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Title: A theoretical and experimental investigation of an X-ray fluorescence system for in vivo analysis of heavy elements
Author: Shamsale Zafarghandi, M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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A Monte Carlo model with a flexible geometry has been developed to aid the design and otpimization of an annular source for in vivo x ray fluorescence (XRF) analysis of heavy metals. A small change in the geometry can modify the scattered background and the fluorescence signal which will contribute to the minimum detection limit of the system. The clinical motivation for the measurement of some heavy metal such as platinum is the need to investigate the kinetics of Pt-based chemotherapy drugs used for the treatment of head and neck tumours in cancer patients. Accurate measurement of tumour Pt concentration can provide important information in establishing dose-response relationships and therefore optimizing treatment to obtain maximum therapeutic effect. The model incorporates a number of variance reduction techniques to improve the accuracy in the final spectrum obtained in the detector. A new technique for calculating dose and fluence in tissue has resulted in a more uniform distribution of dose and fluence with a better accuracy in averaged dose in an arbitrary square cell in the rz-plane. The simulation of Compton scattering in tissue was modified by incorporating the Doppler shift of bound electrons as well as the incoherent scattering factor. Since the concentration of heavy metals does not modify the scattered x ray in the tissue significantly, the radiation from the heavy metal is calculated by combining the fluence data, the cross section of the heavy metal and its concentration in the tissue in a separate program. The change in geometry was made by moving the detector to the front aperture of the source detector collimator, which allowed the collection of more scattered background and fluorescence signal at the detector. The modified system gives a better detection limit, showing an improvement by a factor of 5 at the surface, decreasing smoothly to a factor of 2 at a depth of 30 mm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available