PET/CT tops angiography in diagnosis of coronary disease

One of the first studies of its kind has found integrated PET/CT to be a highly accurate method for diagnosing coronary artery disease. Hybrid imaging could become clinically viable in this setting, complement CT coronary angiography, and challenge MRI.

Standard imaging with coronary angiography is costly compared with alternatives such as CT angiography or intravascular coronary ultrasound, and it is also invasive and carries a small risk. Angiography cannot predict the physiologic implications of stenoses such as ischemic recurrence or vessel reocclusion after lytic therapy.

An average 30% of coronary angiograms yield clinically insignificant disease. An imaging test combining functional and anatomic capabilities should avoid unnecessary coronary angiography, and PET/CT could be that test, according to Dr. Mehdi Namdar and colleagues at the University Hospital of Zurich in Switzerland.

Researchers enrolled 25 consecutive patients who underwent CT angiography and PET scanning on a four-slice PET/CT system. All patients had been referred for a PET myocardial perfusion scan due to a clinical history of coronary disease. They had previously undergone coronary angiography for recurrent chest pain.

The investigators compared PET/CT, PET, and coronary angiography and found the hybrid's high negative predictive value helped them pick the right candidates for revascularization. They published their findings in the June issue of the Journal of Nuclear Medicine.

Seven arterial segments could not be evaluated by CT because of rapid vessel motion, but they were correctly categorized by PET alone. The integration of more powerful CT scanners into hybrids should overcome such shortcomings and step up clinical implementation of the technique, the researchers said. Cardiac imaging experts concur.

While current PET/CT systems are excellent for neurological and oncological applications, better temporal and spatial resolution should benefit cardiac applications. Hybrids with 64-slice CT components should soon make PET/CT clinically viable in this setting, said Dr. U. Joseph Schoepf, director of CT research and development at the Medical University of South Carolina in the U.S.

Motion artifacts or severe calcification affects some coronary artery segments and limits the accurate assessment of stenosis. PET could enhance coronary CTA's overall accuracy for lesion detection in such cases, add critical information on the physiological significance of a coronary lesion, and improve therapeutic decisions, Schoepf said.

PET/CT will not replace CT coronary angiography. Cost makes the use of a hybrid for the routine workup of suspected coronary artery disease prohibitive. Consideration of cost and utility between hybrid imaging and MRI, however, may mean reduced business for MRI. The cost for cardiac MRI is higher than for cardiac CT, and MRI and PET provide similar information on cardiac function and metabolism, he said.

But PET remains a complex, costly, and time-consuming modality still facing difficulties with spatial resolution. Heightened patient awareness, on the other hand, makes CT's radiation burden a problem. Although CTA is a much simpler procedure than MRA, cardiac imagers expect competition from improved MRI, said Dr. J. Paul Finn, chief of cardiovascular imaging at UCLA.