Search

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and green approach to synthesizing reduced graphene oxide with ellagic acid (rGO-EA). To investigate the application of a graphene derivative in ultrasound contrast agents, rGO-EA was dispersed in saline solution and mixed with SonoVue (SV) to fabricate SV@rGO-EA microbubbles. To determine the properties of the product, analyses were performed, including ultraviolet–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectrum (XPS), X-ray diffraction analysis (XRD) and zeta potential analysis. Additionally, cell viability measurements and a hemolysis assay were conducted for a biosafety evaluation. SV@rGO-EA microbubbles were scanned at various mechanical index values to obtain the B-mode and contrast-enhanced ultrasound (CEUS) mode images in vitro. SV@rGO-EA microbubbles were administered to SD rats, and their livers and kidneys were imaged in CEUS and B-mode. The absorption of rGO-EA resulted in an enhanced echo intensity and mechanical index tolerance of SV@rGO-EA, surpassing the performance of SV microbubbles both in vitro and in vivo. This work exhibited the application potential of graphene derivatives in the field of ultrasound precision medicine. [ABSTRACT FROM AUTHOR]

Objectives: Lung ultrasound (LUS) is a powerful and accessible clinical tool for pulmonary diagnosis, but risk of pulmonary capillary hemorrhage (PCH) presents a safety issue. The dependence of PCH in a rat model of LUS was evaluated for image frames‐per‐second (fps) and associated on‐screen Mechanical Index (MIOS) and Thermal Index (TI). Methods: A Philips iE33 machine with L15‐7io probe was used to scan anesthetized rats in a warmed water bath. B mode was applied at 9 MHz with settings of 34, 61 and 118 fps. After 2 minutes of exposure at an MIOS setting, samples were obtained for assessment of PCH areas on the lung surface. Ultrasound parameters were measured to determine the in situ MIIS at the lung surface. Results: The PCH trend counter‐intuitively decreased with increasing fps, with areas of 19.5 mm2 for 34 fps (MIOS = 1.0, TI = 0.8, 4080 images), 9.6 mm2 at 61 fps (MIOS = 1.0, TI = 0.5, 7320 images) and 7.5 mm2 at 118 fps (MIOS = 1.1, TI = 0.4, 14,160 images). The PCH was not significantly different for 34 fps (TI = 0.5, MIOS = 0.8) (10.7 mm2), compared to 61 and 118 fps, above, indicating some value for the TI as a predictive indicator of PCH. MIIS thresholds were 0.42, 0.46, and 0.49 for 34, 61 and 118 fps, respectively. Conclusions: The increase in PCH at low fps was associated with delivering more relatively high amplitude grazing pulse exposures during slower image scans. No significant PCH was found for the MIOS setting of 0.5, corresponding to in MIIS values of 0.35–0.39. [ABSTRACT FROM AUTHOR]

Intravenous microbubble oscillation in the presence of ultrasound has the potential to yield a wide range of therapeutic benefits. However, the likelihood of vessel damage caused by mechanical effects has not been quantified as a function of the numerous important parameters in therapeutic ultrasound procedures. In this study, we examined the effects of microbubbles injected into the vasculature of the earthworm. It was found that the elastic properties of earthworm blood vessels are similar to those of arteries in older humans, and that earthworms are well suited to the large number of experiments necessary to investigate safety of procedures involving microbubble oscillation in sonicated vessels. Microbubbles were infused into earthworm vessels, and the rupture time during sonication was recorded as a function of ultrasound frequency, pulse repetition frequency and acoustic pressure. A modified mechanical index (MMI) was defined that successfully captured the trends in rupture probability and rupture time for the different parameter values, creating a database of vessel rupture thresholds. In the absence of bubbles, the product of MMI squared and rupture time was approximately constant, indicating a possible radiation-force effect. The MMI was an effective correlating parameter in the presence of bubbles, though the mathematical dependence is not yet apparent. The results of the study are expected to be valuable in designing more refined studies in vertebrate models, as well as informing computational models. [ABSTRACT FROM AUTHOR]

