Podcast
Questions and Answers
What causes the Doppler-shift in the ultrasound (US) signal reflected by blood cells?
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?
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?
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?
In the Color-Doppler technique, what do red and blue colors represent?
Which of the following describes sound pressure in ultrasound?
Which of the following describes sound pressure in ultrasound?
Why do speed differences arise between particles in a medium during the propagation of ultrasound?
Why do speed differences arise between particles in a medium during the propagation of ultrasound?
What component of the Doppler-shift solely matters when the ultrasound beam is not aligned with the blood flow direction?
What component of the Doppler-shift solely matters when the ultrasound beam is not aligned with the blood flow direction?
What frequency range does the Doppler-shift typically fall into?
What frequency range does the Doppler-shift typically fall into?
What is the primary method used in linear scanning to generate a 2D image?
What is the primary method used in linear scanning to generate a 2D image?
What is a benefit of using sector scanning?
What is a benefit of using sector scanning?
What is a primary advantage of introducing the scanner directly into body cavities?
What is a primary advantage of introducing the scanner directly into body cavities?
What does spatial resolution in ultrasound imaging refer to?
What does spatial resolution in ultrasound imaging refer to?
What is axial resolution in ultrasound imaging?
What is axial resolution in ultrasound imaging?
What is the typical resolution limit for axial imaging in ultrasound?
What is the typical resolution limit for axial imaging in ultrasound?
An example of an imaging artefact in ultrasound is what phenomenon?
An example of an imaging artefact in ultrasound is what phenomenon?
What primarily determines axial resolution in ultrasound imaging?
What primarily determines axial resolution in ultrasound imaging?
What is the primary purpose of the damping unit in the transducer?
What is the primary purpose of the damping unit in the transducer?
How does Time Gain Compensation affect echo signals from deeper tissues?
How does Time Gain Compensation affect echo signals from deeper tissues?
What relationship does the thickness of the piezoelectric plate have with the wavelength of the US pulse in ideal cases?
What relationship does the thickness of the piezoelectric plate have with the wavelength of the US pulse in ideal cases?
What effect results from the friction caused by the motion of smaller and larger particles in ultrasound?
What effect results from the friction caused by the motion of smaller and larger particles in ultrasound?
What is the ideal thickness of the couplant layer in relation to the emitted US wavelength?
What is the ideal thickness of the couplant layer in relation to the emitted US wavelength?
What happens to the cohesive bonds between molecules in a liquid when subjected to high intensity ultrasound?
What happens to the cohesive bonds between molecules in a liquid when subjected to high intensity ultrasound?
Which of the following is a significant result of high intensity ultrasound absorption in a medium?
Which of the following is a significant result of high intensity ultrasound absorption in a medium?
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?
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?
What secondary effect can be induced by the primary effects of ultrasound?
What secondary effect can be induced by the primary effects of ultrasound?
Which of the following describes how the transducer operates in pulse-echo methods?
Which of the following describes how the transducer operates in pulse-echo methods?
What is the purpose of High Intensity Focused Ultrasound (HIFU)?
What is the purpose of High Intensity Focused Ultrasound (HIFU)?
What factor influences the intensity of echo signals received by the transducer?
What factor influences the intensity of echo signals received by the transducer?
In which scenario is Extracorporeal Shockwave Lithotripsy (ESWL) used?
In which scenario is Extracorporeal Shockwave Lithotripsy (ESWL) used?
Why is the speed of ultrasound propagation in soft tissues important in medical imaging?
Why is the speed of ultrasound propagation in soft tissues important in medical imaging?
What is the approximate maximum sound pressure value generated during ESWL?
What is the approximate maximum sound pressure value generated during ESWL?
What is a contributing factor to the effective stone breaking mechanism in ESWL?
What is a contributing factor to the effective stone breaking mechanism in ESWL?
What is the typical duration of an emitted US pulse in medical imaging?
What is the typical duration of an emitted US pulse in medical imaging?
How can the pulse repetition time (PRT) impact ultrasound imaging?
How can the pulse repetition time (PRT) impact ultrasound imaging?
In A-mode ultrasound imaging, what is displayed on the x-axis?
In A-mode ultrasound imaging, what is displayed on the x-axis?
Which equation can be used to determine the distance from the transducer to a reflecting surface?
Which equation can be used to determine the distance from the transducer to a reflecting surface?
What distinguishes B-mode imaging from A-mode imaging?
What distinguishes B-mode imaging from A-mode imaging?
What does M-mode imaging primarily visualize?
What does M-mode imaging primarily visualize?
What is a characteristic of two-dimensional B-mode images?
What is a characteristic of two-dimensional B-mode images?
What is the purpose of measuring echo arrival time in ultrasound imaging?
What is the purpose of measuring echo arrival time in ultrasound imaging?
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.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
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!
