Figure 5b. Drawings illustrate BRTO techniques for reducing the dosage of EOI in cases involving a large shunt. (a) Further advancement of a balloon catheter. EOI is injected via the catheter, which has been advanced into the more proximal portion of the draining vein. (b) Selective injection via a microcatheter. EOI is injected via the microcatheter, which has been advanced through the balloon catheter into the varices.