B-K Medical Pro Focus 2202, User Manual

Page: 224 / 356

224 Chapter 15
Table 15-7. Variables in vascular calculation formulas.
Calculation Accuracy
Factors Affecting Accuracy
The accuracy of the calculation is influenced by:
• Accuracy of the measured input parameter. This is shown in the General
Transducer Information (BB0555).
•
Accuracy of the empirically determined equations
•
Rounding errors
•
Selected noise reduction
•
Accuracies of the curve definition
•
Accuracy of the Doppler spectrum.
Variable Definition
F
max
maximum frequency at a particular time
t
SS
time of start of the systole
t
PS
time of peak systole
t
MD
time of minimum diastole
t
ED
time of end diastole
t
1
, t
2
2 points in time
t
2
- t
1
time difference between 2 measured points
dt time between spectral lines
A area of the vessel
A
1
, D
1
transverse area (diameter) of the vessel lumen before the stenosis
A
2
, D
2
transverse area (diameter) of the stenotic part of the vessel
n number of measurements
V
n
(t) maximum velocity (in m/s) at time t
number of spectral lines from the start of systole to the end of diastole t
ED
t
SS
–
dt
----------------------