CT body imagers embrace 3D coronal reformations

Body CT imagers are increasingly turning away from axial images and toward coronal reformations. The move helps radiologists in three ways. It reduces the number of images radiologists have to view, it allows them to report more findings, and it increases their confidence in their diagnoses.

For coronal image interpretation to become the standard of care, however, the radiology community needs a change in attitude. Such a change would occur quickly if radiologists would use 3D postprocessing regularly, said Dr. Sunit Sebastian, a research associate at Emory University School of Medicine.

"Advances in multislice CT have substantially increased the number of axial slices radiologists must read. It is imperative to prepare ourselves by using coronal reformats, not only because there are fewer images to interpret-up to a 40% decrease in the number of images-but also to provide more information," Sebastian said.

Sebastian and colleagues conducted the first study that analyzed the value of independent coronal reformatted images to evaluate routine CT of the gastrointestinal tract. They reported the results at the Society of Computed Body Tomography and Magnetic Resonance meeting in April.

Researchers reviewed the records of 50 patients who underwent MSCT for GI tract indications using a 64-slice scanner. Technologists reconstructed the axial images at the CT console to obtain 0.625-mm multiplanar reformatted images. Postprocessing required less than a minute. Two abdominal radiologists were trained on 50 separate exams to overcome the learning curve associated with viewing coronal images.

The average interpretation time of coronal reformats (5.5 minutes) and axial images (six minutes) did not differ significantly. But both readers reported significantly more findings on coronal evaluations (264 and 255) compared with axial images (232 and 227).

The readers also reported higher confidence on coronal evaluations compared with axial images and had good interobserver agreement.

Dr. Alec J. Megibow, past president of the SCBT/MR and vice chair for education at New York University, prefers the term "interactive 3D volume rendering" rather than the more restrictive "coronal reformats." For some cases, coronal reformats may not be the best way to view the pathology.

"The point is that MSCT allows you to get beyond the axial," he said. "Different data displays can provide a more cohesive picture of the disease processes. If you are just in the coronal plane, 90 degrees to where the axial was, I don't think you would get the full benefit of the MSCT scanner. So you need to have some degree of interactivity to prescribe the correct angle of reconstruction or evaluation."

Megibow finds interactive 3D volume rendering particularly effective for CT urography, especially for a comprehensive workup of hematuria, which involves review of the kidneys, ureters, and bladders in an intravenous pyelography-type display with the added benefit of CT contrast. It has become the new standard of care, he said.

Megibow's referral in-box for CT enterography has been overflowing after a recent talk to a group of gastroenterologists on the subject. They asked him why their radiologists weren't doing CT enterography.