Court, Laurence Edward;
(1995)
An investigation into the use of charge-coupled devices for digital mammography.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis describes the design, optimisation, construction and evaluation of a laboratory based digital mammography system which uses phosphor coated charge-coupled devices (CCDs) for x-ray detection. The size mismatch between the breast and the CCD is overcome by operating the CCD in time delay and integration (TDI) mode and scanning across the breast. Multiparameter optimisations have been carried out for a wide range of digital mammography system configurations and requirements, with the aim of optimising the image quality for a given patient dose. The influence of slot width, exposure time, focal spot size, detector resolution and noise level, dose restrictions, patient thickness and x- ray tube target on the system configuration to give optimum image quality is examined. The system is fully characterised in terms of responsivity, dark current, modulation transfer functions (MTFs), noise power spectra (NPS) and spatial frequency dependent detective quantum efficiency (DQE(f)). Direct interactions of x-rays with the CCD are shown to give a significant increase in the high frequency values of the MTF. These interactions also act as a source of noise and act to significantly reduce the DQE(f) at all frequencies. A subjective comparison of images produced with the optimised prototype system with those produced using a conventional film-screen detector shows that these interactions must be removed if the prototype system is to produce images of equal quality to those currently produced using film-screen combinations. Other improvements to the system are suggested.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | An investigation into the use of charge-coupled devices for digital mammography |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Health and environmental sciences; Charge-coupled devices |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10102636 |
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