Costa RM1, Omena TP2, Coelho KA3, Pereira WCA3, von Kruguer MA3
1National Cancer Institute (INCA), Rio de Janeiro, Brazil, 2UFRJ, Physical Therapy Department, Rio de Janeiro, Brazil, 3COPPE/UFRJ, Biomedical Enginnering Program, Rio de Janeiro, Brazil
Background: Ultrasound therapy is commonly applied to clinical practice. Therapeutic dosages depend on the combination between effective intensity and irradiation time. As the effective intensity is a ratio between the emitted power and effective radiation area (ERA), it is fundamental to know this parameter. Previous works have shown that ultrasound equipment usually present variability on their performance due to poor quality control and a lack of periodic evaluation. So, this scenario may raise doubts about the effectiveness of treatments.
Purpose: To evaluate the relationship between the heated area and estimated ERA on a medium irradiated by an ultrasound equipment (thermochromic test body).
Methods: The thermochromic test body, was developed at the Ultrasound Laboratory of the Biomedical Engineering Program/COPPE/UFRJ/Brazil. It is made of a cylindrical plate of diameter 3.7 cm and height 5.8 mm. It is based on a mixture between the silicon RTV615B with a thermochromic pigment powder
(FORSCHER Colors & Effects/São Paulo/Brazil), which loses the color at 45°C, on the proportion of 0,5% of the total volume, and then it is added to RTV615A.
The experimental set up was composed of: thermochromic test body, 3 ultrasound devices (Avatar III, KLD, SP, Brazil), digital camera (DSC-W730, Sony®) focal distance 4.5 - 36 mm; tripod, computer with an algorithm in Matlab® (Mathworks Inc., Natick, MA) to calculate the heated area. The effective intensity was measured at the laboratory according to IEC 61689 (2013). Irradiation protocol was: continuous mode, 1.0 W.cm-2, 30 seconds. The experiment was repeated 10 times for each transducer, so, 30 thermal images were analyzed.
Results: Devices 1, 2 and 3 had estimated ERAs of 4.67cm2, 4.70 cm2 and 3.58 cm2. Effective intensities were 1.03W.cm-2, 1.03W.cm-2 and 1.02W.cm-2. Average heated area for devices 1, 2 and 3 were: 1.31±0.24 cm2, 1.47±0.22 cm2, 1.01±0.21 cm2. Notice that device 3 that has the smallest ERA produced the smallest heated area, although the effective intensity was the same for the 3 cases. The linear relationship between the ERA and thermal images was y = 0.24x + 0.24 (R2 = 0,83). It was observed that all ERA values were smaller than those specified by the manufacturer (5.0cm2). At 1 MHz and 1,0 W.cm-2 all thermochromic test body became burned and lost their reversibility.
Conclusion(s): Comparison of the thermal images between the ERA of 3 ultrasound devices, with same manufacturer, and same irradiation protocol (1MHz, continuous, 30s, 1W.cm2) produced different heated areas, which suggests that ERA is an important parameter for estimating therapeutic treatment dosages.
Implications: The results suggest that thermochromic test bodies can be used as a first evaluation of the ERA and for monitoring its changes as the devices are used along time.
ix.
Keywords: Ultrasound, Physical therapy, effective radiation area
Funding acknowledgements: CNPq and Faperj.
Purpose: To evaluate the relationship between the heated area and estimated ERA on a medium irradiated by an ultrasound equipment (thermochromic test body).
Methods: The thermochromic test body, was developed at the Ultrasound Laboratory of the Biomedical Engineering Program/COPPE/UFRJ/Brazil. It is made of a cylindrical plate of diameter 3.7 cm and height 5.8 mm. It is based on a mixture between the silicon RTV615B with a thermochromic pigment powder
(FORSCHER Colors & Effects/São Paulo/Brazil), which loses the color at 45°C, on the proportion of 0,5% of the total volume, and then it is added to RTV615A.
The experimental set up was composed of: thermochromic test body, 3 ultrasound devices (Avatar III, KLD, SP, Brazil), digital camera (DSC-W730, Sony®) focal distance 4.5 - 36 mm; tripod, computer with an algorithm in Matlab® (Mathworks Inc., Natick, MA) to calculate the heated area. The effective intensity was measured at the laboratory according to IEC 61689 (2013). Irradiation protocol was: continuous mode, 1.0 W.cm-2, 30 seconds. The experiment was repeated 10 times for each transducer, so, 30 thermal images were analyzed.
Results: Devices 1, 2 and 3 had estimated ERAs of 4.67cm2, 4.70 cm2 and 3.58 cm2. Effective intensities were 1.03W.cm-2, 1.03W.cm-2 and 1.02W.cm-2. Average heated area for devices 1, 2 and 3 were: 1.31±0.24 cm2, 1.47±0.22 cm2, 1.01±0.21 cm2. Notice that device 3 that has the smallest ERA produced the smallest heated area, although the effective intensity was the same for the 3 cases. The linear relationship between the ERA and thermal images was y = 0.24x + 0.24 (R2 = 0,83). It was observed that all ERA values were smaller than those specified by the manufacturer (5.0cm2). At 1 MHz and 1,0 W.cm-2 all thermochromic test body became burned and lost their reversibility.
Conclusion(s): Comparison of the thermal images between the ERA of 3 ultrasound devices, with same manufacturer, and same irradiation protocol (1MHz, continuous, 30s, 1W.cm2) produced different heated areas, which suggests that ERA is an important parameter for estimating therapeutic treatment dosages.
Implications: The results suggest that thermochromic test bodies can be used as a first evaluation of the ERA and for monitoring its changes as the devices are used along time.
ix.
Keywords: Ultrasound, Physical therapy, effective radiation area
Funding acknowledgements: CNPq and Faperj.
Topic: Electrophysical & isothermal agents
Ethics approval required: No
Institution: UFRJ
Ethics committee: not necessary
Reason not required: work has not been performed on animals and humans
All authors, affiliations and abstracts have been published as submitted.
