Pathology Image Exchange: The Dutch Digital Pathology Platform for Exchange of Whole-Slide Images for Efficient Teleconsultation, Telerevision, and Virtual Expert Panels.

Among the many uses of digital pathology, remote consultation, remote revision, and virtual slide panels may be the most important ones. This requires basic slide scanner infrastructure in participating laboratories to produce whole-slide images. More importantly, a software platform is needed for exchange of these images and functionality to support the processes around discussing and reporting on these images without breaching patient privacy. This poses high demands on the setup of such a platform, given the inherent complexity of the handling of digital pathology images. In this article, we describe the setup and validation of the Pathology Image Exchange project, which aimed to create a vendor-independent platform for exchange of whole-slide images between Dutch pathology laboratories to facilitate efficient teleconsultation, telerevision, and virtual slide panels. Pathology Image Exchange was released in April 2018 after technical validation, and a first successful validation in real life has been performed for hematopathology cases.

Myocardial fibrosis and pro-fibrotic markers in end-stage heart failure patients during continuous-flow left ventricular assist device support.

OBJECTIVES: During support with a left ventricular assist device (LVAD), partial reverse remodelling takes place in which fibrosis plays an important role. In this study, we analysed the histological changes and expression of fibrotic markers in patients with advanced heart failure (HF) during continuous-flow LVAD (cf-LVAD) support. METHODS: In 25 patients, myocardial tissue at the time of LVAD implantation (pre-LVAD) was compared with tissue from the explanted left ventricle (post-LVAD). Interstitial fibrosis and cardiomyocyte size were analysed pre- and post-LVAD. Plasma was obtained from all patients before and during LVAD support. Plasma levels, cardiac mRNA and protein expression of brain natriuretic peptide (BNP), galectin-3 (Gal-3), connective tissue growth factor (CTGF), osteopontin (OPN) and transforming growth factor ß-1 were determined. RESULTS: Fibrosis increased during cf-LVAD unloading (P < 0.05). Cardiomyocytes elongated (P < 0.05), whereas cross-sectional area did not change. BNP, Gal-3, CTGF and OPN were significantly elevated pre-LVAD in comparison with controls. BNP decreased significantly after 1 month of cf-LVAD support (P < 0.001) to near-normal levels. Pro-fibrotic markers remained elevated in comparison with controls. CONCLUSIONS: cf-LVAD support is associated with lengthening of cardiomyocytes, without alterations in diameter size. Remarkably, myocardial fibrosis increased as well as circulating pro-fibrotic markers. Whether the morphological changes are a direct effect of reduced pulsatility during cf-LVAD support or due to HF progression requires further investigation.

Distinct phenotypes of cardiac allograft vasculopathy after heart transplantation: a histopathological study.

INTRODUCTION: Long-term survival after heart transplantation (HTx) is hampered by cardiac allograft vasculopathy (CAV). Better understanding of the pathophysiological mechanisms of CAV might have considerable consequences for therapeutic approaches in the future. The aim of the present study was to investigate the histological phenotypes of CAV in relation with clinical patient characteristics. METHODS AND RESULTS: Coronary cross-sections from 51 HTx patients were obtained at autopsy. CAV was observed in 42 patients (82%). Three histological CAV phenotypes were identified (H-CAV 1-3). No CAV (H-CAV 0) is as seen in normal coronary arteries; intimal thickening consisting of a layer of longitudinal oriented smooth muscle cells. In H-CAV 1 to 3 a second intimal layer is formed, on top of the longitudinal oriented smooth muscle cell layer, with predominantly mononuclear inflammatory infiltrate in loose connective tissue (H-CAV 1), smooth muscle cells in different orientation (H-CAV 2), or a fibrotic intimal lesion (H-CAV 3). H-CAV type was significantly related with time after transplantation, age at transplantation, the amount of atherosclerotic disease and the occurrence of infection. In addition, morphometric analysis revealed that higher H-CAV types have a relatively larger intimal area, that is compensated for by expansive arterial remodeling of the artery. CONCLUSION: CAV in an ongoing process that can be classified into three different phenotypes; inflammatory lesions, lesions rich of smooth muscle cells and fibrotic lesions. Our results suggest that these phenotypes are related to time after transplantation, age at transplantation, the amount of atherosclerotic disease and the occurrence of infection.

