A good positioning technique is essential for obtaining accurate diagnostic information in radiography. In this study, we developed the imaging techniques which produce a plane image using CT images in order to assist the students' positioning practice under the X-ray equipment. First, we scanned the skull phantom by CT (Computed tomography) and obtained CT images. Next, we measure the positioning information of the phantom by using scene analysis. And we calculated the plane image from CT image data corresponding to the detected phantom position. As a result, we could obtain the plane image having the sufficient image quality to observe the examination organ with a display. As performing positioning practice without exposure of X-rays, students could acquire positioning skills in a short time. It is expected that our techniques are useful for students practicing their positioning skills.