A medical device assembly is provided for removable insertion into a catheter with a lumen. The medical device assembly comprises an electromagnetic radiation (EMR) source for providing non-ultraviolet, therapeutic EMR having an intensity sufficient to inactivate one or more infectious agents and/or to stimulate healthy cell growth causing a healing effect, and a removable EMR conduction system at least partially insertable into and removable from the lumen of the catheter. The EMR conduction system has at least one optical element providing axial propagation of the therapeutic EMR through an insertable elongate body. The elongate body may have an exterior surface between a coupling end and a distal end tip that has at least one modified portion permitting the radial emission of therapeutic EMR from the elongate body proximate the modified portion. Such modified portion may be gradient along the exterior surface.
