Ultrasonic resonant and spectral echography.
Duration: 3 years
Funded by grant (DPI2016-78876-R-AEI/FEDER, UE) from the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERDF / FEDER)
Start: January 2017
End: December 2019
Resonant Ultrasound (ECERES). ECERES will apply to tissues and materials whose geometry can generate resonances or, at least, interference between different echoes (e.g. homogeneous or laminated tissues with planar, spherical or cylindrical geometry). ECERES will use spectral analysis techniques to analyze these resonances and/or interferences and will implement algorithms for the solution of the inverse problem (IP) to extract the tissue information: thickness, impedance, stiffness, damping, structure, etc., an important innovation in the field of medical diagnosis.
Unlike conventional ultrasound techniques operating in the time domain that require high frequencies and large bandwidths to discern between different echoes, the proposal ECERES will perform the separation in the frequency domain, making possible to operate at lower frequencies, allowing larger penetration ranges, the study of more attenuating tissues and extracting more information. The main problems encountered relate to achieve efficient transducers for ECERES and the increased complexity of data analysis and signal processing.
Thus, the project objectives relate to three aspects: i) development of new transduction techniques for ECERES ii) development of techniques for signal processing and for solution of IP applicable to ECERES to extract tissue information iii) test and analysis of ECERES in selected medical applications.
i) Development of transducers technology with bandwidth >100%, capable to miniaturize the transducers and to produce both single elements and arrays. Two frequency ranges of interest are identified: 0.1-3.0 and 2.0-20 MHz. For the high frequency range, piezocomposite materials will be used, while for low frequency range (the most difficult one), the use of ferroelectrets is proposed. This is a significant innovation because this material has not been used so far in this field. Initial tests carried out by the group have shown that it can be an excellent alternative. These materials require specific electronic excitation and reception stages, which are also part of the proposed technological development.
ii) As starting point previous contributions by the group will be used. These contributions employ algorithms based on the stochastic descent method. The adequacy of these methods to this problem will be tested and some alternatives will be analyzed, as the algorithms of Gauss-Newton, Levenberg-Marquard and Broyden-Fletcher-Goldfarb-Shanno.
iii) We have identified three potential application fields (where conventional ultrasound techniques are already employed) so that the development of the technology go even from its initial stages with the proposed applications. These applications refer to the determination of thickness, rigidity, and structure of cornea, skin and arterial wall. Cornea: diagnosis of glaucoma, before surgery studies, etc. Currently 20-50 MHz ultrasound is used. Skin: alterations due to different conditions, presence of cancerous lesions. Currently 12-20 MHz ultrasound is used. Arterial wall thickness and diameter: diagnosis of state of the wall, arteriosclerosis, etc., conventional techniques employ 5-10 MHz frequency range while intravascular endoscopy currently operates in the range: 40-150 MHz. The technology developed (transducers + electronics + processing) will consider this three applications for validation and industrial transfer.