Report from SNM: Fusion software improves presentation of cardiac SPECT/CT studies

Researchers are still learning from myocardial perfusion misregistration issues with hybrid SPECT and multislice CT systems. But fusing information acquired on separate scanners using special software seems a practical, clinically useful alternative for the diagnosis of coronary artery disease.

That was the idea behind two studies presented at the 2007 SNM meeting.

Researchers at Cedars-Sinai Medical Center in Los Angeles, for instance, used multimodality fusion software to perform volumetric alignment of myocardial perfusion SPECT and 64-slice CT angiography data from 20 consecutive patients.

The technique allowed simultaneous blood flow analysis with an accurate depiction of coronary artery stenosis. Although this could also be accomplished using hybrid scanners, the software approach is more flexible since the combined information is required only in a subset of cases, said principal investigator Piotr Slomka, Ph.D., a research scientist at Cedars' Artificial Intelligence in Medicine Program.

"We can use the best CT angiography equipment and SPECT at much lower cost than the dedicated combined scanner," Slomka said.

Researchers successfully fused SPECT and MSCT data from all patients, with minimal operator dependence, in less than 20 seconds per case. The technique allowed coronary tree visualization and mapping for quantitative analysis.

Using the combined data, investigators identified more left anterior descending, left circumflex, and right coronary artery disease than with either modality alone. Six cases of coronary territory definition and three contours on myocardial perfusion SPECT were corrected based on MSCT data. Likewise, functional information provided by SPECT helped stenosis assessment in nine of 60 arteries not visible by MSCT.

The study validates previous work suggesting that combined 3D SPECT and CT perfusion displays are superior to either modality alone, according to Dr. Josef Machac, vice chair of the SNM's cardiovascular scientific program.

"This has been speculated on previously, but now we have empirical evidence that it is true," Machac said.

In another study, researchers from Emory University and the Vall d'hebron Hospital in Barcelona used a similar 3D coronary mapping technique in patients with suspected coronary artery disease.

Investigators fused data from 34, 16, 32, and 18 patients who underwent scanning with SPECT, PET, 16-slice, and 64-slice CT, respectively. 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 compared with nuclear imaging alone.

For more information from the Diagnostic Imaging archives:

Journal review: SPECT/CT misregistration

Cardiac PET/CT gains clinical recognition

Cardiac SPECT/CT exploits both modalities' strengths

SPECT/CT cardiac study stands out as image of the year