-
A decreased pulse duration produces:
- Better axial resolution
- decreased PD; increased listening time; increased frequency; decreased wavelength; decreased SPL; wider bandwidth
-
The source of the acoustic enhancement artifact is:
Due to a structure with a low attenuation rate
-
Wavelength is determined by the:
Sound source
-
The technique used in most color Doppler systems used to obtain the mean Doppler frequency shift is:
Fast Fourier transform/ spectral analysis
-
The term signal to noise ratio describes:
- Comparison of reflector signal in image to amount of contamination (noise)
- High ratio = good (increased contrast resolution)
-
The typical dynamic range in the amplifier is:
60-100dB
-
Decreasing the wavelength improves:
- Axial resolution
- decreased wavelength; increased frequency; decreased SPL; wider bandwidth; decreased PD; increased listening time
-
As tube radius increases, resistance:
Decreases
-
As frequency increases, half intensity depth:
Decrease
-
A large amplitude pulse (voltage) from the pulser results in:
Increased frequency
-
If the sample volume depth is doubled, the Nyquist limit will be ____ of the original.
- 1/2
- Nyquist =1/2 PRF
- Increase maximum imaging depth attainable x 2 > decrease PRF x 2 > decrease nyquist limit in half
-
What will improve detection of slow flow?
- Low PRF / scale control
- Increase color gain
- Increase pulse packet size
- Decrease Doppler angle
-
The effect on the ultrasound image when the dynamic range is increased is:
- Increase in the # of shades of grey
- Low contrast image
-
Heating of soft tissue is proportional to:
Intensity of ultrasound energy and exposure time
-
In color Doppler, the ensemble length controls the number of:
Pulses required to produce one scan line of color information (3 pulse minimum)
-
What is the maximum number of displayed shades of gray in a 7-bit processor?
-
Advantages for increasing color ensemble length:
- Improve the accuracy of the estimate
- Determine the variance (turbulence)
- Improved detection of slow flow
-
Huygen's Principle describes:
Constructive interference produces the typical hour glass shape of the sound feild
-
Which of the following scanned from the top would evaluate the dead zone?
-
The initial amplitude is determined by :
Acoustic power control/voltage applied to the transducer
-
Which of the following best describes apodization?
- Method to control sidelobes
- The use of variable strength voltage pulses to the crystal during focusing
-
Propagation speed is determined by the:
- Medium
- Propagation speed =density x velocity
-
As fluid viscosity increases, flow rate will:
Decrease
-
The source of the artifact indicated by the yellow arrow is:
-
What effect will increasing the voltage delivered to the transducer have on amplitude?
Increase the amplitude
-
Which of the following displays the lowest intensity value in pulsed-wave ultrasound?
-
-
When comparing Write magnification with Read magnification, Write magnification:
- Write magnification magnifies the image before the image is stored
- Better image resolution due to smaller pixel size
-
The impedance of the matching layer is:
In between that of the crystal (solid) and the coupling gel (liquid)
-
What determines the power of the ultrasound field?
Voltage applied to the crystal element (acoustic power control)
-
When all other parameters are held constant, tripling the reflector velocity will result in:
3 x the acoustic impedance value (z)
-
The cause of this artifact (double aorta - white lines) is:
-
The resonant frequency of the ultrasound pulse is determined by:
Crystal thickness
-
Which of the following system components generates the signals to focus and steer the sound field?
Beam former
-
When the pulse repetition period is increased:
- PRF decreases
- Increase PRP > decrease PRF > increase imaging depth > decrease frequency > increase wavelength
-
Which Doppler technique has poor range resolution?
Continuous wave doppler
-
Propagation speed error results in which of the following sonographic characteristics?
Improper reflector position due to increased RTT
-
The use of contrast agents in sonography:
Has not been approved for use in the states
-
Which intensity is the greatest during the pulse?
Intensity in the focal zone
-
Pulse echo imaging typically employs a duty factor of ___ percent?
<1%
-
At a soft tissue/air interface, the percentage of sound transmitted will be:
<1%
-
In clinical applications, maximum reflection amplitude occurs with:
Normal incidence
-
The type of real-time system that employs a combination of electronic focusing and mechanical steering is:
-
Spectral analysis is used to:
- Display quantitative info from pulsed doppler
- X axis: frequency shift
- Y axis: time
-
The best example of a Rayleigh scatterer is:
Red blood cells
-
A transducer has a very wide slice thickness. This may produce:
Averaging of peripheral and central echoes (slice thickness artifact)
-
Which of the following scanned from the top would evaluate axial resolution?
