1. SpringerPlus, Jun 30, 2016, Hepatocellular adenoma: comparison between real-time contrast-enhanced ultrasound and dynamic computed tomography Authors: Wei Wang, et al
2. NanoWerk, Jun 30, 2016, Graphene coated microbubbles as superior photoacoustic imaging contrast agent By Michael Berger
Wang, W et al. SpringerPlus (2016) 5: 951. doi:10.1186/s40064-016-2406-z
Jun 30, 2016
Hepatocellular adenoma: comparison between real-time contrast-enhanced ultrasound and dynamic computed tomography
Authors: Wei Wang, Jin-Ya Liu, Zheng Yang, Yue-Feng Wang, Shun-Li Shen, Feng-Lian Yi, Yang Huang, Er-Jiao Xu, Xiao-Yan Xie, Ming-De Lu, Zhu Wang, Li-Da Chen
To investigate and compare the contrast-enhanced ultrasound (CEUS) features of histologically proven HCA with those of contrast-enhanced computed tomography (CECT).
Eighteen patients with proven hepatic adenoma by pathology were retrospectively selected from the CEUS database. Fourteen of them had undergone liver CECT exams. The basic features on unenhanced imaging and the enhancement level and specific features on contrast-enhanced imaging were retrospectively analyzed, and the differences between CEUS and CECT were compared.
All the HCAs showed hyper-enhancement in the arterial phase. During the portal and late phases, 12 HCAs (12/18, 66.7 %) on CEUS and 11 (11/14, 78.6 %) on CT showed washout. On CEUS, 10 (10/18, 55.5 %) showed centripetal filling in the arterial phase and persistent peripheral rim enhancement. Five of them (61.1 %, 11/18) showed delayed central washout in the portal or late phase. However, on CECT, 2 (14.3 %, 2/14) and 4 (28.6 %, 4/14) HCAs showed persistent enhancement of the peripheral rim and central non-enhancing hemorrhage areas, respectively.
Compared with dynamic CT, CEUS was superior at characterizing specific dynamic features. Considering that it is radiation-free, readily availability and easy to use, CEUS is suggested as the first line imaging tool to diagnose HCA.
Jun 30, 2016
Graphene coated microbubbles as superior photoacoustic imaging contrast agent
By Michael Berger
(Nanowerk Spotlight) Researchers have demonstrated that the coupling of pristine graphene sheets on practically any polymer surface can be accomplished in mild reaction conditions and in aqueous medium. The method leaves intact the 2D planar structure of graphene preserving its original features.
This novel hybrid construct enables in vivo photoacoustic signal enhancement and is a very promising step forward for an implementation of photoacoustic imaging (PAI), a powerful preclinical diagnostic tool.
Imaging and drug delivery based on miniaturized devices are keys in the future of personalized medicine. One of the main issues is the disease detection in the earliest stages. This increases the chance of success of any therapy. PAI is among the imaging methods with the highest resolution and this allows a less invasive way to detect tumors at very early stages. The targeting is key both for a localized diagnostic and to bring a drug focally to the diseased tissue.
The photoacoustic effect, discovered and studied by Bell more than 135 years ago (Nature, "Selenium and the Photophone"), occurs when light hits an absorber and the locally accumulated thermal energy is converted and dissipated in mechanical energy by the emission of ultrasound waves and detected by a transducer.
The light wavelength used in biomedical diagnostics is in the near infrared (NIR) spectral window, where light is less attenuated by the tissue (and water). Endogenous metabolites such as haemoglobin of red blood cells behave in this way.
"This effect is used in photoacoustic imaging (PAI) and it can be enhanced by exogenous devices as for example our hybrid assembly made by the stable coupling of pristine graphene with microbubbles," Gaio Paradossi, a professor in the Dipartimento di Scienze e Tecnologie Chimiche at Università di Roma Tor Vergata, explains to Nanowerk. "The efficiency in the enhancement of the photoacoustic signal makes such device an unprecedented multimodal contrast agent for ultrasound and PAI."
Paradossi and his team just reported in ACS Applied Materials & Interfaces ("Graphene Meets Microbubbles: A Superior Contrast Agent for Photoacoustic Imaging") a proof of concept, tested in vivo, where they fabricated a hybrid injectable device for use as an efficient and versatile photoacoustic contrast agent.
