Microbubble contrast agents: a new era in ultrasound

Contrast-enhanced plane-wave ultrasound imaging of the rat eye

Preclinical imaging, especially of rodent models, plays a major role in experimental ophthalmology. Our aim was to determine if ultrasound can be used to visualize and measure flow dynamics in the retrobulbar vessels supplying and draining the eye and the potential of contrast microbubbles to provide image and measurement enhancement. To accomplish this, we used a 128-element, 18 MHz linear array ultrasound probe and performed plane-wave imaging of the eyes of Sprague Dawley rats. Compound images were acquired by emitting unfocused wavefronts at multiple angles and combining echo data from all angles to form individual B-scans. Multiple imaging sequences were utilized, compounding up to six angles, with imaging rate of up to 3000 compound B-scans per second and sequence durations from 1.5 to 180 s. Data were acquired before and after intravenous introduction of contrast microbubbles. We found the total power of the Doppler signal in the image plane to increase approximately 20 fold after injection of contrast, followed by an exponential decay to baseline in about 90 s, The best-fit time constant of the decay averaged 41 s. While major vessels and the retinal/choroidal complex were evident pre-contrast, they were dramatically enhanced with contrast present, with details such as choroidal arterioles seen only with contrast. Ocular arteriovenous transit time determined from comparative enhancement curves in arteries and veins was approximately 0.2 s. In conclusion, plane wave ultrasound, especially with enhancement by contrast microbubbles, offers a means for the study of ocular hemodynamics using the rat eye as a model.

Ultrasound-Responsive Conversion of Microbubbles to Nanoparticles to Enable Background-Free in Vivo Photoacoustic Imaging

Photoacoustic (PA) imaging based on the photon-to-ultrasound conversion allows the imaging of optical absorbers in deep tissues with high spatial resolution. However, the inherent optical absorbance of biomolecules (e.g., hemoglobin, melanin, etc.) would show up as tissue background signals to interfere with signals from the contrast agent during in vivo PA imaging, limiting the imaging sensitivity. Herein, an ultrasound (US)-responsive PA imaging probe based on microbubbles (MBs) containing gold nanoparticles (Au NPs) is designed for in vivo "background-free" PA imaging. The obtained Au@lip MBs with separated Au NPs decorated within the lipid shell of MBs show low PA signals under near-infrared (NIR) excitation. Interestingly, under exposure to US pulses, those Au@lip MBs would burst to form nanoscale aggregates of Au@lip NPs, which exhibit significantly enhanced NIR PA signals due to their red-shifted surface plasmon resonance. Therefore, by subtracting the PA image captured pre-US burst from that captured post-US burst, the tissue background PA signals could be deducted to enable background-free PA imaging with high sensitivities as demonstrated by multiple ex vivo and in vivo experiments. This work presents a simple yet effective strategy to deduct background signals during PA imaging, which is promising for accurate PA detection of targets in tissues with a strong background.

Contrast-enhanced ultrasound imaging using pulse inversion spectral deconvolution

A contrast-enhanced ultrasound (CEUS) imaging approach, termed pulse inversion spectral deconvolution (PISD), is introduced. The approach uses two Gaussian-weighted Hermite polynomials to form two inverted pulse sequences. The two inversed pulses are then used to filter ultrasound (US) backscattered data and discrimination of the linear and nonlinear signal components. A research US scanner equipped with a linear array transducer was used for data acquisition. The receive data from all channels are shaped using plane wave imaging beamforming with angular compounding (from one to nine angles). In vitro data was collected with a tissue mimicking flow phantom perfused with an US contrast agent using PISD and traditional nonlinear (NLI) US imaging as comparison. The role of imaging frequency (between 4.5 and 6.25 MHz) and mechanical index (from 0.1 to 0.3) were evaluated. Preliminary in vivo data was collected in the hindlimb of three healthy mice. Preliminary experimental findings indicate that the PISD contrast-to-tissue ratio was improved nearly ten times compared to the NLI US imaging approach. Also, the spatial resolution was improved due to the effect of deconvolution and spatial angular compounding. Overall, PISD is a promising postprocessing technique for real-time CEUS imaging.

Glyco-functionalised quantum dots and their progress in cancer diagnosis and treatment

Despite all major breakthroughs in recent years of research, we are still unsuccessful to effectively diagnose and treat cancer that has express and metastasizes. Thus, the development of a novel approach for cancer detection and treatment is crucial. Recent progress in Glyconanotechnology has allowed the use of glycans and lectins as bio-functional molecules for many biological and biomedical applications. With the known advantages of quantum dots (QDs) and versatility of carbohydrates and lectins, Glyco-functionalised QD is a new prospect in constructing biomedical imaging platform for cancer behaviour study as well as treatment. In this review, we aim to describe the current utilisation of Glyco-functionalised QDs as well as their future prospective to interpret and confront cancer.

Engineered 3D Microvascular Networks for the Study of Ultrasound-Microbubble-Mediated Drug Delivery

Localized and targeted drug delivery can be achieved by the combined action of ultrasound and microbubbles on the tumor microenvironment, likely through sonoporation and other therapeutic mechanisms that are not well understood. Here, we present a perfusable in vitro model with a realistic 3D geometry to study the interactions between microbubbles and the vascular endothelium in the presence of ultrasound. Specifically, a three-dimensional, endothelial-cell-seeded in vitro microvascular model was perfused with cell culture medium and microbubbles while being sonicated by a single-element 1 MHz focused transducer. This setup mimics the in vivo scenario in which ultrasound induces a therapeutic effect in the tumor vasculature in the presence of flow. Fluorescence and bright-field microscopy were employed to assess the microbubble-vessel interactions and the extent of drug delivery and cell death both in real time during treatment as well as after treatment. Propidium iodide was used as the model drug while calcein AM was used to evaluate cell viability. There were two acoustic parameter sets chosen for this work: (1) acoustic pressure: 1.4 MPa, pulse length: 500 cycles, duty cycle: 5% and (2) acoustic pressure: 0.4 MPa, pulse length: 1000 cycles, duty cycle: 20%. Enhanced drug delivery and cell death were observed in both cases while the higher pressure setting had a more pronounced effect. By introducing physiological flow to the in vitro microvascular model and examining the PECAM-1 expression of the endothelial cells within it, we demonstrated that our model is a good mimic of the in vivo vasculature and is therefore a viable platform to provide mechanistic insights into ultrasound-mediated drug delivery.

