Radiosurgery is a technique for excising and ablating soft tissue lesions that has established its role as a useful tool in dermatology and other specialties, particularly neurosurgery.
The technique uses electrical energy, which is converted into heat as a result of tissue resistance. Unlike electrocautery, heat is generated in tissues themselves and the electrode remains cold.
The wave form can be adjusted, allowing it to be used in several situations (see box 1). In dermatological practice, the most useful adjustment is combined cutting and coagulation. Bipolar coagulation allows very precise coagulation using bipolar forceps. This is useful in microsurgery.
| BOX 1: USES FOR RADIOSURGERY |
|Adjusting the wave form means the technique can be used for|
Loop electrodes are most frequently used. Ball-ended and needle electrodes are also available. A passive electrode needs to be placed in close proximity to the patient. Considerable smoke can be generated and units usually come with a vacuum extractor.
The tissues to be treated need to be moistened with normal saline before the electrode is applied and kept moist throughout the procedure. Radiosurgery will not work on dry tissue.
Unlike electrocautery, minimal pressure should be exerted on the tissues.
It is all too easy for the inexperienced operator to excise more tissue than necessary by applying too much pressure. The radio wave does the cutting.
Radiosurgery is most useful when removing benign polypoid and sessile lesions, such as skin polyps and naevi. In the case of polyps, excision is performed through the base of the pedicle with a loop electrode. In the case of sessile lesions, a loop electrode is used to excise through the base of the lesion.
Small lesions can be excised in one piece. Larger lesions are best excised piecemeal. Radiosurgery can also be very useful for removing xanthelasmata and excising benign scrotal lesions.
Precautions and limitations
A number of initial precautions should be taken, including determining whether the patient has a pacemaker, because some cardiac pacemakers can be affected by radiosurgery. Discuss this with the patient's cardiologist or pacing technician.
Inflammable skin cleansers must not be used beforehand and as with electrocautery, there is a small risk of explosion in the presence of concentrated oxygen.
Electrical shocks and burns can be avoided by not allowing any part of the patient to touch metal and ensuring the clinician wears rubber gloves.
Delayed bleeding is rare. It is best prevented by using local anaesthetics combined with adrenaline.
Although radiosurgery in treating skin malignancies is not absolutely contraindicated, it is of limited use in this situation, for two reasons.
First, it is sometimes difficult for the clinician to be sure that the lesion has been completely excised and second, tissue damage caused by the technique can make histological assessment of the lesion extremely difficult, particularly at the resection margins.
Thanks to colleagues at Thornhills Medical Practice for allowing me to present the cases and to Sue Bowman for help with photography.
- Dr Tim Cantor is a GPSI in dermatology at Thornhills Medical Practice, Larkfield, Kent
Brown JS. Minor surgery - a textbook and atlas . Arnold, London, 1997; 300-26.
|CASE STUDY 1: VULVAL POLYP |
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|A 39-year-old woman presented with a large vulval skin polyp that had been growing for five years. It had begun to snag on her underwear. It was easily removed under local anaesthesia with a radio wave loop through the base of its pedicle. The skin defect was closed with two 4/0 vicryl sutures. Histology confirmed it as a benign fibroepithelial polyp. |
|CASE STUDY 2: NAEVUS |
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|A 38-year-old woman presented with a clinically benign sessile naevus of her right upper arm, which was catching on her clothing. It had bled in the past following trauma. It was removed under local anaesthesia with a radio wave loop through its base. There was no significant blood loss and further cautery to control bleeding was not required. Histological examination confirmed that it was a benign intradermal naevus. |
|CASE STUDY 3: SKIN POLYP |
|A 65-year-old man presented with a broad-based skin polyp on his back that had been slowly growing over several years. It had begun to cause him discomfort when he sat on hard-backed chairs. Under local anaesthesia, it was excised through its base with a radio wave loop. Some electrocautery was required to control the bleeding. |
|CASE STUDY 4: SCROTAL CYST |
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|A 29-year-old man presented with a moderately large sebaceous cyst on his scrotum. Local anaesthetic (2% lidocaine with adrenaline 1 in 200,000) was injected around the entire lesion. It was then excised with some overlying skin, using a radio wave needle. The scrotal skin defect was closed with six 4/0 vicryl sutures. Histology confirmed the diagnosis. |
|CASE STUDY 5: NECK LESION|
|A 61-year-old woman presented with a clinically benign sessile lesion on the right side of her neck. It seemed to be growing. She was keen to have it removed because she had had a basal cell carcinoma excised from her left upper arm four months earlier. The neck lesion was removed with a radio wave loop, but appeared to have some invasive features macroscopically. The base of the wound was thoroughly curetted and cauterised. On histology, it proved to be a benign seborrhoeic keratosis.|