285 Critical Comparison of 31 Commercially Available Digital Slide Systems in Pathology Marcial García Rojo, MD, PhD, Gloria Bueno García, PhD, Carlos Peces Mateos, BSCS, Jesús González García, MD, Manuel Carbajo Vicente, MD, PhD Virtual microscopy is a general concept that includes different aspects related to this process spanning from the image acquisition to the visuali- zation systems. Because the digital image is not less real than the one provided by the optical micro- scope, we believe that the term virtual microscopy is not an accurate term, and we prefer the term digital microscopy. Virtual microscopy systems are currently capable of complete digitization of the histology and cytology slides, a process known as whole-slide imaging (WSI). Nowadays, they are available in mul- tiple formats and commercial solutions. The history of these virtual devices is rather recent. The first virtual microscopy system was described in 1997 by the Computer Science Department at University of Maryland and the Pathology Depart- ment at Johns Hopkins Hospital, Baltimore, Maryland. 1,2 To the best of our knowledge, there are no recent reviews on the state of the art for possible virtual microscopy solutions. In 2003, the European Organization for Research and Treatment on Cancer (EORTC) published the results of a poll on virtual T he term virtual microscopy is used to describe the acquisition and storage of microscopy dig- ital images. The digital images may consist of a selected area or the whole histology or cytology slide, without being limited to just one or a few regions of interest. Virtual microscopy therefore allows access to all regions of interest within a sample slide by using a personal computer (PC) or digital device without use of the microscope. 1 Advances in new technologies for complete slide digiti- zation in pathology have allowed the appearance of a wide spectrum of technologic solutions for whole-slide scanning, which have been classified into motorized microscopes and scanners. This article describes techni- cal aspects of 31 different digital microscopy systems. The most relevant characteristics of the scanning devices are described, including the cameras used, the speed of digitization, and the image quality. Other aspects, such as the file format, the compression techniques, and the solutions for visualization of digital slides, (including diagnosis-aided tools) are also considered. Most of the systems evaluated allow a high-resolution digitization of the whole slide within about 1 hour using a ×40 objec- tive. The image quality of the current virtual microscopy systems is suitable for clinical, educational, and research purposes. The efficient use of digital microscopy by means of image analysis systems can offer important benefits to pathology departments. Keywords: virtual microscopy; whole slide scanning; motorized microscope From Pathology Dept. Hospital General de Ciudad Real, Spain (MGR, JGG, MCV); Engineering School, Universidad de Castilla-La Mancha, Ciudad Real, Spain (GBG); Information Systems Technologies Area, Castilla–La Mancha Health Service (SESCAM), Toledo, Spain (CPM). This review is based on a previous work published in Spanish in Revista Española de Patología 2005;38:207-220. Tables and illustrations have been reproduced with permission of the editor. Address correspondence to: Marcial Garcia-Rojo, MD, PhD, Pathology Department, Hospital General de Ciudad Real. Calle Tomelloso s/n. 13005 Ciudad Real. Spain; e-mail: marcial@ cim.es. International Journal of Surgical Pathology Volume 14 Number 4 October 2006 285-305 © 2006 Sage Publications 10.1177/1066896906292274 http://ijsp.sagepub.com hosted at http://online.sagepub.com Techniques in Pathology