ABSTRACT
Analogue Videodermoscopy Between 1980 and 1990, advances in video technology led to the development of instruments that displayed dermoscopic images on a screen.(1) The first videodermoscope had a tele camera with video resolution connected to an optical dermo scope and a television screen with video recorders to record examinations. However, during this period, the dermoscopic examination using these equipment produced only lowquality images, which is due to the low resolution of the firstgenera tion video cameras, and other cumbersome documentation and datasaving procedures; for example, the maximum television resolution is 768 x 576 pixel for the European PAL broadcast system and less for the American NTSC, where pixel is the basic image unit; analogue video recorders of the 1980s often had less than 400 horizontal lines. Low quality and technical limitations prevented the widespread use of videodermoscopy.(2)
Digital Videodermoscopy Between 1990 and 2000, computerized instruments for digitizing images from telecameras connected to videodermoscopes became common. Digital dermoscopic images can be obtained by conver sion from video telecameras connected to digital cards or by use of highresolution digital telecameras or digital cameras coupled with special dermoscopy adaptors. Computerized systems proved more practical for managing examinations because they offered the pos sibility of saving personal and private data of patients, together with digital images of pigmented skin lesions (Figure 2.1).(2, 3)
In the case of video telecameras, the signal acquisition peripheral required a chargecoupled device (3CCD) or sen sor for the red, green, and blue bands, in order to keep image quality high during sampling.(1, 4) Digital telecameras have better quality for the equivalent video characteristics because they do not require any conversion. They can have a USB (usu ally amateur grade) or Firewire (professional grade, faster and
better quality) interface. Much higher resolution is possible with digital telecameras than is possible with analogue video telecameras and this has clear diagnostic advantages, as digital dermoscopy systems of this type can reach a picture resolution of 1280 x 1,024 pixels, with images observed in vivo at 15 to 25 photograms per second on computer screens (Figure 2.2). Digital cameras provide exceptionally high resolutions (up to 3,000 x 2,000 are common) but have the disadvantage of not providing full resolution images in vivo but only after the images have been saved.
