Cryosurgery denotes the therapeutic ablation of tissues by
cold. Its use was first described by Arnott in 1851 for the
treatment of carcinoma of the cervix, but never attained clinical
prominence due to lack of a simple controlled means of applying
cold to tissues. The introduction, 100 years after Arnott's
original treatise of cryogenic apparatus based on the circulation
of liquid nitrogen³⁰ reawakened interest in this form of treatment.
Despite its widespread application in many of the surgical
specialities over the last eight years, little experimental effort
has been made to quantitate the destructive effect of low
temperatures used in this way. From the surgeon's point of view
it is essential to know what factors determine the quantity of
tissue water frozen under any given conditions, to what extent this
phase change of water produces cellular death and how he can best
control his freezing to produce optimal destruction.
This paper is a study of:-
(1) The macroscopic and microscopic changes which occur in
tissue after single and repetitive freeze -thaw cycles.
(Repetitive freeze -thaw cycles indicate successive freezing and
thawing at the same site as opposed to multiple freeze -thaw cycles
where the successive applications are at different sites.)
(2) Those variable factors which determine the size of the
cryolesion (the spherical zone of ice surrounding a cryoprobe in
tissue) and these may be subdivided as being: -
(a) Related to the environment.
(b) Related to the cryoprobe.
(c) Related to the tissues.
These three aspects of the problem will be considered
The cryogenic apparatus used throughout these experiments was
the Linde-Cooper Cryosurgery Unit CE 2A (Union Carbide Corporation)
which utilises circulating liquid nitrogen (- 196 °C) through a partially insulated operating cryoprobe. Two standard probes
whose freezing tips approximated to hemispheres 2.5 mm and 5 mm
respectively were used.
A second prototype instrument, supplied by the Hymatic
Company, was used which generates cold by the Joule Thomson effect
involving rapid expansion of pressurised Argon (2,500 p.s.i.)
through a tight nozzle. The cooling probe of this
machine carried four microthermocouples embedded at 0.14 cm intervals in a non -heat conducting plastic extension.
The resultant frozen tissue was measured through an operating
microscope incorporating an eye -piece graticule scale permitting
measurements with an accuracy up to 0.02 cm.
The macroscopic and microscopic changes which follow the freezing
of tissues resemble ischaemic infarction and are productive of a fibrous scar within six weeks of freezing. Histological death of
tissue extends throughout the whole frozen volume and is considered
the result of ischaemia rather than crystal formation.
Absolute prediction of the volumes of tissue frozen in vivo
by consideration of the variable physical factors involved will not
be possible until more information is available regarding local
tissue blood flows and the thermal properties of human tissues.
At present, thermocouples provide the most accurate means of
control available and the ways in which an analysis of the thermal
gradients in frozen and unfrozen tissue can aid in their intelligent
use has been outlined.