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Thank you for sharing. Microbubble suspension size and concentration analysis. Both showed an average decrease in bubble size after insonation of up to 0.
Maximum bubble excursion during insonation. Modelling results are presented in Figure 3 as maximum radial excursion against initial microbubble diameter.
The data suggest that albumin Maximum Bubble Excursion microns 0. In contrast to our high speed 0. Maximum microbubble excursion following excitation with a 10 cycle, gauss-windowed, 0.
We hypothesise that this apparent disparity may be a symptom of parameterising the model appropriately and further work is required to investigate the suitability of the model in this context.
The level of transfection using freshly prepared microbubbles is comparable to our previous work with Sonovue Browning et al.
Mice which were treated with microbubbles fabricated more than 4 hours prior to administration displayed negligible levels of transfection.
Summary Our findings indicate that the acoustic properties of albumin microbubbles can be manipulated for the purposes of gene transfection by controlling the concentration of albumin used during fabrication, without compromising the microbubble yield or significantly influencing the mean diameter.
A reduction in albumin concentration results in more flexible microbubbles which exhibit greater radial excursion during single bubble investigation at low frequency, and greater total and non-linear scattering during bulk acoustic studies at clinical imaging frequencies.
Single bubble modelling was used to anticipate the behaviour of the microbubble preparations at 6 MHz, as employed during our pre-clinical work.
These results indicate that similar improvements in acoustic response may be expected for in-house prepared albumin microbubbles over SonoVue at higher acoustic frequencies, and we hypothesise that manipulation of microbubble elasticity will lead to greater acoustic activity and may be used to improve transfection in vivo as compared to stiffer microbubble preparations.
Work is on-going to establish the relative improvement in transfection which may be achievable, but has been limited by the poor stability of our in-house albumin preparation.
These preliminary results have also led to the discovery that the ability for microbubbles to be used for transfection is significantly reduced when administered more than 4 hours post fabrication.
As discussed above, poor stability could present challenges for the application of these microbubbles in vivo.
Further work will focus on improving microbubble stability, further optimisation of microbubble parameters and more comprehensive investigation of their application and efficacy in vivo.
Conclusions Bulk acoustics, high speed optical imaging and modelling has improved our understanding of the differences in behaviour of bubbles made at different albumin concentrations.
These findings will be used to inform our in vivo transfection work using these bubbles and demonstrates that detailed acoustic characterisation forms an important step in optimisation of microbubbles for any application.
All animal work was conducted under the authority of a UK Home office project licence as required by the Animals Scientific Procedures Act References 4.
Browning, R. Marmottant, P. Mulvana, H. Porter, T. Imaging 11 2 pp. Sennoga, C. Yong-feng, D.
Yaoxue Xuebao. This technique commonly known as near infrared spectroscopy or NIRS is, however, limited by strong optical scattering in tissue.
The measurement accounts for a large volume of tissue, therefore NIRS provides only a bulk estimate of tissue oxygenation rather than being sensitive to more localised changes in blood oxygenation.
Combining focused ultrasound US with diffuse light provides a way to improve this unsatisfactory spatial resolution2. Hybrid acousto-optic techniques rely on US to modulate the properties of the tissue such as the refractive index and scattering in a highly localised region, which in turn modulates the optical field.
The time-varying portion of the detected light then provides information about photons which have passed through the US focal region.
However, this US-modulated light signal is very weak compared with the un-modulated light which does not pass through the focal region.
It has previously been shown by the authors using a computational model that microbubbles can enhance the USmodulated signal3 Figure 1 , by exploiting the changes in optical scattering that occur when microbubbles oscillate under US.
This technique is proposed as a method for improving the sensitivity of NIRS to large blood vessels4. Experimental work with tissue phantoms is used to verify the results of the model.
A phantom consisting of a blood-filled tube surrounded by a scattering medium is insonified by a 1 MHz US transducer tone burst , in the beam path of nm laser light CW.
The Figure 1: Effect of bubble concentration on US-modulated optical signal strength ratio of modulated light to un-modulated signal is measured by a photodetector to demonstrate the change in US-modulation due to the presence of microbubbles in the blood.
Gibson A. Murray T. Honeysett J. Fujiwara, T. Sugiura Mechanical Engineering, Faculty of Science and Technology, Keio University, Japan Introduction Microbubbles are widely used in medical imaging with ultrasound, to enhance endocardial boundary delineation.
Furthermore, its potential use for drug and gene deliveries attracts attention in recent years. Bubble dynamics have to be clarified for practical use of such systems.
Bubble-wall interactions have been investigated by many researchers. Effects of walls cannot be neglected for bubbles located in narrow capillaries and near walls.
However, most studies regard a wall as rigid and thus neglect their elasticity. Microbubbles are usually confined in space through a blood vessel or an elastic capillary fiber, therefore the elasticity of the wall has to be considered.
To the best of our knowledge, the effect has not been quantified clearly to this date. Method In this study, we try to clarify the dynamics of a bubble near an elastic wall.
We regard the wall as a beam, so as to express the wall elasticity. For the first step of this study, we consider only the first mode of the beam vibration; therefore, the model can be more simplified as a spring-mass system.
Results We compared results of an elastic wall model with those of a rigid wall model using the method of image.
In both cases the bubble resonance frequency decreases with decreasing distance to the wall. On the other hand, the most noticeable difference between the interaction of the bubble with the rigid wall and that with the elastic wall appears in the maximum amplitude of oscillation at the wall, which increases in the case of a rigid wall and decreases for an elastic wall.
