Cryosurgical Techniques

Abstract

The following chapter deals with the cryosurgical techniques. Using basic cryosurgical instruments, the reader will learn how to use spraying tips, probes, chambers, tweezers, and cones. There are six basic techniques—open, semi-open, close, semi-close, tweezers, and intralesional—and they will be covered thorough the chapter. For each one, the equipment and the common and some nonconventional uses will be presented.

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

FormalPara Key Points

• There are six common cryosurgical techniques: open, semi-open, close, semi-close, tweezers, and intralesional.

• Each one uses different equipment. Each technique tends to be used for different types of lesions (open technique in benign, close technique in malignant), but there are special uses that will improve the cryosurgical outcome.

1 Introduction

Once the correct equipment is available, mastering certain techniques is the focus. For each technique, there is specific equipment, and there are some common indications. First, one has to feel confident and master the common techniques; after this occurs, one can begin to apply techniques in nonconventional manners.

For the sake of clarity, techniques have been named as follows:

• 1. Open or spraying technique

• 2. Semi-open technique

• 3. Close or probe technique

• 4. Semi-close or chamber technique

• 5. Tweezers technique

• 6. Intralesional technique

2 Common Cryosurgical Techniques [1]

2.1 Open or Spray Technique

This is probably the most utilized cryosurgical technique. The cryogen (LN) is sprayed out from the unit through nozzles (tips or terminals) of different apertures (Chap. 4) directly on the skin surface [1].

As LN exits through a standard aperture, it forms a conical pattern and cools upon expansion (Joule-Thomson process). With the unit kept perpendicular to the skin, this cone will cool in a uniform manner and have a height (h) which corresponds to the distance of the nozzle opening to the skin, a radius (r) which is the distance from the center of the freezing area towards the periphery, and a side length (s) (Fig. 5.1).

Fig. 5.1

Sprayed LN exits, forming a conical pattern. This cone will have a height (h) which corresponds to the distance from the tip opening to the skin, a radius (r) which is the distance from the center of the freezing area towards the periphery, and a side length (s)

Once LN reaches the skin surface, the freezing front advances horizontally on the skin surface as well as vertically (in depth) following an isotherm pattern (Fig. 5.2). Isotherms are temperature zones of equal temperature; the isotherm pattern in skin freezing will have a center where the temperature is the lowest, and the temperature at the periphery where it will be the highest.

Fig. 5.2

Superficial freezing front extends radially. In depth, it does so in approximately a half sphere with concentric isothermal rings

There are three important points to keep in mind when using the spray technique:

• 1. Tip diameter. The amount of released LN will depend on the diameter of the tip opening. Larger openings release more LN. Choose small openings for delicate, superficial freezing and whenever you need to be sure to freeze a small and well-defined lesion (like a lentigo). Large openings are used to freeze large tumoral masses or extended large lesions. A small opening will result in a slower freezing. It will take longer to freeze a lesion (Fig. 5.3).

  Fig. 5.3

  

  Diameter of aperture. For nozzles placed at the same distance, perpendicular to the skin and different apertures, the larger aperture will release more LN. Freezing will be faster, larger in superficial surface and deeper

• 2. Distance. The distance between the releasing tip and the lesion is very important. Since air is a bad conductor, the farther away you spray, the less freezing you will achieve. Furthermore, the spray angle is not constant for larger h (distance to the skin). Since spray coverage will depend on the spray angle, the distance has to be maintained constant. Keep this in mind and always work at the same distance from the subject (Fig. 5.4).

  Fig. 5.4

  

  Distance from the skin. For two nozzles with the same aperture, both spraying perpendicular to the surface, the more distant one will freeze less

• 3. Inclination. The cone of LN released from a unit parallel to the skin will be spherical. Instead, if the unit is not kept parallel to the skin, it will be an oblique cone. A tilted spraying will result in an irregular freezing: the side closer to the skin will have a lower temperature and therefore experience larger destruction, while the other end will have a higher temperature (less destruction) (Fig. 5.5).

