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8 terms

Basic Physics Terms

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Ultrasound
Utilizes sound waves of very high frequency (2MHz or greater). It is propagated via waves of compression and rarefaction, and requires a medium (tissue) for travel. The higher the frequency, the less depth penetration, however the resolution is improved.
Resolution
-Is the parameter of an ultrasound imaging system that characterizes its ability to detect closely spaced interfaces and displays the echoes from those interfaces as distinct and separate objects. The better the resolution, the greater the clarity of an ultrasound image.
Axial Resolution
Is the minimum required reflector separation along the direction of propagation required to produce separate reflections. Good axial resolution is achieved with short spatial pulse lengths. Short spatial pulse lengths are a result of higher frequency and higher damped transducers. Therefore the higher the frequency the better the resolution.
Lateral Resolution
Is the minimum reflector separation perpendicular to the direction of propagation required to produce separate reflections. Good lateral resolution is achieved with narrow acoustic beams. A narrow acoustic beam is the result of a long near zone and a small angle of divergence in the far zone.
Transducers
Convert one form of energy to another. Ultrasound transducers convert electric energy into ultrasound energy and vice versa. Transducers operate on piezoelectricity meaning that some Materials (ceramics, quartz) produce a voltage when deformed by an applied pressure, and reversely results in a production of pressure when these materials are deformed by an applied voltage.
Pulsed Transducers
Consists of one transducer element which functions as both the source and receiving transducers.
Mechanical Probes
Allows the sweeping of the ultrasound beam through the tissues rapidly and repeatedly. This is accomplished by oscillating a transducer. The oscillating component is immersed in a coupling liquid within the transducer assembly.In our case the coupling fluid is deionized water. It is important that the fluid is bubble free, so that your image is not compromised. Check the water level in the transducer assembly before scanning and if you see air bubbles, make sure you fill it with the deionized water.
Attenuation
A decrease in amplitude and intensity, as sound travels through a medium. Attenuation occurs with absorption(conversion of sound to heat), reflection (portion of sound returned from the boundary of a medium, and scattering (diffusion or redirection of sound in several directions when encountering a particle suspension or a rough surface).These different forms of attenuation are responsible for artifacts that may be in your image. Some of these artifacts are useful and some are not. Some artifacts are produced by improper transducer location or machine settings.