Digital Teaching Files for Beginners

By Gregory L. Katzman, MD, MA

Gregory L. Katzman, MD, MA has reported no financial interest, arrangement or affiliation with a commercial organization that may have a direct or indirect influence in the subject matter of this presentation.

Introduction:

For decades, the standard model for teaching files was the film-based ACR set found within every academic institution. In the early 1990's, the ACR adopted a digital display method, which primarily consisted of scanned-film analog images, converted to a digital format, and placed onto laserdisc media. This was short-lived, as a few years later the CD-ROM became the de facto standard storage media, which is where we are today. Several commercially available sources for Digital Teaching Files (DTFs) are also currently available on CD-ROM.

As a larger number of radiology departments become filmless, there will be an ever increasing need for methods to manipulate digital images directly from the sources of origin, for use in presentations, publications, or DTFs. Eventually, no films will be generated at all, and image display (for any purpose) will rely on electronic methods. Daily clinical case review and long-term image storage and retrieval will rely on an institution's PACS system. However, for academic purposes such as the generation of materials for presentation at local teaching conferences or external scientific meetings, a portable technique is necessary that is easy, reliable, and inexpensive and can be transported on any laptop computer. Preferably, such a system should be platform independent, equally useful with all systems including Macintosh OS, Windows, or UNIX.

Although many equipment manufacturers have product lines which include all radiologic modalities (such as CR, CT, MR, digital fluoroscopy, and digital angiography), and traditionally image header information was proprietary, the international adoption of the DICOM standard has created a common thread from which we can begin to manipulate images in a platform independent way.

In this section of the syllabus, the reader will be introduced to the basics of DICOM images, image formats for desktop or laptop use, image storage possibilities, and finally software and methodologies for constructing DTFs. Simple flowcharts have been included outlining the process being discussed.

Starting Out:

Initially, one must transfer the DICOM images of interest from a source of origin, to the user's desktop computer. Although this sounds trivial, it can be a very difficult step, primarily depending on the level(s) of security in place within the user's network. More than likely, the ability for network transfer of files will require conversations with hospital IT personnel and PACS managers, and may require that special privileges be granted. Detailed discussion of this is beyond the scope of this syllabus section, and thus an assumption will be made that DICOM images are accessible to the user, and saved upon his or her desktop computer hard drive.

DICOM images will need to be converted to a common image format, such as JPEG (Joint Photographic Experts Group) or GIF (Graphics Interchange Format), so that they may be further manipulated. Software that performs this function is readily available as freeware, shareware, or commercially, for both PC and Macintosh computers. A good listing of many of these DICOM conversion programs can be found at: www.mrc-cbu.cam.ac.uk/~chris.rorden/dicom.htm#intro . This site includes links that will also enable software downloading. Available choices should fit any user's platform and budgetary constraints.

Although many image formats exist in the world of desktop computing, two formats have come out on top as the formats of choice: JPEG and GIF. Briefly, JPEG is a "lossy" compression technique that can reduce images up to about 5% of their normal size. This technique loses data (hence the term "lossy") during the act of compression, Should the user choose a high degree of compression, the image may become grainy and artifacts may be introduced. GIF is a lossless compression technique (unlike JPEG) that can also reduce image size. Because of the method by which it compresses, it works best with images that have few colors, and it may not compress at all an image that is complex (with thousands or millions of colors or shades). In general, JPEG has been utilized by the graphics community whenever complex images with many colors or shades are being used. GIF has been utilized whenever the image being manipulated contains less than 256 colors and contains broad expanses of a single color or shade comprising a majority of the image. For example, a scanned photograph compresses better with JPEG, whereas a business logo compresses better with GIF. For purposes of radiologic studies, complex images with a wide grayscale may benefit from JPEG storage methods, but with a caveat that the degree of compression chosen should be selected such that the compression does not introduce artifacts. This may require testing the image with various compression settings (low, medium, high, or maximum), something that can now easily be performed by Adobe Photoshop (www.adobe.com/products/photoshop/main.html). By choosing the "Save for Web" option, one can actually see a preview of the image quality before selecting a final choice for compression method or degree.

Once images are generated in a JPEG or GIF format, they will rapidly begin to accumulate on one's hard drive. Consider how many images reside in a film-based teaching file, and you will understand the magnitude of the problem inherent in organizing a large volume of electronic images. As storage media become cheaper, location becomes less of a problem, however categorization remains a difficulty. Concerning storage, hard drives are now routinely 60 GB plus in size, thus the number of JPEG/GIF images (at 10-50 KB) that can be stored may number into the tens of thousands. Other storage alternatives include various forms of removable media, which range in size from 250 MB for an Iomega Zip drive, to 2 GB for the Iomega Jazz drive. CD-ROM drives are now also inexpensive, many of which offer write and rewrite capability, allowing for up to 700 MB of storage space. Lastly, DVD-R drives are becoming commonplace and can store nearly 5 GB. There is no easy answer to the problem of local organization for hundreds or even thousands of image files. The easiest approach at this time is to simply organize images within a hierarchy of folders/directories on a disease and/or modality basis. Any method implemented will likely be heavily influenced by personal bias. The author of this syllabus section maintains an electronic image warehouse of JPEG and GIF images on an internal 40 GB hard drive, categorized on an alphabetized disease process basis.

