ultrasonics ppt

PHYSICS

NAME:HARSHIL. R. SHAHEN NO:151080106025BRANCH:CIVILSEM:2SUBJECT:ULTRASONICS(PHYSICS) SUMBITED BY MEDHA MAM

2.8 Ultrasonics

The Frequency of a Sound Wave

Audible Range: 20 Hz ----- 20,000 Hz.

Infrasonic waves: Sound waves with frequencies < 20 Hz.

Ultrasonic waves:

Sound waves with frequencies > 20,000 Hz.

Bats and ultrasonic sound waves

Bats use ultrasonic frequencies up to 100 kHz for locating their food sources and navigating.

Infrasonics

Rhinoceroses use infrasonic frequencies as low as 5 Hz to call one another.

Piezoelectric Transducer

Piezoelectric transducer is used to produce and detect Ultrasonic Waves.

It is a quarts crystal which converts electrical oscillations into mechanical vibrations (sound) and vice versa.

Applications of Ultrasound in Medicine

1. Ultrasonic Scanner

2. The cavitron ultrasonic surgical aspirator (CUSA)

3. Bloodless surgery: High-intensity focused ultrasound (HIFU)

4. The Doppler flow meter

Ultrasonic Scanner

Ultrasound reflects from boundaries between two different media. Ultrasound can be used to identify a wide range of soft tissues, whereas X-rays are useful primarily in seeing hard tissue, such as bones.

Ultrasound is non-ionizing, doesn’t ionize atoms or break up molecular bonds.

It is safe to use in obstetrics.

The cavitron ultrasonic surgical aspirator (CUSA)

Neurosurgeons use a cavitron ultrasonic surgical aspirator (CUSA) to “cut out” brain tumors without adversely affecting the surrounding healthy tissue.

Bloodless surgery High-intensity focused

ultrasound (HIFU)Another application of ultrasound is in a new type of bloodless surgery, which can eliminate abnormal cells, such as those in benign hyperplasia of the prostate gland.

This technique is known as HIFU (high-intensity focused ultrasound). It is analogous to focusing the sun’s electromagnetic waves by using a magnifying glass and producing a small region where the energy carried by the waves can cause localized heating. Ultrasonic waves can be used in a similar fashion.

The waves enter directly through the skin and come into focus inside the body over a region that is sufficiently well defined to be surgically useful. Within this region the energy of the waves causes localized heating, leading to a temperature of about 56 °C (normal body temperature is 37 °C), which is sufficient to kill abnormal cells. The killed cells are eventually removed by the body’s natural processes.

Doppler Flow Meter

A Doppler flow meter measures the speed of red blood cells.

Research ArticlesCompressibility of gastrointestinal tract tumors during transabdominal sonographic examination: A clue to the diagnosis of gastrointestinal lymphoma (p 59-62)Yasutomo Fujii, Nobuyuki Taniguchi, Harumi Koibuchi, Yoshikazu Yasuda, Hideo NagaiPublished Online: Jul 30 2007 3:37PMDOI: 10.1002/jcu.20393

Sonographic examination of the appendix in acute infectious enteritis and acute appendicitis (p 63-66)Koichi Yabunaka, Toshizo Katsuda, Shigeru Sanada, Hidetoshi Yatake, Tsunemasa FukutomiPublished Online: Jul 27 2007 2:02PMDOI: 10.1002/jcu.20394

Ductus venosus blood flow resistance and congenital heart defects in the second trimester (p 72-78)Jeng Hsiu Hung, Chong Yau Fu, Jen-Her Lu, Chia-Yi Selena HungPublished Online: Aug 3 2007 1:45PMDOI: 10.1002/jcu.20406

2.9 InfrasonicsInfrasonics refers to waves whose frequencies lie below the audible frequency range.

Earthquake waves are infrasonic waves. There are 3 types of earthquake waves:

S-wave: A transverse body wave, can only propagate in solid rock.

P-wave: A longitudinal body wave, propagates at the speed of sound, and has a very large range.

L-wave: The wave that forms along a boundary between two mediums such as air and ground and is responsible for the immense damage that can occur in large earthquakes.

A variety of animals and birds are sensitive to infrasonic waves. Many zoologists believe that the sensitivity of such animals as elephants or cattle could provide them with an early warning of earthquakes and weather disturbances.

Motion SicknessFor vibration at very low frequencies, motion sickness of people in boats must have been one of the earliest noticeable effects. The human body is particularly sensitive to vibrations and infrasound near 7 Hz, at which frequency there is an overall mechanical resonance of organs in the abdominal and chest cavities.

From:http://www.answers.com/topic/infrasound?cat=technology

Waves 1 and Wave 2

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