BK Medical bkSpecto, Advanced User'S Manual

Page: 87 / 164

bkSpecto Advanced User Guide (16-01642-01) Exam Types 87
When the Doppler angle is turned off or altered, the results are recalculated.
Reduction
The %Reduction measurement uses the area of the vessel before or after the stenosis
and the area of the vessel at the stenosis (residual lumen) to calculate the degree (%)
of stenosis. You can base the stenosis calculation on the distance across the vessel or
the area of the vessel lumen.
To find the reduction measurement, freeze the image, tap Measure and select
%Reduction . After you select the measurement type, tap on the image to place your
measurement points.
Reduction Based on Ellipses
When you use areas to calculate stenosis, make one area measurement to measure
each of the following:
1
Tap %Reduction and measure the total lumen of the vessel.
2
Tap to set the measurement. A new caliper is displayed inside the ellipse or
circle.
3
Measure the residual lumen of the vessel.
4
Tap to set the measurement.
The result on the monitor is continuously updated while you position the second
ellipse or circle.
RI and PI (Resistance Index and Pulsatility Index)
The resistance index (Pourcelot index) is based on the peak systolic velocity (V
max
)
and the end-diastolic minimum velocity ED (V
ed
) in a supply vessel. RI indicates the
level of impedance to blood flow; a high RI suggests increased peripheral vascular
resistance.
The pulsatility index represents the hemodynamic conditions in a vessel. It is based
on the peak systolic velocity (V
max
), the maximum velocity at minimum diastole
(V
min-diast
), and the average (V
mean
) of the peak (max) flow velocity curve. PI
describes the elasticity of the vessel combined with the level of peripheral resistance.
The A/B ratio (Stuart index) is calculated as the ratio between PS (V
ps
) and ED (V
ed
).
The advantage of using indices rather than absolute velocities is that the indices are
independent of the insonation angle.
Doppler Angle
Active? (Yes/No) Velocity or Frequency
No Frequency measured at intersection of marker line and Doppler curve.
Yes Velocity measured, and frequency parameters replaced by
corresponding velocity parameters, (dF by dV, FACC by ACC, F1 and F2
by V1 and V2.)