Observation by confocal laser scanning microscopy showed that interaction between MB and target cells resulted in a rapid internalization in cellular compartments and to a lesser extent in the cytoplasm. Capture of MB by APC resulted in phagolysosomal targeting as verified by double staining with anti-lysosome-associated membrane protein-1 monoclonal antibody and decrease of internalization by phagocytosis inhibitors. Fluorescent MB injected subcutaneously (s.c.) in mice were found to be associated with CD11c(+)DC in lymph nodes draining the injection sites 24 h after administration. Altogether, our study demonstrates that MB can successfully target APC both in vitro and in vivo, and thus may serve as a potent Ag delivery system without requirement for ultrasound-based sonoporation. This adds to the potential of applications of MB already extensively used for diagnostic imaging in humans.

Enhancement of vancomycin activity against biofilms by using ultrasound-targeted microbubble destruction

Treating biofilm infections on implanted medical devices is formidable, even with extensive antibiotic therapy. The aim of this study was to investigate whether ultrasound (US)-targeted microbubble (MB) destruction (UTMD) could enhance vancomycin activity against Staphylococcus epidermidis RP62A biofilms. Twelve-hour biofilms were treated with vancomycin combined with UTMD. The vancomycin and MB (SonoVue) were used at concentrations of 100 μg/ml and 30% (vol/vol), respectively, in studies in vitro. After US exposure (0.08 MHz, 1.0 W/cm(2), 50% duty cycle, and 10-min duration), the biofilms were cultured at 37 °C for another 12 h. The results showed that many micropores were found in biofilms treated with vancomycin combined with UTMD. Biofilm densities (A(570) values) and the viable counts of S. epidermidis recovered from the biofilm were significantly decreased compared with those of any other groups. Furthermore, the highest percentage of dead cells was found, using confocal laser scanning microscopy, in the biofilm treated with vancomycin combined with UTMD. The viable counts of bacteria in biofilms in an in vivo rabbit model also confirmed the enhanced effect of vancomycin combined with UTMD. UTMD may have great potential for improving antibiotic activity against biofilm infections.

Diagnostic value of contrast-enhanced ultrasound, computed tomography and magnetic resonance imaging for focal liver lesions: a meta-analysis

The diagnostic performance of contrast-enhanced ultrasound (CEUS), contrast-enhanced computed tomography (CECT) and contrast-enhanced magnetic resonance imaging (CEMRI) was determined in patients with focal liver lesions (FLLs) in a meta-analysis. Meta-Disc version 1.4 was used to describe and calculate sensitivity, specificity, summary receiver operating characteristic (SROC) curves and area under the curve (AUC). In the 25 included studies, the pooled estimate of CEUS studies for sensitivity, specificity and diagnostic odds ratio (DOR) was 87% (95% CI 85-88), 89% (95% CI 87-91) and 78.84 (95% CI 29.40-211.40), respectively. Sensitivity, specificity and DOR were 86% (95% CI 84-88), 82% (95% CI 77-86) and 26.34 (95% CI 8.32-83.39), respectively, for the CECT studies. Sensitivity, specificity and DOR were 85% (95% CI 82-88), 87% (95% CI 83-91) and 48.37 (95% CI 15.87-147.45), respectively, for the CEMRI studies. SROC analysis indicated that the diagnostic value of CEUS for FLLs is not significantly different from that of CECT and CEMRI.

Predicting lymph node status in patients with early gastric carcinoma using double contrast-enhanced ultrasonography

INTRODUCTION

Double contrast-enhanced ultrasonography (DCUS) is a new method we used in predicting lymph node metastasis (LNM) in patients with early gastric cancer.

MATERIAL AND METHODS

Seventy-six patients with early gastric cancer diagnosed by gastroscope and confirmed by pathology after operation were examined using DCUS preoperatively. Group N1 included 15 patients with LNM and group N0 61 patients without LNM.

RESULTS

In group N1, 13 patients (87%) had marked hyperenhancement during early arterial phase using DCUS, and 2 patients (13%) were unmarked as hyperenhancement. In group N0, 24 patients (39%) had marked hyperenhancement during early arterial phase using DCUS, and 37 patients (61%) had unmarked hyperenhancement. The sensitivity and specificity of marked hyperenhancement in predicting LNM in patients with early gastric cancer was 86.7% and 60.7% respectively, and the Youden's index was 0.474. The κ value of this method was 0.89.

CONCLUSIONS

Double contrast-enhanced ultrasonography is a new valuable method to evaluate LNM at an early stage of gastric cancer and prognosis of early gastric cancer preoperatively.