Construction of DTFs can take any of a number of paths, and the reader will need to choose whichever he or she is most comfortable with. There exist two broad categories of methodologies for DTF construction, which are:

Do the work yourself.
Let someone else do the work for you.

With regards to making DTFs yourselves, five methods will be presented, all of which are readily available and relatively easy. These options range from methods that are free, to ones that will require purchasing commercial software (none of which are prohibitively expensive).

Method 1: Image Viewers

(Figure 1)

The first option is to display images with a simple image viewer. This is a free option, as all computers come equipped with some freeware image software. These programs allow a rudimentary method of display, and will not have any accompanying text or annotation. This isn't so much a teaching file method, as it is simple image display.

Method 2: Word Processors

(Figure 2)

Modern word processors are very advanced, and contain many features that can prove useful for constructing teaching files, and are therefore a second option. As nearly everyone currently uses a word processor, this is also a "free" alternative, and a method will be discussed using Microsoft Word. Both the Macintosh and PC versions of this program are nearly identical, and the following discussion uses terminology used by both.

In Microsoft Word, text can be entered into a format of preference. For example, the first page may contain the patient's presenting signs and symptoms. Subsequent pages may contain images from various modalities, a text overview of radiologic findings, a list of differential diagnoses, and references. Images can be easily inserted by choosing the "Insert: Picture: From File" menu selection. Clicking the mouse within the image will then allow placement within the page, and even resizing if necessary. After all images are inserted, the entire file (text and images together) can be saved as a Word document. Such a teaching file can then be copied onto storage media, displayed on any computer with Microsoft Word (be it Macintosh or Windows), e-mailed, or even distributed from within a web page. The same process is also easily performed using Corel WordPerfect.

Method 3: Presentation software

(Figure 3)

A very popular method of generating presentations for meetings utilizes presentation software, such as Microsoft PowerPoint. Along with Microsoft Word, this is software that is included within the Microsoft Office Suite, and thus is also readily available. Not only can PowerPoint presentations be used for scientific presentations, but they can also be used as an easy method for the construction of DTFs. Such a teaching file can then be copied onto storage media, displayed on any computer with Microsoft PowerPoint (be it Macintosh or Windows), e-mailed, or even distributed from within a web page.

Method 4: Web based files

Currently, a popular method for constructing a DTF is as a web page, which can be distributed or stored, placed on an intranet, or made available to the public on the WWW. This fourth method is slightly more difficult than the preceding ones, however as software is becoming more advanced, ease of use is improving rapidly.

Web pages allow linking between pages, thus allowing a teaching file to easily be broken into components which remain separate (hence "hidden") from each other. For example, one may have an introductory page listing pertinent patient data with links to various topics which are only displayed should the reader choose them. For example, a link to "Images" would load a page of appropriate radiology images, perhaps even in order of acquisition or even importance. Thus, the WWW format holds truer to a teaching file format, allowing a stepwise presentation of facts and/or material for review, on the path to a diagnosis. There are primarily three approaches to web design; some will require an understanding of the fundamentals of HTML (hypertext markup language), others will not, and all are briefly discussed below.

(Figure 4)

The easiest approach to construct a WWW DTF utilizes an existing teaching file that has been initially assembled with a word processor such as Microsoft Word or Corel WordPerfect, as discussed above (Figure 4).

Both of these software programs (as well as other word processors) allow saving (or exporting) a document as an HTML file. One would simply construct the document, save it as an HTML file, and then display it within a web browser. Since most people are already familiar with, and own, their word processing software, this allows for an easy, rapid and essentially free method of constructing a WWW teaching file. Additionally, it requires no knowledge of HTML. The main disadvantage of this method is that it creates a very boring and visually unexciting WWW document that will be displayed as a single, long, continuous sheet of information and images. Thus, the real advantages of using an HTML file are lost.

A second approach for WWW file construction is to use freeware or shareware applications developed specifically for the creation of HTML pages. Popular choices include PageSpinner or HoTMetaL for the Macintosh and Web Media Publisher or Web Gateway for Windows. The advantage of this category of software is that it is either free or relatively inexpensive, and it allows the author to utilize the inherent advantages of HTML documents. Disadvantages arise from limitations of the software itself. In this case, the adage "you get what you pay for" is very true. Most of these programs require at least a rudimentary knowledge of HTML in order to build the WWW page(s), and additional programming or "coding" of HTML will likely be necessary. Thus, for the novice, this approach is discouraged.

