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Use of the internet for teaching in nuclear medicine
Use of the Internet for Teaching in Nuclear Medicine Jerold W. Wallis and J. Anthony Parker The Internet provides several new capabilities for education in nuclear medicine, including learning at a distance, facilitation of collaboration, increased availability of training resources, and ability to develop interactive teaching materials. Dedicated case-authoring software aided development of digital teaching files at the Mallinckrodt Institute of Radiology and the Joint Program in Nuclear Medicine. Accesses to these two teaching files from sites around the world have
grown rapidly. Improvements in the speed of the Internet will allow inclusion of more images at higher resolution and more extensive use of cine. Development of server-based software will allow simulation of the actual image-reading environment. A better understanding of how to use this new media will spur continued expansion in use of the Internet for nuclear medical education.
HE INTERNET and particularly the World Wide Web (WWW) has had an explosive growth over the past few years and it appears that it will continue to grow rapidly. This new media has allowed many new types of communication to take place and has resulted in a shift in the way many operations are conducted. Physicians are learning how to take advantage of the many new capabilities this medium provides. One of the early impacts in nuclear medicine has been the development of Internet-based teaching files. 1-3 This report describes what has been already been done and considers potentials for future development of Internet-based teaching. When Web addresses (also known as uniform resource locators or URLs) are available for the sites mentioned in this review, a dagger symbol (t) has been inserted to indicate that the full URL is listed in the Appendix. Traditionally, nuclear medicine is taught using a number of methods. Textbooks, lectures, seminars, and tutorials provide the bulk of the structured learning. As the resident advances, published literature including material such as review articles becomes more important. However, perhaps the major source of learning takes the form of an apprenticeship with supervised interpretation of real patient cases. The advantage of this type of learning is that the relevance of the education is obvious and that being able to relate principles to real patients makes the learning experience memorable. The difficulty with supervised interpretation is that the range of pathology may be limited, and there may be an overabundance of normal cases or cases with common pathology. The teaching file is a method of including more diverse pathology in a supervised teaching environment. Furthermore, the teaching points associated with the case can be more fully developed than during a reading session of a busy clinical service. Ideally, some of the cases can include basic science
relevance, thereby making physics, instrumentation, biology, radiochemistry, radiopharmacy, etc. more meaningful to the student. Although teaching files potentially can be a very important source of education, development of good teaching file material is quite labor intensive. Since producing a teaching file case has educational value in itself, residents usually take an active part in producing teaching files which are then used by subsequent residents. However, there is still a necessity for faculty supervision and teaching files always need more material. The Internet and particularly the WWW has many potential benefits for development of case-based teaching files. The WWW ties servers from anywhere in the world together so that they appear as a unified system to the user. Consequently, the work of developing a teaching file can be distributed over a large number of institutions anywhere in the world. Such a teaching file can include special types of studies performed only at a few institutions, and takes advantage of expertise of faculty at many different sites. Using the Internet, cases can be supervised by "world experts" in every field. Certain faculty may be best at developing individual cases; other faculty may be best at organizing cases into a coherent course of study; still others may excel at indexing the material. The Internet offers the potential for these different
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Copyright9 1998by W.B. Saunders Company
From the Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO; and the Division of Nuclear Medicine, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA. Address reprint requests to Jerold W. Wallis, MD, Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 Kingshighway, St. Louis, MO 63110-1076. Copyright 9 1998 by W.B. Saunders Company 0001-2998/98/2802-000458. 00/0
Seminars in Nuclear Medicine, Vol XXVIII, No 2 (April), 1998: pp 165-176
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individuals to collaborate, each providing his or her own expertise. The environment for medical education is currently changing. Increasingly, faculty may be responsible for educating residents at multiple hospital sites, and residents may be located at smaller institutions for some or all of their training. However as this environment evolves, it is likely that Internet-based education will help in providing expert instruction. The current capabilities of the Internet are barely adequate for case-based teaching. Even with a very high speed connection, the time to download images or cines is noticeable. Consequently, cases often use a limited set of images or images with limited resolution. It is clear that as the speed of the Internet improves, so will the utility. CASE-BASED TEACHING
Use of teaching file cases in nuclear medicine education more closely models the clinic environment than does passive reading of a radiology textbook. The cases can be presented as unknowns (without display of the diagnosis) so that the resident can play an active role in formulating interpretations. If needed, correlative images from other imaging modalities can be requested. After deciding on a diagnosis, the resident can compare his interpretation with the "expert", who also may provide a discussion of the disease process and a list of other possible diagnoses. Such a teaching file has the advantage over mere observation in the clinic in that the spectrum of disease will be different--a wider variety of unusual or educational cases may be viewed in a much shorter time. This model of teaching has been long utilized in radiology departments using a film-based presentation. More recently, teaching file collections have been created and marketed on video-disks and CD-ROMt by the American College of Radiology, and teaching collections have been placed on the Internet to reach an even wider audience. ~,4,5 I s s u e s in C r e a t i o n of a Digital T e a c h i n g File The process of creating a teaching file case has several defined steps: Selecting a case. Cases are typically selected because they demonstrate representative findings of common disease processes, or because they depict diseases which are important but infrequently encountered in the clinical setting. The diagnosis should be confirmed by another imaging
modality, biopsy, surgery, or clinical followup. Finally, the case should complement others already in the teaching file collection. Importing images. Several methods exist for importing images into a digital teaching file. Since nearly all nuclear medicine gamma cameras have a direct computer interface, the images are available in digital format on the acquisition and processing/ review computers. On Unix-based systems, the screen image may be captured as an X-Windows screen-dump, and then converted to the desired format using freely available utilities such as PBM-Plust and ImageMagikt. On Macintoshbased systems, images typically can be saved in PICT format, and conversion to other formats can be accomplished by many utilities (including the shareware programs GifConverter'~ and GraphicConvertert). When digital data are not available, the film images may be digitized using a film scanner or a digital camera. Alternately, when standard photographs are made of the film images, one can request at time of film developing that a Kodak PhotoCD be made along with the standard slides or prints. This multi-platform CD contains all of the images from the roll of film, stored in a range of different resolutions for subsequent digital use. Writing accompanying text. The text of the teaching case typically includes a (non-revealing) brief history, the diagnosis and full history, findings, brief discussion, and teaching points. Optionally, one can include a more detailed discussion with literature review, references, and a differential diagnosis list. Indexing. Teaching cases may be reviewed in an unselected manner; however, they may also be used in directed learning. Therefore, it is useful if they can be accessed in an organized fashion. A single case may be part of several different groups, eg, an organ system, a pathological process, an imaging technique, etc. One of the powers of an Internet-based system is that the same case can be used in a large number of ways. However, in order to access a case, it needs to be indexed so that it can be acquired from each point of view. An index may be provided by the author, but other individuals can sometimes provide a more useful index. The coding system developed by the ACR indexes one or more findings for a case. It includes two parts--one part cites the anatomical location of the finding, the other part describes the pathology. For both anatomical location and pathology, the
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codes consist of a sequence of numbers, where each number provides successively more detail. If only the first number is specified, then a large number of cases would be selected from that general anatomic region or general category of pathology. As more numbers are specified, the number of cases identified becomes smaller, but the cases are more specific. It is also desirable to identify the type of procedures which are included for a particular case (eg, CT, MRI, nuclear medicine). Within the modality it may be desirable to identify a particular type of study (e.g. bone scintigraphy, myocardial perfusion scintigraphy). The ACR code and a procedure code are examples of indexes where there is a fixed vocabulary--there is a limited set of possible codes which can be used to describe a case. The benefit of using a fixed vocabulary is that all cases are categorized in a logical taxonomy. The difficulty with using a fixed vocabulary is that the user is constrained. The codes must be updated to reflect new medical knowledge and new procedures. Searching for key words has become a very powerful method of finding material on the Internet. By using one or a few key words or phrases, it is often possible to find a relevant Web page anywhere in the world. If this same type of key word searching can be used with case-based teaching files, the material may be accessed in a fashion which was not originally imagined by the case developers. Natural language processing could potentially add "understanding" to computer generated indexing. An area under development is automatically categorizing images according to content. This type of facility could allow access to case-based features such as heterogeneity or focal defects, or more complex image descriptions. Indexing of image content can be done by a human, but computer image indexing is an area of current research. 6 Indexing is currently an important part of developing a teaching file. Each of these types of indexing has its own strengths and weaknesses. Developments in indexing are likely to make teaching files even more useful. Case review. When teaching cases are published in the conventional literature as case reports, there is a formal peer-review process. In the case of a digital teaching file, some type of review process is still necessary. This may be provided by a
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nuclear medicine physician at the same institution, or at another academic center. Such a review process is especially important if the case is prepared primarily by residents, since they still are in training and may not be acquainted fully with the literature on the topic. Optionally, a place for reader feedback can be incorporated into the final case page, which will aid in peer-review of the case. Publishing. Once the case is complete, it can be made available to the public. In the case of an Internet-based WWW teaching file, this consists of posting the images and text on the WWW server, and establishing links to the case from the "home page" of the teaching file. This home page might consist of a table of contents of the cases on the system. The cases should be formatted in a way to facilitate navigation through the teaching collection, and minimize the time needed to download cases from the Internet. Image format. Several choices exist for the format of WWW images. It is desirable to decrease the size of the image file as much as possible to make transmission over the network more rapid. Reducing the resolution of the primary image source or cropping the image can often save considerable space without losing the teaching point. Although nuclear medicine images are typically collected in "word mode" as 16-bit data, display as 8-bit data (256 gray levels) is nearly always adequate; saving the file as 8-bit data will halve the file size. Further reduction in size can be accomplished using image compression. The most common image compression formats are GIF and JPEG. 7 The Graphics Interchange Format (GIF) uses lossless compression of 8-bit data to achieve an additional --2-fold reduction in image file size. In lossless compression, the file can be expanded to exactly reproduce the original image; no data have been lost. In JPEG compression (from the Joint Photographic Experts Group), further data compression can be achieved through the use of "lossy" techniques. Data are transformed to the frequency domain using the discrete cosine transform (DCT) and higher frequency coefficients are then stored less accurately than low frequency coefficients. The human eye is relatively insensitive to subtle alterations in the high frequency components, so that the expanded image looks nearly identical to the original image. The desired degree of compression can be set by the operator using a "quality factor."
