SPI Exam Review: Chapter 1
In clinical imaging, the wavelength typically measures between:
0.1 to 0.8 mm
The typical range of frequency for diagnostic ultrasound imaging is:
1 to 20 MHz
The DF for CW ultrasound is
100%
What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4cm of soft tissue
12 dB
What is the speed of sound in soft tissue?
1540 m/s
If the angle of incidence is 40 degrees, what is the angle of transmission at the interface if medium 1 has a propagation speed of 1320 m/s and medium 2 has a propagation speed of 1700 m/s?
>40 degrees
An increase in PRF would lead to:
An increase in Duty Factor
The percentage of time that the ultrasound system is producing pulses of ultrasound describes the:
Duty factor
T or F? As amplitude increases, power remains the same
False
T or F? Wavelength is equal to the period divided by the frequency?
False
What term is defined as "the power of a wave divided by the are over which the power is distributed?"
Intensity
Density is typically measured in:
Kilograms per centimeter cubed
Micro denotes:
Millionth
SPL can be calculated by:
Multiplying the number of cycles by the wavelength
Does wavelength relate to the strength of the sound wave?
No. Amplitude, Intensity, Power
What is defined as the number of ultrasound pulses emitted in one second?
PRF
What time is defined as the as the beginning of one pulse to the beginning of the next pulse and, therefore includes both the "on" and "off" time
PRP
What are the units for pressure?
Pascals or pounds per square inch
Only the active time:
Pulse duration
Damping of the sound beam
Reduces the SPL
What requires an oblique interface and a propagation speed mismatch?
Refraction
What law describes the amount of refraction that occurs at an interface?
Snell's Law
What is described as the ability of an object to resist compression and relates to the hardness of a medium?
Stiffness
What are the units of duty factor?
Unitless
What is determined by the sound source and the medium?
Wavelength
Which of the following is described as the distance over which one cycle occurs?
Wavelength
The major component of attenuation is:
absorption
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of:
attenuation
Adding damping to the transducer improves which type of resolution?
axial resolution
As imaging depth increases, the PRF must:
decrease
Determined by sound source only
frequency
Density and propagation speed are ________ related
inversely
What is the change in power if the amplitude triples?
it increases nine times
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of:
lead zirconate titanate
Sound is a
longitudinal and mechanical wave
Out of water, soft tissue, bone, and lung tissue, which has the lowest propagation speed?
lung tissue
Which of the following is an appropriate unit of measurement for propagation speed?
millimeters per microsecond (mm/us)
The attenuation coefficient in soft tissue is equal to
one-half of the operating frequency
Pressure is typically expressed in:
pascals
If only the density of a medium is increased, then the:
propagation speed will decrease
the portion of the sound beam where the molecules are farther apart describes an area of
rarefaction
The change in the direction of the original sound wave that occurs when sound interacts with two different tissue types that have a different propagation speed is referred to as:
refraction
What is the change in intensity if the power decreases by half?
the intensity is halved
Would 0.5 MHz be considered ultrasonic?
yes
The prefix "centi" denotes
Hundredths
As imaging depth increases, PRP:
Increases
The maximum or minimum value of an acoustic variable minus the equilibrium value of that variable describes the:
amplitude
Out of air, bone, soft tissue, and water, which has the highest propagation speed?
bone
Areas of high pressure and density are referred to as:
compressions
The inertia of a medium describes its:
density