Hepatic clearance of Sonazoid perfluorobutane microbubbles by Kupffer cells does not reduce the ability of liver to phagocytose or degrade albumin microspheres

Quantitative Pharmacokinetics Reveal Impact of Lipid Composition on Microbubble and Nanoprogeny Shell Fate

Microbubble-enabled focused ultrasound (MB-FUS) has revolutionized nano and molecular drug delivery capabilities. Yet, the absence of longitudinal, systematic, quantitative studies of microbubble shell pharmacokinetics hinders progress within the MB-FUS field. Microbubble radiolabeling challenges contribute to this void. This barrier is overcome by developing a one-pot, purification-free copper chelation protocol able to stably radiolabel diverse porphyrin-lipid-containing Definity® analogues (pDefs) with >95% efficiency while maintaining microbubble physicochemical properties. Five tri-modal (ultrasound-, positron emission tomography (PET)-, and fluorescent-active) [64 Cu]Cu-pDefs are created with varying lipid acyl chain length and charge, representing the most prevalently studied microbubble compositions. In vitro, C16 chain length microbubbles yield 2-3x smaller nanoprogeny than C18 microbubbles post FUS. In vivo, [64 Cu]Cu-pDefs are tracked in healthy and 4T1 tumor-bearing mice ± FUS over 48 h qualitatively through fluorescence imaging (to characterize particle disruption) and quantitatively through PET and γ-counting. These studies reveal the impact of microbubble composition and FUS on microbubble dissolution rates, shell circulation, off-target tissue retention (predominantly the liver and spleen), and FUS enhancement of tumor delivery. These findings yield pharmacokinetic microbubble structure-activity relationships that disrupt conventional knowledge, the implications of which on MB-FUS platform design, safety, and nanomedicine delivery are discussed.

Lysozyme microspheres incorporated with anisotropic gold nanorods for ultrasound activated drug delivery

We report on the fabrication of lysozyme microspheres (LyMs) incorporated with gold nanorods (NRs) as a distinctive approach for the encapsulation and release of an anticancer drug, 5-Fluorouracil (5-FU). LyMs with an average size of 4.0 ± 1.0 µm were prepared by a sonochemical method and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). The LyMs were examined using hydrophobic (nile red) as well as hydrophilic (trypan blue) dyes under confocal laser scanning microscopy (CLSM) to obtain information about the preferential distribution of fluorescent molecules. Notably, the fluorescent molecules were accumulated in the inner lining of LyMs as the core was occupied with air. The encapsulation efficiency of 5-FU for LyMs-NR was found to be ∼64%. The drug release from control LyMs as well as LyMs incorporated with NRs was investigated under the influence of ultrasound (US) at 200 kHz. The total release for control LyMs and LyMs incorporated with gold NRs was found to be ∼70 and 95% after 1 h, respectively. The density difference caused by NR incorporation on the shell played a key role in rupturing the LyMs-NR under US irradiation. Furthermore, 5-FU loaded LyMs-NR exhibited excellent anti-cancer activity against the THP-1 cell line (∼90% cell death) when irradiated with US of 200 kHz. The enhanced anti-cancer activity of LyMs-NR was caused by the transfer of released 5-FU molecules from bulk to the interior of the cell via temporary pores formed on the surface of cancer cells, i.e., sonoporation. Thus, LyMs-NR demonstrated here has a high potential for use as carriers in the field of drug delivery, bio-imaging and therapy.

Evaluation of Liposome-Loaded Microbubbles as a Theranostic Tool in a Murine Collagen-Induced Arthritis Model

Rheumatoid arthritis (RA) is an autoimmune disease characterized by severe inflammation of the synovial tissue. Here, we assess the feasibility of liposome-loaded microbubbles as theranostic agents in a murine arthritis model. First, contrast-enhanced ultrasound (CEUS) was used to quantify neovascularization in this model since CEUS is well-established for RA diagnosis in humans. Next, the potential of liposome-loaded microbubbles and ultrasound (US) to selectively enhance liposome delivery to the synovium was evaluated with in vivo fluorescence imaging. This procedure is made very challenging by the presence of hard joints and by the limited lifetime of the microbubbles. The inflamed knee joints were exposed to therapeutic US after intravenous injection of liposome-loaded microbubbles. Loaded microbubbles were found to be quickly captured by the liver. This resulted in fast clearance of attached liposomes while free and long-circulating liposomes were able to accumulate over time in the inflamed joints. Our observations show that murine arthritis models are not well-suited for evaluating the potential of microbubble-mediated drug delivery in joints given: (i) restricted microbubble passage in murine synovial vasculature and (ii) limited control over the exact ultrasound conditions in situ given the much shorter length scale of the murine joints as compared to the therapeutic wavelength.

Value of contrast-enhanced harmonic endoscopic ultrasound for diagnosing hepatic metastases of pancreatic cancer: A prospective study

BACKGROUND AND AIMS

This study aimed to compare contrast-enhanced harmonic endoscopic ultrasound (CH-EUS) with fundamental B-mode endoscopic ultrasonography (EUS) and contrast-enhanced computed tomography (CE-CT) for the diagnosis of left hepatic lobe metastases of pancreatic adenocarcinoma.

METHODS

In this single-center prospective study, CE-CT, EUS, and CH-EUS were performed to detect left hepatic lobe metastases in patients with pancreatic adenocarcinoma, and the detection rates were compared between EUS plus CH-EUS and the other two modalities. Subgroup comparisons of between-modality detection rate were performed in patients with only metastases of <10 mm. The number of pancreatic adenocarcinoma patients whose clinical stage and treatment strategy were changed because of EUS plus CH-EUS findings was also assessed.

RESULTS

Thirty-one patients were diagnosed with left hepatic lobe metastases. For overall detection of left hepatic lobe metastases, EUS plus CH-EUS had significantly higher accuracy (94.3%) than CE-CT (86.7%) and EUS alone (87.6%) (P = 0.021 and P = 0.020, respectively). For detection of left hepatic lobe metastases < 10 mm, EUS plus CH-EUS (93.3%) was significantly superior to CE-CT (84.4%) and EUS alone (85.6%) (P = 0.021 and P = 0.020, respectively). In five of the 11 patients in whom only CH-EUS allowed detection of hepatic metastases, the stage and/or treatment strategy of the pancreatic adenocarcinoma was changed after CH-EUS.

CONCLUSION

This study demonstrated that EUS plus CH-EUS has advantages over CE-CT and EUS alone with regard to the accuracy of detecting left hepatic lobe metastases, particularly small hepatic metastases and accurate staging.

Current role of intraoperative ultrasonography in hepatectomy

Hepatectomy had a high mortality rate in the previous decade because of inadequate techniques, intraoperative blood loss, liver function reserve misdiagnoses, and accompanying postoperative complications. However, the development of several modalities, including intraoperative ultrasonography (IOUS), has made hepatectomy safer. IOUS can provide real-time information regarding the tumor position and vascular anatomy of the portal and hepatic veins. Systematic subsegmentectomy, which leads to improved patient outcomes, can be performed by IOUS in open and laparoscopic hepatectomy. Although three-dimensional (3D) computed tomography and gadoxetic acid-enhanced magnetic resonance imaging have been widely used, IOUS and contrast-enhanced IOUS are important modalities for risk analyses and making decisions regarding resectability and operative procedures because of the vital anatomical information provided and high sensitivity for liver tumors, including "disappearing" liver metastases. Intraoperative color Doppler ultrasonography can be used to delineate the vascular anatomy and evaluate the blood flow volume and velocity in hepatectomy patients and recipients of deceased- and living-donor liver transplantation after vessel reconstruction and liver positioning. For liver surgeons, IOUS is an essential technique to perform highly curative hepatectomy safely, although recent advances have also been made in virtual modalities, such as real-time virtual sonography with 3D visualization.

