A cryoprobe is a medical device that uses extreme cold to freeze and destroy abnormal tissue, take tissue samples, or treat irregular heart rhythms. It works by rapidly expanding compressed gas inside a sealed needle-like instrument, dropping the probe tip to temperatures as low as −165°C. Cryoprobes range from slim, flexible instruments thin enough to pass through a bronchoscope in the lungs to balloon-tipped catheters designed to treat the heart.
How a Cryoprobe Generates Cold
A cryoprobe is essentially a high-pressure, closed-loop gas expansion system built into a needle or catheter. Compressed argon gas travels through the probe’s inner channel until it reaches a narrow opening, called a throttle, near the tip. When the gas is forced through this throttle, it expands rapidly to atmospheric pressure. That sudden expansion causes the gas temperature to plunge, a principle in physics known as the Joule-Thomson effect. It’s the same reason an aerosol can feels cold when you spray it.
The cold from the expanding gas transfers through the metallic walls of the probe tip and into the surrounding tissue. The spent, depressurized gas vents back out through the probe’s hub, keeping the system in a continuous loop. When doctors need to warm the probe and thaw tissue, they switch to helium, which has the opposite behavior: it heats up when it expands. This freeze-thaw cycling is a deliberate part of most cryoprobe procedures because repeated cycles cause more thorough tissue destruction.
What Freezing Does to Tissue
When a cryoprobe drops tissue below −40°C, water inside cells freezes into ice crystals that physically puncture cell membranes and internal structures. At the same time, the freezing process pulls liquid water out of cells through osmosis, concentrating the remaining solutes to toxic levels and causing severe dehydration. These two mechanisms, direct ice damage and osmotic stress, kill cells immediately.
A second wave of destruction follows. Damaged cells release signaling molecules that recruit immune cells to the area, triggering an inflammatory response that can persist for weeks or even months as the body clears dead tissue. Blood vessels in the frozen zone also sustain damage, cutting off blood supply and starving any surviving cells of oxygen. The combination of immediate freezing injury, delayed immune response, and vascular shutdown is what makes cryoprobe treatment effective against tumors and other target tissues.
Tumor Ablation
Cryoprobe-based ablation is used to treat tumors in the kidney, liver, lung, prostate, and breast. More recently, it has expanded to soft tissue tumors like desmoid tumors, vascular malformations, sarcomas, and pelvic lesions. The procedure is percutaneous, meaning the probe is inserted through the skin rather than through open surgery, which reduces recovery time and avoids the risks of general anesthesia in many cases.
Doctors guide the probe into position using imaging. CT is the most common choice because it provides detailed anatomical views, though it requires repeated scans that add radiation exposure. Ultrasound offers real-time feedback but struggles to clearly show the ice ball that forms around the probe tip. MRI gives the best soft tissue contrast but is slower and more expensive. Newer electromagnetic navigation systems integrate with CT to provide continuous, real-time tracking of the probe, reducing the need for repeated scans.
During ablation, one or more cryoprobes are placed directly into the tumor. As the probes cool, an ice ball forms around each tip and grows outward. The goal is to extend the ice ball beyond the tumor’s edges to ensure complete destruction. Argon-based devices can reach roughly −125°C within the first minute of freezing, while liquid nitrogen systems drop even further, to around −165°C within three minutes.
Heart Rhythm Treatment
Cryoablation has become a standard treatment for atrial fibrillation. In this application, the cryoprobe takes the form of a balloon catheter threaded through a vein into the heart. The balloon is inflated at the opening of each pulmonary vein, where the electrical signals that trigger atrial fibrillation typically originate. Freezing the tissue at these sites creates scar tissue that blocks the faulty signals.
The critical temperature for permanently disabling heart tissue is −30°C. Reaching that threshold quickly is a strong predictor of a successful procedure. Because the esophagus sits close to the back of the heart, doctors monitor esophageal temperature during the freeze and stop if it drops below 25°C to prevent thermal injury.
The most common complication specific to cardiac cryoablation is temporary irritation of the phrenic nerve, which controls the diaphragm. Transient phrenic nerve effects occur in roughly 6 to 11% of patients, but persistent effects lasting beyond the procedure happen in only about 1 to 2% of cases. Nearly all resolve within a year, and cases lasting longer than 12 months are exceedingly rare, reported in about 0.2% of patients in large studies. Overall major complication rates for the procedure range from 2 to 7%.
Lung Biopsies
Cryoprobes have changed how pulmonologists collect tissue from the lungs. Traditional forceps biopsies taken through a bronchoscope are small and often crushed during collection, making them difficult for pathologists to interpret. A cryoprobe biopsy solves both problems. A flexible probe, typically 1.9 mm or 2.4 mm in diameter, is threaded through the bronchoscope’s working channel and advanced into the target area of the lung. The tip is activated for about five seconds, freezing the surrounding tissue onto the probe. The entire bronchoscope is then pulled out along with the probe, because the frozen tissue sample is too large to fit back through the instrument’s channel.
The samples are larger, better preserved, and free of the crush artifacts that plague forceps biopsies. This is particularly valuable for diagnosing interstitial lung diseases like idiopathic pulmonary fibrosis, where traditional biopsies often fail to capture enough intact tissue for a confident diagnosis. The procedure is typically reserved for cases where standard biopsies have failed or are unlikely to yield enough tissue.
Skin Lesion Treatment
In dermatology, cryoprobes are one of several tools used to apply extreme cold to skin lesions. The closed or contact technique presses a probe cooled with liquid nitrogen directly against the skin. This differs from the more common open spray technique, where liquid nitrogen is sprayed onto the lesion freehand. The probe method offers more precise targeting, which matters when treating lesions near sensitive structures like the eyes or when the goal is to limit damage to surrounding healthy skin.
Benign conditions treated this way include seborrheic keratoses, warts, skin tags, molluscum contagiosum, and sun spots. Precancerous and cancerous lesions, including actinic keratoses, basal cell carcinomas, and noninvasive squamous cell carcinomas, can also be treated with cryosurgery. For pedunculated lesions (those hanging from a stalk), a variation of the technique uses forceps or needle drivers cooled with liquid nitrogen to grasp and freeze the growth simultaneously.
How Cryoprobe Sizes Vary by Use
Cryoprobes are built to match their intended target. Lung biopsy probes are slim and flexible, with outer diameters of 1.9 mm or 2.4 mm, designed to navigate the branching airways of the lungs through a bronchoscope. Percutaneous ablation probes used for tumors are thicker and rigid, resembling large-gauge needles that can be inserted through the skin under image guidance. Cardiac cryoballoon catheters are larger still, with an inflatable balloon at the tip sized to seal against the openings of pulmonary veins. Dermatology probes come in various flat or rounded tip shapes optimized for surface contact with skin lesions. The core physics is the same across all of them: compressed gas, rapid expansion, and extreme cold delivered exactly where it’s needed.