Department of Clinical Neuroscience, Karolinska Institute, Solna, Sweden -
Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden -
Q J Nucl Med Mol Imaging. 2023 Sep;67(3):215-222. doi: 10.23736/S1824-4785.22.03389-1. Epub 2022 Feb 4.
Attenuation correction (AC) is an important topic in PET/MRI and particularly challenging after brain tumor surgery, near metal implants, adjacent bone and burr holes. In this study, we evaluated the performance of two MR-driven AC methods, zero-echo-time AC (ZTE-AC) and atlas-AC, in comparison to reference standard CT-AC in patients with surgically treated brain tumors at C-methionine PET/MRI.
This retrospective study investigated seven postoperative patients with neuropathologically confirmed brain tumor at C-methionine PET/MRI. Three AC maps - ZTE-AC, atlas-AC and reference standard CT-AC - were generated for each patient. Standardized uptake values (SUV) were obtained at the metal implant, adjacent bone and burr hole. Standard uptake ratio (SUR) SURmetal/mirror, SURbone/mirror and SURburrhole/mirror were then calculated and analyzed with Bland-Altman, Pearson correlation and intraclass correlation reliability.
Smaller mean percent bias range (Bland-Altman) was found for ZTE-AC than atlas-AC in all analyses (metal ZTE -0.46 to -0.02, metal atlas -3.57 to -3.26; bone ZTE -4.60 to -2.16, bone atlas -5.25 to -3.81; burr hole ZTE -0.95 to -0.52, burr hole atlas 7.86 to 8.87). Percent SD range (Bland-Altman) was large for both methods in all analyses, with lower absolute values for ZTE-AC (ZTE 7.02-8.49; atlas 11.47-14.83). A very strong correlation (Pearson correlation) was demonstrated for both methods compared to CT-AC (ZTE ρ 0.97-0.99, P<0.001; atlas ρ 0.88-0.91, P≤0.009) with higher absolute values for ZTE. An excellent intraclass correlation coefficient was found across all analyses for ZTE, atlas and CT maps (ICC ≥0.88).
ZTE for MR-driven PET attenuation correction presented a more comparable performance to reference standard CT-AC at the postoperative site. ZTE-AC may serve as a useful diagnostic tool for MR-driven AC in patients with surgically treated brain tumors.
在 PET/MRI 中，衰减校正（AC）是一个重要的课题，尤其是在脑肿瘤手术后、靠近金属植入物、临近骨骼和骨孔的情况下，校正尤其具有挑战性。在这项研究中，我们评估了两种基于磁共振的 AC 方法，即零回波时间 AC（ZTE-AC）和图谱 AC，与术后接受 C-蛋氨酸 PET/MRI 的脑肿瘤患者的参考标准 CT-AC 进行比较。
本回顾性研究调查了七名经神经病理学证实的脑肿瘤术后患者的 C-蛋氨酸 PET/MRI。为每位患者生成了三个 AC 图——ZTE-AC、图谱 AC 和参考标准 CT-AC。在金属植入物、相邻骨骼和骨孔处获得标准化摄取值（SUV）。然后计算并分析标准摄取比值（SUR），包括 SURmetal/mirror、SURbone/mirror 和 SURburrhole/mirror，使用 Bland-Altman 分析、Pearson 相关性和组内相关可靠性进行分析。
在所有分析中，ZTE-AC 的平均百分比偏差范围（Bland-Altman）均小于图谱 AC（金属 ZTE -0.46 至 -0.02，金属图谱 -3.57 至 -3.26；骨骼 ZTE -4.60 至 -2.16，骨骼图谱 -5.25 至 -3.81；骨孔 ZTE -0.95 至 -0.52，骨孔图谱 7.86 至 8.87）。两种方法在所有分析中的百分比标准差范围（Bland-Altman）都较大，ZTE-AC 的绝对值较小（ZTE 7.02-8.49；图谱 11.47-14.83）。与 CT-AC 相比，两种方法均表现出非常强的相关性（Pearson 相关性）（ZTE ρ 0.97-0.99，P<0.001；图谱 ρ 0.88-0.91，P≤0.009），ZTE 的绝对值较高。在所有分析中，ZTE、图谱和 CT 图谱的组内相关系数均较高（ICC≥0.88）。
在术后部位，基于磁共振的 ZTE 进行 PET 衰减校正的性能与参考标准 CT-AC 更具可比性。ZTE-AC 可作为脑肿瘤术后患者基于磁共振的 AC 的一种有用的诊断工具。
