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Author: L. Hoff Publisher: Springer Science & Business Media ISBN: 9401706131 Category : Medical Languages : en Pages : 218
Book Description
Contrast agents for medical ultrasound imaging is a field of growing interest. A large amount of literature has been published on the medical applications of such contrast agents. However, there is no textbook giving a broad overview of the physics and acoustics of the agents. This monograph aims to fill this gap. The book is written by a physicist, from a physics point of view, and it tries to draw links from the physics and acoustics to the medical imaging methods, but medical applications are mainly included for background information. The book consists of nine chapters. The first three chapters give a broad overview of the acoustic theory for bubble-sound interaction, both linear and nonlinear. Most contrast agents are stabilized in a shell, and this shell can have a strong influence on the interaction between the bubbles and the ultrasound. The effect of the shell is given special attention, as this is not easily found in other bubble literature. The following chapters, 4, 5, 6, and 7, describe experimental and theoretical methods used to characterize the acoustic properties of the agents, and results of studies on some agents. Chapter 8 shows how the theory and the experimental results can be combined and used to model various phenomena by means of computer simulations. The main purpose of the simulations is to get insight into the mechanisms behind the described phenomena, not to get accurate predictions and values. The book is aimed at both newcomers into the field, as well as those who are more experienced but want better insight into the acoustics of the contrast bubbles.
Author: L. Hoff Publisher: Springer Science & Business Media ISBN: 9401706131 Category : Medical Languages : en Pages : 218
Book Description
Contrast agents for medical ultrasound imaging is a field of growing interest. A large amount of literature has been published on the medical applications of such contrast agents. However, there is no textbook giving a broad overview of the physics and acoustics of the agents. This monograph aims to fill this gap. The book is written by a physicist, from a physics point of view, and it tries to draw links from the physics and acoustics to the medical imaging methods, but medical applications are mainly included for background information. The book consists of nine chapters. The first three chapters give a broad overview of the acoustic theory for bubble-sound interaction, both linear and nonlinear. Most contrast agents are stabilized in a shell, and this shell can have a strong influence on the interaction between the bubbles and the ultrasound. The effect of the shell is given special attention, as this is not easily found in other bubble literature. The following chapters, 4, 5, 6, and 7, describe experimental and theoretical methods used to characterize the acoustic properties of the agents, and results of studies on some agents. Chapter 8 shows how the theory and the experimental results can be combined and used to model various phenomena by means of computer simulations. The main purpose of the simulations is to get insight into the mechanisms behind the described phenomena, not to get accurate predictions and values. The book is aimed at both newcomers into the field, as well as those who are more experienced but want better insight into the acoustics of the contrast bubbles.
Author: Gaio Paradossi Publisher: Springer Science & Business Media ISBN: 8847014948 Category : Technology & Engineering Languages : en Pages : 199
Book Description
Recent advancements in nano/micro materials and related characterization approaches allow the design of a new type of ultrasound contrast agents (UCAs) with enhanced multifunctional behaviour. This is chance is also supported by the recent achievements in modelling and signal processing. This book provides the state of art of the research activity of two successful European projects, TAMIRUT and SIGHT, addressing an integrated system, encompassing the contrast agent, the hardware equipment and the processing strategies, as a key tool for a combined diagnostic and therapeutic approaches (theranostics) in medical ultrasound. The work provides a highlight of the state of art in the research of novel ultrasound contrast agents (UCAs). Main progresses on the multifunctional aspects of next-generation UCAs concern targeting and drug release properties, perfusion and biointerface behaviour, ultrasound scattering performance, signal processing, electronic equipment.
