Among the diverse technologies required to make medical information resources more accessible are those having to do with efficient storage, improved image quality, application-specific man-machine interfaces, pattern recognition for feature extraction, and efficient transmission.
In the research agenda for document imaging, the following areas are of interest: compression of two-tone images; OCR and image enhancement preprocessing to make it more reliable, such as automated border removal, skew detection and page orientation detection; user interfaces allowing easy manipulation of the images; efficient page description and markup languages; scaling and scale-to-gray algorithms for image quality improvement.
In the document imaging projects, a key element is the scanning that is needed to create a suitable image store. In the process of scanning, SP stages are: automated border (page edge effects) detection and removal, automated page orientation detection, automated skew detection. All of these not only aid the capture of the document images with high visual quality level, but also provide the quality needed for subsequent processing such as accurate optical character recognition. Also, in the display of the document images, other useful processing includes: subsampling scaling (from the scanned 300 dpi image to VGA or SVGA resolution), and scale-to-gray to increase readability by shading the image in suitable gray levels rather than black or white. Ordinary scaling replaces groups of pixels by a single pixel, either black or white, while scale-to-gray replaces them with pixels of intermediate gray values. Ordinary scaling allows fast compression via runlength coding but the characters often appear broken, and readability could be impaired. Scale-to-gray increases readability by shading the character edges, but image compression is slow.
In the case of digitized x-rays and color originals, the following areas are of particular interest: compression of multiple gray level images; design and optimum selection of quantization tables for the DCT process within JPEG; automated and user-directed segmentation based on pattern recognition for feature extraction by mathematical morphology techniques; noise removal by morphologic operators; contrast enhancement by histogram equalization; image classification using statistical classification algorithms. Any algorithm that claims enhancement or useful segmentation must carefully be validated to demonstrate that the enhancement or segmentation are indeed useful to the user radiologist or other MD.
Of particular concern to the ongoing development of the NII is that transmission over the Internet of digitized images is relatively slow, especially for large files such as those resulting from the scanning of x-rays. For example, cervical and lumbar x-rays when scanned result in files approximately 5 and 10 MB respectively. This motivates both improved means of lossless compression, for speeding transmission of exact representations, and improved means for validating lossy compressed images in specific applications. Published research suggests that lossy compression, with reproduction visually indistinguishable from original images, can yield a ratios conservatively estimated at 10:1, five times that of typical lossless compression algorithms. This is clearly applicable in some areas such as recall, education, and research, but it is a matter of controversy in critical applications such as clinical diagnosis. Hence it is important both to improve the quality of lossy compression algorithms and to develop, with the help of engineers, radiologists, and biostatisticians, careful validation procedures to quantify the diagnostic quality and utility of an image.
One possibility for speeding lossless compression is the use of multisocket transmission methods based on the observation that during a conventional single socket linkup the transaction overhead for TCP/IP limits the effective rate at which data can be transferred. However, if the image to be transmitted were to be sectioned, each section assigned a pair of sockets (at the transmission and receiving ends), and the sections transmitted and reconstructed at the other end, the effective transfer rate could be higher. Preliminary tests have shown a three-fold increase in transmission speed for about 20 socket pairs.
Another element in access is the increasingly distributed nature of medical information at many points on the Internet. There is also a trend toward multimedia workstations that enable a user to view, manipulate and seamlessly move among different data types on the desktop. Both these trends motivate intelligent gateways to the appropriate information sources, the extraction of the query-driven data, and reconstruction of the data at the client workstation for presentation to the user for viewing and to possibly do further processing and analysis.