Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
Department of Nuclear Medicine, Sant'Orsola Hospital, University of Bologna, Bologna, Italy.
J Nucl Med. 2017 Jul;58(7):1167-1173. doi: 10.2967/jnumed.116.180802. Epub 2017 Jan 6.
Metalic implants may affect attenuation correction (AC) in PET/MR imaging. The purpose of this study was to evaluate the effect of susceptibility artifacts related to metallic implants on adjacent metabolically active lesions in clinical simultaneous PET/MR scanning for both time-of-flight (TOF) and non-TOF reconstructed PET images. We included 27 patients without implants but with confirmed F-FDG-avid lesions adjacent to common implant locations. In all patients, a clinically indicated whole-body F-FDG PET/MR scan was acquired. Baseline non-TOF and TOF PET images were reconstructed. Reconstruction was repeated after the introduction of artificial signal voids in the AC map to simulate metallic implants in standard anatomic areas. All reconstructed images were qualitatively and quantitatively assessed and compared with the baseline images. In total, 51 lesions were assessed. In 40 and 50 of these cases (non-TOF and TOF, respectively), the detectability of the lesions did not change; in 9 and 1 cases, the detectability changed; and in 2 non-TOF cases, the lesions were no longer visible after the introduction of metallic artifacts. The inclusion of TOF information significantly reduced artifacts due to simulated implants in the femoral head, sternum, and spine ( = 0.01, 0.01, and 0.03, respectively). It also improved image quality in these locations ( = 0.02, 0.01, and 0.01, respectively). The mean percentage error was -3.5% for TOF and -4.8% for non-TOF reconstructions, meaning that the inclusion of TOF information reduced the percentage error in SUV by 28.5% ( < 0.01). Qualitatively, there was a significant reduction of artifacts in the femoral head, sternum, and spine. There was also a significant qualitative improvement in image quality in these locations. Furthermore, our study indicated that simulated susceptibility artifacts related to metallic implants have a significant effect on small, moderately F-FDG-avid lesions near the implant site that possibly may go unnoticed without TOF information. On larger, highly F-FDG-avid lesions, the metallic implants had only a limited effect. The largest significant quantitative difference was found in artifacts of the sternum. There was only a weak inverse correlation between lesions affected by artifacts and distance from the implant.
金属植入物可能会影响 PET/MR 成像中的衰减校正 (AC)。本研究的目的是评估与金属植入物相关的磁化率伪影对临床同时进行的 TOF 和非 TOF 重建 PET 图像的代谢活跃病变的影响。我们纳入了 27 名无植入物但有确认的 F-FDG 摄取病变紧邻常见植入物部位的患者。所有患者均进行了临床指征明确的全身 F-FDG PET/MR 扫描。重建了基线非 TOF 和 TOF PET 图像。在 AC 图中引入人工信号缺失以模拟标准解剖区域中的金属植入物后，重复重建。对所有重建图像进行定性和定量评估，并与基线图像进行比较。共评估了 51 个病变。在 40 个和 50 个病变中（非 TOF 和 TOF 分别），病变的可检测性未发生变化；在 9 个和 1 个病变中，可检测性发生了变化；在 2 个非 TOF 病例中，引入金属伪影后病变不再可见。包含 TOF 信息可显著减少模拟植入物在股骨头、胸骨和脊柱处的伪影（=0.01、0.01 和 0.03）。它还改善了这些部位的图像质量（=0.02、0.01 和 0.01）。TOF 重建的平均百分比误差为-3.5%，非 TOF 重建的平均百分比误差为-4.8%，这意味着包含 TOF 信息可使 SUV 的百分比误差降低 28.5%（<0.01）。定性分析表明，股骨头、胸骨和脊柱处的伪影明显减少。这些部位的图像质量也有显著改善。此外，我们的研究表明，与金属植入物相关的模拟磁化率伪影对靠近植入物部位的小的、中等程度的 F-FDG 摄取病变有显著影响，如果没有 TOF 信息，这些病变可能会被忽略。对于较大的、高度摄取 F-FDG 的病变，金属植入物的影响有限。最大的定量差异出现在胸骨伪影。受伪影影响的病变与植入物的距离之间仅存在微弱的负相关。
