Techniques abet diagnosis and display in daily practice

What pundits have been predicting for years appears to be coming true: 3D is becoming as valuable for diagnosis as for display. From a solo radiology practice in Florida to Stanford University's sophisticated 3D lab, manipulation of images in multiple planes and creation of surface-shaded images, maximum intensity projections, and volume renderings are becoming routine in CT interpretation.

"Three-D permits diagnoses that would be impossible without it," said Dr. Robert Novelline, director of emergency radiology at Massachusetts General Hospital. "In the past, it was primarily a display tool, but today it's a diagnostic tool as well."

That's not to say 3D has relinquished its role as clinical communicator. In the ER, for example, 3D displays injuries to clinicians in a familiar and easily recognized format. It conveys critical information that might otherwise require reviewing hundreds of individual 2D slices, Novelline said at the 2005 Symposium on Multidetector-Row CT.

From routine to rare, the range of cases that can benefit from 3D is vast. Dr. Mark Herbst, a solo radiologist and head of St. Petersburg Radiology in Florida, values both the diagnostic and display capabilities of 3D for CT and MR.

"It's easy enough for me to say, 'arthritis' or 'displaced fragments' in the report," he said. "But when I show referring physicians the images, it's over the top. And if a solo practitioner can use 3D software to enhance his practice, anyone can."

Herbst uses his PACS, 3D interpretation, Web-based reporting, and teleradiology network to read images for 40 centers in Florida. Including 3D images in reports has made him a better radiologist, he said.

"Talk about 'evidence-based' medicine.' If I write 'herniation' in the report, I have to make sure the accompanying image supports that," he said. "If it doesn't, I find another image or change my diagnosis. It makes me much more careful about what I say."

With data sets for an average case now numbering in the thousands of images, multislice CT has spurred radiologists to integrate 3D techniques into their diagnostic routine. At the University of California, Davis, 3D software is an integral part of the facility's PACS. The goal is to help radiologists deal with slice overload, according to Dr. Anthony Seibert, a professor of radiology. The software is used to provide a wide range of multiplanar reconstructions and 3D renderings, drilling from one level of sophistication to the next in just a few clicks (see "Software lets readers explore new ways to view image information," October 2003, page 79).

"There are two main reasons for using 3D," said Dr. Matthew Barish, director of the 3D and image processing lab at Brigham and Women's Hospital in Boston. "The first is the ability to display complex anatomy to referring physicians and surgeons using only one or a few images. It would require a large number of axial images to communicate the same amount of information. The second is actual diagnosis. Certain things are apparent on 3D images that radiologists tend to overlook."

Radiologists may find that multiplanar reformations provide the greatest utility for day-to-day practice.

"When I talk about 3D to other radiologists, I emphasize that up to 90% of what you are doing this for is multiplanar reformats," said Dr. Shawn Teague, an assistant professor of radiology at Indiana University School of Medicine in Indianapolis.

Regardless of the 3D application or technique employed, the radiologist's goal remains the same: to optimize disease detection, define disease extent for management, and improve patient treatment. Three-D supports all of those goals.

On the following pages, readers will find numerous ways to get up to speed in 3D, examples of 3D use in a range of settings, training goals, and tips from users on how to evaluate 3D trends in integrated systems.

Ms. Dakins is feature editor of Diagnostic Imaging.