title: PET recognition of pulmonary metastases on PET/CT imaging: impact of attenuation-corrected and non-attenuation-corrected PET images.
abstract: OBJECTIVE
  The aims of this study were to assess the performance of FDG PET at PET/CT imaging for the detection of pulmonary metastases and to evaluate differences in lesion detectability on attenuation-corrected (AC) and non-attenuation corrected (NAC) PET images.
  
  
  METHODS
  The institutional PET/CT database was searched for patients with pulmonary metastases of 3-60 mm in diameter. Ninety-two patients with 438 metastases to the lungs were included in the study. The primary tumours were 33 malignant melanomas, 12 carcinomas of unknown primary, 11 colorectal carcinomas, eight differentiated thyroid carcinomas, seven aggressive non-Hodgkin's lymphomas, six head and neck cancers, three breast cancers, two prostate cancers and ten others. Lesion detectability was visually compared between PET and CT and between AC and NAC PET images using a five-point scale.
  
  
  RESULTS
  Of the 438 pulmonary metastases, 174 were detected with FDG PET (39.7%), six of them on NAC images only (not significant). Visual scores were higher on NAC images in 41.4% and equal in 54.6% of lesions. The sensitivity of FDG PET increased significantly from 0.405 for metastases of 5-7 mm in diameter to 0.784 for lesions of 8-10 mm and to 0.935 for lesions measuring 11-29 mm in diameter. No metastases smaller than 5 mm in diameter were seen on PET images.
  
  
  CONCLUSIONS
  FDG PET/CT is useful for the assessment of pulmonary metastases. The frequency of lesion detection is similar for AC and NAC PET images. A reduced sensitivity of FDG PET has to be considered for lesions smaller than 11 mm in diameter.
authors.affiliation: Department of Nuclear Medicine, University Hospital Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany. michael.reinhardt@ukb.uni-bonn.de
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Reinhardt
authors.forename: Nicole
authors.initials: N
authors.lastname: Wiethoelter
authors.forename: Alexander
authors.initials: A
authors.lastname: Matthies
authors.forename: Alexius Y
authors.initials: AY
authors.lastname: Joe
authors.forename: Holger
authors.initials: H
authors.lastname: Strunk
authors.forename: Ursula
authors.initials: U
authors.lastname: Jaeger
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Biersack
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18