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📋 TAMIL NADU Dr. MGR MEDICAL UNIVERSITY

BPT 3rd Year - Paper II: Electrotherapy II (HF & Actinotherapy)

Sub Code: 6282 (2020-2025) + 6260 (2011-2021) - COMPLETE ANALYSIS + ANSWERS

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PART 1: REPEATED QUESTIONS FREQUENCY

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🔴 15-MARK REPEATED QUESTIONS (Sub Code 6282: 2020-2025)

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🔴 20-MARK REPEATED QUESTIONS (Sub Code 6260: 2011-2021)

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🔵 5-MARK REPEATED QUESTIONS (Both Sub Codes Combined)

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PART 2: ALL 15-MARK ANSWERS

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✅ Q1. ULTRASOUND THERAPY

(Asked 3 times in 6282 + 6 times in 6260 = MOST IMPORTANT QUESTION)

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DEFINITION

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PRODUCTION OF ULTRASOUND

Piezoelectric Effect (Reverse):

Components:

[High Frequency Generator]
         ↓
  [Coaxial Cable]
         ↓
  [Transducer/Soundhead]
   - Piezoelectric crystal (PZT)
   - Backing material
   - Metal casing
         ↓
  [Coupling Medium - gel/water]
         ↓
     [Patient Tissue]

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BEAM CHARACTERISTICS

Near Field (Fresnel Zone):

• Close to transducer
• Beam is parallel but IRREGULAR intensity
• Formula: r²/λ (r = crystal radius, λ = wavelength)

Far Field (Fraunhofer Zone):

• Beyond near field
• Beam DIVERGES
• More uniform intensity

BNR (Beam Non-Uniformity Ratio):

• Ratio of peak to average intensity
• Should be ≤ 6:1 (lower = safer, more uniform)
• High BNR = "hot spots" = burns risk

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PARAMETERS OF ULTRASOUND

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PHYSIOLOGICAL EFFECTS

A. Thermal Effects (Continuous Mode):

1. Raises tissue temperature (especially collagen-rich: tendons, joint capsules)
2. Increased blood flow (vasodilation)
3. Increased tissue extensibility (softens collagen)
4. Reduces muscle spasm
5. Mild analgesic (counter-irritation)

B. Non-Thermal Effects (Pulsed Mode):

1. Cavitation - formation & oscillation of gas bubbles in fluid
   • Stable cavitation = gentle oscillation → beneficial
   • Unstable/inertial cavitation = violent collapse → harmful (avoided in therapy)
2. Acoustic Streaming - unidirectional fluid movement along cell membranes → promotes healing
3. Micro-massage - compression/rarefaction of tissues at cellular level
4. Increased cell membrane permeability - enhanced calcium ion uptake → cell repair
5. Mast cell degranulation - releases histamine → promotes tissue healing
6. Fibroblast stimulation - increases collagen synthesis

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THERAPEUTIC EFFECTS

1. Pain relief (analgesic)
2. Reduces muscle spasm
3. Wound healing and tissue repair
4. Softens scar tissue and adhesions
5. Increases joint ROM
6. Reduces edema (sub-acute)
7. Anti-inflammatory
8. Enhances drug delivery (Phonophoresis)

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TECHNIQUES OF APPLICATION

1. Direct Contact Method (most common):

• Apply coupling gel to skin
• Move transducer in SLOW circular/stroking movements (3-4 cm/s)
• Maintain firm, constant contact
• NEVER hold still → causes hot spots and burns

2. Underwater (Immersion) Method:

• For irregular surfaces (hands, feet, ankles)
• Submerge body part in degassed water
• Hold transducer 1-2 cm from skin
• Water acts as coupling medium

3. Water Bag Method:

• Water-filled plastic bag placed on irregular area
• Transducer applied over the bag

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CLINICAL APPLICATIONS

1. Soft tissue injuries (sprains, strains, tendinitis)
2. Shoulder - frozen shoulder, rotator cuff
3. Knee - OA knee, patellofemoral syndrome
4. Plantar fasciitis
5. Tennis elbow
6. Carpal tunnel syndrome
7. Chronic wound/ulcer healing
8. Scar management
9. Calcific tendinitis

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CONTRAINDICATIONS

1. Malignancy
2. Growing epiphyses (children)
3. Pregnant uterus
4. Eyes, testes, heart
5. Spinal cord (laminectomy sites)
6. Acute infection
7. DVT
8. Pacemaker (over it)
9. Hemorrhagic disorders

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✅ Q2. PULSED SHORT WAVE DIATHERMY (PSWD)

(Asked 3 times in 6282 - MOST REPEATED in newer papers!)

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DEFINITION

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PRINCIPLE

Continuous vs Pulsed:

CONTINUOUS SWD:
████████████████  → HIGH mean power → THERMAL

PULSED SWD:
██  ██  ██  ██   → LOW mean power → NON-THERMAL
ON  OFF ON  OFF

Mark : Space Ratio:

• Mark = ON time (pulse duration: 65-400 microseconds)
• Space = OFF time (pulse interval)
• Example: Mark:Space = 1:100 → very low duty cycle → truly non-thermal
• Mean Power = Peak Power × Duty Cycle

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PRODUCTION / MACHINE CIRCUIT

[Mains Power Supply]
        ↓
[Master Oscillator] → generates 27.12 MHz
        ↓
[Pulse Modulator] → chops into ON/OFF pulses
        ↓
[Power Amplifier]
        ↓
[Patient Circuit with Drum Electrode]
        ↓
      PATIENT

Key Components:

1. Triode valve / transistor - generates HF oscillations
2. LC Circuit (inductor + capacitor) - determines 27.12 MHz frequency
3. Timing circuit - controls pulse duration and interval
4. Drum electrode - inductive coil applicator (most used for PSWD)

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ELECTRODES / APPLICATORS

1. Drum Electrode (MOST COMMON for PSWD):

• Flat coiled wire in plastic drum housing
• Produces inductive (magnetic) field
• Placed 1-2 cm above skin (no contact)
• Convenient and easy to apply

2. Capacitor Pads:

• Two metal plate electrodes
• Produces electrostatic (capacitive) field
• More for CSWD

3. Cable Electrode:

• Flexible cable coiled around limb
• Inductive field
• Good for limbs and spine

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PHYSIOLOGICAL & THERAPEUTIC EFFECTS

Non-Thermal (PRIMARY) Effects:

1. Mast cell degranulation → releases histamine → promotes healing
2. Increased cell membrane permeability → enhanced ion transport
3. Fibroblast stimulation → collagen synthesis, wound healing
4. Edema reduction → reduces acute and chronic edema
5. Anti-inflammatory → reduces prostaglandins, substance P
6. Nerve regeneration → accelerates axonal growth and myelination
7. Bone healing → stimulates osteoblasts (osteogenesis)
8. Wound healing → promotes granulation, epithelialization

Thermal Effects (higher dose/intensity):

• Increased blood flow
• Muscle relaxation
• Collagen extensibility

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DOSAGE

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INDICATIONS

1. Acute soft tissue injuries (sprains, strains)
2. Post-traumatic edema
3. Wound healing (pressure sores, diabetic ulcers)
4. Fracture healing (delayed/non-union)
5. Post-surgical edema and healing
6. Peripheral nerve injuries
7. Pelvic inflammatory conditions
8. OA (cartilage repair)
9. Tennis elbow, Achilles tendinitis

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CONTRAINDICATIONS

1. Metal implants / pacemakers (absolute)
2. Malignancy
3. Pregnancy (over abdomen)
4. Active hemorrhage
5. Acute infection / sepsis
6. Contact lenses (over eye area)
7. Impaired sensation areas

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PSWD vs CSWD COMPARISON

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✅ Q3. INFRA-RED RADIATION (IRR)

(Asked 2 times in 6282 + 5 times in 6260)

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DEFINITION

Classification:

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GENERATORS OF IRR

A. LUMINOUS GENERATORS (Near IR / Short Wave):

• Tungsten wire heated to 2000-3000°C
• Produces visible red/white light + near IR
• NO warm-up time needed
• Immediate output
• Portable
• Deep penetration (near IR)

• Large incandescent bulb
• Treats large areas
• No warm-up needed

• Mercury vapor lamp
• Produces UV + visible light + IR
• Used for tanning, acne, general UV treatment
• Warm-up: 5-10 minutes

LUMINOUS LAMP:
[Metal reflector dish]
[Incandescent bulb/filament]
→ emits visible light + near IR
→ penetrates 5-10 mm

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B. NON-LUMINOUS GENERATORS (Far IR / Long Wave):

• Resistance wire wound on ceramic element
• Heated to 400-500°C (lower than luminous)
• WARM-UP TIME: 5-10 minutes required before use
• Produces mainly long-wave (far) IR
• Superficial penetration only (1-2 mm)
• No glare - more comfortable
• Safer (lower source temperature)

NON-LUMINOUS GENERATOR STRUCTURE:
[Resistance wire] → wound on ceramic former
[Ceramic element] → in metal reflector dish
[Metal reflector] → concentrates radiation
[Adjustable stand] → height/angle adjustment

• Multiple non-luminous bulbs in a metal cradle/arch
• Patient lies under the cradle
• Treats large areas (trunk, back, both legs)
• Even, comfortable heat

• Tunnel-shaped unit with UV + IR lamps
• Whole body treatment
• Used for psoriasis, generalized skin conditions

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PHYSIOLOGICAL EFFECTS OF IRR

1. Skin temperature rise: Increases 1-3°C
2. Erythema: Immediate reddening (vasodilation of dermal capillaries); fades quickly after treatment
3. Vasodilation: Increased local blood flow (hyperemia)
4. Sweating: Sweat gland stimulation
5. Increased metabolic rate: Raised temperature → more tissue metabolism
6. Muscle relaxation: Warmth relieves spasm
7. Sedation of sensory nerves: Mild analgesia (pain relief)
8. Near IR only: Increases extensibility of collagen in deeper tissues

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THERAPEUTIC EFFECTS

1. Pain relief
2. Reduces muscle spasm
3. Increases local circulation
4. Preparation for massage / mobilization / exercise
5. Mild wound healing (increases blood supply)
6. Skin conditions (mild pressure sores, dermatitis)
7. Superficial joint arthritis

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TECHNIQUE OF APPLICATION

1. Inspect skin for burns, scars, or broken areas
2. Test temperature sensation (hot and cold)
3. Remove clothing from area
4. Warm up non-luminous lamp 5-10 minutes

1. Position lamp at correct distance (45-60 cm for non-luminous; 45-90 cm for luminous)
2. Lamp must be at 90° angle (right angle) to skin surface - Cosine Law
3. Duration: 15-30 minutes
4. Check skin every 5 minutes
5. Patient must not touch lamp

