Motion Correction in Hybrid PET/MRI Cardiac Imaging

每年约有500,000名心脏病患者接受心脏成像测试，以调查心脏组织血流量减少的程度，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没有堵塞的患者，即稳定性冠状动脉疾病。直到最近，这项被称为单光子发射计算机断层扫描或SPECT的程序进行的测试，提供的结果只能检测到心脏血流的相对异常。最近人们意识到，30%-40%的SPECT测试应该被能够检测绝对定量的测试所取代。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)。到目前为止，PET已成为首选的方法。尽管心脏正电子发射计算机断层扫描可以对心脏中的血流进行所需的绝对定量，但由于呼吸和心脏跳动使图像变得模糊，所以图像无法检测出小于1到2厘米的异常。从核磁共振心脏成像的异常可以看出，即使是小于1厘米的异常也需要检测出来。最近发展了一种混合成像方法，即PET/MRI混合成像方法，可以同时对心脏进行PET和MRI成像。由于MRI可以产生其中心脏运动被校正的图像，因此可以使用与心脏PET图像同时收集的心脏MRI图像来校正针对心脏运动的PET图像。这项提议将混合PET/MRI制造商(西门子)、伦敦安大略省的一家放射学公司(伦敦X射线协会)和加拿大领先的混合PET/MRI研究小组(劳森成像研究计划)结合在一起，以进一步开发MRI引导的心脏PET图像的运动校正。预计每年将有大约20万加拿大心脏病患者受益。

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.