Ultraviolet therapy (UV Therapy)

What is Ultraviolet therapy (UV Therapy)?

• Ultraviolet radiation (UVR) has been an effective treatment for a number of chronic skin disorders, and its ability to alleviate these conditions has been well-documented.
• Although non-ionizing, exposure to ultraviolet (UV) radiation is still damaging to deoxyribonucleic acid integrity and has a number of unpleasant side effects ranging from erythema (sunburn) to carcinogenesis.
• As the conditions treated with this therapy tend to be chronic, exposures are repeated and can be high, increasing the lifetime probability of an adverse event or mutagenic effect.
• Despite the potentially detrimental effects, quantitative ultraviolet dosimetry for phototherapy is an underdeveloped area and better dosimetry would allow clinicians to maximize biological effects whilst minimizing the repercussions of overexposure.
• This review gives a history and insight into the current state of UVR phototherapy, including an overview of the biological effects of UVR, a discussion of UVR production, illness treated by this modality, cabin design, and the clinical implementation of phototherapy, as well as clinical dose estimation techniques.
• Several dose models for ultraviolet phototherapy are also examined, and the need for an accurate computational dose estimation method in ultraviolet phototherapy is discussed.

Types of Ultraviolet therapy (UVR):

Ultraviolet A (UVA):

• Long UV.
• Penetrates to the dermis.
• Responsible for the development of the slow natural tan.

Ultraviolet B (UVB):

• Medium UV, erythemal UV.
• Produced new pigment formation.
• Sunburn.
• Vitamin D synthesis.
• Responsible for inducing skin cancer.

Ultraviolet C (UVC):

• Short UV , germicidal UV .
• Does not reach the surface of the earth.

Production of Ultraviolet therapy:

• The therapeutic UVR is produced by a mercury vapour lamp which consists of a QUARTZ BURNER TUBE evacuated from the air and containing traces of argon gas and mercury under reduced pressure.
• An electrode is inserted at each end of the burner.
• The current is applied to the electrodes.
• The mercury vapour and the passage of electrons through the vapour establish the UVR.

Ultraviolet generators:

Air-cooled lamps:

• It is also called a high-pressure mercury-vapour burner and Hanovia alpine sun lamp
• This is often U-shaped so that it acts more or less as a point source.
• The burner is made from quartz
• This material allows the passage of ultraviolet can withstand very high temperatures and has a fairly low coefficient of expansion.
• In the tubes enclosed to argon gas at a low pressure, a small quantity of mercury, an electrode is sealed into either end.
• Surrounding the ends are two metal caps across which a high potential difference is applied in order to ionize the argon.
• Argon is normally stable and inert so in order to pass a current through the tube the argon atoms must be ionized.
• A considerable amount of energy is required to ionize the argon and obtained by applying a very high potential difference [400 volts]
• Across the tube, via the metal caps at either end, for a fraction of a second.

How to work a high-pressure mercury-vapour burner?

• Once the argon has been ionized, the normal main voltage between the electrodes causes the positive and negative particles to move through the burner, constituting an electric current.
• The electron moves to the positive terminal and then around the circuit, the positive ions move to the negative terminal and collect an electron.
• Overall, exactly the same number of electrons leave the burner at the positive terminal as enter at the negative.
• As the two-way movement of charged particles takes place, collisions between moving flow across the tube.
• This current flow can be seen as a glow discharge, and as with any electrical current considerable heat is produced.
• Eventually, sufficient heat is produced to vaporize the liquid mercury inside the tube, and this mercury vapour itself becomes ionized.
• Ultraviolet radiation is produced partly as the energy released by the recombination of electron and positive mercury ions and partly by photons released when excited electrons return from a higher-energy quantum shell to their normal shell within the mercury atoms.

