Using high-frequency radio wave technology in veterinary surgery - Veterinary Medicine
  • SEARCH:
Medicine Center
DVM Veterinary Medicine Featuring Information from:

ADVERTISEMENT

Using high-frequency radio wave technology in veterinary surgery
Does radiosurgery have a place in your practice? These factors can help you determine whether you should consider it as an alternative to incising tissue with a scalpel.


VETERINARY MEDICINE


Frequency

The final factor in the equation is the denominator, frequency. Radiosurgical instruments operate at frequencies of 3.8 to 4 MHz. Electrocautery devices operate at much lower frequencies, in the 300- to 500-kHz range. Higher frequencies result in less lateral distribution of heat from the incision and more accurate application of energy.2 Interestingly, 4 MHz appears to be the ideal frequency, in that frequencies higher than 4 MHz can create channeling, thus damaging tissue distant to the incision, and higher frequencies increase the risk of sparking, resulting in excessive lateral heat transfer.7

PROS AND CONS OF VARIOUS CUTTING INSTRUMENTS

Tissue cuts are produced when tissue fibers are divided by a concentrated application of energy. To understand the advantages and disadvantages of instruments used to divide tissue, you must understand how cuts are made and how different tissues respond to cuts. Three principal factors are involved in the cutting process: the properties of the tissue to be incised, the shape of the instrument, and its guidance by the surgeon.8

Tissue properties

A key property of tissue is sectility. Tissue sectility is determined by the degree fibers are cut compared with how much they shift as energy is applied. Tissues of high sectility are more easily cut, while those of low sectility are apt to remain intact. Sectility may be enhanced by increasing tension directly in front of the cutting instrument and by increasing the speed of the cutting device's travel. Placing tension on low-sectility tissue while making an incision requires extensive mechanical support and may create a final incision that looks quite different from that initially intended by the surgeon. The eyelids are good examples of low-sectility tissue. They are difficult to incise in their normal state, but cutting is enhanced through mechanical support (e.g. chalazion forceps).

Instrument shape

The action of a scalpel is determined by the sharpness and shape of the blade. The sharper the cutting edge, the less the tissue resistance, which results in more efficient cuts. The length of the cutting surface is also important. A longer blade edge has greater lateral resistance, resulting in the blade's following the path of least resistance when guided parallel to the blade's cutting surface.8 Shorter blades have less lateral resistance, allowing a surgeon to manipulate the blades around surfaces. So blade length is directly proportional to the ease with which a surgeon makes a straight incision but inversely proportional to the ease tissue is incised along contours. Scalpel blades are ideal for cutting tissues of high sectility, especially in cases in which long straight cuts are desired. Lasers and radiosurgical electrodes offer the advantage of being point cutting devices (devices with very short blade length, or, in the case of these modalities, no blade length) in which there is no lateral resistance, allowing the cut to be completely controlled by a surgeon.

Since tissue resistance is not a factor with lasers or radiosurgical devices, tissue sectility is not a factor. This allows a surgeon to make precise cuts with minimal tissue support. The cutting ability of the laser is determined by the source of atoms being excited to emit energy as photons. Examples of lasers used in veterinary medicine include carbon dioxide, neodymium:yttrium-aluminum-garnet (Nd:YAG), and diode lasers. Carbon dioxide lasers are commonly used in veterinary medicine to incise skin and other superficial tissues. Carbon dioxide lasers produce an infrared light (10,600 nm) that is invisible to people. The slower a surgeon passes the laser beam across the tissue, the deeper the cut; however, similar to radiosurgical electrodes, the slower the passage, the greater the lateral heat distribution. The wavelength of light emitted by a laser also determines its effectiveness in ablating tissue. For example, carbon dioxide laser light is preferentially absorbed by water, and cells with high water content are vaporized as they absorb carbon dioxide laser energy; thus, high-moisture tissues will be more effectively removed. Diode lasers emit a light preferentially absorbed by melanin, so pigmented tissue is more effectively removed.

As previously discussed, many factors are involved in determining the incision made with radiosurgery, including the shape and size of the active electrode. Fine-wire electrodes concentrate the radio wave into tissue with immediate contact. The radio wave vaporizes cells contacting the electrode. Once the cells are vaporized, the resulting air gap between the electrode and adjacent tissue serves as insulation to prevent lateral heat transmission. The length of the exposed wire will determine the depth of the incision. Larger-diameter electrodes transfer the radio wave less efficiently and, while vaporizing cells in contact with the electrode, allow the transfer of some heat laterally to enhance hemostasis.


ADVERTISEMENT

Source: VETERINARY MEDICINE,
Click here