Ultrasound Waves and Properties Quiz
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Ultrasound Waves and Properties Quiz

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Questions and Answers

What causes the Doppler-shift in the ultrasound (US) signal reflected by blood cells?

  • The frequency of the US changes due to motion of the blood cells. (correct)
  • The size of blood cells alters the wavelength of US.
  • The intensity of the US affects the scattering by blood cells.
  • Blood cells move at different velocities relative to the transducer.

    • What value does the Doppler-shift formula utilize when the US beam is parallel to the blood flow?

  • $f_D = (2v^2/c)f$
  • $f_D = (2v/c)f$ (correct)
  • $f_D = (v^2/c)f$
  • $f_D = (v/c)f$

    • What happens to the Doppler-shift when the ultrasound beam comes perpendicular to the direction of blood flow?

  • Doppler-shift is zero. (correct)
  • Doppler-shift is maximized.
  • Doppler-shift is inversely proportional to frequency.
  • Doppler-shift is halved.

    • In the Color-Doppler technique, what do red and blue colors represent?

    <p>Red indicates flow towards the transducer, blue indicates away.</p> Signup and view all the answers

    Which of the following describes sound pressure in ultrasound?

    <p>It is directly proportional to ultrasound intensity.</p> Signup and view all the answers

    Why do speed differences arise between particles in a medium during the propagation of ultrasound?

    <p>Particles have different sizes.</p> Signup and view all the answers

    What component of the Doppler-shift solely matters when the ultrasound beam is not aligned with the blood flow direction?

    <p>The cosine of the angle between blood flow and ultrasound beam.</p> Signup and view all the answers

    What frequency range does the Doppler-shift typically fall into?

    <p>Audio frequency range from 20 Hz to 20 kHz</p> Signup and view all the answers

    What is the primary method used in linear scanning to generate a 2D image?

    <p>Moving the scanner in one straight line</p> Signup and view all the answers

    What is a benefit of using sector scanning?

    <p>It allows scanning through intercostal spaces when examining thoracic organs.</p> Signup and view all the answers

    What is a primary advantage of introducing the scanner directly into body cavities?

    <p>It minimizes the absorption of ultrasound signals.</p> Signup and view all the answers

    What does spatial resolution in ultrasound imaging refer to?

    <p>The minimal distance between two points that can be distinguished in an image.</p> Signup and view all the answers

    What is axial resolution in ultrasound imaging?

    <p>The ability to identify two structures lying along the axis of the ultrasound beam.</p> Signup and view all the answers

    What is the typical resolution limit for axial imaging in ultrasound?

    <p>~ 0.5 mm</p> Signup and view all the answers

    An example of an imaging artefact in ultrasound is what phenomenon?

    <p>Shadowing occurring behind reflecting structures like stones</p> Signup and view all the answers

    What primarily determines axial resolution in ultrasound imaging?

    <p>The frequency of the ultrasound wave</p> Signup and view all the answers

    What is the primary purpose of the damping unit in the transducer?

    <p>To stop reverse vibrations and produce short US pulses</p> Signup and view all the answers

    How does Time Gain Compensation affect echo signals from deeper tissues?

    <p>It amplifies echo signals from deeper tissues</p> Signup and view all the answers

    What relationship does the thickness of the piezoelectric plate have with the wavelength of the US pulse in ideal cases?

    <p>It should be equal to half the wavelength of the US pulse.</p> Signup and view all the answers

    What effect results from the friction caused by the motion of smaller and larger particles in ultrasound?

    <p>Micro massage</p> Signup and view all the answers

    What is the ideal thickness of the couplant layer in relation to the emitted US wavelength?

    <p>One-fourth of the emitted US wavelength</p> Signup and view all the answers

    What happens to the cohesive bonds between molecules in a liquid when subjected to high intensity ultrasound?

    <p>They can be broken, leading to cavitation bubbles.</p> Signup and view all the answers

    Which of the following is a significant result of high intensity ultrasound absorption in a medium?

    <p>Temperature increase in the medium</p> Signup and view all the answers

    What is achieved by having the acoustic impedance of the couplant layer equal to the geometric mean of the impedances of the piezoelectric crystal and body tissues?

    <p>Maximized sound transmission efficiency into tissues</p> Signup and view all the answers

    What secondary effect can be induced by the primary effects of ultrasound?

    <p>Dispergation of solid materials</p> Signup and view all the answers

    Which of the following describes how the transducer operates in pulse-echo methods?

    <p>The same transducer alternates between generation and detection.</p> Signup and view all the answers

    What is the purpose of High Intensity Focused Ultrasound (HIFU)?

    <p>To induce hyperthermia for tumor eradication</p> Signup and view all the answers

    What factor influences the intensity of echo signals received by the transducer?

    <p>The absorption coefficient of the tissues</p> Signup and view all the answers

    In which scenario is Extracorporeal Shockwave Lithotripsy (ESWL) used?

    <p>To break kidney stones using high intensity shock waves</p> Signup and view all the answers

    Why is the speed of ultrasound propagation in soft tissues important in medical imaging?

    <p>It allows for the calculation of distances from echoing surfaces.</p> Signup and view all the answers

    What is the approximate maximum sound pressure value generated during ESWL?

    <p>40 MPa</p> Signup and view all the answers

    What is a contributing factor to the effective stone breaking mechanism in ESWL?

