Signal characteristic and enhancement patterns of pancreatic adenocarcinoma: evaluation with dynamic gadolinium enhanced MRI

AIM

To determine the signal characteristics and enhancement patterns of proven pancreatic adenocarcinomas at 1.5 T and to compare these results with contrast enhanced computed tomography (CECT).

MATERIALS AND METHODS

Twenty-five patients, mean age 73 years, with proven pancreatic adenocarcinoma were imaged at 1.5 T using in- and opposed-phase, gradient-echo (GRE), T1-weighted sequences, T2 weighting using either a short tau inversion recovery (STIR) or frequency selective, fat-suppressed turbo spin echo (TSE) sequence, and with a three-dimensional (3D), fat-suppressed, GRE T1 sequence before, during the arterial, venous, and equilibrium phases after Gadolinium administration. Fourteen of the 25 patients underwent CECT. Magnetic resonance imaging (MRI) examinations were evaluated by two observers in consensus for size, signal characteristics, and enhancement patterns, and the results were compared with CECT.

RESULTS

The mean size of pancreatic adenocarcinomas was 32 mm. On unenhanced T1-weighted images, 12 of 25 lesions (48%) were hypointense, 13 (52%) were isointense. On STIR/T2, 11 of 25 (44%) pancreatic adenocarcinomas were hyperintense, 14 (56%) were isointense. All 25 (100%) adenocarcinomas were hypointense during the arterial phase. Twenty (80%) and 17 (68%) remained hypointense in the venous phase and equilibrium phases, respectively. In seven of 14 (50%) cases, the pancreatic mass was iso-attenuating to the pancreatic parenchyma during both the pancreatic and venous phases of CECT.

CONCLUSION

The results of the present study showed that all 25 pancreatic adenocarcinomas were hypointense to pancreatic parenchyma during the arterial phase. Moreover, MRI may be useful in patients with a high suspicion of pancreatic carcinoma that is not visualized during CECT.

Glycolytic metabolites and intracellular signaling in the pancreatic beta cell

In the pathways modulating the secretion of insulin and other physiologically important molecules, the critical role played by calcium in the moment-to-moment regulation of secretory processes may be modulated by additional factors, and these factors may include the glycolytic metabolites. We studied these early glucose breakdown products for effects on calcium release and inositol 1,4, 5-trisphosphate (IP3) binding to the IP3 receptor in a pancreatic beta cell preparation. The physiological significance of the response was also examined in terms of the insulinotropic effects of these metabolites. In studies of calcium release from the pancreatic beta cell, the metabolite 2,3-bisphosphoglycerate (DPG) exerted a statistically significant stimulatory effect on calcium release. A lesser but nonetheless significant effect also occurred in the presence of 3-phosphoglycerate and glucose-6-phosphate. The DPG-induced effect was concentration dependent. It is likely that the effects of DPG and other glycolytic metabolites on pancreatic beta cell signaling are physiologically significant inasmuch as we were also able to demonstrate that DPG and other glycolytic metabolites promoted the release of insulin from the pancreatic beta cell.