A systematic review of diagnostic techniques to determine tissue perfusion in patients with peripheral arterial disease

Introduction: Peripheral arterial disease (PAD) may cause symptoms due to impaired tissue perfusion of the lower extremity. So far, assessment of PAD is mainly performed by determination of stenosis or occlusion in the large arteries and does not focus on microcirculation. Several diagnostic techniques have been recently introduced that may enable tissue perfusion measurements in the lower limb; however, most have not yet been implemented in clinical daily practice. This systematic review provides an overview of these diagnostic techniques and their ability to accurately detect PAD by peripheral tissue perfusion. Areas covered: A literature search was performed for articles that described a diagnostic technique to determine tissue perfusion in patients with known PAD compared with healthy controls. Expert opinion: So far, transcutaneous oxygen measurements are most often used to measure tissue oxygenation in PAD patients, but evidence seems too low to define this technique as a gold standard, and implementing this technique for home monitoring is difficult. New potentially suitable diagnostic tests should be non-invasive, contact-free, and quick. Further research is needed for all of these techniques before broad implementation in clinical use is justified, in hospital, and for home monitoring.

A mathematical model of sonoporation using a liquid-crystalline shelled microbubble

In recent years there has been a great deal of interest in using thin shelled microbubbles as a transportation mechanism for localised drug delivery, particularly for the treatment of various types of cancer. The technique used for such site-specific drug delivery is sonoporation. Despite there being numerous experimental studies on sonoporation, the mathematical modelling of this technique has still not been extensively researched. Presently there exists a very small body of work that models both hemispherical and spherical shelled microbubbles sonoporating due to acoustic microstreaming. Acoustic microstreaming is believed to be the dominant mechanism for sonoporation via shelled microbubbles. Rather than considering the shell of the microbubble to be composed of a thin protein, which is typical in the literature, in this paper we consider the shell to be a liquid-crystalline material. Up until now there have been no studies reported in the literature pertaining to sonoporation of a liquid-crystalline shelled microbubble. A mathematical expression is derived for the maximum wall shear stress, illustrating its dependency on the shell's various material parameters. A sensitivity analysis is performed for the wall shear stress considering the shell's thickness; its local density; the elastic constant of the liquid-crystalline material; the interfacial surface tension and; the shell's viscoelastic properties. In some cases, our results indicate that a liquid-crystalline shelled microbubble may yield a maximum wall shear stress that is two orders of magnitude greater than the stress generated by commercial shelled microbubbles that are currently in use within the scientific community. In conclusion, our preliminary analysis suggests that using liquid-crystalline shelled microbubbles may significantly enhance the efficiency of site-specific drug delivery.

Evaluation of lymph node metastasis in a rabbit tumor model: correlations between contrast-enhanced ultrasound and pathologic findings

Purpose

The purpose of this study was to evaluate the ability of contrast-enhanced ultrasonography (CEUS) with microbubbles to detect metastatic lymph nodes (LNs) for treatment planning and prognosis.

Methods

For the metastatic LN model, ground VX₂ tumor tissues were injected subcutaneously in 12 rabbits, just below the right hind limb. The rabbits were classified into three groups based on the LN area: group A (n=4, >1.9 cm² ), group B (n=4, 1-1.9 cm² ), and group C (n=4, <1 cm² ). The LNs were monitored on CEUS for 10 seconds after injecting 2.5 mL of microbubbles. The percent area of metastatic LNs was calculated on pathologic images and compared with CEUS images.

Results

In group A, the mean percent area of metastasis was 40.7%±19.4%. In all cases of metastasis, round-shaped perfusion defects were clearly observed in CEUS images. The metastatic areas were strongly correlated with pathologic findings. The mean percent area in group B was 21.5%±14.4%. The CEUS findings showed multiple nodular perfusion defects, clearly revealing the metastatic areas. In group B, the CEUS and pathologic findings were concordant for three of the four cases. The mean percent area in group C was 9.1%±6.4%. However, in this group, CEUS only detected a small perfusion defect in one case.

Conclusion

CEUS has the potential to depict characteristic imaging features of metastatic LNs but still has limitations in early detection.

Investigation of Microbubble Detection Methods for Super-Resolution Imaging of Microvasculature

Ultrasound super-resolution techniques use the response of microbubble (MB) contrast agents to visualize the microvasculature. Techniques that localize isolated bubble signals first require detection algorithms to separate the MB and tissue responses. This work explores the three main MB detection techniques for super-resolution of microvasculature. Pulse inversion (PI), differential imaging (DI), and singular value decomposition (SVD) filtering were compared in terms of the localization accuracy, precision, and contrast-to-tissue ratio. MB responses were simulated based on the properties of Sonovue and using the Marmottant model. Nonlinear propagation through tissue was modeled using the k-Wave software package. For the parameters studied, the results show that PI is most appropriate for low frequency applications, but also most dependent on transducer bandwidth. SVD is preferable for high frequency acquisition where localization precision on the order of a few microns is possible. PI is largely independent of flow direction and speed compared to SVD and DI, so is appropriate for visualizing the slowest flows and tortuous vasculature. SVD is unsuitable for stationary MBs and can introduce a localization error on the order of hundreds of microns over the speed range 0-2 mm/s and flow directions from lateral (parallel to probe) to axial (perpendicular to probe). DI is only suitable for flow rates >0.5 mm/s or as flow becomes more axial. Overall, this study develops an MB and tissue nonlinear simulation platform to improve understanding of how different MB detection techniques can impact the super-resolution process and explores some of the factors influencing the suitability of each.

Ultrasound-activated microbubbles as a novel intracellular drug delivery system for urinary tract infection

The development of new modalities for high-efficiency intracellular drug delivery is a priority for a number of disease areas. One such area is urinary tract infection (UTI), which is one of the most common infectious diseases globally and which imposes an immense economic and healthcare burden. Common uropathogenic bacteria have been shown to invade the urothelial wall during acute UTI, forming latent intracellular reservoirs that can evade antimicrobials and the immune response. This behaviour likely facilitates the high recurrence rates after oral antibiotic treatments, which are not able to penetrate the bladder wall and accumulate to an effective concentration. Meanwhile, oral antibiotics may also exacerbate antimicrobial resistance and cause systemic side effects. Using a human urothelial organoid model, we tested the ability of novel ultrasound-activated lipid microbubbles to deliver drugs into the cytoplasm of apical cells. The gas-filled lipid microbubbles were decorated with liposomes containing the non-cell-permeant antibiotic gentamicin and a fluorescent marker. The microbubble suspension was added to buffer at the apical surface of the bladder model before being exposed to ultrasound (1.1 MHz, 2.5 Mpa, 5500 cycles at 20 ms pulse duration) for 20 s. Our results show that ultrasound-activated intracellular delivery using microbubbles was over 16 times greater than the control group and twice that achieved by liposomes that were not associated with microbubbles. Moreover, no cell damage was detected. Together, our data show that ultrasound-activated microbubbles can safely deliver high concentrations of drugs into urothelial cells, and have the potential to be a more efficacious alternative to traditional oral antibiotic regimes for UTI. This modality of intracellular drug delivery may prove useful in other clinical indications, such as cancer and gene therapy, where such penetration would aid in treatment.

