New tool facilitates fusion and visualization of multimodal studies

Multimodality visualization of pathologies is often preferable to single-modality studies, yet little research has been devoted to the fusion of registered multimodal imaging studies.

Researchers at the Rochester Institute of Technology recently announced the availability of Fusion Viewer, a free solution for visualizing 3D data sets (J Digit Imaging 2007 Oct 25 [Epub ahead of print]).

"The most significant advantage of the Viewer is its capabilities in examining multiple data sets simultaneously," said Carl Baum, Ph.D., of RIT's Carlson Center for Imaging Science.

Not only does Fusion Viewer keep multiple data sets synchronized; it also provides tools for displaying them as a single color data set.

The need for such a solution is even more urgent now that commercial PET/CT scanners are readily available and PET/MR scanners are being prototyped.

"Often, registered images are simply presented next to each other," Baum said.

This can be risky, particularly if the images are being used to plan procedures such as biopsies. Baum has found that radiologists may have misregistration errors of over a centimeter when reading registered images this way.

This registration error occurs even if the images are perfectly registered, due to how the human visual system and mind interpret the data, Baum said.

"This error is particularly significant in modalities that show different information, such as an MRI showing structure and a PET showing metabolic activity," he said.

The most common proposal to avoid this problem is to combine the two (or more) gray-scale images into a single color image, he said.

"Our study also showed that the way we combine images has a significant impact on the ability of radiologists to access information from the combined images," Baum said.

Even small variations in color can effect the utility of an image.

Fusion Viewer was designed to provide a framework supporting these different techniques for fusing images.

"The hope is the tool will serve to facilitate additional research on fusing and presenting medical data," Baum said.

In addition to fusing capabilities, Fusion Viewer provides several options for mapping 16-bit data sets onto an 8-bit display, including windowing, automatically and dynamically defined tone transfer functions, and histogram-based techniques. Both traditional maximum intensity projections and MIPs of fused volumes are supported.

Fusion Viewer is currently distributed as freeware. The system will run on any Windows computer with Microsoft's .NET Framework installed. A Mac version is pending.