Radiologic Assessment of Pancreatic Disease (RAPiD) Study: Association of Quantitative MRI Features with Pancreas Secretory Function in Suspected Chronic Pancreatitis

Abstract

Purpose: MRI has emerged as a non-invasive imaging test in pancreatic disease [Sainani, Am J Gastro 2009]. Our research group has reported qualitative MRI features associated with pancreas dysfunction [Conwell, Am J Gastro 2011, abs]. In this current investigation we calculated several previously described quantitative MRI parameters and determined their association with pancreas function [Balci, J Magn Reson Imaging 2010 ]. Aim: Identify quantitative MRI features associated with abnormal pancreas secretory function. Methods: The following quantitative features were recorded: non-contrast signal intensity ratios (SIR) of the pancreas to the liver and spleen; contrast-enhanced arterial-venous ratio (AV ratio) and arterial-delayed ratio (AD ratio); baseline main pancreatic duct (MPD) diameter and percent change in MPD diameter from baseline to post-secretin maximum (% change). Pancreas secretory function was assessed by peak bicarbonate concentration (mEq/L) in pancreatic fluid, collected by secretin-stimulated endoscopic pancreatic function test: abnormal function (<75 mEq/L). Abnormal secretory function was further subdivided into mild dysfunction (74-65 mEq/L; 2-3 SD below mean) and marked dysfunction (<65 meq/L; <3 SD below mean). Univariate analysis (Mann-Whitney, t-test and Kruskal-Wallis) was performed to determine association of quantitative MRI features with normal and grades of abnormal [mild, marked] pancreas function. Results: One hundred one subjects were included. Sixty subjects (59%) had normal pancreas function (mean [HCO3] 89 ± 10 mEq/L), 14 (14%) had mild pancreas secretory dysfunction (mean [HCO3] 71 ± 3 mEq/L) and 27 (27%) had marked pancreas secretory dysfunction (mean [HCO3] 46 ± 12 mEq/L) (p<0.001). The three groups were similar in age (overall mean 48 ± 14 years; 0.889), gender distribution (overall 37% male; 0.793) and race (86% Caucasian; 0.823). When normal (n=60) and abnormal (n=41) were compared, the following three (3) MRI features (p-value) were observed in the abnormal group: decreased SIR (0.033), decreased AD ratio (0.046) and increased MPD diameter at baseline (0.013). When normal (n=60) was compared to the mild (n=14) and marked (n=27) subdivisions, none (0) of the features distinguished between normal and mild dysfunction. Four (4) features distinguished between normal and marked dysfunction: decreased AV ratio (0.035), decreased AD ratio (0.005), increased baseline MPD diameter (0.002) and decreased percent change in MPD diameter (non-compliance) after secretin (0.004). Conclusion: Several quantitative MRI features were associated with abnormal pancreatic secretory function. Quantitative MRI features were unable to differentiate normal function from mild pancreatic secretory dysfunction.