Conclusion We proposed a simple spring-mass model for analysis of the bubble oscillations near an elastic wall. The model can approximately describe effects of the elastic wall on bubble oscillations.
Liposome loaded microbubble is a newly developed system, and it has been proved for considerable improvement of gene transfer efficiency .
This study mainly focuses on characterization of liposome loaded microbubbles through ultra-high speed imaging. Physical parameters of microbubbles are derived from resonance spectroscopy for better understanding of ultrasonic behavior of liposome loaded microbubbles.
Methods Liposome loaded bubbles were characterized by comparing with non liposome loaded bubbles through optical approach. Individual microbubbles with radius ranging from 0.
Ultra-high speed imaging was used to record images through the whole frequency range in a single run.
Characteristic resonance curve, which varies with microbubble sizes and viscoelastic properties, can be constructed through frequency spectrum of radius time curves.
Resonance curve provide two parameters: resonance frequency and damping coefficient. Shell elasticity can be determined by fitting the spectroscopy curve with a linear oscillator model from Marmottant et al.
In addition, shell viscocity of microbubbles can be derived from damping coefficient of resonance curve . Results Resonance curve of microbubbles were compared, which gives an indication of the different characteristics between liposome loaded and non liposome loaded microbubbles.
See Figure 1. In general, compared with bare bubbles, liposome loaded microbubbles have lower elasticity and higher viscosity, which is in accordance with different surface structure and rheology of the two groups of microbubbles.
Resonance frequency, elasticity and viscosity parameters derived from this study can be applied in further modeling of liposome loaded microbubbles.
This study will facilitate future ultrasound parametric study of drug delivery with drug loaded contrast agents.
Resonance curve of bare bubble and liposome loaded microbubble, both of which have radius of 4. Reference 1.
Lentacker, et al. The central effector cells in antitumor immunity are cytotoxic T-lymphocytes CTLs. Figure 1 gives an overview of the application of this technique in cancer immunotherapy.
Luciferase expression was then measured at different time points. As shown in figure 3 ultrasound-mediated delivery of mRNA complexes led to efficient transfection of DCs.
No luciferase was detected when only mRNA lipoplexes were added to the cells. Maximal levels of luciferase were detected 6 hours after ultrasound exposure.
Figure 4 - 23 - Our data demonstrate a proof-of-concept that mRNA loaded microbubbles and ultrasound can be used to transfect DCs.
In contrast to current ex vivo transfection methods applied in the field of DC-based vaccines, this technique offers interesting perspectives towards future in vivo loading of DCs.
First of all, ultrasound-guided delivery assures local uptake of nucleic acids, only in ultrasound exposed tissues. Secondly, microbubbles are FDA approved as contrast agents in ultrasonic imaging.
During dobutamine, exercise, or vasodilator stress echocardiography, the incremental data provided with MPI has improved the detection of significant coronary artery disease, and MPI was better than wall motion at predicting outcome.
It has also assisted in the evaluation of chest pain in the emergency department, and provided prognostic data in the evaluation of a patient following ST segment elevation myocardial infarction.
Barriers to its widespread utilization include a lack of formal training programs which will teach both cardiologists and other health professionals how to perform these studies; b lack of approval to utilize ultrasound contrast for perfusion imaging from regulatory agencies throughout the world; c lack of any reimbursement for performing perfusion imaging with rest or stress echocardiography; and d insufficient data from multi-center trials to support it as a replacement for radionuclide perfusion imaging.
Nonetheless, there is consistent data from single center studies to support the concept that MPI with MCE improves the prediction of patient outcome following dobutamine, exercise, and vasodilator stress echocardiography, and that the spatial and temporal resolution of real time MCE exceeds that of radionuclide imaging.
The barriers to widespread utilization can be overcome by a developing advocacy groups who will provide evidence to regulatory agencies supporting the safety and incremental efficacy of MPI with MCE; b developing physicianinitiated multi-center trials which will test the efficacy of MPI with MCE in detecting coronary artery disease and predicting patient outcome during both rest and stress echocardiography; and c providing training programs to assist academic centers in developing MPI with MCE as part of their educational curriculum to train physicians, cardiology fellows, and sonographers.
The utilization of diagnostic ultrasound to perform bedside MPI still has the potentnial to dramatically improve the detection of coronary artery disease and improve patient risk stratification, while simultaneously reducing the need for more costly non-invasive and invasive testing that require significant amounts of ionizing radiation.
Prognostic value of dobutamine stress myocardial contrast perfusion echocardiography. Circulation ; Detection of myocardial perfusion in multiple echocardiographic windows with one intravenous injection of microbubbles using transient response second harmonic imaging.
J Am Coll Cardiol ; Detection of angiographically significant coronary artery disease with accelerated intermittent imaging after intravenous administration of ultrasound contrast material.
Am Heart J ; Real-time perfusion imaging with low mechanical index pulse inversion Doppler imaging. Safety of dobutamine stress realtime myocardial contrast echocardiography.
Safety and efficacy of commercially available ultrasound contrast agents for rest and stress echocardiography a multicenter experience.
J Am Coll Cardiol ; 8. J Am Coll Cardiol Img ; 9. Real-time assessment of myocardial perfusion and wall motion during bicycle and treadmill exercise echocardiography: comparison with single photon emission computed tomography.
Detection of coronary artery disease with myocardial contrast echocardiography: Comparison with 99mTc-sestamibi single-photon emission computed tomography.
