High-frequency ultrasonic imaging system: A preliminary small animals study

Angiogenesis plays an important role in cancer proliferation and metastasis. Since the assessments of the microvascular status can yield clinically significant information, assessing the microcirculation would be of particular interest in tumor diagnosis and prognosis. Our goal in this study is to build up a real-time a high resolution ultrasonic imaging system with a higher imaging dynamic range and temporal resolution to observe tumor microcirculation in a small animal model. The imaging system with transmissions of 25-MHz pulse provides a spatial resolution on the order of 150 μm. We introduced in vivo experiments to estimate the tumor microcirculation changes in swept-scanning mode. The results indicated that we successfully traced and monitored the mice tumor growth in a time-course study. The tumor volume was calculated with an ellipsoid model based on acquired 3-D B-mode ultrasound images. The capillaries distribution was depicted by color Doppler image modes. The results show that the tumor core and periphery two regions correspond to different histogram patterns of blood flow velocity. Potential applications of the high-frequency ultrasonic imaging system include tumor perfusion assessment by using ultrasound contrast agents and molecular imaging in small animals.