Relationship between PET-FDG and MRI apparent diffusion coefficients in brain tumors

Area of Science:

• Neuroimaging
• Oncology
• Radiology

Background:

• Brain tumors exhibit complex cellularity and metabolic activity.
• Positron emission tomography (PET) with 2-deoxy-2[(18)F]fluoro-D-glucose ([(18)F]FDG) measures metabolic activity.
• Diffusion-weighted magnetic resonance imaging (DWI) with apparent diffusion coefficients (ADC) assesses tissue microstructure.

Purpose of the Study:

• To investigate the relationship between [(18)F]FDG PET and ADC values in brain tumors.
• To determine if metabolic activity correlates with water diffusion characteristics in brain lesions.

Main Methods:

• Fifteen patients with 18 metastatic brain lesions were included.
• Evaluated using gadolinium-enhanced fast spoiled gradient echo (Gd-FSPGR), DWI with ADC maps, and [(18)F]FDG PET.
• Regions of interest (ROIs) were analyzed, and linear regression was performed on PET and ADC ratios.

Main Results:

• An inverse correlation was observed between [(18)F]FDG PET and ADC ratios (r(2)=0.2746, P=0.0256).
• High PET ratios corresponded to low ADC ratios, and vice versa.
• This suggests that areas with high metabolic activity have restricted water diffusion.

Conclusions:

• Preliminary data indicate an inverse relationship between [(18)F]FDG PET uptake and ADC values in brain tumors.
• Higher cellularity may lead to increased impedance of water diffusion (low ADC) and higher [(18)F]FDG uptake.
• Conversely, lower cellularity is associated with increased ADC and decreased [(18)F]FDG uptake.