Minimally invasive probe system capable of performing both cryosurgery and hyperthermia treatment on target tumor in...

Cryosurgery is a clinical therapy aiming at the destruction of diseased target tissues through a controlled deep freezing and subsequent rewarming. It has recently been realized that freezing immediately followed by a rapid and strong heating of the target tissues would significantly improve the treatment effect. However, most of the currently available cryoprobe systems are only capable of performing a single freezing function. To accommodate to the rapid growth of the combined freezing and heating therapy of tumor treatment, we have developed a new cryoprobe system with a powerful heating feature, which can be conveniently applied to destroy the tumor in deep tissue using a minimally invasive approach. Its operation performance will be characterized through a series of experimental tests in air, water, phantom gel, in vitro tissues and rabbits under anaesthesia. This system is perhaps the first one aiming at performing both cryosurgery and hyperthermia on target tumors. Therefore, it provides the clinicians with more choices and algorithms on treating a specific diseased tissue. Further, strain sensors and thermocouples were applied to simultaneously record the transient temperature and the thermal stress fields over the tissues subjected to freezing and strong heating. It was observed that a sudden change in the transient thermal stress was often induced when phase change occurs, which may imply that an evident thermal stress occurs at the liquid-solid interface. This modifies the commonly accepted viewpoint that no stress should exist at the liquid-like phase change interface. Further, implementations of this new system in clinical cryosurgery or hyperthermia are discussed. In addition to the applications in tumor treatment, the present system can also be very useful in fundamental research such as revealing the thermal stress mechanisms in tissues due to quick freezing and heating, which is hard to do otherwise. One interesting result presented in this paper is the experimental discovery of shock rings induced in the biomaterials around the probe, due to alternant freezing and heating by the present system.