Arch Dermatol Res DOI 10.1007/s00403-010-1087-7 123 MINI REVIEW Sidestream dark Weld imaging: the evolution of real-time visualization of cutaneous microcirculation and its potential application in dermatology Curt M. Treu · Omar Lupi · Daniel A. Bottino · Eliete Bouskela Received: 9 June 2010 / Revised: 22 September 2010 / Accepted: 24 September 2010  Springer-Verlag 2010 Abstract Technological advances during the last years have enhanced the image quality of the microcirculation. Intravital microscopy (IM) has been considered the “gold standard” for many years, but it can be used mostly in anes- thetized animals which is a disadvantage. The nailfold vide- ocapillaroscopy, a non-invasive examination that includes a microscope with an epiillumination system, came after- ward, but its major disadvantage is the restricted area avail- able for investigation namely the nailfold capillary bed. The orthogonal polarization spectral (OPS) imaging technique, where reXected light allows the visualization of the micro- circulation, was the next non-invasive exam, but it still pre- sents some drawbacks such as suboptimal capillary visualization and image blurring due to red blood cell movements. Excessive probe pressure modiWes red blood cell velocity. There is suboptimal imaging of capillaries due to motion-induced image blurring by movements of OPS device, tissue and/or Xowing red blood cells. Side- stream dark Weld (SDF) imaging is the newest tool for microcirculatory research. Illumination is provided by con- centrically placed light-emitting diodes to avoid image blurring and to enhance image contrast. It represents a sim- ple and non-invasive imaging technique, with low cost, good portability and high sensitivity that provides Wne, well-deWned images. In addition, the microcirculation can be studied through laser Doppler Xowmetry (LDF) or reXectance-mode confocal-laser-scanning microscopy (RCLM). However, LDF cannot show microcirculatory vessels and high cost of RCLM can be an inconvenience. New applications of SDF technique could include skin microcirculatory evaluation and allow dermatological stud- ies on psoriasis, skin tumors and leprosy. Keywords Nailfold videocapillaroscopy · Orthogonal polarization spectral imaging · Sidestream dark Weld imaging · Microcirculation Introduction Since the Wrst description of cells by Robert Hooke on 1665, researchers worldwide have made great eVort to learn about this microuniverse. William Harvey described the blood circulation in a closed-circuit system on the seven- teenth century initiating the Wrst steps toward the discovery of the microcirculation. Why is it so important to study the microcirculation? Because the correct function of the microcirculation is a prerequisite for tissue nutrition and oxygen supply [64]. Indeed, almost all diseases have some kind of microcirculatory impairment during their history course. As visualization of the microcirculatory environment is not simple, many technological attempts have been done in the last 200 years to enhance its image quality. For exam- ple, IM has been the Wrst “gold standard” for the study of microcirculation in vivo in humans [5, 20]. IM shows capillaries, arterioles and venules that can be analyzed morphologically and functionally. In this way, C. M. Treu · O. Lupi · D. A. Bottino · E. Bouskela Clinical and Experimental Research Laboratory on Vascular Biology (BioVasc), Biomedical Center, State University of Rio de Janeiro, Pavilhão Reitor Haroldo Lisboa da Cunha, térreo, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro, RJ 20.550-013, Brazil C. M. Treu (&) Av. Canal de Marapendi, 2500 Bl.4 Apt. 903 Barra da Tijuca, Rio de Janeiro, RJ 22.631-051, Brazil e-mail: curttreu@gmail.com