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Title: A scattering method for bone density measurements with polychromatic sources
Author: Koligliatis, Thanos
ISNI:       0000 0001 3601 5464
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1990
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The aim of this thesis has been to investigate the use of x-ray tubes as irradiating sources in Compton scatter bone densitometry in order to diagnose early osteoporosis. The use of polychromatic sources requires that effects such as multiple scatter and beam polychromaticity are taken into account. The effect of multiple scatter was evaluated for a series of different size anthropomorphic phantoms which represent sites of interest in osteoporosis studies, namely the lower forearm, the femoral neck and the lumbar spine. It was found that multiple scatter is a highly geometrical problem and the effects of multiple scatter are least important at scattering angles between 30° (for a large examination site) and 60° (for a small examination site). For a scattering angle of 50°, typical multiple scatter correction factors (mcfs) are 0.46, 0.45 and 0.35 respectively, for the lower forearm, femoral neck and lumbar spine phantoms studied. The effect of beam polychromaticity on density measurements is much less important than that of multiple scatter. Information from the computer model was used to design and build a densitometer. Densities were measured in-vitro using anthropomorphic phantoms. Different collimator systems were studied and higher precision was achieved with multihole focussing detector collimators. Pre-patient photon beam filtration had only a small effect on the precision of the measurements whereas the dose was decreased by a factor of 5 under these conditions. The performance and the stability of the x-ray generator were found to be a limiting factor in the precision of the density measurements.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Osteoporosis