Digital image acquisition using a consumer-type digital camera in the anatomic pathology setting

Imaging is central to anatomic pathology. The captured images are used for documentation, archiving, teaching, and publication. The advent of low-cost, consumer-type, high-end digital cameras has provided a convenient, easy-to-use alternative for routine image acquisition. The various applications for digital image acquisition in anatomic pathology include, among others, digitizing conventional photographs, digital gross photography and digital macrophotography, digitizing radiographic images, and digital photomicrography. This article reviews digital image acquisition in the anatomic pathology setting using a consumer-type digital camera. The camera type chosen as an example for the discussion was selected for its popularity and wide use among pathologists and for its potential to function as a sole image input device in all applications combined. Techniques and accessories to further increase the functionality of the camera and help overcome some of the commonly encountered problems in some applications are described.     

Digital image capture applied to electron microscopic examination of renal biopsies

AIMS: Digital image capture systems to replace traditional film cameras are now available for most electron microscopes. For a diagnostic electron microscope laboratory the test of this new technology is in its application to the examination of renal biopsy specimens. METHODS: A long-term comparison is made between the work procedures employed with conventional film photography versus digital image capture in routine renal biopsy examination. RESULTS: Digital image capture has lead to a reduction in turnaround time and allows for more images to be collected per case, providing more diagnostic information. Ultrastructural measurement is made easier, accuracy of patient records is improved and electronic communication of results is more accessible. Significant operational cost savings are also possible. CONCLUSION: A quicker and more comprehensive assessment of renal biopsy specimens is possible using digital image capture for ultrastructural examination.     

Cost-effective handling of digital medical images in the telemedicine environment

BACKGROUND: This paper concentrates on strategies for less costly handling of medical images. Aspects of digitization using conventional digital cameras, lossy compression with good diagnostic quality, and visualization through less costly monitors are discussed. METHOD: For digitization of film-based media, subjective evaluation of the suitability of digital cameras as an alternative to the digitizer was undertaken. To save on storage, bandwidth and transmission time, the acceptable degree of compression with diagnostically no loss of important data was studied through randomized double-blind tests of the subjective image quality when compression noise was kept lower than the inherent noise. A diagnostic experiment was undertaken to evaluate normal low cost computer monitors as viable viewing displays for clinicians. RESULTS: The results show that conventional digital camera images of X-ray images were diagnostically similar to the expensive digitizer. Lossy compression, when used moderately with the imaging noise to compression noise ratio (ICR) greater than four, can bring about image improvement with better diagnostic quality than the original image. Statistical analysis shows that there is no diagnostic difference between expensive high quality monitors and conventional computer monitors. CONCLUSION: The results presented show good potential in implementing the proposed strategies to promote widespread cost-effective telemedicine and digital medical environments.     

Use of a digital film scanner to enhance low-power bright field photomicrography

 Low-power bright field photomicrographs often suffer from insufficient sharpness, uneven illumination, and colour hues. Using a film scanner, commercially available and designed for digitizing 35-mm transparencies, we directly scanned microscopic slides that carried dye-labelled and stained sections. The digital images covered a field of up to 24×36 mm and revealed excellent sharpness, absolutely even illumination and superior colour reproduction as compared to conventional photomicrographs taken with binoculars, macro lenses, or microscopes. As the method requires neither specialized instrumentation nor expert knowledge of photomicrographic techniques, it reduces costs and saves time. The high-quality digital survey micrographs can easily be used for image processing, image analysis and morphometry. Thus, this new method is valuable not only for pathology, embryology, histochemistry, and the neurosciences, but also for the exchange of low-power micrographs via the internet and for computer media that are increasingly used in medical education. Accepted: 17 April 1998     

Digital processing of microradiographic and fluorochromic images from bone biopsy

