Biomedical Engineering

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Browsing Biomedical Engineering by Subject "antibubble"

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    Characterization of Antibubbles Response under Sonication In Terms of Size Distribution and Destruction Threshold for Use in Drug Delivery
    (Addis Ababa University, 2023-06) Mahider Yifru; Dawit Assefa (PhD); Michiel Postema (PhD) Co-Advisor
    Antibubbles are gas bubbles containing liquid droplets. Due to their acoustic property, they are preferable for different medical applications such as drug delivery and ultrasonic harmonic imaging. In drug delivery, they are used as drug carrier for effective treatment of diseases such as cancer. In order to ensure safe and targeted drug delivery, the behaviors of the drug carriers (antibubbles) need to be studied. The aim of the current research was to study response of antibubbles under sonication and determine destruction threshold which can lead to fragmentation under ultrasound pulse having safe mechanical index (MI) with reduced undesired mechanical and thermal bio-effects. Gray-scale video frames of antibubbles were used for this research, which were generated through laboratory experiment. Matlab and ImageJ platforms were used for effective detection of antibubbles and determination of their respective size before, during and after sonication together with destruction threshold. The proposed algorithm involves extraction of texture features form the video frames based on the local gray level co-occurrence matrix (GLCM) and a watershed scheme for segmentation of the antibubbles. Once antibubbles are detected, their size distribution under ultrasound pulse with varying acoustic pressures was analyzed. The investigation carried out under sonication of low pressure ultrasound waves (0.2 MPa and 0.4 MPa) showed that the antibubbles oscillate repeatedly with series of stable contraction and expansion but will not undergo fragmentation. This property of antibubbles interaction with low pressure ultrasound wave makes them very useful and preferable to be used as a drug carrier in a way of manipulating the antibubble movement through the blood vessel to the target region. In case of antibubble sonication under higher acoustic pressure wave (0.6 MPa and 1 MPa), their oscillations become more asymmetric which finally lead to fragmentation. The MI of 0.6 MPa and 1Mpa ultrasound pulses are 0.6 and 1 respectively, where significant risk of cavitation is considered for MI > 0.7. The destruction threshold analysis showed that antibubbles under acoustic pressure of 0.6 MPa experience fragmentation when their size during maximum expansion is approximately twice that of their initial size intermes of area, i.e. Amax ≈ 2.1 Ai. In the case of 1 MPa acoustic pressure Amax ≈ 2.8 Ai, showing that ultrasound pulse with acoustic pressure of 0.6 MPa is considered safe compared to 1 MPa for use in drug delivery with the capacity to induce fragmentation and effective targeted drug release.