POS1129 OPTIMIZATION OF DUAL ENERGY COMPUTED TOMOGRAPHY POST-PROCESSING TO REDUCE LOWER LIMB ARTIFACTS IN GOUT

Background: Dual energy computed tomography (DECT) is highly accurate for the diagnosis of gout. However, many artifacts have been described (1,2) such as nail bed, skin, beam hardening, sub-millimeter and vascular artifacts). Their presence can lead to a risk of over-diagnosis (false positives). Objectives: Main objective of this case-control study was to determine the optimal DECT settings post-treatment parameters (ratio and attenuation coefficient (HU)) in order to reduce the frequency of lower limb artifacts in patients with suspected gout of the lower limbs. Methods: Seventy-seven patients hospitalized for suspected gout arthritis (feet/ankles and/or knees) who received a DECT imaging were consecutively included (final diagnosis of 43 gout and 34 other rheumatic disorders). Different post-treatment settings were evaluated from the Syngovia software: an R1 (standard) setting with a ratio at 1.36 and minimum attenuation at 150 HU; an R2 setting with a ratio at 1.28 and minimum attenuation at 170 HU and an R3 setting with a ratio at 1.28 and minimum attenuation at 120 HU. The frequency of each artifact according to the 3 settings was determined. Diagnostic accuracy of R1 and R2 settings has been calculated. Correlations between artefacts and patient’s clinical characteristics were obtained by performing a Spearman test. Results: The R2 setting (170 HU, ratio=1.28) significantly reduced the presence of knee and foot/ankle artifacts compared to the standard R1 setting (85% and 94% decrease in beam hardening and clumpy artifacts in the ankle and foot, respectively (p Conclusion: Applying a ratio of 1.28 and a minimum attenuation of 170 HU (R2 settings) in DECT post-processing eliminates the majority of the artifacts located on the lower limbs, particularly the clumpy artifact and the beam hardening artifact. References: [1]Neogi T, Jansen TLTA, Dalbeth N, Fransen J, Schumacher HR, Berendsen D, et al. 2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis. 2015;74:1789-98. [2]Mallinson PI, Coupal T, Reisinger C, Chou H, Munk PL, Nicolaou S, et al. Artifacts in dual-energy CT gout protocol: a review of 50 suspected cases with an artifact identification guide. AJR 2014;203:W103-109. Disclosure of Interests: None declared.