Kremkau - Chapter 3 Exercises

A couple medium on the skin surface eliminates reflection caused by ________ a. Air b. Skin c. Matching layer d. Element

A

A focused beam is divided into three regions, called the ________ zone, the ________ zone, and the ________ zone a. Near, focal, far b. Narrow, wide, extended c. Forward, middle, reverse d. Low, medium, high

A

A higher-frequency transducer produces a ________ near-zone length a. Longer b. Shorter c. Unchanged d. None of the above

A

A phased linear array with a single line of elements can focus in ________ dimension(s) a. One b. Two c. Three d. Five

A

A transducer converts one form of ________ to another a. Energy b. Force c. Image d. Scan

A

An unfocused 3.5 MHz, 13 mm transducer produces three-cycle pulses. The axial resolution in soft tissue is ________ mm a. 0.7 b. 1.4 c. 13 d. 26

A

Axial resolution is the minimum reflector separation required along the direction of the ________ ________ to produce separate ________ a. Scan lines, echoes b. Sound travel, amplitudes c. Double reflectors, lines d. Scan lines, amplitudes

A

Damping material reduces the ________ of the transducer and ________ of the diagnostic system a. Efficiency, sensitivity b. Frequency, sensitivity c. Frequency, efficiency d. Frequency, penetration

A

Doubling the number of cycles per pulse causes axial resolution to be ________ a. Doubled b. Increased c. Degraded d. Halved

A

Elements in linear arrays are in the form of ________ a. Rectangles b. Squares c. Rings d. Disks

A

For pulses traveling through soft tissue in which the frequency is 3 MHz and there are four cycles per pulse, the axial resolution is ________ mm a. 1.0 b. 1.5 c. 2.5 d. 3.0

A

Lateral resolution is equal to ________ ________ in the scan plane a. Beam width b. Pulse length c. Beam length d. Pulse height

A

Mixtures of a piezoelectric ceramic and a nonpiezoelectric polymer are called ________ a. Composites b. Piezopolymers c. Ceramopolyers d. Piezocomposites

A

The distance from a transducer to the location of the narrowest beam width produced by a focused transducer is called focal ________ a. Length b. Width c. Depth d. Height

A

The term transducer is used to refer to a transducer ________ or to a transducer ________ a. Element, assembly b. Matching, element c. Backing, damping d. Backing, assembly

A

Transducer arrays are transducer assemblies with several transducer ________ a. Elements b. Layers c. Cables d. Backings

A

Transducer size is also called ________ a. Aperture b. Zone c. Bandwidth d. Width

A

Which of the following is not decreased by damping? a. Refraction b. Pulse duration c. Spatial pulse length d. Efficiency e. Sensitivity

A

Which of the following improve sound transmission from the transducer element into the tissue? (more than one correct answer) a. Matching layer b. Doppler effect c. Damping material d. Coupling medium e. Refraction

A, D

________ and ________ describe how arrays are constructed (select two) a. Linear b. Phased c. Sequenced d. Vector e. Convex

A, E

Match the following (answers may be used more than once): a. Linear array ________ b. Phased array ________ c. Convex array ________ 1. Voltage pulses are applied in succession to groups of elements across the face of a transducer 2. Voltage pulses are applied to most or all elements as a group, but with small time differences

A: 1 B: 2 C: 1

Match the transducer type with the display formats in figure 3.36 a. Linear array: ________ b. Convex array: ________ c. Phased array: ________ d. Vector array: ________ e. Phased linear array: ________

A: 1 B: 4 C: 3 D: 5 E: 2

Match each transducer characteristic with the sound beam characteristic it determines (answer may be used more than once): a. Element thickness: ________, ________, and ________ b. Element width: ________ c. Element shape (flat or curved): ________ d. Damping: ________ 1. Axial resolution 2. Lateral resolution 3. Operating frequency

