Microwave ablation has become an increasingly common, less invasive method of surgically eliminating pathological or abnormal growths within the human body by targeted exposure to the effects of microwave radiation. From the first human to scratch an itch with a fingernail to the ophthalmologist who can restore vision by shaving off a layer of the eye’s cornea with a laser beam, the surgical removal of unhealthy biological tissue is one of the cornerstones of medicine. Although other ablation methods — both old and new — exist, safely controlled microwaves are proving to be a viable tool of surgery for many medical disorders.
Ablation is the removal of material from the surface of an object. Microwaves are electromagnetic radiation just beyond the infrared spectrum, with frequencies narrow enough to affect matter in its wake at the molecular level. Microwave ablation surgery employs a device capable of generating microwaves that destroy unwanted cells within a localized energy field. There are other alternative ablation techniques as well, including cryoablation with a freezing coolant, alternating current radio frequencies and high frequency ultrasound vibration. Only a physician, in consultation with an interventional radiologist, can determine whether microwave ablation will be the best therapy for a particular medical condition.
Radiology had already been applied to medical purposes for several decades, but it was not until modern technology had refined the means of delivery that its practical use in surgery accelerated. Energy output is now focused and controlled to a small area; power generators are portable. Probes have miniaturized to allow minimally invasive surgical introduction through catheter or endoscope. Computed tomography (CT) scans and X-ray tomography enable interior image guidance with the precision to target even small, precancerous tumors.
A typical microwave ablation machine will consist of a generator whose frequency, power and duration output can be controlled to affect the size and rate of tissue ablation. It is connected by a thin, flexible conductor to an applicator whose tip is a tiny microwave antenna, usually disposable. The terminal antenna radiates the microwave energy in a small, roughly spherical field, within which water molecules in particular vibrate in sympathy and generate heat sufficient to “cook” and kill living human tissue matter. Depending on the specific treatment, dead tissue is allowed to remain as scarring, it might slough off and be expelled by the body naturally, or a follow-up procedure might be required for tissue removal.
While older and perfected surgical ablation techniques, including open procedures for abrasion or excision, predominate the operating room, the increasing success of microwave thermotherapy has seen its wider application across many medical fields. The method is a frequent option for endometrial ablation to control excess bleeding and other disorders of the female uterus. It is another treatment tool for oncologists in the difficult fight against cancer. Microwave ablation surgery is even being used endoscopically through three small chest incisions on the actively beating heart of patients not sedated under general anesthesia for the treatment of atrial fibrillation and other cardiac disorders.