title: Diffusion-weighted MRI: usefulness for differentiating intrapancreatic accessory spleen and small hypervascular neuroendocrine tumor of the pancreas.
abstract: BACKGROUND
  Image findings of intrapancreatic accessory spleen (IPAS) can closely resemble those of neuroendocrine tumor (NET) of the pancreas.
  
  
  OBJECTIVE
  To investigate the usefulness of diffusion-weighted imaging (DWI) for differentiating IPAS from small (≤3 cm) hypervascular NET of the pancreas.
  
  
  METHODS
  The visually assessed signal intensity of pancreatic lesions compared with the spleen on DWI (b value of 1000 s/mm(2)) and the apparent diffusion coefficient (ADC) values were compared in 25 patients with IPAS and 31 patients with small hypervascular NET. Two blinded radiologists independently rated their confidence in differentiating the two conditions and compared the diagnostic performance of contrast-enhanced magnetic resonance imaging (CE-MRI) alone with that of combined CE-MRI and DWI.
  
  
  RESULTS
  The isointensity of the pancreatic lesions compared with the spleen on DWI was more frequently observed in IPAS than in NET (92% vs. 12.9%, P < 0.001). The mean ADC value was significantly lower in IPAS than in NET (0.90 × 10(-3) mm(2)/s vs. 1.44 × 10(-3) mm(2)/s, P < 0.001). The sensitivity and specificity of ADC quantification for differentiating the two conditions when using 1.07 × 10(-3) mm(2)/s as the cut-off value were 96% and 93.5%, respectively. For both readers, the area under the receiver operating characteristic curve and accuracy in differentiating the two conditions of combined CE-MRI and DWI were significantly greater than those of CE-MRI alone (P ≤ 0.039).
  
  
  CONCLUSIONS
  Visual assessment of DWI and ADC quantification were useful in differentiating IPAS from small hypervascular NET of the pancreas.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Bo-Kyeong
authors.initials: BK
authors.lastname: Kang
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea kimjhrad@amc.seoul.kr.
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Byun
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Seung Soo
authors.initials: SS
authors.lastname: Lee
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Hyoung Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: So Yeon
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Moon-Gyu
authors.initials: MG
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis*; D015588:Observer Variation; D009942:Organometallic Compounds; D010179:Pancreas / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013154:Spleen / Q000002:abnormalities* / Q000473:pathology; D013158:Splenic Diseases / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine
keywords: Intrapancreatic accessory spleen; apparent diffusion coefficient; contrast-enhanced MRI; diffusion weighted MRI; pancreatic neuroendocrine tumor