Schematics of the approach. (Reprinted with permission by American Chemical Society)
In their present work, the researchers present a technique to couple pristine graphene with polymer shelled microbubbles. The design is based on poly(vinyl alcohol) (PVA) polymer microbubbles, which are stably coupled to pristine graphene sheets through surfactant moieties covalently bound to the available functional groups on the microbubbles surface.
"At the center of our work is pristine graphene, the intact form of graphene," Paradossi points out. "Most of the applications reported in the literature highlights the use of graphene oxide (GO) or reduced graphene oxide (RGO). These forms of graphene, not directly obtained by graphite exfoliation, derive from chemical modifications of the 2D structure of graphene in very harsh conditions, which introduce kinks and irregularities in the carbonic material."
"Such modifications make GO and RGO more reactive and more processable than pristine graphene, but jeopardize the electrical, optical and mechanical properties of this material," he adds.
In their present work, the researchers present a technique to couple pristine graphene with polymer shelled microbubbles.
"Why polymer shelled microbubbles are such an exotic support for pristine graphene? Microbubbles are the best contrast agents for enhancing ultrasounds and it is a natural choice if ultrasound or photoacoustic imaging are the goals," says Paradossi. "Another important issue pointed out in our paper is the exceptional stability of the coupling to the polymer surface of the microbubbles is an asset for the biocompatibility of graphene."
This work contains several novel elements:
The use of pristine graphene leaves unchanged its relevant properties.
A general strategy for attaching pristine graphene to a large number of hydrophilic polymer surfaces in a stable way using mild conditions and aqueous media.
The assembly of a truly hybrid system where a hydrophobic moiety, i.e. graphene, is coupled with a hydrophilic moiety, i.e. the poly (vinyl alcohol) shelled microbubble, to obtain a novel multifunctional device implementing the potentialities of the photoacoustic imaging.
These results have been a by-product of the work presently carried out within the frame of the European project TheraGlio – Developing theranostics for Gliomas, where the goal is to develop a multimodal imaging system for Theranostics (therapy + diagnosis) of patients bearing malignant glioma, the most common primary brain tumour.
FESEM images of (a) G/PVA 2.5% (w/w), (b) G/PVA 5% (w/w), and (c) G/PVA 10% (w/w); insets, magnified graphene flakes on PVA microbubble shell of the selected zones. The arrows indicate graphene sheets. (Reprinted with permission by American Chemical Society)
The results also build on a method recently developed by Paradossi's group where graphene sheets were stably anchored to PVA hydrogels (The Journal of Physical Chemistry B, "Soft Confinement of Graphene in Hydrogel Matrixes"). This method consists of the ultrasound exfoliation of graphite assisted by a surfactant in aqueous medium followed by the tethering to the polyvinyl alcohol chemical hydrogels via the surfactant functional moieties.
Going forward, the team will address the biocompatibility of their graphene microbubbles; the ability to target pathological cells tissues; and ultrasound assisted drug delivery.
As for the biocompatibility, graphene is anchored to the surface of the PVA shelled microbubble in a stable way and loss of graphenic material was not monitored in physiological media. PVA, is already known as a biocompatible polymer and it was used for the fabrication of echogenic microbubbles with long shelf-life and good chemical versatility (see: Gaio Paradossi “Hydrogels Formed by Cross-linked Poly(vinyl alcohol)” in Polymeric Biomaterials: Structure and Function, Volume 1).
"However, for such hybrid system an increase of biocompatibility should be expected by surface pegylation," says Paradossi. "The chemical versatility of the shell can allow tumor tissues to be targeted by conjugating the peptide sequences as cyclic RGD or hyaluronic acid on the PVA microbubble surface. RGD is known to bind the receptor of αVβ3 integrins, a family of membrane proteins, which is over expressed by tumor cells."
"Analogously, grafting hyaluronic acid, a polysaccharide present in the extracellular matrix of mammals, on the PVA surface is a mean to address the graphene/microbubble device on the receptor of CD44, another membrane protein over expressed by tumor cells."
