Apparatus to control power applied to an endoluminal radio frequency (RF) ablation electrode used in vessel occlusion, comprising an RF energy source and control unit to determine impedance passing through the electrode, 108, 118, and while the impedance is no more than 150 Ω, perform steps of: (i) ramp-up power of the RF signal to a first power level of 40 W over a period of no more than 10 seconds, 106； (ii) maintain the RF signal at the first power level for a given period, 116. When the impedance exceeds 150 Ω the RF signal is output at a second, lower power level for a predetermined period, 112. The second power level may be applied without moving the electrode. The whole process may be repeated with the electrode moved within the vessel, 124. The control unit may initially carry out a low power impedance check, 100, 102.
