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Showing papers in "Ultrasound in Medicine and Biology in 2017"


Journal ArticleDOI
TL;DR: This document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of prostate diseases.
Abstract: The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced guidelines for the use of elastography techniques, including basic science, breast, liver and thyroid elastography. Here we present elastography in prostate diseases. For each available technique, procedure, reproducibility, results and limitations are analyzed and recommendations are given. Finally, recommendations are given based on the level of evidence of the published literature and on the WFUMB expert group's consensus. This document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of prostate diseases.

196 citations


Journal ArticleDOI
TL;DR: The underlying principles of thermal mechanisms and the physical interactions of ultrasound with biological tissues are reviewed and adverse health effects derived from cellular studies, animal studies and clinical reports are reviewed to provide insight into the in vitro and in-vivo bio-effects of ultrasound.
Abstract: Ultrasound is widely used for medical diagnosis and increasingly for therapeutic purposes. An understanding of the bio-effects of sonography is important for clinicians and scientists working in the field because permanent damage to biological tissues can occur at high levels of exposure. Here the underlying principles of thermal mechanisms and the physical interactions of ultrasound with biological tissues are reviewed. Adverse health effects derived from cellular studies, animal studies and clinical reports are reviewed to provide insight into the in vitro and in vivo bio-effects of ultrasound.

177 citations


Journal ArticleDOI
TL;DR: The current status and future perspectives of point of care ultrasound are discussed, with particular attention given to the different uses of PoC-US and its clinical significance, including within emergency and critical care medicine, cardiology, anesthesiology, rheumatology, obstetrics, neonatology, gynecology, gastroenterology and many other applications.
Abstract: Over the last decade, the use of portable ultrasound scanners has enhanced the concept of point of care ultrasound (PoC-US), namely, “ultrasound performed at the bedside and interpreted directly by the treating clinician.” PoC-US is not a replacement for comprehensive ultrasound, but rather allows physicians immediate access to clinical imaging for rapid and direct solutions. PoC-US has already revolutionized everyday clinical practice, and it is believed that it will dramatically change how ultrasound is applied in daily practice. However, its use and teaching are different from continent to continent and from country to country. This World Federation for Ultrasound in Medicine and Biology position paper discusses the current status and future perspectives of PoC-US. Particular attention is given to the different uses of PoC-US and its clinical significance, including within emergency and critical care medicine, cardiology, anesthesiology, rheumatology, obstetrics, neonatology, gynecology, gastroenterology and many other applications. In the future, PoC-US will be more diverse than ever and be included in medical student training.

139 citations


Journal ArticleDOI
TL;DR: This systematic review covers freehand 3-D US imaging between 1970 and 2017, highlighting the current trends in research fields, the research methods, the main limitations, the leading researchers, standard assessment criteria and clinical applications.
Abstract: Two-dimensional ultrasound (US) imaging has been successfully used in clinical applications as a low-cost, portable and non-invasive image modality for more than three decades. Recent advances in computer science and technology illustrate the promise of the 3-D US modality as a medical imaging technique that is comparable to other prevalent modalities and that overcomes certain drawbacks of 2-D US. This systematic review covers freehand 3-D US imaging between 1970 and 2017, highlighting the current trends in research fields, the research methods, the main limitations, the leading researchers, standard assessment criteria and clinical applications. Freehand 3-D US systems are more prevalent in the academic environment, whereas in clinical applications and industrial research, most studies have focused on 3-D US transducers and improvement of hardware performance. This topic is still an interesting active area for researchers, and there remain many unsolved problems to be addressed.

99 citations


Journal ArticleDOI
TL;DR: For a data set containing 42 malignant and 75 benign tumors from 117 patients, seven selected sonoelastomic features achieved an area under the receiver operating characteristic curve of 0.917, revealing superiority over the principal component analysis, deep polynomial networks and manually selected features.
Abstract: A radiomics approach to sonoelastography, called "sonoelastomics," is proposed for classification of benign and malignant breast tumors. From sonoelastograms of breast tumors, a high-throughput 364-dimensional feature set was calculated consisting of shape features, intensity statistics, gray-level co-occurrence matrix texture features and contourlet texture features, which quantified the shape, hardness and hardness heterogeneity of a tumor. The high-throughput features were then selected for feature reduction using hierarchical clustering and three-feature selection metrics. For a data set containing 42 malignant and 75 benign tumors from 117 patients, seven selected sonoelastomic features achieved an area under the receiver operating characteristic curve of 0.917, an accuracy of 88.0%, a sensitivity of 85.7% and a specificity of 89.3% in a validation set via the leave-one-out cross-validation, revealing superiority over the principal component analysis, deep polynomial networks and manually selected features. The sonoelastomic features are valuable in breast tumor differentiation.