Novel contrast agent Visphere™ is feasible for contrast-enhanced ultrasonography in dogs

Contrast-enhanced ultrasonography provides a more functional diagnostic image than conventional ultrasonography. This prospective exploratory study compared the novel contrast agent, Visphere^™ , with commercial contrast agents in five healthy Beagle dogs. Visphere^™ has the smallest diameter and highest concentration compared with Sonazoid^® and SonoVue^® . Each dog received an intravenous injection of Visphere^™ , Sonazoid^® , or SonoVue^® . Images were recorded for 300, 600, and 60 s in the heart, liver, and left kidney, respectively. The mean pixel values of the regions of interest for each organ were expressed as time intensity curves (TIC). The agents all improved the visualization of left ventricular endocardial border delineation in the heart, and had similar TICs and clinical useful durations. In contrast, Visphere^™ expressed the highest mean pixel value in the liver parenchyma at an early observation time and maintained the intensity until 600 s, like Sonazoid^® . The renal evaluation results indicated there were no statistically significant differences in time-to-peak for the renal cortex or medulla among the agents. Compared with the other two agents, SonoVue^® had the lowest peak enhancement for the renal cortex and medulla. No dogs had any adverse reactions during or after the study. All three agents provided adequate results for left ventricular endocardial border delineation, and Visphere^™ may have the same potential as Sonazoid^® to detect and characterize hepatic lesions. Visphere^™ and Sonazoid^® may offer better visualization quality to evaluate renal function. In conclusion, the novel contrast agent, Visphere^™ , is comparable with commercial agents and could be applied in different major organs in dogs.

A New Method to Quantify Concentration of Microbubbles in Attenuating Media Using Bubble Destruction Curve Analysis of the Contrast-Enhanced Ultrasound

It is known that the microbubbles of Sonazoid are accumulated in the liver parenchyma due to the phagocytosis of Kupffer cells in the sinusoid. Because this phagocytic function decreases due to the progression of fibrosis in chronic liver disease, the deterioration of the liver function may be quantified by measuring the concentration of the accumulated Sonazoid microbubbles. In this article, a new method to quantify the concentration of microbubbles accumulated in attenuating media is proposed. This method utilizes the contrast-enhanced imaging with high mechanical index, measures the depth of the bubble destruction for each frame and analyze the shape of the destruction curve to estimate the concentration of the bubbles. A phantom experiment was performed with various concentrations of the contrast agent Sonazoid solution as well as various attenuation coefficients of the viscous media. Because of the theoretical model proposed, the estimated attenuation indexes, related to the concentration of Sonazoid microbubbles, were independent of the background attenuation of the propagating medium. The result suggest it has a potential to quantify Sonazoid concentration in the liver parenchyma more precisely against different liver attenuation conditions.

Flash Imaging Used in the Post-vascular Phase of Contrast-Enhanced Ultrasonography is Useful for Assessing the Progression in Patients with Hepatitis C Virus-Related Liver Disease

Sonazoid is a commonly used contrast agent for characterizing liver tumors in ultrasonography (US). We performed flash imaging in the post-vascular phase of contrast-enhanced US (CEUS) to investigate associations between collapse of Sonazoid microbubbles (MB) and progression of liver disease. This study enrolled 409 patients (205 men, 204 women) with hepatitis C virus-related liver disease (CLD) between 2007 and 2017 (mean age 60 ± 14 y; range 20-90 y). In the post-vascular phase, 10 min after administering Sonazoid, flash imaging was performed to burst MB in the liver parenchyma; the range of bubble destruction was measured from the surface of the liver. The range of bubble destruction, stage of fibrosis, shear wave velocity (Vs), serologic markers and fibrosis-4 (FIB4) index were analyzed in 259 patients who underwent liver biopsy. Fibrosis stage was F0-1 in 108 patients, F2 in 73, F3 in 38 and F4 in 40. In 150 patients with cirrhosis, diagnosis was made based on imaging findings. The range of bubble destruction was 42.0 ± 10.4 mm in F0-1 patients, 42.9 ± 13.2 mm in F2, 51.5 ± 15.9 mm in F3 and 55.4 ± 17.3 mm in F4 and was significantly increased according to progression of fibrosis staging. The range of bubble destruction was positively correlated with Vs (r = 0.34; p < 0.01), total bilirubin (r = 0.25; p < 0.01) and FIB4 index (r = 0.38; p < 0.01). In contrast, the range of bubble destruction was negatively correlated with serum levels of albumin (r = -0.34; p < 0.01), platelet count (r = -0.35; p < 0.01) and prothrombin time (r = -0.36; p < 0.01). The results indicated that flash imaging in the post-vascular phase of CEUS was a non-invasive assessment and could predict disease progression in patients with CLD.

Spatial and temporal profile of cisplatin delivery by ultrasound-assisted intravesical chemotherapy in a bladder cancer model

Non-muscle invasive bladder cancer is one of the most common tumors of the urinary tract. Despite the current multimodal therapy, recurrence and progression of disease have been challenging problems. We hereby introduced a new approach, ultrasound-assisted intravesical chemotherapy, intravesical instillation of chemotherapeutic agents and microbubbles followed by ultrasound exposure. We investigated the feasibility of the treatment for non-muscle invasive bladder cancer. In order to evaluate intracellular delivery and cytotoxic effect as a function to the thickness, we performed all experiments using a bladder cancer mimicking 3D culture model. Ultrasound-triggered microbubble cavitation increased both the intracellular platinum concentration and the cytotoxic effect of cisplatin at the thickness of 70 and 122 μm of the culture model. The duration of enhanced cytotoxic effect of cisplatin by ultrasound-triggered microbubble cavitation was approximately 1 hr. Based on the distance and duration of delivery, we further tested the feasibility of repetition of the treatment. Triple treatment increased the effective distance by 1.6-fold. Our results clearly showed spatial and temporal profile of delivery by ultrasound-triggered microbubble cavitation in a tumor-mimicking structure. Furthermore, we demonstrated that the increase in intracellular concentration results in the enhancement of the cytotoxic effect in a structure with the certain thickness. Repetition of ultrasound exposure would be treatment of choice in future clinical application. Our results suggest ultrasound-triggered microbubble cavitation can be repeatable and is promising for the local control of non-muscle invasive bladder cancer.

Effect of treatment support on preventing local recurrence of hepatocellular carcinoma directly adjacent to the diaphragm

Treatment support is anticipated to improve the results of radiofrequency ablation (RFA) treatment in cases in which visualization of tumors using the conventional B-mode is unclear. In the present study, the effectiveness of treatment support for RFA reducing the local recurrence rate of hepatocellular carcinoma (HCC) that are located directly adjacent to the diaphragm, and which are difficult to visualize with B-mode ultrasound imaging, was investigated. A total of 103 HCC tumors measuring <5 cm, which were located abutting the diaphragm, and which were difficult to visualize using the B-mode, were treated using RFA. Thirty-three of those HCC tumors were treated using RFA without treatment support, whereas the remaining 70 HCC tumors were treated using RFA with treatment support, including artificial pleural effusion, contrast-enhanced ultrasonography (CEUS) with the contrasting agent, Sonazoid™, and fusion imaging, either alone or in combination to improve the visualization of the tumors. The rate of local recurrence, and factors affecting local recurrence, were analyzed. Local recurrences were confirmed in 17 of the 103 nodules (16.50%). The overall rate of local recurrence was 13.1% at 6 months, and 20.2% at 12 months. The rate of local recurrence using RFA with artificial pleural effusion was significantly lower compared with those cases of HCC tumors treated without artificial pleural effusion (P=0.008). Similarly, the rate of local recurrence for CEUS RFA with Sonazoid™ was significantly lower compared with those cases of HCC tumors treated without Sonazoid™ (P=0.00081). In a multivariate analysis, CEUS RFA with Sonazoid™ and artificial pleural effusion contributed to the decrease in the rate of local recurrence (hazard ratios, 0.075 and 0.143, respectively). Based on these results, it is possible to conclude that CEUS with Sonazoid™ as a treatment support was the most effective method for reducing the rate of local recurrences abutting the diaphragm that are difficult to visualize using B-mode ultrasonography.

