Microcatheter for delivering a substance (e.g., infusion agent including embolization material and/or contrast enhancing material) in a small blood vessel towards a target bodily part. Includes a single lumen surrounded by tubular wall having outer diameter and opened at both ends; tubular wall proximal portion is connectable to a pressure source and reservoir containing infusion agent, and tubular wall distal portion ends with a tip; the tubular wall distal portion includes an infusion agent flow disruption section configured to disrupt passage therethrough of incoming retrograded flow of infusion agent, during continuous delivery of infusion suspension from the reservoir to the tip. Disclosed are methods using the microcatheter for performing local embolization in a small blood vessel feeding a (for example, cancerous) target bodily part, and for delivering infusion agent in a small blood vessel towards such target bodily part. Also disclosed are devices and methods for filtering non-target infusion agent.