The positioning skill of the radiological technologist is essential for obtaining accurate diagnostic information of an organ and for reducing X-ray exposure in radiography. We previously reported on the development of a computed tomography (CT) image-based training tool. A three-dimensional phantom was produced by using computer graphics. Positioning was performed on a PC, and the plane image corresponding to the performed positioning was produced and displayed. In this study, the algorithm which produces the plane image from the CT image data was improved in order to obtain an image quality comparable to the X-ray image obtained by the Computed radiography (CR) system. The CT value and linear attenuation coefficient were calculated from the CT image data based on the fundamental interactions between X-rays and an object. By using the linear attenuation coefficient, a plane image with the same image quality as the CR image could be produced.