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Ultrasound imaging (US) (Ultrasound basics: (• Acoustic parameters: (o…
Ultrasound imaging (US)
Ultrasound basics:
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• Acoustic parameters:
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o Intensity (0,01-300W/cm2); adjustable
o Wavelenght (0,1-0,8mm) ST; determined
by source and medium; not adjustable
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Attenuation:
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• Decrease in intensity, power and amplitude
• Includes scattering, diffraction and absorption phenomena
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Propagation:
• Homogenous media is characterized by acoustic impedance, Z
– Analogous to electrical impedance: as impedance increases it inhibits velocity of the particles (current) for a given acoustic pressure (voltage)
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– 𝑐: acoustic wave velocity in a tissue, depends on its density
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Reflection, refraction, scattering
Reflection occurs likely when the dimension of the boundary is more than a few wavelengths of the sound
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Refraction: change in the direction of the transmitted wave. It occurs when oblique incidence and different speed sounds of the mediums
Scattering:
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Rayleigh scattering: reflection equally in all directions. When dimensions are much smaller than the beam's wavelength. example: red blood cells