Bone biopsy is an essential technique for the diagnosis of metabolic bone disease and the skeletal response to remedial therapeutic maneuvers. Among many approaches in analyzing the biopsy specimen, the imaging technique offers the greatest potential. The objective of this paper is to describe the methodologies developed for digital processing of microradiographic and fluorochromic images from bone biopsy. This procedure requires a microscope with conventional and ultraviolet illuminations, a vidicon camera with three color filters, a general purpose image processing system with three image memories, a digital computer with some specially tailored software programs. A good specimen preparation from bone biopsy is a prerequisite in assuring the success of the method. The methodology for processing the microradiographs is based on a completely developed procedure of black and white image processing. Production run is in progress. The methodology for processing the fluorochromic images is based on true color imaging, although the procedure is still preliminary, early results obtained so far are promising.     

An Image Analysis Workstation Designed for Multiple Users: Application of Quantitative Digital Imaging Techniques to Electron Microscopy

The purpose of the present study is to describe the setup of an image analysis workstation designed for multiple users, and to show the application of digital imaging techniques to the analysis of electron microscopic images. The image analysis system consists of a conventional light microscope mounted on a table-top, vibration-free platform, a light box for viewing negatives, two separate video cameras, a switch box, a video monitor, a digitizing tablet, a computer, and mor-phometric software packages. The system can quantitate the amount that each of the 256 gray levels contributes to the image, perform morpho-metric analysis (eg, shape and size) on individual gray level-defined subimages, and perform statistical analysis. Each operator has access to his or her own data and program setups through the use of 21.4-Mb removable Bernoulli cartridges. This setup for multiple users prevents the cluttering of the hard drive of the computer and avoids the possibility of accidentally removing the stored data of another user. The quantitative capabilities of the digital imaging system is demonstrated using an image of a normal lymphocyte and an apoptotic cell (ie, a cell which has undergone programmed cell death), both captured on the same electron microscopic negative. A comparison of the histograms of nuclear densities determined for these two cells reveals subtleties in gray level distribution not appreciated by the naked eye.     

An image analysis workstation designed for multiple users: application of quantitative digital imaging techniques to electron microscopy.

The purpose of the present study is to describe the setup of an image analysis workstation designed for multiple users, and to show the application of digital imaging techniques to the analysis of electron microscopic images. The image analysis system consists of a conventional light microscope mounted on a table-top, vibration-free platform, a light box for viewing negatives, two separate video cameras, a switch box, a video monitor, a digitizing tablet, a computer, and morphometric software packages. The system can quantitate the amount that each of the 256 gray levels contributes to the image, perform morphometric analysis (eg, shape and size) on individual gray level-defined subimages, and perform statistical analysis. Each operator has access to his or her own data and program setups through the use of 21.4-Mb removable Bernoulli cartridges. This setup for multiple users prevents the cluttering of the hard drive of the computer and avoids the possibility of accidentally removing the stored data of another user. The quantitative capabilities of the digital imaging system is demonstrated using an image of a normal lymphocyte and an apoptotic cell (ie, a cell which has undergone programmed cell death), both captured on the same electron microscopic negative. A comparison of the histograms of nuclear densities determined for these two cells reveals subtleties in gray level distribution not appreciated by the naked eye.     

Comparison of radiographic image quality from four digitization devices as viewed on computer monitors

The objective of this study was to compare the quality of radiographic images digitized from commercial-grade and consumer-grade digital cameras and scanners as viewed on computer monitor. Radiographic images were digitized from hardcopy film using a commercial-grade laser scanner, a consumer-grade desktop flatbed scanner, a commercial-grade digital camera, and a consumer-grade digital camera. The quality of images without and with grayscale histogram adjustment was evaluated subjectively by 10 board-certified radiologists. Optical density response was evaluated objectively using a grayscale test pattern. There was no significant difference in subjective quality among images digitized with the commercial scanner, consumer scanner, and commercial camera. The quality of images digitized with the consumer camera was lower than the other 3. Objective tests showed the commercial scanner to have the most linear optical density response. For the purpose of viewing images on a computer monitor, a consumer-grade desktop scanner can produce images of similar quality to those produced by more expensive laser commercial-grade scanners and digital cameras and provides cost-efficient means to digitize radiographic plain films. A consumer-grade camera may not be optimal for use in this setting.     

