Preliminary Study of MR Diffusion Tensor Imaging of Pancreas for the Diagnosis of Acute Pancreatitis

<div><p>Objectives</p><p>To evaluate the feasibility of differentiating between acute pancreatitis (AP) and healthy pancreas using diffusion tensor imaging (DTI) and correlate apparent diffusion coefficient (ADC) /fractional anisotropy (FA) values with the severity of AP.</p><p>Material and Methods</p><p>66 patients diagnosed with AP and 20 normal controls (NC) underwent DTI sequences and routine pancreatic MR sequences on a 3.0T MRI scanner. Average ADC and FA values of the pancreatic were measured. Differences of FA and ADC values between the AP group and the NC group with AP and healthy pancreas were compared by two-sample independent t-test. The severity of AP on MRI was classified into subgroups using MR severity index (MRSI), where the mean FA and ADC values were calculated. Relationship among the FA values, ADC values and MRSI were analyzed using Spearman's rank correlation coefficients.</p><p>Results</p><p>The pancreatic mean ADC value in the AP group (1.68 ± 0.45×10⁻³mm²/s) was significantly lower than in the NC group (2.09 ± 0.55×10⁻³mm²/s) (P = 0.02); the same as mean FA value (0.39 ± 0.23 vs 0.54 ± 0.12, P = 0.00). In the subgroup analysis, the pancreatic ADC and FA value of edema AP patients was significantly higher than necrosis AP patients with P = 0.000 and P = 0.001respectively. In addition, as severity of pancreatitis increased according to MRSI, lower pancreatic ADC (r = -0.635) and FA value (r = -0.654) were noted.</p><p>Conclusion</p><p>Both FA and ADC value from DTI can be used to differentiate AP patients from NC. Both ADC and FA value of pancreas have a negative correlation with the severity of AP.</p></div

Comparison of the FA and ADC value between edematous and necrotic AP.

<p>Comparison of the FA and ADC value between edematous and necrotic AP.</p

A 40-year-old woman with mild AP.

<p>Fat suppression Lava-flex T1 (a) and FRFSE T2 (b) weighted images show the swollen pancreatic tissue, the thickened fascia of pancreas (arrows) and edematous peripancreatic fat (arrowhead). DTI(c) shows the increased signal in pancreatic parenchyma, particularly pancreatic head (arrowhead) and fuzzy peripancreatic fat (arrow).</p

A 43-year-old woman with moderate AP and cholecystolithiasis.

<p>Fat suppression Lava-flex T1 (a) and FRFSE T2 (b) weighted images show the swollen pancreatic tissue, and edematous peripancreatic fat (arrowhead). DTI(c) shows the swollen pancreatic parenchyma.</p

Correlation of the pancreas ADC and FA value with AP severity determined by the MRSI.

<p>Correlation of the pancreas ADC and FA value with AP severity determined by the MRSI.</p

The pancreatic mean ADC value (a) and FA value (b) contrast between in the AP group and normal group, we can gain that the pancreatic ADC value and FA value in the AP group was significantly lower than in the normal group.

<p>The pancreatic mean ADC value (a) and FA value (b) contrast between in the AP group and normal group, we can gain that the pancreatic ADC value and FA value in the AP group was significantly lower than in the normal group.</p

The parameters of routine pancreatic MR sequences at 3.0T.

<p>The parameters of routine pancreatic MR sequences at 3.0T.</p

A 76-year-old woman with severe necrosis AP.

<p>Lava-flex T1 (a), FRFSE T2 (b), contrast Lava-flex T1(c), DTI(d), ADC map (e) and FA map (f) weighted images show a well-marginated necrosis area without enhancement located in the whole pancreatic tissue(arrow) and a pseudocyst in omental sac.</p

Three typical same ROIs placement within the highest SI area in pancreas in AP group on signal intensity image (a), ADC map (b) and FA map (C).

<p>Three typical same ROIs placement within the highest SI area in pancreas in AP group on signal intensity image (a), ADC map (b) and FA map (C).</p

MRSI scoring system.

<p>MRSI scoring system.</p