68Ga- FAPI PET/CT imaging in Neuromelioidosis – Promising tracer to supplement diagnosis and response assessment

Introduction: Neuromelioidosis is central nervous system (CNS) involvement of melioidoses, caused by gram negative saprophytic bacteria named Burkholderia pseudo-mallei . Its CNS involvement is rare, but has high mortality and morbidity. Gallium-68-labeled fibroblast activation protein inhibitor ( ⁶⁸ Ga-FAPI) PET/CT is a novel molecular imaging PET tracer, found useful in infection/inflammation imaging apart from tumours and shows no significant physiological uptake in the normal brain parenchyma. Hence it shows promising role in brain imaging. Aim and objective: To evaluate the potential use of ⁶⁸ Ga-FAPI PET/CT imaging in neuromelioidosis and compare it with FDG PET/CT imaging. Material and Methods Both ⁶⁸ Ga- FAPI and ¹⁸ F-FDG PET/CT brain imaging were performed in three patients with suspected or proven Neuromelioidosis (two male and one female patient, age between 17–58 years, median age- 38 years) and compared with each other. Results Total four brain lesions were evaluated in three patients. ¹⁸ F-FDG SUVmax range was 4.8–13.1 (median- 8.1) and median Target to background ratio (TBR) was 1.2. On ⁶⁸ Ga- FAPI PET/CT, SUVmax range was 1.6–6.5 (median 4.4) with median TBR- 32.2. ⁶⁸ Ga- FAPI PET/CT findings were concordant with MRI findings in all four lesions. ⁶⁸ Ga-FAPI PET/CT was evaluated for response assessment in one patient and was superior to MRI. Conclusion ⁶⁸ Ga- FAPI PET/CT is superior than ¹⁸ F-FDG PET/CT and is a useful imaging tool for diagnosis, disease mapping and response evaluation in neuromelioidosis with better lesion to background contrast.