PET/MR Found Best Imaging Modality for Detecting Coronary Arterial Disease

The hybrid molecular imaging technique called positron emission tomography and magnetic resonance (PET/MR) imaging, which provides vital data about cardiac and arterial function, has been found to be an effective molecular imaging tool for detecting coronary artery disease (CAD), according to a recent study. 

The researchers presented their findings at the Society of Nuclear Medicine and Molecular Imaging’s 2014 annual meeting, held June 7-11, 2014, in St. Louis (MO, USA). Ischemic heart disease, a narrowing of the arteries supplying blood to the heart, is a leading cause of death worldwide. Individuals suspected of having CAD frequently undergo a stress test called myocardial perfusion imaging (MPI) to target areas of arterial ischemia and risk of myocardial infarction, or heart attack. Many patients undergo a molecular imaging scan called single photon emission computed tomography (SPECT); however, recently PET/MR has emerged as a potential alternative due to its superiority for imaging the structures of soft tissues and the physiologic function of the heart. This study revealed that PET/MR is consistently accurate using coronary angiography as the reference standard for detecting CAD. 

“By combining two advanced imaging modalities, PET and MR, cardiac PET/MR imaging allows a union of anatomic information with MR and functional information with PET for a comprehensive view of the of the heart,” said lead author Jeffrey M.C. Lau, MD, PhD, from Washington University in St. Louis (MO, USA). “This allows us to predict or rule out coronary artery disease with more certainty, and in some instances, it allows us to detect disease processes such as areas of hibernating heart muscle that would not have been detected using conventional stress testing methods like SPECT.” 

Moreover, cardiac perfusion PET/MR can be performed in a shorter timeframe than SPECT and is associated with a lower dose of radiation per procedure, and MR can be used to produce an almost cinematic, multiple-frame sequence of the motion in specific regions of the heart muscle, most notably the left ventricle, which pumps oxygenated blood back into the body through the aorta. PET imaging also provides quantitative data about blood flow in addition to the visual interpretation of disease. 

The study involved 10 patients with reversible ischemia as indicated by SPECT-MPI. Scientists administered a radionuclide PET imaging agent called N-13 ammonia in addition to an MR contrast agent called gadolinium and the pharmaceutical Regadenoson, which imitates the stress of exercise. Regadenoson was developed by Astellas Pharma, Inc. (Tokyo, Japan).

The researchers optimized the cardiac PET/MR imaging protocol to register areas of reduced perfusion of blood using MR with PET data regarding myocardial blood flow. The findings showed that PET/MR imaging was very accurate in diagnostic coronary artery diseases. In this small sample, PET/MR had 100% sensitivity, 80% specificity, and 100% negative predictive value (NPV). Those numbers compare favorably to SPECT in this study group. 

This study was conducted in conjunction with Siemens Medical Solutions (Erlangen, Germany).

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