Purpose: The safety of acoustic radiation force impulse (ARFI) elastography, which applies higher acoustic power with a longer pulse duration (PD) than conventional diagnostic ultrasound, is yet to be verified. We assessed the ARFI-induced lung injury risk and its relationship with peak rarefactional pressure amplitude (PRPA) and mechanical index (MI). Methods: Eighteen and two rabbits were included in the ARFI (0.3-ms push pulses) and sham groups, respectively. A 5.2-MHz linear probe was applied to the subcostal area and aimed at both lungs through the liver for 30 ARFI emissions. The derated PRPA varied among the six ARFI groups—0.80 MPa, 1.13 MPa, 1.33 MPa, 1.70 MPa, 1.91 MPa, and 2.00 MPa, respectively. Results: The occurrence of lung hemorrhage and the mean lesion area among all samples in the seven groups were 0/6, 0/6, 1/6 (1.7 mm2), 4/6 (8.0 mm2), 4/6 (11.2 mm2), 5/6 (23.8 mm2), and 0/4 (sham), respectively. Logistic regression analysis showed that derated PRPA was significantly associated with lung injury occurrence (odds ratio: 207, p < 0.01), with the threshold estimated to be 1.1 MPa (MI, 0.5). Spearman's rank correlation showed a positive correlation between derated PRPA and lesion area (r = 0.671, p < 0.01). Conclusion: This study demonstrated that the occurrence and severity of ARFI-induced lung hemorrhage increased with a rise in PRPA under clinical conditions in rabbits. This indicates a potential risk of lung injury due to ARFI elastography, especially when ARFI is unintentionally directed to the lungs during liver, heart, or breast examinations. [ABSTRACT FROM AUTHOR]

In the context of ultrasonic hepatic shear wave elasticity imaging (SWEI), measurement success has been determined to increase when using elevated acoustic output pressures. As SWEI sequences consist of two distinct operations (pushing and tracking), acquisition failures could be attributed to (i) insufficient acoustic radiation force generation resulting in inadequate shear wave amplitude and/or (ii) distorted ultrasonic tissue motion tracking. In the study described here, an opposing window experimental setup that isolated body wall effects separately between the push and track SWEI operations was implemented. A commonly employed commercial track configuration was used, harmonic multiple-track-location SWEI. The effects of imaging through body walls on the pushing and tracking operations of SWEI as a function of mechanical index (MI), spanning 5 different push beam MIs and 10 track beam MIs, were independently assessed using porcine body walls. Shear wave speed yield was found to increase with both increasing push and track MI. Although not consistent across all samples, measurements in a subset of body walls were found to be signal limited during tracking and to increase yield by up to 35% when increasing electronic signal-to-noise ratio by increasing harmonic track transmit pressure. [ABSTRACT FROM AUTHOR]

There is an urgent need to realize precise clinical ultrasound with ultrasound contrast agents that provide high echo intensity and mechanical index tolerance. Graphene derivatives possess exceptional characteristics, exhibiting great potential in fabricating ideal ultrasound contrast agents. Herein, we reported a facile and green approach to synthesizing reduced graphene oxide with ellagic acid (rGO-EA). To investigate the application of a graphene derivative in ultrasound contrast agents, rGO-EA was dispersed in saline solution and mixed with SonoVue (SV) to fabricate SV@rGO-EA microbubbles. To determine the properties of the product, analyses were performed, including ultraviolet–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectrum (XPS), X-ray diffraction analysis (XRD) and zeta potential analysis. Additionally, cell viability measurements and a hemolysis assay were conducted for a biosafety evaluation. SV@rGO-EA microbubbles were scanned at various mechanical index values to obtain the B-mode and contrast-enhanced ultrasound (CEUS) mode images in vitro. SV@rGO-EA microbubbles were administered to SD rats, and their livers and kidneys were imaged in CEUS and B-mode. The absorption of rGO-EA resulted in an enhanced echo intensity and mechanical index tolerance of SV@rGO-EA, surpassing the performance of SV microbubbles both in vitro and in vivo. This work exhibited the application potential of graphene derivatives in the field of ultrasound precision medicine.

