This Journal Club presentation provides a summary and discussion of the following free access article published in UOG: Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency. K. Karl, K.O Kagan, R. Chaoui Volume 39, Issue 2, Date: February 2012, pages 164-168 This can be accessed here: http://onlinelibrary.wiley.com/doi/10.1002/uog.10137/abstract

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
25 3–6 per 10,000 births 25
Birth prevalence (/10,000)
Birth prevalence (/10,000)
20
20
3-6 per 10,000
• Prenatal diagnosis
15
births
• Folic acid fortification
15
10
10
5
5
0
0
1930s1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
1930s
Year
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. Open spina Bifida
Prenatal Detection
History MS AFP Ultrasound*
5% 75% 98%
*2nd trimester
MS AFP, maternal serum alpha fetoprotein.
Detection rate by ultrasound at 11-14 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. 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
NT
• 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
Operator 1 Operator 2 Operator 1 Operator 2
Median (IQR) (mm) 2.1 (1.9–2.4) 2.1 (1.8–2.3) 2.2 (1.9–2.4) 2.2 (1.8-2.2)
Intraoperator SD (mm) 0.091 0.088 0.054 0.067
Intraclass correlation 0.940 0.939 0.982 0.971
Mean difference (mm) –0.09 Reference* 0.01 –0.09
*The mean of the two manual measurements of operator 2 was considered the ‘gold standard’.

15. Results
95% limits of agreement
Manual Semi-automated
Intraoperator –0.26 and 0.23 mm –0.17 and 0.17 mm
Interoperator & intermethod* –0.34 and 0.17 mm –0.20 and 0.23 mm
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. Intra- and interoperator reliability of manual and semi-automated
measurements of intracranial translucency
Karl et al., UOG 2012
Strengths Limitations
• SonoNT can be used • Unknown reliability
reliably for IT with variations in
• Benefit for less gestation and anatomy
experienced operators • Possible misdiagnosis
• High repeatability of Blake’s pouch cyst
as spina bifida

17. 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

18. Intra- and interoperator reliability of manual and semi-automated measurements
of intracranial translucency
Karl et al., UOG 2012
Discussion points
• What is the recurrence risk for spina bifida after having one affected
pregnancy?
• What medical advice should be given to parents regarding a future
pregnancy in the above scenario?
• If a recurrence occurs, will it always be limited to the fetal spine?
• What is the difference between exencephaly, anencephaly and
encephalocele?
• Can the above be diagnosed with confidence at 11–14 weeks’ gestation
by ultrasound?
• Is measurement of intracranial translucency (IT) reproducible and
reliable enough to be tested in clinical practice?
• Do we know how sensitive measurement of IT is in the detection of
spina bifida?