Diffusion-weighted Imaging: New Paradigm in Diagnosis of Early Acute Pancreatitis

BACKGROUND

Diffusion-weighted imaging (DWI) has come up as a newer diagnostic modality for the diagnosis of early functional changes in various organs including the pancreas. DWI has shown the ability of early and accurate diagnosis of inflammatory pathologies, before the appearance of morphological changes on imaging.

OBJECTIVES

The objectives of this study were to study the diagnostic accuracy of DWI in the diagnosis of early acute interstitial pancreatitis.

MATERIALS AND METHODS

The present retrospective observational study was conducted at the department of radiodiagnosis of a tertiary teaching hospital for 1 year. Fifty patients who underwent magnetic resonance imaging of the pancreas with clinical or laboratory diagnosis of early pancreatitis were included in the study. The diagnostic accuracy of DWI was analyzed on the basis of quantitative (apparent diffusion coefficient [ADC] values) evaluation in the diagnosis of early acute pancreatitis. Threshold values for ADC were derived for differentiation of inflamed versus normal pancreas. Sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV) were obtained by drawing the receiver operating characteristic (ROC) curve.

RESULTS

The mean ADC values in the patient group (0.882 × 10 -3 mm 2 /s ± 0.102) were significantly lower than the control group (1.178 × 10 -3 mm 2 /s ± 0.232) with P < 0.001. The ROC curve deciphered a cutoff value of 0.937 × 10 -3 mm 2 /s with a sensitivity of 84%, specificity of 86%, PPV of 85.71%, and NPV of 84.31% for diagnosis of acute pancreatitis using quantitative ADC values.

CONCLUSION

DWI can thus be a succinct modality for early diagnosis of pancreatitis with excellent diagnostic accuracy and superlative advantage of lack of contrast and radiation in comparison to computed tomography scan.

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.