Objective: Focused ultrasound (FUS) combined with microbubble-mediated blood-brain barrier (BBB) opening (FUS-BBBO) is not only a promising technique for clinical applications but also a powerful tool for preclinical research. However, existing FUS devices for preclinical research are expensive, bulky, and lack the precision needed for small animal research, which limits the broad adoption of this promising technique by the research community. Our objective was to design and fabricate an affordable, easy-to-use, high-precision FUS device for small animal research. Methods: We designed and fabricated in-house mini-FUS transducers (∼$80 each in material cost) with three frequencies (1.5, 3.0, and 6.0 MHz) and integrated them with a stereotactic frame for precise mouse brain targeting using established stereotactic procedures. The BBB opening volume by FUS at different acoustic pressures (0.20–0.57 MPa) was quantified using T1-weighted contrast-enhanced magnetic resonance imaging of gadolinium leakage and fluorescence imaging of Evans blue extravasation. Results: The targeting accuracy of the device as measured by the offset between the desired target location and the centroid of BBBO was 0.63 ± 0.19 mm. The spatial precision of the device in targeting individual brain structures was improved by the use of higher frequency FUS transducers. The BBB opening volume had high linear correlations with the cavitation index (defined by the ratio between acoustic pressure and frequency) and mechanical index (defined by the ratio between acoustic pressure and the square root of frequency). The correlation coefficient of the cavitation index was slightly higher than that of the mechanical index. Conclusion: This study demonstrated that spatially accurate and precise BBB opening was achievable using an affordable and easy-to-use FUS device. The BBB opening volume was tunable by modulating the cavitation index. This device is expected to decrease the barriers to the adoption of the FUS-BBBO technique by the broad research community. [ABSTRACT FROM AUTHOR]

Nano-silica sol was used to modify the recycled brick-concrete mixed aggregate, and then they were used to prepare recycled concrete. The variation of mechanical index was analyzed with the age of recycled concrete. The quantitative relationships between different mechanical indicators were established. SEM images were used to explore the modification mechanism of nano-silica sol. The results showed that the compressive strength of the cubes, splitting tensile strength, flexural strength, and axial compressive strength of the 28-day nano-recycled concrete increased by 13.3%, 4.3%, 2.1% and 19.4%, compared with those of the recycled concrete, respectively. A good correlation between mechanical indices of nano-recycled concrete, the splitting tensile strength and flexural strength are in line with power function. The axial compressive strength and cubic compressive strength are in line with linear function, and the ratio between axial compressive strength and cubic compressive strength is closer to the ordinary concrete. [ABSTRACT FROM AUTHOR]

The aim of the study was to explore the optimal mechanical indexes (MIs) for low-intensity ultrasound (LIUS) combined with microbubbles to enhance tumor blood perfusion and improve drug concentration in pancreatic cancer-bearing nude mice. Fifty-four nude mice bearing bilateral pancreatic tumors on the hind legs were randomly divided into three groups (the MI was set at 0.3, 0.7 and 1.1 in groups A, B and C, respectively). Five nude mice in each group were intravenously injected with the fluorescent dye DiR iodide (DiIC18(7),1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide); for each mouse, one tumor was treated with LIUS combined with microbubbles, and the contralateral tumor was exposed to sham ultrasound. In vivo fluorescence imaging was performed to detect the enrichment of intratumoral DiR iodide. Twelve mice in each group were intravenously injected with doxorubicin (DOX) and underwent ultrasound therapy as described above. Tumor blood perfusion changes were quantitatively evaluated with pre- and post-treatment contrast-enhanced ultrasound (CEUS, MI = 0.08). One hour after the post-treatment CEUS, nude mice were sacrificed to determine the DOX concentration in tumor tissue; one mouse in each group was sacrificed after ultrasound treatment for tumor hematoxylin-eosin staining examination. CEUS quantitative analysis and in vivo fluorescence images confirmed that LIUS at MI = 0.3 combined with microbubbles was able to enhance tumor blood flow and increase regional fluorescence dye DiR iodide concentration. The DOX concentration on the therapeutic side was significantly higher than that on the control side after ultrasound-stimulated (MI = 0.3) microbubble cavitation (USMC) treatment (1.45 ± 0.53 μg/g vs. 1.07 ± 0.46 μg/g, t = -5.163, p = 0.001). However, in groups B and C, there were no significant differences in DOX concentration between the therapeutic and control sides (Z = -0.297, -0.357, p = 0.766, 0.721). No hemorrhage or other tissue damage was observed in hematoxylin-eosin-stained tumor specimens of both sides in all groups. LIUS at MI = 0.3 combined with microbubbles was able to enhance tumor blood perfusion and improve local drug concentration in nude mice bearing pancreatic cancer. [ABSTRACT FROM AUTHOR]

