Evaluation of therapeutic ultrasound equipment performance

Newly Designed 3D-Printed Sonication Test Cell Optimized for In Vitro Sonication Experiments

OBJECTIVE

Precise control over the ultrasound field parameters experienced by biological samples during sonication experiments in vitro may be quite challenging. The main goal of this work was to outline an approach to construction of sonication test cells that would minimize the interaction between the test cells and ultrasound.

METHODS

Optimal dimensions of the test cell were determined through measurements conducted in a water sonication tank using 3D-printed test objects. The offset of local acoustic intensity variability inside the sonication test cell was set to value of ±50% of the reference value (i.e., local acoustic intensity measured at last axial maximum in the free-field condition). The cytotoxicity of several materials used for 3D printing was determined using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay.

RESULTS

The sonication test cells were 3D printed from polylactic acid material, which was not toxic to the cells. Silicone membrane HT-6240, which was used to construct the bottom of the test cell, was found to reduce ultrasound energy minimally. Final ultrasound profiles inside the sonication test cells indicated the desired variability of local acoustic intensity. The cell viability in our sonication test cell was comparable to that of commercial culture plates with bottoms constructed with silicone membrane.

CONCLUSION

An approach to construction of sonication test cells minimizing the interaction of the test cell and ultrasound has been outlined.

Linear Relationship between the Effective Radiation Area and Thermal Images on a Thermochromatic Test Body with 1-MHz Ultrasonic Transducers

The performance of therapeutic ultrasonic (TUS) devices has a high degree of variability because of the fragility of the equipment (its transducer in particular) and its handling. These facts raise doubts about the effectiveness and safety of treatments employing such devices. Currently there is no simple way to adequately verify the performance of these devices. In our first experiments, we used a thermochromatic test body (typically a cylindrical plate 3.7 cm in diameter and 5.8 mm high) irradiated with therapeutic transducers driven by a standard radiofrequency (RF) generator. Results revealed a linear relationship between the thermal image areas, generated by the transducer's irradiation, and their respective effective radiation areas (ERAs), suggesting a good correlation. With five 3-MHz transducers, our group also observed the linear relationship using commercial TUS RF driving devices. In the present work, we used four 1-MHz transducers with their respective TUS RF driving devices and verified that there is a linear relationship between the thermal images and the ERAs at intensities of 1.0 ± 0.1 and 0.5 ± 0.05 W/cm². The linear relationship obtained at both intensities confirms the suggestion that these thermochromatic test bodies can be used as the first evaluation of the ERAs and can monitor their changes with use. Moreover, if a previous assessment of the ERA and transducer intensities is performed, it is possible to follow the variation in ERA simply by monitoring the test body thermal stain.

Therapeutic ultrasound experiments in vitro: Review of factors influencing outcomes and reproducibility

Current in vitro sonication experiments show immense variability in experimental set-ups and methods used. As a result, there is uncertainty in the ultrasound field parameters experienced by sonicated samples, poor reproducibility of these experiments and thus reduced scientific value of the results obtained. The scope of this narrative review is to briefly describe mechanisms of action of ultrasound, list the most frequently used experimental set-ups and focus on a description of factors influencing the outcomes and reproducibility of these experiments. The factors assessed include: proper reporting of ultrasound exposure parameters, experimental geometry, coupling medium quality, influence of culture vessels, formation of standing waves, motion/rotation of the sonicated sample and the characteristics of the sample itself. In the discussion we describe pros and cons of particular exposure geometries and factors, and make a few recommendations as to how to increase the reproducibility and validity of the experiments performed.

Efeitos adversos da eletrotermofototerapia em clínicas da cidade de Cascavel - PR

RESUMO Esta pesquisa teve como objetivo identificar os principais efeitos adversos observados por fisioterapeutas com o uso de aparelhos de eletrotermofototerapia em clínicas da cidade de Cascavel, Paraná. A amostra contou com 35 clínicas e destas, 25 foram alvo de coleta após triagem, cujos dados foram obtidos por questionários em forma de entrevista semiestruturada. Nestes se questionava aos responsáveis pelo serviço de eletrotermofototerapia sobre a ocorrência de efeitos adversos experienciados durante atividades laborais na clínica. Observou-se que a Neuroestimulação Elétrica Transcutânea (TENS) apresentou problemas em 64% dos casos, com 36% devido a irritações cutâneas e 28% a dor. O aparelho de ondas curtas apresentou efeitos adversos em 60%, em que 40% foram queixas de dor e 20% causaram queimaduras leves. Já acerca do ultrassom terapêutico foram relatados efeitos adversos em 52%, sendo 32% de quadros de dor e 20% de casos com náuseas. A laserterapia de baixa potência demonstrou efeito adverso em 36%, com relatos de aumento da sensibilidade local. Por fim, os aparelhos de média frequência apresentaram efeitos adversos em apenas 20% dos casos, de queixas de náuseas. A quantidade de tais efeitos encontrados foi importante, porém sua gravidade não causou grande preocupação.

