Embodiments of the present invention relate to multiple needle
catheter-based injection systems to deliver a plug of a therapeutic or
other agent. A medical device may include a catheter with a distal end, a
proximal end and a catheter lumen extending therebetween and an outer
needle disposed in the catheter lumen with a distal end and a proximal
end and an outer needle lumen extending therebetween. The medical device
may include an inner needle with a distal end and a proximal end, the
inner needle being disposed in the outer needle lumen and the distal end
of the inner needle to receive and hold a therapeutic plug, and a needle
control mechanism coupled to the proximal ends of the outer needle and
the inner needle, the needle control mechanism to independently and
jointly control ejection and retraction of the outer and inner needles to
deliver the therapeutic plug into a target tissue site.