For those who are writing the SPI- Ultrasound physics exam. I have notes for sale it is about 1500 multiple choices sets for ARDMS -spi exam = 50 USA DOLLARS. I study those notes and passed my exam 670/700 . If you want to buy i can copy the notes and send them to you in e mail or by mail you can reach me atdrsteveramsey@gmail.com . I will also include some of the ideas about the 12 simulation questions. The payment with PayPal to drsteveramsey@gmail.com , fetal gender , Saad Ismail
you can also see my new blog www.moleopedia.com
Before I start the Artifact lecture; I share with you these sites , safe and secure sites that contains more than 2000 MC ultrasound physics questions and answers for the SPI- ARDMS Ultrasound physics.
Artifacts are an error in imaging. They are a misrepresentation of anatomy, whether causing something to appear that does not represent actual anatomy, or causing anatomy that is present to not be visualized, or not visualized properly.Some artifacts may be avoidable and arise secondary to improper scanning technique.
Other artifacts are generated by the physical limitations of the modality. US artifacts can be understood with a basic appreciation of the physical properties of the ultrasound beam, the propagation of sound in matter, and the assumptions of image processing. US artifacts arise secondary to errors inherent to the ultrasound beam characteristics, the presence of multiple echo paths, velocity errors, and attenuation errors.
The beam width, side lobe, reverberation, comet tail, ring-down, mirror image, speed displacement, refraction, attenuation, shadowing, and increased through transmission artifacts are encountered regularly.
There are certain assumptions that US systems assume are true, artifacts appear when these are violated
The six assumptions are as follows:
- Sound travels in a straight line
- Sound travels directly to a reflector and back
- Sound travels in soft tissue at exactly 1540 m/s
- Reflections arise only from structures positioned in the beam’s main axis
- The imaging plane is very thin
- The strength of a reflection is related to the characteristics of the tissue creating the reflection
Reverberation Artifact / Comet Tail / Ring Down
- Part of the propagation path group
- The three assumptions that fail and produce propagation artifacts are
- Transmitted waves travel in a straight line
- All echoes originate along the transducer axis only
- Sound waves travel at 1540 m/s in soft tissue
Reverberation
Caused by bouncing back and forth of the sound wave between two strong reflectors that are parallel to the ultrasound beam
- Reflections “ping pong” between structure and transducer
- Resembles a ladder or venetian blind
- Multiple, equally spaced echoes
- Located at ever increasing depths, each echo is deeper than the next
- 1st and 2nd reflections closest to transducer are real, the multiple reflections displayed beneath the real reflector are artifacts
Helpful- Drop in echo strength is partially counteracted by attenuation
Hinders-Each subsequent reflector is weaker than prior ones
Prevention-Move transducer and beam to various angles to avoid reverberation and to see area that was covered by artifact
Comet tail
- Sound wave between two very closely spaced reflectors that merge and generate a series of closely spaced, discrete echoes
- usually caused by small calcifications and metal objects like surgical pin
- could also arise from the vibration of small highly reflective surfaces such as air bubbles
- this happens more often when the reflectors are located in a medium with high propagation speed.
- appears distal to the highly reflective structure as a single solid hyperechoic (bright white) “tail” and is parallel to the sound beams main axis
- the complexity of the pattern depends on size, shape, and composition of the reflector, also the scan orientation and distance from the transducer
- usually in otherwise echo free areas on the image
Helpful- used in ruling out pneumothorax
- If a pneumothorax is present, air within the pleural space hinders the propagation of ultrasound waves, thereby preventing the formation of comet tail artifacts
Hinders-significant loss of energy so the sound is not able to reach a far depth. not able to view underneath reflector because of tail
Prevention- move the transducer beam to different angles to see the area hidden by tail
Ring down Artifact
small gas bubbles produce reflections after the transducer receives the initial reflection and the transducer thinks the sound is coming from structures deeper in the body.
- The ringing is from the high amplitude, repetitive striking of the crystal
- appear as hyperechoic (bright white) parallel bands that reach to the bottom of the image and represent the continuous ringing transmitted back to the crystal.
