Nanomaterials incorporated ultrasound contrast agents for cancer theranostics

Nanotechnology provides various nanomaterials with tremendous functionalities for cancer diagnostics and therapeutics.Recently, theranostics has been developed as an alternative strategy for efficient cancer treatment through combination of imaging diagnosis and therapeutic interventions under the guidance of diagnostic results. Ultrasound(US) imaging shows unique advantages with excellent features of real-time imaging, low cost, high safety and portability, making US contrast agents(UCAs)an ideal platform for construction of cancer theranostic agents. This review focuses on the development of nanomaterials incorporated multifunctional UCAs serving as theranostic agents for cancer diagnostics and therapeutics, via conjugation of superparamagnetic iron oxide nanoparticles(SPIOs), Cu S nanoparticles, DNA, si RNA, gold nanoparticles(GNPs), gold nanorods(GNRs), gold nanoshell(GNS), graphene oxides(GOs), polypyrrole(PPy) nanocapsules, Prussian blue(PB) nanoparticles and so on to different types of UCAs. The cancer treatment could be more effectively and accurately carried out under the guidance and monitoring with the help of the achieved theranostic agents. Furthermore, nanomaterials incorporated theranostic agents based on UCAs can be designed and constructed by demand for personalized and accurate treatment of cancer, demonstrating their great potential to address the challenges of cancer heterogeneity and adaptation, which can provide alternative strategies for cancer diagnosis and therapeutics.

Characterization of the interaction of nanobubble ultrasound contrast agents with human blood components

Nanoscale ultrasound contrast agents,or nanobubbles,are being explored in preclinical applications ranging from vascular and cardiac imaging to targeted drug delivery in cancer.These sub-micron particles are approximately 10x smaller than clinically available microbubbles.This allows them to effectively traverse compromised physiological barriers and circulate for extended periods of time.While various aspects of nanobubble behavior have been previously examined,their behavior in human whole blood has not yet been explored.Accordingly,herein we examined,for the first time,the short and long-term effects of blood components on nanobubble acoustic response.We observed differences in the kinetics of backscatter from nanobubble suspensions in whole blood compared to bubbles in phosphate buffered saline(PBS),plasma,or red blood cell solutions(RBCs).Specifically,after introducing nanobubbles to fresh human whole blood,signal enhancement,or the magnitude of nonlinear ultrasound signal,gradually increased by 22.8±13.1%throughout our experiment,with peak intensity reached within 145 s.In contrast,nanobubbles in PBS had a stable signal with negligible change in intensity(1.7±3.2%)over 8 min.Under the same conditions,microbubbles made with the same lipid formulation showed a56.8±6.1%decrease in enhancement in whole blood.Subsequent confocal,fluorescent,and scanning electron microscopy analysis revealed attachment of the nanobubbles to the surface of RBCs,suggesting that direct interactions,or hitchhiking,of nanobubbles on RBCs in the presence of plasma may be a possible mechanism for the observed effects.This phenomenon could be key to extending nanobubble circulation time and has broad implications in drug delivery,where RBC interaction with nanoparticles could be exploited to improve delivery efficiency.

Ultrasound contrast agents from microbubbles to biogenic gas vesicles

Microbubbles have been the earliest and most widely used ultrasound contrast agents by virtue of their unique features:such as non-toxicity,intravenous inject-ability,ability to cross the pulmonary capillary bed,and significant enhancement of echo signals for the duration of the examination,resulting in essential preclinical and clinical applications.The use of microbubbles functional-ized with targeting ligands to bind to specific targets in the bloodstream has further enabled ultrasound molecular imaging.Nevertheless,it is very challenging to utilize targeted microbubbles for molecular imaging of extra-vascular targets due to their size.A series of acoustic nanomaterials have been developed for breaking free from this constraint.Especially,biogenic gas vesicles,gas-filled protein nanostructures from microorganisms,were engineered as thefirst biomolecular ultrasound contrast agents,opening the door for more direct visual-ization of cellular and molecular function by ultrasound imaging.The ordered protein shell structure and unique gasfilling mechanism of biogenic gas vesicles endow them with excellent stability and attractive acoustic responses.What’s more,their genetic encodability enables them to act as acoustic reporter genes.This article reviews the upgrading progresses of ultrasound contrast agents from microbubbles to biogenic gas vesicles,and the opportu-nities and challenges for the commercial and clinical translation of the nascentfield of biomolecular ultrasound.

