CLT Laser Treatment Parameters & Dosage 3 — Questions and Answers
Question 1: Which chromophore is the PRIMARY target for 1064 nm Nd:YAG laser treatments?
- Oxyhemoglobin
- Water
- Melanin
- Deep dermal melanin and tattoo pigment (Correct answer)
Correct answer: Deep dermal melanin and tattoo pigment
The 1064 nm wavelength penetrates deeply and is selectively absorbed by deep dermal melanin and exogenous pigments such as tattoo ink, with less melanin competition than shorter wavelengths.
Question 2: A patient with a pacemaker presents for low-level laser therapy over the chest area. The MOST appropriate action is to:
- Proceed with reduced power settings
- Avoid treatment over and near the pacemaker site (Correct answer)
- Increase pulse duration to minimize electromagnetic interference
- Use a longer wavelength to bypass the device
Correct answer: Avoid treatment over and near the pacemaker site
Laser therapy near implanted electronic devices such as pacemakers is contraindicated due to potential electromagnetic interference that could disrupt device function.
Question 3: Increasing the repetition rate of a pulsed laser from 2 Hz to 10 Hz while maintaining the same pulse energy will:
- Decrease total fluence delivered over time
- Increase average power but not change peak power (Correct answer)
- Decrease peak power while increasing average power
- Have no effect on either average or peak power
Correct answer: Increase average power but not change peak power
Average power = pulse energy × repetition rate, so more pulses per second raises average power; peak power per pulse remains determined by pulse energy and duration.
Question 4: The phenomenon of 'selective photothermolysis' requires that the wavelength used is:
- Scattered equally by all skin layers
- Preferentially absorbed by the target chromophore over surrounding tissues (Correct answer)
- Reflected maximally by the target to avoid overheating
- Transmitted entirely through skin without absorption
Correct answer: Preferentially absorbed by the target chromophore over surrounding tissues
Selective photothermolysis relies on a wavelength that is preferentially absorbed by the intended target (chromophore) while minimally absorbed by surrounding structures.
Question 5: Which of the following BEST describes the role of contact cooling during laser hair removal?
- It increases laser penetration depth
- It protects the epidermis from thermal damage while the target follicle is heated (Correct answer)
- It enhances melanin absorption of laser energy
- It allows the use of shorter wavelengths
Correct answer: It protects the epidermis from thermal damage while the target follicle is heated
Contact cooling removes heat from the epidermis before, during, or after a laser pulse, protecting it while the deeper follicle, with a longer TRT, remains heated.
Question 6: In photobiomodulation, which unit is used to express the DOSE delivered to tissue?
- Watts (W)
- Hertz (Hz)
- Joules per centimeter squared (J/cm²) (Correct answer)
- Nanometers (nm)
Correct answer: Joules per centimeter squared (J/cm²)
Dose in photobiomodulation is expressed as energy density (J/cm²), reflecting the total energy deposited per unit area of tissue.
Question 7: A treatment area of 5 cm² is treated with a fluence of 20 J/cm². What is the total energy delivered?
- 4 J
- 25 J
- 100 J (Correct answer)
- 200 J
Correct answer: 100 J
Total energy = Fluence × Area = 20 J/cm² × 5 cm² = 100 J.
CLT Laser Treatment Parameters & Dosage 3
Which chromophore is the PRIMARY target for 1064 nm Nd:YAG laser treatments?