Author: Yanjun Gong Publisher: ISBN: Category : Languages : en Pages : 294
Book Description
Abstract: Lipid-coated microbubbles, which have been widely used in diagnostic ultrasound as contrast agents, also show promising applications in medical therapy. The knowledge of acoustic behaviors and shell properties with respect to Ultrasound Contrast Agents (UCA) microbubbles can greatly enhance and extend their clinical applications. A polydimethylsiloxane (PDMS-based microfluidic flow-focusing device was fabricated to produce lipid-coated microbubbles with narrow size distribution and controllable mean diameters (3-12um). These monodisperse microbubbles show unique acoustic properties compared with commercial UCA microbubbles with wide size distribution, which makes it possible to investigate the relationship between microbubble size and attenuation coefficient, resonance frequency, or backscattering experimentally. Our studies show that monodisperse microbubbles can be tailored for optimal contrast enhancement in ultrasound imaging. By using an ultrasound spectroscopy method, the frequency-dependent attenuation coefficient for monodisperse microbubbles and polydisperse microbubbles were measured and compared. The results showed that decreasing the width of the microbubble size distribution would lead to a reduction in the bandwidth, and an increase in the magnitude of the attenuation spectrum. The resonance frequency determined by the attenuation coefficient peak was inversely proportional to the mean diameter of the monodisperse microbubble suspension. These conclusions corroborated the theoretical predications. The dependence of resonance frequency on acoustic pressure and lipid composition have also been examined and compared with theoretical calculations. The results demonstrated that the lipid shell of microbubbles behaviors nonlinearly, even at low pressure, which results in a decrease of resonance frequency as incident pressure was increased, approaching the resonance frequency of uncoated bubbles. Moreover, the length of the lipid hydrocarbon chain impacts the dependences of shell stiffness, attenuation coefficient, and resonance frequency on the excitation pressure. The frequency-dependent backscattering coefficients for monodisperse microbubbles have been investigated using a broadband pulses technique over different sizes, concentrations and pressures. The experimental results showed the same size-dependent resonance peaks as attenuation coefficient. It demonstrated that increasing the acoustic pressure caused a frequency shift of resonance peak, but no significant changes on magnitude. A linear dependence on microbubble concentration for backscatter coefficient was confirmed. In addition, the pressure-dependent backscattering coefficients at 2.25 MHz were studied. It is interesting to note that with the increase of incident pressure, the change of backscattering coefficients values, increase or decrease, were strongly dependent on the mean size of microbubbles.
Author: Shirshendu Paul Publisher: ISBN: 9781321254129 Category : Drug delivery systems Languages : en Pages : 368
Book Description
Micron- to nanometer - sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes, are being actively developed for possible clinical implementations in diagnostic imaging and ultrasound mediated drug/gene delivery. Contrast microbubbles (1-10 micron in diameter) contain a low solubility gaseous core stabilized by an encapsulation made of lipids/proteins/polymers/surfactants. Echogenic liposomes (ELIPs), which combine the advantages of liposomes such as biocompatibility and ability to encapsulate both hydrophobic and hydrophilic drugs with a strong reflection of ultrasound, are also excellent candidates for concurrent ultrasound imaging and drug delivery applications. The primary objective of this thesis is to characterize the acoustic behavior and the ultrasound-mediated content release of these contrast agents for developing multi-functional ultrasound contrast agents. The first part of this thesis reports the investigation of encapsulated microbubbles utilized as ultrasound contrast agents, whereas the second part reports the experimental characterizations of echogenic liposomes (ELIPs) and echogenic polymersomes. Contrast microbubbles are nonlinear systems capable of generating a subharmonic response i.e., response at half the excitation frequency, which can improve image quality by providing a higher signal to noise ratio. However, design and development of contrast microbubbles with favorable subharmonic behavior requires accurate mathematical models capable of predicting their nonlinear dynamics. To this goal, 'strainsoftening' viscoelastic interfacial models of the encapsulation were developed and subsequently utilized to formulate a modified form of the Rayleigh-Plesset equation to model the nonlinear dynamics of these encapsulated microbubbles. A hierarchical twopronged approach of modeling -- a model is applied to one set of experimental data to obtain the model parameters (material characterization), and then the model isvalidated against a second independent experiment -- is demonstrated in this thesis for two lipid coated (Sonazoid"!and Definity®) and a few polymer (polylactide) encapsulated microbubbles. We performed in vitro acoustic characterization with these contrast microbubbles, i.e., determined the material properties of their encapsulations and compared model predictions with experimental observations. The