Purpose of Review: High mechanical index impulses from a diagnostic transducer are utilized in myocardial perfusion imaging, but can also be utilized therapeutically in three cardiovascular applications: (a) thrombus dissolution (sonothrombolysis), (b) improving microvascular flow in ischemic territories (sonoperfusion), and (c) targeted drug and nucleic acid delivery. The targeted therapeutic effect appears to be based on acoustic cavitation of the intravascular microbubbles which results in endothelial shear and pore formation, as well as mechanical destruction of thrombi. Recent Findings: Within the last 5 years, clinical trials have been performed in acute myocardial infarction demonstrating successful reductions in myocardial infarct size with sonothrombolysis added to current guideline-based treatment. In patients with severe peripheral arterial disease, brief improvements in calf microvascular blood flow have been observed for 1 h after 10 min of sonoperfusion therapy. Summary: Targeted ultrasound therapies are developing for prevention of microvascular obstruction in acute coronary syndromes and peripheral vascular disease. [ABSTRACT FROM AUTHOR]

Microbubbles (MBs) are 1 to 10 µm gas particles stabilized by an amphiphilic shell capable of responding to biomedical ultrasound with strong acoustic signals, allowing them to be commonly used in ultrasound imaging and therapy. The composition of both the shell and the core determines their stability and acoustic properties. While there has been extensive characterization of the dissolution, oscillation, cavitation, collapse and therefore, ultrasound contrast of MBs under static conditions, few reports have examined such behavior under hydrodynamic flow. In this study, we evaluate the interplay of ultrasound parameters (five different mechanical indices [MIs]), MB shell parameter (shell stiffness), type of gas (perfluorocarbon for diagnostic imaging and xenon as a therapeutic gas), and a flow parameter (flow rate) on the ultrasound signal of phospholipid-stabilized MBs flowing through a latex tube embedded in a tissue-mimicking phantom. We find that the contrast gradient (CG), a metric of the rate of decay of contrast along the length of the tube, and the contrast peak (CP), the location where the maximum contrast is reached, depend on the conditions of flow, imaging, and MB material. For instance, while the contrast near the flow inlet of the field of view is highest for a softer shell (dipalmitoylphosphatidylcholine [DPPC], C16) than for stiffer shells (distearoylphosphatidylcholine [DSPC], C18, and dibehenoylphosphatidylcholine [DBPC], C22), the contrast decay is also faster; stiffer shells provide more resistance and hence lead to slower MB dissolution/destruction. At higher flow rates, the CG is low for a fixed length of time because each MB is exposed to ultrasound for a shorter period. The CG becomes high for low flow rates, especially at high incident pressures (high MI), causing more MB destruction closer to the inlet of the field of view. Also, the CP shifts toward the inlet at low flow rates, high MIs, and low shell stiffness. We also report the first demonstration of sustained ultrasound flow imaging of a water-soluble, therapeutic gas MB (xenon). We find that an increased MB concentration is necessary for obtaining the same signal magnitude for xenon MBs. In summary, this study builds a framework depicting how multiple variables simultaneously affect the evolution of MB ultrasound contrast under flow. Depending on the MB composition, imaging conditions, transducer positioning, and image processing, building on such a framework could potentially allow for extraction of additional diagnostic information than is commonly analyzed for physiological flow. [ABSTRACT FROM AUTHOR]

The quality of contrast‐enhanced ultrasound (CEUS) imaging performed with high‐frequency convex and linear transducers is often suboptimal. A common solution to improving the microbubble signal is by increasing the volume of the ultrasound contrast agent being administered. An alternative technique to improve the signal from the contrast agent is to adjust the mechanical index (MI). This study aimed to compare the manufacturer's default MI to an optimal MI (as determined by the best contrast‐to‐tissue ratio) for improving the CEUS image quality using linear and convex transducers. This study found that in most cases, the default CEUS MI setting by the manufacturer is often suboptimal, and increasing the MI is necessary to improve the contrast‐to‐tissue ratio and image quality. The MI can be modified by the clinician during the study to improve the quality of the clinical CEUS examination. [ABSTRACT FROM AUTHOR]

