Card Set Information

2010-10-08 12:46:51
Us physics

Exam 2
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  1. Piezoelectric crystal
    • rigid man made ceramic
    • part of the piezoelectric effect
  2. Time Gain Compensation
    A method of increasing amplification of the signal with depth to compensate for loss caused by attenuation
  3. Dynamic Range
    a measure of the span of signal magnitudes that can be represented or processed by the various components of a system
  4. Gain
    methos of increaing amplification of the overall gain
  5. B-mode
    • 2D/ real time
    • two dimensional grey scale imaging in real time
  6. m-mode
    is udes in echocardiography and displays of an echo structure such as a heart valve (depth v. time)
  7. Color Doppler
    visualization of presence, characteristics and direction of blood flow
  8. Spectral Doppler
    allows us to qualify velocities and characteristics of blood flow in a specific location
  9. State the range equation and apply it to the production of sonographic images.
    • · Depth into tissue= velocity of sound in tissue x time between sent and
    • received divided by 2
    • ·D=cT/2
    • ·D: distance c:1540 m/s T: pulse echo round trip 13 microseconds= 1
    • centimeter
    • · Looks at time elapsed, for echo to return to the transducer, determines
    • the depth of echo signal on display
  10. Describe the component parts of an ultrasound
    • -Timer (clock)
    • -Tansmitter (voltage pulse, generator)
    • -Tx (transducer)---patient----back to Tx
    • · Receiver (computer)-processes electrical voltage signal detected by
    • crystal
    • ·Display—maybe storage
  11. What types of procedures are the different types of transducers used for?
    • -Sector: Needle placement, cardiac, ABD, liver,
    • spleen, kidney, pelvis
    • -Linear: Vascular, small parts, carotid, testicle,
    • thyroid
    • -Curvilinear: OB, ABD, GYN, TV
    • -Radial: endoscopic, intercavity, TV, TR,
    • intervascular, CAD
  12. Characterize transducers by image shape/configuration,
    frequency, footprint.
    • -Sector: pie shape:2.0/5.0 :small
    • -Linear: rectangular:7.0/up :large
    • -Curvilinear: broadened pie:3.0/5.0 :large
    • -Radial: wagon wheel:14.0/20.0 (TV-5.0/7.0) :very
    • small
  13. Ampllification
    • overall gain
    • uniformly amplifies all returning voltage signal
  14. Compensation
    • TGC
    • variable amplification, based on distance of echo to transducer
  15. Compression
    • log compression, grey scale, dynamic range
    • adjust for attenuation of sound tissue. Allows uniform display of similar tissue at any depth. Proportional decrese in signal amplitude. Without losing min and max signals
  16. demodulation/ rectification
    • no knob
    • goes from AC to DC changing signal shape
    • rectification (AC>DC)
  17. rejection
    • Doppler wall filter
    • eliminates the weak signals and keeps the rest. Minimizes background nois and wall motion artifacts
  18. Plug flow
    • blood is going the same velocity in the vessel
    • large/ medium diameter vessels (AO, femoral, ECA (face) and common iliac)
    • Triphasic (bidirectional)
    • High resistance vascular bed
  19. Parabolic Flow
    • Laminar flow/ layered flow
    • majority of arteries in the body
    • Low resistance
  20. Identify 5 ways to reduce or eliminate aliasing from the display
    • -decrease tx frequency
    • -lower baseline
    • -increase velocity range
    • -increase PRF
    • -switch to CW, because it is not see
  21. Describe how yo recognize aliasing on PW spectral displays and color Doppler displays:
    • -Spectral the wave forms will be filled in instead of empty
    • -Color borrows colors for other color bar
  22. Describe why and how aliasing occurs
    • Aliasing is when blood velocities peak over the
    • range of velocities given or blood changes directions