The microbubbles can also be converted to drug delivery systems by loading drugs directly on the surface by physisorption. Ultrasound can be used to excite the microbubbles – to 'shake' them – and release the drug molecules.
"More sophisticated methods are under study in our lab, consisting in tethering liposomes on the shell containing oligonucleotides cargo which can be transfected upon ultrasound irradiation," Paradossi notes.
In conclusion, anchoring graphene on PVA microbubble surfaces opens the way to leap from the use in small size animals functional imaging to a high resolution clinical diagnostic tool, by combining the appealing features of both PVA microbubble (as efficient ultrasound scatterer) and graphene (as strong NIR absorber with high thermal conductivity).
Copyright © Nanowerk
1. Chemical & Engineering News, Jun 20, 2016, Ultrasound implant safely opens blood-brain barrier in patients; New method could help anticancer drugs reach brain tumors
By Michael Torrice
2. PLOS ONE, Jun 20, 2016, Sonophoresis Using Ultrasound Contrast Agents: Dependence on Concentration Authors: Donghee Park, et al
Chemical & Engineering News
Volume 94 Issue 25 | p. 6 | News of The Week
Issue Date: June 20, 2016 | Web Date: June 17, 2016
Jun 20, 2016
Ultrasound implant safely opens blood-brain barrier in patients
New method could help anticancer drugs reach brain tumors
By Michael Torrice
The cells lining blood vessels in the brain form tight, tough-to-penetrate junctions that prevent toxic molecules from slipping into the brain.
Unfortunately, this blood-brain barrier also blocks cancer drugs from reaching tumor cells in the brain, creating a significant drug-delivery problem.
Now, preliminary results from a Phase I/II clinical trial suggest that a small implant that emits ultrasound waves can safely open the blood-brain barrier in people, potentially allowing drugs in (Sci. Transl. Med. 2016, DOI: 10.1126/scitranslmed.aaf6086).
Scientists have previously tested ultrasound methods in animals and found that the techniques can aid drug delivery to the brain. These methods often rely on injecting microbubbles—typically fluorinated gases encapsulated in lipid spheres. The sound waves cause these bubbles to expand and compress. That mechanical energy helps loosen the junctions between endothelial cells lining blood vessels.
To translate such a treatment into people, the company CarThera, founded by Alexandre Carpentier, a neurosurgeon at Pitié-Salpêtrière Hospital, in Paris, developed SonoCloud, an 11.5-mm-diameter ultrasound transducer that surgeons can implant in a hole in patients’ skulls. Carpentier envisions a brain-cancer patient receiving such an implant after a tumor biopsy or a surgery to remove parts of a tumor.
In the new study, the team reported data from 15 glioblastoma patients who had received the implant. Before these patients were treated with the cancer drug carboplatin, they received a 2.5-minute ultrasound session.
By using magnetic resonance imaging to watch a gadolinium contrast agent enter the brain, the researchers found that these sessions opened the blood-brain barrier. And the patients didn’t experience adverse effects from the ultrasound—no signs of hemorrhaging, no complaints of pain, and no indications that speech or motor control was disrupted.
CarThera will start a Phase III trial in 2017 to assess how ultrasound treatments can improve chemotherapy for brain cancer patients. Also, Carpentier is interested in determining if the device can help treat Alzheimer’s disease. Some studies in animals suggest that ultrasound can clear out toxic protein plaques from the brain, in part, by temporarily opening the blood-brain barrier.
Nathan McDannold of Harvard Medical School says the clinical trial data are an impressive milestone for the ultrasound therapy field. He is working on similar methods that don’t rely on an implant and instead use an external array of 1,000 ultrasound transducers to focus on a target in the brain. So, he says, although the SonoCloud is more invasive, it is a simpler system.
