Motion Correction in Hybrid PET/MRI Cardiac Imaging

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Some 500,000 cardiac patients per year have a cardiac imaging test to investigate the extent that blood flow has been reduced in heart tissue i.e. ischemic heart disease. This primarily includes patients who have narrowing but not blockage of one or more of the blood vessels delivering blood to the heart muscle i.e. stable coronary artery disease. Until recently this test, performed with a procedure called Single Photon Emission Computed Tomography or SPECT, provided results that could only detect relative abnormalities in heart blood flow. It has been recently realized that 30-40% of the SPECT tests should be replaced with a test that can detect absolute quantitation. Three new tests have emerged that can offer absolute blood flow measurements: Positron Emission Tomography (PET), perfusion X-ray Computed Tomography (pCT) and Contrast Enhanced Magnetic Resonance Imaging (CEMRI). To date PET has become the method of choice. Although cardiac PET can produce the needed absolute quantitation of blood flow in the heart the images cannot detect abnormalities smaller than 1 to 2cm in size because the images are blurred by breathing and heart beating. It is known from MRI heart imaging abnormalities that abnormalities even smaller than 1cm are important to detect. Recently a hybrid imaging method has been developed wherein the heart can be imaged simultaneously by PET and MRI i.e. hybrid PET/MRI. Because MRI can produce images wherein heart motion is corrected it is possible to use the heart MRI images collected at the same time as the heart PET images to correct the PET images for heart motion. This proposal brings together the hybrid PET/MRI manufacturer (Siemens), a London Ontario radiology company (London X-Ray Associates) and the foremost hybrid PET/MRI Canadian research group (Lawson Imaging Research Program) to further develop MRI guided motion correction of cardiac PET images. It is anticipated that some 200,000 Canadian heart patients will benefit each year.