A: 1, 2, 3 B: 2 C: 2 D: 1

A 5 MHz unfocused transducer with an element thickness of 0.4 mm, an element width of 13 mm, and a near-zone length of 14 cm produces two-cycle pulses. Determine the following: a. Operating frequency if thickness is reduced to 0.2 mm: ________ MHz b. Axial resolution in the cose of (a): ________ mm at 5 MHz: c. Depth at which lateral resolution is best: ________ cm d. Lateral resolution at 14 cm: ________ mm e. Lateral resolution at 28 cm: ________ mm f. This transducer can be focused at depths less than ________ cm

A: 10 B: 0.15 C: 14 D: 6.5 E: 13 F: 14

Match the following transducer assembly parts with their function: a. Cable ________ b. Damping material ________ c. Piezoelectric element ________ d. Matching layer ________ 1. Reduces reflection at transducer surface 2. Converts voltage pulses to sound pulses 3. Reduces pulse duration 4. Conducts voltage pulses

A: 4 B: 3 C: 2 D:1

A sector image is a result of sector steering of the beam. This means that pulses travel in ________ direction(s) from a common ________ at the transducer face a. Two different, end b. Different, origin c. The same, point d. The same, end

B

A smaller aperture produces a(n) ________ near-zone length a. Longer b. Shorter c. Unchanged d. None of the above

B

A transducer ________ is part of a transducer ________ a. Pulse, amplitude b. Element, assembly c. Cable, matching d. Backing, damping

B

For a particular transducer element material, if a thickness of 0.4 mm yields an operating frequency of 5 MHz, the thickness required for an operating frequency of 10 MHz is ________ mm a. 0.1 b. 0.2 c. 0.3 d. 0.5

B

For an unfocused transducer, the best lateral resolution (minimum beam width) is ________ the transducer width. This value of lateral resolution is found at a distance from the transducer face that is equal to the ________ ________ length a. Equal to, near zone b. Half, near zone c. Equal to, far zone d. Half, far zone

B

If frequencies less than ________ MHz are used, axial resolution is not sufficient a. 0.1 b. 2 c. 5 d. 20

B

If the elements of a phased array are pulsed in rapid succession from right to left, the resulting beam is ________ a. Steered right b. Steered left c. Focused

B

If there are three cycles of a 1 mm wavelength in a pulse, the axial resolution is ________ mm a. 1.0 b. 1.5 c. 2.5 d. 3.0

B

If there are two cycles per pulse, the axial resolution is equal to the ________. At 5 MHz in soft tissue, this is ________ mm a. Wavelength, 5.0 b. Wavelength, 0.3 c. Duration, 1.54 d. Duration, 0.2

B

Operating frequency ________ when transducer element thickness is increased a. Increases b. Decreases c. Is unchanged d. None of the above

B

The range of frequencies useful for most applications of diagnostic medical ultrasound is ________ to ________ MHz a. 0.1, 15 b. 2, 20 c. 1, 10 d. 1, 5

B

The region between the transducer and the focal region is the ________ length a. Narrow zone b. Near zone c. Wide zone d. Far zone

B

Ultrasound transducers operate on the ________ principle a. Piezomagnetic b. Piezoelectric c. Electropiezo d. Electromagnetic

B

Which three things determine beam diameter for a disk transducer? a. Pulse duration b. Frequency c. Aperture d. Distance from disk face e. Efficiency

B, C, D

________, ________, and ________ describe how arrays are operated (select three) a. Linear b. Phased c. Sequenced d. Vector e. Convex

B, C, D

Lateral resolution is determined by ________ (there is more than one correct answer to the question) a. Damping b. Frequency c. Aperture d. Number of cycles in the pulse e. Distance from the transducer f. Focusing

B, C, E, F

The damping layer is in front/back of the element

Back

An electric voltage pulse, when applied to a transducer, produces an ultrasound ________ of a(n) ________ that is equal to that of the voltage pulse a. Pulse, amplitude b. Intensity, amplitude c. Pulse, frequency d. Pulse, duration

