Effect of frequency on entrance and propagation pattern of high-frequency (radiofrequency) electrical currents in biologic tissues.

BACKGROUND

Radiofrequency electrical currents have a tendency to move toward the center of the bulk of biologic tissues.

OBJECTIVES

To evaluate the effect of the frequency of currents on their entrance and propagation pattern in biologic tissues.

MATERIALS AND METHODS

Three electrosurgical generators with 0.4, 1.5, and 3 MHz frequency outputs were studied. Current was applied using a metallic needle introduced into a piece of cow liver, with different amounts of energy delivered at multiple points. Cross-sections of the liver were then studied for tissue effect. The diameters of the coagulated areas at the deepest and most superficial parts were measured. The tendency of the currents for penetration in the deeper layers of tissue rather than in the superficial layers was assessed using the superficial diameter/deep diameter ratio.

RESULTS

Diameter of coagulated area was larger around deeper parts than around superficial parts of the electrode. No correlation between frequency of current and the superficial/deep diameter ratio of the coagulation zone was found.

CONCLUSION

Radiofrequency currents have a tendency to move toward the center of the tissue. Frequency of current over the range of 0.4-3 MHz did not show any effect on this tendency.