Laser-Based Cancer Diagnostics and Therapy - Tissue Optics considerations.
(1995)- Abstract
- Near-IR light penetrates deeply into tissue, but as the scattering coefficient is much
larger than the absorption coefficient in this wavelength region, direct viewing
through tissue is very difficult. In order to detect and locate inhomogeneities
located inside tissue a time-resolved technique was developed, based on gated
viewing, i.e. detecting the first arriving photons with the shortest path through the
tissue. The focus was on developing a technique to substitute X-rays for finding
breast tumours. Mode-locked lasers and diode lasers were used as light sources. As
detection techniques time-correlated single photon counting was used as well as a
streak camera.... (More) - Near-IR light penetrates deeply into tissue, but as the scattering coefficient is much
larger than the absorption coefficient in this wavelength region, direct viewing
through tissue is very difficult. In order to detect and locate inhomogeneities
located inside tissue a time-resolved technique was developed, based on gated
viewing, i.e. detecting the first arriving photons with the shortest path through the
tissue. The focus was on developing a technique to substitute X-rays for finding
breast tumours. Mode-locked lasers and diode lasers were used as light sources. As
detection techniques time-correlated single photon counting was used as well as a
streak camera. Tumours were detected in in vitro breast specimens. Tissue
phantoms were used to study the influence of different optical properties on the
gated viewing results and to explore the limitations and benefits of the technique.
It was found that the scattering properties influence the results more than the
absorption properties of the tissue. A computer model was developed to simulate
the photon propagation in a highly scattering environment. The model solves the
time-dependent diffusion equation in three dimensions and with inhomogeneities
implanted into the tissue model. The model was further developed to multiple
sources and Fourier transformation of the result for comparison with frequencydomain
studies.
The time-dependent curves obtained in the near-IR region contain information on
the optical properties of the tissue under investigation. A multi-spectral technique
was developed to be able to extract the optical properties over a large wavelength
region simultaneously. Sub-ps white light, generated with a high power laser, was
used as light source and a streak camera in combination with a spectrometer as
detector. The technique was applied to in vivo tissue investigations as well as to
tissue phantoms.
Laser-induced fluorescence (LIF) studies were performed in order to detect
superficial tumours. As excitation source a nitrogen pumped dye laser was used
and an optical multi-channel analyser as well as a multi-colour imaging technique
was used for detection. Investigations were performed on skin lesions as well as in
the bladder. Tumour demarcation was observed using exogenous chromophores as
well as the endogenous tissue fluorescence. A computer program was developed
for convenient evaluation of fluorescence spectra.
Photodynamic therapy (PDT) were performed on superficial skin lesions using oamino
levulinic acid as photosensitiser. A frequency-doubled Nd:YAG pumping a
dye laser was used as light source. The PDT treatments showed good results. PDT
was combined with LIF studies as well as with measurements of optical properties
using an integrating sphere technique. It was found that the absorption coefficient
increased due to the PDT treatment. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2259998
- author
- Berg, Roger
- supervisor
- opponent
-
- unknown], [unknown
- publishing date
- 1995
- type
- Thesis
- publication status
- published
- subject
- keywords
- Fysicumarkivet A:1995:Berg
- pages
- 271 pages
- publisher
- Division of Atomic Physics, Department of Physics, Faculty of Engineering, LTH, Lund University
- defense location
- n/a
- defense date
- 1995-01-01 01:01:00
- language
- English
- LU publication?
- no
- id
- ad68794d-f4fc-4834-b5b5-8c281014deb7 (old id 2259998)
- date added to LUP
- 2016-04-04 12:13:55
- date last changed
- 2018-11-21 21:09:47
@phdthesis{ad68794d-f4fc-4834-b5b5-8c281014deb7,
abstract = {{Near-IR light penetrates deeply into tissue, but as the scattering coefficient is much<br/><br>
larger than the absorption coefficient in this wavelength region, direct viewing<br/><br>
through tissue is very difficult. In order to detect and locate inhomogeneities<br/><br>
located inside tissue a time-resolved technique was developed, based on gated<br/><br>
viewing, i.e. detecting the first arriving photons with the shortest path through the<br/><br>
tissue. The focus was on developing a technique to substitute X-rays for finding<br/><br>
breast tumours. Mode-locked lasers and diode lasers were used as light sources. As<br/><br>
detection techniques time-correlated single photon counting was used as well as a<br/><br>
streak camera. Tumours were detected in in vitro breast specimens. Tissue<br/><br>
phantoms were used to study the influence of different optical properties on the<br/><br>
gated viewing results and to explore the limitations and benefits of the technique.<br/><br>
It was found that the scattering properties influence the results more than the<br/><br>
absorption properties of the tissue. A computer model was developed to simulate<br/><br>
the photon propagation in a highly scattering environment. The model solves the<br/><br>
time-dependent diffusion equation in three dimensions and with inhomogeneities<br/><br>
implanted into the tissue model. The model was further developed to multiple<br/><br>
sources and Fourier transformation of the result for comparison with frequencydomain<br/><br>
studies.<br/><br>
The time-dependent curves obtained in the near-IR region contain information on<br/><br>
the optical properties of the tissue under investigation. A multi-spectral technique<br/><br>
was developed to be able to extract the optical properties over a large wavelength<br/><br>
region simultaneously. Sub-ps white light, generated with a high power laser, was<br/><br>
used as light source and a streak camera in combination with a spectrometer as<br/><br>
detector. The technique was applied to in vivo tissue investigations as well as to<br/><br>
tissue phantoms.<br/><br>
Laser-induced fluorescence (LIF) studies were performed in order to detect<br/><br>
superficial tumours. As excitation source a nitrogen pumped dye laser was used<br/><br>
and an optical multi-channel analyser as well as a multi-colour imaging technique<br/><br>
was used for detection. Investigations were performed on skin lesions as well as in<br/><br>
the bladder. Tumour demarcation was observed using exogenous chromophores as<br/><br>
well as the endogenous tissue fluorescence. A computer program was developed<br/><br>
for convenient evaluation of fluorescence spectra.<br/><br>
Photodynamic therapy (PDT) were performed on superficial skin lesions using oamino<br/><br>
levulinic acid as photosensitiser. A frequency-doubled Nd:YAG pumping a<br/><br>
dye laser was used as light source. The PDT treatments showed good results. PDT<br/><br>
was combined with LIF studies as well as with measurements of optical properties<br/><br>
using an integrating sphere technique. It was found that the absorption coefficient<br/><br>
increased due to the PDT treatment.}},
author = {{Berg, Roger}},
keywords = {{Fysicumarkivet A:1995:Berg}},
language = {{eng}},
publisher = {{Division of Atomic Physics, Department of Physics, Faculty of Engineering, LTH, Lund University}},
title = {{Laser-Based Cancer Diagnostics and Therapy - Tissue Optics considerations.}},
url = {{https://lup.lub.lu.se/search/files/5958354/2302161.pdf}},
year = {{1995}},
}