Communication Dans Un Congrès Année : 2020

Ultrafast Radial Modulation Imaging

Résumé

Microbubbles may be detected by nonlinear ultrasound techniques or by the decorrelation through their motion using spatio-temporal filters (e.g. SVD). However, at high frequency (15 MHz), nonlinear techniques are less efficient and if spatio-temporal filters work very well, it concerns only moving microbubbles. Radial modulation imaging (RMI) allows the detection of fixed and slowly moving microbubbles at high frequency by the use of a dual-frequency excitation (manipulation and imaging frequencies). Imaging pulses during rarefaction and compression of the manipulation frequency are subtracted to remove tissue signals. However, the synchronization between the imaging pulses in RMI is non-trivial and the time-delay difference due to dispersion of the imaging pulse has to be corrected. To simplify and improve the RMI process, we propose ultrafast radial modulation imaging (uRMI). Diluted Sonovue was injected in a flow phantom, insonified by two confocal transducers (an array at 15MHz and a single element at 1 MHz). The single element generated a continuous excitation close to 1 MHz and the array ultrafast acquisitions. Ultrafast radial-modulation imaging consisted of addressing the microbubbles at different stages of their oscillations using the beat frequency between the ultrafast imaging and the modulation. For each acquisition, 1000 images were acquired, demodulated by a lock-in amplifier and beamformed. The uRMI technique was compared to other techniques to detect microbubbles: amplitude modulation, microbubble disruption, and SVD filter. The contrast-to-tissue ratios obtained with uRMI were up to 14.8 dB for the different conditions. It increased with the amplitude of excitation of the low frequency and decreased with the flow speed. URMI provided the best CTR without flow and for flow speed lower than 1 mm/s, higher than SVD filter, microbubbles disruption and amplitude modulation. This technique is then promising for ultrasound molecular imaging application and to complete microvascular cartography obtained by ultrasound localization microscopy.

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Dates et versions

hal-03240235 , version 1 (29-05-2021)

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Identifiants

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Pauline Muleki Seya, Kailiang Xu, Mickaël Tanter, Olivier Couture. Ultrafast Radial Modulation Imaging. Forum Acusticum, Dec 2020, Lyon, France. pp.1057-1058, ⟨10.48465/fa.2020.0232⟩. ⟨hal-03240235⟩
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