Contrast-enhanced ultrasound (CEUS) in pediatric blunt abdominal trauma

Baseline ultrasound is the first-choice technique in traumatic hemodynamically stable children, and is essential in the early assessment of unstable patients to detect hemoperitoneum or other potentially fatal conditions. Despite the technological advancements in new ultrasound equipment and the experience of the operators, it is not always possible to rule out the presence of parenchymal traumatic lesions by means of baseline ultrasound nor to suspect them, especially in the absence of hemoperitoneum. For this reason, in the last decades, basic ultrasound has been associated with contrast-enhanced ultrasound (CEUS) to evaluate the stable little patient in cases such as low-energy blunt abdominal trauma. Because it relies on second-generation contrast agents, the CEUS technique allows for better detection of parenchymal injuries. CEUS has been demonstrated to be almost as sensitive as contrast-enhanced CT in the detection of traumatic injuries in patients affected by low-energy isolated abdominal trauma, with levels of sensitivity and specificity up to 95%. A very important point in favor of CEUS is its capacity to help distinguish the healthy patient, who can be discharged, from the one needing prolonged monitoring, operative management or hospitalization. Finally, we also have the ability to follow-up on low-grade traumatic lesions using CEUS, always keeping in mind patients' clinical conditions and their hemodynamics.

Multicolor nanobubbles for FRET/ultrasound dual-modal contrast imaging

The aim of this paper is to develop a novel fluorescence/ultrasound dual-modal contrast agent. We prepared multicolor nanobubbles by doping with three fluorescent dyes for combined fluorescence and contrast enhanced ultrasound imaging. The nanobubbles based on fluorescence resonance energy transfer (FRET) with different doping dye ratio combinations exhibited multiple colors under single wavelength excitation, allowing multiplexed assays for various biomedical applications. In vitro and in vivo ultrasound imaging indicated that nanobubbles have great contrast enhancement capability. In vivo fluorescence imaging showed the excellent ability to provide simultaneous multicolor imaging. The novel multicolor nanobubbles may have great potential for a variety of applications in the study of life science and clinical medicine.

Engineering molecular imaging strategies for regenerative medicine

The reshaping of the world's aging population has created an urgent need for therapies for chronic diseases. Regenerative medicine offers a ray of hope, and its complex solutions include material, cellular, or tissue systems. We review basics of regenerative medicine/stem cells and describe how the field of molecular imaging, which is based on quantitative, noninvasive, imaging of biological events in living subjects, can be applied to regenerative medicine in order to interrogate tissues in innovative, informative, and personalized ways. We consider aspects of regenerative medicine for which molecular imaging will benefit. Next, genetic and nanoparticle-based cell imaging strategies are discussed in detail, with modalities like magnetic resonance imaging, optical imaging (near infra-red, bioluminescence), raman microscopy, and photoacoustic microscopy), ultrasound, computed tomography, single-photon computed tomography, and positron emission tomography. We conclude with a discussion of "next generation" molecular imaging strategies, including imaging host tissues prior to cell/tissue transplantation.

Current and Future Approaches for Effective Cancer Imaging and Treatment

Cancer poses a major health problem, not only due to cancer-related deaths but also because of treatment toxicities. This review discusses early diagnosis and strategies to overcome treatment difficulties, to facilitate recovery, and prevent deaths. Generally, noninvasive techniques such as computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and positron emission computed tomography (PET), and their hybrid systems, including SPECT/CT, PET/CT, and PET/MRI, are used in diagnosis of cancer. Cancer treatment in clinics still comprises conventional methods such as chemotherapy, radiotherapy, and surgery. However, these techniques and methods are often inadequate. Therefore, new approaches, including the formulation of actively and/or passively targeted nanosized drug delivery systems and combined treatment protocols, are being investigated. In this article, conventional cancer imaging and treatment are reviewed. In addition, the formulation of nanosized systems and their use in cancer treatment are discussed and combined diagnostic and therapeutic (theranostic) approach are proposed as additional cancer therapies.

Use of Contrast-Enhanced Ultrasound in the Assessment of Uterine Fibroids: A Feasibility Study

Contrast-enhanced ultrasound (CEUS) is an innovative ultrasound technique capable of visualizing both the macro- and microvasculature of tissues. In this prospective pilot study, we evaluated the feasibility of using CEUS to visualize the microvasculature of uterine fibroids and compared CEUS with conventional ultrasound. Four women with fibroids underwent gray-scale ultrasound, sonoelastography and power/color Doppler scans followed by CEUS examination. Analysis of CEUS images revealed initial perfusion of the peripheral rim, that is, a pseudo-capsule, followed by enhancement of the entire lesion through vessels traveling from the exterior to the interior of the fibroid. The pseudo-capsules exhibited slight hyper-enhancement, making a clear delineation of the fibroids possible. The centers of three fibroids exhibited areas lacking vascularization, information not obtainable with the other imaging techniques. CEUS is a feasible technique for imaging and quantifying the microvasculature of fibroids. In comparison with conventional ultrasound imaging modalities, CEUS can provide additional diagnostic information based on the microvasculature.