- displayed as fuzzy gray echoes below each hyperechoic reverberation echo
Helpful-little energy is lost from ring down
Hinders- the ring down effect is very bright and will continue very deep
- cannot view what is beneath the ring down effect
Prevention- Move the transducer beam to different angles to avoid the brightness and see the area affected by the artifact. It is relatively rare to observe a significant ringdown artifact on a modern scanner.
Shadowing
Description of Artifact:
- Highly attenuating/reflective structure causes shadowing posterior to the structure
- Shadowing by refraction
- Distal echoes weaker (appear darker, like a shadow)
- Shadowing posterior to a solid structure
- Attenuation causes sound waves weaken as propagates thru medium (↓amplitude, intensity, power)
o ↑ attenuation in gas & fat
- Impedance affects travel of sound thru a medium
o ↑ Impedance ↓reflection ↑density
Category: Attenuation.
Cause: Missing information, Technique cause: indifferent, improper scanning, improper setting, poor ultrasound system
Defines Assumption:The strength of a reflection is related to the characteristics of the tissue creating the reflection.
- Hypoechoic/anechoic region extending beneath structures as a result of too much attenuation
Hindrance, Helpful or Both:Hindrance: Prevents visualization from true anatomy on scan by covering anatomy with an anechoic shadow. Helpful: Is often useful to determine the nature of masses and structure
How to Prevent:
- Image structure in several angles to avoid missing information
- ↓ with spatial compounding (and other speckle reduction techniques)
- Change lateral/axial resolution
o ↓ frequency, ↓ attenuation, ↓AR
o ↓ BD, ↓LR
Enhancement
Description of Artifact: Improper hyperechoic region due to low attenuation
- ULS will penetrate the fluid filled structure
- ↑ echoes posterior to low attenuating structure
- Opposite of shadowing
- Common posterior to fluid filled structures (↓ attenuator)
o Gallbladder, Urinary bladder, Ovarian cysts
o Simple cyst, Hematomas (clean), Abscess (clean)
- Unrelated to speed of sound thru medium
- Attenuation causes sound waves weaken as they propagate in medium (↓amplitude, intensity, power)
- Impedance affects travel of sound thru a medium
o ↑ Impedance ↓reflection ↑density
Category: Attenuation
Cause: Improper brightness. Technique cause: Indifferent, improper scanning, improper setting, poor ultrasound system
Defies Assumption:Intensity of reflection related to characteristic of tissue
- Hyperechoic region posterior to a fluid-filled structure
How to Prevent:
↓ beam intensity in focal region/widen beam
Adjust TGC in the far field , Use spatial compounding or other speckle reducing techniques. e frequency
Use different angles to get around enhancement
Hindrance, Helpful or Both: Helpful: can provide confirmation of fluid component within structure
o Ex: Uterus sitting behind the urinary bladder
o Ex. Cyst with posterior attenuation = fluid filled
- Hindrance: Distort diagnostic info by giving improper brightness to structures posterior to a low attenuating (fluid-filled) structure
- A hyperechoic side-to-side region
- ↑ intensity at the focus
- Special form of enhancement
- Has the same appearance as incorrect TGC setting
- Created from phased array tx
- Attenuation causes sound waves weaken as they propagate in medium (↓amplitude, intensity, power)
- Impedance affects travel of sound thru a medium
o ↑ Impedance ↓reflection ↑density
Category: Attenuation
Cause: Improper brightness. Technique cause: Indifferent, improper scanning, improper setting, poor ultrasound system
Defies Assumption:Intensity of reflection related to characteristic of tissue
A hyperechoic horizontal region at the depth of the focus
How to Prevent: ↓ with spatial compounding (and other speckle reduction techniques). Adjust TGC in region of enhancement
Hindrance , Helpful or Both:Hindrance: Distorts visualization of true anatomy by creating improper brightness
- Helpful: It may provide valuable diagnostic information that helps to characterize tissue
age
Category ;A form of reverberation (multiple reflections)
- A propagating artifact
What is a mirror image?
- A duplicate of a true reflector
- AKA ghost artifact
Cause ; Created when sound reflects off a highly reflective surface, and is redirected toward a second structure.
