Using high-frequency radio waves is a relatively new addition to the armaments of veterinary dermatologists. Not to be confused with either radiation therapy or electrocautery, radiosurgery uses radio waves between 2.0-4.0 MHz (it has been determined that the ideal radio frequency for cutting tissues is approximately 4 MHz) to incise, excise, ablate and coagulate without damaging surrounding tissue. The frequency generated is intermediate between that used in AM radio signals and television. In fact, radio wave surgery is much more like laser surgery than either electrocautery or radiation therapy. The waveform does not generate heat and therefore allows tissue manipulation with very little risk of scar formation. Cutting is accomplished by vaporizing cells in the immediate path of the electrode causing them to split apart, not by cautery nor pressure. Adjacent cell layers remain unaffected. The active electrode remains "cold" yet sterile throughout the surgery and procedures can be accomplished with either general or local anesthesia. The affordable price for a complete unit makes it a viable option for most veterinary practices. When you consider all these advantages, radiosurgery is an ideal tool in clinical dermatology for both biopsy and surgical excision of lesions.
Advantages of Radio Wave Surgery
Excellent for both cutting and coagulation
Rapid local hemostasis
Very little tissue damage--good cosmetic effect
Tissue morphology preserved
Sterilizes as it cuts
Little postoperative pain
Can be used with either general or local anesthesia
Unit is lightweight and portable
Different electrode tips for different applications
Affordable
Disadvantages of Radio Wave Surgery
Practice necessary to gain proficiency
Must be cautiously used near combustible chemicals and gases
Possibility of skin burns if used improperly
Produces unpleasant odor if smoke evacuator (vacuum) isn't used
Initial expense to purchase unit
Contraindicated for cutting cartilage or bone
Evaluation of clinical applications was based on use of the Ellman SurgitronTM (Ellman International, Inc., Hewlett, N.Y.), which utilizes four currents (fully filtered and fully rectified, fully rectified, partially rectified, and fulguration) and operates at 3.8 MHz and 140 watts. The unit acts as radio transmitter and depressing a foot pedal transduces the waveform to a variety of handpiece attachments. Cutting is achieved as the radio waves cause the water in the cells to volatize. A vacuum (smoke evacuator) line removes the plume that may occur over the operating site. A passive electrode placed under or in the vicinity of the patient acts more like an antenna to focus the radio waves than as a ground plate. Direct metal-to-skin contact is not needed and the electrode is even coated with plastic to prevent accidental burning. The unit is self-grounded and separate grounding of the patient is not required.
Two important goals of any surgical procedure are to minimize tissue damage and to obtain adequate hemostasis. Both can be readily achieved with radiosurgery. The more the waves of the radio frequency current are rectified and filtered, the less lateral heat production and thus the less tissue damage. Minimal lateral heat is produced when the power setting is properly adjusted. It should be just sufficient to coagulate or to vaporize the cells and separate the tissues. In addition, the quicker the movement, the less production of lateral heat since the electrode should not be in contact with the tissue any longer than is necessary to produce the desired effect.
The fully filtered and fully rectified setting (90% cutting, 10% coagulation) is used for incisions using paintbrush strokes to cut. The radio waves cut the tissue; there is no need to "drag" the instrument. If there is resistance to the cutting procedure, the intensity should be slightly increased. If the setting is too high, sparking will be evident. Moistening the region with a gauze square or swab soaked in water or saline will reduce tissue resistance and encourage the electrode to "glide" through the tissue. Never use alcohol or spirit-based skin antiseptics that might be ignited by an errant spark. The electrode should be kept clean and directed perpendicularly to the skin surface. Some hemostasis is provided with the fully filtered setting, but if additional coagulation is needed, the fully-rectified setting can be selected. This allows cutting with enhanced hemostasis (50% cutting; 50% coagulation) and the spark-gap output is moderately damped. Adequate hemostasis is provided for all blood vessels less than 2 mm in diameter; ligation is recommended for larger vessels. Even more hemostatic control can be achieved using a ball electrode or bipolar forceps with the partially rectified setting (10% cutting, 90% coagulation). Electrofulguration can be achieved by plugging the handpiece into a separate port and holding the electrode 1-3mm from the tissue and moving it so as to cause sparks and the formation of an eschar. The actual amount of tissue destruction depends on the current intensity, the length of time for which the current flows, the density and moisture content of the tissue, and the distance of the electrode from the tissue.
Biopsies and Excisional Surgeries
Cutaneous biopsies are easy to perform with radiosurgery. For small lesions, it is best to use a marker to define the borders of the lesion (where necessary) and infiltrate the subcutaneous fat with 1-2 mL lidocaine (with or without epinephrine). It is not necessary to apply any germicides to the skin surface and, in fact, alcohol and flammable compounds are contraindicated. Gently touching the surface with a gauze compress moistened with saline or water will help decrease tissue "drag". For small lesions, the loop electrode is ideal for complete excision. It is held perpendicular to the skin surface and the loop will literally perform a shave biopsy or complete excision depending on the size of the lesion. The electrode tip should always be activated by the foot pedal before contacting the skin. When histologic detail is required, only the fully-filtered, fully-rectified waveform (cutting) should be used. Once the lesion has been removed, it can be applied to a clean dry gauze before being added to a jar of buffered formalin. For long, linear biopsies, it is best to apply the tissue to a piece of tongue depressor or cardboard to decrease folding, before adding the sample to the formalin. For large lesions, a vari-tip electrode or a scalpel blade attachment can be used to make an elliptical incision. Once the biopsy has been performed, a gauze square can be used to blot the surface, making the edges and any bleeding vessels more apparent. The blended, fully rectified setting can then be used to smooth edges and provide hemostasis. With oozing and incomplete hemostasis, a ball electrode and the partially rectified setting will provide for additional electrocoagulation. When taking biopsies of potentially infected tissue, it is comforting to know that the radiosurgery electrode sterilizes as it cuts and will not seed infectious agents along the incision line. Post-surgical care is limited to keeping the area clean; a topical antiseptic can be used where necessary.
Indications
Radiosurgery has the potential to be a valuable tool to the veterinary dermatologist. It not only offers extremely cosmetic results, but it can be used to quickly biopsy a variety of tissues without causing scarring. It also allows excisional surgeries on an outpatient or inpatient basis. The versatility of the system allows for the excision of irregularly-shaped lesions that typically could not be adequately sampled with a biopsy punch and without requiring more conventional surgical approaches. In addition, hemostasis is readily achieved and the procedure can be done aseptically because the waveform sterilizes as it cuts.
Regarding treatment, radiosurgery is an excellent tool for removing a variety of cutaneous lesions such as sebaceous gland hyperplasias, skin tags, papillomas, basal cell tumors, nevi and keratoses. Even deeper and larger lesions can be managed by utilizing the Vari-tip or scalpel blade electrodes to make more traditional elliptical incisions.
References
1. Nesbitt, G; Ackerman, L: Canine & Feline Dermatology, Veterinary Learning Systems, 1998, 498pp.