Quantitative analysis of diffusion-weighted magnetic resonance imaging of the pancreas: Usefulness in characterizing solid pancreatic masses

Purpose: To evaluate whether measurement of apparent diffusion coefficient (ADC) and pure diffusion coefficient (D) can help to characterize solid pancreatic masses. Materials and Methods: Diffusion-weighted MR imaging was performed in both a patient group (n = 71; pancreatic cancer [n = 47], mass-forming pancreatitis [n = 13], solid pseudopapillary neoplasm [n = 6], and neuroendocrine tumor [n = 5]) and a normal control group (n = 11) by applying three b-factors of 0, 500, and 1000 sec/mm². ADC₅₀₀, ADC₁₀₀₀, D (ADC using b = 500 and 1000 sec/mm²), and perfusion fraction (f, 1- exp [-500 sec/mm² x (ADC₅₀₀ - D)]) of normal pancreas, pancreatic cancer, and mass-forming pancreatitis were compared using the Kruskal-Wallis test. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance and optimal cutoff value of these parameters in differentiating pancreatic cancer from mass-forming pancreatitis. Results: Normal pancreas had significantly higher mean ADC₅₀₀, ADC₁₀₀₀, and f than either pancreatic cancer (P < 0.001, < 0.001, and 0.004, respectively) or mass-forming pancreatitis (P < 0.001, < 0.001, and 0.002, respectively). ADC₅₀₀, ADC₁₀₀₀, and D of mass-forming pancreatitis were significantly lower than those of pancreatic cancer (P = 0.002, 0.004, and 0.014, respectively). Sensitivities and specificities in the diagnosis of pancreatic cancer were 72.3% and 76.9% for ADC₅₀₀, 87.2% and 69.2% for ADC₁₀₀₀, 87.2% and 61.5% for D, and 42.6% and 92.3% for f, respectively. Conclusion: Measurement of ADC and D may be helpful in differentiating pancreatic cancers from mass-forming pancreatitis.