Viscoelastic Multiscale Mechanical Indexes for Assessing Liver Fibrosis and Treatment Outcomes.

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.

Frame Rate Exposimetry for Pulmonary Capillary Hemorrhage During Lung Ultrasound.

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.

The Green Synthesis of Reduced Graphene Oxide Using Ellagic Acid: Improving the Contrast-Enhancing Effect of Microbubbles in Ultrasound.

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.

Optimization of Mechanical Indices for Clinical Contrast-Enhanced Ultrasound.

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.

Evaluation of the Scan Duration and Mechanical and Thermal Indices Applied for the Diagnostic Ultrasound Examinations.

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.

Effect of Acoustic Cavitation on Mouse Spermatogonial Stem Cells: Colonization and Viability.

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.

Advances in Ultrasound Therapeutics.

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. Targeted ultrasound therapies are developing for prevention of microvascular obstruction in acute coronary syndromes and peripheral vascular disease.

Standard echocardiography versus very-low mechanical index contrast-imaging: left ventricle volumes and ejection fraction multi-reader variability and reference values in a subgroup with no risk factors or cardiac disease.

We retrospectively assessed the rest-phase images of 300 contrast stress- echocardiograms, during which very-low mechanical index (VLMI) imaging with ultrasound enhancing agents (UEAs) was routinely acquired in addition to greyscale echocardiography; intra- and inter-reader variability for left ventricle (LV) volumes and ejection fraction (LVEF) at rest was established in the overall cohort and normal values were calculated in the subset of subjects with no cardiac risk factors or cardiac disease and a normal stress-echocardiogram. Current recommendations for chamber quantification using echocardiography advise the use of UEAs in case of insufficient quality of endocardial visualization, but normal values for LV volumes and LVEF using UEAs have never been published using currently recommended VLMI method. Single-centre retrospective study, enrolling subjects referred to contrast stress- echocardiography for suspect coronary artery disease, including the acquisition of both standard 2D greyscale and bolus UEAs with VLMI, regardless of the image quality. This enables offline measurement of the LV volumes and LVEF for both greyscale and UEAs-VLMI images at rest in all subjects. Images were allocated to 3 readers in random order. Normal range for LV volumes and LVEF was also derived in a subset of apparently healthy subjects. In the 298 exams finally assessed, measurement variability among the three readers was lower with UEAs-VLMI, in particular for end-systolic volumes (intra-class correlation coefficient for concordance improved from 0.855 to 0.916, for LVEF from 0.68 to 0.783, p < 0.01), intra- observer variability reduced (Lin's correlation coefficient for LVEF from 0.747 to 0.857, p < 0.01). Normal mean indexed LV end-diastolic volume with UEAs-VLMI, compared to greyscale imaging, was + 14 ml/m2, while LVEF was + 5 to + 6% points. This is the largest study specifically addressing UEAs-VLMI imaging and comparing data with standard greyscale imaging; it demonstrates a reduction in measurement variability of LV volumes and LVEF. Normal reference values for VLMI ultrasound are reported for the first time in comparison with greyscale values.

Diagnostic Ultrasound Safety Review for Point-of-Care Ultrasound Practitioners.

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.

Pulmonary Capillary Hemorrhage Induced by Acoustic Radiation Force Impulse Shear Wave Elastography in Ventilated Rats.

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 H2 O 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.

Comparison Between Low Mechanical Index and High Mechanical Index Contrast Modes of Contrast-Enhanced Ultrasonography: Evaluation of Perfusion Defects of Hypervascular Hepatocellular Carcinomas During the Post-Vascular Phase.