C

Axial resolution depends directly on ________ a. The peak amplitude b. Spatial echo distance c. Spatial pulse length d. Spatial pulse width

C

Focusing in section thickness can be accomplished with ________ elements or a ________ a. Curved, sequencer b. Round, sequencer c. Curved, lens d. Round, lens

C

If the elements of a phased array are pulsed in rapid succession from outside in, the resulting beam is ________ a. Steered right b. Steered left c. Focused

C

Increasing frequency improves resolution because ________ is reduced, thus reducing ________ a. Attenuation, depth of penetration b. Attenuation, spatial pulse length c. Wavelength, spatial pulse length d. Wavelength, depth of penetration

C

Lateral resolution is improved by ________ a. Damping b. Pulsing c. Focusing d. Matching e. Absorbing

C

Lateral resolution is the minimum ________ between two reflectors at the same depth such that when a beam is scanned across them, two separate ________ are produced a. Separation, propagations b. Amplitude, propagations c. Separation, echoes d. Amplitude, echoes

C

Near-zone length increases with increasing source ________ and ________ a. Amplitude, intensity b. Amplitude, frequency c. Aperture, frequency d. Aperture, amplitude

C

Shorter time delays between elements fired from outside in result in ________ curvature in the emitted pulse and a ________ focus a. No, weak b. Less, shallower c. Less, deeper d. Greater, shallower e. Greater, deeper

C

Single-element transducers are in the form of ________ a. Squares b. rectangles c. Disks d. Ovals

C

The lower the upper limits of the frequency range useful in diagnostic ultrasound are determined by ________ and ________ requirements, respectively a. Penetration, attenuation b. Penetration, resolution c. Resolution, penetration d. Attenuation, Resolution

C

The matching layer has ________ impedance a. High b. Low c. Intermediate d. Zero

C

To operate a transducer at more than one frequency requires ________ a. Narrow bandwidth b. Moderate bandwidth c. Broad bandwidth d. No bandwidth

C

What are the axial resolutions in figure 3.35, A-B? a. 5 mm, 4, mm b. 4 mm, 3 mm c. 3 mm, 2 mm d. 2 mm, 1 mm

C

Which of the following transducer(s) can focus at 6 cm? a. 5 MHz, near-zone length of 5 cm b. 4 MHz, near-zone length of 6 cm c. 4 MHz, near-zone length of 10 cm d. B and C e. None of the above

C

Which transducer element has the longest near zone? a. 6 mm, 5 MHz b. 6 mm, 7 MHz c. 8 mm, 7 MHz

C

A rectangular image is a result of linear scanning of the beam. This means that pulses travel in ________ ________ direction(s) from ________ starting point(s) across the transducer face a. Two different, one b. Many different, many c. The same, one d. The same, different

D

An unfocused 3.5 MHz, 13 mm transducer will yield a minimum beam width (best LR) of ________ mm a. 3.5 b. 13 c. 26 d. 6.5

D

At what depth is the best lateral resolution in figure 3.13, C? a. 1 cm b. 2 cm c. 3 cm d. 4 cm

D

Because diagnostic ultrasound pulses are usually two or three cycles long, axial resolution is usually equal to ________ to ________ wavelengths a. 2, 3 b. 4, 6 c. 1, 3.5 d. 1, 1.5

D

Doubling the frequency causes axial resolution to be ________ a. Doubled b. Increased c. Degraded d. Halved

D

Electronic focusing in section thickness requires multiple rows of ________ a. Lenses b. Matchers c. Dampers d. Elements

D

For a focused transducer, the best lateral resolution (minimum beam width) is found in the ________ region a. Near b. Far c. Local d. Focal

D

If frequencies higher than ________ MHz are used, penetration is not sufficient for most applications a. 0.1 b. 2 c. 5 d. 20

D

In ________ and ________ arrays, pulses travel out in different directions from different starting points on the transducer face a. Linear, convex b. Convex, phased c. Phased, vector d. Convex, vector

