P12.02: Fetal thymus volume estimated with Virtual Organ Computer-aided AnaLysis (VOCAL) in normal pregnancies

Abstract

Objective: To asses the learning curve for the observed to expected fetal lung area to head circumference ratio (O/E LHR) calculation in fetuses with congenital diaphragmatic hernia (CDH). Methods: Three trainees with the theoretic knowledge, but without prior experience in the O/E LHR measurement were selected. Each trainee and one experienced explorer measured the O/E LHR in the contralateral lung to the side of the hernia by firstly, manual tracing of the lung borders and secondly, by multiplication of the longest diameters in a cohort of 95 consecutive CDH fetuses. The average difference between the three trainees and the expert in the O/E LHR measurement was calculated. A difference below 10% was considered as accurate measurement. The average learning curve was delineated using the cumulative sum analysis (CUSUM). Results: The CUSUM plots demonstrate that the learning curve was surmounted by 77 and 71 cases performed for the area obtained by the manual tracing and multiplication of the longest diameter methods, respectively. Conclusion: The minimum number of scans required for an inexperienced sonographer to become competent in examining the O/E LHR is on average 70.