OBJECTIVES: We evaluated the detection rates for perfusion defects in hypervascular hepatocellular carcinomas comparing the low mechanical index (MI) and high MI contrast modes during the post-vascular phase (PVP) of contrast-enhanced ultrasonography. METHODS: Seventy-eight patients with 84 hypervascular hepatocellular carcinomas (mean diameter, 23.4 ± 11.2 mm) were selected for this retrospective study. All the patients underwent whole-liver scanning using conventional ultrasonography before injection of a perflubutane-based contrast agent (Sonazoid), and all the detected nodules were classified as either hypoechoic or hyperechoic nodules. Next, hypoechoic and hyperechoic nodules were evaluated using contrast-enhanced ultrasonography, and the presence of a perfusion defect was assessed for each nodule using both the low MI (0.2-0.3) and the high MI (0.7-1.2) contrast modes during the PVP (10 minutes after injection). The data were analyzed using the McNemar test. RESULTS: Forty-four nodules were classified as hypoechoic nodules, and the remaining 40 nodules were classified as hyperechoic nodules using conventional ultrasonography. The detection rate for perfusion defects determined using the high MI contrast mode was higher than that determined using the low MI contrast mode in hyperechoic nodules during the PVP (low MI, 58% [23 of 40]; high MI, 90% [36 of 40]; P < .0001). However, no significant difference was observed between the low MI and the high MI contrast modes in hypoechoic nodules (low MI, 80% [35 of 44]; high MI, 89% [39 of 44]; P = .125). CONCLUSION: Compared with the low MI contrast mode, the high MI contrast mode was more sensitive for detecting perfusion defects in hypervascular hepatocellular carcinomas in patients with hyperechoic nodules during the PVP.

In vivo study of enhanced chemotherapy combined with ultrasound image-guided focused ultrasound (USgFUS) treatment for pancreatic cancer in a xenograft mouse model.

OBJECTIVES: This study was designed to investigate whether focused ultrasound (FUS) treatment with a higher mechanical index (MI) can enhance the effects of combined chemotherapy more than with a lower MI, and to evaluate the feasibility of the chemotherapy combined with FUS at a higher MI as an alternative treatment protocol. METHODS: Mice in the first study were divided into six groups: control, chemotherapy only (GEM), two groups treated with FUS only at two different MIs, and two groups treated with chemotherapy and FUS (GEM + FUS). Mice were treated with a single-session treatment; one session consisted of three weekly treatments and 1 week of follow-up monitoring. In the second study, mice were assigned to two groups (GEM, GEM + FUS) and treated with four treatment sessions. RESULTS: In the single-session treatment, tumor growth was most effectively suppressed in GEM + FUS group with a higher MI. Tumor growth rate was significantly lower in GEM + FUS group than in GEM group for multiple-session treatment. Specifically, three of ten mice in GEM + FUS group showed complete remission. CONCLUSIONS: This study demonstrated that FUS at a higher MI can enhance chemotherapy outcomes more than at a lower MI and demonstrated the potential of FUS in combination with chemotherapy as a new cancer treatment protocol. KEY POINTS: • Combined treatment of chemotherapy and focused ultrasound can effectively suppress tumor growth. • For the focused ultrasound treatment conditions used in this study, focused ultrasound with relatively higher mechanical index shows more enhanced therapeutic outcomes than with the lower mechanical index. • Combination therapy shows the possibility as a new cancer treatment protocol.

No. 359-Obstetric Ultrasound Biological Effects and Safety.

OBJECTIVE: To review the biological effects and safety of obstetric ultrasound. OUTCOME: Outline the circumstances in which safety may be a concern with obstetric ultrasound. EVIDENCE: The 2005 version of this guideline was used as a basis and updated following a Medline search and review of relevant publications. Sources included guidelines and reports by Health Canada and the American Institute of Ultrasound in Medicine. VALUES: Review by principal author and the Diagnostic Imaging Committee of the SOGC. The quality of evidence and classification of recommendations have been adapted from the Report of the Canadian Task Force on the Periodic Health Examination. BENEFITS, HARMS, AND COSTS: Obstetric ultrasound should only be done for medical reasons, and exposure should be kept as low as reasonably achievable because of the potential for tissue heating. Higher energy is of particular concern in the following scenarios: Doppler studies (pulsed, colour, and power), first trimester ultrasound with a long trans-vesical path (>5 cm), second or third trimester exams when bone is in the focal zone, when scanning tissue with minimal perfusion (embryonic), or in patients who are febrile. Operators can minimize risk by limiting dwell time and exposure to critical structures. It is also important to be aware of equipment-generated exposure information.

Does Intravenous Infusion Influence Diagnostic Ultrasound-Induced Pulmonary Capillary Hemorrhage?

