Abstract
OBJECTIVE: To assess the technical feasibility and diagnostic benefit of CT iterative metal artifact reduction (iMAR) in patients with metal implants undergoing positron emission tomography (PET/CT. METHODS: PET/CTs of 100 patients with metal implants in different anatomical localization were retrospectively analyzed. CT data were reconstructed with iMAR and without iMAR (noMAR) and used in comparison for PET attenuation correction, generating iMAR-corrected and noMAR PET data. The effect of iMAR on quantitative CT and PET analysis was assessed by measurements of Hounsfield units (HUs) and standard uptake values (SUV) in predefined anatomical structures and pathological lesions in the vicinity of metal implants. Diagnostic confidence for lesion delineation was assessed using a 3-point scale. RESULTS: For artifact-affected structures, mean HU of iMAR corrected CT significantly differed compared to noMAR CT and standard deviations were significantly lower [e.g. M. masseter: 71.01 ± 22.34 HU (iMAR) vs 98.89 ± 92.18 HU (noMAR), p < .01]. SUVs did not significantly differ in artifact-affected structures [e.g. M. masseter: SUVmean 0.96 ± 0.54 (iMAR) vs 0.97 ± 0.55 (noMAR); p > .89] and pathological findings [SUVmean 10.78 (iMAR) vs 10.81 (noMAR); p > .98] between iMAR and noMAR PET. Qualitatively, delineation was significantly improved in iMAR corrected CT for the interpretation of anatomical and pathological structures [e.g. score of pathologic lesions: 2.80 (iMAR) vs 2.31 (noMAR); p < .01]. CONCLUSION: The use of iMAR in PET/CT significantly improves delineation of anatomical and pathological structures in the vicinity of metal implants in CT. PET quantification and PET image quality are not significantly affected by the use of iMAR-based attenuation correction independent of the presence of metal implants. ADVANCES IN KNOWLEDGE: IMAR is a feasible algorithm in PET/CT improving CT image quality in the vicinity of metal implants without affecting PET quantification and can therefore be implemented in the clinical routine.