-
Which of the following parameters directly relates to heating of tissues?
- Increase thermal index
- Increased frequency or output power
-
Which of the following rod groups scanned from side A would evaluate axial resolution?
Rod group B
-
What factors would produce the greatest TI values?
- High frequency
- Narrow focal zone
- Stationary color doppler
-
What factors would produce the greatest MI values?
Low frequency, high intensity
-
The artifact indicated by the arrow is due to:
- Reverberation/ comet tail
- Large acoustic impedance missmatch
-
Which system control manipulations would best limit patient exposure to ultrasound energy?
- Decrease scan time
- M-mode vs. color doppler or pulsed wave
- Decrease frequency
-
A transducer has a very wide slice thickness. This may produce:
- Filling defect of a cystic/anechoic structure
- Filling in of vessels / small cyts
-
Which of the following produces the split image artifact?
- fat/muscle interface near the surface
- i.e. linea alba
-
Which of the following types of tissue will demonstrate the greatest temperature elevation?
- embryo <8 weeks conception
- head, brain, and spine of any fetus or neonate
- eye in any patient
-
Which of the following digital scan converters would display the best contrast resolution?
- 8 bit
- 8 is the current standard
- 2n = shades of gray, where n = bits in a computer word
-
Bioeffects have been observed in experimental animals with focused intensities greater than:
1 W/cm2
-
On an A-Mode display, the height of the spike represents:
The echo intensity
-
The System Gain function is performed in the:
Beam former
-
What is the maximum number of displayed shades of gray in a 6-bit processor?
26 = 64
-
What determines the power of the ultrasound field?
Voltage applied to the transducer
-
The typical pulse repetition frequency range for clinical imaging applications is:
-
The term signal to noise ratio is:
The ratio of signal amplitude to the variation in noise
-
In cardiac imaging, reducing the size of the sector angle will:
Increase the frame rate
-
If the imaging depth is quartered, the frame rate will be:
Quadrupled
-
The signal processing function that eliminates the negative component of the signal is termed:
Rectification
-
Adjusting the TGC controls affects the settings in the:
Beam former
-
The ability to distinguish between adjacent structures producing similar echo amplitudes is termed:
Contrast resolution
-
When the pulse repetition period is increased:
Imaging depth is decreased
-
If the gain is increased by 6 dB, the power has been increased by a factor of:
4
-
When comparing Write magnification with Read magnification, Write magnification:
Improves spatial resolution compared to read magnification
-
During real time imaging, if the scan line density is reduced to 1/2, the maximum frame rate is:
Doubled
-
Preprocessing programs are performed in the:
Image processor
-
If the original acoustic power is 100 mW and the power control is increased by 3 dB, the new power is _____ mW.
200
-
In real time systems, the range equation is used to determine reflector:
Depth
-
The typical dynamic range in the amplifier is:
60-100
-
The sonographer has increased the size of the sector width to image a large mass. What can the sonographer do to maintain the same temporal resolution before this adjustment?
Decrease the number of focal zones.
-
Increasing the pulse repetition frequency will:
Decrease the maximum imaging depth
-
Reflector B is twice the distance from the transducer as reflector A. It takes ______ times as long for an echo to arrive from reflector B as from reflector A.
2
-
The computer parameter that limits the number of brightness levels available to display on the image matrix is:
Number of bits in computer word
-
The primary method that the sonographer uses to control frame rate during real time imaging is:
Imaging depth
-
Which mode has time the unit of measurement on one axis?
M-mode
-
Flow through a blood vessel is determined by:
- 1. Pressure difference
- 2. Vascular resistance
-
Vessel diameter increase as _____ increases.
Pressure
-
Veins or arteries, which are more distensible?
Veins are 6-10 x as distensible as arteries
-
Arteries
- Transport blood to tissues
- High pressure
-
Arterioles
- Last, smallest branches of the arterial system
- Act as "control valves" for blood flow into capillaries
-
Capillaries
Exchange between blood and interstital spaces
-
Vasodilitation occurs when?
- During exercise
- After a meal
-
Vasoconstriction occurs when?
