ABSTRACT
Abstract Introduction In the last 28 years, the scientific community has been using elastography to evaluate the mechanical properties of biological tissue. The aim of this work was the optimization of the UDmV method, presented in Part I of the series, by means of modifying the technique employed to generate the reference sine and cosine functions, used for phase-quadrature demodulation, and determining how this modification improved the performance of the method. Additionally, the UDmV was employed to characterize the acoustic and mechanical properties of a 7% gelatin phantom. Methods A focused transducer, T F, with a nominal frequency of 2.25 MHz, was used to induce the shear waves, with frequency of 97.644 Hz. Then, the modified UDmV method was used to extract the phase and quadrature components from ultrasonic RF echo-signals collected from four positions along the propagation path of the shear wave, which allowed the investigation of the medium vibration caused by wave propagation. The phase velocity, c s, and attenuation, α s, of the phantom were measured and employed in the calculation of shear modulus, μ, and viscosity, η. Results The computational simulation demonstrated that the modification in UDmV method resulted in more accurate and precise estimates of the initial phases of the reference sinusoidal functions used for phase-quadrature demodulation. The values for c s and μ of 1.31 ± 0.01 m·s-1 and 1.66 ± 0.01 kPa, respectively, are very close to the values found in the literature (1.32 m·s-1 and 1.61 kPa) for the same material. Conclusion The UDmV method allowed estimating of the acoustic and viscoelastic parameters of phantom.
ABSTRACT
Abstract Introduction Therapeutic ultrasound (TUS) is a widespread modality in physiotherapy, and the water bag technique is a coupling method employed in the presence of anatomical irregularities in the treatment area. The aim of the present study is to evaluate the acoustic attenuation of the water bag and its effectiveness as a TUS coupling agent. Methods The rated output powers (ROPs) of the TUS equipment were evaluated based on IEC 61689. Then, a radiation force balance was used to measure ROP with and without a water bag (latex and nitrile gloves filled with deionized water) between a TUS transducer and the cone-shaped target of the balance. Each experiment was performed five times for each nominal power (0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0 W) and in the following configurations: without the water bag (A), with nitrile gloves and with (B) and without (C) a height controller, and latex gloves with (D) and without (E) height controller. ROPs obtained in different media were compared. Results The highest relative error of ROP was 16.72% for 0.5 W. Although the power values of the equipment were within the range recommended by IEC, there was a significant difference between the ROP values measured with A and with B, C and D. Conclusion As intensity differences below 0.5 W/cm2 are considered clinically not relevant, conditions A, B, C, D, or E can be used interchangeably.