Ch. 4 Desceibing Pulsed Waves Flashcards
How are anatomic images created?
Via pulses of acoustic energy to create a picture
What is pulsed sound?
Collections of cycles that travel together
What are the two components of pulsed ultrasound?
Transmit and receive
Define pulse duration
Time from start of pulse to the end of pulse. Units of time. 0.3 microseconds to 0.2 microseconds. Determined by sound source. Not adjustable by me.
How to calculate pulse duration?
of cycles *period
OR
# of cycles/ frequency
What characteristics create pulses of long duration?
Many cycles in pulse. Individual cycles with long periods.
What characteristics create pulses of short duration?
Few cycles in pulse. Individual cycles with short periods.
Define spatial pulse length
Distance that pulse occupies in space from start to end. Distance in mm. 0.1-1.0mm. Both determine. Not adjustable.
What is SPL directly/inversely proportional to?
Directly proportional to #of cycles and wavelength. Inversely proportional to frequency
What creates long pulses?
Many cycles in pulse. Cycles with longer wavelength.
What creates short pulse length?
Fewer cycles in pulse. Cycles with shorter wavelengths.
What is pulse repetition period?
Time from start of 1 pulse to start of next pulse. (1pulse duration +1 listening time). Time. 100 microseconds to 1ms. Sound source and imaging depth. Yes adjustable.
How are PRP and depth of view related?
-depth increases, PRP increases.
-depth decreases, PRP decreases.
What is PRF?
Number of pulses that a system transmits into the body each second. Number of pulses per second. Hz/sec. 1k-10k. Sound source. Yes adjustable.
What is relationship between imaging depth and PRF?
Shallow imaging = higher PRF
Deep imaging= lower PRF