CORRECT POSITION (90°):
    LAMP
     |
     | ← 90° = maximum absorption
     |
  [SKIN]

INCORRECT (45°):
    LAMP
    /
   / ← cos 45° = less absorption
  /
[SKIN]

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PRECAUTIONS

1. Maintain correct distance
2. Lamp at right angles
3. Never leave patient alone
4. Test sensation before treatment
5. Protect eyes from luminous lamps
6. Remove makeup/oil (can absorb excess heat)
7. Do not apply on impaired sensation areas

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CONTRAINDICATIONS

1. Impaired temperature sensation
2. Acute dermatitis / skin infection
3. Bleeding disorders
4. DVT in area
5. Severe peripheral vascular disease
6. Over eyes (without protection)

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✅ Q4. SHORT WAVE DIATHERMY (SWD)

(Asked 6 times in 6260 + 1 time in 6282)

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DEFINITION

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PRODUCTION

LC Oscillator Circuit:

[Mains 220V AC]
      ↓
[Transformer] → steps up voltage
      ↓
[Rectifier] → AC to DC
      ↓
[LC Oscillator] → generates 27.12 MHz
   L = Inductor (coil)
   C = Capacitor
   Frequency = 1/(2π√LC)
      ↓
[Power Amplifier] → amplifies to 500W+
      ↓
[Patient Tuning Circuit]
      ↓
   PATIENT

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METHODS OF APPLICATION

1. CONDENSER FIELD METHOD (Capacitor Method):

• Two metal pad electrodes placed on opposite sides of body part
• An electrostatic field passes THROUGH the tissues
• Body part acts as dielectric between the plates

CONTRAPLANAR:
[PAD 1]
   ↕ ← electrostatic field through tissue
[PAD 2]
(electrodes opposite sides)

2. CABLE / INDUCTOTHERMY METHOD:

• Insulated cable wound 3-4 turns around body part
• An inductive (magnetic) field produced
• Eddy currents induced in tissues → produce heat
• Good for muscles (high water content)
• Used for: limbs, spine

CABLE METHOD:
===== ← cable coiled around limb
[LIMB]
=====
=====

3. DRUM ELECTRODE (Monode / Diplode):

• Pre-formed drum with internal coil
• Placed 1-3 cm above skin (air gap)
• Most convenient and commonly used
• Produces inductive field
• Most uniform heating

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ELECTRODE SPACING RULES (Very Important!)

1. Electrodes must be equally spaced from the patient on both sides
2. Distance from each electrode to skin = at least the electrode's own thickness
3. If closer electrode → more heat produced under that side → burns risk
4. Air gap must be maintained at all times

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PHYSIOLOGICAL EFFECTS

1. Tissue temperature rise (1-5°C)
2. Increased metabolic rate
3. Vasodilation → increased blood flow (hyperemia)
4. Muscle relaxation → reduces tone and spasm
5. Analgesic effect → gate control stimulation
6. Increased capillary permeability → better tissue nutrition
7. Increased collagen extensibility → joint stiffness reduces
8. Bactericidal (at high temperatures)

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THERAPEUTIC EFFECTS / INDICATIONS

1. Chronic OA, RA (sub-acute phase)
2. Muscle spasm (back pain, neck pain)
3. Bursitis (sub-acromial, trochanteric)
4. Tendinitis
5. Pelvic inflammatory conditions (gynaecology)
6. Post-fracture stiffness
7. Chronic sinusitis / ENT
8. Disc lesions

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CONTRAINDICATIONS

1. Metal implants (absolute - heats up → burns)
2. Pacemakers (absolute)
3. Pregnancy (abdomen)
4. Malignancy
5. Active TB
6. Hemorrhagic conditions
7. Growing epiphyses (children)
8. Impaired sensation

DANGERS

1. Burns (incorrect technique, unequal spacing)
2. Burns from metal objects (jewelry, pins, clips)
3. Eye damage
4. Burns from moist dressings/plaster
5. Electric shock

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✅ Q5. LASER

(Asked 1 time in 6282 + 4 times in 6260)

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DEFINITION

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PROPERTIES OF LASER (CMCP)

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PRODUCTION PRINCIPLES

1. Stimulated Emission:

     [EXCITED ATOM]
          |
Photon IN → Atom releases 2 identical photons OUT
(stimulated emission)

2. Population Inversion:

3. Components of a Laser:

[Energy Pump Source]
(electrical, flash lamp, diode)
        ↓
[Lasing Medium / Active Medium]
(gas, crystal, semiconductor)
        ↓
[Optical Resonator]
(two mirrors: one 100% reflective, one partial)
        ↓
[LASER BEAM OUTPUT]

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TYPES OF LASER

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BIOLOGICAL EFFECTS (PHOTOBIOMODULATION)

Primary Effects:

1. Photochemical - light energy converted to chemical energy → ATP production
2. Photophysical - increased mitochondrial activity
3. Photobiological - altered cell signaling, DNA/RNA synthesis

Secondary (Cellular) Effects:

1. Enhanced ATP production → increased cellular energy
2. Collagen synthesis → tissue repair
3. Fibroblast proliferation → wound healing
4. Mast cell degranulation → healing mediators
5. Endorphin release → pain relief
6. Serotonin increase → analgesic effect
7. Vasodilation → increased blood flow
8. Macrophage activation → immune response

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TECHNIQUE OF APPLICATION

1. Contact Technique:

• Probe placed directly on skin with light pressure
• Used for trigger points, acupuncture points
• Most common

2. Non-Contact (Scanning):

• Probe held 0.5-1 cm from skin
• For larger areas

3. Grid Technique:

• Area divided into grid
• Each square treated for set time
• Used for wounds, large areas

Parameters:

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CLINICAL APPLICATIONS

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CONTRAINDICATIONS / SAFETY

1. Malignancy (must NOT irradiate tumor)
2. Thyroid gland (direct irradiation)
3. Pregnant uterus
4. Eyes - MUST wear goggles (both patient AND therapist - corneal damage risk!)
5. Photosensitive patients / medications
6. Pacemakers
7. Epileptics (pulsed laser)
8. Growth plates in children

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✅ Q6. CRYOTHERAPY

(Asked 1 time in 6282 + 3 times in 6260)

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DEFINITION

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PHYSIOLOGICAL EFFECTS OF COLD

Local Effects:

1. Vasoconstriction - immediate response (reduces blood flow)
2. Hunting Reaction (Lewis Reaction) - after prolonged cold: alternating vasoconstriction and vasodilation every 15-30 min (prevents frostbite/tissue death)
3. Decreased metabolic rate - reduces oxygen demand → protects ischemic tissue
4. Reduced nerve conduction velocity → analgesia
5. Reduced muscle spindle activity → reduces spasticity/spasm
6. Analgesia (gate control + reduced nerve conduction)
7. Reduced edema (in acute injury - vasoconstriction limits fluid extravasation)

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METHODS OF APPLICATION

1. ICE PACK / COLD PACK (Most Common):

• Crushed ice in plastic bag wrapped in damp towel
• Applied 10-20 minutes
• Towel between ice and skin (prevents ice burns)
• Use: Acute injuries, OA, post-surgical swelling

2. ICE MASSAGE:

• Ice cube rubbed in circular/stroking motions
• Duration: 5-10 minutes direct on skin
• Patient experiences: Cold → Burning → Aching → Numbness (CBAN)
• Use: Trigger points, small localized areas, plantar fasciitis

3. COLD COMPRESSION UNIT (Cryo-cuff):

• Combines cold + compression simultaneously
• Sleeve filled with cold water + intermittent pressure
• Use: Post-surgical knee, ankle

4. ICE WATER IMMERSION (Cold Bath):

• Limb immersed in cold water (10-15°C)
• Duration: 10-20 minutes
• Use: Hands, feet, ankle conditions

5. VAPOCOOLANT SPRAY (Ethyl Chloride / Fluoromethane):

• Sprayed from can - evaporation produces rapid cooling
• Duration: few seconds
• Use: Spray and stretch technique, trigger points, DOMS

6. CRYOKINETICS:

• Cold applied first (10-20 min) → area numbed
• Then active exercises performed
• Purpose: Pain-free early mobilization after injury
• Use: Ankle sprains, post-surgical rehabilitation

7. CRYOSTRETCH:

• Cold applied to spastic/tight muscle
• Followed by gentle stretching
• Use: Muscle spasm, spasticity

8. CONTRAST BATH:

• Alternating hot (38-44°C) and cold (10-18°C) water immersion
• Ratio: 4 min hot : 1 min cold
• "Vascular exercise" → pumping action reduces swelling
• Use: Sub-acute ankle sprains, edema

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BIOPHYSICS OF CRYOTHERAPY

• Conduction: Ice pack, cold bath (direct contact)
• Evaporation: Vapocoolant spray
• Convection: Cold water immersion

• Skin → drops to 10-15°C quickly
• Subcutaneous tissue → slower (5-10 min)
• Muscle → slowest (depends on body fat thickness)

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THERAPEUTIC EFFECTS

1. Acute injury management - limits secondary hypoxic injury
2. Pain relief
3. Anti-inflammatory (acute phase)
4. Reduces spasticity
5. Post-exercise recovery (reduces DOMS)
6. Allows earlier exercise (cryokinetics)
7. Reduces acute edema

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CONTRAINDICATIONS

1. Raynaud's disease / cold hypersensitivity
2. Cryoglobulinemia
3. Cold urticaria
4. Peripheral vascular disease
5. Impaired sensation (ice burn risk)
6. Open wounds
7. Paroxysmal cold hemoglobinuria

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✅ Q7. MICROWAVE DIATHERMY (MWD)

(Asked 1 time in 6282 + 3 times in 6260)

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DEFINITION

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PRODUCTION - THE MAGNETRON

Magnetron (Key Component):

MAGNETRON STRUCTURE:
         [Cathode - heated filament at centre]
                 |
        Electrons spiral outward
                 |
         [Anode ring with resonant cavities]
         (strong perpendicular magnetic field
          causes electrons to spiral & interact
          with cavities → generate 2450 MHz waves)
                 |
         [Microwave output]
                 |
         [Waveguide/coaxial cable]
                 |
         [Dipole antenna in applicator]
                 |
             PATIENT

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APPLICATORS

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PHYSIOLOGICAL EFFECTS

1. Deep tissue heating (3-5 cm depth - mainly muscle)
2. Increased blood flow (vasodilation)
3. Increased metabolic rate
4. Muscle relaxation
5. Analgesia
6. Increased collagen extensibility

