Department of Biomedical Engineering, University of Melbourne, Melbourne, Victoria, Australia.
Melbourne Brain Centre Imaging Unit, University of Melbourne, Melbourne, Victoria, Australia.
J Nucl Med. 2024 May 1;65(5):781-787. doi: 10.2967/jnumed.123.266188.
Amyloid-β (Aβ) accumulation in Alzheimer disease (AD) is typically measured using SUV ratio and the centiloid (CL) scale. The low spatial resolution of PET images is known to degrade quantitative metrics because of the partial-volume effect. This article examines the impact of spatial resolution, as determined by the reconstruction configuration, on the Aβ PET quantitation in both cross-sectional and longitudinal data. The cross-sectional study involved 89 subjects with 20-min [F]florbetapir scans generated on an mCT (44 Aβ-negative [Aβ-], 45 Aβ-positive [Aβ+]) using 69 reconstruction configurations, which varied in number of iteration updates, point-spread function, time-of-flight, and postreconstruction smoothing. The subjects were classified as Aβ- or Aβ+ visually. For each reconstruction, Aβ CL was calculated using CapAIBL, and the spatial resolution was calculated as full width at half maximum (FWHM) using the barrel phantom method. The change in CLs and the effect size of the difference in CLs between Aβ- and Aβ+ groups with FWHM were examined. The longitudinal study involved 79 subjects (46 Aβ-, 33 Aβ+) with three 20-min [F]flutemetamol scans generated on an mCT. The subjects were classified as Aβ- or Aβ+ using a cutoff CL of 20. All scans were reconstructed using low-, medium-, and high-resolution configurations, and Aβ CLs were calculated using CapAIBL. Since linear Aβ accumulation was assumed over a 10-y interval, for each reconstruction configuration, Aβ accumulation rate differences (ARDs) between the second and first periods were calculated for all subjects. Zero ARD was used as a consistency metric. The number of Aβ accumulators was also used to compare the sensitivity of CL across reconstruction configurations. In the cross-sectional study, CLs in both the Aβ- and the Aβ+ groups were impacted by the FWHM of the reconstruction method. Without postreconstruction smoothing, Aβ- CLs increased for a FWHM of 4.5 mm or more, whereas Aβ+ CLs decreased across the FWHM range. High-resolution reconstructions provided the best statistical separation between groups. In the longitudinal study, the median ARD of low-resolution reconstructed data for the Aβ- group was greater than zero whereas the ARDs of higher-resolution reconstructions were not significantly different from zero, indicating more consistent rate estimates in the higher-resolution reconstructions. Higher-resolution reconstructions identified 10 additional Aβ accumulators in the Aβ- group, resulting in a 22% increased group size compared with the low-resolution reconstructions. Higher-resolution reconstructions reduced the average CLs of the negative group by 12 points. High-resolution PET reconstructions, inherently less impacted by partial-volume effect, may improve Aβ PET quantitation in both cross-sectional and longitudinal data. In the cross-sectional analysis, separation of CLs between Aβ- and Aβ+ cohorts increased with spatial resolution. Higher-resolution reconstructions also exhibited both improved consistency and improved sensitivity in measures of Aβ accumulation. These features suggest that higher-resolution reconstructions may be advantageous in early-stage AD therapies.
淀粉样蛋白-β（Aβ）在阿尔茨海默病（AD）中的积累通常使用 SUV 比值和百分位（CL）量表来衡量。众所周知，由于部分容积效应，PET 图像的低空间分辨率会降低定量指标。本文研究了重建配置决定的空间分辨率对横断面和纵向数据中 Aβ PET 定量的影响。
在横断面研究中，89 名参与者进行了 20 分钟的[F]florbetapir 扫描，使用 69 种重建配置在 mCT 上生成（44 名 Aβ-阴性[Aβ-]，45 名 Aβ-阳性[Aβ+]），这些配置在迭代更新、点扩散函数、飞行时间和后重建平滑方面各不相同。参与者根据视觉进行 Aβ-或 Aβ+分类。对于每种重建，使用 CapAIBL 计算 Aβ CL，并使用桶形幻影方法计算全宽半最大值（FWHM）作为空间分辨率。检查了 CL 的变化以及 Aβ-和 Aβ+组之间 CL 差异的效应大小与 FWHM 的关系。
在纵向研究中，79 名参与者（46 名 Aβ-，33 名 Aβ+）进行了三次 20 分钟的[F]flutemetamol 扫描，在 mCT 上生成。使用 20 的 CL 作为截止值对参与者进行 Aβ-或 Aβ+分类。所有扫描均使用低、中、高分辨率配置进行重建，并使用 CapAIBL 计算 Aβ CL。由于假定在 10 年的间隔内线性 Aβ 积累，对于每种重建配置，对所有参与者计算了第二和第一个时期之间的 Aβ 积累率差异（ARD）。零 ARD 用作一致性指标。还使用 Aβ 积累者的数量来比较不同重建配置的 CL 敏感性。
在横断面研究中，Aβ-和 Aβ+组的 CL 均受重建方法的 FWHM 影响。没有后重建平滑时，对于 FWHM 为 4.5mm 或更大的情况，Aβ- CL 会增加，而 Aβ+ CL 则会在整个 FWHM 范围内下降。高分辨率重建提供了最佳的组间统计学分离。在纵向研究中，Aβ-组低分辨率重建数据的中位 ARD 大于零，而高分辨率重建的 ARD 与零没有显著差异，表明高分辨率重建的速率估计更一致。高分辨率重建在 Aβ-组中发现了 10 个额外的 Aβ 积累者，与低分辨率重建相比，组大小增加了 22%。高分辨率重建将阴性组的平均 CL 降低了 12 分。
固有受部分容积效应影响较小的高分辨率 PET 重建，可能会提高横断面和纵向数据中 Aβ PET 定量的准确性。在横断面分析中，Aβ-和 Aβ+队列之间的 CL 分离随着空间分辨率的提高而增加。高分辨率重建还表现出改善的一致性和 Aβ 积累测量的敏感性。这些特征表明，高分辨率重建可能在早期 AD 治疗中具有优势。
