Biological effects of ultrasound: development of safety guidelines

Nyborg, Wesley L.

doi:10.1016/s0301-5629(00)00243-x

Cited by 48 publications

(22 citation statements)

References 186 publications

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“…Care should be taken to adjust these parameters for lower exposure. Fetal exposure to ultrasound is limited by the US Food and Drug Administration (FDA) to a maximum spatial peak temporal average intensity of 720 mW/cm and maximum mechanical index of 1.9 (21). British Medical Ultrasound Society handles the thermal effect by means of duration of exposure (22).…”

Section: Discussionmentioning

confidence: 99%

Shear wave elastography of placenta: in vivo quantitation of placental elasticity in preeclampsia

Kılıç¹,

Kayadibi²,

Yüksel³

et al. 2015

Diagn Interv Radiol

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Section: Discussionmentioning

confidence: 99%

Shear wave elastography of placenta: in vivo quantitation of placental elasticity in preeclampsia

Kılıç¹,

Kayadibi²,

Yüksel³

et al. 2015

Diagn Interv Radiol

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“…The MI was limited to 1.9, which was found for a 2.25 MHz pre-enactment transducer. [23] Thus, the net effect of the 1992 change in guideline limits was to increase the SPTA intensity allowed for obstetrical ultrasound from 94 mW/cm 2 to 720 mW/cm 2 (the values of the TI are not limited specifically). The allowed pulse parameter values also increased.…”

Section: Physical Mechanisms and Adverse Bioeffectsmentioning

confidence: 99%

Safety Assurance in Obstetrical Ultrasound

Miller

2008

Seminars in Ultrasound, CT and MRI

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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.

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“…The main mechanism for increased release is thought to be related to acoustic cavitation, which is the formation and/or activity of gas-or vapour-filled bubbles in the medium exposed to ultrasound (Larina et al 2005). Such bubbles can collapse violently and disrupt the structure of the particles, because of the very high shear stresses in the region of the collapse, the shock wave produced by the collapse and/or the emission of a high-speed liquid jet from the bubble towards the particle surface (Nyborg 2001). There may also be chemical effects owing to free radicals produced by the high temperatures reached inside the bubble during collapse (Mornstein 1997).…”

Section: In Vitro Releasementioning

confidence: 99%

One-step electrohydrodynamic production of drug-loaded micro- and nanoparticles

Enayati

Ahmad

Stride

et al. 2009

J. R. Soc. Interface.

100

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The objective of this work was to produce drug-loaded nanometre-and micrometre-scale particles using a single-step process that provides control over particle size and size distribution. Co-axial electrohydrodynamic processing was used, at ambient temperature and pressure, with poly(lactic-co-glycolic acid) as the polymeric coating material and oestradiol as the encapsulated drug. The particle diameter was varied from less than 120 nm to a few micrometres, by simple methodical adjustments in the processing parameters ( polymer concentration and applied voltage). In vitro studies were performed to determine the drug release profile from the particles during unassisted and ultrasound-stimulated degradation in simulated body fluid. An encapsulation efficiency of approximately 70% was achieved and release of the drug was sustained for a period of over 20 days. Exposing the particles to ultrasound (22.5 kHz) increased the rate of release by approximately 8 per cent. This processing method offers several advantages over conventional emulsification techniques for the preparation of drug-loaded particles. Most significantly, process efficiency and the drug's functionality are preserved, as complex multistep processing involving harsh solvents, other additives and elevated temperatures or pressures are avoided. Production rates of 10 12 particles min 21 can be achieved with a single pair of co-axial needles and the process is amenable to being scaled up by using multiple sets.

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Biological effects of ultrasound: development of safety guidelines

Cited by 48 publications

References 186 publications

Shear wave elastography of placenta: in vivo quantitation of placental elasticity in preeclampsia

Shear wave elastography of placenta: in vivo quantitation of placental elasticity in preeclampsia

Safety Assurance in Obstetrical Ultrasound

One-step electrohydrodynamic production of drug-loaded micro- and nanoparticles

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