Abstract: A medical diagnostic X-ray machine (CT scanner) is disclosed using a technique of filtered or compensated back-projection or layergram to form a picture of a patient slice.

Abstract: Radiographic apparatus is described in which an X-ray tube incorporates a cathode which is heavily driven to produce a strong electron beam. In order to minimize the demands placed on the cathode, the X-radiation emitted by the tube (or the electron beam produced by the cathode and causing the emission of the X-radiation) is monitored and used to control the supply of energy (e.g. heater current) to the cathode.

Abstract: Radiographic apparatus is provided to evaluate the absorption coefficient of a body at each of a plurality of locations distributed over a cross-sectional slice of the body of a patient. A source directs a fan-shaped distribution of radiation through the slice and is orbited to direct the radiation from a plurality of directions. Detectors are provided to detect the radiation emergent from the body along a plurality of paths. A lateral can, which may be along a curved path, is superimposed on the source motion. This is arranged so that over a predetermined time period, it substantially cancels the orbital motion to effect a part of a lateral scan and give some parallel paths through the body. Over several time periods there can be erected a full set of beam paths which not only partly overlap to give comparison of detector sensitivities but also provide the parallel set which although not essential is useful for the convolution processing.

Abstract: In a computerized tomographic apparatus in which relative movement occurs between a fan of radiation and a bank of detectors, at least some of the detectors are required to receive radiation over a range of angles of incidence while at the same time being insensitive to scattered radiation. A dynamic collimating arrangement is described which enables each detector to accommodate said relative movement but nevertheless intercepts a substantial amount of scattered radiation.

Abstract: In computerized tomographic equipment the absorption of penetrating radiation is measured along a plurality of beam paths passing through a region of the body of a patient at different dispositions. Different available processing techniques which may be used with such data require the paths to be distributed in particular ways in relation to the body, for example, in a uniform distribution and in sets of parallel paths. The arrangement of this invention allows the data to be arranged as for paths of different distribution to those for which it was obtained. These paths can be uniform or parallel or both as desired and some may be notional.

Abstract: In an apparatus for examining a body by means of penetrating radiation a source is arranged to direct radiation through the body and a plurality of detectors are arranged to receive it thereafter. The source and detector are arranged to scan the body to obtain data for use in obtaining a distribution of absorption of the radiation for part of the body. For correction for differences in the relative sensitivities of the detectors they are arranged in pairs to examine radiation along substantially identical paths and for correction for drift each detector is caused to examine a substantially identical path at different times.

Abstract: In a radiographic apparatus, a source of radiation is arranged to scan a planer spread of radiation in a plane (or substantially in a plane) about the body of a patient being examined. A plurality of detector devices is arranged to provide data representing the absorption of the radiation along a plurality of paths within the spread, for different orientations in the plane, for processing to determine a distribution of absorption coefficients for a planar (or substantially planar) slice of the body. The arrangement is such that a predetermined number of the detector devices is irradiated by the spread of radiation at any time, and the actual devices irradiated change progressively as the scan progresses.

Abstract: In a method of constructing a representation of the distribution of absorption in a planar region of a body interpolation is provided, between data signals representing absorption of radiation along parallel paths, to provide signals for an increased number of such paths as required for the processing used. The interpolation is performed by forming differences of second or higher order, subdividing the differences and then combining them by running additions.

Abstract: Radiographic apparatus utilizing a plurality of radiation-sensitive detectors to quantify the radiation emerging from a body along respective paths is provided with means for compensating for differences between the sensitivities of the various detectors. The compensating means includes an arrangement for displacing the source of the radiation relative to the detectors and for utilizing output signals obtained from one detector when the source is in its undisplaced and displaced positions respectively to predict what the output of a second detector, closely adjacent the first, should be if the sensitivities of the two detectors were equal. By comparing the prediction with the actual output signal provided by the second detector, differences in sensitivity are evaluated and allowed for. A technique for convolving difference signals rather than net signals is also disclosed.

