Physics of ultrasound

Periodic motion causes pressure waves in the media, the physical surroundings. In the diagram, when the piston is spinning forward compresses the Mediterranean. And is transmitted through pressure on the medium. As the piston moves back and forth, and creates more compressions transmitted through the Mediterranean, such as cars down a highway. And more rapidly and the piston moves back and forth, and closer one is pressure on the next one.


Sound waves are made of high-pressure and low pressure and pulses travel through an intermediary. In areas with high pressure (pressure), where particles are squeezed together; area of low pressure (rarefaction) is the particles were spread apart. Along the sound wave is the distance between two successive pulses of high pressure, two successive pulses of low pressure. Wavelength decreases with increasing frequency sound. We hear the sound is normally 20 to 20 000 cycles per second. Ultrasound means sound which has a frequency higher than our regular session. Ultrasound used for medical purposes is one of the Hz (one million cycles per second) to 20 MHz. Ultrasound do not use the usually higher than 10 MHz. Higher frequency ultrasound could be a sharper images, but these images are fainter because the tissue to absorb high-frequency energy more easily. Just like any other type of sound, and high frequency ultrasound, and the shorter wavelength. Ultrasound has from about 1.5 mm.





The speed of ultrasound does not depend on frequency. The speed of ultrasound depends on what material or tissue is traveling where, comprehensive and spacing of material particles and the strength of attraction between particles of all articles have an impact on the speed of ultrasound as it passes through. Ultrasound travels faster in dense materials and slower in the compression of the material. Soft tissue in the sound travels at 1500 m / s, in the bones around 3400 m / s, and in the air 330 m / sec.



Over the past two decades, ultrasound has undergone many advances in imaging technology such as Ramadi, a large scale, real-time ultrasound imaging, high resolution 7.5-10 MHz transducers, the flow of color Doppler and more.



Ultrasound is reflected on the border between different materials. Ultrasound is very good and reflects where the soft tissue to meet with the air, or soft tissue meets the bone, or bone, where he will meet with the air. The frequency is unchanged as the sound travels through various tissues. This means that in healthy tissue, which travels more slowly, and the decrease of wavelength. Just as the spacing between cars on the highway narrows when you slow down for construction, pressure areas were jammed together when the wave slows down the sound.



Ultrasound produced by the adapter. Adapter is a device that takes power from one source, and conversion of energy to another form, and hand over power to another target. In this case the adapter acts like a loudspeaker and microphone. Transducer converts electric signals of the ultrasound waves, catching waves reflected again converted to electrical signals. Returned to the electrical signals from an adapter is used to form images on the TV screen.



Attenuation is the loss of energy, and expressed the change in intensity, and energy through an intermediary. Is measured intensity ultrasound in watts per square centimeter. DB used to express the difference between the intensity ultrasound. For example, when the ultrasound a hundred times less dense, and the attenuation is -20 dB (decibels), and when ultrasound is one thousand times less dense, and the attenuation is -30 dB.



Attenuation rate is called the attenuation coefficient. To soft tissue, and the attenuation coefficient is half the frequency in length. For example, it will be 8 MHz signal loses 4 dB per centimeter of travel.



Ultrasound has a wide range of technical improvements that led to the availability of high resolution real time gray scale imaging, and tissue assessment consistent, color, strength, and more.