International classification: A61N 5/06 Solution to the technical problem for which patent protection is requested Solution to the technical problem for which patent protection is requested is a portable illuminator for external photodynamic therapy for medicinal and cosmetic purposes, which employs a"cluster"of light-emitting diodes as a light source. Although primarily intended for photodynamic therapy, the invention can also be used for bio- stimulation by light.

Technical background As already known, external photodynamic therapy is a method of medical treatment for pathological skin changes which utilizes photo-sensitizers and lights. Photo-sensitizers are mostly derivatives of porphyrine, while light sources used for photodynamic therapy are bulbs, lasers, arc lamps, fluorescent tubes and light-emitting diodes.

Today, the most frequently used photo-sensitizer is the 5-aminolevulinic acid (abbr.

5-ALA); the abbreviation ALA-PDT is already accepted worldwide for photodynamic therapy which uses 5-aminolevulinic acid as photo-sensitizers. The reason for such a wide range of the use of 5-ALA in photodynamic therapy is the simplicity of its application.

Suspicious pathological change on skin is covered by solution or cream containing 5-ALA, overlaid by a non-transparent covering which is left for 4-24 hours to take effect. During that time proto-porphyrine IX (PpIX) forms in the area of the skin beneath which 5-ALA has penetrated, much more prominently in the areas affected by pathological changes- tumours-than in healthy skin because tumour cells rid themselves of PpIX at a much slower rate than do healthy cells. PpIX is a photo-sensitizer which is beneficial both for diagnostics and therapy of pathological changes on skin. The maximum degree of absorption occurs at a wave length of about 407 nm, followed by gradually decreasing maximums at wave lengths of about 504 nm, 575 nm, and the lowest degree at about 637 nm.

Diagnostics utilizes the highest maximum at about 407 nm. By illuminating the PpIX with light the wave length of which is about 407 nm, fluorescence of PpIX occurs in the red section of the spectrum, with a maximum level being reached at about 635 nm. Since the accumulation of PpIX in skin affected by pathological changes is considerably higher than is the case in healthy skin, the intensity of fluorescent light of pathological changes of skin is going to be several times stronger than the intensity of fluorescence of healthy skin.

In other words, diagnostics are reduced to the observation of the red fluorescent light- skin areas with a pronounced fluorescence have suffered pathological changes.

In the course of illumination with PpIX light of a wave length of about 407 nm, PpIX fluoresces, single-bond oxygen is released from the PpIX molecule and in the process the PpIX molecule is destroyed, but the released single-bond oxygen forms a strong bond with the surrounding molecular cells and oxidises them, which ultimately leads to their death.

Since the concentration of PpIX in tumorous cells is several times higher than in healthy cells, selectivity is achieved regarding the destruction of tumorous cells, which is much higher than the destruction of healthy cells. This is the principle of photodynamic therapy by way of the PpIX photo-sensitizer in treating pathological changes on skin. Single-bond oxygen is also released when all other absorption maximums of PpIX are illuminated.

Bearing in mind that the absorption maximums weaken as their wave length increases, and in order to achieve the same therapeutic effect, it is necessary to utilize the highest intensity of light for illumination of the lowest absorption maximum with a wave length of about 635 nm, and the lowest light intensity for the highest absorption maximum with a wave length of about 407 nm. However, the shorter the light wave length, the shallower its penetration into the skin : light with a wave length of 407 nm penetrates the skin to a depth of about 2mm, while the penetration of light with a wave length of 635 nm is over 1 cm.

This means that the larger and deeper the tumours are in the skin, the greater the wave length of the light utilized has to be. The existing devices target two maximums: a short wave absorption maximum of about 407 nm for shallow tumours such as keratosis, or a long wave absorption maximum of about 635 nm for deeper tumours.

Apart from the above described PpIX photo-sensitizer which forms in the tissue from 5- ALA, photodynamic therapy is also performed with other photo-sensitizers such as haematoporphyrin, the short wave and long wave absorption maximums of which are very close to the analogous PpIX maximums (long wave absorption maximum of

haematoporphyrin is at 630 nm). The difference in relation to 5-ALA is that other photo- sensitizers must be introduced directly into the tissue.

The existing portable illuminators for external photodynamic therapy based on halogen bulbs (for instance, Patent W09852205), are cumbersome due to the low efficaciousness of a bulb during transformation of electric energy into light of the wave lengths optimal for photodynamic therapy. Bearing in mind that bulbs transform the majority of electric energy into infrared-thermal radiation, it is necessary to have cooling ventilators and filters for the elimination-from the remaining visible spectrum-of infrared radiation, as well as optical filters in colour for the separation of the segment optimal for photodynamic therapy-usually in the red segment of the spectrum.

