Pulsed Doppler signal processing for use in mice: applications

We have developed a high-frequency, high-resolution Doppler spectrum analyzer (DSPW) and compared its performance against an adapted clinical Medasonics spectrum analyzer (MSA) and a zero-crossing interval histogram (ZCIH) used previously by us to evaluate cardiovascular physiology in mice. The aortic velocity (means ± SE: 92.7 ± 2.5 versus 82.2 ± 1.8 cm/s) and aortic acceleration (8194 ± 319 versus 5178 ± 191 cm/s²) determined by the DSPW were significantly higher compared to those by the MSA. Aortic ejection time was shorter (48.3± 0.9 versus 64.6 ± 1.8 ms) and the isovolumic relaxation was longer (17.6 ± 0.6 versus 13.5 ±0.6 ms) when determined by the DSPW because it generates shorter temporal widths in the velocity spectra when compared to the MSA. These data indicate that the performance of the DSPW in evaluating cardiovascular physiology was better than that of the MSA. There were no significant differences between the aortic pulse wave velocity determined by using the ZCIH (391 ± 16 cm/s) and the DSPW (394 ± 20 cm/s). Besides monitoring cardiac function, we have used the DSPW for studying peripheral vascular physiology in normal, transgenic, and surgical models of mice. Several applications such as the detection of high stenotic jet velocities (>4 m/s), vortex shedding frequencies (250 Hz), and subtle changes in wave shapes in peripheral vessels which could not obtained with clinical Doppler systems are now made possible with the DSPW.