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Monte Carlo simulations of the light interaction with blood vessels in human skin in the red wavelength region
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
1998 (English)In: Proceedings of SPIE, 3252(06),44-53 / [ed] A V Priezzhev, T Asakura, J D Briers, San José: SPIE , 1998, 44-53 p.Conference paper, Published paper (Refereed)
Abstract [en]

An attempt was made at determining if the elastically backscattered Doppler shifted light from cutaneous blood vessels merely emanates from the peripheral parts, or also from the more central core of these vessels, after illumination by red laser light (632 nm). A multilayered, semi-infinite Monte Carlo model of human skin was constructed accordingly, with separate layers or epidermis, dermis including blood, inferior vascular plexus and subcutaneous fat. Two concentric cylinders of infinite length and with varying diameters, representing core and peripheral parts of a blood vessel, were located at various depths in the skin model, either in the superior or inferior vascular plexus. In order to test the stability of the model predictions, widely varying values of the optical properties were employed in the calculations, trying to encompass most of the extreme values found in the literature. The number of photons Doppler shifted by a fixed size central core of a small blood vessel, is independent of the volume of blood surrounding this core in the rest of the blood vessel, provided the total number of detected photons is maintained constant, and the vessel dimensions are within human physiological limits. For the source/detector system simulated (one optical fiber 700 micrometer diameter), backscattered light Doppler shifted in superficial blood vessels constituted almost all the photons detected, with only very few photons having interacted with the inferior plexus.

Place, publisher, year, edition, pages
San José: SPIE , 1998. 44-53 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-32585DOI: 10.1117/12.311897Local ID: 18499ISBN: 9780819426918 (print)OAI: oai:DiVA.org:liu-32585DiVA: diva2:253408
Conference
Optical Diagnostics of Biological Fluids Ill, Bi0S'98, San Jose, CA, USA, 1998
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-09-12Bibliographically approved
In thesis
1. Photon migration in tissue: laser induced fluorescence for cancer diagnostics and influence of optical properties on microvascular Doppler spectroscopy
Open this publication in new window or tab >>Photon migration in tissue: laser induced fluorescence for cancer diagnostics and influence of optical properties on microvascular Doppler spectroscopy
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser induced flourescence (LIF) is an "optical biopsy" method, based on the selective accumulation of fluorophores in neoplastic tissue. Two recently developed, non-photosensitizing tumor seeking carotenoporphyrins were assessed regarding tumor selectivity, and biodistribution, in experimental animals. A tumor to peritumoral ratio of 5-6:1 was seen in the background free substance related fluorescence in vivo, as well as ex vivo. Cerebral cortex and skeletal muscle displayed a low, and liver a high substance related fluorescence.

Laser Doppler flowmetry (LDF) is based on the spectral broadening of monochromatic light, that interacts with moving red blood cells in tissue. The power spectral density of the backscattered light can be processed to yield an estimate of microvascular tissue perlusion. Using a Monte Carlo simulation model of human skin, it is demonstt·ated that for a particular light delivery/detection arrangement, Doppler shifted photons that originate from the central core and peripheral parts of blood vessels of physiological dimensions, both contribute to the detected signal. Further, more than 10 times as many photons will interact with the superficial as with the deep vascular plexus. However, due to greater velocities and concentrations of the moving scatterers, the profound circulation still may yield a greater contribution to the LDF perfusion estimate.

A multiple polynomial regression method for prediction of photon pathlength and optical properties in tissue, at surlace source detector separations up to two millimeters, was developed. Using the diffuse, backscattered reflectance profile from an array of optical sensors as predictors in the model resulted in root-meansquare errors of less than three per cent for the estimated pathlength. Caucasian human skin displayed a maximum in vivo variation of ~35 % in the photon pathlength between individuals in similar locations, and within individuals comparing fingertip and forearm skin, as a result of varying optical properties.

Assuming a homogenous tissue perlusion, the pathlength variations will induce a corresponding variation in the LDF petfusion signal, which can be compensated for by linearization and pathlength normalization, making intra- and interindividual comparisons of the LDF perfusion estimate feasible.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 123 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 735
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29435 (URN)14781 (Local ID)91-7373-179-X (ISBN)14781 (Archive number)14781 (OAI)
Public defence
2002-05-31, Administrationsbyggnadens aula, Universitetssjukhuset, Linköping, 13:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-10-08Bibliographically approved

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Nilsson, Gert

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