Nixon-Hill, Miranda Helen Sarah;
(2022)
Developing a home monitoring system for patients with chronic liver disease using a smartphone.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Liver disease is a growing problem in the UK, and one of the major causes of working-age premature death. Patients with advanced liver disease are typically admitted to hospital on multiple occasions, where they are stabilised before discharge. At home, there is little or no monitoring of their condition available, making it difficult to time additional treatment. Here, a system for non-invasive assessment of serum bilirubin level is proposed, based on imaging the white of the eye (sclera) using a smartphone. Elevated bilirubin level manifests as jaundice, and is a key indicator of overall liver function. Smartphone imaging makes the system low cost, portable and non-contact. An ambient subtraction technique based on subtracting data from flash/ no-flash image pairs is leveraged to account for variations in ambient light. The subtracted signal to noise ratio (SSNR) metric has been developed to ensure good image quality. Values falling below the experimentally-determined threshold of 3.4 trigger a warning to re-capture. To produce device-independent results, mapping approaches based on image metadata and colour chart images were compared. It was found that introducing a one-time calibration step of imaging a colour chart for each device leads to the best compatibility of results from different phones. In a clinical study at the Royal Free Hospital, London, over 100 sets of patient scleral images were captured with two different smartphones and paired clinical information was recorded. A filtering algorithm was developed to tackle the high density of blood vessels and specular reflection observed in the images, yielding a 94% success rate. Strong cross-sectional and longitudinal correlations of scleral yellowness and serum bilirubin level were found of 0.89 and 0.72 respectively (both p<0.001). When the proposed processing was applied, results from the two phones were demonstrated to be compatible. These results demonstrate the strong potential for the system as a monitoring tool.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Developing a home monitoring system for patients with chronic liver disease using a smartphone |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10161478 |
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