Development of an optical skin-tissue phantom for visible light radiation studies: experimental measurements and Monte Carlo simulation

Development of an optical skin-tissue phantom for visible light radiation studies: experimental measurements and Monte Carlo simulation

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dc.contributor.author	Yusoff, Muhammad Nur Salihin
dc.date.accessioned	2015-05-27T09:00:48Z
dc.date.available	2015-05-27T09:00:48Z
dc.date.issued	2014-09
dc.description.abstract	This study was carried out to analyse the Monte Carlo (MC) modelling of light-skin diffuse reflectance, with the ultimate goal to develop physical models (phantoms) for use in optical skin studies. The preliminary work was evaluation of computation performance of a personal computer equipped with compute unified device architecture−graphic processing unit (CUDA−GPU) in the simulation of light-skin diffuse reflectance spectra using GPU-based MC code (CUDAMCML). CUDAMCML offers an extremely practical computation time of 6.4 minutes compared to MCML which took 7.6 hours to complete the computation. Thus, a total of 71.19-fold speed-up performance was achieved. The accuracy of result was high with differences of diffuse reflectance values of 0.03–0.68% between CUDAMCML and MCML. The acceleration by CUDA−GPU offers capability of running bulk data in computer-aided skin tissue modelling. The second part of research involved an analysis of sensitivity and response of light-skin diffuse reflectance spectra to multi-design skin-tissue models and characteristics. This analysis showed the importance of melanin depth distribution which should be considered in designing multi-layered skin-tissue model. Addition of complexity to the model causes only less than two minutes increment of computation time. Increase of melanin concentration reduced the values of diffuse reflectance over the spectrum while the profile of ‘W’ curve became less-defined. Increase of blood concentration also decreased the values of diffuse reflectance (particularly for wavelengths < 600 nm) but the profile of ‘W’ curve became more-defined. Increase of epidermal and dermal thicknesses influence the diffuse reflectance spectra but not for subcutaneous fat thickness. The understanding from this work could assist in designing an appropriate skin-tissue model for simulation and aid in choosing an effective light region for skin diagnosis. The third part was evaluation on the challenges, limitations, and possible applications of poly(vinyl alcohol) cryogel (PVA-C) obtained via salt modification. A method for PVA-C production based on modification of the xviii PVA-C properties by rock-salt addition was presented which could simplify the production process and shorten the fabrication time. Under limit of 7.5% concentration, addition of rock-salt was effective in enhancing optical reflectance of PVA-C and producing smoother morphology. Meanwhile, 493, 514, and 626 nm wavelengths showed different response to addition of rock-salt concentration but not to water ratio. The PVA-C obtained via salt modification might be useful for mimicry of certain tissues in optical studies. In the final work, a new approach in fabrication of optical tissue phantoms was proposed by using an integrated materials consist of agar, PVA emulsion, silicone rubber, black poster colour (BPC), and NaCl. The fabrication was simple and convenient with good compatibility between materials components. The absorption coefficient of BPC was found almost flat across 500−700 nm while at 532 and 633 nm it was correlated linearly with BPC concentration. The scattering coefficient of PVA reduced about 75% from its initial values over 500−700 nm while at 532 and 633 nm it was correlated exponentially with PVA concentration. This fabrication approach could reduce specular reflectance, improve accuracy of measurements, and sustain the long-term stability of the tissue phantoms, which might be useful for studying light distribution in skin tissue.	en_US
dc.identifier.uri	http://hdl.handle.net/123456789/787
dc.subject	Optical Skin-Tissue Phantom	en_US
dc.title	Development of an optical skin-tissue phantom for visible light radiation studies: experimental measurements and Monte Carlo simulation	en_US
dc.type	Thesis	en_US

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