18 F-DPA714 PET/MRI as a potential imaging tool for detecting possible antibody-negative autoimmune encephalitis: a prospective study.

Background and Objectives: Conventional magnetic resonance imaging (MRI) used for detecting possible antibody-negative autoimmune encephalitis (AIE) often fails to meet the diagnostic requirements of this disease. Positron emission tomography (PET) with a translocator protein radioligand can help visualize microglia distribution density in inflammation-related diseases, thereby offering potentially incremental value to conventional MRI for the in vivo assessment of possible antibody-negative AIE.
Methods: In this prospective study, 15 participants diagnosed with possible antibody-negative AIE and 10 healthy controls were enrolled (ClinicalTrials.gov: NCT05293405, dated March 15, 2022). All participants underwent hybrid ¹⁸ F-DPA714 PET/MRI and evaluation for modified Rankin scale (mRS) score, clinical assessment scale for AIE (CASE), and appropriate antibodies. A positive finding was defined as the intensity of ¹⁸ F-DPA714 uptake that was above a threshold of mean standardized uptake value ratio (SUVR) + two standard deviations of SUVR within the corresponding brain regions of healthy controls.
Results: The positive detection rate of ¹⁸ F-DPA714 PET for possible antibody-negative AIE was significantly higher than that of brain MRI (10/15 [67%] vs. 3/15 [20%]; P = 0.039). In addition, both the intensity and extent of ¹⁸ F-DPA714 uptake were significantly associated with the CASE score (P = 0.002 and 0.001). Meanwhile, SUVR levels in the cerebellar region were significantly higher in patients with ataxia than in those without ataxia (P = 0.006). Furthermore, ¹⁸ F-DPA714 uptake decreased in 5/10 [50%] patients who underwent follow-up PET/MRI, which mirrored their symptom relief.
Conclusion: ¹⁸ F-DPA714 PET demonstrated its potentially incremental value to conventional MRI for detecting possible antibody-negative AIE.
Competing Interests: Declarations. Conflicts of interest: Meng HY, He L, Chunyu HX, Zhou QM, Wang J, Qu Q, Hai WX, Zhang Y, Li B, Zhang M and Chen S declare that they have no conflict of interest. Ethical standard statement: This single-center prospective study was approved by the Ethics Committee of Ruijin Hospital, Shanghai Jiao Tong University School of Medicine (2021CER375) (ClinicalTrials.gov: NCT05293405).
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