Emi, LLC

Christopher Archibald LeMay

Godfrey N Hounsfield

Robert J Froggatt

Robert Paul Randall

John Edward Best

Alan George Blay

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.

Radiography

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.

During demonstration of a job sequence by an operator, an image error signal generated by a camera raster, is fed into a register, where it corrects the actual raster position, which is then stored in a data store. A tachometer signal from a joint of a model of a robot arm being manipulated by the operator is subtracted from a corresponding tachometer signal on the robot arm and passed to a processor. The processor uses an iterative procedure to evaluate a set of constants from the tachometer signals from the model. The servo signals are subsequently used to enable the robot arm to repeat the job sequence.

Robot control systems

A CT scanner is disclosed in which sets of X-radiation measurements, each set being for a fan-shaped distribution of beam paths, are used by a convolving circuit as though they were for sets of parallel beam paths. The inaccuracies due to this are countered by using correction factors, one for each pixel of the final picture of the patient slice, which correction factors are derived by the use of a phantom of known X-ray response. In addition, a special interpolation technique is disclosed to facilitate accurate back projection.

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.

Radiology

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.

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. In examining a body by means of X-rays or other penetrating radiation, signals are derived representing the logarithm of the absorption of individual beams in sets of parallel beams which are passed through the body in a single plane at many different angles. Corresponding to each such signal there is derived a summation signal produced by a process of convolution using a convolution function of a special form which is such that the convolution can be effected in a recirculatory circuit. An image of the plane section is reconstructed by selectively superimposing the summation signals producing the effect of what may be termed a compensated layergram.

In an ultrasonic investigating apparatus a transducer can receive reflections from points in the body for which the position in one direction is relatively well known as a result of accurate range gating but for which the position in another direction is relatively less known in view of the relatively wide ultrasound beams used. Thus the reflections are only known as originating from lines in the body. These line integrals of reflection of ultrasonic energy are processed by methods appropriate to line integrals in general, as known for line integrals of X-ray absorption for example, to more accurately position the reflecting points in the body. A propagation velocity distribution can also be determined for the body to further improve the accuracy.

Ultrasonic apparatus

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.

In a computerized tomographic system in which a fan of radiation effects a rotational scan and the detectors are fixed, collimation is achieved by means of plates hinged adjacent the detectors. The plates are moved by means of a ring, the center of which is caused to execute a circular motion about the center of rotation of the system. The ring carries projections which engage with the ends of the plates remote from the detectors.

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.

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.

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Osterley, United Kingdom

Christopher Archibald LeMay