Andrew Carter

Electrical Engineer

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Applications of Sound in Medicine

The use of sound in medicine started since long time ago. Doctors have used stethoscopes to listen to human body’s internal sounds since the early 19th century and the ultrasound imaging has develop to a powerful device in obstetrics and other medical aspects that expectant mothers need to know the gender of their offspring by 20 weeks of development. Also it is used to examine some organs and blood flow and sound reflects at boundary of tissues with different densities

Today scientists are continuing to study and seek more advanced applications of sound in medicine. An acoustical energy can be concentrated used for imaging and curing a variety of ailments which includes cancer, stroke, and Parkinson’s disease. Sound waves can be focused deep inside the body to manage hemorrhages or internal blood clothing, they can help to assist doctors in giving drugs to specific areas in tissues, and they can prevent adverse bacterial infections.

Neurosurgeons use a device called a cavitron ultrasonic surgical aspirator (CUSA) to take away brain tumors once thought to be very difficult to operate. The probe breaks any section of the tumor that it fells and the remains are removed out of the brain with a saline solution. With the help of the tip of the probe which is small, the surgeon can selectively remove small bits of malignant tissue without destroying or damaging the surrounding healthy tissue.

The Doppler flow meter is a plays an important part in medical application of the Doppler effect. This device gauges the speed and control of blood flow by transmitting and receiving elements that are placed directly on the skin. The transmitter release a continuous sound, when the sound is echoed from the red blood cells, its frequency is changed in a kind of Doppler effect because the cells are in motion. The receiving element senses the reflected sound, and an electronic counter calculates its frequency, which is Doppler-shifted relative to the transmitter frequency.

The Doppler flow meter can be also used to set regions where blood vessels have narrowed since much flow speeds occur in the narrowed regions, according to some medical studies. Also, the Doppler flow meter can be used to sense the movement of a fetal heart as early as 8–10 weeks after formation.

Ultrasonography (sonography) uses multiple acoustic transducers to convey pulses of sound into a material. When a sound wave came across with a material with a different density, a part of the sound wave is reflected back to the probe and is sensed as an echo. The duration it takes for the echo to move back to the probe is computed and used to calculate the depth of the tissue interface causing the echo.

The higher the difference between acoustic impedances the larger the echo is. If the pulse strikes gases or solids the density difference is so much that most of the acoustic energy is reflected and it becomes impractical to see deeper.

Tags: sound, ultrasound, medicine

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