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27 December 1995 Optical instrumentation suitable for a real-time dosimetry during photodynamic therapy
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The aim of a dosimetry for the photodynamic therapy (PDT) is to optimize the therapeutic index: destruction of the pathological areas without impairing surrounding healthy tissue. The sensitizer concentration (PS), the global extinction factor (Sigma) eff and the partial pressure of oxygen PO2 in the tumor are the parameters to be studied from the backscattered light during irradiation. A spectrofluorimeter, suitable for flexible endoscopes, has been designed for measurement of (PS) in situ; kinetics of fixation of the sensitizer in the tumor and in healthy tissues allow the user to choose the optimal schedule for treatment; follow-up of the variation of (PS) during irradiation gives an idea of the photochemical reactions. To measure (Sigma) eff in the situation of an interstitial treatment we use the backscattered signal of the excitating light collected through the emitting fiber itself and several contiguous receiving optical fibers. The prototype of this device is 2 mm in diameter. The calculation of the depth of penetration allows computation of light isodoses in the tumor. To have an idea of the available oxygen we measure the absorption of red light by reduced haemoglobin. A general organization chart of the dosimetry shows the various parameters and interactions working towards the therapeutic result.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

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