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Laser-Based Cancer Diagnostics and Therapy - Tissue Optics considerations.

Berg, Roger (1995) In Lund Reports in Atomic Physics LRAP-184.
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)
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Fysicumarkivet A:1995:Berg
in
Lund Reports in Atomic Physics
volume
LRAP-184
pages
271 pages
publisher
Division of Atomic Physics, Department of Physics, Faculty of Engineering, LTH, Lund University
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1995-01-01 01:01
language
English
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@misc{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},
  keyword      = {Fysicumarkivet A:1995:Berg},
  language     = {eng},
  pages        = {271},
  publisher    = {ARRAY(0xa850c28)},
  series       = {Lund Reports in Atomic Physics},
  title        = {Laser-Based Cancer Diagnostics and Therapy - Tissue Optics considerations.},
  volume       = {LRAP-184},
  year         = {1995},
}