0 [{"id":310555,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:15:47","updated_at":"2017-12-13 20:31:30","questionName":"The following are true about theoretical plane waves in ultrasound, except","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":1,"explanation":"Whereas spherical waves spread out attenuating pressure by 1\/r, planar waves do not spread out, and thus maintain their full amplitude.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310554,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:14:30","updated_at":"2017-12-13 20:31:30","questionName":"In ultrasound, with an incident planar wave that is not perpendicular to a boundary where the acoustic impedance Z changes, the following are true: I. Reflection will always occur. II. Refraction will occur if and only if the wave velocity c changes. III. Particle velocity v will always equal wave velocity c on either side of the boundary","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":0,"explanation":"Refraction depends only on c. Reflection depends only on Z and the angle of incidence. Particle velocity v is generally much slower than wave velocity c.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310563,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:21:38","updated_at":"2017-12-13 20:31:31","questionName":"The following are true about theoretical plane waves in ultrasound, except","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":9,"explanation":"They are approximated within the Very Near Field of the transducer, not in the Fraunhofer zone. In the Fraunhofer zone the waves diverge at a constant angle acting more like spherical waves","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310561,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:20:25","updated_at":"2017-12-13 20:31:31","questionName":"In ultrasound, which of the following is not true about the field pattern, an example of which is shown below (the figure actually shows a field pattern for light, but is analogous to that found with ultrasound).","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":"uploads\/bioe-1330-ch-10-11\/Chap10-11Q8.JPG","position":7,"explanation":"The Fraunhofer zone, otherwise known as the far field is labeled \u201cD.\u201d","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310565,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:22:55","updated_at":"2017-12-13 20:31:31","questionName":"Which of the following statements is false about the use of the complex exponential in modeling ultrasound, (or all are true)?","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":11,"explanation":"The use of complex exponentials instead of real sinusoids encapsulates phase in such a way that algebra and calculus are straightforward, and is the heart of not only ultrasound design, but of modern optics. A linear system with superposition of the waves","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310562,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:21:01","updated_at":"2017-12-13 20:31:31","questionName":"In ultrasound, with an incident planar wave that is not perpendicular to a boundary where the acoustic impedance Z changes, which of the following is (are) TRUE? I. Refraction will always occur. II. Reflection will always occur. III. Particle velocity v is generally much less than wave velocity c.","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":8,"explanation":": Refraction requires a non-perpendicular angle and a change in the speed of propagation, c = \u03c1Z, where \u03c1 is density. Therefore, c can still be the same in two materials, even though Z is different, if \u03c1 is also different. Therefore I is false. Reflection","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310567,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:24:49","updated_at":"2017-12-13 20:31:31","questionName":"Which of the following statements is (are) true about the pulse-echo mode of operation in a phased array ultrasound scanner? I. The same transducers usually generate and receive the ultrasound pulses. II. The beam is steered by changing the duration of the transmit pulse envelope. III. Color Doppler is possible with pulse-echo ultrasound.","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":13,"explanation":"The beam is steered by changing the relative delay for each of the elements of the array, not the duration of the transmit pulse envelope","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310564,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:22:13","updated_at":"2017-12-13 20:31:31","questionName":"The following are true about the waves used in clinical ultrasound imaging, except","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":10,"explanation":"Absorption in biological tissue is roughly proportional to frequency and thus inversely proportional to wavelength, given that velocity (in soft tissue) is fairly constant at around 1540 meters\/second.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310556,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:16:27","updated_at":"2017-12-13 20:31:30","questionName":"The following are true about the waves used in clinical ultrasound imaging, except","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":2,"explanation":"Clinical ultrasound uses compression waves.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310557,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:17:02","updated_at":"2017-12-13 20:31:30","questionName":"In ultrasound, the space being imaged is organized into three regions. In each region, a particular approximation best describes the beam pattern. Those approximations are I - the Fraunhofer approximation II - the geometric appoximation (the very near field) III - the Fresnel approximation In what order do the corresponding regions of space occur, as one moves away from the transducer?","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":3,"explanation":"The order is geometric (very near field), Fresnel (near field), and then Fraunhofer (far field).","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310560,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:19:08","updated_at":"2017-12-13 20:31:31","questionName":"Which of the following statements is false about the piezoelectric crystals used in ultrasound transducers?","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":6,"explanation":"The transmitting constant and receiving constants don\u2019t even have the same physical units, so they will certainly not have the same numerical values.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310566,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:24:12","updated_at":"2017-12-13 20:31:31","questionName":". Which of the following statements is false about resolution in ultrasound?","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":12,"explanation":"Lateral resolution generally decreases (gets worse) with increasing range.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310559,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:18:27","updated_at":"2017-12-13 20:31:31","questionName":". Which of the following statements is false about the use of the complex exponential in modeling ultrasound?","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":5,"explanation":"The use of complex exponentials instead of real sinusoids encapsulates phase in such a way that algebra and calculus are straightforward, and is the heart of not only ultrasound design, but of modern optics. A linear system with superposition of the waves","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310568,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:25:23","updated_at":"2017-12-13 20:31:31","questionName":"Posterior enhancement (through transmission) is a type of ultrasound artifact often used in diagnosis because","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":14,"explanation":"Posterior enhancement makes tissue beyond a fluid filled structure appear brighter.","question_score_id":null,"lang":null,"questionAudioPath":null},{"id":310558,"quiz_id":"15767","answer_id":null,"answerType_id":"0","created_at":"2017-10-27 20:17:39","updated_at":"2017-12-13 20:31:31","questionName":"Which of the following statements is false about the Fraunhofer zone? (or all are true)","questionTimeSeconds":"0","questionTimeMinutes":"2","questionImagePath":null,"position":4,"explanation":"These are all true. Null points on the axis do occur in the Fresnel zone, but in the far field the aperture appears small enough that the field pattern is only fall off with distance squared and otherwise only varies with angle off the axis.","question_score_id":null,"lang":null,"questionAudioPath":null}]

