Acoustic radiation force impulse elastography for differentiation of benign and malignant thyroid nodules with concurrent Hashimoto's thyroiditis.

PubMed

Liu, Bo-Ji; Xu, Hui-Xiong; Zhang, Yi-Feng; Xu, Jun-Mei; Li, Dan-Dan; Bo, Xiao-Wan; Li, Xiao-Long; Guo, Le-Hang; Xu, Xiao-Hong; Qu, Shen

2015-03-01

The purpose of the study was to explore the diagnostic performance of acoustic radiation force impulse (ARFI) elastography in differential diagnosis between benign and malignant thyroid nodules in patients with coexistent Hashimoto's thyroiditis (HT). A total of 141 pathological proven nodules in 141 HT patients (7 males and 134 females, mean age 50.1 years, range 23-75 years) received conventional ultrasound (US), elasticity imaging (EI) and ARFI elastography, including virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ), before surgery. Shear wave velocity (SWV) and SWV ratio were measured for each nodule on VTQ. The US, EI and ARFI elastography features were compared between benign and malignant nodules in HT patients. Receiver operating characteristic curve (ROC) analyses and area under curve (AUC) were performed to assess the diagnostic performance. Pathologically, 70 nodules were benign and 71 nodules were malignant. Significant differences were found between benign and malignant nodules in HT patients for EI (EI score) and ARFI (VTI grade and SWV) (all P value <0.05). The AUCs for EI, VTI, SWV and SWV ratio were 0.68 [95% confidence interval (CI): 0.59-0.77], 0.90 (95% CI: 0.84-0.95), 0.77 (95%CI: 0.70-0.85) and 0.74 (95%CI: 0.66-0.82), respectively. The cut-off points were EI score ≥3, VTI grade ≥4, SWV ≥2.58 m/s and SWV ratio ≥1.03, respectively. In conclusion, ARFI elastography is useful for differentiation between benign and malignant thyroid nodules in HT patients. The diagnostic performance of ARFI elastography is better than EI.

Biomechanical properties of crystalline lens as a function of intraocular pressure assessed noninvasively by optical coherence elastography

NASA Astrophysics Data System (ADS)

Wu, Chen; Aglyamov, Salavat R.; Liu, Chih-Hao; Han, Zhaolong; Singh, Manmohan; Larin, Kirill V.

2017-02-01

Many ocular diseases such as glaucoma and uveitis can lead to the elevation of intraocular pressure (IOP). Previous research implies a link between elevated IOP and lens disease. However, the relationship between IOP elevation and biomechanical properties of the crystalline lens has not been directly studied yet. In this work, we investigated the biomechanical properties of porcine lens as a function of IOP by acoustic radiation force optical coherence elastography.

Design of a phased array for the generation of adaptive radiation force along a path surrounding a breast lesion for dynamic ultrasound elastography imaging.

PubMed

Ekeom, Didace; Hadj Henni, Anis; Cloutier, Guy

2013-03-01

This work demonstrates, with numerical simulations, the potential of an octagonal probe for the generation of radiation forces in a set of points following a path surrounding a breast lesion in the context of dynamic ultrasound elastography imaging. Because of the in-going wave adaptive focusing strategy, the proposed method is adapted to induce shear wave fronts to interact optimally with complex lesions. Transducer elements were based on 1-3 piezocomposite material. Three-dimensional simulations combining the finite element method and boundary element method with periodic boundary conditions in the elevation direction were used to predict acoustic wave radiation in a targeted region of interest. The coupling factor of the piezocomposite material and the radiated power of the transducer were optimized. The transducer's electrical impedance was targeted to 50 Ω. The probe was simulated by assembling the designed transducer elements to build an octagonal phased-array with 256 elements on each edge (for a total of 2048 elements). The central frequency is 4.54 MHz; simulated transducer elements are able to deliver enough power and can generate the radiation force with a relatively low level of voltage excitation. Using dynamic transmitter beamforming techniques, the radiation force along a path and resulting acoustic pattern in the breast were simulated assuming a linear isotropic medium. Magnitude and orientation of the acoustic intensity (radiation force) at any point of a generation path could be controlled for the case of an example representing a heterogeneous medium with an embedded soft mechanical inclusion.

Model-based optical coherence elastography using acoustic radiation force

NASA Astrophysics Data System (ADS)

Aglyamov, Salavat; Wang, Shang; Karpiouk, Andrei; Li, Jiasong; Emelianov, Stanislav; Larin, Kirill V.

2014-02-01

Acoustic Radiation Force (ARF) stimulation is actively used in ultrasound elastography to estimate mechanical properties of tissue. Compared with ultrasound imaging, OCT provides advantage in both spatial resolution and signal-to-noise ratio. Therefore, a combination of ARF and OCT technologies can provide a unique opportunity to measure viscoelastic properties of tissue, especially when the use of high intensity radiation pressure is limited for safety reasons. In this presentation we discuss a newly developed theoretical model of the deformation of a layered viscoelastic medium in response to an acoustic radiation force of short duration. An acoustic impulse was considered as an axisymmetric force generated on the upper surface of the medium. An analytical solution of this problem was obtained using the Hankel transform in frequency domain. It was demonstrated that layers at different depths introduce different frequency responses. To verify the developed model, experiments were performed using tissue-simulating, inhomogeneous phantoms of varying mechanical properties. The Young's modulus of the phantoms was varied from 5 to 50 kPa. A single-element focused ultrasound transducer (3.5 MHz) was used to apply the radiation force with various durations on the surface of phantoms. Displacements on the phantom surface were measured using a phase-sensitive OCT at 25 kHz repetition frequency. The experimental results were in good agreement with the modeling results. Therefore, the proposed theoretical model can be used to reconstruct the mechanical properties of tissue based on ARF/OCT measurements.

Fontan Circulation in Adult Patients: Acoustic Radiation Force Impulse Elastography as a Useful Tool for Liver Assessment.

PubMed

Melero-Ferrer, Josep Lluís; Osa-Sáez, Ana; Buendía-Fuentes, Francisco; Ballesta-Cuñat, Antonio; Flors, Lucía; Rodríguez-Serrano, María; Calvillo-Batllés, Pilar; Arnau-Vives, Miguel-Ángel; Palencia-Pérez, Miguel A; Rueda-Soriano, Joaquín

2014-07-01

The development of liver fibrosis and cirrhosis due to long-standing liver congestion is known to occur in adult patients with Fontan circulation. Hepatic elastography has shown to be a useful tool for the noninvasive assessment and staging of liver fibrosis in chronic liver diseases, although the utility of this technique in Fontan patients remains to be adequately studied. Twenty-one patients with Fontan circulation underwent an abdominal ultrasound and an acoustic radiation force impulse (ARFI) elastography. In order to compare the results from this group, a cohort of 14 healthy controls and another group containing 17 patients with cirrhosis were included. The association between the velocity values measured with elastography and clinical and analytical parameters were also studied. Mean shear waves propagation velocity in liver tissue in the Fontan group was 1.86 ± 0.5 m/s, with 76% of patients over the cirrhosis threshold (1.55 m/s). The control group had a mean velocity of 1.09 ± 0.06 m/s, while the cirrhotic group obtained 2.71 ± 0.51 m/s. Seven patients with Fontan circulation had increased liver enzymes. Liver ultrasound showed evidence of chronic liver disease in six patients. Velocity values obtained in the presence or absence of analytical or liver ultrasound abnormalities showed significant differences in the univariate analysis (P = .04 and P = .03 respectively). In conclusion, ARFI elastography showed increased wave propagation velocity values in the Fontan population suggesting increased liver stiffness which could be related to advanced fibrosis. A statistically significant association between ARFI values and the presence of analytical and ultrasound abnormalities has been demonstrated. © The Author(s) 2014.

Quantitative Shear Wave Velocity Measurement on Acoustic Radiation Force Impulse Elastography for Differential Diagnosis between Benign and Malignant Thyroid Nodules: A Meta-analysis.

PubMed

Liu, Bo-Ji; Li, Dan-Dan; Xu, Hui-Xiong; Guo, Le-Hang; Zhang, Yi-Feng; Xu, Jun-Mei; Liu, Chang; Liu, Lin-Na; Li, Xiao-Long; Xu, Xiao-Hong; Qu, Shen; Xing, Mingzhao

2015-12-01

The aim of this study was to evaluate the diagnostic performance of quantitative shear wave velocity (SWV) measurement on acoustic radiation force impulse (ARFI) elastography for differentiation between benign and malignant thyroid nodules using meta-analysis. The databases of PubMed and the Web of Science were searched. Studies published in English on assessment of the sensitivity and specificity of ARFI elastography for the differentiation of thyroid nodules were collected. The quantitative measurement of ARFI elastography was evaluated by SWV (m/s). Meta-Disc Version 1.4 software was used to describe and calculate the sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio and summary receiver operating characteristic curves. We analyzed a total of 13 studies, which included 1,854 thyroid nodules (including 1,339 benign nodules and 515 malignant nodules) from 1,641 patients. The summary sensitivity and specificity for differential diagnosis between benign and malignant thyroid nodules by SWV were 0.81 (95% confidence interval [CI]: 0.77-0.84) and 0.84 (95% CI: 0.81-0.86), respectively. The pooled positive and negative likelihood ratios were 5.21 (95% CI: 3.56-7.62) and 0.23 (95% CI: 0.17-0.32), respectively. The pooled diagnostic odds ratio was 27.53 (95% CI: 14.58-52.01), and the area under the summary receiver operating characteristic curve was 0.91 (Q* = 0.84). In conclusion, SWV measurement on ARFI elastography has high sensitivity and specificity for differential diagnosis between benign and malignant thyroid nodules and can be used in combination with conventional ultrasound. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Acoustic radiation force impulse shear wave elastography (ARFI) of acute and chronic pancreatitis and pancreatic tumor.

PubMed

Goertz, Ruediger S; Schuderer, Johanna; Strobel, Deike; Pfeifer, Lukas; Neurath, Markus F; Wildner, Dane

2016-12-01

Acoustic Radiation Force Impulse (ARFI) elastography evaluates tissue stiffness non-invasively and has rarely been applied to pancreas examinations so far. In a prospective and retrospective analysis, ARFI shear wave velocities of healthy parenchyma, pancreatic lipomatosis, acute and chronic pancreatitis, adenocarcinoma and neuroendocrine tumor (NET) of the pancreas were evaluated and compared. In 95 patients ARFI elastography of the pancreatic head, and also of the tail for a specific group, was analysed retrospectively. Additionally, prospectively in 100 patients ARFI was performed in the head and tail of the pancreas. A total of 195 patients were included in the study. Healthy parenchyma (n=21) and lipomatosis (n=30) showed similar shear wave velocities of about 1.3m/s. Acute pancreatitis (n=35), chronic pancreatitis (n=53) and adenocarcinoma (n=52) showed consecutively increasing ARFI values, respectively. NET (n=4) revealed the highest shear wave velocities amounting to 3.62m/s. ARFI elastography showed relevant differences between acute pancreatitis and chronic pancreatitis or adenocarcinoma. With a cut-off value of 1.74m/s for the diagnosis of a malignant disease the sensitivity was 91.1% whereas the specificity amounted to 60.4%. ARFI shear wave velocities present differences in various pathologies of the pancreas. Acute and chronic pancreatitis as well as neoplastic lesions show high ARFI values. Very high elasticity values may indicate malignant disease of the pancreas. However, there is a considerable overlap between the entities. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Acoustic radiation force due to arbitrary incident fields on spherical particles in soft tissue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Treweek, Benjamin C., E-mail: btreweek@utexas.edu; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

Acoustic radiation force is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic radiation force on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the force. As these properties vary, the force computation shows changes in magnitudemore » and direction, which may enable more accurate noninvasive determination of tissue properties.« less

Acoustic radiation force due to arbitrary incident fields on spherical particles in soft tissue

NASA Astrophysics Data System (ADS)

Treweek, Benjamin C.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

2015-10-01

Acoustic radiation force is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic radiation force on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the force. As these properties vary, the force computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.

Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis

PubMed Central

Cañas, Teresa; Maciá, Araceli; Muñoz-Codoceo, Rosa Ana; Fontanilla, Teresa; González-Rios, Patricia; Miralles, María; Gómez-Mardones, Gloria

2015-01-01

Background. Liver disease associated with cystic fibrosis (CFLD) is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI) imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF) were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence. PMID:26609528

Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis.

PubMed

Cañas, Teresa; Maciá, Araceli; Muñoz-Codoceo, Rosa Ana; Fontanilla, Teresa; González-Rios, Patricia; Miralles, María; Gómez-Mardones, Gloria

2015-01-01

Liver disease associated with cystic fibrosis (CFLD) is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI) imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF) were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence.

Acoustic radiation force impulse elastography of the kidneys: is shear wave velocity affected by tissue fibrosis or renal blood flow?

PubMed

Asano, Kenichiro; Ogata, Ai; Tanaka, Keiko; Ide, Yoko; Sankoda, Akiko; Kawakita, Chieko; Nishikawa, Mana; Ohmori, Kazuyoshi; Kinomura, Masaru; Shimada, Noriaki; Fukushima, Masaki

2014-05-01

The aim of this study was to identify the main influencing factor of the shear wave velocity (SWV) of the kidneys measured by acoustic radiation force impulse elastography. The SWV was measured in the kidneys of 14 healthy volunteers and 319 patients with chronic kidney disease. The estimated glomerular filtration rate was calculated by the serum creatinine concentration and age. As an indicator of arteriosclerosis of large vessels, the brachial-ankle pulse wave velocity was measured in 183 patients. Compared to the degree of interobserver and intraobserver deviation, a large variance of SWV values was observed in the kidneys of the patients with chronic kidney disease. Shear wave velocity values in the right and left kidneys of each patient correlated well, with high correlation coefficients (r = 0.580-0.732). The SWV decreased concurrently with a decline in the estimated glomerular filtration rate. A low SWV was obtained in patients with a high brachial-ankle pulse wave velocity. Despite progression of renal fibrosis in the advanced stages of chronic kidney disease, these results were in contrast to findings for chronic liver disease, in which progression of hepatic fibrosis results in an increase in the SWV. Considering that a high brachial-ankle pulse wave velocity represents the progression of arteriosclerosis in the large vessels, the reduction of elasticity succeeding diminution of blood flow was suspected to be the main influencing factor of the SWV in the kidneys. This study indicates that diminution of blood flow may affect SWV values in the kidneys more than the progression of tissue fibrosis. Future studies for reducing data variance are needed for effective use of acoustic radiation force impulse elastography in patients with chronic kidney disease.

The diagnostic performance of shear-wave elastography for liver fibrosis in children and adolescents: A systematic review and diagnostic meta-analysis.

PubMed

Kim, Jeong Rye; Suh, Chong Hyun; Yoon, Hee Mang; Lee, Jin Seong; Cho, Young Ah; Jung, Ah Young

2018-03-01

To assess the diagnostic performance of shear-wave elastography for determining the severity of liver fibrosis in children and adolescents. An electronic literature search of PubMed and EMBASE was conducted. Bivariate modelling and hierarchical summary receiver-operating-characteristic modelling were performed to evaluate the diagnostic performance of shear-wave elastography. Meta-regression and subgroup analyses according to the modality of shear-wave imaging and the degree of liver fibrosis were also performed. Twelve eligible studies with 550 patients were included. Shear-wave elastography showed a summary sensitivity of 81 % (95 % CI: 71-88) and a specificity of 91 % (95 % CI: 83-96) for the prediction of significant liver fibrosis. The number of measurements of shear-wave elastography performed was a significant factor influencing study heterogeneity. Subgroup analysis revealed shear-wave elastography to have an excellent diagnostic performance according to each degree of liver fibrosis. Supersonic shear imaging (SSI) had a higher sensitivity (p<.01) and specificity (p<.01) than acoustic radiation force impulse imaging (ARFI). Shear-wave elastography is an excellent modality for the evaluation of the severity of liver fibrosis in children and adolescents. Compared with ARFI, SSI showed better diagnostic performance for prediction of significant liver fibrosis. • Shear-wave elastography is beneficial for determining liver fibrosis severity in children. • Shear-wave elastography showed summary sensitivity of 81 %, specificity of 91 %. • SSI showed better diagnostic performance than ARFI for significant liver fibrosis.

Ultrasound Elastography: The New Frontier in Direct Measurement of Muscle Stiffness

PubMed Central

Brandenburg, Joline E.; Eby, Sarah F.; Song, Pengfei; Zhao, Heng; Brault, Jeffrey S.; Chen, Shigao; An, Kai-Nan

2014-01-01

The use of brightness-mode ultrasound and Doppler ultrasound in physical medicine and rehabilitation has increased dramatically. The continuing evolution of ultrasound technology has also produced ultrasound elastography, a cutting-edge technology that can directly measure the mechanical properties of tissue, including muscle stiffness. Its real-time and direct measurements of muscle stiffness can aid the diagnosis and rehabilitation of acute musculoskeletal injuries and chronic myofascial pain. It can also help monitor outcomes of interventions affecting muscle in neuromuscular and musculoskeletal diseases, and it can better inform the functional prognosis. This technology has implications for even broader use of ultrasound in physical medicine and rehabilitation practice, but more knowledge about its uses and limitations is essential to its appropriate clinical implementation. In this review, we describe different ultrasound elastography techniques for studying muscle stiffness, including strain elastography, acoustic radiation force impulse imaging, and shear-wave elastography. We discuss the basic principles of these techniques, including the strengths and limitations of their measurement capabilities. We review the current muscle research, discuss physiatric clinical applications of these techniques, and note directions for future research. PMID:25064780

Comparison of strain and acoustic radiation force impulse elastography of breast lesions by qualitative evaluation.

PubMed

Zhao, Qing; Wang, Xiao-Lei; Sun, Jia-Wei; Jiang, Zhao-Peng; Tao, Lin; Zhou, Xian-Li

2018-04-13

To compare the diagnostic performance of conventional strain elastography (CSE) and acoustic radiation force impulse (ARFI) induced SE for qualitative assessment of breast lesions and evaluate the additional value of the two techniques combined with Breast Imaging Reporting and Data System (BI-RADS) respectively for the differentiation of benign and malignant breast lesions. In a cohort of 110 women, the conventional ultrasound (US) features and the elasticity scores of CSE and ARFI induced SE were recorded. The diagnostic performances of BI-RADS, elastography and BI-RADS plus elastography were evaluated, including the area under the receiver operating characteristic curve (AUROC), sensitivity, specificity and accuracy. Pathologically, there were forty-eight malignant and sixty-two benign breast lesions in the final analysis. The AUCs for CSE and ARFI induced SE are similar (CSE, 0.807; ARFI induced SE, 0.846; p > 0.05), however, the specificity of the latter method was significantly higher than that of CSE (83.9% vs. 58.1%, p = 0.004) in differentiating breast lesions. The accuracy and specificity of BI-RADS plus ARFI induced SE (84.5%, 80.6%, respectively) were significantly higher than BI-RADS alone (73.6%, 54.8%, respectively) and BI-RADS plus conventional SE (72.7%, 56.5%, respectively), respectively (p < 0.05) without loss of sensitivity. Our study showed that BI-RADS plus ARFI induced SE had a better diagnostic performance in the diagnosis of breast lesions in comparison with BI-RADS alone or BI-RADS plus CSE.

Ultrasound elastographic techniques in focal liver lesions

PubMed Central

Conti, Clara Benedetta; Cavalcoli, Federica; Fraquelli, Mirella; Conte, Dario; Massironi, Sara

2016-01-01

Elastographic techniques are new ultrasound-based imaging techniques developed to estimate tissue deformability/stiffness. Several ultrasound elastographic approaches have been developed, such as static elastography, transient elastography and acoustic radiation force imaging methods, which include point shear wave and shear wave imaging elastography. The application of these methods in clinical practice aims at estimating the mechanical tissues properties. One of the main settings for the application of these tools has been liver stiffness assessment in chronic liver disease, which has been studied mainly using transient elastography. Another field of application for these techniques is the assessment of focal lesions, detected by ultrasound in organs such as pancreas, prostate, breast, thyroid, lymph nodes. Considering the frequency and importance of the detection of focal liver lesions through routine ultrasound, some studies have also aimed to assess the role that elestography can play in studying the stiffness of different types of liver lesions, in order to predict their nature and thus offer valuable non-invasive methods for the diagnosis of liver masses. PMID:26973405

Ultrasound elastographic techniques in focal liver lesions.

PubMed

Conti, Clara Benedetta; Cavalcoli, Federica; Fraquelli, Mirella; Conte, Dario; Massironi, Sara

2016-03-07

Elastographic techniques are new ultrasound-based imaging techniques developed to estimate tissue deformability/stiffness. Several ultrasound elastographic approaches have been developed, such as static elastography, transient elastography and acoustic radiation force imaging methods, which include point shear wave and shear wave imaging elastography. The application of these methods in clinical practice aims at estimating the mechanical tissues properties. One of the main settings for the application of these tools has been liver stiffness assessment in chronic liver disease, which has been studied mainly using transient elastography. Another field of application for these techniques is the assessment of focal lesions, detected by ultrasound in organs such as pancreas, prostate, breast, thyroid, lymph nodes. Considering the frequency and importance of the detection of focal liver lesions through routine ultrasound, some studies have also aimed to assess the role that elestography can play in studying the stiffness of different types of liver lesions, in order to predict their nature and thus offer valuable non-invasive methods for the diagnosis of liver masses.

Acoustic radiation force impulse elastography: comparison and combination with other noninvasive tests for the diagnosis of compensated liver cirrhosis.

PubMed

Pfeifer, Lukas; Adler, Werner; Zopf, Steffen; Siebler, Jürgen; Wildner, Dane; Goertz, Ruediger S; Schellhaas, Barbara; Neurath, Markus F; Strobel, Deike

2017-05-01

The aim of this study was to compare acoustic radiation force impulse (ARFI) elastography with other noninvasive tests and to develop a new score for the assessment of liver fibrosis/cirrhosis. B-mode ultrasound (including high-frequency liver surface evaluation), routine blood tests, ARFI quantification, and mini-laparoscopic liver evaluation were obtained in compensated patients scheduled for mini-laparoscopic biopsy. Our new cirrhosis score (CS) for the assessment of liver cirrhosis, based on a linear combination of ARFI, platelet (PLT), liver surface, and prothrombin index (PI), was calculated by linear discriminant analysis. Its performance was compared with ARFI-elastography, APRI, FIB-4, alanine aminotransferase (ALT)/aspartate aminotransferase (AST)-ratio, PLT, and PI. For the diagnosis of cirrhosis, a combined gold standard (cirrhosis at histology and/or at macroscopic liver evaluation) was used. In total, 171 patients, of whom 38 had compensated cirrhosis, were included. The CS was significantly better for the diagnosis of cirrhosis compared with ARFI (P=0.028), APRI (P=0.012), PLTs (P=0.013), PI (P=0.025), and ALT/AST ratio (P=0.001), but not the FIB-4 score (P=0.207), with an area under the receiver operating characteristic curve of 0.92 [95% confidence interval (CI): 0.87-0.97], 0.86 (95% CI:0.79-0.93), 0.80 (95% CI: 0.72-0.87), 0.79 (95% CI: 0.7-0.87), 0.81 (95% CI: 0.73-0.89), 0.72 (95% CI:0.64-0.81), and 0.86 (95% CI: 0.8-0.93), respectively. Sensitivity, specificity, positive predictive value, and negative predictive value for CS were 87%, 86%, 63%, and 96%, respectively. The FIB-4 score was significantly superior to the APRI score (P=0.041) and the ALT/AST ratio (P=0.011), with no significant difference from ARFI elastography (P=0.88) for the diagnosis of cirrhosis. Combining ARFI elastography with other noninvasive tests that are used routinely in the workup of patients with suspected liver disease can improve diagnostic accuracy for compensated liver cirrhosis as compared with ARFI elastography alone. The FIB-4 score showed an overall comparable diagnostic accuracy to ARFI-elastography for compensated cirrhosis.

The diagnostic performance of shear wave elastography for malignant cervical lymph nodes: A systematic review and meta-analysis.

