Development of a computerised tomographic gamma-ray scanning system for non-destructive testing
The process of computerised tomography (CT) has been developed for
medical imaging purposes using a variety of X-ray scannars. So far,
little attention has been paid to industrial applioaticns of
technique, largely because of the constraints of expense.
An investigation was made of the suitability of one medical scanner, the
EMI CT5005, as an industrial scanning tool. This showed up a variety of
problems when scanning non-medical objects, and suggested an alternative
approach to the problem. This was to construct an experimental scanner
based on gamma-ray sources, to overcome the problems of beam hardening,,
and provide versatility and, perhaps, portability. The greatest
limitation on this sort of device is the time needed to produce a scan.
However, even with small laboratory sources it seemed possible to
produce a usable scanner.
This experimental scanner was constructed and developed to the stage of
producing very acceptable images, albeit of moderate resolution.
This thesis outlines the basic theory of reconstructing images using CT,
and describes the considerations leading to the development of the
experimental scanner. The scanner itself is described, along with
details of control, data processing, and the problems encountered. The
statistical limitations on the scanner are described, and the way these
affect the quality of the final CT image is investigated in detail. A
variety of applications of the scanner are suggested, both in its
present form and with foreseeable development, and a catalogue of the
scans obtained using the scanner is provided.