Techniques for imaging a blood vessel are described. A transducer attached to a catheter is guided to a first site within a blood vessel. The catheter is moved to a second site proximal to the first site at a speed selected to enable the transducer to generate a signal indicative of a geometry wall, the lumen, and a portion of the side branch. A first image of the blood vessel obtained from the signal is oriented with a second image of the blood vessel such that a first portion of the first image aligns with a second portion of the second image.
