Transfer functions of US transducers for harmonic imaging and bubble responses
| Autor: | J. Borsboom, Nico de Jong, Guillaume Matte, Jeroen Sijl, Paul L. M. J. van Neer |
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| Přispěvatelé: | Physics of Fluids, Faculty of Science and Technology, Cardiology |
| Rok vydání: | 2007 |
| Předmět: |
Acoustics and Ultrasonics
Reciprocity Transducers Near and far field Efficiency Transfer function Optics Sensitivity Image Interpretation Computer-Assisted High harmonic generation Computer Simulation METIS-244704 Ultrasonography Physics Transducer Microbubbles Hydrophone business.industry Natural frequency Fundamental frequency Models Theoretical IR-78827 Harmonics Computer-Aided Design business |
| Zdroj: | Ultrasonics, 46(4), 336-340. Elsevier |
| ISSN: | 1874-9968 0041-624X |
| Popis: | Current medical diagnostic echo systems are mostly using harmonic imaging. This means that a fundamental frequency (e.g., 2 MHz) is transmitted and the reflected and scattered higher harmonics (e.g., 4 and 6 MHz), produced by nonlinear propagation, are recorded. The signal level of these harmonics is usually low and a well-defined transfer function of the receiving transducer is required. Studying the acoustic response of a single contrast bubble, which has an amplitude in the order of a few Pascal, is another area where an optimal receive transfer function is important. We have developed three methods to determine the absolute transfer function of a transducer. The first is based on a well-defined wave generated by a calibrated source in the far field. The receiving transducer receives the calibrated wave and from this the transfer functions can be calculated. The second and third methods are based on the reciprocity of the transducer. The second utilizes a calibrated hydrophone to measure the transmitted field. In the third method, a pulse is transmitted by the transducer, which impinges on a reflector and is received again by the same transducer. In both methods, the response combined with the transducer impedance and beam profiles enables the calculation of the transfer function. The proposed methods are useful to select the optimal piezoelectric material (PZT, single crystal) for transducers used in reception only, such as in certain 3D scanning designs and superharmonic imaging, and for selected experiments like single bubble behavior. We tested and compared these methods on two unfocused single element transducers, one commercially available (radius 6.35 mm, centre frequency 2.25 MHz) the other custom built (radius 0.75 mm, centre frequency 4.3 MHz). The methods were accurate to within 15%. |
| Databáze: | OpenAIRE |
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