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It may be possible to tolerate a higher level of compression in a teaching collection, compared to that required for initial diagnostic use. Preliminary evaluation suggests that a 20-fold compression compared to the original 16-bit data still results in images that are nearly indistinguishable from the original images. 8 The GIF format was initially the most widely supported format on the WWW. Now both the GIF and JPEG formats are very widely supported. Because of its compression-encoding scheme, the GIF format often provides the best compression for drawings and images such as logos consisting of line segments and geometric figures. The JPEG format often provides better compression for pictures with more complex content. It would also be possible to create a teaching file server that utilized the DICOM medical imaging file format. Digital images in this format might be readily available in a department that used a DICOM-based picture archival system. However, DICOM images are not readily viewable in the standard Web browser, and may not achieve the degree of compression available in a JPEG-based teaching file server. Authoring software. The language of the WWW is the HyperText Markup Language (HTML). 9 HTML files are usually readable by humans, as they consist predominantly of the text that is displayed on the screen. In addition, there are special "tags" to indicate text formatting, and "links" to designate computer addresses of images and associated Web pages. For example, (B) summary (/B) would place the word "summary" in boldface when displayed in a Web browser (eg, Netscape), and the link (IMG SRC=http://gamma.wustl.edu/med-ctr.git) would insert a GIF image of the Washington University Medical Center into the Web page when it is displayed; this image is located on the computer with name "gamma" residing in the wustl.edu network domain. It would be inconvenient to require that all the nuclear medicine case authors also be experts in HTML. Fortunately, there are several alternatives. Modern HTML editors (eg, Netscape Navigator Gold, Adobe Pagemill or Claris Home Page) function more like conventional word processors, and hide the HTML-specific tags from the user. Such programs could be used to individually craft each case page with only minimal knowledge of HTML. Alternately, it is possible to design a data-entry
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form in a database system that allows collection of the parts of the case into separate fields. These fields can then be combined utilizing a standard template to produce a case page, similar to the way a mail-merge operation combines your name into a standard form-letter. The process of combining the fields would most likely take place once, at the time of case creation, to yield a file stored on the computer disk. A more complex system might assemble the parts of the case dynamically, when the case is requested for viewing. This would have the advantage that it would be easy to make modifications in the page layout that would automatically affect all the existing cases without having to rewrite them. In addition, certain portions of text might be shared between cases, such as generic descriptions of disease entities. However, this more complex system would put a substantially heavier load on the computer functioning as the Web server, and such a database approach might be more difficult to maintain. Linking images with text. Once the images are in the desired format and have been transferred to the Web server, they still need to be linked with the text accompanying the case. Again, this either requires knowledge of HTML or use of authoring software that will insert the links semi-automatically. Page design image presentation issues. Given the slow network transmission speeds and the limited screen size of the users computer, it would be undesirable to attempt to present all the patient images simultaneously. One option would be initially to present a text-only page, with links to the images which could be loaded upon request. Alternately, the most important image of the case could appear automatically, with ancillary images available via links. Some sites have used postage-stampsized images (sometimes referred to as "thumbnails") of all available image data on the initial page, which expand to full screen when the user clicks on them. Even with these techniques, only relevant images typically are shown, which differs from the clinical environment in which the physician must be more careful to search for the important images from among a larger patient study. As noted above, it is desirable for each case to have separate "known" and "unknown" pages, where the latter hides the diagnosis and discussion to allow the reader time to formulate his own opinion about the case.
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Tiered access. When creating an on-line teaching file, it is useful to have different levels of access. As cases are prepared, portions of the case may be placed on the Web server. It would be undesirable for viewers from outside the authoring institution to be able to view the partially completed cases. Levels of access that might be desirable include (a) in preparation, (b) awaiting local peer review, (c) approved for local viewing only, (d) approved for full network access. Image manipulation/cine. Standard viewing of JPEG and GIF images in Web browsers is simple and convenient (Fig 1A), but lacks the image manipulation capabilities frequently required for optimal image interpretation. In particular, adjustment of the color table (eg, upper and lower levels, or window width and position) occasionally is required to view images with a wide range of image intensities. If the browser preferences are set for external image display in a platform-specific helper
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Fig 1. (A) Text in HTML format is sent from the server (top) to the client (bottom), and is shown on the user's screen in a window created by his browser software. Standard browsers can also display images in GIF and JPEG formats. If the HTML text includes a data entry form, then the completed form may be sent back to the server. (B) Images in TIFF and DICOM formats cannot be displayed by the browser. However, if the user has previously installed platform-specific software designed for viewing these formats on his local hard drive, the browser can "hand-off" the images to these helper applications. Note that browser "plug-ins," which are also not platform-independent, can give similar capabilities as do helper applications. (C) Java programs can be written to have expanded image viewing capabilities, including viewing of TIFF, GIF, DICOM and JPEG files with image manipulation. This Java code can be automatically sent along with the images from the server to the user. The principal advantage of Java is its platform independence; it can run under many different operating systems.
application (rather than in the Web browser) as in figure 1B, it is possible to for the images to appear in an application that offers color table control (eg, NIH-Imaget or Osirist). Dynamic display of images (cine movies) also can be useful in nuclear medicine. One possible way to create a cine display is by use of an animated GIF image, as specified by the GIF 89a standard# Such images can be created relatively easily, but when viewed in Web browsers, the user lacks control over cine speed, and does not have image zoom or color table control. A second movie format is MPEG (created by the Motion Picture Experts Group). This format employs JPEG compression within frames, but also utilizes forward and backward inter-frame compression to yield a smaller file size than achievable by JPEG alone. However, the compression algorithms are substantially more complex, frequently requiring specialized hardware for the compression step. Viewing can be done in platform-specific "helper applications," which may offer zoom and frame rate adjustments, but typically lack color table control. With the coming together of computers and high definition TV, there should be considerable improvements in cine capabilities. A more flexible viewer can be created in the Java language, containing cine, color table control, and other features at the discretion of the programmer. Java has emerged recently as a platform independent programming language for use in WWW applications. It has the advantage that a single program can run on multiple existing hardware platforms and operating systems, including Windows 95, MacOS, and Unix, and it is central to the new hardware and software developments. In addition, the software can be automatically downloaded on-the-fly along with the images, without specific user intervention (Fig 1C). Such viewers have recently developed by several groups. 8,1~ The major disadvantage of this approach is the relative complexity of the programming needed. Additionally, the slight differences between evolving Java implementations on different platforms can create difficulty in achieving a stable cross-platform program. Searching. The simplest searching technique would be a text-word search based on the diagnosis (Fig 2). A more complex search engine can be created, depending on the type of case indexing performed, as described earlier. Searches might be
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Fig 2. The search capability in the MIR Nuclear Medicine Teaching File, shown here, allows search by diagnosis or by ACR anatomic and pathologic groups. The form used in the JPNM Teaching File has similar capabilities.
based on modality (eg, all bone scintigraphy studies), pathologic group (eg, all neoplasms), specific diagnosis, or case complexity (eg, simple cases for a medical student conference). When viewing a specific case, it may be useful to be able to automatically search for other examples of the same diagnosis, or other cases of different diagnosis but similar appearance. The former is relatively easy to implement, while the latter is more complex, requiring a feature-based classification system.
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server to produce thumbnail sketches and attached to the case upon submission to the Web server of a image linking form (Fig 3). Cases can be accessed by ACR anatomic index, by author, or by type of exam. They may be viewed as unknowns or as full cases. The presentation is created on the fly from database elements. When presented as an unknown, the clinical history and images without annotation are provided. The student can the proceed to a description of the findings with annotated images, and then to a discussion of the teaching points. When presented as a full case all of the material is displayed together. Presenting the same material formatted as either an unknown or a full case is an example of repurposing content, for different educational purposes. The MIR experience. The MIR nuclear medicine teaching filet at the Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis became available for public access in September, 1994.1 One or two cases are selected each week from those presented at the weekly followup conference. Image capture is done digitally using X-Window screen dumps; once the portion of the screen is selected by the operator, the image is automatically converted to GIF format and transmitted to our Web server. Secondary images,
E x a m p l e s : Two A c a d e m i c A p p r o a c h e s
The JPNM experience. The JPNM teaching filet at the Joint Program in Nuclear Medicine in Boston was started with a series of bone scintigraphy cases digitized from an existing hard copy teaching file. The teaching file was made available for public access in January of 1994 from a server at the Francis A. Countway Library of Medicine. The early cases were entered into a template using raw HTML. Subsequently, software was written to allow entry into a database on the server using the "forms" capabilities of HTML (Fig 1A). Different portions of the case are saved in different fields in the database. The Joint Program hospitals have heterogeneous computer resources, so several methods are used for image capture and processing. Captured images are uploaded by FTP (file transfer protocol). They are automatically processed on the
Fig 3. This figure shows a portion of the image linking form for case entry into the JPNM teaching file. The "Image Findings" portion of the case is entered into the t e x t box at the top of the form. For each image in the case, the filename of the image, a caption for the image, and a portion of text to link the image with are entered. If the image is not linked to text, then it will be shown as a thumbnail. If a t e x t phase from the case report is included, then the image file will be link to it. Images without annotations are displayed on the unknown page; all images are shown for a full case report. A provision is made for graphics, such as cines, that cannot be automatically converted to thumbnail images.
