Boellaard Ronald, Rausch Ivo, Beyer Thomas, Delso Gaspar, Yaqub Maqsood, Quick Harald H, Sattler Bernhard
Department of Radiology and Nuclear Medicine, VU Medical Center, Amsterdam 1081 HV, The Netherlands; European Association of Nuclear Medicine Research Ltd., Vienna 1060, Austria; and European Association of Nuclear Medicine Physics Committee, Vienna 1060, Austria.
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna 1090, Austria.
Med Phys. 2015 Oct;42(10):5961-9. doi: 10.1118/1.4930962.
Integrated positron emission tomography/magnetic resonance (PET/MR) systems derive the PET attenuation correction (AC) from dedicated MR sequences. While MR-AC performs reasonably well in clinical patient imaging, it may fail for phantom-based quality control (QC). The authors assess the applicability of different protocols for PET QC in multicenter PET/MR imaging.
The National Electrical Manufacturers Association NU 2 2007 image quality phantom was imaged on three combined PET/MR systems: a Philips Ingenuity TF PET/MR, a Siemens Biograph mMR, and a GE SIGNA PET/MR (prototype) system. The phantom was filled according to the EANM FDG-PET/CT guideline 1.0 and scanned for 5 min over 1 bed. Two MR-AC imaging protocols were tested: standard clinical procedures and a dedicated protocol for phantom tests. Depending on the system, the dedicated phantom protocol employs a two-class (water and air) segmentation of the MR data or a CT-based template. Differences in attenuation- and SUV recovery coefficients (RC) are reported. PET/CT-based simulations were performed to simulate the various artifacts seen in the AC maps (μ-map) and their impact on the accuracy of phantom-based QC.
Clinical MR-AC protocols caused substantial errors and artifacts in the AC maps, resulting in underestimations of the reconstructed PET activity of up to 27%, depending on the PET/MR system. Using dedicated phantom MR-AC protocols, PET bias was reduced to -8%. Mean and max SUV RC met EARL multicenter PET performance specifications for most contrast objects, but only when using the dedicated phantom protocol. Simulations confirmed the bias in experimental data to be caused by incorrect AC maps resulting from the use of clinical MR-AC protocols.
Phantom-based quality control of PET/MR systems in a multicenter, multivendor setting may be performed with sufficient accuracy, but only when dedicated phantom acquisition and processing protocols are used for attenuation correction.
集成正电子发射断层扫描/磁共振（PET/MR）系统通过专用的MR序列进行PET衰减校正（AC）。虽然MR-AC在临床患者成像中表现良好，但在基于体模的质量控制（QC）中可能会失败。作者评估了不同协议在多中心PET/MR成像中用于PET QC的适用性。
使用三个组合式PET/MR系统对美国国家电气制造商协会（National Electrical Manufacturers Association）NU 2 2007图像质量体模进行成像：一台飞利浦Ingenuity TF PET/MR、一台西门子Biograph mMR和一台GE SIGNA PET/MR（原型）系统。根据欧洲核医学协会（EANM）FDG-PET/CT指南1.0对体模进行填充，并在一张床位上扫描5分钟。测试了两种MR-AC成像协议：标准临床程序和专用的体模测试协议。根据系统不同，专用体模协议对MR数据采用两类（水和空气）分割或基于CT的模板。报告了衰减恢复系数（RC）和标准化摄取值（SUV）恢复系数的差异。进行了基于PET/CT的模拟，以模拟在AC图（μ图）中看到的各种伪影及其对基于体模的QC准确性的影响。
临床MR-AC协议在AC图中导致了大量误差和伪影，根据PET/MR系统的不同，重建PET活性的低估高达27%。使用专用的体模MR-AC协议时，PET偏差降低到了-8%。对于大多数对比对象，平均和最大SUV RC符合欧洲放射性核素成像质量控制（EARL）多中心PET性能规范，但仅在使用专用体模协议时。模拟证实实验数据中的偏差是由使用临床MR-AC协议导致的不正确AC图引起的。
在多中心、多供应商环境下，对PET/MR系统进行基于体模的质量控制可以达到足够的准确性，但前提是使用专用的体模采集和处理协议进行衰减校正。
