Stack viewing improves radiology presentations

Radiologists attending this year's RSNA meeting will discover that many presenters have adopted a new tool that allows them to manipulate image stacks just as they would on a PACS workstation.

The standard presentation platform (Microsoft's PowerPoint) does not provide radiologists the ability to interact with images as they do in clinical practice, making presentation of 3D information difficult. The solution, called StackViewer, enables them to easily and interactively display stacks of images in PowerPoint presentations.

That was not previously possible because software tools were created as ActiveX controls, with a number of inherent limitations, said StackViewer designer Dr. Benoit Desjardins, director of the cardiovascular MR/CT research lab at the University of Michigan.

"No tool had been able to save the images in a stack within the PowerPoint file itself," said coauthor Thomas Gniadek, a second-year medical student at Yale University. "Thus, moving a presentation file to a different computer required moving a directory of image files along with it."

Although installing ActiveX controls on a computer is relatively simple, it requires another step that can hinder transfer and distribution of presentations. And ActiveX controls do not run on Mac OS X. StackViewer allows stacks of 2D images to be displayed interactively on Windows-based or Mac OS X computers without compromising portability or compatibility. The researchers describe their technology in the September issue of the American Journal of Roentgenology.

"The real beauty of our tool is that all the code to interact with the stacks of images is integrated in the PowerPoint presentation," Desjardins said.

This means that no additional software has to be installed on the computer to view the stacks. StackViewer components are embedded directly into PowerPoint files when the presentations are created, yielding true portability. Presenters simply click on a paused stack of images and it becomes interactive. Moving the cursor up and down over the image changes the displayed image in the stack. There is a direct correspondence between the vertical position of the cursor on the displayed image and the index of the displayed image in the stack. Moving the cursor toward the top of the visible image displays images earlier in the stack, whereas moving it toward the bottom displays images later in the stack.

Stacks also can be linked, which is useful for showing the same features in two different window settings; for example, a lung window and a soft-tissue window setting for a chest CT or two examinations separated in time to show disease evolution.

"Our goal is to bring the same ability radiologists have in the reading room to presentations at local and national meetings," Desjardins said.

Desjardins created the tool in 2002, but it proved difficult to use. Last year, he teamed up with Gniadek to create an interface, and StackViewer is the result.

The latest version of StackViewer can be downloaded free of charge at http://www.StackViewer.com. Asked why he is giving the software away, Desjardins said he wants all radiologists to use it.

"After all, I'm in academic radiology, so you know I'm not in it for the money," he said.