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THERAPEUTIC EFFECTS / INDICATIONS

1. Shoulder conditions (bursitis, tendinitis)
2. Hip and knee arthritis
3. Chronic back / neck pain
4. Pelvic inflammatory conditions
5. Sinusitis
6. Large muscle conditions (thigh, back)

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CONTRAINDICATIONS / DANGERS

Contraindications:

1. Eyes - cataracts (absolute!)
2. Testes - impairs spermatogenesis (absolute!)
3. Metal implants / pacemakers
4. Pregnancy
5. Moist dressings / plaster cast
6. Malignancy
7. Growing epiphyses

Dangers:

1. Cataract formation - microwave heats lens of eye
2. Testicular damage - hyperthermia → spermatogenesis impaired
3. Burns from metal / moist dressings
4. Pacemaker malfunction
5. Selective overheating of water-rich structures

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✅ Q8. ULTRA VIOLET RADIATION (UVR)

(Asked 1 time in 6282 + 3 times in 6260)

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DEFINITION

Classification:

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GENERATORS OF UVR

1. WATER-COOLED MEDIUM PRESSURE MERCURY VAPOR LAMP (KROMAYER LAMP):

• Mercury vapor in quartz tube
• Water jacket for cooling → allows CONTACT with skin
• Can be used in direct skin contact or underwater
• Very intense, all UV bands
• No warm-up needed
• Used for: small areas, wounds, sinus tracts

KROMAYER LAMP:
[Metal housing]
[Quartz tube - mercury vapor]
[Water cooling jacket around quartz]
[Contact cone/aperture - for localizing treatment]
→ Can touch skin directly (due to water cooling)

2. ALPINE SUN LAMP (Hanovia Type):

• Mercury vapor + iron arc
• Portable
• Produces UVA + UVB + visible light + near IR
• Used for general UVR at distance
• Warm-up: 5-10 minutes

3. THERAKTIN TUNNEL:

• Tunnel-shaped unit
• Multiple fluorescent UV lamps
• Patient lies INSIDE the tunnel
• Whole body irradiation
• Used for: psoriasis, generalized skin conditions

4. AIR-COOLED LOW PRESSURE LAMP:

• Fluorescent type
• Mainly UVC (bactericidal)
• Less therapeutic use

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ERYTHEMA DOSES

Minimal Erythema Dose (MED) / E1 Test:

Erythema Grades:

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PHYSIOLOGICAL EFFECTS

1. Erythema - vasodilation of dermal capillaries (peaks 6-12 hours)
2. Vitamin D synthesis - UVB converts 7-dehydrocholesterol → Vit D₃
3. Melanin production (tanning) - melanocytes stimulated → protective tanning
4. Bactericidal - UVC damages bacterial DNA → kills surface pathogens
5. Epidermal thickening - hyperplasia of stratum corneum (protective)
6. General stimulation - improved mood, immune stimulation
7. Photosensitization - some drugs increase UV sensitivity

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THERAPEUTIC USES

1. Psoriasis (PUVA)
2. Wound healing (bactericidal + promotes healing)
3. Acne vulgaris (kills P. acnes bacteria)
4. Vitamin D deficiency / rickets
5. Pressure sores / ulcers
6. Eczema / dermatitis
7. Neonatal jaundice (phototherapy)

---

CONTRAINDICATIONS

1. Drug photosensitivity (tetracyclines, NSAIDs, phenothiazines)
2. Known photosensitivity conditions (lupus erythematosus, xeroderma pigmentosum)
3. Acute systemic illness
4. Hyperthyroidism
5. Malignancy

---

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PART 3: ALL 5-MARK ANSWERS (TOP REPEATED)

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✅ 5-MARK: CONTRAST BATH (Asked 17 times - #1 MOST REPEATED!)

• Hot water tank: 38-44°C
• Cold water tank: 10-18°C

Step 1: HOT water (38-44°C)  → 4 minutes
Step 2: COLD water (10-18°C) → 1 minute
Step 3: HOT water            → 4 minutes
Step 4: COLD water           → 1 minute
(Repeat for total 20-30 min)
Finish: COLD for acute | WARM for chronic
Ratio: 4:1 (hot:cold)

1. Alternating vasodilation and vasoconstriction ("vascular exercise")
2. Reduces edema - pumping mechanism
3. Increases local circulation
4. Analgesia
5. Reduces stiffness

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✅ 5-MARK: HYDROCOLLATOR PACK / MOIST HOT PACKS (Asked 13 times)

• Canvas/nylon outer cover
• Silica gel filling (hydrophilic - absorbs and holds water)
• Various sizes (standard, cervical, oversize)

• Stainless steel tank
• Thermostatically controlled at 70-75°C
• Packs stored in hot water ready for use

1. Remove pack from unit with tongs
2. Wrap in 6-8 layers of dry towel (VERY IMPORTANT!)
3. Apply over treatment area
4. Duration: 15-20 minutes
5. Check skin every 5 minutes

Pack (70-75°C) → [6-8 towel layers] → Patient skin

1. Superficial tissue warming (skin to 40-44°C)
2. Vasodilation → increased blood flow
3. Muscle relaxation
4. Analgesia (sedation of nerve endings)
5. Increased metabolic rate

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✅ 5-MARK: PULSED SHORT WAVE DIATHERMY (PSWD) (Asked 11 times)

• Mark:Space ratio = ON time : OFF time
• E.g., 1:100 ratio = very non-thermal
• Mean power = Peak power × Duty cycle

1. Mast cell degranulation → healing
2. Increased cell membrane permeability
3. Fibroblast stimulation → collagen synthesis
4. Edema reduction
5. Anti-inflammatory
6. Nerve regeneration
7. Bone healing (osteoblast stimulation)
8. Wound healing

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✅ 5-MARK: LASER - PROPERTIES / TYPES / TECHNIQUES (Asked 15 times)

1. Coherent - all photons in phase
2. Monochromatic - single wavelength
3. Collimated - parallel beam (doesn't diverge)
4. Polarized - single plane oscillation

• He-Ne: 632 nm (red) - wound healing, pain
• GaAs: 850-904 nm - musculoskeletal
• GaAlAs: 630-830 nm - wound healing, pain

1. ATP production (photochemical)
2. Collagen synthesis (wound healing)
3. Fibroblast proliferation
4. Endorphin release (pain relief)
5. Anti-inflammatory
6. Vasodilation

• Contact: probe on skin (trigger points)
• Grid: area divided into grid (wounds)
• Scanning: cluster probe (large areas)

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✅ 5-MARK: MICROWAVE DIATHERMY (Asked 14 times)

• Director A/B (flat areas) - placed 5-10 cm from skin
• Cylindrical C type (limbs)

• EYES → cataracts (most important!)
• TESTES → impairs sperm production
• Metal implants, pacemakers, pregnancy

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✅ 5-MARK: CRYOTHERAPY IN ACUTE ANKLE SPRAIN (Asked Sep 2021, 6282)

• P = Protection (brace/support)
• R = Rest
• I = Ice (cryotherapy)
• C = Compression
• E = Elevation

1. Apply within 30 min of injury
2. Crushed ice in bag wrapped in damp towel
3. Applied over lateral ankle/swollen area
4. Duration: 20 minutes every 2-3 hours
5. Continue for 24-72 hours (acute phase)

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✅ 5-MARK: LAWS GOVERNING RADIATION (Asked 4 times)

1. Inverse Square Law:

• Double the distance → ¼ the intensity
• If dist = 50 cm, I = 1 unit; dist = 100 cm, I = ¼ unit
• Application: UVR dose calculation

2. Cosine Law (Lambert's Cosine Law):

• Max at 90° (lamp perpendicular to skin)
• Zero at 0° (lamp parallel to skin)
• Application: Position lamp at right angles to skin

3. Grotthus-Draper Law:

• Radiation that passes through without absorption = no effect

4. Bunsen-Roscoe Law (Reciprocity):

• Same effect: high intensity short time OR low intensity long time

5. Wien's Displacement Law:

• Hotter source = more blue/UV radiation

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✅ 5-MARK: PUVA THERAPY (Asked 3 times)

1. Psoralen (photosensitizer) taken orally or applied topically
2. UVA exposure 2-4 hours after psoralen
3. Psoralen activated by UVA → binds to DNA
4. Forms DNA cross-links → slows keratinocyte proliferation

• Oral: Methoxsalen (8-MOP) - taken 2 hours before UVA
• Topical/Bath: Patient soaks in psoralen solution

• Start: 1-3 J/cm²
• Increase: 0.5-1 J/cm² per session
• Frequency: 2-3 times/week
• Course: 20-30 sessions

1. Psoriasis (primary)
2. Vitiligo
3. Mycosis fungoides
4. Refractory eczema
5. Alopecia areata

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✅ 5-MARK: ELECTRODE SPACING IN SWD (Asked 7 times)

1. Both electrodes equally spaced from the skin
2. Minimum distance from skin = at least equal to electrode size
3. If one electrode closer → more heat under that side
4. Electrodes should be equal in size
5. Air gap minimum 1-2 cm at all times

• Cable wound 3-4 turns
• Turns must NOT overlap
• Produces eddy currents in muscle

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✅ 5-MARK: WHIRLPOOL BATH (Asked 3 times)

• Acute: Cold (15-20°C)
• Sub-acute/Chronic: Warm (33-38°C)
• Wound debridement: 35-39°C

1. Thermal effect (heat/cold based on setting)
2. Mechanical massage (water turbulence)
3. Buoyancy - reduces weight bearing (Archimedes principle)
4. Hydrostatic pressure - reduces edema
5. Increased local circulation
6. Muscle relaxation

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✅ 5-MARK: PHYSIOLOGICAL EFFECTS OF UVR (Asked 11 times)

1. Erythema - vasodilation of dermal capillaries, peaks 6-12 hours, intensity depends on dose (E1 to E4)
2. Vitamin D synthesis - UVB converts 7-dehydrocholesterol → Vitamin D₃ (cholecalciferol)
3. Pigmentation (tanning) - melanin produced by melanocytes; delayed tanning via UVA
4. Bactericidal action - UVC damages bacterial DNA → kills pathogens on skin surface
5. Epidermal hyperplasia - thickening of stratum corneum = protective response
6. General stimulation - improved mood, CNS stimulation, immune enhancement
7. Photosensitization - drugs like tetracyclines, phenothiazines increase sensitivity to UV

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✅ 5-MARK: THERAKTIN TUNNEL (Asked 3 times)

