Sistema de varredura para aquisição e processamento de sinais ultrassônicos para caracterização de meios biológicos

Abstract

The use of ultrasound for material characterization has been applied with satisfactory results since the 50's. Such success is justified by its non-invasive and non-ionizing characteristics, as well as its low implementation cost when compared to other techniques. This research presents the development of a scanning system for the acquisition and processing of ultrasonic signals for the characterization of biological media through the use of the Broadband Ultrasound Attenuation (BUA) and the Specific Attenuation of the ultrasonic waves. The system hardware consists of switched sources, power drivers for driving the step motors and positioning of the transducers, and a microcontrolled electronic system responsible for the acquisition of ultrasound signals. The tests to validate the system used the transmission-reception method of the ultrasonic signal, being done in an acoustic tank. In order to characterize an in vitro biological medium, two ultrasound phantoms were used to simulate a normal bone structure with attenuation of 75 ± 5 dB/MHz (model CIRS 06301) and an osteoporotic one, with attenuation of 50 ± 5 dB/MHz (model CIRS 06302). The obtained results using the scanning system were 74.58 ± 12.99 dB/MHz for the CIRS 06301 phantom (normal bone structure) and 57.42 ± 3.61 dB/MHz for the CIRS 06302 phantom (osteoporotic bone structure), with percentage errors for the BUA mean values of 0.56 % and -14.84 %, respectively, indicating that the developed scanning system may be used in the material characterization area, such as to predict the risk of fractures due to osteoporosis.