Understanding Ultrasound Physics - SPI Exam Review - ARTIFACTS

True or False? Grading lobes are attributed only to array transducers.

True. Grating lobes are associated with array transducers.

How does slice thickness artifact commonly express itself? A. fill in of cystic structures B. improper brightness of reflectors C. strong linear echoes D. absence of reflectors

A. fill in of cystic structures Slice thickness artifact results in reflections placed on the image that do not correlate with the anatomical position of the reflector. Therefore, anechoic structures in the imaging plane are filled in with echoes from structures above or below the imaging slice.

Acoustic artifacts include: (more than one answer may be correct.) A. images of reflectors in an inappropriate position B. Images of reflectors with improper shape C. images of reflectors with incorrect brightness D. images that do not correspond to anatomical structures

A. images of reflectors in an inappropriate position B. Images of reflectors with improper shape C. images of reflectors with incorrect brightness D. images that do not correspond to anatomical structures An artifact is an error in imaging. All of the choices indicate a type of error, and therefore, are artifacts.

While using a linear sequential array transducer during a color Doppler exam, the shape of the grayscale image is most often _______, Whereas the shape of the color Doppler portion of the image is _______. A. rectangular, parallelogram B. rectangular, sector C. sector, trapezoid D. square, rectangular

A. rectangular, parallelogram The shape of a grayscale image using a linear sequential array is rectangular. However, the sound beams used for Doppler are steered at an angle, creating a parallelogram shaped region.

Which artifact is created by sound moving through a medium with a propagation speed less than soft tissue? A. Vertical misregistration B. Horizontal misregistration C. Lateral resolution D. Ring down

A. Vertical misregistration Vertical misregistration occurs when pulses do not travel at the speed of sound and soft tissue (1540 m/sec.) the reflections on the image will be placed at depths deeper than the actual position of the reflector in the body.

What is true of acoustic speckle? A. Its effects are mild and it tends to slightly degrade images B. it is a rare artifact that does not occur in real time imaging C. its effects are dramatic D. it is eliminated with apolarization

A. Its effects are mild and it tends to slightly degrade images Even though it does not accurately represent reflectors in the medium, acoustic speckle is often considered "tissue texture." it tends to contribute to overall image degradation.

What is a comet tail artifacts fundamental mechanism of formation? A. Reflection B. Rarefaction C. Refraction D. attenuation

A. Reflection Comet tail artifacts appear on an image as a result of numerous reflections between two closely spaced reflectors.

Which process causes mirror image artifact? A. Reflection B. Refraction C. propagation speed error D. attenuation

A. Reflection Mirror imaging is created by an unexpected and uncorrected reflection of the ultrasound pulse of a strong reflector.

6 distinct, equally space reflections appear on an image at ever increasing depths. What type of artifact is this? A. Reverberation B. Ring down C. Mirror imaging D. Longitudinal Resolution

A. Reverberation Reverberations are multiple , equally spaced reflections.

Grating lobes are produced by the same mechanism as which other artifact? A. Side lobes B. reverberation C. Transaxial lobes D. acoustic speckle

A. Side lobes side lobes and grating lobes are similar in that they represent acoustic energy transmission in a direction other than the main axis of an acoustic beam.

Two small cysts, positioned perpendicular to the main axis of a sound beam, are 2.4 MM apart. What determines whether they appear as two distinct images on the systems display? A. The beam width B. the pulse length C. the PRF D. the TGC

A. The beam width The ability to correctly image structures that lie close to each other in a direction perpendicular to the main axis of the ultrasound beam is called lateral resolution . Lateral resolution is primarily determined by the width of the acoustic pulse.

Sidelobe artifact usually results in all of the following except _______ . A. hollow structures appearing "filled in" On the image B. reflectors not appearing on an image C. reflectors appearing in improper locations on the image D. reflectors appearing in multiple locations on the image

B. reflectors not appearing on an image It is unlikely that a side lobe artifact would result in the absence of a reflector on an image. With side lobes, it is more likely that additional reflections will appear on the image.

