Huang Chuan, Ackerman Jerome L, Petibon Yoann, Normandin Marc D, Brady Thomas J, El Fakhri Georges, Ouyang Jinsong
Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Department of Imaging, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Radiology, Harvard Medical School, Boston, MA 02115, USA.
Department of Radiology, Harvard Medical School, Boston, MA 02115, USA; Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA 02129, USA.
Neuroimage. 2014 May 1;91:129-37. doi: 10.1016/j.neuroimage.2013.12.061. Epub 2014 Jan 10.
Brain PET scanning plays an important role in the diagnosis, prognostication and monitoring of many brain diseases. Motion artifacts from head motion are one of the major hurdles in brain PET. In this work, we propose to use wireless MR active markers to track head motion in real time during a simultaneous PET-MR brain scan and incorporate the motion measured by the markers in the listmode PET reconstruction. Several wireless MR active markers and a dedicated fast MR tracking pulse sequence module were built. Data were acquired on an ACR Flangeless PET phantom with multiple spheres and a non-human primate with and without motion. Motions of the phantom and monkey's head were measured with the wireless markers using a dedicated MR tracking sequence module. The motion PET data were reconstructed using list-mode reconstruction with and without motion correction. Static reference was used as gold standard for quantitative analysis. The motion artifacts, which were prominent on the images without motion correction, were eliminated by the wireless marker based motion correction in both the phantom and monkey experiments. Quantitative analysis was performed on the phantom motion data from 24 independent noise realizations. The reduction of bias of sphere-to-background PET contrast by active marker based motion correction ranges from 26% to 64% and 17% to 25% for hot (i.e., radioactive) and cold (i.e., non-radioactive) spheres, respectively. The motion correction improved the channelized Hotelling observer signal-to-noise ratio of the spheres by 1.2 to 6.9 depending on their locations and sizes. The proposed wireless MR active marker based motion correction technique removes the motion artifacts in the reconstructed PET images and yields accurate quantitative values.
脑正电子发射断层扫描（PET）在多种脑部疾病的诊断、预后评估及监测中发挥着重要作用。头部运动产生的运动伪影是脑PET成像的主要障碍之一。在本研究中，我们提出在PET-MR同步脑扫描过程中使用无线MR有源标记实时跟踪头部运动，并将标记测量的运动信息纳入列表模式PET重建中。我们构建了多个无线MR有源标记和一个专用的快速MR跟踪脉冲序列模块。在具有多个球体的ACR无框PET体模以及有或无运动的非人灵长类动物上采集了数据。使用专用的MR跟踪序列模块通过无线标记测量体模和猴子头部的运动。对运动PET数据进行了有无运动校正的列表模式重建。静态参考被用作定量分析的金标准。在体模和猴子实验中，基于无线标记的运动校正消除了未进行运动校正的图像上明显的运动伪影。对来自24个独立噪声实现的体模运动数据进行了定量分析。基于有源标记的运动校正使热（即放射性）球体和冷（即非放射性）球体的球与背景PET对比度偏差分别降低了26%至64%和17%至25%。根据球体的位置和大小，运动校正使球体的通道化霍特林观察者信噪比提高了1.2至6.9。所提出的基于无线MR有源标记的运动校正技术消除了重建PET图像中的运动伪影，并产生了准确的定量值。
