# Test 4 Chapters 14-18

 What denotes maximum velocity in both directions that can be displayed without aliasing? Velocity Scale What removes data below a specific frequency? Wall filter What assigns various shades of color and brightness to depict different velocities? Color map What is it when the color doppler information wrapping around color bar when velocities exceed Nyquist limit? Aliasing What is improper assignment of color due to movement of tissue? Flash What control should be adjusted to show more detail in the waveform? Sweep speed What is zero area on Doppler display called? Baseline What sets the threshold below which weak flow signals are not displayed? Reject What is it when the magnitude of each frequency component is plotted with respect to frequency? Power spectrum What shows magnitude of flow, not velocity information? Power Doppler What is the number of pulses used to interrogate single color line of sight? Ensemble length What is the 3-D region from where doppler information is obtained? Sample volume What is complete loss of flow coherence? Turbulence What is vertical thickening of Doppler spectrum that corresponds to turbulent flow? Spectral broadening What is the display type where the x-axis is the time and y-axis is amplitude of doppler signal? Spectral waveform What is the mathematical formula that separates waveform into a series of single-frequency, sine waves? Fast Fourier Transform (FFT) What is it when flow in vessels changes over time, and blood flow patterns are displayed as a function of time? Doppler spectral waveform What are the three variables of Doppler spectral waveform? frequency, magnitude, and time are displayed What is the vertical axis of spectral display? Frequency What is the horizontal axis of spectral display? Time What is frequency information  of spectral display converted to? Velocity information What is detection mode where fewer transmit pulses are applied along the scan line as compared to spectral analysis, and as a result, are less sensative to slow flow and flow in smaller vessels? Autocorrelation What are the number of pulses used to interrogate one color doppler scan line? Ensemble length Larger ensemble length equals what? more accurate frequency estimates that equal a lower frame rate What can reverse the color flow of an image? Color-map invert What causes amplification to all color Doppler signals? Color gain What sets threshold below which weak flow is not displaye, noise rejection technique, independent of 2D? Color reject What combines color flow data in successive frames for smoother appearance of flow, more averaging equals degraded temporal resolution? Color persistence What is eliminated if it don't meet minimum frequency citreia? Color wall filter(Can eliminate noise from wall motion if set too high, real velocity info may also be eliminated) What shows amplitude or intensity of doppler signal with no velocity info? Power Doppler What depends on sample volume and attenuation of surrounding tissue? Power Doppler What is not angle dependent and yields no directional information; uses increased persistence and very sensitive to motion artifact (flash)? Power Doppler What type of doppler has theses four factors; motion discrimination, temporal resolution, spatial resoution and uniformity? Color Doppler What causes no color flow to be displayed posterior to attenuation sturctures? Attenuation What cause depth ambiguity artifact to occur and can place flow in a more superficial location? High Pusle Repition Frequency (PRF) What occurs if velocity is higher than range set by operator, inapropriate color display which "wraps around" from top of color bar to bottom, or vice versa? Color aliasing Attenuation, High PRF, Color aliasing, multiple angle artifact, mirror image artifact, color bleed, color noise, misregistration of color, and color bruit are all what? Color Doppler Artifacts Color flow Doppler alows the operator to evaluate a more broad area to help figure out where to use ___________  _________. Spectral Doppler What depends on the relative velocity between source and reciever, the transmitted frequency, the acoustic velocity of the medium, and the Doppler angle as given by the Doppler shift equation? Doppler shift frequency For a constant reflector velocity, the detected Doppler shift frequency decreases as the Doppler angle is __________. Increased What predicts that an increase in reflector velocity will cause a higher Doppler shift frequency? Doppler shift equation A graphic plot of power spectrum as a function of time is called? Doppler spectral waveform Authorcloseea ID186478 Card SetTest 4 Chapters 14-18 DescriptionChapter 14-18 Updated2012-12-02T02:59:26Z Show Answers