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and secondary images available via text links. Indexing and searching fields include diagnosis, ACR anatomic and pathologic groups, study type, and study difficulty. An example of the search capability based on the index is shown in Fig 2. Two levels of tiered access are available, with studies-in-preparation demarcated as such, and only accessible locally within the division. Once studies are approved by an attending physician with password access, the cases become available generally over the Web. A link at the bottom of each case allows for entry of reader comments, which are visible to all users of the teaching file.
Growth and Use of the Digital Teaching Files
Fig 4. The figure illustrates selected portions of the formsbased case entry system used in the MIR Nuclear Medicine Teaching File. Use of pop-up menus allow the user to designate anatomic and pathologic categories. Scrolling lists allow selection of study type and images. The diagnosis, teaching points, and other fields (not shown) are entered into text boxes. Data is then submitted to the server to create the teaching file case. A similar forms-based entry system is used at the JPNM Teaching File, although the case creation, indexing, and image linking steps at JPNM utilize separate forms.
such as radiographs, typically are not available digitally. Instead, slides are made of the radiographs, and then digitized using a Macintosh-based slide scanner for subsequent FTP transfer to the Web server. Data entry is done in the Web browser using a form with fields for each part of the teaching case An example of the case entry form used at MIR is shown in Fig 4. This form combines entry of basic information (diagnosis, teaching points, findings, discussion, etc.) into text boxes with indexing of the study using "pop-up" menus containing the basic ACR anatomic and pathologic groups. In addition, the form contains a list of images previously sent to the server, which can be selected to attach them to the case. When the data entry is complete, the teaching file engine builds the unknown and known case pages from the entered information, and adds the case to the teaching file index. To conserve computer resources, the case components are assembled at time of case creation or editing, rather than on-the-fly at the time of case viewing. Cases are presented with the primary image shown on the initial case page,
The MIR Nuclear Medicine Teaching file now has over 160 completed cases. Analysis of the Web server log file shows that the teaching file is currently getting over 2,000 "hits" per day, where a hit is a request for a text or graphic file from the Web site. Since it takes about 5 hits to view a case, this corresponds to about 400 cases viewed per day. Teaching file use is doubling approximately every 9 months, as shown in Fig 5. About 6% of accesses are from within Washington University, and about 10% are from other educational institutions in the United States. Commercial network sites (eg, aol.com) comprise 24% of accesses, 2% are from U.S. government sites, 28% are from sites outside the United States, and an additional 30% is from non-Washington University sites of uncertain loca70000 60000 50000 40000 -
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Fig 5. Graph indicating the dramatic growth of usage of the teaching file at the Mallinckrodt Institute of Radiology, Washington University, St. Louis. Viewing one case generates approximately 5 "hits" on the teaching file server, so peak usage is about 12,000 cases viewed per month.
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tion. The most common international sites are South Korea (16%), Canada (3%), and Australia (1.5%), with a large number of other countries contributing less than 1% to total usage. The JPNM has 72 teaching file cases with accompanying discussion and 12 short cases showing an interesting finding. A typical screen display while viewing a teaching file is shown in Fig 6. The JPNM teaching file is currently getting about 600 "hits" per day. About 2% of accesses are from within Harvard University, about 7.5% are from other educational institutions in the United States. Commercial sites comprise 30% of accesses, less than 1% are from U.S. government sites, and an additional 25% are from sites of uncertain location. The most common international sites are Australia (2.8%), United Kingdom (1.9%), Canada (1.8%) and Germany (1.8%), although the usage varies considerably from time to time. Other than the location from which accesses
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come, it is not known who is using these teaching files or for what purpose. Both teaching files are used at both institutions predominantly by radiology and nuclear medicine residents to supplement and increasingly to supplant existing hard copy teaching files. The teaching files are used also in at least some other training programs. The teaching files may be used by medical students and by other residents or for continuing medical education. Interestingly, the predominant feedback is from patients and other non-medical users. OTHER NUCLEAR MEDICINE REFERENCES ON THE INTERNET
Several text-based nuclear medicine references are available on the Internet. An ambitious project is the Nuclear Medicine Review Handbookt of the University of Texas Health Science Center. This online reference is text-only, but because of the nature of the WWW, it is able to include sample
Fig 6. This figure shows a typical screen view while reviewing a JPNM teaching file case. In the foreground are three display windows, On the left is a cine display of a GI bleeding study, In the center is a static image showing the location of the bleeding point on the 5 minute image and activity in an ileo-neobladder on a delayed image. On the right is an X-ray image from the angiographic study, In the background is the Imaging Findings and Discussion portion of the case report.
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images by means of pointers to other teaching collections located elsewhere on the Internet. The Medline database is available from many sources, including medical libraries, commercial database suppliers, and its creator, the National Library of Medicine (NLM). In past years, the primary route of access had been non-graphical (VT100) terminals using telnet or modems to reach commercial user accounts. Such accounts typically had charges per minute, as well as additional charges for abstract viewing. The combination of increased computer power and use of resourcesparing Web access has dramatically lowered the cost of providing this database to the public. In fact, the NLM recently has made the medline database available for free to WWW users.t Conventional journals are starting to have a presence on the Web, including some journals of interest to the nuclear medicine community. An online index of the article titles and abstracts is available for the European Joumal of Nuclear Medicine,t the Journal of Nuclear Cardiology, t and Nuclear Medicine Communicationst; the Journal of Nuclear Medicinet is also starting to make information available. Radiology has spawned an electronic counterpart, the RSNA Electronic Journal (RSNA-EJ).t Several additional nuclear medicine resources predate the emergence of the WWW. Lunist was started in 1990 as a nuclear medicine "bulletin board" to which members can post messages and upload/download images. In 1995, it was converted to Web format, with images viewable online and a variety of discussion topics for its 1750 members from 44 countries. In contrast, the NucMed mailburster, created by Trevor Cradduck in 1987, allows mail-group members to have a single mail message automatically forwarded to its 872 members in the nuclear medicine field throughout the world. A list of nuclear-medicine related mailbursters can be found on the Medical Physics Intemet site.# Additional image-based nuclear medicine resources are available via the WWW. This includes atlases of myocardial'~ and braini" SPECT located at Harvard, an online version of "Let's Play P e t " t from UCLA, 4 "My PET" t from Rush-PresbyterianSt. Luke's Medical Center in Chicago, as well as many other sites containing a variety of types of nuclear medicine images. Further information about these and other nuclear medicine sites can be found
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at the SNM Computer and Instrumentation Council home page.t FORMAL EDUCATION OVER THE INTERNET Continuing medical education (CME) via the Internet is starting to become available. The combination of text/graphic image display and use of HTML forms allows registered users to answer questions regarding presented material by clicking on radio-buttons. A technologist CME credit program# was recently started on the Society of Nuclear Medicine Web site.l" Similar programs for physicians have been designed, but it is unclear how well they will compete with existing CME mechanisms, such as local conferences, specialty meetings (sometimes in exotic locations), and mail-based quizzes based on journals, newsletters containing article summaries or audiotape material. There has recently been interest in physics training resources on the Internet. In the near future, Web pages are unlikely to replace the excellent physics textbooks available today. 13 The main advantage of using the Web for physics education is the potential for interactive demonstrations. For example, researchers at the University of Michigan have created a reconstruction server, which allows the user to experiment with different methods of tomographic reconstruction. ~4 A page created by Ken Castlemant acts as an adjunct to his text "Digital Image Processing ''15 by providing additional examples of image manipulation and short programs to be run in MathCad by the user, keyed to specific sections of the text. Another commercial sitet allows one to interactively assess tradeoffs in collimator design. At some point in the future, it may become possible to present a physics course over the Internet, complete with videocasting of the lecture, online course aids, and problem sets. This awaits both an expanded network infrastructure to support this level of network traffic, as well as a better financial model for the Web to make such an effort economically viable. FUTURE POTENTIAL
When computers were first introduced into nuclear medicine, they had very limited capabilities. They were best at manipulating curves, but had very limited ability to deal with images. We have seen marked changes in computer capabilities, so that now computers are used even with high resolution radiographic images. Uses which were
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beyond the imagination only a few years ago are now commmonplace. We are at the very start of the use of the Internet for medical education. Hopefully, we shall see continued, rapid development in Internet capabilities over the next few decades. The teaching file application needs much higher capacity networking bandwidth to allow for full-size, full-resolution images to be included, and adequately displayed. Inclusion of an entire study would allow for more realistic simulation of the clinical environment. Increased Internet capacity would also allow for other teaching possibilities-the netcast of lectures, videoconferencing, and downloadable software provide the potential for more interaction. These capabilities have the potential for a dramatic impact on teaching methods. CAUTIONS
The Internet provides new ways of communicating and the potential of many benefits for medical education. However, we are just learning how to use this new medium, and we need to be vigilant for potential pitfalls in its use. The ease and rapidity with which material on the Internet can change is both a strength and a potential weakness. Network addresses change often, so that links or references to material on the Internet often point to nothing. Similarly, a link or a reference may lead to an object which has changed and is no longer relevant. The stability of paper publishing needs to be integrated with the timeliness and flexibility of the network. Furthermore, users need to be able to access new information at a site without having to go through the whole site. The Computer and Instrumentation Council of the Society of Nuclear Medicine convened a focus group? on the Internet in August of 1994. 5 One issue which was addressed was an etiquette for collaboration (see Table 1). This etiquette is an attempt to start addressing how to collaborate in sharing of Internet-based material. Copyright and authorship sections make suggestions which seek to make sure that each persons contribution to a project is clearly recognized. A major potential of the Internet is to create a resource which is more valuable that can be produced at a single institution. Linking between separate teaching files is the simplest example of how this can be done. Slightly more complicated is indexing material at another site. Both linking and indexing are relatively straightforward in terms of etiquette.
