parenchymal atrophy definitionpancreatic parenchymal atrophycerebral parenchymal atrophydiffuse parenchymal atrophyglobal parenchymal atrophybrain parenchymal atrophyneuro parenchymal atrophymild parenchymal atrophybrain parenchymal volume lossdiffuse parenchymal volume loss brainmild brain parenchymal volume lossparenchymal volume