The low profile can be further reduced to aid insertion, if desired, by enclosing the structure 56 within a constricted introducing sleeve, or by coating the structure 56 with a lubricious material, such as silicone, or both. [0064] As FIGS. 3 and 4 show, the interior bore 60 of the catheter tube 50 can be coupled (via the fitting 122) to a source 68 of fluid, for example, sterile saline, or a rad