Microwave applicators are becoming more prevalent in cancer ablation therapy due to factors of penetration, high
power, and shortened treatment time. These applicators create the largest zones of necrosis of available energy sources.
Progress has been made both with interstitial applicators for surgical, laparoscopic, or radiological approaches, as well as
surface applicators that provide hemostasis or precoagulation prior to resection. Most commonly, the applicators operate
at 915 MHz or 2450 MHz, and are well matched to tissue. Surgical applicators are as large as 5.6 mm and have the
capability to operate at 100-200 W. With smaller applicators, internal cooling may be required to avoid heating sensitive
skin surfaces if used percutaneously or laparoscopically. With the interstitial applicators, animal studies have shown a
strong relationship between power and ablation volume, including reaching a steady-state plateau in performance based
more on power level and less on time. As shown in-vivo, MW surface applicators are very efficient in surface
coagulation for hemostasis or precoagulation and in the treatment of surface breaking lesions. These applicators are also
capable of deep penetration as applied from the surface. Characteristic treatment times for interstitial applicators are
four minutes and for surface applicators, one minute or less is sufficient. Examples will be shown of multi-organ results
with surface coagulation using high-power microwaves. Finally, future trends will be discussed that include treatment
planning, multiple applicators, and navigation.