Differentiation of pancreatic carcinoma and mass-forming focal pancreatitis: qualitative and quantitative assessment by dynamic contrast-enhanced MRI combined with diffusion-weighted imaging

Abstract

Differentiation between pancreatic carcinoma (PC) and mass-forming focal pancreatitis (FP) is invariably difficult. For the differential diagnosis, we qualitatively and quantitatively assessed the value of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) in PC and FP in the present study. This study included 32 PC and 18 FP patients with histological confirmation who underwent DCE-MRI and DWI. The time-signal intensity curve (TIC) of PC and FP were classified into 5 types according to the time of reaching the peak, namely, type I, II, III, IV, and V, respectively, and two subtypes, namely, subtype-a (washout type) and subtype-b (plateau type) according to the part of the TIC profile after the peak. Moreover, the mean and relative apparent diffusion coefficient (ADC) value between PC and FP on DWI were compared. The type V TIC was only recognized in PC group (P < 0.01). Type IV b were more frequently observed in PC (P = 0.036), while type- IIa (P < 0.01), type- Ia (P = 0.037) in FP. We also found a significant difference in the mean and relative ADC value between PC and FP. The combined image set of DCE-MRI and DWI yielded an excellent sensitivity, specificity, and diagnostic accuracy (96.9%, 94.4%, and 96.0%). The TIC of DCE-MRI and ADC value of DWI for pancreatic mass were found to provide reliable information in differentiating PC from FP, and the combination of DCE-MRI and DWI can achieve a higher sensitivity, specificity, and diagnostic accuracy.

Keywords: diffusion-weighted imaging; dynamic contrast-enhanced MRI; mass-forming focal pancreatitis; pancreatic carcinoma.

Figure 1. Patterns of the TIC from DCE MRI of the pancreas

According to the time of a peak (18s, 45s, 75s, 2.5min, 4min after bolus injection of contrast material), namely, type-I, II, III, IV, V, respectively A. Then, according to the part of the TIC profile after the peak time, the type of the masses were classified into two subtypes, subtype-a (washout, the contrast enhancement decrease more than 10% of the peak time) and subtype-b (plateau, the contrast enhancement does not decrease more than 10% after the peak time) B.

Figure 2. Representative pancreatic T2-weighted image (A), DWI with a b value of 600 s/mm² (B), T1-weighted image (C), ADC map (D), DCE-MR images (E), and TIC profiles (F, G) in a 49-year-old man with pancreatic carcinoma in the head of pancreas (white arrow)

DCE-MR images: 18s, 45s, 75s, 2.5 and 4 min aftercontrast injection with constant gray scale. The ROIs of mass and non-mass adjacent parenchyma (NAP) indicated with black circle and black triangle. Pancreatic mass demonstrates type-IV b TIC which shows a slow, gradually increasing enhancement pattern followed by a plateau, while NAP demonstrates type-II aTIC which shows a rapidly increasing then gradually decreasing enhancement pattern. DWI shows pancreatic mass is clearly seen as hyperintense with a well-defined margin.

Figure 3. Representative pancreatic T2-weighted image (A), DWI with a b value of 600 s/mm² (B), T1-weighted image (C), ADC map (D), DCE-MR images (E), and TIC profiles (F, G) in a 62-year-old man with pancreatic carcinoma in the tail of pancreas (white arrow)

DCE-MR images: 18s, 45s, 75s, 2.5 and 4min aftercontrast injection with constant gray scale. The ROIs of mass and non-mass adjacent parenchyma (NAP) indicated with black circle and black triangle. Pancreatic mass demonstrates type-VTIC which shows a slow, gradually increasing enhancement pattern, while NAP demonstrates type-II aTIC which shows a rapidly increasing then gradually decreasing enhancement pattern. DWI shows pancreatic mass is clearly seen as isointense withmoderately-defined margin.

Figure 4. Representative pancreatic T2-weighted image (A), DWI with a b value of 600 s/mm² (B), T1-weighted image (C), ADC map (D), DCE-MR images (E), and TIC profiles (F, G) in a 55-year-old man with mass-forming chronic focal pancreatitis in the head of pancreas (white arrow)

DCE-MR images: 18s, 45s, 75s, 2.5 and 4min after contrast injection with constant gray scale. The ROIs of mass indicated with black circle and non-mass adjacent parenchyma (NAP) was located in pancreatic body. Pancreatic mass demonstrates type-III a TIC which shows a gradual increase followed by a more slowly decreasing enhancement pattern, while NAP demonstrates type-II a TIC which shows a relatively rapid increasing then gradually decreasing enhancement pattern. DWI shows pancreatic mass is clearly seen as isointense with ill-defined margin.

Figure 5. Representative pancreatic T2-weighted image (A), DWI with a b value of 600 s/mm² (B), T1-weighted image (C), ADC map (D), DCE-MR images (E), and TIC profiles (F, G) in a 43-year-old man with mass-forming chronic focal pancreatitis in the head of pancreas (white arrow)

DCE-MR images: 18s, 45s, 75s, 2.5 and 4min after contrast injection with constant gray scale. The ROIs of mass indicated with black circle and non-mass adjacent parenchyma (NAP) was located in pancreatic body. Pancreatic mass and NAP all demonstrates type-I a TIC which shows a rapidly increasing then gradually decreasing enhancement pattern. DWI shows pancreatic mass is clearly seen as isointense/mild-hyperintense with ill-defined margin.

Figure 6. Boxplots of the ADC value of the mass and non-mass adjacent parenchyma (NAP) of pancreatic carcinoma (PC) and mass-forming focal pancreatitis (FP)

Figure 7. Receiver operating characteristic curves used to evaluate diagnostic performance of the DCE-MRI, DWI, and combined imaging sets, respectively (area under ROC: 0.885 ± 0.052, 0.913 ± 0.041, and 0.979 ± 0.018) for differentiation between pancreatic carcinoma and mass-forming focal pancreatitis

Figure 8. Receiver operating characteristic curves used to evaluate diagnostic performance of ADC value, ADC contrast ratio and combined of them, respectively (area under ROC: 0.852 ± 0.059, 0.821 ± 0.061, and 0.913 ± 0.041) for differentiation between pancreatic carcinoma and mass-forming focal pancreatitis