A real-time high frame rate high frequency ultrasonic system for cardiac imaging in small animals

Small animals, especially mice, have become widely used models for studies of genes and human diseases. For cardiac imaging in mice, whose hearts beat at a rate higher than 300 beats per minute, the spatial and temporal resolution of current clinical ultrasonic scanners are far from ideal and simply inadequate for such applications. In this research, a real-time high frequency (30~50MHz) ultrasound imaging system was developed with a frame rate of 130 frames per second (fps) and spatial resolution of 50 microns for cardiac applications in small animals. The mechanical scanning of the device was provided by a sector scanner using a magnetic drive mechanism and a digital servo controller for high speed and accuracy. A very light-weight (< 0.28 g), single element, focused transducer was specially designed and constructed to reduce the motor load and achieve high frame rates. To ensure equally spaced scan lines and minimize jitters, the imaging electronics were triggered according to the angular position of the transducer to compensate for the varying speed of the sector motor. In vivo experiments on adult mice and mouse embryos showed that real time ultrasound imaging at a frame rate of 130 fps could demonstrate detailed depiction of cardiac function with adequate spatial resolution, which allows researchers to examine and monitor small animal cardiac function.