Catheter systems of the invention involve guided and informed dissolution of occlusions in blood vessels. According to certain aspects, a catheter system of the invention includes an elongate body defining a first lumen and comprising a distal portion, an inner member configured for insertion into the first lumen, the inner member comprising an energy source configured to deliver therapeutic energy to a treatment site, and an imaging assembly located at the distal portion of the elongate body. In some embodiments, the catheter system includes a functional flow sensor in addition to or as an alternative to the imaging assembly.