Role for contrast-enhanced ultrasound in assessing complications after kidney transplant

Kidney transplantation(KT)is an effective treatment for end-stage renal disease.Despite their rate has reduced over time,post-transplant complications still represent a major clinical problem because of the associated risk of graft failure and loss.Thus,post-KT complications should be diagnosed and treated promptly.Imaging plays a pivotal role in this setting.Grayscale ultrasound(US)with color Doppler analysis is the first-line imaging modality for assessing complications,although many findings lack specificity.When performed by experienced operators,contrast-enhanced US(CEUS)has been advocated as a safe and fast tool to improve the accuracy of US.Also,when performing CEUS there is potentially no need for further imaging,such as contrast-enhanced computed tomography or magnetic resonance imaging,which are often contraindicated in recipients with impaired renal function.This technique is also portable to patients’bedside,thus having the potential of maximizing the cost-effectiveness of the whole diagnostic process.Finally,the use of blood-pool contrast agents allows translating information on graft microvasculature into time-intensity curves,and in turn quantitative perfusion indexes.Quantitative analysis is under evaluation as a tool to diagnose rejection or other causes of graft dysfunction.In this paper,we review and illustrate the indications to CEUS in the post-KT setting,as well as the main CEUS findings that can help establishing the diagnosis and planning the most adequate treatment.

Liver metastases:Contrast-enhanced ultrasound compared with computed tomography and magnetic resonance

The development of ultrasound contrast agents with excellent tolerance and safety profiles has notably improved liver evaluation with ultrasound(US)for several applications,especially for the detection of metastases.In particular,contrast enhanced ultrasonography(CEUS)allows the display of the parenchymal microvasculature,enabling the study and visualization of the enhancement patterns of liver lesions in real time and in a continuous manner in all vascular phases,which is similar to contrast-enhanced computed tomography(CT)and contrast-enhanced magnetic resonance imaging.Clinical studies have reported that the use of a contrast agent enables the visualization of more metastases with significantly improved sensitivity and specificity compared to baseline-US.Furthermore,studies have shown that CEUS yields sensitivities comparable to CT.In this review,we describe the state of the art of CEUS for detecting colorectal liver metastases,the imaging features,the literature reports of metastases in CEUS as well as its technique,its clinical role and its potential applications.Additionally,the updated international consensus panel guidelines are reported in this review with the inherent limitations of this technique and best practice experiences.

Non-thermal ablation of rabbit liver VX2 tumor by pulsed high intensity focused ultrasound with ultrasound contrast agent:Pathological characteristics

AIM： To investigate the pathological characteristics of non-thermal damage induced by pulsed high intensity focused ultrasound （PHIFU） combined with ultrasound contrast agent （UCA）, SonoVue （Bracco SpA, Milan, Italy） in rabbit liver VX2 tumor. METHODS： Liver VX2 tumor models were established in 20 rabbits, which were divided randomly into PHIFU combined with ultrasound contrast agent group （PHIFU ＋ UCA group） and sham group. In the PHIFU ＋ UCA group, 0.2 mL of SonoVue was injected intravenously into the tumor, followed by ultrasound exposure of Isp 5900 W/cm^2. The rabbits were sacrificed one day after ultrasound exposure. Specimens of the exposed tumor tissues were obtained and observed pathologically under light microscope and transmission electron microscope. The remaining tumor tissues were sent for 2,3,5-Triphenyltetrazolium chloride （TTC） staining. RESULTS： Before Trc staining, tumor tissues in both the sham and the PHIFU ＋ UCA groups resembled gray fish meat, After TIC staining, the tumor tissues were uniformly stained red, with a clear boundary between tumor tissue and normal tissue, Histological examination showed signs of tumor cell injury in PHIFU ＋ UCA group, with cytoplasmic vacuoles of various sizes, chromatin margination and karyopyknosis. Electron microscopic examination revealed tumor cell volume reduction, karyopyknosis, chromatin margination, intercellular space widening, the presence of high electro＇n-density apoptotic bodies and vacuoles in cytoplasm. CONCLUSION： The non-thermal effects of PHIFU combined with UCA can be used to ablate rabbit liver VX2 tumors.

FEASIBILITY STUDY OF AN ULTRASOUND CONTRAST AGENT(LEVOVIST) IN COLOR DOPPLER IMAGING OF LIVER NEOPLASMS

The purpose of this study was to determine the efficacy of using an ultrasound contrast agent(levovist)to enhance the color Doppler imaging of liver neoplasms.Thirty patients with hepatic tumors were enrolled in this study.After intravenous administration of levovist,the color Doppler signals of normal hepatic vessels were enhanced.In various hepatic tumors,the different patterns of tumor vascularity were observed,which had not been demonstrated in conventional non contrast color Doppler imaging.In 11 of 16 patients with hepatocarcinoma,additional color Doppler signals were observed in the central part of the tumors.On the contrary,3 patients with metastatic liver lesions the enhanced color Doppler signals appear only at the peripheral of tumors.A typical rim like color enhancement was seen in 2 of the 3 cases.In six patients with hepatic hemangiomas contrast enhanced color Doppler imaging demonstrated the blood vessels at the margin of the neoplasms.Contrast enhanced color Doppler imaging improves the visualization of the hepatic neoplasm vascularity.This technique holds great promise for detecting small liver tumors and differentiating hepatic neoplasms.

Nonlinear response of ultrasound contrast agent microbubbles:From fundamentals to applications

Modelling and biomedical applications of ultrasound contrast agent （UCA） microbubbles have attracted a great deal of attention. In this review, we summarize a series of researches done in our group, including （i） the development of an all-in-one solution of characterizing coated bubble parameters based on the light scattering technique and flow cytometry; （ii） a novel bubble dynamic model that takes into consideration both nonlinear shell elasticity and viscosity to eliminate the dependences of bubble shell parameters on bubble size; （iii） the evaluation of UCA inertial cavitation threshold and its relationship with shell parameters; and （iv） the investigations of transfection efficiency and the reduction of cytotoxicity in gene delivery facilitated by UCAs excited by ultrasound exposures.

PREPARATION OF POLYELECTROLYTE MULTILAYER COATED MICROBUBBLES FOR USE AS ULTRASOUND CONTRAST AGENT

Objeelive To prepare and characterize polyelectrolyte multilayer film coated microbubbles for use as ultrasound contrast agent （UCA） and evaluate its effects in ultrasonic imaging on normal rabbit＇s fiver parenchyma. Methods Perfluorocarbon （PFC）-containing microbubbles （ST68-PFC） were prepared by sonication based on suffactant （ Span 60 and Tween 80）. Subsequently, the resulting ST68-PFC microbubbles were coated using oppositely charged polyelectrolytes by microbubble-templated layer-by-layer self-assembly technique via electrostatic interaction. The enhancement effects in ultrasonic imaging on normal rabbit＇s liver parenchyma were assessed. Results The obtained microbubbles exhibited a narrow size distribution. The polyelectrolytes were successfully assembled onto the surface of ST68-PFC microbubbles. In vivo experiment showed that polyelectrolyte multilayer film coated UCA effectively enhanced the imaging of rabbit＇s liver parenchyma. Conclusions The novel microbubbles UCA coated with polyelectrolyte multilayer, when enabled more function, has no obvious difference in enhancement effects compared with the pre-modified microbubbles. The polymers with chemically active groups （ such as amino group and carboxyl group） can be used as the outermost layer for attachment of targeting ligands onto microbubbles, allowing selective targeting of the microbubbles to combine with desired sites.

