Children's hospital dedicates 64-slice CT to pediatrics

Mention 64-slice scanners, and the conversation inevitably turns to the heart: coronary angiography, cardiac assessment, the looming battle with cardiologists. At Children's Hospital and Health Center in San Diego, radiologists have put a new twist on this discussion, applying GE's LightSpeed VCT exclusively to pediatrics.

"We use the VCT to do things we have never done at Children's," said Dr. John Hauschildt, head of education for the resident program and a primary user of the volumetric CT since its installation in August.

The 64-slice scanner has opened a noninvasive route to the assessment of congenital heart disease and vascular disorders while reducing sedation for more routine CT applications. The VCT has wrested control of diagnostic cases from the cardiac cath lab, which had been pediatricians' mainstay for evaluating children with congenital heart disease and for planning and following up interventions. Because corrective surgery is usually done in stages, children may have 10 or 20 cardiac caths over a lifetime.

"Each one carries the risks and costs of catheterization, as well as the radiation exposure and anesthesia," Hauschildt said.

Very young patients must be heavily sedated during cardiac cath, which can take hours to perform, he said. But the CT alternative takes only three to four seconds and does not require sedation.

The VCT provides higher resolution images than cardiac cath, showing connections between the vessels, holes in the heart, anatomy of the pulmonary veins and arteries, and the aortic arch. Volumetric acquisition provides an additional benefit over cardiac cath.

"You can view the images any way you want," Hauschildt said. "In cath, you are limited to one or two planes."

Customized reconstruction offers another perk: an outside view looking in. Cardiac cath shows only the inside of the heart and coronaries, which is not as helpful.

"When you do surgery, you are operating from the outside in, not from the inside out," he said.

The noninvasive nature of CT and its lower radiation dose add to the list of advantages. The staff at Children's Hospital in San Diego are therefore more inclined to use CT to diagnose congenital heart disease and to plan for and follow up on surgery. It is not without drawbacks, however.

CT does not provide the quantitative measurements physicians rely on, such as pressure gradients across the pulmonary arterial bed or stenosis. Radiologists at Children's Hospital are turning to cardiac MR for these measurements and to echocardiography for others, such as flow data.

But the VCT is an unmitigated hit for routine applications. Scans of the chest and abdomen are completed in a fraction of the time needed by past-generation CT technologies.

"Children who previously were under general anesthesia or deep sedation because they were mentally handicapped or too young to follow directions now can be done with the VCT without anesthesia," Hauschildt said. "That is not only a lot cheaper and safer, but it means they don't have to stay in the hospital for a few hours to recover from the anesthesia."

The staff are exploring other pediatric uses for the VCT, including examination of vessels of the brain, abdomen, and extremities. The early results have been promising.

"We can get images similar to or even more useful than conventional x-ray angiography," he said.

Perfusion imaging may be next. It has already been used to examine the brains of young patients and may be extended to other body parts, such as tumors and solid organs of the abdomen. The San Diego radiologists will explore these applications cautiously, balancing the value of the information they can obtain against the risks of radiation exposure.

"Although the manufacturers have done a lot on the newer generation scanners to limit the radiation dose, it is still a significant dose for children, and we want to make sure that what we are getting is worth what we are giving," Hauschildt said.