Table 1. Guidelines for Sharing and Re-use of Internet Documents Etiquette General Internet ethic: sharing and cooperation Copyright Copyright or hyperlink to copyright should be on each document No unauthorized commercial use Documents should include date, revision number and revision date Authorship Clearly identified on each document Inclusion of e-mail address encouraged Identification of primary author clearly retained during reuse Linking to documents at other sites Encouraged Not required, but polite to inform primary author Desirable that the primary author not change URL after posting Indexing of documents at other sites Encouraged Not required, but polite to inform primary author Repurposing of document components Rich potential for providing new view of document Desirable that the primary author indicate granularity of reuse allowed Issues for etiquette evolution What is the atom of information? How is authorship clearly maintained? How is quality assured? Note: The word "document" is used to mean a self-contained multimedia entity. A document can stand on its own, and an author can assure the quality of a document. Reprinted by permission of the Society of Nuclear Medicine from: Parker JA, et al.: Collaboration using Internet for development of case-based teaching files: report of the Computer and Instrumentation Council Internet Focus Group. J Nucl Med 1996;37:178-184.
A more powerful potential is repurposed items between sites. Material originally developed for a teaching file case might be reused in a lecture about a related subject. Repurposing increases the utility of the original effort. However, an issue which is unclear is how an author maintains the integrity of his work. For example, suppose the derivative work makes an implication with which the original author disagrees. How does the original author prevent that implication from being attributed to him? One way would be to require access only to the whole work. But that would defeat the virtue of being able to reuse portions of a work. It may be helpful if the primary author specifies the granularity of reuse of material; however, the best etiquette for this type of collaboration is under evolution. Anyone with an account on an Internet server
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can say whatever he or she wishes. Therefore, the quality of the information on the Internet can be quite variable. This might at first seem to be a major problem with the Internet; however, it is not so different from other forms of communication. The difference is that there are established methods of identifying quality--we learn to identify journals, individuals, organizations, institutions, publishers, etc. These same methods of assuring quality will be developed on the Internet. Development of "peerreview" and other mechanisms to assure quality for the user are also necessary to allow authors to obtain appropriate academic credit for their efforts. Both the Mallinckrodt Institute of Radiology and the Joint Program in Nuclear Medicine have authoring software for their teaching files freeing the author from dealing directly with the details of HTML. The major use of these programs is by computer-interested individuals. The Web has not yet been fully embraced by the educators. Use of Internet-based educational material is growing rapidly (Fig 5), but there has been only gradual growth of Internet-based materials. Development of materials is currently the limiting step in the usefulness of the Internet for medical education. Improvement in Internet capabilities, improvement in the authoring environment, and recognition of Internet publication as a valid academic activity may encourage more of the teaching faculty to use the Internet. The Internet is an exciting new medium for medical education with great potentials such as learning-at-a-distance and facilitation of collaboration between distant sites. Use of the Internet is in its infancy both with regard to its inherent capabilities and our understanding of how to use it. Increases in network capacity will improve speed of access and encourage authors to use higher resolution images and more cine presentations. Server-based software will allow more accurate emulation of the real image interpreting environment for teaching. Perhaps more important, it will allow new paradigms for interactive teaching.
APPENDIX
Web Addresses for sites mentioned in the text are listed below, organized by paper subheadings. An online version of this list may be found at http:// www.telport.com/- glowniak/seminars.html/.
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ACR Learning File CD-ROM information: http://www.acr.org/departments/educ/edu_fst.html PBM-Plus: also known as NETPBM, available from many WWW sites including http://www.arc.umn.edu/GVL/Software/netpbm.html and http://www.pa.msu.edu/ftp/pub/unix ImageMagick: available from several sites including http://www.wizards.dupont.com/cristy/Image Magick.html GIFConverter: available from several sites including http://www.kamit.com/gifconverter.html and http://hyperarchive.lcs.mit.edu/HyperArchive/ SearchForm.html GraphicConverter: available from several sites including http://www.lemkesoft.de/and http://hyperarchive.lcs.mit.edu/HyperArchive/ SearchForm.html JPNM teaching file: http://www.med.harvard.edu/ JPNM/ MIR nuclear medicine teaching file: http:// gamma.wustl.edu/home.html NIH Image: http://rsb.info.nih.gov/NIH-Image/ Osiris: http://expasy.hcuge.ch/www/UIN/html 1/ proj ects/osiris/osiris.html Other Nuclear Medicine References on the Internet
Nuclear Medicine Review Handbook: http:// nucmedread.uthscsa.edu/williams/wmstoc.htm NLM medline access: http://www.ncbi.nlm.nih. gov/PubMed/or http://www.nlm.nih.gov/databases/freemedl.html European Journal of Nuclear Medicine: http:// link. springer, de/link/s ervice/j ournal s/00259/ Journal of Nuclear Cardiology: http://www.mosby.com/Mosby/Periodicals/Medical/ JNC/nc.html Nuclear Medicine Communications: http://www. nuclearmed.com/ Journal of Nuclear Medine: http://www.snm.org/ pub.html RSNA-EJ: http://ej.rsna.org/ Lunis: http://lunis.luc.edu/lunis/
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Medical Physics on the Internet--An overview: http://dmnu-pet5.hcuge.ch/Habib/Medphys.html Atlas of Myocarial SPECT: http://www.med. harvard.edu/BWHRad/Cardiac/ Atlas of Brain SPECT: http:www.med.harvard.edu/BWHRad/Brain SPECT/BrSPECT.html Let;s P l a y Pet: h t t p : / / l a x m i . n u c . u c l a . e d u : 8 0 0 0 / Ipp/ M y PET: h t t p : / / w w w . w p . c o m / b u k e t / m y p e t . h t m l SNM Computer and Instrumentation Council: http://gamma.wustl.edu/caic.html
Formal Education Technologist CME: http://www.snm.org/quiz/ S o c i e t y o f N u c l e a r M e d i n e : http : / / w w w . s n m . o r g / Digital Image Processing: http://www.phoenix. net/-castlman/ I n t e r a c t i v e c o l l i m a t o r design: h t t p : / / w w w . n u f i .com
Cautions SNM Computer and Instrumentation Council I n t e r n e t f o c u s g r o u p report: http://www.med.harvard.edu/JPNM/Publications/ J N u c l M e d 1 9 9 6 37 178/
REFERENCES
1. Wallis J, Miller M, Miller T, et al: An Internet-based nuclear medicine teaching file. J Nucl Med 36:1520-1527, 1995 2. Galvin J, D'Alessandro M, Kurihara Y, et al: Distributing an electronic thoracic imaging teaching file using the Interact, Mosaic, and personal computers. Am J Roentgenol 164:475478, 1995 3. Holman B, Mammone G, Robert A, et al: An approach to education, decision support, information dissemination, and collaboration via the World Wide Web. RSNAej http://ej.rsna.org/ EJ_0_96/0010-96.sit/title_page.html, 1996 (passwords available at http://ej.rsna.org/) 4. Gambhir S, Strommer J, Shen C, et al: The interactive PET whole body and brain atlas: An Internet-based multimedia learning system for PET. J Nucl Med 38:309P, 1997 5. Parker J, Wallis J, Halama J, et al.: Collaboration using Interact for the development of case-based teaching files. J Nucl Med 37:178-184, 1996 6. Tagare H, Jaffe C, Duncan J: Medical image databases: a content-based retrieval approach. J Am Med Inform Assoc 4:184-198, 1997 7. Murray J, VanRyper W: Encyclopedia of Graphics File Formats. Sebastopol, CA: O'Reilly and Associates, Inc., 1994
8. Phung N, Wallis J: An Internet-based, interactive nuclear medicine image display system implemented in the Java programming language. J Nucl Med 38:210P, 1997 9. December J, Randall N: The World Wide Web Unleashed. Indianapolis, IN: Sams Publishing, 1994 10. Wendt R, Hazle J, Schomer D, et al.: Demonstration of a World-Wide-Web-based viewer for DICOM-formatted medical images. J Nucl Med 38:310P, 1997 11. Hooper P, Fulham M: NM TeleWeb: A picture archiving system for nuclear medicine using Internet technologies. J Nucl Med 38:311P, 1997 12. Truong D, Huang S: Image analysis through the World Wide Web. J Nucl Med 38:309P, 1997 13. Sorenson J, Phelps M: Physics in Nuclear Medicine, 2nd Ed. New York, NY: Grune & Stratton, Inc., 1987 14. Clinthorne N, Chiao P: Framework for community-wide evaluation of nuclear medicine data-processing methods. J Nucl Med 38:215P, 1997 15. Castleman K: Digital Image Processing. Upper Saddle River, NJ: Prentice-Hall, 1995
grown rapidly. Improvements in the speed of the Internet will allow inclusion of more images at higher resolution and more extensive use of cine. Development of server-based software will allow simulation of the actual image-reading environment. A better understanding of how to use this new media will spur continued expansion in use of the Internet for nuclear medical education.