The lateral resolution of four ultrasound systems appear below. Which will produce the finest quality picture? A. 2 CM B. 4 MM C. 6 MM D. 8 HM

B. 4 MM Resolution is reported in units of distance, with smaller values producing higher quality pictures. Choice B is a smallest number and therefore represents the system with the best images based on lateral resolution.

With standard diagnostic imaging instrumentation, which has the higher numerical value? A. Axial resolution B. Lateral resolution C. Neither; They have identical values

B. Lateral resolution In terms of image accuracy, axial resolution is usually better than a lateral resolution. The number assigned to lateral resolution is higher than to axial resolution.

Which technique of a linear array transducer design has virtually eliminated the appearance of grating lobe artifact on modern ultrasound systems? A. Demodulation B. Subdicing C. deconvolution D. None of the above

B. Subdicing The process of sub dicing has almost eliminated the appearance of grating lobe artifact on linear array transducer systems. Sub dicing consists of dividing each of the crystals in the array into smaller pieces. Sub dice pieces are then fired simultaneously as if they were a single crystal . This minimizes grating lobes.

Where is a mirror image artifact located? A. Sometimes shallower on the image than in the body B. always deeper on the image than in the body C. sometimes the same depth on the image as in the body D. never deeper on the image than in the body

B. always deeper on the image than in the body A mirror image artifact occurs when the pulse bounces off a strong reflector (such as the diaphragm) and then strikes a second reflector. the pulses path is lengthened by the mirroring, and the second reflection (Artifact) is always displayed at an abnormally great depth.

When enhancement occurs, where does it appear on the image? A. In the near field B. deeper than a weak attenuator C. in the far field D. shallower than a weak reflector

B. deeper than a weak attenuator Enhancement occurs after an ultrasound pulse has traveled through a low attenuating tissue and appears on the image deeper (distal) then that structure.

The analysis of Doppler Spectra using _______ is most accurate. A. Zero crossing detectors B. fast fourier transforms C. time interval histograms D. chirp Z transforms

B. fast fourier transforms The fast fourier transform, or FFT, is the most accurate spectral analysis technique. Techniques such as zero crossing, time interval histograms, and chirp Z were initially used to assess Doppler Spectra, but are now obsolete. Fast fourier analysis became popular when computers were incorporated into ultrasound systems.

If a sound pulse travels through a large mass at a speed of 1.2 mm/microsecond, what happens to the position of echoes from reflectors deeper than the mass? A. They are placed in too shallow a location on the image B. they are placed in too deep a location on the image C. they are likely to be placed at the correct depth

B. they are placed in too deep a location on the image The mass has a slow propagation speed when compared with soft tissue. All structures distal to the mass will be placed at too great a depth on the image. The reflections on the image will be farther than the reflectors true anatomical position.

Spectral analysis of color flow Doppler is most commonly performed by which of the following techniques? A. Zero crossing detectors B. fast fourier transforms C. autocorrelation D. Chirp Z transforms

C. autocorrelation Autocorrelation is a technique of choice for spectral analysis of color Doppler. Although the most accurate technique is the FFT, autocorrelation is better suited to process the enormous amount of data acquired in a color Doppler study.

Where are shadowing artifacts commonly seen on an acoustic scan? A. Deeper than a structure with a high impedance B. shallower than a structure with a low propagation speed C. deeper than a structure with a high attenuation D. Alongside of a structure with a low elastance

C. deeper than a structure with a high attenuation Shadowing occurs on an image at locations beneath strong attenuators. For example, a region deeper than a gallstone may be affected by shadowing.

With which of the following pulses would lateral resolution be worst? A. 10 MHz, 4 mm beam diameter, Four cycles per pulse B. 4 MHz, 4 mm beam diameter, two cycles per pulse C. 7.5 MHz, 8 mm beam diameter, two cycles per pulse D. 6 MHz, 2 mm beam diameter, two cycles per pulse

C. 7.5 MHz, 8 mm beam diameter, two cycles per pulse Lateral resolution artifact is related to the diameter of the ultrasound beam. Narrow beams have the best lateral resolution. Wide beams have the worst lateral resolution. Choice C, with a beam diameter of 8 mm, is most likely to produce a lateral resolution artifact.

Which of these pulses is least likely to produce an axial resolution artifact? A. 10 MHz, 8 mm beam diameter, 6 cycles per pulse B. 4 MHz, 4 mm beam diameter, 2 cycles per pulse C. 9 MHz, 8 mm beam diameter, 2 cycles per pulse D. 6 MHz, 2 mm beam diameter, 2 cycles per pulse

C. 9 MHz, 8 mm beam diameter, 2 cycles per pulse Short pulses are least likely to produce an axial resolution artifact. Short pulses are those with a high frequency and few cycles per pulse. Although choice C does not have the highest frequency, it has only two cycles per pulse, and therefore is the shortest of the four pulses.

With standard diagnostic imaging instrumentation, which has the higher numerical value? A. Axial resolution B. Lateral resolution C. Elevational resolution

C. Elevational resolution In terms of image accuracy, elevational resolution, determined by slice thickness, is the cause of greatest image degradation. The numerical value assigned to elevational resolution is higher than the others.

Unexpectedly low attenuation results in which of the artifacts listed below? A. Refraction B. Attenuation C. Enhancement D. shadowing

C. Enhancement Enhancement occurs with unexpectedly low rates of attenuation.

What is the cause of acoustic speckle? A. Refraction B. Attenuation C. Interference of tiny acoustic wavelets D. resonance of particles in the near field

C. Interference of tiny acoustic wavelets Acoustic speckle is produced by the constructive and destructive interference of small acoustic waves reflected from small reflectors in the near field.

Which of the following determines the spatial resolution of an image on a monitor? A. Strength of the electron beam B. form of phosphor coating of the screen C. Number of lines of the monitors display D. the pulse duration

C. Number of lines of the monitors display The image displayed on a monitor is composed of a number of horizontal lines. The detail within the image, called spatial resolution, is determined by the number of TV lines on the screen.

Ultrasound systems are designed to automatically _______ . A. display similar structures with equal brightness, regardless of depth B. position structures at the correct depth, regardless of the medium C. display all reflections on a line corresponding to the main axis of the sound beam, regardless of refraction D. Select the optimal beam width based on the clinical application

C. display all reflections on a line corresponding to the main axis of the sound beam, regardless of refraction Ultrasound systems assume that all reflections are created from reflectors that lie directly along the main axis of the ultrasound beam. An artifact is created when pulses refract and change directions.

What is the meaning of the term "analysis" in the context of spectral analysis of Doppler signals? A. Building a sophisticated signal from components B. building a simplified signal from components C. identifying the building blocks or components of a complex signal D. measuring a complex signal then modifying its information content

C. identifying the building blocks or components of a complex signal The term analysis defines the act of scrutinizing an object to determine what individual components are incorporated within it. In Doppler analysis, the complex signal is broken down into its more basic ingredients.

In diagnostic imaging, how does multi path artifact affect the image? A. Poor angular resolution B. Creation of hyperechoic regions C. mild image degradation D. Gross horizontal misregistration

C. mild image degradation Multipath artifact does not manifest itself in a pronounced manner. The primary result of this artifact is mild image degradation.

Which artifact is not affected by the shape or dimensions of an ultrasound pulse? A. Lateral resolution B. Slice thickness C. mirror imaging D. longitudinal resolution

C. mirror imaging Of the artifacts listed, only mirror imaging is unrelated to the size , shape, or geometry of the ultrasound pulse. The others depend in some way on the pulses characteristics.

