This is a transversal study with biopsies and cytologies obtained from the Hospital General de Ciudad Real (HGCR) archives. Eight slides (see Table 1) were randomly selected (6 biopsies and 2 cytologies). They were digitized using Aperio Scanscope XT (40×, JPEG200 compression, version 8) and Olympus SIS dotslide (40×, CMW compression, version 1.2 build 2992). Virtual slide files (Aperio SVS files and Olympus VSI files) were copied to two different servers (external servers and hospital server), each of them running 3 different web servers for virtual slides (Aperio web server, Olympus SIS NetImage Server, and Aurora mScope). Aurora mScope was used to access both Aperio SVS files and Olympus VSI files.
Five pathologists studied to time needed to access images of each virtual slide, selecting a panoramic view, 10 low magnification fields, and 20 high magnification fields. In all cases, images were shown with a maximized window. All times were recorded in seconds.
An external server, a multi-domain dedicated server of the Spanish Society of Pathology running Aurora mScope server http://www.telepatologia.es/ was used. The Olympus SIS NetImage Server was installed in a server located at: http://www.hgcr.es/hgcrui/WebImage/index.aspx
Internet Aperio web server is available at http://www.hgcr.es/html/
Each pathologist accessed all eight images both using the HGCR intranet 1 GB Ethernet connection and residential Internet connection. Residential Asymmetric Digital Subscriber Line (ADSL) was 2520 Kbps/270 Kbps (mean values).
In the hospital environment, the same computer was used (Fujitsu Siemens Esprimo E, AMD Sempron Processor 3600+, 1 GB RAM, Serial ATA II hard disk, 17" scenic view A17-2 monitor). In the residential environment, each pathologist used a different computer (from notebooks with 512 GB RAM with a 15" screen to high performance desktop computers (CPU Intel Core2 6700 2.66 GHz, 3 GB RAM, Serial ATA-300 7200 RPM hard disk with a 21" monitor). All web viewers were run using Microsoft Internet Explorer in Windows XP operating system.
All measurements were made using a screen size of 1024 × 768 pixels.
The following variables were recorded twice (first with intranet servers and then accessing external servers using residential ADSL connection), using maximized/full screen window:
1. Time to show complete virtual slide panoramic view (default overview)
2. Time to show complete 10× image (recording 10 fields)
3. Time to show complete 20× image (recording 10 fields)
4. Time to show complete 40× image (recording 10 fields)
Quantitative data analysis was performed using Kirkman's tools  and confirmed with the SPSS statistical package (version for SESCAM). Means and SDs of the differences were then calculated, and the corresponding paired t tests were performed. Statistical significance was assumed at a P value of less than or equal to 0.05.