title: 68Ga-DOTATOC PET/CT of neuroendocrine tumors: spotlight on the CT phases of a triple-phase protocol.
abstract: The diagnostic value of neuroendocrine tumor (NET) imaging using PET with integrated CT is dependent on both components. This retrospective study assessed the value of the single CT phases of a triple-phase (early arterial, portal-venous inflow, and venous) CT protocol in comparison to (68)Ga-DOTATOC PET in a masked reading.
  
  
  METHODS
  (68)Ga-DOTATOC PET/CT examinations from 51 patients with known or suspected NET were included. Two readers assessed the data of PET and each of the 3 CT phases for NET lesions independently (using a 3-point score: 1 = benign, 2 = indeterminate, and 3 = malignant) and by consensus (using binary benign/malignant interpretation only). Only lesions within the field of the abdominal scan were evaluated. Clinical and imaging follow-up, histopathology (if available), and the decision of an interdisciplinary truth-panel served as a standard of reference. In addition to the calculation of standard statistical parameters (including general linear mixed models), interobserver reliability was estimated (Cohen's κ).
  
  
  RESULTS
  Of 510 abdominal lesions observed, 354 were classified as malignant. Sensitivity was 77.1% for combined triple-phase CT, 53.4% for arterial CT, 66.1% for portal-venous CT, 66.9% for venous CT, and 72.8% for PET. The respective specificities were 85.3%, 92.9%, 92.3%, 89.7%, and 97.4%, and the respective accuracies were 79.6%, 65.5%, 74.1%, 73.9%, and 80.4%. Although arterial CT was found to be inferior to PET, portal-venous CT, and venous CT (P < 0.001), the differences between the other scans were not significant. Detection was exclusively by PET for 16.1% of lesions, by triple-phase CT for 20.3%, by arterial CT for 0.5%, by portal-venous CT for 3.9%, and by venous CT for 3.9%. Regarding interobserver reliability, the κ-value was 0.768 for PET, 0.391 for triple-phase CT, 0.577 for arterial CT, 0.583 for portal-venous CT, and 0.482 for venous CT.
  
  
  CONCLUSIONS
  No CT phase can be omitted in NET imaging, and the triple-phase protocol continues to be strongly recommended also for PET/CT.
authors.affiliation: Klinik für Radiologie und Nuklearmedizin, Universitätsklinikum Magdeburg A.ö.R., Magdeburg, Germany. juri.ruf@med.ovgu.de
authors.forename: Juri
authors.initials: J
authors.lastname: Ruf
authors.forename: Jan
authors.initials: J
authors.lastname: Schiefer
authors.forename: Christian
authors.initials: C
authors.lastname: Furth
authors.forename: Ortud
authors.initials: O
authors.lastname: Kosiek
authors.forename: Siegfried
authors.initials: S
authors.lastname: Kropf
authors.forename: Friederike
authors.initials: F
authors.lastname: Heuck
authors.forename: Timm
authors.initials: T
authors.lastname: Denecke
authors.forename: Marianne
authors.initials: M
authors.lastname: Pavel
authors.forename: Andreas
authors.initials: A
authors.lastname: Pascher
authors.forename: Bertram
authors.initials: B
authors.lastname: Wiedenmann
authors.forename: Holger
authors.initials: H
authors.lastname: Amthauer
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000503:physiopathology; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000098:blood supply / Q000000981:diagnostic imaging*; D015588:Observer Variation; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D011169:Portal Vein / Q000503:physiopathology; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D015282:Octreotide