Safety Assurance in Obstetrical Ultrasound

Abstract

Safety assurance for diagnostic ultrasound in obstetrics began with a tacit assumption of safety allowed by a federal law enacted in 1976 for then-existing medical ultrasound equipment. The implementation of the 510(k) pre-market approval process for diagnostic ultrasound resulted in the establishment of guideline upper limits for several examination categories in 1985. The obstetrical category has undergone substantial evolution from initial limits (I. e., 46 mW/cm 2 spatial peak temporal average (SPTA) intensity) set in 1985. Thermal and mechanical exposure indices, which are displayed on-screen according to an Output Display Standard (ODS), were developed for safety assurance with relaxed upper limits. In 1992, with the adoption of the ODS, the allowable output for obstetrical ultrasound was increased both in terms of the average exposure (e. g. to a possible 720 mW/cm 2 SPTA intensity) and of the peak exposure (via the Mechanical Index). There has been little or no subsequent research with the modern obstetrical ultrasound machines to systematically assess potential risks to the fetus using either relevant animal models of obstetrical exposure or human epidemiology studies. The assurance of safety for obstetrical ultrasound therefore is supported by three ongoing means: (I) review of a substantial but uncoordinated bioeffect research literature, (ii) the theoretical evaluation of diagnostic ultrasound exposure in terms of thermal and nonthermal mechanisms for bioeffects, and (iii) the skill and knowledge of professional sonographers. At this time, there is no specific reason to suspect that there is any significant health risk to the fetus or mother from exposure to diagnostic ultrasound in obstetrics. This assurance of safety supports the prudent use of diagnostic ultrasound in obstetrics by trained professionals for any medically indicated examination.

New Zealand sonographers do not outperform their European or American colleagues in the knowledge of ultrasound safety

“…Safety considerations in diagnostic ultrasound have been broadly published in numerous science and review papers 3 , 4 , 5 , 6 , 7 . Professional organisations such as the ASUM 8 , 9 , 10 , 11 , 12 , 13 , 14 , American Institute for Ultrasound in Medicine (AIUM) 15 , British Medical Ultrasound Society (BMUS) 16 , 17 and others provide prolific references to the safe use of ultrasound, ALARA and in some cases, recommended TI and MI values 17 .…”

Electroacoustic response of 1-3 piezocomposite transducers for high power applications

“…1. 6 For the generation of high power ultrasound, high electromechanical coupling k ij and mechanical quality factor Q m of piezoelectric transducers are desired, where the high electromechanical coupling factor permits effective energy conversion from electrical energy to mechanical energy, while the high mechanical quality factor reduces heat generation under high power operation. The electroacoustic power efficiency is also improved with increasing vibration velocity (v) of a piezoelectric material, which is related to the acoustic output power, and proportional to the product of electromechanical coupling and mechanical quality factor.…”

Comparison of Angiogenesis in Bone Defect Healing Process due to the Difference in the Frequency of Low-Intensity Pulsed Ultrasound (LIPUS)

“…But, it seems to be difficult to use a higher intensity with 3 Mhz frequency of LIUPS, because intensity of LIPUS is defined as the range of intensity 0.5 to 50 mW/cm 2 . In addition, it was reported 100 mW/cm 2 statement value was the upper limits in the safety statement made by the American Institute of Ultrasound in Medicine (AIUM) 26) . In the case of LIPUS exposure for human extracted socket, these effects need to reach deeper area than this animal model.…”