title: Use of laxative-augmented contrast medium in the evaluation of colorectal foci at FDG PET.
abstract: OBJECTIVE
  To compare the diagnostic accuracy of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in the detection of colon lesions with that of delayed PET/computed tomography (CT) performed after the administration of a laxative-augmented contrast medium.
  
  
  METHODS
  All patients gave written informed consent according to the guidelines issued by the institutional review board. In a prospective study performed from November 2005 to December 2006, images obtained in 847 patients were reviewed by two physicians in consensus. Colorectal FDG uptake on initial PET images that exceeded background FDG accumulation was graded as minimal, equivocal, or positive. When the initial PET scan revealed a colorectal region of increased uptake, either oral or anal laxative-augmented contrast medium was administered on the basis of the site of colorectal FDG focus and delayed PET/CT was performed. Initial PET findings were reevaluated and revised when necessary. Comparison was performed on a per-patient basis. Findings at histopathologic analysis and clinical follow-up served as the reference standard. The accuracy of PET was compared with that of PET/CT by using the McNemar test.
  
  
  RESULTS
  Colorectal FDG foci were seen on initial images in 137 patients. Uptake on the initial images was reported as minimal in 14 patients, equivocal in 68, and positive in 55. With use of a laxative-augmented contrast medium and delayed PET/CT, the proportions of equivocal and positive results decreased by 84% (57 of 68 patients) and 58% (18 of 31 patients), respectively. The accuracy of delayed PET/CT in the depiction of colorectal cancer was greater than that of initial PET (93.4% [128 of 137 patients] vs 71.5% [98 of 137 patients], respectively; P < .01).
  
  
  CONCLUSIONS
  Delayed PET/CT with laxative-augmented contrast medium is more accurate than initial PET alone in the detection of colorectal cancer. This approach has promise as a tool for guiding decisions about how to treat patients with colorectal FDG foci.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101193/-/DC1.
authors.affiliation: Department of Nuclear Medicine and PET Center, Shin Kong Wu Ho-Su Memorial Hospital, No. 95 Wenchang Rd, Shilin District, Taipei 111, Taiwan.
authors.forename: Yen-Kung
authors.initials: YK
authors.lastname: Chen
authors.forename: Jui-Hao
authors.initials: JH
authors.lastname: Chen
authors.forename: Chih-Cheng
authors.initials: CC
authors.lastname: Tsui
authors.forename: Hsuan-Hung
authors.initials: HH
authors.lastname: Chou
authors.forename: Ru-Hwa
authors.initials: RH
authors.lastname: Cheng
authors.forename: Jainn-Shiun
authors.initials: JS
authors.lastname: Chiu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019343:Citric Acid; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007482:Iothalamate Meglumine; D054368:Laxatives; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012015:Reference Standards; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D054368:Laxatives; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D019343:Citric Acid; C110422:magnesium citrate; D007482:Iothalamate Meglumine