Can semi-quantitative parenchymal MR imaging parameters be useful for monitoring the disease severity in chronic pancreatitis in a longitudinal study

HypothesisParenchymal MR imaging biomarkers T1 score, and arterio-venous enhancement ratio (AVR) wouldchange with severity of chronic pancreatitis (CP).Materials and MethodsThis retrospective longitudinal study included 37 CP subjects (23 male 14 female) who either progressed(n= 22, mean age: 54 [range 21 - 75yrs]) or remained stable (n= 15, mean age: 56 [range 37 – 76yrs]) atthe Indiana University Health System. Progression of disease severity was determined by changing theCambridge classification grade from 0, 1, or 2 to 3 or 4. The average time difference between the MRIswas 6.7 years (range: 0.6 -15.3yrs). MR imaging was performed using the Institution’s clinical MRIprotocol. All studies included T1-weighted gradient echo sequence performed before contrast and afterintravenous contrast injection of Gadobutrol (Bayer HealthCare Pharmaceuticals) during the arterial andpancreatic venous phases. T1 score is calculated by taking the ratio of the mean unenhanced T1-weighted signal intensity (SI) of the pancreatic parenchyma to the spleen. AVR is calculated using theformula AVR = SI arterial – SI unenhanced / SI venous – SI unenhanced.ResultsThere was a significant decrease in T1 score between the initial (mean: 1.23, 95% CI:1.1 to 1.4) andfollow-up MRI (mean: 0.96, 95% CI: 0.87 to 1.06) for the chronic pancreatitis (CP) subjects who hadprogressed disease severity determined by Cambridge classification (p= 0.0012). There was nosignificant difference in the T1 score of subjects who did not progress on follow-up imaging (p=0.052).There was a significant decrease in AVR of the subjects who progressed between the initial (mean: .93,95% CI: 0.77 to 1.08) and the follow-up MRI (mean: 0.66, 95% CI: 0.48 to 0.83) for patients withprogressed disease (p=0.02). However, those who remained in the same disease severity group did notshow significant difference (p=0.066).ConclusionThis longitudinal study suggests that semi-quantitative parameters T1 score, and arterio-venousenhancement ratio of the pancreatic parenchyma can be used to monitor progression of CP. Largepopulation multi-center studies are warranted to verify these results.