Infrared mapping of ultrasound fields generated by medical transducers: feasibility of determining absolute intensity levelsстатья
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Дата последнего поиска статьи во внешних источниках: 24 октября 2013 г.
Аннотация:In recent years, considerable progress has been achieved in the use of infrared techniques for measuring thermal and acoustic fields of high intensity focused ultrasound (HIFU) transducers. The method is based on infrared camera measurement of the temperature rise induced by low amplitude short ultrasonic bursts in a thin absorber. Here the method is extended to estimate the absolute intensity values of HIFU transducers. The implemented approach correlated the temperature rise measured in an absorber with the use of an IR camera and the pressure distribution measured in water using a hydrophone. The measurements were carried out for two focused HIFU transducers and a flat physiotherapy transducer. Corresponding correction factors between the free field intensity and temperature were obtained and allowed the conversion of temperature images to intensity distributions. The system described in this paper was able to map in good detail focused and unfocused ultrasound fields with millimeter-sized structure and with local time average intensity from below 0.1 W/cm2 to at least 50 W/cm2. Significantly higher intensities could be measured simply by reducing the duty cycle.