Pharmacokinetics of Perfluorobutane after Intra-Venous Bolus Injection of Sonazoid in Healthy Chinese Volunteers

Sonazoid is an ultrasound contrast agent based on microbubbles (MB) containing perfluorobutane (PFB) gas. Sonazoid is approved in Japan, Korea and Norway for contrast-enhanced ultrasonography of focal liver lesions and focal breast lesions (Japan only). The objective of this study was to determine the pharmacokinetics (PKs) and safety of Sonazoid in Chinese healthy volunteers (HVs) and to evaluate the potential for ethnic differences in PKs between Chinese and Caucasian HVs. Sonazoid was administered as an intra-venous bolus injection at the clinical dose of 0.12 μL or 0.60 μL MB/kg body weight to two groups of eight Chinese HVs. Expired air and blood samples were collected and analyzed using a validated gas chromatographic tandem mass spectrometry method, and the main PK parameters were calculated. The highest PFB concentrations in blood were observed shortly after intra-venous administration of Sonazoid, and elimination of PFB was rapid. In the 0.12 μL MB/kg body weight cohort, PFB concentrations above the limit of quantification were observed for only 10 to 15 min post-injection. In the 0.60 μL MB/kg body weight cohort, PFB concentrations above the limit of quantification were observed for 60 min post-injection, and the shape of the elimination curve suggested a biphasic elimination profile. The maximum observed concentration (C_max) values of PFB in blood were 2.3 ± 1.1 and 19.1 ± 9.2 ng/g for the 0.12 and 0.60 μL MB/kg body weight dose groups (mean ± standard deviation). Area under the curve values were 10.1 ± 2.7 and 90.1 ± 38.3 ng × min/g for the 0.12 and 0.60 μL MB/kg body weight dose groups. C_max values of PFB in exhaled air were 0.35 ± 0.2 and 2.4 ± 0.7 ng/mL for the 0.12 and 0.60 μL MB/kg body weight dose groups. Assessment of laboratory parameters, vital signs, oxygen saturation and electrocardiograms revealed no changes indicative of a concern. The PK profile and safety data generated in the Chinese HVs were comparable to previous data for Caucasian HVs.

Liver Function Assessment Using Parenchyma-Specific Contrast-Enhanced Ultrasonography

The aim of this study was to assess hepatic functional reserve by analyzing the hepatic parenchyma enhancement curve of parenchyma-specific contrast-enhanced ultrasonography (CEUS). Fifty-two patients with cirrhosis who underwent CEUS and indocyanine green tests (ICG) because of a focal liver lesion were enrolled. We evaluated the hemodynamic-related parameters of the time-intensity curve and compared these findings with the ICG retention rate at 15 min (ICG R15). The correlation between the time from peak to one half (s) and ICG R15 was statistically significant and was relatively proportional to the ICG R15. A cut-off value of 149 s was determined for the time from peak to one half for abnormal ICG R15 (>14). The sensitivity and specificity were 85.7% and 92.3%, respectively, for the detection of abnormal ICG R15. In conclusion, the time from peak to one half of the time-intensity curve of parenchyma-specific CEUS of the liver can be a useful parameter to predict the hepatic reserve in liver cirrhosis.

Evolution of contrast agents for ultrasound imaging and ultrasound-mediated drug delivery

Ultrasound (US) is one of the most frequently used diagnostic methods. It is a non-invasive, comparably inexpensive imaging method with a broad spectrum of applications, which can be increased even more by using bubbles as contrast agents (CAs). There are various different types of bubbles: filled with different gases, composed of soft- or hard-shell materials, and ranging in size from nano- to micrometers. These intravascular CAs enable functional analyses, e.g., to acquire organ perfusion in real-time. Molecular analyses are achieved by coupling specific ligands to the bubbles' shell, which bind to marker molecules in the area of interest. Bubbles can also be loaded with or attached to drugs, peptides or genes and can be destroyed by US pulses to locally release the entrapped agent. Recent studies show that US CAs are also valuable tools in hyperthermia-induced ablation therapy of tumors, or can increase cellular uptake of locally released drugs by enhancing membrane permeability. This review summarizes important steps in the development of US CAs and introduces the current clinical applications of contrast-enhanced US. Additionally, an overview of the recent developments in US probe design for functional and molecular diagnosis as well as for drug delivery is given.

Contrast-enhanced sonography with Sonazoid as a new diagnostic tool for splenic hamartoma: a single case report

Detection of reticuloendothelial system (RES) cells is essential for the differential diagnosis of splenic hamartoma. Among the imaging techniques using contrast agents phagocytosed by RES cells, contrast-enhanced ultrasonography (CEUS) with Sonazoid is less invasive and less costly than (99m)Tc-labeled colloid scintigraphy. We report a case of non-symptomatic splenic hamartoma in a 40-year-old woman detected as an abdominal tumor by screening ultrasonography. The tumor was 4 cm in diameter, round, slightly hypoechoic, and associated with a cystic lesion. The tumor region was stained on enhanced computed tomography with prolonged enhancement, while the cystic lesion was not. The mass appeared as mainly isointense with partial hyperintensity on T1-weighted and as a mixed hypo- and hyperintense region on T2-weighted magnetic resonance images. (99m)Tc-labeled colloid scintigraphy demonstrated uptake in only the tumor region. CEUS with Sonazoid revealed that the tumor was mainly hypervascular with non-enhanced areas in the early vascular phase, but the hypervascular region appeared also as a hyperechoic area (indicating microbubble phagocytosis) in the post-vascular phase. Thus, CEUS with Sonazoid revealed all three cardinal features of splenic hamartoma: hypervascularity, presence of RES cells, and tissue heterogeneity. Splenectomy and histopathology confirmed the presence of a splenic hamartoma with associated hematoma. CEUS with Sonazoid is a promising new diagnostic tool for splenic hamartoma.

Oscillatory Dynamics and In Vivo Photoacoustic Imaging Performance of Plasmonic Nanoparticle-Coated Microbubbles

Microbubbles bearing plasmonic nanoparticles on their surface provide contrast enhancement for both photoacoustic and ultrasound imaging. In this work, the responses of microbubbles with surface-bound gold nanorods-termed AuMBs-to nanosecond pulsed laser excitation are studied using high-speed microscopy, photoacoustic imaging, and numerical modeling. In response to laser fluences below 5 mJ cm(-2) , AuMBs produce weak photoacoustic emissions and exhibit negligible microbubble wall motion. However, in reponse to fluences above 5 mJ cm(-2) , AuMBs undergo dramatically increased thermal expansion and emit nonlinear photoacoustic waves of over 10-fold greater amplitude than would be expected from freely dispersed gold nanorods. Numerical modeling suggests that AuMB photoacoustic responses to low laser fluences result from conductive heat transfer from the surface-bound nanorods to the microbubble gas core, whereas at higher fluences, explosive boiling may occur at the nanorod surface, producing vapor nanobubbles that contribute to rapid AuMB expansion. The results of this study indicate that AuMBs are capable of producing acoustic emissions of significantly higher amplitude than those produced by conventional sources of photoacoustic contrast. In vivo imaging performance of AuMBs in a murine kidney model suggests that AuMBs may be an effective alternative to existing contrast agents for noninvasive photoacoustic and ultrasound imaging applications.

Evaluation of contrast Sonazoid-enhanced ultrasonography for the detection of hepatic metastases in breast cancer

Background

The present study was aimed to evaluate the usefulness of contrast Sonazoid-enhanced ultrasonography (US) for the detection of hepatic metastases in breast cancer patients and compare the clinical efficacy and sensitivity of this technique with conventional contrast unenhanced B-mode US in follow-up examinations of breast cancer patients with liver metastasis.

Methods

We assessed a total of 84 hepatic tumors from 24 patients diagnosed with or suspected of having metastatic cancer. These hepatic nodules were diagnosed through imaging, including dynamic magnetic resonance imaging (MRI), contrast-enhanced computed tomography (CECT) scan, B-mode US or contrast Sonazoid-enhanced US (SEUS). Differences in the sensitivity between US and SEUS were compared using MR imaging, CECT, and follow-up imaging.

