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Chapter 3 Sonography Principles & Instruments I questions and answers.
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Chapter 3 Sonography Principles & Instruments I questions and answers.
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Chapter 3 SonographyPrinciples & Instruments I
questions and answers
Transudcer
Any device that converts energy from on form to another
3 construction parts to transucer
1.)Damping, "back layer" 2.) Piezoelectric elements, "crystals" 3.)
"face" matching layer
Piezoelectric effect
A property of certain materials to create a voltage when pressure is
applied or when the material is mechanically deformed
How do Ultrasound transducers use the piezoelectric effect?
They convert electricity into ultrasound pulses ad the returning u/s
pulses from the body back into electricity.
operating frequency is also called
Resonate frequency
What is the most used material in piezoelectricity?
PZT- lead zirconate titanate
What is the Curie point?
the temperature at which a crystal will lose PE properties
Advantages of CMUTS vs PZT?
It has broader bandwidth that improves detail resolution
What is a sequenced array?
A small group of crystals if "fired" simultaneously to produce the
ultrasound beam.
What is a phased array(steering)?
, the voltages are applied to all the elements but at different times.
This allows the bean to be steered.... Pulse goes left, beam goes
right
What is a Convex Array?
Curved voltages that produce a sector image.
What is operating frequency?
the natural or preferred frequency of the element
How does thickness effect operating frequency?
Thinner elements operate at higher frequencies.
What determines operating frequency?
Propagation speed and thickness of element
What must fractional bandwidth be, ATLEAST?
At-least 70%
How does focus increase resolution?
it creates a longer pulse, giving us a longer focal region
Greater Curve vs. Lesser Curve
Greater- puts the focus closer to the transducer and Lesser puts it
deeper.
What is axial resolution determined by?
the ability to accurately identify reflectors that are arranged
parallel to the ultrasound beam
What is lateral resolution?
Ability to distinguish reflectors in the direction perpendicular to
beam propagation
What determines axial resolution?
Spatial Pulse Length (SPL)
What is a phased linear array?
A linear array that is sequenced
Disadvantages to electrical focus?
Slow frame rate
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