前田 一雄

Kazuo MAEDA

鳥取大学医学部産科婦人科

Department of Obstetrics and Gynecology, Tottori University School of Medicine

キーワード :

After closure of the group study on the bioeffect of CW ultrasound, research works for pulsed ultrasound were initiated in the group supported by the fund of Japanese Ministry of Health and Welfare in 1977 and lasted till 1979. The group was composed by K. Maeda, M. Ide, S. Sakamoto, M. Suzuki, K. Kurachi, K. Sekiba, T. Shimizu, H. Takeuchi, M. Hogaki and T. Morohashi.
A standard pulsed ultrasound generator, USP-1, was developed by Ide for the experiments in our group studies. Ultrasound frequency was 2 MHz, pulse width 3 to 10 μs, repetition 250 to 1000 Hz. Maximum intensity was 0.5 W/cm² in SATA and 50 to 60 W/cm² in SATP.
Kurachi et al. exposed human lymphocytes to the highest intensity ultrasound of USP-1, but no increase of chromosomal aberration was observed. They also reported no hemolysis nor by SEM detectable shape change of red blood cell after exposures to weak diagnostic nor intense experimental pulsed ultrasound in vitro for 24 hr and 12 hr respectively.
Amniotic origin cultured JTC-3 cell was exposed to intense USP-1 pulsed ultrasound by Maeda et al., and critical level was suspected to be 20 W/cm² in SATP and 240 mW/cm² in SPTA when the growth was evaluated 7 days after the exposure.
Akamatsu et al. reported morphological change and developmental retardation of preimplanted rat embryo after exposure to intense USP-1 ultrasound for 720 min, and the critical point was 600 mW/cm² in SATA with 10 μs pulse width and 1 kHz repetition.
Sakamoto et al. exposed pregnant ICR mouse to 2 MHz pulsed ultrasound with 180 μs pulse width and 150 Hz repetition for 5 min. Fetal anomaly increased after exposure to mean intensity 600 mW/cm² ultrasound.
Suzuki et al. found the increase of fetal C₃H/He mouse anomaly after the exposure to USP-1 ultrasound for 5 min with 5 μs pulse width, 1 kHz repetition and 1.2 W/cm² SPTA. Lower intensity or narrow pulse width produced no increase of anomaly.
Shimizu et al. exposed pregnant Chinese hamster to the highest intensity ultrasound of USP-1, but no increase of fetal anomaly was observed.
In clinical study, Sakamoto et al. found no increase of neonatal anomaly after pulsed ultrasound diagnosis in comparison to the period of no ultrasonic diagnosis and that of the use of Doppler equipments without pulsed ultrasound.
With the purpose to reduce the exposure to pulsed ultrasound, Morohashi et al. reported that the lowest level of diagnostic pulsed ultrasound was theoretically 0.001 W/cm². They also produced a real-time B-mode scanner of which output was as low as 0.01 W/cm² in peak value. Kurachi et al. studied the technique of ultrasonic diagnosis in early pregnancy in order to diagnose a patient with the least exposure to pulsed ultrasound.