NON-INVASIVE FUNCTIONAL PET – A NOVEL APPROACH TO ASSESS TASK-SPECIFIC CEREBRAL GLUCOSE METABOLISM
Authors: Godbersen *Godber Mathis , Falb Pia , Klug Sebastian , Silberbauer Leo Richard , Reed Murray Bruce , Nics Lukas , Hacker Marcus , Lanzenberger Rupert , Hahn Andreas 
Published: February 2025

Abstract

Background
The assessment of dynamic changes in the cerebral glucose metabolism through a single PET scan holds significant promise for advancing our knowledge of brain function in both health and disease. Unlike fMRI, functional positron emission tomography (fPET) using [18F] Fludeoxyglucose ([18F]FDG) offers a measure of neuronal activity independent of neurovascular coupling [1,2]. However, the necessity for an arterial input function poses challenges, as it can be unpleasant for participants and also increases experimental complexity [1–3]. These limitations hinder the widespread adoption of fPET across various settings, including the clinical routine.

Aims & Objectives
We aimed to investigate the feasibility of conducting fPET without the need for an arterial or any other input function.

Methods
52 healthy subjects (23.2 ± 3.3 years, 24 female) performed Tetris® during an [18F]FDG fPET scan. Data acquisition, processing and general linear model (GLM) analysis were performed as described in [4]. The cerebral metabolic rate of glucose (CMRGlu) was absolutely quantified using the Patlak plot and arterial input function, which was our gold standard. Simplified fPET parameters (percent signal change (%SC) of GLM beta values and %SC of CMRGlu) from a voxel-wise whole-brain and a region-wise analysis were compared (all p&lt;0.05 FWE corrected cluster level following p&lt;0.001 uncorrected voxel threshold).

Results
The voxel-wise analysis revealed nearly identical activation patterns for both approaches in brain regions characteristic for the Tetris® task (i.e., the occipital cortex, frontal eye field and intraparietal sulcus). The ROI-wise analysis resulted in strong correlations between %SC of beta values and %SC of CMRGlu (all r &gt;0.998) (Fig 1).

Discussion & Conclusion
Relative to a baseline condition, fPET can enable the non-invasive assessment of task-specific changes in the cerebral glucose metabolism. Removing the requirement for an invasive (arterial) input function makes this promising neuroimaging tool more accessible for various applications, including clinical routine and research. Future work may use fPET to study other cognitive tasks, or assess the metabolic changes resulting from brain stimulation treatments [5], in both healthy participants as well as patient collectives.

References
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