  Fig. 5.5

  

  For two nozzles that share the same size of aperture and distance but different positions (one perpendicular to the skin surface and the other tilted), freezing of the tilted spray will cause irregular freezing (colder in the area close to the opening and warmer at the distal extreme)

As LN hits the skin and freezing begins, the skin turns white. With pendular movements (Fig. 5.6), whiteness appears in every area the LN has reached, giving a false freezing front. Pendular movements are used for very superficial freezing, as is the case in cryopeelings. It is a good idea to delineate in advance with a marker the lesion and the margins because freezing (ice whiteness and the edema) can blur the margins.

Fig. 5.6

Spraying turns the surface skin white. By freezing without moving the unit, freezing will spread from the center outward. With swinging or brush movements, the skin turns white but for a shorter period since freezing is very superficial

For spray freezing where one needs to guarantee a regular freezing front, it is necessary to maintain a stable freezing at the center and allow it to expand towards the periphery. Maintain the same distance and the same position. This technique has also been called the time spot freeze [2].

Having more than one nozzle helps adjust to different needs. For instance, there is a spray nozzle called advance acne aperture (Brymill®). It produces a spray pattern which appears flat and elongated. It is used for acne lesions, and it is particularly useful for cryopeelings.

The open technique is ideal in:

• Superficial flat lesions, like lentigos solaris

• Dome-shaped or thick lesions, such as seborrheic keratosis or small keloids

• Superficial freezing for cryobiopsy (Chap. 7)

• Irregular tumoral masses where the irregularity of the surface would not enable probe use

The open technique should be avoided in:

• Protruding skin lesions (like skin tags). Freezing elongated lesions with the open technique will cause an unnecessary rim of healthy skin to freeze, with a resulting hypo- or hyperpigmented spot.

• In orifices (nose, mouth).

• In vascular lesions unless you freeze in an intermittent manner and allow the freezing front to advance slowly until it reaches the bottom (see the discussion of the pyogenic granuloma technique in Chap. 12).

2.1.1 Advantages

• It tends to be quicker and less laborious than other techniques.

• It is especially convenient in multiple lesions, such as seborrheic keratosis.

• Since there is no contact, there is no risk of sticking on the surface and over-freezing. Once the spraying stops, thawing begins.

• It is ideal when treating irregular bulky tumors that cannot be curetted.

• Since there is no contact, it is the safest technique. There is no contact with blood or other secretions.

2.1.2 Disadvantages

• Swinging the unit as you freeze can cause false freezing fronts and yield the wrong impression of having frozen the whole lesion at the expected temperature.

• Distance and tilting is operator dependent and will change the outcome of a procedure.

• Its initial impact on the skin, once freezing starts, can startle the patient.

• Peri lesional LN spattering is possible which might cause discomfort.

2.2 Semi-open Technique

It is as a variation of the spraying technique [3] in which the released spray is constrained into one area. The limits are set by a rubber cone, the opening on a lexan plate, or an otoscope disposable specula tip (Fig. 5.7). Metal cones should never be used because they are excellent conductors of cold and they will get stuck to the surface, causing addition destruction.

Fig. 5.7

Sprayed LN can be confined with lexan plastic plates, rubber cones, or otoscopes

Concentrating LN in a limited area will cause faster and deeper freezing.

The opening of the attachment has to fit the lesion. If it is too large, you will be freezing unnecessary healthy skin. If it is too small, the entire lesion will not be included.

It is the ideal for:

• Small warts or molluscum contagiosum

It should be disregarded if:

• You do not have a cone of the correct size or the cone or aperture on the lexan plate.

2.2.1 Advantages

• Freezing is faster.

It is less painful. Part of the pain sensation might be caused by the splashing (spattering) of the LN drops over the healthy skin. This problem is reduced by having the lesion restrained within the cone. Part of the pain is also believed to be due to sputtering caused by LN “boiling” from liquid to gas [3].

• Children are distracted by the presence of the lexan plate or specula. They seem to tolerate the procedure better. It sometimes gets stuck for a few seconds and that amuses them.

• Costrainers are usually easily available.

2.2.2 Disadvantages

• Need to have the proper constrainer that adjust to the size of the lesion.

• It is limited in use to lesions of up to 6–8 mm.

• There is no visibility of the superficial freezing front.

2.3 Close or Probe Technique

This technique is performed by using probes, which are closed-circuit systems into which LN travels from the unit and finally exits through a rubber hose [4].