Results

A total of 79 nodules were diagnosed as metastatic tumors. The remaining nodules were diagnosed as benign tumors (hepatic hemangioma: n = 3; local fatty change: n = 2). SEUS precisely detected the presence or absence of hepatic tumors in the 24 patients examined, showing a sensitivity of 98.8 % (83 of 84 lesions) for total imaged solid liver lesions, with an accuracy of 98.7 % (78 of 79 lesions) for total metastatic breast cancer lesions. In contrast, conventional B-mode US imaging revealed hepatic tumor lesions at a sensitivity of 66.7 % (56 of 84 lesions) and an accuracy of 64.6 % (51 of 79 lesions), respectively. Furthermore, the false positive and false negative rates were, respectively, 6.33 and 29.1 % for B-mode US and 0 and 1.3 % for SEUS. Moreover, twenty-seven metastatic tumors and five benign lesions (3 hemangiomas and 2 focal fatty changes/sparings) were imaged using SEUS but not conventional B-mode US. Significant differences in diagnostic accuracy rates between contrast Sonazoid-enhanced US and conventional B-mode US were observed (Wilcoxon signed rank test: p = 0.0009). No severe adverse events occurred during SEUS after the administration of Sonazoid, except for a grade 1 skin reaction and nausea in one patient.

Conclusion

These results suggested that Sonazoid could be safely administrated to breast cancer patients with liver metastatic disease. Thus, contrast Sonazoid-enhanced US is a feasible and more effective method than B-mode US for the detection of hepatic metastasis, particularly for small metastatic breast cancer lesions less than 14 mm in diameter, showing significant high sensitivity and accuracy.

Usefulness of contrast-enhanced intraoperative ultrasound in identifying disappearing liver metastases from colorectal carcinoma after chemotherapy

BACKGROUND

Preoperative chemotherapy sometimes makes colorectal liver metastases disappear or diminish. Contrast-enhanced intraoperative ultrasound (CE-IOUS) using perflubutane may identify such metastases.

METHODS

Among 131 consecutive patients who underwent hepatic resection, 86 had received preoperative chemotherapy. Of these patients, 72 were examined using contrast-enhanced computed tomography (CE-CT), gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (EOB-MRI), contrast-enhanced ultrasound (CEUS), intraoperative ultrasound (IOUS), and CE-IOUS; these patients were the subject of the present study. Effects of IOUS and CE-IOUS to search for disappearing liver metastases (DLM) and tumors with a diameter of 1 cm or less based on the preoperative imaging were assessed.

RESULTS

A total of 32 DLMs were noted in 11 patients. Four DLMs were identified using IOUS, and 16 DLMs (including the four DLMs identified using IOUS) were identified using CE-IOUS. Of the 16 DLMs that were missed using both IOUS and CE-IOUS, nine were resected using anatomical resection and seven were not resected. One of the nine resected DLMs was histologically proven to be adenocarcinoma. Three of the seven unresected DLMs showed tumor regrowth during a postoperative follow-up examination. CE-IOUS identified 79 % of the 19 DLMs that were ultimately confirmed as liver metastases, whereas IOUS identified 21 % of them (p < 0.004). Among the 202 tumors that were identified using preoperative imaging, 54 were 1 cm or less in diameter. The sensitivity of CE-IOUS for these tumors were superior to CE-CT (p < 0.04) and IOUS (p < 0.04), respectively.

CONCLUSIONS

CE-IOUS might be necessary after preoperative chemotherapy for colorectal liver metastasis.

Renal retention of lipid microbubbles: a potential mechanism for flank discomfort during ultrasound contrast administration

BACKGROUND

The etiology of flank pain sometimes experienced during the administration of ultrasound contrast agents is unknown. The aim of this study was to investigate whether microbubble ultrasound contrast agents are retained within the renal microcirculation, which could lead to either flow disturbance or local release of vasoactive and pain mediators downstream from complement activation.

METHODS

Retention of lipid-shelled microbubbles in the renal microcirculation of mice was assessed by confocal fluorescent microscopy and contrast-enhanced ultrasound imaging with dose-escalating intravenous injection. Studies were performed with size-segregated microbubbles to investigate physical entrapment, after glycocalyx degradation and in wild-type and C3-deficient mice to investigate complement-mediated retention. Urinary bradykinin was measured before and after microbubble administrations. Renal contrast-enhanced ultrasound in human subjects (n = 13) was performed 7 to 10 min after the completion of lipid microbubble administration.

RESULTS

In both mice and humans, microbubble retention was detected in the renal cortex by persistent contrast-enhanced ultrasound signal enhancement. Microbubble retention in mice was linearly related to dose and occurred almost exclusively in cortical glomerular microvessels. Microbubble retention did not affect microsphere-derived renal blood flow. Microbubble retention was not influenced by glycocalyx degradation or by microbubble size, thereby excluding lodging, but was reduced by 90% (P < .01) in C3-deficient mice. Urinary bradykinin increased by 65% 5 min after microbubble injection.

CONCLUSIONS

Lipid-shelled microbubbles are retained in the renal cortex because of complement-mediated interactions with glomerular microvascular endothelium. Microbubble retention does not adversely affect renal perfusion but does generate complement-related intermediates that are known to mediate nociception and could be responsible for flank pain.

Theranostic oxygen delivery using ultrasound and microbubbles

Means to overcome tumor hypoxia have been the subject of clinical investigations since the 1960's; however these studies have yet to find a treatment which is widely accepted. It has been known for nearly a century that hypoxic cells are more resistant to radiotherapy than aerobic cells, and tumor hypoxia is a major factor leading to the resistance of tumors to radiation treatment as well as several cytotoxic agents. In this manuscript, the application of ultrasound combined with oxygen-carrier microbubbles is demonstrated as a method to locally increase dissolved oxygen. Microbubbles can also be imaged by ultrasound, thus providing the opportunity for image-guided oxygen delivery. Simulations of gas diffusion and microbubble gas exchange show that small amounts (down to 5 vol%) of a low-solubility osmotic gas can substantially increase microbubble persistence and therefore production rates and stability of oxygen-carrier microbubbles. Simulations also indicate that the lipid shell can be engineered with long-chain lipids to increase oxygen payload during in vivo transit. Experimental results demonstrate that the application of ultrasound to destroy the microbubbles significantly enhances the local oxygen release. We propose this technology as an application for ultrasound image-guided release of oxygen directly to hypoxic tissue, such as tumor sites to enhance radiotherapy.

Value of post-vascular phase (Kupffer imaging) by contrast-enhanced ultrasonography using Sonazoid in the detection of hepatocellular carcinoma

BACKGROUND

We evaluated the sensitivity and specificity of post-vascular phase (Kupffer imaging) by contrast-enhanced ultrasonography (CEUS) using perflubutane microbubbles (Sonazoid) in comparison with conventional B-mode ultrasonography (US) for the detection of hepatocellular carcinoma (HCC) nodules.

METHODS

A total of 100 treatment-naïve HCC patients admitted at our hospital between December 2007 and June 2009 were consecutively enrolled. The sensitivity and specificity of conventional and contrast-enhanced US were evaluated on a liver segment basis using dynamic CT as a reference standard. Movie files of conventional and enhanced US were stored separately for each segment (e.g., lateral, medial, anterior, and posterior) and reviewed randomly by two blinded readers.

RESULTS

A total of 138 HCC nodules (mean diameter 20.3 mm) were detected in 123 of 400 segments. Detection sensitivity of B-mode US was 0.837 for reader A and 0.846 for reader B, and that of CEUS was 0.732 for reader A and 0.831 for reader B. Specificity of B-mode US was 0.902 for reader A and 0.949 for reader B, and that of CEUS was 0.986 for reader A and 0.978 for reader B. CEUS false positives were mainly due to misidentification of hepatic cysts. A significant proportion of false-negative nodules are hyperechoic in B-mode US, likely because echogenicity hampers visualization of the defect in Kupffer imaging.

