GE's first high-definition CT enters clinical operation

GE Healthcare's LightSpeed CT750 HD began operating in late May at a luminary site near the company's Wisconsin R&D offices. It is the first in a planned network of beta clinical sites slated to put the ultrapremium CT through its paces before the company begins commercialization.

GE Healthcare claims the CT750 HD boosts spatial resolution to 230 microns and improves contrast by 33% or more. Froedtert Hospital, an affiliate of the Medical College of Wisconsin in Milwaukee, is putting those claims to the test.

Froedtert's first clinical case has produced images of the abdomen showing both hard and soft tissue, as well as an orthopedic implant. A major focus of the Froedtert research, however, will be above the abdomen-the coronary arteries. Dr. W. Dennis Foley, director of Froedtert's digital imaging section, will use the scanner's unique abilities to subtract calcium from the coronary CT angiograms to reduce blooming artifact. Calcium subtraction could be the most significant improvement in coronary CT angiography since this technique was developed, according to Foley.

"Let's say we could actually image the coronary arteries without having to mentally subtract blooming due to calcium," he said. "That would put you on a par with the coronary arteriogram. In fact, the differences then between coronary CTA and cardiac cath might not be significant."

The CT750 HD will be positioned as a general-purpose radiological scanner that excels at visualizing all parts of the body. In the marketing blitz sure to come as RSNA 2008 draws near, GE will emphasize soft-tissue visualization in the bowel, bladder, prostate, liver, muscle, and even the arms and legs.

As competition in the CT market heats up, GE will be at a disadvantage when comparing the width of its detector against the 320-row detector onboard Toshiba's Aquilion One. But GE strategists hope to neutralize the issue with a technique that rapidly moves the GE detector back and forth to cover a wider area. This Volume Shuttle extends the reach of the company's new detector enough to dynamically cover whole organs, including the heart, lungs, brain, and liver.

In matchups against Siemens' other premium CT scanners, GE will emphasize the LightSpeed CT750 HD's resolution of 21.5 line pairs/cm in the body, a marked advance over the 14 to 16-lp/cm benchmark for current 64-slice systems, according to the company.

Based on measurements done by GE that compare the HD with current 64-slice technologies, image quality will improve by 33% for the body, and spatial resolution will improve to 230 microns-about the thickness of a human hair. Cardiac imaging will improve about 47% from between 8 and 10 lp/cm to between 12 and 14 lp/cm. GE will further showcase x-ray dose reductions of 50% in scans throughout the body that are similar to those achieved using methods applied on earlier LightSpeed versions when imaging the heart.

If the LightSpeed CT750 HD lives up to company claims, it could have a dramatic impact on medical imaging in areas of the body far from the heart. The system has the potential to draw data from 101 separate energy levels to reveal information specific to certain clinical conditions.

Calcium might be subtracted from arterial plaque at 80 kVp, thereby eliminating calcium blooming. Images obtained between 100 kVp and 110 kVp show about 50% less beam hardening. This savings, in turn, may be used to improve the visualization of orthopedic prostheses. A newly developed x-ray tube, generator, and detector allow the system to switch energies in 0.5 msec.

But the ability to tap into this energy range may offer much more: the ability to tune images to the optimal energy for viewing specific types of tissue. Certain sweet spots may exist for certain types of visualization. Liver lesions, for example, may appear best in the range between 75 kVp and 83 kVp, according to preliminary research.

The cornerstone of the new GE systems is a detector made principally from garnet. The chemical structure of this gemstone has been enhanced with proprietary materials to improve its sensitivity to radiation. The x-ray tube adjusts the shape and energy of focal spots. Its newly formulated data acquisition system optimizes information management, while improved reconstruction software and hardware do the postprocessing.

The footprint and frame of the new scanner are indistinguishable from those of its predecessors. The only externally discernible differences are a subtle change in coloring and imprint of the GE meatball on the right front and the letters HD on the side.