Nd:YAG laser-induced hyperthermia treatment of spontaneously occurring veterinary head and neck tumors.

Conventional hyperthermia treatment of superficial tumors in the oral cavity is troublesome due to difficulty in accessing the lesion. A new hyperthermia technique employing near-infrared radiation delivered through a flexible silica optical fiber is described. The system consisted of an Nd:YAG laser for tissue heating, a He-Ne laser for aiming beam, a computer-controlled optical shutter, an interstitial thermometer, computer, and a printer. A 3-m-long 600-microns silica fiber delivered laser energy to the tumor via surface illumination. Using the aiming beam, the spot size was adjusted to include 5 mm of surrounding normal tissue. A thermocouple implanted in the tumor base provided temperature feedback to maintain desired hyperthermic temperature within the lesion. Three spontaneously occurring canine (two squamous cell carcinomas on the gum, one pigmented melanoma on the hard palate) and one feline tumor (squamous cell carcinoma on the nose) have been treated with Nd:YAG laser hyperthermia. Hyperthermia was delivered at 43.5 degrees C for 1 h. All animals received standard radiation treatment prior to hyperthermia. Nd:YAG laser hyperthermia allowed effective and efficient delivery of heat to veterinary nasal and oral lesions otherwise not treatable with conventional heating techniques.