Contrast-enhanced ultrasound measurement of pancreatic blood flow dynamics predicts type 1 diabetes progression in preclinical models

In type 1 diabetes (T1D), immune-cell infiltration into the islets of Langerhans (insulitis) and β-cell decline occurs many years before diabetes clinically presents. Non-invasively detecting insulitis and β-cell decline would allow the diagnosis of eventual diabetes, and provide a means to monitor therapeutic intervention. However, there is a lack of validated clinical approaches for specifically and non-invasively imaging disease progression leading to T1D. Islets have a denser microvasculature that reorganizes during diabetes. Here we apply contrast-enhanced ultrasound measurements of pancreatic blood-flow dynamics to non-invasively and predictively assess disease progression in T1D pre-clinical models. STZ-treated mice, NOD mice, and adoptive-transfer mice demonstrate altered islet blood-flow dynamics prior to diabetes onset, consistent with islet microvasculature reorganization. These assessments predict both time to diabetes onset and future responders to antiCD4-mediated disease prevention. Thus contrast-enhanced ultrasound measurements of pancreas blood-flow dynamics may provide a clinically deployable predictive marker for disease progression in pre-symptomatic T1D and therapeutic reversal.

On-chip generation of microbubbles in photoacoustic contrast agents for dual modal ultrasound/photoacoustic in vivo animal imaging

Dual-modal photoacoustic (PA) and ultrasound (US) contrast agents are becoming increasingly popular in recent years. Here, a flow-focusing junction based microfluidic device is used for the generation of nitrogen microbubbles (<7 μm) in two photoacoustic contrast agents: methylene blue (MB) and black ink (BI). The microbubble diameter and production rate could be precisely controlled in both MB and BI solutions. Microbubbles were collected from the outlet of the microfluidic device and optical microscope was used to study the size distributions in both solutions. Next, the microbubbles in both solutions were injected into tubes for phantom imaging experiments. Signal to noise ratio (SNR) of both US, PA imaging experiments were calculated to be 51 dB, 58 dB in MB + microbubbles and 56 dB, 61 dB in BI + microbubbles, respectively. Finally, the microbubbles were injected into the urinary bladder of rats for in vivo animal imaging. The SNR in US imaging with MB + microbubbles and BI + microbubbles were 41 dB and 48 dB, respectively. Similarly, the SNR in PA imaging with the same solutions were 32 dB and 36 dB, respectively. The effect of size and concentration of microbubbles in both MB and BI solutions, on the US and PA signals, has been examined.

Ultrasound-Mediated Microbubble Destruction Suppresses Melanoma Tumor Growth

Melanoma is one of the most aggressive types of cancer, and its incidence has increased rapidly in the past few decades. In this study, we investigated a novel treatment approach, the use of low-intensity ultrasound (2.3 W/cm² at 1 MHz)-mediated Optison microbubble (MB) destruction (UMMD) to treat melanoma in a flank tumor model. The effect of UMMD was first evaluated in the melanoma cell line B16 F10 (B16) in vitro and then in mice inoculated with B16 cells. MB⁺B16 cells were exposed to US in vitro, resulting in significant cell death proportional to duty cycle (R² = 0.74): approximately 30%, 50%, 80% and 80% cell death at 10%, 30%, 50% and 100% DC respectively. Direct implantation of tumors with MBs, followed by sonication, resulted in retarded tumor growth and improved survival (p = 0.0106). Immunohistochemical analyses confirmed the significant changes in expression of the cell proliferation marker Ki67 (p = 0.037) and a microtubule-associated protein 2 (p = 0.048) after US + MB treatment. These results suggest that UMMD could be used as a possible treatment approach in isolated melanoma and has the potential to translate to clinical trials.

Porphyrin-Loaded Pluronic Nanobubbles: A New US-Activated Agent for Future Theranostic Applications

Sonodynamic therapy (SDT) has become a promising noninvasive approach for cancer therapy. The treatment exploits the ability of particular molecules (i.e., porphyrins) to be excited by ultrasound and produce reactive oxygen species (ROS) during their decay process. These reactive species, in turn, result in cell death. To capitalize on the real-time visualization and on-demand delivery of ultrasound contrast agents, this study aims to combine porphyrins with nanobubbles (NBs) to obtain an ultrasound-activated theranostic agent that exploits the SDT activity in vitro. Two porphyrin classes, exposing different hydrophobic side chains, were synthesized. NB size and encapsulation efficiency were markedly dependent on the porphyrin structure. The combination of these porphyrin and NBs resulted in a significant reduction in cell viability upon sonication in pilot studies performed on the LS 174T colorectal cancer cell line.

Effects of pH on nano-bubble stability and transport in saturated porous media

An understanding of nano-scale bubble (NB) transport in porous media is important for potential application of NBs in soil/groundwater remediation. It is expected that the solution chemistry of NB water highly influences the surface characteristics of NBs and porous media and the interaction between them, thus affecting the stability and transport characteristics of NB. In this study, in addition to stability experiments, one-dimensional column transport experiments using glass beads were conducted to investigate the effects of pH on the NB transport behavior. The results showed that the NBs were more stable under higher pH. Column transport experiments revealed that entrapment of NBs, especially larger ones, was enhanced in lower-pH water, likely suggesting pH-dependent NB attachment and physical straining, both of which are also probably influenced by bubble size. Although relatively smaller NBs were released after switching the eluting fluid to one with lower ionic strength, most of the NBs in lower-pH water were still retained in the porous media even altering the chemical condition.

Diagnostic Accuracy of Hepatic Vein Arrival Time Performed with Contrast-Enhanced Ultrasonography for Cirrhosis: A Systematic Review and Meta-Analysis

Background/Aims

We identified reports in the literature regarding the diagnostic accuracy of hepatic vein arrival time (HVAT) measured by contrast-enhanced ultrasonography (CEUS) to assess hepatic fibrosis in cirrhosis.

Methods

The Ovid MEDLINE, Embase, and Cochrane databases were searched for all studies published up to 23 July 2015 that evaluated liver status using CEUS and liver biopsy (LB). The QUADAS-II (quality assessment of diagnostic accuracy studies-II) was applied to assess the internal validity of the diagnostic studies. Selected studies were subjected to a meta-analysis with MetaDisc 1.4 and RevMan 5.3.

Results

A total of 12 studies including 844 patients with chronic liver disease met our inclusion criteria. The overall summary sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of the HVAT measured by CEUS for the detection of cirrhosis compared to LB were 0.83 (95% confidence interval [CI], 0.77 to 0.89), 0.75 (95% CI, 0.69 to 0.79), 3.45 (95% CI, 1.60 to 7.43), and 0.28 (95% CI, 0.10 to 0.74), respectively. The summary diagnostic odds ratio (random effects model) was 15.23 (95% CI, 3.07 to 75.47), the summary receiver operator characteristics area under the curve was 0.74 (standard error [SE]=0.14), and the index Q was 0.69 (SE=0.11).

Conclusions

Based on a systematic review, the measurement of HVAT by CEUS exhibited an increased accuracy and correlation for the detection of cirrhosis.