88 citations


Journal ArticleDOI
TL;DR: TE-LSM correlated well with hepatic venous pressure gradient and represented good diagnostic performance in diagnosing clinically significant portal hypertension and for use as a sensitive screening tool, the subgroup with low cut-off values of 13.6-18 kPa is proposed.
Abstract: We aimed to evaluate the correlation between liver stiffness measurement using transient elastography (TE-LSM) and hepatic venous pressure gradient and the diagnostic performance of TE-LSM in assessing clinically significant portal hypertension through meta-analysis. Eleven studies were included from thorough literature research and selection processes. The summary correlation coefficient was 0.783 (95% confidence interval [CI], 0.737–0.823). Summary sensitivity, specificity and area under the hierarchical summary receiver operating characteristic curve (AUC) were 87.5% (95% CI, 75.8–93.9%), 85.3 % (95% CI, 76.9–90.9%) and 0.9, respectively. The subgroup with low cut-off values of 13.6–18 kPa had better summary estimates (sensitivity 91.2%, specificity 81.3% and partial AUC 0.921) than the subgroup with high cut-off values of 21–25 kPa (sensitivity 71.2%, specificity 90.9% and partial AUC 0.769). In summary, TE-LSM correlated well with hepatic venous pressure gradient and represented good diagnostic performance in diagnosing clinically significant portal hypertension. For use as a sensitive screening tool, we propose using low cut-off values of 13.6–18 kPa in TE-LSM.

81 citations


Journal ArticleDOI
TL;DR: New objective parameters and criteria for CLD diagnosis employing SWE images provided by the present study can be considered an important step toward color-based interpretation, and could assist radiologists' diagnostic performance on a daily basis after being installed in a PC and employed retrospectively, immediately after the examination.
Abstract: The purpose of the present study was to employ a computer-aided diagnosis system that classifies chronic liver disease (CLD) using ultrasound shear wave elastography (SWE) imaging, with a stiffness value-clustering and machine-learning algorithm. A clinical data set of 126 patients (56 healthy controls, 70 with CLD) was analyzed. First, an RGB-to-stiffness inverse mapping technique was employed. A five-cluster segmentation was then performed associating corresponding different-color regions with certain stiffness value ranges acquired from the SWE manufacturer-provided color bar. Subsequently, 35 features (7 for each cluster), indicative of physical characteristics existing within the SWE image, were extracted. A stepwise regression analysis toward feature reduction was used to derive a reduced feature subset that was fed into the support vector machine classification algorithm to classify CLD from healthy cases. The highest accuracy in classification of healthy to CLD subject discrimination from the support vector machine model was 87.3% with sensitivity and specificity values of 93.5% and 81.2%, respectively. Receiver operating characteristic curve analysis gave an area under the curve value of 0.87 (confidence interval: 0.77–0.92). A machine-learning algorithm that quantifies color information in terms of stiffness values from SWE images and discriminates CLD from healthy cases is introduced. New objective parameters and criteria for CLD diagnosis employing SWE images provided by the present study can be considered an important step toward color-based interpretation, and could assist radiologists' diagnostic performance on a daily basis after being installed in a PC and employed retrospectively, immediately after the examination.

71 citations


Journal ArticleDOI
TL;DR: The introduced method, namely double-stage DMAS (DS-DMAS), results in an approximately 25% lower level of side lobes compared with DMAS, and leads to 23%, 22% and 43% improvement in signal-to-noise ratio, full width at half-maximum and contrast ratio, respectively, compared with the DMAS beamformer.
Abstract: In ultrasound (US) imaging, delay and sum (DAS) is the most common beamformer, but it leads to low-quality images. Delay multiply and sum (DMAS) was introduced to address this problem. However, the reconstructed images using DMAS still suffer from the level of side lobes and low noise suppression. Here, a novel beamforming algorithm is introduced based on expansion of the DMAS formula. We found that there is a DAS algebra inside the expansion, and we proposed use of the DMAS instead of the DAS algebra. The introduced method, namely double-stage DMAS (DS-DMAS), is evaluated numerically and experimentally. The quantitative results indicate that DS-DMAS results in an approximately 25% lower level of side lobes compared with DMAS. Moreover, the introduced method leads to 23%, 22% and 43% improvement in signal-to-noise ratio, full width at half-maximum and contrast ratio, respectively, compared with the DMAS beamformer.

70 citations


Journal ArticleDOI
TL;DR: A unique multifunctional drug delivery system consisting of microbubbles stabilized by polymeric nanoparticles (NPMBs), enabling ultrasound-mediated drug delivery is investigated, to determine if increased tumor uptake had a therapeutic benefit.
Abstract: Compared with conventional chemotherapy, encapsulation of drugs in nanoparticles can improve efficacy and reduce toxicity. However, delivery of nanoparticles is often insufficient and heterogeneous because of various biological barriers and uneven tumor perfusion. We investigated a unique multifunctional drug delivery system consisting of microbubbles stabilized by polymeric nanoparticles (NPMBs), enabling ultrasound-mediated drug delivery. The aim was to examine mechanisms of ultrasound-mediated delivery and to determine if increased tumor uptake had a therapeutic benefit. Cellular uptake and toxicity, circulation and biodistribution were characterized. After intravenous injection of NPMBs into mice, tumors were treated with ultrasound of various pressures and pulse lengths, and distribution of nanoparticles was imaged on tumor sections. No effects of low pressures were observed, whereas complete bubble destruction at higher pressures improved tumor uptake 2.3 times, without tissue damage. An enhanced therapeutic effect was illustrated in a promising proof-of-concept study, in which all tumors exhibited regression into complete remission.

