ABSTRACT
Navigation is important in Computed Tomography Virtual Endoscopy (CTVE) functions. Existing navigation methods involve planning and pre-calculating of a fixed path before the viewpoint flight inside the targeted organs. This includes path construction, centering, smoothing and multi-branch processing. This paper proposes a 3D navigation method which was achieved by utilizing the compatibility of the 3D navigation and the ray casting 3D rendering method, without the necessity of planning and pre-calculating a fixed path, eliminating the multi-branch problems. In our 3D navigation method, the viewpoint direction and location are tracked in real time when the viewpoint is inside the organs. At the same time it presents and controls the direction changes and location changes of the viewpoint in x, y, z dimensions. With interactive control of the viewpoint, it can fly in any direction in 3D, not only along a fixed path, thus eliminating multi-branch problems. The viewpoint locations and directions will change smoothly and will be used to calculate the current scene of CTVE. Accelerated ray casting is used to render 3D scenes, which is compatible with the 3D navigation method. In Minimum Intensity Projection (MinIP) applications, if the conventional MinIP reconstruction method is used, realistic results cannot be achieved when they are rotated in multi-directions because the Computed Tomography (CT) images always contain empty regions surrounding the tissue regions. The conventional MinIP reconstruction algorithm always chalks up a minimum intensity voxel which relates to the empty regions instead of the tissue regions. To solve such valid voxel searching problems, seed-filling algorithms are used to fill the empty regions of each slice automatically. The empty voxels are labeled automatically and are avoided in MinIP calculation to gain correct results in all directions.