The use of digital images in pathology

Digital images are routinely used by the publishing industry, but most diagnostic pathologists are unfamiliar with the technology and its possibilities. This review aims to explain the basic principles of digital image acquisition, storage, manipulation and use, and the possibilities provided not only in research, but also in teaching and in routine diagnostic pathology. Images of natural objects are usually expressed digitally as ‘bitmaps’—rectilinear arrays of small dots. The size of each dot can vary, but so can its information content in terms, for example, of colour, greyscale or opacity. Various file formats and compression algorithms are available. Video cameras connected to microscopes are familiar to most pathologists; video images can be converted directly to a digital form by a suitably equipped computer. Digital cameras and scanners are alternative acquisition tools of relevance to pathologists. Once acquired, a digital image can easily be subjected to the digital equivalent of any conventional darkroom manipulation and modern software allows much more flexibility, to such an extent that a new tool for scientific fraud has been created. For research, image enhancement and analysis is an increasingly powerful and affordable tool. Morphometric measurements are, after many predictions, at last beginning to be part of the toolkit of the diagnostic pathologist. In teaching, the potential to create dramatic yet informative presentations is demonstrated daily by the publishing industry; such methods are readily applicable to the classroom. The combination of digital images and the Internet raises many possibilities; for example, instead of seeking one expert diagnostic opinion, one could simultaneously seek the opinion of many, all around the globe. It is inevitable that in the coming years the use of digital images will spread from the laboratory to the medical curriculum and to the whole of diagnostic pathology. © 1997 John Wiley & Sons, Ltd.     

Comparison of radiographic image quality from four digitization devices as viewed on computer monitors

The objective of this study was to compare the quality of radiographic images digitized from commercial-grade and consumer-grade digital cameras and scanners as viewed on computer monitor. Radiographic images were digitized from hardcopy film using a commercial-grade laser scanner, a consumer-grade desktop flatbed scanner, a commercial-grade digital camera, and a consumer-grade digital camera. The quality of images without and with grayscale histogram adjustment was evaluated subjectively by 10 board-certified radiologists. Optical density response was evaluated objectively using a grayscale test pattern. There was no significant difference in subjective quality among images digitized with the commercial scanner, consumer scanner, and commercial camera. The quality of images digitized with the consumer camera was lower than the other 3. Objective tests showed the commercial scanner to have the most linear optical density response. For the purpose of viewing images on a computer monitor, a consumer-grade desktop scanner can produce images of similar quality to those produced by more expensive laser commercial-grade scanners and digital cameras and provides cost-efficient means to digitize radiographic plain films. A consumer-grade camera may not be optimal for use in this setting.     

Correction of uneven illumination (vignetting) in digital microscopy images

BACKGROUND: Many digital microscopy images suffer from poor illumination at the peripheries (vignetting), often attributable to factors related to the light path between the camera and the microscope. A commonly used method for correcting this has been to use the illumination of an empty field as a correction filter (white shading correction). AIMS: To develop an alternative shading correction method that does not require this additional image. METHODS:/Results: This report outlines an alternative shading correction method that is based upon the intrinsic properties of the image, which are revealed through Gaussian smoothing. The technique can be implemented within Adobe Photoshop or other graphics editing software and works well with both haematoxylin and eosin and immunohistochemical images. CONCLUSIONS: This technique provides an effective means of optimising digital microscopy image appearances for printing, image analysis, or telepathology.     

