Ultraviolet Radiation Therapy and its physiological effects.

Introduction

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The Ultraviolet Radiation Therapy is a therapeutic application of radiant energy from the ultraviolet region of the electromagnetic spectrum which is being used for the treatment of a various skin disorders. The Ultraviolet region of the spectrum corresponds to electromagnetic radiation which has wavelength 100-400nm.

Ultraviolet Radiation is used for the treating various dermatological conditions such as pressure sores, folliculitis, wound healing, acne and psoriasis. It is mainly used in physiotherapy practice due to advancement in the pharmacological agents.

Ultraviolet radiation therapy is broadly divided into 3 types-

UV-A- It has wavelength 315nm-400nm.

UV-B- It has wavelength 280nm-315nm.

UV-C- It has wavelength less than 280nm.

This division allows the distinction between the effects of solar and artificial Ultraviolet exposer on living species.

Ultraviolet-A penetrates human skin more efficiently than UV-B . Ultraviolet Radiation has both beneficial and harmful effects depending upon the type of organism.

Types of Mercury Vapor Lamp

There are three various types of Mercury Lamps which produce ultraviolet rays used by the physiotherapist to manage various skin disorders.

• High Pressure Mercury Vapor Lamp– These lamp is in the shape of capital alphabet “U” glass which contains argon gas at a low pressure and a very low amount of mercury. Both the ends of glass is sealed and connected with electrodes which has positive and negative. The high voltage current of 400V is given to the tube to ionize argon gas. The flow of current through argon gas in the tube produces heat which leads to vaporization of mercury atom.
• The atoms of the mercury become excited by collision with the electrons flowing between the lamp and electrodes. The excited state of electrons returns back to the normal state in the mercury atom which release some of the energy they have absorbed in the form of radiation.
• Kromayer Lamp- It is a type of high pressure mercury vapor ultraviolet lamp. It is all surrounded by the water jacket. The cool water which is present in it circulated over the lamp absorbs infrared rays, this helps kromayer lamp tissue friendly so the lamp can be placed over the tissues because there will be no damage and no tissue burn occurs.
• Fluorescent Lamp- It is a type of low pressure mercury lamp which has coating of phosphor inside the glass tube. Each one of the tube is about 120cm long and these glass allows long ultraviolet rays to pass through it. The coating of the phosphor of the glass known as envelope. The phosphor at low pressure in mercury vapor absorbs short ultraviolet rays spectral line at a wavelength of 253.7nm. This results in emission of the long wave length UVR by the phenomenon of fluorescence. The spectrum of each tube depends upon the type of phosphor coated.
• Theraktin Tunnel- It is a semi-cylindrical frame in which four fluorescent tubes are mounted on their own parabolic reflector . The length of each fluorescent tube is usually 120cm but it can be adjustable decrease or increase for even irradiation. The Theraktin Tunnel produces ultraviolet rays with spectrum of 280-400nm, a narrow band output fluorescent tube is also used to produce specific range of wavelength and one of the tube produces wavelength around 311nm.
• Psoralen Ultraviolet A– The patients who are suffering from Psoriasis are treated with the wavelength of 315nm-400nm (UVRA). The special type of fluorescent lamp are mounted on a wall of vertical battery on all the four sides of box. The patient is surrounded by all the four side of box and the box contain 48 tubes. After the patient has taken the photoactive drugs which is Psoralen, the treatment last about 2 hours. This treatment is also known as PUVA- Psoralen Ultraviolet A.

Physiological Effects

The effects of Ultraviolet radiation in tissue include absorption of the photons by chromophores in the skin. which involves the photochemical reaction which induce molecular changes in cell and tissue biological which depend on wavelength, radiation exposure and the ultraviolet source.

• Pigmentation– It is the production of melanin in the deeper layer of the epidermis, the production and then migration of melanin to the superficial layer of the skin leads to darkening of the skin and thickening of the corneum. Pigmentation may either be constitutive or facultative.
• Epidermal Hyperplasia– Thickening of both the epidermis and stratum corneum due to division of the epidermal cells. The hyperplasia begins to occur around 72 hours of the exposure of UVR, it also limits the damage of skin to further ultraviolet rays.
• Erythema- Ultraviolet radiation increases the blood circulation in the superficial layer of skin , low doses of UV rays both 280nm and 315nm wavelength there is increase in blood flow , high doses results to decrease in the flow of blood. There is enlargement and engorgement of minute blood vessels in the corneum results in erythema. These process helps in the formation of granulation tissues that leads to tissue repair.
• Vitamin-D Production– Low dose UVB 280nm-315nm exposure induces the production of vitamin D in the skin. Ultraviolet B converts sterols present in the skin as 7 dehydrocholesterol into vitamin D.

Calculation of doses

Exposure time needed to produce a faint erythema of the skin is 24hours after exposure. Area of skin to be tested should have pigmentation similar to area to be treated. Patient returns in 24 hours and a visual inspection determines (MED) Minimal Erythemal Dose.

• Sub-erythemal Dose:- Area tested reveals no erythema in 24 hours after exposure to UVR.
• Minimal Erythemal Dose:- Area showing erythema lasting 24 hours.
• First Degree Erythemal Dose:- (E1=2.5*MED) this last upto 48 hours.
• Second Degree Erythemal Dose:- (E2=5*MED) Evidence of intense erythema with edema, pigmentation and peeling that will last up to 72 hours.
• Third Degree Erythemal Dose:- (E3=10*MED) It will leads to erythema with severe blistering and exudation limited to an area no larger than 24 sq cm.

Indication of Ultraviolet Radiation

• Psoriasis
• Wound Healing
• Infected Wound
• Vitiligo
• Acne
• Septic Wounds
• Aseptic Wounds
• Pressure Sores
• Osteomalacia
• Sinusitis
• Rickets
• Alopecia
• Scleroderma

Contraindication of Ultraviolet Radiation

• Acute Psoriasis
• Acute Eczema
• Skin grafting
• Hyperthyroidism
• Sarcoidosis
• Pellagra
• Herpes Simplex
• Renal and hepatic insufficiencies

Adverse Effects of Ultraviolet Radiation

• Formation of Cataract
• Decrease function of sebaceous and sweat glands
• Wrinkled and dry skin
• Loss of elastic properties of the connective tissues
• Skin Cancer
• Burn
• Shock
• Damage to eyes
• Premature skin aging

To learn more about Ultraviolet Radiation Therapy watch the video given below-

To learn more about Ultrasound Therapy click the link given here- https://physiocontent.com/ultrasound-therapy-ust-principles/

To learn more about Laser therapy click the link given here- https://physiocontent.com/laser-therapy-lllt-physiological-effects/