Physics, Penny book Ch. 1 Questions
The ability of an object to resist compression and relates to the hardness of a medium
Stiffness
In clinical imaging, the wavelength measures between
.1 and .8 mm
All relate to strength of the sound wave
Amplitude, Intensity, Power
Which of the following would have the highest propagation speed
Bone
Areas of high pressure and density
Compressions
Determined by the sound source only
Frequency
The prefix "centi" denotes
Hundredths
Micro denotes
Millionth
Which is considered ultrasonic
1 MHz
The typical range of frequency for diagnostic ultrasound imaging
1 to 20 MHz
The duty factor for continuous wave ultrasound is
100%
What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue?
12 dB
Which is considered 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
The major component of attenuation is
Absorption
The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the
Amplitude
An increase in pulse repetition frequency would lead to
An increase in duty factor
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of
Attenuation, Absorption and Scattering
What is defined as the ability of the ultrasound system to image structures taht are positioned parallel to the sound beam as separate structures?
Axial resolution
As imaging depth increases, the pulse repetition frequency must
Decrease
The inertia of the medium describes its
Density
True of wavelength
Determined by both the medium and the sound source Inversely related to frequency Directly related to period
The percentage of time that the ultrasound system is producing pulses of ultrasound describes the
Duty factor
As imaging depth increases, pulse repetition period
Increases
If pulse repetition frequency increases, then the duty factor
Increases
What is essentially equal to the power of a wave divided by the area over which the power is distributed?
Intensity
What is the change in intensity if the power decreases by half?
Intensity is halved
Density and propagation speed are
Inversely related
What is the change in power if the amplitude triples?
It increases nine times
Density is typically measured in
Kilograms per centimeter cubed
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of
Lead ziconate titanate
Which of the following would have the lowest propagation speed
Lung tissue
Sound is technically a
Mechanical and longitudinal wave
Spatial pulse length can be calculated by
Multiplying the number of cycles, times the wavelength
The attenuation coefficient in soft tissue is equal to
One half of the operating frequency
Pressure is typically expressed in
Pascals
What is pressure measured in?
Pascals or pounds per square inch
If only the density of a medium is increased, then the
Propagation speed will decrease
True of power
Proportional to amplitude squared Intensity is proportional to power Power is measured in milliwatts
Defined as only the active time
Pulse duration
Defined as the number of ultrasound pulses emitted in 1 second
Pulse repetition frequency
What is defined as the beginning of one pulse to the beginning of the next pulse, and therefore includes both the "on" and "off" time?
Pulse repetition period
The portion of the sound beam where the molecules are pulled apart describes an area of
Rarefaction
Damping of the sound beam
Reduces the spatial pulse length
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
The amount of refraction that occurs at an interface
Snell's Law
The ability of an object to resist compression Increasing stiffness increases propagation speed May also be referred to as elasticity
True of stiffness
Determined by sound source and medium
Wavelength
The distance over which one cycle occurs
Wavelength
Which of the following is an appropriate unit of measurement for propagation speed?
millimeters per microsecond (mm/us)