Increased brain uptake of ¹⁸F-AV45 visualized by PET is a key biomarker for Alzheimer disease (AD). The SUV ratio (SUVR) is widely used for quantification, but is subject to variability based on choice of reference region and changes in cerebral blood flow. Here we validate the SUVR method against the gold standard volume of distribution (V_T) to assess cross-sectional differences in plaque load. Methods: Dynamic 60-min ¹⁸F-AV45 (291 ± 67 MBq) and 1-min ¹⁵O-H₂O (370 MBq) scans were obtained in 35 age-matched elderly subjects, including 10 probable AD, 15 amnestic mild cognitive impairment (aMCI), and 10 cognitively healthy controls (HCs). ¹⁸F-AV45 V_T was determined from 2-tissue-compartment modeling using a metabolite-corrected plasma input function. Static SUVR was calculated at 50–60 min after injection, using either cerebellar gray matter (SUVR_CB) or whole subcortical white matter (SUVR_WM) as the reference. Additionally, whole cerebellum, pons, centrum semiovale, and a composite region were examined as alternative references. Blood flow was quantified by ¹⁵O-H₂O SUV. Data are presented as mean ± SEM. Results: There was rapid metabolization of ¹⁸F-AV45, with only 35% of unchanged parent remaining at 10 min. Compared with V_T, differences in cortical Aβ load between aMCI and AD were overestimated by SUVR_WM (+4% ± 2%) and underestimated by SUVR_CB (−10% ± 2%). V_T correlated better with SUVR_WM (Pearson r: from 0.63 for posterior cingulate to 0.89 for precuneus, P < 0.0001) than with SUVR_CB (Pearson r: from 0.51 for temporal lobe [P = 0.002] to 0.82 for precuneus [P < 0.0001]) in all tested regions. Correlation results for the alternative references were in between those for CB and WM. ¹⁵O-H₂O data showed that blood flow was decreased in AD compared with aMCI in cortical regions (−5% ± 1%) and in the reference regions (CB, −9% ± 8%; WM, −8% ± 8%). Conclusion: Increased brain uptake of ¹⁸F-AV45 assessed by the simplified static SUVR protocol does not truly reflect Aβ load. However, SUVR_WM is better correlated with V_T and more closely reflects V_T differences between aMCI and AD than SUVR_CB.

PET显示的¹⁸ F-AV45的脑摄取增加是阿尔茨海默病（AD）的关键生物标志物。SUV比（SUVR）被广泛用于量化，但会因参考区域的选择和脑血流量的变化而变化。在这里，我们根据金标准分布体积（V _T）验证SUVR方法，以评估斑块负荷的横截面差异。方法：在35位年龄相匹配的老年受试者中进行了60分钟的动态¹⁸分钟F-AV45（291±67 MBq）和1分钟的¹⁵ O-H ₂ O（370 MBq）扫描，其中包括10例可能的AD，15例轻度轻度认知障碍（ aMCI）和10个认知健康对照（HCs）。¹⁸ F-AV45 V使用代谢物校正的血浆输入函数从2组织隔室模型确定_T。注射后50-60分钟，以小脑灰质（SUVR _CB）或整个皮质下白质（SUVR _WM）作为参考，计算静态SUVR 。另外，检查了整个小脑，脑桥，中心半卵和一个复合区域作为替代参考。通过¹⁵ O-H ₂ O SUV定量血流。数据表示为平均值±SEM。结果：¹⁸ F-AV45快速代谢，在10分钟时仅保留35％的未改变亲本。与V _T比较，SUVR _WM（+ 4％±2％）高估了aMCI和AD之间的皮质Aβ负荷差异，而SUVR _CB（-10％±2％）低估了皮质Aβ负荷。V _T与SUVR _WM（Pearson r：后扣带的0.63到足前神经的0.89，P <0.0001）的相关性比SUVR _CB（Pearson r：从颞叶的0.51 [ P = 0.002]到足前神经的0.82 [ P < 0.0001]）。替代参考的相关结果介于CB和WM之间。¹⁵ O-H ₂O数据显示，与aMCI相比，在皮质区域（−5％±1％）和参考区域（CB，−9％±8％； WM，−8％±8％），AD的血流减少。结论：通过简化的静态SUVR协议评估的¹⁸ F-AV45的大脑摄取增加并未真正反映Aβ负荷。但是，SUVR _WM与V _T的相关性更好，并且比SUVR _CB更能反映aMCI和AD之间的V _T差异。