Honey, I shrunk the bubbles: microfluidic vacuum shrinkage of lipid-stabilized microbubbles

We present a microfluidic technique that shrinks lipid-stabilized microbubbles from O(100) to O(1) μm in diameter - the size that is desirable in applications as ultrasound contrast agents. We achieve microbubble shrinkage by utilizing vacuum channels that are adjacent to the microfluidic flow channels to extract air from the microbubbles. We tune a single parameter, the vacuum pressure, to accurately control the final microbubble size. Finally, we demonstrate that the resulting O(1) μm diameter microbubbles have similar stability to microfluidically generated microbubbles that are not exposed to vacuum shrinkage. We anticipate that, with additional scale-up, this simple approach to shrink microbubbles generated microfluidically will be desirable in ultrasound imaging and therapeutic applications.

Microbubbles used for contrast enhanced ultrasound and theragnosis: a review of principles to applications

Ultrasound was developed several decades ago as a useful imaging modality, and it became the second most popular diagnostic tool due to its non-invasiveness, real-time capabilities, and safety. Additionally, ultrasound has been used as a therapeutic tool with several therapeutic agents and in nanomedicine. Ultrasound imaging is often used to diagnose many types of cancers, including breast, stomach, and thyroid cancers. In addition, ultrasound-mediated therapy is used in cases of joint inflammation, rheumatoid arthritis, and osteoarthritis. Microbubbles, when used as ultrasound contrast agents, can act as echo-enhancers and therapeutic agents, and they can play an essential role in ultrasound imaging and ultrasound-mediated therapy. Recently, various types of ultrasound contrast agents made of lipid, polymer, and protein shells have been used. Air, nitrogen, and perfluorocarbon are usually included in the core of the microbubbles to enhance ultrasound imaging, and therapeutic drugs are conjugated and loaded onto the surface or into the core of the microbubbles, depending on the purpose and properties of the substance. Many research groups have utilized ultrasound contrast agents to enhance the imaging signal in blood vessels or tissues and to overcome the blood-brain barrier or blood-retina barrier. These agents are also used to help treat diseases in various regions or systems of the body, such as the cardiovascular system, or as a cancer treatment. In addition, with the introduction of targeted moiety and multiple functional groups, ultrasound contrast agents are expected to have a potential future in ultrasound imaging and therapy. In this paper, we briefly review the principles of ultrasound and introduce the underlying theory, applications, limitations, and future perspectives of ultrasound contrast agents.

Fabrication of ultrasound-responsive microbubbles via coaxial electrohydrodynamic atomization for triggered release of tPA

A single-step fabrication method, coaxial electrohydrodynamic atomization (CEHDA), was developed to synthesize drug-loaded microbubbles (MBs) for combination treatment of ischemic stroke. The bioactivity of therapeutic agent (tPA, tissue plasminogen activator) after preparation was evaluated, showing that CEHDA could be very promising method for producing MBs with therapeutic functions. The bubble performance and tPA release profiles were also examined by exposing the bubbles to 2MHz ultrasound of various intensities. The results showed that the mean diameter of tPA-loaded MBs was found to fluctuate about its original diameter when exposed to ultrasound and higher intensity ultrasound was more effective in triggering the burst of CEHDA MBs. High ultrasound-triggered bubble disintegration effectiveness in a short period (first 5min) fits well with the requirement of short ultrasound exposure time for human brain. Moreover, a numerical model was also applied to investigate the stability of the fabricated MBs in the bloodstream. It was found that MB dissolution time increased with initial radius, decreased with initial surface tension and increased with initial shell resistance but it was barely affected by the average excessive bloodstream pressure.

Contrast-Enhanced Ultrasound Reveals Exercise-Induced Perfusion Deficits in Claudicants

Background

Contrast-Enhanced Ultrasonography (CEUS) is an imaging modality allowing perfusion quantification in targeted regions of interest of the lower extremity that has not been possible with color-flow imaging or with measurement of ankle brachial indices. We developed a protocol to quantify lower extremity muscle perfusion impairment in PAD patients in response to exercise.

Methods and findings

Thirteen patients with Rutherford Class I-III Peripheral Arterial Disease (PAD) and no prior revascularization procedures were recruited from the Baltimore Veterans Affairs Medical Center and compared with eight control patients without PAD. CEUS interrogation of the index limb gastrocnemius muscle was performed using an intravenous bolus of lipid-stabilized microsphere contrast before and after a standardized treadmill protocol. Peak perfusion (PEAK) and time to peak perfusion (TTP) were measured before and after exercise. Between and within group differences were assessed. Control subjects demonstrated a more rapid TTP (p<0.01) and an increase in peak perfusion (PEAK, p=0.02) after exercise, when compared to their baseline measures. Patients with PAD demonstrated TTP and PEAK measures equivalent to controls at baseline (p=0.39, p=0.71, respectively). However, they exhibited no significant exercise-induced changes in perfusion (TTP p=0.49 and PEAK 0.67, respectively compared to baseline). After exercise, normal subjects had significantly shorter TTP (p=0.04) and greater PEAK (p=0.02) than PAD patients.

Conclusion

Consistent with their lack of ischemic symptoms at rest, class I to III claudicant PAD patients showed similar perfusion measures (TTP and PEAK) at rest. PAD patients, however, were unable to increase perfusion in response to exercise, whereas controls increased perfusion significantly. This corresponds with claudication and limited walking capacity observed in PAD. CEUS with bolus injection offers a convenient, objective, quantitative and visual physiologic assessment of perfusion limitation in specific muscle groups of PAD patients. This has the potential for substantial clinical and research utility.