nonlinear elastic models developed were successful in predicting several experimentally observed behaviors e.g., low subharmonic thresholds and "compression-only" radial oscillations. Results indicate that neglecting the polydisperse size distribution of contrast agent suspensions, a common practice in the literature, can lead to inaccurate predictions and unsatisfactory results. Recent numerical investigations of the nonlinear dynamics of encapsulated microbubbles from our group contradicted previously published experimental results on the dependence of subharmonic behaviors on ambient pressure. We wanted to investigate this issue through new in vitro acoustic experiments by designing a modified experimental setup. Preliminary results indicate that the previously published conclusion that subharmonic response from contrast microbubbles linearly decreases with increasing ambient pressure might not be correct under all excitation conditions; it may both increase or decrease under appropriate excitations in conformity with the results of numerical investigations. Experimental characterization of the ELIPs and polymersomes was performed with the goal of demonstrating their potential as ultrasound agents with simultaneous imaging and drug/gene delivery applications -- 'dual-purpose' contrast agents. Carefully performed experiments conclusively demonstrate the ultrasound reflectivity (echogenicity) of the liposomes prepared using an established protocol. Although, no subharmonic response from these ELIPs was observed, altering the constituents of the lipid bilayer and polymerizing it generated a subharmonic response indicating that the echogenic properties of ELIPs can be controlled by altering the preparation protocol. Our results indicate that the freeze-thaw cycle and lyophilization in presence of mannitol followed by reconstitution in a buffer was critical for generating echogenic response from these liposomes. A finite amount of mannitol (above 100 mM) proved critical for echogenicity, but increasing the mannitol concentration above that amount did not change the echogenicity. Lyophilized powders create a polydisperse suspension of liposomes upon reconstitution, which in turn results in a response without a distinct resonance peak. We believe that the echogenicity of the liposomes results from the larger diameter liposomes present in this polydisperse suspension. In spite of the conclusive experimental evidence of echogenicity, the underlying mechanisms are not completely understood primarily due to the uncertainty regarding the exact location of the gas pockets. An accurate knowledge of the locations and dimensions of the gas pockets is critical for developing improved mathematical models of their acoustic behaviors. For the experimental validation of the concept of 'dual-purpose' contrast agents, four novel formulations were investigated--a lipopeptide conjugated ELIP formulation that can be triggered by the extracellular enzyme matrix metalloproteinase-9 (MMP- 9), a polymer coated redox triggered ELIP formulation for cytosolic drug delivery, pH sensitive liposomes with tunable echogenicity capable of drug-release in mildly acidic micro-environment and redox sensitive echogenic polymersomes. Both in vitro acoustic studies and ultrasound imaging (the latter performed in NDSU by our collaborators) demonstrated the echogenicity of each of these formulations. Although, ultrasound excitation (
Author: Aaron Fenster Publisher: Taylor & Francis ISBN: 1439866295 Category : Medical Languages : en Pages : 331
Book Description
Up-to-Date Details on Using Ultrasound Imaging to Help Diagnose Various DiseasesDue to improvements in image quality and the reduced cost of advanced features, ultrasound imaging is playing a greater role in the diagnosis and image-guided intervention of a wide range of diseases. Ultrasound Imaging and Therapy highlights the latest advances in usin
Author: Thomas Albrecht Publisher: Springer Science & Business Media ISBN: 9788847003040 Category : Medical Languages : en Pages : 76
Book Description
The value of ultrasound contrast agents (USCA) in everyday clinical practice depends on the pharmacokinetics, the signal processing, and the contrast-specific imaging modalities. Second-generation USCA, are blood pool agents that do not leak into the organ tissue to be examined but remain in the intravascular compartment increasing the Doppler signal amplitude during their dynamic vascular phase. Taking advantage of the stability of their microbubbles, they can withstand the acoustic pressure of insonation much better than first-generation contrast media, which results in an increased half-life of the agent and, consequently, in a prolonged diagnostic window. Concomitant with the improvement of contrast agents, different contrast-specific imaging modalities have been developed which, used in combination with USCA and a low mechanical index, allow continuous real-time grey-scale imaging. These recent technical improvements have opened new possibilities in the use of USCA in a variety of indications. Written by internationally renowned experts, the contributions gathered in this book give an overview of current and possible future new applications of USCA in routine and clinical practice.
Author: L. Hoff
Author: L. Hoff
Author: Peter Johan Anton Frinking
Author: Gaio Paradossi
Author: Yanjun Gong
Author: Shirshendu Paul
Author: Michał Mleczko
Author: Aaron Fenster
Author: Jon Nathan Marsh
Author: Thomas Albrecht
Author: