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Photobiomodulation Science Flashcards

7 cards from real CLT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which chromophore in the skin primarily absorbs blue and green light wavelengths, limiting their tissue penetration?

    Answer: Melanin

    Melanin strongly absorbs shorter visible wavelengths (blue/green), making it a major barrier to tissue penetration for wavelengths below 600 nm.

  2. The term 'biphasic dose response' in PBM therapy means:

    Answer: Low doses stimulate and high doses inhibit biological processes

    The biphasic dose response (Hormesis) describes how PBM at low doses promotes healing while excessively high doses can inhibit or damage the same biological processes.

  3. Which of the following photochemical pathways is activated when PBM light is absorbed by porphyrins?

    Answer: Generation of singlet oxygen and ROS that trigger signaling cascades

    Porphyrins absorb PBM wavelengths and generate low-level ROS including singlet oxygen, which serves as secondary messengers in the signaling cascade.

  4. What does the term 'spot size' refer to in PBM treatment parameters?

    Answer: The cross-sectional area of the laser beam at the tissue surface, typically measured in cm²

    Spot size is the cross-sectional area of the laser beam at the treatment surface in cm², which directly affects the irradiance (W/cm²) calculation.

  5. PBM therapy's effect on lymphocyte activity is best described as:

    Answer: Dose-dependent modulation that can either stimulate or reduce lymphocyte proliferation

    PBM demonstrates biphasic immune modulation on lymphocytes, with optimal doses stimulating immune function and excessive doses potentially reducing lymphocyte proliferation.

  6. Which measurement unit is used to express the total energy delivered to a treatment point in PBM?

    Answer: Joules (J)

    Joules measure total energy (Power × Time = Joules) and represent the total photon energy delivered to a single treatment point or area.

  7. What is the significance of the 'contact vs. non-contact' delivery method in PBM treatment?

    Answer: Contact delivery compresses tissue, reducing blood content and increasing effective penetration depth

    Applying the laser probe with contact pressure blanches tissue by displacing blood, reducing hemoglobin absorption and allowing more light energy to penetrate deeper structures.