Understanding the relationship between lateral spread of freeze and depth of freeze.

The predictable relationship between lateral spread of freeze and depth of freeze is a keystone concept in the clinical evaluation of "depth dose" of cryosurgical procedures. This relationship can be readily determined and understood by carrying out simple experiments using potato models and checked directly by measurements on patients. When using specialized treatment methods such as the "cone-spray" technique with liquid nitrogen, it is necessary to limit the technique to properly selected cases and to spray the treated surfaces evenly if the predictable ratio of depth of freeze to lateral spread of freeze is to be used.