Chapter 2: Ultrasound Transducers

Which of the following electrical patterns produces electronic focusing of the ultrasound beam? a. curved b. sloped c. spiral d. circular

A. A curved firing pattern of the piezoelectric elements indicates focusing of the beam.

To produce a transducer with a higher frequency one should: a. use a thinner piezoelectric element b. use a thicker piezoelectric element c. use more damping d. use less damping

A. A thinner piezoelectric element will yield a higher frequency. A thicker piezoelectric element will yield a lower frequency.

Which of the following would cause a decrease in temporal resolution? a. increased line density b. decreased sector size c. single transmit zone d. increased PRF

A. An increase in line density would decrease temporal resolution. The other choices would all improve temporal resolution (frame rate).

Which of the following is not a synonym for axial resolution? a. angular b. range c. depth d. radial

A. Angular resolution is a synonym for lateral resolution, not axial resolution.

Which of the following is not a method of creating 3D images? a. broadband technology b. 2D array technology c. freehand technique d. mechanical technique

A. Broadband technology permits a variety of frequencies to be used as part of imaging, but not to create 3D images. 2D (matrix) arrays, freehand technique, and mechanically driven transducers can be used to create 3D images.

Which of the following transducers is not used for imaging? a. continuous-wave transducers b. curved sequenced array transducers c. linear sequenced array transducers d. phased array transducers

A. CW transducers do not produce an image, only spectral Doppler.

Which type of interference results in a higher-amplitude sound wave? a. constructive interference b. destructive interference c. true interference d. false interference

A. Constructive interference occurs when in-phase waves meet and the amplitudes of the two waves are added to form one large wave.

Which transducer has no range resolution? a. continuous-wave transducers b. curved sequenced array transducers c. linear sequenced array transducers d. phased array transducers

A. Continuous-wave (CW) transducers do not time how long it takes pulses to travel so they have no range resolution. In other words, no image is produced.

Imaging transducers typically have: a. low-quality factors, wide bandwidths b. high-quality factors, narrow bandwidths c. low-quality factors, narrow bandwidths d. high-quality factors, wide bandwidths

A. Imaging transducers have low quality factors ("Q factor") and wide bandwidths. Remember that "quality" in this sense means the "purity" of the beam, not image quality. Low Q-factor and wider bandwidths are owing to damping, which is used to shorten the spatial pulse length.

Which of the following is true concerning the frequency and the near-zone length, assuming a single-element, unfocused transducer? a. the higher the frequency, the longer the near-zone length b. the lower the frequency, the longer the near-zone length c. frequency and near-zone length are not related d. increasing the frequency causes divergence in the near field

A. In a single-element, unfocused transducer, the higher the frequency, the longer the near zone length.

Which resolution typically has the lowest number in clinical imaging? a. longitudinal b. lateral c. transverse d. azimuthal

A. Most transducers usually have better axial resolution than lateral resolution. The synonyms for axial resolution are LARRD: longitudinal, axial, radial, range, and depth. The synonyms for lateral resolution are LATA: lateral, angular, transverse, and azimuthal.

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? a. range resolution b. angular resolution c. contrast resolution d. transverse resolution

A. Range resolution, also referred to as axial resolution, is the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam.

Which of the following is not a component of spatial resolution? a. frame resolution b. contrast resolution c. axial resolution d. elevational resolution

A. Spatial resolution consists of axial, lateral, elevation, and contrast resolution.

Which of the following is represented as time, or the ability to display structures in real time? a. temporal resolution b. axial resolution c. longitudinal resolution d. contrast resolution

A. The higher the temporal resolution, or frame rate, the better the ability to represent structures in real time.

Which of the following best describes the components of the damping material? a. epoxy resin loaded with tungsten b. resin made with lead zirconate titanate c. polyvinylidene fluoride d. tungsten impregnated with lead

A. The matching layer is composed of epoxy resin loaded with tungsten.

Which of the following transducers can be described as having the scan lines originate from a common point of origin? a. sector array b. vector array c. curvilinear array d. linear sequenced array

A. The sector array comes to a point at the top because all of the scan lines come from a common point of origin.

Which of the following is not a true statement? a. lateral resolution varies with depth b. a larger aperture results in a shorter near-zone length c. a larger aperture produces less divergence in the far field d. lateral resolution may also be referred to as azimuthal resolution

B. A larger aperture results in a longer near zone length, not a shorter near zone length.

Damping material produces all of the following except: a. decreased sensitivity b. increased SPL c. wide bandwidths d. low-quality factors

