Thermal ablation is a medical procedure that uses extreme heat or cold to destroy abnormal tissues, such as tumors. As an alternative to conventional surgery, this technique involves applying focused energy directly to a target area to kill unwanted cells. The destroyed tissue is then gradually absorbed by the body over several months.
Methods of Thermal Ablation
Heat-based, or hyperthermic, methods use various energy sources to elevate tissue temperatures, causing irreversible cell damage. The goal is to heat the target tissue to at least 60 degrees Celsius. This temperature causes coagulative necrosis, a process where the structural proteins of the cells are altered, leading to their death.
One of the most established heat-based methods is Radiofrequency Ablation (RFA). RFA uses high-frequency electrical currents delivered through a needle-like probe inserted into the target tissue. The electrical current agitates ions in the surrounding cells, creating frictional heat that conducts outward and destroys the abnormal cells.
Microwave Ablation (MWA) is another hyperthermic technique that uses electromagnetic waves to heat tissue. Unlike RFA, MWA directly heats a volume of tissue by causing water molecules to rapidly realign with an oscillating electric field. This molecular agitation generates significant heat, allowing for faster and larger ablation zones compared to RFA. MWA can also be more effective in tissues with high impedance, like bone or lung.
Other heat-based methods include Laser Interstitial Thermal Therapy (LITT) and High-Intensity Focused Ultrasound (HIFU). LITT, or laser ablation, uses focused light energy from a fiberoptic probe, which converts to heat at the probe’s tip to destroy tissue. HIFU is a non-invasive technique that focuses ultrasonic waves deep within the body, converting acoustic energy into heat at a specific point without an incision.
Cryoablation uses extreme cold to eradicate diseased tissue. This method circulates a cryogen, such as argon gas, through a specialized probe called a cryoprobe. The rapid expansion of the gas at the probe’s tip creates a significant temperature drop, freezing the surrounding tissue. Cell death occurs as intracellular ice crystals form, damaging cell structures, while ice in the surrounding space causes dehydration.
Medical Applications and Targeted Tissues
In oncology, thermal ablation is frequently used to destroy solid tumors in the liver, kidneys, lungs, and bones, particularly for patients who are not candidates for surgery. It is often applied to tumors smaller than five centimeters and can be used alone or with other treatments like chemotherapy. The choice between methods like RFA and MWA depends on the tumor’s size, location, and proximity to large blood vessels.
Cardiology is another field for thermal ablation, specifically for correcting heart rhythm disorders (arrhythmias). Atrial fibrillation, a common irregular heartbeat, is frequently treated with cardiac ablation. Either radiofrequency energy or cryoablation is delivered via a catheter to the heart. The energy creates small scars on the heart tissue to block the abnormal electrical signals causing the arrhythmia, restoring a normal rhythm.
Vascular medicine uses thermal ablation to treat conditions such as varicose veins. Endovenous thermal ablation uses laser or radiofrequency energy delivered through a catheter to heat and close the affected vein. This procedure, a minimally invasive alternative to vein-stripping surgery, redirects blood flow to healthier veins and alleviates symptoms.
Thermal ablation also treats benign conditions. It is used to destroy non-cancerous thyroid nodules, reducing their size and relieving symptoms. Gynecologists may use the technique for uterine fibroids as a less invasive option than hysterectomy. The technology is also employed for pain management by destroying nerve endings that transmit chronic pain signals.
The Ablation Procedure
Before the procedure, patients undergo imaging scans like CT, MRI, or ultrasound. These images allow the physician to map the precise location, size, and shape of the target tissue. Patients also receive specific instructions, which may include fasting or stopping certain medications like blood thinners.
On the day of the procedure, the patient is positioned on a treatment table with monitors for heart rate and blood pressure. Anesthesia is administered for comfort, ranging from local with sedation to general anesthesia, depending on the procedure. The treatment is minimally invasive, performed through a small puncture or incision in the skin.
Guided by real-time imaging, the physician inserts a thin, needle-like probe through the skin and into the target tissue. Once the probe is in the correct position, the energy source is activated. The ablation can last from a few minutes to half an hour, and the probe may be repositioned to treat a larger area.
After the treatment, the probe is removed, and a simple dressing is applied to the skin opening, which generally does not require stitches. The patient is moved to a recovery area for a short observation. Many thermal ablation procedures are performed on an outpatient basis or require only a short hospital stay, allowing for a quicker recovery than open surgery.