Differential diagnosis of pancreatic tumors using ultrasound contrast imaging

Background. The development of equipment and contrast agents for ultrasound imaging has contributed to major breakthroughs in the diagnosis of pancreatic tumors. We aimed to determine the diagnostic effectiveness of contrast ultrasound with Levovist, using the Agent Detection Imaging (ADI) technique, in 50 patients with pancreatic tumors. Methods. We studied 50 cases of histologically proven pancreatic disease; 39 carcinomas, 2 endocrine tumors, 4 intraductal papillary mucinous carcinomas (IPMCs), and 5 cases of tumor-forming pancreatitis (TFP). Vascular and perfusion images of contrast-enhanced ultrasound (CE-US) were used for the evaluation of tumor vascularity and parenchymal perfusion of the tumor, respectively. The hemodynamics of the tumor, and the diagnostic capacity of CE-US were compared with those shown by computed tomography (CT). The histological diagnosis in all cases was made from either biopsy or surgical specimens. Results. Thirty-four cases of pancreatic carcinoma (87%) showed a hypovascular and hypoperfusion pattern. The endocrine tumors showed a heterogeneous hypervascular and hyperperfusion pattern. All IPMC cases showed hypervascularity of the nodules inside the tumors. TFP showed an isovascular and homogeneous isoperfusion pattern. When tumors showing a hypovascular or hypoperfusion pattern on CE-US were diagnosed as carcinomas, 34 of the 39 carcinomas (87%) fit this criterion, with a 95% confidence interval (CI) of 73%- 96%, whereas, on CT, 31 of the 39 were diagnosed as carcinoma; (sensitivity, 79%). The sensitivity and accuracy of CT were inferior to those of CE-US. Results of comparison between the CE-US findings and the histological diagnosis were as follows. The one papillary adenocarcinoma showed a hypervascular and hyperperfusion pattern; the 32 well or moderately differentiated adenocarcinomas showed a hypovascular and hypoperfusion pattern; and in the poorly differentiated adenocarcinomas, 2 cases of scirrhous type showed a hypovascular and hypoperfusion pattern, and the 4 cases of medullary type showed an isovascular and isoperfusion pattern. Conclusions. The differences in vascularity of pancreatic carcinomas depicted by CE-US were associated well with differences in histology. CE-US, by the ADI technique, is useful for the diagnosis of pancreatic tumors.