Whole slide images for primary diagnostics of urinary system pathology: a feasibility study.

INTRODUCTION: During the last decade, whole slide images (WSI) have been used in many areas of pathology such as teaching, research, digital archiving, teleconsultation and quality assurance testing. However, WSI have as yet not much been used for upfront diagnostics because of the lack of validation studies. OBJECTIVES: The aim of this study was to test the feasibility of WSI for primary diagnosis of urinary tract pathology. MATERIALS AND METHODS: 100 consecutive urinary tract biopsies and resections which had been diagnosed conventionally between the years 2008-2009 were scanned at 20× magnification, and rediagnosed by two pathologists on WSI, having the original clinical information available, but blinded to the original diagnoses. Original and WSI diagnoses were compared and classified as concordant, slightly discordant (without clinical consequences) and discordant. RESULTS: Original and WSI based rediagnosis were concordant in 87% of the cases. Original and WSI diagnosis were slightly discordant in 8% of cases. Major discrepancies with clinical or prognostic implications were founded in only 5 cases. However, for 6 out of the 13 discrepancies, WSI based diagnoses were considered to be better than the original diagnoses. CONCLUSION: Primary diagnostics of urinary tract specimens can be reliably done on WSI. Further improvements of image resolution may help to increase diagnostic accuracy and WSI acceptance in routine pathology.

Automatic nuclei segmentation in H&E stained breast cancer histopathology images.

The introduction of fast digital slide scanners that provide whole slide images has led to a revival of interest in image analysis applications in pathology. Segmentation of cells and nuclei is an important first step towards automatic analysis of digitized microscopy images. We therefore developed an automated nuclei segmentation method that works with hematoxylin and eosin (H&E) stained breast cancer histopathology images, which represent regions of whole digital slides. The procedure can be divided into four main steps: 1) pre-processing with color unmixing and morphological operators, 2) marker-controlled watershed segmentation at multiple scales and with different markers, 3) post-processing for rejection of false regions and 4) merging of the results from multiple scales. The procedure was developed on a set of 21 breast cancer cases (subset A) and tested on a separate validation set of 18 cases (subset B). The evaluation was done in terms of both detection accuracy (sensitivity and positive predictive value) and segmentation accuracy (Dice coefficient). The mean estimated sensitivity for subset A was 0.875 (±0.092) and for subset B 0.853 (±0.077). The mean estimated positive predictive value was 0.904 (±0.075) and 0.886 (±0.069) for subsets A and B, respectively. For both subsets, the distribution of the Dice coefficients had a high peak around 0.9, with the vast majority of segmentations having values larger than 0.8.

Going fully digital: Perspective of a Dutch academic pathology lab.

During the last years, whole slide imaging has become more affordable and widely accepted in pathology labs. Digital slides are increasingly being used for digital archiving of routinely produced clinical slides, remote consultation and tumor boards, and quantitative image analysis for research purposes and in education. However, the implementation of a fully digital Pathology Department requires an in depth look into the suitability of digital slides for routine clinical use (the image quality of the produced digital slides and the factors that affect it) and the required infrastructure to support such use (the storage requirements and integration with lab management and hospital information systems). Optimization of digital pathology workflow requires communication between several systems, which can be facilitated by the use of open standards for digital slide storage and scanner management. Consideration of these aspects along with appropriate validation of the use of digital slides for routine pathology can pave the way for pathology departments to go "fully digital." In this paper, we summarize our experiences so far in the process of implementing a fully digital workflow at our Pathology Department and the steps that are needed to complete this process.

Whole slide images for primary diagnostics of paediatric pathology specimens: a feasibility study.

