SPI pratice exam 4 Flashcards
*Which of the following is a component that stores digital echo signal information?
- receiver
- scan converter
- pulser
- CRT monitor
scan converter
*The digital memory is a part of the scan converter.
The scan converter holds a series of memory locations that map directly to pixels of the digital display. The primary function of the scan converter is transformation of B-mode data into an image representation in digital memory. This operation includes a remapping of every displayed pixel to specific scan vectors and ranges, such that proper image geometry is obtained. With each successive scan frame, scan converter memory is overwritten and the new information displayed on the monitor.
Analog-to-digital conversion involves transformation of a continuous signal into a discrete binary representation of the kind used in computers.
digital-to-analog converter, whose purpose is to convert the digital image information into standard video formats, such as NTSC or S-Video that allow the exam to be recorded on analog devices, such as printers and video recorders.
The pulser supplies the voltage to the PE element.
The receiver collects the electrical signals generated by the returned reflection
A CRT monitor is a type of display that has a vacuum tube and phosphorus screen
*note:
A calorimeter is used to measure the:
- sensitivity of Doppler TDR
- PRF of the US system
- Attenuation of the beam
- power of the beam
power of the beam
*a calorimeter is a type of TDR that converts sound energy into heat to assess the power of the beam
*What system control can be used to reduce the appearance of clutter on a color Doppler image?
- increasing persistence
- decreasing PRF
- increasing color threshold
- decreasing color priority
color priority
*Color priority: adjusts the threshold setting; determines if a pixel is displayed as shade of grey, black or white or as a color.
Lower threshold setting display less color = lower color priority
higher threshold setting display more color = higher color priority
**If the peak pressure gradient in a vessel is 36 mmHg, what is the velocity of the flow?
- 1cm/s
- 3m/s
- 2cm/s
- 4cm/s
3m/s
*Bernouli equation: PPG (peak pressure gradient) = 4V2
36mmHg = 4V2
V = 3
*What can be done to improve the visualization of the anterior aortic wall?
- scan from a more lateral approach
- decrease the threshold setting
- center the probe with the ultrasound beam perpendicular to the aortic wall
- increase the compression
3
*perpendicular incidence of the beam to the reflector will increase specular reflection. increasing the amount of specular reflection will improve the visibility of the anterior aortic wall.
*Which system component is not needed when an LCD monitor is used?
- scan converter
- beam former
- analog to digital converter
- digital to analog converter
digital to analog converter
*LCD monitors accept the digital signal and do not need this component
*IF the output power setting is at 100% and this indicate 0dB, decreasing the power by:
- 6dB will decrease the power output to 25% of the original power
- 6dB will decrease the power output by a factor of 4
- 6dB will decrease the power output by a factor of 2
- 3dB will decrease the power output to 25% of the original power
1
*A reduction in power of 3 dB indicate a decrease of 50% original power.
Every 3dB that the power decreases will decrease the power by another 50%.
decreasing another 3dB will reduce another 50% from already-deceased power, which is the ¼ of the original power
*While scanning, you decide to increase the image contrast. What console control will be adjusted?
- reduce demodulation
- increase compression
- increase overall gain
- increase rejection
increase rejection
*Contrast refers to the difference between the image densities of two areas. Increasing contrast will create more black and white.
Increasing rejection will reduce the number of low level echoes (shades of grey) displayed on the image, therefore creating a more black and white image
WHen does the first caliper go when measuring the accerelation time on PW Doppler?
Use your mouse to position the cursor over the correct part of the 3rd waveform and click to set the answer
*As a sound wave travels through soft tissue, what happens to the period of the wave?
- increases
- decreases
- remain constant
- unable to determine
remain constant
*the period of the wave does not change as the wave travels.
Period is reciprocal of frequency, and frequency also remains constant as the wave travels
*increasing the number of bits per pixel in an image memory will improve the:
- detail resolution
- elevational resolution
- temporal resolution
- contrast resolution
contrast resolution
*Contrast resolution = ability of a display to distinguish between echoes of different intensities. Increasing the number of bits per pixel will improve the contrast resolution
Which of the following exams would require the storage of a 2-3 seconds digital clip of the real time image?
- color Doppler evaluation of renal perfusion
- documentation of needle placement in a thyroid biopsy
- evaluation of the wall motion of the LV
- PW Doppler evaluation of venous reflux
3
*digital clips are useful in documenting echo, fetal echo, and fetal movement during a biophysical profile
When evaluating heavily calcified arteries, what system settings should be increased to improve the demonstration of flow in the vessels?
- velocity scale and persistence
- color gain and angle insonation
- persistence and sensitivity
- frequency and output power
3
*arterial calcification can limit 2D and color Doppler evaluation
To evaluate heavily calcified arteries use multiple imaging planes, increase color Doppler gain, increase sensitivity and presistence level
*What type of TDR produce this image?
vector phased array
*note
sector: pie shape
vector: pie shape with flat top
Which of the following adjustment would improve the appearance of microbubble contrast on the image?
- turn off the harmonic imaging
- increase the thermal index
- use multiple focal zone
- decrease output power
4
*note:
increasing output power would increase beam intensity causing the contrast microbubbles to burst
adding multiple focal zones would increase intensity in several areas and increase the premature bursting of the contrast bubble
Which of the following artifacts cause the appearance of false echoes on the image beside the actual structure?
