A recent Science Daily article reports a team of researchers led by Massachusetts General Hospital (MGH) radiologists has developed a computed-tomography-based heart scan protocol that identifies both narrowing of coronary arteries and areas of myocardial ischemia – restricted blood flow to heart muscle tissue – giving a better indication of clinically significant coronary artery disease. This is among the first demonstrations of the use of cardiac CT [computed tomography] to detect both coronary artery stenosis and resulting myocardial ischemia simultaneously in a single examination, according to a cardiac imaging specialist at the MGH Heart Center.

A CT scan uses conventional X-rays to produce cross-sectional images of anatomic structures and can detect plaques in coronary arteries. But the appearance of plaques on CT images may not indicate whether or not they actually compromise the heart muscle’s blood supply.

More detailed full body scan 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 surgery.

Previous studies showed that CT heart scans can identify areas of restricted coronary blood supply in resting individuals. The MGH-led study was designed to see whether a comprehensive cardiac CT examination could incorporate myocardial perfusion studies in both resting and stress situations provided by CT imaging.

CT-based perfusion imaging’s accuracy 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. The radiation dose of the three CT scans did not exceed the dosage involved in the SPECT stress perfusion study because the cardiologists in the study used new radiation-dose-reduction techniques.

Nuclear perfusion, while providing imaging information that can help guide patient treatment, has limitations that can lead to either false negative or false positive findings. 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. The study was relatively small, and further tests must be conducted a larger multicenter trial to investigate the additional value of CT perfusion studies.