An embodiment includes a system comprising: a catheter; an optic fiber having a long axis and a short axis that is orthogonal to the long axis; first and second radiopaque elements coupled to the optic fiber; a first wire coupled to the optic fiber and extending from the first radiopaque element to the second radiopaque element; a fluid; wherein (a)(i) the first wire wraps at least partially around an exterior surface of the optic fiber; (a)(ii) an outer diameter of the first wire and an outer diameter of the optic fiber are collectively less than an inner diameter of the catheter, and (a)(iii) the first wire is configured to center the optic fiber within the catheter within a plane orthogonal to the long axis.