3D scheme helps relieve network congestion

Improved resolution from CT and MR studies may be a boon for 3D reconstruction, but the resulting data deluge can slow down image transmission times. Researchers in India have developed a 3D multiresolution scheme especially suited for transmission of large image volume, according to a presentation at the 2003 RSNA meeting.

The technique provides multiresolution-based thick slab, not available for 2D image viewing, said Sudipta Mukhopadhyay, Ph.D., lead engineer at Global Imaging Technology Laboratories, GE India Technology Center, in Bangalore.

With spatial multiresolution, the same image can be viewed at different resolutions. Mukhopadhyay explained that if you start with a 512 x 512 image, 2D and 3D multiresolution can provide 256 x 256, 128 x 128, or 64 x 64 images.

In 3D image viewing, multiresolution is also applied to the axial direction. If the user starts with a block of eight frames, using multiresolution in the axial direction provides eight-, four-, two-, and one-frame views representing that block, he said.

"In other words, we can view all frames in full axial resolution or lower axial resolution, a facility absent in 2D schemes," Mukhopadhyay said.

Modern scanners provide better axial resolution compared with earlier versions. While this is good for 3D reconstruction, radiologists have to go through more images, which means productivity takes a hit.

The more pertinent question is, Do radiologists want to view 1-mm nodules in a particular anatomy?

"Radiologists may settle for a resolution less than what the scanner can provide," Mukhopadhyay said. "For some procedures, they still opt for 5-mm thickness. Then, after the reading, if they want a higher resolution image, they have to rescan, meaning added delay and increased cost."

In the method described by Mukhopadhyay, scanners can take the image at highest resolution and have the 3D scheme provide images at the same or lower axial resolution - all supported from same bitstream.

This means 3D reconstruction can get maximum benefit of the scan resolution and radiologists can choose the resolution (slice thickness) they want to view.

"They can choose some lower resolution, then if they find something interesting can dynamically switch to higher resolution," Mukhopadhyay said. "This allows radiologists to choose the slice thickness they feel appropriate, thereby saving time."

Since all resolutions are generated from same bitstream, each radiologist can individually select the thickness number for viewing the same exam, he said.