Evaluation of hepatocellular carcinoma by contrast-enhanced sonography: correlation with pathologic differentiation

OBJECTIVES

The purpose of this study was to determine whether contrast-enhanced sonography can be used to differentiate histopathologic grades of hepatocellular carcinoma.

METHODS

This study included 54 patients with hepatocellular carcinomas. All patients underwent fundamental and contrast-enhanced sonographic examinations. Auto-tracking contrast quantification software was used to determine the contrast arrival time, time to peak, peak intensity, contrast-enhanced time, wash-out time, enhancement slope, and clearance slope of the lesions. All lesions were confirmed by surgery. The hepatocellular carcinoma lesions were divided into 2 groups according to the World Health Organization grading system: group 1 (well-differentiated hepatocellular carcinomas) and group 2 (moderately to poorly differentiated carcinomas). The enhancement parameters between the groups were compared using a Student t test.

RESULTS

Fourteen of 20 well-differentiated lesions showed a "fast-in, slow-out" enhancement pattern, whereas 6 showed a "fast-in, fast-out" pattern. Thirty-three of 34 moderately to poorly differentiated lesions showed a fast-in, fast-out pattern, whereas only 1 showed a fast-in, slow-out pattern. The differences in the time to peak, contrast-enhanced time, wash-out time, enhancement slope, and clearance slope between the groups were statistically significant (P < .05), whereas the differences in the arrival time and peak intensity were not significant (P > .05).

CONCLUSIONS

The contrast patterns of well-differentiated and moderately to poorly differentiated hepatocellular carcinomas were quite different on contrast-enhanced sonography. The time to peak, contrast-enhanced time, and wash-out time of the well-differentiated hepatocellular carcinomas were longer than those of the moderately to poorly differentiated carcinomas, whereas the enhancement slope and clearance slope of the well-differentiated lesions were lower those that of the moderately to poorly differentiated lesions.

Polymeric microbubbles for ultrasonic molecular imaging and targeted therapeutics

Gas-filled microbubbles ultrasound agent have received wide attention, not only because they can improve ultrasound signals, but also they can be used as drug/gene carriers. Among all types of microbubbles fabricated by different membrane materials and core gases, polymer-shell microbubbles are highly promising. Polymeric microbubbles are more stable than other soft shell microbubbles in vivo. Under destructive ultrasound, polymer-stabilized microbubbles disintegrate and emit a strong non-linear signal, which enables ultrasound imaging with superior sensitivity. Except for ultrasound imaging, polymeric microbubbles could also be applied as drug/gene-delivery system. The thick polymeric shells allow loading a large amount of drugs. Meanwhile, site-specific targeting and controlled drug release in the area of interest can be realized through chemical and physical modification. In this review, we highlight some of the recent examples on polymeric microbubbles and their applications in ultrasound molecular imaging and drug delivery.

Development and characterization of new nanoscaled ultrasound active lipid dispersions as contrast agents

Ultrasound contrast agents are widely used in clinical diagnosis. In recent years, the use of ultrasound contrast agents as therapeutic agents has gained a lot of attention. Of special interest are ultrasound-enhanced gene delivery in various tissues (e.g. cardiac, vascular, skeletal muscle and tumor tissue), ultrasound-enhanced protein delivery (e.g. insulin delivery) and ultrasound-enhanced delivery of small chemicals (e.g. doxorubicin, vancomycin). Commercially available ultrasound contrast agents such as SonoVue® or Optison® are ranged in a size of 2-8 μm. These micronscaled agents show a good ultrasound contrast enhancement and thus they are used for diagnostic imaging. But they are not suitable for targeted drug delivery to tumor tissues or blood clots because for these applications particles smaller than 700 nm are needed. In the present study, we developed new nanoscaled ultrasound contrast agents with a size between 70 and 300 nm. The lipid formulations show excellent contrast intensities using diagnostic ultrasound of about 1.4 MHz. The negatively charged colloidal dispersions are long-time stable under physiological conditions without loss of ultrasound reflectivity. The adjustable supramolecular organization of the carriers depends on the composition and varies from micellar to liposomal structures. The small size and the circulation stability of these systems make them promising for novel diagnostics and controlled drug release applications.

