photo: CT-pet
CT scans can detect plaques in
coronary arteries; © sxc

The appearance of plaques on CT images may not indicate whether or not they actually compromise the heart muscle's blood supply. More detailed angiographic images obtained via invasive cardiac catheterization give a better picture of how obstructive a plaque may be. Perfusion studies utilizing technologies such as MRI scans or the nuclear medicine technologies SPECT and PET reveal areas where limited blood flow has damaged the heart muscle, information that can determine whether a patient can be treated with drugs or requires surgical intervention.

The MGH-led study enrolled 34 cardiac patients who recently had SPECT stress tests and were likely to also require angiography via cardiac catheterization.

Participants first had a cardiac CT taken while receiving an infusion of adenosine, which produces physiologic stress symptoms such as elevated heart rate and blood pressure. When vital signs returned to normal several minutes after the adenosine infusion, a resting cardiac CT was taken. Both of those scans involved the use of contrast material, and to detect areas with little or no contrast agent – indicating restrictions to the myocardial vasculature – a third CT scan was taken 7 minutes later.

The accuracy of CT-based perfusion imaging in diagnosing coronary artery narrowing that significantly affected myocardial perfusion was virtually the same as SPECT stress imaging, and the results of coronary CT angiography also compared favorably to those of cardiac catheterization. Because the investigators used new radiation-dose-reduction techniques, the radiation dose of the three CT scans did not exceed the dosage involved in the SPECT stress perfusion study.

"While nuclear perfusion imaging provides information that can help guide patient treatment, it has limitations that can lead to either false negative or false positive findings," the study's principal investigator Ricardo C. Cury explains. "The ability to acquire anatomical visualization of coronary artery stenosis together with physiological assessment of myocardial perfusion in a single study could improve diagnostic accuracy while potentially reducing costs and radiation exposure. “


COMPAMED.de; Source: Massachusetts General Hospital