The present invention relates to a medical probe which consists of a cannula with a multilumen stylet inside. The multilumen contains at least two lumen. Both the multilumen as well as the cannula may have beveled ends. In the lumen straight optical fibers (i.e. no angle end face) are present that can be connected at the proximal end to a console. The cannula, multilumen, fiber system forming the medical probe comprises at least in one of the lumen of the multilumen more than one optical fiber. Preferably the source and detector fibers for the fluorescence detection are contained in one single lumen of the multilumen.