Circulation ; Assessment of myocardial perfusion by harmonic power Doppler imaging at rest and during adenosine stress: Comparison with 99m Tc-sestamibi SPECT imaging.
Janardhanan R, Senior R. Accuracy of dipyridamole myocardial contrast echocardiography for the detection of residual stenosis of the infarct-related artery and multivessel disease early after acute myocardial infarction.
Combined assessment of microvascular integrity and contractile reserve improves differentiation of stunning and necrosis after acute anterior wall myocardial infarction.
J Am Coll Cardiol ; Intravenous myocardial contrast echocardiography predicts recovery of dysynergic myocardium early after acute myocardial infarction.
Tsutsui J, et. Eur Heart Journal ; Lepper W, Hoffmann R, Kamp O, et al: Assessment of myocardial reperfusion by intravenous myocardial contrast echocardiography and coronary flow reserve after primary percutaneous transluminal coronary angiography in patients with acute myocardial infarction.
Prognostic value of myocardial viability detected by myocardial contrast echocardiography early after acute myocardial infarction. The extent of microvascular damage during myocardial contrast echocardiography is superior to other known indexes of post-infarct reperfusion in predicting left ventricular remodeling.
Microvascular structural correlates of myocardial contrast echocardiography in patients with coronary artery disease and left ventricular dysfunction: implications for the assessment of myocardial hibernation.
Identification of hibernating myocardium with quantitative intravenous myocardial contrast echocardiography: comparison with dobutamine echocardiography and thallium scintigraphy.
Effects of left bundle branch block on cardiac structure, function, perfusion, and perfusion reserve: implications for myocardial contrast echocardiography versus radionuclide perfusion imaging for the detection of coronary artery disease.
Detection of coronary artery disease with perfusion stress echocardiography using a novel ultrasound imaging agent: two Phase 3 international trials in comparison with radionuclide perfusion imaging.
Eur J Echocardiogr ; Detection of coronary artery disease with a continuous infusion of Definity ultrasound contrast during adenosine stress real time perfusion echocardiography.
Echocardiography ; Myocardial contrast echocardiography in assessment of stable coronary artery disease at intermediate dobutamine-induced stresss level.
Real time myocardial contrast echocardiography during supine bicycle stress and continuous infusion of contrast agent.
Cutoff values for myocardial contrast replenishment discriminating abnormal myocardial perfusion. Accelerated stress real-time myocardial contrast echocardiography for the detection of coronary artery disease: comparison with 99mTc single photon emission computed tomography.
J Am Soc Echocardiogr. Value of vasodilator stress myocardial contrast echocardiography and magnetic resonance imaging for the differential diagnosis of ischemic versus nonischemic cardiomyopathy.
Assessment of myocardial perfusion in patients with coronary artery disease. Comparison of myocardial contrast echocardiography and 99mTc MiBI single photon emission computed tomography.
Int J Cardiol ; Noninvasive diagnosis of coronary artery disease in patients with diabetes by dobutamine stress real-time myocardial contrast perfusion imaging.
Diabetes Care ; Comparison of dobutamine stress echocardiography with and without real-time perfusion imaging for detection of coronary artery disease.
Am J Cardiol ; Full-motion pulse inversion power doppler contrast echocardiography differentiates stunning from necrosis and predicts recovery of left ventricular function after acute myocardial infarction.
Contrast echocardiography using intravenous octafluoropropane and real-time perfusion imaging predicts function recovery after acute myocardial infarction.
Soc Echocardiogr ; Usefulness of myocardial contrast echocardiography using low-power continuous imaging early after acute myocardial infarction to predict late functional left ventricular recovery.
Assessment of the physiologic significance of coronary disease with dipyridamole real-time myocardial contrast echocardiography.
Comparison with technetiumm sestamibi single-photon emission computed tomography and quantitative coronary angiography. Dodla S, et. Heart ; Usefulness of real-time myocardial perfusion imaging to to evaluate tissue level reperfusion in patients with non ST-elevation myocardial infarction.
Comparison of real-time contrast echocardiography and low-dose dobutamine stress echocardiography in predicting the left ventricular functional recovery in patients after acute myocardial infarction under different therapeutic intervention.
Int J Cardiol Detection of functional recovery using low-dose dobutamine and myocardial contrast echocardiography after acute myocardial infarction treated with successful thrombolytic therapy.
Echocardiography ; - 27 - Intravenous myocardial contrast echocardiography predicts regional and global left ventricular remodeling after acute myocardial infarction: comparison with low dose dobutamine stress echocardiography.
Michalakis Averkiou University of Cyprus, Nicosia, Cyprus Over the years we have witnessed a surge on the scientific interest for bubble imaging techniques which peaked around and has almost disappeared in the recent years.
The scientific interest was well balanced between academic institutions and equipment industry during the peak years, with industry being the first to express loss of interest.
There was a clear shift in the scientific community from bubble imaging to quantification and parametric imaging, therapy monitoring, molecular imaging, and drug delivery.
Shift towards 3D ultrasound and matrix arrays was also observed, but for contrast has meant extending current 2D knowledge in 3D without breaking any new ground in bubble imaging.
As for matrix arrays, it is quite unfortunate that such technology was utilized only for quick electronic beamforming and missed the opportunity to solve complex acoustic problems including improvements of bubble imaging.
The current state of the art for bubble imaging consists of various flavors of nonlinear pulsing schemes pulse inversion, power modulation, and their hybrid combinations.
Matched filtering, chirps, and codes have also been investigated and used by some companies and researchers but to a lesser degree.
