Ultrasound Bioeffects and Clinical Diagnostic Relevance

概要

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During the approximately one-third century that diagnostic ultrasound has been employed, there have been no verified reports of adverse effects. Ultrasound, at sufficient amplitudes, can produce irreversible biological effects by thermal and nonthermal mechanisms. Thermal effects result from the absorption of ultrasound by tissues. Laboratory studies have documented the response of biological systems to temperature elevation. This has led to the conclusion that expected temperature increases of less than 2℃ can be considered innocuous. However, for an expected temperature increase greater than 2℃, the duration of exposure time should be considered. The nonthermal mechanism of cavitation is known to produce tissue disruption during gas body collapse. Laboratory studies and safety considerations have led to a mechanical index (ML) = p/√<f>. For MI less than 1, the likelihood of cavitation occurring is very low, whereas for MI greater than 1, the examination should be considered to pose a risk (though none has ever been reported). Implementation of on-screen displays of estimates of temperature elevation and cavitation likelihood provides the physician the necessary information for conducting low risk examination.
社団法人応用物理学会の論文
1997-05-30