Clinical value of contrast-enhanced ultrasound in differentiating benign and malignant focal liver lesions

To explore the clinical value of contrast-enhanced ultrasound (CEUS) in differentiating benign and malignant focal liver lesions (FLLs) with SonoVue, CEUS was used to examine 113 patients with focal liver lesions (FLLs) in our hospital during July 2005 to December 2006. All the patients underwent contrast-enhanced CT (CECT) or contrast-enhanced MRI (CEMRI). Except for patients with focal fatty sparings (n=18) and with hemangiomas (n=8), all the patients were confirmed by operation or ultrasonic-guided liver puncture biopsy. A sulfur hexafluoride gas-based contrast agent was used with a MI of 0.15 to 0.17. Forty-eight cases of malignant FLLs, including 30 hepatocellular carcinomas (HCCs), 2 cholangiocarcinomas and 16 metastatic tumors, were detected. Seventy-eight cases of benign FLLs, including 33 hemangiomas, 9 focal nodular hyperplasias (FNHs), 19 focal fatty sparings, 5 abscesses, 7 regenerative nodules and 2 inflammatory pseudo-tumor, were involved. The contrast pattern of benign and malignant FLLs was quite different. CEUS has higher specificity and sensitivity than conventional ultrasound in differentiating benign and malignant FLLs.

Chemotherapy with PLGA microspheres containing docetaxel decreases angiogenesis in human hepatoma xenograft

To investigate the antiangiogenic effect of sustained-release poly (lactic-co-glycolic acid) microspheres containing docetaxel (PMCD) in human hepatoma xenograft. PMCD were prepared by solvent evaporation method with an encapsulation efficiency of 98.7% and a release period of about 3 weeks in vitro. PMCD were intratumorally injected once for mice bearing a human hepatocellular carcinoma. On day 21 post-treatment, the inhibition rate of tumor growth was 72.7% in the high-dose group, indicating a significant antitumor activity. Meanwhile, excellent antiangiogenic effect was observed based on the contrast-enhanced ultrasonography as well as microvessel density determination. Additionally, the real-time fluorescence quantitative PCR revealed that the expressions of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and angiopoietin-2 (Ang2) genes were down-regulated significantly. Interstitial chemotherapy using PMCD was highly effective and safe for the treatment of the human hepatoma xenograft and that decreasing angiogenesis could be one of the most important mechanisms involved in the antitumor activity.

Synergistic effects of sonoporation and taurolidin/TRAIL on apoptosis in human fibrosarcoma

Sonodynamic therapy, in combination with ultrasound contrast agents, proved to enhance the uptake of chemotherapeutics in malignant cells. HT1080 fibrosarcoma cells were treated in vitro with a combination of ultrasound SonoVue™-microbubbles and taurolidine (TRD) plus tumor necrosis factor related apoptosis inducing ligand (TRAIL). Apoptosis was measured by TdT-mediated dUTP-biotin nick end labelling (TUNEL) assay and fluorescence activated cell sorting (FACS) analysis. Gene expression was analysed by RNA-microarray. The apoptotic effects of TRD and TRAIL on human fibrosarcoma are enhanced by sonodynamic therapy and additional application of contrast agents, such as SonoVue™ by 25%. A broad change in the expression of genes related to apoptotic pathways is observed when ultrasound and microbubbles act synchronously in combination with the chemotherapeutics (e.g. BIRC3, NFKBIA and TNFAIP3). Some of these genes have already been proven to play a role in programmed cell death in human fibrosarcoma (HSPA1A/HSPA1B, APAF1, PAWR, SOCS2) or were associated with sonication induced apoptosis (CD44). Further studies are needed to explore the options of sonodynamic therapy on soft tissue sarcoma and its molecular mechanisms.

Formulation and characterization of echogenic lipid-Pluronic nanobubbles

The advent of microbubble contrast agents has enhanced the capabilities of ultrasound as a medical imaging modality and stimulated innovative strategies for ultrasound-mediated drug and gene delivery. While the utilization of microbubbles as carrier vehicles has shown encouraging results in cancer therapy, their applicability has been limited by a large size which typically confines them to the vasculature. To enhance their multifunctional contrast and delivery capacity, it is critical to reduce bubble size to the nanometer range without reducing echogenicity. In this work, we present a novel strategy for formulation of nanosized, echogenic lipid bubbles by incorporating the surfactant Pluronic, a triblock copolymer of ethylene oxide copropylene oxide coethylene oxide into the formulation. Five Pluronics (L31, L61, L81, L64 and P85) with a range of molecular weights (M(w): 1100 to 4600 Da) were incorporated into the lipid shell either before or after lipid film hydration and before addition of perfluorocarbon gas. Results demonstrate that Pluronic-lipid interactions lead to a significantly reduced bubble size. Among the tested formulations, bubbles made with Pluronic L61 were the smallest with a mean hydrodynamic diameter of 207.9 +/- 74.7 nm compared to the 880.9 +/- 127.6 nm control bubbles. Pluronic L81 also significantly reduced bubble size to 406.8 +/- 21.0 nm. We conclude that Pluronic is effective in lipid bubble size control, and Pluronic M(w), hydrophilic-lipophilic balance (HLB), and Pluronic/lipid ratio are critical determinants of the bubble size. Most importantly, our results have shown that although the bubbles are nanosized, their stability and in vitro and in vivo echogenicity are not compromised. The resulting nanobubbles may be better suited for contrast enhanced tumor imaging and subsequent therapeutic delivery.

