The Limitation of the Ultrasound Intensity for Diagnostic Devices in the Japanese Industrial Standards

Abstract

Abstmcr-The limitation of continuous-wave (CW) pulsed ultrasound intensities was discussed in the presentation of the Japanese Industrial Standards (JIS) issued for diagnostic ultrasound devices. The CW ultrasound intensity is limited to 10 mWicm’ in the JIS for ultrasonic Doppler fetal diagnostic devices and for manual scanning B-mode diagnostic equipment. However, the JIS intensity limit for A-mode diagnostic equipment is 100 mW/cmf, because the use of the equipment is restricted to diagnosis of intracranial changes of the adult head and is not used for a pregnant woman nor a fetus. The JIS limits the intensity for M-mode equipment to 40 mW/cm’ or less, and this equipment is used primarily for diagnosis of heart disease. The intensity limit is lowered to the level of B-mode equipment (10 mWlcm’) in the combined use of M- and B-modes. In all cases the intensity specified is the temporal average value, averaged spatially over the transducer face. The limitation of ultrasound intensity in the JIS draft of linear electronic scanning real-time B-mode devices, is similar to that for B-mode equipment. The intensity is measured at a single aperture of every transducer after stopping the electronic scanning. An electronic microbalance method is used in the determination of the ultrasound power and intensity in these standards.