And recently radial modulation, low frequency manipulation of bubbles while imaging at a higher frequency, has also been investigated, but it has not yet found its way on clinical systems.
Technology has utilized some of the important properties and physical phenomena bubbles such as destruction, nonlinearity, low MI excitation for nondestructive imaging and tissue cancellation, nonlinear pulsing schemes, and use of complimentary apertures for amplitude modulation.
However there are still some other properties not fully utilized such as more complicated forms of codes and matched filtering, radial modulation, sub-harmonic response, acoustically induced deflation, self-demodulation, and bubble specific beam forming.
In addition, most ultrasound equipment manufacturers are based in the USA, a country that is also the largest business sector for the main ultrasound companies, where contrast agents are not approved.
Early on the clinical and financial promise of bubble technology was too high but major technological advances were needed that took time and money to be achieved and thus the - 29 - interest fizzled out.
Another reason for the technology stagnation is the cost of bubbles and added complexity of the contrast exam. Do we need further contrast imaging?
Is it adequate what we currently have? What are the problems that must be solved today? Bubble sensitivity which is the most important requirement in perfusion imaging remains penetration limited for average patients, and weak in tough patients cirrhotic livers, large individuals, difficult access.
Another important clinical requirement is image resolution which is medium at best, low usually, and terrible at times.
High frequency-low flow imaging breast, vasa-vasorum are still not fully addressed with present technology.
It is hoped that newer techniques like radial modulation can better address high frequency imaging. Are we at the end of our technological development?
However, some of the issues mentioned above suggest a possible slow down that may be perceived by some as the end of a technological development.
The worst case scenario would be that slow progress will be observed for the foreseeable future and new technologies will also be made available for contrast as well when they become available for the rest of diagnostic ultrasound, e.
Materials and Methods The size characteristics of BR38 microbubbles were measured by Coulter counting The backscatter coefficients and attenuation were determined as a function of frequency Additional measurements included the surface charge, osmolality, viscosity and resistance to hydrostatic pressure A complete set of pharmacological and toxicological studies were conducted on the final formulation, mainly in rats and dogs The blood levels and elimination of the gaseous component C4F10 were determined in the rabbit Contrast-enhanced echographic examinations were performed in pigs focusing on the myocardium and the liver Finally safety testing and preliminary imaging experiments were performed in a Phase I trial on human volunteers.
Conclusions BR38 shows a very good safety profile. Its long persistence, reduced shadowing and high efficacy over a wide range of frequencies will be particularly valuable for myocardial perfusion imaging and abdominal imaging BR38 may also be a promising agent for high frequency imaging during carotid ultrasound.
The obvious advantage of the method is lack of ionising radiation. On the other hand, intravenous application of USCM is being performed extremely rarely in children.
There is one main reason to explain that: experience of the method for intravascular use is very limited, mainly because there is no approval by the EMEA for intravascular use in children.
To assess nature and perfusion of focal lesions and extent of inflammatory diseases, investigators cannot do without contrast media, irrespective of imaging modality.
USCM based sonography for 6 years in adults, mainly in hepatic and renal lesions, but also for detection of organ injuries. For the last 3 years the technique was performed in children and adolescents for characterisation of focal organ lesions, detection of injury impacts and in tumour disease follow-up.
The issue regarding off-label use has to be dealt with. Careful informing patients and parents and the informed consent are mandatory.
Results Over a period of 3 years i. USCM sonography examinations in about 40 children and adolescents were performed. Liver, spleen, kidney, thyroid and the small intestine were assessed.
All examinations were of diagnostic value. No adverse reactions in the patients occured. Consequently, there is very little expertise in paediatric sonographers.
Regarding the author's experience, USCM enhanced sonography is safe, effective and very helpful in some cases. Children should benefit from this technique the same way as adults do.
Nevertheless, spread of expertise's knowledge is important and help from the manufacturers should be demanded.
Loer 1,2, Christa Boer 1,2 and R. Introduction General anesthesia is associated with an increased activity of the sympathetic nervous system, which may lead to alterations in myocardial blood flow MBF.
Historically, the lack of a suitable, intraoperative and noninvasive imaging technique impeded investigation of the influence of general anesthesia on MBF.
It is unclear whether this technique is applicable in the intraoperative setting, since positioning of the anesthetized patient and mechanical ventilation may influence the quality of transthoracic images necessary for quantification of flow.
Therefore, the aim of this study was to investigate the feasibility of MCE for intraoperative measurement of MBF and to study the effect of general anesthesia on myocardial perfusion.
Methods Eight cardiovascular healthy patients 3 women, 5 men; age years scheduled for general anesthesia were included. Integrity of cardiovascular autonomic control was confirmed using autonomic function tests.
MCE was performed before and during the administration of 1. Paired t-tests were used for comparison of dependent samples.
Results In the preoperative setting, basal MBF was 1. In all patients intraoperative opacification of the myocardium was feasible resulting in a basal MBF of 1.
Alterations in MBF in response to adenosine- - 33 - induced hyperemia were comparable for the preoperative and intraoperative measurements, indicated by flow reserves of 3.
Conclusions Quantification of myocardial blood flow using myocardial contrast echocardiography is safe and feasible in the intraoperative setting.
These preliminary data show no significant difference in flow reserve for the preoperative and intraoperative setting.
However, more measurements should be performed to confirm this observation. Imaging modalities such as CT, MRI and positron emission tomography PET have been used to assess perfusion changes in monitoring antivascular therapies in cancer patients.
