GE LOGIQ 500 Advanced Reference Manual page 165

Performing STVOL Measurement
CAUTION
Stepper Volume Formula
LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0
Stepper Volume (STVOL) is the method used to calculate the
volume of an organ using the LOGIQ
Transaxial Probe and a mechanical stepping device that moves
the probe in fixed increments.
The stepper volume measurement works only in B-Mode with
Convex Scan (NOT available Linear scan).
Stepper Volume (STVOL) is the method used to calculate the
volume of an organ using the LOGIQ
Transaxial Probe and a mechanical stepping device that moves
the probe in fixed increments.
The calculation is based on the fact that each step or area
measurement is taken at equal stepper increments. The area
measured at each slice is then used to compute the total
volume of the organ, according to the following model:
For N slices, there are N–1 volumes between the slices plus a
small volume at each end.
It is assumed that the small volumes of the end caps are cones
with a base equal to the measured area of the end slice and
height equal to the slice spacing. The cones will have volumes
V=A d/3 and A d/3 for slices 1 and N respectively, where d is
1 N
the spacing between the slices.
The volumes between the slices are assumed to be segments
of a paraboloid of revolution, where the volume between any
slice n and n+1 is (A
n+
The sum of the volumes between slices is:
V=d [ (A A /2)+(A
1+ 2 2+
Therefore, the total volume of the organ is calculated as:
V=d [ (5/6)A A +A
1+ 2 3+....+
Press Freeze to have an Image of the organ to be measured.
The probe should be inserted to its most cephalic position (i.e
base of the prostate).
Press Measurement to fix the STVOL measurement.
Urology Calculations (Option)
500 Urology software,
500 Urology software,
A )d/2.
n+1
A /2)+....+(A A /2)]
3 n–1+ n
(5/6)A ]
N
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