Emi, LLC

Robert J Froggatt

Godfrey N Hounsfield

Christopher Archibald LeMay

Brian L Dalton

William Spencer Percival

John Edward Best

In a computerized tomographic apparatus in which the requisite absorption data are derived by rotating a source of fanned radiation around a body to be examined and detecting radiation emergent from a cross-sectional slice of the body at many times during the rotation the data, when assembled into sets relating to parallel beam paths through the slice, tends to relate to beam paths which are non-uniformly spaced across the slice. Some techniques for processing such data to produce a representation of the variation of absorption of said radiation over the slice should preferably have said data presented thereto in the form of sets relating to substantially uniformly spaced, parallel beam paths. The application of this invention provides considerably more data then is actually required for the processing so that data relating to beam paths of the required numbers and dispositions can be derived therefrom.

Radiography

The invention relates to a flat plate X-ray detector. In one example a back plate of a flat xenon detector has coaxial cables in a conducting solid matrix connected to the power supply. Each cable center conductor is a small capacitor which charges in response to ion collection. The signals are derived via a commutator. In another embodiment the back plate is an anisotropic plate discharged in a spiral pattern similar to a gramophone record groove.

Detector for responding to a two-dimensional pattern of X-radiation

In order to monitor the progress of a deflected electron beam across the target of an X-ray tube, the emitted X-radiation is monitored, by allowing radiation to impinge, via a common aperture, upon two or more radiation sensitive detectors, to produce a progress signal which is compared with an ideal progress signal to generate error signals in the event of departure of the monitored progress from the ideal progress.

X-ray tube arrangements

In a computerized tomographic CT scanner, a lateral scan of a pencil beam of radiation is effected by causing an apertured, annular collar to rotate around a source of a fan-shaped spread of radiation. The motion of the collimator causes a pencil like beam to sweep angularly across the body. Successive sweeps, caused by successive apertures, are in the same direction.

In therapeutic radiographic apparatus it is desirable to maintain the penetrating radiation in passing through tissue to be irradiated, rather than surrounding healthy tissue, despite movements of the patient. A shadowgraph radiographic picture of part of the patient is obtained by derivation from cross-sectional radiographic pictures from computerized axial tomography (CAT) apparatus. A similar shadowgraph picture is obtained, during therapy treatment, by collecting the therapy radiation after passing through the body. The two pictures are compared to determine the position of the therapy radiation relative to the tissue to be irradiated and the position is adjusted in response to the comparison.

Radiographic apparatus

In a scanning radiographic apparatus, of a type which is particularly suitable for examining inanimate objects, a fixed source and detectors irradiate an object to be examined along a plurality of beam paths. The object is moved in relation to the source and detectors to direct the radiation along a sufficient number of beam paths to allow suitable processing. The object is, for that purpose, mounted on a turntable which can also execute a reciprocating lateral motion relative to the source and detectors.

A computerized tomographic apparatus is disclosed, as well as a method of operating such apparatus. In circumstances where collimation between the body under examination and the radiation-sensitive detector means is difficult to apply, errors in evaluated absorption coefficients for locations distributed over a cross-sectional slice of the body due to scatter within the slice are reduced by producing a first estimate of the distribution of said absorption coefficients, using this estimate to obtain an indication of the amount of scatter likely to arise from the various locations when irradiated along different paths and using such indication to effect scatter compensation.

Treatment of absorption errors in computerized tomography

In an apparatus for examining a body with penetrating radiation a source and detector arrangement scan about the body to irradiate the body along a plurality of beam paths lying in a plane. Output signals are provided from weighted components where each component relates to the absorption of the radiation along one of a set of adjacent and substantially parallel beam paths. The weighting is according to a function chosen so that the output signals are restricted to a chosen spatial frequency band to reduce errors in a representation, if the distribution of absorption of the radiation through the body, constructed from the output signals. The weighting may be provided by optical means between scintillator crystals and photomultipliers forming the detector arrangement.

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Southall, United Kingdom

Robert J Froggatt