Quantitative ultrasound and the pancreas: Demonstration of early detection capability

Identifying real-time changes in tissues via quantitative ultrasound (QUS) approaches are clinically significant, particularly if QUS changes correspond to early detection of disease or provide early assessment of treatment success. Thus, understanding sequential steps in disease progression is key for success. Cerulein-induced inflammation of the pancreas (pancreatitis) in rodent models causes a significant release of pancreatic enzymes into blood, and it induces interstitial edema and inflammatory cell infiltration into the pancreas. This degree of pancreatitis is relatively mild: all animals survive the induction of pancreatitis that resolves itself in ~7 days. This makes this model an excellent one for studying ultrasonic attenuation coefficient and backscatter coefficient over time. The edematous stroma, cell shrinkage and death, followed by repopulation by dedifferentiated acinar cells, has certain similarities with the morphologies of some forms of pancreatic carcinoma (PCa). The study has several unique contributions: 1) The cerulein-induced pancreatitis model can be used as a surrogate for the PCa model, particularly for detecting early responses to PCa onset/treatment. 2) Understanding the progression of acute pancreatitis per se is imperative for successful intervention and treatment, especially in the early phases of the disease, before other clinical changes are manifest. Pancreatic AC and BSC (25-55 MHz) were estimated in vivo and ex vivo at baseline (no cerulein injections) and from 2 to 168 hr after cerulein injections. Following euthanasia, the pancreas was evaluated histopathologically and biochemically. There are significant measureable early effects on both in vivo AC and BSC (and their respective ex vivo estimates) relative to baseline controls that reflect the temporal biochemical and morphological effects of cerulein. The general trend is decreased AC and BSC at early time points and then rebound increases relative to controls at later time points. The greatest AC and BSC decreases occurred at 2 hr post-cerulein injections [29% AC (in dB/cm-MHz) decrease and 34% BSC (in dB) decrease, at 25 MHz)], suggesting high likelihood for early detection of either disease onset or response to therapy using quantitative ultrasound measures.