Seeing with Sound: Diagnostic Ultrasound Imaging
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
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.
Current Opinion on the Safety of Diagnostic Ultrasound
Asim Kurjak in CRC Handbook of Ultrasound in Obstetrics and Gynecology, 2019
Cavitation effects require the presence of microbubbles of gas or vapor and are associated with activities surrounding these bubbles. Stable cavitation describes the alternating change of dimensions of gas bubbles which draw the surrounding liquid toward and away from them, setting up strong forces near their surface area. Transient cavitation describes the phenomenon of the rapid collapse of a gas bubble. Associated with this collapse are regions of high pressure and temperatures which can release free radicals which, in turn, can damage cells. Stable cavitation is only set up in continuous excitation exposures, and neither types have been observed in in vitro experiments at intensities below 10 W/cm2. Transient cavitation may be set up with short pulses of the type used in diagnostic applications. It has the potential to cause harmful effects, and attention is being focused to study these effects.5 To date, transient cavitation in vitro has been noted only to happen under experimental conditions requiring the presence of nuclei, and no study has yet been able to demonstrate the presence of any of its effects in mammalian tissues at clinically utilized dosages.
Biomechanics and pathophysiology
Brian Sindelar, Julian E. Bailes in Sports-Related Concussion, 2017
Besides the more popular theory of brain “slosh” directly causing white matter strain and injury; a less known, previously theorized mechanism of TBI has been through cavitation. Cavitation is the formation of bubbles within a liquid following a perturbed state that release high levels of energy when colliding with and bursting upon an object.14,15 Therefore, when a player’s head is struck, cavitation bubbles are presumed to form within the cerebrospinal fluid, travel through this space at high velocities, and cause injury to the brain parenchyma and blood vessels, like a projectile of shotgun pellets. This theory has been exhibited in scientific (hitting a water filled glass vial with a hammer)14,15 and ex vivo animal models16 and therefore hypothesized with a potential application to explain concussive TBI. Without any true clinical evidence or even direct animal models, this theory, though intriguing, is only in its infancy. More recently, this premise has been further reevaluated as a possible mechanism in blast TBI.17–19
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.
Effect of early whole lung lavage at different time-points for promoting the removal of depleted uranium from the lung
Published in International Journal of Radiation Biology, 2021
Weilin Fu, Yao Xiao, Feng Zeng, Xiangyu Chen, Yong Zhu, Zhu Tian, Yi Liang, Rong Li, Minghua Liu
Ultrasonic cleaning technology involves the use of ultrasonic cavitation to remove dirt from object surfaces. It involves rapid and efficient cleaning, is particularly effective for cleaning blind cavities and various geometric objects (Yang and Li 2015), and is widely used in the irrigation of root canals and wounds in the clinic (Konno et al. 2017; Li et al. 2018). In view of the lack of incomplete clearance of radionuclides in the lungs via WLL, our team has invented a feasible, three-lumen bronchial intubation for ultrasonic lung lavage (patent no. ZL201922363247.0). The specific design was as follows: by setting an ultrasonic generator between the liquid outlet and the lower end of the injection port, the cavitation of the ultrasonic wave was used to impact and peel off foreign bodies attached to the inner wall of the alveoli to achieve the purpose of cleaning. Two accessory occluder sacs were set up to ensure that the lungs were completely isolated and did not affect each other; even if leakage occurred, lavage fluid could be discharged from the drain catheter between two suboccluder sacs without affecting the opposite side. In future, we will perform an in-depth study to improve the method of WLL, as well as the binding capacity of the lavage fluid.
Co-delivery of CPP decorated doxorubicin and CPP decorated siRNA by NGR-modified nanobubbles for improving anticancer therapy
Published in Pharmaceutical Development and Technology, 2021
Rui Ma, Jingxue Nai, Jinbang Zhang, Zhiping Li, Fenghua Xu, Chunsheng Gao
To improve the drug concentration in tumor tissue and further tumor cells selectively, functional nanocarriers such as polymers, liposomes, and mesoporous silica have been explored and used successfully for the delivery of cargoes (Qu et al. 2014; Zheng et al. 2015). These nanocarriers improve the selectivity of inhibitors and drugs to tumor cells by enhanced permeability and retention (EPR) effect. To further enhance the controllability of drug release, some stimulus-responsive nanocarriers sensitive to endogenous triggers or external triggers are imported. Microbubbles or nanobubbles (NBs), a kind of contrast agent commonly used in the clinic, are also expanded to deliver drugs because of their obvious advantages (Du et al. 2011; Xie et al. 2015; Lin et al. 2016). These microbubbles or NBs are able to oscillate in response to the exerted cycles of ultrasound (US) and engender cavitation. The inertial cavitation of bubbles may produce ultrasonic signals able to be detected by the US transducer and therefore these bubbles are usually used in imaging of blood vessels and tissues (Bart et al. 2012). The violent cavitation is capable of causing acoustic disruption of bubble carriers and thereby mediating drug delivery (Du et al. 2011; Lin et al. 2016). US is able to penetrate deeply into tissues and focus on regions of the lesion to effectively activate sonosensitizers while peripheral healthy tissue is unaffected (Lin et al. 2016). Therefore, time- and spatial-controlled drug delivery and visualized therapy might be achieved just by utilizing drug-loaded bubbles combined with US.
Related Knowledge Centers
- Inner Cell Mass
- Blastomere
- Cellular Differentiation
- Blastocyst
- Animal Embryonic Development
- Cleavage
- Blastocoel
- Blastulation
- Fertilisation
- Zygote