Tridymite formation :

• The heat produced inside the burner unfortunately causes some of the quartz to change to another form of silica called tridymite.
• Tridymite is opaque to ultraviolet rays and therefore the total output of the lamp gradually falls as the proportion of tridymite increases.
• If the quartz changes to tridymite the resistance is reduced, increasing the intensity of current across the tube.
• Thus the production of ultraviolet is increased but as less is transmitted by the quartz, output is constant
• To allow the stabilizing resistance to be reduced at appropriate times [ approximately every 100 hours ]
• So always note the burning time in a note.
• After 1000 hours of burning, so much tridymite has formed that the whole burner tube needs to be replaced.

Cooling:

• A considerable portion of the output of the high-pressure burner is infrared, which when absorbed by the human body is converted to heat.
• Always safely place a lamp on a patient is 50 cm, otherwise, results in a burn.
• The burner is usually housed in a parabolic reflector, so the position is adjusted by the stand.

Ozone formation:

• The photochemical action of ultraviolet radiation shorter than 250 nm in wavelength on atmospheric oxygen is to form ozone.
• Ozone is a toxic gas but good for ventilation.
• Ozone level is detected by smell.

Water-cooled lamps:

• It is also called kromayer lamp.
• Its construction & work are the same as the air-cooled lamp (high-pressure mercury vapor burner ).
• It is completely enclosed in a jacket of circulating distilled water.
• Purpose of jacket = absorb to infra-red.
• A pump & cooling fan is incorporated into the body of the kromayer lamp in order to cool the water.
• After water circulation should be continued for five minutes after the burner is switched off in order to cool the lamp.
• Water circulation of kromayer head is between two quartz windows which allow the ultraviolet to emerge.
• For the treatment of the sinus = an applicator of quartz is fixed to this window via a special attachment.
• These applicators convey the ultraviolet rays to their tip by total internal reflection, but they absorb ultraviolet rays so a longer dose must be given.
• Advantage = It can be used in contact with the tissue or with a suitable applicator [ body cavity or sinus ]
• Disadvantage = danger of infra-red burn

Fluorescent tubes:

• Solution of mercury lump problems [ produce a certain proportion of short ultraviolet rays ] use to fluorescent tubes.
• Because modern treatment needs long-wave ultraviolet rays without short waves.
• So various types of fluorescent tubes have been produced.
• The spectrum of each tube depends upon the type of phosphor coating.
• Each tube is about 120 cm long and made of a type of glass that allows long-wave ultraviolet to pass.
• The inside of the tube is coated with a special phosphor.
• A low-pressure arc is set up inside the tube between its ends by a process of ionization is same as the air-cooled lamp (high-pressure mercury vapor burner.
• Short ultraviolet rays are produced but adsorb by phosphor & re-emitted at a longer wavelength.
• Output of these fluorescent tubes = UVA & UVB

Theraktin tunnel:

• It is a semi-cylindrical frame in which are mounted four fluorescent tubes.
• Each tube mounted has its own reflector so produces irradiation for treatment.
• Allowing the treatment of the whole body in two halves.
• In Theraktin tunnel fluorescent tubes with a spectrum of 280 – 400 nm are used.

Penetration of the ultraviolet radiation:

• UVA – Dermis level
• UVB – Deep dermis

Test dose of the Ultraviolet therapy:

• To assess the individual patient’s reaction to ultraviolet radiation a test dose is administered.

Air-cooled lamp:

• A suitable area of skin is selected for the test dose and washed to remove grease.
• Three shaped holes cut in a material resistant to the passage of UV [ paper or lint ].
• The middle hole should be approximately 2 cm by 2 cm with the hole on one side larger and the other side smaller.
• This cutting is fixed to the forearm with adhesive plaster.
• The cuttings are of different sizes & shapes in – order to make identification of the erythema easier for the patient.
• Allow the lamp to warm up according to the manufacturer’s instructions.
• Place the PERPENDICULAR to the area being tested and a distance of 60 to 90 cm from the site.
• Expose the 1″ opening would receive the longest exposure time & the last opening would appear pink/red first & then fade/disappear.
• Switch off the lamp.
• Instruct the patient to MONITOR in the forearm every 2 hrs & note which opening or shape appeared pink/red first & when it faded/disappeared.
• The patient is also given a card similar to the opening to make a note.