Jun 20, 2016
Sonophoresis Using Ultrasound Contrast Agents: Dependence on Concentration
Authors: Donghee Park, Gillsoo Song, Yongjun Jo, Jongho Won, Taeyoon Son, Ohrum Cha, Jinho Kim, Byungjo Jung, Hyunjin Park, Chul-Woo Kim, Jongbum Seo
Donghee Park, Chul-Woo Kim
Department of Pathology, Tumor Immunity Medical Research Center, Cancer Research Institute, Seoul National University College of Medicine, Jongno-gu, Seoul, Republic of Korea
Gillsoo Song, Jongho Won, Taeyoon Son, Ohrum Cha, Jinho Kim, Byungjo Jung, Jongbum Seo
Department of Biomedical Engineering, Yonsei University, Wonju, Gangwon-do, Republic of Korea
Gumi Electronics & Information Technology Research Institute, Gumi, Gyeongsangbuk-do, Republic of Korea
School of Electronic Electrical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, Republic of Korea
Sonophoresis can increase skin permeability to various drugs in transdermal drug delivery. Cavitation is recognized as the predominant mechanism of sonophoresis. Recently, a new logical approach to enhance the efficiency of transdermal drug delivery was tried. It is to utilize the engineered microbubble and its resonant frequency for increase of cavitation activity. Actively-induced cavitation with low-intensity ultrasound (less than ~1 MPa) causes disordering of the lipid bilayers and the formation of aqueous channels by stable cavitation which indicates a continuous oscillation of bubbles. Furthermore, the mutual interactions of microbubble determined by concentration of added bubble are also thought to be an important factor for activity of stable cavitation, even in different characteristics of drug. In the present study, we addressed the dependence of ultrasound contrast agent concentration using two types of drug on the efficiency of transdermal drug delivery. Two types of experiment were designed to quantitatively evaluate the efficiency of transdermal drug delivery according to ultrasound contrast agent concentration. First, an experiment of optical clearing using a tissue optical clearing agent was designed to assess the efficiency of sonophoresis with ultrasound contrast agents. Second, a Franz diffusion cell with ferulic acid was used to quantitatively determine the amount of drug delivered to the skin sample by sonophoresis with ultrasound contrast agents. The maximum enhancement ratio of sonophoresis with a concentration of 1:1,000 was approximately 3.1 times greater than that in the ultrasound group without ultrasound contrast agent and approximately 7.5 times greater than that in the control group. These results support our hypothesis that sonophoresis becomes more effective in transdermal drug delivery due to the presence of engineered bubbles, and that the efficiency of transdermal drug delivery using sonophoresis with microbubbles depends on the concentration of microbubbles in case stable cavitation is predominant.
- Ultraschall in Med 2016, Jun 8, 2016, A Milestone: Approval of CEUS for Diagnostic Liver Imaging in Adults and Children in the USA
Ein Meilenstein: Zulassung von CEUS zur Leberdiagnostik an Erwachsenen und Kindern in den USA Authors: K. Seitz, D. Strobe
2. American Chemical Society, Jun 1, 2016, Enzyme-degradable hybrid polymer/silica microbubbles as ultrasound contrast agents Authors: Nadia H Tsao and Elizabeth Anne Howlett Hall
3. Journal of the American Society of Echocardiography, June, 2016, Detection of Carotid Atherosclerotic Plaque Neovascularization Using Contrast Enhanced Ultrasound: A Systematic Review and Meta-Analysis of Diagnostic Accuracy Studies Authors: Runqing Huang, PhD, et al
4. Echo Research and Practice, Jun 1, 2016, Echo your Work!
Ultraschall in Med 2016
Jun 8, 2016
A Milestone: Approval of CEUS for Diagnostic Liver Imaging in Adults and Children in the USA
Ein Meilenstein: Zulassung von CEUS zur Leberdiagnostik an Erwachsenen und Kindern in den USA
Authors: K. Seitz, D. Strobe
The approval of microbubbles with the inert gas sulfur hexafluoride (SF6) and a palmitic acid shell (SonoVue®, Bracco Geneva, CH) for the diagnostic imaging of liver tumors in adults and children by the FDA in the United States represents a milestone for contrast-enhanced ultrasound (CEUS).
This warrants a look back at the history of the development of CEUS. The first publications based on echocardiographic observations of right ventricular contrast phenomena caused by tiny air bubbles following i. v. injection of indocyanine green appeared around 1970   . A longer period of sporadic publications but no real progress then followed since, in contrast to X-ray methods, ultrasound works quite well without a contrast agent.
