A normalized thoracic coordinate system for atlas mapping in 3D CT images

In this paper, a normalized thoracic coordinate system (NTCS) is defined for rapidly mapping the 4D thoracic organ atlas into individual CT volume images. This coordinate system is defined based on the thoracic skeleton. The coordinate values are normalized by the size of the individual thorax so that this coordinate system is universal to different individuals. For compensating the respiratory motion of the organs, a 4D dynamic torso atlas is introduced. A method for mapping this dynamic atlas into the individual image using the NTCS is also proposed. With this method, the dynamic atlas was mapped into the clinical thoracic CT images and rough positions of the organs were found rapidly. This NTCS-based 4D atlas mapping method may provide a novel way for estimating the thoracic organ positions in low-resolution molecular imaging modalities, as well as in modern 4D medical images.