Abstract: An ablation treatment apparatus has a multiple antenna device. The multiple antenna device includes a primary antenna with a lumen, a longitudinal axis and an ablative surface area of length L.sub.1. The multiple antenna device also includes a secondary antenna that is positioned in the primary antenna as the primary antenna is introduced through tissue. A secondary antenna distal end is deployed at a selected tissue site from the primary antenna lumen in a lateral direction relative to the longitudinal axis. A sensor is at least partially positioned at an exterior of the secondary antenna distal end at a distance L.sub.2 from the primary antenna along the secondary antenna distal end. L.sub.2 is at least equal to 1/3 L.sub.1. An energy source is coupled to the primary antenna.

Abstract: An ablation treatment apparatus has a multiple antenna device with a primary antenna and a secondary antenna. The secondary antenna is positioned in a lumen of the primary antenna as the primary antenna is introduced through tissue to a selected tissue site. At the tissue site the secondary antenna is deployed from the primary antenna in a lateral direction relative to a longitudinal axis of the primary antenna. At least a portion of a distal end of the secondary antenna is structurally less rigid than the primary antenna. The primary antenna is constructed to be rigid enough to be introduced and advanced through tissue. A cable couples the energy source to one or more of the antennas.