• Semi-circular or tunnel-shaped metal frame
• 6-8 mercury vapor fluorescent lamps inside
• Patient lies on couch; tunnel placed over patient
• Uniform UV distribution to trunk/back/limbs

1. Treats large areas at once
2. More uniform than single lamp
3. Good for generalized conditions

1. Psoriasis (whole body)
2. Generalized eczema
3. General phototherapy

1. Warm-up 5 minutes before use
2. Clean housing regularly
3. Check output with meter
4. Replace when output falls
5. Record total hours of use

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✅ 5-MARK: KROMAYER LAMP (Asked 2 times)

1. Water cooling → allows direct skin contact without burns
2. Very intense output (all UV bands)
3. Can be used underwater for wound treatment
4. Interchangeable aperture cones (small to large areas)
5. No warm-up needed

1. Small localized skin conditions
2. Wound healing (sinus tracts - contact cone inserted)
3. Underwater UVR for wounds
4. Acne, psoriasis patches
5. Pressure sores, plantar warts

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✅ 5-MARK: TREATMENT OF PSORIASIS (Asked 4 times)

• Oral/topical psoralen → 2-4 hr later UVA exposure
• 2-3 times/week; start 1-3 J/cm²

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✅ 5-MARK: LUMINOUS VS NON-LUMINOUS GENERATORS (Asked 3 times)

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✅ 5-MARK: WAX BATH (Asked 15 times - both codes)

Wash & dry hand → Dip 1-2 sec → Remove → Wait 5 sec
→ Dip again → Repeat 8-12 times
→ Wrap in plastic bag + towel → Rest 15-20 min → Remove

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✅ 5-MARK: PHONOPHORESIS (Asked 2 times)

• Apply drug directly to skin (drug = coupling medium)
• Standard US settings (usually 1 MHz continuous, 1-2 W/cm²)
• Duration: 5-10 minutes

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✅ 5-MARK: RADIATION ENERGY & PROPERTIES

Radio → Microwave → IR → Visible → UV → X-ray → Gamma
SWD     MWD         IRR   Light    UVR  Diagnostic
27MHz   2450MHz    700nm  400-700  100-400nm

1. Travels at speed of light (3 × 10⁸ m/s) in vacuum
2. Transverse wave motion
3. Travels through vacuum (unlike sound)
4. Obeys inverse square law (I ∝ 1/d²)
5. Obeys cosine law (I = I₀ cos θ)
6. Can be reflected, refracted, diffracted, polarized
7. Carries energy: E = hf (h = Planck's constant, f = frequency)
8. Relationship: c = f × λ (speed = frequency × wavelength)

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✅ 5-MARK: HYDROTHERAPY & ITS EFFECTS

1. Buoyancy - reduces effective body weight; non-weight-bearing exercise possible (Archimedes principle)
2. Hydrostatic pressure - pressure on submerged part; reduces edema; aids venous return
3. Viscosity - resistance to movement; used for strengthening exercises
4. Thermal conductivity - conducts heat 25x better than air; efficient heat/cold transfer
5. Turbulence (whirlpool) - massaging effect on tissues

1. Thermal effects (heat or cold)
2. Mechanical effects (buoyancy, pressure, turbulence)
3. Psychological relaxation
4. Facilitates early rehabilitation
5. Allows exercise in reduced-weight-bearing conditions

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🏆 FINAL EXAM STRATEGY SUMMARY

TOP PRIORITY (Will definitely come in exam):

15-MARK - Must Prepare These:

1. Ultrasound (production, effects, techniques) - asked 9 times total
2. PSWD (principles, non-thermal effects) - asked 6 times in 6282
3. Short Wave Diathermy - asked 6 times in 6260
4. Infra-Red Radiation (luminous + non-luminous generators)
5. LASER (production, types, biological effects, application)
6. Cryotherapy (all methods of application)
7. Microwave Diathermy

5-MARK - Must Prepare These (in order):

1. ⭐ Contrast Bath (17 times - write it in your sleep!)
2. ⭐ Cryotherapy (18 times - all methods + effects)
3. ⭐ LASER (properties, types, technique)
4. ⭐ Wax Bath (methods, effects)
5. ⭐ Microwave Diathermy (magnetron, applicators, contraindications)
6. ⭐ Hydrocollator Pack (composition, method, effects)
7. Physiological effects of UVR
8. PSWD (principles, non-thermal effects)
9. Laws governing radiation (Inverse square, Cosine, Grotthus-Draper, Bunsen-Roscoe)
10. PUVA therapy

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📋 ALL 2-MARK QUESTIONS & ANSWERS

BPT 3rd Year - Electrotherapy II (HF & Actinotherapy)

Sub Code 6282 (2020-2025) + Sub Code 6260 (2011-2021)

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1. ELECTRODE SPACING FOR SWD

• Both electrodes must be equally spaced from the patient on both sides
• Minimum distance from skin = at least equal to the electrode size
• If one electrode is closer → more heat under that electrode → burns
• Air gap of minimum 1-2 cm must be maintained
• Equal-sized electrodes must be used on both sides
• Rule: distance from skin ≥ size of electrode

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2. ELECTROSTATIC FIELD

• An electrostatic field is the electric field created between two capacitor plate electrodes in SWD (condenser field method)
• When two metal pads are connected to a high-frequency current, an alternating electrostatic field is set up between them and through the patient's tissues
• The patient's tissues act as the dielectric between the two plates
• Produces both electric and displacement currents in the tissue → generates heat
• Used in the condenser/capacitor pad method of SWD

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3. REVERSE PIEZOELECTRIC EFFECT

• The Piezoelectric effect = mechanical pressure on a crystal → generates electricity
• The Reverse Piezoelectric effect = applying an alternating electrical current to a crystal → causes it to vibrate mechanically (expand and contract)
• This is the basis of Ultrasound production
• Crystal used: Lead Zirconate Titanate (PZT)
• The crystal vibrates at the same frequency as the applied current (1 MHz or 3 MHz)
• These mechanical vibrations produce ultrasound waves

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4. NODES AND ANTINODES

• When an ultrasound wave is reflected back from a surface, it interferes with the incoming wave to form a standing wave
• Node = point of zero amplitude (no vibration) in a standing wave
• Antinode = point of maximum amplitude (maximum vibration)
• In therapeutic ultrasound, standing waves can cause periosteal pain (when antinode falls on bone)
• To prevent: keep transducer moving constantly during treatment
• Standing waves are avoided in therapy by continuous movement of the transducer

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5. ULTRASONIC FIELD

• Near Field (Fresnel Zone):
  • Close to transducer, beam is relatively parallel
  • Intensity is non-uniform and irregular
  • Length = r²/λ (r = crystal radius, λ = wavelength)
• Far Field (Fraunhofer Zone):
  • Beyond near field, beam diverges
  • Intensity is more uniform but lower
• BNR (Beam Non-Uniformity Ratio): Peak intensity ÷ Average intensity; should be ≤ 6:1

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6. PHOTOSENSITIZATION

• Photosensitization = increased sensitivity of the skin to UV radiation due to certain drugs or chemicals
• The skin reacts abnormally to UV (burns at lower doses than normal)

1. Tetracyclines (antibiotics)
2. Phenothiazines (tranquilizers)
3. NSAIDs (piroxicam, naproxen)
4. Sulfonamides
5. Oral contraceptives
6. Psoralen (used therapeutically in PUVA)

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7. SUPER LUMINOUS DIODE LASER

• A Super Luminous Diode (SLD) is a semiconductor device that produces near-infrared light (850-950 nm)
• It is NOT a true laser - it produces incoherent light (unlike laser which is coherent)
• Produces high-intensity broadband light similar to laser
• Does NOT require eye protection (unlike laser)
• Used for: wound healing, pain relief, soft tissue conditions
• Advantage over laser: safer (no coherence → no retinal damage risk), cheaper
• Also called Superluminescent Diode

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8. DANGERS OF SWD

1. Burns - from incorrect electrode spacing, moist skin
2. Burns from metal - jewelry, hairpins, metal implants heat up → burns
3. Eye damage - avoid directing field toward eyes
4. Burns from moist dressings - electrolyte solution concentrates current
5. Electric shock - faulty equipment
6. Pacemaker malfunction - electromagnetic interference
7. Burns under plaster cast - cannot check skin during treatment
8. Damage to growing bone (in children) - avoids heating epiphyses

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9. PROPERTIES OF LASER

1. Coherent - all photons in the same phase, frequency, and direction
2. Monochromatic - single wavelength (single color)
3. Collimated - parallel beam that does NOT diverge with distance
4. Polarized - all waves oscillate in a single plane

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10. HUBBARD TANK

• The Hubbard Tank is a full-body hydrotherapy tank shaped like a figure-8 (butterfly shape)
• Allows the therapist to reach all parts of the patient's body while immersed
• Water is agitated by turbines (whirlpool effect)
• Temperature: typically 34-37°C

1. Burn patients (wound cleaning, debridement)
2. Spinal cord injury rehabilitation
3. Multiple wound dressing changes
4. Polyarthritis (full body exercises in water)
5. Neurological rehabilitation (spasticity, paralysis)

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11. DRUGS USED IN PHONOPHORESIS

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12. DIFFERENCE BETWEEN 1 MHz & 3 MHz ULTRASOUND

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13. PUVA REGIMEN

• Psoralen + UVA therapy
• Patient takes psoralen orally (methoxsalen/8-MOP) 2-4 hours before UVA exposure
• OR: Bath PUVA - patient soaks in psoralen solution immediately before UVA
• Starting dose: 1-3 J/cm² UVA
• Dose increased by 0.5-1 J/cm² each session
• Frequency: 2-3 times per week (never on consecutive days)
• Course: 20-30 sessions
• Used for: Psoriasis, vitiligo, eczema, alopecia areata

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14. USE OF BUTTERFLY ELECTRODE IN SWD

• The butterfly (or diplode) electrode is a double drum electrode shaped like a butterfly
• It has two coils in a single unit facing each other
• Used for treating areas that require the field to pass between two lobes of the electrode
• Suitable for: knee joint (one lobe on each side), face (sinuses), small joints
• Produces inductive field between the two drum sections
• Advantage: no need to set up two separate electrodes; convenient for joints

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15. REFRACTION

• Refraction is the bending of a wave (light, sound, radiation) when it passes from one medium to another of different density/speed
• Occurs because the wave changes speed at the boundary
• Snell's Law: n₁ sin θ₁ = n₂ sin θ₂
• If wave goes from less dense → more dense medium: it slows down and bends toward the normal
• Application in therapy: Ultrasound waves refract at tissue interfaces (skin-fat, fat-muscle); affects direction of beam

