White light diffuse optical spectroscopy for photodynamic therapy dosimetry

Photodynamic therapy (PDT) is an emerging cancer treatment modality that utilizes light-activated drugs (photosensitizer) and laser light to induce cytotoxicity selectively. It is known that blood oxygenation level and photosensitizer concentration in the tissue play important roles in the PDT treatment efficacy [1,2]. The knowledge of these parameters could also improve or predict the efficacy of the treatment outcome [3]. However, there has been no direct means by which one can measure the parameters during PDT treatment in non-invasive manner. Diffuse Optical Spectroscopy (DOS), which acquires tissue information based on optical absorption, provides a nice solution for this. By applying DOS on the target site of PDT, it is possible to assess the photosensitizer concentration, blood oxygen saturation and blood volume through the measurement of Oxy-Haemoglobin (HbO2) and Deoxy-Haemoglobin (Hb) concentration in situ. This technique has been used in the market with mostly contact based probe and a laser source. In this project, a white light based DOS instrument is built with a switchable (contact or remote) probe. In addition, real time data acquisition software using MATLAB and LabVIEW is also developed. The advantage of having a remote probe is its ability to assess blood oxygenation saturation and photosensitizer concentration during a PDT treatment without obstructing the laser used for PDT. It also removes the need to touch the sensitive surface of the patient’s skin. The preliminary result of instrument testing shows successful measurement of the relative changes of tissue blood oxygenation.Bachelor of Engineering (Chemical and Biomolecular Engineering