PubMed

Suh, Chong Hyun; Choi, Young Jun; Baek, Jung Hwan; Lee, Jeong Hyun

2017-01-01

To evaluate the diagnostic performance of shear wave elastography for malignant cervical lymph nodes. We searched the Ovid-MEDLINE and EMBASE databases for published studies regarding the use of shear wave elastography for diagnosing malignant cervical lymph nodes. The diagnostic performance of shear wave elastography was assessed using bivariate modelling and hierarchical summary receiver operating characteristic modelling. Meta-regression analysis and subgroup analysis according to acoustic radiation force impulse imaging (ARFI) and Supersonic shear imaging (SSI) were also performed. Eight eligible studies which included a total sample size of 481 patients with 647 cervical lymph nodes, were included. Shear wave elastography showed a summary sensitivity of 81 % (95 % CI: 72-88 %) and specificity of 85 % (95 % CI: 70-93 %). The results of meta-regression analysis revealed that the prevalence of malignant lymph nodes was a significant factor affecting study heterogeneity (p < .01). According to the subgroup analysis, the summary estimates of the sensitivity and specificity did not differ between ARFI and SSI (p = .93). Shear wave elastography is an acceptable imaging modality for diagnosing malignant cervical lymph nodes. We believe that both ARFI and SSI may have a complementary role for diagnosing malignant cervical lymph nodes. • Shear wave elastography is acceptable modality for diagnosing malignant cervical lymph nodes. • Shear wave elastography demonstrated summary sensitivity of 81 % and specificity of 85 %. • ARFI and SSI have complementary roles for diagnosing malignant cervical lymph nodes.

Ultrasound-based elastography for the diagnosis of portal hypertension in cirrhotics

PubMed Central

Şirli, Roxana; Sporea, Ioan; Popescu, Alina; Dănilă, Mirela

2015-01-01

Progressive fibrosis is encountered in almost all chronic liver diseases. Its clinical signs are diagnostic in advanced cirrhosis, but compensated liver cirrhosis is harder to diagnose. Liver biopsy is still considered the reference method for staging the severity of fibrosis, but due to its drawbacks (inter and intra-observer variability, sampling errors, unequal distribution of fibrosis in the liver, and risk of complications and even death), non-invasive methods were developed to assess fibrosis (serologic and elastographic). Elastographic methods can be ultrasound-based or magnetic resonance imaging-based. All ultrasound-based elastographic methods are valuable for the early diagnosis of cirrhosis, especially transient elastography (TE) and acoustic radiation force impulse (ARFI) elastography, which have similar sensitivities and specificities, although ARFI has better feasibility. TE is a promising method for predicting portal hypertension in cirrhotic patients, but it cannot replace upper digestive endoscopy. The diagnostic accuracy of using ARFI in the liver to predict portal hypertension in cirrhotic patients is debatable, with controversial results in published studies. The accuracy of ARFI elastography may be significantly increased if spleen stiffness is assessed, either alone or in combination with liver stiffness and other parameters. Two-dimensional shear-wave elastography, the ElastPQ technique and strain elastography all need to be evaluated as predictors of portal hypertension. PMID:26556985

Elastography: current status, future prospects, and making it work for you.

PubMed

Garra, Brian S

2011-09-01

Elastography has emerged as a useful adjunct tool for ultrasound diagnosis. Elastograms are images of tissue stiffness and may be in color, grayscale, or a combination of the two. The first and most common application of elastography is for the diagnosis of breast lesions where studies have shown an area under the receiver operating characteristic curve of 0.88 to 0.95 for distinguishing cancer from benign lesions. The technique is also useful for the diagnosis of complex cysts, although different scanners may vary in how they display such lesions. Recent advances in elastography include quantification using strain ratios, acoustic radiation force impulse imaging, and shear wave velocity estimation. These are useful not only for characterizing focal masses but also for diagnosing diffuse organ diseases such as liver cirrhosis. Other near term potential applications for elastography include characterization of thyroid nodules and lymph node evaluation for metastatic disease. Prostate cancer detection is also a potential application, but obtaining high-quality elastograms may be difficult. This area is evolving. Other promising applications include atheromatous plaque and arterial wall evaluation, venous thrombus evaluation, graft rejection, and monitoring of tumor ablation therapy. When contemplating the acquisition of a system with elastography in this rapidly evolving field, a clear picture of the manufacturer's plans for future upgrades (including quantification) should be obtained.

Acoustic radiation force impulse (ARFI) elastography in the evaluation of renal parenchymal stiffness in patients with ureteropelvic junction obstruction.

PubMed

Habibi, Hatice Arioz; Cicek, Rumeysa Yasemin; Kandemirli, Sedat Giray; Ure, Emel; Ucar, Ayse Kalyoncu; Aslan, Mine; Caliskan, Salim; Adaletli, Ibrahim

2017-04-01

To investigate the role of acoustic radiation force impulse (ARFI) elastography in the detection of renal parenchymal damage in kidneys with and without ureteropelvic junction obstruction (UPJO). Twenty-five pediatric patients with a diagnosis of UPJO who underwent surgery and 15 pediatric patients with conservatively managed UPJO were prospectively evaluated with ARFI elastography. Sixteen healthy volunteers constituted the control group. Shear wave velocity (SWV) measurements in the upper, mid, and lower poles of the affected kidney were performed. SWV values of kidneys based on presence of UPJO and hydronephrosis grade were compared. The correlation of SWV values with residual renal function obtained from diethylenetriaminepentaacetic acid or mercaptoacetyltriglycine-3 renal scan was evaluated. Significantly, higher SWV values were found in control kidneys compared to kidneys affected by UPJO. The median SWVs were 2.82 (2.51-3.07) m/s for the control kidneys and 2.36 (2.09-2.53) m/s for the kidneys in the UPJO group (p < 0.001). When UPJO patients were grouped according to the grade of hydronephrosis, grade 0 hydronephrotic kidneys [2.35 (2.11-2.50) m/s] and grade 3-4 hydronephrotic kidneys [1.86 (1.96-2.25) m/s] had significantly lower SWV values compared to grade 1-2 hydronephrotic kidneys [2.62 (2.37-2.90) m/s] (p < 0.05). ARFI as a noninvasive, radiation-free procedure for evaluating parenchymal stiffness may prove useful in the diagnostic work-up and follow-up of children with UPJO-induced renal disease.

The importance of acoustic radiation force impulse (ARFI) elastography in the diagnosis and clinical course of acute pancreatitis.

PubMed

Kaya, Muhsin; Değirmenci, Serdar; Göya, Cemil; Tuncel, Elif Tuba; Uçmak, Feyzullah; Kaplan, Mehmet Ali

2018-05-01

Acute pancreatitis (AP) is characterized by acute inflammation of the pancreas and it has a highly variable clinical course. The aim of our study was to evaluate the value of acoustic radiation force impulse (ARFI) elastography in the diagnosis and clinical course of AP. Consecutive patients with a diagnosis of AP (patients group) and healthy subject (control group) were prospectively enrolled to the study. Demographic features and clinical, laboratory, and radiological data were recorded. Virtual Touch Tissue Quantification (VTQ) was used to implement ARFI elastography. The tissue elasticity is proportional to the square of the wave velocity (SWV). A total of 108 patients (age, 57±1.8 y) and 79 healthy subjects (age, 53.6±1.81 y) were included in the study. There were 100 (92.5%) edematous and 8 (7.4%) necrotizing AP. The mean SWV was significantly higher in the patient group than in the control group (2.43±0.08 vs. 1.27±0.025 m/s, p < 0.001). There was not significant difference between patient and control group regarding age and gender. SWV cutoff value of 1.63 m/s was associated with 100% sensitivity and 98% specificity for the diagnosis of AP. There was not significant difference between patients with and without complications and patients with edematous and necrotizing AP regarding mean SWV value. There was also not significant correlation between mean SWV value and age, mean length of hospital stay, and mean amylase level. ARFI elastography may be a feasible method for the diagnosis of AP, but it has no value for the prediction of clinical course of AP.

Evaluation of Acoustic Radiation Force Impulse (ARFI) for Fibrosis Staging in Chronic Liver Diseases.

PubMed

Gani, Rino Alvani; Hasan, Irsan; Sanityoso, Andri; Lesmana, Cosmas Rinaldi A; Kurniawan, Juferdy; Jasirwan, Chyntia Olivia Maurine; Kalista, Kemal Fariz; Lutfie, Lutfie

2017-04-01

acoustic radiation force impulse (ARFI) is a new proposed noninvasive method for liver fibrosis staging. Integrated with B-mode ultrasonography, ARFI can be used to assess liver tissue condition. However its diagnostic accuracy is still being continuously evaluated. Also, there is lack of data regarding the utilization of ARFI in our population. This study aimed to evaluate the diagnostic value of ARFI as an alternative noninvasive modality for fibrosis staging in chronic hepatitis B and hepatitis C patients in our population. we conducted cross-sectional comparison of ARFI imaging and transient elastography on patients who underwent liver biopsy at Cipto Mangunkusumo Hospital. Fibrosis staging using METAVIR scoring system presented as standard reference. A total of 43 patients underwent liver biopsy was evaluated by ARFI imaging and transient elastography. Cut-off values were determined using receiver-operating characteristic (ROC). both liver stiffness determined by ARFI and transient elastography (TE) were moderately correlated with METAVIR score with value of 0.581 and 0.613, respectively (both P<0.01). Diagnostic accuracy of ARFI predicted significant fibrosis (F≥2) with area under receiver operating characteristic curve (AUROC) of 0.773 (95% CI 0.616-0.930) and even better for cirrhosis (F4 fibrosis), expressed as AUROC of 0.856 (95% CI 0.736-0.975). Transient elastography was better for significant fibrosis with AUROC of 0.761 (95% CI 0.601-0.920) and was best for prediction of cirrhosis, expressed as AUROC of 0.845 (95% CI 0.722-0.968). ARFI is provided with more convenient evaluation of liver tissue condition, and its diagnostic accuracy is not significantly different from TE for staging liver fibrosis.

Ultrasound elastography: the new frontier in direct measurement of muscle stiffness.

PubMed

Brandenburg, Joline E; Eby, Sarah F; Song, Pengfei; Zhao, Heng; Brault, Jeffrey S; Chen, Shigao; An, Kai-Nan

2014-11-01

The use of brightness-mode ultrasound and Doppler ultrasound in physical medicine and rehabilitation has increased dramatically. The continuing evolution of ultrasound technology has also produced ultrasound elastography, a cutting-edge technology that can directly measure the mechanical properties of tissue, including muscle stiffness. Its real-time and direct measurements of muscle stiffness can aid the diagnosis and rehabilitation of acute musculoskeletal injuries and chronic myofascial pain. It can also help monitor outcomes of interventions affecting muscle in neuromuscular and musculoskeletal diseases, and it can better inform the functional prognosis. This technology has implications for even broader use of ultrasound in physical medicine and rehabilitation practice, but more knowledge about its uses and limitations is essential to its appropriate clinical implementation. In this review, we describe different ultrasound elastography techniques for studying muscle stiffness, including strain elastography, acoustic radiation force impulse imaging, and shear-wave elastography. We discuss the basic principles of these techniques, including the strengths and limitations of their measurement capabilities. We review the current muscle research, discuss physiatric clinical applications of these techniques, and note directions for future research. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Robust intravascular optical coherence elastography driven by acoustic radiation pressure

NASA Astrophysics Data System (ADS)

van Soest, Gijs; Bouchard, Richard R.; Mastik, Frits; de Jong, Nico; van der Steen, Anton F. W.

2007-07-01

High strain spots in the vessel wall indicate the presence of vulnerable plaques. The majority of acute cardiovascular events are preceded by rupture of such a plaque in a coronary artery. Intracoronary optical coherence tomography (OCT) can be extended, in principle, to an elastography technique, mapping the strain in the vascular wall. However, the susceptibility of OCT to frame-to-frame decorrelation, caused by tissue and catheter motion, inhibits reliable tissue displacement tracking and has to date obstructed the development of OCT-based intravascular elastography. We introduce a new technique for intravascular optical coherence elastography, which is robust against motion artifacts. Using acoustic radiation force, we apply a pressure to deform the tissue synchronously with the line scan rate of the OCT instrument. Radial tissue displacement can be tracked based on the correlation between adjacent lines, instead of subsequent frames in conventional elastography. The viability of the method is demonstrated with a simulation study. The root mean square (rms) error of the displacement estimate is 0.55 μm, and the rms error of the strain is 0.6%. It is shown that high-strain spots in the vessel wall, such as observed at the sites of vulnerable atherosclerotic lesions, can be detected with the technique. Experiments to realize this new elastographic method are presented. Simultaneous optical and ultrasonic pulse-echo tracking demonstrate that the material can be put in a high-frequency oscillatory motion with an amplitude of several micrometers, more than sufficient for accurate tracking with OCT. The resulting data are used to optimize the acoustic pushing sequence and geometry.

Dynamic and quantitative assessment of blood coagulation using optical coherence elastography

PubMed Central

Xu, Xiangqun; Zhu, Jiang; Chen, Zhongping

2016-01-01

Reliable clot diagnostic systems are needed for directing treatment in a broad spectrum of cardiovascular diseases and coagulopathy. Here, we report on non-contact measurement of elastic modulus for dynamic and quantitative assessment of whole blood coagulation using acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE). In this system, acoustic radiation force (ARF) is produced by a remote ultrasonic transducer, and a shear wave induced by ARF excitation is detected by the optical coherence tomography (OCT) system. During porcine whole blood coagulation, changes in the elastic property of the clots increase the shear modulus of the sample, altering the propagating velocity of the shear wave. Consequently, dynamic blood coagulation status can be measured quantitatively by relating the velocity of the shear wave with clinically relevant coagulation metrics, including reaction time, clot formation kinetics and maximum shear modulus. The results show that the ARFOE-OCE is sensitive to the clot formation kinetics and can differentiate the elastic properties of the recalcified porcine whole blood, blood added with kaolin as an activator, and blood spiked with fibrinogen. PMID:27090437

Dynamic and quantitative assessment of blood coagulation using optical coherence elastography

NASA Astrophysics Data System (ADS)

Xu, Xiangqun; Zhu, Jiang; Chen, Zhongping

2016-04-01

Reliable clot diagnostic systems are needed for directing treatment in a broad spectrum of cardiovascular diseases and coagulopathy. Here, we report on non-contact measurement of elastic modulus for dynamic and quantitative assessment of whole blood coagulation using acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE). In this system, acoustic radiation force (ARF) is produced by a remote ultrasonic transducer, and a shear wave induced by ARF excitation is detected by the optical coherence tomography (OCT) system. During porcine whole blood coagulation, changes in the elastic property of the clots increase the shear modulus of the sample, altering the propagating velocity of the shear wave. Consequently, dynamic blood coagulation status can be measured quantitatively by relating the velocity of the shear wave with clinically relevant coagulation metrics, including reaction time, clot formation kinetics and maximum shear modulus. The results show that the ARFOE-OCE is sensitive to the clot formation kinetics and can differentiate the elastic properties of the recalcified porcine whole blood, blood added with kaolin as an activator, and blood spiked with fibrinogen.

A diffraction correction for storage and loss moduli imaging using radiation force based elastography.

PubMed

Budelli, Eliana; Brum, Javier; Bernal, Miguel; Deffieux, Thomas; Tanter, Mickaël; Lema, Patricia; Negreira, Carlos; Gennisson, Jean-Luc

2017-01-07

Noninvasive evaluation of the rheological behavior of soft tissues may provide an important diagnosis tool. Nowadays, available commercial ultrasound systems only provide shear elasticity estimation by shear wave speed assessment under the hypothesis of a purely elastic model. However, to fully characterize the rheological behavior of tissues, given by its storage (G') and loss (G″) moduli, it is necessary to estimate both: shear wave speed and shear wave attenuation. Most elastography techniques use the acoustic radiation force to generate shear waves. For this type of source the shear waves are not plane and a diffraction correction is needed to properly estimate the shear wave attenuation. The use of a cylindrical wave approximation to evaluate diffraction has been proposed by other authors before. Here the validity of such approximation is numerically and experimentally revisited. Then, it is used to generate images of G' and G″ in heterogeneous viscoelastic mediums. A simulation algorithm based on the anisotropic and viscoelastic Green's function was used to establish the validity of the cylindrical approximation. Moreover, two experiments were carried out: a transient elastography experiment where plane shear waves were generated using a vibrating plate and a SSI experiment that uses the acoustic radiation force to generate shear waves. For both experiments the shear wave propagation was followed with an ultrafast ultrasound scanner. Then, the shear wave velocity and shear wave attenuation were recovered from the phase and amplitude decay versus distance respectively. In the SSI experiment the cylindrical approximation was applied to correct attenuation due to diffraction effects. The numerical and experimental results validate the use of a cylindrical correction to assess shear wave attenuation. Finally, by applying the cylindrical correction G' and G″ images were generated in heterogeneous phantoms and a preliminary in vivo feasibility study was carried out in the human liver.

A diffraction correction for storage and loss moduli imaging using radiation force based elastography

NASA Astrophysics Data System (ADS)

Budelli, Eliana; Brum, Javier; Bernal, Miguel; Deffieux, Thomas; Tanter, Mickaël; Lema, Patricia; Negreira, Carlos; Gennisson, Jean-Luc

2017-01-01

Noninvasive evaluation of the rheological behavior of soft tissues may provide an important diagnosis tool. Nowadays, available commercial ultrasound systems only provide shear elasticity estimation by shear wave speed assessment under the hypothesis of a purely elastic model. However, to fully characterize the rheological behavior of tissues, given by its storage (G‧) and loss (G″) moduli, it is necessary to estimate both: shear wave speed and shear wave attenuation. Most elastography techniques use the acoustic radiation force to generate shear waves. For this type of source the shear waves are not plane and a diffraction correction is needed to properly estimate the shear wave attenuation. The use of a cylindrical wave approximation to evaluate diffraction has been proposed by other authors before. Here the validity of such approximation is numerically and experimentally revisited. Then, it is used to generate images of G‧ and G″ in heterogeneous viscoelastic mediums. A simulation algorithm based on the anisotropic and viscoelastic Green’s function was used to establish the validity of the cylindrical approximation. Moreover, two experiments were carried out: a transient elastography experiment where plane shear waves were generated using a vibrating plate and a SSI experiment that uses the acoustic radiation force to generate shear waves. For both experiments the shear wave propagation was followed with an ultrafast ultrasound scanner. Then, the shear wave velocity and shear wave attenuation were recovered from the phase and amplitude decay versus distance respectively. In the SSI experiment the cylindrical approximation was applied to correct attenuation due to diffraction effects. The numerical and experimental results validate the use of a cylindrical correction to assess shear wave attenuation. Finally, by applying the cylindrical correction G‧ and G″ images were generated in heterogeneous phantoms and a preliminary in vivo feasibility study was carried out in the human liver.

Elastographic techniques of thyroid gland: current status.

PubMed

Andrioli, Massimiliano; Persani, Luca

2014-08-01

Thyroid nodules are very common with malignancies accounting for about 5 %. Fine-needle biopsy is the most accurate test for thyroid cancer diagnosis. Elastography, a new technology directly evaluating the elastic property of the tissue, has been recently added to the diagnostic armamentarium of the endocrinologists as noninvasive predictor of thyroid malignancy. In this paper, we critically reviewed characteristics and applications of elastographic methods in thyroid gland. Elastographic techniques can be classified on the basis of the following: source-of-tissue compression (free-hand, carotid vibration, ultrasound pulses), processing time (real-time, off-line), stiffness expression (qualitative, semi-quantitative, or quantitative). Acoustic radiation force impulse and aixplorer shear wave are the newest and most promising quantitative elastographic methods. Primary application of elastography is the detection of nodular lesions suspicious for malignancy. Published data show a high sensitivity and negative predictive value of the technique. Insufficient data are available on the possible application of elastography in the differential diagnosis of indeterminate lesions and in thyroiditis. Elastography represents a noninvasive tool able to increase the performance of ultrasound in the selection of thyroid nodules at higher risk of malignancy. Some technical improvements and definition of more robust quantitative diagnostic criteria are required for assigning a definite role in the management of thyroid nodules and thyroiditis to elastography.

From supersonic shear wave imaging to full-field optical coherence shear wave elastography

NASA Astrophysics Data System (ADS)

Nahas, Amir; Tanter, Mickaël; Nguyen, Thu-Mai; Chassot, Jean-Marie; Fink, Mathias; Claude Boccara, A.

2013-12-01

Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30,000 images/s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.

Improvement of liver stiffness measurement, acoustic radiation force impulse measurements, and noninvasive fibrosis markers after direct-acting antivirals for hepatitis C virus G4 recurrence post living donor liver transplantation: Egyptian cohort.

PubMed

Alem, Shereen Abdel; Said, Mohamed; Anwar, Ismail; Abdellatif, Zeinab; Elbaz, Tamer; Eletreby, Rasha; AbouElKhair, Mahmoud; El-Serafy, Magdy; Mogawer, Sherif; El-Amir, Mona; El-Shazly, Mostafa; Hosny, Adel; Yosry, Ayman

2018-05-02

Progression of recurrent hepatitis C is accelerated in liver transplant (LT) recipients. Direct-acting antivirals (DAAs) have recently emerged as a promising therapeutic regimen for the treatment of hepatitis C virus infection. Rates of sustained virological response (SVR) have drastically improved since the introduction of DAAs. The aim is to elucidate the changes in liver stiffness measurement (LSM) by transient elastography (TE) as well as acoustic radiation force impulse (ARFI) elastography and fibrosis scores after DAA treatment in LT recipients with hepatitis C virus recurrence. A single-center, prospective study including 58 LT recipients with hepatitis C recurrence who received different sofosbuvir-based treatment regimens. Transient elastography and ARFI elastography values were recorded as well as fibrosis 4 score (FIB-4) and aspartate aminotransferase-to-platelet ratio index were calculated at baseline and SVR at week 24 (SVR24). The outcome was improvement in LSM and at least a 20% decrease in LSM at SVR24 compared with baseline. The sustained virological response was 98.1%. There was improvement of platelet counts, alanine aminotransferase, and aspartate aminotransferase, which in turn caused improvement in fibrosis scores at SVR24. LSM by TE and ARFI elastography decreased from the baseline median value of 6.3 kPa (interquartile range [IQR]; 4.6 to 8.8 kPa) and 1.28 m/s (IQR; 1.07 to 1.53 m/s) to an SVR24 median value of 6.2 kPa (IQR; 4.85 to 8.9 kPa) and 1.12 (IQR; 0.97 to 1.30 m/s), respectively. Logistic regression analysis showed that baseline viral load was the only significant predictor of improvement in LS after DAA therapy at SVR24. Sofosbuvir-based treatment resulted in an early improvement in parameters of liver fibrosis in post-LT patients with hepatitis C recurrence. © 2018 Wiley Periodicals, Inc.

Imaging of optically diffusive media by use of opto-elastography

NASA Astrophysics Data System (ADS)

Bossy, Emmanuel; Funke, Arik R.; Daoudi, Khalid; Tanter, Mickael; Fink, Mathias; Boccara, Claude

2007-02-01

We present a camera-based optical detection scheme designed to detect the transient motion created by the acoustic radiation force in elastic media. An optically diffusive tissue mimicking phantom was illuminated with coherent laser light, and a high speed camera (2 kHz frame rate) was used to acquire and cross-correlate consecutive speckle patterns. Time-resolved transient decorrelations of the optical speckle were measured as the results of localised motion induced in the medium by the radiation force and subsequent propagating shear waves. As opposed to classical acousto-optic techniques which are sensitive to vibrations induced by compressional waves at ultrasonic frequencies, the proposed technique is sensitive only to the low frequency transient motion induced in the medium by the radiation force. It therefore provides a way to assess both optical and shear mechanical properties.

Tissue mimicking materials for the detection of prostate cancer using shear wave elastography: a validation study.