HE INTERNET and particularly the World Wide Web (WWW) has had an explosive growth over the past few years and it appears that it will continue to grow rapidly. This new media has allowed many new types of communication to take place and has resulted in a shift in the way many operations are conducted. Physicians are learning how to take advantage of the many new capabilities this medium provides. One of the early impacts in nuclear medicine has been the development of Internet-based teaching files. 1-3 This report describes what has been already been done and considers potentials for future development of Internet-based teaching. When Web addresses (also known as uniform resource locators or URLs) are available for the sites mentioned in this review, a dagger symbol (t) has been inserted to indicate that the full URL is listed in the Appendix. Traditionally, nuclear medicine is taught using a number of methods. Textbooks, lectures, seminars, and tutorials provide the bulk of the structured learning. As the resident advances, published literature including material such as review articles becomes more important. However, perhaps the major source of learning takes the form of an apprenticeship with supervised interpretation of real patient cases. The advantage of this type of learning is that the relevance of the education is obvious and that being able to relate principles to real patients makes the learning experience memorable. The difficulty with supervised interpretation is that the range of pathology may be limited, and there may be an overabundance of normal cases or cases with common pathology. The teaching file is a method of including more diverse pathology in a supervised teaching environment. Furthermore, the teaching points associated with the case can be more fully developed than during a reading session of a busy clinical service. Ideally, some of the cases can include basic science
relevance, thereby making physics, instrumentation, biology, radiochemistry, radiopharmacy, etc. more meaningful to the student. Although teaching files potentially can be a very important source of education, development of good teaching file material is quite labor intensive. Since producing a teaching file case has educational value in itself, residents usually take an active part in producing teaching files which are then used by subsequent residents. However, there is still a necessity for faculty supervision and teaching files always need more material. The Internet and particularly the WWW has many potential benefits for development of case-based teaching files. The WWW ties servers from anywhere in the world together so that they appear as a unified system to the user. Consequently, the work of developing a teaching file can be distributed over a large number of institutions anywhere in the world. Such a teaching file can include special types of studies performed only at a few institutions, and takes advantage of expertise of faculty at many different sites. Using the Internet, cases can be supervised by "world experts" in every field. Certain faculty may be best at developing individual cases; other faculty may be best at organizing cases into a coherent course of study; still others may excel at indexing the material. The Internet offers the potential for these different
T
Copyright9 1998by W.B. Saunders Company
From the Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO; and the Division of Nuclear Medicine, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA. Address reprint requests to Jerold W. Wallis, MD, Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 Kingshighway, St. Louis, MO 63110-1076. Copyright 9 1998 by W.B. Saunders Company 0001-2998/98/2802-000458. 00/0
Seminars in Nuclear Medicine, Vol XXVIII, No 2 (April), 1998: pp 165-176
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individuals to collaborate, each providing his or her own expertise. The environment for medical education is currently changing. Increasingly, faculty may be responsible for educating residents at multiple hospital sites, and residents may be located at smaller institutions for some or all of their training. However as this environment evolves, it is likely that Internet-based education will help in providing expert instruction. The current capabilities of the Internet are barely adequate for case-based teaching. Even with a very high speed connection, the time to download images or cines is noticeable. Consequently, cases often use a limited set of images or images with limited resolution. It is clear that as the speed of the Internet improves, so will the utility. CASE-BASED TEACHING
Use of teaching file cases in nuclear medicine education more closely models the clinic environment than does passive reading of a radiology textbook. The cases can be presented as unknowns (without display of the diagnosis) so that the resident can play an active role in formulating interpretations. If needed, correlative images from other imaging modalities can be requested. After deciding on a diagnosis, the resident can compare his interpretation with the "expert", who also may provide a discussion of the disease process and a list of other possible diagnoses. Such a teaching file has the advantage over mere observation in the clinic in that the spectrum of disease will be different--a wider variety of unusual or educational cases may be viewed in a much shorter time. This model of teaching has been long utilized in radiology departments using a film-based presentation. More recently, teaching file collections have been created and marketed on video-disks and CD-ROMt by the American College of Radiology, and teaching collections have been placed on the Internet to reach an even wider audience. ~,4,5 I s s u e s in C r e a t i o n of a Digital T e a c h i n g File The process of creating a teaching file case has several defined steps: Selecting a case. Cases are typically selected because they demonstrate representative findings of common disease processes, or because they depict diseases which are important but infrequently encountered in the clinical setting. The diagnosis should be confirmed by another imaging
modality, biopsy, surgery, or clinical followup. Finally, the case should complement others already in the teaching file collection. Importing images. Several methods exist for importing images into a digital teaching file. Since nearly all nuclear medicine gamma cameras have a direct computer interface, the images are available in digital format on the acquisition and processing/ review computers. On Unix-based systems, the screen image may be captured as an X-Windows screen-dump, and then converted to the desired format using freely available utilities such as PBM-Plust and ImageMagikt. On Macintoshbased systems, images typically can be saved in PICT format, and conversion to other formats can be accomplished by many utilities (including the shareware programs GifConverter'~ and GraphicConvertert). When digital data are not available, the film images may be digitized using a film scanner or a digital camera. Alternately, when standard photographs are made of the film images, one can request at time of film developing that a Kodak PhotoCD be made along with the standard slides or prints. This multi-platform CD contains all of the images from the roll of film, stored in a range of different resolutions for subsequent digital use. Writing accompanying text. The text of the teaching case typically includes a (non-revealing) brief history, the diagnosis and full history, findings, brief discussion, and teaching points. Optionally, one can include a more detailed discussion with literature review, references, and a differential diagnosis list. Indexing. Teaching cases may be reviewed in an unselected manner; however, they may also be used in directed learning. Therefore, it is useful if they can be accessed in an organized fashion. A single case may be part of several different groups, eg, an organ system, a pathological process, an imaging technique, etc. One of the powers of an Internet-based system is that the same case can be used in a large number of ways. However, in order to access a case, it needs to be indexed so that it can be acquired from each point of view. An index may be provided by the author, but other individuals can sometimes provide a more useful index. The coding system developed by the ACR indexes one or more findings for a case. It includes two parts--one part cites the anatomical location of the finding, the other part describes the pathology. For both anatomical location and pathology, the
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codes consist of a sequence of numbers, where each number provides successively more detail. If only the first number is specified, then a large number of cases would be selected from that general anatomic region or general category of pathology. As more numbers are specified, the number of cases identified becomes smaller, but the cases are more specific. It is also desirable to identify the type of procedures which are included for a particular case (eg, CT, MRI, nuclear medicine). Within the modality it may be desirable to identify a particular type of study (e.g. bone scintigraphy, myocardial perfusion scintigraphy). The ACR code and a procedure code are examples of indexes where there is a fixed vocabulary--there is a limited set of possible codes which can be used to describe a case. The benefit of using a fixed vocabulary is that all cases are categorized in a logical taxonomy. The difficulty with using a fixed vocabulary is that the user is constrained. The codes must be updated to reflect new medical knowledge and new procedures. Searching for key words has become a very powerful method of finding material on the Internet. By using one or a few key words or phrases, it is often possible to find a relevant Web page anywhere in the world. If this same type of key word searching can be used with case-based teaching files, the material may be accessed in a fashion which was not originally imagined by the case developers. Natural language processing could potentially add "understanding" to computer generated indexing. An area under development is automatically categorizing images according to content. This type of facility could allow access to case-based features such as heterogeneity or focal defects, or more complex image descriptions. Indexing of image content can be done by a human, but computer image indexing is an area of current research. 6 Indexing is currently an important part of developing a teaching file. Each of these types of indexing has its own strengths and weaknesses. Developments in indexing are likely to make teaching files even more useful. Case review. When teaching cases are published in the conventional literature as case reports, there is a formal peer-review process. In the case of a digital teaching file, some type of review process is still necessary. This may be provided by a
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nuclear medicine physician at the same institution, or at another academic center. Such a review process is especially important if the case is prepared primarily by residents, since they still are in training and may not be acquainted fully with the literature on the topic. Optionally, a place for reader feedback can be incorporated into the final case page, which will aid in peer-review of the case. Publishing. Once the case is complete, it can be made available to the public. In the case of an Internet-based WWW teaching file, this consists of posting the images and text on the WWW server, and establishing links to the case from the "home page" of the teaching file. This home page might consist of a table of contents of the cases on the system. The cases should be formatted in a way to facilitate navigation through the teaching collection, and minimize the time needed to download cases from the Internet. Image format. Several choices exist for the format of WWW images. It is desirable to decrease the size of the image file as much as possible to make transmission over the network more rapid. Reducing the resolution of the primary image source or cropping the image can often save considerable space without losing the teaching point. Although nuclear medicine images are typically collected in "word mode" as 16-bit data, display as 8-bit data (256 gray levels) is nearly always adequate; saving the file as 8-bit data will halve the file size. Further reduction in size can be accomplished using image compression. The most common image compression formats are GIF and JPEG. 7 The Graphics Interchange Format (GIF) uses lossless compression of 8-bit data to achieve an additional --2-fold reduction in image file size. In lossless compression, the file can be expanded to exactly reproduce the original image; no data have been lost. In JPEG compression (from the Joint Photographic Experts Group), further data compression can be achieved through the use of "lossy" techniques. Data are transformed to the frequency domain using the discrete cosine transform (DCT) and higher frequency coefficients are then stored less accurately than low frequency coefficients. The human eye is relatively insensitive to subtle alterations in the high frequency components, so that the expanded image looks nearly identical to the original image. The desired degree of compression can be set by the operator using a "quality factor."
