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Acquiring tomographic images from panoramic X-ray scanners

We propose a new method to acquire three-dimensional tomographic images of a large object from a dental panoramic X-ray scanner which was originally designed to produce a panoramic image of the teeth and jaws on a single frame. The method consists of two processes; (i) a new acquisition scheme to acquire the tomographic projection data using a narrow detector, and (ii) a dedicated model-based iterative technique to reconstruct images from the acquired projection data. In conventional panoramic X-ray scanners, the suspension arm that holds the X-ray source and the narrow detector has two moving axes of the angular movement and the linear movement. To acquire the projection data of a large object, we develop a new data acquisition scheme that can emulate an acquisition of the projectional view in a large detector by stitching narrow projection images, each of which is formed by a narrow detector, and design a trajectory to move the suspension arm accordingly. To reconstruct images from the acquired projection data, an accelerated model-based iterative reconstruction method derived from the ordered subset convex maximum-likelihood expectation-maximization algorithm is used. In this method each subset of the projection data is constructed by collecting narrow projection images to form emulated tomographic projectional views in a large detector. To validate the performance of the proposed method, we tested with a real dental panoramic X-ray system. The experimental results demonstrate that the new method has great potential to enable existing panoramic X-ray scanners to have an additional CT’s function of providing useful tomographic images.