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Carpenter, James (2014) Low bandwidth laser doppler blood flowmetry. PhD thesis, University of Nottingham.

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Abstract

Laser Doppler Blood Flowmetry (LDBF) has for several decades been applied to measure the flow of red blood cells in living tissue. Laser Doppler Perfusion Imaging (LDPI), a recent advancement which enables full-field blood flow visualisation, is gaining clinical acceptance in fields such as burn diagnostics.

However, video-rate full-field imagers with appropriate sensor and processing capability require large financial and physical resources and this has prompted the development of under-specified systems. These systems may reduce the bandwidth and processing complexity but the question of how they perform compared to their fully specified counterparts remains. The advantages of these cheaper and often highly reconfigurable systems are recognised and so it is beneficial to ask whether any novel processing schemes can reduce the resultant error.

Here a reduced bandwidth LDBF signal processing system has been modelled. Bayesian Inference has been used to show that the Pareto distribution is a likely model for the LDBF power spectrum, despite often being cited as exponential. Methods of evaluating microvascular blood flow have been described and compared. Additionally, one fast algorithm's effectiveness has been explained, and a novel and accurate method using the Hilbert transform has been presented.

By understanding how aliasing modifies the frequency distribution, Bayesian Inference has been used to correct the blood flow output towards gold-standard values. The technique has been shown to correct the output of a low bandwidth CMOS camera imaging a rotating diffuser.

Low bandwidth LDPI systems may be suitable for certain clinical applications where sensitivity to high flow is not required. However, where sensitivity to higher flow than baseline is required, e.g. in burn diagnostics, low bandwidth systems may underestimate the true blood flow leading to misdiagnosis. Nevertheless, low bandwidth systems could be used in this scenario if reliable post-processing is employed, such as that suggested by this thesis.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Crowe, J.A. Hayes-Gill, B.R.
Keywords:	Laser Doppler blood flowmetry, Laser Doppler perfusion imaging, burns and scalds, treatment
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools:	UK Campuses > Faculty of Engineering > Department of Electrical and Electronic Engineering
Item ID:	14267
Depositing User:	EP, Services
Date Deposited:	21 Oct 2014 08:55
Last Modified:	16 Dec 2017 00:20
URI:	https://eprints.nottingham.ac.uk/id/eprint/14267

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