Kobe University, Kobe, Japan

www.kobe-u.ac.jp/en

A team of scientists at the Kobe University Graduate School of Engineering and the Graduate School of Medicine has jointly developed the world’s first new mercury-free light source that produces ultraviolet radiation for medical applications. The technology for the “made-to-order skin treatment equipment” is currently being certified as a medical instrument, with sales are expected to begin in October 2015. (See Figure 1)

Fig. 1 – Prototype of the made-to-order skin treatment device.
The researchers say that this equipment can effectively treat skin diseases such as atopic dermatitis, leucoderma, and psoriasis. Because it can deliver high-intensity radiation to only the affected area, it should reduce treatment time and patients’ stress levels.

How It Works

Ultraviolet radiation, which is divided into UVA (wave length: 400 to 315 nm), UVB (wave length: 315 to 280 nm), and UVC (wave length: less than 280 nm), is common in medical and environmental fields as well as in industry. However, many ultraviolet light sources are mercury- based. But, due to the adoption of the Minamata Convention on Mercury in October 2013, the production and import/export of products with a mercury content above a certain threshold, such as illumination lamps, will be prohibited as of 2020, in principle, leading to an urgent need to develop mercury-free light sources.

Since 2007, Professor Kita Takashi has been developing non-hazardous and environmentally friendly deep ultraviolet phosphors to realize nonmercury ultraviolet light sources. His work led to the development of electron- beam excitation-type and plasma excitation-type light sources. In particular, his plasma excitation-type ultraviolet light source, which is a mercury-free source that radiates UVB, has been investigated for phototherapy as a medical treatment since 2012 in collaboration with industry.

Fig. 2 – Green-phosphor plates in this photo demonstrate bright UV emission from the module.
Their efforts have resulted in the world’s first film-type ultraviolet light source that produces ultraviolet radiation from plasmas via a phosphor containing gadolinium as a contrast agent for medical imaging of the human body, instead of via mercury that has a high environmental load. This mercury-free light source is optimal for phototherapy treatments that do not burn the skin because it emits light at a wavelength of 310 nm, which is close to the narrowband UVB frequently used at present in medical settings. (See Figure 2)

Unlike conventional electron-beam excitation methods for phosphor excitation, the plasma excitation method employs technology similar to that used in plasma televisions, allowing a large area to be economically treated. However, its biggest advantage is its ability to pinpoint the location where light is delivered. Hence, the device can precisely deliver UVB radiation only to the affected area.