It is noteworthy that the foundations for further development were primarily laid in Europe. The development and approval (1991) of the contrast agent Echovist® by a German contrast manufacturer for echocardiography unsuitable for passing through lungcapillaries   resulted in the first extracardiac indications, e. g. for detecting retrovesical reflux and tubal patency, in the mid-1980 s   . The sensitivity of color Doppler was not able to compensate for the lack of an ultrasound contrast agent compared to CT with its obligatory contrast administration.
Studies of SHU 508 – microbubbles of air moderately stabilized with galactose and palmitic acid – began in 1990        and the contrast agent was then introduced in 1995 in Germany as Levovist®. The most important publications by Blomley, Cosgrove, Leen, and Albrecht are named here on a representative basis     .
SHU 508 along with other US contrast agents provided impressive proof of the superiority of CEUS for the diagnosis of liver metastases. However, practical application remained complicated and required skill and technical know-how because of a lack of suitable software on US units     . The monograph regarding the use of contrast agent in the liver by Wermke and Gaßmann is impressive but unfortunately only available in German . In addition to being applied in the heart and the liver, CEUS was first used in transcranial applications  and in vessels , the kidneys , and the breast . Measurements at transit times were also of particular interest . It was difficult to convince ultrasound device manufacturers of the need to adapt US units to US contrast agents and not vice versa.
The breakthrough came with low MI phase contrast inversion and the introduction of SonoVue® in many European countries in 2001. This more stable US contrast agent is easy to use and is becoming indispensable in diagnostic imaging of the liver         . Studies have shown its excellent tolerability  and diagnostic reliability comparable to that of MDCT and MRI in the liver  . Today it would be unimaginable to diagnose liver tumors without CEUS . This also applies to very small lesions  .
EFSUMB published the first CEUS guidelines in 2004  which have since been reissued and divided into hepatic  and extrahepatic applications . The first recommendations regarding quantitative assessment have also been published .
The increasing scientific interest in CEUS is evident based on the greater number of PubMed hits for Echovist®(ca. 130), Levovist® (ca. 500) and SonoVue® (ca. 1500) as well as on the fact that publications regarding CEUS comprise almost 20 % of UiM/EJU articles in the last 10 years. The number of CEUS articles in UiM/EJU continues to be high                         .
In the clinical reality, CEUS has been able to become established alongside CT and MRI according to the saying “better is the enemy of good”  as the method of choice after B-mode ultrasound in the evaluation of liver tumor malignancy in Germany, where the technically challenging method is promoted. In the case of unclear CT and MRI findings, CEUS performed by an experienced examiner/clinician often provides the solution, particularly in the case of small lesions, and is the last resort before US-guided biopsy  . However, there is a lack of competent CEUS examiners and Germany continues to be the world champion of X-ray examinations with no noticeable reverse trend. In almost every doctor’s office and hospital, ultrasound costs are by far not fully covered, resulting in an extremely high frequency of CT use with CT being available to everyone regardless of insurance status.
The USA is now in the starting position for CEUS. It will be exciting to see how the method will develop there. The FDA’s decision to approve sulfur hexafluoride (Lumason® = SonoVue®) should be considered against the background of the radiation exposure caused by CT examinations and the fact that MRI using gadolinium-containing contrast agents is no longer considered noninvasive because of nephrogenic systemic fibrosis (NSF) and the accumulation of the agent in the cerebrum. An essential point of the campaign regarding the avoidance of diagnostic radiation exposure triggered in the USA by the publications of Brenner et al.   was that the agent was approved for use in the liver even for children   – still off label in Europe – without additional comprehensive studies due to the available scientific results and the very low side effects profile of Lumason® (= SonoVue®). It is admittedly unclear why other indications (except the heart which has been approved since 2014) are excluded even though the microbubbles as a pure blood pool contrast agent can be diagnostically used in the entire vascular system and bed of all organs. To our knowledge, there is no such restriction on the approval of X-ray contrast agents.
Like echocardiography and emergency ultrasound, CEUS began in Europe but will probably only establish its final diagnostic value as a “reimport”.
This is a major opportunity to permanently define the role of Ultrasound as a highly valuable, patient-centered imaging method in the German health care system.
This may prompt some of our international readers to reflect upon the role of CEUS in their own countries.