Critical comparison of 31 commercially available digital slide systems in pathology

Advances in new technologies for complete slide digitization in pathology have allowed the appearance of a wide spectrum of technologic solutions for whole-slide scanning, which have been classified into motorized microscopes and scanners. This article describes technical aspects of 31 different digital microscopy systems. The most relevant characteristics of the scanning devices are described, including the cameras used, the speed of digitization, and the image quality. Other aspects, such as the file format, the compression techniques, and the solutions for visualization of digital slides, (including diagnosis-aided tools) are also considered. Most of the systems evaluated allow a high-resolution digitization of the whole slide within about 1 hour using a x40 objective. The image quality of the current virtual microscopy systems is suitable for clinical, educational, and research purposes. The efficient use of digital microscopy by means of image analysis systems can offer important benefits to pathology departments.     

Acquiring images with very high resolution using a composing method

Composing microscopic images of very high resolution from several parts posed some problems. One of them was the necessity to adjust the focusing level when moving from one part to another. Re-focusing lead to problems with joining the image parts, which did not correspond exactly, and the area of image fusion was noticeable. A computer program was developed to overcome these problems. Our program worked with all the image parts together to find their optimal order for image fusion. Individual image parts were joined using a steep gradient running along a randomly generated curve. This method gave good results even in images with background or holes in the tissue. The method of composing large images from individual parts was used for digitizing the skin lymphoma collection of the Institute of Dermatology, University Hospital, Zürich. This collection of digital images is a part of the 6th version of Hypertext atlas of Dermatopathology at www.muni.cz/atlases.     

多信息融合的彩色细胞图像分割方法

本文就从病理切片的彩色图像中提取细胞核的有关方法作了研究,提出了有效的分割方法的策略。该方法以数学形态学为主要工具,可以利用细胞的多个特征,较好地解决了病理显微图像背景杂,光照不均及粘连团聚现象等因素给分割带来的困难。     

A computer driven photoscanner for medical imaging

A novel and versatile instrument for producing high quality monochrome and colour hard-copy of medical images from an array of digital information is described. Images are produced on standard photographic print paper mounted on the bed of a conventional X-Y plotter by scanning a time-modulated light source over the paper using a computer driven raster. A matrix board gives control of both greyscale and colour attribution. Examples of NMR images produced by the system are presented. A refinement of the technique which allows two variables to be displayed on one image is also described.     

通过屏幕检测获取数字化X射线照片密度的方法

目的找到一种在数字化X射线照片打印前预测照片密度的方法,以实现更好的照片质量控制,避免在照片密度调整过程中不必要的浪费。方法通过编写计算机程序检测屏幕上指定位置的输出值。采用适当条件对铝梯进行投照,投照后在工作站上调整图像。使得铝梯各阶对比良好,保存并打印图像。在屏幕上由低到高对铝梯各阶进行采样,获取屏幕上各点输出值。使用密度计对打印后的照片进行测量,获得照片上铝梯各阶对应的照片密度。绘制密度曲线,再与相应的照片密度相关联。结果通过上述方法对100张照片进行检测．将对应点预测值和密度计实际测量值进行比较,误差小于5％。结论该方法是对数字化X射线照片密度预测的一种新的尝试．通过一个小程序跨越了从影像的屏幕显示到照片打印之间的多个设备和程序调试环节．直接将屏幕上的输出值和打印后的照片密度进行关联。通过检测屏幕输出值获得照片密度的预测值。     

Color Error in the Digital Camera Image Capture Process

The color error in images taken by digital cameras is evaluated with respect to its sensitivity to the image capture conditions. A parametric study was conducted to investigate the dependence of image color error on camera technology, illumination spectra, and lighting uniformity. The measurement conditions were selected to simulate the variation that might be expected in typical telemedicine situations. Substantial color errors were observed, depending on the measurement conditions. Several image post-processing methods were also investigated for their effectiveness in reducing the color errors. The results of this study quantify the level of color error that may occur in the digital camera image capture process, and provide guidance for improving the color accuracy through appropriate changes in that process and in post-processing.     