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16. PROPERTIES OF HIGH FREQUENCY CURRENTS

1. Frequency: > 100,000 Hz (100 kHz)
2. No muscle contraction - frequency too high for nerve/muscle stimulation (accommodation occurs)
3. No electrolytic burns - ions cannot follow the rapidly alternating direction
4. No electrolytic effects - no true galvanic effects
5. Produces heat in tissues (diathermy effect)
6. Penetrates deeply into tissues
7. Not felt as electrical sensation by patient - only felt as heat
8. Examples: SWD (27.12 MHz), MWD (2450 MHz), Ultrasound (1-3 MHz)

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17. LAWS GOVERNING RADIATION

1. Inverse Square Law: I ∝ 1/d² (intensity reduces with square of distance)
2. Cosine Law: I = I₀ cos θ (max absorption when beam is perpendicular to surface)
3. Grotthus-Draper Law: Only radiation that is absorbed can produce a biological effect
4. Bunsen-Roscoe Law: Effect = Intensity × Time (E = I × T)
5. Wien's Displacement Law: Higher temperature → shorter peak wavelength

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18. COHERENCE (of Laser)

• Coherence is the property of laser light where all photons are in the same phase, frequency, and direction
• There are two types:
  • Temporal coherence: waves are in phase over time (same wavelength/frequency)
  • Spatial coherence: waves are in phase across the beam width (parallel beam)
• Coherence gives laser its ability to be focused to a tiny spot with very high energy density
• Ordinary light (bulb, sun) is incoherent - photons in random phases and directions
• Coherence is what makes laser collimated and monochromatic

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19. FLUIDOTHERAPY

• Fluidotherapy is a dry superficial heating modality using a bed of finely ground corn husks (cellulose particles) suspended in warm air
• The fluidized particles behave like a liquid (buoyancy + heat)
• Temperature: 38-48°C (adjustable)
• Body part inserted into the unit
• Provides: heat + light massage + desensitization

1. Superficial heating
2. Pain relief
3. Reduces stiffness
4. Desensitization of hypersensitive areas
5. Light mechanical stimulation

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20. SENSITIZERS USED IN UVR

1. Psoralen (used therapeutically in PUVA - for psoriasis, vitiligo)
2. Coal tar (used in Goeckerman regimen for psoriasis)
3. Acridine (yellow dye sensitizer)
4. Eosin (photosensitizer)
5. Bergamot oil (contains psoralen - natural sensitizer)
6. Rose bengal (ophthalmic sensitizer)
7. Quinine (anti-malarial - sensitizer)
8. Tetracyclines (drug photosensitizer - undesirable)

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21. ELECTRIC BURN

• Electric burn is tissue damage caused by passage of electric current through the body
• The heat generated (Joule's Law: H = I²Rt) causes burns at entry and exit points
• In electrotherapy, electric burns occur due to:
  1. High current density under small electrodes
  2. Damaged/broken skin (lower resistance → more current)
  3. Moist dressings concentrating current
  4. Poor electrode contact (sparking)
  5. Metal objects under electrode
• Types: Entry wound (usually small, deep) + Exit wound (larger, explosive)
• Prevention: test skin, ensure good electrode contact, avoid over moist areas

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22. TRIODE VALVE

• A Triode valve (vacuum tube) is an electronic component used in older SWD machines to generate high-frequency oscillations
• It has 3 elements:
  1. Cathode - emits electrons when heated
  2. Grid - controls electron flow
  3. Anode (plate) - collects electrons

[Cathode] → electrons → [Grid controls flow] → [Anode]

• By varying the grid voltage, the triode amplifies and oscillates the current
• In modern machines, transistors have replaced triode valves
• The oscillation frequency = 27.12 MHz for SWD

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23. CARE OF UVR LAMP

1. Warm-up time: Allow 5-10 minutes warm-up before treatment (Alpine sun lamp)
2. Cooling: Allow to cool before handling; never switch off and immediately restart
3. Cleaning: Wipe lens with dry cloth regularly (dust reduces output)
4. Output testing: Test with UVR meter at regular intervals; output decreases with use
5. Record hours: Keep a log of total hours used; replace when output falls below therapeutic level
6. Distance calibration: Recheck standard test distance regularly
7. Handling: Never touch bulb with bare hands (skin oils reduce lamp life)
8. Storage: Store in dry place, protect from moisture

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24. PULSED ELECTROMAGNETIC ENERGY (PEME) / WHAT IS IT

• Pulsed Electromagnetic Energy (PEME) = another name for Pulsed Short Wave Diathermy (PSWD)
• Application of a pulsed, high-frequency (27.12 MHz) electromagnetic field to tissues
• Key feature: delivered in pulses (ON/OFF intervals) → LOW mean power → non-thermal biological effects
• Does NOT generate significant heat in tissues (unlike CSWD)
• The non-thermal effects are the primary therapeutic mechanism
• Used for: acute injuries, edema, wound healing, fracture healing, nerve regeneration

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25. JOULE'S LAW

• H = Heat generated (Joules)
• I = Current (Amperes)
• R = Resistance (Ohms)
• t = Time (seconds)

1. Heat generated is proportional to the square of current (double current → 4× heat)
2. Heat is proportional to resistance
3. Heat is proportional to time

• Explains why tissues with high resistance (fat, bone) get heated more in diathermy
• Explains why damaged/broken skin burns more easily (lower resistance → paradox → actually higher current density)

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26. CONTRAINDICATIONS OF MICROWAVE DIATHERMY

1. Eyes - cataracts (absolute - microwaves heat lens of eye)
2. Testes - impairs spermatogenesis
3. Metal implants / pacemakers
4. Pregnancy
5. Moist dressings / plaster cast
6. Malignancy
7. Growing epiphyses (children)
8. Peripheral vascular disease

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27. WHIRLPOOL BATH

• Whirlpool bath = hydrotherapy unit where water is agitated by turbine/jet motor creating swirling water
• Combined effect: heat + mechanical massage + buoyancy + hydrostatic pressure
• Types: Arm tank, Leg tank, Lowboy tank, Hubbard tank (full body)
• Temperature: Cold (15-20°C) for acute; Warm (33-38°C) for sub-acute/chronic

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28. ELECTROMAGNETIC SPECTRUM

← INCREASING WAVELENGTH
← DECREASING FREQUENCY

Gamma | X-ray | UV | Visible | Infrared | Microwave | Radio waves
rays                (400-700nm) (700nm-1mm) (mm-cm)    (cm-m)
                         ↑          ↑           ↑          ↑
                        UVR        IRR         MWD        SWD
                     (100-400nm)             (2450MHz)  (27.12MHz)

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29. DUTY CYCLE

• In pulsed modalities (Pulsed US, PSWD), duty cycle determines how much of the time energy is delivered
• 100% duty cycle = continuous mode (fully thermal)
• 20% duty cycle = 20% ON, 80% OFF → non-thermal (5× less mean power)
• 50% duty cycle = 50% ON, 50% OFF → mild thermal

• Pulsed US: 2 ms ON, 8 ms OFF = 2/10 × 100 = 20% duty cycle
• At 20%: mean intensity = 1 W/cm² × 0.2 = 0.2 W/cm² (effective/mean)

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30. BUOYANCY

• Buoyancy is the upward force exerted by water on a submerged object (Archimedes' Principle)
• Archimedes' Principle: Buoyancy force = weight of water displaced
• In hydrotherapy: buoyancy reduces effective body weight
  • Waist-deep water: ~50% body weight reduced
  • Chest-deep water: ~70-75% body weight reduced
  • Neck-deep water: ~90% body weight reduced

1. Allows early weight-bearing exercises after fractures/surgery
2. Reduces pain during movement
3. Strengthening exercises with reduced joint load
4. Gait training in neurological conditions

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31. COSINE LAW

• Intensity of radiation absorbed by a surface = original intensity × cosine of angle of incidence
• At 90° (perpendicular): cos 0° = 1 → maximum absorption
• At 45°: cos 45° = 0.707 → 70.7% of maximum
• At 0° (parallel): cos 90° = 0 → no absorption

• Position the lamp at right angles (90°) to skin for maximum therapeutic effect
• Applies to IR lamps, UV lamps, and laser application
• Also explains why sunburn is worse at midday (sun overhead = 90°)

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32. EDDY CURRENTS

• Eddy currents are circular electrical currents induced in a conducting material when it is placed in a changing magnetic field (by electromagnetic induction)
• In SWD (cable/inductothermy method): high-frequency alternating magnetic field from the cable induces eddy currents in the patient's tissues
• These eddy currents encounter tissue resistance → generate heat (Joule heating)
• Eddy currents are strongest in tissues with high electrical conductivity (muscle, blood - high water/electrolyte content)
• Fat (low conductivity) → fewer eddy currents → less heating

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33. HELIOTHERAPY

• Heliotherapy = therapeutic use of sunlight for medical conditions
• The sun emits UVA, UVB, UVC (UVC filtered by ozone layer), visible light, and IR
• UVB in sunlight → Vitamin D synthesis
• Used historically for: TB (Finsen light therapy), rickets, psoriasis, skin conditions

• Supervised sun exposure for Vitamin D deficiency
• Seasonal Affective Disorder (SAD) - light therapy
• Psoriasis - natural sunlight + sea bathing (Thalassotherapy)

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34. COLD LASER

• Cold laser = Low Level Laser Therapy (LLLT)
• Called "cold" because it does NOT produce significant heat in tissues (unlike surgical/cutting lasers)
• Uses Class III laser (5-500 mW), typically He-Ne or GaAs type
• Primary effects are photobiological (non-thermal): cell stimulation, not heating

1. Wound healing (fibroblast stimulation, collagen synthesis)
2. Pain relief (endorphin release)
3. Anti-inflammatory
4. Tissue regeneration

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35. ERYTHEMA

• Erythema = redness of the skin due to vasodilation of superficial blood vessels
• In UVR: erythema appears 6-12 hours after irradiation (latent period), peaks at 12-24 hours

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36. INDICATIONS OF WAX THERAPY

1. Rheumatoid Arthritis (hands, feet - sub-acute/chronic)
2. Osteoarthritis of hand joints
3. Post-fracture stiffness of hand/wrist
4. Scleroderma (systemic sclerosis - softens tight skin)
5. Dupuytren's contracture (early)
6. Trigger finger (non-surgical)
7. Post-surgical hand conditions
8. Ligament sprains of small joints (sub-acute)
9. Tenosynovitis (sub-acute/chronic)
10. Any condition requiring superficial heat to hands/feet