CONCLUSIONS

Kupffer imaging by CEUS with Sonazoid showed very high specificity but rather mediocre sensitivity for HCC detection. CEUS is highly suitable for confirmatory diagnosis of HCC; however, caution should be exercised in reaching a diagnosis based only on CEUS.

Usefulness of contrast-enhanced intraoperative ultrasound using Sonazoid in patients with hepatocellular carcinoma

OBJECTIVE

To assess the usefulness of contrast-enhanced intraoperative ultrasound (CE-IOUS) using Sonazoid (gaseous perflubutane) in patients with hepatocellular carcinoma (HCC).

BACKGROUND

Contrast-enhanced intraoperative ultrasound using Sonazoid, a novel ultrasonic contrast agent enabling Kupffer imaging, may enable differentiation of HCC among new focal liver lesions found during fundamental intraoperative ultrasound (fundamental-NFLLs).

METHODS

Between February 2007 and February 2009, a total of 192 consecutive patients were enrolled. Fundamental intraoperative ultrasound and CE-IOUS were performed successively after laparotomy. The vascularity of 1 representative lesion was examined in harmonic mode for approximately 1 minute after the intravenous injection of Sonazoid (vascular phase). Approximately 15 minutes after the vascular phase, total liver scanning in the harmonic mode was commenced (Kupffer phase). One additional injection of Sonazoid was allowed to examine the vascularity of another lesion, if necessary. A tentative diagnosis of HCC was made when a lesion was either hypervascular during the vascular phase or hypoechoic during the Kupffer phase. A final diagnosis of HCC was made on the basis of the results of a histological examination or dynamic computed tomography findings obtained during the 12-month postoperative period.

RESULTS

Seventy-nine fundamental-NFLLs were found in 50 patients (26%), 17 (22%) of which were finally diagnosed as HCC. The sensitivity, specificity, and accuracy of CE-IOUS for differentiating HCC among fundamental-NFLLs were 65%, 94%, and 87%, respectively. Contrast-enhanced intraoperative ultrasound identified 21 additional new hypoechoic lesions in 16 patients, of which 14 lesions (67%) in 11 patients were finally diagnosed as HCC. This prospective study protocol was approved by the institutional review board of the Tokyo University Hospital. An English-language summary of the protocol was submitted (registration ID: UMIN000003046) to the Clinical Trials Registry managed by the University Hospital Medical Information Network in Japan (http://www.umin.ac.jp/ctr/index.htm).

CONCLUSIONS

With help of CE-IOUS using Sonazoid, more accurate intraoperative staging for HCC can be performed.

Activation of microbubbles by short-pulsed ultrasound enhances the cytotoxic effect of cis-diamminedichloroplatinum (II) in a canine thyroid adenocarcinoma cell line in vitro

Ultrasound targeted microbubble destruction has succeeded in delivering drugs and genes. This study was designed to explore characteristics of ultrasound targeted microbubble destruction using short-pulsed diagnostic ultrasound. Canine thyroid adenocarcinoma cells were exposed to short-pulsed diagnostic ultrasound in the presence of cis-diamminedichloroplatinum (II) (cisplatin) and ultrasound contrast agent Sonazoid(®) microbubbles. The cytotoxic effect of cisplatin was enhanced by short-pulsed diagnostic ultrasound and microbubbles. Incubation time with microbubbles influenced the cytotoxic effect of cisplatin. However, exposure duration did not affect the cytotoxic effect of cisplatin. Therefore, short-pulsed diagnostic ultrasound may activate microbubbles near cells and deliver cisplatin into cells. In addition, activation of microbubbles may be concluded in a short time. Our results suggest that short exposure duration could be potentially sufficient to induce efficient drug delivery by ultrasound targeted microbubble destruction using short-pulsed diagnostic ultrasound.

Contrast enhanced ultrasound in the detection of liver metastases: a prospective multi-centre dose testing study using a perfluorobutane microbubble contrast agent (NC100100)

OBJECTIVE

To conduct a dose testing analysis of perfluorobutane microbubble (NC100100) contrast-enhanced ultrasound (CEUS) to determine the optimal dose for detection of liver metastases in patients with extra-hepatic primary malignancy.

METHODS

157 patients were investigated with conventional US and CEUS. CEUS was performed following intravenous administration of perfluorobutane microbubbles (using one dose of either 0.008, 0.08, 0.12 or 0.36 μL/kg body weight). Three blinded off-site readers recorded the number and locations of metastatic lesions detected by US and CEUS. Contrast enhanced CT and MRI were used as the "Standard Of Reference" (SOR). Sensitivity, specificity and accuracy of liver metastasis detection with US versus CEUS, for each dose group were obtained. Dose group analysis was performed using the Chi-square test.

RESULTS

165 metastases were present in 92 patients who each had 1-7 lesions present on the SOR. Sensitivity of US versus CEUS (for all doses combined) was 38% and 67% (p = 0.0001). The 0.12 dose group with CEUS (78%) had significantly higher sensitivity and accuracy (70%) compared to other dose groups (p < 0.05).

CONCLUSION

The diagnostic performance of CEUS is dose dependent with the 0.12 μL/kg NC100100 dose group showing the greatest sensitivity and accuracy in detection of liver metastases.

Abdominal imaging findings of a patient with hepatocellular carcinoma associated with glycogen storage disease type 1a

A hepatic tumor was found in a 57-year-old man with glycogen storage disease type 1a (GSD1a) with a mutation in exon 5 of the glucose-6-phosphatase gene (G727T). Partial hepatectomy was performed, and the tumor was histologically diagnosed as moderately differentiated hepatocellular carcinoma (HCC). On contrast-enhanced ultrasonography, the tumor had a late phase defect. Abdominal imaging with other modalities was also performed. More studies are needed to clarify the differences in imaging findings between GSD1a-associated HCC and other tumors such as adenomas.

Design and characterization of targeted ultrasound microbubbles for diagnostic use

Targeted ultrasound (US) contrast agents represent, because of their size (1 to 5 μm), a unique class of diagnostic imaging agents enabling true vascular imaging of conditions like inflammation and tumor angiogenesis. The objective of this study was to develop technology for preparing targeted microbubbles with binding and acoustic properties compatible with diagnostic use. Phosphatidylcholine (PC) was shown to represent the most favorable wall material. Various thiolated peptide binders were effectively conjugated to PC-based microbubbles containing maleimide functionalized lipids (95:5) without the need for biotin-streptavidin or antibody technology. By optimizing the technology, specific targeting of the inflammatory target E-selectin and the angiogenic target VEGFR2 in the presence of 100% serum was achieved. Increased phospholipid chain length from 18 carbons to 22 carbons improved the stability of the microbubbles during US exposure, without compromising binding or acoustic properties.

Targeted renal therapies through microbubbles and ultrasound

Microbubbles and ultrasound enhance the cellular uptake of drugs (including gene constructs) into the kidney. Microbubble induced modifications to the size selectivity of the filtration capacity of the kidney may enable drugs to enter previously inaccessible compartments of the kidney. So far, negative renal side-effects such as capillary bleeding have been reported only in rats, with no apparent damage in larger models such as pigs and rabbits. Although local delivery is accomplished by applying ultrasound only to the target area, efficient delivery using conventional microbubbles has depended on the combined injection of both drugs and microbubbles directly into the renal artery. Conjugation of antibodies to the shell of microbubbles allows for the specific accumulation of microbubbles in the target tissue after intravenous injection. This exciting approach opens new possibilities for both drug delivery and diagnostic ultrasound imaging in the kidney.