The Dynatron Solaris® Ultrasound Machine: Slower Heating Than Textbook Recommendations at 3 MHz, 1.0 W/cm2

CONTEXT

Therapeutic ultrasound clinical parameters are provided in many modality textbooks based on research performed with the Omnisound brand. Literature exists to support variability in heating rates with different manufacturers. It is unknown if the Dynatron Solaris heats at rates consistent with textbook recommendations.

OBJECTIVE

Determine the rate of tissue-temperature increases in the medial triceps surae with the Dynatron Solaris® 708 ultrasound unit.

DESIGN

3 × 13 repeated measures. Independent variables were tissue depth (1.0, 1.75, and 2.5 cm) and time (13 time periods throughout the treatment).

SETTING

Research laboratory.

PARTICIPANTS

30 healthy volunteers (female = 11, male = 19; age 21.30 ± 1.95 y; adipose thickness = 0.54 ± 0.15 cm).

INTERVENTION

 Three thermocouples were inserted into the medial triceps surae at 1.0, 1.75, and 2.5-cm depths. A continuous 3-MHz, 1.0-W/cm² for 20 minutes ultrasound treatment was performed with a Dynatron Solaris 708 machine.

MAIN OUTCOME MEASURES

Intramuscular tissue-temperature increases at each depth throughout the 20-min treatment.

RESULTS

There was a significant main effect of depth (F_2,52 = 29.76, P < 0.001) and time (F_12,312 = 181.59, P < .001) and a significant interaction between times and depths (F_24,624 = 15.49, P < .001). The 1.0-cm depth increased 4.22 ± 1.58°C in 6 min (0.70°C/min rate), the 1.75-cm depth increased 3.93 ± 1.94°C in 10 min (0.39°C/min rate), and the 2.5-cm depth increased 3.60 ± 1.86°C in 20 min (0.18°C/min rate).

CONCLUSIONS

The rate of tissue-temperature increase varied at each depth and the 1.0-cm depth was the only rate similar to textbooks. Clinicians will not reach tissue-temperature goals using Omnisound textbook parameters on the Dynatron Solaris 708 at depths greater than 1.0 cm, which may affect clinicians, educators, and state-certification exams.

Influence of therapeutic ultrasound on the biomechanical characteristics of the skin

BACKGROUND

Skin function is dependent on its biomechanical characteristics, resistance, malleability, and elasticity. Therapeutic ultrasound may increase cutaneous malleability thus and optimize the rehabilitation process on specific diseases. The aim of this study is to evaluate possible alterations of biomechanical characteristics of the normal skin after therapeutic ultrasound application.

METHODS

Thirty-one volunteers took part of the study, and the average age was 31.61 ± 8.37 years old. Biomechanical characteristics evaluation of the skin was performed with the Cutometer MPA 580 (Courage + Khazaka Electronic-Köln, Germany) of 2-mm probe hole and 500-mbar vacuum. Skin characteristics were analyzed before and after therapeutic ultrasound application, and the variables R0 (distensibility), R2 (gross elasticity), and R6 (viscoelasticity) were used for the study. Areas of therapeutic ultrasound application (continuous, 3 MHz, 1 W/cm(2) SATA) were defined at the upper limbs and standardized using a neoprene template. Sociodemographic data of volunteers were analyzed using SPSS 15.0. To analyze the distribution of the data, the Shapiro-Wilk test was used, which showed the normal distribution for R0 values, R2 and R6. For this procedure, the PROC TTEST from SAS® 9.0 software and Minitab 16 software, with significance, was set at the 0.05 level.

RESULTS

In relation to R0, a significant increase (p = 0.001) was observed for the distensibility, when compared to values of pre- (0.3273 mm) and immediately post- (0.3795 mm) resource application which feature a greater distensibility. Related to R2 values, a significant increase (p = .001) of the gross elasticity at pre- (0.8419) and post- (0.8884) therapeutic ultrasound application was found.

CONCLUSIONS

Therapeutic ultrasound promotes significant alterations of the biomechanical characteristics of the skin.

TRIAL REGISTRATION

ClinicalTrials.gov, 1111-1146-7342.

Thermochromic Phantom and Measurement Protocol for Qualitative Analysis of Ultrasound Physiotherapy Systems

Thermochromic test bodies are promising tools for qualitatively evaluating the acoustic output of ultrasound physiotherapy systems. Here, a novel phantom, made of silicone mixed with thermochromic powder material, was developed. Additionally, a procedure was developed to evaluate the stability and homogeneity of the phantom in a metrologic and statistical base. Twelve phantoms were divided into three groups. Each group was insonated by a different transducer. An effective intensity of 1.0 W/cm(2) was applied to each phantom; two operators performed the procedure three times in all phantoms. The heated area was measured after image processing. No statistical difference was observed in the heated areas for different samples or in the results for different operators. The heated areas obtained using each transducer were statistically different, indicating that the thermochromic phantom samples had sufficient sensitivity to represent the heated areas of different ultrasonic transducers. Combined with the evaluation procedure, the phantom provides an approach not previously described in the literature. The proposed approach can be used to quickly assess changes in ultrasonic beam cross-sectional shape during the lifetime of ultrasound physiotherapy systems.