Emi, LLC

Thorn Emi Plc

Colin C Oliver

Godfrey N Hounsfield

Richard G Gillard

Brian Herbert Lill

Stephen Ronald Bates

A communication system utilizing the electrical-supply wiring of mains circuit has an interface unit for an intruder-sensor. Unit has a transmitter for sending FSK-modulated messages and a capacitor to store adequate energy to power transmitter only for the time-duration of a message. The system also has a interface unit for a temperature sensor.

Data communication system

A temperature sensor is incorporated within a housing having a silicon window through which infra-red radiation can enter. Mounted on a support structure is a semiconductor fabrication consisting of a reference junction and a sensing junction, covered with a black absorber. The reference junction is responsive to the temperature of the housing, whereas the sensing junction is responsive to the temperature of the housing and also the temperature of a remote zone from which infra-red radiation can enter the housing via the window. A Peltier heater/cooler controls the temperature of the housing, which temperature is monitored by a sensor to provide a measure of that of the remote zone.

Temperature sensing arrangement

A radiographic apparatus contains at least one source and at least one detector bank mounted on respective concentric annular rings; the patient's body being disposed inside the smaller ring. The rings are rotated in opposite directions and at such respective angular velocities that the effect of a lateral sweep of the detectors and source across the body is achieved with purely rotational movements. Advantageously, one ring carries two sources disposed diametrically opposite one another and the other ring carries three banks of detectors distributed equi-angularly therearound.

Radiography

The output of the circuit is connected to the grid of an X-ray tube (X) by a long cable having a large capacitance (C.sub.c). A 25 kHz variable amplitude drive circuit (1) applies a continuous DC regulating voltage to a first rail (RL2) via a first transformer (T1), rectifier (D1, D2) and a filter (F1). A 25 kHz fixed amplitude drive circuit (2) periodically generates a blanking voltage which is applied to a second rail (RL3) via a second transformer (2), rectifier (D3, D4) and a Zener diode (Z1). The first rail (RL2) is coupled to the second rail (RL3) via a clamping diode (D.sub.c) which is reversed biased by the blanking voltage, so that the regulating voltage is overriden. In order to quickly discharge the large capacitance (C.sub.c) to achieve a rapid transition from blanking voltage to regulating voltage, a discharge path is connected across the output, the path including a transistor (T1). A control circuit (3) comprises a capacitor (C2) which stores an actuating voltage (V.sub.T) produced when the blanking voltage is produced. The circuit (3) also comprises an RC network (R1, C1), in parallel with the control circuit capacitor (C2), the RC junction being connected to the base of the transistor (T1) and to the second rail (RL3). When the blanking voltage is produced the RC junction is maintained at a high voltage and the transistor (T1) is non conductive. During the transition from blanking to regulating, the RC network defines a desired transition voltage which is applied by the transistor (T1) ro the second rail (RL3) and this controls the discharge of the cable capacitance.

Circuit for controlling the grid potential of a pulsed X-ray tube

In a computerized tomographic radiographic apparatus a source directs a fan distribution of radiation through a patient to be detected by a bank of detector devices. The detector devices are disposed on a circular path centered on an axis about which the source orbits. The detectors are fixed relative to the body so that the radiation is incident on different detectors as the source orbits. Each detector devices receives radiation in different orientations, in the fan distribution, at different times.

In a computerized tomographic apparatus, different detectors are caused to receive radiation along substantially the same beam path through the body in order to permit the evaluation of differences in performance of the detectors. This evaluation is average with other evaluations made in respect of the same detector for other beam paths so as to reduce the risk that erroneous performance differences may be evaluated in the event that any of the relevant beam paths lies adjacent a bone edge in a patient's body. Also disclosed are techniques for electronically deflecting the radiation so that part at least of the radiation is taken clear of the body and can be detected to provide reference signals.

In a radiographic apparatus in which a scanning X-ray tube is used it is desirable to properly relate the scanning of the X-ray origin with other scanning motions of the apparatus. In this arrangement a scan progress detector is inserted partly into the radiation to detect its scan motion. In one eXample it is a collimator block to provide a sinusoidal output as the scan progresses. Pulses derived from the sinusoid are compared with signals representing an ideal scan and the differences between them used to correct the source scan control.

In a radiographic apparatus for deriving a representation of the variation of absortion of radiation in a slice of the body of a patient, data are derived which represent the intensity of radiation transmitted through the body. Detectors arranged to receive the transmitted radiation also receive further radiation, scattered within the body, which can cause errors in the final representation. The invention interposes occulting means between the radiation source and some detectors to obtain data representing only scatter to correct the transmission readings of the other detectors. The same detectors may serve both purposes at different times.

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Slough, United Kingdom

Colin C Oliver