Prone transabdominal ultrasonography improves pancreatic tail visualization: a prospective study using CT–ultrasound fusion imaging

PURPOSE: To determine whether prone-position transabdominal ultrasonography improves pancreatic tail visualization compared with conventional supine scanning, as assessed using computed tomography-transabdominal ultrasonography (CT-TUS) fusion imaging. METHODS: This prospective observational study included 50 patients (34 males; median age, 64.5 [interquartile range, 56.5-72] years) undergoing evaluation for pancreatobiliary diseases using TUS and contrast-enhanced CT. Using Smart Fusion technology, CT and real-time TUS images were synchronized, and the pancreatic tail visualization rate was compared between the images obtained in supine and prone positions. Interobserver agreement for the measurable tail length in the prone position was assessed using the intraclass correlation coefficient (ICC: 3,1). Factors associated with pancreatic tail visualization, including sex, age, height, waist circumference, pancreatic tail length and abnormalities, and the renal-pancreatic tail distance, were analyzed using univariate and multivariate regression analyses. RESULTS: The pancreatic tail visualization rate, i.e., proportion of the total tail length visible on TUS compared with that on CT scan, was 37.4% with supine transverse epigastric scanning combined with left subcostal scanning, which was significantly higher (58.2%) when left subcostal scanning was replaced by prone scanning (P < 0.001). Multivariate analysis revealed that increased age was associated with decreased visualization, whereas pancreatic tail abnormalities and a shorter renal-pancreatic tail distance were significantly associated with improved visualization. The interobserver agreement was excellent (ICC [3,1]: 0.903). CONCLUSION: Prone-position scanning significantly improves pancreatic tail visualization compared with the conventional supine method and represents a simple and noninvasive modification of routine ultrasonographic practice.