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)

Spina Bifida 3–6 per 10,000 births 3-6 per 10,000 births 5 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

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 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

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

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

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

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.

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.

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

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

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

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

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

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 (1.8-2.2) 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’.

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 ).

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

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