title: Preoperative detection of pancreatic insulinomas on multiphasic helical CT.
abstract: OBJECTIVE
  The objective was to analyze enhancement characteristics of insulinomas and to determine the ability of multiphase CT to localize these tumors.
  
  
  METHODS
  Prospective interpretations of multiphase helical CT scans were reviewed in 30 patients who had insulinomas resected over a 5-year period. CT scans were retrospectively reviewed to determine enhancement characteristics, tumor conspicuity in each phase of enhancement, and potential causes for false-negative findings.
  
  
  RESULTS
  Sixty-three percent (19/30) of tumors were identified on CT prospectively. An additional six tumors were visualized in retrospect, allowing characterization of 25 (83%) of 30 tumors. Most tumors were hyperdense on at least one phase (n = 19), three tumors were hypoattenuating, and three were isodense and pedunculated. Insulinomas were most conspicuous on the early phase in 15 patients and in the portal venous phase in three. All tumors that underwent pancreatic phase imaging were seen (13/13), whereas three of 18 arterial and six of 25 portal venous phase findings were inconclusive for tumor. In the six examinations with false-negative findings in which the tumor could be seen in retrospect, two tumors were isodense and pedunculated, three were in close proximity to vessels, and one had a cystic appearance.
  
  
  CONCLUSIONS
  Multiphasic CT has a moderate sensitivity in the detection of insulinomas. Most tumors are more conspicuous on the earlier phases of enhancement. The pancreatic phase may be more useful than the arterial phase. Potential sources of false-negative results include tumors adjacent to vessels, pedunculated morphology, or nonhyperattenuating lesions.
authors.affiliation: Department of Radiology, Mayo Clinic and Mayo Foundation, 200 First St. S.W., Rochester, MN 55905, USA. fidler.jeff@mayo.edu
authors.forename: J L
authors.initials: JL
authors.lastname: Fidler
authors.forename: J G
authors.initials: JG
authors.lastname: Fletcher
authors.forename: C C
authors.initials: CC
authors.lastname: Reading
authors.forename: J C
authors.initials: JC
authors.lastname: Andrews
authors.forename: G B
authors.initials: GB
authors.lastname: Thompson
authors.forename: C S
authors.initials: CS
authors.lastname: Grant
authors.forename: F J
authors.initials: FJ
authors.lastname: Service
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007340:Insulinoma / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009098:Multiphasic Screening; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D011300:Preoperative Care; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed