Techniques et instrumentation de la cryochirurgie moderne

Synthèse des récents développements relatifs à la cryochirurgie. (En anglais)
The use of cold temperatures to freeze cancer cells dates back to James Arnott’s first experiments in England using crushed ice and sodium chloride to freeze breast and uterine cancers around 1845. However, it wasn’t before 1961, with Dr. Irving Cooper’s invention of liquid nitrogen cryoprobes that modern cryotherapy came into being.
Since the 80’s, device miniaturization makes it possible to introduce endoscopic cryoprobes through natural channels (bronchia, urethra…) without requiring traditional surgery.
The parallel development of ultrasound echography allowed for the improvement of monitoring techniques and crysosurgery is now used in dermatology, ophthalmology, and cancer treatment. In some cases, the cryorefrigerant is directly poured, sprayed or dabbed on the lesion. This simple treatment is only possible on small lesions and may lack efficiency. The other technique consists in using the cryofluid to cool a probe that will come into contact with the tissues to heal.
A cryoprobe tip is made of thermally conductive metal, generally copper covered with gold to facilitate cleaning. The probe should also be able to heat up quickly so that it can be detached from the treated surface and applied elsewhere. There are various shape and size configurations, but the two main technologies used are liquid nitrogen probes and Joule-Thomson expansion probes.

. In liquid nitrogen probes, liquid nitrogen is brought to the tip where it evaporates in contact with the metal, thus extracting heat from the chosen tissues. Nitrogen evaporation allows for constant temperatures at -196°C. Its main advantage is its capacity to reach very low temperatures which enable rapid and extended freezing of the tissues. However due to thermal inertia while the device is being switched on, the duration of the intervention can be relatively imprecise. The device also offers limited maneuverability.

. In Joule-Thomson expansion cryoprobes, gas at high pressure is released through a tight orifice into a lower-pressure chamber and undergoes an expansion and cooling process that is harnessed by heat exchangers near the probe’s tip. Nitrous oxide (N2O) at ambient temperatures is often used for this purpose, as its expansion allows for temperatures down to -90°C. The device requires a storage bottle and a transfer tube to the probe. Its capacity to be cooled immediately allows for higher precision and control over the duration than the nitrogen system but it requires higher operation temperatures. Nitrous oxide can also act as a hydrocarbon solvent and traces of hydrocarbons can cause irreversible blockage to the system if special care isn’t taken in cleanliness and fluid pureness.

Froid et chirurgie, P. Haberschill et al. Revue Générale du Froid, November 2013

Find out more on cryosurgery by consulting the IIR Informatory Note “Applications of Cryosurgery” on the IIR's Web site (Publications/Informatory Notes section).