DOI: 10.1148/rg.256055065
RadioGraphics 2005;25:1699-1708
© RSNA, 2005
Informatics in Radiology (infoRAD)
Multimedia Extension of Medical Imaging Resource Center Teaching Files1
Guo Liang Yang, MSc,
Aamer Aziz, MD, PhD,
Banukumar Narayanaswami, BEng,
Ananthasubramaniam Anand, MSc,
C. C. Tchoyoson Lim, MD and
Wieslaw Lucjan Nowinski, PhD, DSc
1 From the Biomedical Imaging Laboratory, Agency for Science Technology and Research, Singapore (G.L.Y., A. Aziz, B.N., A. Anand, W.L.N.); and National Neuroscience Institute, Singapore (C.C.T.L.). Presented as an infoRAD exhibit at the 2004 RSNA Annual Meeting. Received March 23, 2005; revision requested May 25 and received July 11; accepted July 18. Supported by the National Healthcare Group and the Biomedical Research Council of the Agency for Science, Technology and Research, Singapore. All authors have no financial relationships to disclose.
Address correspondence to G.L.Y., 30 Biopolis St, 07-01 Matrix, Singapore 138671 (e-mail: glyang{at}sbic.a-star.edu.sg).
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Abstract
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A new method has been developed for multimedia enhancement of electronic teaching files created by using the standard protocols and formats offered by the Medical Imaging Resource Center (MIRC) project of the Radiological Society of North America. The typical MIRC electronic teaching file consists of static pages only; with the new method, audio and visual content may be added to the MIRC electronic teaching file so that the entire image interpretation process can be recorded for teaching purposes. With an efficient system for encoding the audiovisual record of on-screen manipulation of radiologic images, the multimedia teaching files generated are small enough to be transmitted via the Internet with acceptable resolution. Students may respond with the addition of new audio and visual content and thereby participate in a discussion about a particular case. MIRC electronic teaching files with multimedia enhancement have the potential to augment the effectiveness of diagnostic radiology teaching.
© RSNA, 2005
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Introduction
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Medical teaching is as old as the medical profession itself; it is one of the essential responsibilities of the physician that are incorporated in the Hippocratic oath (1). Traditionally, the teaching of radiology has involved the use of case-based files of hard-copy images. With the advent of digital imaging, picture archiving and communication systems, and the World Wide Web, the use of electronic media to enhance radiology teaching has increased, and many methods have been proposed for exploiting the advantages of electronic media in the form of teaching files (2–10). To aid knowledge sharing and collaboration in this area, the RSNA initiated the Medical Imaging Resource Center (MIRC) project (11,12), which has defined a set of protocols and formats to facilitate and standardize the storage, query, and retrieval of radiologic images and related information via the Internet. One of the goals of the MIRC project is to create a virtual global library of teaching materials through Internet links to electronic teaching file repositories at radiology institutions around the world. Toward this end, open-source software for creating and maintaining electronic teaching file sites has been made available at the MIRC site (http://mirc.rsna.org).
Currently, the MIRC electronic teaching files consist of pages of text and images that resemble those in a book, with limited interactivity in regard to document display and quizzes. Although MIRC electronic teaching files are more than adequate as replacements for hard-copy teaching files, they leave untapped the great potential of video and audio media to augment educational content. In radiology education, the process by which the radiologist reaches a diagnosis is just as important as the recognition of disease. A drawback of the static electronic teaching file is its inability to convey the steps in this dynamic process in a way that initiates and encourages interaction between teacher and student. It would be desirable to extend the current MIRC encoding schema to allow the user to manipulate, annotate, and add illustrative graphic elements to a radiologic image step by step, toward the culmination of the interpretive process in a final diagnosis. However, many digital audio and video encoding methods produce large and cumbersome files that can be transmitted only slowly via the Internet. We describe a method for creating interactive multimedia extensions of existing MIRC electronic teaching files. To our knowledge, there is no previously published report about multimedia-enhanced MIRC electronic teaching files.
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Materials and Methods
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Our method is based on the MIRC encoding schema for radiology teaching files but provides additional multimedia capabilities for audio and video encoding, multimedia recording and playback, and Web-based discussion. By using a prototype of a system that we developed, we created multimedia teaching files from existing MIRC electronic teaching files. We then compared the electronic file size and the speed of Internet transmission for our multimedia teaching files with those for multimedia teaching files prepared by using commercially available software for audio and video recording (Windows Media Video; Microsoft, Redmond, Wash). We also obtained informal feedback about the prototype from visitors to our infoRAD exhibit at the 2004 RSNA Annual Meeting (13).
MIRC Teaching Files
The MIRC-defined standard format for electronic teaching files (14) is based on the use of extensible markup language, or XML, with the inclusion of links to binary files such as radiology images. The following snippet from the MIRC document schema shows how images are defined.
<MIRCdocument>
<title>. . . </title>
<image href= "image01.jpg" >. . . </image>
</MIRCdocument>
When a MIRC teaching file that is published on the Internet is accessed with a commonly used Web browser (eg, Internet Explorer; Microsoft), the file is displayed as a series of static Web pages (Fig 1).
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Figure 1. Screen capture of a MIRC electronic teaching file shows typical static display of text and images with a popular Web browser. This teaching file is based on magnetic resonance (MR) images obtained in a 73-year-old man with spinal schwannoma, who presented with back pain.
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Audio and Video Encoding
The multimedia extension of the MIRC electronic teaching file consists of two aspects: digitally encoded audio content and video content. We developed a software program in Java language for audio recording and playback. We evaluated various audio encoding techniques and decided to use the Global System for Mobile Communications standard (15,16) because it enables a compression ratio up to 10-fold that available with uncompressed pulse code modulation while maintaining acceptable audio quality (17).
We defined our own format for video encoding to improve efficiency and achieve a small file size. Instead of using screen capture, we store, in each video frame, the current state (eg, window level, zoom factor, offsets, annotations) of the radiologic image, information that requires significantly fewer bytes than does screen capture. By using the information about the image state, our software application subsequently reconstructs the entire visual record for the user. Figure 2 shows a simplified schematic of our video encoding method. The video file is headed by a number that is preceded by the letters MMT and that indicates a valid multimedia teaching file, followed by the title of the teaching file, a key node table, an image table, and a frame table (Fig 2). The key node table contains entries for all key node data (name, time, and description of each key node point in the video). The radiologic images in the teaching file are stored in the image table, in their original formats and without further compression. For encoding of individual frames of the video file, each frame is assigned an image number that indicates an entry in the image table.
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Figure 2. Partial schematic of video encoding of a multimedia teaching file. The video file consists of multiple frames, each of which contains only information about the image state, and not the radiologic image itself.
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The position and sequence of each image state over time (ie, each frame in the video-encoded format) is stored as an entry in the frame table. Finally, information for all annotations that the user makes on the image, such as a line, arrow, rectangle, circle, ellipsis, or polygon, and for any text added by the user, is stored in the annotation table. For each annotation, different information is saved: For example, for each added line, the coordinates of the starting point and endpoint are recorded; for each circle, the coordinates of the center and the radius are recorded.
Another way to further reduce the storage size for each frame is through the use of flags. For example, if the state of a frame is exactly the same as that of the preceding video frame, only a flag (which occupies less space than the entire video frame) is stored, in addition to the frame sequence number and time stamp. This usually happens when the user records audio content alone, without any on-screen manipulation of the image.
Multimedia Recording and Playback
Recording and playback are both Web based. Users can access the multimedia teaching file capabilities only by using Web browsers such as Microsoft Internet Explorer or Netscape Browser with a Java (level 1.4 or higher) plug-in. Hardware requirements are minimal; a microphone is needed for recording, and speakers or headphones are required for audio playback. A mouse usually is needed to manipulate the image.
The simplified flowchart in Figure 3 illustrates the main steps used to record a multimedia teaching file. Two Java threads are used to record audio and video synchronously and separately. Figure 4 shows the audio and video recording screen. The author first selects an image from the thumbnail panel at the left. This is the active image that will be used for multimedia teaching. The author can change the appearance of the image by altering the window level and zoom factor, and can add annotations such as lines, arrows, rectangles, and text. The author then can select a different image and repeat the process or can toggle between images. During the image manipulation, the author can use the microphone to record an audio narrative that describes the process. The system records and saves the entire process of screen operation, as well as the audio thread, as a multimedia teaching file.
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Figure 4. Photograph shows a user of a MIRC electronic teaching file who is recording a multimedia teaching file by using a mouse and microphone. The user highlights a tumor (schwannoma) on the MR image by using graphic annotations (circle and arrow) while recording an audio commentary about the features that may help radiologists to distinguish the tumor from adjacent normal intervertebral foramina.
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The multimedia teaching file may be previewed immediately by the author and played back later by other users. Figure 5 shows the on-screen display during playback of a file by using the multimedia teaching file playback software. Another example of file playback can be viewed at http://www.mirip.org/mmtfdemo/mmtf.html.
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Figure 5. Screen capture shows the same case as in Figure 4, during playback of the multi-media teaching file. The typical dumbbell-like shape of the tumor is highlighted both in the audio description and with a graphic (white outline) overlay on the MR image. Other users can add their remarks to the multimedia teaching file by clicking on the Comments button.
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Web-based Discussion
We also implemented a Java applet to enable the sequential addition of multimedia teaching files as hot links to a Web page, to create what we refer to as a Web-based discussion thread (Fig 6). Users can initiate discussion about a case by using the multimedia applications in the electronic teaching file, and other users can respond.
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Figure 6. Screen capture shows the Web-based discussion thread in the multimedia teaching file application. By clicking on Create New, users can record their responses to other users’ remarks, thereby adding to the richness of the dialogue.
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Results
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After developing the multimedia teaching file software system, we successfully transferred 160 MIRC electronic teaching file cases into the system and generated several multimedia teaching files. Our multimedia files were about 13 times smaller than those prepared by using Windows Media Video file format. The average multimedia teaching file size is about 130 kB per minute of video recording. As a result, users with a digital subscriber line, or DSL (typical download speed, 25 kB/sec), were able to transfer a multimedia teaching file with a playback time of 3 minutes 10 seconds in about 16 seconds via the Internet. In comparison, it took about 212 seconds to transfer a Windows Media Video file of the same playback duration. Although transfer time may be reduced with higher-speed cable broadband service (eg, 250 kB/sec), downloading is still 13 times faster for a typical multimedia teaching file because of the relatively small size of the file. The Table provides a comparison of files in the two formats and the estimated time to download each type of file at different bandwidths.
When we demonstrated our multimedia teaching file system at the 2004 RSNA Annual Meeting, visiting radiologists were invited to test the system and give us their comments. The general opinion of its features was positive, and there was considerable interest in adopting this new method for radiology education. Users of the system noticed that the multimedia teaching files were not only smaller but also had higher resolution than did their Windows Media Video–format counterparts. Many visitors remarked that the high compression ratio that had to be used to reduce the latter files for transmission via the Internet resulted in a transmitted image quality that was unacceptable for radiology education. Conversely, our multimedia teaching files, which included the original images reproduced with full fidelity to clarity and detail, were preferred by the users (Fig 7).
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Figure 7a. Screen captures show the same frame from video recordings made by using the Windows Media Video software (a) and the multimedia teaching file applications (b). The multimedia file is smaller, has a shorter download time, and has better image quality for radiology teaching. The multimedia teaching file applications allowed the teacher not only to highlight the subdural hematoma (red outline) and a shift in the midline (green outline) but also to record an audio description of the findings on the computed tomographic image of a 56-year-old man with head injury.
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Figure 7b. Screen captures show the same frame from video recordings made by using the Windows Media Video software (a) and the multimedia teaching file applications (b). The multimedia file is smaller, has a shorter download time, and has better image quality for radiology teaching. The multimedia teaching file applications allowed the teacher not only to highlight the subdural hematoma (red outline) and a shift in the midline (green outline) but also to record an audio description of the findings on the computed tomographic image of a 56-year-old man with head injury.
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Discussion
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Radiology teaching differs from other medical teaching in that radiology is more heavily dependent on images and graphics. With the widespread adoption of the Digital Imaging and Communications in Medicine standard, the potential is great for the educational use of digital radiologic images. The RSNA MIRC initiative is a first step toward realizing this possibility through a unified schema that enables teaching files to be exchanged and searched via the Web. Our group has designed and developed several MIRC-compliant electronic teaching file applications (including the current system) and demonstrated them at the 2002, 2003, and 2004 RSNA Annual Meetings (13,18–20). These systems are now used in routine radiology teaching activities in several hospitals.
However, for teaching diagnostic skills in radiology, it is important to convey the process by which a diagnosis is reached, and this cannot be adequately done with the use of static images only. The student must be able to perceive the features that differentiate the abnormality from surrounding tissues, to consider the nature and significance of these features, to sequentially view other anatomic locations for supportive evidence, and to weigh the relative probabilities of several competing diagnoses. This process of detection, identification, and analysis, although it is familiar and intuitive to the practicing radiologist and teacher, must be dissected into discrete components if it is to be adequately captured and conveyed digitally through a multimedia extension to the MIRC electronic teaching file. The process of diagnosis then may be presented didactically with visual keys (arrows), outlines, and annotations (text labels) by using the teaching file as a sort of electronic chalkboard.
We implemented a new method that allows a teacher to record on-screen manipulations of radiologic images as a multimedia teaching file that is small enough to be transferred quickly via the Web. The major limitations of other multimedia or video formats used for radiology teaching are the large file size and low image quality. For example, if each frame contains a radiologic image with 100 kB of information, then a 10-minute video with playback at a rate of 5 frames per second requires 3000 frames, or about 300 MB of information. Because the frame rate must be at least 5 frames per second to maintain continuity, we made the frame as small as possible to reduce the total video file size. We developed an efficient frame encoding method that does not store the whole image in each frame and yet contains all the information necessary to reconstruct the on-screen image. This is done by encoding only the original image status and any subsequent changes. Furthermore, because in our method the radiologic image is stored only once and is not further compressed, we are able to achieve acceptable image resolution, an important criterion for user acceptance. These features enable the teacher to convey the step-by-step process of diagnosis and support a more interactive method of radiology teaching.
Furthermore, with the use of simple Web technology, virtual discussion groups can be created to enrich learning by adding another layer of interaction between teachers and students. If students have any doubts after viewing a multimedia teaching file, they can record their questions in the same electronic file by using audio and visual operations. The teacher then can respond with further additions to the multimedia file. (Fig 5 shows the Comments button that may be used for the purpose of commenting or responding.) Teachers and students thus can participate jointly in the discussion thread, an application that is familiar to Web users, but in this case it is multi-media files that are exchanged instead of text.
A further potential application of this method may be in the testing of students’ knowledge. A radiologic image with a brief history may be given to the student, who then interprets it while using audio and visual operations to record the decision-making process leading to the diagnosis. The teacher can assess and grade the student not just according to whether the diagnosis is correct but also according to the completeness of the thought process used to reach the diagnosis. This virtual oral examination could even be carried out remotely, without a need for the examiner and candidate to be in the same room.
Currently, a multimedia teaching file can be created only as an attachment and not as an integral component of the MIRC electronic teaching file. In the future, it may be possible to amend the MIRC schemas to allow the direct incorporation of multimedia content into an electronic teaching file, so that users can take full advantage of multi-media functionality. Although we have developed a method to enhance the teaching of radiologic interpretation, its applicability to diagnostic radiology education is limited. This method does not address the teaching of radiology procedures, such as the placement of an ultrasound probe.
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Conclusions
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In this article, we describe a new way of using multimedia to record and teach the process of radiologic image interpretation. We enhanced MIRC electronic teaching files by developing an encoding technique that creates audio and video file attachments that are small enough to be transmitted via the Web and at the same time maintain acceptable image resolution. Electronic teaching files augmented with multimedia may enhance learning and may lead to broader acceptance and adoption of MIRC standards for radiology education.
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TAKE-HOME POINTS
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The addition of multimedia video and sound to electronic teaching files has the potential to enhance the teaching of radiologic image interpretation.
By using a new file format, multimedia teaching material can be recorded and transmitted quickly with the associated digital images via the World Wide Web.
The incorporation of multimedia into initiatives such as those of the Medical Imaging Resource Center may help augment remote learning in diagnostic radiology.
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Acknowledgments
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We thank all of the radiologists who contributed the MIRC electronic teaching files that were used to develop the multimedia enhancement method reported in this article, and all of the people who participated in its evaluation at the 2004 RSNA Annual Meeting.
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Footnotes
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Abbreviations: MIRC = Medical Imaging Resource Center
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References
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Abstract
Introduction