Testicular contrast harmonic imaging to evaluate intratesticular perfusion alterations in patients with varicocele

PURPOSE

To determine whether changes in intratesticular microcirculation perfusion affect spermatogenesis in patients with left varicocele we performed testicular contrast harmonic imaging.

MATERIALS AND METHODS

A total of 90 patients with left varicocele (oligospermia in 50 and normozoospermia in 40) and 36 controls without varicocele (oligospermia in 16 and normozoospermia in 20) were enrolled in the study. Before contrast harmonic imaging all participants were evaluated by clinical examination, hormonal analysis, semen sample and scrotal ultrasound. We calculated contrast material arrival time in the arteriolar circulation (wash-in), time to peak in arterial circulation, arrival time in the venular circulation (washout) and mean transit time in each testis on contrast harmonic imaging.

RESULTS

We found no difference in the distribution rate of varicocele grade in patients with vs without oligospermia. All contrast harmonic imaging parameters were significantly higher in patients with varicocele plus normozoospermia or oligospermia and controls. We found no significant differences in contrast harmonic imaging parameters in patients with lower varicocele grading with respect to the higher grades. In patients with varicocele we found a negative linear correlation between total sperm count and left mean transit time (r = -0.29). In a multivariate model left mean transit time was the only independent predicting parameter of oligospermia (p <0.05). Mean transit time greater than 36 seconds predicted oligospermia in patients with left varicocele with 78% sensitivity and 58% specificity.

CONCLUSIONS

To our knowledge we report for the first time that testicular contrast harmonic imaging may be a new diagnostic tool able to improve our knowledge about the influence of varicocele on intratesticular microcirculation.

Effect of observer experience in the differentiation between benign and malignant liver tumors after ultrasound contrast agent injection

OBJECTIVE

The purpose of this study was to assess the impact of the observer level of experience on the diagnostic performance of contrast-enhanced ultrasound imaging (CEUS) for differentiation between benign and malignant liver tumors.

METHODS

From a computerized search, we retrospectively identified 286 biopsy-proven liver tumors (105 hepatocellular carcinomas, 48 metastases, 7 intra-hepatic cholangiocarcinomas, 33 liver hemangiomas, and 93 nonhemangiomatous benign lesions) in 235 patients (140 male and 95 female; mean age +/- SD, 56 +/- 11 years) who underwent CEUS after sulfur hexafluoride-filled microbubble injection. The digital cine clips recorded during the arterial (10-35 seconds from injection), portal (50-120 seconds), and late (130-300 seconds) phases were analyzed by 6 independent observers without experience (group 1, observers 1-3) or with 2 to 10 years of experience in CEUS (group 2, observers 4-6). Specific training in the diagnostic and interpretative criteria was provided to the inexperienced observers. Each observer used a 5-point scale to grade diagnostic confidence: 1, definitely benign; 2, probably benign; 3, indeterminate; 4, probably malignant; or 5, definitely malignant on the basis of the enhancement pattern during the arterial phase and enhancement degree during the portal and late phases compared with the liver (hypoenhancement indicating malignant and isoenhancement to hyperenhancement indicating benign).

RESULTS

The analysis of observer diagnostic confidence revealed higher intragroup (kappa = 0.63-0.83) than intergroup (kappa = 0.47-0.63) observer agreement. The experienced observers showed higher diagnostic performance in malignancy diagnosis than did inexperienced observers (overall accuracy: group 1, 63.3%-72.8%; group 2, 75.9%-93.1%; P < .05, chi(2) test).

CONCLUSIONS

The diagnostic performance of CEUS in liver tumor characterization was dependant on the observer's level of experience.

Contrast-enhanced ultrasound with SonoVue: differentiation between benign and malignant focal liver lesions in 317 patients

PURPOSE

The aim of the study was to investigate the ability of contrast-enhanced sonography (CEUS) with the contrast agent SonoVue to differentiate between benign and malignant focal liver lesions.

METHODS

In a prospective study, we examined 317 patients (204 males, 113 females, aged 59 +/- 12 years) with focal liver lesions detected by B-mode gray-scale sonography. After intravenous injection of 1.2 mL SonoVue, the liver was examined continuously for 3 minutes using low-MI sonography with contrast-specific software. Final diagnosis was established by histopathology, CT, MRI, or HIDA-scintigraphy.

