Tuned RF energy for selective treatment of atheroma and other target tissues and/or structures

A system for analyzing a lumen wall of a body lumen, the system comprising:

• a probe having a proximal end, a distal end, and a radially expandable electrode array disposed near the distal end for circumferentially engaging the lumen wall;
• a power source coupled to the electrode array such that, when the electrode array engages the vessel lumen wall, an electrical circuit comprising the power source, the selected electrodes of the array, and engaged vessel lumen wall can be defined;
• and
• a processor coupled with the variable frequency power source, the processor comprising computer-readable media embodying software instructions configured to characterize an eccentric target material of the lumen wall by monitoring a characteristic of the electrical circuit.