Contrast-enhanced sonography of pancreatic ductal carcinoma using agent detection imaging

Purpose The aim of this study was to evaluate the enhancement behavior of pancreatic ductal carcinoma by contrast-enhanced sonography with agent detection imaging (ADI), and to clarify the origin of microbubble signals by comparisons with histological findings of resected specimens. Methods The subjects were 21 patients with resectable pancreatic carcinoma. The final histological diagnosis was tubular adenocarcinoma in 20 cases, and anaplastic carcinoma in one case. Ultrasound examinations were performed using an Acuson Sequoia 512 series system, and the contrast agent (Levovist) was injected intravenously in doses of 7 ml (300 mg/ml). The ADI signals (in the tumor) were recorded continuously for 30 s after an injection of Levovist (vascular image) and then obtained intermittently (30 s time-intervals) until the signal had diminished in pancreatic tissue (perfusion image). Results Contrast enhancement of the tumor was observed in 71.4% of subjects on the vascular image and 76.3% of subjects on the perfusion image. Enhancement patterns on the vascular image were classified into three types: VI-1 (linear enhancement), VI-2 (spotty enhancement), and VI-3 (no enhancement). VI-1, VI-2, and VI-3 were seen in 9 (42.8%), 6 (28.6%), and 6 (28.6%) of the 21 cases, respectively. Enhancement patterns on the perfusion image were classified into four types: PI-1 (diffuse uneven enhancement), PI-2 (spotty enhancement), PI-3 (peripheral enhancement), and PI-4 (negative enhancement). The incidence of PI-1, PI-2, PI-3, and PI-4 was 4.8%, 42.9%, 28.6%, and 23.8%, respectively. With respect to resectable cases, these enhancement patterns were compared with histological findings, i.e., the distribution of blood vessels in the tumor, remaining pancreatic tissues in the tumor, differentiation of types of adenocarcinoma, volume of stroma, and invasion types of carcinoma. The enhanced patterns consequently corresponded to either the distribution of the blood vessels or the remaining pancreatic tissues in the tumor. Conclusion This study indicated that pancreatic ductal carcinoma is frequently enhanced by microbubbles, and the signals seem to originate from fine blood vessels and the remaining pancreatic tissues in the tumor.