A method for biological tissue ablation includes shaping a shapeable RF antenna to accommodate the contour of a body vessel adjacent a biological tissue load; generating a train of radio frequency (RF) energy pulses at an output frequency for transmission in a transmission line to the shapeable RF antenna adjacent the biological tissue load; sensing a reflected signal and a forward signal of the RF energy pulses; and adjusting output frequency of the RF energy pulses to effect a substantial match of transmission line impedance with shapeable RF antenna and biological tissue load impedance.