George W. Seeley, Ph.D.*t. Kevin MCNeiII, M.S.t. William J. Dallas, ph.d.*t. Past

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1 RathoGphlcsdexten Displays in radiology: Curnutafiveindoxterms: Past, present, a nd future George W. Seeley, Ph.D.*t Kevin MCNeiII, M.S.t William J. Dallas, ph.d.*t Past. Almost immediately after Wilhelm Konrad Roentgen announced the discovery of the x ray in 1895, imaging techniques based on the discovery were implemented all over the world. In medicine, it was quickly noted that the possibility of noninvasively viewing the inside of the human body would have tremendous impact on health care. In the United States, the first medical use of the x ray was on February 3, 1896 at Dartmouth College. Figure 1 is a photograph of that historic. occasion. In this case a photographic plate enclosed in a light proof plate holder was used. The image was taken by Edwin Brandt Frost who was a professor of astronomy at Dartmouth. He later recalled that the. image was satisfactory after a 20 minute exposure and showed the fracture very clearly (1). Even Thomas A. Edison became interested in developing equipment based on the discovery. Figure 2 shows him examining a hand through a fluoroscope built in his laboratory in 189o. From the Department of Radiology () and the Optical Sciences Center (t), University of Arizona. Tucson. Work supported in part by the Toshiba Corporation. Address reprint requests to G.W. Seeley. Ph.D.. Department of Radiology, Arizona Health Sciences Center, University of Arizona, Tucson, AZ Figure 1 This plate depicts the first use of x rays for diagnostic purposes in the United States. It took place at Dartmouth College on February 3, Volume 7, Number #{243}, Monograph #{149}November 1987 #{149}RadioGraphics 1261

2 Perception and display in diagnostic imaging Seeiey et al. Figure 2 Again in 1896 Thomas A. Edison is seen viewing a hand of one of his employees using an x-ray device developed in his laboratory. The photographic and fluoroscopic processes first utilized in those early imagings are still being employed in one form or another, and will continue to be used into the foreseeable future. Static photographic film images displayed on a light box have become the main means of displaying radiographic images. However, many other types of displays have also been used. Moving images are utilized in angiography (film) and gastrointestinal (video tape) imaging. Color displays are used in nuclear medicine and stereoscopic imaging was used in fluoroscopy. Paper has also been used in the past (nuclear medicine) to capture an image and is seeing a resurgence today as a low cost storage medium. Viewing images on a CRT has become more prevalant over the years, especially with the introduction of nuclear medicine, ultrasound, CT and MRI. Since the discovery of the x ray, the medical profession has found many new ways to image the inside of the human body, but the main means of viewing the resulting images has remained basically the same. Figure 3 depicts this process. A fixed, static, film image is backlit by a lightbox using Iwo 17 inch fluorescent bulbs. Figure 4 depicts the process of diagnosing an image using this display system. The image is viewed on the light box and the radiologist uses information about the patient supplied with the images to make a diagnosis. Before making that diagnosis, he may also call on another colleague for consultation if he feels the need for another opinion, or occasionally he may consult reference books dealing with different diseases RadioGraphics #{149}November 1987 #{149}Volume 7, Number 6, Monograph

3 Seeiey et al. Perception and display in diagnostic imaging I Consult F- ) RadIologIst I.. Information Patient I Review :: Dx Past/Present/Future Figure 3 A typical reading room, demonstrating the standard method of displaying radiographs at this time. Figure 4 A schematic diagram of the process of diagnosis. The film image is viewed and the radiologist, using all the pertinent information available, makes his diagnosis. Present The computer revolution in society in general and in medicine specifically has resulted in a demand for the development of more versatile display systems. One of the main requirements of these new display systems is that they be able to exhibit, equally well, all the present image types and new ones that might be developed in the future. Another requirement is that they be capable of integration into a picture archiving and communication (PAC) system. Figure 5 is a graphic representation of a PAC system. The intent of PAC systems is not only to speed up the reading of images and to reduce costs, but also to increase the diagnostic accuracy of the radiologist. Images would be acquired either digitally or by digitizing film, would be shipped on the network to or from the archive, would then be reviewed on an electronic viewing console. All information relevant to the patient would also be accessible through the hospital information system (HIS) and radiology information system (RIS). The advantages of such a system in radiology are quite numerous. One of the main advantages is to speed up the dignostic process by eliminating time-consuming preparation on the part of the radiologist and support personnel. In addition, it accesses images much faster than even an alternator can. Thus, more images can be read in a given time. Another PACS Figure 5 A diagram of a picture archiving and communication system (PACS). Digital images are acquired, transported on the network, viewed at an electronic viewing station and archived on disk. The hospital and radiology information system (HIS and RIS) are also connected to this network and pertinent patient data is readily available. Volume 7, Number 6, Monograph #{149}November 1987 #{149}RadioGraphics 1263

