A system for infusing particles into a patient at a predetermined site in the vasculature, which comprises: an elongated catheter having a tubular-shaped wall with an inner surface and an outer surface, wherein the inner surface of the wall defines a central lumen extending between a proximal end and a distal end of the catheter; an inflatable balloon mounted on the outer surface of the catheter wall; an inflator connected in fluid communication with the balloon for selectively inflating the balloon to control and regulate the flow of blood in the vasculature past the catheter; characterized by having a reinforcement member (102, 102') positioned in contact with a section of the catheter wall encircling a portion of the central lumen, wherein the reinforcement member is positioned under the inflatable balloon, to strengthen the catheter wall and to maintain a substantially constant cross-section for the central lumen during an inflation of the balloon; a source of the particles suspended in a fluid, wherein the source is connected in fluid communication with the proximal end of the catheter; a substantially cylindrical shaped separator (32/68) in fluid communication with the particle source, wherein the separator has a proximal end and a distal end and is formed with a plurality of longitudinally aligned, parallel lumens (40a-c), with each lumen dimensioned to receive particles therethrough; an infusion device for moving particles from the source, through the separator, and into the vasculature of the patient; and wherein the inflator can selectively configure the balloon from a base configuration to a secondary configuration, wherein the balloon is deflated in the base configuration and inflated in the secondary configuration; wherein the catheter defines an axis; and wherein the balloon is extendable in a radial direction outward from the catheter to control blood flow around the catheter in a direction substantially parallel to the axis. an elongated catheter having a tubular-shaped wall with an inner surface and an outer surface, wherein the inner surface of the wall defines a central lumen extending between a proximal end and a distal end of the catheter; an inflatable balloon mounted on the outer surface of the catheter wall; an inflator connected in fluid communication with the balloon for selectively inflating the balloon to control and regulate the flow of blood in the vasculature past the catheter; characterized by having a reinforcement member (102, 102') positioned in contact with a section of the catheter wall encircling a portion of the central lumen, wherein the reinforcement member is positioned under the inflatable balloon, to strengthen the catheter wall and to maintain a substantially constant cross-section for the central lumen during an inflation of the balloon; a source of the particles suspended in a fluid, wherein the source is connected in fluid communication with the proximal end of the catheter; a substantially cylindrical shaped separator (32/68) in fluid communication with the particle source, wherein the separator has a proximal end and a distal end and is formed with a plurality of longitudinally aligned, parallel lumens (40a-c), with each lumen dimensioned to receive particles therethrough; an infusion device for moving particles from the source, through the separator, and into the vasculature of the patient; and wherein the inflator can selectively configure the balloon from a base configuration to a secondary configuration, wherein the balloon is deflated in the base configuration and inflated in the secondary configuration; wherein the catheter defines an axis; and wherein the balloon is extendable in a radial direction outward from the catheter to control blood flow around the catheter in a direction substantially parallel to the axis.