Physics FINAL

Which of the following is the best estimate for the attenuation coefficient of sound traveling in soft tissue?

0.45 dB/cm/MHz

Which of the following would be considered ultrasonic?

1 MHz

The typical range of frequency for diagnostic ultrasound imaging is:

1 to 20 MHz

The impedance of a transducer active element is 1,900,000 rayls and for the skin is 1,400,000 rayls. What is an acceptable impedance for the matching layer?

1,726,000 rayls

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

The following are all ultrasound frequencies except:

15.0 kHz

Which of the following is considered the speed of sound in soft tissue?

1540 m/s

Which of the following waves is ultrasonic and least useful in diagnostic imaging?

24,000 Hz

If the power increases double the original value, how many decibels is this change?

3

If the transmitted pulse has frequencies from 3.5 MHz to 6.5 MHz, what is the bandwidth?

3.0 MHz

A sound wave, with an intensity of 40 W/cm2, strikes a boundary and is totally reflected. What is the reflected intensity?

40 W/cm2

Which of following waves has the longest period?

4Hz

The major component of attenuation is:

Absorption

A reciprocal relationship means that

All Choices are correct

The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the:

Amplitude

Which of the following best describes the line identified by the letter C?

Amplitude

Terms that can be used to describe the strength of a sound beam are

Amplitude and intensity

An increase in pulse repetition frequency would lead to:

An increase in duty factor

All of the following are true of power except:

As amplitude increases, power remains the same Power is measured in milliwatts

As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of

Attenuation, Absorption, and Scattering

Which of the following shortens the length of the pulse by decreasing the number of cycles in the pulse?

Backing material

Which of the following could not be used as the coupling medium (gel)?

Barium sulfate

Which of the following would have the highest propagation speed?

Bone

How are ultrasound transducers typically sterilized?

Cold-sterilization methods

When the elasticity of a medium is high, the _________ is high.

Compressibility

Areas of high pressure and density are referred to as:

Compressions

Which of the following is the part of the transducer that stops the ringing of the element?

Damping material

Which of the following is not true of damping?

Damping worsens axial resolution

As imaging depth increases, the pulse repetition frequency must:

Decrease

As the frequency of an acoustic variable increases, the wavelength

Decreases

The percentage of time that the ultrasound system is producing pulses of ultrasound describes the:

Duty factor

Which of the following best describes the components of the damping material?

Epoxy resin loaded with tungsten

If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, the main or center frequency of the transducer is 6 MHz.

False

The wavelength of the 2 MHz transducer is shorter than the 5 MHz transducer

False

Two piezoelectric crystals are made from the same material. The thicker crystal will make a pulsed transducer with a higher frequency.

False

Which of the following is determined by the sound source only?

Frequency

With a pulsed wave transducer, which of the following occurs if the PZT thickness is doubled?

Frequency is halved

How thick is the element if the frequency is 3 MHz?

Half the wavelength of the wave in the PZT

Which will create the slowest speed of sound?

High density, low stiffness

Damping material produces all of the follwinf except..

Increased SPL

As imaging depth increases, pulse repetition period:

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

What is the change in power if the amplitude triples?

It increases nine times

All of the following are true of wavelength except:

It is equal to the period divided by the frequency

What does heat sterilization do to an ultrasound transducer?

Kills pathogens and destroys transducer

Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of:

Lead zirconate titanate

Imaging transducers have:

Low quality factors, wide bandwidths

Sound is technically a:

Mechanical and longitudinal wave

Micro denotes

Millionth

Spatial pulse length can be calculated by

Multiplying the number of cycles times the wavelength

An angle of 123 degrees is

Obtuse

The attenuation coefficient in soft tissue is equal to:

One half of the operating frequency

Which of the following is defined as the number of ultrasound pulses emitted in l second?

PRF

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?

PRP

Place the following in order of highest to lowest impedance.

PZT, matching layer, gel, skin

Pressure is typically expressed in:

Pascals

Which of the following best describes the line identified by the letter D?

Period

All of the following relate to the strength of the sound wave except:

Pressure

Which statement is true considering the propagation speed of sound through air?

Propagation speed in air is slower than in soft tissue

If only the density of a medium is increased, then the:

Propagation speed will decrease

Which of the following is defined as only the "on" time?

Pulse duration

The _______ of the transducer is the ratio of the operating frequency to the bandwidth

Q factor

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

If both propagation speed and frequency double, the wavelength will

Remain the same

Which best describes sound waves?

Series of compressions and rarefactions

Which of the following describes the amount of refraction that occurs at an interface?

Snell's law

The term bulk modulus is related to which quality?

Stiffness

Which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium?

Stiffness

All of the following are true of stiffness except

Stiffness and propagation speed are indirectly associated

Which statement is correct regarding sound travel through a medium?

The molecules oscillate (vibrate) back and forth to create and transmit the sound wave

Which of the following describes the result of destructive interference?

The resulting wave is smaller than the original wave

A very LOW "Q" factor transducer is more common than high "Q" factor for diagnostic imaging.

True

To produce a transducer with a higher frequency one should:

Use a thinner piezoelectric element

Intensity is typically measured in:

Watts per centimeter squared

Which of the following is described as the distance over which one cycle occurs?

Wavelength

Which of the following is determined by the sound source and medium?

Wavelength

A decibel is

a relationship between two levels

The propagation speed in soft tissue is

an average of the speed in several types of tissue

The piezoelectric effect is best described as

deformation from voltage sent to the crystals

If intensity remains the same while the power is doubled, what happens to beam area?

doubled

If beam area is reduced by half and the power stays the same, the intensity

doubles

Which of the following would cause the PZT properties to be eliminated?

high temperatures

The prefix "centi" denotes:

hundredths

Which of the following is NOT a result of the damping layer?

increase sensitivity

In soft tissue, the attenuation is

increased with tissue thickness

Which is not an acoustic variable?

intensity

Density and propagation speed are:

inversely related

The fundamental or operating frequency

is affected by the thickness of the PZT element

If the angle of incidence is 40o, 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?

it is greater than 40 degrees

Which of the following is an appropriate unit of measurement for propagation speed?

millimeters Per microsecond (mm/µs)

What is pressure measured in?

pascals or pounds per square inch

Place the following in order of fastest to slowest propagation speed

solid, liquid, gas

All of the following are true of sound waves except:

they are transverse

Which of the following are most important in producing the frequency of the beam in soft tissue?

thickness of the PZT elements

Which of the following affect the frequency of the transmitted beam from CW ultrasound?

ultrasound system electronics

Directly related means

when one item increases or decreases, the second item responds the same direction