Quantitative Conspicuity of Pancreatic Canine Insulinoma: A Comparison of Dynamic 4D CT and Dual-Source, Dual-Energy Bolus-Triggered Multiphase CT Imaging

The aim of this retrospective study was to compare lesion conspicuity—the visibility of a lesion relative to surrounding tissue—and CT characteristics of pancreatic insulinomas in dogs using multiphase dual-energy CT (DECT) and dynamic 4D perfusion CT. Seventy dogs with insulinomas, confirmed either cytologically or histologically, or with clinical and imaging findings consistent with the diagnosis, were included. Forty dogs underwent perfusion CT and 30 underwent multiphase DECT on a dual-source, dual-energy CT scanner (192 × 2 detector configuration). Imaging evaluations focused on arterial and portal phases for DECT, and early arterial, late arterial, pancreatic, and portal venous phases for perfusion CT. Tumor conspicuity was quantified using the tumor-to-pancreas ratio (TPR) and contrast-to-noise ratio (CNR), while time-to-peak (TTP) enhancement was recorded for both tumors and pancreatic parenchyma. Perfusion CT demonstrated significantly higher TPR and CNR values compared to DECT (p < 0.001), indicating improved tumor visibility. The late arterial phase of perfusion CT, although not statistically significant, showed the highest median TPR and CNR. Mean TTP for tumors was 38.8 s, slightly earlier than the pancreatic parenchyma (41.25 s). In conclusion, perfusion CT appears to enhance visualization of insulinomas in dogs, particularly between 34 and 44 s after contrast injection, aligning with the late arterial phase of perfusion CT.