• Development of three novel cryoprobes using heat transfer control was carried out to improve the cooling technique in cryosurgery. • Peltier cryoprobes were developed to achieve precise temperature control and high cooling power and to aim at controlling a frozen region as thin as possible for accurate skin cryosurgery. The cooling rate and the lowest temperature of the cooling section can be controlled by a PID controller. The minimum controllable frozen depth was calculated and it indicated that the Peltier cryoprobe could control a frozen depth larger than 400 im. Additionally, the results of an animal experiment clarified that the necrosis depended strongly on the lowest temperature; only epidermis was necrotized at −30°C, and dermis was also necrotized in some samples at −40°C. • A flexible cryoprobe without vacuum insulation was developed by using a liquid refrigerant and its isenthalpic expansion for the treatment of stomach cancer with the endoscopic instrument. The cooling performance was evaluated experimentally and it was confirmed that the proposed cryoprobe enables one to freeze the agar gel within 12 s. The experiment of repetition of cooling and heating by utilizing the Peltier effect indicated that the flexible cryoprobe could easily perform heat transfer control by adjusting the electric current. An animal experiment was also conducted in order to estimate the availability of the flexible cryoprobe. In that experiment, the skin surface froze within 80 s. It is clear that the repetition of cooling and heating is more effective for destruction of the cells than continuous long time cooling. • An ultrafine cryoprobe 0.55 mm in diameter and cooled by the boiling heat transfer of a refrigerant was developed for treatments of a very small affected area and cryosurgery in a blood vessel with a catheter. The ultrafine cryoprobe cooled by HFC-23 in the liquid phase showed that the surface temperature was −50°C when the cryoprobe was thermally insulated. It is obvious that this cryoprobe has the large heat capacity to achieve cooling in a small region. A freezing experiment with agar at 37°C was conducted. The surface temperature in the frozen region was reached at about −35°C. In 5 min, the radius of the frozen region was approaching 3 mm. The experimental results indicate that the ultrafine cryoprobe has sufficient cooling power to create a frozen region in the living body.
|Title of host publication||Modern Cryosurgery for Cancer|
|Publisher||World Scientific Publishing Co.|
|Number of pages||38|
|ISBN (Print)||9814329657, 9789814329651|
|Publication status||Published - 2012 Jan 1|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)