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Measurement Techniques
Published in Marvin C. Ziskin, Peter A. Lewin, Ultrasonic Exposimetry, 2020
Marvin C. Ziskin, Peter A. Lewin
The acoustic radiation force is the time-average force exerted by an acoustic field on an object. The acoustic radiation force may often be of relevance in ultrasonic fields in various circumstances, in biological tissues, and elsewhere. The type of instrument used to accomplish the task is generally referred to as the radiation force balance, although gravimetric balances in the strict sense constitute only one group of the devices. The irrelevance of the additional constant is often referred to as the so-called Langevin condition in the literature and generally attributed to the open-vessel situation typical of usual radiation force measurements. There is a large variety of radiation force devices with which various force-measuring methods are applied. The suspension wire(s) penetrating the water surface may lead to disturbing buoyancy and surface tension forces. The radiation force is obtained by extrapolating the signal back to the moment of switching the transducer.
Dictionary
Published in Mario P. Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Ultrasound. The use of ultrahigh-frequency sound waves to generate anatomic images based upon the reflection of the sound waves at different tissue interfaces. Acoustic radiation at frequencies above the range of human hearing; sound of frequency greater than 20 kHz.
Physiology of Hearing
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Soumit Dasgupta, Michael Maslin
As a starting point one might consider a scenario whereby no force is applied to a region of air. In such a scenario, the air molecules are said to be at ambient (or atmospheric) pressure. When an object in the region vibrates, a force is applied to those air molecules that are in contact with the object, causing their displacement. For example, take the loudspeaker shown in Figure 48.1. As the diaphragm of the loudspeaker moves to the right of its centre position, the air molecules at the surface of the diaphragm are displaced to the right. This movement causes the air molecules to be pushed closer to adjacent air molecules that are further over to the right. Relative to the ambient pressure, a localized pressure increase is produced and this pressure increase is known as compression. Next, when the diaphragm of the loudspeaker moves back through its centre position and over to the left, those air molecules that were displaced to the right are now drawn to the left. When the displaced molecules reach their centre (equilibrium) position, the pressure will momentarily be equal to ambient pressure, but as the molecules move further to the left they are drawn increasingly further apart from their adjacent air molecules. The pressure will now drop below the ambient pressure and this decrease in pressure is called rarefaction. As each molecule vibrates backwards and forwards around its equilibrium position, alternating regions of compression and rarefaction arise. If these pressure variations can be detected by the ear, they can be described as sound. (It is worth noting that the variations in density of the air molecules shown in Figure 48.1 have been exaggerated for the purposes of illustration. In reality, pressure fluctuations associated with sound are only a small fraction of the overall atmospheric pressure.) Since air is a continuous and elastic medium, the pressure variations will propagate away from the source such that sound generated by the source can be detected in regions of air that are remote. This is known as acoustic radiation.
Production of acoustic radiation force using ultrasound: methods and applications
Published in Expert Review of Medical Devices, 2018
Many biomedical applications have been developed over the past two decades that utilize acoustic radiation force (ARF). Before these methods were developed a considerable amount of theoretical and fundamental work was done, which has been reviewed by Sarvazyan [1]. Additional, application-specific reviews of using ARF have also been published in the literature [2–5]. These reviews separately cover some of the topics addressed in this review. The general classes of applications include the measurement of mechanical properties, the manipulation of particles or cells, the modulation of cellular behavior, and the bioeffects related to the use of ARF. Ultrasound waves are transmitted into tissue or the medium of interest, and the momentum of the waves is transferred to the medium to cause deformation or particle displacement. The interactions of the ultrasound waves can be tailored by different methods of focusing or utilizing specific boundary conditions for optimizing the use of ARF to deliver forces in a noncontact manner. This review will focus on the how the application of ARF both in time and space enables different biomedical applications. This review will also detail some of the commercial implementations that use ARF.
Synergistic ultrasonic biophysical effect-responsive nanoparticles for enhanced gene delivery to ovarian cancer stem cells
Published in Drug Delivery, 2020
Chun Liufu, Yue Li, Yan Lin, Jinsui Yu, Meng Du, Yuhao Chen, Yaozhang Yang, Xiaojing Gong, Zhiyi Chen
Sonoprinting is the key mechanism to understand the ultrasonic bioeffects of ultrasound triggered nanoparticle-loaded MBs (De Cock et al., 2016; Roovers et al., 2019a,b). When PSP@MB is exposed in the ultrasonic field, PSP@MB not only has cavitation, but also acoustic radiation. Acoustic radiation can be divided into primary acoustic radiation and secondary acoustic radiation. Sonoprinting is another strong piece of evidence to explain the mechanism of ultrasonic-triggered PSP@MB mediated gene delivery of OCSCs in vitro and in vivo. A good gene delivery system also includes stable blood circulation translation, gene protection, and controllable gene release, hence PSP@MB as a gene delivery carrier was prepared and characterized (Figure 2).
Military and industrial performance: the critical role of noise controls
Published in International Journal of Audiology, 2019
Kurt. D. Yankaskas, Jeffrey M. Komrower
Often, it is not possible to isolate the source and stop the vibrational energy transmission. In this situation, the methodology for preventing acoustic radiation would be to reduce the vibration of the radiating structure. In the example shown in Figure 3, where a structural bulkhead was radiating acoustic energy into a compartment during launch, a unique spray-on damping treatment, which was developed through another ONR SBIR (N04-221) (Meyer 2012), was applied to the bulkhead. This treatment reduced noise levels in the space by 4–6 dB. This damping treatment has also been successfully applied to radiating ductwork in several power plants – another example of technology developed through Navy programmes, successfully deployed on other applications. Silencers are typically used, for example where there is a loud fan, as was the case in several of the power plants previously mentioned. These fans were high volume units used to provide cooling air flow to the generators. Acoustic silencers, placed at the fan exhaust, which function by absorbing the acoustical energy, successfully reduced noise levels by 4–8 dB. Acoustic silencers can also be employed in hydraulic lines, which often emit high energy acoustic tones, to reduce noise. An excellent example of this can be found in Yankaskas and Fast (1999). In this example, the raising and lowering of the jet blast deflector (JBD) used during aircraft carrier launches, was creating a loud hydraulic orifice noise. The solution was to create a bi-directional multi-orifice muffler to replace the existing orifices in the JBD hydraulic lines. This fix was successful, resulting in noise attenuations of over 20 dB.