A Novel Hybrid Approach for Cephalometric Landmark Detection

Cephalometric analysis has an important role in dentistry and especially in orthodontics as a treatment planning tool to gauge the size and special relationships of the teeth, jaws and cranium. The first step of using such analyses is localizing some important landmarks known as cephalometric landmarks on craniofacial in x-ray image. The past decade has seen a growing interest in automating this process. In this paper, a novel hybrid approach is proposed for automatic detection of cephalometric landmarks. Here, the landmarks are categorized into three main sets according to their anatomical characteristics and usage in well-known cephalometric analyses. Consequently, to have a reliable and accurate detection system, three methods named edge tracing, weighted template matching, and analysis based estimation are designed, each of which is consistent and well-suited for one category. Edge tracing method is suggested to predict those landmarks which are located on edges. Weighted template matching method is well-suited for landmarks located in an obvious and specific structure which can be extracted or searchable in a given x-ray image. The last but not the least method is named analysis based estimation. This method is based on the fact that in cephalometric analyses the relations between landmarks are used and the locations of some landmarks are never used individually. Therefore the third suggested method has a novelty in estimating the desired relations directly. The effectiveness of the proposed approach is compared with the state of the art methods and the results were promising especially in real world applications.