RESULTS

Two hundred nine patients had malignant focal lesions, including 107 hepatocellular carcinomas, 70 metastases, 26 cholangiocellular carcinomas, and 6 other types of malignancy. One hundred eight patients had benign focal lesions, including 30 regenerative nodules, 30 hemangiomas, 13 cases of focal nodular hyperplasia, 12 abscesses, 8 cases of necrosis, 7 cases of focal steatosis areas, and 8 other benign lesions. Hypoenhancement or no enhancement in the late phase was found in 91% of the malignant lesions but in only 37% of the benign lesions (p < 0.001, sensitivity = 64%, specificity = 93%). Hyperenhancement in the late phase was found in 20% of the benign lesions but in none of the malignant lesions (p < 0.001, sensitivity = 21%, specificity = 100%). Hyperenhancement in the early phase with diffuse complete enhancement was found in 30% of the patients with malignant lesions but in only 2% of the patients with benign lesions (p < 0.001, sensitivity = 30%, specificity = 98%). CEUS had a sensitivity of 90%, a specificity of 99%, and an accuracy of 89% in the diagnosis of malignant liver lesions.

CONCLUSION

CEUS is helpful in the differentiation between benign and malignant focal liver lesions.

Detection Of Focal Liver Lesions In Cirrhotic Liver Using Contrast-Enhanced Ultrasound

Patients with liver cirrhosis are at increased risk of hepatocellular carcinoma (HCC). Conventional or baseline ultrasound (BUS) is often used as the first-line tool for HCC surveillance or detection, but the accuracy of BUS in HCC detection or differentiation from other focal liver lesions (FLLs) is limited. Contrast-enhanced ultrasound (CEUS) represents a recent revolution in the field of ultrasonography and it has become increasingly important in the detection and evaluation of FLLs. In CEUS, HCC typically exhibits arterial hyper-enhancement and portal-venous washout represented by hypo-enhanced lesions in the portal venous and late phases. The detection rate of HCC was significantly higher with CEUS compared with BUS. Even regenerative or some dysplastic nodules may exhibit arterial hyper-enhancement as they are differentiated from HCC by its iso-enhancing pattern in portal and late phases. The contrast-enhancement patterns of other different types of benign and malignant FLLs, as well as their detection rates with CEUS, were also discussed.

Adverse reactions after the use of sulphur hexafluoride (SonoVue) echo contrast agent

The aim of the present study was to analyse the adverse effects of SonoVue echo contrast in a consecutive series of 352 cardiac patients during a 4-year period. During 352 consecutive cardiac SonoVue studies, seven patients (2.0%) experienced adverse effects. Four patients (1.1%) had mild allergic reactions causing skin erythema and mild sinus tachycardia, and three patients (0.9%) experienced a severe allergic reaction resulting in (nonfatal) shock. The reported incidence of adverse effects of SonoVue echo contrast in this consecutive series of cardiac patients seems markedly higher than those reported in a company postmarketing analysis.

Growth and dissolution of an encapsulated contrast microbubble: effects of encapsulation permeability

Gas diffusion from an encapsulated microbubble is modeled using an explicit linear relation for gas permeation through the encapsulation. Both the cases of single gas (air) and multiple gases (perfluorocarbon inside the bubble and air dissolved in surrounding liquid) are considered. An analytical expression for the dissolution time for an encapsulated air bubble is obtained; it showed that for small permeability the dissolution time increases linearly with decreasing permeability. A perfluorocarbon-filled contrast microbubble such as Definity was predicted to experience a transient growth because of air infusion before it dissolves in conformity with previous experimental findings. The growth phase occurs only for bubbles with a critical value of initial mole fraction of perfluorocarbon relative to air. With empirically obtained property values, the dissolution time of a 2.5-micron diameter (same as that of Definity), lipid-coated octafluoropropane bubble, with surface tension 25 mN/m, is predicted to be 42 min in an air-saturated medium. The properties such as shell permeability, surface tension and relative mole fraction of octafluoropropane are varied to investigate their effects on the time scales of bubble growth and dissolution, including their asymptotic scalings where appropriate. The dissolution dynamics scales with permeability, in that when the time is nondimensioanlized with permeability, curves for different permeabilities collapse on a single curve. Investigation of bubbles filled with other gases (nonoctafluoropropane perfluorocarbon and sulfur hexafluoride) indicates longer dissolution time because of lower solubility and lower diffusivity for larger gas molecules. For such micron-size encapsulated bubbles, lifetime of hours is possible only at extremely low surface tension (<1 mN/m) or at extreme oversaturation.