Motion Correction in Hybrid PET/MRI Cardiac Imaging

每年约有50万名心脏病患者接受心脏成像检查，以调查心脏组织中血流减少的程度，即缺血性心脏病。这主要包括向心肌输送血液的一条或多条血管变窄但未堵塞的患者，即稳定型冠状动脉疾病。直到最近，这项测试是通过一种称为单光子发射计算机断层扫描（SPECT）的方法进行的，其结果只能检测到心脏血流的相对异常。最近已经认识到，30-40%的SPECT测试应该被一种可以检测绝对定量的测试所取代。目前已经出现了三种可以提供绝对血流测量的新测试：正电子发射断层扫描（PET）、灌注x射线计算机断层扫描（pCT）和对比增强磁共振成像（CEMRI）。迄今为止，PET已成为首选的方法。尽管心脏PET可以产生所需的心脏血流的绝对定量，但由于呼吸和心脏跳动使图像模糊，因此图像不能检测到小于1至2cm的异常。从MRI心脏成像异常可知，即使小于1cm的异常也很重要。最近开发了一种混合成像方法，其中心脏可以同时通过PET和MRI成像，即混合PET/MRI。由于MRI可以产生校正心脏运动的图像，因此可以使用与心脏PET图像同时收集的心脏MRI图像来校正心脏运动的PET图像。该提案将PET/MRI混合制造商（西门子），伦敦安大略放射学公司（伦敦x射线协会）和最重要的PET/MRI混合加拿大研究小组（劳森成像研究计划）联合起来，进一步开发MRI引导心脏PET图像的运动校正。预计每年约有20万加拿大心脏病患者将受益。

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.