Laser-based portable illuminators, the wave length of which tallies with one of the photo-sensitizer absorption maximums-usually in the infra-red segment of the spectrum (for instance, Patent No. US5068515) -are the most expensive light sources for photodynamic therapy due to the high cost of the lasers themselves. Illuminators based on discreet light-emitting diodes are effective in the transformation of electric energy into light energy, but they are used for stationary illuminators since a number of light-emitting diodes are required if the intensity required for phototherapy is to be achieved (for instance, illumination lamps based on discreet light-emitting diodes produced by PHOTOCURE). A discreet light-emitting diode is a miniature lamp, 3 mm or 5 mm in diameter, whose light source is a small crystal of a light-emitting diode, its most common dimension being 0.3 mm x 0.3 mm.

Disclosure of invention The subject invention is a portable illuminator for external phototherapy which employs a new type of lamp as a light source. The lamp is consists of a considerable number of small crystals of light-emitting diodes, closely and evenly spaced in two dimensions on a base which conducts thermal energy and isolates electrical energy. The crystals are encased in transparent optical material such as silicon or epoxy, or are hermetically sealed in a capsule with a glass window. This new source of light, consisting of a considerable number of small crystals of light-emitting diodes, was named"Cluster LED" (Light Emitting Diode). Since the light-emitting diodes emit light as a Lambert source-into the hemisphere, the cluster is fitted into a reflector of a suitable shape-most usually paraboloidal, which considerably reduces the divergence of radiated light. Further

divergence reduction is achieved by placing an appropriately shaped dioptre in front of the reflector. This combination of a cluster, reflector and dioptre creates a new type of lamp based on light-emitting diodes-a"cluster-lamp"of light-emitting diodes, or cluster LED lamp. This invention employs the"cluster LED lamp"as a light source for photodynamic therapy, since it is inexpensive, light and effective. Available on the market are highly efficient clusters which emit light in the violet segment of the spectrum, with a maximum emission at 405 nm and a spectral half-width of less than 20 nm-which is ideal both for the ALA-photodynamic diagnostics and for ALA-photodynamic therapy of shallow tumours. Also available on the market are highly effective clusters that radiate in the red segment of the spectrum with a maximum emission at 645 nm and a spectral width of below 20 nm, which is ideal for ALA-photodynamic therapy of deeper tumours. Both clusters can be used for photodynamic diagnostics and for haematoporphyrine therapy.

Using clusters which emit light in other segments of the spectrum, and which correspond to the absorption maximums of other sensitizers, this invention can also be used for photodynamic therapy with those photo-sensitizers. The invention comprises one such cluster of light-emitting diodes together with pertaining reflective-dioptrical optics-which are also available on the market-fitted into a compact casing with appropriate electronics and a rectifier. Such an illuminator weighs little, it is easy to transport and, during therapy, it can be either hand-held or mounted on its stand.

Technical innovation of the invention Technical innovation of the invention is that it ensures the execution of a compact, easily portable, inexpensive and highly effective illuminator for external photodynamic therapy.

Brief description of drawings Fig. 1 Cross-section of the light-emitting diode cluster Fig. 2 Cross-section of the light-emitting diode cluster-lamp Fig. 3 Cross-section of the portable illuminator for photodynamic therapy Fig. 4 Variation of the portable illuminator with a lightguide instead of a window Detailed description of at least one of the ways of realizing the invention with examples provided and with reference to the design drawing Fig. 1 Presents the cross-section of the light-emitting diode cluster in order to obtain a clearer understanding of the execution of the invention. The light-emitting diode cluster