Microbubble ultrasound contrast agent with three esters and carboxylic methyl cellulose as main shell materials: Its preparation and imaging evaluation

Objective: To study on the preparation process of a new surfactant-based microbubble ultrasound contrast agent and to evaluate its contrast effects in vivo. Methods: Microbubble ultrasound contrast agent with three ester surfactants and other additives as its shell materials was prepared by sonication. Sulfur hexafluoride was adopted as the inner gas of the microbubbles. New methods through the combination of optical microscope and some softwares were used to measure the size distribution and the concentration of the microbubbles. Some parameters such as the pH value of the phosphate buffer, quantity of the carboxylic methyl cellulose in the shell materials, selection of the ultrasound power and process time, were studied. Six hybirded dogs were used to verify the in vivo contrast imaging of the contrast agent using second harmonic power Doppler modality. Safety and persistent time of the agent inner animal body were also investigated. Results: Ultrasound contrast agent prepared in the experiment had an average microbubble diameter of 3.95 microns with concentration of 3.6×109 microbubbles per millilitre. Carboxylic methyl cellulose was found as an important shell material which had obviously effect on the microbubble stability and production even with a little quantity. The buffer pH value also had a key role on the microbubble formation and the final production. When the buffer pH value reached 7.4, there was no microbubble produced. Under the approximate microbubble production, process time could be shorten with the increasing ultrasound power. The obvious ultrasound contrast imaging effects were detected in the dog's heart chamber and liver as well as kidney using only one millilitre agent when diluted. The agent was found safe to the dogs. At the same time, persistent time of the agent was found over 20 min in the dog's body. Conclusion: The new ultrasound contrast agent prepared in the experiment has high microbubble production and concentration, narrow microbubble size distribution ranging in several microns, well stability, little dosage needed in the contrast, well safety to the dogs and long persistent time, obvious contrast imaging effect in the dog's heart chamber, kidney and liver. These experiment data indicate that the new ultrasound contrast agent with three ester surfactants and carboxylic methyl cellulose as its main shell materials can be further developed for clinical purposes.

Experimental system for perfusion imaging and time-intensity processing based on ultrasound contrast agent

Objective： To present a self-developed experimental system for basic studies of blood perfusion imaging and time-intensity evaluating based on ultrasound contrast agent. Methods ： The experimental system performed the image reconstruction and time-intensity processing with radio frequency signals. The system was comprised of ultra-high speed hardware data acquisition interface and low computational cost algorithms. The self-made contrast agent ,blood mimic phantom and capillary phantom model were used to validate the experimental system. Results： The images acquired in blood phantoms with linear-array and curve-array transducers were given. The time-intensity curves corresponding to selected region of interestsequence were demonstrated. It was also shown the time-intensity based decay curves and a decay of ultrasound contrast agent under different ultrasound powers. Conclusion： Several suited from two in vitro phantom models show that the experimental system can be used to f blood perfusion and further clinical studies of microvasculature perfusion.

The combined time-frequency analysis of the acoustic signals backscattered from ultrasonic contrast agents in the evaluation of the blood perfusion

Objective: To analyze the non-periodic, unstable and even chaotic echoes scattered from microbubbles which are extremely sensitive and may easily collapse, fragment or shrink when ultrasound contrast agents are exposed to ultrasound (US) irradiation. Methods: The combined time-frequency analysis was applied to the original signals instead of the traditional Fourier spectral analysis technique. Results: The results obtained from simulation as well as experiment showed that the subharmonic, 2nd harmonic and ultra harmonic of the microbubbles occurred during the oscillation and varied with time. The dependence on the incident ultrasonic amplitude and microbubble parameters were established. Conclusion: The transient echoes backscattered from the ultrasound agent in the evaluation of the blood perfusion can be analyzed thoroughly by the technique of combined-frequency analysis and the time detail of the frequency contents can be revealed.