INTRODUCTION: Whole slide images (WSI) have been used in many pathology applications such as teleconsultation, teaching and research, but not in primary diagnostics. The aim of this study was to test the feasibility of using WSI in primary diagnostics of paediatric pathology specimens and placental tissue. MATERIALS AND METHODS: Eighty consecutive tissues biopsies and resections from patients under 18 years old were selected, as well as 20 placentas. These cases had been diagnosed in the year 2009 by a single pathologist. The same pathologist who had performed the original diagnosis based on light microscopy was asked to rediagnose these 100 cases on WSI scanned at 20× magnification as well as by light microscopy having the original clinical information available, but blinded to the original light microscopic diagnoses. The original diagnoses were compared with WSI based diagnoses and rediagnoses by light microscopy and classified as concordant, mildly discordant (without clinical consequences) and discordant (with clinical consequences). RESULTS: The original diagnoses were concordant with WSI and light microscopic diagnoses in 90% and 93% of cases respectively, which was not significantly different. Digital reassessment yielded eight mild discrepancies and two discrepant cases (2%) where the difference in diagnoses could have clinical implications for the patient. Light microscopic reassessment showed seven mild discrepancies. It turned out to be difficult to identify nucleated red blood cells on WSI, even when scanned at 40×. CONCLUSIONS: Primary diagnostics of paediatric tissue biopsies and resections can generally well be done on WSI. However, some difficulties were encountered in examining placenta tissue where the identification of nucleated red blood cells may need higher resolution or even scanning at multiple focus depths, which is well possible on most current slide scanners.

Whole slide images as a platform for initial diagnostics in histopathology in a medium-sized routine laboratory.

INTRODUCTION: Whole slide imaging is the process of digitizing glass slides and the creation of Whole Slide Images (WSI), which enable the examination of pathology samples on a computer screen in a manner comparable to light microscopy. WSI have been used for different applications in pathology but their use for primary diagnostics is still limited. Implementing WSI for primary diagnostics would be a turning point necessitating extensive validation to unravel pitfalls and difficulties that could be encountered within the routine workflow. This article is aimed to describe the gradual integration of WSI into routine pathology diagnostics in a medium-sized routine pathology laboratory. METHODS: This project was started with optimizing the digital work environment including the setting up of validation studies, scanning preferences, storing WSI and the implemented adjustments to the workflow for the laboratory and the pathologist. Afterwards scanning glass slides was initiated in the department of pathology at the Atrium Medical Center, Heerlen, The Netherlands, for performing primary diagnostics of breast biopsies. Later this was extended to other specimen types including resections. RESULTS: The validation studies yielded a high concordance rate between WSI and conventional diagnoses. Routine primary WSI based diagnosis was possible in 82.1% of cases. Failure of digital diagnosis was mainly related to poor image quality and logistic problems. CONCLUSION: The quality of the currently produced WSI is sufficient for primary diagnostics in 82.1% of the cases. Improving image quality, adequate retrieval and controlling scanning error will definitely encourage the wide adaptation in routine diagnostics.

Digital pathology for education.

The use of digital slides for educational purposes (both for medical students and during pathology traineeships) will eventually accelerate the acceptance of digital pathology in general. This chapter describes the advantages of using digital slides especially for education. Also the requirements for using digital slides for this purpose are evaluated, including software requirements, the slide scanner and the IT infrastructure needed to provide a robust infrastructure to end users.

Prognostic value of automatically extracted nuclear morphometric features in whole slide images of male breast cancer.

Numerous studies have shown the prognostic significance of nuclear morphometry in breast cancer patients. Wide acceptance of morphometric methods has, however, been hampered by the tedious and time consuming nature of the manual segmentation of nuclei and the lack of equipment for high throughput digitization of slides. Recently, whole slide imaging became more affordable and widely available, making fully digital pathology archives feasible. In this study, we employ an automatic nuclei segmentation algorithm to extract nuclear morphometry features related to size and we analyze their prognostic value in male breast cancer. The study population comprised 101 male breast cancer patients for whom survival data was available (median follow-up of 5.7 years). Automatic segmentation was performed on digitized tissue microarray slides, and for each patient, the mean nuclear area and the standard deviation of the nuclear area were calculated. In univariate survival analysis, a significant difference was found between patients with low and high mean nuclear area (P=0.022), while nuclear atypia score did not provide prognostic value. In Cox regression, mean nuclear area had independent additional prognostic value (P=0.032) to tumor size and tubule formation. In conclusion, we present an automatic method for nuclear morphometry and its application in male breast cancer prognosis. The automatically extracted mean nuclear area proved to be a significant prognostic indicator. With the increasing availability of slide scanning equipment in pathology labs, these kinds of quantitative approaches can be easily integrated in the workflow of routine pathology practice.

Whole slide images for primary diagnostics of gastrointestinal tract pathology: a feasibility study.

During the last decade, whole slide images have been used in many areas of pathology such as teaching, research, digital archiving, teleconsultation, and quality assurance testing. However, whole slide images have as yet not much been used for up-front diagnostics because of the lack of validation studies. The aim of this study was, therefore, to test the feasibility of whole slide images for diagnosis of gastrointestinal tract specimens, one of the largest areas of diagnostic pathology. One hundred gastrointestinal tract biopsies and resections that had been diagnosed using light microscopy 1 year before were rediagnosed on whole slide images scanned at ×20 magnification by 5 pathologists (all reassessing their own cases), having the original clinical information available but blinded to their original light microscopy diagnoses. The original light microscopy and whole slide image-based diagnoses were compared and classified as concordant, slightly discordant (without clinical consequences), and discordant. The diagnoses based on light microscopy and the whole slide image-based rediagnoses were concordant in 95% of the cases. Light microscopy and whole slide image diagnosis in the remaining 5% of cases were slightly discordant, none of these were with clinical or prognostic implications. Up-front histopathologic diagnosis of gastrointestinal biopsies and resections can be done on whole slide images.

Digital pathology: current status and future perspectives.

During the last decade pathology has benefited from the rapid progress of image digitizing technology. The improvement in this technology had led to the creation of slide scanners which are able to produce whole slide images (WSI) which can be explored by image viewers in a way comparable to the conventional microscope. The file size of the WSI ranges from a few megabytes to several gigabytes, leading to challenges in the area of image storage and management when they will be used routinely in daily clinical practice. Digital slides are used in pathology for education, diagnostic purposes (clinicopathological meetings, consultations, revisions, slide panels and, increasingly, for upfront clinical diagnostics) and archiving. As an alternative to conventional slides, WSI are generally well accepted, especially in education, where they are available to a large number of students with the full possibilities of annotations without the problem of variation between serial sections. Image processing techniques can also be applied to WSI, providing pathologists with tools assisting in the diagnosis-making process. This paper will highlight the current status of digital pathology applications and its impact on the field of pathology.

Whole slide images for primary diagnostics in dermatopathology: a feasibility study.

BACKGROUND: During the last decade, whole slide images (WSI) have been used in many areas of pathology such as teaching, research, digital archiving, teleconsultation and quality assurance testing. However, WSI have not regularly been used for routine diagnosis, because of the lack of validation studies. AIM: To test the validity of using WSI for primary diagnosis of skin diseases. MATERIALS AND METHODS: 100 skin biopsies and resections which had been diagnosed light microscopically one year previously were scanned at 20× magnification, and rediagnosed by six pathologists (every pathologist assessed his own cases), having the original clinical information available, but blinded to the original diagnoses. The WSI diagnoses were compared to the initial light microscopy diagnosis and classified as concordant, slightly discordant (without clinical consequences) or discordant. RESULTS: The light microscopy and the WSI based diagnosis were concordant in 94% of the cases. The light microscopy and WSI diagnosis were slightly discordant in 6% of the cases. For one of the slightly discrepant cases the WSI diagnosis was considered better, while the original diagnosis was preferred for the other five cases. There were no discordant cases with clinical or prognostic implications. CONCLUSION: Primary histopathological diagnosis of skin biopsies and resections can be done digitally using WSI.

Discrimination between benign and malignant prostate biopsies using three-dimensional chromatin texture analysis by confocal laser scanning microscopy.