The third approach for WWW file construction is to purchase commercially available software (Figure 5).

(Figure 5)

These programs are usually very powerful, relatively easy to use, and many have a "what you see is what you get" (WYSIWYG) display, ensuring that the user never needs to see or manipulate the underlying HTML programming code. These software packages also usually include very advanced techniques of WWW display, such as dynamic HTML (dHTML), JavaScript, Cascading Style Sheets (CSS), frames, etc. Thus, this software is not only appealing for use by beginners, but for seasoned HTML programmers as well. Unfortunately, all of this power comes at a steeper price. The more popular programs are available for both Macintosh and Windows platforms, and include Macromedia Dreamweaver, Adobe GoLive, and Microsoft FrontPage, with prices ranging from $150 to $300 at the time of this syllabus preparation.

Assuming that the user has chosen a level of web authoring software, the overall approach to WWW DTF construction is the same. Whichever software one selects, the user is urged to spend the time necessary to thoroughly learn the program functions, completing tutorials if available. It should be noted, that the flexibility of WWW documents allows for virtually limitless combinations of display techniques, and appearance is really only limited by one's imagination and knowledge. In the next section, the reader will be taken step-by-step through the creation of a very simple WWW DTF. The author used Dreamweaver, on a Macintosh platform, however Dreamweaver for Windows is virtually identical, and the listed commands apply to both.

Making a WWW DTF

(Figure 6)

Using the program Dreamweaver, an introduction page was first created, and the background, text, and link colors were chosen. This was done by opening the menu selection "Modify: Page Properties" and selecting white in the category "Background", black for "text", and blue for "links", all of which appears on a pop-up menu. Here, the web page title "Introduction" was also entered. This process was repeated for each web page created, in similar fashion. A logo for the author's institution was then placed at the top of the page. The logo had been previously downloaded from an institutional web page by first opening the web page in Microsoft Explorer (Netscape Navigator can also be used), placing the cursor over the desired image, and holding the mouse key down. This opens a pop-up menu, and the command "Download Image To Disk" was chosen. (For a Windows-based computer, clicking the right mouse key over the image will open the same pop-up menu.) The logo was then placed into the web page by choosing the Dreamweaver menu selection "Insert: Image", and selecting the logo image in the subsequent menu. Next, the authors e-mail address was placed below the logo by entering the address text exactly as if one was using a word-processor. This text was then highlighted, and a link was created in the "Property Inspector: Link" box by entering "mailto:author@institution.edu". Below this, text was entered concerning patient information, including presenting signs and symptoms. Finally, in a row across the bottom, the text "Introduction, Images, Radiologic Appearance, Discussion, References" was entered (and will subsequently be referred to as the "links text"), which was utilized for linking purposes later in the creation process. This completed the first WWW page, and it was saved.

A new, second page was created and named "Images". Four thumbnail images were inserted using the "Insert: Image" command, exactly as above, performed four times for each of four images. It should be noted, that these four thumbnail images, and their corresponding full-sized versions, had been prepared beforehand in JPEG format and copied into the folder in which the web pages were being saved. Text was entered to the right of each thumbnail, describing each individual image, i.e. "Sagittal T1 of the cervicothoracic spine". Finally, the "links text" listed above was placed at the bottom, and the second WWW page was saved.

Pages three though six contained only full size versions of the thumbnail images, with a text description, and construction of each was identical. A new page was created and named for its image, which was inserted using the "Insert: Image" command. Description text was entered adjacent to each image. Lastly, the "links text" was placed at the bottom, and each of these WWW pages were saved.

Pages seven through nine were entitled, "Radiologic Appearance, Discussion, References", with the appropriate descriptive text for each section entered upon each page. As above, the "links text" was placed at the bottom, and each of these WWW pages were saved.

To complete the teaching file, links were created between all the pages. Starting with the first page, each of the items within the "links text" were linked to its correspondingly entitled web page. To do this, the folder icon adjacent to the "Link" box in the "Property Inspector Window" was clicked upon, which opened a pop-up menu. Here, the web page to be linked to was chosen, and this process was then repeated for each of the elements in the "links text", and for each of the nine web pages as well.

The preceding section described the creation of a very simple WWW DTF. It should be re-emphasized, that the information included within a WWW teaching file, and the way in which it is presented, is limited only by one's imagination, time commitment, and knowledge of his or her software.