D

Increasing frequency decreases penetration because ________ is increased a. Reflection b. Heating c. Speed d. Attenuation

D

Linear arrays scan beams by ________ element groups a. Phasing b. Steering c. Delaying d. Sequencing

D

Operating frequency is also called ________ ________ a. Operating mode b. Bandwidth mode c. Operating bandwidth d. Resonance frequency

D

The ________ of a transducer element changes when voltage is applied to its faces a. Width b. Height c. Length d. Thickness

D

The addition of damping material to a transducer reduces the number of ________ in the pulse, thus improving ________ ________. It increases ________ a. Amplitudes, detail resolution, frequency b. Amplitudes, lateral resolution, bandwidth c. Cycles, lateral resolution, frequency d. Cycles, axial resolution, bandwidth

D

The matching layer on the transducer surface reduces ________ caused by impedance differences a. Attenuation b. Amplitude c. Transmission d. Reflection

D

The resonance frequency of an element is determined by its ________ a. Width b. Height c. Length d. Thickness

D

Two resolutions may be comparable in the ________ region of a strongly focused beam a. Near b. Far c. Local d. Focal

D

Ultrasound transducers convert ________ energy into ________ energy, and vice versa a. Electric, light b. Heat, electric c. Heat, light d. Electric, ultrasound

D

Ultrasound transducers typically generate pulses of ________ or ________ cycles a. Five, ten b. Five, six c. One, three d. Two, three

D

Sound may be focused by using a. ________ a. Curved element b. Lens c. Phased array d. More than one of the above

D (all of the above)

Lateral resolution does not depend on ________ a. Frequency b. Aperture c. Phasing d. Depth e. Damping

E

The principle on which ultrasound transducers operate is the ________ a. Doppler effect b. Acousto-optic effect c. Acoustoelectric effect d. Cause and effect e. Piezoelectric effect

E

Which of the following transducer frequencies would have the thinnest elements? a. 2 MHz b. 3 MHz c. 5 MHz d. 7 MHz e. 10 MHz

E

Transducer assemblies are also called ________ a. Transducers b. Probes c. Scanheads d. Scan converters e. Skinheads f. More than one of the above

F (A,B,C)

(T/F) Axial resolution is often not as good as lateral resolution in diagnostic ultrasound

False

(T/F) Beam diameter may be reduced in the far zone by focusing

False

(T/F) Damping increases efficiency

False

(T/F) Damping lengthens the pulse

False

(T/F) Focusing reduces the beam diameter at all distances from the transducer

False

(T/F) If better resolution is desired, a lower frequency will help

False

(T/F) When studying an obese subject, a higher frequency likely will be required

False

(T/F) A transducer with a near-zone length of 10 cm can be focused at 12 cm

False (can focus only in the near zone)

(T/F) For a given frequency, a smaller aperture always yields improved lateral resolution

False, in general (Only true near the transducer)

The matching layer is in front/back of the element

Front

Is it practical to attempt to operate a 5 MHz transducer with a bandwidth of 2.5 at 3 and 7 MHz?

No (Because these frequencies are outside the 2.5 MHz bandwidth [3.75 to 6.25 MHz]) 3 and 7 MHz requires a bandwidth of 4 MHz

Is it practical to attempt to operate a 5 MHz transducer with a bandwidth of 1 MHz at 6 MHz?

No (Because these frequencies are outside the bandwidth [4.5 to 5.5 MHz])

(T/F) Beam diameter may be reduced in the near zone by focusing

True

(T/F) For an aperture of a given size, increasing frequency improves lateral resolution

True

(T/F) In exercises 83 and 84, axial resolution is better than lateral resolution

True

(T/F) Lateral resolution varies with distance from the transducer

True

(T/F) Smaller axial resolution is better

True

(T/F) A two-cycle pulse of 5 MHz ultrasound produces separate echoes from reflectors in soft tissue separated by 1 mm

True (axial resolution 0.3 mm)