[F]flortaucipir (FTP) tau PET quantification is known to be affected by non-specific binding in off-target regions. Although partial volume correction (PVC) techniques partially account for this effect, their inclusion may also introduce noise and variability into the quantification process. While the impact of these effects has been studied in cross-sectional designs, the benefits and drawbacks of PVC on longitudinal FTP studies is still under scrutiny. The aim of this work was to study the performance of the most common PVC techniques for longitudinal FTP imaging. A cohort of 247 individuals from the Alzheimer's Disease Neuroimaging Initiative with concurrent baseline FTP-PET, amyloid-beta (Aβ) PET and structural MRI, as well as with follow-up FTP-PET and MRI were included in the study. FTP-PET scans were corrected for partial volume effects using Meltzer's, a simple and popular analytical PVC, and both the region-based voxel-wise (RBV) and the iterative Yang (iY) corrections. FTP SUVR values and their longitudinal rates of change were calculated for regions of interest (ROI) corresponding to Braak Areas I-VI, for a temporal meta-ROI and for regions typically displaying off-target FTP binding (caudate, putamen, pallidum, thalamus, choroid plexus, hemispheric white matter, cerebellar white matter, and cerebrospinal fluid). The longitudinal correlation between binding in off-target and target ROIs was analysed for the different PVCs. Additionally, group differences in longitudinal FTP SUVR rates of change between Aβ-negative (A-) and Aβ-positive (A+), and between cognitively unimpaired (CU) and cognitively impaired (CI) individuals, were studied. Finally, we compared the ability of different partial-volume-corrected baseline FTP SUVRs to predict longitudinal brain atrophy and cognitive decline. Among off-target ROIs, hemispheric white matter showed the highest correlation with longitudinal FTP SUVR rates from cortical target ROIs (R=0.28–0.82), with CSF coming in second (R=0.28–0.42). Application of voxel-wise PVC techniques minimized this correlation, with RBV performing best (R=0.00–0.07 for hemispheric white matter). PVC also increased group differences between CU and CI individuals in FTP SUVR rates of change across all target regions, with RBV again performing best (No PVC: Cohen's = 0.26–0.66; RBV: Cohen's = 0.43–0.74). These improvements were not observed for differentiating A- from A+ groups. Additionally, voxel-wise PVC techniques strengthened the correlation between baseline FTP SUVR and longitudinal grey matter atrophy and cognitive decline. Quantification of longitudinal FTP SUVR rates of change is affected by signal from off-target regions, especially the hemispheric white matter and the CSF. Voxel-wise PVC techniques significantly reduce this effect. PVC provided a significant but modest benefit for tasks involving the measurement of group-level longitudinal differences. These findings are particularly relevant for the estimations of sample sizes and analysis methodologies of longitudinal group studies.

中文翻译：

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纵向 tau PET 研究中的部分体积校正：真的需要吗？

已知 [F]flortaucipir (FTP) tau PET 定量会受到脱靶区域非特异性结合的影响。尽管部分体积校正 (PVC) 技术部分解释了这种影响，但它们的包含也可能在量化过程中引入噪声和变异性。虽然这些效应的影响已在横截面设计中进行了研究，但 PVC 在纵向 FTP 研究中的优点和缺点仍在仔细研究中。这项工作的目的是研究用于纵向 FTP 成像的最常见 PVC 技术的性能。该研究纳入了来自阿尔茨海默病神经影像计划的 247 名受试者，这些受试者同时进行了基线 FTP-PET、淀粉样蛋白-β (Aβ) PET 和结构 MRI，以及后续 FTP-PET 和 MRI。使用 Meltzer（一种简单且流行的分析 PVC）以及基于区域的体素方式 (RBV) 和迭代杨 (iY) 校正，对 FTP-PET 扫描的部分体积效应进行了校正。计算对应于 Braak 区域 I-VI 的感兴趣区域 (ROI)、时间元 ROI 和通常显示脱靶 FTP 结合的区域（尾状核、壳核、苍白球、丘脑）的 FTP SUVR 值及其纵向变化率、脉络丛、半球白质、小脑白质和脑脊液）。对于不同的 PVC，分析了脱靶和目标 ROI 结合之间的纵向相关性。此外，还研究了 Aβ 阴性 (A-) 和 Aβ 阳性 (A+) 之间以及认知未受损 (CU) 和认知受损 (CI) 个体之间纵向 FTP SUVR 变化率的组间差异。最后，我们比较了不同部分体积校正基线 FTP SUVR 预测纵向脑萎缩和认知能力下降的能力。在脱靶 ROI 中，半球白质与皮质目标 ROI 的纵向 FTP SUVR 率的相关性最高（R=0.28-0.82），脑脊液位居第二（R=0.28-0.42）。体素 PVC 技术的应用最大限度地减少了这种相关性，RBV 表现最好（对于半球白质，R=0.00–0.07）。PVC 还增加了 CU 和 CI 个体在所有目标区域的 FTP SUVR 变化率方面的群体差异，而 RBV 再次表现最佳（无 PVC：Cohen's = 0.26–0.66；RBV：Cohen's = 0.43–0.74）。在区分 A- 组和 A+ 组时没有观察到这些改进。此外，体素 PVC 技术增强了基线 FTP SUVR 与纵向灰质萎缩和认知能力下降之间的相关性。纵向 FTP SUVR 变化率的量化受到来自非目标区域的信号的影响，尤其是半球白质和脑脊液。体素 PVC 技术显着减少了这种影响。PVC 对于涉及测量群体水平纵向差异的任务提供了显着但适度的好处。