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37. QUICK ICE

• Quick ice = rapid application of ice to a small area for very short duration (3-5 seconds)
• Used to produce a facilitatory (excitatory) effect on muscles, NOT an inhibitory effect
• Short, rapid cold application → stimulates skin receptors → facilitates muscle contraction
• Used in neurological rehabilitation to stimulate weak/paralyzed muscles
• Different from prolonged cold (which inhibits muscle → used for spasticity)
• Application: ice cube tapped or stroked quickly over the muscle or skin dermatome

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38. DEFINE ULTRASOUND

• Ultrasound is a form of mechanical energy transmitted as longitudinal pressure waves
• Frequency: above 20,000 Hz (20 kHz) - beyond range of human hearing
• Therapeutic ultrasound: 1 MHz or 3 MHz
• Produced by reverse piezoelectric effect of PZT crystals
• Travels through tissues as alternating cycles of compression and rarefaction
• Cannot travel through vacuum (needs a medium - coupling gel/water used)

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39. GRID METHOD (in Laser / UVR)

• Grid technique = dividing the treatment area into a grid of equal squares
• Each square is treated individually for a set time
• Ensures uniform coverage of the entire area
• Used in: LASER therapy (wounds, large areas), UVR treatment of large areas

• Area divided into grid (e.g., 1 cm × 1 cm squares)
• Each grid point treated for calculated time (based on energy density J/cm²)

• Large wound area divided into grid
• Each section receives calculated dose

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40. TRIDYMITE FORMATION

• Tridymite is a form of silica (SiO₂) - a crystalline structure
• In ultrasound therapy: the piezoelectric crystal (quartz) can be damaged if overheated
• When quartz is heated above 870°C, it transforms into tridymite - a different crystal structure
• Tridymite has no piezoelectric properties → the transducer loses its ability to produce ultrasound
• Prevention: Never test the ultrasound in air (run without coupling medium) - the crystal overheats without a medium to absorb energy
• Always use coupling gel during treatment to protect the crystal from overheating

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41. MINIMAL ERYTHEMA DOSE (MED)

• MED = Minimal Erythema Dose = the smallest dose of UVR that produces just perceptible redness (erythema) on the skin, appearing 6-12 hours after irradiation
• Also called E1 dose or First Degree Erythema Dose
• MED is determined by the Test Dose procedure:
  1. Use inner forearm (standard area)
  2. Expose 4 holes in card for different times (e.g., 30, 60, 90, 120 sec)
  3. Read 6-12 hr later
  4. MED = time that produced just perceptible redness

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42. CRYOSTRETCH

• Cryostretch = applying cold to a tight/spastic muscle, followed immediately by passive or active stretching
• Mechanism:
  1. Cold reduces muscle spindle activity (gamma motor neuron inhibition)
  2. Reduces hypertonicity/spasm
  3. Analgesia allows pain-free stretching
  4. Stretching performed while muscle is inhibited
• Method: Ice pack/cold spray on muscle for 10-15 min → immediate stretching
• Used for: Muscle spasticity, muscle guarding, contractures, hamstring/calf tightness
• Produces longer lasting stretch than stretch alone

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43. PERIOSTEAL PAIN IN ULTRASOUND (Prevention)

• Periosteal pain = pain at bone surface during ultrasound treatment
• Caused by standing waves (when ultrasound reflects off bone and interferes with incoming waves → antinodes form at bone surface)
• The antinode of maximum vibration at bone → periosteal irritation → pain

1. Keep transducer moving continuously during treatment (prevents standing wave formation)
2. Use pulsed mode (lower mean intensity)
3. Reduce intensity if patient reports pain over bone
4. Move transducer at speed of 3-4 cm/sec

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44. PRESSURE SORE

• Pressure sore (decubitus ulcer / bedsore) = localized skin and tissue damage from prolonged pressure, usually over bony prominences
• Caused by: ischemia from sustained pressure > capillary pressure (32 mmHg)

1. UVR (Kromayer lamp): Bactericidal, promotes healing (E2-E3 dose)
2. LASER (LLLT): Wound healing, fibroblast stimulation
3. Ultrasound (pulsed): Tissue healing, increases cell permeability
4. PSWD (Dose I): Non-thermal healing
5. Whirlpool: Debridement, cleaning
6. Repositioning (prevention - every 2 hours)

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45. ICE TOWEL METHOD

• Ice towel method = a method of cryotherapy using towels soaked in iced water
• Towels immersed in ice water (4-10°C), wrung out, applied to body area
• Changed frequently (every 2-3 minutes) as they warm up
• Provides larger area coverage than ice pack
• Used for: back, large muscle groups, post-exercise recovery
• Less intense cooling than direct ice pack
• Good for sensitive skin (indirect cold application)

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46. ATTENUATION

• Attenuation = reduction in intensity of a wave (ultrasound, light) as it passes through a medium
• Caused by:
  1. Absorption - energy converted to heat in tissue
  2. Reflection - wave bounces back at interfaces
  3. Scattering - wave diverted in different directions
  4. Refraction - wave bent at boundary

• Attenuation coefficient varies per tissue
• Bone > tendon > muscle > fat > blood (high → low attenuation)
• At 3 MHz: more attenuation (less penetration) than 1 MHz
• Half-value depth (HVD): depth at which intensity is reduced by 50%

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47. CONDUCTION (Heat Transfer)

• Conduction = transfer of heat from a hot object to a cooler one by direct contact (molecule-to-molecule transfer)
• No movement of matter itself - energy passes through the material
• Rate depends on: temperature gradient, thermal conductivity, contact area, thickness

• Hot packs, wax bath → conduction from pack to skin
• Ice pack → conduction from skin to ice
• Hydrocollator pack → conductive heat transfer

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48. DESQUAMATION

• Desquamation = shedding/peeling of the outer layer of skin (stratum corneum)
• In UVR therapy: occurs after E3-E4 dose erythema (3rd-4th degree erythema)
• As part of the skin's response to UV damage → dead skin cells shed
• Also occurs naturally as part of normal skin cell turnover
• In psoriasis: abnormal, excessive desquamation (thick silver scales) is the key feature
• After wax bath: mild desquamation/softening of skin is normal and beneficial

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49. HYDROCOLLATOR PACK (2-mark version)

• Canvas bag filled with silica gel (hydrophilic material)
• Stored in thermostatically controlled unit at 70-75°C
• Wrapped in 6-8 layers of towel before application to prevent burns
• Applied for 15-20 minutes
• Provides moist superficial heat → vasodilation, muscle relaxation, pain relief
• Reusable for 15-20 years

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50. COUPLING MEDIA / COUPLANTS

• Coupling medium = substance applied between the ultrasound transducer and skin to eliminate the air gap (air reflects 99.99% of ultrasound)
• Air is a very poor conductor of ultrasound → coupling medium is essential

1. Acoustic impedance close to skin
2. No air bubbles
3. Non-irritating to skin
4. Good viscosity (stays in place)
5. Does not damage transducer

1. Aquasonic gel (most common)
2. Water (immersion method)
3. Mineral oil
4. Glycerine
5. Drug gels (phonophoresis - diclofenac, hydrocortisone)

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51. PUVA (2-mark version)

• Psoralen + UVA therapy
• Psoralen = photosensitizer taken orally or topically 2-4 hrs before UVA exposure
• UVA activates psoralen → DNA cross-linking → slows cell proliferation
• Used for: Psoriasis (primary), vitiligo, eczema, mycosis fungoides

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52. ACNE VULGARIS

• Acne vulgaris = chronic inflammatory skin condition involving pilosebaceous units (hair follicle + sebaceous gland)
• Caused by: Propionibacterium acnes (bacteria), excess sebum, blocked follicles, hormones

1. UVR (sub-erythema to E1 dose): Bactericidal → kills P. acnes; reduces inflammation
2. Frequency: 3× per week, gradual dose increase
3. Kromayer lamp for localized acne
4. Alpine sun lamp for wider area
5. Avoid UVR during isotretinoin therapy (photosensitizer)

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53. KROMAYER LAMP (2-mark version)

• Water-cooled medium-pressure mercury vapor lamp
• Can be used in direct contact with skin (water cooling allows this)
• Very intense UVR output; all UV bands
• Used for small, localized areas; wounds; sinus tracts; underwater UVR
• No warm-up time needed
• Interchangeable aperture cones for directing beam

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54. ICE PACK / COLD PACK

• Ice pack = crushed ice in a plastic bag wrapped in a damp towel
• Applied for 10-20 minutes per session
• Never apply ice directly on skin (risk of ice burn)
• Mechanism: vasoconstriction → limits edema, secondary hypoxic injury → analgesia
• Used for: acute injuries (PRICE protocol), OA pain, post-surgical swelling
• Commercial gel packs: stored in freezer (-5°C), reusable

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55. PHYSICAL EFFECTS OF HEAT

1. Expansion: Materials expand on heating (thermal expansion)
2. Change of state: Solid → Liquid → Gas (melting, vaporization)
3. Increased molecular velocity: Molecules move faster
4. Decreased viscosity: Fluids become less viscous when heated
5. Increased electrical conductivity (in electrolytes/solutions)
6. Radiation: Hot objects emit electromagnetic radiation (infrared)
7. In tissues: increased metabolic rate, vasodilation, protein denaturation at high temperatures

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56. STRUCTURE OF SKIN

[EPIDERMIS] (outer layer - no blood vessels)
 - Stratum corneum (dead cells - keratin)
 - Stratum granulosum
 - Stratum spinosum
 - Stratum basale (deepest - divides)

[DERMIS] (connective tissue)
 - Blood vessels, lymphatics
 - Hair follicles, sweat glands
 - Sebaceous glands
 - Sensory nerve endings
 - Collagen and elastin fibers

[HYPODERMIS / SUBCUTANEOUS TISSUE]
 - Fat (adipose tissue)
 - Deeper blood vessels
 - Loose connective tissue

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57. LAWS OF REFRACTION

1. The refracted ray, incident ray, and normal at the point of incidence are all in the same plane
2. The ratio of sine of angle of incidence to sine of angle of refraction = constant (refractive index)
   • n₁/n₂ = sin θ₂ / sin θ₁

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58. PRECAUTIONS OF ULTRA VIOLET RADIATIONS

1. Eye protection - goggles for patient AND therapist (UV causes conjunctivitis, cataracts)
2. Test dose - always determine MED before therapeutic doses
3. Drug history - check for photosensitizing medications
4. Expose only treated area - protect surrounding skin
5. Maintain correct distance - as per lamp specification
6. Skin inspection - before each treatment
7. Warm-up lamp - before measuring distance/applying treatment (output changes during warm-up)
8. Never look at lamp directly
9. Sensitizers - avoid during tetracycline/photosensitizing drug therapy

