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Ultraviolet Radiation (UVR) - Complete Overview as a Therapeutic Modality

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1. Introduction

Cosmic rays → X-rays → UVR (100-400 nm) → Visible light → Infrared → Microwaves → Radiowaves

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2. Classification / Types of UVR

Note: UVB is the most biologically active and therapeutically important band in physiotherapy.

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3. Sources / Production of UVR

Natural Source

• The sun - via heating of a body to incandescent temperature

Artificial Sources (Therapeutic)

A. Air-Cooled Lamps (High-pressure mercury vapor)

• Example: Hanovia Alpine Sun Lamp
• Wavelength: ~253 nm (short wavelength)
• Emit UVR, infrared, and visible light
• UVR falls within UVB range
• Used for: generalized skin conditions (acne, psoriasis)
• Mainly produce erythema and photochemical reactions
• Tridymite formation - heat causes quartz tube to change to tridymite (another form of silica), which is opaque to UVR, causing output to fall; a variable resistance is included to increase potential difference and compensate

B. Water-Cooled Lamps (Low-pressure mercury vapor)

• Example: Kromayer Lamp
• Water jacket surrounds the burner with continually circulating water (removes heat/infrared)
• Delivers "cold UVR" - pure UVR without heat
• Can be used in contact with skin (wounds, body cavities)
• Wavelength: 253.7 nm (germicidal)

C. Fluorescent Tubes / Narrowband UVB

• Operate on same principle as gas discharge lamps
• Most commonly used today in phototherapy units
• Narrowband UVB (NB-UVB): 311-312 nm - most effective therapeutic wavelength

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4. Physical Properties of UVR

1. Reflection - reflected from smooth shiny surfaces
2. Refraction - bends when passing through media of different optical density
3. Absorption - absorbed by tissues; causes biological effects
4. Penetration - limited penetration; UVC penetrates least, UVA penetrates deepest

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5. Physiological / Biological Effects of UVR

Immediate Effects (Acute)

Delayed / Chronic Effects

• Epidermal thickening - increased Malpighian layer (protective response)
• Decreased skin sensitivity after repeated exposure
• Premature skin aging (photoaging) - UVA-mediated collagen/elastin degradation
• Immunosuppression - depletion of Langerhans cells, altered antigen presentation, regulatory T-cell expansion
• DNA mutations - UV signature mutations (C→T and CC→TT transitions), particularly in SCC and melanoma
• Skin cancer - risk of BCC, SCC, and melanoma with chronic exposure

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6. Erythema Reactions / Dosimetry

Minimal Erythema Dose (MED)

Erythema Grades (E-doses)

Dosimetry Protocols (from Fitzpatrick's Dermatology)

• Expose 1 cm² areas on inner forearm or lower back
• NB-UVB: doses of 200, 400, 600, 800, 1000, 1200 mJ/cm²
• BB-UVB: doses of 20, 40, 60, 80, 100, 120 mJ/cm²
• Read at 24 hours
• Start treatment at 50-70% of MED

• Given 2-5 times per week
• Increase dose by 10-20% each session (NB-UVB) or 25% for first 10 treatments then 10% (BB-UVB)
• 70/20 Rule (general): Start at 70% MED, increase by 20% each successive treatment

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7. Therapeutic Indications (Uses)

Primary / Dermatological Uses

PUVA (Photochemotherapy)

• Psoralen + UVA combination
• Psoralens (photosensitizing drugs) intercalate into DNA and crosslink with UVA irradiation
• Highly effective for psoriasis, vitiligo, CTCL

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8. Contraindications

Absolute Contraindications

• Photosensitivity disorders (e.g., lupus erythematosus, polymorphous light eruption, xeroderma pigmentosum)
• Active tuberculosis (skin TB)
• Skin cancer / history of skin cancer
• Pellagra (niacin deficiency - photosensitive)
• Porphyria
• Acute eczema / dermatitis (active inflamed phase)
• Febrile conditions
• Radiation therapy - irradiated areas