Effect of acoustic parameters on the cavitation behavior of SonoVue microbubbles induced by pulsed ultrasound

SonoVue microbubbles could serve as artificial nuclei for ultrasound-triggered stable and inertial cavitation, resulting in beneficial biological effects for future therapeutic applications. To optimize and control the use of the cavitation of SonoVue bubbles in therapy while ensuring safety, it is important to comprehensively understand the relationship between the acoustic parameters and the cavitation behavior of the SonoVue bubbles. An agarose-gel tissue phantom was fabricated to hold the SonoVue bubble suspension. 1-MHz transmitting transducer calibrated by a hydrophone was used to trigger the cavitation of SonoVue bubbles under different ultrasonic parameters (i.e., peak rarefactional pressure (PRP), pulse repetition frequency (PRF), and pulse duration (PD)). Another 7.5-MHz focused transducer was employed to passively receive acoustic signals from the exposed bubbles. The ultraharmonics and broadband intensities in the acoustic emission spectra were measured to quantify the extent of stable and inertial cavitation of SonoVue bubbles, respectively. We found that the onset of both stable and inertial cavitation exhibited a strong dependence on the PRP and PD and a relatively weak dependence on the PRF. Approximate 0.25MPa PRP with more than 20μs PD was considered to be necessary for ultraharmonics emission of SonoVue bubbles, and obvious broadband signals started to appear when the PRP exceeded 0.40MPa. Moreover, the doses of stable and inertial cavitation varied with the PRP. The stable cavitation dose initially increased with increasing PRP, and then decreased rapidly after 0.5MPa. By contrast, the inertial cavitation dose continuously increased with increasing PRP. Finally, the doses of both stable and inertial cavitation were positively correlated with PRF and PD. These results could provide instructive information for optimizing future therapeutic applications of SonoVue bubbles.

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically-heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced.

Energy-triggered drug release from polymer nanoparticles for orthopedic applications

Sequestra, present in many cancers and orthopedic infections, provide a safe harbor for the development of drug resistance. In the face of burgeoning drug resistance, the importance of nanoscale, microenvironment-triggered drug delivery cannot be overestimated. Such strategies may preserve pharmaceutical efficacy and significantly alter the etiology of many orthopedic diseases. Although temperature-, pH- and redox-responsive nanoparticle-based systems have been extensively studied, local drug delivery from polymeric nanoparticles can be triggered by a variety of energy forms. This review offers an overview of the state of the field as well as a perspective on the safety and efficacy of ultrasound, hyperthermia and radio frequency-triggered internal delivery systems in a variety of applications.

Superhydrophobic Cones for Continuous Collection and Directional Transportation of CO2 Microbubbles in CO2 Supersaturated Solutions

Microbubbles are tiny bubbles with diameters below 50 μm. Because of their minute buoyant force, the microbubbles stagnate in aqueous media for a long time, and they sometimes cause serious damage. Most traditional methods chosen for elimination of gas bubbles utilize buoyancy forces including chemical methods and physical methods, and they only have a minor effect on microbubbles. Several approaches have been developed to collect and transport microbubbles in aqueous media. However, the realization of innovative strategies to directly collect and transport microbubbles in aqueous media remains a big challenge. In nature, both spider silk and cactus spines take advantage of their conical-shaped surface to yield the gradient of Laplace pressure and surface free energy for collecting fog droplets from the environment. Inspired by this, we introduce here the gradient of Laplace pressure and surface free energy to the interface of superhydrophobic copper cones (SCCs), which can continuously collect and directionally transport CO₂ microbubbles (from tip side to base side) in CO₂-supersaturated solution. A gas layer was formed when the microbubbles encounter the SCCs. This offers a channel for microbubble directional transportation. The efficiency of microbubble transport is significantly affected by the apex angle of SCCs and the carbon dioxide concentration. The former provides different gradients of Laplace pressure as the driving force. The latter represents the capacity, which offers the quantity of CO₂ microbubbles for collection and transportation. We believe that this approach provides a simple and valid way to remove microbubbles.

High-Resolution US of Rheumatologic Diseases

For the past 15 years, high-resolution ultrasonography (US) is being routinely and increasingly used for initial evaluation and treatment follow-up of rheumatologic diseases. This imaging technique is performed by using high-frequency linear transducers and has proved to be a powerful diagnostic tool in evaluation of articular erosions, simple and complex joint and bursal effusions, tendon sheath effusions, and synovitis, with results comparable to those of magnetic resonance imaging, excluding detection of bone marrow edema. Crystal deposition diseases including gouty arthropathy and calcium pyrophosphate deposition disease (CPPD) have characteristic appearances at US, enabling differentiation between these two diseases and from inflammatory arthropathies. Enthesopathy, which frequently accompanies psoriatic and reactive arthritis, also has a characteristic appearance at high-resolution US, distinguishing these two entities from other inflammatory and metabolic arthropathies. The presence of Doppler signal in examined joints, bursae, and tendon sheaths indicates active synovitis. Microbubble echo contrast agents augment detection of tissue vascularity and may act in the future as a drug delivery vehicle. Frequently, joint, tendon sheath, and bursal fluid aspirations and therapeutic injections are performed under US guidance. The authors describe the high-resolution US technique including gray-scale, color or power Doppler, and contrast agent-enhanced US that is used in evaluation of rheumatologic diseases of the wrist and hand and the ankle and foot in their routine clinical practice. This article demonstrates imaging findings of normal joints, rheumatoid arthritis, gouty arthritis, CPPD, psoriatic and reactive arthritis, and osteoarthritis.

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), CuS nanoparticles, DNA, siRNA, 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.

Preliminary Analysis of Clinical Situations Involved in Quantification of Contrast-Enhanced Ultrasound in Crohn's Disease

To assess influencing factors for quantitative analysis of contrast-enhanced ultrasound (CEUS) in Crohn's disease (CD), dynamic CEUS examinations from 77 consecutive CD patients were recorded. Peak intensity (PI) values were calculated using the pre-installed quantification software of the ultrasound scanner. The influence of depth, pressure from the ultrasound probe and intraluminal gas was analyzed. The PI value of the anterior wall was lower than that of the posterior wall when the depth was ≤3.4 cm (17.9 dB vs. 21.3 dB; p < 0.05) or evident pressure was exerted (19.1 dB vs. 22.5 dB; p < 0.01). In the presence of intraluminal gas, the PI of the anterior wall was higher than that of the posterior wall (20.7 dB vs. 18.8 dB; p < 0.05). Nevertheless, no significant difference was found between the PI value of anterior and posterior walls when the depth was >3.4 cm (19.8 dB vs. 20.3 dB), moderate pressure was exerted (20.5 dB vs. 21.1 dB) or luminal gas was excluded between the two bowel walls (18.9 dB vs. 21.2 dB; p ≥ 0.05). The factors of depth, pressure from the ultrasound probe and intraluminal gas can affect the quantification results of CEUS. It is preferable to place the region of interest in the posterior wall when luminal gas is absent and in the anterior wall when luminal gas is present. In the latter case, more attention should be paid to reducing pressure by the ultrasound probe.

