Chapter 3 Flashcards
(58 cards)
Define Period
the time is takes a wave to vibrate a single cycle
What unit is Period reported in?
Units of time (microseconds, seconds)
What is the typical value of the period in diagnostic ultrasound?
0.06 to 0.5 microseconds
Is the Period determined by the source, the media, or both?
the source only
Can the Period be adjusted by the sonographer?
Nope
Define Frequency
the number of events that occur in a specific duration of time
What unit is frequency reported in?
units per second, 1/sec, Hz
What is the typical value of the frequency in diagnostic ultrasound?
2 MHz - 15 MHz
Is the Frequency determined by the source, the media, or both?
the source only
Can the frequency be adjusted by the sonographer?
nope
What are the range of frequencies audible to humans?
20 Hz - 20,000 Hz (20 KHz)
What is the range of frequency used in Diagnostic Ultrasound?
2 - 15 MHz
How are frequency and period related to each other?
They are reciprocals. f = 1/P and P=1/f
Which of these waves is ultrasonic and most useful in diagnostic sonography?
A. 400 MHz
B. 4 MHz
C. 2 kHz
D. 200,000 Hz
B. Only one within diagnostic range
Which of the following waves has the longest period?
A. 2 MHz
B. 4,000 Hz
C. 6 Hz
D. 1 kHz
C. This is the lowest frequency, therefore the longest period.
What three parameters describe the size or magnitude of the wave?
Amplitude, Power, Intensity
How is Amplitude seen on an ultrasound?
Brightness
How do you calculate Amplitude?
(Max-Min) / 2 = A
Is Amplitude determined by the source, the media, or both?
The source initially, but decreases as the sound propagates.
Is the Amplitude adjustable?
Yes
How is Amplitude different from peak-to-peak amplitude?
Amplitude is measured the middle to the max or min. Peak-to-peak measures from the min to the max. Therefore peak-to-peak = 2 x amplitude.
Define Power
the rate of energy transfer or the rate at which work is performed
What is Power measured in?
Watts
How are amplitude and power related?
power = amplitude^2. Directly related.
