Transducers III Flashcards
The beam diameter is equal to the width of the?
crystal
The near zone is also called?
Fresnol zone
The far zone is also called?
Fraunhofer zone
At one NZL the beam diameter is equal to?
1/2 transducer diameter
At 2 X NZL the beam diameter is equal to?
transducer diameter
Focusing only occurs in which zone?
Near zone
Formula for NZL of a nonfocused beam
d^2 / 4x wavelength OR d^2 x F/6
Range is also called?
time of flight or go-return time
Equation for time of flight
T= 2D/C
what is time of flight
amount of time it takes echo to travel into patient
What is the microsecond rule
for every 1 cm it takes 13 microseconds to travel
True or False: A focused beam produces a stronger echo than an unfocused beam
True
Focusing improves _______ and ________
lateral resolution; transducer sensitivity
What are the two types of mechanical focusing?
External and internal
External focusing
adding lens or mirror
Internal focusing
adding a curved element
Huygen’s principle
pattern from group of crystals is the summation of all wave patterns
Two types of electronic focusing
transmit (variable) and receive (dynamic)
Which type of electronic focusing is under the sonographer’s control?
transmit (variable)
Increasing the number of focal zones will decrease ?
the frame rate
What helps restore frame rate?
co-processing
Which type of electronic focusing is not under the sonographer’s control?
Receive (Dynamic)
Beam divergence depends on?
transducer diameter and frequency
Crystal diameter and beam divergence are _______ related
inversely
