⁶⁸Gallium Chloride PET/CT as a novel functional imaging technique in the evaluation of invasive fungal rhinosinusitis (IFRS)

Objectives Aim of this study was to evaluate the utility of ⁶⁸Gallium Chloride (GaCl₃) PET/CT as a functional imaging tool in IFRS

Methods In this prospective study, clinically suspected cases of IFRS were included after written informed consent. Patients who had undergone local intervention in the past 4 weeks were excluded. GaCl₃ synthesis (<10 min procedural time) was done using inhouse generator. PET/CT imaging was performed using dedicated PET/CT scanners at 1 hr and 2 hr intervals. All these patients then underwent biopsy / surgical intervention within a mean duration of 3 days after the imaging. Results were compiled by comparing the dual time point PET / CT imaging findings with the histopathology (HP)

Results A total of 23 patients (17 males, 6 females; 19-73 years; mean 40.6) were included. 11 patients were new cases while 12 patients were currently suspected with persistent / recurrent disease. Of the 23, 10 patients showed abnormal GaCl₃ uptake. Of these 10, HP revealed active IFRS in 7 patients (6 invasive mucormycosis (IMM) and 1 invasive aspergillosis (IAG)). Of the three HP negative cases, two patients had pathological involvement (cerebral) inaccessible to representative biopsy who on follow up scans revealed resolution of tracer uptake after antifungal therapy. Third patient was a seropositive patient who died of infective complications after three months. Of the 13 PET negative cases, HP was positive in 6 (all of which were IAG) and rest of the 7 are HP negative. All these patients received either surgery / antifungal therapy and were stable on mean follow up of 10.7 months. Dual point imaging revealed increase in SUV values (mean ∆SUV 39.20%) of pathological uptake in 2 hr images with reduced bloodpool clearance and improved image quality

Conclusions We conclude that ⁶⁸Gallium Chloride appears to be a simple, safe, easy to prepare, generator produced PET radiotracer with potential role in the evaluation of invasive mucormycosis