Intra- and interoperator reliability of manual and semi-automated measurements of intracranial translucency.

Abstract

To assess the reproducibility of fetal intracranial translucency (IT) measurements performed manually or with SonoNT(®), a semi-automated caliper placement technique recently introduced for nuchal translucency thickness (NT) measurement. This was a retrospective study using 116 stored images of the head (mid-sagittal plane) from normal fetuses in dorsoposterior position at 11-13 weeks. Two experienced operators each measured the IT separately, twice manually and twice using the semi-automated software. Intraoperator and interoperator repeatability were assessed. The mean of the two manual measurements of the more experienced Operator 2 was considered as the 'gold standard'. Seven cases were excluded as the IT could not be recognized by the semi-automated software. In the remaining 109 cases, the interquartile range of the mean IT measurement was 1.9-2.4 mm for Operator 1 and 1.8-2.3 mm for Operator 2 for both the manual and the semi-automated IT measurements. The intraoperator SD for manual measurements was 0.091 mm for Operator 1 and 0.088 mm for Operator 2, and for semi-automated measurements it was 0.054 mm for Operator 1 and 0.067 mm for Operator 2. Concerning interoperator bias of the manual measurements, the mean difference between Operator 1 and Operator 2 was - 0.09 (95% CI, - 0.11 to - 0.07) mm. With respect to the gold standard, the mean bias of the semi-automated measurements was 0.01 (95% CI - 0.01 to 0.03) mm for Operator 1 and - 0.09 (95% CI - 0.11 to - 0.07) mm for Operator 2, indicating good agreement. Manual IT measurements are reproducible. In addition, IT can be assessed reliably using the semi-automated NT algorithm, leading to standardization of the IT assessment process.