Monash Biomedical Imaging, Melbourne, Vic, 3800 Australia.
Turner Institute for Brain and Mental Health, Monash University, Melbourne, Vic, 3800 Australia.
Cereb Cortex. 2021 May 10;31(6):2855-2867. doi: 10.1093/cercor/bhaa393.
Simultaneous [18F]-fluorodeoxyglucose positron emission tomography functional magnetic resonance imaging (FDG-PET/fMRI) provides the capacity to image 2 sources of energetic dynamics in the brain-glucose metabolism and the hemodynamic response. fMRI connectivity has been enormously useful for characterizing interactions between distributed brain networks in humans. Metabolic connectivity based on static FDG-PET has been proposed as a biomarker for neurological disease, but FDG-sPET cannot be used to estimate subject-level measures of "connectivity," only across-subject "covariance." Here, we applied high-temporal resolution constant infusion functional positron emission tomography (fPET) to measure subject-level metabolic connectivity simultaneously with fMRI connectivity. fPET metabolic connectivity was characterized by frontoparietal connectivity within and between hemispheres. fPET metabolic connectivity showed moderate similarity with fMRI primarily in superior cortex and frontoparietal regions. Significantly, fPET metabolic connectivity showed little similarity with FDG-sPET metabolic covariance, indicating that metabolic brain connectivity is a nonergodic process whereby individual brain connectivity cannot be inferred from group-level metabolic covariance. Our results highlight the complementary strengths of fPET and fMRI in measuring the intrinsic connectivity of the brain and open up the opportunity for novel fundamental studies of human brain connectivity as well as multimodality biomarkers of neurological diseases.
同时进行的 [18F]-氟代脱氧葡萄糖正电子发射断层扫描功能磁共振成像（FDG-PET/fMRI）可以同时成像大脑中的两个能量动力学源——葡萄糖代谢和血液动力学反应。功能磁共振成像连接已极大地有助于描述人类大脑中分布式网络之间的相互作用。基于静态 FDG-PET 的代谢连接已被提议作为神经疾病的生物标志物，但 FDG-sPET 不能用于估计个体水平的“连接”度量，只能进行跨个体的“协方差”度量。在这里，我们应用高时间分辨率的连续输注功能正电子发射断层扫描（fPET）来同时测量功能磁共振成像连接的个体代谢连接。fPET 代谢连接的特点是半球内和半球间的额顶连接。fPET 代谢连接与 fMRI 的相似性主要表现在大脑顶叶和额顶叶区域。值得注意的是，fPET 代谢连接与 FDG-sPET 代谢协方差的相似性很小，表明代谢性脑连接是一个非遍历过程，不能从群体水平的代谢协方差推断个体脑连接。我们的研究结果突出了 fPET 和 fMRI 在测量大脑固有连接方面的互补优势，为人类大脑连接的新的基础研究以及神经疾病的多模态生物标志物开辟了机会。
