Chapter 14 - Cryosurgery Flashcards
At what temperature does liquid nitrogen operate?
A) −196°C B) −20°C C) −40°C D) −89°C
A) −196°C
What temperature range is critical for tissue thawing during cryosurgery?
A) −30°C to −20°C B) −25°C to −20°C C) −40°C to −30°C D) −15°C to −10°C
B) −25°C to −20°C
What is the typical temperature a cryosurgery probe can cool down to?
A) −20°C B) −40°C C) −89°C D) −196°C
C) −89°C
What percentage of cells are affected by cryonecrosis in high-water content tissues?
A) 100% B) 75% C) 50% D) 90%
A) 100%
How many freeze-thaw cycles are optimal for maximal tissue destruction?
A) 1 B) 2 C) 3 D) 4
B) 2
What is the primary cryogen used in equine medicine?
A) Carbon dioxide B) Gaseous nitrous oxide C) Liquid nitrogen D) Helium
C) Liquid nitrogen
What is the initial suggested temperature and duration for tissue destruction?
A) −30°C for 1 minute B) −20°C for 1 minute C) −20°C for 5 minutes D) −10°C for 10 minutes
B) −20°C for 1 minute
What percentage of horses showed regression of untreated sarcoids after treatment with cryosurgery?
A) 100% B) 50% C) 75% D) 90%
C) 75% (implied as significant but not explicitly stated)
How much higher temperature do peripheral lesions typically reach during cryosurgery?
A) 5°C B) 10°C C) 15°C D) 20°C
B) 10°C
What is the cooling capability of nitrous oxide in terms of temperature?
A) −196°C B) −89°C C) −40°C D) −20°C
B) −89°C
What is the maximum exposure temperature for cancer cells to ensure cell destruction using the double-freeze protocol?
A) −20°C B) −30°C C) −40°C D) −50°C
C) −40°C
What is the mechanism of injury from freezing that causes immediate cell death?
A) Endothelial damage B) Ice crystal formation C) Vascular stasis D) Recrystallization
B) Ice crystal formation
What happens to ice crystals during thawing at temperatures between −25°C and −20°C?
A) They freeze more B) They fuse to form large crystals C) They disappear D) They expand in size
B) They fuse to form large crystals
What temperature is suggested for optimal cryoablative dose in tumors?
A) −10°C B) −20°C C) −30°C D) −40°C
C) −30°C
What is a potential drawback of using contact freezing with solid probes?
A) It cools too quickly B) It is difficult to control C) It warms up quickly in contact with tissue D) It doesn’t freeze tissue
C) It warms up quickly in contact with tissue
What can cause inadvertent frost lesions during cryosurgery?
A) Too much liquid nitrogen dripping down B) Using a cold probe C) Prolonged freezing time D) Direct contact with the skin
A) Too much liquid nitrogen dripping down
What type of cell is more sensitive to cryonecrosis due to its high mitotic rate?
A) Fibrocytes B) Epithelial cells C) Muscle cells D) Nerve cells
B) Epithelial cells
hat causes progressive microcirculation failure after thawing?
A) Cryogenic agents B) Ice crystal formation C) Endothelial damage D) Rapid freezing
C) Endothelial damage
How does the cryogen nitrous oxide compare to liquid nitrogen in terms of cooling temperature?
A) Nitrous oxide is colder B) They are the same C) Nitrous oxide is warmer D) Liquid nitrogen is much colder
D) Liquid nitrogen is much colder
How much higher is the thermal conductivity of tissue after the first freeze cycle?
A) 10% B) 20% C) 30% D) 40%
B) 20%
What percentage of patients required lower temperatures to destroy tumor cells than initially suggested?
A) 50% B) 60% C) 70% D) 80%
C) 70%
How many times should the freeze-thaw cycle be repeated for optimal effectiveness?
A) Once B) Twice C) Three times D) Four times
B) Twice
What type of lesions are best treated with nitrous oxide?
A) Large tumors B) Small cutaneous lesions C) Internal tumors D) Deep tissue lesions
B) Small cutaneous lesions
What should be avoided when using open-cell foams during cryosurgery?
A) They conduct heat well B) They absorb the cryogen C) They are inexpensive D) They provide insulation
B) They absorb the cryogen
What condition is specifically treated with cryosurgery in equine medicine?
A) Osteoarthrosis B) Proximal suspensory desmitis C) Equine sarcoids D) Fractures
C) Equine sarcoids
What is the benefit of using spray systems over contact probes?
A) They are easier to control B) They can freeze larger areas C) They are less expensive D) They remove more heat from the tissue
D) They remove more heat from the tissue
What does cryonecrosis particularly affect in high-water content cells?
A) Membranes B) Nuclei C) Organelles D) Cytoplasm
C) Organelles
How does the cooling rate affect the formation of intracellular ice crystals?
A) Faster cooling increases crystal formation B) Slower cooling increases crystal formation C) No effect D) It only affects extracellular crystals
A) Faster cooling increases crystal formation
What happens during the thawing phase that exacerbates cell damage?
A) Water enters damaged cells B) Cells rehydrate C) Increased blood flow occurs D) Crystals dissolve completely
A) Water enters damaged cells
What percentage of the cryosurgical technique focuses on avoiding damage to surrounding tissue?
A) 30% B) 50% C) 70% D) 100%
C) 70%
What is the impact of lower temperatures on cancer cell destruction?
A) No impact B) Increased effectiveness C) Decreased effectiveness D) Only affects normal cells
B) Increased effectiveness
How long should cells be exposed to −30°C to achieve destruction?
A) 1 minute B) 2 minutes C) 5 minutes D) 10 minutes
A) 1 minute
What factor affects the variation in cooling rates within a tumor?
A) Tumor size B) Proximity to the probe C) Type of cryogen used D) Depth of the lesion
B) Proximity to the probe
What is the ideal application method for large lesions?
A) Single chilled probe B) Multiple chilled probes C) Direct pouring D) Hand-held spraying
B) Multiple chilled probes
Figure 14-1. The Cryopen is a small hand-held device for gaseous nitrous oxide cryotherapy. It is easy to use but only suited for small cutaneous lesions and for ophthalmologic applications.
Figure 14-3. Spray cups come in a variety of sizes so that the cup can be fitted over a tumor, and as the spray is applied, droplets form a liquid pool contained by the cup. This prevents runoff generated by the spray method.
Figure 14-2. Special container used to deliver liquid nitrogen through a self-pressurizing spray gun. A thermocouple needle is to the left of the pyrometer, which is used to measure the temperature achieved in and beyond the limits of the targeted tissue.
Figure 14-4. Self-made PVC cup placed over a large debulked sarcoid on the inner thigh of a horse. The liquid nitrogen will be poured into the cup using a thermos flask. Thermocouple needles have been placed and a contact gel has been used to ensure good sealing between the cup and the skin.
Figure 14-5. Solid probes come in a variety of sizes, each fitted with a separate plastic handle that does not become chilled as the probe is immersed in liquid nitrogen.
Figure 14-7. Hollow liquid nitrogen circulation probe to which a conducting solid copper probe is attached, to provide continuous controlled freezing of a sarcoid lesion on the ventral abdomen. Contact gel and thermocouple needles have been used.
Figure 14-6. A special container is used into which liquid nitrogen is poured and the contact probe is immersed to attain the proper temperature before applying it to a lesion.
