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

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.

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 ¹⁸F-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 ¹⁸F-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.

The positive detection rate of ¹⁸F-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 ¹⁸F-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, ¹⁸F-DPA714 uptake decreased in 5/10 [50%] patients who underwent follow-up PET/MRI, which mirrored their symptom relief.

¹⁸F-DPA714 PET demonstrated its potentially incremental value to conventional MRI for detecting possible antibody-negative AIE.