B. Damping material decreases the spatial pulse length by decreasing the number of cycles (n) in a pulse.

Which of the following is the resolution in the third dimension of the beam? a. lateral resolution b. elevational resolution c. contrast resolution d. longitudinal resolution

B. Elevational resolution refers to the resolution in the third dimension of the beam, the slice-thickness plane.

Along with crystal diameter (aperture), the divergence in the far field is also determined by which of the following? a. spatial pulse length b. frequency c. propagation speed d. line density

B. Frequency, along with crystal diameter (aperture), determines the divergence in the far field.

If the depth is increased and the frame rate is unchanged, what else must have decreased? a. the pulse repetition period b. the number of lines per frame c. the duty factor d. the output power

B. If the depth is increased, the frame rate would typically decrease. According to the question, it didn't. Therefore, something else decreased to cancel out frame rate. If the number of lines per frame is decreased, that would increase the frame rate, causing no change to the frame rate.

Temporal resolution relates to which of the following? a. lateral resolution b. frame rate c. range ambiguity d. element diameter

B. Temporal resolution is another term for frame rate.

Which of the following describes the range of frequencies present within the beam? a. matching layer b. bandwidth c. array d. wavefront

B. The bandwidth is the range of frequencies within the sound beam. All of today's PW transducers are considered broadband, which means they have a range of frequencies available for use.

Which of the following is true of the diameter of the sound beam in the Fresnel zone? a. it increases with distance from the transducer b. it decreases with distance from the transducer c. it does not change with distance from the transducer d. it is unpredictable

B. The diameter of the beam in the near zone (Fresnel zone) decreases from the face of the transducer to the focal zone.

Which of the following best describes the frame rate? a. the frame rate is equal to the pulse repetition frequency multiplied by the lines per frame b. the frame rate is equal to the pulse repetition frequency divided by the lines per frame c. the frame rate is equal to the pulse repetition period divided by the lines per frame d. the frame rate is equal to the pulse repetition period multiplied by the lines per frame

B. The frame rate is equal to the pulse repetition frequency divided by the lines per frame.

Which of the following facilitates the transmission of sound from the element into the patient's skin? a. damping material b. matching layer c. tungsten covering d. focusing material

B. The matching layer is the component of the transducer that is used to minimize the impedance mismatch between that of the element and that of the patient's skin.

The portion of the transducer that comes in contact with the patient is the: a. backing material b. matching layer c. wire d. damping material

B. The matching layer, or face of the transducer, is the part of the transducer that comes in contact with the patient.

Which of the following produces a pie-shaped image? a. linear sequenced array b. phased array c. curved sequenced array d. convex transducer

B. The phased array produces a pie-shaped, or sector image. Some phased array transducers produce a vector shape image, which is like a sector but has a flat top.

Which of the following transducers is also referred to as a sector or vector transducer? a. linear sequential array b. phased array c. continuous-wave transducer d. curved sequential array transducer

B. The phased array transducer is also referred to as a sector or vector transducer.

How are ultrasound transducers typically sterilized? a. heating to the Curie temperature b. cold-sterilization methods c. autoclaving d. alcohol immersion

B. Ultrasound transducers are typically disinfected using a cold high-level disinfectant solution, although transducers may be sterilized using a warmed hydrogen peroxide solution in a tabletop device.

Which of the following would most likely decrease beam divergence in the far field? a. large crystal diameter, low frequency b. small crystal diameter, low frequency c. large crystal diameter, high frequency d. small crystal diameter, high frequency

C. A large crystal diameter (aperture) and high frequency would decrease the beam divergence in the far field.

Which of the following would most likely increase the near-zone length? a. large crystal diameter, low frequency b. small crystal diameter, low frequency c. large crystal diameter, high frequency d. small crystal diameter, high frequency

C. A large crystal diameter (aperture) and high frequency would increase the near zone length the most compared to the other options listed.

Which of the following is not true of damping? a. damping decreases the number of cycles in a pulse b. damping decreases spatial pulse length c. damping worsens axial resolution d. damping decreases the sensitivity of the transducer

C. Damping improves axial resolution by shortening the pulse. The pulse is shorter because damping decreases "n," the number of cycles in a pulse.

Which of the following describes the result of destructive interference? a. the resulting wave is much larger than the original wave b. the resulting wave is a little larger than the original wave c. the resulting wave is smaller than the original wave d. destructive interference does not occur with diagnostic imaging

C. Destructive interference occurs when out-of-phase waves meet. The amplitude of the resultant wave is smaller than either of the original waves.