Theraktin tunnel :

• The test dose is the same as the air-cooled lamp but with larger holes [ 4 cm by 4 cm ].
• Placed on the abdomen, the rest of the body is screened.

Kromayer lamp:

• The test dose is the same as the air-cooled lamp but with smaller holes [ 0.25 by 0.25 ].

Patient preparation for treatment with Ultraviolet therapy:

• Wear goggles.
• Observe &monitor the skin condition.
• Keep skin moist following exposure to UVR.
• Pigmentation changes are to be expected & are a normal response.
• Prolonged & repeated exposure leads to premature aging.

Degree of erythma for Ultraviolet therapy

Skin response to Ultraviolet therapy:

• It depends upon:

1 – Quantity of UVR energy applied to the skin :

Output of the lamp.

• low volt [ 30 – 110 V] high – amp [ 5 A ]
• High volt [ 3000 V ] low – amp [ 15 mA ]
• Distance between the lamp and the skin.
• The angle at which radiation falls on the skin.
• Time for which radiation is applied on the skin.

2 – Biological responsiveness of skin:

• The sensitivity of skin :

Calculation of dosage:

• First of all, give to E1 dose
• E2 = 2.5 X E1
• E3 = 5 X E1
• E4 = 10 X E1
• Double E4 = 20 X E1
• E4 & Double E4 are used for open wounds.

Progression of dosage for ultraviolet radiation :

• Exposure to UVR should not be repeated until the erythema caused by a previous dose has faded.
• Thinking of the epidermis makes it necessary to increase the exposure in order to repeat the erythemal reaction at each successive dose.

Progression of doses for ultraviolet radiation:

• To repeat E1 25 %of the preceding dose is added.
• To repeat E2 50 %of the preceding dose is added.
• To repeat E3 75 %of the preceding dose is added.
• To repeat E4 75 %of the preceding dose is added.

Selection of dosage level for ultraviolet radiation:

• E1 = Given to the body area
• E2 = May not be given to up to 20 % of total body area
• E3 = May not be given to up to 250 cm 2 of normal skin
• E4 = May not be given to an area up to 25 cm 2 of normal skin

Frequency of ultraviolet radiation treatment:

• A sub erythemal dose may be given daily.
• An E1 may be given alternate days.
• An E2 should be given twice a week.
• An E3 should be given 2 weeks apart.
• An E4 only very local areas not frequently given.

• When treating non-skin areas such as pressure areas of ulcers, all doses may be given daily as there is no erythema ration produced.

Calculation of new dose :

• To irradiate a smaller area the source is moved nearer to the patient but the time of exposure must be altered to maintain the same intensity in accordance with low of inverse squares.

• New time = Old time x ( New distance )2/( Old distance ) 2

Physiological effects of ultra-violet radiation:

• The UVR physiological effects may be divided into 2 groups :

1. Local = effects produced locally in the area
2. General = results form a widespread irradiation

Local effect of ultraviolet radiation:

Erythema:

• Damage to cells causes the release of histamine-like substances from the epidermis and superficial dermis.
• A gradual diffusion of this chemical takes place until sufficient has accumulated around the blood vessels in the skin to make them dilate.
• The greater the quantity of histamine-like chemicals produced, the sooner & fiercer the reaction.
• for erythema reaction has been used to classify doses of ultraviolet given to patients.
• erythema is produced by a wavelength shorter than 315 nm.

Pigmentation:

• It is developed within two days of irradiation.
• Ultraviolet stimulates meloncytes in the skin to produce melanin, which is then passed to numerous adjacent cells.
• The melanin forms an umbrella over the uncles of the cells to protect them from ultraviolet radiation.
• Pigmentation substantially reduces the penetration of UVB.