- lobe artifacts and mirror image artifacts
- speckle artifacts and twinkle artifacts
- refraction artifacts and mirror image artifacts
- lobe artifacts and refraction artifacts
4
*grating lobe and refraction artifacts cause the appearance of false echoes on the image beside the actual structure.
*mirror image artifact cause the appearance of a second structure that is deeper than the actual structure
*a sound wave leaves its source to travel through the liver and a reflected wave returns 2 microseconds later. what is the distance from the source to the reflector?
- 1.5cm
- 1.5mm
- 3cm
- 3mm
1.5mm
*watch the unit
distance = c x time
distance =( 1540m/s) (0.000002s)/2
distance = 0.00154m or 1.54mm
Which TDR component improves elevational resolution?
- matching layer
- acoustic lens
- damping layer
- pulser
acoustic lens
a sound wave strikes a border at a 90 degree angle. the second media has a higher density but both media have the same propagation speed. what will occur at this border?
- refraction will occur
- the propagation speed will increase in the second media
- 100 transmission will occur
- reflection will occur
4
*the acoustic impedance is determined by the density and the propagation speed.
the difference in density indicated a difference in impedance which is necessary for reflection to occur.
perpendicular incidence and difference in impedance will allow reflection to occur
**What term indicates the phenomenon of a PW Doppler tracing displaying a wider distribution of the velocity of blood cells with varying degrees of arterial blockage?
- spectral broadening
- turbulence
- laminar flow
- occlusion
spectral broadening
*spectral broadening refers to PW Doppler tracing displaying a wider distribution of the velocity of blood cells with varying degrees of arterial blockage.
*turbulence r_efers to the disruption of laminar flow causing eddy currents within the vessel._ turbulence is displayed as spectral broadening on a PW Doppler tracing
*your department recently upgraded the display monitors from a 512 x 512 matrix to a 1024 x 1024 matrix. How will this affect the image displayed?
- improved contrast resolution
- increased Q factor
- degraded temporal resolution
- improved elevational resolution
1
*a larger image matrix will offer the ability to display more pixels of information and more shades of grey which improves contrast resolution
- which of the following factors affect the focal length of the TDR?
- element thickness and diameter
- element frequency and PRF
- element diameter and frequency
- element diameter, frequency and thickness
3
element diameter and frequency are directly related to the focal length of a TDR
*_______ artifact is caused by refraction and results in subtle image degradation
- comet tail
- scatter
- misregistration
- multipath
multipath
*multipath artifact is caused by refraction and results in subtle image degradation.
misregistration occurs due to propagation speed errors and an error in echo placement
scatter is a sound wave phenomenon, not an artifact
comet tail artifact are reflection artifact
*the vertical axis on the m-mode display represents the ______
depth of the reflector
*the vertical axis on the m-mode display represents the depth of the structure
the horizontal axis represents time
***Which of the following lists the normal range of intensities used in diagnostic Doppler US?
- 100-1000 mW/cm
- 0.2-400W/cm
- 100-1000mW/cm2
- 0.2-400mW/cm
4
*average range of diagnostic intensities for all types of US imaging: 0.002-0.5 W/cm2 or 2mW/cm2 to 500mW/cm2
*Average range of Doppler intensities: 0.2-400mW/cm2
*average range of 2D imaging: 0.1-300mW/cm2
*Rayleigh scatter increases with:
- temperature elevation in tissue where US beam passes through
- deceasing depth
- high velocity blood flow
- increasing probe frequency
4
*higher frequencies are related to increased Rayleigh scatter
there is 100% reflection when the beam strikes an interface at ____
critical angle
Which of the following will lead to more color displayed in real time in the abdominal aorta?
- decrease color gain
- increase sample size
- decrease color threshold
- increase frame rate
increase frame rate
increasing frame rate will improve temporal resolution = more color image in real time
*Also small sample size will increase frame rate, thus more color display in real time
**What part of the US system is responsible for changing the elements function back and forth from transmit to receive?
- scan converter
- FFT
- TDR
- beam former
beam former
*the transmit and receive switch in the beam former is responsible for switching the element function back and forth between transmit and receive
Which of the following is a limitation of Power Doppler?
- only detects flow moving toward the probe
- inability to display flow velocities less than 10cm/s
- inability to display flow velocities greater than 150cm/s
- has slower frame rates than color Doppler
4
*limitation of power Doppler includes the lack of flow direction and velocity information, slower frame rates than color Doppler and increased susceptibility to flash artifact
Grating lobes most commonly:
- are produced by highly reflective boundaries
- reduce the visibility of color Doppler
- occur with linear arrays
- result in missing information on the image
3
grating lobe mostly occur with linear array TDR
***As the propagation speed of the crystal increases, the frequency of the TDR:
- decreases
- does not change
- increases
- depends on the thickness and diameter of the crystal
increases
*tricky question…read the question well
Which of the following Doppler measurements require the waveform to be traced from start of systole to the end of diastole?
- resistive inde
- pulsatility index
- s/d/ ratio
- acceleration time
pulsatility index
*pulsatility index compares the peak velocity to the mean velocity throughout one cardiac cycle. In order to obtain the mean velocity, tracing of the waveform is required.
*resistive index uses the peak systolic and end diastolic velosities to assess resistance in a vessel. A single caliper is placed at the peak systolic velocity and one at the end diastolic velocity