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59. ICE MASSAGE (2-mark version)

• Rubbing an ice cube directly on skin in circular/stroking motions
• Duration: 5-10 minutes
• Patient progression: Cold → Burning → Aching → Numbness (CBAN)
• Treatment begins when numbness is achieved
• Used for: trigger points, small areas, plantar fasciitis, DOMS
• Provides deeper cooling than ice pack (direct contact, no towel barrier)

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60. PSORIASIS

• Psoriasis = chronic, non-contagious autoimmune skin disorder with abnormally rapid keratinocyte proliferation
• Cell turnover: 3-5 days (vs normal 28-30 days)
• Appearance: salmon-red, raised, thick silvery scaly plaques
• Common sites: elbows, knees, scalp, lumbosacral area

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61. COOLING OF LAMP / PREPARATION OF LAMP

1. After switching off UV lamp, do NOT restart immediately - allow to cool (10-15 min)
2. The mercury must recondense before lamp can be restarted
3. Restarting hot mercury lamp fails - output will be incorrect until fully cooled
4. The lamp output drops during cooling phase - do not treat during this phase
5. Also: lens/housing must cool before cleaning or storing

1. Check machine and cables for damage
2. Ensure patient is free of metal objects
3. Position electrode at correct distance
4. Tune the machine to patient (resonance indicator)
5. Gradually increase output

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62. OHM'S LAW

• V = Voltage (Volts)
• I = Current (Amperes)
• R = Resistance (Ohms)

• V = IR (Voltage = Current × Resistance)
• I = V/R (Current = Voltage ÷ Resistance)
• R = V/I (Resistance = Voltage ÷ Current)

• Lower skin resistance (moist skin, broken skin) → more current for same voltage → risk of burns
• Explains importance of dry, intact skin for electrotherapy

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63. INDUCTANCE

• Inductance is the property of a coil (inductor) to oppose changes in current by generating an opposing electromagnetic force
• Symbol: L, Unit: Henry (H)
• When AC flows through a coil: changing current → changing magnetic field → induces opposing EMF (self-induction)
• Inductive reactance (XL) = 2πfL (increases with frequency)
• In SWD: the inductor (coil) is part of the LC oscillator circuit that generates 27.12 MHz
• Cable electrode of SWD = acts as inductor around patient → induces eddy currents in tissues

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64. LEWIS HUNTING REACTION

• Lewis Hunting Reaction (Cold-Induced Vasodilation / CIVD) = the alternating cycle of vasoconstriction and vasodilation that occurs in response to prolonged cold application
• Named after Thomas Lewis (1930)

1. Cold applied → vasoconstriction (0-5 min) → skin cools
2. Prolonged cold → vasodilation opens (5-15 min) → skin warms slightly (redness)
3. Vasoconstriction returns → vasodilation → cycles every 15-30 minutes

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65. PHOTOSENSITIZERS (2-mark version)

1. Psoralen (therapeutic - PUVA for psoriasis/vitiligo)
2. Coal tar (Goeckerman regimen)
3. Tetracyclines (undesirable drug reaction)
4. Phenothiazines (undesirable drug reaction)
5. NSAIDs (piroxicam)
6. Acridine dye
7. Bergamot oil

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66. TYPES OF LASER (2-mark version)

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67. MERCURY VAPOR LAMP AND ITS USES

• Mercury vapor lamp = lamp containing mercury vapor enclosed in quartz/glass tube
• When electrical discharge passes through mercury vapor → UV + visible light produced
• Types: Low pressure (mainly UVC), Medium pressure (UVA+UVB+UVC), High pressure

1. UVR therapy (psoriasis, acne, wound healing)
2. PUVA therapy - UVA source
3. Bactericidal sterilization (UVC)
4. Theraktin tunnel and Kromayer lamp both use mercury vapor
5. Street lighting (high pressure)

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68. ICE BURN

• Ice burn = frostbite-like tissue injury caused by prolonged direct contact of ice/freezing agent with skin
• Ice (0°C) is much colder than skin - prolonged contact → vasoconstriction → ischemia → tissue injury
• Appears as: white/pale patch → red → blisters (similar to thermal burn)

1. Never apply ice directly to bare skin - always use a damp towel as barrier
2. Limit application to 20 minutes maximum
3. Check skin appearance and patient sensation during treatment
4. Do not apply cold to areas of impaired circulation or sensation

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69. MAGNETRON (2-mark version)

• Magnetron is a vacuum tube device used to generate microwaves at 2450 MHz in MWD machines
• Has: central cathode (heated filament) + outer anode with resonant cavities
• Strong perpendicular magnetic field causes electrons to spiral outward
• Spiraling electrons interact with resonant cavities → generate 2450 MHz microwave oscillations
• Output fed via waveguide to the applicator/electrode
• The magnetron is the key/heart component of the Microwave Diathermy unit

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70. CRYOKINETICS (2-mark version)

• Cryokinetics = combination of cold application + active exercises
• Sequence: Cold applied (ice pack, 20 min) → numbness achieved → immediately perform active exercises
• Purpose: cold provides temporary analgesia → patient can exercise pain-free → earlier rehabilitation
• Advantages: earlier mobilization, maintains range of motion, prevents atrophy
• Used for: acute ankle sprains, post-surgical knee, ligament injuries

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71. ERYTHEMA (same as above - repeated for 2-mark reference)

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72. HELIUM-NEON (He-Ne) LASER

• He-Ne laser = gas laser using Helium-Neon gas as lasing medium
• Wavelength: 632 nm (visible red light)
• Power: typically 1-50 mW (Class III - LLLT)
• Penetration: superficial (1-2 mm)
• First practical continuous wave laser (1960)

1. Wound healing (superficial wounds, pressure sores)
2. Pain relief (trigger points, acupuncture points)
3. Herpes simplex (cold sores)
4. Scar management
5. Superficial tendinitis

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73. PIEZOELECTRIC EFFECT

• Direct Piezoelectric Effect: Mechanical pressure on certain crystals (quartz, PZT) → generates electrical voltage
• Reverse Piezoelectric Effect: Applying alternating electrical current to crystal → crystal vibrates mechanically → produces ultrasound

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74. ADHESIVE CAPSULITIS (FROZEN SHOULDER)

• Adhesive capsulitis = inflammation and fibrosis of the glenohumeral joint capsule → pain + restricted ROM
• Also called "Frozen Shoulder"

1. Painful (freezing) phase - 3-9 months
2. Frozen phase - 9-12 months
3. Thawing phase - 12-24 months

1. SWD/MWD - deep heat → reduces stiffness
2. Ultrasound - breaks adhesions, softens capsule
3. LASER/TENS - pain relief
4. Wax bath (not useful for shoulder - but heat modalities)
5. Exercises - pendulum, stretching, Codman's

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75. CRYOSPRAY (VAPOCOOLANT SPRAY)

• Cryospray = cold spray containing ethyl chloride or fluoromethane (fluro-methyl) or liquid nitrogen
• When sprayed: liquid rapidly evaporates → absorbs heat → rapid cooling
• Duration: few seconds
• Causes very rapid superficial cooling

1. Spray and stretch technique - spray on tight muscle → immediate stretch
2. Trigger point therapy
3. Minor procedural analgesia (injections, venepuncture)
4. DOMS relief

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76. RUBY LASER

• Ruby laser = first practical laser, invented by Theodore Maiman, 1960
• Lasing medium: Synthetic ruby crystal (aluminum oxide + chromium ions Cr³⁺)
• Wavelength: 694 nm (red visible light)
• Pumping: Flash lamp (pulsed)
• Output: Pulsed (not continuous)

1. Dermatology: tattoo removal, pigmented lesion removal
2. Hair removal (laser epilation)
3. Research

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77. CAVITATION

• Cavitation = formation of gas/vapor bubbles in tissue fluids during ultrasound application, due to alternating pressure waves

1. Stable (transient) cavitation:
   • Bubbles oscillate in size gently with the sound wave
   • Therapeutic - promotes acoustic streaming and cell membrane changes
   • Used therapeutically at normal intensities
2. Unstable (inertial) cavitation:
   • Bubbles grow then collapse VIOLENTLY
   • Produces extreme local pressure, temperature, free radicals
   • HARMFUL - causes tissue destruction
   • Avoided in therapy by keeping intensity within safe limits and moving transducer

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78. TENOSYNOVITIS

• Tenosynovitis = inflammation of the tendon sheath (synovial sheath surrounding a tendon)
• Common sites: wrist tendons (de Quervain's), hand/finger flexors

1. Ultrasound (pulsed): Reduces inflammation, promotes healing
2. PSWD (Dose I-II): Non-thermal, reduces acute inflammation
3. LASER (LLLT): Anti-inflammatory, analgesic
4. Wax bath (sub-acute) - increases local circulation
5. Ice (acute phase) - reduces swelling and pain
6. Splinting + rest during acute phase

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79. RICKETS

• Rickets = deficiency disease in children due to Vitamin D deficiency → poor calcium/phosphate absorption → soft, weak bones

• UVB radiation converts 7-dehydrocholesterol in skin → Vitamin D₃ (cholecalciferol)
• Vitamin D₃ → liver → 25-OH Vit D → kidney → active form (1,25 dihydroxy Vit D / calcitriol)
• Calcitriol → increases Ca and P absorption from gut → bone mineralization
• Heliotherapy (sunlight) and UVR therapy used to treat/prevent rickets

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80. TREATMENT FOR ACNE

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81. EDDY CURRENTS (2-mark version)

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82. MAGNETRON (repeated - see #69)

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83. NEAR FIELD / FAR FIELD

• Near field (Fresnel): close to transducer, irregular intensity, parallel beam
• Far field (Fraunhofer): further away, diverging beam, more uniform intensity
• Near field length = r²/λ

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84. INVERSE SQUARE LAW

• Intensity of radiation is inversely proportional to the square of the distance from the source
• Double the distance → ¼ the intensity
• Half the distance → 4× the intensity

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85. OSCILLATOR CIRCUIT

• Oscillator circuit = electronic circuit that generates repetitive alternating current oscillations at a specific frequency
• In SWD: LC Oscillator (Tank Circuit) generates 27.12 MHz
• L = Inductor (coil), C = Capacitor
• Frequency = 1/(2π√LC)
• How it works: Capacitor charges → discharges through inductor → electromagnetic oscillation → capacitor recharges → cycle repeats
• The frequency is determined by the values of L and C

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86. PARAMETERS OF ULTRASOUND (2-mark version)