Ticking of epidermis:

• Sudden over-activity of the basal layer of the epidermis causes a marked ticking ,.
• Particularly of the stratum corn um which may become three times the normal thickness.
• This substantially reduces UV penetration.
• So in order for subsequent treatments to have the same effect the dose must be increased.

Pilling :

• The increased thickness of the epidermis is eventually lost as desqauamation ( pilling )
• when this happens the resistance of the skin to UV is substantially lowered.

Antibiotic effect:

• Short ultra-violet rays can destroy bacteria and other small organisms such as fungi commonly found in wounds.
• E4 dose effectively destroys all such organisms.

General effects of Ultraviolet therapy:

Production of vitamin D:

• In the presence of UV, dihydrocholesterol in the sebum is converted to vitamin D in the skin.
• Vitamin D is necessary for the absorption of calcium and so has a role to play in the normal formation of bones and teeth.
• In hospitals, elderly patients are given ultraviolet light as a treatment to promote the production of vitamin D, reduce osteoporosis, and decrease the frequency of fractures.
• But this treatment is applied very carefully [ monitoring dosage and preventing form risk ]

Solar elastosis and aging:

• The normal aging process of the skin is accelerated if there is continued exposure to UV.
• There is thinning of the epidermis
• Loss of epidermis ridges
• Loss of melanocytes
• Dryness as a result of poor function of sebaceous and sweat glands
• Winking from lack of dermal connective tissue.

The esophylactic effect:

• General UVA irradiation stimulates reticulo endothelial system leads to the ingestion of bacteria & produces antibodies against bacteria & toxins.
• So the resistance of the body to infection is increased & this is known as the esophylactic effect.

General tonic effect:

• It is being claimed that because of general UV irradiation has a general tonic effect.
• Appetite & sleep being improved.
• Nervousness & irritability decreased.

Photosensitization:

• There is sometimes an enhanced response of the skin to ultraviolet radiation.
• The agent responsible is usually a chemical present in the skin that absorbs the ultraviolet and transfers the energy to adjacent tissue molecules in a photo-chemical reaction.
• Photosensitizers may be ingested or applied directly to the skin.
• Photosensitivity may be deliberately produced in a patient’s skin.
• By local application of a substance such as coal tar.
• By the ingestion of a substance such as a psoralen.

Indications of Ultraviolet therapy :

Acne:

• It is a skin condition that presents pustules, papules, and comedone blocking the hair follicles and sebaceous glands on the face, back, and chest.
• An E2 dose of ultraviolet radiation may be given to the patient.

Aim of this treatment:

• An erythema will bring more blood to the skin and so improve the condition of the skin.
• Desquamation will remove comedone and allow free drainage of sebum, thus reducing the number of lesions.
• The UVR will have a sterilizing effect on the skin.
• Although ultra-violet radiation has been used in the treatment of acne for some time, a number of reservations have Been expressed about its use.

• The intensity of the dose needed (E2 +) Is often painful and cosmetically unsightly to the skin.

Psoriasis

• It is skin conditions that present localized plaques in which the rate of cell turnover from the basal layer through to the superficial layer is too rapid.

Aim of this treatment

• Decrease the rate of DNA synthesis in cells of the skin
• Thus slowing down their proliferation.

• Treatment can be given using the Leeds regimen or PUVA.

Leeds regimen :

• In the Leeds regimen the sensitivity of the patient’s skin to UVR is increased by the local application of coal – tar, added to a bath prior to treatment.
• Dithranol cream is applied to the lesions after the treatment.
• The patient’s reaction to UVR is tested in the sensitized condition.
• A sub-erythemal dose (half-E1) is given to the patient, using a Theraktin tunnel or an air-cooled lamp at 100 cm.
• The dose is repeated daily, increased by 12 1/2 percent each time.
• Psoriasis improves with sub-erythemal doses but is aggravated by actual sunburn or doses of E1 +.