OBJECTIVE: To evaluate the clinical usefulness of computing three-dimensional (3-D) nuclear texture features on prostate biopsy specimens to discriminate among benign, prostatic intraepithelial neoplasia (PIN), and malignant specimens. STUDY DESIGN: Twelve prostate cancer biopsy specimens were selected, diagnosed as either benign (N = 4), PIN (N = 4), or malignant (N = 4). Sections 14 microm thick were stained. 3-D image stacks of selected benign and malignant areas were obtained by confocal laser scanning microscopy (CLSM) and analyzed off-line using in-house-developed software for 3-D semiautomated segmentation and calculation of texture features. The power of the 3-D texture features to discriminate among the pooled benign (N = 1,507), PIN (N = 673), and malignant nuclei (N = 1,251) was established by multivariate linear discriminant analysis. RESULTS: A total of 68.8% of the benign nuclei, 77.2% of the PIN nuclei, and 78.5% of the malignant nuclei could be classified correctly after cross validation. CONCLUSION: Quantification of changes in the distribution of nuclear chromatin by means of 3-D texture feature computation on CLSM images allows discriminating most benign and malignant prostate nuclei, which could be useful in cases that are difficult to diagnose morphologically.

Creation of a fully digital pathology slide archive by high-volume tissue slide scanning.

Digital slide scanners for scanning glass slides are becoming increasingly popular because current scanners are fast enough and produce good enough images for diagnostic purposes, education, and research. Also, the price for storing vast amounts of data has decreased over the last years, and this trend is expected to continue. Where most laboratories use their scanners mainly for education and research with limited financial and technical implications, we decided to face the huge challenges of prospectively setting up a fully digital pathology slide archive, primarily aiming to optimize the preparation and running of clinicopathological conferences. In this article, we describe the setup of our digital archiving solution and discuss the technical challenges we had to overcome. To give insight in the performance of our digital archive, we provide some statistics as well. We also present our thoughts on future developments in the area of digital slide scanning.

A restaining method to restore faded fluorescence in tissue specimens for quantitative confocal microscopy.

The aim of this study was to develop a procedure to remove the TO-PRO-3 fluorescent dye from tissue sections and restain with TO-PRO-3, still allowing calculation of DNA content and distribution by confocal laser scanning microscopy (CLSM). This would allow repeated measurements on the same tissue sections and prevents loss of tissue material from valuable clinical samples. Thick sections (14 microm) were cut from a paraffin block of adrenal tissue and stained using TO-PRO-3. Image stacks were acquired by CLSM. Thereafter, three destaining approaches were tested based on incubation, at different temperatures and durations, in the medium that is normally used to dissolve TO-PRO-3. The same areas were imaged again to measure residual fluorescence and were subsequently restained and imaged again. The intensity of the images acquired after initial staining and restaining were compared. A number of 3-D (texture) features computed after segmentation of nuclei were compared as well. The best destaining result was obtained by incubation of sections at 37 degrees C in preheated medium twice for 20 min. On average, the 3-D feature values were comparable with those after initial staining. With the described protocol it is possible to remove TO-PRO-3 fluorescence from tissue sections that can successfully be restained with minimal influence on fluorescence intensity and nuclear chromatin distribution.

Discrimination between benign and malignant prostate tissue using chromatin texture analysis in 3-D by confocal laser scanning microscopy.

BACKGROUND: Analysis of chromatin texture may improve both the diagnosis and the assessment of the prognosis of prostate cancer. Confocal laser scanning microscopy (CLSM) allows performing measurements in nuclei reconstructed in 3-D. The aim of this study was to evaluate the clinical usefulness of 3-D texture analysis of prostate tissue. METHODS: Image stacks of eight prostate cancer sections were obtained by CLSM of both benign and malignant areas. Texture feature values were computed for individual nuclei. The discriminative power of the texture features was established by receiver operating characteristic (ROC) analysis and linear discriminant analysis (LDA). RESULTS: Texture features were identified that could discriminate between benign and malignant nuclei. LDA correctly classified 89% of the nuclei of the pooled set of benign and malignant nuclei. CONCLUSIONS: 3-D nuclear texture features allow discrimination of most benign and malignant prostate nuclei. We estimate that the classification rates can be increased by improving the image quality.