They are built with metal and some are Teflon-coated to reduce the risk of sticking to the surface of the lesion. Freezing is constant, not dependent on the operator because they contact the skin. Distance is not an issue because it is also a constant given by the size of the probe. Since metal is an excellent conductor of cold, probes freeze very fast, and the freezing front is deeper than the one obtained by spray freezing (Fig. 5.8a, b).

Fig. 5.8

(a) Freezing with a probe will cause a half sphere freezing ball. (b) With the spraying technique, the shape is more like a hat: deep in the center and thinner at the periphery. The final depth in probe freezing is deeper (4 × 2) than in spray freezing (4 × 1.5)

A requirement when using probes is to have a flat lesion surface [5]. If the probe does not completely contact the surface of the lesion, there will be “pockets” of air between the probe and the lesion. The sum of theses spaces is called “interphase,” and these are air spaces. Since air is a poor conductor of cold, the larger the interphase, the less effective the freezing (Fig. 5.9).

Fig. 5.9

Probes need to be applied to a flat surface. If the probe does not completely contact the surface of the lesion, air “pockets” between the probe and the lesion (“interphase”) will raise the final freezing temperature

Probes come in different forms and diameters. The ideal probe is one that best fits the lesion you plan to treat. The more probes available, the more options to choose from. When choosing a probe, it needs to fit as best as possible the diameter of the lesion. As a rule of thumb, it is better to use a slightly smaller probe than a larger one. The latter will not allow visualization of the freezing front and thus tend to over-freeze. If it is too small, the center of the lesion will be destroyed very deeply (more than needed) before the freezing front reaches the periphery (Fig. 5.10a–c).

Fig. 5.10

(a–c) In relation to the lesion: A probe that is too small will freeze the center of the lesion in excess (a). If the probe is larger than the lesion (b), it will not allow visualization of the freezing front and there will be tissue destruction of perilesional normal skin. Therefore, if a probe of the exact size (c) is not available, it is better to use a slightly smaller one than a larger one

Care should be taken when working in humid areas like the oral mucosa or previously curettaged tumors. Even Teflon-coated probes can get stuck to the surface. One trick is to previously freeze the probe. This will reduce the chances of it sticking to a wet surface. If in spite of the precautions the probe gets stuck to the surface, do not try to detach it. Avoid maneuvers aiming at forcing the probe off of the site. Pulling out the probe can cause breakage of the tissue, unnecessary damage, and profuse bleeding. Always allow thawing. To avoid excess freezing, let some warm water run over it: As a precaution, always keep some warm water at hand when using a probe. By using this approach, the probe will immediately separate. On the other hand, if one wants the probe adhered to the surface (as for eyelid tumors) pre wetting or applying some ultrasound gel will do the job.

Care should also be taken with the releasing hose. Since LN comes out of the hose under pressure, one can inadvertently burn the patient, nurse, or even oneself. A free hose can whiplash and startle the patient.

Before freezing, the hose has a free end that moves back and forth. Grab it with your hands and set it in the desired position. In a few seconds, it will freeze (due to the continuous release of LN) and stay in place.

The probe technique is ideal for:

• Skin cancer. It is the ideal technique for skin destruction of deeply seated lesions.

• Vascular tumors, where you need to use pressure over the tumor to “squeeze” the blood out.

• Eyelid lesions or other lesions near orifices.

It should be avoided in:

• Irregular surface tumors where there will not be proper contact of the probe with the surface.

• Extra care should be taken in wet mucous areas. Water will form ice and keep the probe stuck for a longer period after releasing the unit trigger.

2.3.1 Advantages

• Fast and deep freezing

• Allows pressure over vascular lesion, emptying it of its warm content

2.3.2 Disadvantages

• It requires having a complete set of probes.

• Needs the correct surface.

• Risk of sticking to the surface and involuntarily breaking the surface.

2.4 Semi-close or Chamber Technique

Chambers are metal cones with a rubber safety ring at one end (in order to avoid cutting or damaging the skin) and a small aperture from which LN exits. These need to be firmly planted onto the skin in order to keep the liberated LN inside the cone. They have a blowoff (or release) hose to liberate LN just as in probes.

The turbulence generated inside the cone makes this freezing very potent, and it is usually reserved for skin cancer, particularly metastatic skin disease.

