From the Departments of PET/MR Engineering (T.W.D.) and Clinical Development (C.M.B.), GE Healthcare, 3200 N Grandview Blvd, Waukesha, WI 53188; and Department of Radiology, University of Wisconsin-Madison, Wisconsin Institutes for Medical Research, Madison, Wis (N.K.M., S.A.H., A.B.M.).
Radiology. 2021 Jan;298(1):166-172. doi: 10.1148/radiol.2020200967. Epub 2020 Nov 3.
Background During simultaneous PET/MRI, flexible MRI surface coils that lay on the patient are often omitted from PET attenuation correction processing, leading to quantification bias in PET images. Purpose To identify potential PET image quality improvement by using a recently developed lightweight MRI coil technology for the anterior array (AA) surface coil in both a phantom and in vivo study. Materials and Methods A phantom study and a prospective in vivo study were performed with a PET/CT scanner under three conditions: no MRI surface coil (standard of reference), traditional AA coil, and lightweight AA coil. AA coils were not used in attenuation correction processing to emulate clinical PET/MRI. For the phantom study, PET images were reconstructed with and without time of flight (TOF) to assess quantification accuracy and uniformity. The in vivo study consisted of 10 participants (mean age, 66 years ± 10 [standard deviation]; six men) referred for a PET/CT oncologic examination who had undergone imaging between October 2019 and February 2020. Assessment of image quantification bias (defined as the standard error of the mean values) was conducted by comparing mean liver region of interest standardized uptake values with the no-coil standard of reference. A Wilcoxon signed-rank test was used to establish significance. Results For TOF and non-TOF, respectively, the phantom study revealed a mean PET quantification bias of -9.0% and -8.6% with the traditional AA coil and a mean PET quantification bias of -4.3% and -4.0% with the lightweight AA coil. The coefficients of variation reduced from 4.3% and 6.2% with the traditional AA coil to 2.1% and 2.7% with the lightweight AA coil, which demonstrated a homogeneity benefit from the lightweight coil that was greater with, versus without, TOF reconstruction. For the in vivo study, the mean liver standardized uptake value error was -5.9% with the traditional AA coil ( = .002 vs no coil) and -2.4% with the lightweight AA coil ( = .004 vs no coil). Conclusion The lightweight anterior array coil reduced PET image quantification bias by more than 50% compared with the traditional coil. Using the lightweight coil and performing time of flight-based reconstruction each reduced the variation of error. © RSNA, 2020
背景 在同时进行的 PET/MRI 中，放置在患者身上的灵活 MRI 表面线圈通常会从 PET 衰减校正处理中省略，导致 PET 图像的定量偏差。
目的 利用最近开发的轻便 MRI 线圈技术，对前阵列（AA）表面线圈进行体模和体内研究，以确定潜在的 PET 图像质量改善。
材料与方法 使用 PET/CT 扫描仪在三种条件下进行体模研究和前瞻性体内研究：无 MRI 表面线圈（参考标准）、传统 AA 线圈和轻便 AA 线圈。为了模拟临床 PET/MRI，AA 线圈未用于衰减校正处理。对于体模研究，使用和不使用飞行时间（TOF）重建 PET 图像，以评估定量准确性和均匀性。体内研究包括 10 名参与者（平均年龄，66 岁±10[标准差]；6 名男性），他们因进行 PET/CT 肿瘤检查而接受了成像，成像时间为 2019 年 10 月至 2020 年 2 月。通过比较平均肝脏感兴趣区标准化摄取值与无线圈参考标准，评估图像定量偏差（定义为平均值的标准误差）。使用 Wilcoxon 符号秩检验确定显著性。
结果 对于 TOF 和非 TOF，体模研究分别显示传统 AA 线圈的平均 PET 定量偏差为-9.0%和-8.6%，轻便 AA 线圈的平均 PET 定量偏差为-4.3%和-4.0%。变异系数从传统 AA 线圈的 4.3%和 6.2%降低到轻便 AA 线圈的 2.1%和 2.7%，这表明轻便线圈的均匀性受益更大，而与 TOF 重建相比，没有 TOF 重建。对于体内研究，传统 AA 线圈的平均肝脏标准化摄取值误差为-5.9%（ =.002 与无线圈），轻便 AA 线圈为-2.4%（ =.004 与无线圈）。
结论 与传统线圈相比，轻便的前阵列线圈使 PET 图像定量偏差降低了 50%以上。使用轻便线圈并进行基于飞行时间的重建，可使误差变化降低。
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