GB1512571A - Process and apparatus for the determination of the spatial distribution of radioactivity in an object - Google Patents

Abstract

1512571 Radio-active position detector INSTITUT PASTEUR 25 April 1975 [25 April 1974 27 Aug 1974] 17234/75 Heading GIA [Also in Division H1] A proportional counter detector for sensing the spatial distribution of radio-activity within an object differs from the prior art indicated generally in Fig. 1 in that provision is made for mounting the radio-active sample inside the detector on supports 38. It is stated that this increases counting efficiency since the low energy particles for which the detector is intended e.g. the emission from 125 I , need travel only a short distance before collection on wire 6. In operation 1300 volts are maintained between wire 6 and cathode 8' and a mixture of gases e.g. argon and methane is introduced into chamber 9 to raise it to a pressure above atmospheric. Radio-active emission e.g. γ-rays ionizes the gas creating a charge on wire 6 resulting in a current pulse to each end of the wire 6. The difference in timing of such pulses from the two ends is sensed by a time-amplitude converter D receiving signals from threshold detectors 14 connected to the two wire ends. The resulting amplitude is registered as a position along a horizontal axis on multi-channel analyzer E and all the particles for each position are registered along a vertical axis to produce a histogram. Pulses below a given minimum amplitude, indicative of particles travelling too far, are eliminated by gating converter D receiving pulses from a minimum threshold detector 18. Two dimensional measurements may be made.