- In a resting state
- With fasting
-
Venules
Collect blood from capillaries and connect to larger veins
-
Veins
- Blood returned to heart
- Body contians many more veins than all other parts of the vascular system
-
AO/ICV
Have the smallest cross-section area and therefore the highest velocity
-
Relationship of velocity to area
Velocity is inverse to area
-
Energy derived from the cardiac pump
Potential/pressure energy
-
Potential energy
- Pressure/stored energy
- Derived from the cardiac pump
- Distends vessels and stores energy
-
Kinetic energy
- Energy of motion
- KE < PE due to distensibility of vessels
-
Kinetic energy can increase due to:
- Increase in flow>> i.e. exercise
- Stenosis (increased velocity)
-
Movement of fluid between 2 points requires:
- Difference in energy
- Difference in pressure
-
Example of low resistance
- Organs
- Low resistance = greater energy difference = greater flow
-
Example of high resistance
- Resting muscle
- High resistance = less flow
-
Pouseuille's law
Defines relationship between pressure, volume flow, and resistance
-
The longer the vessel the _____ the resistance.
- Higher
- High pressure is required to maintain flow
-
The shorter the vessel the ____ the flow volume.
Higher
-
What has the most significant impact on flow rate?
- Radius of the vessel
- Smaller the radius, the higher the resistance
-
Smaller the radius, the _____ the resistance.
Higher (and higher pressure)
-
Plug flow
- Flat profile
- Seen in stenotic area
- Same velocity throughout vessel (slower flow at wall)
-
Laminar flow
- Most common flow pattern
- Seen during systole in smaller arteries
- Flow in center is highest and gradually tapers as it reaches the wall of the vessel
-
Disturbed flow is signified by?
Spectral broadening
-
Mathematical number to determine when flow turbulence will occur?
Reynold's number
-
Reynolds number for when turbulance will occur
2000 Re or higher
-
Harmonic resonance produced by flow turbulence transmitted into vessel walls is known as
audible bruit
-
Where is normal disturbed flow visualized throughout the cardiac cycle?
-
Significant stenosis
70% blockage
-
Tardus parvus
Dampened wave forn distal to a stenosis
-
Monophasic flow
- Low resistance, continuous and steady throughout S and D
- Seen in normal arteries that supply low resistance vascular beds -liver, spleen, brain, kidneys
-
Triphasic flow
- Highest resistance to flow
- Antegrade/forward flow during systole
- Retrograde/reverse flow during diastole
- Seen in distal AO/iliac arteries
-
Cosine of the doppler angle is ______ly related to the doppler angle.
- Inversely related
- Angle of 0 = cosine 1.00
- Angle of 90 = cosine 0
-
Increase transmit frequency and _____ the size of the Doppler shift
Increase
-
Decrease velocity of flow and _____ the size of the Doppler shift.
Decrease
-
Increase the Doppler angle and _____ the size of the Doppler shift.
Decrease
-
Decrease the Doppler angle and ______ the size of the Doppler shift.
Increase
-
Cosine = 0
- 90 degree angle
- No Doppler shift
-
Cosine = 1.00
- 0 degree angle
- Largest Doppler shift
-
With spectral analysis the frequency is displayed on which axis?
Vertical y axis
-
What is displayed on the X axis of spectral analysis?
Time
-
Amplitude or power is displayed as what on spectral analysis?
Brightness
-
FFT
- Fast fourier time
- Current computer program for analyzing and displaying spectral representation
-
How can aliasing be eliminated?
- Increase PRF (increased nyquist limit)
- Shift baseline
- Increase size of angle
- Decrease transmit frequency
-
Main disadvantage of pulsed Doppler is?
