GE Logiq 500, User Manual

Page: 248 / 579

OB Measurements and Formulas
LOGIQ 500 Basic Users Manual
2233658–100 Rev. 0
9–11

USA Method (cont’d)
Calc
Mnemonic Calc Name Input Measurements Formula
Author
Reference
OFD Occipito Fron-
tal Diameter HC by ellipse or two dis-
tance Longest axis from HC
measurement n/a
S/D Ratio Systolic/
Diastolic Ratio two Doppler blood flow
peak velocities S/D=V
systole
/V
diastole
*NOTE*
n/a
A/B Ratio Velocities
Ratio two Doppler blood flow
peak velocities A/B = V
1
/V
2
n/a
PI Pulsatility In-
dex two Doppler blood flow
peak velocities and TAMAX PI=(V
max
–V
diastole
)/
TAMAX *NOTE*
n/a
RI Resistivity In-
dex two Doppler blood flow
peak velocities RI=(V
max
–V
diastole
)/
V
max
*NOTE*
n/a
EFW #1 Estimated
Fetal Weight Average of BPD and Aver-
age of AC EFW=10^(-1.7492+0.1
66*BPD+ (0.046*AC)–
((2.646*AC*BPD)/1000)) Shepard, AJOG,
142:47, 1982
EFW #2 Estimated
Fetal Weight Average of FL and
Average of AC EFW=10^(1.304+
(0.05281*AC)+
(0.1938*FL)– (0.004*
AC*FL)) Hadlock-
Radiology
150:535, 1984
EFW #3 Estimated
Fetal Weight Average of BPD,
Average of AC and Average
of FL EFW=10^(1.335–0.003
4*AC*FL)+
(0.0316*BPD)+
0.0457*AC)+ (0.158*
FL) Hadlock, AJOG,
151:333, 1985
EFW #4 Estimated
Fetal Weight Average of FL,
Average of AC and Average
of HC EFW=10^(1.326–
(0.00326*AC*FL)) +
(0.0170*HC)+
(0.0438*AC)+
(0.158*FL)) Hadlock, AJOG,
151:333, 1985
EFW #5 Estimated
Fetal Weight Average of FL,
Average of AC,
Average of HC and Average
of BPD EFW=10^(1.3596–
(0.00386*AC*FL))+
(0.0064*HC)+
(0.00061*BPD*AC)+(0.
0424*AC)+ (0.174*FL) Hadlock, AJOG,
151:333, 1985
EFW Graph Estimated
Fetal Weight
Graph EFW Calculation LOG EFW Mean (g) =
0.578 + (0.332 * MA) –
(0.00354 * MA
2
)
1SD = 0.127 * EFW
Mean
Hadlock,
Radiology, 1991;
181
EFW[g]=exp(0.578+0.332*MA–0.00354*MA^2) where MA is menstrual age [weeks]
*NOTE*: V
diastole
= V
min
or V
end–diastole
(depends on preset selection)
Table 9–3. OB Calculation Formulas Part 1—USA Version Factory Defaults (cont‘d)