Evaluation of contrast-enhanced ultrasonography using perfluorobutane (Sonazoid(®)) in patients with small hepatocellular carcinoma: comparison with dynamic computed tomography

This study aimed to elucidate the efficacy of contrast-enhanced ultrasonography (CEUS) with perfluorobutane (Sonazoid(®)) in the diagnosis of hepatocellular carcinomas (HCCs), particularly small HCCs, by comparing the results with dynamic computed tomography (Dy-CT). Seventy-nine nodules in 69 patients with chronic liver disease, suspected as HCCs were studied. The nodules were selected based on the results of B-mode ultrasonography and/or Dy-CT conducted between January and August 2007. The nodules were divided into two groups: the S-group with tumors ≤2 cm (49 nodules), and the L-group with tumors >2 cm (30 nodules). Typical HCCs were defined, and the nodules were enhanced and shown as defects in the arterial and late phase of Dy-CT, respectively. Target lesions were scanned using CEUS, and the results were compared with those of Dy-CT. The L-group nodules diagnosed as HCCs using Dy-CT were also diagnosed as HCCs using CEUS. In the S-group, the diagnostic sensitivity of CEUS was 94.7% and the specificity was 81.8%. We diagnosed two liver tumors that were detected by CEUS but not by Dy-CT; biopsies revealed one tumor to be a well-differentiated HCC and the other to be an atypical adenomatous hyperplasia. The sensitivity and specificity of CEUS against HCC were high even in the small-size HCCs. Thus, Sonazoid is useful in the screening for small HCCs.

Evaluation of local recurrence after treatment for hepatocellular carcinoma by contrast-enhanced ultrasonography using Sonazoid: comparison with dynamic computed tomography

PURPOSE

To evaluate the effectiveness of contrast-enhanced ultrasonography (CEUS) using Sonazoid for the diagnosis of the local recurrence after treatment for hepatocellular carcinoma (HCC) by comparing it with dynamic CT.

METHODS

Seventy-one patients with 87 HCC lesions (mean +/- SD; 19.5 +/- 9.6 mm) underwent CEUS using Sonazoid and dynamic CT after radiofrequency ablation (n = 55), transcatheter arterial chemoembolization (n = 22), or radiofrequency ablation combined with transcatheter arterial chemoembolization (n = 10). Two hepatologists (observer 1; 10 years of experience, and 2; 20 years of experience) reviewed the CEUS and dynamic CT images independently and evaluated presence or absence of the local recurrence. Diagnostic performance for the local recurrence was assessed using receiver operating characteristic curve analysis.

RESULTS

The Az value for dynamic CT was significantly lower in observer 1 than 2 (p < 0.05). The sensitivity of CEUS was 79% in observer 1 and 83.9% in observer 2, and that of dynamic CT was 83.9% and 90.3%, respectively. The specificity of CEUS was 96%, and that of dynamic CT was 92%, in both observers.

CONCLUSION

This study suggests that CEUS using Sonazoid is less affected by the observer's experience and is more accurate in the diagnosis of local recurrence after treatment for HCC than dynamic CT.

The assessment of microvascular flow and tissue perfusion using ultrasound imaging

Imaging microvascular flow is of diagnostic value for a wide range of diseases including cancer, inflammation, and cardiovascular disease. The introduction of microbubbles as ultrasound contrast agents offers significant signal enhancement to the otherwise weakly scattered signal from blood in the circulation. Microbubbles provide maximum impedance mismatch, but are not linear scatterers. Their complex response to ultrasound has generated research on both their behaviour and their scattered-signal processing. Nearly 20 years ago signal processing started with simple spectral filtering of harmonics showing contrast-enhanced images. More recent pulse encoding techniques have achieved good cancellation of tissue echoes. The good quality contrast-only images enabled ultrasound contrast-imaging applications to be established in microvascular measurements in the liver and the myocardium. The field promises to advance the quantification of microvascular flow kinetics.

Clinical translation in the treatment of hepatocellular carcinoma following the introduction of contrast-enhanced ultrasonography with Sonazoid

Some hepatocellular carcinoma (HCC) nodules are detectable with dynamic computed tomography, but not by conventional B-mode ultrasonography (US). Contrast-enhanced US (CEUS) with Sonazoid, a new injectable contrast agent, has been used in Japan since January 2007. The primary advantage of this agent is the ability to maintain observations continuously in the Kupffer phase. We assessed the clinical role of CEUS with Sonazoid for radiofrequency ablation (RFA). From January 2005 to December 2008, 1142 patients were treated with surgical resection, RFA, percutaneous ethanol injection or transcatheter arterial chemoembolization, following the exclusion of those patients treated with chemotherapy or supportive care. The patients included in the study were divided into the pre-CEUS (n=451, 2005 and 2006) and post-CEUS (n=691, 2007 and 2008) groups. Clinical background (e.g., etiology, Child-Pugh classification, tumor node metastasis stage, percentage of patients matched with Milan criteria and selected therapies) was compared between the two groups. In addition, naïve cases were compared between the groups. There were 130 naïve HCC cases in the pre-CEUS group and 171 in the post-CEUS group. Although there were no significant differences for clinical background, the percentage of RFA cases increased from 21 (n=95) to 32% (n=219) and from 32 (n=41) to 52% (n=89) for total and naïve subjects, respectively, after CEUS was introduced (P<0.01). In naïve cases treated with RFA, tumor numbers in the post-CEUS group were larger than those of the pre-CEUS group (1.15±0.48 vs. 1.40±0.67; P<0.01). CEUS with Sonazoid, therefore, makes it possible to perform RFA in a considerable number of HCC cases that would otherwise be invisible by conventional B-mode US.

Three cases of angiomyolipoma: diagnostic imaging by contrast-enhanced ultrasonography

We used contrast-enhanced ultrasound using the Sonazoid microbubble contrast agent to diagnose three cases of hepatic angiomyolipoma, which is a rare benign tumor. Some characteristic findings are obtained in the early vascular phase, for example fork-like tumor vessels. However, a variety of findings are seen after the early vascular phase because of microbubbles circulating the vascular enriched tumor.

Preclinical acute toxicology study of surfactant-stabilized ultrasound contrast agents in adult rats

Gas-filled microbubbles are used as contrast agents in diagnostic ultrasound imaging. A preclinical, acute toxicity study of 2 surfactant-stabilized ultrasound contrast agents (ST68 and ST44) was conducted. Subjects were 104 Sprague-Dawley rats (experimental doses, 0.1, 0.2, 0.8, and 1.0 mL/kg; control, 1.0 mL/kg saline) that were studied for 14 days after contrast; clinical signs, weight, blood, and urine were evaluated. Histopathology was performed following euthanasia. Of the 40 animals receiving ST44, 4 died prematurely and a dose dependency was demonstrated (P = .011), whereas in the ST68 groups only 1 death occurred (no dose dependency; P = .48). Only the weight of rats injected with ST44 varied significantly (P = .0003). This dependency was also found for 3 of 5 urine parameters and 4 of 36 blood parameters (P < .05). For ST68, only 1 urine parameter showed significance (P < .0001). Giant cell infiltration in the lungs was significantly higher than controls in the ST44 0.1 mL/kg and the ST68 0.8-1.0 mL/kg groups (P < .01). It is concluded that the prudent choice for future nonrodent, toxicology studies and potentially for human clinical trials is ST68 (given the deaths in the ST44 groups).

Definition of contrast enhancement phases of the liver using a perfluoro-based microbubble agent, perflubutane microbubbles

To define the contrast enhancement phases in the liver with perflubutane microbubbles, the liver enhancement time-intensity curves were investigated in 14 healthy volunteers. The agent was injected intravenously as a bolus and the liver was imaged with an ultrasound scanner as long as 4h after the injection. Time-intensity curves from the hepatic artery, the intrahepatic portal vein, the hepatic vein and the parenchyma of the liver were obtained from the liver ultrasound images. The arrival of the agent in the hepatic artery, the portal vein and the hepatic vein were visually distinguishable and the mean arrival times were 19.2, 24.3 and 32.2 s after the injection, respectively. The signal intensity in these vessels increased rapidly after the arrival of the contrast and gradually reverted to baseline after the peak. In contrast, within 5 min after the injection, the intensity in the parenchyma increased and reached a plateau, which persisted for at least 2h. The contrast enhancement phases in the liver with perflubutane microbubbles could be defined as two major phases-a vascular phase, in which the vessels are enhanced between 15 s and 10 min after injection, and a Kupffer phase, in which the parenchyma is enhanced 10 min after injection. The vascular phase is divided into three subphases: the arterial phase (15 to 45 s after injection); the portal phase (45 s to 1 min after injection); and the vasculo-Kupffer phase (1 to 10 min after injection).

