ABSTRACT
Abstract Introduction Ultrasound used in diathermic therapies aims to achieve temperatures between 40 and 45 °C, since temperatures above 45 °C are known to cause tissue necrosis and burns. Many studies have been conducted to investigate the effect of therapeutic ultrasound in the presence of metallic implants, using phantoms (test samples) and in vivo and ex vivo animal models. In most of these studies, the ultrasound probe is fixed in one area, while in clinical practice, it is recommended that it be moved to avoid possible local overheating. Objective To analyze the thermal field at the muscle-bone interface in phantoms in the presence or absence of metallic implants after the application of therapeutic ultrasound. Methods Phantoms composed of layers simulating fat and muscle, and a layer of beef rib bone, with and without a titanium metallic implant, were prepared. The experiment involved different intensities (1.0, 1.5, and 2.0 W/cm2) and exposure times (5 and 10 minutes), common in clinics, with linear scanning of the probe. Results The experiments indicated that the muscle/implant interface heated less than the muscle/bone interface, especially at intensities of 1.5 and 2.0 W/cm2, after 5 and 10 minutes of treatment. Conclusion The results suggest the possibility of using therapeutic ultrasound in patients with metallic implants, encouraging future research to develop evidence-based protocols and safe recommendations in physiotherapy.
Resumo Introdução O ultrassom utilizado em terapias diatérmicas visa atingir temperaturas entre 40 e 45 °C, sabendo-se que temperaturas acima de 45 °C podem causar necrose tecidual e queimaduras. Muitas pesquisas têm sido realizadas para estudar o efeito do ultrassom terapêutico na presença de implantes metálicos, utilizando phantoms (corpos de prova) e animais in vivo e ex vivo. Na maioria dessas pesquisas, o cabeçote ultrassônico está fixo em uma área, enquanto que na prática clínica recomenda-se que ele seja movimentado para evitar eventuais sobreaquecimentos locais. Objetivo Analisar o campo térmico na interface músculo-osso em phantoms na presença ou ausência de implantes metálicos após a aplicação do ultrassom terapêutico. Métodos Foram elaborados phantoms compostos de camadas simuladoras de gordura e músculo e de uma camada de osso de costela bovina, sendo esta com e sem implante metálico de titânio. O experimento envolveu diferentes intensidades (1.0, 1.5 e 2.0 W/cm2) e tempos de exposição (5 e 10 minutos) comuns em clínica, com varredura linear do cabeçote. Resultados Os experimentos indicaram que a interface músculo/implante aqueceu menos do que a interface músculo/osso, especialmente nas intensidades de 1.5 e 2.0 W/cm2, após 5 e 10 minutos de tratamento. Conclusão Os resultados obtidos apontam para a possibilidade de utilização do ultrassom terapêutico em pacientes com implantes metálicos, incentivando pesquisas futuras para desenvolver protocolos baseados em evidências e recomendações seguras na fisioterapia.
ABSTRACT
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.