In an unfocused, single-element transducer, the width at the focal point of the sound beam measures how much compared to the beam width at the face of the transducer? a. one-fourth b. one-third c. one-half d. equal

C. In an unfocused, single-element transducer, the focal point measures one half of the beam width at the face of the transducer.

Which of the following would be best utilized for imaging of deep structures in the abdomen? a. endocavitary transducer b. linear sequenced array transducer c. curved sequenced array transducer d. continuous-wave transducer

C. Of the choices listed, the curved sequence array would be best suited for imaging abdominal structures. Endocavitary probes tend to be high frequency and linear transducers have a limited depth and near field of view. Continuous-wave transducers do not produce an image.

Which of the following is defined as changing the timing of the shocking of the elements in order to shape and steer the beam? a. angulation b. focusing c. phasing d. bundling

C. Phasing is a method of focusing and/or steering the beam by applying electrical impulses to the piezoelectric elements with small time differences between shocks.

Which of the following shortens the length of the pulse by decreasing the number of cycles in the pulse? a. matching material b. piezoelectric element c. backing material d. PZT

C. The backing material, also known as the damping material of the transducer assembly, reduces the number of cycles produced in a pulse.

Which of the following is the part of the transducer that stops the ringing of the element? a. matching layer b. housing c. damping material d. insulator

C. The damping material, same as backing material, is the part of the transducer assembly that reduces the number of cycles produced in a pulse.

Which of the following may also be referred to as the far zone? a. frame zone b. Fresnel zone c. Fraunhofer zone d. frankincense zone

C. The far zone may also be referred to as the Fraunhofer zone.

Along with the image depth, which of the following also determines the frame rate? a. axial resolution b. damping c. number of lines per frame d. lateral resolution

C. The frame rate is determined by the number of lines per frame/line density, number of focal zones, and the imaging depth (PRF).

Which of the following will not affect temporal resolution? a. line density b. image depth c. spatial pulse length d. number of focal zones

C. The spatial pulse length has no effect on temporal resolution. The other choices listed all cause a change in temporal resolution, or frame rate.

Which of the following is not a characteristic of an unfocused single-element transducer? a. at the face of the transducer, the beam diameter is equal to the element diameter b. at a distance of one near-zone length, the beam diameter is equal to one half of the diameter of the element c. at a distance of two near-zone lengths, the beam diameter again equals the element diameter d. at the face of the transducer, the beam diameter is twice the size of the element thickness.

D. Assuming an unfocused, single-element transducer, at the face of the transducer, the beam diameter is equal to the element diameter.

Which of the following would cause an increase in frame rate? a. multifocusing b. increased line density c. increased imaging depth d. increased PRF

D. Decreasing the imaging depth, which is the same as increasing the PRF, would increase the frame rate.

What does heat sterilization do to an ultrasound transducer? a. gives it better axial resolution b. improves the lateral resolution of the transducer c. kills all the bacteria and viruses d. kills pathogens and destroys the transducer

D. Heat sterilization will kill pathogens but will unfortunately destroy the transducer as well. Piezoelectric elements in a transducer can never be taken to the Curie point or beyond after they are created.

What states that waves are the result of the interference of many wavelets produced at the face of the transducer? a. Curie's principle b. Snell's law c. Bernoulli's law d. Huygen's principle

D. Huygen's principle states that waves are the results of the interference of many wavelets produced at the face of the transducer.

Which type of resolution is an accurate representation of moving structures? a. lateral resolution b. azimuthal resolution c. spatial resolution d. temporal resolution

D. Temporal resolution, also known as frame rate, is the ability to display moving structures in real time.

Which of the following would be considered the narrowest part of a sound beam? a. far zone b. near zone c. Fresnel zone d. focal zone

D. The focus is the narrowest part of the ultrasound beam. The beam narrows in the near (Fresnel) zone and diverges in the far (Fraunhofer) zone.

Which of the following is not true of the linear sequenced array transducer? a. rectangular shape image b. firing is sequential c. electronically focused d. the elements are arranged in a ring

D. The linear sequenced array does not have elements arranged in a ring.

Which of the following is not a true statement about a mechanical transducer? a. it uses a motor to steer the beam b. most transducers are no longer mechanical c. may be focused with a lens or phased focused d. there are no moving parts

D. The mechanical transducer does have moving parts because the piezoelectric element is mounted to a motor. These obsolete transducers had fixed focus and frequency.