Medical Imaging Systems · Ultrasound Imaging · 2 marks · Multiple choice
A longitudinal ultrasound wave meets a muscle–kidney boundary at 60°. Acoustic impedances are 1.70×10⁵ and 1.62×10⁵ g cm⁻² s⁻¹; sound speeds are 1590 and 1560 m/s respectively. Transducer frequency is 1.5 MHz. Find transmitted angle in degrees (nearest integer) and intensity transmission coefficient (two decimals).
Snell’s law gives sinθt=(1560/1590)sin60°, so θt≈58.2°, rounded fifty-eight. For pressure transmission tp=2Z₂cosθi/(Z₂cosθi+Z₁cosθt). The transmitted-to-incident ray-intensity ratio is (Z₁/Z₂)tp²≈.94. Thus C. Multiplying this ratio by cosθt/cosθi instead gives the normal energy-flux coefficient, a different quantity.
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