Usefulness of Sonazoid contrast-enhanced ultrasonography for hepatocellular carcinoma: comparison with pathological diagnosis and superparamagnetic iron oxide magnetic resonance images

OBJECTIVE

We investigated the usefulness of Sonazoid contrast-enhanced ultrasonography (Sonazoid-CEUS) in the diagnosis of hepatocellular carcinoma (HCC). The examination was performed by comparing the images during the Kupffer phase of Sonazoid-CEUS with superparamagnetic iron oxide magnetic resonance (SPIO-MRI).

METHODS

The subjects were 48 HCC nodules which were histologically diagnosed (well-differentiated HCC, n=13; moderately differentiated HCC, n=30; poorly differentiated HCC, n=5). We performed Sonazoid-CEUS and SPIO-MRI on all subjects. In the Kupffer phase of Sonazoid-CEUS, the differences in the contrast agent uptake between the tumorous and non-tumorous areas were quantified as the Kupffer phase ratio and compared. In the SPIO-MRI, it was quantified as the SPIO-intensity index. We then compared these results with the histological differentiation of HCCs.

RESULTS

The Kupffer phase ratio decreased as the HCCs became less differentiated (P<0.0001; Kruskal-Wallis test). The SPIO-intensity index also decreased as HCCs became less differentiated (P<0.0001). A positive correlation was found between the Kupffer phase ratio and the SPIO-MRI index (r=0.839). In the Kupffer phase of Sonazoid-CEUS, all of the moderately and poorly differentiated HCCs appeared hypoechoic and were detected as a perfusion defect, whereas the majority (9 of 13 cases, 69.2%) of the well-differentiated HCCs had an isoechoic pattern. The Kupffer phase images of Sonazoid-CEUS and SPIO-MRI matched perfectly (100%) in all of the moderately and poorly differentiated HCCs.

CONCLUSION

Sonazoid-CEUS is useful for estimating histological grading of HCCs. It is a modality that could potentially replace SPIO-MRI.

Gray-scale contrast-enhanced ultrasonography of sentinel lymph nodes in a metastatic breast cancer model

RATIONALE AND OBJECTIVES

Previous studies showed it was possible to employ sonographic contrast agent for identification of the sentinel lymph nodes (SLNs). This study is to investigate the usefulness of SonoVue (a sonographic contrast agent) and gray-scale contrast-enhanced ultrasonography (CEUS) for detecting the SLNs in a metastatic breast cancer model.

MATERIALS AND METHODS

CEUS was performed in 12 female rabbits with breast VX2 tumor after subcutaneous administration of SonoVue. The site, number, and pattern of enhancement of the SLNs were observed and recorded. After CEUS, 0.5 mL of blue dye was injected into the same location as SonoVue and the SLNs were detected by surgical dissection. The findings of CEUS were compared with those of blue dye.

RESULTS

Of the 12 tumors assessed, a total of 17 enhanced SLNs were detected by CEUS. Among them, a single SLN was detected in eight tumors, two SLNs in three tumors, and three SLNs in one tumor. All the SLNs showed partial enhancement on CEUS. Nineteen SLNs were identified by blue dye with surgical dissection. There were no false-positive CEUS findings in terms of SLN detection. The overall sensitivity of CEUS for detecting SLNs was 89.5% (17/19). Among the 17 SLNs detected by CEUS, tumor metastases were identified histopathologically in 4 SLNs, whereas proliferation of lymphatic tissue was identified in the other 13 SLNs.

CONCLUSIONS

CEUS combined with SonoVue is useful for detecting SLNs, although it may not be helpful for detecting metastases in SLNs.

Efficacy of perflubutane microbubble-enhanced ultrasound in the characterization and detection of focal liver lesions: phase 3 multicenter clinical trial

OBJECTIVE

The purpose of this study was to assess the efficacy and safety of contrast-enhanced ultrasound performed with perflubutane microbubbles in comparison with unenhanced ultrasound and dynamic CT in the characterization of focal liver lesions during the vascular phase of imaging and in the detection of lesions during the Kupffer phase.

SUBJECTS AND METHODS

A total of 196 patients were enrolled at 15 centers in Japan. Vascular phase images were obtained before contrast injection until 1 minute after injection. Kupffer phase images were obtained 10 minutes after injection. Dual-phase CT was performed as determined by standard clinical practice at each center. Unenhanced ultrasound, contrast-enhanced ultrasound, and CT images were read by blinded reviewers, and the results they reached regarding characterization and detection were compared with reference standard findings made by onsite investigators. The safety observation period was 72 hours after contrast administration.

RESULTS

Among the 190 patients included in the characterization analysis, the accuracy of contrast-enhanced ultrasound (88.9%) was significantly greater than that of unenhanced ultrasound (68.4%) and dynamic CT (80.5%) (p < 0.001 and p = 0.008). Among the 191 patients in the detection analysis, the efficacy of contrast-enhanced ultrasound in detection of lesions was significantly higher than that of unenhanced ultrasound and dynamic CT (p < 0.001 and p = 0.008), predominantly because more metastatic lesions were detected (both p < 0.001). In particular, contrast-enhanced ultrasound was superior to dynamic CT in the detection of metastatic lesions measuring 1 cm or smaller. The incidence of adverse events was 49.2% and that of adverse drug reactions was 10.4%. All adverse drug reactions were mild.

CONCLUSION

Compared with unenhanced ultrasound and dynamic CT, contrast-enhanced ultrasound with perflubutane microbubbles improved diagnostic efficacy in both characterization and detection of focal liver lesions with no serious adverse drug reactions.

Targeted microbubbles for imaging tumor angiogenesis: assessment of whole-body biodistribution with dynamic micro-PET in mice

PURPOSE

To evaluate in vivo whole-body biodistribution of microbubbles (MBs) targeted to tumor angiogenesis-related vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) by using dynamic micro-positron emission tomography (PET) in living mice.

MATERIALS AND METHODS

Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. Lipid-shell perfluorocarbon-filled MBs, targeted to VEGFR2 via anti-VEGFR2 antibodies, were radiolabeled by conjugating the radiofluorination agent N-succinimidyl-4-[(18)F]fluorobenzoate (SFB) to the anti-VEGFR2 antibodies. These MBs were then injected intravenously into nude mice (n = 4) bearing angiosarcomas, and the whole-body biodistribution of these probes was assessed for 60 minutes by using dynamic micro-PET. Results were compared with ex vivo gamma counting (n = 6) and immunofluorescence staining (n = 6). Control studies in angiosarcoma-bearing mice were performed with injection of the radiolabeled antibodies alone (n = 3) or free SFB (n = 3). A mixed-effects regression of MB accumulation on fixed effects of time and tissue type (tumor or muscle) and random effect of animal was performed.

RESULTS

VEGFR2-targeted MBs rapidly cleared from the blood circulation (50% blood clearance after approximately 3.5 minutes) and accumulated in the liver (mean, 33.4% injected dose [ID]/g +/- 13.7 [standard deviation] at 60 minutes) and spleen (mean, 9.3% ID/g +/- 6.5 at 60 minutes) on the basis of micro-PET imaging. These findings were confirmed with ex vivo gamma counting. Uptake of targeted MBs was significantly higher (P < .0001) in tumor than in adjacent skeletal muscle tissue. Immunofluorescence staining demonstrated accumulation of the targeted MBs within hepatic Kupffer cells and splenic macrophages. Biodistribution of the radiolabeled antibodies and free SFB differed from the distribution of the targeted MBs.

CONCLUSION

Dynamic micro-PET allows assessment of in vivo biodistribution of VEGFR2-targeted MBs.

Contrast-enhanced intraoperative ultrasonography equipped with late Kupffer-phase image obtained by sonazoid in patients with colorectal liver metastases

AIM: To find occult metastases during hepatectomy in patients with colorectal cancer liver metastases (CRCLM), contrast-enhanced intraoperative ultrasonography (CE-IOUS) was performed using a new microbubble agent, sonazoid, which provides a parenchyma-specific contrast image based on its accumulation in the Kupffer cells.

