Fusion imaging a powerful tool in diagnosing heart disease
A more accurate diagnosis by combining two different types of images to get a more precise idea of the hearts problem can make a world of difference in combating heart disease. Researchers at this week’s SNM 2007 in Washington, D.C., revealed their work with SPECT and CT imaging for heart disease diagnosis.

"By combining the physiological (or functional) images of the blood flow to the heart muscle at stress and at rest with the high-resolution anatomical depiction of coronary arteries and their blockages, we can determine the diagnosis of coronary artery disease more accurately," said Piotr Slomka, a research scientist with the Artificial Intelligence in Medicine Program at the departments of Medicine and Imaging at Cedars-Sinai Medical Center in Los Angeles, Calif.

"The idea is to combine two different images of the heart obtained by two different techniques: single photon emission computed tomography (SPECT) and cardiac computed tomography (CT) angiography," said Slomka.

A cardiac CT angiography is a tomographic x-ray procedure that provides highly useful images of the heart’s coronary vessels. SPECT is a noninvasive imaging technique that uses radioactive substances to produce 3D images of the blood flow to the heart muscle. The radioactive substances do not long remain in the body.

"These scans are obtained at different times—and even at different locations—but our computer software puts the information together in 3D," he said. "This synergistic integration allows simultaneous analysis of the heart muscle blood flow with a highly accurate image of coronary arteries and their blockages.”

"It eliminates the limitations of imaging with either SPECT or CT alone," added Slomka.

About 7 million Americans suffer from coronary heart disease, and about 500,000 die from the disease annually. Coronary artery disease, the most common form of heart disease, occurs when the arteries that supply blood to the heart muscle become hardened and narrowed, said Slomka.

"The fusion can be used selectively for the diagnosis of patients who undergo one of the exams (either SPECT or CT angiography) with inconclusive results because there was some difficulty in interpretation. In these difficult cases, a complementary anatomical or physiological scan—and this kind of image integration—helps a physician make a better diagnosis," said Slomka. Additional research is needed. "We need to obtain more data to determine which patients would benefit most from this technique. We need to further automate the software to provide highly accurate alignment of the images," he added.

Regarding the research, Josef Machac, SNM's Scientific Program Committee cardiovascular vice chair, said, "This work illustrates the value of a combined 3D display of blood flow together with CT angiography imaging data."

"Used together in this way, the modalities demonstrate performance superior to that of either modality alone. This has been speculated on previously, but now we have empirical evidence that it is true," added Machac.