Pulsed Ultrasound and Imaging Flashcards
What is pulse?
ultrasound energy that starts and stops again shortly after
As pulse duration decreases, what happens to the frequency?
It increases
What is pulse repetition frequency?
Number of transmit pulses per second
What is the pulse echo prinicple?
Measure the time between transmission of transmit pulse and the reception of each echo, machine then calculates distance between probe and structure that causes the echo
A large depth of penetration forces the US machine to use what?
low pulse repetition frequency (decreased rate of imaging)
Is frame rate directly proportional to the PRF?
Yes
Is frame rate directly proportional to the number of pulses required to produce each image?
No, inversely proportional
What is temporal resolution?
The machines ability to satisfactorily image moving structures
What is a linear probe useful for?
Flat surfaces
Which probe has a wider field of view? Linear or curvy?
Curvy
Explain the field of view for a phased array probe
Good field of view at depth but not superfically
What is the footprint?
Contact area of the probe
What is B mode?
Brightness
2D
What is M mode?
Motion mode
1D
What is A mode?
Amplitude mode
1D
What is the piezoelectrial transducer?
Transmits electrical signal into acoustic energy and back again
What is the pulse repetition period?
Time from beginning of one pulse to the beginning of the next pulse
What does lens do?
Helps focus the beam and protect the transducer
What does the housing of the probe do?
Acts as electrical insulator (protection)
What does the backing on the transducer do?
Shortens pulse by removing vibrational energy
What does the matching layers on the transducer do?
help transfer the ultrasound energy from the elements to the medium
What does the acoustic absorber do?
prevent sound waves from reflecting off hard surfaces, which reduces the amount of airborne noise within a space
What does the PZT do on the transducer?
Transmits electrical energy to acoustic energy and vice versa
What is beam sweeping?
Process of moving the ultrasound beam across the field of view (linear/curvy use electronic sweeping by selecting new aperature)
What is beam steering?
altering the angle of the ultrasound beam with respect to the transducer without moving the probe.
How many elements are used to steer the beam in a phased array probe?
All elements
How many elements are used to steer the beam in a linear probe?
A set of elements to produce a single beam
How many KHz is ultrasound?
20KHz
If we increase the ultrasound frequency, what happens to axial resolution?
Shortens pulse duration and improves axial resolution
