Segmentation and display of hepatic vessels and metastases

In order to visualize the spatial relationships between three-dimensional structures within the liver, we have developed a method for segmentation of the liver and employed non-linear projection techniques to display the hepatic structures, in particular the hepatic vessels and metastatic tumors, from a number of angles. Ultrafast computed tomography was employed to obtained cross-sectional images of the liver as contrast material flowed through the hepatic vessels. The technique for segmentation of the liver is semi-automated, based on histogram analysis and region growing, and allows manual correction of the boundaries of the liver. The pixels composing the liver are defined to lie within the closed contour of the determined boundary. Projections of the vessels were obtained using a maximum-intensity-projection technique and an integration technique which employed a lower-bound threshold. Projections of metastases were obtained using a minimum-intensity-projection technique and an integration technique which employed an upper-bound threshold. Views of the structures were then generated at a number of angles relative to the sagittal plane so as to assist in visualization of the three-dimensional spatial relationships.