- The redirection causes a replica (copy) of the structure to incorrectly appear on the image
- Shows structures that exist on one side of a strong reflector on the other side as well
- The artifact is located deeper than the real structure
- The mirror is always located along a straight line between the transducer and the artifact
- Can appear in gray scale imaging and color Doppler
*example: crosstalk artifact: a mirror image artifact that appears on a Spectral Doppler display, makes the flow pattern appear bidirectional (above and below the baseline) caused by high Doppler gains
- The true reflector and the artifact are equal distances from the mirror
- Common around the diaphragm and pleura Violated Assumptions
- Sound travels in a straight line, Sound travels directly to a reflector and back to the transducer.Decrease overall gain, Change beam angle
Helpful or Hinderance; Hindrance: The mirror image is not helpful in determining a diagnosis; it is simply a replica of the real anatomy placed incorrectly on the image.
*Note: The artifact is always deeper than the true anatomy and the distance between the mirror and the real anatomy verse the artifact are equal distances. The angled line is the mirror, the copy of the cystic structure is the artifact Mirror image artifact in color
Mirror image in color doppler. Speed Error
Category: propagation ;Cause: when the sound wave propagate through a medium at a speed other than that of a soft tissue (1.54km/s) the correct number of the reflector are displayed but they appear at incorrect depth
What assumption: The assumption of the a value for speed of sound in soft tissue is exactly 1540 m/s or1.54mm/us is invalid. leading to 13 us rule is incorrect .
Description of Artifact:Speed errors are created when wave propagates at a speed other than 1540 m/sec.
- The correct number of reflectors are displayed; however, they appear at incorrect depths.
- The actual wave can travel faster or slower that 1540 m/sec causing artifacts.
- If the sound travels faster than expected, the distances are underestimated causing the go-return time to be too short.
- If the sound travels slower than expected, the distances are overestimated causing the go-return time to be too long.
- APPEARANCE: Correct # of reflectors are displayed
- Incorrect depth displayed for the reflectors
- Reflectors appear as a step-off; structures are split or cut
- -If sound propagates faster than expected, the reflectors will be placed too shallow on the image
- -If sound propagates slower than expected, the reflectors will be placed too deep on the image
- far from the transducer, distance are overestimated ,number are too large
How to prevent: Change the angle of the beam which may help minimize the difference of propagating speed.
- Speed error artifact is not preventable, however, it is important to recognize that it can cause incorrect placement of the reflectors on the display
Hindrance, Helpful or Both: This artifact is a hindrance because the reflected echoes being displayed are incorrectly placed.
- It is important to be able to distinguish between incorrect placements of these echoes and avoid interpreting the image incorrectly; if you cannot duplicate the incorrect placement of the reflectors on two different images it probably is an artifact.
- Reflectors are placed too deep in the image
- Distance is over estimated
- Kidney’s cortex appears with a step-off to the border
Diaphragm appears split or cut. Go-Return Time too long within the liver parenchyma
Weaker beams that span outward from a single element transducers in directions different from the primary or main beam
SLIDE LOBE ‘ Description:Created by weak beams of single element transducers traveling at angle to main beam. Lobes encounter a strong reflector (hyperechoic area), the reflected energy will be added to the energy from the main beam
Category:Propagation group
Causes: Energy is sent in a direction other than beam’s main axis
Strong reflector in this path creates reflection that is misinterpreted as being along beam’s main axis.
Width and length mode vibrations, immediate reverberations at crystal-tissue interfaces, and interference phenomena
What assumption:All reflections are in path of beam’s main axis. Spurious echoes in the near field of image. Second copy of true reflector. Anatomic reflector appears multiple times on image. Placed to the side of the true anatomy at same depth
How to prevent:Use of multiple views, will not appear in all views
Apodization- increased voltage to center elements and less to outer elements also reduce sensitivity of outer elements
Hinderance/ Helpful/Both:Hinderance- duplication of true anatomy with false reflection
Additional weak beams span outward from an array transducer that are stronger than the sidelobes of elements
Description:Created by weak beams of array transducers traveling at angle to main beam. Measuring the time of flight to an object located outside the main beam and placing the detected echo as if located along path of main beam
Category:Propagation Group
Causes:Energy is sent in a direction other than beam’s main axis
Strong reflector in this path creates reflection that is misinterpreted as being along beam’s main axis
What assumption:All reflections are in path of beam’s main axis.
Copy of artifact side by side with real reflector.
Artifact will normally appear weaker than true reflector
Placed to the side of the true anatomy at same depth
How to Prevent: Use of multiple views, will not appear in all views
Subdicing- diving crystal into smaller pieces
Apodization- increased voltage to center elements and less to outer elements
also reduce sensitivity of outer elements
Hinderance- duplication of true anatomy with false reflection
Change in direction of sound beam as it passes a boundary
Description:Sound pulses change direction during transmission
The beam is bent away from the propagation path at an angle equal to angle of incidence.
Category:Propagation Group
Causes:Beam encounters interface at oblique incidence and BB2M have different propagating speeds
What assumption:Sound travels in a straight line. Second copy of true reflector. Anatomic reflector appears multiple times on image
Placed to the side of the true anatomy at same depth
How to prevent:When speeds of two media are the same
The angle of incidence and transmission will be equal
Hinderance- Duplication of true reflector that makes think two of same thing.
Refraction may cause single gestation to appear as a double gestation (trans view)
What is Slice Thickness? A resolution, propagating artifact
AKA section thickness or partial volume artifact
Beam width perpendicular to the scan plane causes section thickness
Cause; Occurs when the beam dimension is greater than the reflector size . Elevation resolution- determined by the thickness of the imaging plane
o Thinner planes have less chance of artifact occurring
The imaging plane is neither thin nor uniform thickness, the beam flares out, reflections from structures above or below the assumed imaging plane may appear in the image
Ex: False debris in a simple cyst
Thicker portions of the slice have inferior elevational resolution compared to thinner portions
Assumptions. It is assumed that the imaging plane is extremely thin
This is invalid because the imaging plane is 3-dimensional, neither thin nor uniform
Is Slice Thickness Helpful? Slice thickness is a hindrance because it can appear as sludge or debris. Can lead to false diagnosis
How to Eliminate Slice Thickness; Use tissue harmonic imaging- the sound beam in this mode is narrower than gray-scale mode. Use 1 ½ transducer arrays – create thinner imaging planes
Description of artifact
Multipath artifact arises when the ultrasound beam hits a boundary at an angle and part of the original echo returns to the transducer while other part is reflected off a second boundary before returning back to the transducer
t takes the beam more time to travel back to the transducer. So for example, if a structure is actually located 7cm deep the machine will perceive the time to be 20cm and places the dot in a different position than it actually should be.
Category’ Propagation path error
Cause ;Indifferent
Assumption ;A pulse travels directly to a reflector and then back to the transducer is invalid.
Reflections are produced by structures located in the main axis of the beam is invalid
Hindrance ;Multipath artifacts may improperly display the position of an object due to longer path lengths
Incorrect axial location of an interface due to increased time
Multipath also results in slight changes that can’t be clearly be identified on the image
Image appears deeper or misplaced
In this image of the liver, small dots can be seen within the lumen of the gallbladder which represents a multipath artifact, Situations where artifact occurs . Improperly located
How to prevent; Change angle of the beam, Change depth
lection of Multipath artifact
Reflection is defined by sound moving in the opposite direction compared to the beam.
It is affected by the different type of reflectors and the impedance between two boundaries.
With multipath artifacts, the transducer receives reflections from structures that are not in the main axis of the beam due to different beam paths.
CURVED/OBLIQUE REFLECTORS
Description of artifact; As a sound beam hits a curved or oblique boundary, some of the reflected sound is directed away from the transducer.
Curved/Oblique reflectors redirect sound waves in many different directions (like scattering)
Therefore reflectors may appear absent on the image, weak or different from other similar reflecting boundaries due to longer path lengths and beam attenuation
The further sound travels, the greater the attenuation, & weaker the beam becomes
Image above shows a curved/oblique reflectors redirecting the sound waves in many different directions
Category ;Propagation path error
Cause ;Indifferent
Assumption; A pulse travels directly to a reflector and then back to the transducer is invalid.
