Chapter 5　Imaging in Dermatology

Dermatosis is a term that refers to diseases of the integumentary system，which includes everything on the surface of the body：skin，nails，and hair.Dermatosis is a common and frequently-occurring disease in the clinic.There is a wide variety of dermatosis with the feature of easy recurrence and long term treatment.Nowadays，the serious air pollution increases the incidence of dermatosis，and the pathogenic factors are constantly escalating.The World Health Organization（WHO）has announced that dermatosis will be the most infectious disease with the highest incidence and disability rate in the 21st century.Owing to the living conditions and environment，dermatosis is more common in areas of poor economic development and poverty，and the age of patients with pathological dermatosis is getting younger and the number is increasing.In particular，due to inadequate understanding of the condition of patients，the condition is always delayed.Besides，the easy recurrence and high cost of dermatosis have sounded the alarm for the people's healthy life，as well as for economic and social development.In view of the wide variety of dermatosis and complex conditions，non-invasive，in-situ，real-time and dynamic dermatological imaging diagnostic technology has been developed to characterize suspicious skin lesions and provide objective and quantitative evaluation indicators，which has become a clinical requirement for dermatology.

The diagnosis of dermatosis relies heavily on visual observation of the skin.Before the emergence of professional dermatological imaging technology，dermatologists could only use the naked eyes to directly identify the diagnosis，which is based on subjective judgment and professional background and clinical experience in long-term clinical practice of dermatologists.Cases were only described in text，and the image data could not be retained，which was not conducive to follow-up diagnosis and follow-up and comparison of efficacy.Later，although manual drawing and wax model making improved the condition to a certain extent，the drawing and model making process was cumbersome and required professional talents，which lacked universality.With the continuous development of science and technology，computer tomography（CT），magnetic resonance imaging（MRI），positron emission tomography（PET），ultrasound imaging，and various optical imaging technologies such as dermoscopy，skin confocal technology，multiphoton imaging，optical coherent tomography and photoacoustic imaging have emerged.The optical imaging technologies can visualize suspicious skin lesions，and achieve non-invasive，in-situ，real-time imaging of subcutaneous tissue to varying degrees，providing an objective evaluation basis for clinical diagnosis.The promotion and complementation between imaging technologies in dermatology and skin histopathology will inevitably lead to the rapid development of modern dermatology.(https://www.daowen.com)