Ultrasound Transducers

Special small ultrasound transducers, often referred to as endoscopic transducers, have been designed which can be inserted into blood vessels to examine blockages in arteries (43). These transducers operate at approximately 20 MHz and have a viewing distance of less than a centimeter. Such devices are capable of producing ultrasound images of the inside of arteries and veins. The quaUty of the ultrasound image is sufficient to determine the type of blockage. 

In fact, this last configuration (a sonochemical cell where the electrodes and the ultrasound transducer tip are directly dipped into the working solution) is the most used experimental configuration [38], see Fig. 4.2a, which we will name electrode-apart-transducer configuration. The relative orientation between the transducer tip and electrode surfaces has been taken into account when the electrode is placed so... 

Fig. 15.3 Typical experimental arrangement for the study of multi-bubble sonoluminescence. The ultrasound transducer used here is 515 kHz and produces a standing wave pattern in the reaction cell. A horn-type sonifier (usually 20 kHz) can also be used in such an arrangement...

Aerogels are used in diermal insulation, catalysis, detection of high energy particles, piezoceramic, ultrasound transducers, integrated circuits, and as dehydrating agents. 

Figure 9 Ultrasound transducer arrangement in the test section (a) side view and (b) front view.

Ultrasound tomography (UST), 205 Ultrasound transducer arrangement, 14 Urea-formaldehyde microcapsules, 67 UVP-DUO systems, 2, 7, 12-13 UVP measurements. See Ultrasonic velocity profiler (UVP) measurements... 

Mount the ultrasound transducer on a mechanical arm in a plastic container filled with degassed water. 

Ultrasound imaging is a non-invasive, portable and relatively inexpensive imaging modality, which is used extensively in the clinic. An ultrasound transducer (also called scanhead) sends short pulses of a high-frequency sound wave (1-10 MHz) into the body. At interfaces between two types of tissue, the wave will be refracted and part of the sound wave is reflected back due to Snells law. How much is reflected depends on the densities of the respective tissues, and thus the speed of the sound wave within the different tissues. In addition, parts of the sound wave are also backscattered from small structures at tissue boundaries or within the tissue. High-frequency sound waves propagate weU through soft tissue and fluids, but they are more or less stopped by air or bone. In clinical practice, this limitation is referred to as an acoustic window . The transducer not only sends the wave into the body but also receives part of the reflected and/or backscattered wave, also named echo . In clinical practice, ultrasound is used in a... 

Figure 10 Aerogel quarterwave impedance matching layer for a piezoceramic ultrasound transducer. For maximized output power the acoustic impedance of the aerogel layer must be Za = (ZpZo) 72, Typical thickness d is around 0.1 mm for/= 1 MHz.

In the pitch catch method, two ultrasound transducers are used, one as a transmitter and one as a recaver. However, unlike the TTU method, the pitch catch transducers may be on the same side of the part or oriaited in a number of ways for the ultrasound to progress from one transducer to the otha". The intapretalion is usually based on changes in detected signal strength or frequency and calibrated against a known test sample. 

Intracardiac echocardiography is emerging as an ideal real-time modality to guide intracardiac interventional procedures. ICE allows accurate appreciation of cardiac anatomy and detailed visualization of specific anatomic structures, the most important factors in planning and guiding catheter-based interventional techniques [15-17]. In our daily practice, ICE is performed using a commercially available 9-F/9 MHz ultra-ICE catheter-based ultrasound transducer (EP Technologies, Boston Scientific, San Jose, CA, USA). The Ultra ICE catheter is introduced percutaneously into the... 

Cheung AH, Wang KY, Jiranek GC et al (1992) Evaluation of a 20-MHz ultrasound transducer used in diagnosing porcine small bowel ischemia. Invest Radiol 27 217-223... 

In order to do so, the subjects are usually seated with their back against the gamma camera and the ultrasound transducer is positioned in the region of the umbilicus. The first measurement is performed within 1 min of meal ingestion, followed by subsequent images at intervals depending on which meal is used. Ultrasound T50 is defined as the time when the antral area is decreased to half its maximum (Horowitz et al. 1993). 

CMUT devices are used in the real-time in vivo imaging applications with an improved performance over the existing medical ultrasound transducers. A wafer-bonded CMUT probe showed a bandwidth of 130 %... 

Hunt, J. W., Arditi, M., and Foster, F. S. (1983), Ultrasound transducers for pulse-echo medical imaging, IEEE Trans. Biomed. Eng., 30 453-481. 

Kun-Hong et al. [54] studied the gelation time as a function of the pH value. However, they did not give any detail of the ultrasound transducer device. They prepared sonosols with = 10 with acidic water (HCl). As a first step, the pH was set to 2.7 and then increased to 4.7 with NH4OH. Instantaneous gelation occurred at a pH = 5.5 or higher. 

In 1841, Swiss physicistJean-Daniel Golladon conducted experiments regarding sound transmission in Lake Geneva he determined that sound traveled more than four times faster in water than in air. In 1881, French physicist Pierre Gurie, who is well known for his work regarding ionizing radiation, discovered the piezoelectric effect, which later made the development of the ultrasound transducer possible. 

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