Figure 3. A loop electrode is used to remove a small skin mass. The loop is placed over the lesion, and the mass is grasped
with forceps. The electrode is activated and brought through the tissue. A shaving technique can then be used if the base
of the lesion remains and requires removal.
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Many specially designed electrodes can be used in oral, dermatologic, reproductive, and ophthalmic surgery. For example, loop
electrodes are especially useful for removing small skin masses. If some of the lesion remains, the tissue can be shaved with
the electrode until all abnormal tissue is removed (Figure 3).
3 Distichia and ectopic cilia of the eyelids can be eliminated by inserting a 0.004-in-diameter wire electrode along the hair
shaft and applying a small amount of power (Figure 4).
4,5
Although not part of the formula, the passive electrode is important as well. The passive electrode is the antenna that receives
radio waves emitted from the active electrode and returns the energy to the machine. Unlike an electrocautery unit, the passive
electrode is not a grounding terminal, so it does not have to be in direct contact with the skin and does not require conductive
gels. Placing the passive electrode close to the surgical area decreases the power required to cut tissue, reducing the possibility
of lateral thermal damage. The interaction between the passive and active electrodes is similar to that of your car radio
in that the radio (passive electrode) has a clearer signal when you are closer to the transmitter (active electrode).
Contact time with tissue
Active electrode contact time with the tissue is directly proportional to the lateral heat transferred to tissue. A well-planned
surgical approach and experience with radiosurgery improve efficiency, reducing tissue contact time. If you perform reconstructive
or blepharoplasty procedures, marking the area to be incised with a skin marking pen is helpful.
Power intensity
Proper power intensity varies with the tissue being cut. Correct power application allows for enough generated heat to volatilize
cells at the tip of the electrode. With proper power intensity, the electrode passes smoothly through the tissue with no sparking
or resistance. Insufficient power causes lateral accumulation of heat because of drag. Drag from an improperly powered electrode
tends to increase hemorrhage because tissue is torn rather than cut. Likewise, excessive power results in excessive lateral
heat because of sparking.
Waveform
Figure 4. Focal distichia may be removed from the eyelid margin by using a very low power setting and a small-diameter wire
electrode. The electrode is slid down beside the hair and activated, destroying the hair follicle. No resistance is felt when
the hair is removed if the follicle is properly destroyed.
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Four waveforms are used in radiosurgery. The fully filtered, or continuous, waveform is a continuous high-frequency wave that
produces a smooth cutting action. The continuous waveform generates the least amount of lateral heat. When the continuous
waveform is delivered by a fine-wire electrode, the incision is comparable to that made by a scalpel.1
The fully rectified modulated waveform differs from the continuous waveform by inducing a minute pulsation of the wave; this
slightly reduces the efficiency of the cut. The fully rectified modulated waveform generates some lateral heat that is useful
in hemostasis. When combined with a large-diameter needle electrode, the fully rectified modulated waveform is excellent for
subcutaneous dissection.
For more vascular tissues in which hemostasis is critical, you may select the partially rectified modulated waveform. This
waveform is an intermittent transmission of high-frequency waves that increases lateral heat transmission, resulting in excellent
hemostasis. Blood vessels up to 1/16 of an inch may be sealed with the electrode in the partially rectified modulated waveform mode. Alternatively, hemostasis
may be achieved by an indirect method while in this mode by touching the electrode to a hemostat while it grasps the vessel.
The indirect method is familiar to any surgeon who has used electrocautery for coagulation in a similar manner.
Finally, there is the fulguration, or spark-gap, waveform. This waveform delivers a mutated electric current that rapidly
dehydrates tissue in contact with the active electrode. Much of the tissue destruction produced in this mode is limited by
the insulating effect of carbonized tissue, the air space the spark must jump to contact the tissue, and the movement of the
electrode by the surgeon. The spark-gap waveform mode is not used when cutting skin or any tissue in which scar formation
would be detrimental. This mode has been used in combination with a ball electrode to treat anal fistulas in people.6
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