CLT Laser Technology & Equipment 3 — Questions and Answers
Question 1: Which laser type uses a gas mixture of carbon dioxide as the active medium and emits at 10,600 nm?
- CO2 laser (Correct answer)
- Nd:YAG laser
- Alexandrite laser
- Ruby laser
Correct answer: CO2 laser
The CO2 laser emits at 10,600 nm in the mid-infrared spectrum and is strongly absorbed by water, making it effective for tissue ablation and resurfacing.
Question 2: What property of a laser beam is described by the term 'coherence'?
- All photons travel in phase with one another (Correct answer)
- All photons have the same energy level
- The beam does not diverge over distance
- The beam contains only one polarization
Correct answer: All photons travel in phase with one another
Coherence means the light waves in a laser beam maintain a fixed phase relationship, enabling constructive interference and extremely focused energy delivery.
Question 3: The Er:YAG laser (2940 nm) is preferred over CO2 (10,600 nm) for superficial skin resurfacing because it:
- Has 10–16× greater water absorption, allowing more precise ablation with less thermal damage (Correct answer)
- Produces longer pulses that seal blood vessels more effectively
- Penetrates deeper into the dermis
- Requires no cooling system
Correct answer: Has 10–16× greater water absorption, allowing more precise ablation with less thermal damage
At 2940 nm, Er:YAG matches the peak absorption of water more closely than CO2, resulting in precise micro-ablation with minimal collateral thermal injury.
Question 4: Which parameter directly controls the depth of laser energy penetration into tissue?
- Wavelength (Correct answer)
- Pulse repetition rate
- Beam divergence angle
- Electrical input power
Correct answer: Wavelength
Wavelength determines how deeply photons penetrate tissue because each tissue chromophore has characteristic absorption coefficients at specific wavelengths.
Question 5: A fractional laser creates an array of micro-treatment zones (MTZs) separated by untreated tissue columns. What is the primary clinical benefit of this approach?
- Faster healing due to migration of cells from untreated zones (Correct answer)
- Higher total energy delivery per session
- Elimination of the need for topical anesthesia
- Deeper penetration without wavelength change
Correct answer: Faster healing due to migration of cells from untreated zones
Sparing columns of untreated tissue between MTZs provides a reservoir of intact cells that accelerate re-epithelialization and collagen remodeling.
Question 6: Which safety feature prevents accidental laser emission when the handpiece is not properly seated or the door is open?
- Interlock system (Correct answer)
- Beam attenuator
- Energy monitor
- Optical feedback loop
Correct answer: Interlock system
Interlock systems automatically interrupt laser emission when protective covers are removed or treatment room doors are opened, preventing accidental exposure.
Question 7: In a long-pulsed laser designed for vascular treatments, increasing the pulse duration while keeping fluence constant will:
- Reduce peak power and decrease collateral thermal damage to nearby structures (Correct answer)
- Increase peak power and improve melanin targeting
- Have no effect on tissue response
- Increase ablation depth
Correct answer: Reduce peak power and decrease collateral thermal damage to nearby structures
Longer pulses lower peak power, spreading heat delivery over time, which reduces non-specific thermal damage to surrounding tissue for large vascular targets.
CLT Laser Technology & Equipment 3
Which laser type uses a gas mixture of carbon dioxide as the active medium and emits at 10,600 nm?