Investigation of acoustic waves emitted by heart for tomographic reconstruction

• Grant number: 14/04121-0
• Support Opportunities: Regular Research Grants
• Duration: June 01, 2014 - May 31, 2016
• Field of knowledge: Engineering - Biomedical Engineering - Medical Engineering
• Principal Investigator: Sergio Shiguemi Furuie
• Grantee: Sergio Shiguemi Furuie
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Anatomical and functional information on human structures are of fundamental importance for the diagnosis and treatment of diseases. The majority of the imaging equipment uses external sources, such as electromagnetic radiation or acoustics to interrogate the structures. However, we have a natural, periodic source that is the heart emitting acoustic waves. These waves are generated by the closing of the valves, turbulence of the blood flow and movement of the walls. The hypothesis of this project is that the high frequency part, in ultrasound range, can be used as source for the tomographic reconstruction of thoracic structures, including the heart. The objective is the investigation of the potential of periodic acoustic waves emitted by the heart for the solution of the inverse problem. It is well known that the quality of the diffraction tomography based on multiple transducers is dependent on wavelength. Therefore, it is important to verify the existence of energy in the ultrasound frequency. In addition, the project will also focus on solving two inverse problems: a) space localization of the sources; b) tomography of the heterogeneous medium that is consistent with the detected signals. The use of scattered waves to determine internal object properties has also been studied in diverse areas, such as geophysical, sonar and non destructive tests. Several groups have been researching this subject, aiming at lesser time of reconstruction and better quality in the images. The methodology proposed in the present project consists of: a) analysis of the spectrum of the acoustic waves emitted by the heart; b) inverse problem to locate the sources; c) inverse problem to characterize the medium of propagation. The evaluation will be based on numerical simulations with increasing level of noise, and on physical phantoms constructed with homogeneous and heterogeneous material, simulating a slice of the heart and adjacent tissues. The metric will be based on the normalized quadratic mean error and on the maximum error between the estimated and the predefined parameters. The project is complex; however, it is important to investigate the possible limits of the proposal. Alternative methods that may improve and complement current equipments can bring up new clinical procedures in benefit of the patients. (AU)