OBJECTIVES: Pulmonary diagnostic ultrasound (US) can induce pulmonary capillary hemorrhage (PCH) in mammals. This singular biological effect of diagnostic US imaging was discovered more than 25 years ago but remains poorly understood. Our objective here was to investigate rapid infusion of intravenous fluids as a possible stressor for capillaries, which might enhance pulmonary diagnostic US-induced PCH. METHODS: Rats were anesthetized with Telazol (Zoetis, Inc, Kalamazoo, MI), which yielded relatively low pulmonary diagnostic US-induced PCH, or Telazol and xylazine, which yielded relatively high pulmonary diagnostic US-induced PCH. Groups of rats were not infused or infused either with normal saline, 10% mannitol, or 5% albumin. Rats were scanned in a warmed water bath with B-mode US for 5 minutes with a 7.6-MHz linear array set to different mechanical index values to obtain exposure response information. Pulmonary capillary hemorrhage was observed as comet tail artifacts in the image and measured on the lung surface. RESULTS: For Telazol anesthesia, all of the PCH results were very low, with no significant differences at the maximum output with an in situ peak rarefactional pressure amplitude of 2.1 MPa (on-screen mechanical index, 0.9). The addition of xylazine to the Telazol anesthetic significantly enhanced the PCH (P < .001) without infusion and likewise for the mannitol and albumin infusion. Saline infusion eliminated this enhancement, with significantly reduced PCH for Telazol-plus-xylazine anesthesia (P < .001); however, both mannitol and albumin infusion resulted in significantly more PCH than saline infusion (P < .01). CONCLUSIONS: These results show PCH dependence on the specific intravenous infusion fluid and illustrate the complex importance of physiologic parameters for US-induced PCH.

Improvement of Detection Sensitivity of Microbubbles as Sensors to Detect Ambient Pressure.

Microbubbles are considered a promising tool for noninvasive estimation of local blood pressure. It is reported that the subharmonic scattering amplitude of microbubbles decreases by 9 to 12 dB when immersed in the media under an ambient pressure variation from 0 to 180 mmHg. However, the pressure sensitivity still needs to be improved to satisfy clinical diagnostic requirements. Here, we investigated the effects of acoustic parameters on the pressure sensitivity of microbubbles through measuring the acoustic attenuation and scattering properties of commercially available SonoVue microbubbles. Our results showed that the first harmonic, subharmonic, and ultraharmonic amplitudes of microbubbles were reduced by 6.6 dB, 10.9 dB, and 9.3 dB at 0.225 mechanical index (MI), 4.6 dB, 19.8 dB, and 12.3 dB at 0.25 MI, and 18.5 dB, 17.6 dB, and 12.6 dB at 0.3 MI, respectively, when the ambient pressure increased from 0 to 180 mmHg. Our finding revealed that a moderate MI (0.25⁻0.4) exciting microbubbles could significantly improve their sensitivities to detect ambient pressure.

Assessment of Thermal and Mechanical Indices as Acoustic Output Parameters Used in Obstetric Ultrasound in Saudi Arabia.

BACKGROUND: Patient safety is paramount in ultrasound procedures, particularly in obstetric ultrasounds involving both the mother and fetus. The thermal and mechanical indices (TI and MI) serve as crucial indicators of the acoustic output during ultrasound. Clinicians and specialists must know these indices and ensure they are within safe ranges. This study aimed to assess the parameters of acoustic output power employed in obstetric ultrasound (thermal and mechanical index). METHODOLOGY: A cross-sectional observational study conducted at Maternity and Children's Hospital in Al-Madina Al-Munawwarah, the data was collected from obstetric scanning of 411 pregnant females using a data collection sheet including gravida and women's age, gestational age, scan mode, scan time, and thermal and mechanical index (TI and MI) values. RESULTS: The study found that there were significant differences in safety indices measurement between different modes; in Pulsed Doppler, mean Thermal Index Bone (TIb) had the highest value (1.60±0.40), and the Mechanical Index (MI) was the lowest (0.68±0.33). There were insignificant differences in safety indices values in different modes in different trimesters. The thermal indices of soft tissue and bony structure (TIs and TIb) of brightness mode (B-mode) were constant in all trimesters, but the MI in the first trimester was lower than in the other trimesters. CONCLUSION: This study found significant differences in TIs, TIb, and MI in different modes of obstetric ultrasound. Pulsed Doppler ultrasonography had the highest TIb value and a lower MI value. The ultrasound acoustic exposure output parameters were within the standard's recommended limit.

Acoustic radiation force impulse-induced lung hemorrhage: investigating the relationship with peak rarefactional pressure amplitude and mechanical index in rabbits.

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.

Safety of Ultrasound Exposure: Awareness of Ultrasound Bioeffects among Saudi Sonographers.

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.

Quantifying the Impact of Imaging Through Body Walls on Shear Wave Elasticity Measurements.

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.