B-Mode and Doppler Measurement Tools

Question 1

What are the four measurements taken to estimate gestational age?

Answer 1

• Biparietal Diameter
• Head circumference
• Femur length
• Abdomen circumference

Question 2

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

Answer 2

0 +/- 1%

Question 3

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

Answer 3

1 +/- 1%

Question 4

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

Answer 4

Transvaginal - tight membrane curvature.

Question 5

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

Answer 5

0-1%

Question 6

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

Answer 6

-2 - +4%

Question 7

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

Answer 7

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

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

Question 8

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

Answer 8

• 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.

Question 9

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

Answer 9

• 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]

Question 10

How can ejection fraction be calculated?

Answer 10

• 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%.

Question 11

How can volume assessment be made more accurate?

Answer 11

• 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.

Question 12

How is a mitral valve regurgitation assessment performed?

Answer 12

• 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.

Question 13

How is fractional shortening measured using M-Mode ultrasound?

Answer 13

• 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