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It may be possible to tolerate a higher level of compression in a teaching collection, compared to that required for initial diagnostic use. Preliminary evaluation suggests that a 20-fold compression compared to the original 16-bit data still results in images that are nearly indistinguishable from the original images. 8 The GIF format was initially the most widely supported format on the WWW. Now both the GIF and JPEG formats are very widely supported. Because of its compression-encoding scheme, the GIF format often provides the best compression for drawings and images such as logos consisting of line segments and geometric figures. The JPEG format often provides better compression for pictures with more complex content. It would also be possible to create a teaching file server that utilized the DICOM medical imaging file format. Digital images in this format might be readily available in a department that used a DICOM-based picture archival system. However, DICOM images are not readily viewable in the standard Web browser, and may not achieve the degree of compression available in a JPEG-based teaching file server. Authoring software. The language of the WWW is the HyperText Markup Language (HTML). 9 HTML files are usually readable by humans, as they consist predominantly of the text that is displayed on the screen. In addition, there are special "tags" to indicate text formatting, and "links" to designate computer addresses of images and associated Web pages. For example, (B) summary (/B) would place the word "summary" in boldface when displayed in a Web browser (eg, Netscape), and the link (IMG SRC=http://gamma.wustl.edu/med-ctr.git) would insert a GIF image of the Washington University Medical Center into the Web page when it is displayed; this image is located on the computer with name "gamma" residing in the wustl.edu network domain. It would be inconvenient to require that all the nuclear medicine case authors also be experts in HTML. Fortunately, there are several alternatives. Modern HTML editors (eg, Netscape Navigator Gold, Adobe Pagemill or Claris Home Page) function more like conventional word processors, and hide the HTML-specific tags from the user. Such programs could be used to individually craft each case page with only minimal knowledge of HTML. Alternately, it is possible to design a data-entry
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form in a database system that allows collection of the parts of the case into separate fields. These fields can then be combined utilizing a standard template to produce a case page, similar to the way a mail-merge operation combines your name into a standard form-letter. The process of combining the fields would most likely take place once, at the time of case creation, to yield a file stored on the computer disk. A more complex system might assemble the parts of the case dynamically, when the case is requested for viewing. This would have the advantage that it would be easy to make modifications in the page layout that would automatically affect all the existing cases without having to rewrite them. In addition, certain portions of text might be shared between cases, such as generic descriptions of disease entities. However, this more complex system would put a substantially heavier load on the computer functioning as the Web server, and such a database approach might be more difficult to maintain. Linking images with text. Once the images are in the desired format and have been transferred to the Web server, they still need to be linked with the text accompanying the case. Again, this either requires knowledge of HTML or use of authoring software that will insert the links semi-automatically. Page design image presentation issues. Given the slow network transmission speeds and the limited screen size of the users computer, it would be undesirable to attempt to present all the patient images simultaneously. One option would be initially to present a text-only page, with links to the images which could be loaded upon request. Alternately, the most important image of the case could appear automatically, with ancillary images available via links. Some sites have used postage-stampsized images (sometimes referred to as "thumbnails") of all available image data on the initial page, which expand to full screen when the user clicks on them. Even with these techniques, only relevant images typically are shown, which differs from the clinical environment in which the physician must be more careful to search for the important images from among a larger patient study. As noted above, it is desirable for each case to have separate "known" and "unknown" pages, where the latter hides the diagnosis and discussion to allow the reader time to formulate his own opinion about the case.
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Tiered access. When creating an on-line teaching file, it is useful to have different levels of access. As cases are prepared, portions of the case may be placed on the Web server. It would be undesirable for viewers from outside the authoring institution to be able to view the partially completed cases. Levels of access that might be desirable include (a) in preparation, (b) awaiting local peer review, (c) approved for local viewing only, (d) approved for full network access. Image manipulation/cine. Standard viewing of JPEG and GIF images in Web browsers is simple and convenient (Fig 1A), but lacks the image manipulation capabilities frequently required for optimal image interpretation. In particular, adjustment of the color table (eg, upper and lower levels, or window width and position) occasionally is required to view images with a wide range of image intensities. If the browser preferences are set for external image display in a platform-specific helper
Servers
//~
/
Clients
"
\\
(browsers)
Fig 1. (A) Text in HTML format is sent from the server (top) to the client (bottom), and is shown on the user's screen in a window created by his browser software. Standard browsers can also display images in GIF and JPEG formats. If the HTML text includes a data entry form, then the completed form may be sent back to the server. (B) Images in TIFF and DICOM formats cannot be displayed by the browser. However, if the user has previously installed platform-specific software designed for viewing these formats on his local hard drive, the browser can "hand-off" the images to these helper applications. Note that browser "plug-ins," which are also not platform-independent, can give similar capabilities as do helper applications. (C) Java programs can be written to have expanded image viewing capabilities, including viewing of TIFF, GIF, DICOM and JPEG files with image manipulation. This Java code can be automatically sent along with the images from the server to the user. The principal advantage of Java is its platform independence; it can run under many different operating systems.
application (rather than in the Web browser) as in figure 1B, it is possible to for the images to appear in an application that offers color table control (eg, NIH-Imaget or Osirist). Dynamic display of images (cine movies) also can be useful in nuclear medicine. One possible way to create a cine display is by use of an animated GIF image, as specified by the GIF 89a standard# Such images can be created relatively easily, but when viewed in Web browsers, the user lacks control over cine speed, and does not have image zoom or color table control. A second movie format is MPEG (created by the Motion Picture Experts Group). This format employs JPEG compression within frames, but also utilizes forward and backward inter-frame compression to yield a smaller file size than achievable by JPEG alone. However, the compression algorithms are substantially more complex, frequently requiring specialized hardware for the compression step. Viewing can be done in platform-specific "helper applications," which may offer zoom and frame rate adjustments, but typically lack color table control. With the coming together of computers and high definition TV, there should be considerable improvements in cine capabilities. A more flexible viewer can be created in the Java language, containing cine, color table control, and other features at the discretion of the programmer. Java has emerged recently as a platform independent programming language for use in WWW applications. It has the advantage that a single program can run on multiple existing hardware platforms and operating systems, including Windows 95, MacOS, and Unix, and it is central to the new hardware and software developments. In addition, the software can be automatically downloaded on-the-fly along with the images, without specific user intervention (Fig 1C). Such viewers have recently developed by several groups. 8,1~ The major disadvantage of this approach is the relative complexity of the programming needed. Additionally, the slight differences between evolving Java implementations on different platforms can create difficulty in achieving a stable cross-platform program. Searching. The simplest searching technique would be a text-word search based on the diagnosis (Fig 2). A more complex search engine can be created, depending on the type of case indexing performed, as described earlier. Searches might be
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Fig 2. The search capability in the MIR Nuclear Medicine Teaching File, shown here, allows search by diagnosis or by ACR anatomic and pathologic groups. The form used in the JPNM Teaching File has similar capabilities.
based on modality (eg, all bone scintigraphy studies), pathologic group (eg, all neoplasms), specific diagnosis, or case complexity (eg, simple cases for a medical student conference). When viewing a specific case, it may be useful to be able to automatically search for other examples of the same diagnosis, or other cases of different diagnosis but similar appearance. The former is relatively easy to implement, while the latter is more complex, requiring a feature-based classification system.
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server to produce thumbnail sketches and attached to the case upon submission to the Web server of a image linking form (Fig 3). Cases can be accessed by ACR anatomic index, by author, or by type of exam. They may be viewed as unknowns or as full cases. The presentation is created on the fly from database elements. When presented as an unknown, the clinical history and images without annotation are provided. The student can the proceed to a description of the findings with annotated images, and then to a discussion of the teaching points. When presented as a full case all of the material is displayed together. Presenting the same material formatted as either an unknown or a full case is an example of repurposing content, for different educational purposes. The MIR experience. The MIR nuclear medicine teaching filet at the Mallinckrodt Institute of Radiology, Washington University School of Medicine in St. Louis became available for public access in September, 1994.1 One or two cases are selected each week from those presented at the weekly followup conference. Image capture is done digitally using X-Window screen dumps; once the portion of the screen is selected by the operator, the image is automatically converted to GIF format and transmitted to our Web server. Secondary images,
E x a m p l e s : Two A c a d e m i c A p p r o a c h e s
The JPNM experience. The JPNM teaching filet at the Joint Program in Nuclear Medicine in Boston was started with a series of bone scintigraphy cases digitized from an existing hard copy teaching file. The teaching file was made available for public access in January of 1994 from a server at the Francis A. Countway Library of Medicine. The early cases were entered into a template using raw HTML. Subsequently, software was written to allow entry into a database on the server using the "forms" capabilities of HTML (Fig 1A). Different portions of the case are saved in different fields in the database. The Joint Program hospitals have heterogeneous computer resources, so several methods are used for image capture and processing. Captured images are uploaded by FTP (file transfer protocol). They are automatically processed on the
Fig 3. This figure shows a portion of the image linking form for case entry into the JPNM teaching file. The "Image Findings" portion of the case is entered into the t e x t box at the top of the form. For each image in the case, the filename of the image, a caption for the image, and a portion of text to link the image with are entered. If the image is not linked to text, then it will be shown as a thumbnail. If a t e x t phase from the case report is included, then the image file will be link to it. Images without annotations are displayed on the unknown page; all images are shown for a full case report. A provision is made for graphics, such as cines, that cannot be automatically converted to thumbnail images.
