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Towards non-invasive, in-vivo quantification of haemoglobin concentrations using spectroscopic optical coherence tomography

Versteegen, D.P.E. (2021) Towards non-invasive, in-vivo quantification of haemoglobin concentrations using spectroscopic optical coherence tomography.

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Abstract:Anaemia is a condition in which the concentration of red blood cells in blood is too low. Anemia has several causes, for example iron deficiency, nutritional deficiencies and acute or chronic inflammation. A lower concentration of red blood cells can result in fatigue, weakness or shortness of breath. Anaemia is common among neonates, especially preterm neonates. The diagnosis is assessed by drawing blood and analysis by a haematology analyzer. Due to their limited total blood volume, neonates can loose up to 30\% of their total blood volume by sampling. A method to compensate for this loss, is by a red blood cell transfusion. Up to 90\% of preterm neonates require at least one red blood cell transfusion. In recent years, non-invasive devices have been developed to measure the haemoglobin concentration. These devices have a limited accuracy, due to using an average optical path length. Optical Coherence Tomography (OCT) is a non-invasive, promising technique, which has the advantage of a known and controllable optical path length. Therefore, OCT has the potential to measure in-vivo haemoglobin concentrations at a higher accuracy than currently available devices. This thesis focuses mainly on the characterization of a spectral-domain OCT setup and performing pilot in-vivo haemoglobin concentration measurements. Chapters 1, 2 and 3 give an introduction to OCT, a theoretical background and explains basic OCT principles. Chapter 4 describes the characterization of the setup according to the wavelength bandwidth, axial resolution, galvanometer scanner, lateral resolution, depth of field, signal-to-noise ratio, full-spectrum sensitivity roll-off and the spectrally dependent roll-off. Each of these characteristics of OCT is explained and measured (except for the depth of field). The theoretical values align with the experimentally obtained values. Chapter 5 describes the measurements on blood-mimicking phantoms. The retrieved total attenuation spectra and fitted absorption and scattering coefficients did not have a high accuracy. Chapter 6 explains OCT angiography, which is used to image blood vessels in the skin. This chapter also explains the result of a phase variance method, which is used on an in-vivo skin data set.Phase variance contrast was a tool to visualize regions of potential haemoglobin and to fit healthy haemoglobin concentrations to. Overall, the setup has been characterized by eight characteristics, where the theoretical values align with the theoretical ones. Furthermore, pilot in-vivo measurements of the skin have been performed, which were processed by a phase variance algorithm. The regions with high phase variance corresponded to a fitted total haemoglobin concentration within the limits of healthy adults (12-18 g/dl). However, despite the strong indication of blood by the phase variance and the fitted haemoglobin concentrations, the accuracy of these measurements is limited by noise. As a whole, this work has taken the first step toward non-invasive, in-vivo quantification of the total haemoglobin concentration.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:42 biology, 44 medicine
Programme:Biomedical Engineering MSc (66226)
Link to this item:http://purl.utwente.nl/essays/85620
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