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Calorímetro diferencial para estudo do padr?o de aquecimento gerado por feixes ultrass?nicos terapêuticos

DOI: 10.4322/rbeb.2012.035

Keywords: differential calorimeter, ultrasound, heating, physiotherapy.

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Abstract:

the present work describes the project and construction of a differential calorimeter designed to evaluate the heating generated by ultrasound beam in therapeutic levels. the calorimeter consists of two identical aluminum cylindrical chambers (for measurement and reference) filled with biological tissue mimicking material (phantom). each chamber is fitted with six thermocouples type e (0.24 mm diameter) disposed along the wave propagation central axis, between the depths of 10-60 mm, distant 10 mm from each other. the power curve and the value of the effective radiation area (era) of the two transducers were estimated. from these data, the effective intensity was determined. the calorimeter was tested by using an ultrasound equipment of physiotherapy, operating at the frequencies 1 and 3 mhz, continuous mode, nominal intensities 0.5, 1.0, 1.5 and 2.0 w.cm-2 and irradiation time 180 seconds. a sequence of eight protocols of measurement was repeated 10 times. at both frequencies, there was a decline of heating along the depth and the phantom region that heated the most corresponded to 10 mm of depth, in all intensities employed. the greatest increase in temperature occurred after application of 2.0 w.cm-2, with averages of 6.7 ± 1.0 oc and 12.6 ± 1.2 oc, at 1 mhz and 3 mhz, respectively. the proposed calorimeter may be useful for identifying possible local temperature maxima (hot spots) that appear along the central axis beam.

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