Akira Okumura

Inter-hospital PACS designed for teleradiology and teleconference using a secured high-speed network

We developed a tele-radiology and tele-conference system between our related hospitals. This system consisted of the image database, the WWW server, WWW browsers, high resolution CRT displays, the videoconference system and an asynchronous transfer mode (ATM) network. In advance X-ray images were stored into the Image Save And Carry magneto- optical (MO) disks, then images on the MO were transferred to the image database. The image database was created from MO disks. Total amount of images reached 100 GB and the number of the image was 65,000. The ATM network connected the hospitals each other. The ATM network device provided the permanent virtual circuit function. The transmission speed was from 6Mbit/second to 155 Mbit/second. The client station consisted of the WWW browser and the super high definition CRT display which had the 2k X 2k full color frame memory and 54 X 54 cm square display area. The result of the query was transformed to a hypertext markup language. Then a browser on a client machine displayed the result. The server could retrieve some images in about ten seconds and transmit an image from a server to a client in 2-10 seconds that depend on the network speed. At the tele- radiology, both terminals could display same image and physicians could talk each other by the videoconference system. We solved the security problems by the PVC methods and the on time password device. The ATM network showed the high transmission performance and good security. Physicians were able to use this system with no special training and this system brought us an effective utilization of the image.

Performance analysis of compression techniques for pathological microscopic images

Telepathology is aiming at pathological diagnoses based on microscopic images of cell samples through broadband networks. The number of pixels in pathological microscopic (PM) images is said to be approximately 4 to 6 million. In this paper, digital PM images are made without films using a super high definition (SHD) image prototype system, which has more than double the number of pixels and frame frequency than those of HDTV images. First, color distribution and a spatial spectrum are analyzed in order to estimate compression characteristics of the images. In addition, the lossless and lossy JPEG coding characteristics are investigated. In the lossless compression, the PM images have compression ratios which are very close to 1, while the general images have compression ratios around 2. The PM image compression ratios in the lossy JPEG coding, where the L*a*b* color difference is less than 2 to 3, are found to almost equal those of the lossless JPEG (Joint Photographic Coding Experts Group) using arithmetic coding. The PM image coding performance in the lossy JPEG coding is also found to be inferior to that of general images including still life images, portraits, and landscapes.

Development of a networked four-million-pixel pathological and radiological digital image presentation system and its application to medical conferences

The wide spread of digital technology in the medical field has led to a demand for the high-quality, high-speed, and user-friendly digital image presentation system in the daily medical conferences. To fulfill this demand, we developed a presentation system for radiological and pathological images. It is composed of a super-high-definition (SHD) imaging system, a radiological image database (R-DB), a pathological image database (P-DB), and the network interconnecting these three. The R-DB consists of a 270GB RAID, a database server workstation, and a film digitizer. The P-DB includes an optical microscope, a four-million-pixel digital camera, a 90GB RAID, and a database server workstation. A 100Mbps Ethernet LAN interconnects all the sub-systems. The Web-based system operation software was developed for easy operation. We installed the whole system in NTT East Kanto Hospital to evaluate it in the weekly case conferences. The SHD system could display digital full-color images of 2048 x 2048 pixels on a 28-inch CRT monitor. The doctors evaluated the image quality and size, and found them applicable to the actual medical diagnosis. They also appreciated short image switching time that contributed to smooth presentation. Thus, we confirmed that its characteristics met the requirements.

Quasi-real-time telemedical checkup system for x-ray examination of UGI tract based on high-speed network

We constructed a high-speed medical information network testbed, which is one of the largest testbeds in Japan, and applied it to practical medical checkups for the first time. The constructed testbed, which we call IMPACT, consists of a Super-High Definition Imaging system, a video conferencing system, a remote database system, and a 6 - 135 Mbps ATM network. The interconnected facilities include the School of Medicine in Keio University, a companys clinic, and an NTT R&D center, all in and around Tokyo. We applied IMPACT to the mass screening of the upper gastrointestinal (UGI) tract at the clinic. All 5419 radiographic images acquired at them clinic for 523 employees were digitized (2048 X 1698 X 12 bits) and transferred to a remote database in NTT. We then picked up about 50 images from five patients and sent them to nine radiological specialists at Keio University. The processing, which includes film digitization, image data transfer, and database registration, took 574 seconds per patient in average. The average reading time at Keio Univ. was 207 seconds. The overall processing time was estimated to be 781 seconds per patient. From these experimental results, we conclude that quasi-real time tele-medical checkups are possible with our prototype system.

Telepathology system for microscopic images utilizing superhigh-definition imaging system over B-ISDN

It has been recognized early on that digitizing medical information makes diagnostic technology more advanced and efficient. In order to convert image information, which comprises the majority of all medical information, into digital data, various technologies including those for input, processing, transmission storage, and display need to develop at roughly the same pace. To data, there have been few cases where this has been done. However, recent major advances in high-resolution image input/output, image encoding, super-fast transmission, high-capacity storage, and other technologies have intensified the drive towards digitizing and networking all medical information. This paper will show that the spread of super-high-speed networks capable of transmitting large amounts of data in a short time is indispensable for accurate medical diagnosis, and that this will make it possible to realize an integrated medical information syste. A target application for the medical image diagnosis of the Super High Definition imags being developed by the authors of this paper is telepathology, which particularly demands high-quality images. In this paper, we will study, among other things, the concrete issues crucial to building and networking a digital system and the approach to resolving such issues. We will also report on the building of our experimental system that fulfills such demands as well as discuss a pathological microscopic image transmission system with image quality that will not lower diagnostic accuracy and fast response and good operability that will not make diagnosticians feel impatient. Finally, we will discuss a test in which we remotely operated a microscope over an ATM line to prove that it is possible to capture, transmit, and display a still super-high-definition digital image with a resolution of 2,048 X 2,048 pixels in about 5 seconds.

Signal characteristics and compression performance evaluation of digital pathological microscopic images with up to SHD resolution

Digitizing high-quality microscopic images and developing input/output technology for displaying those results is critical to tele-pathology in which pathological microscopic images are transferred to remote locations where they are diagnosed by specialists. This paper will discuss the results achieved by directly digitizing pathological microscopic images at a 2k by 2k resolution, and then using a super high definition imaging system to analyze their signals and evaluate compression performance. We will start off by digitizing samples that a pathologist will actually use in making a diagnosis, and then analyze their color distribution and spatial frequencies characteristics by comparing them to general images. This will make it apparent that such pathological images characteristically contain high spatial frequency in their chrominance components. We will also discuss the evaluation results of color differences for L.a.b space and compression ratios achieved when using JPEG to encode pathological images. We will also present a subjective evaluation of the influence sub- sampling of chrominance components has on image quality.

Nearly lossless compression for very high quality color images

Existing image coding systems can be categorized into lossy and lossless coding methods. Nearly lossless compression, which attains both higher compression performance than lossless compression and higher image quality than lossy compression, is required in the applications such as medicine or printing. This paper proposes a nearly lossless coding method in which distortion is restricted to within a predetermined range. RGB input signals are transformed into one luminance and two chrominance components, and the magnitudes of these luminance and chrominance components are adjusted in the encoder so that the reconstructed RGB signals have minimum distortion after inverse color transformation in the decoder. The prediction residual signals of these level-adjusted components are entropy coded. As a result, the reconstructed RGB signals have coding distortion levels of only plus one or minus one, and this restricted distortion never accumulates even if encoder/decoder couples are connected in tandem because all encoders and decoders operate in synchronization.