However all these modalities have disadvantages such as invasiveness, availability and costs which may limit their application into routine clinical practice.
With hundreds of oncology therapeutics in current and future development, assessment of early response has invariably proved to be disappointing to date as compared with the pre-clinical animal studies.
Traditional medical imaging techniques, such as dynamic contrast-enhanced computerized tomography CT , magnetic resonance imaging MRI , and ultrasound US , have been used routinely to monitor the therapeutic effects of cancer intervention.
However as anti-angiogenic or anti-vascular therapies are predominantly cytostatic, current criteria for monitoring response are clearly inadequate as they reflect only late changes and are unable to identify non-responders at an early time-point 4.
In addition, the development of vascular-targeted agents and their clinical usage are also costly; hence accurate, reproducible and non-invasive imaging methods of assessing their effectiveness at an earlier stage are required.
The outcome of the meeting will be presented. The associated needs of pharmaceutical companies can be broken into three groups: today current imaging biomarkers , tomorrow targeted imaging , and future site drug delivery.
Currently in oncology clinical trials, CEUS is used for quantification of tumor blood flow and associated perfusion surrogate endpoints.
These imaging biomarkers can serve not only in the monitoring of treatment, but also in stratification of patients and in development of prognostic factors.
Numerous institutions have developed potential methodologies, but to apply CEUS in multi-site clinical trials, standardization is needed in techniques and in analysis with implementation independent of equipment.
Healthcare is moving towards more personalized medicine, and target identification can help to understand underlying biological processes and pathways and to assist in patient selection.
A prime example is in oncology where recent studies have been aimed at tailoring therapies based on tumor characteristics such as protein expression.
A longer term goal in the pharmaceutical industry is for site-targeted drug delivery. The conversion from standard parenteral delivery of compounds would result in asymmetric, preferential drug distribution to desired tissues and cells leading to increased drug concentration at desired sites and decreased toxicity elsewhere.
Research areas of relevance include enabling extravasation, demonstrating efficacy, monitoring clearance, determining off-target toxicity, and establishing feasibility in the clinic.
Germany Different low MI techniques like pulse inversion, power amplitude exist for contrast imaging have been developed during the last decade.
Due to its imaging process, temporal and spatial resolution, partly being caused by blooming artifacts, are lacking behind B-mode imaging.
Most contrast software solutions have a low dynamic range as well, so differences in local contrast concentration cannot be dissolved adequately.
A homogeneously enhanced image over the whole depth is often missed, which is a major limitation in the sensitivity to detect small liver lesions.
A frame rate like in B-mode imaging allows the visual detection of flow direction even in arteries. It ranges between 26 fps and 55 fps depending on the image size width, line density and to some extend to its depth.
Using a high dynamic range differences in bubble concentration can be imaged for example in tumor tissue and infectious disease.
The different bubble concentration in hepatic arteries and veins can be clearly seen during the arterial phase.
A high spatial resolution is mandatory for the detection of focal organ lesions. Pixel size in HIREC mode no company name is comparable to that of B-mode images and thus allows the detection of liver metastases down to 3mm.
Disadvantage of HIREC may come up when echogenic tissue is not suppressed sufficiently, so a contrast wash out cannot go below the pre-contrast level and may therefore be missed.
Not only characterization but also detection of the liver tumor is the role of Sonazoid contrast imaging because Sonazoid has a liver specific Kupffer phase imaging.
Twenty-seven patients with 57 hepatic metastases and 6 patients without hepatic metastasis underwent conventional B-mode US and CEUS in the liver-specific Kupffer phases of Sonazoid.
We used the diagnoses established by contrast-enhanced multi-detector row computed tomography MDCT as the standard of reference.
All ultrasound scanning was performed by an experienced radiologist with a routine clinical procedure. All scanning data were archived with digital cine clips.
A Windows-PC based review system, which can display pairs of cine clips for B-mode and contrast-enhanced US side by side, was developed for off-site observer study.
Seven radiologists interpreted each case individually first conventional B-mode only, and then the combination with contrast-enhanced US by identifying locations of possible candidates for hepatic metastasis with their confidence ratings.
The figure of merit FOM values, sensitivity, and false-positives per case were estimated for B-mode US alone, and for the combination of conventional B-mode and contrast-enhanced US.
The analysis of variances for multireader-multi-case matrix of pseudo FOM values was used for testing a statistically significant difference between two modes of interpretations.
For all readers, the sensitivities of the combined US imaging mean In the jackknife analysis, there was a statistically significant difference between mean FOM values for the combined imaging 0.
To evaluate the clinical utility of a computer-aided diagnosis CAD scheme for the improvement of diagnostic performance of radiologists for differentiation of focal liver lesions on contrast enhanced ultrasound with Sonazoid.
Our data set contained focal liver lesions from cases, consisted of 27 metastases, 27 hemangiomas, and 53 hepatocellular carcinomas HCCs.
Histological differentiation of HCCs is as follows; 17 well-differentiated, 26 moderately differentiated, and 10 poorly differentiated hepatocellular carcinomas.
Pathologies of all cases except for hemangiomas were determined based on biopsy or surgical specimens.
The observer study was conducted with seven radiologists with experience in CEUS of the liver, all of whom were first asked to give confidence ratings regarding benign or malignant; second, if malignant, whether metastasis or HCCs; finally to select one of 5 classifications matched to the unknown focal liver lesions.
The overall sensitivity of our CAD for differentiation of 5 types of focal liver lesions included in the database was For all seven participants, as to benign vs.
