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Inflammatory, Hypersensitivity and Immune Lung Diseases, including Parasitic Diseases.
Published in Fred W Wright, Radiology of the Chest and Related Conditions, 2022
Necrosis or abscess formation may lead to cavitation. With some pneumonias (e.g. staphylococcal) pneumatocoeles may occur, probably as a result of a flap-valve type of mechanism within smaller distorted bronchi (Illus. PNEUMATOCOELES). Such pneumatocoeles may in turn lead to a generalised or loculated (e.g. inter-lobar) pneumothorax. Complicating pleural effusions and/or empyemata may follow either type of consolidation.
Basic and Technical Aspects of Ultrasound
Published in Arianna D'Angelo, Nazar N. Amso, Ultrasound in Assisted Reproduction and Early Pregnancy, 2020
Cavitation is a mechanical effect that occurs in tissue due to the passage of the mechanical ultrasound wave. This effect is not as a result of heating but due to the presence of gas-filled microbubbles or cavities in the exposed tissue, which can oscillate or collapse under the pressure of the ultrasound beam. This can produce high shear forces or pressures as well as heat, which can damage cell membranes or produce highly reactive free radicles. Once again, an index has been developed in an attempt to account for the effects of cavitation, and this is known as the mechanical index (MI).
Seeing with Sound: Diagnostic Ultrasound Imaging
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
Another very promising method of improving the potency of medications, particularly targeting the brain tissues, is based on the use of ultrasound cavitation. Recall our discussion of cavitation in Section 4.11. Local pressure decreases when the trough of an ultrasound wave passes. This can lead to boiling, or creation of vapor-filled bubbles. Cavitation can be of two types: inertial and stable. In inertial cavitation, the vapor bubbles quickly burst, causing mechanical damage to tissue or even light emission. In a regime of stable cavitation occurring at a lower intensity of ultrasound, the vapor bubbles undergo periodic expansion and contraction. Research shows that such oscillations can enhance drug transport across the walls of blood microvessels. This effect is potentially important for brain tissues where drugs in blood microvessels face the so-called blood–brain barrier. In a similar approach, scientists are currently studying the possibility of using microbubble contrast agents originally developed to increase tissue echogenicity (Section 4.16) in ultrasound imaging. As in the case of stable cavitation, low-intensity ultrasound waves can cause expansion and contraction of these microbubbles, which in turn can increase stress on the walls of blood vessels and enhance the drug transport.
Ultrasound-sensitive cRGD-modified liposomes as a novel drug delivery system
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Nour M. AlSawaftah, Vinod Paul, Doua Kosaji, Leen Khabbaz, Nahid S. Awad, Ghaleb A. Husseini
Arginine-glycine-aspartic acid (RGD), is a polypeptide that plays a vital role in cell adhesion, cellular differentiation, migration, and attachment to the extracellular matrix (ECM). RGD peptides have linear and cyclic structures. However, the steric hindrance of the structure of the cyclic RGD (cRGD) makes them resist proteolysis and have the ability to bind with higher affinities to integrin receptors compared to linear RGD peptides. Moreover, RGD has a relatively high and specific affinity towards αvβ3 integrins over-expressed in tumour neovasculature. Previous studies have shown that liposomes conjugation to RGD peptides has great potential for cancer therapy [18–20]. To trigger the release of therapeutic agents from liposomes, ultrasound is emerging as a promising mechanism for spatiotemporal drug release from drug-loaded liposomes. The effects of ultrasound as a triggering mechanism can be divided into thermal effects due to the increase in the medium’s temperature as energy is absorbed, and mechanical effects due to acoustic cavitation. Acoustic cavitation is the formation, growth, and collapse of bubbles in a medium due to pressure changes. Stable cavitation is when the bubble’s radius varies about an equilibrium value, while inertial (transient) cavitation is when the bubbles grow rapidly, expanding to 2- or 3-fold their resonant size and then collapse violently [21–23]. The occurrence of cavitation depends on the frequency and intensity of ultrasound, as well as the availability and number of cavitation nuclei.
Additional information of bitewings to first time clinical examination of caries and restoration status in permanent dentition
Published in Acta Odontologica Scandinavica, 2022
Azam Bakhshandeh, Kim Ekstrand, Nils-Erik Fiehn, Vibeke Qvist
Previous studies have shown that clinical assessment of early occlusal and approximal dentine caries lesion in the posterior regions has low sensitivity but relatively high specificity [5–7]. It means that caries lesions might be overlooked by clinical-tactile examination. Bitewing radiographs (BWs) are the most often used supplementary tool to clinical examination in detection of primary caries and caries adjacent to restorations lesions especially on approximal surfaces [8,9]. Radiographical detection of all types of dentine caries has high specificity with limited risk of false positive diagnosis [10,11]. Furthermore, radiographical assessment has higher sensitivity but lower specificity in detecting cavitation on approximal surfaces compared to clinical assessment [12]. In a systematic review, it was reported that radiographs were more accurate than tactile detection of approximal caries adjacent to restorations with limited risk of false-positive diagnoses [1].
Recent developments on foaming mechanical and electronic techniques for the management of varicose veins
Published in Expert Review of Medical Devices, 2019
C. Davide Critello, Salvatore A. Pullano, Thomas J. Matula, Stefano De Franciscis, Raffaele Serra, Antonino S. Fiorillo
The production of foams always requires an energy input to generate bubbles within a liquid [46], and cavitation is the physical manifestation involving a phase transition due to an external mechanical disturbance. In its most general form, cavitation is the creation and/or activity of gas or vaporous bubbles. Usually, it occurs by increasing the temperature of the liquid (e.g., boiling), creating turbulence in a liquid (i.e., hydrodynamic cavitation), or sending a sound wave through a liquid (i.e., acoustic cavitation). The formation of cavitation depends on the liquid characteristics, gas concentration level, and presence of impurities, among other things. Cavitation is sometimes undesired, as it can lead to damage (even to hardened materials), leading to material failure. However, it has been positively deployed in a wide variety of fields such as chemistry, food science, and biomedical applications, including drug delivery [47], tumor ablation [48], lithotripsy [49] and histotripsy [50], to cite a few examples.