70 citations


Journal ArticleDOI
TL;DR: Using a newly developed ultralight ultrasonic probe and an optimized ultrasonic sequence, fUS imaging of brain vasculature and whisker stimulation-induced barrel cortex activation in awake and freely moving mice is performed, validating transcranial fUS for brain imaging, without anesthesia-induced bias, for behavioral studies.
Abstract: Functional ultrasound (fUS) imaging by ultrasensitive Doppler detection of blood volume was previously reported to measure adult rat brain activation and functional connectivity with unmatched spatiotemporal sampling (100 μm, 1 ms), but skull-induced attenuation of ultrasonic waves imposed skull surgery or contrast agent use. Also, fUS feasibility remains to be validated in mice, a major pre-clinical model organism. In the study described here, we performed full-depth ultrasensitive Doppler imaging and 3-D Doppler tomography of the entire mouse brain under anesthesia, non-invasively through the intact skull and skin, without contrast agents. Similar results were obtained in anesthetized young rats up to postnatal day 35, thus enabling longitudinal studies on postnatal brain development. Using a newly developed ultralight ultrasonic probe and an optimized ultrasonic sequence, we also performed minimally invasive full-transcranial fUS imaging of brain vasculature and whisker stimulation-induced barrel cortex activation in awake and freely moving mice, validating transcranial fUS for brain imaging, without anesthesia-induced bias, for behavioral studies.

69 citations


Journal ArticleDOI
TL;DR: High SWV was associated with high spasticity and poor function of the post-stroke upper limb, suggesting possible use as a reliable quantitative measure for disease progression and treatment follow-up.
Abstract: Current clinical evaluations of post-stroke upper limb spasticity are subjective and qualitative. We proposed a quantitative measurement of post-stroke spastic muscle stiffness by using shear-wave ultrasound elastography and tested its reliability. Acoustic radiation force impulse with shear wave velocity (SWV) detection was used to evaluate stiffness of the biceps brachii muscles at 90° and 0° elbow flexion. In 21 control subjects, SWV did not significantly differ between dominant and non-dominant sides at either flexion angle (0°: p = 0.311, 90°: p = 0.436). In 31 patients who had recent stroke, SWV was significantly greater on the paretic side than on the non-paretic side at both 90° (2.23 ± 0.15 m/s vs. 1.88 ± 0.08 m/s, p = 0.036) and 0° (3.28 ± 0.11 m/s vs. 2.93 ± 0.06 m/s, p = 0.002). The physical appearance of arms and forearms of our patients and controls prevented blinding of the rater to paretic or non-paretic side. At 90°, SWV on the paretic side correlated positively with modified Ashworth scale and modified Tardieu scale (spasticity severity) and negatively with Stroke Rehabilitation Assessment of Movement score (motor function impairment). The intra-class correlation coefficients of intra-rater and inter-rater reliability for SWV measurements were classified as excellent. In conclusion, high SWV was associated with high spasticity and poor function of the post-stroke upper limb, suggesting possible use as a reliable quantitative measure for disease progression and treatment follow-up.

Journal ArticleDOI
TL;DR: In this article, the diagnostic accuracy of transient elastography for diagnosis and staging hepatic fibrosis in people with alcoholic liver disease when compared with liver biopsy was evaluated. But, the authors could not identify the optimal cut-off values for differentiating the five stages of liver fibrosis.
Abstract: Background The presence and progression of hepatic (liver) fibrosis into cirrhosis is a prognostic variable having impact on survival in people with alcoholic liver disease. Liver biopsy, although an invasive method, is the recommended 'reference standard' for diagnosis and staging of hepatic fibrosis in people with liver diseases. Transient elastography is a non-invasive method for assessing and staging hepatic fibrosis. Objectives To determine the diagnostic accuracy of transient elastography for diagnosis and staging hepatic fibrosis in people with alcoholic liver disease when compared with liver biopsy. To identify the optimal cut-off values for differentiating the five stages of hepatic fibrosis. Search methods The Cochrane Hepato-Biliary Group Controlled and Diagnostic Test Accuracy Studies Registers, The Cochrane Library, MEDLINE (OvidSP), EMBASE (OvidSP), and the Science Citation Index Expanded (last search August 2014). Selection criteria Diagnostic cohort and diagnostic case-control study designs that assessed hepatic fibrosis in participants with alcoholic liver disease with transient elastography and liver biopsy, irrespective of language or publication status. The study participants could be of any sex and ethnic origin, above 16 years old, hospitalised or managed as outpatients. We excluded participants with viral hepatitis, autoimmunity, metabolic diseases, and toxins. Data collection and analysis We followed the guidelines in the draft Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy. Main results Five retrospective and nine prospective cohort studies with 834 participants provided data for the review analyses. Authors of seven of those studies sent us individual participant data. The risk of bias in the included studies was high in all but three studies. We could identify no serious concerns regarding the applicability of the studies in answering the main study question of our review, namely to use transient elastography to diagnose hepatic fibrosis. We could not identify the optimal cut-off values for the fibrosis stages. The definition of the diagnosis of alcoholic liver disease was not provided in one study and was not clearly defined in two studies, but it was clear in the remaining 11 studies. The study authors used different liver stiffness cut-off values of transient elastography for the hepatic fibrosis stages. There was only one study (103 participants) with data on hepatic fibrosis stage F1 or worse, with a cut-off of 5.9 kPa, and reporting sensitivity of 0.83 (95% confidence interval (CI) 0.74 to 0.90) and specificity of 0.88 (95% CI 0.47 to 1.00). The summary sensitivity and specificity of transient elastography for F2 or worse (seven studies with 338 participants and with cut-offs around 7.5 kPa (range 7.00 to 7.8 kPa)) were 0.94 and 0.89 with LR+ 8.2 and LR- 0.07, which suggests that transient elastography could be useful to rule out the presence of significant hepatic fibrosis, thus avoiding liver biopsy. Due to the wide range of cut-off values (from 8.0 to 17.0 kPa) found in the 10 studies with 760 participants with hepatic fibrosis F3 or worse, we fitted a hierarchical summary receiver operating characteristic (HSROC) model and estimated a summary ROC (SROC) curve. The sensitivity of the 10 studies varied from 72% to 100% and the specificity from 59% to 89%. We performed an additional analysis by including the studies with a cut-off value of around and equal to 9.5 kPa (range 8.0 to 11.0 kPa). The summary sensitivity and specificity of transient elastography (eight studies with 564 participants) were 0.92 and 0.70 with LR+ 3.1 and LR- 0.11, which suggests that transient elastography could also be useful to rule out the presence of severe hepatic fibrosis (F3 or worse), avoiding liver biopsy. We carried out a sensitivity analysis by considering only the studies with a cut-off value equal to 9.5 kPa and the result did not differ. We performed an HSROC analysis and reported an SROC curve for hepatic fibrosis stage F4 (cirrhosis). The HSROC analysis suggested that when the cut-off value changes, there is a wide variation in specificity and a more limited variation in sensitivity. We performed an additional analysis with the studies with the most commonly used cut-off value of 12.5 kPa. The summary sensitivity and specificity of transient elastography (seven studies with 330 participants) were 0.95 and 0.71 with LR+ 3.3 and LR- 0.07, which again suggests that transient elastography could be useful to rule out the presence of cirrhosis, avoiding liver biopsy. Authors' conclusions We identified a small number of studies with a few participants and were unable to include several studies, which raises the risk of outcome reporting bias. With these caveats in mind, transient elastography may be used as a diagnostic method to rule out liver cirrhosis (F4) in people with alcoholic liver disease when the pre-test probability is about 51% (range 15% to 79%). Transient elastography may also help in ruling out severe fibrosis (F3 or worse). Liver biopsy investigation remains an option if the certainty to rule in or rule out the stage of hepatic fibrosis or cirrhosis remains insufficient after a clinical follow-up or any other non-invasive test considered useful by the clinician. The proposed cut-off values for the different stages of hepatic fibrosis may be used in clinical practice, but caution is needed, as those values reported in this review are only the most common cut-off values used by the study authors. The best cut-off values for hepatic fibrosis in people with alcoholic liver disease could not be established yet. In order to diagnose correctly the stage of hepatic fibrosis in people with alcoholic liver disease using transient elastography assessment, the studies should consider a single aetiology. Hepatic fibrosis should be diagnosed with both transient elastography and liver biopsy and in this sequence, and transient elastography cut-off values should be pre-specified and validated. The time interval between the two investigations should not exceed three months, which is the interval mainly valid for people without cirrhosis, and assessment of results should be properly blinded. Only studies with low risk of bias, fulfilling the Standards for Reporting of Diagnostic Accuracy may answer the review question.

Journal ArticleDOI
TL;DR: A recently standardized ultrasound technique for measuring subcutaneous adipose tissue (SAT) was applied to normal-weight, overweight and obese persons, showing high measurement accuracy and reliability can be obtained in all groups, from lean to overweight and obesity, provided that measurers are trained appropriately.
Abstract: A recently standardized ultrasound technique for measuring subcutaneous adipose tissue (SAT) was applied to normal-weight, overweight and obese persons. Eight measurement sites were used: upper abdomen, lower abdomen, erector spinae, distal triceps, brachioradialis, lateral thigh, front thigh and medial calf. Fat compression was avoided. Fat patterning in 38 participants (body mass index: 18.6–40.3 kgm −2 ; SAT thickness sums from eight sites: 12–245 mm) was evaluated using a software specifically designed for semi-automatic multiple thickness measurements in SAT (sound speed: 1450 m/s) that also quantifies embedded fibrous structures. With respect to ultrasound intra-observer results, the correlation coefficient ρ = 0.999 ( p

Journal ArticleDOI
TL;DR: It is valuable to train midwives in POCUS to use an ultrasound tablet device and transmit images and reports via the internet to radiologists for review of accuracy, and excellent correlation between final outcomes of the pregnancies and diagnoses is found.
Abstract: Point-of-care ultrasound (POCUS) has become a topical subject and can be applied in a variety of ways with differing outcomes. The cost of all diagnostic procedures including obstetric ultrasound examinations is a major factor in the developing world and POCUS is only useful if it can be equated to good outcomes at a lower cost than a routine obstetric examination. The aim of this study was to assess a number of processes including accuracy of images and reports generated by midwives, performance of a tablet-sized ultrasound scanner, training of midwives to complete ultrasounds, teleradiology solution transmissions of images via internet, review of images by a radiologist, communication between midwife and radiologist, use of this technique to identify high-risk patients and improvement of the education and teleradiology model components. The midwives had no previous experience in ultrasound. They were stationed in rural locations where POCUS was available for the first time. After scanning the patients, an interim report was generated by the midwives and sent electronically together with all images to the main hospital for validation. Unique software was used to send lossless images by mobile phone using a modem. Transmission times were short and quality of images transmitted was excellent. All reports were validated by two experienced radiologists in our department and returned to the centers using the same transmission software. The transmission times, quality of scans, quality of reports and other parameters were recorded and monitored. Analysis showed excellent correlation between provisional and validated reports. Reporting accuracy of scans performed by the midwives was 99.63%. Overall flow turnaround time (from patient presentation to validated report) was initially 35 min but reduced to 25 min. The unique mobile phone transmission was faultless and there was no degradation of image quality. We found excellent correlation between final outcomes of the pregnancies and diagnoses on the basis of reports generated by the midwives. Only 1 discrepancy was found in the midwives' reports. Scan results versus actual outcomes revealed 2 discrepancies in the 20 patients identified as high risk. In conclusion, we found that it is valuable to train midwives in POCUS to use an ultrasound tablet device and transmit images and reports via the internet to radiologists for review of accuracy. This focus on the identification of high-risk patients can be valuable in a remote healthcare facility.

Journal ArticleDOI
TL;DR: Findings confirmed and strengthen findings presented in previous work indicating that UST sound speed imaging yields viable markers of breast density in a manner consistent with mammography, the current clinical standard.
Abstract: A population of 165 women with negative mammographic screens also received an ultrasound tomography (UST) examination at the Karmanos Cancer Institute in Detroit, MI. Standard statistical techniques were employed to measure the associations between the various mammographic- and UST-related density measures and various participant characteristics such as age, weight and height. The mammographic percent density (MPD) was found to have similar strength associations with UST mean sound speed (Spearman coefficient, r s = 0.722, p s = 0.737, p s = 0.568, p s = 0.715, p s = −0.239, p = 0.002), UST median sound speed (r s = −0.226, p = 0.004) and MPD (r s = −0.204, p = 0.008). Relationships were found to be inversely and moderately associated between body mass index (BMI) and the UST mean sound speed (r s = −0.429, p s = −0.447, p s = −0.489, p

Journal ArticleDOI
TL;DR: Ultrasound plaque characteristics (GSM, DWAs and black areas) represent histopathologic markers associated with plaque vulnerability and were associated with inflammation and inflammation on histopathology examination.
Abstract: Inflammation and angiogenesis play major roles in carotid plaque vulnerability. The purpose of this study was to determine whether gray-scale features of carotid plaques are associated with histologic markers for inflammation. Thirty-eight individuals completed a dedicated research carotid ultrasound exam before carotid endarterectomy. Gray-scale analysis was performed on plaque images to measure plaque echogenicity (gray-scale median [GSM] pixel brightness), plaque area, presence of discrete white areas (DWAs) and the percent of black area near the lumen on any one component of the plaque. Plaques with higher ultrasound GSM had greater percent calcification (p = 0.013) on histopathology. Presence of an ultrasound DWA was associated with more plaque hemosiderin (p = 0.0005) and inflammation (p = 0.019) on histopathology examination. The percent of plaque black area in any one component was associated with a higher score for macroscopic ulceration (p = 0.028). Ultrasound plaque characteristics (GSM, DWAs and black areas) represent histopathologic markers associated with plaque vulnerability. ClinicalTrials.gov identifier: NCT02476396.

Journal ArticleDOI
TL;DR: Two-dimensional SWE had diagnostic accuracy comparable to that of TE for liver fibrosis staging in patients with chronic hepatitis B (CHB) infection using liver biopsy as the reference standard.
Abstract: This study compared 2-D shear wave elastography (SWE) and transient elastography (TE) for liver fibrosis staging in patients with chronic hepatitis B (CHB) infection using liver biopsy as the reference standard. Patients with CHB infection who underwent liver biopsy were consecutively included. After exclusions, 257 patients were analyzed. Two-dimensional SWE resulted in a significantly higher rate of reliable measurements (98.1%, 252/257) than TE (93.0%, 239/257) (p = 0.011). Liver stiffness measurements of the two examinations exhibited a strong correlation (r = 0.835, p 0.05). Two-dimensional SWE had diagnostic accuracy comparable to that of TE for liver fibrosis staging. The measurements that the two techniques provide are not interchangeable.

Journal ArticleDOI
TL;DR: In conclusion, during ESE, the comet map of lung water accumulation follows a predictable spatial pattern with wet spots preferentially aligned with the third IS and along the AA and MA lines.
Abstract: Various lung ultrasound (LUS) scanning modalities have been proposed for the detection of B-lines, also referred to as ultrasound lung comets , which are an important indication of extravascular lung water at rest and after exercise stress echo (ESE). The aim of our study was to assess the lung water spatial distribution ( comet map ) at rest and after ESE. We performed LUS at rest and immediately after semi-supine ESE in 135 patients (45 women, 90 men; age 62 ± 12 y, resting left ventricular ejection fraction = 41 ± 13%) with known or suspected heart failure or coronary artery disease. B-lines were measured by scanning 28 intercostal spaces (ISs) on the antero-lateral chest, 2nd–5th IS, along with the midaxillary (MA), anterior axillary (AA), mid-clavicular (MC) and parasternal (PS) lines. Complete 28-region, 16-region (3rd and 4th IS), 8-region (3rd IS), 4-region (3rd IS, only AA and MA) and 1-region (left 3rd IS, MA) scans were analyzed. In each space, the B-lines were counted from 0 = black lung to 10 = white lung. Interpretable images were obtained in all spaces (feasibility = 100 %). B-lines (>0 in at least 1 space) were present at ESE in 93 patients (69%) and absent in 42. More B-lines were found in the 3rd IS and along AA and MA lines. The B-line cumulative distribution was symmetric at rest (right/left = 1.10) and asymmetric with left lung predominance during stress (right/left = 0.67). The correlation of per-patient B-line number between 28-S and 16-S (R 2 = 0.9478), 8-S (R 2 = 0.9478) and 4-S scan (R 2 = 0.9146) was excellent, but only good with 1-S (R 2 = 0.8101). The average imaging and online analysis time were 5 s per space. In conclusion, during ESE, the comet map of lung water accumulation follows a predictable spatial pattern with wet spots preferentially aligned with the third IS and along the AA and MA lines. The time-saving 4-region scan is especially convenient during stress, simply dismissing dry regions and focusing on wet regions alone.

Journal ArticleDOI
Yurong Hong1, Zhiyan Luo1, Guoqiang Mo1, Ping Wang1, Qin Ye1, Pintong Huang1 
TL;DR: CEUS is a promising tool in conjunction with conventional US for the pre-operative prediction of metastatic cervical lymph nodes in patients with PTC.
Abstract: The objective of this study was to prospectively evaluate the diagnostic accuracy of contrast-enhanced ultrasonography (CEUS) in differentiating between benign and metastatic cervical lymph nodes in patients with papillary thyroid cancer (PTC). Three hundred nineteen cervical lymph nodes (162 metastatic from PTC and 157 benign) were evaluated using conventional ultrasonography (US) and CEUS before biopsy or surgery. Metastatic lymph nodes more often manifested centripetal or asynchronous perfusion, hyper-enhancement, heterogeneous enhancement, perfusion defects and ring-enhancing margins than benign lymph nodes at pre-operative CEUS (all p values

Journal ArticleDOI
TL;DR: Shear waves are present on the septal wall after mitral and aortic valve closure, thus providing an opportunity to assess stiffness in early systole and early diastole and it is found that the propagation velocity only mildly increased with shear wave frequency.
Abstract: Cardiac muscle stiffness can potentially be estimated non-invasively with shear wave elastography. Shear waves are present on the septal wall after mitral and aortic valve closure, thus providing an opportunity to assess stiffness in early systole and early diastole. We report on the shear wave recordings of 22 minipigs with high-frame-rate echocardiography. The waves were captured with 4000 frames/s using a programmable commercial ultrasound machine. The wave pattern was extracted from the data through a local tissue velocity estimator based on one-lag autocorrelation. The wave propagation velocity was determined with a normalized Radon transform, resulting in median wave propagation velocities of 2.2 m/s after mitral valve closure and 4.2 m/s after aortic valve closure. Overall the velocities ranged between 0.8 and 6.3 m/s in a 95% confidence interval. By dispersion analysis we found that the propagation velocity only mildly increased with shear wave frequency.

Journal ArticleDOI
TL;DR: Simulations performed using a Rayleigh-Plesset-type model accounting for buckling and a dynamic finite-element analysis suggest that buckling is the mechanism behind the generation of harmonics and will inform the development of GV-based contrast agents and pulse sequences to optimize their detection with ultrasound.
Abstract: Gas vesicles (GVs) are a new and unique class of biologically derived ultrasound contrast agents with sub-micron size whose acoustic properties have not been fully elucidated. In this study, we investigated the acoustic collapse pressure and behavior of Halobacterium salinarum gas vesicles at transmit center frequencies ranging from 12.5 to 27.5 MHz. The acoustic collapse pressure was found to be above 550 kPa at all frequencies, nine-fold higher than the critical pressure observed under hydrostatic conditions. We illustrate that gas vesicles behave non-linearly when exposed to ultrasound at incident pressure ranging from 160 kPa to the collapse pressure and generate second harmonic amplitudes of −2 to −6 dB below the fundamental in media with viscosities ranging from 0.89 to 8 mPa·s. Simulations performed using a Rayleigh–Plesset-type model accounting for buckling and a dynamic finite-element analysis suggest that buckling is the mechanism behind the generation of harmonics. We found good agreement between the level of second harmonic relative to the fundamental measured at 20 MHz and the Rayleigh–Plesset model predictions. Finite-element simulations extended these findings to a non-spherical geometry, confirmed that the acoustic buckling pressure corresponds to the critical pressure under hydrostatic conditions and support the hypothesis of limited gas flow across the GV shell during the compression phase in the frequency range investigated. From simulations, estimates of GV bandwidth-limited scattering indicate that a single GV has a scattering cross section comparable to that of a red blood cell. These findings will inform the development of GV-based contrast agents and pulse sequences to optimize their detection with ultrasound.

Journal ArticleDOI
TL;DR: The constituents of unmyelinated axonal tissue alone are found to be sufficient to generate de novo action potentials under ultrasound, the stimulation of which is significantly correlated to the presence of inertial cavitation and is never observed in its absence.
Abstract: Appreciation for the medical and research potential of ultrasound neuromodulation is growing rapidly, with potential applications in non-invasive treatment of neurodegenerative disease and functional brain mapping spurring recent progress. However, little progress has been made in our understanding of the ultrasound–tissue interaction. The current study tackles this issue by measuring compound action potentials (CAPs) from an ex vivo crab walking leg nerve bundle and analysing the acoustic nature of successful stimuli using a passive cavitation detector (PCD). An unimpeded ultrasound path, new acoustic analysis techniques and simple biological targets are used to detect different modes of cavitation and narrow down the candidate biological effectors with high sensitivity. In the present case, the constituents of unmyelinated axonal tissue alone are found to be sufficient to generate de novo action potentials under ultrasound, the stimulation of which is significantly correlated to the presence of inertial cavitation and is never observed in its absence.

Journal ArticleDOI
TL;DR: In a cycle of bubble growth and collapse, characteristic times at which mechanical damage is likely to occur and dominant mechanisms acting at each time were identified.
Abstract: Histotripsy is a developing focused ultrasound procedure that uses cavitation bubbles to mechanically homogenize soft tissue. To better understand the mechanics of tissue damage, a numerical model of single-bubble dynamics was used to calculate stress, strain and strain rate fields produced by a cavitation bubble exposed to a tensile histotripsy pulse. The explosive bubble growth and its subsequent collapse were found to depend on the properties of the surrounding material and on the histotripsy pulse. Stresses far greater than gigapascals were observed close to the bubble wall, but attenuated by four to six orders of magnitude within 50 μm from the bubble wall, with at least two orders of magnitude attenuation occurring within the first 10 μm from the bubble. Elastic stresses were found to dominate close to the bubble wall, whereas viscous stresses tended to persist farther into the surroundings. A non-dimensional parameter combining tissue, waveform and bubble properties was identified that dictates the dominant stress (viscous vs. elastic) as a function of distance from the bubble nucleus. In a cycle of bubble growth and collapse, characteristic times at which mechanical damage is likely to occur and dominant mechanisms acting at each time were identified.

Journal ArticleDOI
TL;DR: Findings show that use of oxygen as a carrier gas can result in a substantial diminution of BBB disruption, and should be taken into account when comparing studies from different researchers and in translating this method to humans.
Abstract: Numerous researchers are investigating the use of microbubble-enhanced ultrasound to disrupt the blood–brain barrier (BBB) and deliver drugs to the brain. This study investigated the impact of using oxygen as a carrier gas for anesthesia on microbubble activity and BBB disruption. Targets in mice were sonicated in combination with administration of Optison microbubbles (100 μL/kg) under isoflurane anesthesia with either oxygen or medical air. A 690-kHz focused ultrasound transducer applied 10-ms bursts at peak pressure amplitudes of 0.46–0.54 MPa (n = 2) or 0.34–0.36 MPa (n = 5). After sonication of two locations in one hemisphere, the carrier gas for the anesthesia was changed and the sonications were repeated in the contralateral hemisphere. The BBB disruption, measured via contrast-enhanced magnetic resonance imaging, was significantly greater (p

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TL;DR: Rectus femoris echo intensity is associated with muscle strength, but not endurance, in younger and older men.
Abstract: We examined correlations between echo intensity and muscle strength and endurance Rectus femoris echo intensity, maximal voluntary contraction (MVC) force and time to task failure during a 50% MVC task were determined for 12 younger (mean age = 25 y) and 13 older (mean age = 74 y) men Bivariate correlations between echo intensity and normalized MVC force were similar for younger and older men, but was only statistically significant for the latter (younger r = −0559, p = 0059; older r = −0580, p = 0038) When all patients were combined, the correlation was significant ( r = −0733, p r = −0382, p = 0221; older r = −0347, p = 0246; all patients r = −0229, p = 0270) Rectus femoris echo intensity is associated with muscle strength, but not endurance, in younger and older men

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TL;DR: Ex vivo measurements of a rat lung in which edema was simulated by adding phosphate-buffered saline revealed a linear relationship between the fluid volume fraction and L*.
Abstract: The purpose of the study described here was to showcase the application of ultrasound to quantitative characterization of the micro-architecture of the lung parenchyma to predict the extent of pulmonary edema. The lung parenchyma is a highly complex and diffusive medium for which ultrasound techniques have remained qualitative. The approach presented here is based on ultrasound multiple scattering and exploits the complexity of ultrasound propagation in the lung structure. The experimental setup consisted of a linear transducer array with an 8-MHz central frequency placed in contact with the lung surface. The diffusion constant D and transport mean free path L* of the lung parenchyma were estimated by separating the incoherent and coherent intensities in the near field and measuring the growth of the incoherent diffusive halo over time. Significant differences were observed between the L* values obtained in healthy and edematous rat lungs in vivo. In the control rat lung, L* was found to be 332 μm (±48.8 μm), whereas in the edematous lung, it was 1040 μm (±90 μm). The reproducibility of the measurements of L* and D was tested in vivo and in phantoms made of melamine sponge with varying air volume fractions. Two-dimensional finite difference time domain numerical simulations were carried out on rabbit lung histology images with varying degrees of lung collapse. Significant correlations were observed between air volume fraction and L* in simulation (r = -0.9542, p < 0.0117) and sponge phantom (r = -0.9932, p < 0.0068) experiments. Ex vivo measurements of a rat lung in which edema was simulated by adding phosphate-buffered saline revealed a linear relationship between the fluid volume fraction and L*. These results illustrate the potential of methods based on ultrasound multiple scattering for the quantitative characterization of the lung parenchyma.

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TL;DR: The results of this study indicate that microtripsy has the potential to be a safe and effective treatment for deep vein thrombosis in a porcine model.
Abstract: Histotripsy is a non-invasive therapeutic technique that uses ultrasound generated from outside the body to create controlled cavitation in targeted tissue, and fractionates it into acellular debris. We have developed a new histotripsy approach, termed microtripsy, to improve targeting accuracy and to avoid collateral tissue damage. This in vivo study evaluates the safety and efficacy of microtripsy for non-invasive thrombolysis in a porcine deep vein thrombosis model. Acute thrombi were formed in left femoral veins of pigs (∼35 kg) by occluding the vessel using two balloon catheters and infusing with thrombin. Guided by real-time ultrasound imaging, microtripsy thrombolysis treatment was conducted in 14 pigs; 10 pigs were euthanized on the same day (acute) and 4 at 2 wk (subacute). To evaluate vessel damage, 30-min free-flow treatment in the right femoral vein (no thrombus) was also conducted in 8 acute pigs. Blood flow was successfully restored or significantly increased after treatment in 13 of the 14 pigs. The flow channels re-opened by microtripsy had a diameter up to 64% of the vessel diameter (∼6 mm). The average treatment time was 16 min per centimeter-long thrombus. Only mild intravascular hemolysis was induced during microtripsy thrombolysis. No damage was observed on vessel walls after 2 wk of recovery, venous valves were preserved, and there was no sign of pulmonary embolism. The results of this study indicate that microtripsy has the potential to be a safe and effective treatment for deep vein thrombosis in a porcine model.

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TL;DR: A machine-learning method to assess automatically that transventricular ultrasound images of the fetal brain have been correctly acquired and meet the required clinical standard is described and it is shown that the automatic verification method approaches human expert assessment.
Abstract: During routine ultrasound assessment of the fetal brain for biometry estimation and detection of fetal abnormalities, accurate imaging planes must be found by sonologists following a well-defined imaging protocol or clinical standard, which can be difficult for non-experts to do well. This assessment helps provide accurate biometry estimation and the detection of possible brain abnormalities. We describe a machine-learning method to assess automatically that transventricular ultrasound images of the fetal brain have been correctly acquired and meet the required clinical standard. We propose a deep learning solution, which breaks the problem down into three stages: (i) accurate localization of the fetal brain, (ii) detection of regions that contain structures of interest and (iii) learning the acoustic patterns in the regions that enable plane verification. We evaluate the developed methodology on a large real-world clinical data set of 2-D mid-gestation fetal images. We show that the automatic verification method approaches human expert assessment.

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TL;DR: The MG of both limbs in children with unilateral spastic CP is smaller and, based on quantitative ultrasound, structurally different from that of TD children.
Abstract: Three-dimensional ultrasound (3-DUS) was used to examine the size and appearance of the medial gastrocnemius (MG) muscle in children with unilateral cerebral palsy (CP). Twenty-six children with CP and 10 typically developing (TD) children participated. Three-dimensional US images of both limbs in children with CP and the right limb in TD children were analysed using quantitative methods to determine muscle volume, global echo intensity, global echo pattern and regional echo intensity. Significant differences in MG volume and all echo parameters were found between TD and CP children. The more involved limb was smaller and had higher echo intensity and a more heterogenous echo pattern compared with the TD group. Compared with that of the more involved limb, the MG of the less involved limb was larger but had a similar echo appearance. The MG of both limbs in children with unilateral spastic CP is smaller and, based on quantitative ultrasound, structurally different from that of TD children.