title: The additional value of attenuation correction CT acquired during 18F-FDG PET/CT in differentiating mature from immature teratomas.
abstract: BACKGROUND
  Increased F-FDG uptake is often seen in soft-tissue components or in neuronal components of teratomas, which makes differentiation of mature and immature teratoma difficult using only F-FDG uptake. The distribution pattern of fat and calcification in teratomas is characteristic on CT, which can also be well seen on attenuation correction CT (AC-CT). We hypothesize that the fat and calcification distribution patterns on AC-CT taken during PET/CT will provide additional diagnostic information in differentiating between mature and immature teratomas.
  
  
  METHODS
  This retrospective study included 34 patients (44 masses; mean age 32 ± 16.3 years, range 0.2-70 years) who underwent F-FDG PET/CT before surgical resection for teratomas. F-FDG equal to or higher than the liver was visually considered positive. AC-CT images acquired during PET/CT were reviewed for calcification and fat distribution patterns. AC-CT findings for immature teratomas were scattered fat and/or disperse coarse calcification. Pathologic results were categorized into mature and immature teratomas. SUVmax and AC-CT findings were correlated with pathologic results.
  
  
  RESULTS
  Out of the 44 lesions, 11 teratomas were immature, with higher F-FDG uptake in these tumors (7.8 ± 4.10 vs. 2.1 ± 2.28, P < 0.001). SUVmax higher than 2.8 were 91% accurate, but fat and/or calcification patterns on AC-CT were extremely helpful in reducing false-positive findings based on F-FDG uptake alone.
  
  
  CONCLUSIONS
  Characteristic fat and calcification patterns on AC-CT of PET/CT were extremely helpful in differentiating mature from immature teratomas, especially in mature teratomas with increased F-FDG uptake. This can potentially reduce unnecessary radiation exposure from additional contrast-enhanced CT.
authors.affiliation: From the *Department of Nuclear Medicine, Yonsei University Health System, Seoul, and †Yonsei University Medical School, Seoul, Korea.
authors.forename: Arthur
authors.initials: A
authors.lastname: Cho
authors.forename: Se-woong
authors.initials: SW
authors.lastname: Kim
authors.forename: Jiyoun
authors.initials: J
authors.lastname: Choi
authors.forename: Wonjun
authors.initials: W
authors.lastname: Kang
authors.forename: Jong-doo
authors.initials: JD
authors.lastname: Lee
authors.forename: Mijin
authors.initials: M
authors.lastname: Yun
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003710:Demography; D003937:Diagnosis, Differential; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007223:Infant; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D013724:Teratoma / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18