Comparison of 18F-DPA714 PET/MRI and 18F-FDG PET/CT in patients with autoimmune encephalitis: a cross-sectional study.

BACKGROUND AND AIM: The positive detection rate of MRI in autoimmune encephalitis (AIE) patients is low, often failing to make a rapid and accurate localization diagnosis. Both 18F-DPA714 and 18F-FDG PET imaging techniques have shown their advantages in the diagnosis of AIE. Therefore, the aim of this study was to conduct a head-to-head comparison of the diagnostic value between 18F-DPA714 and 18F-FDG PET in patients with AIE.

METHODS

This cross-sectional study included 23 antibody-positive and 2 possible antibody-negative AIE patients, along with 10 healthy controls. All patients underwent sequential 18F-DPA714 PET/MRI and 18F-FDG PET/CT examinations within one week. A follow-up of 6 to 12 months after the baseline examinations was performed to assess the change of patients' clinical symptoms. Positive findings for 18F-DPA714 PET were defined as Z-score above 2.0 in the corresponding brain regions of healthy controls. Positive results for 18F-FDG PET were indicated by the Z-score above 2.0 or below -2.0 obtained after comparison with the normal population database.

RESULTS

Both 18F-FDG PET and 18F-DPA714 PET showed higher positivity rates than MRI (81% vs 44%, P = 0.006 and 76% vs 44%, P = 0.008, respectively). A statistically significant association was found between the uptake intensity and extent of 18F-DPA714 but not 18F-FDG with the mRS scores and the CASE scores. Patients with epilepsy showed a significantly higher uptake in the whole-cortex of both 18F-DPA714 (P = 0.0014) and 18F-FDG (P = 0.0051) and in the temporal lobe of 18F-FDG (P = 0.0216) compared to those patients without. Higher 18F-DPA714 SUVR (P < 0.001) and lower 18F-FDG SUVR (P < 0.001) in the whole-cortex of patients with long-term cognitive impairment than those patients without were observed.

CONCLUSION

18F-DPA714 PET showed its better correlation with disease severity of AIE than 18F-FDG PET, serving as a supplementary tool to 18F-FDG PET and MRI.