DMS Physics Exam 1

Which of the following is the resolution in the third dimension of the beam?

Elevational resolution

Which of he following would be considered the narrowest part of a sound beam?

Focus

The portion of the transducer that comes in contact with the patient is the:

Footprint

Which of the following is not a component of spatial resolution?

Frame resolution

Which of the following may also be referred to as the far zone?

Fraunhaufer Zone

What states that waves are the result of the interference of many wavelets produced at the face of the transducer?

Huygens Principle

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. Intensity = Power Intensity = Amplitude2 Power = Amplitude2

Density is typically measured in:

Kilograms per centimeter cubed (Kg/Cm^3)

Which of the following transducers is also referred to as a sector or vector transducer?

Linear Sequential Array

Which of the following would have the lowest propagation speed?

Lung: Remember the lungs are filled with air

Which of the following facilitates the transmission of sound from the element into the patient's skin?

Matching Layer

Spatial pulse length can be calculated by:

Multiplying the number of cycles times the wavelength

Which of the following is defined as the number of ultrasound pulses emitted in 1 second?

PRF

Pressure is typically expressed in:

Pascals

What is pressure measured in?

Pascals (Pa)

Which of the following produces a pie-shaped image?

Phased Array

Which of the following is defined as changing the timing of the shocking of the elements in order to shape and steer the beam?

Phasing

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

Propagation speed will decrease

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 (PRP)

Which of the following is defined as only the active time?

Pulse duration

Damping of the sound beam:

Reduces the spatial pulse length

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

Snell's Law

All of the following are true of stiffness except:

Stiffness and propagation speed are indirectly associated

Which of the following is represented as time, or the ability to display structures in real time?

Temporal Resolution

Which type of resolution is an accurate representation of moving structures?

Temporal Resolution

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 13 20 m/s and medium 2 has a propagation speed of 1700 m/s?

The angle of transmission is greater than >40 deg If the propagation speed of medium 2 is less than the propagation speed of medium 1, then the angle of transmission will be less than the angle of incidence.

Which of the following is not true of the linear sequenced array transducer?

The elements are arranged in a ring

Which of the following is true concerning the frequency and the near zone length?

The higher the frequency, the longer the near zone length

Along with image depth, which of the following also determines the frame rate?

The number of lines per frame

Which of the following describes the result of destructive interference?

The resulting wave is smaller than the original wave

Which of the following is not a true statement about a mechanical transducer?

There are no moving parts

What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue?

Total attenuation = atten. coefficient x distance. Atten. Coefficient = frequency/2 So, 3dB/cm x 4cm = 12

To produce a transducer with a higher frequency on should:

Use a thinner PZT element

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

Wavelength

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

Wavelength Think: Sound parameters are API: amplitude, power, intensity

Which of the following is not a true statement?

a larger aperture results in a shorter near zone length

The major component of attenuation is:

absorption

An increase in pulse repetition frequency would lead to:

an increase in duty factor

Which of the following is not a synonym for axial resolution?

angular

Which of the following is the type of transducer that utilizes elements arranged in a concentric pattern?

annular array

Which type of transducers are no longer used?

annular array transducer

Which of the following is not a characteristic of an unfocued single-element transducer?

at the face of the transducer, the beam is twice the size of the element

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

attenuation, absorption, and scattering (all of the above)

Which resolution is best in clinical imaging?

axial

What is defined as the ability of the ultrasound system to image structures that are positioned parallel to the sound beam as separate structures?

axial resolution

In clinical imaging, the wavelength measures between:

between 0.1 and 0.8 mm

Which of the following would have the highest propagation speed?

bone

Which type of interference results in a larger sound wave?

constructive interference

Which of the following transducers is not used for imaging?

continuous wave

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

Which of the following would cause an increase in frame rate?

decreased imaging depth

As imaging depth increases, the pulse repetition frequency must:

decreases As you increase depth, you have to send the signal deeper, therefore less US pulses are emitted because it must wait for the echoes to get back to the transducer.

The inertia of the medium describes its:

density

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

Along with crystal diameter, the divergence in the far field is also determined by which of the following?

frequency

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

frequency

The attenuation coefficient in soft tissue is equal to:

frequency/2

The prefix "centi" denotes:

hundredths

Which of the following would cause a decrease in temporal resolution?

increased line density

As imaging depth increases, pulse repetition period:

increases

What is the change in power if the amplitude triples?

increases by 9 times power = amplitude^2

If pulse repetition frequency increases, then the duty factor:

increases. Since duty factor is the fraction of time that the system transmits sound/"on time", Increasing the PRF will cause the Duty Factor to be on longer/increase

Density and propagation speed are:

inversely related

Which of the following is true of the diameter of the sound beam in the Fresnel zone?

it decreases

Which of the following will decrease beam divergence in the far field?

large crystal diameter, high frequency

Which of the following will increase the near zone length?

large crystal diameter, high frequency

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

Which of the following transducers uses a motor for steering the beam?

mechanical

Micro denotes:

millionth

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

mm/Us (microseconds)

Which of the following is defined as the minimum distance two reflectors can be, parallel to the beam, and still appear on the screen as two dots?

range resolution

The portion of the sound beam where the molecules are pulled apart describes an area of:

rarefaction

The change in the directions 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

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

stiffness

All of the following are true of wavelength except:

the formula for Wavelength is NOT period/frequency

Which of the following best describes the frame rate?

the frame rate is equal to the PRF divided by the lines per frame.

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

wavelength

Which of the following would be considered an advantage of a curved linear array over a phased array transducer?

wider near field

Which of the following would be considered ultrasound?

1 MHz

The typical range of frequency for diagnostic ultrasound imaging is:

1-20 MHz

In an unfocused, single-element transducer, the focal point of the sound beam measures how much of the total beam width?

1/2

The duty factor for continuous wave ultrasound is:

100%

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

1540 m/s

Sound is technically a:

A mechanical longitudinal wave

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

Amplitude

Which of the following would be best utilized for imaging of deep structures in the abdomen?

Annulary Array Transducer

All of the following are true of power except:

As amplitude increases, power remains the same power and amplitude are directly related

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 is the range of frequencies present within the beam?

Bandwidth

How are ultrasound transducers typically sterilized?

Chemical Sterilization

Areas of high pressure and density are referred to as:

Compressions

Which of the following electrical patterns produces electronic fousing of the ultrasound beam?

Curve

Damping material produces all of the following except:

Decreased sensitivity

What does heat sterilization do to an ultrasound transducer?

Depolarizes