Use of focus point for plane acquisition to improve reproducibility in fetal biometry

Abstract

ObjectivesTo assess reproducibility of ultrasound measurements for fetal biometry, using a ‘focus point’ (FP) for the acquisition of the relevant plane.Methods80 women with singleton normal pregnancies were included in the study at University College London Hospital, UK, between 18 and 37 weeks. Planes to measure head circumference (HC), abdominal circumference (AC) and femur length (FL) were obtained twice by sonographers with different experience, blind to each other, the first time requesting to obtain the plane referring to a standard image, the second time using the focus point. The focus point is a unique plane landmark that once identified, the sonographer is asked to rotate the probe along the 3 axes (x, y, z) to acquire the relevant plane keeping the focus point in view (cavum septum pellucidum for HC, 2/3 of the umbilical vein for AC and one of the two diaphyses for FL). Sonographers were either in training or with the experience of >3000 scans performed. Intra‐ and interobserver reproducibility were assessed using Bland‐Altman plots reporting absolute values or percentages.ResultsOverall reproducibility was good with 95% confidence intervals (CI) being <8%. Reproducibility was improved using the focus point compared with acquiring the plane without using the focus point, (95% CI <4% versus <6% for intra‐ and <7% versus <8% for interobserver reproducibility respectively). Findings were independent from sonographer seniority and plane acquired.ConclusionsFetal biometry reproducibility is improved with the use of the focus point for plane acquisition regardless of sonographer experience. We propose this method to be implemented in clinical practice and for training in fetal biometry.This article is protected by copyright. All rights reserved.