Chapter 15 - Laser in Veterinary Surgery Flashcards
(177 cards)
What are the four types of lasers currently used in veterinary medicine?
A) CO2, Nd, Ho, and diode B) CO2, HeNe, Nd, and argon C) Nd, diode, ruby, and excimer D) CO2, argon, HeNe, and Ho
A) CO2, Nd, Ho, and diode
What is the wavelength range of visible light?
A) 100 to 400 nm B) 400 to 700 nm C) 700 to 1000 nm D) 1000 to 1500 nm
B) 400 to 700 nm
At what wavelength are CO2 lasers most effective for tissue incision?
A) Greater than 2500 nm B) 600 to 1400 nm C) 1064 nm D) 800 nm
A) Greater than 2500 nm
What is the power density of a CO2 laser set to 50 W with a focal spot size of 0.16 mm?
A) 6300 W/cm² B) 248,880 W/cm² C) 150,000 W/cm² D) 100,000 W/cm²
B) 248,880 W/cm²
How many watts is the CO2 laser in continuous mode set to in the second example?
A) 50 W B) 10 W C) 8 W D) 5 W
C) 8 W
What is the approximate power density of a CO2 laser set to 8 W with a focal spot size of 0.4 mm?
A) 248,880 W/cm² B) 6300 W/cm² C) 10,000 W/cm² D) 5000 W/cm²
B) 6300 W/cm²
What is the energy equivalent of 1 joule?
A) 1 W × 1 sec B) 2 W × 1 sec C) 0.5 W × 2 sec D) 1 W × 2 sec
A) 1 W × 1 sec
What type of tissue reaction occurs when the laser beam is absorbed?
A) Reflection B) Transmission C) Coagulation D) All of the above
D) All of the above
What tissue component is primarily responsible for absorption in surgical lasers?
A) Air B) Hemoglobin C) Bone D) Muscle
B) Hemoglobin
What is the typical effect of thermal energy generated by lasers?
A) Immediate healing B) Vaporization C) Cooling D) None of the above
B) Vaporization
What temperature must tissue reach to be completely vaporized?
A) 50°C B) 75°C C) 100°C D) 200°C
C) 100°C
How is power density expressed in surgical lasers?
A) W/m² B) W/cm C) W/cm² D) J/m²
C) W/cm²
What is the typical range of wavelengths for diode lasers?
A) 2500 to 3000 nm B) 600 to 900 nm C) 400 to 600 nm D) 700 to 1400 nm
B) 600 to 900 nm
What type of lasers are primarily used for coagulation?
A) CO2 lasers B) Nd lasers C) Diode lasers D) Both B and C
Diode and Nd lasers
D) Both B and C
How does increasing the laser wattage affect power density?
A) It decreases power density B) It does not affect power density C) It increases power density D) It only affects tissue reaction
C) It increases power density
Figure 15-1. Wavelengths of surgical lasers (in nm). Ultraviolet (UV) wavelengths are generally absorbed by protein, whereas the visible and infrared wavelengths are generally absorbed by water or pigmented melanin or hemoglobin. Wavelengths in common veterinary use are in gray. Er, Erbium; GAA, gallium-aluminum-arsenide; Ho, holmium; KTP, potassium titanyl phosphate; Nd, neodymium; YAG, yttrium-aluminum-garnet.
Figure 15-2. Tissue absorption of common surgical laser wavelengths. The visible spectrum is beneath the visible range. The near-infrared GAA diode and Nd:YAG lasers are highly absorbed by dark pigment. However, note the increased absorption of the GAA diode on the water curve compared with the Nd:YAG laser. The Ho:YAG and CO2 lasers are both highly absorbed by water. Er, Erbium; GAA, gallium-aluminum-arsenide; Ho, holmium; Nd, neodymium; UV, ultraviolet; YAG, yttrium-
aluminum-garnet.
The spot size of a laser beam is measured in millimeters and the following formula can be used to calculate the power density:
Figure 15-3. Power density decreases with the square of the increase in spot size, which in turn increases with distance from the surface. The beams depicted are all CO2 laser beams from machines set to 50 W. The power densities shown below each demonstrate the profound reduction in tissue effect by increasing spot size. Moving the hand piece away from the tissue increases spot size.
Figure 15-5. Absorption length of various wavelengths of surgical lasers in nonpigmented skin. Wavelengths commonly used in veterinary medicine are marked dark gray; wavelengths (nm) are stated beside the names. The far-infrared Ho:YAG and CO2 lasers are highly absorbed by water; therefore, they penetrate minimally into skin, whereas the near-infrared Nd:YAG or GAA Diode lasers are absorbed more by the darker pigments of the deeper layers. DTP, Diagnostic and therapy systems for psychology; GAA, gallium-aluminum-arsenide; Ho, holmium; Nd, neodymium; YAG, yttrium-aluminum-garnet.
Figure 15-4. Focusing hand piece that would be used on an articulating arm of a CO2 laser. The arrow points to the spot of maximum focus for creating a precise incision with minimal effect on margins of wound. The stylus contacts the tissue to fix the focal point and provide a feel on the tissue for making the incision. Below that point, power decreases with distance from the end of the stylus. Slight defocus allows vaporization of tissue with a relatively high-power density, and more distance reduces power density to coagulation of tissue protein.
Figure 15-6. Range of tissue changes from laser beam. With sufficient power density, a laser beam has a central area of tissue vaporization/ablation shown by the crater in this drawing. A layer of carbonization occurs when tissue that has been significantly heated cools to produce char. The area of thermal necrosis is where tissue is heated beyond physiologic limits and later sloughs off. The goal of incisive surgery is to use adequate power density to create as little carbonization and thermal necrosis as possible.
Figure 15-7. Pulsed laser energy compared with continuous laser energy. Pulsing higher power densities for short durations (vertical bars) produces a more efficient tissue effect with less collateral tissue heating compared with a continuous beam (horizontal bar) emitting the same average power (fluence). The tissue cools slightly between the pulses.
What is a common effect of multiple inefficient passes with a laser?
A) Decreased wound width B) Increased thermal injury C) Improved healing D) None of the above
B) Increased thermal injury