Targeted UVB

Phototherapy is the use of light or ultraviolet radiation to treat a variety of skin conditions. Over the years, this industry has made several significant advancements, the most recent of which is focused phototherapy.
Laser and nonlaser methods are included in the term “targeted phototherapy.”

 

What is Targeted UVB

Targeted phototherapy, also known as concentrated phototherapy, focused phototherapy, and microphototherapy, uses special delivery mechanisms to provide UV light directly targeted at the skin lesion.

Advantages of targeted phototherapy over conventional phototherapy

  • Only the affected areas are exposed, while the unaffected portions are spared, resulting in less acute side effects such as erythema (sunburn) and a lower long-term risk of skin cancer in the unaffected skin.
  • High-doses of energy are delivered quickly, and treatment sessions are brief.
  • Patient annoyance is reduced through fewer and more frequent clinic visits.
  • Treatment of tough locations such the scalp, nose, genitals, oral mucosa, and ears is possible.
  • Phototherapy equipment that target specific areas take up less room. The bulky devices used in traditional phototherapy take a lot of space.
  • Easy to administer to children. Large devices used in traditional phototherapy are often intimidating to children.

 

Disadvantages of targeted phototherapy

  • Targeted phototherapy equipment can be more expensive than standard phototherapy equipment.
  • If the lesions cover more than 10% of the body, targeted phototherapy is not suggested.
  • Because of the cost and time necessary in treatment, they are insufficient to treat large sections of skin.

Mechanism of Action

The majority of targeted phototherapy systems (laser or nonlaser) generate UVB light, with peak emission in the narrowband wavelength region (around 308-311 nm)

The following mechanisms have been proposed to explain UV‘s efficacy in the treatment of skin diseases:

  • As with vitiligo, stimulation of melanocyte-stimulating hormone leads to enhanced melanocyte proliferation and melanogenesis.
  • Histamine secretion from both basophils and mast cells is reduced in histaminic conditions such as urticaria pigmentosa.
  • UVB radiation has a variety of different impacts on the skin, including changes in cytokine production and local immunosuppression, both of which aid in the treatment of skin diseases.

     

Devices for targeted phototherapy

Targeted phototherapy depends on devices that can emit non-ionising radiation that can penetrate the affected area of skin. This can be achieved using different laser and non-laser sources.

Excimer laser

Excimer lasers emit light in the ultraviolet spectrum. The 193-nm argon-fluoride laser, 248-nm krypton-fluoride laser, 351-nm xenon-fluoride laser, and the 308-nm xenon-chloride laser are all examples. The lasing material in these lasers is a blend of noble gas and halogen.

Companies like Photomedex (XTRAC®; USA) and Alcon (Wave Light®; USA) have launched FDA-approved excimer laser devices.

These machines have a number of drawbacks, including a high cost, a large weight and mass, and maintenance challenges. They are exclusively offered in a few specialist clinics in the United States.

Monochromatic excimer therapy

Excilite® (DEKA, Florence, Italy; 304nm), Pxlite (308nm), and Exciplex (Excimer Therapies; 308 nm) are examples of monochromatic excimer non-laser focused phototherapy sources. In comparison to excimer lasers, these units are less bulky, less expensive, and have a greater treatment surface.

Non-laser targeted phototherapy

Traditional sources of broadband or narrowband UV radiation can now be delivered with precision thanks to technological advancements.

The majority of these machines use a UV-emitting high-pressure burner. Energy is sent directly to the lesion via fibre-optic cable connections.

Some of these machines have an advantage over excimer systems in that they can produce UVA (330-380 nm) and UVB (narrowband; 290-330nm) spectra.

Multiple delivery programs and automatic calibration are available on these devices, allowing for fast administration of predetermined dosages and a shorter treatment period.

They are much smaller than laser equipment, have less maintenance issues, and are also less expensive.

In recent years, several machines have been commercialized outside of the United States, including Dualight® (Theralight Inc USA; emits both UVA and UVB radiation in the range 330-380 nm) and Bioskin® (emits both UVA and UVB radiation in the range 290-330 nm) (narrowband UVB 280-300nm, available only in Italy). Levia® and Lumera® are two other targeted phototherapy devices available in the United States and sold by Daavlin (Ohio, USA).

Safety of targeted phototherapy

Exposure to ultraviolet light causes skin aging and cancer. When only a little amount of skin is exposed to it, as with targeted phototherapy, the hazards are reduced.

  • Acute phototoxicity (sunburn) from UVB can induce redness and blistering in the first 4–6 hours after exposure, peaking at 12–24 hours.
  • Because male genitalia are particularly susceptible to the development of skin malignancies, they should be protected throughout every treatment session.

 

Contraindications for targeted phototherapy

The following are absolute contraindications to any form of phototherapy:

  • Xeroderma pigmentosum
  • Systemic lupus erythematosus
  • Basal cell naevus / Gorlin syndrome
  • Photosensitivity disorders
  • History of malignant melanoma

The following are among some of the relative contraindications of phototherapy:

  • Young age
  • Risk factors for melanoma, e.g. many moles
  • History of nonmelanoma skin cancer
  • Photosensitizing medications
  • Significant past UV exposure (sun damage)
  • History of arsenic exposure, ionizing radiation, cyclosporine, or other immune suppressing medications

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