American Chemical Society
Jun 1, 2016
Enzyme-degradable hybrid polymer/silica microbubbles as ultrasound contrast agents
Authors: Nadia H Tsao and Elizabeth Anne Howlett Hall
The fabrication of an enzyme-degradable polymer/silica hybrid microbubble is reported that produces an ultrasound contrast image. The polymer, a triethoxysilane end-capped polycaprolactone (SiPCL), is used to incorporate enzyme-degradable components into a silica microbubble synthesis, and to impart increased elasticity for enhanced acoustic responsiveness. Formulations of 75, 85 and 95 wt% SiPCL in the polymer feed, produced quite similar ratios of SiPCL and silica in the final bubble but different surface properties. The data suggest that different regions of the microbubbles were SiPCL-rich: the inner layer next to the polystyrene template core and the outer surface layer, thereby creating a sandwiched silica-rich layer of the bubble shell. Overall, the thickness of the microbubble shell was dependent on the starting TEOS concentration and the reaction time. Despite the layered structure, the microbubble could be efficiently degraded by lipase enzyme, but was stable without enzyme. The ultrasound contrast showed a general trend of increase in image intensity with SiPCL feed ratio, although the 95 wt% SiPCL bubbles did not produce a contrast image, probably due to bubble collapse. At higher normalized peak negative acoustic pressure (mechanical index, MI), a non-linear frequency response also emerges, characterized by the third harmonic at around 3f0, and increases with MI. The threshold MI transition from linear to non-linear response increased with decrease in SiPCL.
Journal of the American Society of Echocardiography
Volume 29, Issue 6, June 2016, Pages 491–502
Detection of Carotid Atherosclerotic Plaque Neovascularization Using Contrast Enhanced Ultrasound: A Systematic Review and Meta-Analysis of Diagnostic Accuracy Studies
Authors: Runqing Huang, PhDa, d, Sahar S. Abdelmoneim, MB, BCha, Caroline A. Ball, MDb,
Lara F. Nhola, MDa, Ann M. Farrell, MLSc, Steven Feinstein, MDe, Sharon L. Mulvagh, MDa, ,
Intraplaque neovascularization is considered an important indicator of plaque vulnerability. Contrast-enhanced ultrasound (CEUS) of carotid arteries improves imaging of carotid intima-media thickness and permits real-time visualization of neovascularization of the atherosclerotic plaque. The authors conducted a systematic review and meta-analysis to evaluate the accuracy of CEUS-detected carotid atherosclerotic plaque.
A systematic search was performed to identify studies published in the MEDLINE, Embase, Scopus, and Web of Science databases from 2004 to June 2015. Studies evaluating the accuracy of quantitative analysis and qualitative analysis (visual interpretation) for the diagnosis of intraplaque neovascularization compared with histologic specimens and/or clinical diagnosis of symptomatic plaque were included. Parameters evaluated were plaque quantitative CEUS intensity and the visual grading of plaque CEUS. A random-effects meta-analysis was used to pool the likelihood ratios (LRs), diagnostic odds ratios, and summary receiver operating characteristic curves. Corresponding areas under the curves were calculated.
The literature search identified 203 studies, 20 of which were selected for systematic review; the final meta-analysis included seven studies. For qualitative CEUS, pooled sensitivity was 0.80 (95% CI, 0.72–0.87), pooled specificity was 0.83 (95% CI, 0.76–0.89), the pooled positive LR was 3.22 (95% CI, 1.67–6.18), the pooled negative LR was 0.24 (95% CI, 0.09–0.64), the pooled diagnostic odds ratio was 15.57 (95% CI, 4.94–49.03), and area under the curve was 0.894. For quantitative CEUS, pooled sensitivity was 0.77 (95% CI, 0.71–0.83), pooled specificity was 0.68 (95% CI, 0.62–0.73), the pooled positive LR was 2.34 (95% CI, 1.69–3.23), the pooled negative LR was 0.34 (95% CI, 0.25–0.47), the pooled diagnostic odds ratio was 7.06 (95% CI, 3.6–13.82), and area under the curve was 0.888.
CEUS is a promising noninvasive diagnostic modality for detecting intraplaque neovascularization. Standardization of quantitative analysis and visual grading classification is needed to increase reliability and reduce technical heterogeneity.
Echo Research and Practice
Jun 1, 2016
Echo your Work!
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