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The role of blood pooling and fibre positioning in Interstitial Photodynamic Therapy

Orth, Christopher (2008) In Lunds Report on Atomic Physics FAF820 20081
Atomic Physics
Abstract
For the dosimetry of interstitial photodynamic therapy (IPDT), the fibre positioning and the distributed light fluence that activates the treatment are essential. With sufficient supply of oxygen and photosensitiser, the treatment effect depends entirely on the distributed light. By proper dosimetry, the illumination is limited to the tumour and adjacent sensitive tissues are spared.

The fibre positioning was optimised using a fast and reliable stochastic algorithm. In this work, algorithms for a similar optimisation process were analysed, the problem of finding the locations for radioactive seeds in brachytherapy. The differentiating circumstances are that for IPDT a smaller number of sources are used and that there is no requirement... (More)
For the dosimetry of interstitial photodynamic therapy (IPDT), the fibre positioning and the distributed light fluence that activates the treatment are essential. With sufficient supply of oxygen and photosensitiser, the treatment effect depends entirely on the distributed light. By proper dosimetry, the illumination is limited to the tumour and adjacent sensitive tissues are spared.

The fibre positioning was optimised using a fast and reliable stochastic algorithm. In this work, algorithms for a similar optimisation process were analysed, the problem of finding the locations for radioactive seeds in brachytherapy. The differentiating circumstances are that for IPDT a smaller number of sources are used and that there is no requirement on
the maximum dose delivered to the tumour. The established fast Simulated Annealing algorithm was settled upon and adapted to fit the special conditions of IPDT. As an alternative, the random step algorithm from the previous thesis by Hjelm and Ericsson 5 was investigated. The new software was implemented into Matlab to allow for further improvements
of the dosimetric system. The investigations showed that these two algorithms are fast and reliable and suit the special IPDT problem. Future work should be focused on improving the conditions under which they work, i.e. the objective function.

When blood pooling appears at the fibre tips, light is attenuated and the dosimetry is altered. Therefore, the concept of effective attenuation μeff , independent of the blood, was investigated. Spatially-resolved measurements confirmed that measurable damping factors can indeed be determined, that vary only slightly with the wavelength. Real-time monitoring and compensation during treatment could therefore be possible. Errors in μeff of a fibre surrounded by small blood pools were less than 15% with roughly a−1 i 15±5mm−1 times damping. (Less)
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author
Orth, Christopher
supervisor
organization
course
FAF820 20081
year
type
H2 - Master's Degree (Two Years)
subject
publication/series
Lunds Report on Atomic Physics
report number
LRAP-393
language
English
id
1528762
date added to LUP
2010-01-14 16:55:06
date last changed
2012-03-14 14:54:07
@misc{1528762,
  abstract     = {For the dosimetry of interstitial photodynamic therapy (IPDT), the fibre positioning and the distributed light fluence that activates the treatment are essential. With sufficient supply of oxygen and photosensitiser, the treatment effect depends entirely on the distributed light. By proper dosimetry, the illumination is limited to the tumour and adjacent sensitive tissues are spared.

The fibre positioning was optimised using a fast and reliable stochastic algorithm. In this work, algorithms for a similar optimisation process were analysed, the problem of finding the locations for radioactive seeds in brachytherapy. The differentiating circumstances are that for IPDT a smaller number of sources are used and that there is no requirement on
the maximum dose delivered to the tumour. The established fast Simulated Annealing algorithm was settled upon and adapted to fit the special conditions of IPDT. As an alternative, the random step algorithm from the previous thesis by Hjelm and Ericsson 5 was investigated. The new software was implemented into Matlab to allow for further improvements
of the dosimetric system. The investigations showed that these two algorithms are fast and reliable and suit the special IPDT problem. Future work should be focused on improving the conditions under which they work, i.e. the objective function.

When blood pooling appears at the fibre tips, light is attenuated and the dosimetry is altered. Therefore, the concept of effective attenuation μeff , independent of the blood, was investigated. Spatially-resolved measurements confirmed that measurable damping factors can indeed be determined, that vary only slightly with the wavelength. Real-time monitoring and compensation during treatment could therefore be possible. Errors in μeff of a fibre surrounded by small blood pools were less than 15% with roughly a−1 i 15±5mm−1 times damping.},
  author       = {Orth, Christopher},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lunds Report on Atomic Physics},
  title        = {The role of blood pooling and fibre positioning in Interstitial Photodynamic Therapy},
  year         = {2008},
}