Infrared image to evaluate the selective (directional) freezing due to localized injection of thermally important...

Cryosurgery is a minimally invasive surgical technique that employs the destructive effect of freezing to eradicate benign or malignant tumors which are difficult or even impossible to be extirpated by conventional surgery. Recently, we proposed a method for flexibly controlling the freezing scale during cryosurgery by percutaneously injecting thermally important functional solutions into the target tissues. This method can also help modify the direction of the iceball formation which is desirable for a successful cryosurgery for treating tumors with complex anatomical structure. To evaluate the effect of controlling the size, shape and direction of the iceball formation by injecting solutions with specific thermal properties into the target tissues, a medical infrared thermometer was introduced in this paper to map the temperature profile over the whole surface above the treated area. The cryosurgical procedure was performed using a minimally invasive cryoprobe cooled by liquid nitrogen in order to obtain a deep regional freezing. Meanwhile, one thermocouple was also amounted in the tip of the probe to record the transient temperature in order to detect the freezing and thawing effect on the tissues. The obtained infrared image was applied to monitor and evaluate the whole process. Simulation experiments on biological tissues (fresh pork and liver) were performed in vitro and four different liquids were injected into the test materials, which were distilled water, an aqueous suspension of aluminum nano-particles in water, ethanol and a 10% solution of the cryoprotective agent dimethylsulfoxide, (Me2SO), respectively. It was clearly demonstrated that the localized injection of an appropriate solution could effectively regulate the tumor-killing area via directional freezing. The study also suggested that infrared imaging can be used as an effective way to monitor and evaluate the selective freezing process, which will provide important information to help enhance fr- eezing damage to the target diseased tissues while preserving the normal tissues from injury.