Objective: Although epidemiological studies have failed to show the harmful effects of ultrasound in humans, as a form of energy, ultrasound has the potential to cause bio‐effects in tissues. Therefore, clinical guidelines have been established for ultrasound technology related to human safety, which include Thermal (TI) and mechanical (MI) indices. The appropriate TI and MI ranges for embryonic examinations are between 0–1.0 and 0–0.4, respectively. The accepted TI and MI ranges are 0–2.0 and 0–1.9, respectively, for general ultrasound examinations. In addition, the scan duration should be kept as low as possible. Therefore, the present study aimed at evaluating the scan duration, TI, and MI as measures of acoustic output during ultrasound studies. Methods: A cross‐sectional descriptive study was conducted for patients undergoing pregnancy checkups, routine checkups, and initial diagnosis ultrasound examinations. Samples were selected from imaging departments of 4 educational hospitals based on convenience sampling and 321 checklists completed by direct observation of ultrasound examinations. Results: For pregnancy scans, the mean TI and MI were obtained as 0.32 ± 0.27 and 1.15 ± 0.13, respectively. For non‐pregnancy examinations, the mean value of TI and MI were 0.30 ± 0.29 and 1.07 ± 0.35, respectively. Therefore, mean TI for pregnancy and non‐pregnancy examinations and mean MI for non‐pregnancy studies obtained lower than the permitted values, while the mean MI was higher than the permitted level for first trimester of pregnancy. Also, relatively suitable scan durations were seen in reviewed studies. Conclusion: From this study, it may be concluded that the reported ultrasound scans were safe. [ABSTRACT FROM AUTHOR]

Microbial induced calcite precipitation is a new aeolian sand fixation technology, which has more significant advantages over traditional technology. To investigate the effect of chemical treatment on bio-cementation of aeolian sand, the experiment of calcium carbonate deposit generated by microbial induced calcite precipitation and the experiment of sand fixation by microbial induced calcite precipitation were firstly carried out to study the effects of different treatment methods on calcium carbonate yield. Then, the changes of mechanical strength and shear strength indexes of aeolian sand were compared through direct shear test. Finally, the sand fixation effects under different chemical treatment methods were analyzed by means of particle size analysis and microscopic morphology observation. The results show that microbial induced calcite precipitation can effectively improve the mechanical properties of aeolian sand. When the concentration of treatment solution is 0.9 moVL, the improvement of mechanical strength is the most significant, and the corresponding shear strength index changes are also the most obvious. The microorganism corresponding to 0.6 moVL treatment solution has the highest rate of mineral production, and the continuous increase of calcium ion concentration will not be conducive to the improvement of mineral deposition efficiency. Calcium carbonate minerals will adhere to the surface of aeolian sand treated by microorganism-induced mineralization, so the particle size change of aeolian sand can be taken as an index reflecting mineralization. [ABSTRACT FROM AUTHOR]

Tissue harmonic signal quality has been shown to improve with elevated acoustic pressure. The peak rarefaction pressure (PRP) for a given transmit, however, is limited by the Food and Drug Administration guidelines for mechanical index. We have previously demonstrated that the mechanical index overestimates in situ PRP for tightly focused beams in vivo, due primarily to phase aberration. In this study, we evaluate two spatial coherence-based image quality metrics-short-lag spatial coherence and harmonic short-lag spatial coherence-as proxy estimates for phase aberration and assess their correlation with in situ PRP in simulations and experiments when imaging through abdominal body walls. We demonstrate strong correlation between both spatial coherence-based metrics and in situ PRP (R2 = 0.77 for harmonic short-lag spatial coherence, R2 = 0.67 for short-lag spatial coherence), an observation that could be leveraged in the future for patient-specific selection of acoustic output. [ABSTRACT FROM AUTHOR]

In this study, 3-D non-linear ultrasound simulations and experimental measurements were used to estimate the range of in situ pressures that can occur during transcutaneous abdominal imaging and to identify the sources of error when estimating in situ peak rarefaction pressures (PRPs) using linear derating, as specified by the mechanical index (MI) guideline. Using simulations, it was found that, for a large transmit aperture (F/1.5), MI consistently over-estimated in situ PRP by 20%-48% primarily owing to phase aberration. For a medium transmit aperture (F/3), the MI accurately estimated the in situ PRP to within 8%. For a small transmit aperture (F/5), MI consistently underestimated the in situ PRP by 32%-50%, with peak locations occurring 1-2 cm before the focal depth, often within the body wall itself. The large variability across body wall samples and focal configurations demonstrates the limitations of the simplified linear derating scheme. The results suggest that patient-specific in situ PRP estimation would allow for increases in transmit pressures, particularly for tightly focused beams, to improve diagnostic image quality while ensuring patient safety. [ABSTRACT FROM AUTHOR]

