Pancreatic neuroendocrine tumor: added value of fusion of T2-weighted imaging and high b-value diffusion-weighted imaging for tumor detection

Eur J Radiol. 2012 May;81(5):e746-9. doi: 10.1016/j.ejrad.2012.01.032. Epub 2012 Mar 3.

Abstract

Objectives: 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.

MeSH terms

  • Diffusion Magnetic Resonance Imaging / methods*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neuroendocrine Tumors / diagnosis*
  • Pancreatic Neoplasms / diagnosis*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Subtraction Technique*