Usg principles Flashcards
(29 cards)
What physical principle allows ultrasound imaging in the body?
Interaction of sound waves with tissues and structures.
How are ultrasound waves produced in the transducer?
By applying short bursts of alternating electrical current to crystals, causing them to expand and contract via the piezoelectric effect.
What kind of wave is an ultrasound wave?
A longitudinal mechanical wave.
What does the transducer do with reflected sound waves?
Converts them from mechanical energy back into electrical energy.
Why must the transducer be in direct contact with the body?
To transmit and receive ultrasound waves effectively.
What frequency range is typically used in urologic ultrasound imaging?
3.5 to 20 MHz.
What determines the pixel brightness in a grayscale ultrasound image?
The amplitude of the sound wave.
What is axial resolution in ultrasound?
The ability to distinguish between two objects along the direction of the sound wave.
What improves axial resolution?
Higher frequency of sound waves.
What is lateral resolution in ultrasound?
The ability to distinguish objects that are side by side and equidistant from the transducer.
What affects lateral resolution?
The width of the ultrasound beam and its focus.
What is the average velocity of ultrasound in human tissues?
1540 meters per second.
How are frequency and wavelength related in ultrasound?
They are inversely related.
What is the main trade-off in selecting ultrasound frequency?
Resolution versus depth of penetration.
What happens to ultrasound waves at tissue boundaries?
They are reflected, allowing imaging.
What causes scattering in ultrasound?
Sound waves striking small or irregular objects.
What does the term ‘speckling’ refer to?
Interference patterns seen in fine internal histology of organs.
What is ultrasound wave absorption?
Conversion of mechanical energy to heat.
How does frequency affect absorption?
Higher frequency increases absorption and limits penetration.
What are ultrasound artifacts?
Image misrepresentations caused by wave-tissue interactions.
What causes acoustic shadowing?
Strong reflection or attenuation at a tissue interface.
What is ‘increased through transmission’?
Enhanced echogenicity of tissues behind a fluid-filled structure due to less attenuation.
How can you reduce acoustic shadow artifacts?
By changing the angle, frequency, or focal zone.
What causes edging artifacts?
Refraction of sound waves at a curved interface.
