A therapeutic agent delivery system comprising: a catheter having a proximal end and an opposite distal end, the catheter having a body with a lumen (930a, 930b) defined therein; the body further comprising a proximal section disposed closest to the proximal end of the catheter, and a distal section disposed closest to the distal end of the catheter, the lumen (930a, 930b) extending through both the proximal and distal sections (920, 935), the proximal section including a region being made from an elastically deformable material; a stylet that includes an outer body member axially displaceable relative to an inner body member, the inner body member having at its distal end a shoulder followed by an arm of reduced diameter, the stylet being configured such that, in use, at least a portion of the arm extends into the lumen of the distal section of the catheter; and a deployment member disposed between the outer body member and the arm, with a proximal surface of the deployment member supported by the shoulder; the system being configured such that, when the stylet is inserted into the lumen (930a, 930b) so that at least a portion of the arm of the inner body member extends into the lumen of the distal section of the catheter, axial displacement of the outer body member relative to the inner body member sufficient to clear the deployment member allows the deployment member to release, and wherein the deployment member is configured to expand radially when released, imposing a radial force on the elastically-deformable region of the catheter body, causing its outer diameter to enlarge and form a bulbous region. a catheter having a proximal end and an opposite distal end, the catheter having a body with a lumen (930a, 930b) defined therein; the body further comprising a proximal section disposed closest to the proximal end of the catheter, and a distal section disposed closest to the distal end of the catheter, the lumen (930a, 930b) extending through both the proximal and distal sections (920, 935), the proximal section including a region being made from an elastically deformable material; a stylet that includes an outer body member axially displaceable relative to an inner body member, the inner body member having at its distal end a shoulder followed by an arm of reduced diameter, the stylet being configured such that, in use, at least a portion of the arm extends into the lumen of the distal section of the catheter; and a deployment member disposed between the outer body member and the arm, with a proximal surface of the deployment member supported by the shoulder; the system being configured such that, when the stylet is inserted into the lumen (930a, 930b) so that at least a portion of the arm of the inner body member extends into the lumen of the distal section of the catheter, axial displacement of the outer body member relative to the inner body member sufficient to clear the deployment member allows the deployment member to release, and wherein the deployment member is configured to expand radially when released, imposing a radial force on the elastically-deformable region of the catheter body, causing its outer diameter to enlarge and form a bulbous region.