(1) consists of a considerable number of small crystals of light-emitting diodes (2), which are arranged bi-dimensionally on a base that is electrically insulated and able to conduct thermal energy (3), and is itself fixed to a metal base (4). The crystals of light-emitting diodes (2) are encased in transparent optic material (5), silicon or epoxy, but they can also be hermetically sealed in a capsule with a glass window. Electric energy supply for the light-emitting diode cluster (1) is fed via the contact (6) to which the light-emitting diodes crystals are connected (2). The light-emitting diode cluster (1) is secured with screws to an appropriate cooler (7). A light-emitting diode cluster is available on the market as a ready- made light source with a maximum emission of wave lengths in different segments of the spectrum-visible, ultraviolet and infrared. The existing light-emitting diode clusters emitting in the visible spectrum have maximums distributed along the entire spectrum- depending on the producer. At this point in time the market offers clusters with maximums in the visible spectrum at, for example, 405 nm, 430 nm, 450 nm, 467 nm, 505 nm, 520 nm, 525 nm, 590 nm, 596 nm, 620 nm, 630 nm, 635 nm, 660 nm, 690 nm, 700 nm, 760 nm ; in the ultraviolet segment at, for example, 385 nm, 395 nm ; in the infrared segment at, for example, 810 nm, 850 nm, 910 nm, 940 nm. There are also RGB clusters, and clusters emitting white light, with spectral half-widths ranging from 20 nm to 50 nm, depending on the emission wave length. The technology of light-emitting diodes is undergoing intense development and improvements can be expected, on the one hand of their effectiveness and power, and on the other hand of emissions in other wave lengths of the spectrum- both in the visible and infrared segment, and particularly in the ultraviolet segment where development it in its initial stages. Wider selection of spectrum wave lengths makes it possible to construct an illuminator for external photodynamic therapy, not only on the basis of ALA, but also of other photo-sensitizers.

Fig. 2 Presents the light-emitting diode cluster lamp (10) comprising a light-emitting diode cluster (1), reflector (8) and dioptre (9). The reflector (8) can be made of metal or plastic with a steam-bonded reflective layer on the inside. The aim is to collect as much light emitted by the light-emitting diode crystals into the hemisphere, and to form a beam of as low a divergence and as high a homogeneity as possible. The most common form of the reflector is one of a rotational paraboloid, although it can also be spherical, conical or some other suitable form. Dioptre (9) serves to further reduce divergence and increase the homogeneity of the beam. Dioptre can be a lens, a spherical or a spherical plane, the

Fresnel lens, axicon or window. Almost all combinations of a reflector and dioptre, manufactured by producers of light-emitting diode clusters in parallel with their products, can be used as well as own constructions.

Fig. 3 Presents one of the possible versions of constructing the invention-portable illuminator for photodynamic therapy-where dimensions of some positions are not proportional, the aim being to make those positions prominent in the figure. Other versions are also possible without jeopardising the essence of the invention. Portable illuminator for photodynamic therapy (11) consists of a casing (14) of minimal dimensions within which the light-emitting diode cluster (1) is affixed to a cooler (13), while the reflector (8) with a dioptre (9) is fitted to the cluster. The light beam emitted from the dioptre (9) passes through a window (12). The cooler (13) is cooled by air flowing through the holes (16) which a cooling ventilator (15) directs towards the cooler (13). The regulatory electronics (17) feed the light-emitting diode cluster (1) with constant power, and the cooling ventilator (15) supplies it with constant voltage. The illuminator (11) is activated by a switch (19) which is connected to the regulatory electronics (17). The power supply for regulatory electronics is provided by the external rectifier-adaptor, via a connector (18).

The beam of light issuing from the illuminator (11) is divergent, which means that by increasing the distance to the skin surface the beam can illuminate various sized lesions.

The illuminator (11) can be mounted on a stand (20) thereby making it possible to fix the height and the angle of the illuminator for the duration of the therapy. If a lesion is smaller than the diameter of the illuminator light beam, the illuminator (11) can be hand-held, and the lesion can be covered by the illuminator (11) window (12). In order to avoid the need to disinfect the window (12) on each occasion it is used, prior to therapy the window (12) is covered by adhesive foil which is discarded following therapy.

Fig. 4 Presents a variation of the portable illuminator for photodynamic therapy (11) in which the window (12) is replaced by a lightguide (21). Thze lightguide (21) has a circular section and is in contact with the dioptre (9) in order to utilize as much light issuing from the dioptre as possible. The lightguide (21) can be made of a tough transparent material such as glass, which makes disinfection simple. It can also be of transparent plastic or some elastic transparent material such as silicon, in which case disinfection is replaced by a disposable adhesive foil applied to the lightguide (21) prior to therapy, and discarded afterwards. During therapy the lightguide (21) comes into contact with the

lesion, and is therefore foreseen for small lesions. The lightguide (21) surface that comes into contact with the lesion is slightly rounded in order to reduce the possibility of damage to the lesion. Therapy with this variation of the illuminator (11) can be administered by holding the illuminator (11) in one's hand. This variation is particularly suitable for photobiostimulation, particularly if using the light emitting diode cluster (1) that emits light with a wave length of about 635 nm, which is closest to the HeNe laser wave length (633 nm), commonly used for photobiostimulation.

Method of industrial or other application of the inventions The method of industrial or other application of the invention is visible from the description of the invention.