Physics Boards Final Reveiw
Card Set Information
Physics Boards Final Reveiw
Physics Ultrasound ARDMS
Physics Final reveiw
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:
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:
Decreasing the wavelength improves:
decreased wavelength; increased frequency; decreased SPL; wider bandwidth; decreased PD; increased listening time
As tube radius increases, resistance:
As frequency increases, half intensity depth:
A large amplitude pulse (voltage) from the pulser results in:
If the sample volume depth is doubled, the Nyquist limit will be ____ of the original.
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:
Propagation speed =density x velocity
As fluid viscosity increases, flow rate will:
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:
Which of the following system components generates the signals to focus and steer the sound field?
When the pulse repetition period is increased:
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?
At a soft tissue/air interface, the percentage of sound transmitted will be:
In clinical applications, maximum reflection amplitude occurs with:
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
: frequency shift
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:
# 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:
Impedance is equal to:
density x velocity
c x p
As resistance increases, flow volume:
The generation of the artifact displayed in this image (>) is due to:
An increase in frequency will decrease all of the following EXCEPT:
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:
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
: hypoechoid sludge
: 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?
Continuous wave Doppler has a Duty Factor of ___ %.
To maximize reflection from a specular reflector, the sonographer should strike the interface at ______ 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:
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 = amplitude
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?
A device commonly used to measure the output of diagnostic ultrasound systems is:
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:
Which of the following varies with distance from the transducer?
The pulse repetition period is the reciprocal of:
Storage of several preceeding frames describes:
Refraction is due to:
Velocity difference at an interface
Which artifact is associated with reverberation and resonance in a small gas bubble or surgical staple?
As propagation speed and density values increase, acoustic impedance:
z = c x p
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
# of focal zones
As frequency increases, the beam width will:
Which transducer frequency in MHz would be best to use to avoid aliasing?
The signal processing function that eliminates the negative component of the signal is termed:
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: