10.0 The Physics of UltrasoundUltrasound is sound with frequencies higher than the highest frequency that can be heard by human beings >20KHz). Medical ultrasound operates typically between 1 and 10MHz. The propogation characteristics are defined in the theory of acoustics and medical ultrasound is principally concerned with compression waves rather than shear waves.•Basic acoustic physics, wave equation•Plane, spherical wave solutions of the wave equation•Wave propogation in media, energy, intensity, reflection, refraction•Transmission, reflection coefficients, attenuation in media, scattering •Doppler effect•Beam formation and focusing•Beam patterns, diffraction formulation•Paraxial, Fresnel and Fraunhofer approximations
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Important points from Ultrasound 1 Lecture•Bulk compressibility, •Ultrasound in tissue is principally a longitudinal (compressive) wave•Wave equation in various geometries (plane wave, spherical wave)•Speed of sound and density of various biological materials•Acoustic Impedance Z=ρc•Acoustic Energy, Power Intensity.•Transmission, Reflection for wave Amplitude and Intensity•Quarter wave (λ/4) matching layer conceptdpdVV11cAnimation courtesy of Dr. Dan Russell, Kettering University21212ZZZZIIRirI212214ZZZZIITitITI+ RI=1(pressure is different!)