-
Increasing the pulse repetition frequency will:
- Decrease the maximum imaging depth
- Increase PRF, decrease PRP, decrease max imaging depth
-
The computer parameter that limits the number of brightness levels available to display on the image matrix is:
# of bits in a word
-
Temporal resolution is determined by:
- Imaging depth
- Sector width
- # of focal zones
-
Based on this delay sequence (black crystals on the left), the sound field will:
-
The method for sterilizing transducers is:
-
Increasing the number of scan lines per frame
Increases detail resolution
-
Widening of the sound field is demonstrated in the:
Far feild/ Fraunhaufer zone
-
A very narrow spectrum of frequencies under systole and diastole represents blood flow that is:
Low resistance/ monophasic
-
The minimum pulse packet size in color Doppler is:
3 pulse minimum
-
Mirror image artifact results in which of the following sonographic characteristics?
Ghost image of real reflector is seen on opposite side of the "mirror"
-
For focused ultrasound, there are no confirmed signicant biological effects in mammalian tissue for exposures below:
1 W/cm2
-
-
As resistance increases, flow volume:
decreases
-
The generation of the artifact displayed in this image (>) is due to:
-
An increase in frequency will decrease all of the following EXCEPT:
- Increase frequency
- Decrease wavelength
- Decrease SPL
- Decrease PD
- Increase axial resolution
-
The approximate clinical frame rate (per second) for a real time image to be flicker-free is:
~15 per second
-
Continuous wave transducers consist of:
- CW = 2 transducers
- Large fixed sample volume
- Poor range resolution
- No velocity limit (NO ALIASING!!)
-
If the pulsed Doppler sample volume depth is decreased, the PRF will:
Decrease
-
Exceeding the Curie point of the element will result in:
Destroying the crystals
-
What conditions will result in aliasing of the Doppler frequency shift?
- Exceeding the nyquist limit
- Sampling at very deep imaging depths
-
Side lobe artifact results in which of the following sonographic characteristics?
- Energy distribution out side of main beam profile
- Nonspecular example: hypoechoid sludge
- Specular example: hyperechoic septa
-
Which of the following body tissues will most likely increase acoustic speckle?
Body tissues with higher attenuation rates (adipose tissue and muscle)
-
If the transducer Q value is low, the bandwidth will be:
Low Q = more damping material, shorter pulse, *wider bandwidth*, decreased wavelength, increased frequency, increased axial resolution
-
The sonographer can change the initial intensity by manipulating:
Acoustic power control
-
What is the diameter of the sound field at one near-zone length when using a 6 mm, 2.5 MHz transducer?
2.5mm
-
Continuous wave Doppler has a Duty Factor of ___ %.
100%
-
To maximize reflection from a specular reflector, the sonographer should strike the interface at ______ degrees.
90 degrees
-
The sonographer has overestimated the Doppler angle of incidence while using angle correction. This error will cause:
Underestimation of velocity
-
Cavitation is the result of:
High intensity and low frequency
-
When all other parameters are held constant, an increase in the Doppler angle will result in:
Decrease the Doppler shift
-
A sound field demonstrates the most uniform intensity in the:
Focal zone
-
Doppler shift information is determined by which type of reflector?
Rayleigh scatter (RBCs)
-
Determine the power if the amplitude of the wave is 4.
Power = amplitude2
2
-
Lateral resolution is determined by the:
Beam width (focusing)
-
Bandwidth can be increased by:
Wide bandwidth, increased damping material, short pulse, higher frequency shorter wavelength
-
What is the product of the number of cycles in the pulse and the pulse period?
Pulse duration = period x # of cycles in a pulse
-
Which of the following is most likely related to pixel density?
Detail resolution
-
A device commonly used to measure the output of diagnostic ultrasound systems is:
Hydrophone
-
Poor lateral resolution results in which of the following sonographic characteristics?
Inability to distiguish reflectors located at the same depth (side by side) in the sound field
-
Absorption of ultrasound energy is highest in:
Bone
-
Which of the following varies with distance from the transducer?
Intensity
-
The pulse repetition period is the reciprocal of:
PRF
-
Storage of several preceeding frames describes:
Cine-loop
-
Refraction is due to:
- Oblique incidence
- Velocity difference at an interface
-
Which artifact is associated with reverberation and resonance in a small gas bubble or surgical staple?
Comet tail
-
As propagation speed and density values increase, acoustic impedance:
-
The acoustic impedance of the damping material is:
The same z value as the crystal
-
Which Doppler angle produces the smallest error estimate?
0 degrees/ cosine of 1.0
-
The frame rate of a real time system does not depend on the:
- Sector size/lines per frame
- Depth
- # of focal zones
-
As frequency increases, the beam width will:
Decrease
-
Which transducer frequency in MHz would be best to use to avoid aliasing?
Low frequency
-
The signal processing function that eliminates the negative component of the signal is termed:
Rectification
-
Which artifact most frequently results in fill-in of small vessels or anechoic structures?
Slice thickness artifact
-
If the imaging depth is quartered, the frame rate will be:
Quadruples
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