Purpose: To quantitatively and qualitatively evaluate whether low monoenergetic images at 50 keV demonstrate improved diagnostic conspicuity compared to conventional images for imaging of acute pancreatitis.
Material and Methods: A retrospective study of 50 clinically indicated contrast enhanced CT exams conducted on a single source DECT (IQON, Philips, Eindohoven) was performed. All patients (mean age 52 (±17); 18/32 female/male) presented with elevated pancreatic enzymes and had both clinical and radiographic signs of acute pancreatitis. First, representative conventional and monoenergetic images from each case were randomized, anonymized and presented to four abdominal radiologists to assess preferences in detection of fat stranding and parenchymal involvement. Next, an ROI was drawn along the necrotic, inflamed and normal pancreatic parenchyma for HU, CNR and SNR values measurements from the most representative single image in which parenchymal abnormalities were identified. Comparison of these parameters on the conventional and low monoenergetic images was performed.
Results: Although a clear preference for the detection of subtle fat stranding was noted for the conventional images (85%, P<0.05), there was clear preference for the monoenergetic images among all readers to evaluate the demarcation between the inflammatory and necrotic versus the normal pancreatic parenchyma (92%, P<0.05). This enabled the reviewers to detect additional small foci (< 1 cm) of involved parenchyma on the monoenergetic images in x (28%) cases. Overall, 18/50 (36%) presented with parenchymal necrosis, and 32/50 (64%) without. Although ratios of normal to abnormal parenchyma were the same (2.3 for both conventional and mono), the absolute difference between the parenchyma was increased by almost two folds (102.21 for mono 55.18 for conventional). Moreover, significant increases were seen in the monoenergetic SNR (10.79, SD-4.04 compared to 5.55, SD-1.7 respectively) and CNR (15.86, SD-4.16 compared to 9.39, SD-2.27 respectively) compared to the conventional images.
Conclusions: Monoenergetic images enable significant better tissue assessment and improved demarcation between the inflamed or necrotic to the adjacent healthy pancreatic parenchyma. This is likely due to a significant and consistent increase in the delta, CNR and SNR compared to the conventional ones. Given the strong preference for monoenergetic images by abdominal radiologists seen in the study, their use should be strongly considered whenever pancreatitis is clinically suspected.
