Exam 2 Flashcards
What is the range of period commonly found in waves produced by ultrasound systems?
.06- .5us
With standard ultrasonic imaging, what happens to the period of a wave as it propagates?
Remains the same
What determines the period of an ultrasound wave?
The transducer
Which of the following units are appropriate to describe the period of an acoustic wave?
Minutes Meters Microseconds Mm/us Cubic centimeters
Minutes
Microseconds
True or false? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.
False
What term describes the number of cycles that an acoustic variable completes in a second?
Frequency
Which of the following cannot be considered a unit of frequency?
Per day Cycles/sec Hz Hertz Cycles
Cycles- informs us of the number of events but not of the duration of time
What is the range of frequencies emitted by transducers used in ultrasonic imaging?
1 to 3 MHz
1 to 1,000 kHz
-10,000 to +10,000Hz
2,000,000 to 15,000,000 Hz
2,000,000 to 15,000,000 Hz
What establishes the frequency of an ultrasound wave?
The transducer
True or false?
With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.
False
When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?
Remains unchanged
-imaging depth and frequency are unrelated
Ultrasound is defined as a sound with a frequency of ___.
Greater than .02MHz
Infrasound is defined as a sound with a frequency of ___.
Less than 20 Hz
True or false?
Waves in the ultrasound range behave in the same general manner as sound waves that are audible.
True
-primary diff btw audible waves and ultrasonic waves is that humans can hear audible waves
What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?
Humans can’t hear them
What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz?
Humans can’t hear them
The frequency of a continuous acoustic wave is 5 MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency?
Frequency is the reciprocal of the period.
5MHz
True or false?
The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continuous.
True
True or false?
If the periods of the two waves are the same, then the frequencies of the waves must also be the same.
True
Compare two sound waves A and B. The frequency of wave A is 1/3 that of wave B. How does the period of wave A compare with the period of wave B?
A is 3x as long as B
Frequency and period are reciprocals
____ is the reciprocal of period.
Frequency
As one increases, the other decreases
When multiplied, the result is unity
A wave with a period of 1/100th of a second has a frequency of ___ per second.
100 per second or 100Hz
What determines the initial amplitude of an ultrasound wave?
The transducer
True or false?
With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.
True