Investig Magn Reson Imaging.  2016 Dec;20(4):241-249. 10.13104/imri.2016.20.4.241.

Added Value of Diffusion Weighted Imaging for Detecting Pancreatic Abnormality in Patients with Clinically Suspected Acute Pancreatitis

Affiliations
  • 1Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Korea. radiresi@gmail.com
  • 2Department of Radiology, Myongji Hospital, Goyang-si, Korea.

Abstract

PURPOSE
To evaluate the added value of diffusion weighted imaging (DWI) to computed tomography (CT) for detecting pancreatic abnormality in patients with clinically suspected acute pancreatitis (AP).
MATERIALS AND METHODS
203 patients who underwent abdomen CT and subsequent DWI to do a workup for epigastric pain were analyzed. Two blinded radiologists independently performed an interval reading based on CT image sets first, then based on combined CT and DWI image sets. The diagnostic criterion on DWI was the increased signal intensity in the pancreas to that of the spleen. For quantitative analysis, the third radiologist measured ADC value of the pancreas in each patient.
RESULTS
For AP (n = 43), the sensitivity for detecting pancreatic abnormality increased, from 42% to 70% for reader 1 (P < 0.05) and from 44% to 72% for reader 2 (P < 0.05). For borderline pancreatitis (n = 42), the sensitivity also increased, from 10% to 26% for reader 1 (P < 0.05) and from 7% to 29% for reader 2 (P < 0.05). The mean ADC values (unit, × 10⁻³ mm²/s) were significantly different among the three groups (for AP, 1.09 ± 0.16; for borderline pancreatitis, 1.28 ± 0.2; for control, 1.46 ± 0.15, P < 0.05).
CONCLUSIONS
Sensitivity for detecting pancreatic abnormality increased significantly after adding DWI to CT in patients with clinically suspected AP.

Keyword

Diffusion-weighted magnetic resonance imaging; Computed tomography; Pancreas; Inflammation

MeSH Terms

Abdomen
Diffusion*
Humans
Inflammation
Pancreas
Pancreatitis*
Spleen

Figure

  • Fig. 1 Flowchart of the case accrual process.

  • Fig. 2 Added value of additional DWI for identifying radiological abnormality in the pancreas in patients with acute pancreatitis (AP), as demonstrated in a 61-year-old woman. She visited the emergency room with acute epigastric pain, and her laboratory test revealed elevated serum amylase and lipase levels (2586 U/L and 2416 U/L, respectively), which were over three times of the normal limits. The normal cut-off level of serum amylase is 168 U/L, and that of serum lipase is 60 U/L. (a) Axial CT image on portal venous phase showing no significant abnormality in the pancreas. At the first reading session, both readers recorded that there was no remarkable abnormality in the pancreas on this axial CT image. (b) Axial diffusion weighted image (b = 800 s/mm2) showing diffusely increased signal intensity throughout the pancreas, which is higher than that of spleen. After the combined reading of DWI and CT on second reading session, both readers changed their confidence score from 1 to 5 (definite AP). (c) Axial diffusion weighted image (b = 800 s/mm2) of the pancreas in a 60-year-old woman out of control group.

  • Fig. 3 Added value of additional DWI for detecting radiological pancreatic abnormality in patients with borderline pancreatitis, as demonstrated in a 71-year-old man. He visited the emergency room with acute epigastric pain and obstructive jaundice, and his initial laboratory test revealed an elevated serum lipase (99 U/L) level, which was less than three folds of normal serum lipase, and a normal level of serum amylase (129 U/L). The normal cut-off level of serum amylase is 168 U/L, and that of serum lipase is 60 U/L. (a) There were no significant abnormal findings in the pancreas on the portal venous phase of axial CT images. Both readers reported that there was no definite evidence of acute pancreatitis (AP) (confidence score of 1) at the first reading session. (b) On axial diffusion weighted image (b = 800 s/mm2), the pancreas showed a diffusely increased signal intensity throughout the whole pancreas parenchyma, which was similar to that of the spleen. Both readers changed their confidence score from 1 to 5 (definite AP) after the combined reading of DWI and CT on second reading session.

  • Fig. 4 Box and whisker plot comparing the mean ADC values of pancreas among acute pancreatitis (AP), borderline pancreatitis, and control groups. The mean ADC values (unit, × 10-3 mm2/s) were significantly different among the three groups (for AP, 1.09 ± 0.16; for borderline pancreatitis, 1.28 ± 0.2; for control, 1.46 ± 0.15, P < 0.0001). The middle line in each box represents the median. The lower and upper boundaries of the boxes represent the lower and upper quartiles (25th and 75th percentiles, respectively). The whiskers indicate the range from the maximum to the minimum calculated ADC values. ▼△ = outlier

  • Fig. 5 Receiver operating characteristic curves for distinguishing acute pancreatitis from control group for pancreatic ADC value (solid line) and ADC ratio (pancreas/spleen, dashed line). The area under the curve (AUC) of the pancreatic ADC value was not significantly different from that of the ADC ratio (AUC, 0.964; 0.923, respectively, P = 0.0514).


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