Characterization of Left Ventricular Assist Device–Specific Infection by Whole-Body Parametric PET Imaging

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Clinical molecular imaging with PET has an evolving role in the diagnosis and treatment of left ventricular assist device (LVAD)–specific infection. We analyzed the added value of parametric whole-body [18F]FDG PET images for the multifaceted assessment of local inflammatory response to infection and characterization of systemic organ networks and explored the prognostic significance of systems-based parameters. Methods: Twenty-three patients with suspected device-specific infection were prospectively enrolled and underwent multipass [18F]FDG PET/CT with direct Patlak reconstruction between January 2020 and March 2023. Three sets of images were generated: SUV-equivalent images, parametric images of the maximum metabolic rate of [18F]FDG (MRFDG), and parametric images of the distribution volume of [18F]FDG. Images were analyzed for the presence and extent of infection, differential spatial distribution of signal in parametric images, and signal contrast. We then aimed to characterize the association between PET signal and inflammatory markers from peripheral blood, results of microbial cultures, and systemic organ networks identified in whole-body PET. Results: Visually increased uptake at the driveline exit site, subcutaneous driveline, outflow graft, and pump pocket was found in 74%, 30%, 26%, and 17% of patients, respectively, and findings were concordant between SUV images and MRFDG images. Quantitative MRFDG analysis provided accurate identification of driveline exit site infection. Improved contrast was found in MRFDG images (P ≤ 0.0003). Analysis of parametric images revealed spatial heterogeneity caused by differential contribution of MRFDG, blood volume, and distribution volume of [18F]FDG in infectious lesions. Blood-based inflammatory markers (e.g., monocyte count) (P = 0.0217) were associated with MRFDG but not SUVs. Finally, there was an association between the internal LVAD components signal and hematopoietic organ signal in MRFDG images (e.g., bone marrow signal; P = 0.0353), highlighting systemic interactions. Conclusion: [18F]FDG PET/CT allows for the diagnosis and characterization of the extent of LVAD-specific infections. Parametric MRFDG images provide improved contrast, refined biologic understanding of the relative contribution of signal components to the measured PET signal in infection, correlation with circulating immune biomarkers in peripheral blood, and characterization of systemic interactions.

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