In addition, as to metastasis vs. The overall sensitivity of all observers was also improved from The use of the CAD can significantly improve the diagnostic performance of radiologists for differential diagnosis of the focal liver lesions on CEUS.
This talk will focus on new developments in ultrasound molecular imaging techniques. For atherosclerotic disease high-risk molecular phenotype has either focused on the detection of early but aggressive disease or the development of complex end-stage plaques that are prone to atherothrombotic events.
This talk will focus on how molecular imaging of endothelial cell adhesion molecules that are involved in the inflammatory component of atherosclerosis, as well as activated hemostatic pathways which produce a prothrombotic and pro-inflammatory phenotype.
How these technologies can be used to evaluate risk and to assess new therapies that are targeted at high risk events will be discussed.
Part of this discussion will also involve the molecular and cellular participants in the remodeling of the vasa vasorum and development of plaque neovessels which have been associated with propensity for disease progression and atherothrombotic events.
Molecular imaging of angiogenesis in peripheral vascular disease will also be discussed. In this setting, molecular imaging in concert with perfusion imaging has been able to provide important insight into the regulatory process of arteriogenesis and also to evaluate the mechanism of effect of pro-angiogenic therapies such as stem cell therapy.
Needles1, J. Mehi1, N. Chaggares1, R. Castelino2, N. Sacadura1, A. Heinmiller1, C. Bilan-Tracey1, C. Theodoropoulos1, D. Hirson1, and F.
Foster 1,2 1. By increasing the center frequency of the ultrasound system and maintaining bandwidth, the resolution of the CEUS image can be greatly improved.
An increase in frequency will inevitably result in a tradeoff in sensitivity to the microbubbles, as their resonant frequencies are in the low MHz range and nonlinear propagation from tissue signals becomes more problematic at higher frequencies.
This talk will focus on the advances in the field of contrast imaging aimed at trying to solve issues related to resolution and sensitivity, and outline areas where tradeoffs exist.
Recent developments in transducer and system technology will be presented, along with Photoacoustic PA imaging combined with micro-ultrasound.
This is an exciting technique that uses laser light to create ultrasound, and can improve sensitivity to contrast agents that are undetectable with ultrasound alone, while maintaining equivalent resolution.
Methods Transducer Development A comparison study between two high-frequency array transducers was conducted with a commercially available micro-ultrasound system Vevo , VisualSonics.
The original MS transducer was used in previous studies for contrast imaging in mice Needles et al.
It was originally designed for small animal imaging at depths corresponding to the penetration of 20 MHz ultrasound mm.
Its success in contrast agent detection in the 20 MHz range was owed to its frequency characteristics, but its elevation resolution, particularly in the near field mm , was - 41 - always less then optimal.
This is often apparent in the corresponding B-Mode image used to guide the placement of a nonlinear contrast imaging scan plane.
A prototype phantom Gammex Inc. The transmit focus of the ultrasound system was set to 8 mm, corresponding to the geometrically-fixed elevation focus of the new MSSC transducer.
The images of the phantom spheres and wires were then compared, qualitatively and quantitatively, between the two transducers to assess near-field elevation resolution, lateral resolution and axial resolution.
The image planes were aligned as closely as possible between each scan, and were chosen to encompass as much of the kidney cortex and medulla as possible for assessing the perfusion of the microcirculation, while avoiding the larger renal blood vessels.
The simultaneously acquired BMode and Contrast images were compared qualitatively, and a contrast-to-tissue ratio CTR was calculated.
Increasing the Frequency of Nonlinear Microbubble Detection The same micro-ultrasound system Vevo , VisualSonics was modified to perform nonlinear contrast imaging at 30 MHz, using an amplitude modulation based approach Needles et al.
Microbubbles were loaded with gold nanoparticles GNP using a previously described technique Seo et al. For determination of the presence of MB signal in vivo, PA images of the axillary lymph node were collected at 21 MHz using nm and nm laser light, both pre- and post-infusion of MB into the forepaw of an adult CD1 mouse and a subtracted image was generated.
Axillary and brachial lymph nodes were excised and imaged to verify the source of the MB signal. Results Transducer Development Results from the cyst phantom are shown in Fig.
Some of the anechoic spheres 1 and 2 are barely visible with the current contrast transducer MS and others of smaller diameter are not visible at all due to out of plane clutter 3.
Deeper spheres 4 are not well focused as the transmit focus is located at 8 mm in both images, however, they are visible in the MS image due the 15 mm elevation focus of this transducer.
It is also apparent that the shallower elevation focus of the MSSC leads to poorer imaging penetration depth as signal level starts to fall off below 12 mm.
This can be observed in the image of the wire phantom shown in Fig. Results from the in vivo comparison are shown in Fig. The differences between the two transducers are subtle, but nonetheless difference can be observed, particularly in the B-Mode images.
The MSSC image has better detail around the border of the kidney 1 , which is likely a result of less out of plane clutter in the near field.
In terms of the nonlinear contrast image, the larger slice thickness of the MS leads to more bubbles contributing to the contrast image and a larger signal.
For example, in the tissue surrounding the kidney 2 the signal appears very bright and cannot be separated from the organ itself. Compared to the MSSC, which has a smaller slice thickness, there is better delineation between the highly vascularized kidney and the surrounding tissue.
In terms of the peak intensity of contrast detection in the kidney, both transducers had a CTR in the range of dB.