PubMed

Cao, Rui; Huang, Zhihong; Varghese, Tomy; Nabi, Ghulam

2013-02-01

Quantification of stiffness changes may provide important diagnostic information and aid in the early detection of cancers. Shear wave elastography is an imaging technique that assesses tissue stiffness using acoustic radiation force as an alternate to manual palpation reported previously with quasistatic elastography. In this study, the elastic properties of tissue mimicking materials, including agar, polyacrylamide (PAA), and silicone, are evaluated with an objective to determine material characteristics which resemble normal and cancerous prostate tissue. Acoustic properties and stiffness of tissue mimicking phantoms were measured using compressional mechanical testing and shear wave elastography using supersonic shear imaging. The latter is based on the principles of shear waves generated using acoustic radiation force. The evaluation included tissue mimicking materials (TMMs) within the prostate at different positions and sizes that could mimic cancerous and normal prostate tissue. Patient data on normal and prostate cancer tissues quantified using biopsy histopathology were used to validate the findings. Pathologist reports on histopathology were blinded to mechanical testing and elastographic findings. Young's modulus values of 86.2 ± 4.5 and 271.5 ± 25.7 kPa were obtained for PAA mixed with 2% Al(2)O(3) particles and silicone, respectively. Young's modulus of TMMs from mechanical compression testing showed a clear trend of increasing stiffness with an increasing percentage of agar. The silicone material had higher stiffness values when compared with PAA with Al(2)O(3). The mean Young's modulus value in cancerous tissue was 90.5 ± 4.5 kPa as compared to 93.8 ± 4.4 and 86.2 ± 4.5 kPa obtained with PAA with 2% Al(2)O(3) phantom at a depth of 52.4 and 36.6 mm, respectively. PAA mixed with Al(2)O(3) provides the most suitable tissue mimicking material for prostate cancer tumor material, while agar could form the surrounding background to simulate normal prostate tissue.

The efficiency of acoustic radiation force impulse (ARFI) elastography in the diagnosis and staging of carpal tunnel syndrome.

PubMed

Arslan, Harun; Yavuz, Alpaslan; İlgen, Ferda; Aycan, Abdurrahman; Ozgokce, Mesut; Akdeniz, Hüseyin; Batur, Abdussamet

2018-01-12

The aim of the present study was to quantify the stiffness of the median nerve (MN) at the carpal tunnel inlet by acoustic radiation force impulse (ARFI) elastography and to evaluate whether ARFI can be used in diagnosis and staging of carpal tunnel syndrome (CTS). Sonographic examinations of 96 wrists in 50 patients were included in the study. The cross-sectional area and stiffness of the MN were quantitatively measured by B-mode ultrasonography (USG) and ARFI. The findings of CTS were assigned to four groups: (I) normal (n = 21), (II) mild (n = 39), (III) moderate (n = 38), and (IV) severe (n = 19). The differences between CTS patients and controls and the differences in electrodiagnostic tests among subgroups were statistically compared. ROC analysis was performed to determine the cut-off values between subgroups. Bilateral CTS was present in 46 patients (92 wrists) and unilateral CTS in four patients. Of the 96 nerves in the 50 symptomatic "idiopathic CTS" patients (48 women, 2 men; mean age 45.9 years, range 23-73 years), 39 (40.4%) were mild, 38 (39.8%) were moderate, and 19 (19.8%) were severely affected. When compared to controls, MN stiffness was significantly higher in the CTS group (P < 0.001); furthermore, it was higher in the severe or extreme severity group than the mild or moderate severity group (P < 0.001). A 3.250 m/s cut-off value on ARFI revealed sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 81, 82, 95.1, 50, and 82%, respectively. The MN stiffness measured by ARFI elastography is significantly higher in patients with CTS then in controls. ARFI elastography appears to be a highly efficient imaging modality for the diagnosis and staging of these patients.

Tissue mimicking materials for the detection of prostate cancer using shear wave elastography: A validation study

PubMed Central

Cao, Rui; Huang, Zhihong; Varghese, Tomy; Nabi, Ghulam

2013-01-01

Purpose: Quantification of stiffness changes may provide important diagnostic information and aid in the early detection of cancers. Shear wave elastography is an imaging technique that assesses tissue stiffness using acoustic radiation force as an alternate to manual palpation reported previously with quasistatic elastography. In this study, the elastic properties of tissue mimicking materials, including agar, polyacrylamide (PAA), and silicone, are evaluated with an objective to determine material characteristics which resemble normal and cancerous prostate tissue. Methods: Acoustic properties and stiffness of tissue mimicking phantoms were measured using compressional mechanical testing and shear wave elastography using supersonic shear imaging. The latter is based on the principles of shear waves generated using acoustic radiation force. The evaluation included tissue mimicking materials (TMMs) within the prostate at different positions and sizes that could mimic cancerous and normal prostate tissue. Patient data on normal and prostate cancer tissues quantified using biopsy histopathology were used to validate the findings. Pathologist reports on histopathology were blinded to mechanical testing and elastographic findings. Results: Young's modulus values of 86.2 ± 4.5 and 271.5 ± 25.7 kPa were obtained for PAA mixed with 2% Al2O3 particles and silicone, respectively. Young's modulus of TMMs from mechanical compression testing showed a clear trend of increasing stiffness with an increasing percentage of agar. The silicone material had higher stiffness values when compared with PAA with Al2O3. The mean Young's modulus value in cancerous tissue was 90.5 ± 4.5 kPa as compared to 93.8 ± 4.4 and 86.2 ± 4.5 kPa obtained with PAA with 2% Al2O3 phantom at a depth of 52.4 and 36.6 mm, respectively. Conclusions: PAA mixed with Al2O3 provides the most suitable tissue mimicking material for prostate cancer tumor material, while agar could form the surrounding background to simulate normal prostate tissue. PMID:23387774

Standard value of ultrasound elastography using acoustic radiation force impulse imaging (ARFI) in healthy liver tissue of children and adolescents.

PubMed

Eiler, J; Kleinholdermann, U; Albers, D; Dahms, J; Hermann, F; Behrens, C; Luedemann, M; Klingmueller, V; Alzen, G F P

2012-10-01

Ultrasound elastography by acoustic radiation force impulse imaging (ARFI) is used in adults for non invasive measurement of liver stiffness, indicating liver diseases like fibrosis. To establish ARFI in children and adolescents we determined standard values of healthy liver tissue and analysed potentially influencing factors. 132 patients between 0 and 17 years old were measured using ARFI. None of them had any liver disease or any other disease that could affect the liver secondarily. All patients had a normal ultrasound scan, a normal BMI and normal liver function tests. The mean value of all ARFI measurements was calculated and potentially influencing factors were analysed. The mean value of all ARFI elastography measurements was 1.16 m/sec (SD ± 0.14 m/sec). Neither age (p = 0.533) nor depth of measurement (p = 0.066) had no significant influence on ARFI values, whereas a significant effect of gender was found with lower ARFI values in females (p = 0.025), however, there was no significant interaction between age groups (before or after puberty) and gender (p = 0.276). There was an interlobar difference with lower values in the right liver lobe compared to the left (p = 0.036) and with a significantly lower variance (p < 0.001). Consistend values were measured by different examiners (p = 0.108), however, the inter examiner variance deviated significantly (p < 0.001). ARFI elastography is a reliable method to measure liver stiffness in children and adolescents. In relation to studies which analyse liver diseases, the standard value of 1.16 m/sec (± 0.14 m/sec) allows a differentiation of healthy versus pathological liver tissue. © Georg Thieme Verlag KG Stuttgart · New York.

High-resolution harmonic motion imaging (HR-HMI) for tissue biomechanical property characterization

PubMed Central

Ma, Teng; Qian, Xuejun; Chiu, Chi Tat; Yu, Mingyue; Jung, Hayong; Tung, Yao-Sheng; Shung, K. Kirk

2015-01-01

Background Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a useful technique for clinicians to perform disease diagnosis and determine stages of many diseases. Many acoustic radiation force (ARF) based elastography, including acoustic radiation force impulse (ARFI) imaging and harmonic motion imaging (HMI), have been developed to remotely assess the elastic properties of tissues. However, due to the lower operating frequencies of these approaches, their spatial resolutions are insufficient for revealing stiffness distribution on small scale applications, such as cancerous tumor margin detection, atherosclerotic plaque composition analysis and ophthalmologic tissue characterization. Though recently developed ARF-based optical coherence elastography (OCE) methods open a new window for the high resolution elastography, shallow imaging depths significantly limit their usefulness in clinics. Methods The aim of this study is to develop a high-resolution HMI method to assess the tissue biomechanical properties with acceptable field of view (FOV) using a 4 MHz ring transducer for efficient excitation and a 40 MHz needle transducer for accurate detection. Under precise alignment of two confocal transducers, the high-resolution HMI system has a lateral resolution of 314 µm and an axial resolution of 
147 µm with an effective FOV of 2 mm in depth. Results The performance of this high resolution imaging system was validated on the agar-based tissue mimicking phantoms with different stiffness distributions. These data demonstrated the imaging system’s improved resolution and sensitivity on differentiating materials with varying stiffness. In addition, ex vivo imaging of a human atherosclerosis coronary artery demonstrated the capability of high resolution HMI in identifying layer-specific structures and characterizing atherosclerotic plaques based on their stiffness differences. Conclusions All together high resolution HMI appears to be a promising ultrasound-only technology for characterizing tissue biomechanical properties at the microstructural level to improve the image-based diseases diagnosis in multiple clinical applications. PMID:25694960

High-resolution harmonic motion imaging (HR-HMI) for tissue biomechanical property characterization.

PubMed

Ma, Teng; Qian, Xuejun; Chiu, Chi Tat; Yu, Mingyue; Jung, Hayong; Tung, Yao-Sheng; Shung, K Kirk; Zhou, Qifa

2015-02-01

Elastography, capable of mapping the biomechanical properties of biological tissues, serves as a useful technique for clinicians to perform disease diagnosis and determine stages of many diseases. Many acoustic radiation force (ARF) based elastography, including acoustic radiation force impulse (ARFI) imaging and harmonic motion imaging (HMI), have been developed to remotely assess the elastic properties of tissues. However, due to the lower operating frequencies of these approaches, their spatial resolutions are insufficient for revealing stiffness distribution on small scale applications, such as cancerous tumor margin detection, atherosclerotic plaque composition analysis and ophthalmologic tissue characterization. Though recently developed ARF-based optical coherence elastography (OCE) methods open a new window for the high resolution elastography, shallow imaging depths significantly limit their usefulness in clinics. The aim of this study is to develop a high-resolution HMI method to assess the tissue biomechanical properties with acceptable field of view (FOV) using a 4 MHz ring transducer for efficient excitation and a 40 MHz needle transducer for accurate detection. Under precise alignment of two confocal transducers, the high-resolution HMI system has a lateral resolution of 314 µm and an axial resolution of 
147 µm with an effective FOV of 2 mm in depth. The performance of this high resolution imaging system was validated on the agar-based tissue mimicking phantoms with different stiffness distributions. These data demonstrated the imaging system's improved resolution and sensitivity on differentiating materials with varying stiffness. In addition, ex vivo imaging of a human atherosclerosis coronary artery demonstrated the capability of high resolution HMI in identifying layer-specific structures and characterizing atherosclerotic plaques based on their stiffness differences. All together high resolution HMI appears to be a promising ultrasound-only technology for characterizing tissue biomechanical properties at the microstructural level to improve the image-based diseases diagnosis in multiple clinical applications.

Acoustic radiation force impulse (ARFI) elastography for detection of renal damage in children.

PubMed

Göya, Cemil; Hamidi, Cihad; Ece, Aydın; Okur, Mehmet Hanifi; Taşdemir, Bekir; Çetinçakmak, Mehmet Güli; Hattapoğlu, Salih; Teke, Memik; Şahin, Cahit

2015-01-01

Acoustic radiation force impulse (ARFI) imaging is a promising method for noninvasive evaluation of the renal parenchyma. To investigate the contribution of ARFI quantitative US elastography for the detection of renal damage in kidneys with and without vesicoureteral reflux (VUR). One hundred seventy-six kidneys of 88 children (46 male, 42 female) who had been referred for voiding cystourethrography and 20 healthy controls were prospectively investigated. Patients were assessed according to severity of renal damage on dimercaptosuccinic acid (DMSA) scintigraphy. Ninety-eight age- and gender-matched healthy children constituted the control group. Quantitative shear wave velocity (SWV) measurements were performed in the upper and lower poles and in the interpolar region of each kidney. DMSA scintigraphy was performed in 62 children (124 kidneys). Comparisons of SWV values of kidneys with and without renal damage and/or VUR were done. Significantly higher SWV values were found in non-damaged kidneys. Severely damaged kidneys had the lowest SWV values (P < 0.001). High-grade (grade V-IV) refluxing kidneys had the lowest SWV values, while non-refluxing kidneys had the highest values (P < 0.05). Significant negative correlations were found between the mean quantitative US elastography values and DMSA scarring score (r = -0.788, P < 0.001) and VUR grade (r = -0.634, P < 0.001). SWV values of the control kidneys were significantly higher than those of damaged kidneys (P < 0.05). Our findings suggest decreasing SWV of renal units with increasing grades of vesicoureteric reflux, increasing DMSA-assessed renal damage and decreasing DMSA-assessed differential function.

Clutter elimination for deep clinical optoacoustic imaging using localised vibration tagging (LOVIT)☆

PubMed Central

Jaeger, Michael; Bamber, Jeffrey C.; Frenz, Martin

2013-01-01

This paper investigates a novel method which allows clutter elimination in deep optoacoustic imaging. Clutter significantly limits imaging depth in clinical optoacoustic imaging, when irradiation optics and ultrasound detector are integrated in a handheld probe for flexible imaging of the human body. Strong optoacoustic transients generated at the irradiation site obscure weak signals from deep inside the tissue, either directly by propagating towards the probe, or via acoustic scattering. In this study we demonstrate that signals of interest can be distinguished from clutter by tagging them at the place of origin with localised tissue vibration induced by the acoustic radiation force in a focused ultrasonic beam. We show phantom results where this technique allowed almost full clutter elimination and thus strongly improved contrast for deep imaging. Localised vibration tagging by means of acoustic radiation force is especially promising for integration into ultrasound systems that already have implemented radiation force elastography. PMID:25302147

Acoustic Radiation Force Impulse Elastography in Determining the Effects of Type 1 Diabetes on Pancreas and Kidney Elasticity in Children.

PubMed

Sağlam, Dilek; Bilgici, Meltem Ceyhan; Kara, Cengiz; Yılmaz, Gülay Can; Çamlıdağ, İlkay

2017-11-01

The aim of this study is to determine the effects of type 1 diabetes on pancreas and kidney elasticity in children, using acoustic radiation force impulse ultrasound elastography. Sixty autoantibody-positive patients with type 1 diabetes (45% girls; mean [± SD] age, 11.7 ± 4.4 years; range, 1.9-19.3 years) admitted to the pediatric endocrinology outpatient clinic and 32 healthy children (50% girls; mean age, 10.2 ± 3.8 years; range, 2.1-17.3 years) were included in the study. Acoustic radiation force impulse elastography measurements were performed of the kidneys and pancreas in both groups. Body mass index, duration of diabetes, HbA1c levels, and insulin dosage of patients with type 1 diabetes were recorded. The mean shear-wave velocities of the pancreas were 0.99 ± 0.25 m/s in patients with type 1 diabetes and 1.09 ± 0.22 m/s in healthy control subjects; the difference was not significant (p = 0.08). The median shear-wave velocities of the right and left kidneys in patients with type 1 diabetes were 2.43 ± 0.29 and 2.47 ± 0.25 m/s, respectively. There were no significant differences in the shear-wave velocities of the right and left kidneys between the patients with type 1 diabetes and the healthy control subjects (p = 0.91 and p = 0.73, respectively). Correlation analysis showed no correlation between the shear-wave velocities of the pancreas and kidney versus HbA1c level, duration of diabetes, insulin dosage, height, weight, and body mass index of the patients with type 1 diabetes. The current study showed no significant difference in the shear-wave velocity of kidneys in children with type 1 diabetes with normoalbuminuria compared with the healthy control subjects. We also observed that the shear-wave velocity of the pancreas in children with type 1 diabetes and healthy control subjects did not differ significantly.

Effects of compression force on elasticity index and elasticity ratio in ultrasound elastography

PubMed Central

Sasaki, Y; Sakamoto, J; Kamio, T; Nishikawa, K; Otonari-Yamamoto, M; Wako, M

2014-01-01

Objectives: The purpose of this study was to investigate the relationship between compression force and hardness values in ultrasound elastography. Methods: Ultrasound elastography was performed using an elastography phantom, comprising inclusions with different elasticities and echogenicities. The compression force was set to approximately 100 gw (light force) and approximately 500 gw (heavy force). The elasticity index (EI) of the inclusion was measured. The EI was a relative hardness value of a structure within an elastographic image. Similarly, the EI of the background was measured as a reference. The elasticity ratio (ER) was calculated as the EI of the inclusion divided by the EI of the reference. Results: The hardness of the phantom could be discerned with both the EI and ER, regardless of the compression force. The EI and ER with heavy force tended to be higher than those with light force, but the difference was not significant. A strong correlation was observed between the EI and ER of soft structures, whereas the correlation between the EI and ER of hard structures was weak, and the ER values varied widely. Conclusions: The EI offers potential as a good indicator for assessing the hardness. PMID:24592929

Acoustic Radiation Force Impulse Quantification in the Evaluation of Thyroid Elasticity in Pediatric Patients With Hashimoto Thyroiditis.

PubMed

Yucel, Serap; Ceyhan Bilgici, Meltem; Kara, Cengiz; Can Yilmaz, Gulay; Aydin, H Murat; Elmali, Muzaffer; Tomak, Leman; Saglam, Dilek

2018-05-01

To evaluate the parenchymal elasticity of the thyroid gland with acoustic radiation force impulse imaging in pediatric patients with Hashimoto thyroiditis and to compare it with healthy volunteers. Twenty-six patients with Hashimoto thyroiditis and 26 healthy volunteers between 6 and 17 years were included. The shear wave velocity (SWV) values of both thyroid lobes in both groups were evaluated. The age and sex characteristics of the controls and patients with Hashimoto thyroiditis were similar. The SWV of the thyroid gland in patients with Hashimoto thyroiditis (mean ± SD, 1.67 ± 0.63 m/s) was significantly higher than that in the control group (1.30 ± 0.13 m/s; P < .001). There was no significant difference between the thyroid lobes in both groups. A receiver operating characteristic curve analyses showed an optimal cutoff value of 1.41 m/s, with 73.1% sensitivity, 80.8% specificity, a 79.2 % positive predictive value, and a 75.0% negative predictive value (area under the curve, 0.806; P < .001). In patients with Hashimoto thyroiditis, there was a positive correlation between the SWV values versus anti-thyroperoxidase (Pearson r = 0.46; P = .038). There were no correlations between age, body mass index, thyroid function test results, and anti-thyroglobulin values and versus SWV values. Also, no significant differences were seen between the groups for gland size, gland vascularity, and l-thyroxine treatment. Acoustic radiation force impulse elastography showed a significant difference in the stiffness of the thyroid gland between children with Hashimoto thyroiditis and the healthy group. Using acoustic radiation force impulse elastography immediately after a standard ultrasound evaluation may predict chronic autoimmune thyroiditis. © 2017 by the American Institute of Ultrasound in Medicine.

Quantitative shear wave optical coherence elastography (SW-OCE) with acoustic radiation force impulses (ARFI) induced by phase array transducer

NASA Astrophysics Data System (ADS)

Song, Shaozhen; Le, Nhan Minh; Wang, Ruikang K.; Huang, Zhihong

2015-03-01

Shear Wave Optical Coherence Elastography (SW-OCE) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. One of the main challenges in shear wave elastography is to induce a reliable source of shear wave; most of nowadays techniques use external vibrators which have several drawbacks such as limited wave propagation range and/or difficulties in non-invasive scans requiring precisions, accuracy. Thus, we propose linear phase array ultrasound transducer as a remote wave source, combined with the high-speed, 47,000-frame-per-second Shear-wave visualization provided by phase-sensitive OCT. In this study, we observed for the first time shear waves induced by a 128 element linear array ultrasound imaging transducer, while the ultrasound and OCT images (within the OCE detection range) were triggered simultaneously. Acoustic radiation force impulses are induced by emitting 10 MHz tone-bursts of sub-millisecond durations (between 50 μm - 100 μm). Ultrasound beam steering is achieved by programming appropriate phase delay, covering a lateral range of 10 mm and full OCT axial (depth) range in the imaging sample. Tissue-mimicking phantoms with agarose concentration of 0.5% and 1% was used in the SW-OCE measurements as the only imaging samples. The results show extensive improvements over the range of SW-OCE elasticity map; such improvements can also be seen over shear wave velocities in softer and stiffer phantoms, as well as determining the boundary of multiple inclusions with different stiffness. This approach opens up the feasibility to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative measurement of tissue biomechanical property.

Erratum. Correction to: Hu X, et al. Acoustic Radiation Force Impulse (ARFI) Elastography for non‑invasive evaluation of hepatic fibrosis in chronic hepatitis B and C patients: a systematic review and meta-analysis. Med Ultrason 2017; 19(1):23-3.

PubMed

2017-06-01

The authors have been made aware of the errors that appeared at Corresponding author: correct phone number 86-10-63138297 and correct email qianlinxue2002@163.com, and also at acknowledgements: correct grant no. 2014-3-009.

Acoustic Radiation Force Impulse Elastography for Efficacy Evaluation after Hepatocellular Carcinoma Radiofrequency Ablation: A Comparative Study with Contrast-Enhanced Ultrasound

PubMed Central

Xu, Xiaohong; Luo, Liangping; Chen, Jiexin; Wang, Jiexin; Zhou, Honglian; Li, Mingyi; Jin, Zhanqiang; Chen, Nianping; Miao, Huilai; Lin, Manzhou; Dai, Wei; Ahuja, Anil T.; Wang, Yi-Xiang J.

2014-01-01

Aim. To explore acoustic radiation force impulse (ARFI) elastography in assessing residual tumors of hepatocellular carcinoma (HCC) after radiofrequency ablation (RFA). Materials and Methods. There were 83 HCC lesions among 72 patients. All patients were examined with ARFI, contrast enhanced ultrasound (CEUS), and CT or MRI. Tumor brightness on virtual touch tissue imaging (VTI) and shear wave velocity (SWV) were assessed before and approximately one month after RFA. Results. There were 14 residual tumors after RFA. VTI showed that all the tumors were darker after RFA. VTI was not able to distinguish the ablated lesions and the residual tumors. 13 residual tumor lesions were detected by CEUS. All completely ablated nodules had SWV demonstration of x.xx., while with those residual nodules, 6 tumors had x.xx measurement and 8 tumors had measurable SWV. nine lesions with residual tumors occurred in cirrhosis subjects and 5 lesions with residual tumors occurred in fibrosis subjects; there was no residual tumor in the normal liver subjects. Conclusion. VTI technique cannot demonstrate residual tumor post RFA. While SWV measurement of less than x.xx is likely associated with residual tumors, measurement of less than x.xx cannot exclude residual tumors. Liver cirrhosis is associated with decreased chance of a complete ablation. PMID:24895624

Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity.

PubMed

Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T; Wang, Ruikang K; O'Donnell, Matthew

2016-12-23

Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea.

Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

PubMed Central

Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O’Donnell, Matthew

2016-01-01

Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea. PMID:28008920

Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

NASA Astrophysics Data System (ADS)

Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

2016-12-01

Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea.

Impact of nonlinear distortion on acoustic radiation force elastography.

PubMed

Draudt, Andrew B; Cleveland, Robin O

2011-11-01

High-intensity focused ultrasound (HIFU) produces an acoustic radiation force that induces tissue displacement, which can be measured by monitoring time shifts in the backscattered signals from interrogation pulses. If the pulse occurs simultaneously with the HIFU, the arrival time of the backscatter will be biased because nonlinearity associated with the HIFU changes the local sound speed. Measurements of the pressure field using 1.1 MHz HIFU and a 7.5 MHz pulse in water exhibited a nonlinearly induced apparent displacement (NIAD) that varied with the HIFU pressure, propagation distance and the timing of the pulse relative to the HIFU. Nonlinear simulations employing the KZK equation predicted NIADs that agreed with measurements. Experiments with chicken breast demonstrated a NIAD with magnitude similar to that expected from the radiation force. Finally it was shown that if two pulses were fired with different phases relative to the HIFU, then upon averaging, the NIAD could be mitigated. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

External vibration multi-directional ultrasound shearwave elastography (EVMUSE): application in liver fibrosis staging.

PubMed

Zhao, Heng; Song, Pengfei; Meixner, Duane D; Kinnick, Randall R; Callstrom, Matthew R; Sanchez, William; Urban, Matthew W; Manduca, Armando; Greenleaf, James F; Chen, Shigao

2014-11-01

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called external vibration multi-directional ultrasound shearwave elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A 2-D shear wave speed map was reconstructed from each individual shear wave field, and a final 2-D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver magnetic resonance elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging.

External Vibration Multi-directional Ultrasound Shearwave Elastography (EVMUSE): Application in Liver Fibrosis Staging

PubMed Central

Zhao, Heng; Song, Pengfei; Meixner, Duane D.; Kinnick, Randall R.; Callstrom, Matthew R.; Sanchez, William; Urban, Matthew W.; Manduca, Armando; Greenleaf, James F.

2014-01-01

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called External Vibration Multi-directional Ultrasound Shearwave Elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A two-dimensional (2D) shear wave speed map was reconstructed from each individual shear wave field, and a final 2D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver Magnetic Resonance Elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging. PMID:25020066

Evaluation of experimental methods for assessing safety for ultrasound radiation force elastography.

PubMed

Skurczynski, M J; Duck, F A; Shipley, J A; Bamber, J C; Melodelima, D

2009-08-01

Standard test tools have been evaluated for the assessment of safety associated with a prototype transducer intended for a novel radiation force elastographic imaging system. In particular, safety has been evaluated by direct measurement of temperature rise, using a standard thermal test object, and detection of inertial cavitation from acoustic emission. These direct measurements have been compared with values of the thermal index and mechanical index, calculated from acoustic measurements in water using standard formulae. It is concluded that measurements using a thermal test object can be an effective alternative to the calculation of thermal index for evaluating thermal hazard. Measurement of the threshold for cavitation was subject to considerable variability, and it is concluded that the mechanical index still remains the preferred standard means for assessing cavitation hazard.

Amplitude-modulated ultrasound radiation force combined with phase-sensitive optical coherence tomography for shear wave elastography

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

2015-03-01

Tissue stiffness can be measured from the propagation speed of shear waves. Acoustic radiation force (ARF) can generate shear waves by focusing ultrasound in tissue for ~100 μs. Safety considerations and electronics abilities limit ultrasound pressures. We previously presented shear wave elastography combining ARF and phase-sensitive optical coherence tomography (PhS-OCT) [1]. Here, we use amplitude-modulated ARF to enhance shear wave signal-to-noise ratio (SNR) at low pressures. Experiments were performed on tissue-mimicking phantoms. ARF was applied using a single-element transducer, driven by a 7.5 MHz, 3-ms, sine wave modulated in amplitude by a linear-swept frequency (1 to 7 kHz). Pressures between 1 to 3 MPa were tested. Displacements were tracked using PhS-OCT and numerically compressed using pulse compression methods detailed in previous work [2]. SNR was compared to that of 200-μs bursts. Stiffness maps were reconstructed using time-of-flight computations. 200-μs bursts give barely detectable displacements at 1 MPa (3.7 dB SNR). Pulse compression gives 36.2 dB at 1.5 MPa. In all cases with detectable displacements, shear wave speeds were determined in 5%-gelatin and 10%-gelatin phantoms and compared to literature values. Applicability to ocular tissues (cornea, intraocular lens) is under investigation.

Elastography for the pancreas: Current status and future perspective

PubMed Central

Kawada, Natsuko; Tanaka, Sachiko

2016-01-01

Elastography for the pancreas can be performed by either ultrasound or endoscopic ultrasound (EUS). There are two types of pancreatic elastographies based on different principles, which are strain elastography and shear wave elastography. The stiffness of tissue is estimated by measuring the grade of strain generated by external pressure in the former, whereas it is estimated by measuring propagation speed of shear wave, the transverse wave, generated by acoustic radiation impulse (ARFI) in the latter. Strain elastography is difficult to perform when the probe, the pancreas and the aorta are not located in line. Accordingly, a fine elastogram can be easily obtained in the pancreatic body but not in the pancreatic head and tail. In contrast, shear wave elastography can be easily performed in the entire pancreas because ARFI can be emitted to wherever desired. However, shear wave elastography cannot be performed by EUS to date. Recently, clinical guidelines for elastography specialized in the pancreas were published from Japanese Society of Medical Ultrasonics. The guidelines show us technical knacks of performing elastography for the pancreas. PMID:27076756

Elastography for the pancreas: Current status and future perspective.

PubMed

Kawada, Natsuko; Tanaka, Sachiko

2016-04-14

Elastography for the pancreas can be performed by either ultrasound or endoscopic ultrasound (EUS). There are two types of pancreatic elastographies based on different principles, which are strain elastography and shear wave elastography. The stiffness of tissue is estimated by measuring the grade of strain generated by external pressure in the former, whereas it is estimated by measuring propagation speed of shear wave, the transverse wave, generated by acoustic radiation impulse (ARFI) in the latter. Strain elastography is difficult to perform when the probe, the pancreas and the aorta are not located in line. Accordingly, a fine elastogram can be easily obtained in the pancreatic body but not in the pancreatic head and tail. In contrast, shear wave elastography can be easily performed in the entire pancreas because ARFI can be emitted to wherever desired. However, shear wave elastography cannot be performed by EUS to date. Recently, clinical guidelines for elastography specialized in the pancreas were published from Japanese Society of Medical Ultrasonics. The guidelines show us technical knacks of performing elastography for the pancreas.

Noninvasive assessment of liver fibrosis in patients with chronic hepatitis B.

PubMed

Enomoto, Masaru; Morikawa, Hiroyasu; Tamori, Akihiro; Kawada, Norifumi

2014-09-14

Infection with hepatitis B virus is an important health problem worldwide: it affects more than 350 million people and is a leading cause of liver-related morbidity, accounting for 1 million deaths annually. Hepatic fibrosis is a consequence of the accumulation of extracellular matrix components in the liver. An accurate diagnosis of liver fibrosis is essential for the management of chronic liver disease. Liver biopsy has been considered the gold standard for diagnosing disease, grading necroinflammatory activity, and staging fibrosis. However, liver biopsy is unsuitable for repeated evaluations because it is invasive and can cause major complications, including death. Several noninvasive evaluations have been introduced for the assessment of liver fibrosis: serum biomarkers, combined indices or scores, and imaging techniques including transient elastography, acoustic radiation force impulse, real-time tissue elastography, and magnetic resonance elastography. Here, we review the recent progress of noninvasive assessment of liver fibrosis in patients with chronic hepatitis B. Most noninvasive evaluations for liver fibrosis have been validated first in patients with chronic hepatitis C, and later in those with chronic hepatitis B. The establishment of a noninvasive assessment of liver fibrosis is urgently needed to aid in the management of this leading cause of chronic liver disease.

Extended optical theorem in isotropic solids and its application to the elastic radiation force

NASA Astrophysics Data System (ADS)

Leão-Neto, J. P.; Lopes, J. H.; Silva, G. T.

2017-04-01

In this article, we derive the extended optical theorem for the elastic-wave scattering by a spherical inclusion (with and without absorption) in a solid matrix. This theorem expresses the extinction cross-section, i.e., the time-averaged power extracted from the incoming beam per its intensity, regarding the partial-wave expansion coefficients of the incident and scattered waves. We also establish the connection between the optical theorem and the elastic radiation force by a plane wave in a linear and isotropic solid. We obtain the absorption, scattering, and extinction efficiencies (the corresponding power per characteristic incident intensity per sphere cross-section area) for a plane wave and a spherically focused beam. We discuss to which extent the radiation force theory for plane waves can be used to the focused beam case. Considering an iron sphere embedded in an aluminum matrix, we numerically compute the scattering and elastic radiation force efficiencies. The radiation force on a stainless steel sphere embedded in a tissue-like medium (soft solid) is also computed. In this case, resonances are observed in the force as a function of the sphere size parameter (the wavenumber times the sphere radius). Remarkably, the relative difference between our findings and previous lossless liquid models is about 100% in the long-wavelength limit. Regarding some applications, the obtained results have a direct impact on ultrasound-based elastography techniques and ultrasonic nondestructive testing, as well as implantable devices activated by ultrasound.

Guidelines for Finite Element Modeling of Acoustic Radiation Force-Induced Shear Wave Propagation in Tissue-Mimicking Media

PubMed Central

Palmeri, Mark L.; Qiang, Bo; Chen, Shigao; Urban, Matthew W.

2017-01-01

Ultrasound shear wave elastography is emerging as an important imaging modality for evaluating tissue material properties. In its practice, some systematic biases have been associated with ultrasound frequencies, focal depths and configuration, transducer types (linear versus curvilinear), along with displacement estimation and shear wave speed estimation algorithms. Added to that, soft tissues are not purely elastic, so shear waves will travel at different speeds depending on their spectral content, which can be modulated by the acoustic radiation force excitation focusing, duration and the frequency-dependent stiffness of the tissue. To understand how these different acquisition and material property parameters may affect measurements of shear wave velocity, simulations of the propagation of shear waves generated by acoustic radiation force excitations in viscoelastic media are a very important tool. This article serves to provide an in-depth description of how these simulations are performed. The general scheme is broken into three components: (1) simulation of the three-dimensional acoustic radiation force push beam, (2) applying that force distribution to a finite element model, and (3) extraction of the motion data for post-processing. All three components will be described in detail and combined to create a simulation platform that is powerful for developing and testing algorithms for academic and industrial researchers involved in making quantitative shear wave-based measurements of tissue material properties. PMID:28026760

Role of acoustic radiation force impulse and shear wave velocity in prediction of preterm birth: a prospective study.

PubMed

Agarwal, Arjit; Agarwal, Shubhra; Chandak, Shruti

2018-06-01

Background Preterm birth is one of the important causes of neonatal morbidity where we rely on subjective criteria such as modified Bishop's scoring and contemporary sonographic measurement of cervical length. Acoustic radiation force impulse (ARFI) is a technological advancement in elastography that can be employed in prediction of cervical softening and preterm labor. Purpose To evaluate the role of ARFI technique and shear wave velocity (SWV) estimates as a predictor of preterm birth and its comparison with other clinical and sono-elastographic measures. Material and Methods Thirty-four pregnant women (gestation age = 28-37 weeks age) showing features suggestive of preterm labor were included and evaluated with modified Bishop's score, cervical length by ultrasound (US), ARFI to derive Elastography index (EI), and SWV of the cervix. The patients were later divided into two groups, using the clinical outcome of preterm or term delivery. Results Twenty patients delivered at term (gestational age > 37 weeks) and 14 were preterm. Receiver operating characteristics (ROC) curves showed SWV with highest sensitivity and specificity (93% and 90%, respectively) for the prediction of preterm birth at a cutoff value of 2.83 m/s. EI and modified Bishop's score were comparable to each other, but were less sensitive techniques. Conclusion Elastographic assessment of antenatal cervix is a novel technique of virtual palpation of internal os and can be utilized as an objective criterion for preterm birth prediction.

Does acoustic radiation force elastography improve the diagnostic capability of ultrasound in the preoperative characterization of masses of the parotid gland?

PubMed

Zengel, Pamela; Notter, Florian; Clevert, Dirk A

2018-06-06

Ultrasound is the method of choice for preoperative evaluation of tumours of the parotid glands. However, existing methods do not allow for clear differentiation between the most common benign tumours and malignant tumours. The aim of our study was to evaluate if acoustic radiation force, Virtual Touch Quantification (VTQ) elastography helps to improve the preoperative evaluation of parotid masses. We investigated the parenchyma of 102 parotid glands, 14 lymph nodes of healthy volunteers and 51 tumours of the parotid gland via ultrasound, colour Doppler ultrasound and VTQ. The results were matched with histopathology and analyzed. The perfusion in pleomorphic adenoma, the most frequent benign tumour of the parotid gland, was significantly lower in comparison to malignant tumours. All tumours showed statistically significant higher perfusion in comparison to the parenchyma or the lymph nodes of the gland. Shear wave velocity of the user-defined region of interest was statistically significant more frequently an overflow value higher than 8.5 m/s in total tumours in comparison to parenchyma or lymph nodes. The different tumour types presented no significant difference in the shear wave velocity. VTQ in combination with classical ultrasound examination provides additional data useful in distinguishing between benign and malignant tumours and thus shows promise for integration into preexisting ultrasound protocols. However, despite the improvement, clear differentiation of tumours is still not possible and further investigation is recommended.

Acoustic radiation force induced resonance elastography of coagulating blood: theoretical viscoelasticity modeling and ex vivo experimentation

NASA Astrophysics Data System (ADS)

Bhatt, Manish; Montagnon, Emmanuel; Destrempes, François; Chayer, Boris; Kazemirad, Siavash; Cloutier, Guy

2018-03-01

Deep vein thrombosis is a common vascular disease that can lead to pulmonary embolism and death. The early diagnosis and clot age staging are important parameters for reliable therapy planning. This article presents an acoustic radiation force induced resonance elastography method for the viscoelastic characterization of clotting blood. The physical concept of this method relies on the mechanical resonance of the blood clot occurring at specific frequencies. Resonances are induced by focusing ultrasound beams inside the sample under investigation. Coupled to an analytical model of wave scattering, the ability of the proposed method to characterize the viscoelasticity of a mimicked venous thrombosis in the acute phase is demonstrated. Experiments with a gelatin-agar inclusion sample of known viscoelasticity are performed for validation and establishment of the proof of concept. In addition, an inversion method is applied in vitro for the kinetic monitoring of the blood coagulation process of six human blood samples obtained from two volunteers. The computed elasticity and viscosity values of blood samples at the end of the 90 min kinetics were estimated at 411  ±  71 Pa and 0.25  ±  0.03 Pa · s for volunteer #1, and 387  ±  35 Pa and 0.23  ±  0.02 Pa · s for volunteer #2, respectively. The proposed method allowed reproducible time-varying thrombus viscoelastic measurements from samples having physiological dimensions.

Changes in liver stiffness measurement using acoustic radiation force impulse elastography after antiviral therapy in patients with chronic hepatitis C.

PubMed

Chen, Sheng-Hung; Lai, Hsueh-Chou; Chiang, I-Ping; Su, Wen-Pang; Lin, Chia-Hsin; Kao, Jung-Ta; Chuang, Po-Heng; Hsu, Wei-Fan; Wang, Hung-Wei; Chen, Hung-Yao; Huang, Guan-Tarn; Peng, Cheng-Yuan

2018-01-01

To compare on-treatment and off-treatment parameters acquired using acoustic radiation force impulse elastography, the Fibrosis-4 (FIB-4) index, and aspartate aminotransferase-to-platelet ratio index (APRI) in patients with chronic hepatitis C (CHC). Patients received therapies based on pegylated interferon or direct-acting antiviral agents. The changes in paired patient parameters, including liver stiffness (LS) values, the FIB-4 index, and APRI, from baseline to sustained virologic response (SVR) visit (24 weeks after the end of treatment) were compared. Multiple regression models were used to identify significant factors that explained the correlations with LS, FIB-4, and APRI values and SVR. A total of 256 patients were included, of which 219 (85.5%) achieved SVR. The paired LS values declined significantly from baseline to SVR visit in all groups and subgroups except the nonresponder subgroup (n = 10). Body mass index (P = 0.0062) and baseline LS (P < 0.0001) were identified as independent factors that explained the LS declines. Likewise, the baseline FIB-4 (P < 0.0001) and APRI (P < 0.0001) values independently explained the declines in the FIB-4 index and APRI, respectively. Moreover, interleukin-28B polymorphisms, baseline LS, and rapid virologic response were identified as independent correlates with SVR. Paired LS measurements in patients treated for CHC exhibited significant declines comparable to those in FIB-4 and APRI values. These declines may have correlated with the resolution of necroinflammation. Baseline LS values predicted SVR.

Quantified elasticity mapping of ocular tissue using acoustic radiation force optical coherence elastography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Qu, Yueqiao; He, Youmin; Zhang, Yi; Ma, Teng; Zhu, Jiang; Miao, Yusi; Dai, Cuixia; Silverman, Ronald; Humayun, Mark S.; Zhou, Qifa; Chen, Zhongping

2017-02-01

Age-related macular degeneration and keratoconus are two ocular diseases occurring in the posterior and anterior eye, respectively. In both conditions, the mechanical elasticity of the respective tissues changes during the early onset of disease. It is necessary to detect these differences and treat the diseases in their early stages to provide proper treatment. Acoustic radiation force optical coherence elastography is a method of elasticity mapping using confocal ultrasound waves for excitation and Doppler optical coherence tomography for detection. We report on an ARF-OCE system that uses modulated compression wave based excitation signals, and detects the spatial and frequency responses of the tissue. First, all components of the system is synchronized and triggered such that the signal is consistent between frames. Next, phantom studies are performed to validate and calibrate the relationship between the resonance frequency and the Young's modulus. Then the frequency responses of the anterior and posterior eye are detected for porcine and rabbit eyes, and the results correlated to the elasticity. Finally, spatial elastograms are obtained for a porcine retina. Layer segmentation and analysis is performed and correlated to the histology of the retina, where five distinct layers are recognized. The elasticities of the tissue layers will be quantified according to the mean thickness and displacement response for the locations on the retina. This study is a stepping stone to future in-vivo animal studies, where the elastic modulus of the ocular tissue can be quantified and mapped out accordingly.

Probe Oscillation Shear Wave Elastography: Initial In Vivo Results in Liver.

PubMed

Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Trzasko, Joshua D; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

2018-05-01

Shear wave elastography methods are able to accurately measure tissue stiffness, allowing these techniques to monitor the progression of hepatic fibrosis. While many methods rely on acoustic radiation force to generate shear waves for 2-D imaging, probe oscillation shear wave elastography (PROSE) provides an alternative approach by generating shear waves through continuous vibration of the ultrasound probe while simultaneously detecting the resulting motion. The generated shear wave field in in vivo liver is complicated, and the amplitude and quality of these shear waves can be influenced by the placement of the vibrating probe. To address these challenges, a real-time shear wave visualization tool was implemented to provide instantaneous visual feedback to optimize probe placement. Even with the real-time display, it was not possible to fully suppress residual motion with established filtering methods. To solve this problem, the shear wave signal in each frame was decoupled from motion and other sources through the use of a parameter-free empirical mode decomposition before calculating shear wave speeds. This method was evaluated in a phantom as well as in in vivo livers from five volunteers. PROSE results in the phantom as well as in vivo liver correlated well with independent measurements using the commercial General Electric Logiq E9 scanner.

Differences of standard values of Supersonic shear imaging and ARFI technique - in vivo study of testicular tissue.

PubMed

Trottmann, M; Rübenthaler, J; Marcon, J; Stief, C G; Reiser, M F; Clevert, D A

2016-01-01

To investigate the difference of standard values of Supersonic shear imaging (SSI) and Acoustic Radiation Force Impulse (ARFI) technique in the evaluation of testicular tissue stiffness in vivo. 58 healthy male testes were examined using B-mode sonography and ARFI and SSI. B-mode sonography was performed in order to scan the testis for pathologies followed by performance of real-time elastography in three predefined areas (upper pole, central portion and lower pole) using the SuperSonic® Aixplorer ultrasound device (SuperSonic Imagine, Aix-en-Provence, France). Afterwards a second assessment of the same testicular regions by elastography followed using the ARFI technique of the Siemens Acuson 2000™ ultrasound device (Siemens Health Care, Germany). Values of shear wave velocity were described in m/s. Parameters of elastography techniques were compared using paired sample t-test. The values of SSI were all significantly higher in all measured areas compared to ARFI (p < 0.001 to p = 0.015). Quantitatively there was a higher mean SSI wave velocity value of 1,1 compared to 0.8 m/s measured by ARFI. SSI values are significantly higher than ARFI values when measuring the stiffness of testicular tissue and should only be compared with caution.

Non-Invasive Evaluation of Cystic Fibrosis Related Liver Disease in Adults with ARFI, Transient Elastography and Different Fibrosis Scores

PubMed Central

Oltmanns, Annett; Güttler, Andrea; Petroff, David; Wirtz, Hubert; Mainz, Jochen G.; Mössner, Joachim; Berg, Thomas; Tröltzsch, Michael; Keim, Volker; Wiegand, Johannes

2012-01-01

Background Cystic fibrosis-related liver disease (CFLD) is present in up to 30% of cystic fibrosis patients and can result in progressive liver failure. Diagnosis of CFLD is challenging. Non-invasive methods for staging of liver fibrosis display an interesting diagnostic approach for CFLD detection. Aim We evaluated transient elastography (TE), acoustic radiation force impulse imaging (ARFI), and fibrosis indices for CFLD detection. Methods TE and ARFI were performed in 55 adult CF patients. In addition, AST/Platelets-Ratio-Index (APRI), and Forns' score were calculated. Healthy probands and patients with alcoholic liver cirrhosis served as controls. Results Fourteen CF patients met CFLD criteria, six had liver cirrhosis. Elastography acquisition was successful in >89% of cases. Non-cirrhotic CFLD individuals showed elastography values similar to CF patients without liver involvement. Cases with liver cirrhosis differed significantly from other CFLD patients (ARFI: 1.49 vs. 1.13 m/s; p = 0.031; TE: 7.95 vs. 4.16 kPa; p = 0.020) and had significantly lower results than individuals with alcoholic liver cirrhosis (ARFI: 1.49 vs. 2.99 m/s; p = 0.002). APRI showed the best diagnostic performance for CFLD detection (AUROC 0.815; sensitivity 85.7%, specificity 70.7%). Conclusions ARFI, TE, and laboratory based fibrosis indices correlate with each other and reliably detect CFLD related liver cirrhosis in adult CF patients. CF specific cut-off values for cirrhosis in adults are lower than in alcoholic cirrhosis. PMID:22848732

Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method.

PubMed

Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping

2015-05-01

We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan.

SU-E-J-76: Incorporation of Ultrasound Elastography in Target Volume Delineation for Partial Breast Radiotherapy Planning: A Comparative Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juneja, P; Harris, E; Bamber, J

2014-06-01

Purpose: There is substantial observer variability in the delineation of target volumes for post-surgical partial breast radiotherapy because the tumour bed has poor x-ray contrast. This variability may result in substantial variations in planned dose distribution. Ultrasound elastography (USE) has an ability to detect mechanical discontinuities and therefore, the potential to image the scar and distortion in breast tissue architecture. The goal of this study was to compare USE techniques: strain elastography (SE), shear wave elastography (SWE) and acoustic radiation force impulse (ARFI) imaging using phantoms that simulate features of the tumour bed, for the purpose of incorporating USE inmore » breast radiotherapy planning. Methods: Three gelatine-based phantoms (10% w/v) containing: a stiff inclusion (gelatine 16% w/v) with adhered boundaries, a stiff inclusion (gelatine 16% w/v) with mobile boundaries and fluid cavity inclusion (to mimic seroma), were constructed and used to investigate the USE techniques. The accuracy of the elastography techniques was quantified by comparing the imaged inclusion with the modelled ground-truth using the Dice similarity coefficient (DSC). For two regions of interest (ROI), the DSC measures their spatial overlap. Ground-truth ROIs were modelled using geometrical measurements from B-mode images. Results: The phantoms simulating stiff scar tissue with adhered and mobile boundaries and seroma were successfully developed and imaged using SE and SWE. The edges of the stiff inclusions were more clearly visible in SE than in SWE. Subsequently, for all these phantoms the measured DSCs were found to be higher for SE (DSCs: 0.91–0.97) than SWE (DSCs: 0.68–0.79) with an average relative difference of 23%. In the case of seroma phantom, DSC values for SE and SWE were similar. Conclusion: This study presents a first attempt to identify the most suitable elastography technique for use in breast radiotherapy planning. Further analysis will include comparison of ARFI with SE and SWE. This work is supported by the EPSRC Platform Grant, reference number EP/H046526/1.« less

Noninvasive biomarkers in non-alcoholic fatty liver disease: Current status and a glimpse of the future

PubMed Central

Fitzpatrick, Emer; Dhawan, Anil

2014-01-01

The development of non invasive biomarkers of disease has become a major focus of interest in nonalcoholic fatty liver disease (NAFLD). The large prevalence of the disease and the invasive nature of the investigation means that screening with liver biopsy is impractical. In addition to screening, the differentiation of those with simple steatosis vs steatohepatitis and fibrosis is clinically important as the prognosis of each differs. Serum biomarkers may be a combination of simple markers derived from large data sets or direct markers of disease activity. Serum markers of inflammation, apoptosis and oxidative stress in addition to fibrosis have been extensively studied in patients with NAFLD. Other techniques such as transient elastography, magnetic resonance elastography and acoustic radiation force imaging are becoming more established as noninvasive methods of detecting fibrosis in a variety of chronic liver conditions in addition to NAFLD. Newer high throughput methods such as proteomics and glycomics allow the nonhypothesis-driven identification of novel markers and may also potentially contribute to our understanding of the pathogenesis of the condition. This review addresses some of the methodological issues which need to be considered in the search for the ideal biomarker. It is likely that a combination of serum biomarkers and techniques such as transient elastography may provide the optimal diagnostic discrimination however this remains to be proven in large studies. PMID:25152587

Non-invasive measurement of liver and pancreas fibrosis in patients with cystic fibrosis.

PubMed

Friedrich-Rust, Mireen; Schlueter, Nina; Smaczny, Christina; Eickmeier, Olaf; Rosewich, Martin; Feifel, Kirstin; Herrmann, Eva; Poynard, Thierry; Gleiber, Wolfgang; Lais, Christoph; Zielen, Stefan; Wagner, Thomas O F; Zeuzem, Stefan; Bojunga, Joerg

2013-09-01

Patients with cystic fibrosis (CF) have a relevant morbidity and mortality caused by CF-related liver-disease. While transient elastography (TE) is an established elastography method in hepatology centers, Acoustic-Radiation-Force-Impulse (ARFI)-Imaging is a novel ultrasound-based elastography method which is integrated in a conventional ultrasound-system. The aim of the present study was to evaluate the prevalence of liver-fibrosis in patients with CF using TE, ARFI-imaging and fibrosis blood tests. 106 patients with CF were prospectively included in the present study and received ARFI-imaging of the left and right liver-lobe, ARFI of the pancreas TE of the liver and laboratory evaluation. The prevalence of liver-fibrosis according to recently published best practice guidelines for CFLD was 22.6%. Prevalence of significant liver-fibrosis assessed by TE, ARFI-right-liver-lobe, ARFI-left-liver-lobe, Fibrotest, Fibrotest-corrected-by-haptoglobin was 17%, 24%, 40%, 7%, and 16%, respectively. The best agreement was found for TE, ARFI-right-liver-lobe and Fibrotest-corrected-by-haptoglobin. Patients with pancreatic-insufficiency had significantly lower pancreas-ARFI-values as compared to patients without. ARFI-imaging and TE seem to be promising non-invasive methods for detection of liver-fibrosis in patients with CF. Copyright © 2013 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.

Added value of Virtual Touch IQ shear wave elastography in the ultrasound assessment of breast lesions.

PubMed

Ianculescu, Victor; Ciolovan, Laura Maria; Dunant, Ariane; Vielh, Philippe; Mazouni, Chafika; Delaloge, Suzette; Dromain, Clarisse; Blidaru, Alexandru; Balleyguier, Corinne

2014-05-01

To determine the diagnostic performance of Acoustic Radiation Force Impulse (ARFI) Virtual Touch IQ shear wave elastography in the discrimination of benign and malignant breast lesions. Conventional B-mode and elasticity imaging were used to evaluate 110 breast lesions. Elastographic assessment of breast tissue abnormalities was done using a shear wave based technique, Virtual Touch IQ (VTIQ), implemented on a Siemens Acuson S3000 ultrasound machine. Tissue mechanical properties were interpreted as two-dimensional qualitative and quantitative colour maps displaying relative shear wave velocity. Wave speed measurements in m/s were possible at operator defined regions of interest. The pathologic diagnosis was established on samples obtained by ultrasound guided core biopsy or fine needle aspiration. BIRADS based B-mode evaluation of the 48 benign and 62 malignant lesions achieved 92% sensitivity and 62.5% specificity. Subsequently performed VTIQ elastography relying on visual interpretation of the colour overlay displaying relative shear wave velocities managed similar standalone diagnostic performance with 92% sensitivity and 64.6% specificity. Lesion and surrounding tissue shear wave speed values were calculated and a significant difference was found between the benign and malignant populations (Mann-Whitney U test, p<0.0001). By selecting a lesion cut-off value of 3.31m/s we achieved 80.4% sensitivity and 73% specificity. Applying this threshold only to BIRADS 4a masses, we reached overall levels of 92% sensitivity and 72.9% specificity. VTIQ qualitative and quantitative elastography has the potential to further characterise B-mode detected breast lesions, increasing specificity and reducing the number of unnecessary biopsies. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

ARFI quantitative elastography of the submandibular glands. Normal measurements and the diagnosis value of the method in radiation submaxillitis.

PubMed

Badea, Alexandru Florin; Tamas Szora, Attila; Ciuleanu, Elisabeta; Chioreanu, Ioana; Băciuţ, Grigore; Lupşor Platon, Monica; Badea, Radu

2013-09-01

Evaluation of Acoustic Radiation Force Impulse Imaging (ARFI) elastography performance in predicting the elasticity of the submandibular glands in normal situations and after radiation therapy. A number of 54 normal submandibular glands from 27 voluntary subjects and 33 pathological submandibular glands (radiation submaxillities) from 18 patients who had undergone radiation therapy for various cervical and facial oncological conditions were included in study. All the patients had undergone a B mode ultrasonography (Tissue Harmonic Imaging, 8-14 MHz) while the submandibular volume was determined and subsequently an ARFI examination while the shear wave velocity (SWV) was measured (in the central, peripheral and subcapsular areas, with the results expressed in m/s). In the volunteers' group the mean value of the SWV of the left submandibular gland was 1.68 ± 0.46 m/s, determined in the centre of the gland, 1.88 ± 0.4 m/s in the periphery (corresponding to the subcapsular parenchyma) and the SWV of the right submandibular gland was 1.74 ± 0.35 m/s (centrally) and 1.84 ± 0.43 m/s in the periphery. The mean value of all measurements was 1.82 ± 0.41 m/s. The mean volume of the glands was 7.97 ± 2.63 cm3. In the group of patients who had underwent radiation therapy (at least 35Gy), the mean value of the SWV was 2.24 ± 0.49 m/s centrally and 2.1 ± 0.58 m/s in the periphery on the left and 1.99 ± 0.5 m/s centrally and 2.21 ± 0.52 m/s in the periphery on the right. The mean value of all the measurements was 2.13 ± 0.52 m/s and the mean volume of the gland was 5.95 ± 4.16 cm3. Elastography using ARFI technique is a valid examination in the evaluation of the normal and pathological submandibular gland stiffness. The values of the shear wave velocities that correspond to a normal stiffness, determined through the ARFI technique, are similar in the two glands. After cervical and facial radiation therapy the values of the SWV are increased, indicating a change in the consistency of the gland thus implying a structural transformation. The ARFI technique can be used in the evaluation of the salivary glands pathology.

Imaging shear wave propagation for elastic measurement using OCT Doppler variance method

NASA Astrophysics Data System (ADS)

Zhu, Jiang; Miao, Yusi; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

2016-03-01

In this study, we have developed an acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) method for the visualization of the shear wave and the calculation of the shear modulus based on the OCT Doppler variance method. The vibration perpendicular to the OCT detection direction is induced by the remote acoustic radiation force (ARF) and the shear wave propagating along the OCT beam is visualized by the OCT M-scan. The homogeneous agar phantom and two-layer agar phantom are measured using the ARFOE-OCE system. The results show that the ARFOE-OCE system has the ability to measure the shear modulus beyond the OCT imaging depth. The OCT Doppler variance method, instead of the OCT Doppler phase method, is used for vibration detection without the need of high phase stability and phase wrapping correction. An M-scan instead of the B-scan for the visualization of the shear wave also simplifies the data processing.

WE-E-9A-01: Ultrasound Elasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emelianov, S; Hall, T; Bouchard, R

2014-06-15

Principles and techniques of ultrasound-based elasticity imaging will be presented, including quasistatic strain imaging, shear wave elasticity imaging, and their implementations in available systems. Deeper exploration of quasistatic methods, including elastic relaxation, and their applications, advantages, artifacts and limitations will be discussed. Transient elastography based on progressive and standing shear waves will be explained in more depth, along with applications, advantages, artifacts and limitations, as will measurement of complex elastic moduli. Comparisons will be made between ultrasound radiation force techniques, MR elastography, and the simple A mode plus mechanical plunger technique. Progress in efforts, such as that by the Quantitativemore » Imaging Biomarkers Alliance, to reduce the differences in the elastic modulus reported by different commercial systems will be explained. Dr. Hall is on an Advisory Board for Siemens Ultrasound and has a research collaboration with them, including joint funding by R01CA140271 for nonlinear elasticity imaging. Learning Objectives: Be reminded of the long history of palpation of tissue elasticity for critical medical diagnosis and the relatively recent advances to be able to image tissue strain in response to an applied force. Understand the differences between shear wave speed elasticity measurement and imaging and understand the factors affecting measurement and image frame repletion rates. Understand shear wave propagation effects that can affect measurements, such as essentially lack of propagation in fluids and boundary effects, so important in thin layers. Know characteristics of available elasticity imaging phantoms, their uses and limitations. Understand thermal and cavitational limitations affecting radiation force-based shear wave imaging. Have learning and references adequate to for you to use in teaching elasticity imaging to residents and technologists. Be able to explain how elasticity measurement and imaging can contribute to diagnosis of breast and prostate cancer, staging of liver fibrosis, age estimation of deep veinous fhrombosis, confirmation of thermal lesions in the liver after RF ablation.« less

[Contrastive study on conventional ultrasound, compression elastography and acoustic radiation force impulse imaging in the differential diagnosis of benign and malignant breast tumors].

PubMed

Zhang, Lu; Zhou, Ping; Deng, Jin; Tian, Shuangming; Qian, Ying; Wu, Xiaomin; Ma, Shuhua; Li, Jiale

2014-12-01

To evaluate the diagnostic performance of conventional ultrasound, compression elastography (CE) and acoustic radiation force impulse imaging (ARFI) in differential diagnosis of benign and malignant breast tumors. A total of 98 patients with liver lesions were included in the study. The images of conventional ultrasound, CE and the values of virtual touch tissue quantification (VTQ) of breast lesions were obtained. The diagnostic performance of conventional ultrasound, CE and ARFI were assessed by using pathology as the gold standard, and then evaluate the diagnosis efficiency of these three approaches in differential diagnosing benign and malignant breast tumors. The specificity, sensitivity and accuracy in the diagnosis of malignant breast tumors for conventional ultrasound were 80.0%, 81.1% and 81.7%, respectively, whereas for CE elastic score were 85.7%, 86.7% and 86.3%, respectively. With a cutoff value of 3.71 for the SR, the sensitivity, specificity, accuracy in diagnosis of malignant breast tumors were 97.1%, 83.3% and 88.4%, respectively. With a cutoff value of 3.78 m/s for VTQ, the sensitivity, specificity, accuracy in diagnosis of malignant breast tumors were 94.3%, 91.7% and 92.6%, respectively. The difference in diagnosis efficiency among ARFI, CE and conventional ultrasound in differential diagnosis of benign and malignant breast tumors was significant (P< 0.05). Conventional ultrasound, CE and ARFI are all useful for the differential diagnosis of benign and malignant breast tumors. But the diagnosis efficiency of ARFI is superior to CE and conventional ultrasound. The three approaches can help each other in differential diagnosis of benign and malignant breast tumors.

Elasticity standard values of the Achilles tendon assessed with acoustic radiation force impulse elastography on healthy volunteers: a cross section study.

PubMed

Wakker, Jonas; Kratzer, Wolfgang; Graeter, Tilmann; Schmidberger, Julian

2018-05-09

To determine normal values for acoustic radiation force impulse (ARFI) shear wave elastography of the Achilles tendon. Using the VTIQ mode with the Acuson S3000™ (Siemens Healthcare, Erlangen, Germany), we measured the shear wave velocity (SWV) in m/s and the diameter in mm of both Achilles tendons in 182 healthy volunteers. The tendon was displayed in a sagittal view with a relaxed tendon. The parameters were tested for correlations with the anthropometric data of the subjects, between the genders and different age groups, as well as information obtained from the history, such as smoking and sporting activities. Using a sagittal acoustic window, we determined a mean SWV of 9.09 ± 0.71 m/s for the left Achilles tendon and 9.17 ± 0.61 m/s for the right. There was a significant difference between the results for the right and left side (p < 0.05). The diameter on the left was 4.7 ± 0.9 mm. On the right, it was 4.8 ± 0.9 mm. Likewise there was a significant difference between the results for the diameter of the left and right side (p < 0.05). Neither gender, body mass index (BMI) nor age had a significant effect on either of the measured parameters (p > 0.05). The same goes for the consumption of tobacco and alcohol (p > 0.05). Age, gender, BMI, smoking or the consumption of alcohol did not affect either the elasticity or the diameter of the Achilles tendon.

Accuracy of transient elastography-FibroScan®, acoustic radiation force impulse (ARFI) imaging, the enhanced liver fibrosis (ELF) test, APRI, and the FIB-4 index compared with liver biopsy in patients with chronic hepatitis C.

PubMed

Ragazzo, Taisa Grotta; Paranagua-Vezozzo, Denise; Lima, Fabiana Roberto; de Campos Mazo, Daniel Ferraz; Pessoa, Mário Guimarães; Oliveira, Claudia Pinto; Alves, Venancio Avancini Ferreira; Carrilho, Flair José

2017-10-01

Although liver biopsy is the gold standard for determining the degree of liver fibrosis, issues regarding its invasiveness and the small amount of liver tissue evaluated can limit its applicability and interpretation in clinical practice. Non-invasive evaluation methods for liver fibrosis can address some of these limitations. The aim of this study was to evaluate the accuracy of transient elastography-FibroScan®, acoustic radiation force impulse (ARFI), enhanced liver fibrosis (ELF), the aspartate aminotransferase-to-platelet ratio index (APRI), and the FIB-4 index compared with liver biopsy in hepatitis C. We evaluated chronic hepatitis C patients who were followed at the Division of Clinical Gastroenterology and Hepatology, Hospital das Clínicas, Department of Gastroenterology of University of São Paulo School of Medicine, São Paulo, Brazil, and who underwent liver biopsy. The accuracy of each method was determined by a receiver operating characteristic (ROC) curve analysis, and fibrosis was classified as significant fibrosis (≥F2), advanced fibrosis (≥F3), or cirrhosis (F4). The Obuchowski method was also used to determine the diagnostic accuracy of each method at the various stages of fibrosis. In total, 107 FibroScan®, 51 ARFI, 68 ELF, 106 APRI, and 106 FIB-4 analyses were performed. A total of 107 patients were included in the study. The areas under the ROC curve (AUROCs) according to fibrosis degree were as follows: significant fibrosis (≥F2): FibroScan®: 0.83, FIB-4: 0.76, ELF: 0.70, APRI: 0.69, and ARFI: 0.67; advanced fibrosis (≥F3): FibroScan®: 0.85, ELF: 0.82, FIB-4: 0.77, ARFI: 0.74, and APRI: 0.71; and cirrhosis (F4): APRI: 1, FIB-4: 1, FibroScan®: 0.99, ARFI: 0.96, and ELF: 0.94. The accuracies of transient elastography, ARFI, ELF, APRI and FIB-4 determined by the Obuchowski method were F0-F1: 0.81, 0.78, 0.44, 0.72 and 0.67, respectively; F1-F2: 0.73, 0.53, 0.62, 0.60, and 0.68, respectively; F2-F3: 0.70, 0.64, 0.77, 0.60, and 0.67, respectively; and F3-F4: 0.98, 0.96, 0.82, 1, and 1, respectively. Transient elastography remained the most effective method for evaluating all degrees of fibrosis. The accuracy of all methodologies was best at F4.

Non-invasive diagnosis of hepatitis B virus-related cirrhosis

PubMed Central

Lee, Sangheun; Kim, Do Young

2014-01-01

Chronic hepatitis B (CHB) infection is a major public health problem associated with significant morbidity and mortality worldwide. Twenty-three percent of patients with CHB progress naturally to liver cirrhosis, which was earlier thought to be irreversible. However, it is now known that cirrhosis can in fact be reversed by treatment with oral anti-nucleotide drugs. Thus, early and accurate diagnosis of cirrhosis is important to allow an appropriate treatment strategy to be chosen and to predict the prognosis of patients with CHB. Liver biopsy is the reference standard for assessment of liver fibrosis. However, the method is invasive, and is associated with pain and complications that can be fatal. In addition, intra- and inter-observer variability compromises the accuracy of liver biopsy data. Only small tissue samples are obtained and fibrosis is heterogeneous in such samples. This confounds the two types of observer variability mentioned above. Such limitations have encouraged development of non-invasive methods for assessment of fibrosis. These include measurements of serum biomarkers of fibrosis; and assessment of liver stiffness via transient elastography, acoustic radiation force impulse imaging, real-time elastography, or magnetic resonance elastography. Although significant advances have been made, most work to date has addressed the diagnostic utility of these techniques in the context of cirrhosis caused by chronic hepatitis C infection. In the present review, we examine the advantages afforded by use of non-invasive methods to diagnose cirrhosis in patients with CHB infections and the utility of such methods in clinical practice. PMID:24574713

Ultrasound Elastography: Review of Techniques and Clinical Applications

PubMed Central

Sigrist, Rosa M.S.; Liau, Joy; Kaffas, Ahmed El; Chammas, Maria Cristina; Willmann, Juergen K.

2017-01-01

Elastography-based imaging techniques have received substantial attention in recent years for non-invasive assessment of tissue mechanical properties. These techniques take advantage of changed soft tissue elasticity in various pathologies to yield qualitative and quantitative information that can be used for diagnostic purposes. Measurements are acquired in specialized imaging modes that can detect tissue stiffness in response to an applied mechanical force (compression or shear wave). Ultrasound-based methods are of particular interest due to its many inherent advantages, such as wide availability including at the bedside and relatively low cost. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these can be classified into strain imaging methods that use internal or external compression stimuli, and shear wave imaging that use ultrasound-generated traveling shear wave stimuli. While ultrasound elastography has shown promising results for non-invasive assessment of liver fibrosis, new applications in breast, thyroid, prostate, kidney and lymph node imaging are emerging. Here, we review the basic principles, foundation physics, and limitations of ultrasound elastography and summarize its current clinical use and ongoing developments in various clinical applications. PMID:28435467

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography.

PubMed

Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

2016-09-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) "push beam" to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a "strain-like" compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥ 19 dB) between the target and background.

Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography

PubMed Central

Mellema, Daniel C.; Song, Pengfei; Kinnick, Randall R.; Urban, Matthew W.; Greenleaf, James F.; Manduca, Armando; Chen, Shigao

2017-01-01

Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) “push beam” to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a “strain-like” compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥19 dB) between the target and background. PMID:27076352

Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications.

PubMed

Taljanovic, Mihra S; Gimber, Lana H; Becker, Giles W; Latt, L Daniel; Klauser, Andrea S; Melville, David M; Gao, Liang; Witte, Russell S

2017-01-01

In the past 2 decades, sonoelastography has been progressively used as a tool to help evaluate soft-tissue elasticity and add to information obtained with conventional gray-scale and Doppler ultrasonographic techniques. Recently introduced on clinical scanners, shear-wave elastography (SWE) is considered to be more objective, quantitative, and reproducible than compression sonoelastography with increasing applications to the musculoskeletal system. SWE uses an acoustic radiation force pulse sequence to generate shear waves, which propagate perpendicular to the ultrasound beam, causing transient displacements. The distribution of shear-wave velocities at each pixel is directly related to the shear modulus, an absolute measure of the tissue's elastic properties. Shear-wave images are automatically coregistered with standard B-mode images to provide quantitative color elastograms with anatomic specificity. Shear waves propagate faster through stiffer contracted tissue, as well as along the long axis of tendon and muscle. SWE has a promising role in determining the severity of disease and treatment follow-up of various musculoskeletal tissues including tendons, muscles, nerves, and ligaments. This article describes the basic ultrasound physics of SWE and its applications in the evaluation of various traumatic and pathologic conditions of the musculoskeletal system. © RSNA, 2017.

Applicability of shear wave elastography of the major salivary glands: values in healthy patients and effects of gender, smoking and pre-compression.

PubMed

Mantsopoulos, Konstantinos; Klintworth, Nils; Iro, Heinrich; Bozzato, Alessandro

2015-09-01

Our aim in this study was to determine normal shear wave elastography (SWE) values for the parenchyma of the major salivary glands and to evaluate the influences of gender, smoking, side and type of gland and varying amounts of ultrasound probe pressure on SWE values. Twenty-five consecutive healthy patients were examined with ultrasound. SWE velocities were measured with acoustic radiation force imaging in the hilum and central region of both glands with "normal" and very low pressure. Mean SWE velocities were 1.854 m/s for the parotid gland and 1.932 m/s for the submandibular gland. No statistically significant differences were detected between males and females, smokers and non-smokers, parotid and submandibular gland and left and right sides. Greater pre-compression with the ultrasound probe resulted in a statistically significant increase in the SWE values of both salivary glands (p < 0.000). The degree of pre-compression by the ultrasound transducer should be standardized, so that the reliability and reproducibility of this innovative method can be improved. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications

PubMed Central

Gimber, Lana H.; Becker, Giles W.; Latt, L. Daniel; Klauser, Andrea S.; Melville, David M.; Gao, Liang; Witte, Russell S.

2017-01-01

In the past 2 decades, sonoelastography has been progressively used as a tool to help evaluate soft-tissue elasticity and add to information obtained with conventional gray-scale and Doppler ultrasonographic techniques. Recently introduced on clinical scanners, shear-wave elastography (SWE) is considered to be more objective, quantitative, and reproducible than compression sonoelastography with increasing applications to the musculoskeletal system. SWE uses an acoustic radiation force pulse sequence to generate shear waves, which propagate perpendicular to the ultrasound beam, causing transient displacements. The distribution of shear-wave velocities at each pixel is directly related to the shear modulus, an absolute measure of the tissue’s elastic properties. Shear-wave images are automatically coregistered with standard B-mode images to provide quantitative color elastograms with anatomic specificity. Shear waves propagate faster through stiffer contracted tissue, as well as along the long axis of tendon and muscle. SWE has a promising role in determining the severity of disease and treatment follow-up of various musculoskeletal tissues including tendons, muscles, nerves, and ligaments. This article describes the basic ultrasound physics of SWE and its applications in the evaluation of various traumatic and pathologic conditions of the musculoskeletal system. ©RSNA, 2017 PMID:28493799

Shear Wave Imaging of Breast Tissue by Color Doppler Shear Wave Elastography.

PubMed

Yamakoshi, Yoshiki; Nakajima, Takahito; Kasahara, Toshihiro; Yamazaki, Mayuko; Koda, Ren; Sunaguchi, Naoki

2017-02-01

Shear wave elastography is a distinctive method to access the viscoelastic characteristic of the soft tissue that is difficult to obtain by other imaging modalities. This paper proposes a novel shear wave elastography [color Doppler shear wave imaging (CD SWI)] for breast tissue. Continuous shear wave is produced by a small lightweight actuator, which is attached to the tissue surface. Shear wave wavefront that propagates in tissue is reconstructed as a binary pattern that consists of zero and the maximum flow velocities on color flow image (CFI). Neither any modifications of the ultrasound color flow imaging instrument nor a high frame rate ultrasound imaging instrument is required to obtain the shear wave wavefront map. However, two conditions of shear wave displacement amplitude and shear wave frequency are needed to obtain the map. However, these conditions are not severe restrictions in breast imaging. This is because the minimum displacement amplitude is [Formula: see text] for an ultrasonic wave frequency of 12 MHz and the shear wave frequency is available from several frequencies suited for breast imaging. Fourier analysis along time axis suppresses clutter noise in CFI. A directional filter extracts shear wave, which propagates in the forward direction. Several maps, such as shear wave phase, velocity, and propagation maps, are reconstructed by CD SWI. The accuracy of shear wave velocity measurement is evaluated for homogeneous agar gel phantom by comparing with the acoustic radiation force impulse method. The experimental results for breast tissue are shown for a shear wave frequency of 296.6 Hz.

