| Co-Investigator(Kenkyū-buntansha) |
MIYOSHI Kei Shinshu University, Faculty of Medicine, Assistant, 医学部, 助手 (30293509)
FUJIWARA Takayuji Shinshu University, Faculty of Medicine, Professor, 医学部, 教授 (40181416)
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| Research Abstract |
This series of experiments was conducted to investigate the relationship between frequency, output intensity, duration of exposure and depth of target tissue on increase in temperature in post-mortem pig tissues exposed to therapeutic ultrasound. Prior to the main study, a few procedural pre-studies were conducted, as the results were necessary to formulate the procedure for the main study. The first pre-study was a reliability study to determine the pre and post test reliability of the measurement devices: the infrared spot thermometer (Minolta HT-11) and the infrared video thermography unit (Avio TVS 2000) (unpublished data). The second pre-study examined the effect of varying the speed of the moving transducer (1Hz, 2Hz and 3Hz) on temperature increase. The results showed that there was no difference in temperature increase at all three speeds. However, for practical reasons, 2Hz was the recommended speed for subsequent studies. The next pre-study examined the effect of low and high
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intensities on irreversible thermal injuries in "fresh" post-mortem pig tissues. This qualitative histological study was carried out at 1 and 3 MHz, and eight intensities: 0 (control), 0.5, 1.0, 1.5 w/cm2 (1 and 3MHz) and 2.0 w/cm2 (1MHz). Results showed that the highest intensity (2.0 w/cm2, 1 MHz) was the only intensity that caused irreversible thermal injuries to the epidermis.
The main study was conducted at 2 frequencies (1 and 3MHz), eight intensities (0.1, 0.3, 0.5, 0.7, 0.9, 1.1 and 1.5 w/cm2), for 10 minutes exposure, followed by 10 minutes post-exposure at 6 depths of target tissue (0 or skin surface, and 1, 2, 3, 4 and 5 cm below skin surface). The results showed that a higher frequency, a higher intensity, a higher duration of exposure, and a superficial target site, all contribute to a greater increase in tissue temperature. The results of this study was used to formulate a model to assist clinicians and users of therapeutic ultrasound to determine the most appropriate dosage (based on expected increase in tissue temperature at a specific target site) for the treatment of soft tissue injuries and for hyperthermic treatment of cancer cells. Less
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