block

The following are true about theoretical plane waves in ultrasound, except

Select the correct answer(s).  

(0/0)

Explanation

Whereas spherical waves spread out attenuating pressure by 1/r, planar waves do not spread out, and thus maintain their full amplitude.

---

Their general solution includes the superposition of a forward-traveling wave and a backward-traveling wave.

They can be viewed equally well as functions of time or of distance.

Spatial variation occurs only along one particular dimension

They are approximated within the Very Near Field near the center of the ultrasound transducer, where the transducer appears very large.

Their pressure is attenuated by 1/r where r is the distance traveled.

none

In ultrasound, with an incident planar wave that is not perpendicular to a boundary where the acoustic impedance Z changes, the following are true: I. Reflection will always occur. II. Refraction will occur if and only if the wave velocity c changes. III. Particle velocity v will always equal wave velocity c on either side of the boundary

Select the correct answer(s).  

(0/0)

Explanation

Refraction depends only on c. Reflection depends only on Z and the angle of incidence. Particle velocity v is generally much slower than wave velocity c.

---

II and III

I

I, II, and III

I and III

I and II

none

The following are true about theoretical plane waves in ultrasound, except

Select the correct answer(s).  

(0/0)

Explanation

They are approximated within the Very Near Field of the transducer, not in the Fraunhofer zone. In the Fraunhofer zone the waves diverge at a constant angle acting more like spherical waves

---

No attenuation occurs with distance along the direction of propagation.

Their general solution includes the superposition of a forward-traveling wave and a backward-traveling wave

They are approximated within the Fraunhofer zone.

Spatial variation occurs only along one particular dimension orthogonal to the plane of the wave

They can be viewed equally well as functions of time or of distance.

none

In ultrasound, which of the following is not true about the field pattern, an example of which is shown below (the figure actually shows a field pattern for light, but is analogous to that found with ultrasound).

Select the correct answer(s).  

(0/0)

Explanation

The Fraunhofer zone, otherwise known as the far field is labeled “D.”

---

In the region labeled “D” the field pattern becomes a function simply of angle from the axis

The label “B” marks the Very Near Field, where the aperture appears infinitely large

The label “C” marks the Fraunhofer zone.

The label “A” marks the aperture (or indicator function) of the transducer.

The field pattern represents a pattern of standing waves of constructive and destructive interference for a given aperture and wavelength, and is independent of the particular target being scanned.

none

Which of the following statements is false about the use of the complex exponential in modeling ultrasound, (or all are true)?

Select the correct answer(s).  

(0/0)

Explanation

The use of complex exponentials instead of real sinusoids encapsulates phase in such a way that algebra and calculus are straightforward, and is the heart of not only ultrasound design, but of modern optics. A linear system with superposition of the waves

---

It allows for the imaginary component of a physical quantity, by requiring that the imaginary component will be canceled by a complex conjugate.

All are true.

It generally assumes superposition of the ultrasound waves in a linear system

It permits mathematically tenable integration of many sources of ultrasound waves converging on a single point to determine the extent of constructive or destructive interference.

It is also the foundation of much of modern optics.

none

In ultrasound, with an incident planar wave that is not perpendicular to a boundary where the acoustic impedance Z changes, which of the following is (are) TRUE? I. Refraction will always occur. II. Reflection will always occur. III. Particle velocity v is generally much less than wave velocity c.

Select the correct answer(s).  

(0/0)

Explanation

: Refraction requires a non-perpendicular angle and a change in the speed of propagation, c = ρZ, where ρ is density. Therefore, c can still be the same in two materials, even though Z is different, if ρ is also different. Therefore I is false. Reflection

---

I and II

I, II, and III

I and III

only III

II and III

none

Which of the following statements is (are) true about the pulse-echo mode of operation in a phased array ultrasound scanner? I. The same transducers usually generate and receive the ultrasound pulses. II. The beam is steered by changing the duration of the transmit pulse envelope. III. Color Doppler is possible with pulse-echo ultrasound.

Select the correct answer(s).  

(0/0)

Explanation

The beam is steered by changing the relative delay for each of the elements of the array, not the duration of the transmit pulse envelope

---

I, II, and III.

II and III.

I and III

I

I and II

none

The following are true about the waves used in clinical ultrasound imaging, except

Select the correct answer(s).  

(0/0)

Explanation

Absorption in biological tissue is roughly proportional to frequency and thus inversely proportional to wavelength, given that velocity (in soft tissue) is fairly constant at around 1540 meters/second.

---

Their absorption coefficient in biological tissue is largely independent of wavelength

Velocity in soft tissue (not air or bone) is fairly constant at around 1540 meters/second (< ±10%)

They are primarily compression rather than shear waves.

They are used primarily to detect changes in acoustic impedance.

Distance to a target is determined by time of flight.

none

The following are true about the waves used in clinical ultrasound imaging, except

Select the correct answer(s).  

(0/0)

Explanation

Clinical ultrasound uses compression waves.

---

They do not travel well through air or bone.

Their absorption coefficient in biological tissue is roughly proportional to frequency.

Distance to a target is determined by time of flight.

They are primarily shear rather than compression waves.

They are generally produced in short bursts

none

In ultrasound, the space being imaged is organized into three regions. In each region, a particular approximation best describes the beam pattern. Those approximations are I - the Fraunhofer approximation II - the geometric appoximation (the very near field) III - the Fresnel approximation In what order do the corresponding regions of space occur, as one moves away from the transducer?

Select the correct answer(s).  

(0/0)

Explanation

The order is geometric (very near field), Fresnel (near field), and then Fraunhofer (far field).

---

I, III, II

III, I, II

I, II, III

II, III, I

II, I, III

none

Which of the following statements is false about the piezoelectric crystals used in ultrasound transducers?

Select the correct answer(s).  

(0/0)

Explanation

The transmitting constant and receiving constants don’t even have the same physical units, so they will certainly not have the same numerical values.

---

The resonant frequency of a crystal (typically 1-20 MHz in medical ultrasound) is largely determined by the thickness of that crystal

An induced electric field produces strain (mechanical displacement), which causes an acoustic wave

Energy is mainly lost due to damping by the acoustic backing behind the crystal, which is intentionally included to shorten the duration of the transmit pulse.

An incoming acoustic wave creates mechanical displacement, which creates an electrical potential.

The strain produced by a unit electric field (“transmitting constant” in meters per volt) and the potential produced by unit stress (“receiving constant” in volt-meters per Newton) are always numerically equal values.

none

. Which of the following statements is false about resolution in ultrasound?

Select the correct answer(s).  

(0/0)

Explanation

Lateral resolution generally decreases (gets worse) with increasing range.

---

Resolution increases (gets better) with increasing frequency.

Resolution is manifested by a “resolution cell” within which many actual reflectors create a total reflection of variable brightness, accounting for speckle.

Resolution in the range direction generally stays constant with increasing range.

Resolution in the range direction is limited by the duration of the envelope of the transmitted pulse.

Lateral resolution generally increases (gets better) with increasing range.

none

. Which of the following statements is false about the use of the complex exponential in modeling ultrasound?

Select the correct answer(s).  

(0/0)

Explanation

The use of complex exponentials instead of real sinusoids encapsulates phase in such a way that algebra and calculus are straightforward, and is the heart of not only ultrasound design, but of modern optics. A linear system with superposition of the waves

---

It is also the foundation of much of modern optics.

It allows for the imaginary component of a physical quantity, by assuming that the imaginary component will be canceled by a complex conjugate.

It permits mathematically tenable integration of many sources of ultrasound waves converging on a single point to determine the extent of constructive or destructive interference.

It generally assumes superposition of the ultrasound waves.

It applies only to single crystals and not to phased arrays.

none

Posterior enhancement (through transmission) is a type of ultrasound artifact often used in diagnosis because

Select the correct answer(s).  

(0/0)

Explanation

Posterior enhancement makes tissue beyond a fluid filled structure appear brighter.

---

it helps determine the velocity of blood flowing through a vessel.

it can differentiate a solid mass vs a fluid filled cyst, where this may not be possible CT.

it can cause a reflection of the image at a very large discontinuity in acoustic impedance, such as between the lung and the diaphram

it enables speckle tracking of cells within the fluid in any direction, even orthogonal to the ultrasound beam.

it can measure the blood volume of the ventricle.

none

Which of the following statements is false about the Fraunhofer zone? (or all are true)

Select the correct answer(s).  

(0/0)

Explanation

These are all true. Null points on the axis do occur in the Fresnel zone, but in the far field the aperture appears small enough that the field pattern is only fall off with distance squared and otherwise only varies with angle off the axis.

---

All are true.

There are null points due to destructive interference off the axis in this zone.

There are no null points due to destructive interference along the axis in this zone.

The field pattern is basically a function of angle off the axis.

It is also known as the “far field”.