ARDMS - SPI Study Questions and Answers 2023

ARDMS - SPI Study Questions and Answers 2023 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