Pulsed Doppler signal processing for use in mice: design and evaluation.

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Medical Imaging

Background:

• Clinical Doppler systems have limitations in accurately measuring high-velocity blood flow and rapid physiological events in small animal models.
• Existing methods lack the necessary temporal and spatial resolution for detailed analysis of mouse cardiovascular dynamics.

Purpose of the Study:

• To develop and validate a high-frequency, real-time pulsed Doppler system for precise physiological signal acquisition and analysis in mice.
• To overcome the limitations of clinical Doppler systems in mouse research by enhancing resolution and data processing capabilities.

Main Methods:

• Developed a system with sampling rates up to 125 kilosamples/s (ksps) and real-time software-controlled data acquisition.
• Utilized complex fast Fourier transforms (FFTs) with varying segment sizes for high temporal (0.1 ms) and frequency resolution.
• Evaluated system performance using frequency-swept signals simulating mouse blood velocity and acceleration, with probes up to 20 MHz.

Main Results:

• The system processed signals up to 125 kHz and accelerations of 20 MHz/s, corresponding to velocities up to 960 cm/s.
• Achieved high temporal resolution (0.1 ms) and frequency resolution (122-1953 Hz), enabling measurement of high stenotic jet velocities.
• Demonstrated smooth spectrogram transitions without artifacts and processed signals with periods as low as 2 ms, exceeding clinical Doppler system sweep speeds.

Conclusions:

• The developed high-frequency Doppler system offers significantly higher spatial and temporal resolution compared to adapted clinical systems for mouse studies.
• This advanced system enables more precise measurements of blood velocities and small temporal events in mice.
• Facilitates detailed cardiovascular research in mice by providing superior data acquisition and analysis capabilities.