title: Pancreatic neuroendocrine tumor: added value of fusion of T2-weighted imaging and high b-value diffusion-weighted imaging for tumor detection.
abstract: OBJECTIVE
  To investigate the added value of fusion of high b-value diffusion-weighted images (DWI) and T2-weighted (T2) MR images for the detection of pancreatic neuroendocrine tumors (PNT).
  
  
  METHODS
  18 patients with 18 histologically proven PNT were included. Two radiologists independently and retrospectively reviewed four randomized images sets (T2+T1, DWI, T2+DWI, and DWI+T2 fusion). Lesion detection confidence level was assessed using a three grade score (no lesion; uncertain lesion and certain lesion); lesion size and signal intensity were recorded. Apparent diffusion coefficients (ADC) of tumor and adjacent pancreas were measured.
  
  
  RESULTS
  Readers 1 and 2 respectively detected 14/18 and 16/18 lesions on T2+T1, 13/18 and 12/18 on DWI, 16/18 and 15/18 on T2+DWI and 17/18 and 16/18 on DWI+T2 fusion. Lesion median size was 16 mm (range: 7 mm-40 mm), 22% were hyperfunctioning (all insulinomas) and 72% were low-grade (Rindi 1). All tumors except one (with cystic component) showed lower ADC than adjacent pancreatic parenchyma. Fusion imaging had significantly better detection score by both authors (p<0.005) and provided the higher inter-reader agreement (kappa 0.7). DWI alone had the worst score for both readers.
  
  
  CONCLUSIONS
  Fusion images improve the detection of PNT, especially in patients with small isointense lesions on conventional MR sequences.
authors.affiliation: Hôpital Erasme - Université Libre de Bruxelles Medical Imaging Department, MRI Division, Route de Lennik 808, 1070 Brussels, Belgium. epmrenata@gmail.com
authors.forename: Renata
authors.initials: R
authors.lastname: Brenner
authors.forename: Thierry
authors.initials: T
authors.lastname: Metens
authors.forename: Maria
authors.initials: M
authors.lastname: Bali
authors.forename: Pieter
authors.initials: P
authors.lastname: Demetter
authors.forename: Celso
authors.initials: C
authors.lastname: Matos
mesh_terms: D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis*; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique