title: Respiratory-gated imaging in metabolic evaluation of small solitary pulmonary nodules: 18F-FDG PET/CT and correlation with histology.
abstract: OBJECTIVE
  The aim of the study was to evaluate the effect of 2-((18)F)-fluoro-2-deoxy-D-glucose ((18)F-FDG)-PET/computed tomography (CT) respiratory-gated imaging [four-dimensional (4D)] in the metabolic evaluation of small solitary pulmonary nodules and analyze the cutoff maximum standardized uptake value (SUV(max)) of 2.5 in classifying and distinguishing benign/malignant pulmonary pathologies in 4D studies.
  
  
  METHODS
  Thirty-two patients with pulmonary lesions measuring 2 cm or less were included during their scheduled (18)F-FDG PET/CT examinations. The whole-body PET/CT acquisition (3D) was followed by a chest-centered PET/CT (4D) study synchronized with the respiratory cycle. The SUV(max) percentage difference (%Diff SUV(max)) was calculated. The nodule size, localization, and relationships with histological/cytological findings were studied.
  
  
  RESULTS
  Fifteen nodules were 10 mm or smaller and 17 were larger than 10 mm [mean size = 12 mm (7-20)]. The mean 3D-SUV(max) was 2.5 (0.7-6.1) and the mean 4D-SUV(max) 3.2 (0.9-7.2) (P < 0.001). The mean %Diff SUV(max) was 38% for all patients (7-90), 45% in subcentimetric (7-90%) and 31% (7-75%) in supracentimetric lesions (P = NS). Histology was obtained in 23/32 (72%) cases and the pathologic benign/malignant ratio was 4/19. Malignancies were diagnosed as lung adenocarcinoma, solitary metastases, large cell lung carcinoma, and sarcoma in 13 (41%), 3 (9%), 2 (6%), and 1 (3%) case, respectively. Malignant lesions showed mean 4D-SUV(max) of 3.8 (1.2-7.2). The cutoff SUV(max) of 2.5 did not classify and distinguish between benign/malignant pulmonary pathologies, neither in 3D nor in 4D studies.
  
  
  CONCLUSIONS
  Respiratory gating improves the detectability and metabolic evaluation of solitary pulmonary nodules, mostly those that are subcentimetric. However, as expected, the cutoff SUV(max) of 2.5 does not distinguish between benign/malignant lesions in either 4D or 3D studies.
authors: aNuclear Medicine Department, AP-HP, Hotel Dieu University Hospital bFaculty of Medicine, Paris Descartes University cChest Surgery Department, AP-HP, Cochin University Hospital dRadiology Department eNuclear Medicine Department, Institut Curie, Paris, France.
authors: Karim
authors: K
authors: Farid
authors: Xavier
authors: X
authors: Poullias
authors: Marco
authors: M
authors: Alifano
authors: Jean-Francois
authors: JF
authors: Regnard
authors: Vincent
authors: V
authors: Servois
authors: Nadine
authors: N
authors: Caillat-Vigneron
authors: Slavomir
authors: S
authors: Petras
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis / Q000378:metabolism; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18