Physics · MU Sofia

11. Ultrasound Properties of ultrasound.

Covers the defining properties of ultrasound: frequencies above 20,000 Hz, absorption by tissues that can disrupt cells and microorganisms, and cavitation at high intensity. It then explains the piezoelectric effect in its direct and inverse forms, echography based on reflection at boundaries of differing acoustic impedance, and sonography. Doppler effect and Doppler sonography for blood flow are followed by medical uses, from prenatal 2D imaging to lithotripsy of kidney stones.

Inside: 1 section · 3 labelled pictures · 10 flashcards · 2 min

Topic 12 of 42 in the MU Sofia syllabus for Physics (Medicine, Year 1). The free AceMed note covers it in 1 section, about 301 words (2 min of reading), with 10 flashcards.

In this note

  1. Introduction

Introduction

Summary

  • Ultrasound technology leverages high-frequency sound waves (above 20,000 Hz) for various medical applications, including diagnostics and treatment. The piezoelectric effect is central to ultrasound generation and detection, involving the conversion between mechanical stress and electric charge in certain materials. Echography and sonography use ultrasound waves to visualize internal body structures by detecting reflections from tissue boundaries with differing acoustic impedances. The Doppler effect and its application in Doppler sonography are crucial for assessing blood flow, detecting shifts in frequency caused by the movement of blood cells relative to the ultrasound probe. These technologies facilitate numerous medical applications, from 2D imaging in prenatal care to therapeutic uses like breaking up kidney stones.
  • Ultrasound Properties:
  • Frequencies above 20,000 Hz, inaudible to humans.
  • Mechanically waves absorbed by tissues, useful for cell and microorganism disruption.
  • High-intensity ultrasound can induce cavitation and luminescence.
  • Utilized in echography, where ultrasound is reflected at boundaries between media of different acoustic impedances.
  • Piezoelectric Effect:
  • Direct Piezoelectric Effect: Generation of an electric charge in response to mechanical stress.
  • Inverse Piezoelectric Effect: Material deformation resulting from an applied electric field.
  • Fundamental to ultrasound device functionality, converting electrical signals into ultrasonic waves and vice versa.
  • Sonography and Echography:
  • Sonography: Imaging technique using ultrasound to visualize internal structures like tendons and muscles.
  • Echography: Utilizes the reflection of sound waves to create images, with the degree of reflection varying by tissue impedance.
  • Doppler Effect and Sonography:
  • Doppler Effect: Frequency change observed when there is relative motion between the sound source and observer.
  • Doppler Sonography: Primarily used to assess blood flow, detecting frequency shifts caused by the movement of blood cells.
  • Medical Applications:
  • 2D Imaging: Widely used in prenatal ultrasound scans, creating images by sending and receiving ultrasound beams.
  • Therapeutic Applications: Includes breaking up kidney stones through focused ultrasonic energy, a process known as lithotripsy.

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