Ultrasound-Guided Delivery of siRNA and a Chemotherapeutic Drug by Using Microbubble Complexes: In Vitro and In Vivo Evaluations in a Prostate Cancer Model

Objective

To evaluate the effectiveness of ultrasound and microbubble-liposome complex (MLC)-mediated delivery of siRNA and doxorubicin into prostate cancer cells and its therapeutic capabilities both in vitro and in vivo.

Materials and Methods

Microbubble-liposome complexes conjugated with anti-human epidermal growth factor receptor type 2 (Her2) antibodies were developed to target human prostate cancer cell lines PC-3 and LNCaP. Intracellular delivery of MLC was observed by confocal microscopy. We loaded MLC with survivin-targeted small interfering RNA (siRNA) and doxorubicin, and delivered it into prostate cancer cells. The release of these agents was facilitated by ultrasound application. Cell viability was analyzed by MTT assay after the delivery of siRNA and doxorubicin. Survivin-targeted siRNA loaded MLC was delivered into the xenograft mouse tumor model. Western blotting was performed to quantify the expression of survivin in vivo.

Results

Confocal microscopy demonstrated substantial intracellular uptake of MLCs in LNCaP, which expresses higher levels of Her2 than PC-3. The viability of LNCaP cells was significantly reduced after the delivery of MLCs loaded with siRNA and doxorubicin (85.0 ± 2.9%), which was further potentiated by application of ultrasound (55.0 ± 3.5%, p = 0.009). Survivin expression was suppressed in vivo in LNCaP tumor xenograft model following the ultrasound and MLC-guided delivery of siRNA (77.4 ± 4.90% to 36.7 ± 1.34%, p = 0.027).

Conclusion

Microbubble-liposome complex can effectively target prostate cancer cells, enabling intracellular delivery of the treatment agents with the use of ultrasound. Ultrasound and MLC-mediated delivery of survivin-targeted siRNA and doxorubicin can induce prostate cell apoptosis and block survivin expression in vitro and in vivo.

Are nanotheranostics and nanodiagnostics-guided drug delivery stepping stones towards precision medicine?

The progress in medical research has led to the understanding that cancer is a large group of heterogeneous diseases, with high variability between and within individuals. This variability sprouted the ambitious goal to improve therapeutic outcomes, while minimizing drug adverse effects through stratification of patients by the differences in their disease markers, in a personalized manner, as opposed to the strategy of "one therapy fits all". Nanotheranostics, composed of nanoparticles (NPs) carrying therapeutic and/or diagnostics probes, have the potential to revolutionize personalized medicine. There are different modalities to combine these two distinct fields into one system for a synergistic outcome. The addition of a nanocarrier to a theranostic system holds great promise. Nanocarriers possess high surface area, enabling sophisticated functionalization with imaging agents, thus gaining enhanced diagnostic ability in real-time. Yet, most of the FDA-approved theranostic approaches are based on small molecules. The theranostic approaches that are reviewed herein are paving the road towards personalized medicine through all stages of patient care: starting from screening and diagnostics, proceeding to treatment and ending with treatment follow-up. Our current review provides a broad background and highlights new insights for the rational design of theranostic nanosystems for desired therapeutic niches, while summoning the hurdles on their way to become first-line diagnostics and therapeutics for cancer patients.

Theragnostic ultrasound using microbubbles in the treatment of prostate cancer

The use of gas-filled microbubbles in perfusion monitoring as intravascular ultrasound contrast agents has recently become more common. Additionally, microbubbles are employed as carriers of pharmaceutical substances or genes. Microbubbles have great potential to improve the delivery of therapeutic materials into cells and to modify vascular permeability, causing increased extravasation of drugs and drug carriers. Prostate cancer is the most common neoplasm in Europe and America, with an incidence twice to three times that of lung and colorectal cancer. Its incidence is still rising in Asian countries, including Japan and Korea. In this review, we present current strategies regarding the synthesis of microbubbles with targeted ligands on their surfaces, with a focus on prostate cancer.

Improving ovarian cancer imaging with LHRH-NBs: an experimental study

Purpose

Our previous study used freeze-drying and biotin–avidin binding methods and obtained nontargeted nanobubbles (N-NBs) and ovarian cancer-targeting nanobubbles (LHRH-NBs, luteinizing hormone-releasing hormone nanobubbles). Our study also identified the physical and chemical properties of these two contrast agents, and validated the targeting ability and underlying mechanisms of LHRH-NBs in vitro. The present study investigated the imaging of N-NBs and LHRH-NBs in nude mice and their binding with tissues.

Methods

The nude mice models of xenografts were divided into three groups, N-NB, LHRH-NB, and SonoVue. These contrast agents were injected via the caudal vein to observe the imaging of ovarian cancer. Fluorescence microscope was used to observe the penetration of N-NBs and LHRH-NBs through the vascular endothelial gaps. Immunofluorescence was used to observe the penetration of N-NBs and LHRH-NBs through vascular endothelial gaps and binding to the tumor cells.

Results

The imaging intensity and duration were not significantly different between N-NBs and LHRH-NBs. The imaging intensity in the N-NB and LHRH-NB groups was not significantly different compared with the SonoVue group; however, the imaging duration in the N-NB and LHRH-NB groups was significantly longer than in the SonoVue group (P < 0.001). Both N-NBs and LHRH-NBs penetrated through the vascular endothelial gaps. After penetrating through the vascular endothelial gapes, LHRH-NBs could target and bind to the tumor cells.

Conclusions

N-NBs and LHRH-NBs are of good imaging effectiveness and relatively long imaging duration. LHRH-NB is a potent contrast agent for imaging ovarian cancer, while achieving targeted delivery of drugs to the site of ovarian cancer.

Diagnostic imaging of blunt abdominal trauma in pediatric patients

Trauma is a leading cause of morbidity and mortality in childhood, and blunt trauma accounts for 80-90 % of abdominal injuries. The mechanism of trauma is quite similar to that of the adults, but there are important physiologic differences between children and adults in this field, such as the smaller blood vessels and the high vasoconstrictive response, leading to the spreading of a non-operative management. The early imaging of children undergoing a low-energy trauma can be performed by CEUS, a valuable diagnostic tool to demonstrate solid organ injuries with almost the same sensitivity of CT scans; nevertheless, as for as urinary tract injuries, MDCT remains still the technique of choice, because of its high sensitivity and accuracy, helping to discriminate between an intra-peritoneal form a retroperitoneal urinary leakage, requiring two different managements. The liver is the most common organ injured in blunt abdominal trauma followed by the spleen. Renal, pancreatic, and bowel injuries are quite rare. In this review we present various imaging findings of blunt abdominal trauma in children.

