| 摘要 |
PHN 8803 30.1.78 A device for computer tomography in which a patient to be examined is irradiated in different directions by a flat, fan-shaped beam of X-rays which is generated by an X-ray source having a comparatively small emissive surface area. The locally transmitted radiation is measured by means of an X-ray detector comprising a series of detection elements which are arranged on an arc of a circle and which have a comparatively small radiation entrance surface area. A computer is used to calculate the density distribution of the irradiated part of the patient on the basis of the measuring data. During an examination, the Xray source and the X-ray detector rotate in opposite directions about a common axis of rotation which extends transversely of the plane of the fan-shaped beam. The distance between the radiation entrance surfaces of the detection elements and the axis of rotation equals the distance between the emissive surface of the X-ray source and the axis of rotation. Because the X ray source and the X-ray detector rotate in opposite directions, the patient to be examined is scanned by the X-ray source and a detection element in mutually substantially parallel, consecutive paths. Differences in the sensitivity of detection elements do not become manifest as annular interference patterns in the calculated density distribution. |