Enhanced endoscopic ultrasound imaging for pancreatic lesions: The road to artificial intelligence

Early detection of pancreatic cancer has long eluded clinicians because of its insidious nature and onset.Often metastatic or locally invasive when symptomatic,most patients are deemed inoperable.In those who are symptomatic,multi-modal imaging modalities evaluate and confirm pancreatic ductal adenocarcinoma.In asymptomatic patients,detected pancreatic lesions can be either solid or cystic.The clinical implications of identifying small asymptomatic solid pancreatic lesions(SPLs)of<2 cm are tantamount to a better outcome.The accurate detection of SPLs undoubtedly promotes higher life expectancy when resected early,driving the development of existing imaging tools while promoting more comprehensive screening programs.An imaging tool that has matured in its reiterations and received many image-enhancing adjuncts is endoscopic ultrasound(EUS).It carries significant importance when risk stratifying cystic lesions and has substantial diagnostic value when combined with fine needle aspiration/biopsy(FNA/FNB).Adjuncts to EUS imaging include contrast-enhanced harmonic EUS and EUS-elastography,both having improved the specificity of FNA and FNB.This review intends to compile all existing enhancement modalities and explore ongoing research around the most promising of all adjuncts in the field of EUS imaging,artificial intelligence.

Ultrasound-mediated transdermal drug delivery of fluorescent nanoparticles and hyaluronic acid into porcine skin in vitro

Transdermal drug delivery （TDD） can effectively bypass the first-pass effect. In this paper, ultrasound-facilitated TDD on fresh porcine skin was studied under various acoustic parameters, including frequency, amplitude, and exposure time. The delivery of yellow-green fluorescent nanoparticles and high molecular weight hyaluronic acid （HA） in the skin samples was observed by laser confocal microscopy and ultraviolet spectrometry, respectively. The results showed that, with the application of ultrasound exposures, the permeability of the skin to these markers （e.g., their penetration depth and concentration） could be raised above its passive diffusion permeability. Moreover, ultrasound-facilitated TDD was also tested with/without the presence of ultrasound contrast agents （UCAs）. When the ultrasound was applied without UCAs, low ultrasound frequency will give a better drug delivery effect than high frequency, but the penetration depth was less likely to exceed 200 p.m. However, with the help of the ultrasound-induced microbubble cavitation effect, both the penetration depth and concentration in the skin were significantly enhanced even more. The best ultrasound-facilitated TDD could be achieved with a drug penetration depth of over 600 p.m, and the penetration concentrations of fluorescent nanoparticles and HA increased up to about 4-5 folds. In order to get better understanding of ultrasound-facilitated TDD, scanning electron microscopy was used to examine the surface morphology of skin samples, which showed that the skin structure changed greatly under the treatment of ultrasound and UCA. The present work suggests that, for TDD applications （e.g., nanoparticle drug carriers, transdermal patches and cosmetics）, protocols and methods presented in this paper are potentially useful.

Basic physical, acoustic properties, and in vitro ultrasound imaging enhancement of the lipid-coated microbubbles

Aim To research on a stable microbubble with good acoustic properties and excellent imaging enhancing effect, and to make it to be a promising agent for the enhancement of ultrasound imaging in the ultrasound diagnosis of cardiovascular system diseases. Methods The morphology, size and zeta potential of lipid-coated microbubbles （LCM）, the acoustic properties of backscatter, and the second harmonic scatter of LCM were determined. Furthermore, the relationship between the concentrations and the amplitude values of the second harmonic was investigated by testing the intensities of the second harmonic at different concentrations. The imaging effect of LCM was also studied in vitro. Results The mean diameter of LCM was 3.38 μm with 95% of the bubbles under 5 μm. The scatter signal generated by microbubbles was observed under different concentrations in the bistatic modes while the position of transmitting transducer and receiving transducer was orthogonal. The intensity of the second harmonic scatter fell with the decrease of microbubble concentration. The increase rate of the second harmonic amplitude values generated by the microbubbles versus that by physiological saline was linear with the natural logarithm of bubble concentrations. The LCM could enhance the ultrasound image of thrombus. Conclusion The LCM exhibited good physical state and acoustic properties, which could increase the imaging quality.

