Investigation of diffuse reflectance spectroscopy and acousto-optics for deep tissue imaging and diagnostics
Loading...
Files
Full Text E-thesis
Date
2024
Authors
Amissah, Michael
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
This dissertation explores two frontiers of optical technologies in biophotonics: diffuse reflectance spectroscopy (DRS) and acousto-optic interactions in tissues. The work capitalizes on the potential of DRS for objective surgical examinations of tissues, focusing on colorectal cancer (CRC) as a case study. It uses DRS as a tool for real-time surgical guidance, offering surgeons the unparalleled ability to distinguish between healthy and malignant tissues during operations. A total of over 2889 spectral data, spanning both visible and near-infrared wavelength ranges, were used in this study. These spectra were collected from excised tumors and tissue samples from 47 patients who underwent colorectal cancer surgeries. The wavelength response to the biochemical composition of CRC were explored using two different source to detector distances (SDD) or probes. The study with short-SDD probe yielded (93.5 ± 2.4)% sensitivity and (94.0 ± 1.7)% specificity whereas
using long-SDD probe to sample deeper tissue layers yielded (96.1 ± 1.8)% sensitivity, (95.7 ± 0.6)% specificity. Furthermore, the acousto-optic approach was employed for non-invasive sensing of optical changes in blood-mimicking fluids with varying viscosities in blood-mimicking fluids (acqeous glycerol) from 2 cP to 7 cP which covers the range of human blood viscosities. The acousto-optic signal and in effect, the modulation depth was found to have a negative correlation to increase in glycerol concentration of non scattering samples while there was a direct relationship with increased optical scattering. This was achieved by employing
coherent light with digital heterodyne holography as an ultrasound-tagged light detection mechanism. The holograhic detection of acousto-optic signal for studying tissue decorrelation times via flow dynamics was explored. The decorrelation times were found to decrease as flow speed increases. Insights gained from these studies are important for advancing understanding of fluid mechanics in deep tissue dimensions and could be useful in developing tools for non-invasive, in situ monitoring of blood viscosity changes during surgical operations, as well as for diagnosing blood coagulopathies.
Description
Keywords
Diffuse reflectance spectroscopy , Acousto-optics , Digital holography , Colorectal cancer , Decorrelation , Ultrasound -tagged light
Citation
Amissah, M. 2024. Investigation of diffuse reflectance spectroscopy and acousto-optics for deep tissue imaging and diagnostics. PhD Thesis, University College Cork.