This invention relates generally to a patch, controller and method for the photodynamic therapy (PDT) of a dermal lesion such as actinic keratosis, basal carcinoma and psoriasis. More particularly, this invention relates to a portable combination controller and patch and method for applying photodynamic therapy (PDT) to a dermal lesion using a light or photoactivated photopharmaceutical.
Bodies, sheet or layer forms, of hydrogel or hydrogel materials, particularly transparent hydrogel or hydrogel materials, are well known in the medical field and may comprise, for example, a polyvinyl alcohol with a water matrix. Some of these transparent hydrogel or hydrogel materials are castable and can be cast into intimate contact with other devices. They have been widely adapted to such applications as diagnostic electrodes (for EKG), wound care dressings, and transdermal delivery devices for systemic delivery of pharmaceutical agents. The biocompatability of this class of materials is well established for extended contact with dermal structures.
Much of the prior art in medical applications for hydrogel or hydrogel materials relates to devices and methods for electrical conductivity enhancement. Critical in using hydrogel in many medical applications, such as an electrical interface, is the ability of the hydrogel to form intimate physical contact with skin or dermal structures. U.S. Pat. No. 5,143,071 issued to Keusch et al. on Sep. 1, 1992, has an extensive list and description of prior art hydrogels suitable for this purpose, and this patent is incorporated herein by reference.
A concurrent body of prior art embraces hydrogels or hydrocolloids, as wound dressings and dressings impregnated with pharmaceutical compounds. Representative of this prior art is U.S. Pat. No. 5,156,601 to Lorenze et al. Further, the work of Gombotz et al., Proc. Intl. Symp. Cont. Rel. Bioact. Mtl., Vol. 19, 1992, describes the rapid release of complex compounds from hydrogels to skin or dermal structures.
U.S. Pat. No. 5,079,262 issued to Kennedy et al. discloses a method of detection and treatment of malignant and non-malignant lesions utilizing 5-amino-levulinic acid ("ALA"). ALA is administered to a patient in an amount sufficient to induce biosynthesis of proto-porphyrin IX in the lesions, and is followed by exposure of the treated lesions to a photoactivating light in the range of 350-640 nm. ALA is taught to be administered to a patient orally, topically or by injection. This patent is incorporated herein by reference.
None of the prior art references teach or suggest using hydrogel as an optical, chemical and fluidic coupling agent for light in the photodynamic therapy of dermal lesions. Since its first reported clinical use at the turn of the century, photodynamic therapy has been accomplished using light projected to the dermal treatment site from sources at some distance from the site. Modern photodynamic therapy (from 1978 onward) has developed light delivery protocols using artificial sources such as tungsten halogen or xenon arc lamps with wavelength filtration to activate photopharmaceuticals. All of the above light sources have been used in projective, field-illuminating devices that flood the target treatment field or site in the treatment of superficial cutaneous lesions with light containing a wavelength designed to activate the photopharmaceutical. These references generally teach that the dosimetry of applied photodynamic therapy can be controlled and varied by varying the intensity and/or duration of the photoactivating light applied to a photopharmaceutical performing photodynamic therapy.
In the case of the tungsten and xenon-arc sources, extensive filtration of the available light flux is essential to restrict the delivered energy to appropriate wavelengths that photoactivate the photopharmaceutical in the target dermal structures. Colored glass or interference filters used with these sources transmit some portion of unwanted wavelengths, notably in the infrared region, and can cause thermal effects that may mask the effect of photoactivity with an undesirable heating effect that also preferentially damages malignant tissue. High-power surgical lasers, even when de-focussed, also can induce undesirable thermal effects. The work of Svaasland, Photochem/Photobiol., 1985, measured this effect and its impact on PDT protocols.
Dosimetry of delivered photodynamically effective light to a dermal treatment site is extremely difficult using current projective optics. Mathematical modeling of skin optics has been a slow and difficult process. Recent publications by Van Gemert et al., IEEE Trans. Biomed. Eng., Vol. 36; 12, 1989, critically reviewed the prior work and presents a 4-layer model of light-dermal tissue interaction. This publication is incorporated herein by reference. Van Gemert et al. elaborates on the advantages and effectiveness of the diffusion model of light transport in tissue, which depends upon the efficient coupling of the externally applied light to the target tissue. A later publication by R. Rox Anderson, Optics of the Skin, Clinical Photomedicine, Dekker Publication, 1993, reviews the two basic processes which govern the optics or behavior of light in skin, namely, light absorption and light scattering. This publication is incorporated herein by reference.