Objectives: The mechanical index has long been one of the main criteria used to assess the safety limits for therapeutic medical applications. However, the safety of the mechanical index parameter is considered to be unknown in male fertility, which has a very significant role in vitro conditions. In this study, the effect of cavitation interactions due to mechanical index regions was evaluated on spermatogonial stem cells. Methods: The acoustic pressure and mechanical index equations at the low intensities and the intended frequency were modeled and solved. The mechanical index average of 40 kHz frequency was selected as subthreshold, 0.70, and above the cavitation threshold. Neonatal spermatogonial stem cells were cultured. Spermatogonial stem cells are stimulated by low‐level ultrasound for 5 days and colonization and viability evaluated on the seventh day. Results: Based on modeling, the mechanical index average was chosen as 0.40, 0.51, 0.75, and 0.89. The mechanical index of 0.40 and 0.89 resulted in a number of colonies of 93 ± 4 and 32 ± 4, respectively. An increase in colony diameter could be observed for a 0.40 mechanical index during all days of the culture that in the culture on the seventh day had the largest average colony diameter of 174.05 ± 1.22 μm in comparison with other groups (p < 0.05). The cell viability was not significantly different among the groups. Conclusion: The results suggest that a low‐intensity ultrasound of 40 kHz with a 0.40 mechanical index can be effective in increasing the proliferation and colonization of spermatogonia in stem cells during culture. [ABSTRACT FROM AUTHOR]

The principle of cotton fiber creep recovery and stress relaxation based on viscoelasticity was studied. The constitutive model for cotton fiber creep and stress relaxation was established. The creep value and variation of cotton fibers were tested under different compressive load. The results showed that the creep and stress relaxation of cotton fibers represented nonlinear viscoelasticity. The mechanical behaviors like creep recovery and stress relaxation for cotton fibers were well evaluated by nonlinear viscoelasticity model. In the scope of the study, by adding more load, the creep recovery value of cotton fibers was increased and the creep recovery mechanical index was enlarged. As the strain value of cotton fibers increase, the mechanical index of stress relaxation was enlarged. [ABSTRACT FROM AUTHOR]

L'échographie de contraste pour analyse de la perfusion myocardique est une technique ancienne, qui arrive à maturité grâce un profil de sécurité satisfaisant des produits de contraste échographiques et l'avancée technologique des échographes. L'utilisation au cours d'un test d'ischémie est réalisable par des équipes expérimentées. L'utilisation de la perfusion, à l'aide d'index mécanique très bas, est en revanche plus simple pour le dépistage d'un thrombus apical, l'évaluation de la viabilité, la caractérisation des tumeurs intracardiaques, et les syndromes coronariens aigus pour lesquels l'électrocardiogramme n'est pas informatif. Dans ces situations, l'échographie contraste est un examen largement disponible qui permet de recueillir des informations importantes, au lit du patient. Myocardial perfusion assessment with contrast echocardiography has been studied for more than 25 years. It is a feasible and safe technique. Rather it has an additional value in pharmacologic stress test remains unclear. However, with adequate settings (using both low and very low mechanical index), perfusion analysis can be very useful for the diagnosis of apical thrombus or tumor, viability assessment, and acute coronary syndrome with non-informative ECG. [ABSTRACT FROM AUTHOR]

This review article combines the reports on the biophysical effects in ultrasonography and provides the rationale behind the mechanical index (MI) and thermal index (TI) complying with the Output Display Standard (ODS). Safe ultrasonic doses are determined according to specific rules, and the screen displays the associated quantities MI and TI. The introduced indices MI and TI take into account the physical mechanism of interaction between ultrasounds and biological tissue, which depends on the temporal and spatial parameters of the acoustic field generated by ultrasound transducers. The predicted temperature increase is determined using three different tissue models: homogeneous, layered and bone/tissue interface. [ABSTRACT FROM AUTHOR]

Potential ultrasound exposure safety issues are reviewed, with guidance for prudent use of point‐of‐care ultrasound (POCUS). Safety assurance begins with the training of POCUS practitioners in the generation and interpretation of diagnostically valid and clinically relevant images. Sonographers themselves should minimize patient exposure in accordance with the as‐low‐as‐reasonably‐achievable principle, particularly for the safety of the eye, lung, and fetus. This practice entails the reduction of output indices or the exposure duration, consistent with the acquisition of diagnostically definitive images. Informed adoption of POCUS worldwide promises a reduction of ionizing radiation risks, enhanced cost‐effectiveness, and prompt diagnoses for optimal patient care. [ABSTRACT FROM AUTHOR]

