title: Respiratory gated PET/CT of the liver: A novel method and its impact on the detection of colorectal liver metastases.
abstract: OBJECTIVE
  To evaluate the diagnostic performance of a new method for respiratory gated positron emission tomography (rgPET/CT) for colorectal liver metastases (CRLM), secondly, to assess its additional value to standard PET/CT (PET/CT).
  
  
  METHODS
  Forty-three patients scheduled for resection of suspected CRLM were prospectively included from September 2011 to January 2013. None of the patients had previously undergone treatment for their CRLM. All patients underwent PET/CT and rgPET/CT in the same session. For rgPET/CT an in-house developed electronic circuit was used which displayed a color-coded countdown for the patient. The patients held their breath according to the countdown and only the data from the inspiration breath-hold period was used for image reconstruction. Two independent and blinded readers evaluated both PET/CT and rgPET/CT separately. The reference standard was histopathological confirmation for 73 out of 131 CRLM and follow-up otherwise.
  
  
  RESULTS
  Reference standard identified 131 CRLM in 39/43 patients. Nine patients accounted for 25 mucinous CRLM. The overall per-lesion sensitivity for detection of CRLM was for PET/CT 60.0%, for rgPET/CT 63.1%, and for standard+rgPET/CT 67.7%, respectively. Standard+rgPET/CT was overall significantly more sensitive for CRLM compared to PET/CT (p=0.002) and rgPET/CT (p=0.031). The overall positive predictive value (PPV) for detection of CRLM was for PET/CT 97.5%, for rgPET/CT 95.3%, and for standard+rgPET/CT 93.6%, respectively.
  
  
  CONCLUSIONS
  Combination of PET/CT and rgPET/CT improved the sensitivity significantly for CRLM. However, high patient compliance is mandatory to achieve optimal performance and further improvements are needed to overcome these limitations. The diagnostic performance of the evaluated new method for rgPET/CT was comparable to earlier reported technically more complex and expensive methods.
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway; Institute of Clinical Medicine, University of Oslo, P.O. Box 1171 Blindern, 0318 Oslo, Norway. Electronic address: anselm.schulz@gmail.com.
authors.forename: Anselm
authors.initials: A
authors.lastname: Schulz
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway; Institute of Clinical Medicine, University of Oslo, P.O. Box 1171 Blindern, 0318 Oslo, Norway. Electronic address: UXGODJ@ous-hf.no.
authors.forename: Johannes Clemens
authors.initials: JC
authors.lastname: Godt
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway. Electronic address: UXJORM@ous-hf.no.
authors.forename: Johann Baptist
authors.initials: JB
authors.lastname: Dormagen
authors.affiliation: The Intervention Centre, Oslo University Hospital, Postboks 4950 Nydalen, 0424 Oslo, Norway. Electronic address: JONHOL@ous-hf.no.
authors.forename: Jon Erik
authors.initials: JE
authors.lastname: Holtedahl
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway; Department of Nuclear Medicine and PET-Center, Aarhus University Hospital, Norrebrogade 44, DK-8000 Aarhus C, Denmark. Electronic address: tvbog@aol.com.
authors.forename: Trond Velde
authors.initials: TV
authors.lastname: Bogsrud
authors.affiliation: Department of Hepato-Pancreato-Biliary Surgery, Oslo University Hospital, Postboks 4950 Nydalen, 0424 Oslo, Norway. Electronic address: uxknab@ous-hf.no.
authors.forename: Knut Jørgen
authors.initials: KJ
authors.lastname: Labori
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway; Institute of Clinical Medicine, University of Oslo, P.O. Box 1171 Blindern, 0318 Oslo, Norway. Electronic address: NILKLO@ous-hf.no.
authors.forename: Nils-Einar
authors.initials: NE
authors.lastname: Kløw
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Postboks Pb 4956 Nydalen, 0424 Oslo, Norway. Electronic address: bat@ous-hf.no.
authors.forename: Tore
authors.initials: T
authors.lastname: Bach-Gansmo
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging; D008113:Liver Neoplasms / Q000175:diagnosis* / Q000556:secondary; D008297:Male; D064847:Multimodal Imaging / Q000379:methods*; D016609:Neoplasms, Second Primary / Q000175:diagnosis*; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Diagnostic performance; Liver; Metastases; PET/CT; Respiratory gated PET/CT