What type of artifact causes a reflection to be placed at an incorrect depth? A. Lateral incertitude B. shadowing C. range ambiguity D. Indeterminate relaxation

C. range ambiguity Range ambiguity means that uncertainty exists regarding the depth of a structure in the body.

Which artifact results in improper side-by-side positioning of reflectors? A. Multi path B. comet tail C. refraction D. Reverberation

C. refraction Refraction artifact results from an acoustic pulse bending and changing direction. This change of direction is not corrected by the ultrasound system and results in an improper lateral location of reflectors on the image.

What artifact results from an ultrasound beam having a finite and measurable 3 dimensional profile? A. Acoustic speckle B. multi path artifact C. slice thickness artifact D. grating lobe artifact

C. slice thickness artifact Slice artifact occurs because a sound beam has a thickness. Although the sonographer imagines that the imaging plane is extremely thin, the beam actually has a measurable thickness, thickness artifact results in some reflectors appearing in the image even though they are positioned above or below the idealized imaging plane.

What assumption is violated when a refracted sound wave is processed? A. Waves travel directly to and from a reflector B. sound travels at an average speed of 1.54 mm/microsecond C. sound travels in a straight line D. the acoustic imaging plane is very thin

C. sound travels in a straight line Ultrasound systems create images on the basis of certain assumptions. Artifacts occur when these assumptions are invalid. Refraction artifact results from sound traveling in a crooked or bent line while the ultrasound system assumes a straight path.

If an ultrasound pulse travels through a large mass in the body at a speed of 1.2 mm/microsecond, what happens to the position of all echoes produced from reflectors shallower than the mass? A. They are placed in too shallow a location on the image B. they are placed in too deep a location on the image C. they are likely to be placed at the correct depth

C. they are likely to be placed at the correct depth The mass has a propagation speed different than that of soft tissue. Only structures deeper than the mass will be affected. However, this question asks about reflectors that are shallower than the mass. Reflections from structures shallower than the mass are not affected by this speed difference.

With depth resolution, _______. A. too many reflectors appear on the image B. reflectors are placed too deep on the image C. too few reflectors are on the image D. reflectors appear too shallow on the image

C. too few reflectors are on the image Depth resolution is the ability to distinguish two reflectors that lie close to each other along the main axis of the beam. Most errors in depth resolution result in fewer reflections placed on the image than are actually in the body. depth resolution is another name for axial resolution.

Which situation will commonly produce reverberation artifact? A. Two masses that lie perpendicular to the sound beam's main axis B. two weak reflectors that lie close to each other along the axis of the beam C. two strong reflectors that lie along the main axis of the beam D. a single highly reflective mass

C. two strong reflectors that lie along the main axis of the beam Reverberations are commonly produced by a pair of strong reflectors that lie along the main axis of an ultrasound beam.

What causes enhancement artifact? A. Sound beams bending B. linear array transducer architecture C. unexpectedly low acoustic attenuation D. Acoustic energy radiating in a direction other than the beam's main axis

C. unexpectedly low acoustic attenuation Enhancement artifact appears directly below structures with atypically low attenuation. Cystic structures often create enhancement artifacts since fluids within the cyst often attenuate sound to a lesser extent than surrounding tissues.

What causes side lobe artifacts? A. sound beams bending B. linear array transducer architecture C. unexpectedly low acoustic attenuation D. Acoustic energy radiating in a direction other than the beam's main axis

D. Acoustic energy radiating in a direction other than the beam's main axis A side lobe is produced when a significant amount of acoustic energy is directed along a line other than the main axis of the acoustic pulse.

Which of these produces shadowing? A. Reverberation B. Multi path C. reflection D. Attenuation

D. Attenuation Shadowing results from atypical attenuation, the weakening of ultrasound pulses.

Which artifact is not related to the unexpected reflection of an acoustic wave? A. Multi path B. comet tail C. reverberation D. Lateral resolution

D. Lateral resolution Lateral resolution is an artifact that is not associated with abnormal reflection. Lateral resolution artifacts are related to beam diameter.

