Method of Forming Layered Images of Objects From Superposition Images of Different Image Planes

The invention relates to a method of forming a layered image of a three-dimensional object which is irradiated from different directions by a plurality of radiation sources.

U.S. Pat. No. 3,499,146 describes a method where object layers can be decoded from a number of simultaneously recorded simultaneous-superposition images of an irradiated three-dimensional object. This method enables three-dimensional reconstruction of an object by the formation of a layered image. The recording of the simultaneous-superposition images on X-ray films which are arranged one underneath the other, however, is not efficient.

The present invention has for its object to record a three-dimensional object, irradiated simultaneously from a number of directions, so that separate coded superposition images are formed in different image planes, and that given layers of the object are decodable.

This object is achieved in accordance with the invention in that on a mechanically moved detector face n coded superposition images of a single movement phase are sequentially recorded in different image planes. The decoding of the n superposition images so that these images are successively electronically superposed and summed, is realized by means of a coordinate matrix whose coordinates correspond to the geometry of the radiation source distribution, for a number of times which equals the number of radiation sources, with the result that each time the same layer of the object is decoded n times and the n decoded layers are summed to form a layered image.

The detector face is mechanically moved at a high speed, for example in milliseconds so that a number of coded superposition images of a single movement phase can be recorded in different image planes. The method can thus be used for the display of moving three-dimensional objects such as the beating heart. The all layers of moving object recorded during a movement phase can subsequently be decoded.

Because the formation of the layered image is realized so that the coded superposition images recorded in the various image planes are successively electronically superposed in a shifted manner and summed for a number of times which equals the number of radiation sources, a layer of the object is multiply decoded and the number of decoded layers is summed to form a layered image. The layered image formed from a plurality of coded superposition images in different image planes, has an advantage over the single decoded layer of a superposition image in that the signal-to-noise ratio is better; in comparison with the simultaneous method it has the advantage that the complex recording on X-ray films is eliminated.

The drawing diagrammatically shows an embodiment for sequential recording of coded superposition images. The object 2 in the FIGURE is simultaneously irradiated by a plurality of X-ray sources 1, a superposition image thus being formed on the flat entrance screen 3 of an electro-optical image converter 4. Continuous or intermittent movement of the image converter 4 in the direction 5 within the recording range .iota. produces a continuously or intermittently changing superposition image on the entrance screen 3. The coded superposition images are transferred from the entrance screen 3 to the output screen 7 via an optical or electronic lens 6, and are optically or electronically stored therefrom. The superposition images of the different image planes 8 with the distances .DELTA. .iota. can be recorded in different manners.

In the case of continuously switched on X-ray tubes 1, the coded superposition images are derived from the output screen 7 with the normal image frequencies of the optical or electronic recording devices.

Alternatively, it is possible to flash the X-ray tubes 1 by means of a control unit 9 during the movement of the image converter 4, the flashed superposition images being derived from the output screen 7 at the same time. By fast movement of the image converter in the direction 5 within the recording range .iota., a number of recordings of a movement phase can be made. Alternating movement of the image converter also enables cinematrographic recording of coded superposition images of moving objects.

The superposition images which appear as shadow images on the detector face can also be recorded and stored with the aid of optical means.