Luis Eduardo Maggi

Ultrasonic attenuation and speed in phantoms made of polyvinyl chloride-plastisol and graphite powder

Biological phantoms are very useful for controlled experiments on biomedical ultrasound. Nevertheless they are normally made of organic materials with short time-duration. We have studied the ultrasonic properties of test-blocks made of polyvinyl chloride-plastisol (PVCP) that are very stable in time. In this work, we analyzed ultrasonic (US) attenuation and speed at 1 MHz, as a function of temperature (15–45°C) of five phantoms made with PVCP and different concentrations of graphite powder (0, 0.5, 1, 2, and 5%) using the classical transmission method. US speed diminishes almost linearly (from 1408 to 1333 m.s−1) as temperature increases. In general attenuation lied between 0.73 and 0.09 dB.cm−1, but presenting a more complex behavior. For graphite concentrations of 0.5 and 1%, attenuation was lower than for 0% and for the other two phantoms (2 and 5% concentrations) attenuation was higher. This behavior can be perhaps due to the fact that the fabrication temperature for 0.5 and 1% was 140°C and for the ...

Comparison of two ultrasonic phantom manufacturing protocols made of polyvinyl chloride Plastisol

Ultrasonography is an important and well-accepted technique, once it is noninvasive and capable of giving complementary information that helps the radiologist classifying lesions. Consequently, it is worthy to invest in the design and production of phantoms to provide support to controlled experiments as well as help training health professionals, and Computer Aided-Diagnoses systems. However, there is a need in the literature for a standardised protocol that helps further comparison studies. In this study, two ultrasonic phantoms were constructed to mimic soft tissue. The material used in these phantoms is the polyvinyl chloride plastisol - PVCP, a well-known material used in other areas. The protocols differ at its heating tools: Electric and microwave stove. Eight phantoms for each protocol were made, and their respective ultrasound propagation speed and attenuation coefficients were compared, showing a statistical difference between speeds but no difference in attenuation. The two manufacturing protocols demonstrated to be useful for phantom confection with no significant changes in acoustics properties. This paper is a valuable tool at the demand for protocols standardisation.

Evaluation of acoustic and thermal properties of gellan-gum phantom to mimic biological tissue

A hydrogel-based (gellan gum) tissue mimicking material (TMM) was developed. Its acoustic and thermal properties were characterized. The hydrogel was combined with different sizes of glass spheres. The acoustic properties (attenuation coefficient and the speed of sound) were obtained as a function of the temperature range 20 to 45° C. Specific heat was determined experimentally by the standard mixture method for the same temperature range. The attenuation coefficient presented a quasi-linear dependence on the frequency, such as the most of mammalian tissues. The mean value was 0.59f 0,85 dB·cm-1, at 30° C from 1 to 10MHz. The results suggest that the developed TMM has potential for several applications: development of standard dosimetry techniques, validation numerical models and determination the efficacy of hyperthermia devices.

Analysis of different techniques for measuring the attenuation coefficient in ultrasonic phantom

This work describes some techniques for estimating the attenuation coefficient of longitudinal wave in a phantom made with RTV615 (GE) and silicone. The AWAY method presented results with lower standard deviation when RMS or FFT was applied to analyze the ultrasonic signal. Furthermore, it was observed that the use of APPARENT AWAY method with the FFT has sensitivity to number of cycles of the burst used, because the increased number of cycles considerably reduced the standard deviation of the results. However, if the number of cycles is greater than 10, the application of FFT and RMS methods gave similar results and should provide the same standard deviation.