Cells that are in the process division are vulnerable to damage by AC
electric fields that have specific frequency and field strength
characteristics. The selective destruction of rapidly dividing cells can
therefore be accomplished by imposing an AC electric field in a target
region for extended periods of time. Some of the cells that divide while
the field is applied will be damaged, but the cells that do not divide
will not be harmed. This selectively damages rapidly dividing cells like
bacteria, but does not harm normal cells that are not dividing. Since the
vulnerability of the dividing cells is strongly related to the alignment
between the long axis of the dividing cells and the lines of force of the
electric field, improved results can be obtained when the field is
sequentially imposed in different directions.