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Echo Physics

Echo Physics

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Echo Physics

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  1. Echo Physics Stephen Devries, MD

  2. Velocity = Frequency(transducer) x Wavelength Smaller wavelength Greater resolution • Velocity changes with media • increases through muscle (1580 m/sec) • decreases through fat (1450 m/sec) • markedly decreases through air (330 m/sec)

  3. Amplitude is strength of signal (measured in log of decibels) Increase of 6 dB is a doubling of signal amplitude Power is a function of amplitude

  4. Ultrasound Transducer • Pizoelectric crystals, stimulated by AC, generate sound waves • Pizoelectric crystals, deformed by received sound waves, produce current

  5. Increasing Frequency Extends Near Field Resolution

  6. Continuous Wave Doppler

  7. Pulse Doppler

  8. Velocity as a Hemodynamic Measurement Modified Bernoulli Equation Pressure Gradient = 4V2

  9. Several Descriptors of “Gradient”