(A)WSIs of kidney allograft glomerulus (Upper left: H&E, Upper right: Methenamine sliver trichrome, Lower: H&E) were scanned with a 40X objective lens, 0.95 N.A. plasma cells), viral inclusions, and glomerular basement membrane abnormalities( Figure 1) others report similar problems and pathologists reluctance to relinquish native 40X scans( 5, 9). In the senior author’s experience, however, native 40X scans are needed to resolve kidney and liver transplantation pathology challenges, such as inflammatory cell subtypes(e.g. This setup offers a compromise of resolution, larger field area, file size, and scan times practical enough to approach clinical applicability. Commercial vendors usually quote 20X scan time per cm2 of tissue. Scan time, or time required to convert a glass slide into a WSI, depends largely on the scanner’s objective lens: higher resolution 40X scans have smaller fields of view and more z-planes that require more image captures and result in longer scan times and larger files sizes than lower resolution 20X WSI. This “traditional microscope” image-capture approach inherently results in a scanning “bottleneck” limiting throughput. Optimally-focused individual fields or image strips are then “quilted” together to create seamless two-dimensional(2D) WSIs( 8). Focusing algorithms and robotics adjust the objective along tissue z-plane topography while moving the slide continuously in X and Y planes. Advances in digital imaging techniques, robotics, and computing are providing new “toolkits” enabling pathologists to extract more information from tissue samples and increase the histopathology value proposition.Ĭurrent slide scanners are software-driven, robotically-controlled microscope systems: a stage moves continuously under a uni-ocular microscope equipped with a high-speed camera that captures each field. Despite shortcomings, however, conventional histology quickly provides a wealth of difficult to replace information about structural integrity, spatial and temporal relationships, and rare events/cells, which depend on traditional light and fluorescence microscopes. Compared to less-invasive monitoring techniques, such as peripheral blood and fluid mRNA arrays and proteomics/metabolomics( 2, 3), the risk-benefit ratio and relative “value proposition” of routine histopathology are decreasing. Limitations and Strengths of Conventional Histopathologyīiopsies used for allograft monitoring are invasive, expensive, potentially morbidity- and mortality-producing, an unpleasant patient experience, subject to sampling error, and interpretations are prone to bias, subjectivity and inter-observer variability( 1). Regardless, challenges will be overcome and these technologies will enable transplant pathologists to increase information extraction from tissue specimens and contribute to cross-platform biomarker discovery for improved outcomes. Cost, complexities of implementation, fluid/evolving standards, and unsettled medical/legal and regulatory issues remain as challenges. Current utilization for teaching, quality assurance, conferencing, consultations, research and clinical trials is evolving toward implementation for low-volume, high-complexity clinical services like transplantation pathology. Included are side-by-side comparisons, objective biopsy finding quantification, multiplexing, automated image analysis, and electronic data and resource sharing. Pathologists now team with hardware and software engineers to exploit remarkable developments in digital imaging, nanoparticle multiplex staining, and computational image analysis software to bridge the traditional histology - global “–omic” analyses gap. Nevertheless, except for immunostaining, no transformative advancements have “modernized” routine microscopy in over 100 years. Microscopic biopsy analysis, however, provides valuable and unique information: a) spatial-temporal relationships b) rare events/cells c) complex structural context and d) integration into a “systems” model. “-Omics” analysis of tissues, peripheral blood and fluids and targeted serologic studies provide mechanistic insights into allograft injury not currently provided by conventional histology. Conventional histopathology is the gold standard for allograft monitoring, but its value proposition is increasingly questioned.
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