CDT CDT Phototherapy & Light-Based Treatments 2 — Questions and Answers
Question 1: Which phototherapy modality requires the patient to ingest or apply a photosensitizing agent before treatment?
- Narrowband UVB
- Broadband UVB
- PUVA (Correct answer)
- Excimer laser
Correct answer: PUVA
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?
- Psoriasis
- Actinic keratoses (Correct answer)
- Vitiligo
- Atopic dermatitis
Correct answer: Actinic keratoses
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?
- 5 minutes
- 30 minutes
- 1–3 hours (Correct answer)
- 24 hours
Correct answer: 1–3 hours
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?
- Infrared laser
- Blue or red light (Correct answer)
- X-ray
- Microwave
Correct answer: Blue or red light
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?
- Clark Level
- Fitzpatrick Skin Type (Correct answer)
- Breslow Scale
- ABCDE Rule
Correct answer: Fitzpatrick Skin Type
The Fitzpatrick Skin Type scale (I–VI) classifies skin by UV reactivity and guides individualized starting doses for phototherapy.
Question 6: What is the typical frequency of narrowband UVB phototherapy sessions per week?
- Daily (7×/week)
- 2–3 times per week on non-consecutive days (Correct answer)
- Once per month
- Once per week only
Correct answer: 2–3 times per week on non-consecutive days
Narrowband UVB is administered 2–3 times per week on non-consecutive days to allow skin recovery while maintaining therapeutic effect.
CDT CDT Phototherapy & Light-Based Treatments 2
Which phototherapy modality requires the patient to ingest or apply a photosensitizing agent before treatment?