1. UOG Journal Club: February 2012
Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency
K. Karl, K. O. Kagan and R. Chaoui
Volume 39, Issue 2, Date: February 2012, pages 164–168
Journal Club slides prepared by Dr Asma Khalil
(UOG Editor for Trainees)

2. Spina Bifida 3–6 per 10,000 births 3-6 per 10,000 births5 10 15 20 25
1930s
Birth prevalence (/10,000)
Year
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Prenatal diagnosis
Folic acid fortification
3–6 per 10,000 births
Rankin J et al., Paediatr Perinat Epidemiol 2000
Centre for Disease Control and Prevention statistics 2011
Boyd PA et al., J Med Screen 2011

3. Detection rate by ultrasound at 11-14 weeks is 14%
Open spina Bifida
Prenatal Detection
History 5%
MS AFP
75%
Ultrasound*
98%
*2nd trimester
MS AFP, maternal serum alpha fetoprotein.
Detection rate by ultrasound at weeks is 14%
Wald N et al., Lancet 1974
Nicolaides KH et al., Lancet 1986
Campbell J et al., Obstet Gynecol 1987
Syngelaki A et al., Prenat Diagn 2011

4. OB,occipital bone; Th, Thalamus.
First-trimester detection of open spina bifida using intracranial translucency (IT)
Normal
Open spina bifida
BS,brainstem; BSOB, brainstem–occipital bone distance; f.CM, future cisterna magna;
OB,occipital bone; Th, Thalamus.
Chaoui R et al., UOG 2011

5. B, brainstem;T, thalamus;
M, midbrain; My, medulla oblongata.
Chaoui R et al., UOG 2009

6. Normal Open spina bifida
Chaoui R et al., UOG 2009

7. Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency
Karl et al., UOG 2012
Retrospective; 116 stored images at 11–13 weeks; IT measurement
Objective
Examine whether the assessment of IT at 11–13 weeks can be further standardized by using the semi-automated NT algorithm, SonoNT®, in comparison to manual measurement.

8. Methodology 11–13 weeks Mid-sagittal plane Dorsoposterior position
Two experienced operators
Twice manually and twice using the semi-automated software (SonoNT®)
Intraoperator and interoperator repeatability
BS,brainstem; f.CM, future cisterna magna;
OB,occipital bone; Plex.chor., choroid plexus; Th, Thalamus.

9. Manual Semi-automated
The mean of the two manual measurements of the more experienced operator 2 was considered the ‘gold standard’.

10. Methodology - manual measurement
Magnify the image
Place the cursor on the inner border of the echogenic posterior brainstem border and on the inner border of the 4th ventricle choroid plexus
The longest vertical distance in the middle portion

11. Methodology – semi-automated
Corresponding ‘edge enhancement image’ that reflects the differences  in brightness rather than the brightness itself 
Define the echogenic lines delineating the translucency
Calipers placed automatically on the inner borders (inner–inner)
Left and central images show semi-automated measurement of nuchal translucency, Moratalla J et al., UOG 2010

12. Methodology – semi-automated
The measurement algorithm connects every point on one of the two echogenic lines to all points on the other line, then selects the minimum distance for each point
From these minimum distances, it selects the largest as the final translucency measurement
Left and central images show semi-automated measurement of nuchal translucency, Moratalla J et al., UOG 2010

13. IT vs NT semi-automated measurement
IT has a more complex shape
Risk of incorrect recognition of borders due to neighbouring structures
Vertical borders close to the echogenic edges of the brainstem and choroid plexus
Lateral borders rather narrow over the IT region
Square frame rather than rectangular
Smaller frame
Moratalla J et al., UOG 2010

14. Results Manual Semi-automated 0.091 0.088 0.054 0.067 0.940 0.939
Intraoperator SD (mm)
0.091
Median (IQR) (mm)
2.1 (1.9–2.4)
Operator 1
Manual
0.088
2.1 (1.8–2.3)
Operator 2
0.054
2.2 (1.9–2.4)
Semi-automated
0.067
2.2 ( )
Intraclass correlation
0.940
0.939
0.982
0.971
Mean difference (mm)
–0.09
Reference*
0.01
*The mean of the two manual measurements of operator 2 was considered the ‘gold standard’.

15. Results 95% limits of agreement Manual Semi-automated
–0.26 and 0.23 mm
Manual
–0.17 and 0.17 mm
Semi-automated
Interoperator & intermethod*
–0.34 and 0.17 mm
–0.20 and 0.23 mm
Intraoperator
Good overall agreement with a trend towards larger measurements using the semi-automated approach
*versus the gold standard (the mean of the two manual measurements of operator 2 ).

16. Strengths Limitations
Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency
Karl et al., UOG 2012
Strengths
SonoNT can be used reliably for IT
Benefit for less experienced operators
High repeatability
Limitations
Unknown reliability with variations in gestation and anatomy
Possible misdiagnosis of Blake’s pouch cyst as spina bifida

17. Conclusion Manual IT measurements are reproducible
Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency
Karl et al., UOG 2012
Conclusion
Manual IT measurements are reproducible
IT can be assessed reliably using the semi-automated NT algorithm, leading to standardization of the IT assessment process