Design of LED System for Acne Vulgaris Treatment Chang-Su Kim

ABSTRACT
* Design of LED System for Acne Vulgaris Treatment Using Pulse Width Modulation Chang-Su Kim Department of Biomedical Engineering, Graduate school, Chungnam National University, Daejeon, Korea
* A thesis submitted to the committee of Graduate School of Biomedical Engineering, Chungnam National University in partial fulfillment of the requirements for the degree of Master of Biomedical Engineering conferred in August, 2012.

PDT(Photodynamic Therapy) is a method that kills cancer cells with photochemical and photobiological actions by vitalizing the substance with light that has special wavelength after injecting a photosensitizer that reacts to particular wavelength into body or putting on the body surface. Based on this, this study designed the LED system that emits light to treatment of acne vulgaris which is one of the dermatological lesions. As a wavelength of LED for treatment of acne vulgaris, the 660nm wavelength was selected because it has an effects on curing papule, pustule and acne vulgaris with inflammatory lesions based on its effect on controlling the formation of sebum, eliminating inflammatory reaction and increase of collagen synthesis. The conventional LED treatment system based on Continuous Wave has a high possibility to cause thermal-destruction of tissues when much heat is generated in living tissues with low energy efficiency. In order to prevent the thermal effects, we designed the Pulse Width Modulation( PWM) circuit specially. The LED system was designed by classifying it into timer module, PWM module and optical delivery part. In order to confirm the energy efficiency of PWM method and thermal reaction of living tissues, the stabled energy output and the stability of living tissues were evaluated by measuring the output energy of LED and surfasse temperature of living tissues in comparison with C.W method. In the results, there was the thermal-destruction in the living tissues with high loss of electric power in case of using C.W in order to get LED energy of 1W intensity and 660nm wavelength for treatment of acne vulgaris. However, the energy efficiency was improved by lowering power consumption of LED through PWM by realizing PWM method. Also there is no thermal destruction phenomenon of living tissues, which is considered that PWM method would be more effective and safer than C.W method in case of treatment of acne vulgaris.
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