4 Perception and display in diagnostic imaging Seeley et al advantage is the potential increase in diagnostic accuracy resulting from the radiologist s ability to manipulate the image in real time. This type of system demands an electronic display with a large range of gray levels, high spatial resolution, and rapid image display. The technology which presently has been developed to achieve these goals is the cathode ray tube or CRT. However, there are new technologies that have the potential of achieving these same goals with the added benefits of less bulkiness (i.e., flat screens only a few inches deep) and lower electrical power consumption. Some of these are electroluminescence, light emitting diodes, liquid crystals, and gas discharge. A detailed treatment of these can be found in an article by B. Kazan in Science (2). A prototype of a PAC review console using the CR1 technology can be seen in Figure #{243}. A full description of the rationale behind the console, its capabilities, and uses can be found elsewhere (3,5). This viewing console was developed at the University of Arizona radiology department. As can be seen, it is capable of handling any image type or format. and it was specifically designed to be the viewing console for a PAC system. It makes it possible to manipulate the image being displayed in many different ways. It allows the user to manipulate the contrast, magnify or minify the image, and use a low- or high-pass filter on the image. All of this processing takes place almost instantaneously. Research has shown that the zoom and contrast manipulation capabilities allow the radiologist to access the same diagnostic information as that found on film (4). Using such a system expands the process of diagnosis described above as can be seen in Figure 7. The image is digital. Therefore, the radiologist can manipulate it to gain more information in making his diagnosis. This capability could possibly decrease misdiagnosis resulting from poor technique or failure to see small indications of disease. Figure 6 An electronic viewing console developed at the University of Arizona. MultIple images can be stacked on the screens at very high spatial resolution and accessed independently. Image processing in real time is possible, and the speed of image acquisition is just a few seconds for very large images. Future As research and development on the PAC systems continue, the viewing console will evolve into a major tool in radiology. For example, it can be designed to incorporate many more diagnostic aids than have ever been easily available before. Figure 8 indicates Iwo that should be possible in the near future. With the new compact disk technology now being utilized in the recording and video industry, it should be possible to construct a digital image library of disease(s) and make these accessible through the viewing console to the radiologist. The radiologist would then be able to call up relevant images as needed. This would happen very quickly, and since these images can even be classified as to age, sex, ethnic group, etc., the computer using HIS and RIS information can select images that are matched as closely as 1264 RadioGraphics #{149}November 1987 #{149}Volume 7, Number 6, Monograph

5 Seeiey et al. Perception and display in diagnostic imaging I Consult i-) (- Patient Information 4- image Enhancement Figure 7 The diagnostic process, but this time for digital images. The radiologist can now process the image in real time, thereby eliminating the need for retaking the image due to bad technique. Present I Consult I- Image Library of Disease T Visual Feature Selection Dx Image (Digital) Radiologist Review i-i -I Information Patient Enhancement Image I Figure 8 In the near future the review console I can be programmed to give access to an image library of disease, to utilize visual feature selection techniques that will help in selecting reference images and to aid in automatic image enhancement. IDX1 Near Future possible to the patient being diagnosed. This should help the radiologist come to a more rapid and accurate diagnosis on subtle cases. This aid is the equivalent of having all the above mentioned reference books available instantaneously with the search being done for the radiologist. As can also be seen in Figure 8, another adjunct that could be incorporated in such a display system would be the ability to call up a checklist of salient features and, by using a touch screen or a mouse, identify the diagnostically important features visible in an image. These can be used by the computer to further specify the reference images to be accessed from the image reference library. But, in addition, they can be used by the computer to automatically enhance the relevant portions or structures in the image. All this can be done by the computer quickly and easily. The radiologist will use these functions only when he needs them. The rest of the time they will be invisible to him. Thus, they will not interfere with the orderly process of diagnosis. Volume 7, Number 6, Monograph #{149}November 1987 RadioGraphics 1265

6 Perception and display in diagnostic imaging Seeley et al As indicated in Figure 9, in the far future it may be possible to aid the radiologist even further. Expert systems (ES) and computer feature extraction techniques are now in their infancy, but if they continue to develop at their present rate it may be possible some day to use these methodologies as part of the electronic viewing console. For example, the relevant features could be identified by both the radiologist and the computer and this information utilized as before to enhance the image and to bring up relevant reference images. This information could also be fed into an expert system that, using other information from the HIS and the RIS, would make reasonable guesses as to the possible diagnosis for that patient. The computer s guesses would be called upon, when needed, by the radiologist to enrich the diagnostic process. Much research and development is still needed to attain the new display capabilities described in this article. However, with the rapid growth of computer technology and the fact that radiology is a discipline that demands stateof-the-art technology, it is highly probable that these and other, as yet, undreamed of capabilities will eventually become possible and available. The other articles in this series show the specific research now being conducted to eventually develop such systems. Figure 9 In the far future it may be possible to also add an expert system to the review console to aid the radiologist further in his diagnosis. The expert system will use automatic feature extraction techniques and the HIS and RIS Information to arrive at a probable diagnosis, which can then be accessed by the radiologist when desired. I Consult - Image Library of Disease Visual Feature Selection Far Future References 1. Brecher P. Brecher E. The rays: A history of radiology in the United States and Canada. Baltimore: Williams & Wilkins, Kazan B. Materials aspects of display devices. Science 1980; 208: McNeiJI KM. Fisher HD. Model for radiologic workstation user interface design. Proceedings of the Medical Imaging Conference. SPIE 1987; vol paper , Seeley GW. Robles E. Cannon G. et al. The use of psychophysics as a system design aid: Comparison of film-screen to an electronic review console. Proceedings of the Medical Imaging Conference, SPIE 1987; vol. 767, paper Vercillo R, Fisher HD, Lamoreaux RD. McNeill KM. Digital image review console. Proceedings of the Medical lmaging Conference. SPIE 1987; vol paper Radioraphics #{149}November 1987 #{149}Volume 7, Number 6, Monograph