Amplitude of reflection received by transducer is less or greater than expected (can give incorrect brightness, false or absent reflections). Improper location of structure. Weak or too bright echo amplitudes
Hypoechoic, Hyperechoic, Absence of echoes, Situations where artifacts occur, Improperly located, Improper brightness
How to prevent; change transducer angle, Larger footprint, Use crossbeams
When the structure that is being hit with the sound beam is small and in between the lines, then it will cause an artifact.
Assumption: Reflections arise only from the structures positioned in the beam’s main axis. Sound travels in a straight line
Artifact is an hindrance because it degrades the image detail and produce misleading echoes.
Prevent: Have more lines per frame to improve spatial resolution.
Degradation of the image due to line density.
Spatial Resolution ;Ability to image fine detail and distinguish two closely spaced structures.
Overall detail of image ; Line densitydetermines spatial resolution
Low line density: lines spaced far apart meaning less lines per frame, therefore spatial resolution and poor detail
High line density: lines closely packed meaning more lines per frame, therefore spatial resolution and great detail
For example, if I have 3 lines per frame and the small structure is between the lines, then the artifact will be produced. However, if I have 8 lines per frame then the structure will not be in between the lines; the sound beam will hit the structure on all sides.
Analog Display: Number of scan line comparison
Not Lines of Sight, but lines in display
Pixels = The smallest building block of a digital image= picture element
Pixel density: number of pixels per inch
Low pixel density= less pixels per inch, therefore, each pixel is large and it degrades spatial resolution
High pixel density= more pixels per inch, therefore, each pixel is small and it improves spatial resolution .
Spatial Resolution Artifact . Resolution Artifact =Occurs when the size of the pixel is greater than the size of the reflector.
Prevent: Have high pixel density so the pixel can be as small as the smallest structure for better detail because if it is bigger it will produce an artifact and blur the entire reflection.
The smaller the pixels the greater the detail of the image
Digital Display: Pixel density comparison
Noise: low level echoes as a result of electrical interference, signal processing, spurious reflections.
Assumption: Reflections arise only from structures positioned in the beams main axis.
Noise ; Noise affects the entire image
o For example: an aorta filled in with echoes
o Brightness posterior to diaphragm
Noise is a result of settings:
o When the TGC pods are all on one side
o When Gain is too high
o When Power is too high
Range AType of artifact ;Propagation
What is range ambiguity artifact? It is an echo incorrectly displayed as closer to the surface
Causes; It is produced when a second pulse is emitted before the echoes of the first were received/ high PRF
When the echo travels at a faster rate than the assumed 1540 m/s
High PRF
Assumption; Sound in the body always travels at a speed of 1540 m/s
How to prevent; Increase PRP- the first pulse then has a longer go/return time
Decrease PRF- echo sent to greater depth which = greater listening time
Hinderance because echo is not displayed at the correct depth and may be mistaken for pathology
Description: Speckle is considered an artifact and not normal tissue texture. Speckle is a misplaced echo in structures from weak signals in the wrong parenchyma.
Category: Propagation
Cause:When sound waves interfere with each other
When there is excessive gain on near field
What Assumption:Echo’s strength corresponds to reflectors properties
Description of Artifact:Weak scatterers in tissue giving a granular appearance
Obscures anatomy. Usually appears near the face of the transducer
Reduces contrast resolution in tissue.A form of noise.
Speckle is a result of the interference effects of the scattered sound from the distribution of all the scatters within a tissue.
How to Prevent: Harmonics sends out strong frequencies and receives many transmitted frequency. Receiving strong frequency eliminates speckle. Reduce the gain.
What is Harmonics?
Harmonics is imaging with twice the frequency of the transmitted sound. Also called the second harmonic frequency.
The accumulation of noise and clutter is reduced, because the harmonic signal only has to travel from the tissue back to the transducer.re non-linear
Speckle is a hindrance it does not allow the imaging anatomy to be correctly diagnosed.
Noise often result from Electronic Circuit or Gain too high (Input or output)
Speckle Artifact : Due to scattering properties that misplaces echoes or interference
Noise Artifact ;Description: Noise artifact is when the gain or TGC are too strong and extra fill in’s appear with in anatomy.
