The compton effect gamma camera detector system

Fleming, John Sterland (1975) The compton effect gamma camera detector system. University of Southampton, Doctoral Thesis.

Abstract

A recently proposed technique for the imaging of distributions of a gamma emitting isotope using the Compton effect has considerable potential advantages over current imaging devices. Its operation requires a detector which is capable of the three dimensional positioning of successive Compton interactions occurring within it together with simultaneous measurement of the energy losses at the individual interactions. The preferred form of detector is considered to consist of a number of thin semiconductor radiation detectors, each capable of two dimensional position resolution, stacked on top of one another. In the detector system described each of these two dimensional detectors is an orthogonal electrode silicon surface barrier radiation detector. Parallel gold strips on the etched face of a silicon slice form the surface barrier with the silicon and orthogonal gold strips on the opposite face, which has a lapped finish, form the ohmic contact. Incident gamma rays interacting in the detector give rise to a pulse in one of the strips on each side of the detector. Identification of these strips defines the position of the interaction in two dimensions and measurement of the size of either pulse gives the energy loss. The accuracy with which the detector can measure the position coordinates and the energy loss largely determines the performance of the system as an imaging device. Various techniques for the construction of such two dimensional position sensitive detectors are described and the relative merits of the different methods are discussed with respect to the constructional design and to performance in terms of energy and position resolution. The theory of the factors affecting these parameters and their practical measurement are presented and the results are discussed in relation to the operation of the detectors as the Compton camera detector system. The results indicate the feasibility of constructing a detector system to operate using the Compton camera principle with image resolution equivalent to current imaging devices and with about ten times greater sensitivity. A prototype device to prove the system is currently being built using the detectors described in this thesis.

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