Transmitting acoustic and electromagnetic signals from a catheter balloon

A method of delivering energy to a treatment site, comprising:

• advancing a distal end of a catheter to the treatment site within a patient,
• the catheter having at least a first transducer located in an interior of a first balloon,
• operating the first transducer at an operational frequency where the first transducer transmits an acoustic signal having an acoustic field with multiple lobes along a longitudinal axis of the first transducer,
• each of the lobes having a spatial intensity maximum in a spatial intensity distribution of the acoustic field,
• the spatial intensity distribution being at a surface of the balloon and parallel to a surface of the first transducer,
• the spatial intensity distribution of the first acoustic field having one or more reduced spatial acoustic intensity locations where the spatial intensity of the acoustic field of the first transducer is 50% or less of a value of one of the spatial intensity maxima of the first transducer,
• each of the reduced spatial acoustic intensity locations being between the spatial intensity maxima for lobes that are adjacent to one another along the longitudinal axis of the first transducer, and
• each of the reduced spatial acoustic intensity locations being on the surface of the first balloon between the spatial intensity maxima that are adjacent to one another along the longitudinal axis of the first transducer, the catheter further comprising at least a first electrode configured to transmit an electromagnetic signal, the first electrode being positioned on the first balloon over one of the reduced spatial acoustic intensity locations of the first transducer.