Abstract: A circuit is disclosed for operating upon output signals indicative of the absorption suffered by penetrating radiation on traversing respective beam paths through a substantially planar section of a body under examination to effect a form of convolution of said signals as described in U.S. Pat. No. 3,924,124. The output signals are applied in time sequence to the circuit and each signal is arranged to traverse the circuit and return to the input thereof in time to be added to the next signal in the sequence. In traversing the circuit, however, a signal is multiplied by a factor less than unity; thus the component of a signal circulating in the circuit, as added to successive signals in the sequence, is progressively reduced.

Abstract: In an apparatus for examining a body by means of penetrating radiation a source is arranged to direct a swath of radiation through the body and a plurality of detectors are arranged to receive it thereafter. The source and detectors are arranged to orbit the body to obtain data for use in constructing a distribution of absorption of the radiation for part of the body. To correct for sensitivity variations in the detectors they are arranged to obtain data for radiation, not having passed through the body, from a further standard source at least twice in the orbital movement.

Abstract: In a radiographic apparatus a source of radiation is arranged to scan a planar spread of radiation in a plane about the body of a patient being examined. A plurality of detector devices is arranged to provide data representing the absorption of the radiation along a plurality of paths within the spread, for different orientations in the plane, for processing to determine a distribution of absorption coefficients for a planar slice of the body. The arrangement is such that a predetermined number of the detector devices are irradiated by the spread of radiation at any time and the actual devices irradiated change progressively as the scan progresses.

Abstract: In an X-ray apparatus for examining a body a source of a fan of radiation and detectors of the radiation along beams in the fan are traversed in a plane to provide data for a plurality of sets of parallel beams in the plane. An orbital motion is provided to give data for further sets at different inclinations in the plane. The data can be processed by arrangements using such "parallel" sets. The orbital motion is continuous during the traverse but the extent of angular change in one lateral scan is kept small so that lack of parallelism in the "parallel" sets does not give excessive errors.

Abstract: Radiographic apparatus is described for evaluating the absorption coefficient of a body at each of a plurality of locations distributed over a planar slice disposed cross-sectionally of the body. A source is arranged to produce a fan-shaped, planar beam of radiation which is directed through the body, in the plane of said slice, and the source is orbited around the body about an axis perpendicular to the plane of said slice. Detectors are provided, and orbited in synchronism with the orbital motion of the source, each to detect the radiation emergent from the body along a plurality of paths. In order to render the paths substantially linear despite the orbital motion, a lateral scan is imposed upon the source which is sufficient, over a predetermined time period, to substantially cancel the orbital motion and replace it by a lateral motion.

Abstract: Radiological apparatus is described which is capable of performing analogue superposition of respective signals indicative of the absorption suffered by penetrating radiation on traversing each of a plurality of co-planar, linear paths through a body, some of which paths intersect. The signals are altered by processing to render them suitable for additive superposition, and the superposition is achieved by means of at least one charge storage tube. The altered signals, or signals related thereto, are applied to the target (or targets) of the tube (or tubes) and are deposited on respective linear regions thereof, the orientation of a linear region relative to the target (or targets) corresponding to the orientation relative to the body of the path giving rise to the relevant signal.

Abstract: In a method of constructing a representation of the distribution of absorption in a planar region of a body interpolation is provided, between data signals representing absorption of radiation along parallel paths, to provide signals for an increased number of such paths as required for the processing used. The interpolation is performed by forming differences of second or higher order, subdividing the differences and then combining them by running additions.

Abstract: For examining a body by means of X-rays or other penetrating radiation, data is determined representing the absorption suffered by each of a plurality of beams which are passed through the body. The beams are effectively arranged in a plurality of sets of beams, in a single plane, at many different angles. The arrangement is such that the amount of information provided by the beams is a function, which is in part non-uniform, of the beam position in the set. A reconstruction of the distribution of absorption of the radiation within a part of the body is derived from the absorption data so determined.