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and secondary images available via text links. Indexing and searching fields include diagnosis, ACR anatomic and pathologic groups, study type, and study difficulty. An example of the search capability based on the index is shown in Fig 2. Two levels of tiered access are available, with studies-in-preparation demarcated as such, and only accessible locally within the division. Once studies are approved by an attending physician with password access, the cases become available generally over the Web. A link at the bottom of each case allows for entry of reader comments, which are visible to all users of the teaching file.
Growth and Use of the Digital Teaching Files
Fig 4. The figure illustrates selected portions of the formsbased case entry system used in the MIR Nuclear Medicine Teaching File. Use of pop-up menus allow the user to designate anatomic and pathologic categories. Scrolling lists allow selection of study type and images. The diagnosis, teaching points, and other fields (not shown) are entered into text boxes. Data is then submitted to the server to create the teaching file case. A similar forms-based entry system is used at the JPNM Teaching File, although the case creation, indexing, and image linking steps at JPNM utilize separate forms.
such as radiographs, typically are not available digitally. Instead, slides are made of the radiographs, and then digitized using a Macintosh-based slide scanner for subsequent FTP transfer to the Web server. Data entry is done in the Web browser using a form with fields for each part of the teaching case An example of the case entry form used at MIR is shown in Fig 4. This form combines entry of basic information (diagnosis, teaching points, findings, discussion, etc.) into text boxes with indexing of the study using "pop-up" menus containing the basic ACR anatomic and pathologic groups. In addition, the form contains a list of images previously sent to the server, which can be selected to attach them to the case. When the data entry is complete, the teaching file engine builds the unknown and known case pages from the entered information, and adds the case to the teaching file index. To conserve computer resources, the case components are assembled at time of case creation or editing, rather than on-the-fly at the time of case viewing. Cases are presented with the primary image shown on the initial case page,
The MIR Nuclear Medicine Teaching file now has over 160 completed cases. Analysis of the Web server log file shows that the teaching file is currently getting over 2,000 "hits" per day, where a hit is a request for a text or graphic file from the Web site. Since it takes about 5 hits to view a case, this corresponds to about 400 cases viewed per day. Teaching file use is doubling approximately every 9 months, as shown in Fig 5. About 6% of accesses are from within Washington University, and about 10% are from other educational institutions in the United States. Commercial network sites (eg, aol.com) comprise 24% of accesses, 2% are from U.S. government sites, 28% are from sites outside the United States, and an additional 30% is from non-Washington University sites of uncertain loca70000 60000 50000 40000 -
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Fig 5. Graph indicating the dramatic growth of usage of the teaching file at the Mallinckrodt Institute of Radiology, Washington University, St. Louis. Viewing one case generates approximately 5 "hits" on the teaching file server, so peak usage is about 12,000 cases viewed per month.
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tion. The most common international sites are South Korea (16%), Canada (3%), and Australia (1.5%), with a large number of other countries contributing less than 1% to total usage. The JPNM has 72 teaching file cases with accompanying discussion and 12 short cases showing an interesting finding. A typical screen display while viewing a teaching file is shown in Fig 6. The JPNM teaching file is currently getting about 600 "hits" per day. About 2% of accesses are from within Harvard University, about 7.5% are from other educational institutions in the United States. Commercial sites comprise 30% of accesses, less than 1% are from U.S. government sites, and an additional 25% are from sites of uncertain location. The most common international sites are Australia (2.8%), United Kingdom (1.9%), Canada (1.8%) and Germany (1.8%), although the usage varies considerably from time to time. Other than the location from which accesses
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come, it is not known who is using these teaching files or for what purpose. Both teaching files are used at both institutions predominantly by radiology and nuclear medicine residents to supplement and increasingly to supplant existing hard copy teaching files. The teaching files are used also in at least some other training programs. The teaching files may be used by medical students and by other residents or for continuing medical education. Interestingly, the predominant feedback is from patients and other non-medical users. OTHER NUCLEAR MEDICINE REFERENCES ON THE INTERNET
Several text-based nuclear medicine references are available on the Internet. An ambitious project is the Nuclear Medicine Review Handbookt of the University of Texas Health Science Center. This online reference is text-only, but because of the nature of the WWW, it is able to include sample
Fig 6. This figure shows a typical screen view while reviewing a JPNM teaching file case. In the foreground are three display windows, On the left is a cine display of a GI bleeding study, In the center is a static image showing the location of the bleeding point on the 5 minute image and activity in an ileo-neobladder on a delayed image. On the right is an X-ray image from the angiographic study, In the background is the Imaging Findings and Discussion portion of the case report.
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images by means of pointers to other teaching collections located elsewhere on the Internet. The Medline database is available from many sources, including medical libraries, commercial database suppliers, and its creator, the National Library of Medicine (NLM). In past years, the primary route of access had been non-graphical (VT100) terminals using telnet or modems to reach commercial user accounts. Such accounts typically had charges per minute, as well as additional charges for abstract viewing. The combination of increased computer power and use of resourcesparing Web access has dramatically lowered the cost of providing this database to the public. In fact, the NLM recently has made the medline database available for free to WWW users.t Conventional journals are starting to have a presence on the Web, including some journals of interest to the nuclear medicine community. An online index of the article titles and abstracts is available for the European Joumal of Nuclear Medicine,t the Journal of Nuclear Cardiology, t and Nuclear Medicine Communicationst; the Journal of Nuclear Medicinet is also starting to make information available. Radiology has spawned an electronic counterpart, the RSNA Electronic Journal (RSNA-EJ).t Several additional nuclear medicine resources predate the emergence of the WWW. Lunist was started in 1990 as a nuclear medicine "bulletin board" to which members can post messages and upload/download images. In 1995, it was converted to Web format, with images viewable online and a variety of discussion topics for its 1750 members from 44 countries. In contrast, the NucMed mailburster, created by Trevor Cradduck in 1987, allows mail-group members to have a single mail message automatically forwarded to its 872 members in the nuclear medicine field throughout the world. A list of nuclear-medicine related mailbursters can be found on the Medical Physics Intemet site.# Additional image-based nuclear medicine resources are available via the WWW. This includes atlases of myocardial'~ and braini" SPECT located at Harvard, an online version of "Let's Play P e t " t from UCLA, 4 "My PET" t from Rush-PresbyterianSt. Luke's Medical Center in Chicago, as well as many other sites containing a variety of types of nuclear medicine images. Further information about these and other nuclear medicine sites can be found
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at the SNM Computer and Instrumentation Council home page.t FORMAL EDUCATION OVER THE INTERNET Continuing medical education (CME) via the Internet is starting to become available. The combination of text/graphic image display and use of HTML forms allows registered users to answer questions regarding presented material by clicking on radio-buttons. A technologist CME credit program# was recently started on the Society of Nuclear Medicine Web site.l" Similar programs for physicians have been designed, but it is unclear how well they will compete with existing CME mechanisms, such as local conferences, specialty meetings (sometimes in exotic locations), and mail-based quizzes based on journals, newsletters containing article summaries or audiotape material. There has recently been interest in physics training resources on the Internet. In the near future, Web pages are unlikely to replace the excellent physics textbooks available today. 13 The main advantage of using the Web for physics education is the potential for interactive demonstrations. For example, researchers at the University of Michigan have created a reconstruction server, which allows the user to experiment with different methods of tomographic reconstruction. ~4 A page created by Ken Castlemant acts as an adjunct to his text "Digital Image Processing ''15 by providing additional examples of image manipulation and short programs to be run in MathCad by the user, keyed to specific sections of the text. Another commercial sitet allows one to interactively assess tradeoffs in collimator design. At some point in the future, it may become possible to present a physics course over the Internet, complete with videocasting of the lecture, online course aids, and problem sets. This awaits both an expanded network infrastructure to support this level of network traffic, as well as a better financial model for the Web to make such an effort economically viable. FUTURE POTENTIAL
When computers were first introduced into nuclear medicine, they had very limited capabilities. They were best at manipulating curves, but had very limited ability to deal with images. We have seen marked changes in computer capabilities, so that now computers are used even with high resolution radiographic images. Uses which were
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beyond the imagination only a few years ago are now commmonplace. We are at the very start of the use of the Internet for medical education. Hopefully, we shall see continued, rapid development in Internet capabilities over the next few decades. The teaching file application needs much higher capacity networking bandwidth to allow for full-size, full-resolution images to be included, and adequately displayed. Inclusion of an entire study would allow for more realistic simulation of the clinical environment. Increased Internet capacity would also allow for other teaching possibilities-the netcast of lectures, videoconferencing, and downloadable software provide the potential for more interaction. These capabilities have the potential for a dramatic impact on teaching methods. CAUTIONS
The Internet provides new ways of communicating and the potential of many benefits for medical education. However, we are just learning how to use this new medium, and we need to be vigilant for potential pitfalls in its use. The ease and rapidity with which material on the Internet can change is both a strength and a potential weakness. Network addresses change often, so that links or references to material on the Internet often point to nothing. Similarly, a link or a reference may lead to an object which has changed and is no longer relevant. The stability of paper publishing needs to be integrated with the timeliness and flexibility of the network. Furthermore, users need to be able to access new information at a site without having to go through the whole site. The Computer and Instrumentation Council of the Society of Nuclear Medicine convened a focus group? on the Internet in August of 1994. 5 One issue which was addressed was an etiquette for collaboration (see Table 1). This etiquette is an attempt to start addressing how to collaborate in sharing of Internet-based material. Copyright and authorship sections make suggestions which seek to make sure that each persons contribution to a project is clearly recognized. A major potential of the Internet is to create a resource which is more valuable that can be produced at a single institution. Linking between separate teaching files is the simplest example of how this can be done. Slightly more complicated is indexing material at another site. Both linking and indexing are relatively straightforward in terms of etiquette.