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87. PLANTAR WARTS

• Plantar warts (verruca plantaris) = warts on the sole of foot caused by Human Papillomavirus (HPV)
• Appear as hard, thickened skin with black dots (thrombosed capillaries) on soles
• Painful when walking (pressure flattens them inward)

1. UVR (Kromayer lamp): Contact application over wart; E3-E4 dose; bactericidal/viral effect
2. Cryotherapy (liquid nitrogen): Freezes and destroys wart tissue
3. LASER (CO₂): Vaporizes wart
4. Salicylic acid (medical)

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88. DEPTH OF PENETRATION OF ULTRASOUND

• Higher frequency = less penetration (more energy absorbed superficially)
• 3 MHz heats superficial tissue 3× faster than 1 MHz
• Half-value depth: depth where intensity falls to 50% of surface intensity

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89. DEFINE FREQUENCY

• Frequency = number of complete cycles (oscillations) per second
• Unit: Hertz (Hz) = cycles per second
• Symbol: f
• Relationship: c = f × λ (speed = frequency × wavelength)

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90. DANGERS OF INFRARED RADIATION

1. Burns - most common; from too close distance, impaired sensation, wrong technique
2. Eye damage - glare from luminous lamps; chronic exposure → corneal damage
3. Fainting - if large areas treated (vasodilation → drop in BP)
4. Dehydration - if large areas treated with high intensity (sweating)
5. Erythema ab igne - mottled skin discoloration from repeated IR exposure (heat rash pattern)
6. Burns in areas of impaired sensation (patient cannot report overheating)

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91. WAVELENGTH OF LASERS USED IN THERAPY

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92. WAVELENGTH OF UVB

• UVB wavelength: 280-315 nm
• UVB is the most therapeutically important band:
  • Produces erythema (sunburn)
  • Responsible for Vitamin D synthesis
  • Bactericidal effects
  • Most effective for psoriasis (narrow band UVB = 311 nm is gold standard)

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93. PIGMENTATION

• Pigmentation = increased production of melanin by melanocytes in skin following UV exposure
• UV stimulates melanocytes → increased melanin synthesis → tanning
• Immediate tanning (UVA): Oxidation of existing melanin - appears immediately - transient
• Delayed tanning (UVB/UVA): New melanin synthesized - appears 2-3 days later - lasting

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94. MARK:SPACE RATIO

• Mark = ON time (pulse duration) in PSWD
• Space = OFF time (interval between pulses)
• Mark:Space ratio = ON time : OFF time

• 1:1 = 50% duty cycle (moderate thermal)
• 1:10 = ~9% duty cycle (mild thermal)
• 1:100 = ~1% duty cycle (athermic/non-thermal)
• 1:1000 = maximum non-thermal effect

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95. TEST DOSE / MED TEST

1. Select inner forearm (standard hairless area)
2. Cut 4 holes in a card (each ~2 cm²)
3. Cover 3, expose 1 → after 30 sec, cover 2, expose 2 → after 30 sec, expose 3 → after 30 sec, expose all 4
4. Final times: e.g., 30s, 60s, 90s, 120s
5. Read 6-12 hours later
6. MED = exposure time that produced just perceptible redness

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96. DEFINE INDUCTOTHERMY

• Inductothermy = a method of applying SWD using the cable (inductive) method
• A cable is wound around the body part → high-frequency alternating current produces a changing magnetic field → induces eddy currents in tissues → heat produced
• Body part acts as the secondary coil of a transformer
• Best for heating muscles (high water/electrolyte content - good eddy current conductors)
• Produces mainly muscle heating; bone heats less than with capacitor field method

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97. PARAMETERS OF PULSED SWD

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98. LATENT HEAT OF FUSION

• Latent heat of fusion = the amount of heat absorbed when a solid melts (changes to liquid) at constant temperature
• Or: heat released when liquid freezes (solidifies)
• For ice: latent heat of fusion = 335 J/g (80 cal/g)

• When ice melts → it absorbs large amounts of heat from tissue (335 J/g)
• This is why ice is so effective for cooling: besides being cold (0°C), the melting process absorbs extra heat
• Makes ice more effective than cold water at same temperature

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99. CRYO CUFF

• Cryo cuff = a device that combines cold therapy + compression simultaneously
• A sleeve/cuff filled with iced water is wrapped around the joint (knee, ankle, shoulder)
• Water cooled by ice in an insulated container
• Gravity-driven flow maintains cold water in cuff
• Provides: sustained cold + circumferential compression

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100. ALOPECIA AREATA

• Alopecia areata = autoimmune hair loss condition - patchy hair loss, usually on scalp
• Immune cells attack hair follicles

1. UVR (PUVA): Photochemotherapy - psoralen + UVA; suppresses immune attack on follicles
2. LASER (LLLT - He-Ne, 632 nm): Stimulates hair follicle activity, increases blood flow to follicles
3. Excimer laser (308 nm): targeted UVB therapy for alopecia patches

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101. TUNING IN SWD

• Tuning = adjusting the patient circuit to resonance with the machine circuit in SWD
• At resonance: maximum energy transfer from machine → patient
• The patient circuit (electrode + patient) is tuned by adjusting variable capacitor until resonance indicator (neon lamp/meter) shows maximum
• Importance: ensures maximum power delivery and efficient treatment
• Under-tuned or over-tuned = less power transferred = less effective treatment

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102. COUPLING MEDIA (see #50)

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103. CONVECTION (Heat Transfer)

• Convection = transfer of heat by movement of fluid (liquid or gas)
• Heated fluid rises (less dense), cooler fluid sinks (denser) → creates circulation currents
• Natural convection: hot air rises naturally
• Forced convection: fan, pump forces fluid movement

• Whirlpool bath: water circulates → convective heat transfer to skin
• Fluidotherapy: warm air moves through corn husks → convective heating
• Hot air treatment

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104. PHYSICAL PROPERTIES OF PARAFFIN WAX

1. Melting point: 54-58°C (pure wax); 52-54°C (with mineral oil added)
2. Low thermal conductivity: Releases heat slowly → safe for skin contact
3. High specific heat: Stores large amount of heat
4. Does not evaporate: No moisture loss during treatment
5. Solid at room temperature: Easy to store and apply
6. Odorless and tasteless: Patient friendly
7. Does NOT conduct electricity: Electrically safe
8. Low cost: Inexpensive and widely available

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105. PHONOPHORESIS (2-mark version)

• Use of therapeutic ultrasound to enhance delivery of topical drugs through skin
• Ultrasound temporarily increases skin permeability
• Drug applied to skin → used as coupling medium → US applied over it
• Drug penetrates deeper than with passive application
• Common drugs: Hydrocortisone, Diclofenac, Lidocaine, Ketoprofen

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106. ELECTRODE SPACING IN CONDENSER FIELD (2-mark version)

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107. COLLIMATION

• Collimation = property of laser beam where all rays travel parallel to each other (beam does NOT diverge/spread)
• Unlike ordinary light which spreads in all directions
• Collimation gives laser its ability to:
  1. Travel long distances without losing intensity
  2. Be focused to a tiny spot
  3. Deliver precise, concentrated energy

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108. SCALDS

• Scalds = burns caused by hot liquids or steam (as opposed to dry heat burns)
• In physiotherapy context: scalds from hot packs, hot water, steam
• Example: improperly wrapped hydrocollator pack → water drips → scald

1. Test water temperature before immersion
2. Wrap hot packs adequately
3. Check skin after 5 minutes of hot pack application

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109. EXCITATORY COLD

• Excitatory cold = brief, rapid cold application that produces a facilitatory/stimulatory effect on the nervous system and muscles
• Short, quick cold stimulus → activates skin thermoreceptors → increases muscle tone and activity
• Used in neurological rehabilitation to stimulate weak/hypoactive muscles
• Contrast with prolonged cold → inhibitory → reduces spasticity

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110. MODALITIES FOR LIGAMENT INJURIES

• Ice (cryotherapy): reduces edema, pain
• PSWD (Dose I): non-thermal healing
• TENS: pain relief

• Ultrasound (pulsed): tissue healing
• LASER (LLLT): anti-inflammatory, healing
• Contrast bath: reduces swelling

• SWD/MWD: deep heat, increases extensibility
• Ultrasound (continuous): scar softening
• Wax bath (small joints)

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111. CONTRAPLANAR TECHNIQUE

• Contraplanar = SWD electrode technique where two electrodes are placed on OPPOSITE sides of the body part (front and back, or either side)
• The electromagnetic field passes completely through the body part
• Produces deepest heating of all electrode arrangements
• Used for: hip joint, lumbar spine, knee, shoulder (deep conditions)
• Also called cross-fire technique

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112. INDUCTOR

• Inductor = a coil of wire that stores energy in a magnetic field when current flows through it
• Symbol: L, Unit: Henry (H)
• Opposes changes in current (Lenz's Law)
• In SWD: the inductor is part of the LC oscillator circuit
• The cable electrode of SWD acts as an inductor → produces magnetic field → induces eddy currents in patient

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113. GRID METHOD (already covered in #39)

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114. DEFINE WAVELENGTH

• Wavelength (λ) = distance between two consecutive points in the same phase of a wave (e.g., crest to crest, trough to trough)
• Unit: meters (m), nanometers (nm), micrometers (μm)
• Relationship: λ = c/f (wavelength = speed ÷ frequency)

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115. CAUSES FOR BURNS FOLLOWING SWD

1. Metal objects on patient (jewelry, hairpins, coins) - heat selectively
2. Moist dressings/plaster - electrolyte concentration increases current density
3. Unequal electrode spacing - more heat under closer electrode
4. Sensation impairment - patient cannot report overheating
5. Excessive intensity for the area
6. Direct electrode contact with skin (no air gap)
7. Folded/overlapping towels - hot spots
8. Standing over a radiator or metal surface nearby

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116. COLD SENSITIVITY

• Cold sensitivity = abnormal, exaggerated reaction of tissues to cold, which can lead to tissue damage at temperatures that normally would not cause harm

1. Raynaud's disease/phenomenon - vasospasm in digits with cold exposure
2. Cold urticaria - allergic hives triggered by cold
3. Cryoglobulinemia - abnormal proteins in blood precipitate with cold
4. Cold hemoglobinuria - red blood cell destruction with cold

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117. E2 DOSE OF UVR

• E2 dose (Second Degree Erythema) = 2.5 times the MED
• Produces: definite redness + mild edema, appears within 6 hours
• Duration: 2-3 days
• Followed by slight pigmentation (tanning)
• Used therapeutically for: wound healing (stimulates healing response), alopecia areata, some skin conditions

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📊 MOST REPEATED 2-MARK QUESTIONS SUMMARY

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