Cryosurgery Module

Background Information

Whereas the four other modules in this exhibit address the effects of various forms of energy acting on the body, this module focuses on the removal of thermal energy from living tissues. Traditionally, cryosurgery has been used to treat external tumors such as those on the skin, but recently some physicians have begun using it as a treatment for tumors that occur inside the body.

For internal tumors, liquid nitrogen is circulated through an instrument called a cryoprobe, which is placed in contact with the tumor. The temperature of the cryoprobe is approximately - 196 ° C (- 321 ° F). An ice ball forms as the tissue surrounding the cryoprobe freezes. The ice ball is allowed to extend just past the tumor and into healthy tissue to ensure that all of the diseased tissue is destroyed. This rapid freezing process causes ice crystals to form inside cells, damaging cell membranes and intracellular structures and resulting in cell death. Ice may also form outside of cells, removing available water and causing dehydration of the cells.

After the ice ball has formed, the tissue is slowly warmed. This thawing process causes even more cells to die, often due to a lack of oxygen since damaged blood vessels can no longer function. Doctors repeat these "freeze-thaw cycles" during cryosurgery to maximize the efficacy of the procedure.

The activities in this module explain the cellular effects of cryosurgery and demonstrate how cryosurgery is used to destroy cancerous tumors in the body.