In vivo transfection of enhanced green fluorescent protein in rat retinal ganglion cells mediated by ultrasound-induced microbubbles

BACKGROUND： Studies have demonstrated that ultrasound-mediated microbubble destruction significantly improves transfection efficiency of enhanced green fluorescent protein （EGFP） in in vitro cultured retinal ganglial cells （RGCs）. OBJECTIVE： To investigate the feasibility of ultrasound-mediated microbubble destruction for EGFP transfection in rat RGCs, and to compare efficiency and cell damage with traditional transfection methods. DESIGN, TIME AND SETTING： In vivo, gene engineering experiment. The study was performed at the Central Laboratory, Institute of Ultrasonic Imaging, Chongqing Medical University from March to July 2008. MATERIALS： Eukaryotic expression vector plasmid EGFP and microbubbles were prepared by the Institute of Ultrasonic Imaging, Chongqing Medical University. The microbubbles were produced at a concentration of 8.7 × 10^11/L, with a 2-4 μm diameter, and 10-hour half-life in vitro. METHODS： A total of 50 Sprague Dawley rats were randomly assigned to four groups. Normal controls （n = 5） were infused with 5 μL normal saline to the vitreous cavity; the naked plasmid group （n = 15） was infused with 5 pL EGFP plasmid to the vitreous cavity; in the plasmid with ultrasound group （n = 15）, the eyes were irradiated with low-energy ultrasound wave （0.5 W/cm^2） for a total of 60 seconds （irradiated for 5 seconds, at 10-second intervals） immediately following infusion of EGFP plasmids to the vitreous cavities. In the microbubble-ultrasound group （n = 15）, the eyes were irradiated with the same power of ultrasonic wave immediately following infusion of microbubbles containing EGFP plasmids to the vitreous cavities. MAIN OUTCOME MEASURES： After 7 days, retinal preparations and EGFP expression in RGCs were observed by fluorescence microscopy. RGC quantification in the retinal ganglion cell layer was performed. In addition, EGFP mRNA expression was semi-quantitatively determined by RT-PCR. RESULTS： The transfection efficiency of EGFP to RGCs by microbubbles with ultrasound was significantly greater than the other groups, and no obvious damage was detected in the RGCs. CONCLUSION： Under irradiation of low-frequency ultrasound waves, ultrasound-mediated microbubble destruction was effective and resulted in safe transfection of the EGFP gene to the RGCs.

Decreased phagocytic activity of Kupffer cells in a rat nonalcoholic steatohepatitis model

AIM: To investigate Kupffer cell dynamics and phagocytic activity,using a rat nonalcoholic steatohepatitis (NASH) model. METHODS: Male F344 rats were fed either a control diet or a choline-deficient L-amino acid-defined (CDAA) diet,followed by contrast enhanced ultrasonography (CEUS) using Levovist. The uptake of latex beads by the Kupffer cells was determined by fluorescent microscopy. The status of the Kupffer cells was compared between the two groups,using the immunohistochemical staining technique. RESULTS: After 4 or more wk of the CDAA diet,CEUS examination revealed a decrease in the signal intensity,20 min after intravenous Levovist. Fluorescent microscopic examination showed that the uptake of latex beads by the Kupffer cells was reduced at week 1 and 2 in the study group,compared with the controls,with no further reduction after 3 wk. Immunohistochemical staining revealed no significant difference in the Kupffer cell counts between the control group and the CDAA group. CONCLUSION: CEUS examination using Levovist demonstrated reduced contrast effect and phagocytic activity in the liver parenchymal phase,although the Kupffer cell numbers were unchanged,indicating reduced phagocytic function of the Kupffer cells in the rat NASH model. We believe that CEUS examination using Levovist is a useful screening modality,which can detect NASH in fatty liver patients.

