Electromagnetically induced focused heat in the treatment of surgically created aneurysm models

A hand-held radiofrequency (rf) probe of a novel design based on the principle of the induced current convergence was used to treat aneurysm models using focused hyperthermia. Aneurysms were created surgically in rats by a side-to-side anastomosis between the inferior vena cava and the abdominal aorta or by grafting a donor abdominal aorta from one rat onto the abdominal aorta of another rat. Aneurysms were treated by inserting the 0.3-mm diameter probe tip into the fundus and applying the power for brief periods (0.5-1.5 sec) using a foot pedal. Collapse of the fundus was observed as the result of the heat-induced thrombosis. Thermal distribution in the immediate vicinity of the probe as well as the heating rate were measured in a uniformly dielectric phantom and in rat vessels. The aneurysms were histologically examined immediately, three days, and three weeks after the treatment. Complete obliteration of the aneurysms and patency of the parent arteries were confirmed. Partial integrity of the vessels around the lesion was also confirmed.