Viscoelastic characterization of dispersive media by inversion of a general wave propagation model in optical coherence elastography

NASA Astrophysics Data System (ADS)

Zvietcovich, Fernando; Rolland, Jannick P.; Grygotis, Emma; Wayson, Sarah; Helguera, Maria; Dalecki, Diane; Parker, Kevin J.

2018-02-01

Determining the mechanical properties of tissue such as elasticity and viscosity is fundamental for better understanding and assessment of pathological and physiological processes. Dynamic optical coherence elastography uses shear/surface wave propagation to estimate frequency-dependent wave speed and Young's modulus. However, for dispersive tissues, the displacement pulse is highly damped and distorted during propagation, diminishing the effectiveness of peak tracking approaches. The majority of methods used to determine mechanical properties assume a rheological model of tissue for the calculation of viscoelastic parameters. Further, plane wave propagation is sometimes assumed which contributes to estimation errors. To overcome these limitations, we invert a general wave propagation model which incorporates (1) the initial force shape of the excitation pulse in the space-time field, (2) wave speed dispersion, (3) wave attenuation caused by the material properties of the sample, (4) wave spreading caused by the outward cylindrical propagation of the wavefronts, and (5) the rheological-independent estimation of the dispersive medium. Experiments were conducted in elastic and viscous tissue-mimicking phantoms by producing a Gaussian push using acoustic radiation force excitation, and measuring the wave propagation using a swept-source frequency domain optical coherence tomography system. Results confirm the effectiveness of the inversion method in estimating viscoelasticity in both the viscous and elastic phantoms when compared to mechanical measurements. Finally, the viscoelastic characterization of collagen hydrogels was conducted. Preliminary results indicate a relationship between collagen concentration and viscoelastic parameters which is important for tissue engineering applications.

AN OVERVIEW OF ELASTOGRAPHY – AN EMERGING BRANCH OF MEDICAL IMAGING

PubMed Central

Sarvazyan, Armen; Hall, Timothy J.; Urban, Matthew W.; Fatemi, Mostafa; Aglyamov, Salavat R.; Garra, Brian S.

2011-01-01

From times immemorial manual palpation served as a source of information on the state of soft tissues and allowed detection of various diseases accompanied by changes in tissue elasticity. During the last two decades, the ancient art of palpation gained new life due to numerous emerging elasticity imaging (EI) methods. Areas of applications of EI in medical diagnostics and treatment monitoring are steadily expanding. Elasticity imaging methods are emerging as commercial applications, a true testament to the progress and importance of the field. In this paper we present a brief history and theoretical basis of EI, describe various techniques of EI and, analyze their advantages and limitations, and overview main clinical applications. We present a classification of elasticity measurement and imaging techniques based on the methods used for generating a stress in the tissue (external mechanical force, internal ultrasound radiation force, or an internal endogenous force), and measurement of the tissue response. The measurement method can be performed using differing physical principles including magnetic resonance imaging (MRI), ultrasound imaging, X-ray imaging, optical and acoustic signals. Until recently, EI was largely a research method used by a few select institutions having the special equipment needed to perform the studies. Since 2005 however, increasing numbers of mainstream manufacturers have added EI to their ultrasound systems so that today the majority of manufacturers offer some sort of Elastography or tissue stiffness imaging on their clinical systems. Now it is safe to say that some sort of elasticity imaging may be performed on virtually all types of focal and diffuse disease. Most of the new applications are still in the early stages of research, but a few are becoming common applications in clinical practice. PMID:22308105

Tissue-mimicking bladder wall phantoms for evaluating acoustic radiation force-optical coherence elastography systems.

PubMed

Ejofodomi, O'tega A; Zderic, Vesna; Zara, Jason M

2010-04-01

Acoustic radiation force-optical coherence elastography (ARF-OCE) systems are novel imaging systems that have the potential to simultaneously quantify and characterize the optical and mechanical properties of in vivo tissues. This article presents the construction of bladder wall phantoms for use in ARF-OCE systems. Mechanical, acoustic, and optical properties are reported and compared to published values for the urinary bladder. The phantom consisted of 0.2000 +/- 0.0089 and 6.0000 +/- 0.2830 microm polystyrene microspheres (Polysciences Inc., Warrington, PA, Catalog Nos. 07304 and 07312), 7.5 +/- 1.5 microm copolymer microspheres composed of acrylonitrile and vinylidene chloride, (Expancel, Duluth, GA, Catalog No. 461 DU 20), and bovine serum albumin within a gelatin matrix. Young's modulus was measured by successive compression of the phantom and obtaining the slope of the resulting force-displacement data. Acoustic measurements were performed using the transmission method. The phantoms were submerged in a water bath and placed between transmitting and receiving 13 mm diameter unfocused transducers operating at a frequency of 3.5 MHz. A MATLAB algorithm to extract the optical scattering coefficient from optical coherence tomography (OCT) images of the phantom was used. The phantoms possess a Young's modulus of 17.12 +/- 2.72 kPa, a mass density of 1.05 +/- 0.02 g/cm3, an acoustic attenuation coefficient of 0.66 +/- 0.08 dB/cm/MHz, a speed of sound of 1591 +/- 8.76 m/s, and an optical scattering coefficient of 1.80 +/- 0.23 mm(-1). Ultrasound and OCT images of the bladder wall phantom are presented. A material that mimics the mechanical, optical, and acoustic properties of healthy bladder wall has been developed. This tissue-mimicking bladder wall phantom was developed as a control tool to investigate the feasibility of using ARF-OCE to detect the mechanical and optical changes that may be indicative of the onset or development of cancer in the urinary bladder. By following the methods used in this article, phantoms matching the optical, acoustic, and mechanical properties of other biological tissues can also be constructed.

Nonlinear characterization of elasticity using quantitative optical coherence elastography.

PubMed

Qiu, Yi; Zaki, Farzana R; Chandra, Namas; Chester, Shawn A; Liu, Xuan

2016-11-01

Optical coherence elastography (OCE) has been used to perform mechanical characterization on biological tissue at the microscopic scale. In this work, we used quantitative optical coherence elastography (qOCE), a novel technology we recently developed, to study the nonlinear elastic behavior of biological tissue. The qOCE system had a fiber-optic probe to exert a compressive force to deform tissue under the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to simultaneously quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation. In other words, our qOCE system allowed us to establish the relationship between mechanical stimulus and tissue response to characterize the stiffness of biological tissue. Most biological tissues have nonlinear elastic behavior, and the apparent stress-strain relationship characterized by our qOCE system was nonlinear an extended range of strain, for a tissue-mimicking phantom as well as biological tissues. Our experimental results suggested that the quantification of force in OCE was critical for accurate characterization of tissue mechanical properties and the qOCE technique was capable of differentiating biological tissues based on the elasticity of tissue that is generally nonlinear.

Acoustic Radiation Force Impulse (ARFI) Elastography and Serological Markers in Assessment of Liver Fibrosis and Free Portal Pressure in Patients with Hepatitis B.

PubMed

Li, Jun; Yu, Jie; Peng, Xin-Yu; Du, Ting-Ting; Wang, Jia-Jia; Tong, Jin; Lu, Gui-Lin; Wu, Xiang-Wei

2017-07-23

BACKGROUND The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) elastography, AST-to-platelet ratio index (APRI), and FIB-4 in assessing liver fibrosis and free portal pressure in patients with hepatitis B. MATERIAL AND METHODS We enrolled 126 patients with hepatitis B who underwent liver surgery at the General Surgery Department of the First Affiliated Hospital of Shihezi University Medical School from February 2013 to August 2015. Preoperatively, shear wave velocity (SWV) of the liver was measured with the Siemens S2000 ultrasound system to reflect liver stiffness. Serological markers were collected and fibrosis indices APRI and FIB-4 were calculated. Intraoperatively, liver tissues were harvested and free portal pressure (FPP) was measured. Postoperatively, fibrosis of liver tissues was pathologically staged. RESULTS The results of SWV, APRI, FIB-4, and FPP were all correlated with the degree of liver fibrosis (Spearman correlation coefficients: r=0.777, P<0.001; r=0.526, P<0.001; r=0.471, P<0.001; p<0.000; r=0.675, p<0.000). Receiver operating characteristic curve (ROC) analysis showed that the areas under the curve (AUC) of ARFI, APRI, and FIB-4 in diagnosing liver fibrosis were 0.830, 0.768, and 0.717, respectively, for stage F≥1; 0.861, 0.773, and 0.754, respectively, for stage F≥2; 0.941, 0.793, and 0.779, respectively, for stage F≥3; and 0.945, 0.783, and 0.754, respectively, for stage F=4. SWV, APRI, and FIB-4 were all correlated with FPP (Pearson correlation coefficients: 0.387, P<0.001; 0.446, P<0.001; 0.419, P<0.001). CONCLUSIONS ARFI, APRI, and FIB-4 can assess liver fibrosis in patients with hepatitis B when assessing the portal venous pressure. The difference in diagnostic efficacy between the 3 was not significant.

How useful are ARFI elastography cut-off values proposed by meta-analysis for predicting the significant fibrosis and compensated liver cirrhosis?

PubMed

Bota, Simona; Sporea, Ioan; Sirli, Roxana; Popescu, Alina; Gradinaru-Tascau, Oana

2015-06-01

To evaluate how often do we "miss" chronic hepatitis C patients with at least significant fibrosis (F>/=2) and those with compensated cirrhosis, by using Acoustic Radiation Force Impulse (ARFI) elastography cut-off values proposed by meta-analysis. Our study included 132 patients with chronic hepatitis C, evaluated by means of ARFI and liver biopsy (LB), in the same session. Reliable measurements were defined as: median value of 10 liver stiffness (LS) measurements with a success rate>/=60% and an interquartile range interval<30%. For predicting F>/=2 and F=4 we used the LS cut-offs proposed in the last published meta-analysis: 1.35 m/s and 1.87 m/s, respectively. Reliable LS measurements by means of ARFI were obtained in 117 patients (87.9%). In our study, 58 patients (49.6%) had LS values <1.35 m/s; from these 75.8% had F>/=2 in LB. From the 59 patients (50.4%) with LS values>/=1.35 m/s, only 6.8% had F0 or F1 in LB. Also, in our study, 88 patients (75.3%) had LS values <1.87 m/s; from these only 2.2 % had F4 in LB. From the 29 patients (24.7%) with LS values>/=1.87 m/s, 41.3% had F4 in LB. Both for prediction of at least significant fibrosis and liver cirrhosis, higher aminotransferases levels were associated with wrongly classified patients, in univariate and multivariate analysis. ARFI elastography had a very good positive predictive value (93.2%) for predicting the presence of significant fibrosis and excellent negative predictive value (97.8%) for excluding the presence of compensated liver cirrhosis.

Application of new optical coherence elastography to monitor the mineralization processing in bone tissue engineering constructs

NASA Astrophysics Data System (ADS)

Guan, Guangying; Song, Shaozhen; Huang, Zhihong; Yang, Ying

2015-03-01

Generation of functional tissue in vitro through tissue engineering technique is a promising direction to repair and replace malfunctioned organ and tissue in the modern medicine for various diseases which could not been treated well by conventional therapy. Similar to the embryo development, the generation of tissue in vitro is a highly dynamic processing. Obtaining the feedback of the processing real time is highly demanded. In this study, a new methodology has been explored aiming to monitor the morphological and mechanical property alteration of bone tissue engineering constructs simultaneously. Optical coherence elastography (OCE) equipped with a LDS V201 permanent magnet shaker and a modulated acoustic radiation force (ARF) to provide a vibration signal, has been used for the real time and non-destructive monitoring. A phantom construct system has been used to optimize the measurement conditions in which agar hydrogel with concentration from 0, 0.75 to 2% with/without hydroxyappatite particles have been injected to 3D porous poly (lactic acid) scaffolds to simulate the collagenous extracellular matrix (ECM) and mineralized ECM. The structural and elastography images of the constructs have clearly demonstrated the linear relation with the increased mechanical property versus the increase of agar concentration within the pores of the scaffolds. The MG63 bone cells seeded in the scaffolds and cultured for 4 weeks have been monitored by the established protocol exhibiting the increased mechanical strength in the pore wall where the ECM or mineralized ECM was assumed to be formed in comparison to empty pores. This study confirms that OCE-ARF could become a valuable tool in regenerative medicine to assess the biological events during in vitro culture and conditioning.

A comprehensive review of noninvasive liver fibrosis tests in pediatric nonalcoholic Fatty liver disease.

PubMed

Mansoor, Sana; Collyer, Elizabeth; Alkhouri, Naim

2015-06-01

Nonalcoholic fatty liver disease (NAFLD) and its spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) and fibrosis have been increasing in the pediatric population. The presence and severity of fibrosis in patients with NAFLD are important prognostic factors for the risk of disease progression to cirrhosis. The gold standard for staging liver fibrosis is a liver biopsy. However, given the risks of this procedure, especially in the pediatric population, the development of noninvasive markers to diagnose and monitor progression of NAFLD is desirable. This paper will review recently developed noninvasive methods for diagnosing liver fibrosis in children with NAFLD. These include simple fibrosis scores, advanced biochemical markers, and radiologic imaging studies. Simple fibrosis scores use readily available laboratory tests; available one include AST/ALT ratio, AST to platelet ratio index (APRI), fibrosis (FIB)-4 index, NAFLD fibrosis score (NFS), pediatric NAFLD fibrosis index (PNFI), and pediatric NALFD fibrosis score (PNFS). Advanced biochemical markers include biomarkers of hepatocyte cell death such as cytokeratin 18 fragment levels, and markers of extracellular matrix turnover such as the Enhanced Liver Fibrosis (ELF) test and hyaluronic acid. Radiologic imaging studies estimate liver stiffness as a surrogate for liver fibrosis; these include transient elastography (TE), magnetic resonance elastography (MRE), and acoustic radiation force impulse imaging (ARFI).

Ultrasound elastography in diagnosis and follow-up for patients with chronic recurrent parotitis.

PubMed

Zengel, Pamela; Reichel, Christoph Andreas; Vincek, Teresa; Clevert, Dirk André

2017-01-01

Chronic recurrent parotitis (CRP) is a non-obstructive disease with episodes characterized by painful swelling of the parotid gland. It presents in both a juvenile and an adult form, with no clear information on its actual origin. Diagnosis is based on patient medical history and ultrasound examination but is frequently not correctly identified. Acoustic Radiation Force Impulse Imaging (ARFI) is a novel ultrasound elastography technology that has recently been implemented in the diagnostic work-up of patients with malignancies. This study aimed to answer whether ARFI can reasonably be employed in the initial examination and follow-up during therapy in patients with CRP. Mechanical tissue properties of the salivary glands were analyzed by ARFI in 37 parotid glands of patients with CRP. Having integrated ARFI into our diagnostic protocol for CRP, affected parotid glands were found to exhibit lower tissue elasticity compared to both healthy contralateral glands in the same individuals as well as those of healthy individuals. Most importantly, this method enabled us to quantitatively assess the patient benefit of therapy regarding the recovery of the glands' diseased parenchyma. ARFI provides a quick, easy, and reliable diagnostic tool for the assessment of disease severity and progression in patients with CRP that can be seamlessly implemented into preexisting ultrasound protocols.

Quantitative shear-wave optical coherence elastography with a programmable phased array ultrasound as the wave source.

PubMed

Song, Shaozhen; Le, Nhan Minh; Huang, Zhihong; Shen, Tueng; Wang, Ruikang K

2015-11-01

The purpose of this study is to implement a beam-steering ultrasound as the wave source for shear-wave optical coherence elastography (SW-OCE) to achieve an extended range of elastic imaging of the tissue sample. We introduce a linear phased array ultrasound transducer (LPAUT) as the remote and programmable wave source and a phase-sensitive optical coherence tomography (OCT) as the sensitive shear-wave detector. The LPAUT is programmed to launch acoustic radiation force impulses (ARFI) focused at desired locations within the range of OCT imaging, upon which the elasticity map of the entire OCT B-scan cross section is recovered by spatial compounding of the elastic maps derived from each launch of AFRIs. We also propose a directional filter to separate the shear-wave propagation at different directions in order to reduce the effect of tissue heterogeneity on the shear-wave propagation within tissue. The feasibility of this proposed approach is then demonstrated by determining the stiffness of tissue-mimicking phantoms with agarose concentrations of 0.5% and 1% and also by imaging the Young's modulus of retinal and choroidal tissues within a porcine eye ball ex vivo. The approach opens up opportunities to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative assessment of tissue biomechanical property.

Influence of Tissue Microstructure on Shear Wave Speed Measurements in Plane Shear Wave Elastography: A Computational Study in Lossless Fibrotic Liver Media.

PubMed

Wang, Yu; Jiang, Jingfeng

2018-01-01

Shear wave elastography (SWE) has been used to measure viscoelastic properties for characterization of fibrotic livers. In this technique, external mechanical vibrations or acoustic radiation forces are first transmitted to the tissue being imaged to induce shear waves. Ultrasonically measured displacement/velocity is then utilized to obtain elastographic measurements related to shear wave propagation. Using an open-source wave simulator, k-Wave, we conducted a case study of the relationship between plane shear wave measurements and the microstructure of fibrotic liver tissues. Particularly, three different virtual tissue models (i.e., a histology-based model, a statistics-based model, and a simple inclusion model) were used to represent underlying microstructures of fibrotic liver tissues. We found underlying microstructures affected the estimated mean group shear wave speed (SWS) under the plane shear wave assumption by as much as 56%. Also, the elastic shear wave scattering resulted in frequency-dependent attenuation coefficients and introduced changes in the estimated group SWS. Similarly, the slope of group SWS changes with respect to the excitation frequency differed as much as 78% among three models investigated. This new finding may motivate further studies examining how elastic scattering may contribute to frequency-dependent shear wave dispersion and attenuation in biological tissues.

Generation of remote adaptive torsional shear waves with an octagonal phased array to enhance displacements and reduce variability of shear wave speeds: comparison with quasi-plane shear wavefronts.

PubMed

Ouared, Abderrahmane; Montagnon, Emmanuel; Cloutier, Guy

2015-10-21

A method based on adaptive torsional shear waves (ATSW) is proposed to overcome the strong attenuation of shear waves generated by a radiation force in dynamic elastography. During the inward propagation of ATSW, the magnitude of displacements is enhanced due to the convergence of shear waves and constructive interferences. The proposed method consists in generating ATSW fields from the combination of quasi-plane shear wavefronts by considering a linear superposition of displacement maps. Adaptive torsional shear waves were experimentally generated in homogeneous and heterogeneous tissue mimicking phantoms, and compared to quasi-plane shear wave propagations. Results demonstrated that displacement magnitudes by ATSW could be up to 3 times higher than those obtained with quasi-plane shear waves, that the variability of shear wave speeds was reduced, and that the signal-to-noise ratio of displacements was improved. It was also observed that ATSW could cause mechanical inclusions to resonate in heterogeneous phantoms, which further increased the displacement contrast between the inclusion and the surrounding medium. This method opens a way for the development of new noninvasive tissue characterization strategies based on ATSW in the framework of our previously reported shear wave induced resonance elastography (SWIRE) method proposed for breast cancer diagnosis.

Investigation of the acute plantar fasciitis with contrast-enhanced ultrasound and shear wave elastography - first results.

PubMed

Putz, Franz Josef; Hautmann, Matthias G; Banas, Miriam C; Jung, Ernst Michael

2017-01-01

The plantar fasciitis is a common disease with a high prevalence in public and a frequent cause of heel pain. In our pilot study, we wanted to characterise the feasibility of shear-wave elastography and contrast-enhanced ultrasound (CEUS) in the assessment of the plantar fasciitis. 23 cases of painful heels were examined by B-Mode ultrasound, Power Doppler (PD), shear wave elastography and contrast-enhanced ultrasound before anti-inflammatory radiation. Time-intensity-curves were analysed by the integrated software. The results for area-under-the-curve (AUC), peak, time-to-peak (TTP) and mean-transit-time (MTT) were compared between the plantar fascia and the surrounding tissue. All cases showed thickening of the plantar fascia, in most cases with interstitial oedema (87.0%). Shear wave elastography showed inhomogeneous stiffness of the plantar fascia. 83.3% of cases showed a visible hyperperfusion in CEUS at the proximal plantar fascia in comparison to the surrounding tissue. This hyperperfusion could also be found in 75.0% of cases with no signs of vascularisation in PD. AUC (p = 0.0005) and peak (p = 0.037) were significantely higher in the plantar fascia than in the surrounding tissue. CEUS and shear wave elastography are new diagnostic tools in the assessment of plantar fasciitis and can provide quantitative parameters for monitoring therapy.

Challenging the in-vivo assessment of biomechanical properties of the uterine cervix: A critical analysis of ultrasound based quasi-static procedures.

PubMed

Maurer, M M; Badir, S; Pensalfini, M; Bajka, M; Abitabile, P; Zimmermann, R; Mazza, E

2015-06-25

Measuring the stiffness of the uterine cervix might be useful in the prediction of preterm delivery, a still unsolved health issue of global dimensions. Recently, a number of clinical studies have addressed this topic, proposing quantitative methods for the assessment of the mechanical properties of the cervix. Quasi-static elastography, maximum compressibility using ultrasound and aspiration tests have been applied for this purpose. The results obtained with the different methods seem to provide contradictory information about the physiologic development of cervical stiffness during pregnancy. Simulations and experiments were performed in order to rationalize the findings obtained with ultrasound based, quasi-static procedures. The experimental and computational results clearly illustrate that standardization of quasi-static elastography leads to repeatable strain values, but for different loading forces. Since force cannot be controlled, this current approach does not allow the distinction between a globally soft and stiff cervix. It is further shown that introducing a reference elastomer into the elastography measurement might overcome the problem of force standardization, but a careful mechanical analysis is required to obtain reliable stiffness values for cervical tissue. In contrast, the maximum compressibility procedure leads to a repeatable, semi-quantitative assessment of cervical consistency, due to the nonlinear nature of the mechanical behavior of cervical tissue. The evolution of cervical stiffness in pregnancy obtained with this procedure is in line with data from aspiration tests. Copyright © 2015 Elsevier Ltd. All rights reserved.

Use of ARFI elastography in the prediction of placental invasion anomaly via a new Virtual Touch Quantification Technique.

PubMed

Cim, Numan; Tolunay, Harun Egemen; Boza, Baris; Arslan, Harun; Ates, Can; İlik, İbrahim; Tezcan, Fatih Mehmet; Yıldızhan, Recep; Sahin, Hanım Guler; Yavuz, Alpaslan

2018-03-22

We aimed to evaluate the efficiency of placental elasticity in predicting a placental invasion anomaly with the Virtual Touch Quantification (VTQ) technique. Pregnant women in the third trimester with suspected placental invasion anomaly were enrolled into the research (n = 58). The placenta was evaluated and divided into three equal parts as foetal edge (inner 1/3 of placenta), maternal edge (outer 1/3 of placenta) and the central part (central 1/3 of placenta). Shear wave velocity (SWV) measurements were used in the elastographic evaluation of placentas by VTQ. We performed the measurements at the different regions of placenta for sampling the variety areas of the placenta. Acoustic Radiation Force Impulse (ARFI) Elastography scores were significantly higher in the group in which an invasion was detected during the surgery of patients with preoperative placental invasion suspicion. A significant difference in the measurements of the inner, central and outer third of the placenta between the groups was found (p < .001). In this study, we have shown higher SWV scores of placental measurements of the patients with preoperative suspected anomalies and an invasion detected during their surgery. These findings may reflect an event at the tissue elasticity level and we hope that the use of the VTQ technique may contribute to an early prediction of placental invasions before surgery in the future via new research. Impact statement What is already known on this subject? Placenta invasion anomalies (PIA's) are characterized by haemorrhages which can threat the mother's life. Placental invasion anomalies are among the most important causes of maternal mortality and morbidity. Early diagnosis is very important condition in reducing the mortality and morbidity. Gray scale ultrasonography (US) is mostly used in early diagnosis of PIA's. Acoustic radiation force impulse elastography (ARFI) is a new elastographic ultrasonography technic. We aimed to evaluate a new method in the early diagnosis of PIA's using ARFI technique. There is no study in the diagnosis of PIA's by ARFI in the literature to our knowledge. We think that this original study will contribute to the literature. What do the results of this study add? We showed the accuracy of ARFI in determination of PIA's. ARFI scores were significantly higher in the group in which invasion was detected during surgery of patients with preoperative placental invasion suspicion. What are the implications are of these findings for clinical practice and/or further research? Our findings may reflect an event at the tissue elasticity level and we hope that the use of VTQ technique may contribute to early predict of placental invasions before surgery in the future via new researches. Early diagnosis of placental invasion anomalies may reduce mortality and morbidity.

Value of in vitro acoustic radiation force impulse application on uterine adenomyosis.

PubMed

Bildaci, Tevfik Berk; Cevik, Halime; Yilmaz, Birnur; Desteli, Guldeniz Aksan

2017-11-24

Adenomyosis is the presence of endometrial glandular and stromal tissue in the myometrium. This phenomenon can be the cause of excessive bleeding and menstrual pain in premenopausal women. Diagnosis of adenomyosis may present difficulty with conventional methods such as ultrasound and magnetic resonance imaging. Frequently, diagnosis is accomplished retrospectively based on the hysterectomy specimen. This is a prospective case control study done in vitro on 90 patients' hysterectomy specimens. Acoustic radiation force impulse (ARFI) and color elastography were used to determine the elasticity of hysterectomy specimens of patients undergoing indicated surgeries. Based on histopathological examinations, two groups were formed: a study group (n = 28-with adenomyosis) and a control group (n = 62-without adenomyosis). Elasticity measurements of tissue with adenomyosis were observed to be significantly higher than measurements of normal myometrial tissue (p < 0.01). Uterine fibroids were found to have higher values on ARFI study compared to normal myometrial tissues (p < 0.01). The findings lead to the conclusion that adenomyosis tissue is significantly softer than the normal myometrium. ARFI was found to be beneficial in differentiating myometrial tissue with adenomyosis from normal myometrial tissue. It was found to be feasible and beneficial to implement ARFI in daily gynecology practice for diagnosis of adenomyosis.

An elastography method based on the scanning contact resonance of a piezoelectric cantilever

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Ji; Li, Faxin, E-mail: lifaxin@pku.edu.cn

2013-12-15

Purpose: Most tissues may become significantly stiffer than their normal states when there are lesions inside. The tissue's modulus can then act as an identification parameter for clinic diagnosis of tumors or fibrosis, which leads to elastography. This study introduces a novel elastography method that can be used for modulus imaging of superficial organs. Methods: This method is based on the scanning contact-resonance of a unimorph piezoelectric cantilever. The cantilever vibrates in its bending mode with the tip pressed tightly on the sample. The contact resonance frequency of the cantilever-sample system is tracked at each scanning point, from which themore » sample's modulus can be derived based on a beam dynamic model and a contact mechanics model. Scanning is performed by a three-dimensional motorized stage and the whole system is controlled by a homemade software program based on LabVIEW. Results: Testing onin vitro beef tissues indicates that the fat and the muscle can be easily distinguished using this system, and the accuracy of the modulus measurement can be comparable with that of nanoindentation. Imaging on homemade gelatin phantoms shows that the depth information of the abnormalities can be qualitatively obtained by varying the pressing force. The detection limit of this elastography method is specially examined both experimentally and numerically. Results show that it can detect the typical lesions in superficial organs with the depth of several centimeters. The lateral resolution of this elastography method/system is better than 0.5 mm, and could be further enhanced by using more scanning points. Conclusions: The proposed elastography system can be regarded as a sensitive palpation robot, which may be very promising in early diagnosis of tumors in superficial organs such as breast and thyroid.« less

Developing High-Frequency Quantitative Ultrasound Techniques to Characterize Three-Dimensional Engineered Tissues

NASA Astrophysics Data System (ADS)

Mercado, Karla Patricia E.

Tissue engineering holds great promise for the repair or replacement of native tissues and organs. Further advancements in the fabrication of functional engineered tissues are partly dependent on developing new and improved technologies to monitor the properties of engineered tissues volumetrically, quantitatively, noninvasively, and nondestructively over time. Currently, engineered tissues are evaluated during fabrication using histology, biochemical assays, and direct mechanical tests. However, these techniques destroy tissue samples and, therefore, lack the capability for real-time, longitudinal monitoring. The research reported in this thesis developed nondestructive, noninvasive approaches to characterize the structural, biological, and mechanical properties of 3-D engineered tissues using high-frequency quantitative ultrasound and elastography technologies. A quantitative ultrasound technique, using a system-independent parameter known as the integrated backscatter coefficient (IBC), was employed to visualize and quantify structural properties of engineered tissues. Specifically, the IBC was demonstrated to estimate cell concentration and quantitatively detect differences in the microstructure of 3-D collagen hydrogels. Additionally, the feasibility of an ultrasound elastography technique called Single Tracking Location Acoustic Radiation Force Impulse (STL-ARFI) imaging was demonstrated for estimating the shear moduli of 3-D engineered tissues. High-frequency ultrasound techniques can be easily integrated into sterile environments necessary for tissue engineering. Furthermore, these high-frequency quantitative ultrasound techniques can enable noninvasive, volumetric characterization of the structural, biological, and mechanical properties of engineered tissues during fabrication and post-implantation.

Update on Breast Cancer Detection Using Comb-push Ultrasound Shear Elastography

PubMed Central

Denis, Max; Bayat, Mahdi; Mehrmohammadi, Mohammad; Gregory, Adriana; Song, Pengfei; Whaley, Dana H.; Pruthi, Sandhya; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra

2015-01-01

In this work, tissue stiffness estimates are used to differentiate between benign and malignant breast masses in a group of pre-biopsy patients. The rationale being that breast masses are often stiffer than healthy tissue; furthermore, malignant masses are stiffer than benign masses. The comb-push ultrasound shear elastography (CUSE) method is used to noninvasively assess a tissue’s mechanical properties. CUSE utilizes a simultaneous multiple laterally spaced radiation force (ARF) excitations and detection sequence to reconstruct the region of interest (ROI) shear wave speed map, from which a tissue stiffness property is quantified by Young’s modulus. In this study, the tissue stiffness of 73 breast masses is interrogated. The mean shear wave speeds for malignant masses (3.42 ± 1.32 m/s) were higher than benign breast masses (6.04 ± 1.25 m/s). These speed values correspond to higher stiffness in malignant breast masses (114.9 ± 40.6 kPa) than benign masses (39.4 ± 28.1 kPa and p < 0.001), when tissue elasticity is quantified by Young’s modulus. A Young’s modulus > 83 kPa is established as a cut-off value for differentiating between malignant and benign suspicious breast masses, with receiver operating characteristic curve (ROC) of 89.19% sensitivity, 88.69% specificity, and 0.911 for the area under the curve (AUC). PMID:26688871

Comb-push ultrasound shear elastography of breast masses: initial results show promise.

PubMed

Denis, Max; Mehrmohammadi, Mohammad; Song, Pengfei; Meixner, Duane D; Fazzio, Robert T; Pruthi, Sandhya; Whaley, Dana H; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra

2015-01-01

To evaluate the performance of Comb-push Ultrasound Shear Elastography (CUSE) for classification of breast masses. CUSE is an ultrasound-based quantitative two-dimensional shear wave elasticity imaging technique, which utilizes multiple laterally distributed acoustic radiation force (ARF) beams to simultaneously excite the tissue and induce shear waves. Female patients who were categorized as having suspicious breast masses underwent CUSE evaluations prior to biopsy. An elasticity estimate within the breast mass was obtained from the CUSE shear wave speed map. Elasticity estimates of various types of benign and malignant masses were compared with biopsy results. Fifty-four female patients with suspicious breast masses from our ongoing study are presented. Our cohort included 31 malignant and 23 benign breast masses. Our results indicate that the mean shear wave speed was significantly higher in malignant masses (6 ± 1.58 m/s) in comparison to benign masses (3.65 ± 1.36 m/s). Therefore, the stiffness of the mass quantified by the Young's modulus is significantly higher in malignant masses. According to the receiver operating characteristic curve (ROC), the optimal cut-off value of 83 kPa yields 87.10% sensitivity, 82.61% specificity, and 0.88 for the area under the curve (AUC). CUSE has the potential for clinical utility as a quantitative diagnostic imaging tool adjunct to B-mode ultrasound for differentiation of malignant and benign breast masses.

Update on Breast Cancer Detection Using Comb-Push Ultrasound Shear Elastography.

PubMed

Denis, Max; Bayat, Mahdi; Mehrmohammadi, Mohammad; Gregory, Adriana; Song, Pengfei; Whaley, Dana H; Pruthi, Sandhya; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra

2015-09-01

In this work, tissue stiffness estimates are used to differentiate between benign and malignant breast masses in a group of pre-biopsy patients. The rationale is that breast masses are often stiffer than healthy tissue; furthermore, malignant masses are stiffer than benign masses. The comb-push ultrasound shear elastography (CUSE) method is used to noninvasively assess a tissue's mechanical properties. CUSE utilizes a sequence of simultaneous multiple laterally spaced acoustic radiation force (ARF) excitations and detection to reconstruct the region of interest (ROI) shear wave speed map, from which a tissue stiffness property can be quantified. In this study, the tissue stiffnesses of 73 breast masses were interrogated. The mean shear wave speeds for benign masses (3.42 ± 1.32 m/s) were lower than malignant breast masses (6.04 ± 1.25 m/s). These speed values correspond to higher stiffness in malignant breast masses (114.9 ± 40.6 kPa) than benign masses (39.4 ± 28.1 kPa and p <; 0.001), when tissue elasticity is quantified by Young's modulus. A Young's modulus >83 kPa is established as a cut-off value for differentiating between malignant and benign suspicious breast masses, with a receiver operating characteristic curve (ROC) of 89.19% sensitivity, 88.69% specificity, and 0.911 for the area under the curve (AUC).

Recent advances in the diagnosis and treatment of primary biliary cholangitis

PubMed Central

Huang, Ying-Qiu

2016-01-01

Primary biliary cholangitis (PBC), formerly referred to as primary biliary cirrhosis, is an infrequent progressive intrahepatic cholestatic autoimmune illness that can evolve into hepatic fibrosis, hepatic cirrhosis, hepatic failure, and, in some cases, hepatocellular carcinoma. The disease itself is characterized by T-lymphocyte-mediated chronic non-suppurative destructive cholangitis and elevated serum levels of extremely specific anti-mitochondrial autoantibodies (AMAs). In this article, we will not only review epidemiology, risk factors, natural history, predictive scores, radiologic approaches (e.g., acoustic radiation force impulse imaging, vibration controlled transient elastography, and magnetic resonance elastography), clinical features, serological characteristics covering biochemical markers, immunoglobulins, infections markers, biomarkers, predictive fibrosis marker, specific antibodies (including AMAs such as AMA-M2), anti-nuclear autoantibodies [such as anti-multiple nuclear dot autoantibodies (anti-sp100, PML, NDP52, anti-sp140), anti-rim-like/membranous anti-nuclear autoantibodies (anti-gp210, anti-p62), anti-centromere autoantibodies, and some of the novel autoantibodies], histopathological characteristics of PBC, diagnostic advances, and anti-diastole of PBC. Furthermore, this review emphasizes the recent advances in research of PBC in terms of therapies, including ursodeoxycholic acid, budesonide, methotrexate, obeticholic acid, cyclosporine A, fibrates such as bezafibrate and fenofibrate, rituximab, mesenchymal stem cells transplant, and hepatic transplant. Currently, hepatic transplant remains the only optimal choice with acknowledged treatment efficiency for end-stage PBC patients. PMID:27957241

High-resolution optical polarimetric elastography for measuring the mechanical properties of tissue

NASA Astrophysics Data System (ADS)

Hudnut, Alexa W.; Armani, Andrea M.

2018-02-01

Traditionally, chemical and molecular markers have been the predominate method in diagnostics. Recently, alternate methods of determining tissue and disease characteristics have been proposed based on testing the mechanical behavior of biomaterials. Existing methods for performing elastography measurements, such as atomic force microscopy, compression testing, and ultrasound elastography, require either extensive sample processing or have poor resolution. In the present work, we demonstrate an optical polarimetric elastography device to characterize the mechanical properties of salmon skeletal muscle. A fiber-coupled 1550nm laser paired with an optical polarizer is used to create a fiber optic sensing region. By measuring the change in polarization from the initial state to the final state within the fiber sensing region with a polarimeter, the loading-unloading curves can be determined for the biomaterial. The device is used to characterize the difference between samples with a range of collagen membranes. The loading-unloading curves are used to determine the change in polarization phase and energy loss of the samples at 10%, 20% and 30% strain. As expected, the energy loss is a better metric for measuring the mechanical properties of the tissues because it incorporates the entire loading-unloading curve rather than a single point. Using this metric, it is demonstrated the device can repeatedly differentiate between the different membrane configurations.

In vivo quantification of liver stiffness in a rat model of hepatic fibrosis with acoustic radiation force.

PubMed

Wang, Michael H; Palmeri, Mark L; Guy, Cynthia D; Yang, Liu; Hedlund, Laurence W; Diehl, Anna Mae; Nightingale, Kathryn R

2009-10-01

Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes that accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between liver stiffness measured by radiation force induced shear waves and disease related changes in the liver. An additional aim is to present initial findings on the effects of liver viscosity on radiation force induced shear wave morphology. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl(4)), while five rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares scanner (Siemens Medical Solutions USA, Ultrasound Division, Issaquah, WA, USA). The spatial coherence of radiation force induced shear waves propagating in the viscoelastic rat liver decreased significantly with propagation distance, compared with shear waves in an elastic phantom and a finite element model of a purely elastic medium. Animals were sacrificed after imaging and liver samples were taken for histopathologic analysis and collagen quantification using picrosirius red staining and hydroxyproline assay. At the end of the treatment period, five rats had healthy livers (stage F0), while six had severe fibrosis (F3) and the rest had light to moderate fibrosis (F1 and F2). The measured liver stiffness for the F0 group was 1.5+/-0.1 kPa (mean+/-95% confidence interval) and for F3 livers was 1.8+/-0.2 kPa. In this study, liver stiffness was found to be linearly correlated with the amount of collagen in the liver measured by picrosirius red staining (r(2)=0.43, p=0.008). In addition, stiffness spatial heterogeneity was also linearly correlated with liver collagen content (r(2)=0.58, p=0.001) by picrosirius red staining. These results are consistent with those obtained by Salameh et al. (2007) and Yin et al. (2007b) using animal models of liver fibrosis and MR elastography. This suggests that stiffness measurement using acoustic radiation force can provide a quantitative assessment of the extent of fibrosis in the liver and can be potentially used for the diagnosis, management and study of liver fibrosis.

Modulus reconstruction from prostate ultrasound images using finite element modeling

NASA Astrophysics Data System (ADS)

Yan, Zhennan; Zhang, Shaoting; Alam, S. Kaisar; Metaxas, Dimitris N.; Garra, Brian S.; Feleppa, Ernest J.

2012-03-01

In medical diagnosis, use of elastography is becoming increasingly more useful. However, treatments usually assume a planar compression applied to tissue surfaces and measure the deformation. The stress distribution is relatively uniform close to the surface when using a large, flat compressor but it diverges gradually along tissue depth. Generally in prostate elastography, the transrectal probes used for scanning and compression are cylindrical side-fire or rounded end-fire probes, and the force is applied through the rectal wall. These make it very difficult to detect cancer in prostate, since the rounded contact surfaces exaggerate the non-uniformity of the applied stress, especially for the distal, anterior prostate. We have developed a preliminary 2D Finite Element Model (FEM) to simulate prostate deformation in elastography. The model includes a homogeneous prostate with a stiffer tumor in the proximal, posterior region of the gland. A force is applied to the rectal wall to deform the prostate, strain and stress distributions can be computed from the resultant displacements. Then, we assume the displacements as boundary condition and reconstruct the modulus distribution (inverse problem) using linear perturbation method. FEM simulation shows that strain and strain contrast (of the lesion) decrease very rapidly with increasing depth and lateral distance. Therefore, lesions would not be clearly visible if located far away from the probe. However, the reconstructed modulus image can better depict relatively stiff lesion wherever the lesion is located.

Shear wave elastography using Wigner-Ville distribution: a simulated multilayer media study.

PubMed

Bidari, Pooya Sobhe; Alirezaie, Javad; Tavakkoli, Jahan

2016-08-01

Shear Wave Elastography (SWE) is a quantitative ultrasound-based imaging modality for distinguishing normal and abnormal tissue types by estimating the local viscoelastic properties of the tissue. These properties have been estimated in many studies by propagating ultrasound shear wave within the tissue and estimating parameters such as speed of wave. Vast majority of the proposed techniques are based on the cross-correlation of consecutive ultrasound images. In this study, we propose a new method of wave detection based on time-frequency (TF) analysis of the ultrasound signal. The proposed method is a modified version of the Wigner-Ville Distribution (WVD) technique. The TF components of the wave are detected in a propagating ultrasound wave within a simulated multilayer tissue and the local properties are estimated based on the detected waves. Image processing techniques such as Alternative Sequential Filters (ASF) and Circular Hough Transform (CHT) have been utilized to improve the estimation of TF components. This method has been applied to a simulated data from Wave3000™ software (CyberLogic Inc., New York, NY). This data simulates the propagation of an acoustic radiation force impulse within a two-layer tissue with slightly different viscoelastic properties between the layers. By analyzing the local TF components of the wave, we estimate the longitudinal and shear elasticities and viscosities of the media. This work shows that our proposed method is capable of distinguishing between different layers of a tissue.

Prospective comparison among transient elastography, supersonic shear imaging, and ARFI imaging for predicting fibrosis in nonalcoholic fatty liver disease

PubMed Central

Joo, Sae Kyung; Woo, Hyunsik; Lee, Dong Hyeon; Jung, Yong Jin; Kim, Byeong Gwan; Lee, Kook Lae

2017-01-01

The diagnostic performance of supersonic shear imaging (SSI) in comparison with those of transient elastography (TE) and acoustic radiation force impulse imaging (ARFI) for staging fibrosis in nonalcoholic fatty liver disease (NAFLD) patients has not been fully assessed, especially in Asian populations with relatively lean NAFLD compared to white populations. Thus, we focused on comparing the diagnostic performances of TE, ARFI, and SSI for staging fibrosis in a head-to-head manner, and identifying the clinical, anthropometric, biochemical, and histological features which might affect liver stiffness measurement (LSM) in our prospective biopsy-proven NAFLD cohort. In this study, ninety-four patients with biopsy-proven NAFLD were included prospectively. Liver stiffness was measured using TE, SSI, and ARFI within 1 month of liver biopsy. The diagnostic performance for staging fibrosis was assessed using receiver operating characteristic (ROC) analysis. Anthropometric data were evaluated as covariates influencing LSM by regression analyses. Liver stiffness correlated with fibrosis stage (p < 0.05); the area under the ROC curve of TE (kPa), SSI (kPa), and ARFI (m/s) were as follows: 0.757, 0.759, and 0.657 for significant fibrosis and 0.870, 0.809, and 0.873 for advanced fibrosis. Anthropometric traits were significant confounders affecting SSI, while serum liver injury markers significantly confounded TE and ARFI. In conclusion, the LSM methods had similar diagnostic performance for staging fibrosis in patients with NAFLD. Pre-LSM anthropometric evaluation may help predict the reliability of SSI. PMID:29176844

Comb-Push Ultrasound Shear Elastography of Breast Masses: Initial Results Show Promise

PubMed Central

Song, Pengfei; Fazzio, Robert T.; Pruthi, Sandhya; Whaley, Dana H.; Chen, Shigao; Fatemi, Mostafa

2015-01-01

Purpose or Objective To evaluate the performance of Comb-push Ultrasound Shear Elastography (CUSE) for classification of breast masses. Materials and Methods CUSE is an ultrasound-based quantitative two-dimensional shear wave elasticity imaging technique, which utilizes multiple laterally distributed acoustic radiation force (ARF) beams to simultaneously excite the tissue and induce shear waves. Female patients who were categorized as having suspicious breast masses underwent CUSE evaluations prior to biopsy. An elasticity estimate within the breast mass was obtained from the CUSE shear wave speed map. Elasticity estimates of various types of benign and malignant masses were compared with biopsy results. Results Fifty-four female patients with suspicious breast masses from our ongoing study are presented. Our cohort included 31 malignant and 23 benign breast masses. Our results indicate that the mean shear wave speed was significantly higher in malignant masses (6 ± 1.58 m/s) in comparison to benign masses (3.65 ± 1.36 m/s). Therefore, the stiffness of the mass quantified by the Young’s modulus is significantly higher in malignant masses. According to the receiver operating characteristic curve (ROC), the optimal cut-off value of 83 kPa yields 87.10% sensitivity, 82.61% specificity, and 0.88 for the area under the curve (AUC). Conclusion CUSE has the potential for clinical utility as a quantitative diagnostic imaging tool adjunct to B-mode ultrasound for differentiation of malignant and benign breast masses. PMID:25774978

Longitudinally polarized shear wave optical coherence elastography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Miao, Yusi; Zhu, Jiang; Qi, Li; Qu, Yueqiao; He, Youmin; Gao, Yiwei; Chen, Zhongping

2017-02-01

Shear wave measurement enables quantitative assessment of tissue viscoelasticity. In previous studies, a transverse shear wave was measured using optical coherence elastography (OCE), which gives poor resolution along the force direction because the shear wave propagates perpendicular to the applied force. In this study, for the first time to our knowledge, we introduce an OCE method to detect a longitudinally polarized shear wave that propagates along the force direction. The direction of vibration induced by a piezo transducer (PZT) is parallel to the direction of wave propagation, which is perpendicular to the OCT beam. A Doppler variance method is used to visualize the transverse displacement. Both homogeneous phantoms and a side-by-side two-layer phantom were measured. The elastic moduli from mechanical tests closely matched to the values measured by the OCE system. Furthermore, we developed 3D computational models using finite element analysis to confirm the shear wave propagation in the longitudinal direction. The simulation shows that a longitudinally polarized shear wave is present as a plane wave in the near field of planar source due to diffraction effects. This imaging technique provides a novel method for the assessment of elastic properties along the force direction, which can be especially useful to image a layered tissue.

Comparison of ultrasound B-mode, strain imaging, acoustic radiation force impulse displacement and shear wave velocity imaging using real time clinical breast images

NASA Astrophysics Data System (ADS)

Manickam, Kavitha; Machireddy, Ramasubba Reddy; Raghavan, Bagyam

2016-04-01

It has been observed that many pathological process increase the elastic modulus of soft tissue compared to normal. In order to image tissue stiffness using ultrasound, a mechanical compression is applied to tissues of interest and local tissue deformation is measured. Based on the mechanical excitation, ultrasound stiffness imaging methods are classified as compression or strain imaging which is based on external compression and Acoustic Radiation Force Impulse (ARFI) imaging which is based on force generated by focused ultrasound. When ultrasound is focused on tissue, shear wave is generated in lateral direction and shear wave velocity is proportional to stiffness of tissues. The work presented in this paper investigates strain elastography and ARFI imaging in clinical cancer diagnostics using real time patient data. Ultrasound B-mode imaging, strain imaging, ARFI displacement and ARFI shear wave velocity imaging were conducted on 50 patients (31 Benign and 23 malignant categories) using Siemens S2000 machine. True modulus contrast values were calculated from the measured shear wave velocities. For ultrasound B-mode, ARFI displacement imaging and strain imaging, observed image contrast and Contrast to Noise Ratio were calculated for benign and malignant cancers. Observed contrast values were compared based on the true modulus contrast values calculated from shear wave velocity imaging. In addition to that, student unpaired t-test was conducted for all the four techniques and box plots are presented. Results show that, strain imaging is better for malignant cancers whereas ARFI imaging is superior than strain imaging and B-mode for benign lesions representations.

Ultrahigh resolution optical coherence elastography combined with a rigid micro-endoscope (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fang, Qi; Curatolo, Andrea; Wijesinghe, Philip; Hamzah, Juliana; Ganss, Ruth; Noble, Peter B.; Karnowski, Karol; Sampson, David D.; Kim, Jun Ki; Lee, Wei M.; Kennedy, Brendan F.