These come in different diameters and need to be matched as close as possible to the lesion (Fig. 5.11).

Fig. 5.11

Chambers are metal cones with a rubber safety ring at one end that needs to be firmly placed in order to keep LN inside the cone. They generate a very potent freezing

When first applied to the skin, LN pressure might kick back the whole unit. Start releasing very slowly until you get the feeling that it is held in place.

As with probes, care should be taken with the release hose in order to avoid accidental burns to the patient, nurse, or even oneself.

This technique is ideal for:

• Skin cancer [5]

• Skin metastasis

It should not be used in:

• Benign lesions

2.4.1 Advantages

• Potent, fast, and very deep freezing

• Less risk of sticking to the surface

2.4.2 Disadvantages

• It causes an extremely fast freezing, and there is a risk for over-freezing. Use only if experienced.

2.5 Tweezers Technique

Teflon-coated tweezers [6] are a very simple and useful means of treating filiform or protruding small lesions (Fig. 5.12). They are commercially available through Brymill®, and the instructions for their use are in Table 5.1. Regular tweezers can also be used, but care should be taken that they are grabbed in the correct place to avoid accidental burns to the operator.

Fig. 5.12

Cryotweezers are ideal for protruding lesions where no deep freezing is required

Table 5.1 Basic operating principles for tweezers

Basically, they are meant to be placed into a Styrofoam cup full of LN just to the narrow neck point. They are left there until LN stops bubbling.

They should be wiped with alcohol after each use.

This technique is ideal for:

• Protruding lesions such as skin tags or molluscum

• Cryobiopsy of a protruded lesion (Chap. 7)

It should be avoided in:

• Skin cancer

• Deeply seated lesions

2.5.1 Advantages

• No anesthesia is required.

• Fast and comfortable for the patient.

• Can treat many lesions at once.

• Low risk of hyper- or hypopigmentation.

2.5.2 Disadvantages

• Care should be taken not to burn one hand. This can happen when the tweezers are left for too long in the LN, or placed in a cup with excess LN, or grabbed too distally.

2.6 Intralesional Technique [7]

The intralesional technique consists of passing a thick needle longitudinally through the center of a tumor. It has been mostly proposed for keloids but can also be used for skin metastasis or large malignant tumors. Keloids are deeply seated lesions with a large amount of fibrous tissue (bad conductor of cold). By treating them with the intralesional technique, one preserves the surface skin.

The needle needs to be attached to the unit through a Luer-Lock adapter and then introduced through the tumor by its longer axis until it reappears at the other end. Once the LN is allowed to go through the needle, freezing will occur from the center out (Fig. 5.13). For this technique, one can use regular needle or preferably Teflon-coated ones. There are disposable needles commercially available through Cryoshape® [8, 9] specially designed for keloid treatment.

Fig. 5.13

In the intralesional technique, a thick needle is introduced into the mass in its longest axis. The needle needs to stick out from the other end of the tumor to liberate LN

It is a technique developed for keloids but can also be used for skin metastasis or large malignant deeply seated tumors. It should be avoided for superficial treatment or in vascular lesions.

2.6.1 Advantages

• When used in keloids, it spares the superficial skin.

• In deeply seated metastasis, it is an option of treatment although superficial skin sparing is not an issue.

2.6.2 Disadvantages

• Not simple to do. Requires experience.

• It is time consuming.

• Requires special equipment.

• With freezing, the needle can get stuck in the center of the lesion. Complete thawing is required before attempting to remove the needle.

Essential Tidbits

• Intermittent spraying allows for a more precise freezing. Continuous spraying is faster.

• Smaller apertures release less LN and are very useful for small lesions. Large apertures are best for large tumors.

• Probes are best used on surfaces with no irregularities (like crusts); also works well on compressible lesions (vascular, sebaceous hyperplasias).

• Prefrozen probes tend to stick less to the skin surface.

• Running some warm water helps detach stuck probes.

3 Conclusions

This chapter has presented the most common cryosurgical techniques. They have been summarized in Table 5.2. As one proceeds though the subsequent chapters, one can find nonconventional uses tailored to the patient’s needs.

Table 5.2 Summary of the most common cryosurgical techniques

For the sake of clarity, the names of each technique as indicated in this chapter will be maintained throughout the subsequent chapters.