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)