GB1313098A - Apparatus for recording patterns of electromagnetic radiation - Google Patents

Abstract

1313098 Scintillation camera PICKER CORP 24 June 1970 [27 June 1969] 30691/70 Heading H4F In a scintillation camera in which the output signals from an array of photo-tubes, arranged to detect light flashes produced by a scintillation crystal in response to incident gamma radiation, are selectively combined (decoded) to produce analogue signals representative of the intensity Z and co-ordinates X, Y of the successive light flashes, the co-ordinate signals are converted into digital signals, serially recorded along a record strip, e.g. a magnetic tape for subsequent playback, and reconverted back into analogue signals for display, e.g., on a C.R.T. which may be photographed. The intensity Z and co-ordinate X and Y signals corresponding to each light flash are supplied via an analogue computer to the A/D converter, which computer includes a pulse height analyser so that only co-ordinate signals corresponding to a selected intensity are recorded and displayed. If it is desired to record signals corresponding to two (or more) different intensities (i.e. different radiation energy levels, e.g. radiation emitted by two isotopes) then the photo-tube output signals are supplied to two (or more) analogue computers each including a pulse height analyser. The resulting co-ordinate signals corresponding to different radiation levels are passed to the A/D converter and then stored together with flag signals from the pulse height analysers that indicate from which of the two (or more) channels (analogue computers) the signals being stored are received. If there is only two channels only one flag signal instead of two diffetent flag signals need be generated to identify the signals. In response to a selector switch the X and Y signals may be attenuated by a factor of 2 and signals corresponding to each energy level displayed on separate areas of the display C.R.T. according to the associated flag signals, alternatively all the signals may be displayed to produce a single composite visual display on the C.R.T. screen, or the signals from only one of the channels may be displayed. Calibration of the individual photo-tubes of the scintillation camera may be effected to compensate for variations in gain of any of the photo-tubes or preamplifiers. This calibration is effected using a selector switch which enables any photo-tube output to be selected and fed via a test switch and a multiplexer to a data processor, e.g. an oscilloscope on which a variable-width profile histogram of counts versus horizontal distance or a histogram of counts versus time may be displayed. The display may include a smoothing generator that causes the dots to flow together and present a more continuous pattern. In addition the orientation of the displayed pattern may be rotated. The devices for effecting the analogue to digital conversion and recording of the signals may be switched out of circuit when it is desired to produce a scintillation display quickly.