Kinematic analysis of human walking gait using digital image processing

A system using digital image processing techniques for kinematic analysis of human gait has been developed. The system is cheap, easy to use, automated and provides useful detailed quantitative information to the medical profession. Passive markers comprising black annuli on white card are placed on the anatomical landmarks of the subject. Digital images at the standard television rate of 25 per second are acquired of the subject walking past a white background. The images are obtained, stored and processed using standard commercially available hardware, i.e. video camera, video recorder, digital framestore and an IBM PC. Using a single-threshold grey level, all the images are thresholded to produce binary images. An automatic routine then uses a set of pattern recognition algorithms to locate accurately and consistently the markers in each image. The positions of the markers are analysed to determine to which anatomical landmark they correspond, and thus a stick diagram for each image is obtained. There is also a facility where the positions of the markers may be entered manually and errors corrected. The results may be presented in a variety of ways: stick diagram animation, sagittal displacement graphs, flexion diagrams and gait parameters.     

The value of scatter removal by a grid in full field digital mammography

Our objective in this study was to investigate the usefulness of an anti-scatter grid in digital mammography using a contrast detail phantom. The mammography system we investigated was a GE Senographe 2000D. We carried out phantom measurements under various conditions with and without using the anti-scatter grid. A new version of the CDMAM phantom (version 3.4) was used. This phantom consists of a matrix of square cells with disks of varying size and contrast. For given exposure conditions detectability of these disks can be determined and used for construction of contrast detail curves. Previously, a computer program was developed at our institute that performs a fully automatic analysis of the phantom recordings using the ideal observer model. Breast thickness was simulated by a homogeneous layer of PMMA in the range of 1 to 7 cm. Series of images were recorded for different KeV and target-filter combinations depending on the simulated thickness. The dose was kept constant for each thickness with and without using a grid. It appeared that image quality improved for simulated breast thickness below 5 cm when the grid was removed. In the range from 5 to 7 cm contrast detail curves obtained with or without a grid were similar. Results suggest that for compressed breast thickness in the range of 1 to 7 cm a grid might not be needed in the digital mammography system we investigated. Below 5 cm, omitting the grid may allow lower dose to the patient without losing image quality.     

An observer study comparing spot imaging regions selected by radiologists and a computer for an automated stereo spot mammography technique

We are developing an automated stereo spot mammography technique for improved imaging of suspicious dense regions within digital mammograms. The technique entails the acquisition of a full-field digital mammogram, automated detection of a suspicious dense region within that mammogram by a computer aided detection (CAD) program, and acquisition of a stereo pair of images with automated collimation to the suspicious region. The latter stereo spot image is obtained within seconds of the original full-field mammogram, without releasing the compression paddle. The spot image is viewed on a stereo video display. A critical element of this technique is the automated detection of suspicious regions for spot imaging. We performed an observer study to compare the suspicious regions selected by radiologists with those selected by a CAD program developed at the University of Michigan. True regions of interest (TROIs) were separately determined by one of the radiologists who reviewed the original mammograms, biopsy images, and histology results. We compared the radiologist and computer-selected regions of interest (ROIs) to the TROIs. Both the radiologists and the computer were allowed to select up to 3 regions in each of 200 images (mixture of 100 CC and 100 MLO views). We computed overlap indices (the overlap index is defined as the ratio of the area of intersection to the area of interest) to quantify the agreement between the selected regions in each image. The averages of the largest overlap indices per image for the 5 radiologist-to-computer comparisons were directly related to the average number of regions per image traced by the radiologists (about 50% for 1 region/image, 84% for 2 regions/image and 96% for 3 regions/image). The average of the overlap indices with all of the TROIs was 73% for CAD and 76.8% +/- 10.0% for the radiologists. This study indicates that the CAD determined ROIs could potentially be useful for a screening technique that includes stereo spot mammography imaging.