a catheter assembly is disclosed according to one embodiment of the invention . the assembly includes a catheter body , a housing and a detector . the catheter includes a distal tip , a proximal end , and a fiber optic extending between the proximal end and the distal tip . the housing may include a channel adapted to support at least a portion of the distal tip of the catheter . the may be detector disposed within the housing so as to be spaced a fixed distance from the distal tip of the catheter . methods for providing and calibrating a catheter supported within housing are also disclosed according to other embodiments of the invention .