Assemblies, systems, and methods for infusing therapeutic agents into the body

An infusion method comprising:

• (i) providing an outer catheter body having an interior lumen and including a porous fluid distribution section having a predefined maximum length communicating with the interior lumen;
• (ii) inserting into the outer catheter body an inner catheter body having at least one fluid delivery port for dispensing a fluid from an external source into communication with the porous fluid distribution section for infusion through the porous fluid distribution section, the inner catheter body including a barrier structure proximal of the fluid delivery port, the barrier structure having a reduced dimension condition and an increased dimension condition;
• (iii) manipulating the inner catheter body by sliding the inner catheter body within the outer catheter body when the barrier structure is in a reduced dimension condition along the maximum length of the porous fluid distribution section;
• (iv) manipulating the inner catheter body by placing the barrier structure in an increased dimension condition to press the barrier structure against the interior lumen and form a barrier wall that blocks flow of the dispensed fluid into communication with the porous fluid distribution section proximal of the barrier wall;
• (v) performing (iii) and (iv) to selectively reduce and increase the dimension of the barrier structure within the outer catheter body along the maximum length of the porous fluid distribution section to establish for the infusion catheter assembly a desired effective infusion length, wherein the desired effective infusion length is infinitely variable between the maximum length and any smaller length along the porous fluid distribution section;
• and
• (vi) infusing a fluid through the desired effective infusion length of the porous fluid distribution section.