PUVA:

• Patients on a PUVA regimen take a sensitizing drug derived from psoralen, two hours before exposure to UVR rays.
• In the nucleus of the cell the psoralen bind to DNA in the presence of UVA, and this inhibits DNA synthesis and cell division.
• Dosage on a PUVA regimen is measured using J / cm which means that the output of the generator needs to be measured regularly using special apparatus.
• The dosage depends upon the patient’s skin – type and progressive increases are made in terms of energy density applied rather than in the length of time.

Skin wounds:

Infected wound :

• It is used such as ulcers, pressure sores, or surgical incisions.
• UVB is normally used to achieve this being applied locally to the lesion using a Kromayer lamp and an E3 or E4 dose.
• A progressive increase in dose is unnecessary as there is no skin over the wound.

Aim of this treatment:

• Destroy bacteria
• Remove the slough
• Promote repair

Non-infected wound:

Once infection has cleared it was never present.

Aim of this treatment:

• It stimulates growth or if it was never present.
• Short UVB rays = speed up repair
• Longer UVA rays = damage granulation tissue

Intact skin:

• It is treated with UV if it is in a pressure area that is likely to break down.
• An E1 dose is given in order to increase the circulation through the area and improve skin condition.

Counter-irritation:

• It was used to produce a strong counter-irritation effect over the site of a deep-seated pain.
• An E3 or E4 dose was given and the area was then covered with a dry dressing.

Eczema :

• It is an inflammatory response in the skin associated with edema.
• The patient suffers marked itching with redness, scaling, vesicles & exudation of serum on the skin.
• A mild UVR treatment will help.

Protection for hypersensitive skin :

• The Polymorphic light eruption is the commonest of photodermatoses.
• Increased tolerance to sunlight can be achieved by a course of UVB.
• Start with a very low dose & gradually progress.

Vitamin D deficiency:

• Vitamin D3 is formed in the skin by the action of UVB and C on 7-dihydro cholesterol.
• Natural sunlight can also be curative for vitamin D deficiency diseases.

Mild hypertension :

• The general suberythemal doses of UVB can significantly lower blood pressure.
• It is believed to the due to calcium-regulating hormones associated with increased vitamin D production.

Pruritus:

• The intractable & serious itching that can occur due to raised bile acid levels in biliary cirrhosis or uremia.
• can successfully be treated by sub-erythemal whole-body UVB either alone or in combination with the drug cholestyramine.

Contraindications of Ultraviolet radiation:

• Pulmonary tuberculosis
• Severe cardiac disturbances
• Systemic lupus erythematosis
• Severe diabetes
• Dermatological conditions
• Known photosensitivity
• Photosensitizing medication
• Deep x – rays therapy
• Acute febrile illness
• Recent febrile illness
• Porphyrias
• Pellagra
• Sarcoidosis
• Xeroderma
• Pigmentosum
• Acute psoriasis
• Renal hyperthyroidism
• Generalized dermatitis
• Advanced arteriosclerosis
• Acute eczema
• Herpes simplex
• Hypersensitivity of sunlight

Danger of Ultraviolet therapy:

• Shock
• Eyes = conjunctivitis, iritis, cataract
• Overdose = mainly E4 reaction

Sensitization/sensitizing drug

• A number of drugs &some foods in a few patients are known to sensitize patients to the effect of UVR.

Commonly seen sensitizing groups are :

• Psoralens = sensitizer
• Sulphonna mide = antibiotic
• Phenothiazine = tranquilizer
• Barbiturates
• Gold therapy
• Aspirin & derivatives

Other Electrotherapy Article:

• Infra-Red Therapy
• Long-Wave Diathermy.
• Microwave Diathermy (MWD)

Author: Vaishali Ladva