A fused SPECT/CT image that captures both the coronary arteries and blood flow to the heart by researchers at the University Hospital Zurich in Switzerland was awarded the Image of the Year at the Society of Nuclear Medicine’s (SNM) 53rd Annual Meeting in San Diego. The award is chosen annually by SNM Past President and Historian Henry Wagner Jr., MD, who announced the image at a press conference Monday.
The image, which fused a dual-head SPECT with a 64-slice CT, is part of the study “Comparison of 64-Slice Spiral CT Angiography and Myocardial Perfusion Imaging in Noninvasive Evaluation of Functionally Relevant Coronary Stenoses.” It illustrates the “complementary nature” of two imaging modalities to show coronary anatomy and blood flow to the heart, Wagner said. He noted that the choice of a SPECT/CT image demonstrates its growing clinical significance, this time in addressing heart disease. A PET/CT image won last year.
“Our study shows that purely anatomical imaging of the heart is often insufficient to identify coronary lesions, underlining the need for a combined assessment that may be made possible, and effortless, with future hybrid SPECT/CT or PET/CT scanners,” said Philipp Kaufmann, lead researcher of the study and professor of nuclear cardiology of the University Hospital Zurich in Switzerland. “Our fused images accurately pinpoint blood flow defect to its corresponding artery – and are eye-catching and easy to understand.”
The study from which the collaborated image was selected was completed on a LightSpeed VCT 64-slice CT with myocardial perfusion imaging using Tc-99m tetrofosmin-SPECT via the Millennium VG Series Hawkeye. Both of the units are made by GE Healthcare. The group examined 100 consecutive patients with suspected or known coronary artery disease, and performed electrocardiographic (ECG)-gated MPI and 64-slice CTA on each patient.
The first panel of the image shows conventional cardiac SPECT with 99mTc-tetrofosmin as a radiotracer. The upper row shows two short axis slices after pharmacological stress; the lower row shows the same slices when the body is at rest. Arrows indicate a small perfusion detection on the back side of the heart – visible only on the stress images – showing ischemia or reduced blood flow to the heart muscle in this region of the heart wall.
The middle and right panels show a SPECT/CT fusion of the heart and its coronary arteries obtained by 64-slice CT angiography with the functional information about the corresponding perfusion from cardiac SPECT (represented in orange and yellow) superimposed. The two data sets were acquired on different scanners, then digitally fused in a second step using the GE CardIQ Fusion software package.
The middle panel also shows a front view of the heart and coronary arteries. On the right of the last panel, the heart can be seen from the back (posterior view) revealing nicely the perfusion defect from the SPECT images (blue color, arrows) and the narrowing of the corresponding artery (stenosis), according to Oliver Gaemperli, fellow at the University Hospital Zurich. Posterior defects may be caused by the narrowing of arteries other than the one responsible in this case. “Therefore, the information obtained from either SPECT or CT alone can be insufficient to identify the vessel that is responsible for causing ischemia (culprit lesion),” he said.
In the study, Swiss researchers analyzed 399 coronary arteries and 1,386 coronary segments (including 12 bypass grafts) in 100 patients with coronary artery disease, Gaemperli said. “This technique behind the new generation of CT scanners is pretty exciting,” Kaufmann said, “as it offers high resolution close to that found in conventional angiographies—without the risks inherent in such invasive procedures.” Additional studies must be done to confirm the researchers’ work with high- and low-risk patients, he added.