ARDMS - SPI Study Questions with Complete Solutions

ARDMS - SPI Study Questions with Complete Solutions Which technique utilizes frequency modulation of the transmitted pulse to improve signal to noise ratio? ✔✔spatial compounding Which angle of isonation to blood flo ...

ARDMS - SPI Study Questions with Complete Solutions Which technique utilizes frequency modulation of the transmitted pulse to improve signal to noise ratio? ✔✔spatial compounding Which angle of isonation to blood flow produces the maximum doppler shift? ✔✔180 degrees Which imaging mode requires two elements mounted side by side? ✔✔continuous wave doppler What is a benefit of using contrast agents? ✔✔increased amplitude of the returning dopplers What is the most common cause of localized vertical nonuniformity in a real time b mode image? ✔✔improper time gain compensation Which type of interaction between sound and tissue is most affected by the thermal index (TI)? ✔✔absorption Which control allows adjustment for attenuation at specific depths? ✔✔Time gain compensation Which condition must be present for refraction to occur? ✔✔a difference in tissue propagation speeds and oblique incidence Which technique results in a three dimensional image? ✔✔surface rendering Which action can improve axial resolution of a displayed image? ✔✔increasing the transducer frequency short spl damping Which scenario will produce no doppler shift to the receiver? ✔✔source and receiver moving at the same speed and direction Which technique the sharpness of high contrast boundaries? ✔✔edge enhancement A sound wave propagates fastest through which substance? Bone Muscle Fat or Gas ✔✔Bone In an unfocused transducer, what defines the region between the transducer face and the point where the beam diverges? ✔✔near field When the focal point in a B mode image is electronically changed, which type of focusing is in use? ✔✔Dynamic When a fluid is flowing at a slow and constant rate within a long tube having a uniform diameter, what is the nature of the flow? ✔✔laminar Which frequency is best to evaluate structures lying 1 to 2 cm from the transducer? ✔✔8 MHz - higher frequency What determines the center frequency of a transducer? ✔✔thickness Which term describes the averaging together of scan lines from multiple angles to create one image? ✔✔Spatial compounding What would you do if you had aliasing in the pulsed wave? ✔✔1) drop baseline 2) increase scale 3) change to a lower transducer What is the Nyquist limit? ✔✔1/2 PRF What is the Nyquist limit if a pulsed doppler instrument has a pulse repetition frequency of 16 khz? ✔✔8 khz - 1/2 prf What does coded excitation improve in addition to penetration? ✔✔lateral resolution What does coded excitation improve? ✔✔Improves penetration, axial resolution, spatial resolution and contrast resolution What is the potential affect of increasing prf? ✔✔depth ambiguity depth ambiguity ✔✔the inability to determine the depth of the reflector if the pulses are sent out too fast for them to be timed - can happen with increased prf Which variable can cause an acoustic shadow artifact? ✔✔refraction When using a 5 MHz transducer, in which tissue is the ultrasound wavelength the shortest? ✔✔Fat in this question Use wavelength equation speed over frequency What is an advantage of using a pulsed wave doppler versus continuous wave doppler? ✔✔provides depth specificity Which imaging mode requires a broadband transducer? ✔✔pulsed wave doppler Which factor reduces the likelihood of aliasing in pulsed wave spectral doppler? ✔✔increased Nyquist limit To which acoustic variable is penetration depth inversely related? ✔✔Frequency think about how far the ultrasound wave can penetrate or travel into the body Which factor determines the displayed depth of a reflector? ✔✔Propagation speed of the medium Where a reflector is displayed on the screen how deep Which variable decreases when the number of acoustic lines per frame is increased without changing the maximum depth? ✔✔frame rate How does frequency compounding improve image quality? ✔✔improves dynamic range Thinner pzt crystals = inverse ✔✔high frequency Thicker pzt crystals = inverse ✔✔low frequency Large Diameter & High Frequency = ✔✔Less Divergence/Shallow focus Small Diameter & Low Frequency = ✔✔More Divergence/Deep focus Temporal resolution: ✔✔Best with faster frame rate Best with shortest time to create image Worse with mult focal zone & deeper imaging Relates to frame rate & line density Spatial resolution: ✔✔determined by # of pixels in scan converter axial, lateral, elevational and contrast res. improves with fill in interpolation increases with decreased tx freq Coded excitation: ✔✔a way of processing the pulse to improve contrast resolution improves with axial and penetration allows multi frequency of bflow imaging reduces speckle Attenuation ✔✔improves with tgc Harmonics ✔✔non linear improves lat resolution - has strong beams elimnates near field artifacts eliminates grating lobes improves shadowing from calcifications Dynamic range ✔✔use compression elevational resolution ✔✔determined by the thickness of the imaging plane perpendicular to scan plane frame rate ✔✔improves signal to noise ratio det. by speed of sound in medium and imaging depth adjustable by depth shallow has better higher frame rate lower line density doppler packet - aka ensemble length ✔✔large # and long ensemble lenghts = better velocity measurements sensitive to low flow reduces frame rate and temp resolution PW positives ✔✔gate, angle correct, 1 crystal, depth of sample volume, pw only one that aliases CW positives ✔✔no aliasing high sensitivity 2 crystals