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Seeking to make information on rare and important fossil and extant specimens more readily available, the Center for Instructional Technologies in collaboration with the UT Austin High Resolution X-ray CT facility developed a Java applet viewer – the UTCT InspeCTor – for the Digital Morphology Web site. This tool lets viewers use high-resolution X-ray CT (computed tomography) images interactively. They can browse through available slice planes, access full screen and annotated image files, view text information, and measure distances between features on the images.
As part of the National Science Foundation Digital Libraries Initiative, the Digital Morphology Web site serves unique 2D and 3D visualizations of the internal and external structure of living and extinct vertebrates, and a growing number of invertebrates. One of the major goals of the Digital Morphology project is to develop and implement new software for transforming CT and other tomographic data into novel and informative 3D visualizations of complex biological objects, accessible over the Web.
To serve the need for an image viewer that would allow interactive browsing through a three-dimensional CT dataset over the Web, David Guzman and later Denise Ketcham of the Center for Instructional Technologies were tasked to develop this tool in Java. The initial idea for the UTCT InspeCTor interface was inspired by the Visible Human Project. The slice viewer presents an intuitive way for the user to easily orient themselves and navigate to any slice they wish to examine, as well as the ability to view the image in a higher resolution large format, with annotations. Richard Ketcham of the UT Austin High Resolution X-ray CT facility further refined the tool and is enabling the publication and distribution of datasets using the UTCT InspeCTor on CD-ROM.
The java.awt package classes were used to construct the user interface and to control graphics. Custom components were developed to display the CT slices, provide zooming capabilities and enable measurements. Custom scrollbar components allow rapid scrolling through the slices. The applet was developed using Borland’s JBuilder 4 Professional development environment and JDK 1.1.
The user can view X-ray CT slices through an object from three different planes: the sagittal, horizontal, and coronal planes. Index images with an attached scrolling line are provided on the left-hand side of the viewer window. Dragging with the mouse scrolls through the slice images for that plane. The position of the scrolling line on the index image corresponds to the slice number of the displayed slice image. The slice image is displayed in the upper right side of the viewer window.
The first of two text areas displays information about the currently selected slice: slice number and plane, mouse position, and measuring information. The second text window displays sample information, such as name and collection.
The zooming function allows the user to select the section of the slice that they wish to enlarge. While zoomed, point locating and distance measurements are enabled, as are the forward and backward slice navigation controls. Some detailed information can be obtained from the image by using mouse options: a mouse click will display point coordinates in the text area. By performing a mouse hold-and-drag the user can measure the distance between two points. Points and distances are given in reference to "fossil" coordinates, where the center of the specimen is the x, y, z coordinate point (0, 0, 0). The applet converts pixels to actual dimensions and allows pinpointing of features in three dimensions. Measuring is always enabled, not solely in zoom mode, and the data can be posted to a supplemental text page.
Navigation through the slices can be precisely controlled with buttons. Two buttons on the far left of the button bar provide a means for moving forward or backward one slice. The middle three buttons animate the slices. Animation works best with a high-speed connection and can be disabled for better performance. The 100% button will activate a pop-up window to display a full-scale image of the currently selected slice.
Generally, every fifth slice will be annotated by an expert researcher, and these images can be accessed from a labels button on the applet. A page with a glossary of abbreviations is available using the drop-box at the bottom of the applet frame. Currently only one specimen on the Digital Morphology site—Thrinaxodon liorhinus—is annotated, with others becoming available soon.
The UTCT InspeCTor applet aids researchers and students in the manipulation, interpretation, and dissemination of high-resolution X-ray CT datasets in a collaborative project that will provide a growing library of unique information on comparative organismal morphology. It is an important part of an effort to further research fundamental to the next generation of digital libraries, and to advance the use of globally distributed, networked information resources.