A study of [18F]fluoro-L-dopa PET/computed tomography imaging to evaluate the extent of liver fibrosis.

Purpose: This study aims to evaluate the feasibility of using 6-[18F]fluoro-L-dopa ([18F]FDOPA) PET/computed tomography (PET/CT) imaging, targeting dopamine receptor D1 (DRD1), for the noninvasive assessment of liver fibrosis severity.

Methods: A rat model of liver fibrosis with different degrees of fibrosis was established. [18F]FDOPA PET/CT imaging was performed to measure the radioactivity uptake in the liver. The stage of liver fibrosis was determined through pathological testing, and the correlation between imaging findings and the fibrosis stage was assessed. In addition, the expression levels of DRD1 and dopa decarboxylase (DDC) were detected to evaluate the relationship between liver uptake and DRD1 expression.

Results: The 29 surviving rats were categorized into stages F0-F4 according to the Metavir grading system based on the hematoxylin and eosin and Masson staining pathology findings. Liver radioactivity uptake was significantly and positively correlated with the stage of liver fibrosis (r = 0.8006, P < 0.001). After adjusting for errors using the ratio method, the area under the curve (AUC) for PET/CT imaging to discriminate significant liver fibrosis from no fibrosis and severe liver fibrosis from mild-to-moderate liver fibrosis were 0.9342 and 0.9639, respectively, at the optimal cut-off value. DRD1 expression was significantly correlated with both liver fibrosis stage (r = 0.9412, P < 0.001) and relative uptake value (r = 0.8182, P < 0.001).

Conclusion: [18F]FDOPA PET/CT imaging is a valuable tool for assessing liver fibrosis severity. The level of radioactivity uptake in the liver is significantly correlated with the degree of liver fibrosis and DRD1 expression level.