Fusion software improves CT, SPECT cardiovascular scans

Using special software to fuse myocardial perfusion SPECT and CT angiography data acquired on separate scanners could be a cost-effective alternative for the diagnosis of patients with suspected myocardial disease, according to two studies presented at the 2007 Society of Nuclear Medicine meeting.

High-end PET/CT scanners will always produce a more accurate functional and anatomic rendering of the coronary artery tree. But the high cost of this approach makes sense only for centers dealing with a high volume of patients. Available hybrid SPECT/CT angiography systems are also expensive, and the quality of their images is limited. The SNM papers prove there are ways around hybrid imaging pitfalls, according to Dr. U. Joseph Schoepf, an associate professor of radiology and medicine at the Medical University of South Carolina.

"In our practice, most patients get referred for coronary CTA because of an abnormal nuclear exam. We do not know ahead of time whether these patients will actually have both studies. Bringing together this information is a worthwhile avenue to pursue," Schoepf said.

Researchers at Cedars-Sinai Medical Center in Los Angeles used fusion software to perform volumetric alignment of myocardial perfusion SPECT and 64-slice CTA data from 20 consecutive patients. The technique allowed simultaneous blood flow analysis and accurate depiction of coronary artery stenosis with minimal operator dependence in less than 20 seconds per case.

For the other study, researchers from Emory University and the Vall d'Hebron University Hospital in Barcelona used a similar 3D coronary mapping technique in patients with suspected coronary artery disease. They found that myocardial perfusion data from nuclear imaging fused with CTA provided a higher diagnostic accuracy for global coronary and left anterior descending artery disease than did nuclear imaging alone.

"We can use the best CT angiography equipment and SPECT at much lower cost than the dedicated combined scanner," said principal investigator Piotr Slomka, Ph.D., a research scientist with Cedars' Artificial Intelligence in Medicine Program.

Schoepf and colleagues have been working recently on a third-way solution. They have been evaluating a small, inexpensive prototype SPECT camera that could be wheeled up to a high-end CT scanner when needed and into a corner when not. That system could provide imagers with the ability to perform a nuclear perfusion study and high-end coronary CTA without having to invest in a full-blown PET unit. They have submitted a preliminary study to the RSNA.

"The cost is much more economical, and you do not put the high-end CT scanner in a bind when it's needed for high throughput," Schoepf said.