Contrast-enhanced ultrasound evaluation of pancreatic cancer xenografts in nude mice after irradiation with sub-threshold focused ultrasound for tumor ablation

// Yi Hui Gao 1, 2, *, ** , Lei Wu 1, 2, *, ** , Rui Wang 1, 2 , Qian Guo 1, 2 , Yi Ni Chen 1, 2 , Bing Hu 1, 2 and Li Xin Jiang 1, 2 1 Department of Ultrasonography, Shanghai Jiaotong University Affiliated No. 6 Hospital, Shanghai 200233, PR China 2 Shanghai Institute of Ultrasound in Medicine, Shanghai 200233, PR China * Co-first authors ** These authors have contributed equally to this work Correspondence to: Li Xin Jiang, email: jinger_28@sina.com Keywords: dynamic contrast-enhanced ultrasound, pancreatic cancer, sub-threshold focused ultrasound, evaluation with DCE-US, B-mode US examination Received: January 20, 2017     Accepted: March 09, 2017     Published: March 28, 2017 ABSTRACT We evaluated the efficacy of contrast-enhanced ultrasound for assessing tumors after irradiation with sub-threshold focused ultrasound (FUS) ablation in pancreatic cancer xenografts in nude mice. Thirty tumor-bearing nude mice were divided into three groups: Group A received sham irradiation, Group B received a moderate-acoustic energy dose (sub-threshold), and Group C received a high-acoustic energy dose. In Group B, B-mode ultrasound (US), color Doppler US, and dynamic contrast-enhanced ultrasound (DCE-US) studies were conducted before and after irradiation. After irradiation, tumor growth was inhibited in Group B, and the tumors shrank in Group C. In Group A, the tumor sizes were unchanged. In Group B, contrast-enhanced ultrasound (CEUS) images showed a rapid rush of contrast agent into and out of tumors before irradiation. After irradiation, CEUS revealed contrast agent perfusion only at the tumor periphery and irregular, un-perfused volumes of contrast agent within the tumors. DCE-US perfusion parameters, including peak intensity (PI) and area under the curve (AUC), had decreased 24 hours after irradiation. PI and AUC were increased 48 hours and 2weeks after irradiation. Time to peak (TP) and sharpness were increased 24 hours after irradiation. TP decreased at 48 hours and 2 weeks after irradiation. CEUS is thus an effective method for early evaluation after irradiation with sub-threshold FUS.