Ultrasonic imaging: safety considerations

Haar, Gail ter

doi:10.1098/rsfs.2011.0029

Cited by 89 publications

(64 citation statements)

References 96 publications

(98 reference statements)

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“…The thermal effect occurring during USMB administration is an important issue. In general, a temperature rise of 1.0°C -1.5°C over an indefinite time interval is not considered a safety concern for non-obstetric examinations (Ter Haar, 2011;Harris et al, 2016). A previous report showed the following logarithmic relationship between temperature elevation and the exposure time needed to produce adverse biological effects in animal fetuses for temperatures below 43°C: the necessary exposure time was reduced by a factor of four for every 1°C increase in temperature (Miller and Ziskin, 1989).…”

Section: Discussionmentioning

confidence: 99%

Ultrastructural Changes Associated With the Enhanced Permeability of the Round Window Membrane Mediated by Ultrasound Microbubbles

Lin

Chen

et al. 2020

Front. Pharmacol.

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The round window membrane (RWM) is the most common entryway for local drug and gene delivery into the inner ear, but its permeability can change the treatment outcome. We previously demonstrated a feasible and highly efficient approach using ultrasound-aided microbubble (USMB) cavitation to enhance the permeability of the RWM. Here, we investigated the safety of USMB exposure and the association between temporal changes in RWM permeability and ultrastructure. Experimental guinea pigs were divided into two treatment groups: a control group receiving round window soaking (RWS) with MBs and treatment (USM) groups undergoing 3 (USM-3) or 5 (USM-5) consecutive USMB exposures (1 min/exposure) at an acoustic intensity of 3 W/cm 2 and 1 MHz frequency. The trans-RWM delivery efficiency of biotin-fluorescein isothiocyanate conjugates, used as permeability tracers, revealed a greater than 7-fold higher delivery efficiency for the USM groups immediately after 3 or 5 exposures than for the RWS group. After 24 h, the delivery efficiency was 2.4-fold higher for the USM-3 group but was 6.6-fold higher for the USM-5 group (and 3.7-fold higher after 48 h), when compared to the RWS group. Scanning electron microscopy images of the RWM ultrastructure revealed USMB-induced sonoporation effects that could include the formation of heterogeneous pore-like openings with perforation diameters from 100 nm to several micrometers, disruption of the continuity of the outer epithelial surface layer, and loss of microvilli. These ultrastructural features were associated with differential permeability changes that depended on the USMB exposure course. Fourteen days after treatment, the pore-like openings had significantly decreased in number and the epithelial defects were healed either by cell expansion or by repair by newly migrated epithelial cells. The auditory brainstem response recordings of the animals following the 5-exposure USMB treatment indicated no deterioration in the hearing thresholds at a 2-month follow-up and no significant hair cell damage or apoptosis, based on scanning electron microscopy, surface preparations, and TUNEL assays. USMBs therefore appear to be safe and effective for inner ear drug delivery. The mechanism of enhanced permeability may involve a disruption of the continuity of the outer RWM epithelial layer, which controls transmembrane transport of various substances.

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Section: Discussionmentioning

confidence: 99%

Ultrastructural Changes Associated With the Enhanced Permeability of the Round Window Membrane Mediated by Ultrasound Microbubbles

Lin

Chen

et al. 2020

Front. Pharmacol.

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“…Further research to explore potential bioeffects in humans may prove challenging. While some imaging modalities including X‐ray and computed tomography have known harmful effects, there is a strong public perception of the safety of ultrasound scanning, particularly in imaging the fetus; there is also an expectation that multiple scans will be undertaken during pregnancy to check the health of the baby . The alternative of providing all pregnant patients with a magnetic resonance imaging (MRI) scan is problematic as MRI is not recommended for the first trimester and, in addition, would not feasible owing to the higher costs and limited availability of MRI when compared with that of ultrasound …”