Increasing the Frequency of Nonlinear Microbubble Detection When comparing the performance of 30 MHz contrast imaging to 21 MHz in the kidney it was clear that the effects of attenuation coupled with increased tissue signal and lower sensitivity to the microbubbles, caused very little enhancement in signal dB.
However, when moving to the hind limb tumour model, the improvements in resolution in both the B-Mode and Contrast images were noticeable, as expected from wire target measurements not shown and observed in Fig.
It should also be noted that the 21 MHz image in Fig. This figure demonstrated the ability of the micro-ultrasound system to image a dual contrast agent.
Nonlinear ultrasound detection is capable of detecting the microbubbles, while PA imaging can also detect the GNP bound to the bubble shell.
The PA image of the tube shows the characteristic response of the PA signal in this frequency range for a 1 mm diameter absorber.
Since the data in Fig. For the in vivo data, excision of the lymph nodes showed that the MB had migrated to the axillary lymph node.
Images of this node confirmed this and are shown in Fig. Since the MB is highly absorbent to light near nm, the PA signal was much stronger than at nm.
By subtracting the nm image from the nm image a contrast enhanced PA image was obtained, and yielded a contrast enhancement improvement of 8 dB.
The contrast enhanced image is a subtraction of the single wavelength images at nm and nm. Images of the tumours injected with GNP are shown pre and post-inection in Fig.
Two things are notable about this image: that a new method of contrast detection can be utilized with a micro-ultrasound system, and the fact that this image was obtained using a 40 MHz transducer, a higher frequency than currently used for nonlinear microbubble detection.
It remains to be determined if the nanoparticles in this image are confined to the vascular space, or if they have migrated into the surrounding tissue.
Due to the size of the nanoparticles, it is reasonable to hypothesize that the latter is - 47 - true, thus providing the ability of micro-ultrasound systems to image beyond the vasculature with contrast agent.
Figure 7 - Photoacoustic Imaging of gold nanoparticles in a mouse tumour at 40 MHz with nm light.
Discussion and Conclusions This study has provided an overview of new developments in contrast imaging with micro-ultrasound. Changes to an existing transducer improved the resolution and out of plane clutter rejection for mouse abdominal imaging, and were demonstrated both in vitro and in vivo.
It was also demonstrated qualitatively that an increase in imaging frequency to 30 MHz helped to improve the image resolution for nonlinear microbubble imaging, but should be limited to superficial structures.
In the case of the tumour images at 30 MHz, a doubled dose of microbubbles needed to be administered to see equivalent results as at 21 MHz, and even then the CTR was still 4 dB lower.
In terms of increasing frequency, however, PA imaging presents a new method of detecting contrast in vivo at higher imaging frequencies, as demonstrated by 40 MHz images of GNP in a mouse tumour.
Finally, PA imaging can also improve sensitivity to contrast agents such as MB that are undetectable with ultrasound alone. This has the potential to open up new areas of contrast imaging previously unheard of with micro-ultrasound.
Nonlinear contrast imaging with an array-based micro-ultrasound system. Ultrasound Med Biol a; Development of a combined photoacoustic micro-ultrasound system for estimating blood oxygenation.
Symp, San Diego, b in press. Microfluidic assembly of monodisperse, nanoparticleincorporated perfluorocarbon microbubbles for medical imaging and therapy.
Langmuir ;26; Self-demodulation of high-frequency ultrasound. J Acoust Soc Amer ; Besides, we have shown earlier that chirp reversal improves the contrast detection through an increased contrast to tissue ratio CTR .
Chirp reversal consists in transmitting a first excitation signal being an up-sweep chirp UPF of increasing frequencies with time and a second excitation signal, the down-sweep DNF , being a replica of the first signal, but time reversed with a sweep of decreasing frequencies with time.
The aim of our study is to evaluate the combination of chirp reversal with power modulation CRPM for contrast agent imaging.
The probe was connected to a fully programmable open scanner equipped with analog transmitters M2M, France. Chirp reversal and other traditional contrast agent imaging schemes pulse inversion, power modulation and combinations of them were implemented into the open scanner.
Chirps with linear frequency modulation were transmitted. The chirps were centered at 2. RF data were recorded and then filtered using a matched filter in order to compress the scattered signals and recover the axial resolution.
The compression filter was designed in order to recover both the fundamental and the harmonic components. The transmitted peak negative acoustic pressure was kPa corresponding to a non derated mechanical index of 0.
Traditional multi-excitations schemes such as pulse inversion PI , power modulation PM and their combination PIPM were implemented using chirps with and without chirp reversal approach.
Reference A. Novell, S. Versluis, N. Cardiac events and stroke are often caused by atherosclerotic plaque rupture. It has been shown that vasa vasorum plays an important role in atherosclerotic plaque pathogenesis and stability.
Recent advances in contrast-enhanced ultrasound have shown that this technique can characterize the carotid vasa vasorum and intra-plaque angiogenesis and thus it is potentially a new diagnostic tool to detect plaque vulnerability.
However for the transmit pressures used in these methods the CTR is lowered as a result of nonlinear propagation of the ultrasound wave through the tissue, which causes that the tissue scatter signal also contains second harmonic energy which contaminates the bubble echo signal.
Propagating ultrasound wave does not contain energy at the subharmonic frequency, which revives a strong interest in subharmonic emissions backscattered energy at half the transmit frequency from contrast agents.
In recent studies19 subharmonic imaging SHI has been used for the diagnosis of breast cancer at the transmitting frequency of 4.
