The therapeutic effect of the photodynamic therapy (PDT) depends on a combination of parameters that include drug dose, drug-light interval, oxygen in cells and light irradiance rate. It also varies according to the wavelength distribution of the light source. Finally, a homogeneous and reproducible illumination during the clinical PDT is determinant in preventing under- or overtreatment. So, the aim of Phos-Istos project is to develop light emitting flexible structures for the photodynamic therapy coupled with diode laser for an ambulatory biophotonic medical system. The main challenge in order to ensure the development of such treatment is to guarantee a uniform light illumination of the skin due to the complexity of the human anatomy.The medical kit developed has a double function:- provide homogeneous light emitting source adapted to the human morphology of area to be treated.- monitor the kinetic reaction of photosensitizer and adapt the irradiance according to the patient's response.The treatment against Actinic Keratosis precancerous cells and skin diseases with Phos-Istos becomes:- More successful,- Less painful and provide more comfort,- More sensitive due to the monitoring of photosensitizer reaction during the treatment,- Avoid recurrence and offer a definitive treatment,The pilot trials that will be processed in Phos-Istos project will be made by professionals and will demonstrate the advantages. They will also enable to optimize the product that will be sold at the end of a comparative study with other existing devices and to develop similar solutions for other treatments like psoriasis, basal cell carcinoma and acne.