Background: Diagnostic ultrasound is generally considered as a safe test in pregnancy. To date there is no evidence that ultrasound has caused harm to the developing foetus. However, with the number of obstetric scans on the rise and the steep increase in acoustic output achieved by modern machines, the lack of evidence of absolute safety remains a concern. Acoustic output is under the direct control of the operator and is therefore the operator's responsibility to keep the intensity as low as reasonably achievable. A situation analysis in the South African context was deemed necessary to determine end user knowledge and opinions on safe antenatal ultrasound practice. Aim: The aim of this quantitative descriptive, cross-sectional study was to evaluate the knowledge and practice of health practitioners who perform antenatal scans regarding safety aspects of diagnostic ultrasound. Setting: A self-administered questionnaire was distributed at two national congresses, hosted by the South African Society of Ultrasound and Obstetrics (SASUOG) and South African Society of Obstetricians (SASOG) committees. Method: Quota non-probability sampling allowed for the identification of professional categories capable of providing information relevant to the study objectives. The sample represented a population with experience in obstetric ultrasound. Results: Compared to international studies, South African end users demonstrated better knowledge of safety indices than their international counterparts. It is, however, discouraging that end users still demonstrate insufficient knowledge regarding factors contributing to adverse biological effects. Conclusion: With room for improvement, an effort should be made to comply with international standards through increased training efforts and raising awareness. [ABSTRACT FROM AUTHOR]

The occurrence of the pulmonary capillary hemorrhage (PCH) bioeffect of diagnostic ultrasound in rats was investigated for a SuperSonic Imagine shear wave elastography system (Aixplorer, Supersonic Imagine, Aix-en-Provence, France). The elastography imaging repeated at 1 Hz and consisted of widely spaced B-mode image pulses, supersonic push (SSP) pulses and shear wave imaging (SWI) pulses. Groups of rats anesthetized with ketamine and xylazine, or with ketamine only, were imaged on their right side in a warm water bath for one frame, 30 s and 300 s. The image focus and region of interest were adjusted to give exposure only with the background B-mode imaging, or primarily with the SSP and SWI pulses. A sham group had only low power aiming scans. The lungs were removed 5 min after exposure and evaluated for PCH area and volume. The B mode was notably ineffective and produced significant PCH only at the maximum 0 dB output. The SSP pulses together with the SWI pulses produced significant PCH for 300 s, 30 s and even single image exposures. Peak rarefactional pressure amplitude PCH thresholds for 300 s exposure were the same with or without the B-mode pulses at 1.5 MPa (in situ mechanical index, MIIS = 0.67). A 30 s duration resulted in a slightly increased threshold of 1.7 MPa (MIIS = 0.76). The omission of xylazine from the anesthetic, which reduces the sensitivity of rat lung to PCH occurrence, resulted in an increased threshold of 2.1 MPa (MIIS = 0.94). The unique SSP pulses were much more effective than the B mode, but thresholds were comparable to previous results with other diagnostic ultrasound modes on other systems. [ABSTRACT FROM AUTHOR]

Objectives: Diagnostic ultrasound (DUS) imaging can induce pulmonary capillary hemorrhage (PCH), possibly related to the ultrasonic radiation surface pressure arising from reflection at the lung blood‐air interfaces. Acoustic radiation force impulse (ARFI) elastography is a relatively new DUS mode with high‐energy "push pulses" used to move tissue and generate shear waves. The objective of this study was to characterize PCH induced by the ARFI elastographic mode for comparison with other previously tested DUS modes. Methods: Pulmonary capillary hemorrhage induction was examined for ARFI elastographic frames with 5.7‐MHz push pulses (Acuson S3000; Siemens Medical Solutions, Mountain View, CA), which had a derated PRPA of 2.6 MPa. Groups of rats with tracheal tube placement had no ventilation (spontaneous breathing), intermittent positive pressure ventilation (IPPV), or IPPV plus 8 cm H2O of positive end‐expiratory pressure (PEEP). Exposure was to 1 or 20 manually triggered image frame acquisitions. The PCH area was measured on the lung surface. Results: All 20‐frame exposure groups, and even the single‐frame group, had significant PCH relative to shams. Single‐frame exposures produced significantly less PCH (P = .002) than 20‐frame exposures in rats with a tracheal tube only (spontaneous breathing). The PEEP inhibited the PCH and produced about half of the PCH area induced for IPPV without PEEP (P = .014). Conclusions: The PCH results were comparable with those from a previous study using B‐mode or color Doppler exposure for 5 minutes; however, these modes delivered many more pulses for continuous imaging frames, suggesting that the ARFI elastographic frames were individually much more effective. [ABSTRACT FROM AUTHOR]

