Role of diffusion-weighted MR imaging in diagnosis of acute pancreatitis

Background

The role of diffusion-weighted magnetic resonance imaging (DW-MRI) in the diagnosis of acute pancreatitis is assessed in this study by measuring the apparent diffusion coefficient (ADC) values in acute pancreatitis and comparing them with a control group. The aim of this study is to compare those two groups thus supporting the diagnosis of this disease.

Sixteen patients with acute pancreatitis and 16 control participants underwent diffusion-weighted imaging with b values of 0, 200, and 800. ADC maps were generated from the DW-MRI and ADC values, which were calculated for the pancreas, and the results of the two groups of patients were compared.

Results

The mean pancreatic ADC value in the acute pancreatitis group (1.15 10(−3) mm(2)/s ± 0.28) was significantly lower than in the normal group (1.6 10−3 mm(2)/s ± 0.2). A threshold ADC value of 1.38 10−3 mm(2)/s yielded 81.25%, specificity of 93.75%, positive predictive value of 92.9%, negative predictive value of 83.3%, and accuracy of 91.8%. Pancreatic ADC values were significantly lower in patients with acute pancreatitis than in the control group.

Conclusion

Diffusion-weighted magnetic resonance imaging could be an important supportive tool in the diagnosis of acute pancreatitis.

Optimizing b-values for accurate depiction of pancreatic cancer with tumor-associated pancreatitis on computed diffusion-weighted imaging

PURPOSE

To determine the optimal b-value for accurate depiction of pancreatic cancer (PC) in patients with active tumor-associated pancreatitis (TAP), using computed diffusion-weighted imaging (cDWI) with a range of b-values up to 3000 s/mm².

METHODS

The study protocol was approved by the institutional review board. We retrospectively analyzed 34 consecutive PC cases with active TAP who underwent pancreatectomy without preoperative therapy. Four cDWI datasets with b-values of 1500-3000 s/mm² (cDWI₁₅₀₀-cDWI₃₀₀₀) were generated from the original DWI datasets with b-values of 0 and 1000 s/mm² obtained using a 3-T scanner. Two board-certified radiologists evaluated images qualitatively (tumor conspicuity and total image quality), and another two board-certified radiologists placed regions of interest for quantitative evaluations (apparent diffusion coefficient [ADC] values of both lesions, contrast ratio [CR] of PC to active TAP, and volume ratio [VR] of PC to surgical specimen).

RESULTS

As the b-value increased, tumor conspicuity improved significantly in cDWI₂₀₀₀ and cDWI₂₅₀₀ (P = 0.0121 and 0.0015, respectively), although total image quality decreased in all cDWIs compared with DWI₁₀₀₀ (P < 0.0001). Significantly lower ADC values were seen in PC (P < 0.0001). All cDWI groups showed positive correlation between the tumor conspicuity and ADC difference between PC and TAP. CR increased with the b-value, while VR decreased. Significant equivalence of VR to the surgical specimen was seen on cDWI₂₀₀₀ (P = 0.0031).

CONCLUSION

Accurate depiction of PC was optimal with cDWI₂₀₀₀ in the presence of active TAP.