roper lighting in rendering is essential for visualizing 3D objects, but most visualization software tools still employ simple lighting models. Over the past few years, advances in graphics hardware and the introduction of globalillumination approximations for volume visualization 1-3 have begun to make advanced illumination feasible for visualization. Here, we show how we used global illumination in volume visualizations of x-ray computed tomography (CT) wrist data for evaluating responses to treatment of rheumatoid arthritis (RA). In the task we're studying, physicians or clinical researchers identify and examine bone erosions in RA patients' wrists and hands. To study the disease's progression, multiple CT scans are made over the treatment period. Even though volume rendering has been around for many years, the common practice is still to study individual 2D slices of the data, which leads to two problems. First, in 2D, it's hard to determine the area and extent of erosion, which is a 3D feature. Second, in 2D, it's also hard to identify and compare the same bone erosions from different scans. Although 3D visualization clearly should be used for such tasks, current volume visualization tools raise several issues. For example, local illumination might erroneously increase the prominence of certain surface features, which affects interpretation and diagnosis. To address this issue, we conducted a study with experts who were familiar with the disease process and medical-image interpretation. In particular, we studied tasks for which we believe proper illumination can enhance user performance. Our results indicate that interactive visualization with global illumination helped the experts derive more accurate interpretations of the image data. With clinical needs and the recent advancement of volume visualization technology, this study is timely and points the way for further research.
Global illumination techniques, for example, have been proven to improve the perception of surface features in volume visualization REF .
Using Global Illumination in Volume Visualization of Rheumatoid Arthritis CT Data
IEEE Computer Graphics and Applications
IEEE Computer Graphics and Applications
Medicine Computer Science