Automated Screening for Trisomy 21 by measuring Nuchal Translucency and Frontomaxillary Facial Angle

Combining nuchal translucency (NT) and serum biochemistry during first-trimester screening is accepted as a good model for aneuploidy screening, offering over 92% detection rate. Frontomaxillary facial angle (FMF) measurement has been shown to further improve the screening for trisomy 21. Existing methods that measure NT and FMF, are either manual or semi-automated and may be subject to measurement errors by sonographers. This paper presents an automated and computerized algorithm for the measurement of both NT and FMF. Only fetal images in the neutral position are considered in the study. The FMF angle is calculated by segmenting out the region of interest, line fitting at the frontal bone and upper part of the palate and calculating the angle between the lines. NT measurement is done by automating the calculation of the maximum width of the fluid-filled space under the skin at the back of fetus's neck. The result shows a good accuracy of measurement of both NT and FMF suggesting that it can be used to assist sonographers.