Category:Resolution Artifact
Cause:Sound beam interference that gives interrupted information
Noise is signal that does not convey useful information
Caused by excess gain (improper TGC, Too high of overall gain, too high power)
What Assumption:Affects low-level hypoechoic areas
Noise limits the sensitivity and causes false outputs, Bands of noise across image. Homogeneous Speckle appearance
How to Prevent:The use of Harmonics improves the signal-to-noise ratio decreasing noise. Adding coupling gel reduces inhibition of noise
What is Harmonics? Harmonics is imaging with twice the frequency of the transmitted sound. Also called the second harmonic frequency.
The accumulation of noise and clutter is reduced, because the harmonic signal only has to travel from the tissue back to the transducer.
What is signal to noise? Signal to Noise ratio is comparing the useful information with the useless information.
As output power is increased, signal to noise ration increases improving image quality. Noise is a hindrance because it interferes with being able to receive useful diagnostic information.
- what is the average velocity of ultrasound in soft tissue at 5.0 MHz ?
- (A) 1540 meters per millisecond
(B) 1540 meters per microsecond
(C) 1540 meters per nanosecond
(D) 1540 meters per second correct answer
Red blood cells are an example of a
(A) rayleigh reflector
(B) non-specular reflector
(C) strong reflector correct answer
(D) mirror reflector
Which has a higher acoustic impedance coefficient ?
(A) solid correct
(B) liquid
(C) gas
(D) all the above
A hyperechoic region is
(A) low amplitude
(B) anechoic
(C) echo free
(D) echogenic correct
The angle of refraction is described by
(A) Snell’s law correct
(B) Curie’s principle
(C) Huygen’s principle
(D) speed differences
What is reflection in multiple directions from a reflector that is small relative to
the wavelength
(A) multipath artifact
(B) Snell’s scattering
(C) Hguyens principle
(D) Rayleigh scattering correct
Receiver demodulation can not be controlled by the sonographer
(A) True correct
(B) False
Reflection at a tissue interface depends primarily on
(A) impedance correct
(B) bandwidth
(C) beam profile
(D) velocity differences
Azimuthal resolution is also known as
(A) lateral resolution correct
(B) range resolution
(C) axial resolution
(D) none of the above
What is the Doppler shift frequency in soft tissue if the transmitted frequency is 3
MHz and the velocity of a reflector is 20 cm/s ?
(A) 195 Hz
(B) 390 Hz
(C) 780 Hz correct
(D) 3.07 MHz
(E) 3.14 MHz11. Intensity of the ultrasound beam is proportional to the square root of the acoustic pressure
(A) True
(B) False correct
Aliasing is not a problem with color flow imaging.
(A) True
(B) False correct
Density is an acoustic variable
(A) True correct
(B) False
If the PRF increases, duty factor ___________
(A) Increases correct
(B) decreases
C) remains the same
(D) is unrelated15. A-Mode is mainly used to measure distance
(A) True correct
(B) False16. Period is
A) the amplitude of a wave
(B) the speed of a wave
(C) the time it takes to complete a single cycle correct
(D) the length it takes to complete a single cycle- Spatial pulse length is determined by the
(A) oscillator
(B) pulser
(C) pulse oscillator
(D) all of the above correct
Transmission angle is less than the incident angle if the propagation speed of
(A) medium 2 is less than that of medium 1 correct
(B) medium 1 is higher than that of medium 2
(C) two media are the same
(D) none of the above
Diffraction is the
(A) spreading out of an ultrasound beam correct
(B) bending of the sound beam
(C) dissipation of heat
(D) reverse refraction
Annular array transducers steer the beam
(A) axially
(B) electronically
(C) mechanically correct
(D) none of the above
_______ is a Rayleigh scatterer
(A) lung
(B) liver
(C) red cell correct
(D) diaphragm
A bit is the smallest part of a digital “word”
(A) True correct
(B) False
Velocity times density equals
(A) intensity
(B) duty factor
(C) quality factor
(D) impedance correct
What is the pulse duration for five cycles of 5 MHz ultrasound ?
