Enhancement of edge response in same matrix size of x-ray CT image without special image processing

Multi-detector row computed tomography (MDCT) allows high-edge-response imaging in z-direction by thinner slice compared with the conventional single-detector row CT (SDCT). The edge response in x- and y-direction is, however, basically depending on the reconstruction function or the image processing. In this work, a method of enhancing the edge response in x- and y-direction, without special image processing, is proposed. In this method, projection data of a patient is acquired by high-spatial-frequency sampling, and an edge-enhanced image is reconstructed with same matrix size as a conventional image by averaging the projection data. Edge-enhancement effect in this method employs nonlinearlity of the projection data, and special image processing is not required. In order to verify this proposed method, a large water phantom that consists of five resinous rods and a small one that the similitude rate is 1/2, and is topologically the same as the former large phantom, were scanned, and high-spatial-frequency sampling was simulated. After that, reconstructed images were obtained by averaging the high-spatial-frequency sampled data and edge gradients for some rods were obtained and estimated. As a result, although image noise increased slightly, edge gradients are improved 25 to 97 % without special image processing.