The Use of Radiolabelled 18-F-2-deoxy-2-fluro-glucose (18-Fdg) in Combined Positron Emission Tomography-Computed Tomography (Pet-Ct) to Evaluate Infection: Lessons Learned from A Case Series of 23 Patients with Chronic Granulomatous Disease (Cgd)

RationaleUse of 18-FDG in PET-CT is gaining acceptance in diagnosis and monitoring of infection and inflammatory disorders. We describe lessons learned in patients with CGD.Methods23 CGD patients underwent 18-FDG PET-CT imaging. 10 patients were imaged as part of a dedicated infection work-up, while 13 patients were evaluated during general diagnostic assessment.ResultsFirst, known sites of active bacterial or fungal infection are always associated with intense 18-FDG uptake, but are often surprisingly heterogeneous in comparison to CT. Second, stable pulmonary lesions that are residual sequelae of long resolved infections have 18-FDG uptake on par with background. Third, CGD lymphadenopathy observed by CT, but unrelated to infection, lack intense 18-FDG uptake. Fourth, focal uptake in the musculoskeletal system can be due to recent trauma, so clinical correlation should be ascertained before assuming an infectious process. Fifth, clinical resolution of infection is closely associated with diminished 18-FDG uptake.Conclusions18-FDG PET-CT can define areas of infection, and studies are warranted to determine whether biopsy of areas of highest intensity may result in improved yield. CGD lymphadenopathy or granuloma unrelated to infection is surprisingly lacking in significantly increased 18-FDG uptake. Our observations suggest that it may be possible to use 18-FDG PET-CT to identify the scope and intensity of infection in patients with CGD and, in complex multifocal infection, may better assess overall resolution and response to therapy than CT alone. RationaleUse of 18-FDG in PET-CT is gaining acceptance in diagnosis and monitoring of infection and inflammatory disorders. We describe lessons learned in patients with CGD. Use of 18-FDG in PET-CT is gaining acceptance in diagnosis and monitoring of infection and inflammatory disorders. We describe lessons learned in patients with CGD. Methods23 CGD patients underwent 18-FDG PET-CT imaging. 10 patients were imaged as part of a dedicated infection work-up, while 13 patients were evaluated during general diagnostic assessment. 23 CGD patients underwent 18-FDG PET-CT imaging. 10 patients were imaged as part of a dedicated infection work-up, while 13 patients were evaluated during general diagnostic assessment. ResultsFirst, known sites of active bacterial or fungal infection are always associated with intense 18-FDG uptake, but are often surprisingly heterogeneous in comparison to CT. Second, stable pulmonary lesions that are residual sequelae of long resolved infections have 18-FDG uptake on par with background. Third, CGD lymphadenopathy observed by CT, but unrelated to infection, lack intense 18-FDG uptake. Fourth, focal uptake in the musculoskeletal system can be due to recent trauma, so clinical correlation should be ascertained before assuming an infectious process. Fifth, clinical resolution of infection is closely associated with diminished 18-FDG uptake. First, known sites of active bacterial or fungal infection are always associated with intense 18-FDG uptake, but are often surprisingly heterogeneous in comparison to CT. Second, stable pulmonary lesions that are residual sequelae of long resolved infections have 18-FDG uptake on par with background. Third, CGD lymphadenopathy observed by CT, but unrelated to infection, lack intense 18-FDG uptake. Fourth, focal uptake in the musculoskeletal system can be due to recent trauma, so clinical correlation should be ascertained before assuming an infectious process. Fifth, clinical resolution of infection is closely associated with diminished 18-FDG uptake. Conclusions18-FDG PET-CT can define areas of infection, and studies are warranted to determine whether biopsy of areas of highest intensity may result in improved yield. CGD lymphadenopathy or granuloma unrelated to infection is surprisingly lacking in significantly increased 18-FDG uptake. Our observations suggest that it may be possible to use 18-FDG PET-CT to identify the scope and intensity of infection in patients with CGD and, in complex multifocal infection, may better assess overall resolution and response to therapy than CT alone. 18-FDG PET-CT can define areas of infection, and studies are warranted to determine whether biopsy of areas of highest intensity may result in improved yield. CGD lymphadenopathy or granuloma unrelated to infection is surprisingly lacking in significantly increased 18-FDG uptake. Our observations suggest that it may be possible to use 18-FDG PET-CT to identify the scope and intensity of infection in patients with CGD and, in complex multifocal infection, may better assess overall resolution and response to therapy than CT alone.