Photodynamic Therapy utilizing Interstitial Light Delivery Combined with Spectroscopic Methods

Sammanfattning: Since cancer continues to plague humanity there is large need for development of modalities for both diagnosis and therapy. Most of the currently available methods suffer from serious disadvantages. The treatments, e.g. ionising radiation, chemotherapy, surgery, may themselves induce malignancies or the patient may be physically impaired for a longer period of time. The work presented aims at developing equipment and methods that use light for both detection and treatment of various malignant or pre-malignant conditions. Fundamental knowledge on the interaction between light and tissue is required in order to develop models for the light distribution in tissue. Therefore, basic properties of light-tissue interaction, like refractive index, absorption, scattering, and scattering anisotropy, are introduced. How the physiological status of the tissue affects these properties are discussed. Utilizing the differences in the fluorescence spectra emitted by healthy and malignant tissues, when irradiated with visible light, it is possible to detect and delineate certain lesions. The contrast between diseased and healthy tissue can be further enhanced with the use of a fluorescence tumour marker. The evolution of these tumour markers has been fuelled by the fact that many tumour markers also can be utilized for light therapy. The modality is called photodynamic therapy (PDT) and has now been clinically approved for the treatment of several conditions. The possible indications for this type of treatment are generally limited to thin superficial lesions due to the limited penetration of the light in tissue. The work presented in this thesis mainly relates to overcoming the limited light penetration by leading the light through multiple optical fibres inserted into the tumour. In this way both embedded tumour and/or thick tumours could be an indication for this modality. In addition to that the fibres are used to collect information about relevant parameters of therapeutic interest.