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Vander Teixeira Prado, Ricardo Tokio Higuti

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    This study introduces the instantaneous frequency (IF) image, derived from the instantaneous phase (IP) image. IF images enhance reflector detection and contrast by representing reflectors at a constant level, independent of distance.

    Area of Science:

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    • Signal processing
    • Medical physics

    Background:

    • Conventional amplitude images in ultrasound suffer from variable reflector representation and limited contrast.
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    Purpose of the Study:

    • To introduce and characterize a novel instantaneous frequency (IF) imaging technique.
    • To evaluate the performance of IF images in improving reflector detection and contrast compared to amplitude and IP images.
    • To demonstrate the utility of IF images as a coherence factor and for enhanced interpretation of ultrasound data.

    Main Methods:

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  • Instantaneous phase (IP) images were generated by replacing amplitude information with IP in delay-and-sum beamforming.
  • Instantaneous frequency (IF) images were obtained by differentiating the IP images.
  • Simulations using point spread functions and experiments with a medical phantom were conducted under various conditions (distance, contrast, array type).

    • Main Results:

    • IF images maintain the artifact and sidelobe reduction properties of IP images.
    • Reflectors in IF images are represented by a constant level, determined by the signal's central frequency, improving contrast and reducing distance dependency.
    • IF images demonstrated superior reflector detection and contrast across different experimental scenarios compared to amplitude and IP images.

    Conclusions:

    • The instantaneous frequency (IF) image is a valuable new tool in ultrasound imaging.
    • IF imaging offers improved reflector detection and contrast, overcoming limitations of amplitude and IP images.
    • IF images can serve as an additional information source for interpreting conventional ultrasound data or as a novel coherence factor.