engleski

Using a thermochromic material for testing of physiotherapy ultrasound treatment heads and determination of ultrasound beam quality parameters

Although application of ultrasound in medicine is considered as safe technique it is well known that propagation of ultrasound within tissue produces thermal and nonthermal (mechanical) effects. Those effects are used in physiotherapy to achieve clinical outcomes such as raising tissue temperature, stimulation of bone repair, modifying cellular activities, and decreasing pain. The clinical effects of the ultrasound depend on applied dose. If the acoustic dose is too low there will be no significant clinical effects and if it is too large it can cause tissue injury. Therefore, quality assurance of ultrasonic devices used in medical applications is very important, in order to assure safe application and to prevent patient damage. In this work a non–standardized method was used for quality assurance of ultrasound physiotherapy beams. The method is developed at the National Physical Laboratory (UK) [1] and later is proved to be suitable as a characterisation tool appropriate for use in hospital environment [2]. It consists of exposing the thermochromic tile to the ultrasonic beam thereby forming a thermal image of the intensity profile of transducer. The image is then photographed and analysed in order to determine effective radiating area (ERA) and beam nonuniformity ratio (BNR) for ultrasound physiotherapy transducers. The ERA and BNR were determined for nine clinically used treatment heads with frequencies in the range from 1 MHz to 3.3 MHz, and intensities range from 1 W/cm2 to 2 W/cm2. They were electrically driven with their respective physiotherapy systems, in a way that they would be used in clinical practice. Our results show that proposed method can be used to estimate the effective radiating area (ERA) and to distinguish highly non - uniform ultrasound beams with high value of BNR [3]. Using the theoretical prediction described by W. L. Nyborg [4] we have calculated the expected temperature rise in the thermochromic material.

quality assurance, ultrasound, physiotherapy, effective radiating area (ERA), beam nonuniformity ratio (BNR)

nije evidentirano