Relative Contraindications / Precautions

• Photosensitizing drugs (tetracyclines, sulfonamides, phenothiazines, NSAIDs) - increase sensitivity dramatically
• Hyperthyroidism (increased sensitivity)
• Renal/hepatic disease (impaired metabolism)
• Pregnancy (caution)
• Previous extensive UVR treatment (cumulative cancer risk)
• Eye exposure - strong doses of UVB/C to eyes can cause photokeratitis (arc eye) - protective goggles mandatory

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9. Treatment Technique / Application

Pre-Treatment Assessment

1. Skin type assessment (Fitzpatrick I-VI)
2. MED determination
3. Test dose if uncertain
4. Identify photosensitizing medications

Application Steps

1. Warm-up lamp - allow 5-10 minutes for full output
2. Protect eyes with UV-opaque goggles (patient and therapist)
3. Expose area - position at correct distance (usually 30-90 cm depending on lamp)
4. Time the exposure precisely
5. Cover surrounding skin if treating localized area
6. Document: dose (mJ/cm²), distance, duration, skin response

Distance-Dose Relationship

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10. Dangers / Side Effects of UVR

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11. Summary Table

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• Fitzpatrick's Dermatology, Vol. 1&2 - Phototherapy protocols and NB-UVB dosing tables (p. 3670)
• Dermatology 2-Volume Set 5e - UVR and melanoma risk
• UVR physiotherapy notes - Sreeraj SR - Apparatus, erythema grades, indications
• UVR dose models review - Dosimetry and clinical implementation

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Infrared Radiation (IRR) - Indications & Contraindications

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Quick Reference

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Types of IRR

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Physiological Effects (Mechanism)

1. Cutaneous Vasodilation

• Axon reflex - thermoreceptor stimulation sends antidromic impulses releasing vasoactive mediators
• Chemical mediators - bradykinin (from kallikrein released by sweat glands) increases capillary and venule permeability
• Local spinal cord reflexes

2. Increased Metabolism

• Raised tissue temperature accelerates metabolic rate

3. Increased Tissue Extensibility

• Decreased viscosity of connective tissue
• Decreased joint stiffness
• Increased muscle flexibility
• IRR should always be used in conjunction with stretching and ROM exercises

4. Pain Control (via multiple mechanisms)

• Stimulation of sensory nerves → inhibition of pain at spinal level (gate control)
• Decreased muscle spindle activity → decreased muscle spasm
• Increased pain threshold
• Removal of waste products through improved circulation and venous return

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✅ INDICATIONS

Key point: IRR is indicated for sub-acute and chronic conditions - NOT acute.

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❌ CONTRAINDICATIONS

Absolute Contraindications

Relative Contraindications / Precautions

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Application / Technique

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Dangers of IRR

• Thermal burns - cumulative exposure, impaired sensation, or excess dose (Bailey & Love)
• Erythema ab igne (mottled reddish-brown skin discoloration) - chronic repeated low-level exposure
• Cataracts - chronic eye exposure
• Dehydration - excessive sweating with full-body exposure

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Summary: Indications vs Contraindications

INDICATIONS                         CONTRAINDICATIONS
✅ Chronic/sub-acute pain           ❌ Acute inflammation
✅ Muscle spasm                     ❌ Acute infection
✅ Joint stiffness                  ❌ Impaired sensation
✅ Pre-stretching warm-up           ❌ Impaired circulation
✅ Chronic inflammation             ❌ Open wounds
✅ Healing acceleration             ❌ Malignancy
✅ Fungal skin conditions           ❌ Pregnant uterus
✅ Fibromyalgia                     ❌ Eyes
                                    ❌ Post-radiotherapy
                                    ❌ Unreliable patients

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• Cairo University Physical Therapy Lecture - IRR by Dr. Yasser Aneis
• Bailey and Love's Short Practice of Surgery 28th Ed. - "Infrared radiation generates heat; cumulative exposure can cause thermal burns."
• Physio Care & Cure Clinical Notes