Abstract: A computerized tomographic apparatus is described in which the source produces a fan-shaped distribution of X-rays and the detectors extend across the distribution so as to respectively receive radiation propagated along different beams of the distribution. The source and detectors are rotated around a patient about an axis intersecting a desired cross-sectional slice of the patient. The beam paths, through the body slice, along which radiation is projected for any one source position are divergent, but output signals relating to the totality of beam paths irradiated during a considerable rotational movement of the source around the body can be sorted into sets relating to parallel beam paths, to assist in processing them. However the sets of paths exhibit non-uniformity of spacing which can cause difficulty if convolution processing is employed. In order to reduce or overcome this problem, the present invention provides that the spacing between adjacent beams varies across the distribution.

Abstract: A multiple rate discharge circuit is disclosed for application, for example, to an integrator connected to a radiation detector as used in computerized axial tomography. The integrator is charged for a given time and then allowed to discharge at a first, relatively slow, rate for a predetermined time. If, at the expiry of the predetermined time, charge remains in the integrator, the discharge rate is considerably increased. The second-mentioned discharge rate is preferably about eleven times faster than the just-mentioned rate, and the two rates are achieved by the selective connection of resistive discharge paths to the integrator.

Abstract: The specification discloses a scintillator crystal configuration which enables a group of crystals to be closely packed together, for example in a V-formation. Each crystal receives x-radiation through an input face, which is of small area, and emits light through an output face, to which a photodiode is preferably attached and which is therefore of larger area than the input face. Also disclosed is a medical radiographic apparatus incorporating an X-ray detector unit containing a number of such crystals.

Abstract: In a computerized tomographic apparatus, a scanning device is used to project radiation through a slice disposed cross-sectionally of a body along many sets of pencil-like beam paths. Each set of paths is characterized by being oriented at a respective angle, or in some circumstances a respective mean angle, in the slice. The absorption suffered by the radiation on traversing each beam path is measured and, from all the values of absorption, the coefficient of absorption of the radiation at each of many locations distributed over the slice is calculated. The invention extends the number of paths in some only of the aforementioned sets to include further paths traversing a zone outside the slice and the absorption values relating to these further paths are used to improve the accuracy of the calculation of the coefficients of absorption.

Abstract: In a computerized tomographic apparatus in which a wide angled, fan-shaped distribution of radiation is rotated around a body to be radiographed and detectors are provided to produce electrical output signals indicative of radiation emergent from the body along many beam paths, the signals can be sorted into sets relating to parallel sets of beam paths distributed across a cross-sectional slice of the body. However, the beam paths to which the signals so sorted relate are non-uniformly spaced beam paths, and the invention provides means whereby a processing technique known as convolution, which is of proven usefulness in computerized tomography but which, for best accuracy, operates upon output signals relating to sets of uniformly spaced, parallel beam paths, can be applied to the signals as sorted and a post-processing error compensation is effected to restore accuracy.

Abstract: In a method of examining a body by means of penetrating radiation a source is arranged to provide a fan shaped spread of the radiation and a detector examines the intensity of a plurality of individual beams of radiation defined from the fan. The source and detector are orbited about the body so that the beams are provided at a plurality of angles relative to the body. In the associated processing, the data signals from the detectors are combined so that each combined signal relates to two beams 180.degree. to each other in the orbital movement. A further selection is also made of the data signals so that they are provided to a further processing stage in sets for which each set is of data signals relating to beams which are substantially parallel to each other.

Abstract: In a computerized tomographic apparatus which involves both rotational and translational scanning movements of the source relative to the body, the translational movements are timed so that the radiation passes through, or adjacent, a mobile organ (such as the heart) of the body while that organ assumes a predetermined position, or range of positions, in its movement.

Abstract: For a computerized radiographic apparatus, providing a cross-sectional representation of absorption of radiation in the body of a patient, there is provided a television standard display of cross-section. The display can be high-definition monochrome or in color. An arrangement is provided in which the high definition monochrome is displayed with low saturation color-wash superimposed thereon to highlight significant features in the monochrome picture.

Abstract: Radiographic apparatus is described in which a thin planar slice of the body is examined by a swath of penetrating radiation such as X-rays. Collimators are provided for collimating the radiation after it has passed through the body into a set of beams which are directed into respective detectors. The swath of radiation, the collimeters and the detectors are orbited in the plane of the slice so that the beams pass through the body from many different angular directions. Means are provided for additionally displacing at least the collimators relative to the source so that the relative position of the beams and gaps between the beams are changed during the orbital movement.