Purpose

The simplified reference tissue model (SRTM) is commonly applied for the quantification of brain positron emission tomography (PET) studies, particularly because it avoids arterial cannulation. SRTM requires a validated reference region which is obtained by baseline-blocking or displacement studies. Once a reference region is validated, the use should be verified for each new subject. This verification normally requires volume of distribution (V_T) of a reference region. However, performing dynamic scanning and arterial sampling is not always possible, specifically in elderly subjects and in advanced disease stages. The aim of this study was to investigate the use of non-invasive standardised uptake value (SUV) approaches, in comparison to V_T, as a verification of the previously validated grey matter cerebellum reference region for [¹⁸F]flortaucipir and [¹⁸F]florbetapir PET imaging in Alzheimer’s disease (AD) patients and controls.

Procedures

Dynamic 130-min [¹⁸F]flortaucipir PET scans obtained from nineteen subjects (10 AD patients) and 90-min [¹⁸F]florbetapir dynamic scans obtained from fourteen subjects (8 AD patients) were included. Regional V_T’s were estimated for both tracers and were considered the standard verification of the previously validated reference region. Non-invasive SUVs corrected for body weight (SUV_BW), lean body mass (SUL), and body surface area (SUV_BSA) were obtained by using later time intervals of the dynamic scans. Simulations were also performed to assess the effect of flow and specific binding (BP_ND) on the SUVs.

Results

A low SUV corresponded well with a low V_T for both [¹⁸F]flortaucipir and [¹⁸F]florbetapir. Simulation confirmed that SUVs were only slightly affected by flow changes and that increases in SUV were predominantly determined by the presence of specific binding.

Conclusions

In situations where dynamic scanning and arterial sampling is not possible, a low SUV_{(80–100 min)} for [¹⁸F]flortaucipir and a low SUV_{(50–70 min)} for [¹⁸F]florbetapir may be used as indication for absence of specific binding in the grey matter cerebellum reference region.

中文翻译：

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用于验证 [ 18 F] Flortaucipir 和 [ 18 F] Florbetapir 脑 PET 研究使用先前验证的参考区域的非侵入性标准化摄取值

目的

简化的参考组织模型 (SRTM) 通常用于量化脑正电子发射断层扫描 (PET) 研究，特别是因为它避免了动脉插管。SRTM 需要通过基线阻塞或位移研究获得的经过验证的参考区域。验证参考区域后，应验证每个新受试者的使用情况。该验证通常需要参考区域的分布容积 ( V _T )。然而，执行动态扫描和动脉采样并不总是可行的，特别是在老年受试者和晚期疾病阶段。本研究的目的是研究与V _{T相比，无创标准化摄取值 (SUV) 方法的使用}，作为对阿尔茨海默病 (AD) 患者和对照组中 [ ¹⁸ F]flortaucipir 和 [ ¹⁸ F]florbetapir PET 成像的先前验证的灰质小脑参考区域的验证。

程序

包括从 19 名受试者（10 名 AD 患者）获得的动态 130 分钟 [ ¹⁸ F]florbetapir PET 扫描和从 14 名受试者（8 名 AD 患者）获得的 90 分钟 [ ¹⁸ F]florbetapir 动态扫描。对两种示踪剂的区域V _T进行了估计，并被认为是先前验证的参考区域的标准验证。通过使用动态扫描的后期时间间隔，获得了针对体重 (SUV _BW )、瘦体重 (SUL) 和体表面积 (SUV _{BSA ) 进行校正的无创 SUV。}还进行了模拟以评估流动和特异性结合 (BP _ND ) 对 SUV 的影响。

结果

对于[ ^{18 F]} _flortaucipir和[ ¹⁸ F]florbetapir，低SUV很好地对应于低VT。模拟证实 SUV 仅受流量变化的轻微影响，并且 SUV 的增加主要由特异性结合的存在决定。

结论

在无法进行动态扫描和动脉取样的情况下，[ 18 F]flortaucipir 的低 SUV ^（_{80-100 分钟）}和 [ ¹⁸ F]florbetapir 的低 SUV _{（50-70 分钟）}可用作缺席指征在灰质小脑参考区域的特异性结合。