Table 1. Guidelines for Sharing and Re-use of Internet Documents Etiquette General Internet ethic: sharing and cooperation Copyright Copyright or hyperlink to copyright should be on each document No unauthorized commercial use Documents should include date, revision number and revision date Authorship Clearly identified on each document Inclusion of e-mail address encouraged Identification of primary author clearly retained during reuse Linking to documents at other sites Encouraged Not required, but polite to inform primary author Desirable that the primary author not change URL after posting Indexing of documents at other sites Encouraged Not required, but polite to inform primary author Repurposing of document components Rich potential for providing new view of document Desirable that the primary author indicate granularity of reuse allowed Issues for etiquette evolution What is the atom of information? How is authorship clearly maintained? How is quality assured? Note: The word "document" is used to mean a self-contained multimedia entity. A document can stand on its own, and an author can assure the quality of a document. Reprinted by permission of the Society of Nuclear Medicine from: Parker JA, et al.: Collaboration using Internet for development of case-based teaching files: report of the Computer and Instrumentation Council Internet Focus Group. J Nucl Med 1996;37:178-184.
A more powerful potential is repurposed items between sites. Material originally developed for a teaching file case might be reused in a lecture about a related subject. Repurposing increases the utility of the original effort. However, an issue which is unclear is how an author maintains the integrity of his work. For example, suppose the derivative work makes an implication with which the original author disagrees. How does the original author prevent that implication from being attributed to him? One way would be to require access only to the whole work. But that would defeat the virtue of being able to reuse portions of a work. It may be helpful if the primary author specifies the granularity of reuse of material; however, the best etiquette for this type of collaboration is under evolution. Anyone with an account on an Internet server
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can say whatever he or she wishes. Therefore, the quality of the information on the Internet can be quite variable. This might at first seem to be a major problem with the Internet; however, it is not so different from other forms of communication. The difference is that there are established methods of identifying quality--we learn to identify journals, individuals, organizations, institutions, publishers, etc. These same methods of assuring quality will be developed on the Internet. Development of "peerreview" and other mechanisms to assure quality for the user are also necessary to allow authors to obtain appropriate academic credit for their efforts. Both the Mallinckrodt Institute of Radiology and the Joint Program in Nuclear Medicine have authoring software for their teaching files freeing the author from dealing directly with the details of HTML. The major use of these programs is by computer-interested individuals. The Web has not yet been fully embraced by the educators. Use of Internet-based educational material is growing rapidly (Fig 5), but there has been only gradual growth of Internet-based materials. Development of materials is currently the limiting step in the usefulness of the Internet for medical education. Improvement in Internet capabilities, improvement in the authoring environment, and recognition of Internet publication as a valid academic activity may encourage more of the teaching faculty to use the Internet. The Internet is an exciting new medium for medical education with great potentials such as learning-at-a-distance and facilitation of collaboration between distant sites. Use of the Internet is in its infancy both with regard to its inherent capabilities and our understanding of how to use it. Increases in network capacity will improve speed of access and encourage authors to use higher resolution images and more cine presentations. Server-based software will allow more accurate emulation of the real image interpreting environment for teaching. Perhaps more important, it will allow new paradigms for interactive teaching.
APPENDIX
Web Addresses for sites mentioned in the text are listed below, organized by paper subheadings. An online version of this list may be found at http:// www.telport.com/- glowniak/seminars.html/.
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Case-based Teaching
ACR Learning File CD-ROM information: http://www.acr.org/departments/educ/edu_fst.html PBM-Plus: also known as NETPBM, available from many WWW sites including http://www.arc.umn.edu/GVL/Software/netpbm.html and http://www.pa.msu.edu/ftp/pub/unix ImageMagick: available from several sites including http://www.wizards.dupont.com/cristy/Image Magick.html GIFConverter: available from several sites including http://www.kamit.com/gifconverter.html and http://hyperarchive.lcs.mit.edu/HyperArchive/ SearchForm.html GraphicConverter: available from several sites including http://www.lemkesoft.de/and http://hyperarchive.lcs.mit.edu/HyperArchive/ SearchForm.html JPNM teaching file: http://www.med.harvard.edu/ JPNM/ MIR nuclear medicine teaching file: http:// gamma.wustl.edu/home.html NIH Image: http://rsb.info.nih.gov/NIH-Image/ Osiris: http://expasy.hcuge.ch/www/UIN/html 1/ proj ects/osiris/osiris.html Other Nuclear Medicine References on the Internet
Nuclear Medicine Review Handbook: http:// nucmedread.uthscsa.edu/williams/wmstoc.htm NLM medline access: http://www.ncbi.nlm.nih. gov/PubMed/or http://www.nlm.nih.gov/databases/freemedl.html European Journal of Nuclear Medicine: http:// link. springer, de/link/s ervice/j ournal s/00259/ Journal of Nuclear Cardiology: http://www.mosby.com/Mosby/Periodicals/Medical/ JNC/nc.html Nuclear Medicine Communications: http://www. nuclearmed.com/ Journal of Nuclear Medine: http://www.snm.org/ pub.html RSNA-EJ: http://ej.rsna.org/ Lunis: http://lunis.luc.edu/lunis/
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Medical Physics on the Internet--An overview: http://dmnu-pet5.hcuge.ch/Habib/Medphys.html Atlas of Myocarial SPECT: http://www.med. harvard.edu/BWHRad/Cardiac/ Atlas of Brain SPECT: http:www.med.harvard.edu/BWHRad/Brain SPECT/BrSPECT.html Let;s P l a y Pet: h t t p : / / l a x m i . n u c . u c l a . e d u : 8 0 0 0 / Ipp/ M y PET: h t t p : / / w w w . w p . c o m / b u k e t / m y p e t . h t m l SNM Computer and Instrumentation Council: http://gamma.wustl.edu/caic.html
Formal Education Technologist CME: http://www.snm.org/quiz/ S o c i e t y o f N u c l e a r M e d i n e : http : / / w w w . s n m . o r g / Digital Image Processing: http://www.phoenix. net/-castlman/ I n t e r a c t i v e c o l l i m a t o r design: h t t p : / / w w w . n u f i .com
Cautions SNM Computer and Instrumentation Council I n t e r n e t f o c u s g r o u p report: http://www.med.harvard.edu/JPNM/Publications/ J N u c l M e d 1 9 9 6 37 178/
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1. Wallis J, Miller M, Miller T, et al: An Internet-based nuclear medicine teaching file. J Nucl Med 36:1520-1527, 1995 2. Galvin J, D'Alessandro M, Kurihara Y, et al: Distributing an electronic thoracic imaging teaching file using the Interact, Mosaic, and personal computers. Am J Roentgenol 164:475478, 1995 3. Holman B, Mammone G, Robert A, et al: An approach to education, decision support, information dissemination, and collaboration via the World Wide Web. RSNAej http://ej.rsna.org/ EJ_0_96/0010-96.sit/title_page.html, 1996 (passwords available at http://ej.rsna.org/) 4. Gambhir S, Strommer J, Shen C, et al: The interactive PET whole body and brain atlas: An Internet-based multimedia learning system for PET. J Nucl Med 38:309P, 1997 5. Parker J, Wallis J, Halama J, et al.: Collaboration using Interact for the development of case-based teaching files. J Nucl Med 37:178-184, 1996 6. Tagare H, Jaffe C, Duncan J: Medical image databases: a content-based retrieval approach. J Am Med Inform Assoc 4:184-198, 1997 7. Murray J, VanRyper W: Encyclopedia of Graphics File Formats. Sebastopol, CA: O'Reilly and Associates, Inc., 1994
8. Phung N, Wallis J: An Internet-based, interactive nuclear medicine image display system implemented in the Java programming language. J Nucl Med 38:210P, 1997 9. December J, Randall N: The World Wide Web Unleashed. Indianapolis, IN: Sams Publishing, 1994 10. Wendt R, Hazle J, Schomer D, et al.: Demonstration of a World-Wide-Web-based viewer for DICOM-formatted medical images. J Nucl Med 38:310P, 1997 11. Hooper P, Fulham M: NM TeleWeb: A picture archiving system for nuclear medicine using Internet technologies. J Nucl Med 38:311P, 1997 12. Truong D, Huang S: Image analysis through the World Wide Web. J Nucl Med 38:309P, 1997 13. Sorenson J, Phelps M: Physics in Nuclear Medicine, 2nd Ed. New York, NY: Grune & Stratton, Inc., 1987 14. Clinthorne N, Chiao P: Framework for community-wide evaluation of nuclear medicine data-processing methods. J Nucl Med 38:215P, 1997 15. Castleman K: Digital Image Processing. Upper Saddle River, NJ: Prentice-Hall, 1995