SHI appears to improve the diagnosis of breast cancer relative to conventional ultra-sonography and mammography. In this study, the subharmonic scattering of phospholipid-coated contrast agents BR14, Bracco Research S.
The results of the measurements indicated that: - The subharmonic scattering of the phospholipid-coated contrast agent microbubbles is sufficiently detectable in the frequency range around 10 MHz at low acoustic pressures.
In conclusion, we have shown from single bubble measurements that the subharmonic imaging has a great potential to be exploited in the frequency range mostly suited for carotid imaging.
However this study has to be complemented with forthcoming in vivo studies. The global burden of chronic diseases - Overcoming impediments to prevention and control.
JAMA ; The Symptomatic Carotid Plaque. Stroke ; Hypothesis: vasa vasorum and neovascularization of human coronary arteries.
N Engl J Med ; Zamir M, Silver MD. Vasculature in the Walls of Human Coronary Arteries. Arch Pathol Lab Med ; Stroke ; Feinstein SB.
Contrast-enhanced ultrasound imaging of atherosclerotic carotid plaque neovascularization: a new surrogate marker of atherosclerosis?
Radiology ; Eur J Vasc Endovasc Surg ; Pulse inversion imaging of liver blood flow: improved method for characterizing focal masses with microbubble contrast.
Invest Radiol ; Means for increasing sensitivity in non-linear ultrasound imaging systems. US Patent No. Nondestructive subharmonic imaging.
Subharmonic imaging with microbubble contrast agents: initial results. Ultrason Imaging ; Subharmonic backscattering from ultrasound contrast agents.
Breast lesions: Imaging with contrastenhanced subharmonic US-Initial experience. Kuenen 1,2, M. Mischi1, H. New focal therapies could significantly improve prostate cancer treatment, but they cannot be used efficiently due to a lack of imaging methods.
In fact, the most reliable prostate cancer localization method is currently provided by systematic biopsies, which are invasive and can only provide a poor spatial accuracy.
The potential of contrast-enhanced ultrasound imaging for prostate cancer localization has been gaining interest in the past few years.
In particular, techniques for quantitative measurement of microvascular blood perfusion have been proposed , based on the known correlation between cancer aggressiveness and angiogenesis .
However, no method has yet produced reliable results. We recently proposed contrast-ultrasound dispersion imaging CUDI as a new alternative method .
Whereas angiogenesis-induced changes in the microvascular architecture can cause various opposing effects on perfusion , they have a direct influence on the intravascular dispersion of ultrasound contrast agents.
CUDI is based on contrast-specific ultrasound imaging of the passage of an intravenously injected contrast-agent bolus through the prostate circulation.
Dispersion is then estimated from indicator dilution curves IDCs that are measured at each B-mode video pixel.
In a previous study, the contrast-agent transport was modeled by the convective dispersion equation, enabling the extraction of a local, dispersion-related parameter from each IDC.
This study showed better results for CUDI than for perfusion quantification methods . We now present a method for an indirect estimation of dispersion.
Rather than focusing on each IDC individually, this method exploits the spatial dispersion dynamics by considering the similarity among spatially adjacent IDCs as an indirect measure for dispersion.
The adopted coherence-based similarity analysis is compared with our previous method, as well as with quantitative perfusion estimation methods.
Transrectal ultrasound power modulation imaging frequency 3. An IDC was measured at every pixel of the resulting B-mode video and linearized by compensating for the logarithmic compression.
The spatial coherence is the adopted IDC similarity measure for dispersion estimation. It is computed as the correlation coefficient between IDC magnitude spectra.
IDC arrival time differences, which are rather a measure of perfusion, are incorporated in the IDC phase 0. The fundamental B-mode ultrasound image is shown in the middle, whereas the image on the right shows the correspondinghistology.
As a result, coherence is not sensitive to IDC arrival time differences. The analysis is restricted to frequencies up to 0.
The DC component is also discarded, as it is determined by scanner settings. A ring-shaped spatial kernel determines which pixels are used for this comparison.
Because the axial scanner resolution is 0. Pixels at distances up to 1. A preliminary validation was conducted based on four patients.
Regions of interest representing cancer and normal tissue were selected based on histology data, obtained at the AMC.
The sensitivity and specificity for correct pixel classification were then computed. Results On a pixel basis, there was a good agreement between the coherence images and the histology assessment.
The ROC curve area 0. Compared with other quantitative methods, this method requires no model interpolation.
Alternative similarity measures, as well as a more advanced preprocessing and kernel design may provide additional improvements in the future.
Pallwein, L. Brawer, M. A staging and prognostic marker for human carcinoma, Cancer, 78 2 , pp. Mischi, M. Delorme, S. Knopp, Non-invasive vascular imaging: assessing tumour vascularity, Eur.However, most studies regard prison bs wall as rigid and thus neglect their elasticity. Gibson A. The figure of merit FOM values, sensitivity, and false-positives per case were estimated read article B-mode US alone, and for the combination of this web page B-mode and contrast-enhanced US. Thank you! The fundamental amplitude decreases monotonically for each of the excitation frequencies; however the decrease rate exhibits a frequency-dependent behaviour, as changes in the deflation rate occur sebastian mГјnster different times in the 2. Sao Luis — Manaus — Carupano I subscribed to your Feed as. In addition, The the veil 2019 are masterpiece. This time requirement may reflect alternative mechanisms for agent clearance in the mouse embryo. It was found thatdeviations of the resonance frequency from 25 kmh theory can be compensated by first order corrections as long as buckling is negligible.