METHODS: Eight patients with CRCLM underwent CE-IOUS using sonazoid before hepatectomy. The liver was investigated during a late Kupffer-phase imaging, which is a valuable characteristic of sonazoid.

RESULTS: CE-IOUS using sonazoid provided the early vascular- and sinusoidal-phase images for

10 min followed by the late Kupffer-phase image up to 30 min after the injection of sonazoid. IOUS did not provide new findings of metastatic lesion in the 8 patients. However, during the late Kupffer-phase image of sonazoid, a metastatic lesion was newly found in two of the 8 patients. These newly detected lesions were removed by an additional hepatectomy and histopathologically diagnosed as a metastasis.

CONCLUSION: CE-IOUS using sonazoid can allow surgeons to investigate the whole liver with enough time and to find new metastases intraoperatively.

Benefits of contrast-enhanced sonography for the detection of liver lesions: comparison with histologic findings

OBJECTIVE

The objective of our study was to compare the usefulness of contrast-enhanced sonography with baseline sonography in detecting malignant liver lesions.

SUBJECTS AND METHODS

This prospective study included 116 patients. All patients underwent a preoperative conventional sonography examination followed by sonography after injection of contrast agent combined with the use of perfusion software (vascular recognition imaging or pulse subtraction imaging). Histopathologic analysis was the reference standard used to compare the diagnostic value of baseline sonography versus contrast-enhanced sonography.

RESULTS

Eighty-two patients underwent hepatic surgery, 31 did not because of disseminated lesions, and the remaining three patients did not meet inclusion criteria. Three hundred six surgically proven lesions were taken into account for comparison of the two techniques: 147 were detected on baseline sonography and 177 on contrast-enhanced sonography. Histopathologic analysis revealed 233 malignant and 73 benign lesions. Sensitivity and specificity were improved on contrast-enhanced sonography compared with baseline sonography for the detection of malignant lesions: 68.7% versus 58.8% and 67% versus 50.7%, respectively. Contrast-enhanced sonography detected 23 additional malignant lesions that had been seen as lacuna at the portal venous phase and characterized as 19 benign nodules, thus improving the performance of sonography in 13.7% of the cases.

CONCLUSION

Contrast injection improved the sensitivity and specificity of baseline sonography and should be performed in routine practice if hepatic surgery is being considered for the management of liver lesions.

Pharmacokinetics of perfluorobutane following intravenous bolus injection and continuous infusion of sonazoid in healthy volunteers and in patients with reduced pulmonary diffusing capacity

The ultrasound contrast agent Sonazoidtrade mark was administered as an i.v. bolus injection of 0.6 microL microbubbles/kg body weight or as a continuous infusion over 30 min at a rate of 1.2 microL microbubbles/kg body weight to healthy volunteers and patients with reduced pulmonary diffusing capacity. Expired air and blood samples were collected from 32 subjects and perfluorobutane (PFB) gas was analyzed using validated gas chromatography mass spectrometry methods. Blood concentrations of PFB declined biphasicly with a distribution half-life (t(0.5 to 15)) of 2 to 3 min and an elimination half-life (t(15 to 120)) of 30 to 45 min. Area under the curve (AUC) values in patients with impaired gas diffusion were significantly larger than those in healthy volunteers. The exhalation kinetics were somewhat variable with a PFB elimination half-life (t(15 to 120)) of 28 to 111 min. Clearance of PFB was independent of study population and mode of administration. There were no deaths and no serious adverse events that resulted in the withdrawal of a subject from the study. With the exception that arthralgia predominated in healthy volunteers, healthy volunteers and diseased subjects did not show a different adverse event profile whether Sonazoid was administered as a bolus injection or as an infusion. Assessment of laboratory parameters (serum biochemistry, haematology and urinalysis), vital signs, oxygen saturation and electrocardiograms (ECGs) showed no changes which caused safety concern. (E-mail: Kristin.Landmark@ge.com).

Mechanism of hepatic parenchyma-specific contrast of microbubble-based contrast agent for ultrasonography: microscopic studies in rat liver

OBJECTIVE

The objective of this study was to elucidate the mechanism of hepatic parenchyma-specific contrast of Sonazoid (microbubble contrast agent) using microscopic techniques.

MATERIALS AND METHODS

Sonazoid was intravenously injected into rats to investigate the microbubble dynamics and distribution within hepatic microcirculation in exteriorized liver using intravital microscopy and to observe dose dependency of ultrasound hepatic contrast effect. In vitro and in vivo uptake of microbubbles by Kupffer cells was examined using confocal laser scanning microscopy.

RESULTS

Intravital observation demonstrated freely flowing microbubbles in the sinusoid and some microbubbles co-localized with Kupffer cells. The microbubbles internalized in Kupffer cells were identified with reflected light by confocal laser scanning microscopy. The percentage of Kupffer cells taking up microbubbles was about 1% at clinical dose at which the homogeneous hepatic contrast was observed.

CONCLUSIONS

The hepatic parenchyma-specific contrast by Sonazoid is due to distribution of the microbubbles in Kupffer cells.

The application of microbubbles for targeted drug delivery

Interest in microbubbles as vehicles for drug delivery has grown in recent years, due in part to characteristics that make them well suited for this role and in part to the need the for localized delivery of drugs in a number of applications. Microbubbles are inherently small, allowing transvascular passage, they can be functionalized for targeted adhesion, and can be acoustically driven, which facilitates ultrasound detection, production of bioeffects and controlled release of the cargo. This article provides an overview of related microbubble biofluid mechanics and reviews recent developments in the application of microbubbles for targeted drug delivery. Additionally, related advances in non-bubble microparticles for drug delivery are briefly described in the context of targeted adhesion.

Microbubble ultrasound contrast agents: an update

Microbubble contrast agents for ultrasound (US) have gained increasing interest in recent years, and contrast-enhanced US (CEUS) is a rapidly evolving field with applications now extending far beyond the initial improvements achieved in Doppler US. This has been achieved as a result of the safe profile and the increased stability of microbubbles persisting in the bloodstream for several minutes, and also by the availability of specialized contrast-specific US techniques, which allow a definite improvement in the contrast resolution and suppression of signal from stationary tissues. CEUS with low transmit power allows real-time scanning with the possibility of prolonged organ insonation. Several reports have described the effectiveness of microbubble contrast agents in many clinical applications and particularly in the liver, spleen, and kidneys. CEUS allows the assessment of the macrovasculature and microvasculature in different parenchymas, the identification and characterization of hepatic and splenic lesions, the depiction of septal enhancement in cystic renal masses, and the quantification of organ perfusion by the quantitative analysis of the echo-signal intensity. Other fields of application include the assessment of abdominal organs after traumas and the assessment of vesico-ureteral reflux in children. Finally, tumor-targeted microbubbles make possible the depiction of specific biologic processes.

Phagocytosis of ultrasound contrast agent microbubbles by Kupffer cells

Delayed parenchymal phase images of the liver more than 5 min after IV injection of ultrasound contrast agents are thought to be related to the phagocytosis of contrast agent microbubbles by macrophages. In this study, we examined whether liver-specific macrophages, Kupffer cells, phagocytosed the microbubbles and whether their elimination affected the delayed parenchymal images of the liver. Phase-contrast microscope observations showed that Kupffer cells phagocytosed various contrast agents in vitro. Among the contrast agents used, 99% of Sonazoid and Optison, and 47% of Levovist were phagocytosed, whereas only 7.3% of SonoVue and 0% of Imavist were phagocytosed. Elimination of Kupffer cells in vivo by gadolinium chloride (GdCl(3)) resulted in decreased intensity of the delayed parenchymal images with Sonazoid and Levovist, while SonoVue showed no changes compared with control. Our findings suggested that Kupffer cells phagocytosed contrast agents and they were responsible for the delayed images of contrast ultrasound in the liver.