B-Mode and Doppler Measurement Tools Flashcards

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1
Q

What are the four measurements taken to estimate gestational age?

A
  • Biparietal Diameter
  • Head circumference
  • Femur length
  • Abdomen circumference
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2
Q

What is the approximate accuracy of a transducer taking vertical measurements?

A

0 +/- 1%

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3
Q

What is the approximate accuracy of a transducer taking horizontal measurements?

A

1 +/- 1%

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4
Q

What type of transducers cause the largest error in horizontal measurements?

A

Transvaginal - tight membrane curvature.

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5
Q

What is the expected error when using the ellipse tool to measure circumference?

A

0-1%

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6
Q

What is the expected error when using the ellipse tool to measure area?

A

-2 - +4%

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7
Q

How should a PW-Doppler trace be set up so as to measure blood flow in the carotid artery?

A
  • Use a cine-loop, and scroll to give a good trace

- Adjust the angle correction to lie parallel to the sides of the vessel.

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8
Q

What tools are available on PW-Doppler trace and what do they do?

A
  • Single caliper: Displays velocity values
  • Heart rate tool: displays vertical line at start of r-wave
  • Auto PW: Display max and mean velocity traces, and parameter values (e.g. RI)
  • Time slope tool: gives the rise time of the R-wave (if sweep speed in increased)
  • Volume flow tool: uses auto tools mean velocity trace, and radius measurement to estimate volume flow.
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9
Q

How can the volume of the left ventricle be measured using ultrasound?

A
  • Take a apical four-chamber cine-loop and scroll to end diastole.
  • Use the manual trace tool to draw around the circumference form the mitral valve annulus to the apex and back down.
  • Scanner splits the area into 20 discs and uses Simpson’s rule, V=(pi/4)(L/20)Sigma[a_i^2]
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10
Q

How can ejection fraction be calculated?

A
  • Calculate the volume at end systole and end diastole as usual.
  • Stroke volume, SV = EDV-ESV
  • EF = SV/EDV
  • Normal ejection fraction is in the range 55-70%.
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11
Q

How can volume assessment be made more accurate?

A
  • Bi-plane scanning: repeat area measurement at 90 deg.
    - Simpson’s rule becomes:
    V= (pi/4) (L/20) * Sigma[a_ib_i]
  • 4D imaging: auto contours heart and produces 3D data set. Volume is automatically contoured for each 3D frame.
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12
Q

How is a mitral valve regurgitation assessment performed?

A
  • Flow from mitral valve back into left ventricle during systole converges as a series of hemispherical shells.
  • Adjust the colour-Doppler baseline until aliasing occurs.
  • Proximal iso-velocity surface area (PISA) = 2pir^2
  • MV regurgitant flow rate - PISA x aliasing velocity.
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13
Q

How is fractional shortening measured using M-Mode ultrasound?

A
  • Parasternal long axis view of the heart with m-mode cursor at MV leaflet tips
  • LV volumes are calculated using the Teichholz equation.
  • Left ventricular Internal dimensions (LVID) at systole (s) and diastole (d) measured.
  • Fractional shortening , FS = (LVIDd- LVIDs)/LVIDd
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