Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Light application
Reexamination Certificate
1998-10-08
2002-08-20
Shay, David M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Light application
C607S088000, C600S317000, C128S898000
Reexamination Certificate
active
06436127
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to treatment of psoriasis and other proliferative skin disorders using phototherapeutic techniques.
BACKGROUND OF THE INVENTION
Psoriasis is a chronic, incurable, inflammatory skin condition affecting two to four percent of the world's population. Severity ranges from minor to life-threatening, and often fluctuates. Pathogenesis is unknown, but involves hereditary abnormalities of the immune system, with lymphocyte and neutrophil-mediated inflammation combined with hyperplasia of the epidermis. The epidermis proliferates at about ten times the normal rate. People with psoriasis literally leave a trail of skin flakes, and suffer from chronic itchy lesions, poor temperature regulation, fatigue from constant protein loss, and social stigma to the point of reclusion. There is an associated arthritis which attacks the fingers. The most common form is plaque-type psoriasis, in which well-demarcated lesions appear on the body, with normal skin between them. The plaques are red and scaly, quite different from the surrounding normal skin. The number of plaques ranges from several to several hundred, scattered over the trunk, arms, and legs. Psoriasis tends to spare the face, because ultraviolet (UV) light is therapeutic.
There is no cure for psoriasis. Drug treatments work by anti-inflammatory, antimitotic, hormonal, or immunosuppressive mechanisms. These include topical administration of corticosteroids, tar preparations, and vitamin D3 derivatives, systemic chemotherapy with methotrexate, and immunosuppression with cyclosporin A. Topical treatments are messy and expensive, but are still the main approach for patients with small areas of involvement. Corticosteroids tend to produce partial clearing followed by a “rebound” worse than the original disease severity, cause skin atrophy, and become progressively ineffective over time. Methotrexate is effective but causes liver toxicity. Cyclosporin A has multiple side effects, is expensive, and reserved for severe cases.
Ultraviolet phototherapy with or without photosensitizers, has been a mainstay of psoriasis treatment for many decades. UVB (290-320 nm) phototherapy is practical, effective, and often produces a long remission time after clearing, typically about five months. Psoralen, an extremely potent DNA-crosslinking photosensitizer, is also used orally or topically, followed by exposure to UVA radiation (320-400 nm). This is called Psoralen UVA (PUVA), a type of photochemotherapy. Phototherapy clears plaques in about 90% of patients, by combined mechanisms including apoptosis of keratinocytes, antimetabolic effects of DNA damage, and local and systemic immunosuppression. The patient stands in a “light box” lined with fluorescent lamps or other UV sources, and receives a prescribed fluence, i.e., a therapeutic dose of radiation. Each box is the size of a phone booth and costs about twenty to thirty thousand dollars. Since psoriasis does not usually affect the face, the patient typically wears a mask covering the face and eyes to prevent exposure to the therapeutic radiation. The rate of clearing is variable between patients, and depends on the exposure dose per treatment. An average of 20 to 30 treatments is needed for UVB (given 3 times per week) and an average of 15 to 25 treatments is needed for PUVA (given 2 times per week), depending on aggressiveness of the exposure dose protocol. Hence, it takes several months and many trips to the phototherapy center to clear psoriasis.
The “art” of phototherapy lies in achieving clearing without causing painful sunburn-like reactions. Thus, skin unaffected with psoriasis, i.e., normal skin, limits the therapeutic dose. The minimal erythema dose (MED) in normal skin is defined as the lowest fluence eliciting an inflammatory response, and is used to guide dosimetry. If the patient receives more than 1 MED, a “sunburn” will occur. At 3 MED a painful sunburn with blistering can occur, and at 10 MED a life-threatening burn results. Prior to a phototherapy treatment, the doctor determines the MED for a particular patient. As tanning develops during the course of multiple treatments, the UV fluence is increased, typically by 30 to 50 percent per treatment. At present, phototherapy consists of carefully but aggressively “pushing” the exposure dose based on response of the unaffected skin between plaques of psoriasis.
The cost of phototherapy, based on the number of trips and the clinicians' time, is estimated to be almost 1 billion dollars per year in the US. This does not include the cost of treating of skin cancers induced by phototherapy. In particular, prolonged exposure to UVB and PUVA cause basal cell carcinoma, squamous cell carcinoma, and melanoma. These diseases typically occur in areas of skin between plaques of psoriasis that have been exposed to large cumulative doses of UV radiation during phototherapy.
SUMMARY OF THE INVENTION
The invention features methods and systems for treating inflammatory, proliferative skin disorders, such as psoriasis, with ultraviolet phototherapy. The methods and systems use optical techniques to scan a patient's skin, designate areas of affected skin, and selectively deliver high doses of phototherapeutic ultraviolet radiation to the designated areas. The high dose levels are typically greater than two minimal erythema doses (MED) and often about ten MED. These dose levels are very effective at treating affected areas of skin, but would badly damage unaffected areas of skin, e.g., normal skin. To insure that only areas of skin affected by psoriasis or other disorders are designated for the high doses of UV radiation, the methods and systems use one or more optical diagnostics that relate to independent physiological features of affected skin.
The methods can be implemented by a system, e.g., a robotic system, that scans a patient's skin and constructs a digital map designating affected areas of skin based on one or more optical diagnostics. After a doctor or technician reviews, and possibly modifies, the digital map, the robotic system delivers the phototherapeutic radiation doses to the areas of skin designated by the map.
Alternatively, the automated designation of affected areas of skin and the selective delivery to the designated areas can be implemented with a manual device such as a fiber optic pen or comb. In such cases, a surgeon scans the patient's skin with the device to designate affected areas of skin. The treatment can be performed in real time based on the designation or, alternatively, the designation can be used to construct a digital map of the affected areas to guide subsequent treatment.
In general, the invention features a method for treating a proliferative skin disorder, e.g., psoriasis, in a patient by exposing the patient's skin to radiation; detecting at least one optical diagnostic signal in response to the radiation from a selected area of the patient's skin; determining from the optical diagnostic signal whether the selected area is affected by the skin disorder; and if the selected area is determined to be affected by the skin disorder, delivering an effective dose of phototherapeutic radiation to the selected area, e.g., using a laser, such as a xenon chloride excimer laser. The method can be automated. The selected area can be less than about 1 cm
2
.
In specific embodiments, the phototherapeutic radiation is ultraviolet radiation having a wavelength of about 290 nm to 330 nm, and the effective dose is in the range of about 0.02 J/cm
2
to 1 J/cm
2
. The effective dose can be greater than about two, three, five, or even ten minimal erythema doses (MED). The optical diagnostic signal can relate, or correspond, to diffuse reflectance or fluorescence, for example.
In another embodiment, the exposing step can include delivering a diagnostic dose of radiation from a source, wherein the diagnostic dose is sufficient to excite the fluorescence from the selected area, but is not an effective dose of phototherapeutic radiation, and wherein the delivering s
Anderson Richard Rox
Dwyer Peter J.
Shay David M.
The General Hospital Corporation
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