Lecture 4 Flashcards
Different transducers/probes have different _________
Frequencies
Type of frequency set out from the probe is called
Fundamental frequency
Aka operational frequency
Aka transmit frequency
Fo
2 features of higher frequency
Better quality image
Less penetration/doesn’t go deep into body
2 qualities of low frequency
Worse quality image
Better penetration (think of how bass sounds go through walls)
One way to achieve higher frequency waves is the use of ____
Harmonics
As sound travels through tissue it changes ________
Shape
The change of sinusoidal waves to non sinusodial waveforms is called
Non-linear propagation
Sound moves ______ in more dense areas
Faster
Nonsinusidal waves contain additional _____
Frequencies
When the fundamental frequency is sent out, multiple _______ _______ are produced within the tissue
Harmonic frequencies
Less sinusoidal shape = ______ harmonics
Stronger
Harmonics send out one frequency and get back
Several higher frequencies
In a continuous wave, cycles repeat _______
Indefinitely
In ultrasound we use ________ ______ which are ______ _______
Pulsed ultrasound which are pulsed waves
What is a pulse
A few cycles of ultrasound then separated by gaps of no ultrasound
The gap between pulses can be called _______
Listening time/ downtime
What is pulse repetition frequency
Number of pulses per second
What is pulse repetition period
The time from the beginning of one pulse to the beginning of the next
More pulses occur in one second if time between them _________
Decreases
What is pulse duration
Time that it takes for one pulse to occur (from start of one to start of another)
What is the duty factor
The fraction of time the pulsed ultrasound is on ( ratio to the total PRP )
What is the Spatial pulse length
The length of a pulse
