Abstract and Introduction
Abstract
To reproduce focusing in virtual microscopy, it is necessary to construct 3-dimensional (3D) virtual slides composed of whole slide images with different focuses. As focusing is frequently used for the assessment of Helicobacter pylori colonization in diagnostic pathology, we prepared virtual 3D slides with up to 9 focus planes from 144 gastric biopsy specimens with or without H pylori gastritis. The biopsy specimens were diagnosed in a blinded manner by 3 pathologists according to the updated Sydney classification using conventional microscopy, virtual microscopy with a single focus plane, and virtual 3D microscopy with 5 and 9 focus planes enabling virtual focusing. Regarding the classification of H pylori, we found a positive correlation between the number of focus planes used in virtual microscopy and the number of correct diagnoses as determined by conventional microscopy. Concerning H pylori positivity, the specificity and sensitivity of virtual 3D microscopy using virtual slides with 9 focus planes achieved a minimum of 0.95 each, which was approximately the same as in conventional microscopy. We consider virtual 3D microscopy appropriate for primary diagnosis of H pylori gastritis and equivalent to conventional microscopy.
Introduction
Virtual microscopy is a new technique that enables users to view digital images of whole microscopic slides in high resolution on a computer display. Because virtual slides can be accessed over the Internet worldwide at any time without a microscope, the advantage of this technique is evident. By now, virtual microscopy has become widely applied in histopathologic teaching and proficiency testing. We also use Internet-based virtual microscopy in histopathologic teaching (http://patho.med.uni-magdeburg.de). Virtual microscopy was also applied in virtual tumor banking. The extension of virtual microscopy to diagnostic applications was discussed early and was recently tested in cervical cytology. However, the use of virtual microscopy in diagnostic pathology has not been widely established. Above all, the reliability of virtual microscopy in diagnostic pathology is not sufficiently verified.
Commonly, today's virtual slides contain a single focus plane, providing the most optimal focus of the scanned area. Although a sharp image of 1 focus plane may be sufficient for diagnostic pathology in many situations, focusing may be necessary for the assessment of special structures. Apart from situations in which sections are too thick or folded, experience shows that focusing is frequently used for the assessment of Helicobacter pylori colonization in gastric biopsy specimens. To approach this function in virtual microscopy, more focus planes have to be scanned from microscopic slides to construct 3-dimensional (3D) virtual slides and to enable virtual focusing.
To find out whether virtual 3D microscopy is appropriate for diagnostic pathology and equivalent to conventional microscopy, we digitized slides from 144 cases with gastric biopsies with or without H pylori gastritis using up to 9 focus planes, constituting 144 virtual 3D slides. The cases were diagnosed by 3 consultant pathologists (T.K., M.E., and T.G.) in a blinded manner in 4 rounds using conventional microscopy, virtual microscopy with a single focus plane, and virtual 3D microscopy with 5 and 9 focus planes. On the basis of these results, we discuss the use and the requirements of virtual microscopy in diagnostic pathology.