(A) 0.5 microsecond
(B) 1.0 microsecond correct
(C) 0.25 microsecond
(D) 5.0 microsecond
Aliasing artifacts are unique to
(A) power doppler
(B) pulsed Doppler correct
(C) continuous wave Doppler
(D) none of the above
The intensity reflection coefficient depends on acoustic impedance mismatch
(A) True correct
(B) False
Velocity of sound in a medium is constant regardless of frequency.
(A) True correct
(B) False
Density is not an acoustic variable
(A) True
(B) False answer is b false
If the PRP increases, duty factor ___________
(A) Increases
(B) decreases correct
(C) remains the same
(D) is unrelated
A high PRF is needed to image deep structures
(A) True
(B) False answer is false b
Longitudinal waves are
(A) parallel to the axis of the wave propagation correct
(B) perpendicular to the axis of the wave propagation
(C) compressed perpendicular to the axis of the wave propagation
(D) none of the above
Wavelength has the greatest effect on
(A) lateral resolution
(B) far zone
(C) axial resolution correct
(D) temporal resolution
What is necessary to calculate distance to a reflector ?
(A) density and pulse length
(B) density and round-trip time
(C) attenuation coefficient and reflector amplitude
(D) propagation speed and round-trip time correct answer
Scattering is
(A) redirection of the sound beam in many directions ;correct
(B) bending of the sound beam in any direction
(C) heat conversion
(D) none of the above
The percentage of ultrasound reflected at an air/liquid interface is
(A) 100%
(B) high correct answer
(C) low
(D) none
A specular reflector has surface texture ________ the wavelength of the incident
wave
(A) less than
(B) equal to
(C) irrelevant to correct
(C) greater than
In a cathode ray tube display device the electron beam is steered by
(A) deflection plates correct answer
(B) phased arrays
(C) photon converters
(D) voltages from the scan converter
If it takes 50 microseconds for a pulse to return as an echo, how deep is the
reflector ?
(A) 1 cm
(B) 2 cm
(C) 3 cm correct answer
(D) 4 cm
Q value is determined by
(A) frequency and bandwidth correct answer
(B) pulse duration and bandwidth
(C) impedance and bandwidth
(D) none of the above
Shadowing artifacts are
(A) from velocity change
(B) observed distal to cystic structures
(C) caused by differences in attenuation correct answer
(D) none of the above
A-mode scanning represents the depth of the signal in the horizontal dimension.
(A) True correct answer
(B) False
Poiseuille’s equation states that the volume rate of flow through a vessel is
inversely proportional to
(A) vessel radius
(B) blood density
(C) pressure gradient
(D) blood viscosity correct answer
Temperature is an acoustic variable
(A) True correct answer
(B) False
41; make sure to study the ALARA PRINCIPLE
42.
Spatial pulse length __________ if the frequency is increased
(A) Increases
(B) decreases correct answer
(C) remains the same
(D) is unrelated
The Reynolds number predicts aliasing
(A) True
(B) False answer is b false
Transverse waves are
(A) parallel to the axis of the wave propagation
(B) perpendicular to the axis of the wave propagation ; correct answer
(C) compressed perpendicular to the axis of the wave propagation
(D) none of the above
Beam diameter determines
(A) temporal resolution
(B) the number of scan lines
(C) axial resolution
(D) lateral resolution correct answer
Mirror image artifact is sometimes seen near the
(A) aorta
(B) gall bladder
(C) stomach
(D) diaphragm correct answer
The binary number 1011000 equals the decimal
number
(A) 64
(B) 101
(C) 88 correct answer
(D) 1342
Low frequency transducers have
(A) shorter wavelengths and less penetration
(B) longer wavelengths and greater penetration; correct answer
(C) shorter wavelengths and greater penetration
(D) longer wavelengths and less penetration- For those who are writing the SPI- Ultrasound physics exam. I have notes for sale it is about 1500 multiple choices sets for ARDMS -spi exam = 50 USA DOLLARS. I study those notes and passed my exam 670/700 . If you want to buy i can copy the notes and send them to you in e mail or by mail you can reach me at drsteveramsey@gmail.com . I will also include some of the ideas about the 12 simulation questions. The payment with PayPal to drsteveramsey@gmail.com , fetal gender , Saad Ismail
Thank you for reading.
Steve Ramsey , PhD. Calgary- Alberta , Canada.