Method 5: Acrobat based files

(Figure 7)

The fifth and final method discussed for teaching file construction is the most complex, and utilizes software from Adobe named Acrobat. This program will take any file type as input data (this includes images, word processor documents, web pages, PowerPoint presentations, etc.), and convert it into what is called a Portable Document File (PDF). Such PDF files are read by software from Adobe called Acrobat Reader, which is available for any platform; Macintosh OS, Windows, and UNIX. Most importantly, a PDF file will appear identical on all platforms, which introduces a degree of standardization. The Acrobat software used for constructing the PDF files is available for all platforms, and costs approximately $240 at the time of this writing. However, the software for reading a PDF file is distributed free of charge by Adobe, for all platforms, and is available from many web sites. PDF files can be stored, e-mailed, printed, and placed on an intranet or internet web site. The major disadvantage of this technique is that it adds a level of complexity and cost to an already existing (completed) teaching file. However, it also develops a 100% platform independent file that appears identical on all computers, and can be read by software that is free. For these reasons, Acrobat has become the default standard by which documents are distributed electronically world-wide.

Alternatively, you may decide to let someone else do the work for you! The best example of this method can be found at the MedPix website created by Dr. Smirniotopoulos: rad.usuhs.mil/synapse/medpix.html.

MedPix is a fully web-enabled and cross-platform database that integrates images and textual information. The material is organized by disease category, disease location (organ system), and by patient profiles. The database can be searched through multiple internal text search engines. In addition, search formulations can be sent directly to PubMed, or to other outside search engines with a single keystroke. Registered users may browse the image database through a "slide sorter" module. For those of you who may wish to utilize MedPix for your DTF construction, it is important to note that contributed content may be copyrighted by the original author/contributor, and is used with your permission. The advantage of this process is that it places the mechanical and technical aspects of DTF construction in the hands of someone else, freeing you to concern yourself only with content. The disadvantage is that the DTF resides on the MedPix server and not on your local or institutional network hard-drive.

In summary, you can either construct the DTFs yourself, or enroll in an online DTF agent. For the former, five methods for teaching file construction are presented, ranging from very simple image display to complex files requiring dedicated commercial software. For the latter, the reader can find a good example at the MedPix link given above.

Those who read this chapter in previous ELC syllabi may have noticed little change in content. This is because in the interim, there has been no significant change in the methodologies for creating teaching files, and no standard has been set. However, work is in progress by a number of groups around the country, and hopefully future versions of this chapter will reflect technological advancement and some degree of standardization. Currently, the RSNA has established the Medical Image Resource Center (MIRC), in hopes that national standards can be established for desktop image format, storage methods, DTF presentation and other subjects. Per the RSNA MIRC website:

Medical Imaging Resource Center

Purpose: The MIRC project began with the goal of enabling the medical imaging community to share images and information for education, research and clinical practice. Originally conceived as a central point of storage for such information, MIRC has evolved into a design for a community of libraries linked together through a common index searchable via the Internet. This linking of materials will also encourage convergence on standard formats for images and associated textual information.

Resources: MIRC will provide the tools that will make it easy for sites with existing bodies of information to share them through a central point of access. For authors of new material, it will provide a structured format for teaching files and other documents to ensure that they can be indexed and made accessible using medically significant criteria. For users of these materials, MIRC will provide a Web-browser-based search mechanism that allows free-text queries and searches on medically significant criteria such as patient age and sex, anatomical region, modality, image format, and peer-reviewed status. Sponsored and coordinated by RSNA, MIRC will be a distributed development project, encouraging participation from across the entire medical imaging community.

Institutions can participate as general MIRC sites in three ways:

By implementing MIRC storage and query services

By providing an index of existing materials stored using a database-driven teaching or research library

By providing a site index for a Web-based teaching or research library

Software, documentation, and support for all three methods will be made available by the RSNA.

Individuals or institutions can also utilize MIRC software to create local or regional libraries that they may not wish to share with the entire medical imaging community.

Status: Prototype MIRC software and technical documentation have been developed and are currently being implemented for review and testing by selected sites. It is anticipated that the RSNA's MIRC site will be ready to receive and distribute content prior to the RSNA 2002 annual meeting in November 2002. Exhibits in the infoRAD area of the RSNA meeting will feature case studies by implementers of MIRC sites at leading institutions.

Participation: Institutions that have existing sets of teaching files and other materials, or where there is significant interest in developing such materials, are invited to implement and evaluate the prototype MIRC software. Please make your interest known by sending an email message to informat@rsna.org. If you wish to be made aware when the RSNA MIRC site is open for public review, and be notified about subsequent developments in the MIRC project, please complete and submit the Web form below.

Although this represents a project and software in its infancy, perhaps it will result in a standard by which all radiologists will be able to communicate freely, without fear of proprietary software, incompatible image formats, and inconsistent display methodologies. With such guidelines, discussions regarding the construction and use of DTFs should be much easier in the future.

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