RT Journal Article SR Electronic T1 Quantification of F-18-FDG-uptake in the aortic wall: Is contrast enhanced CT suitable for PET attenuation correction? JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 220P OP 220P VO 48 IS supplement 2 A1 Mark Mueller A1 Joerg Henes A1 Ina Kötter A1 Christina Pfannenberg A1 Matthias Reimold A1 Roland Bares YR 2007 UL http://jnm.snmjournals.org/content/48/supplement_2/220P.1.abstract AB 1053 Objectives: F-18-FDG-PET/CT is increasingly used for the diagnosis and follow up of vasculitis. Artifacts caused by contrast enhanced CT for attenuation correction were described for various organs. Aim of this study was to investigate wether the SUV of the aortic wall may be affected, too. Methods: We retrospectively analyzed 18 PET/CT examinations in 16 patients (27-73 ys, 1 m) with suspected or known vasculitis. Scanner: Siemens Biograph 16. PET data acquisition: 55-84 min. p.i., 3 min per bed position, 3D-mode (LSO-HiRez). CT: (1) Low-dose-native scan with 120 kV, 30 mAs and (2) contrast enhanced CT (late arterial phase) with 120 kV, 120 mAs, 100-120 ml Ultravist 370, flow 2.0-2.6 ml/s. Quantification: FDG-uptake of the aortic wall derived from 70% isocontours (3D) in the aortic arch (AA), thoracic and abdominal aorta (TA, AbA) after attenuation correction (AC) with contrast CT or native CT, expressed as SUV or as ratio to liver tissue. Results: In all aortic segments significant higher SUV were found when using contrast CT (AA: 2,42 ± 0,64 as compared to native CT 1.88 ± 0.45; p < 0.0001). Both quantifications were correlated with R2=0.93 (AA). At the individual level, the SUV was up to 50% higher when contrast CT was used (AA 27.8 ± 9.2%). In the liver, SUV increase of 0-29% (20.09 ± 8.6%) was observed (R2 = 0.88). Effects from the contrast agents could not be compensated by calculating liver ratios (AA/liver: R2 = 0.43). Conclusions: Attenuation correction using constrast enhanced CT leads to not predictable increase of the SUV of the aortic wall. Therefore, data from a native CT should be exclusively used for attenuation correction in vasculitis patients.