Subharmonic scattering of ultrasound contrast agent microbubbles may be an effective and promising tool for portal vein pressure estimation

Portal hypertension(PH)is a commonly observed syndrome in patients with cirrhosis and other chronic liver diseases(1).It is closely associated with severe clinical complications,including upper gastrointestinal hemorrhage,ascites,hepatic encephalopathy,and liver failure(2-6).Portal vein pressure(PVP)is a prognostic indicator for patients with cirrhosis,and PH is a contraindication for hepatectomy(7,8).Currently,the gold standard for assessing PVP is the measurement of PVP gradient[hepatic venous pressure gradient(HVPG)],which is indirectly determined by placing a catheter in the hepatic vein(3).

Advantages of contrast-enhanced ultrasound in the localization and diagnostics of sentinel lymph nodes in breast cancer

Sentinel lymph nodes(SLNs)are the first station of lymph nodes that extend from the breast tumor to the axillary lymphatic drainage.The pathological status of these LNs can predict that of the entire axillary lymph node.Therefore,the accurate identification of SLNs is necessary for sentinel lymph node biopsy(SLNB)to replace axillary lymph node dissection(ALND).The quality of life and prognosis of breast cancer patients are related to proper surgical treatment after the precise identification of SLNs.Some of the SLN tracers that have been identified include radioisotope,nano-carbon,indocyanine green(ICG),and methylene blue(MB).However,these tracers have certain limitations,such as pigmentation,radiation dangers,and the requirement for costly detection equipment.Ultrasound contrast agents(UCAs)have good specificity and sensitivity,and thus can compensate for some shortcomings of the mentioned tracers.This technique is also being applied to SLNB in patients with breast cancer,and can even provide an initial judgment on SLN status.Contrast-enhanced ultrasound(CEUS)has the advantages of high distinguishability,simple operation,no radiation harm,low cost,and accurate localization;therefore,it is expected to replace the traditional biopsy methods.In addition,it can significantly enhance the accuracy of SLN localization and shorten the operation time.

Off-label-use of sulfur-hexafluoride in voiding urosonography for diagnosis of vesicoureteral reflux in children:A survey on adverse events

AIM To evaluate the risk profile of sulfur hexafluoride in voiding urosonography(VUS) based on a large cohort of children.METHODS Since 2011 sulfur hexafluoride(SH,SonoV ue?,Bracco,Italy) is the only ultrasound contrast available in the European Union and its use in children has not been approved.Within a 4-year-period,531 children with suspected or proven vesicoureteral reflux(f/m = 478/53; mean age 4.9 years; 1 mo-25.2 years) following parental informed consent underwent VUS with administration of 2.6 ± 1.2 mL SH in a two-center study.A standardizedtelephone survey on adverse events was conducted three days later.RESULTS No acute adverse reactions were observed.The survey revealed subacute,mostly self-limited adverse events in 4.1%(22/531).The majority of observed adverse events(17/22) was not suspected to be caused by an allergic reaction: Five were related to catheter placement,three to reactivated urinary tract infections,five were associated with perineal disinfection before voiding urosonography or perineal dermatitis and four with a common cold.In five patients(0.9%) hints to a potential allergic cause were noted: Perineal urticaria was reported in three interviews and isolated,mild fever in two.These were minor self-limited adverse events with a subacute onset and no hospital admittance was necessary.Ninety-six point two percent of the parents would prefer future VUS examinations with use of SH.CONCLUSION No severe adverse events were observed and indications of self-limited minor allergic reactions related to intravesical administration of SH were reported in less than 1%.