Yamada Takahiro, Hanaoka Kohei, Morimoto-Ishikawa Daisuke, Yamakawa Yoshiyuki, Kumakawa Shiho, Ohtani Atsushi, Mizuta Tetsuro, Kaida Hayato, Ishii Kazunari
Division of Positron Emission Tomography Institute of Advanced Clinical Medicine, Kindai University Hospital, Osaka, Japan.
Medical Systems Division, Shimadzu Corporation, Kyoto, Japan.
Ann Nucl Med. 2025 Feb;39(2):189-198. doi: 10.1007/s12149-024-01986-6. Epub 2024 Sep 30.
Brain-dedicated positron emission tomography (PET) systems offer high spatial resolution and sensitivity for accurate clinical assessments. Attenuation correction (AC) is important in PET imaging, particularly in brain studies. This study assessed the reproducibility of attenuation maps (µ-maps) generated by a specialized time-of-flight (TOF) brain-dedicated PET system for imaging using different PET tracers.
Twelve subjects underwent both F-fluorodeoxyglucose (FDG)-PET and F-flutemetamol (FMM) amyloid-PET scans. Images were reconstructed with µ-maps obtained by a maximum likelihood-based AC method. Voxel-based and region-based analyses were used to compare µ-maps obtained with FDG-PET versus FMM-PET; FDG-PET images reconstructed using an FDG-PET µ-map (FDG × FDG) versus those reconstructed with an FMM-PET µ-map (FDG × FMM); and FMM-PET images reconstructed using an FDG-PET µ-map (FMM × FDG) versus those reconstructed with an FMM-PET µ-map (FMM × FMM).
Small but significant differences in µ-maps were observed between tracers, primarily in bone regions. In the comparison between the µ-maps obtained with FDG-PET and FMM-PET, the µ-maps obtained with FDG-PET had higher µ-values than those obtained with FMM-PET in the parietal regions of the head and skull, in a portion of the cerebellar dentate nucleus and on the surface of the frontal lobe. The comparison between FDG and FDG × FMM values in different regions yielded findings similar to those of the µ-maps comparison. FDG × FMM values were significantly higher than FDG values in the bilateral temporal bones and a small part of the temporal lobe. Similarly, FMM values were significantly higher than FMM × FDG values in the bilateral temporal bones. FMM × FDG values were significantly higher than FMM values in a small area of the right cerebellar hemisphere. However, the relative errors in these µ-maps were within ± 4%, suggesting that they are clinically insignificant. In PET images reconstructed with the original and swapped µ-maps, the relative errors were within ± 7% and the quality was nearly equivalent.
These findings suggest the clinical reliability of the AC method without an external radiation source in TOF brain-dedicated PET systems.
脑部专用正电子发射断层扫描（PET）系统具有高空间分辨率和灵敏度，可用于准确的临床评估。衰减校正（AC）在PET成像中很重要，尤其是在脑部研究中。本研究评估了一种专门的飞行时间（TOF）脑部专用PET系统生成的衰减图（µ图）在使用不同PET示踪剂成像时的可重复性。
12名受试者接受了氟代脱氧葡萄糖（FDG）-PET和氟代甲磺酸美他莫（FMM）淀粉样蛋白-PET扫描。图像使用基于最大似然的AC方法获得的µ图进行重建。基于体素和基于区域的分析用于比较FDG-PET与FMM-PET获得的µ图；使用FDG-PET µ图（FDG×FDG）重建与使用FMM-PET µ图（FDG×FMM）重建的FDG-PET图像；以及使用FDG-PET µ图（FMM×FDG）重建与使用FMM-PET µ图（FMM×FMM）重建的FMM-PET图像。
在示踪剂之间观察到µ图存在小但显著的差异，主要在骨骼区域。在FDG-PET和FMM-PET获得的µ图比较中，FDG-PET获得的µ图在头部顶叶区域、颅骨、部分小脑齿状核和额叶表面的µ值高于FMM-PET获得的µ值。不同区域FDG与FDG×FMM值的比较结果与µ图比较结果相似。FDG×FMM值在双侧颞骨和颞叶一小部分显著高于FDG值。同样，FMM值在双侧颞骨显著高于FMM×FDG值。FMM×FDG值在右小脑半球一小区域显著高于FMM值。然而，这些µ图中的相对误差在±4%以内，表明它们在临床上无显著意义。在用原始和交换的µ图重建的PET图像中，相对误差在±7%以内，质量几乎相当。
这些发现表明，在TOF脑部专用PET系统中，无需外部辐射源的AC方法具有临床可靠性。
