Izquierdo-Garcia David, Sawiak Stephen J, Knesaurek Karin, Narula Jagat, Fuster Valentin, Machac Joseph, Fayad Zahi A
Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, 1, Gustave L. Levy Place, New York, NY, 10029, USA.
Eur J Nucl Med Mol Imaging. 2014 Aug;41(8):1574-84. doi: 10.1007/s00259-014-2751-5. Epub 2014 Mar 21.
The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard.
Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician.
Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6%, R(2) = 0.98, p < 0.001; beta group 10.31 ± 69.86%, R(2) = 0.97, p < 0.001).
In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10% on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method.
本研究的目的是评估一体化Ingenuity TF PET/MR扫描仪中内置的基于磁共振成像的衰减校正（MRAC）的性能，并将其与作为金标准的基于计算机断层扫描的衰减校正（CTAC）的性能进行比较。
本研究纳入了26例接受临床全身FDG PET/CT成像并随后进行PET/MR成像的患者（平均延迟100分钟）。患者被分为两组：α组（14例患者）在PET/MR成像期间未使用磁共振线圈，β组（12例患者）使用了磁共振线圈（神经血管、脊柱、心脏和躯干线圈）。所有图像均配准到同一空间（PET/MR）。使用基于体素和基于区域的方法（有十个感兴趣区域，ROI）比较了PET/MR重建的两幅使用MRAC和CTAC的PET图像。病变也由一位经验丰富的临床医生进行了比较。
α组和β组之间的体重指数和肺密度存在显著差异。每组内左右肺密度也存在显著差异。β组中使用MRAC的摄取值与使用CTAC的摄取值相比的百分比差异大于α组（α组-0.2±33.6%，R(2)=0.98，p<0.001；β组10.31±69.86%，R(2)=0.97，p<0.001）。
与CTAC相比，MRAC导致PET值平均低估不到10%，尽管一些ROI和病变的差异更大（包括脊柱、肺和心脏）。与α组（未使用线圈成像）相比，β组（使用线圈成像）显示出整体PET定量增加以及变异性增加。使用MRAC和CTAC重建的PET数据显示出一些差异，主要与气腔、金属植入物以及由于MRAC方法的分割限制导致的大骨区域（如骨盆和脊柱）的衰减差异有关。