Section: Discussionmentioning

confidence: 99%

Safety of ultrasound exposure: Knowledge, attitudes and practices of Australasian sonographers

et al. 2017

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Introduction: While perceived as safe, diagnostic ultrasound has the potential to cause biological effects on the body tissues. The aim of this study was to evaluate knowledge, attitudes and practices of Australasian sonographers on bioeffects and safety of ultrasound scanning.Methods: Focus groups were used to develop a questionnaire to explore knowledge, attitudes and practices of ultrasound safety, which was then distributed to Australasian sonographers. Thematic (focus groups) and descriptive (questionnaires) analyses were undertaken.Results: A 37-item questionnaire addressed knowledge, attitudes and practices of ultrasound safety. In 47 collected responses, sonographers demonstrated good familiarity of thermal index (TI) (79%), mechanical index (MI) (68%) and 'as low as reasonably achievable' (ALARA) principle (85%). However, most sonographers could not accurately define TI (13%) and had poor knowledge of safety guidelines relating to TI (19%) and MI (14%). Over 30% were uncertain about their attitudes to ultrasound safety issues. While 52% 'always' and 30% 'most of the time' adhere to ALARA, 37% of sonographers reported never monitoring TI and MI.Discussion: While familiar with safety terms, knowledge of safety guidelines was lacking. Many sonographers were uncertain about their attitudes to the safety of scans; and safety practices involving monitoring for bioeffects were not a high priority.

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“…Note that nonlinearity with high peak pressure is not captured in our Field II simulation. For clinical translation, it is necessary to have the mechanical index to below 1.9 to meet the FDA approved limit (Haar 2011). The decrease in peak pressure can be compensated for by increasing the duty cycle.…”

Section: Discussionmentioning

confidence: 99%

Multi-Focus Beamforming for Thermal Strain Imaging Using a Single Ultrasound Linear Array Transducer

Nguyen

Ding

Leers

et al. 2017

Ultrasound in Medicine & Biology

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Ultrasound-induced thermal strain imaging (TSI) has been used to successfully identify lipid and water-based tissues in atherosclerotic plaques in some research settings. However, TSI faces several challenges to be realized in clinics. These challenges include motion artifacts, displacement tracking accuracy as well as limited heating capability which contributes to low thermal strain signal-to-noise ratio and a limited field of view. The goal of this paper is to address the challenge in heating tissue in TSI. Current TSI systems use separate heating and imaging transducers, which require physically aligning the heating and imaging beams and result in a bulky setup that limits in vivo operation. This paper proposes and evaluates a new design for heating beams that can be implemented on a linear array imaging transducer and can provide an improved heating area and efficiency as compared to previous implementations. The designed heating beams were implemented with a clinical linear array imaging transducer connected to a research ultrasound platform. In-vitro experiments using tissue mimicking phantoms with no blood flow showed that the new design resulted in an effective heating area of approximately 0.85 cm2 and a 0.3°C temperature rise in 2 seconds of heating, which compared well with in- silico finite element simulations. With the new heating beams, TSI was shown to be able to detect a lipid-mimicking rubber inclusion with a diameter of 1 cm from the water-based gelatin background, with a strain contrast of 2.3 (+0.14% strain in the rubber inclusion and −0.06% strain in the gelatin background). Lastly, lipid-based tissue in a 1-cm diameter human carotid endarterectomy (CEA) sample was identified with good agreement to histology.

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Ultrasonic imaging: safety considerations

Cited by 89 publications

References 96 publications

Ultrastructural Changes Associated With the Enhanced Permeability of the Round Window Membrane Mediated by Ultrasound Microbubbles

Ultrastructural Changes Associated With the Enhanced Permeability of the Round Window Membrane Mediated by Ultrasound Microbubbles

Safety of ultrasound exposure: Knowledge, attitudes and practices of Australasian sonographers

Multi-Focus Beamforming for Thermal Strain Imaging Using a Single Ultrasound Linear Array Transducer

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