Aliasing
-
Nyquist Limit
- 1/2 the PRF
- Exceeding this produces aliasing
-
PRF control
Changed the number of pulsed emitted per second
-
Primary advantage of CW Doppler
No velocity limit/ no aliasing
-
Main disadvantage of CW Doppler
- Large fixed sample volume
- POOR RANGE RESOLUTION
-
Color Doppler
- Qualitative, NOT quantitative information
- Will produce aliasing
- Good range resolution
- BART
-
How to eliminate color aliasing
- Increase PRF (scale setting)
- Decrease sample volume depth
- Use larger Doppler angle
- Lower transmit frequency
- Go from triplex(color, image, spectra) to duplex (color, image)
-
Power Doppler
- Encodes amplitude of blood cells
- Provides no info on direction of flow
- NO aliasing and less angle dependant
-
Components of pulsed Doppler instrumentation:
- Pulser
- Gated detector
- Spectral analysis
- Memory
- Display
- Speakers
-
Length of pulses produced by pulser
5-30 cycles
-
The time period for acquisition of Doppler signal is determined by the _____.
Size of the gate
-
Phase shift means
Motion is present
-
Rhythmic cycles or beats produced when waves of different frequencies produce interference are added together and termed
Beat frequency
-
Minimum number of cycles per pulse is?
4
-
Number of cycles required for fast flow
6-10
-
Number of cycles needed for gray scale
2-3 cycles
-
Number of cycles needed for slow flow
20-30
-
Typical sampling rate
25,600 times per second
-
High pass filter
- Rejects all frequencies below the threshold vaule
- Usually 100Hz
- Removes wall thump but not slow flow
-
Low pass filter
- Eliminates high frequency noise
- Improper adjustment can eliminate high frequency (fast) flow
-
One speed estimate has a _____ pulse minimum.
Three
-
More than 3 pulses are required in order to:
- Improve accuracy of the estimate
- Determine the variance
- Improve detection of slow flow
-
Typical ensemble length range
10-20 pulse
-
Increasing ensemble length will ___ frame rate.
Decrease
-
Ensemble length
- AKA pulse packet size
- The number of pulses required to produce one color scan line
-
Transient cavitation refers to :
- AKA collapse cavitation or normal cavitation
- Bubble oscillation so large that the bubble collapses
-
No thermal effects have been documented when the temperature elevation is below ___ degrees.
2
-
A Thermal Index (TI) value of one (1) indicates:
Potential to increase tissue temperature by 1 degree
-
The artifact indicated by the white line can be eliminated by:
Aliasing
-
Which mode has the potential for the highest thermal production?
Color doppler
-
A device commonly used to measure the output of diagnostic ultrasound systems is:
Hydrophone
-
A tumor has a slower propagation speed than the soft tissue average propagation speed. This will result in:
Shadowing
-
A long near zone can be obtained by:
Increase frequency (decrease λ)
-
Higher the ____ the shorter the SPL
Frequency
-
Shorter the SPL the better the ____ resolution
axial
-
SPL=
- SPL= λ x # of cycles in pulse
- Shorter the SPL the better the axial resolution
- Higher the frequency the shorter the SPL
-
Longitudinal or axial resolution is directly dependent on:
- Spatial pulse length
- SPL= λ x # of cycles in pulse
- Shorter the SPL the better the axial resolution
- Higher the frequency the shorter the SPL
-
Generally, ultrasound transducers have better _____ resolution than ________ resolution.
Better axial resolution than lateral resolution
-
Which equipment assumption is violated when refracted echo information is processed?
All echoes come from straight ahead
-
To reduce the Mechanical Index (MI), the sonographer would:
Decrease acoustic power, increase the number of focal zones
-
Mechanism through which ultrasound energy can produce a biological effect
Stable caviatation, transient cavitation, increase in temperature
-
The artifact indicated by " A" is indicates:
Large acoustic impedance missmatch
-
If the focal zone is decreased to 1/5 of its original area, the intensity will:
Increase by 5
-
Which rod groups scanned from side C would evaluate lateral resolution?
Rod group C
-
Side lobe artifact produces which of the following sonographic characteristics?
- Energy distribution outside main beam profile
- Horizontal linear extensions from specular reflector (i.e. septa)
-
The risk of cavitation is considered low when the MI value is ____ or lower.
0.5
-
PhThe area of the sound field characterized by violent intensity changes is:
Near field
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