Development of 3D chromatin texture analysis using confocal laser scanning microscopy.

INTRODUCTION: Analysis of nuclear texture features as a measure of nuclear chromatin changes has been proven to be useful when measured on thin (5-6 microm) tissue sections using conventional 2D bright field microscopy. The drawback of this approach is that most nuclei are not intact because of those thin sections. Confocal laser scanning microscopy (CLSM) allows measurements of texture in 3D reconstructed nuclei. The aim of this study was to develop 3D texture features that quantitatively describe changes in chromatin architecture associated with malignancy using CLSM images. METHODS: Thirty-five features thoughtfully chosen from 4 categories of 3D texture features (discrete texture features, Markovian features, fractal features, grey value distribution features) were selected and tested for invariance properties (rotation and scaling) using artificial images with a known grey value distribution. The discriminative power of the 3D texture features was tested on artificially constructed benign and malignant 3D nuclei with increasing nucleolar size and advancing chromatin margination towards the periphery of the nucleus. As a clinical proof of principle, the discriminative power of the texture features was assessed on 10 benign and 10 malignant human prostate nuclei, evaluating also whether there was more texture information in 3D whole nuclei compared to a single 2D plane from the middle of the nucleus. RESULTS: All texture features showed the expected invariance properties. Almost all features were sensitive to variations in the nucleolar size and to the degree of margination of chromatin. Fourteen texture features from different categories had high discriminative power for separating the benign and malignant nuclei. The discrete texture features performed less than expected. There was more information on nuclear texture in 3D than in 2D. CONCLUSION: A set of 35 3D nuclear texture features was used successfully to assess nuclear chromatin patterns in 3D images obtained by confocal laser scanning microscopy, and as a proof of principle we showed that these features may be clinically useful for analysis of prostate neoplasia.

Implementation of accurate and fast DNA cytometry by confocal microscopy in 3D.

BACKGROUND: DNA cytometry is a powerful method for measuring genomic instability. Standard approaches that measure DNA content of isolated cells may induce selection bias and do not allow interpretation of genomic instability in the context of the tissue. Confocal Laser Scanning Microscopy (CLSM) provides the opportunity to perform 3D DNA content measurements on intact cells in thick histological sections. Because the technique is technically challenging and time consuming, only a small number of usually manually selected nuclei were analyzed in different studies, not allowing wide clinical evaluation. The aim of this study was to describe the conditions for accurate and fast 3D CLSM cytometry with a minimum of user interaction to arrive at sufficient throughput for pilot clinical applications. METHODS: Nuclear DNA was stained in 14 microm thick tissue sections of normal liver and adrenal stained with either YOYO-1 iodide or TO-PRO-3 iodide. Different pre-treatment strategies were evaluated: boiling in citrate buffer (pH 6.0) followed by RNase application for 1 or 18 hours, or hydrolysis. The image stacks obtained with CLSM at microscope magnifications of x40 or x100 were analyzed off-line using in-house developed software for semi-automated 3D fluorescence quantitation. To avoid sectioned nuclei, the top and bottom of the stacks were identified from ZX and YZ projections. As a measure of histogram quality, the coefficient of variation (CV) of the diploid peak was assessed. RESULTS: The lowest CV (10.3%) was achieved with a protocol without boiling, with 1 hour RNase treatment and TO-PRO-3 iodide staining, and a final image recording at x60 or x100 magnifications. A sample size of 300 nuclei was generally achievable. By filtering the set of automatically segmented nuclei based on volume, size and shape, followed by interactive removal of the few remaining faulty objects, a single measurement was completely analyzed in approximately 3 hours. CONCLUSIONS: The described methodology allows to obtain a largely unbiased sample of nuclei in thick tissue sections using 3D DNA cytometry by confocal laser scanning microscopy within an acceptable time frame for pilot clinical applications, and with a CV small enough to resolve smaller near diploid stemlines. This provides a suitable method for 3D DNA ploidy assessment of selected rare cells based on morphologic characteristics and of clinical samples that are too small to prepare adequate cell suspensions.