CDT CDT Phototherapy & Light-Based Treatments 2

Question 1

Which phototherapy modality requires the patient to ingest or apply a photosensitizing agent before treatment?

Accepted Answer

PUVA

Answer

PUVA requires psoralen to be taken orally or applied topically before UVA light exposure to enhance the therapeutic response.

Question 2

Which skin condition is photodynamic therapy (PDT) most commonly used to treat?

Accepted Answer

Actinic keratoses

Answer

PDT is most commonly used for actinic keratoses (precancerous sun-damaged lesions) using aminolevulinic acid (ALA) and activating light.

Question 3

How long before PDT light activation is aminolevulinic acid (ALA) typically applied?

Accepted Answer

1–3 hours

Answer

ALA is applied 1–3 hours before light activation to allow adequate uptake and concentration in target abnormal cells.

Question 4

Which type of light is commonly used to activate ALA during photodynamic therapy?

Accepted Answer

Blue or red light

Answer

Blue light (410 nm) and red light (630 nm) are used to activate ALA because these wavelengths match the photosensitizer's absorption peaks.

Question 5

Which classification system is used to determine appropriate starting phototherapy doses based on skin UV sensitivity?

Accepted Answer

Fitzpatrick Skin Type

Answer

The Fitzpatrick Skin Type scale (I–VI) classifies skin by UV reactivity and guides individualized starting doses for phototherapy.

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