title: Detection of small, functional islet cell tumors in the pancreas: selection of MR imaging sequences for optimal sensitivity.
abstract: OBJECTIVE
  To determine the sensitivity and specificity of magnetic resonance (MR) imaging for depicting pancreatic small, functional islet cell tumors and the minimum number of sequences for expedient diagnosis.
  
  
  METHODS
  Twenty-eight patients clinically suspected to have functional islet cell tumors underwent T1- and T2-weighted spin-echo (SE) MR imaging with and without fat suppression, T2-weighted fast SE imaging, and spoiled gradient-echo (GRE) imaging before and after injection of gadopentetate dimeglumine. Sensitivity, specificity, and the best and minimum number of sequences for definitive diagnosis were determined.
  
  
  RESULTS
  MR images depicted proved islet cell tumors in 17 of 20 patients (sensitivity, 85%). Images were true-negative in eight patients with negative follow-up examination results for more than 1 year. Specificity was 100%; positive predictive value, 100%; and negative predictive value, 73%. Among 20 patients with tumor, T1-weighted SE images with fat suppression and nonenhanced spoiled GRE images each showed lesions in 15 (75%); T2-weighted conventional SE with fat suppression, in 13 (65%); gadolinium-enhanced spoiled GRE, in 12 (60%); and T2-weighted fast SE, in seven of 10 patients (70%).
  
  
  CONCLUSIONS
  MR imaging accurately depicts small islet cell tumors. T2-weighted fast SE and spoiled GRE sequences usually suffice. Gadolinium-enhanced sequences are needed only if MR imaging results are equivocal or negative.
authors.affiliation: Department of Radiology, University of California San Francisco School of Medicine, PO Box 0628, San Francisco, CA 94143-0628, USA.
authors.forename: R F
authors.initials: RF
authors.lastname: Thoeni
authors.forename: U G
authors.initials: UG
authors.lastname: Mueller-Lisse
authors.forename: R
authors.initials: R
authors.lastname: Chan
authors.forename: N K
authors.initials: NK
authors.lastname: Do
authors.forename: P B
authors.initials: PB
authors.lastname: Shyn
mesh_terms: D007516:Adenoma, Islet Cell / Q000175:diagnosis*; D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA