High-frequency color flow imaging of the microcirculation

The extension of ultrasound (US) color flow imaging (CFI) techniques to hig h frequencies ( > 20 MHz) has the potential to provide valuable noninvasive tools for scientific and clinical investigations of blood dow in the micro circulation. We describe the development of a slow-scan CFI system operatin g in the 20-100-MHz range that has been optimized to image the microcircula tion, The apparatus has incorporated elements of a previously reported puls ed-wave Doppler system and is capable of operating in either CFI or pulsed- wave mode. The performance of the CFI system was evaluated at a center freq uency of 50 MHz using two PVDF transducers with -6-dB beam widths of 43 and 60 mu m. The -6 dB-axial resolutions were estimated to be 66 and 72 mu m, respectively. In vivo validation experiments conducted using the murine ear model demonstrated the detection of flow in vessels down to 15-20 mu m in diameter with how velocities on the order of mm per s, Further experiments examining experimental murine tumors confirmed the successful detection of dow in the tumor microcirculation, (C) 2000 World Federation for Ultrasound in Medicine & Biology.