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Title: Method and apparatus for tomography wherein signal profiles derived from an out-fanning beam of penetrating radiation can be reconstructed into signal profiles each corresponding with a beam of parallel incident rays
Claims: I claim: 1. A method of pre-processing radiolical information by means of electronic analogue techniques for use in a process for reconstructing an image of a desired lamina of a subject, said method comprising: projecting substantially flat, out-fanning beams of penetrating radiation through the subject in the plane of the desired lamina at succeeding angular positions; detecting the projected beams passed through the subject to produce a plurality of continuous electrical primary profile signals; recording a plurality of juxtaposed continuous primary signal profiles from said primary profile signals to the subject on a record median along a plurality of recording paths each having a predetermined trajectory and spatial orientation related to the angular position during the projecting of the corresponding beam of penetrating radiation; and scanning and reading-out fragments of a plurality of series of adjacent primary signal profiles from the recorded profiles along a corresponding plurality of scanning paths each having a predetermined trajectory intersecting the corresponding series of the recording paths and also having a spatial orientation relating to the angular positions during the projecting of a corresponding series of the projected beams of penetrating radiation to generate a plurality of secondary profile signals each corresponding to parallel portions of the corresponding series of beams suitable for reconstructing the image of the selected lamina of the subject. 2. An apparatus for forming an image of a lamina of a subject under examination by means of penetrating radiaion comprising a source for producing a substantially flat, out-fanning beam of said penetrating radiation, a support for supporting the subject under examination so that said lamina of the subject is irradiated by said beam in the plane of the lamina, means for detecting the beam passing through the subject and for producing a continuous primary profile signal which is indicative of the radiation absorption in the lamina of the subject as determined by said beam, said support including means for producing relative movement between said subject and an assembly including said source of radiation and said detecting and primary profile signal producing means through a plurality of succeeding angular positions so that a plurality of the primary profile signals can be produced at the corresponding plurality of angular positions, first means for recording a plurality of continuous primary signal profiles corresponding with said plurality of primary profile signals and along a corresponding plurality of recording paths each having a trajectory and spatial relationship corresponding to the respective relative angular position of the subject and the assembly, and second means for scanning a plurality of series of the primary signal profiles along a plurality of scanning paths each having a trajectory intersecting the respective series of the recording paths and for producing a plurality of secondary profile signals each corresponding to parallel portions of a corresponding series of the plurality of beams projected by the source. 3. An apparatus according to claim 2, wherein said first means for recording said primary signal profiles includes record control means arranged so that each of said primary signal profiles is recorded in accordance with an arc-shaped path having a radius R.sub.1, the center of which, in unique relationship with a respective one of said relative angular positions between the subject and the assembly is on a circle having radius R.sub.2, in which R.sub.2 .gtoreq.R.sub.1, around a point 0 representing the axis of rotation of the source of radiation with respect to the subject, the beginning of each primary signal profile being on a circle around said point 0 having radius R.sub.3, in which R.sub.3 .gtoreq.0 but may be <R.sub.2 ; said beam produced by said source has one edge that coincides with the axis of rotation; and said second means for scanning the primary signal profiles includes scan control means arranged so that said plurality of primary, arc-shaped signal profiles are scanned in accordance with likewise arc-shaped paths each having a radius R.sub.2 and a respective centre of curvature M which is in a point on said circle having radius R.sub.1, the center of curvature M corresponding with an end of a diameter of the circle of radius R.sub.1 indicating the direction of parallel beam portions corresponding to the respective series of primary signal profiles scanned. 4. An apparatus according to claim 2 including radiation bounding means for bounding the spreading of the out-fanning beam so that each primary signal profile has such a length corresponding to one half of the respective lamina of the subject, which one half is bounded by said axis of rotation and is completely irradiated. 5. An apparatus according to claim 3 wherein said record control means and said scan control means derive their control signals from electromechanical means for generating and transferring angle information about the relative movement of the subject with respect to the assembly of said source of radiation and said detecting and primary profile signal producing means. 6. An apparatus in accordance with claim 2 wherein said first means is adapted to record a plurality of pluralities of primary signal profiles that are located within concentric, annular areas; and said second means is adapted to scan said plurality of pluralities of primary signal profiles in accordance with a corresponding plurality of pluralities of scanning paths. 7. An apparatus according to claim 2 wherein said first means is adapted to record said primary signal profiles in accordance with essentially linear paths; and said second means is adapted to scan the pattern of primary signal profiles in accordance with arcuate paths intersecting said primary signal profiles. 8. An apparatus according to claim 2 wherein said first means is adapted to record said primary signal profiles in accordance with arcuate paths; and said second means is adapted to scan the pattern of primary signal profiles in accordance with essentially linear paths intersecting said primary signal profiles. 9. An apparatus according to claim 2 wherein said first means is adapted to record said primary signal profiles is accordance with linear paths; and said second means is adapted to scan the thus-recorded primary signal profiles in accordance with likewise linear, parallel paths intersecting the respective primary profiles at a fixed angle. 10. An apparatus according to claim 2 wherein said first means is adapted to record said primary signal profiles in accordance with paths that are longitudinally contiguous with one another; and said second means includes facilities for selectively adjusting the width of the paths along which the respective primary signal profiles are scanned. 11. An apparatus according to claim 2 including delay means for delaying the operation of said second means relative to that of said first means. 12. An apparatus according to claim 11 wherein said delay means includes setting means for setting the delay to be introduced at a selected value. 13. An apparatus according to claim 2 wherein said first and second means are united in a memory device in the form of an electronic image convertor tube, in which tube the respective collection of primary signal profiles is recorded on a target by means of an electron beam, after which the respective signal profiles are scanned. 14. An apparatus according to claim 2 wherein said first means includes a memory device in the form of a cathode ray tube having a persistent phosphor screen, and that said second means includes an image scanning tube, the collection of primary signal profiles recorded on the screen of said cathode ray tube being displayed by optical means on the entrance window of said image scanning tube. 15. An apparatus according to claim 2 wherein said first means includes a memory device in the form of a continuous two-dimensional magnetic sheet memory, and the first and second means include magnetic heads for the recording of the primary signal profiles and the scanning of the secondary signal profiles. Other info: Inventors: Duinker, Simon (Bloemendaal, NL) Application Number: 814989 Filing Date: 1977-07-12 Publication_date: 1979-09-18 Assignee: N.V. Optische Industrie "De Oude Delft" (NL) Primary Class(es): 378/14 378/901 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Smith, Alfred E. Assistant Examiner: Grigsby, T. N. Attorney: O'Brien & Marks |
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