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.
What is the term used for amplitude decrease as it travels through tissue?
attenuation
Is the power determined by the source, media, or both?
Source
Can the Power be adjusted?
yes, of course
Which of the following controls affects the power of the sound beam entering the tissue?
A. Output
B. Frequency
C. Depth
D. Focus
A. Output
Define Intensity
the concentration of energy in a sound beam
What units are use to measure intensity?
watts/ cm^2
Is the intensity determined by the source, media, or both?
the source
How is intensity related to power, amplitude, and area?
Intensity = power / area
Direct to power and amplitude
Inverse to area
Define Wavelength
the distance or length of one complete cycle
What are typical wavelength values?
0.1 to 0.8 mm
Is wavelength determined by the source, media, or both?
BOTH
Can wavelength by adjusted?
No
What is the difference between wavelength and period?
Wavelength measures the distance of a single cycle.
Period measures the time required to complete a single cycle.
What is the wavelength of 1 MHz frequency sound wave in soft tissue?
1.54 mm
Define propagation speed?
the rate at which a sound wave travels through a medium
Is the propagation speed determined by the source, media, or both?
Medium only!
Is propagation speed adjustable?
No
What is the speed of sound in soft tissue?
1,540 m/s
What are the terms elasticity and compressibility used to describe?
Stiffness
How is speed related to stiffness?
directly
How is speed related to density?
inversely
Related? Frequency and period
Inversely
Related? Amplitude and power
directly
Related? Amplitude and intensity
directly
Related? Power and intensity
directly
Related? wavelength and intensity
unrelated
Related? wavelength and frequency
inversely
Related? acoustic velocity and density
inversely
Related? elasticity and speed of sound
inversely
Related? acoustic velocity and compressibility
inversely
Related? stiffness and sound speed
directly
Related? frequency and sound speed
unrelated
Related? frequency and intensity
unrelated
Related? power and frequency
unrelated