    <p>Cavitation in surrounding liquid</p> Signup and view all the answers

    What is the typical duration of an emitted US pulse in medical imaging?

    <p>2-3 cycles long, a few microseconds</p> Signup and view all the answers

    How can the pulse repetition time (PRT) impact ultrasound imaging?

    <p>Longer PRT allows detection of deeper echoes.</p> Signup and view all the answers

    In A-mode ultrasound imaging, what is displayed on the x-axis?

    <p>Arrival time of echo signals</p> Signup and view all the answers

    Which equation can be used to determine the distance from the transducer to a reflecting surface?

    <p>$d=ct/2$</p> Signup and view all the answers

    What distinguishes B-mode imaging from A-mode imaging?

    <p>B-mode displays intensities as pixel brightness.</p> Signup and view all the answers

    What does M-mode imaging primarily visualize?

    <p>Movement of reflecting surfaces over time</p> Signup and view all the answers

    What is a characteristic of two-dimensional B-mode images?

    <p>They generate cross-sectional images of tissues and organs.</p> Signup and view all the answers

    What is the purpose of measuring echo arrival time in ultrasound imaging?

    <p>To calculate the distance between reflecting surfaces.</p> Signup and view all the answers

    Study Notes

    Ultrasound Waves and Properties

    • Reflection: The time it takes for the ultrasound wave to travel to a surface and return (echo) provides information about distance.
    • Speed of sound: The speed of ultrasound in soft tissue is 1540 m/s.
    • Absorption: Intensity (amplitude) of the echo depends on tissue absorption and distance travelled.
    • Time Gain Compensation: Amplifies signals from deeper tissues to compensate for signal loss due to absorption.

    Transducer Components

    • Transducer: Converts electrical energy to mechanical energy and vice versa.
    • Piezoelectric Crystal: Generates and detects sound waves; its thickness is half the wavelength of the US pulse.
    • Damping Unit: Absorbs vibrations propagating in the reverse direction; helps produce short US pulses.
    • Couplant Layer: Protects the piezoelectric crystal from mechanical damage; helps US pulse transmission into the body; ideal thickness is a fourth of the emitted US wavelength.
    • Acoustic Impedance: Ideal matching between crystal, tissue, and couplant layer (Zcouplant = √Zp × Zt).

    Pulse-Echo Methods

    • Pulse Emission: Short US pulses (2-3 cycles) are emitted.
    • Pulse Repetition Time (PRT): The time between emissions of two consecutive pulses; longer PRT allows detection of echoes from deeper tissues.

    Imaging Techniques

    • A-Mode (Amplitude Mode): One-dimensional imaging displaying the intensity of echoes along a line; used to detect reflecting surfaces.
    • B-Mode (Brightness Mode): Displays echo intensity as brightness on a screen; forms the basis of other advanced techniques.
    • M-Mode (Motion Mode): Plots one-dimensional B-mode images over time; used to visualize the movement of reflecting surfaces like heart valves.
    • 2D B-mode Imaging: Cross-sectional images formed by scanning the transducer across the body; used for various diagnostic areas.
    • Linear Scanning: Transducer moves in a straight line to create a 2D image.
    • Sector Scanning: Transducer angle is changed to allow for imaging in limited spaces (e.g., thoracic organs or neonatal cranium).
    • 3D Imaging: Combining multiple 2D images from different directions.

    Imaging Artifacts

    • Shadowing: Occurs behind highly reflective objects (e.g., kidney stones) where US intensity is insufficient to produce echoes from deeper structures.
    • Mirror-Image Artifact: Duplication of an object's image due to reflection from a strongly reflecting surface (e.g., diaphragm).

    Spatial Resolution

    • Axial Resolution: Ability to distinguish objects along the axis of the US beam; limit is ~0.5mm; determined by pulse length and frequency.
    • Lateral Resolution: Ability to distinguish objects positioned side-by-side.

    Doppler Ultrasound

    • Doppler Shift: The frequency difference between transmitted and received US signals due to movement of reflecting objects (e.g., red blood cells).
    • Blood Flow Measurement: Doppler shift (fD) is proportional to blood flow velocity (v) and frequency (f): fD = (2v/c)f.
    • Color Doppler: Displays blood flow direction and velocity using red and blue colours superimposed on 2D B-mode images.

    Effects of Ultrasound

    • Primary Effects: Sound pressure, absorption, cavitation, and mechanical rubbing effect caused by high-frequency, high-amplitude sound waves.
    • Secondary Effects: Dispergation, chemical and biological effects caused by the primary effects of US.

    Therapeutic Applications

    • High Intensity Focused Ultrasound (HIFU): Uses focused high-intensity US for localized heating and cavitation to treat tumours.
    • Extracorporeal Shockwave Lithotripsy (ESWL): High-intensity shock waves are used to break kidney stones; the exact mechanism is still under investigation but likely involves shear forces and cavitation.

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    Related Documents

    Physical Properties of Sound, Ultrasound, Debrecen University 2019

    Description

    This quiz covers essential concepts of ultrasound waves, including reflection, speed of sound in soft tissue, absorption effects, and time gain compensation. It also explores the components of transducers, such as piezoelectric crystals and damping units, crucial for effective ultrasound imaging. Test your knowledge on these key topics in ultrasound technology!

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