IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS, VOL. 18, NO. 4, JULY 2014 1413 Manual Stage Acquisition and Interactive Display of Digital Slides in Histopathology Alessandro Gherardi and Alessandro Bevilacqua, Member, IEEE Abstract—More powerful PC architectures, high-resolution cameras working at increasing frame rates, and more and more ac- curate motorized microscopes have boosted new applications in the field of biomedicine and medical imaging. In histopathology, the use of digital slides (DSs) imaging through dedicated hardware for digital pathology is increasing for several reasons: digital annota- tion of suspicious lesions, recorded clinical history, and telepathol- ogy as a collaborative environment. In this paper, we propose the first method known in the literature for real-time whole slide ac- quisition and displaying conceived for conventional nonautomated microscopes. Differently from DS scanner, our software enables biologists and histopathologists to build and view the DS in real time while inspecting the sample, as they are accustomed to. In addition, since our approach is compliant with existing common microscope positions, provided with camera and PC, this could contribute to disseminate the whole slide technology in the major- ity of small labs not endowed with DS hardware facilities. Experi- ments performed with different histologic specimens (referring to tumor tissues of different body parts as well as to tumor cells), acquired under different setup conditions and devices, prove the effectiveness of our approach both in terms of quality and speed performances. Index Terms—Digital slide (DS), histology, mosaicing, virtual microscopy (VM), whole slide (WS). I. INTRODUCTION C OMPOSING several images in one large image, often named mosaic, is a well-known approach utilized in sev- eral application fields, ranging from panorama stitching [1] and video surveillance [2] to medical imaging [3] and mi- croscopy [4]. The difficulties met in implementing this pro- cedure are related to the specific applications and range from the contemporary motion of both the acquisition device and the objects [1], [2] to the object deformation due to the acquisition by a contact device [3]. The last decade has seen a huge amount of efforts in developing digital imaging techniques in the field of microscopy. Recent advances in the digital imaging hardware, computer vision research together with an increase in the com- putation speed of CPU and GPU architectures, have contributed in this field by providing tools aimed at aiding medical and Manuscript received April 16, 2013; revised July 25, 2013 and September 26, 2013; accepted November 17, 2013. Date of publication January 2, 2014; date of current version June 30, 2014. A. Gherardi is with the Advanced Research Center on Electronic Systems (ARCES), University of Bologna, I-40126 Via Toffano 2/2, Bologna, Italy (e-mail: agherardi@arces.unibo.it). A. Bevilacqua is with ARCES and the Department of Computer Science and Engineering, University of Bologna, I-40136 Viale Risorgimento 2, Bologna, Italy (e-mail: alessandro.bevilacqua@unibo.it). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JBHI.2013.2291998 biological experts in their analysis, either in research, educa- tion, or in clinical settings [5]. In particular, in histopathology, the detection and localization of relevant features of the tis- sue within a histologic sample requires detailed analysis of the tissue elements (i.e., cells membrane, cytoskeleton) at a high magnification, while keeping a reference of an overall view of the tissue structure (i.e., how cells and stroma are organized) at a lower magnification. Pathologists act at different resolutions while making a diagnosis, zooming in and out on the specimen to identify possible lesions [6]. Having a wde digital portions of a slide allows more accurate automatic image analysis, yet more if a robust statistics is re- quired (e.g., in case of texture analysis [7]). Modern microscope systems might allow the acquisition in advance of a digital slide (DS), also called whole slide (WS) when referred to the whole content of the specimen slide [8], or virtual slide (VS) when used in telepathology, aiding the process of making a diagnosis even remotely [9], [10]. This technology is called virtual microscopy (VM) and consists of an automated microscope and a digital imaging system that are exploited to acquire images of the en- tire slide, store such images in tiles, and allow users to view them interactively at different (interpolated) magnifications on a display. The images are acquired at high magnification, since this subsequently enables the pathologists to incrementally add more discriminatory information in order to detect suspicious regions. These systems usually rely on a motorized precision stage where the sample is scanned on a tile-based fashion [11]. The tiles at high magnification are then stored on disks for later processing and analysis. The generated dataset (up to hundreds of GB for large slides at adequate resolution) yields intensive computational demands for processing, storage, and viewing capabilities [12], [13]. For example, even if a precision stage is employed, the mosaic of assembled images requires further processing to eliminate stitching artifacts due to uneven lighting (the well-known problem of vignetting) or misalignments due to finite precision and drift of the motorized stage. Recently, DS acquisition systems through digital scanners have become an option to motorized microscopes and can provide pathologists the DS in few minutes, although these systems are still quite ex- pensive. However, although dedicated software viewers are used to assist the pathologists in their analysis by browsing the DS at different magnifications, just the way experts are accustomed to with a conventional microscope, biologists have to perform their analysis by looking at a monitor rather than through the microscope. In addition, all these systems rely on the acquisi- tion of the DS performed by dedicated hardware, whether they are automated microscopes equipped with a motorized stage 2168-2194 © 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information.