Axial resolution artifacts are due to which of the following? A. Multiple reflections B. beam width C. attenuation D. Pulse length

D. Pulse length The critical factor that influences axial resolution is pulse length. Shorter pulses produce more accurate images than longer pulses . Shorter pulses have improved axial resolution.

What is the most likely cause of ring down artifact? A. Refraction B. Inversion C. Reabsorption D. Reflection

D. Reflection Ring down artifact is thought to result from multiple reflections.

Acoustic focusing of an ultrasound beam may create which artifact? A. Side lobes B. refraction C. Speckle D. enhancement

D. enhancement Focusing of an ultrasound beam may result in very strong reflections from anatomic structures at the depth of the focus. The powerful reflections result in a hyperechoic band that is called focal enhancement or focal banding.

Grating lobes are most common with which type of transducer technology? A. annular array B. continuous wave C. mechanical scanners D. linear arrays

D. linear arrays Grating lobe artifacts are associated with linear array transducers.

How is shadowing artifact expressed? A. Positioning structures too deep on the image B. locating structures in improper lateral position C. Placing reflections in multiple locations D. reflectors being absent on the image

D. reflectors being absent on the image A shadow artifact results from unexpectedly high attenuation. The ultrasound beam deeper than the strong attenuator is so weak that significant anatomical information does not appear on the image.

While imaging a test object, an ultrasound system displays one image 1.8 cm deeper than another. Upon, Measuring the test object, it is found that it is actually 2.0 cm Deeper. What conclusion can be drawn from this? A. Speed of sound in the test object is the same as soft tissue B. speed in the test object is less than that in soft tissue C. attenuation of sound in the test object is less than that in soft tissue D. speed in soft tissue is less than that of the test object

D. speed in soft tissue is less than that of the test object When vertical misregistration occurs it is likely that the speed of sound in the medium differs from 1540 m/sec. if the measurements on the image are less than the true distances, then the speed of sound in the medium is greater than that of soft tissue.

What are the characteristics of a medium that produces comet tail artifact? A. Weak reflectors, closely spaced, low propagation speeds B. strong reflectors, widely spaced, high propagation speeds C. strong reflectors, closely spaced, low propagation speed D. strong reflectors, closely spaced, high propagation speed

D. strong reflectors, closely spaced, high propagation speed A comet tail artifact is similar to a reverberation except that the reflection is a solid hyperechoic line. The comet tail is a solid jet because of strong reflectors with high propagation speeds lying close to each other.

True or False? All artifacts are errors in imaging that do not represent the true anatomy of the imaged organ. Therefore, they are all undesirable and should be eliminated if possible.

False. All artifacts are indeed errors in imaging. However, they may provide useful information . An artifact can provide insight into the physical characteristics of a structure, and help the clinician make a definitive diagnosis. Eliminating all artifacts may exclude important information from appearing on the exam.

Which of the following is not a potential cause of artifact and diagnostic imaging? A. Operator error B. equipment malfunction C. Patient motion D. Ultrasound physics E. none of the above

E. none of the above The four choices, A through D, represent the primary explanations of artifacts commonly seen in diagnostic ultrasound.

True or False? Artifacts are likely to appear when the dimensions of the sound beam area are larger than the dimensions of the reflectors in the body.

True. Artifacts are likely to appear when the dimensions of the sound beam area are larger than the dimensions of the reflectors in the body.

True or False? Side lobe, grating globe, and refraction artifacts all reduce lateral resolution.

True. Lateral resolution is related to structures that lie in a plane perpendicular to the sound beam's main axis . These three artifacts all degrade lateral resolution.

True or False? Grating lobes are a result of substantial acoustic energy directed outward from a linear array transducer, but not along the main axis of the sound beam.

True. This is the exact definition of a grating lobe.