On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging

Micron-sized lipid-stabilised bubbles of heavy gas have been utilised as contrast agents for diagnostic ultrasound (US) imaging for many years. Typically bubbles between 1 and 8 μm in diameter are produced to enhance imaging in US by scattering sound waves more efficiently than surrounding tissue. A potential area of interest for Contrast Enhanced Ultrasound (CEUS) are bubbles with diameters <1 μm or 'nanobubbles.' As bubble diameter decreases, ultrasonic resonant frequency increases, which could lead to an improvement in resolution for high-frequency imaging applications when using nanobubbles. In addition, current US contrast agents are limited by their size to the vasculature in vivo. However, molecular-targeted nanobubbles could penetrate into the extra-vascular space of cancerous tissue providing contrast in regions inaccessible to traditional microbubbles. This paper reports a new microfluidic method for the generation of sub-micron sized lipid stabilised particles containing perfluorocarbon (PFC). The nanoparticles are produced in a unique atomisation-like flow regime at high production rates, in excess of 10(6) particles per s and at high concentration, typically >10(11) particles per mL. The average particle diameter appears to be around 100-200 nm. These particles, suspected of being a mix of liquid and gaseous C4F10 due to Laplace pressure, then phase convert into nanometer sized bubbles on the application of US. In vitro ultrasound characterisation from these nanoparticle populations showed strong backscattering compared to aqueous filled liposomes of a similar size. The nanoparticles were stable upon injection and gave excellent contrast enhancement when used for in vivo imaging, compared to microbubbles with an equivalent shell composition.

Computational dynamics of acoustically driven microsphere systems

We propose a computational framework for the self-consistent dynamics of a microsphere system driven by a pulsed acoustic field in an ideal fluid. Our framework combines a molecular dynamics integrator describing the dynamics of the microsphere system with a time-dependent integral equation solver for the acoustic field that makes use of fields represented as surface expansions in spherical harmonic basis functions. The presented approach allows us to describe the interparticle interaction induced by the field as well as the dynamics of trapping in counter-propagating acoustic pulses. The integral equation formulation leads to equations of motion for the microspheres describing the effect of nondissipative drag forces. We show (1) that the field-induced interactions between the microspheres give rise to effective dipolar interactions, with effective dipoles defined by their velocities and (2) that the dominant effect of an ultrasound pulse through a cloud of microspheres gives rise mainly to a translation of the system, though we also observe both expansion and contraction of the cloud determined by the initial system geometry.

Contrast-enhanced ultrasound (CEUS) in blunt abdominal trauma

Baseline ultrasound is essential in the early assessment of patients with a huge haemoperitoneum undergoing an immediate abdominal surgery; nevertheless, even with a highly experienced operator, it is not sufficient to exclude parenchymal injuries. More recently, a new ultrasound technique using second generation contrast agents, named contrast-enhanced ultrasound (CEUS) has been developed. This technique allows all the vascular phase to be performed in real time, increasing ultrasound capability to detect parenchymal injuries, enhancing some qualitative findings, such as lesion extension, margins and its relationship with capsule and vessels. CEUS has been demonstrated to be almost as sensitive as contrast-enhanced CT in the detection of traumatic injuries in patients with low-energy isolated abdominal trauma, with levels of sensitivity and specificity up to 95%. Several studies demonstrated its ability to detect lesions occurring in the liver, spleen, pancreas and kidneys and also to recognize active bleeding as hyperechoic bands appearing as round or oval spots of variable size. Its role seems to be really relevant in paediatric patients, thus avoiding a routine exposure to ionizing radiation. Nevertheless, CEUS is strongly operator dependent, and it has some limitations, such as the cost of contrast media, lack of panoramicity, the difficulty to explore some deep regions and the poor ability to detect injuries to the urinary tract. On the other hand, it is timesaving, and it has several advantages, such as its portability, the safety of contrast agent, the lack to ionizing radiation exposure and therefore its repeatability, which allows follow-up of those traumas managed conservatively, especially in cases of fertile females and paediatric patients.

Drug Delivery Systems for Imaging and Therapy of Parkinson's Disease

BACKGROUND

Although a variety of therapeutic approaches are available for the treatment of Parkinson's disease, challenges limit effective therapy. Among these challenges are delivery of drugs through the blood brain barier to the target brain tissue and the side effects observed during long term administration of antiparkinsonian drugs. The use of drug delivery systems such as liposomes, niosomes, micelles, nanoparticles, nanocapsules, gold nanoparticles, microspheres, microcapsules, nanobubbles, microbubbles and dendrimers is being investigated for diagnosis and therapy.

METHODS

This review focuses on formulation, development and advantages of nanosized drug delivery systems which can penetrate the central nervous system for the therapy and/or diagnosis of PD, and highlights future nanotechnological approaches.

RESULTS

It is esential to deliver a sufficient amount of either therapeutic or radiocontrast agents to the brain in order to provide the best possible efficacy or imaging without undesired degradation of the agent. Current treatments focus on motor symptoms, but these treatments generally do not deal with modifying the course of Parkinson's disease. Beyond pharmacological therapy, the identification of abnormal proteins such as α -synuclein, parkin or leucine-rich repeat serine/threonine protein kinase 2 could represent promising alternative targets for molecular imaging and therapy of Parkinson's disease.

CONCLUSION

Nanotechnology and nanosized drug delivery systems are being investigated intensely and could have potential effect for Parkinson's disease. The improvement of drug delivery systems could dramatically enhance the effectiveness of Parkinson's Disease therapy and reduce its side effects.

Use of microbubble contrast in the diagnosis of a left ventricular papillary fibroelastoma

A papillary fibroelastoma is a rare, avascular, cardiac tumour that is often found incidentally using transthoracic echocardiography (TTE). Peripheral i.v. injection of a microbubble contrast agent is often used to characterize abnormal masses within the heart allowing further delineation of physical features, the area of attachment, and vascularity of the mass in order to differentiate the growth from a tumour or a thrombus. This case highlights a potential pitfall when assessing a cardiac tumour's vascularity using contrast TTE. A cardiac mass was identified on a TTE of a 53-year-old man and was further investigated with microbubble contrast-enhanced TTE. Contrast TTE imaging suggested a vascularized structure in the left ventricle. However, after histological examination the tumour was found to be entirely avascular.