The immediate release of chemotherapeutics at the target site, along with no premature release in circulation is always challenging. The purpose of this study was to develop a stimuli responsive drug delivery system, composed of lipid supported mesoporous silica nanoparticles (MSNPs) for triggered drug release at the target site and simultaneously avoiding the premature release. MSNPs with a higher drug loading capacity and very slow release were designed so as to enhance release by FDA approved US-irradiation. Doxorubicin, as a model drug, and perfluoropentane (PFP) as a US responsive material, were entrapped in the porous structure of MSNPs. Lipid coating enhanced the cellular uptake and in addition provided a gatekeeping effect at the pore opening to reduce premature release. The mechanical and thermal effects of US induced the conversion of liquid PFP to a gaseous form that was able to rupture the lipid layer, resulting in triggered drug release. The prolonged stability profile and non-toxic behavior made them suitable candidate for the delivery of anticancer drugs. This smart system, with the abilities of better cellular uptake and higher cytotoxic effects on US-irradiation, would be a good addition to the applied side of chemotherapeutic advanced drug delivery systems.

Understanding liver tissue mechanics, particularly in the context of liver pathologies like fibrosis, cirrhosis, and carcinoma, holds pivotal significance for assessing disease severity and prognosis. Although the static mechanical properties of livers have been gradually studied, the intricacies of their dynamic mechanics remain enigmatic. Here, we characterize the dynamic creep responses of healthy, fibrotic, and mesenchymal stem cells (MSCs)-treated fibrotic lives. Strikingly, we unearth a ubiquitous two-stage power-law rheology of livers across different time scales with the exponents and their distribution profiles highly correlated to liver status. Moreover, our self-similar hierarchical theory effectively captures the delicate changes in the dynamical mechanics of livers. Notably, the viscoelastic multiscale mechanical indexes (i.e., power-law exponents and elastic stiffnesses of different hierarchies) and their distribution characteristics prominently vary with liver fibrosis and MSCs therapy. This study unveils the viscoelastic characteristics of livers and underscores the potential of proposed mechanical criteria for assessing disease evolution and prognosis.

Safety standards for clinical diagnostic ultrasonic devices were developed for use in relatively low-frequency systems (1-10 MHz), under the assumption that non-linear effects would be negligible. This article reviews ways in which neglecting non-linear wave propagation affects the measurements and calculations required to comply with safety standards and U.S. Food and Drug Administration guidance that recognizes these standards. An attempt is made to evaluate whether ignoring non-linear effects could result in significant error in the exposure quantities defined in these standards at either low or high frequencies, based on published literature. This article maintains that although non-linear effects have been considered in some parts of safety standards related to hydrophone requirements, the coverage is inadequate, especially for modern equipment with high working frequencies. A new approach is required to assess the magnitude of thermal heating for recently developed high-frequency systems to incorporate non-linear effects. In contrast, the current approach for evaluating the risk of cavitation can be used after appropriate modifications. [ABSTRACT FROM AUTHOR]

Background: Ultrasound tends to produce biological effects on body tissues. Therefore, the application of ultrasound safety rules is needed in all ultrasound examinations to avoid bioeffects that may occur because of a high thermal index (TI) and mechanical index (MI). This study aimed to explore the Saudi sonographers' awareness of ultrasound safety and bioeffects., Methods: A descriptive cross-sectional study was conducted, and the data was collected using an online survey google forms questionnaire disseminated through social media (Telegram, WhatsApp, and Twitter) as an electronic link. A total of 70 participants responded to the survey directly, and then, the data was analyzed using SPSS (Statistical Package for Social Science)., Results: Regarding the awareness of TI and MI, 64.3% of the participants were aware of TI and 65.7% of MI as safety ultrasound indices; moreover, 74.3% of the participants were aware of the ALARA principle "As Low as Reasonably Achievable." Participants' knowledge concerning more heat production in pulsed Doppler ultrasound modes was poor (31.5%). Most of the sonographers, i.e., 77.1% were aware of the relationship between the risk of activation and MI, and 58.6% of the participants were acquainted with the current FDA output limits. In comparison, 58.6% of the participants were aware of the bioeffects of ultrasound contrast agents. There was no significant correlation between the educational level and the degree of awareness of ultrasound bioeffects and safety (P-value> 0.05)., Conclusion: In this study, it was found that sonographers were aware of the theoretical principles of ultrasound safety indices and the ALARA principle, although they had poor knowledge of ultrasound bioeffects in Doppler mode., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)