A Comprehensive Survey on Nuchal Translucency Segmentation and Thickness Estimation

The typical fluid-filled subcutaneous area seen at the back of the foetus' neck in the latter stages of the first and early stages of the second trimester is known as Nuchal Translucency (NT). An essential step in Computer-Aided Diagnosis (CAD) for the early identification of Down Syndrome (DS) is NT testing. In extracting the NT region, conventional segmentation techniques face numerous obstacles, such as indistinct edges, intensity homogeneity, increased time consumption, and a high probability of error. Automatic detection of DS would eliminate these obstacles and result in a quicker and more accurate diagnosis of the foetus. Segmenting NT from ultrasound images is a challenging task. One of them is the substantial overlap between the intensity distributions of NT region clusters and the surrounding background regions. In addition, the morphology of the NT region fluctuates considerably as the foetus rotates. In this research study, a comprehensive survey of well-known methods for estimating NT thickness by using various extracted features is presented along with denoising and segmentation.