Ultrasound Contrast Agents characterization
The MSD Lab work in this field has been mainly addressed to evaluate the dynamic behavior of coated microbubbles in specific US excitation conditions.
The translational effects of US radiation force on either single microbubbles and full populations, have been deeply investigated.
Such behavior has also been characterized in terms of effects on the "Doppler" spectrum, and it was shown that these effects are completely different from those due to bubble rupture mechanisms.
The collaboration with Erasmus MC led to the implementation of a unique acousto-optic set-up, which allowed detailed investigations of the behavior of individual microbubbles subjected to US burst excitation over relatively long time intervals.
Microbubble deflation mechanisms were deeply studied and correlations between these mechanisms and the bubble physical properties have been pointed out. Significant changes in the harmonic content of the echoes of deflating microbubbles have also been demonstrated.
Imaging ultrasound pulses produced by a single element transducer apply radiation force on the bubbles. In the M-Mode display, each trace corresponds to the echoes of a single bubble, its slope depending on the acceleration impressed by the radiation force. The bottom pictures show the Doppler velocities detected at 128 distinct depths (Multigate Doppler Mode). Left: each spotlight corresponds to a different bubble. Right: history of the same bubble velocities over a 2 seconds interval. (from: IEEE Trans UFFC, 54:7,front cover, 2007)
|Images (top) and corresponding full echoes (bottom) of a deflating Definity bubble, recorded at different times. The bubble was insonified at 250 Hz PRF for about 10 s by the sequence P1. These results, in particular,show the bubble response to the 2-MHz transmission frequency. (from: IEEE Trans UFFC, 57:1, 193-202, 2010)
Definity bubble oscillations under excitation with 2-MHz pulses every 20 ms. Heach oscillation (e.g. interval t1) is recorded for 7.5 µs every 5 transmit pulses (i.e. 100 ms). After 6 consecutive recordings (highlighted by the same shade) the experiment is paused for 2 min (interval t2). The bubble resting radius (represented by black dashed lines) decrease during the experiment (7 min long). At the end of the experiment, the bubble shows compressiononly behavior with a resting radius of about 1.4 µm.
- P.Tortoli, V.Michelassi, M.Corsi, D.Righi, Y.Takeuchi, On the interaction between ultrasound and contrast agents during Doppler investigations, Ultrasound in Medicine and Biology, 27:9, 1265-1273, 2001.
- H.J. Vos, F. Guidi, E. Boni and P. Tortoli, Method for microbubble characterization using primary radiation force, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., 54:7, 1333-1345, 2007.
- P. Tortoli, F. Guidi, R. Mori, H. Vos, The use of microbubbles in Doppler ultrasound studies, Medical & Biological Engineering & Computing: Special Issue on "Preparation & clinical use of Microbubbles", 47:8, 827-838, 2009
- F. Guidi, H. Vos, R. Mori, N. de Jong, P. Tortoli, Microbubble characterization through acoustically-induced deflation, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., 57:1, pp. 193-202, 2010.
- J. Viti, R. Mori, F. Guidi, M. Versluis, N. de Jong, and P. Tortoli, Nonlinear Oscillations of Deflating Bubbles, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., 59:12, p.2818-2824, 2012.
- F. Guidi, R. Mori, J. Viti, N. deJong, P.Tortoli. Implementation of arbitrary contrast imaging strategies on an US Open Platform, 2012 IEEE Ultrasonics Symposium Proceedings, Dresda, Ottobre 2012, DOI: 10.1109/ULTSYM.2012.0170 , pp.683-686.
- F. Lin, C. Cachard, R. Mori, F. Varray, F. Guidi, and O. Basset. Ultrasound Contrast Imaging: Influence of Scatterer Motion in Multi-Pulse Techniques, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 60, no. 10, p.2065-2078, 2013.