Temperature changes caused by the difference in the distance between the ultrasound transducer and bone during 1MHz and 3MHz continuous ultrasound : a phantom study

• Published in: Journal of Physical Therapy Science 2015, Vol.27 (1), p.205-208
• Main Authors: AKIHIKO OHWATASHI, SATOSHI IKEDA, KATSUHIRO HARADA, YURIE KAMIKAWA, AKIRA YOSHIDA, KAZUHIRO INOUE, NOBUHIKO YANAGIDA, KIYOHIRO FUKUDOME, RYOJI KIYAMA, TADASU OHSHIGE, TETSUO MAEDA
• Format: Article
• Language: Japanese
• ISSN: 0915-5287

[Abstract.] [Purpose] This study aimed to use a thermograph to observe temperature changes caused by different distances between an ultrasound transducer and bone during 1MHz and 3MHz continuous ultrasound emission on a phantom. [Materials and Methods] We observed the distribution of temperature elevations on a phantom consisting of pig ribs and tissue-mimicking material. One megahertz and 3MHz ultrasound were delivered at 2.0W/cm2 for 5 minutes. To record the temperature changes on the phantom, we took a screenshot of the thermograph with a digital camera every 20 seconds. [Results] With 1MHz ultrasound at the distances of 2 and 3cm, the temperature elevation near the bone was higher than that near the transducer. However, with 3MHz ultrasound, the temperature elevation was higher near the transducer rather than near the bone. At this point, we consider that there is a possibility of heat injury to internal organs in spite of there being no elevation of skin temperature. [Conclusion] When performing ultrasonic therapy, not only should the frequency be taken into consideration, but also the influence of the absorption coefficient and the reflection of the tissue. We visually confirmed the thermal ultrasound effect by thermography. Special attention to the temperature elevation of the internal organs is necessary to avoid injuries.