2017-02-01

The mechanical forces that living cells experience represent an important framework in the determination of a range of intricate cellular functions and processes. Current insight into cell mechanics is typically provided by in vitro measurement systems; for example, atomic force microscopy (AFM) measurements are performed on cells in culture or, at best, on freshly excised tissue. Optical techniques, such as Brillouin microscopy and optical elastography, have been used for ex vivo and in situ imaging, recently achieving cellular-scale resolution. The utility of these techniques in cell mechanics lies in quick, three-dimensional and label-free mechanical imaging. Translation of these techniques toward minimally invasive in vivo imaging would provide unprecedented capabilities in tissue characterization. Here, we take the first steps along this path by incorporating a gradient-index micro-endoscope into an ultrahigh resolution optical elastography system. Using this endoscope, a lateral resolution of 2 µm is preserved over an extended depth-of-field of 80 µm, achieved by Bessel beam illumination. We demonstrate this combined system by imaging stiffness of a silicone phantom containing stiff inclusions and a freshly excised murine liver tissue. Additionally, we test this system on murine ribs in situ. We show that our approach can provide high quality extended depth-of-field images through an endoscope and has the potential to measure cell mechanics deep in tissue. Eventually, we believe this tool will be capable of studying biological processes and disease progression in vivo.

Acoustic radiation force impulse elastography, FibroScan®, Forns’ index and their combination in the assessment of liver fibrosis in patients with chronic hepatitis B, and the impact of inflammatory activity and steatosis on these diagnostic methods

PubMed Central

DONG, DAO-RAN; HAO, MEI-NA; LI, CHENG; PENG, ZE; LIU, XIA; WANG, GUI-PING; MA, AN-LIN

2015-01-01

The aim of the present study was to investigate the combination of certain serological markers (Forns’ index; FI), FibroScan® and acoustic radiation force impulse elastography (ARFI) in the assessment of liver fibrosis in patients with hepatitis B, and to explore the impact of inflammatory activity and steatosis on the accuracy of these diagnostic methods. Eighty-one patients who had been diagnosed with hepatitis B were recruited and the stage of fibrosis was determined by biopsy. The diagnostic accuracy of FI, FibroScan and ARFI, as well as that of the combination of these methods, was evaluated based on the conformity of the results from these tests with those of biopsies. The effect of concomitant inflammation on diagnostic accuracy was also investigated by dividing the patients into two groups based on the grade of inflammation (G<2 and G≥2). The overall univariate correlation between steatosis and the diagnostic value of the three methods was also evaluated. There was a significant association between the stage of fibrosis and the results obtained using ARFI and FibroScan (Kruskal-Wallis; P<0.001 for all patients), and FI (t-test, P<0.001 for all patients). The combination of FI with ARFI/FibroScan increased the predictive accuracy with a fibrosis stage of S≥2 or cirrhosis. There was a significant correlation between the grade of inflammation and the results obtained using ARFI and FibroScan (Kruskal-Wallis, P<0.001 for all patients), and FI (t-test; P<0.001 for all patients). No significant correlation was detected between the measurements obtained using ARFI, FibroScan and FI, and steatosis (r=−0.100, P=0.407; r=0.170, P=0.163; and r=0.154, P=0.216, respectively). ARFI was shown to be as effective in the diagnosis of liver fibrosis as FibroScan or FI, and the combination of ARFI or FibroScan with FI may improve the accuracy of diagnosis. The presence of inflammatory activity, but not that of steatosis, may affect the diagnostic accuracy of these methods. PMID:25651500

Acoustic radiation force impulse elastography, FibroScan®, Forns' index and their combination in the assessment of liver fibrosis in patients with chronic hepatitis B, and the impact of inflammatory activity and steatosis on these diagnostic methods.

PubMed

Dong, Dao-Ran; Hao, Mei-Na; Li, Cheng; Peng, Ze; Liu, Xia; Wang, Gui-Ping; Ma, An-Lin

2015-06-01

The aim of the present study was to investigate the combination of certain serological markers (Forns' index; FI), FibroScan® and acoustic radiation force impulse elastography (ARFI) in the assessment of liver fibrosis in patients with hepatitis B, and to explore the impact of inflammatory activity and steatosis on the accuracy of these diagnostic methods. Eighty‑one patients who had been diagnosed with hepatitis B were recruited and the stage of fibrosis was determined by biopsy. The diagnostic accuracy of FI, FibroScan and ARFI, as well as that of the combination of these methods, was evaluated based on the conformity of the results from these tests with those of biopsies. The effect of concomitant inflammation on diagnostic accuracy was also investigated by dividing the patients into two groups based on the grade of inflammation (G<2 and G≥2). The overall univariate correlation between steatosis and the diagnostic value of the three methods was also evaluated. There was a significant association between the stage of fibrosis and the results obtained using ARFI and FibroScan (Kruskal‑Wallis; P<0.001 for all patients), and FI (t-test, P<0.001 for all patients). The combination of FI with ARFI/FibroScan increased the predictive accuracy with a fibrosis stage of S≥2 or cirrhosis. There was a significant correlation between the grade of inflammation and the results obtained using ARFI and FibroScan (Kruskal‑Wallis, P<0.001 for all patients), and FI (t-test; P<0.001 for all patients). No significant correlation was detected between the measurements obtained using ARFI, FibroScan and FI, and steatosis (r=‑0.100, P=0.407; r=0.170, P=0.163; and r=0.154, P=0.216, respectively). ARFI was shown to be as effective in the diagnosis of liver fibrosis as FibroScan or FI, and the combination of ARFI or FibroScan with FI may improve the accuracy of diagnosis. The presence of inflammatory activity, but not that of steatosis, may affect the diagnostic accuracy of these methods.

A longitudinal magnetic resonance elastography study of murine brain tumors following radiation therapy

NASA Astrophysics Data System (ADS)

Feng, Y.; Clayton, E. H.; Okamoto, R. J.; Engelbach, J.; Bayly, P. V.; Garbow, J. R.

2016-08-01

An accurate and noninvasive method for assessing treatment response following radiotherapy is needed for both treatment monitoring and planning. Measurement of solid tumor volume alone is not sufficient for reliable early detection of therapeutic response, since changes in physiological and/or biomechanical properties can precede tumor volume change following therapy. In this study, we use magnetic resonance elastography to evaluate the treatment effect after radiotherapy in a murine brain tumor model. Shear modulus was calculated and compared between the delineated tumor region of interest (ROI) and its contralateral, mirrored counterpart. We also compared the shear modulus from both the irradiated and non-irradiated tumor and mirror ROIs longitudinally, sampling four time points spanning 9-19 d post tumor implant. Results showed that the tumor ROI had a lower shear modulus than that of the mirror ROI, independent of radiation. The shear modulus of the tumor ROI decreased over time for both the treated and untreated groups. By contrast, the shear modulus of the mirror ROI appeared to be relatively constant for the treated group, while an increasing trend was observed for the untreated group. The results provide insights into the tumor properties after radiation treatment and demonstrate the potential of using the mechanical properties of the tumor as a biomarker. In future studies, more closely spaced time points will be employed for detailed analysis of the radiation effect.

Imaging Feedback of Histotripsy Treatments Using Ultrasound Shear Wave Elastography

PubMed Central

Wang, Tzu-Yin; Hall, Timothy L.; Xu, Zhen; Fowlkes, J. Brian; Cain, Charles A.

2013-01-01

Histotripsy is a cavitation-based ultrasound therapy that mechanically fractionates soft solid tissues into fluid-like homogenates. This paper investigates the feasibility of imaging the tissue elasticity change during the histotripsy process as a tool to provide feedback for the treatments. The treatments were performed on agar tissue phantoms and ex vivo kidneys using 3-cycle ultrasound pulses delivered by a 750-kHz therapeutic array at peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. Lesions with different degrees of damage were created with increasing numbers of therapy pulses from 0 to 2000 pulses per treatment location. The elasticity of the lesions was measured with ultrasound shear wave elastography, in which a quasi-planar shear wave was induced by acoustic radiation force generated by the therapeutic array, and tracked with ultrasound imaging at 3000 frames per second. Based on the shear wave velocity calculated from the sequentially captured frames, the Young’s modulus was reconstructed. Results showed that the lesions were more easily identified on the shear wave velocity images than on B-mode images. As the number of therapy pulses increased from 0 to 2000 pulses/location, the Young’s modulus decreased exponentially from 22.1 ± 2.7 to 2.1 ± 1.1 kPa in the tissue phantoms (R2 = 0.99, N = 9 each), and from 33.0 ± 7.1 to 4.0 ± 2.5 kPa in the ex vivo kidneys (R2 = 0.99, N = 8 each). Correspondingly, the tissues transformed from completely intact to completely fractionated as examined via histology. A good correlation existed between the lesions’ Young’s modulus and the degree of tissue fractionation as examined with the percentage of remaining structurally intact cell nuclei (R2 = 0.91, N = 8 each). These results indicate that lesions produced by histotripsy can be detected with high sensitivity using shear wave elastography. Because the decrease in the tissue elasticity corresponded well with the morphological and histological change, this study provides a basis for predicting the local treatment outcomes from tissue elasticity change. PMID:22711412

Imaging feedback of histotripsy treatments using ultrasound shear wave elastography.

PubMed

Wang, Tzu-Yin; Hall, Timothy L; Xu, Zhen; Fowlkes, J Brian; Cain, Charles A

2012-06-01

Histotripsy is a cavitation-based ultrasound therapy that mechanically fractionates soft solid tissues into fluid-like homogenates. This paper investigates the feasibility of imaging the tissue elasticity change during the histotripsy process as a tool to provide feedback for the treatments. The treatments were performed on agar tissue phantoms and ex vivo kidneys using 3-cycle ultrasound pulses delivered by a 750-kHz therapeutic array at peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. Lesions with different degrees of damage were created with increasing numbers of therapy pulses from 0 to 2000 pulses per treatment location. The elasticity of the lesions was measured with ultrasound shear wave elastography, in which a quasi-planar shear wave was induced by acoustic radiation force generated by the therapeutic array, and tracked with ultrasound imaging at 3000 frames per second. Based on the shear wave velocity calculated from the sequentially captured frames, the Young's modulus was reconstructed. Results showed that the lesions were more easily identified on the shear wave velocity images than on B-mode images. As the number of therapy pulses increased from 0 to 2000 pulses/location, the Young's modulus decreased exponentially from 22.1 ± 2.7 to 2.1 ± 1.1 kPa in the tissue phantoms (R2 = 0.99, N = 9 each), and from 33.0 ± 7.1 to 4.0 ± 2.5 kPa in the ex vivo kidneys (R2 = 0.99, N = 8 each). Correspondingly, the tissues transformed from completely intact to completely fractionated as examined via histology. A good correlation existed between the lesions' Young's modulus and the degree of tissue fractionation as examined with the percentage of remaining structurally intact cell nuclei (R2 = 0.91, N = 8 each). These results indicate that lesions produced by histotripsy can be detected with high sensitivity using shear wave elastography. Because the decrease in the tissue elasticity corresponded well with the morphological and histological change, this study provides a basis for predicting the local treatment outcomes from tissue elasticity change.

Prospective Evaluation of Acoustic Radiation Force Impulse (ARFI) Elastography and High-Frequency B-Mode Ultrasound in Compensated Patients for the Diagnosis of Liver Fibrosis/Cirrhosis in Comparison to Mini-Laparoscopic Biopsy.

PubMed

Pfeifer, L; Zopf, S; Siebler, J; Schwitulla, J; Wildner, D; Wachter, D; Neurath, M F; Strobel, D

2015-12-01

Ultrasound is a well-established noninvasive test for assessing patients with liver disease. This study aims to prospectively compare ultrasound to the new technique elastography (ARFI) for the assessment of liver fibrosis/cirrhosis. High-frequency B-mode ultrasound (liver surface/vein irregularity, liver homogeneity, spleen size), ARFI quantification, mini-laparoscopic liver evaluation including biopsy were prospectively obtained in compensated patients scheduled for liver biopsy. For the diagnosis of cirrhosis, a combined gold standard (cirrhosis at histology and/or at macroscopic liver evaluation) was used. Out of 157 patients, 35 patients were diagnosed cirrhotic. Ultrasound (combination of liver vein and/or surface irregularity) showed no significant difference compared to ARFI quantification for the diagnosis of significant liver fibrosis (Ishak> = 3) and cirrhosis. Diagnosis of cirrhosis had a sensitivity/specificity/PPV/NPV of 83 %(± 12) / 82 %(± 7) / 57 %(± 14) / 94 %(± 4), respectively, with ultrasound and 86 %(± 12) / 81 %(± 7) / 57 %(± 13) / 95 %(± 4), respectively, with ARFI quantification. The sensitivity/specificity/PPV/NPV for the detection of significant fibrosis were 68 %(± 13) / 86 %(± 7) / 71 %(± 13) / 84 %(± 7), respectively, for ultrasound and 70 %(± 12) / 84 %(± 7) / 69 %(± 12) / 84 %(± 7), respectively, for ARFI quantification. ARFI elastography and high-frequency B-mode ultrasound show similar and good results for the diagnosis of compensated liver cirrhosis and high-grade fibrosis. A key benefit of both methods is the high NPV suggesting them as noninvasive exclusion tests. © Georg Thieme Verlag KG Stuttgart · New York.

Measurement of shear wave speed dispersion in the placenta by transient elastography: A preliminary ex vivo study.

PubMed

Simon, Emmanuel G; Callé, Samuel; Perrotin, Franck; Remenieras, Jean-Pierre

2018-01-01

Placental elasticity may be modified in women with placental insufficiency. Shear wave elastography (SWE) can measure this, using acoustic radiation force, but the safety of its use in pregnant women has not yet been demonstrated. Transient elastography (TE) is a safer alternative, but has not yet been applied to the placenta. Moreover, the dispersion of shear wave speed (SWS) as a function of frequency has received relatively little study for placental tissue, although it might improve the accuracy of biomechanical assessment. To explore the feasibility and reproducibility of TE for placental analysis, to compare the values of SWS and Young's modulus (YM) from TE and SWE, and to analyze SWS dispersion as a function of frequency ex vivo in normal placentas. Ten normal placentas were analyzed ex vivo by an Aixplorer ultrasound system as shear waves were generated by a vibrating plate and by using an Aixplorer system. The frequency analysis provided the value of the exponent n from a fractional rheological model applied to the TE method. We calculated intra- and interobserver agreement for SWS and YM with 95% prediction intervals, created Bland-Altman plots with 95% limits of agreement, and estimated the intraclass correlation coefficient (ICC). The mean SWS was 1.80 m/s +/- 0.28 (standard deviation) with the TE method at 50 Hz and 1.82 m/s +/-0.13 with SWE (P = 0.912). No differences were observed between the central and peripheral regions of placentas with either TE or SWE. With TE, the intraobserver ICC for SWS was 0.68 (0.50-0.82), and the interobserver ICC for SWS 0.65 (0.37-0.85). The mean parameter n obtained from the fractional rheological model was 1.21 +/- 0.12, with variable values of n for any given SWS. TE is feasible and reproducible on placentas ex vivo. The frequency analysis of SWS provides additional information about placental elasticity and appears to be able to distinguish differences between placental structures.

Measurement of shear wave speed dispersion in the placenta by transient elastography: A preliminary ex vivo study

PubMed Central

Callé, Samuel; Perrotin, Franck; Remenieras, Jean-Pierre

2018-01-01

Background Placental elasticity may be modified in women with placental insufficiency. Shear wave elastography (SWE) can measure this, using acoustic radiation force, but the safety of its use in pregnant women has not yet been demonstrated. Transient elastography (TE) is a safer alternative, but has not yet been applied to the placenta. Moreover, the dispersion of shear wave speed (SWS) as a function of frequency has received relatively little study for placental tissue, although it might improve the accuracy of biomechanical assessment. Objective To explore the feasibility and reproducibility of TE for placental analysis, to compare the values of SWS and Young’s modulus (YM) from TE and SWE, and to analyze SWS dispersion as a function of frequency ex vivo in normal placentas. Materials and methods Ten normal placentas were analyzed ex vivo by an Aixplorer ultrasound system as shear waves were generated by a vibrating plate and by using an Aixplorer system. The frequency analysis provided the value of the exponent n from a fractional rheological model applied to the TE method. We calculated intra- and interobserver agreement for SWS and YM with 95% prediction intervals, created Bland-Altman plots with 95% limits of agreement, and estimated the intraclass correlation coefficient (ICC). Main results The mean SWS was 1.80 m/s +/- 0.28 (standard deviation) with the TE method at 50 Hz and 1.82 m/s +/-0.13 with SWE (P = 0.912). No differences were observed between the central and peripheral regions of placentas with either TE or SWE. With TE, the intraobserver ICC for SWS was 0.68 (0.50–0.82), and the interobserver ICC for SWS 0.65 (0.37–0.85). The mean parameter n obtained from the fractional rheological model was 1.21 +/- 0.12, with variable values of n for any given SWS. Conclusions TE is feasible and reproducible on placentas ex vivo. The frequency analysis of SWS provides additional information about placental elasticity and appears to be able to distinguish differences between placental structures. PMID:29621270

Quantifying changes in lens biomechanical properties due to cold cataract with optical coherence elastography

NASA Astrophysics Data System (ADS)

Zhang, Hongqiu; Wu, Chen; Singh, Manmohan; Larin, Kirill V.

2018-02-01

Cataract is the most prevalent cause of visual impairment worldwide. Cataracts can be formed due to trauma, radiation, drug abuse, or low temperatures. Thus, early detection of cataract can be immensely helpful for preserving visual acuity by ensuring that the appropriate therapeutic procedures are performed at earlier stages of disease onset and progression. In this work, we utilized a phase-sensitive optical coherence elastography (OCE) system to quantify changes in biomechanical properties of porcine lenses in vitro with induced cold cataracts. The results show significant increase in lens Young's modulus due to formation of the cold cataract (from 35 kPa to 60 kPa). These results show that OCE can assess lenticular biomechanical properties and may be useful for detecting and, potentially, characterizing cataracts.

Performance of shear wave elastography for differentiation of benign and malignant solid breast masses.

PubMed

Li, Guiling; Li, De-Wei; Fang, Yu-Xiao; Song, Yi-Jiang; Deng, Zhu-Jun; Gao, Jian; Xie, Yan; Yin, Tian-Sheng; Ying, Li; Tang, Kai-Fu

2013-01-01

To perform a meta-analysis assessing the ability of shear wave elastography (SWE) to identify malignant breast masses. PubMed, the Cochrane Library, and the ISI Web of Knowledge were searched for studies evaluating the accuracy of SWE for identifying malignant breast masses. The diagnostic accuracy of SWE was evaluated according to sensitivity, specificity, and hierarchical summary receiver operating characteristic (HSROC) curves. An analysis was also performed according to the SWE mode used: supersonic shear imaging (SSI) and the acoustic radiation force impulse (ARFI) technique. The clinical utility of SWE for identifying malignant breast masses was evaluated using analysis of Fagan plot. A total of 9 studies, including 1888 women and 2000 breast masses, were analyzed. Summary sensitivities and specificities were 0.91 (95% confidence interval [CI], 0.88-0.94) and 0.82 (95% CI, 0.75-0.87) by SSI and 0.89 (95% CI, 0.81-0.94) and 0.91 (95% CI, 0.84-0.95) by ARFI, respectively. The HSROCs for SSI and ARFI were 0.92 (95% CI, 0.90-0.94) and 0.96 (95% CI, 0.93-0.97), respectively. SSI and ARFI were both very informative, with probabilities of 83% and 91%, respectively, for correctly differentiating between benign and malignant breast masses following a "positive" measurement (over the threshold value) and probabilities of disease as low as 10% and 11%, respectively, following a "negative" measurement (below the threshold value) when the pre-test probability was 50%. SWE could be used as a good identification tool for the classification of breast masses.

Factors that influence muscle shear modulus during passive stretch.

PubMed

Koo, Terry K; Hug, François

2015-09-18

Although elastography has been increasingly used for evaluating muscle shear modulus associated with age, sex, musculoskeletal, and neurological conditions, its physiological meaning is largely unknown. This knowledge gap may hinder data interpretation, limiting the potential of using elastography to gain insights into muscle biomechanics in health and disease. We derived a mathematical model from a widely-accepted Hill-type passive force-length relationship to gain insight about the physiological meaning of resting shear modulus of skeletal muscles under passive stretching, and validated the model by comparing against the ex-vivo animal data reported in our recent work (Koo et al. 2013). The model suggested that resting shear modulus of a slack muscle is a function of specific tension and parameters that govern the normalized passive muscle force-length relationship as well as the degree of muscle anisotropy. The model also suggested that although the slope of the linear shear modulus-passive force relationship is primarily related to muscle anatomical cross-sectional area (i.e. the smaller the muscle cross-sectional area, the more the increase in shear modulus to result in the same passive muscle force), it is also governed by the normalized passive muscle force-length relationship and the degree of muscle anisotropy. Taken together, although muscle shear modulus under passive stretching has a strong linear relationship with passive muscle force, its actual value appears to be affected by muscle's mechanical, material, and architectural properties. This should be taken into consideration when interpreting the muscle shear modulus values. Copyright © 2015 Elsevier Ltd. All rights reserved.

Acoustic Radiation Force-Induced Creep-Recovery (ARFICR): A Noninvasive Method to Characterize Tissue Viscoelasticity.

PubMed

Amador Carrascal, Carolina; Chen, Shigao; Urban, Matthew W; Greenleaf, James F

2018-01-01

Ultrasound shear wave elastography is a promising noninvasive, low cost, and clinically viable tool for liver fibrosis staging. Current shear wave imaging technologies on clinical ultrasound scanners ignore shear wave dispersion and use a single group velocity measured over the shear wave bandwidth to estimate tissue elasticity. The center frequency and bandwidth of shear waves induced by acoustic radiation force depend on the ultrasound push beam (push duration, -number, etc.) and the viscoelasticity of the medium, and therefore are different across scanners from different vendors. As a result, scanners from different vendors may give different tissue elasticity measurements within the same patient. Various methods have been proposed to evaluate shear wave dispersion to better estimate tissue viscoelasticity. A rheological model such as the Kelvin-Voigt model is typically fitted to the shear wave dispersion to solve for the elasticity and viscosity of tissue. However, these rheological models impose strong assumptions about frequency dependence of elasticity and viscosity. Here, we propose a new method called Acoustic Radiation Force Induced Creep-Recovery (ARFICR) capable of quantifying rheological model-independent measurements of elasticity and viscosity for more robust tissue health assessment. In ARFICR, the creep-recovery time signal at the focus of the push beam is used to calculate the relative elasticity and viscosity (scaled by an unknown constant) over a wide frequency range. Shear waves generated during the ARFICR measurement are also detected and used to calculate the shear wave velocity at its center frequency, which is then used to calibrate the relative elasticity and viscosity to absolute elasticity and viscosity. In this paper, finite-element method simulations and experiments in tissue mimicking phantoms are used to validate and characterize the extent of viscoelastic quantification of ARFICR. The results suggest that ARFICR can measure tissue viscoelasticity reliably. Moreover, the results showed the strong frequency dependence of viscoelastic parameters in tissue mimicking phantoms and healthy liver.

Practice guideline for the performance of breast ultrasound elastography.

PubMed

Lee, Su Hyun; Chang, Jung Min; Cho, Nariya; Koo, Hye Ryoung; Yi, Ann; Kim, Seung Ja; Youk, Ji Hyun; Son, Eun Ju; Choi, Seon Hyeong; Kook, Shin Ho; Chung, Jin; Cha, Eun Suk; Park, Jeong Seon; Jung, Hae Kyoung; Ko, Kyung Hee; Choi, Hye Young; Ryu, Eun Bi; Moon, Woo Kyung

2014-01-01

Ultrasound (US) elastography is a valuable imaging technique for tissue characterization. Two main types of elastography, strain and shear-wave, are commonly used to image breast tissue. The use of elastography is expected to increase, particularly with the increased use of US for breast screening. Recently, the US elastographic features of breast masses have been incorporated into the 2nd edition of the Breast Imaging Reporting and Data System (BI-RADS) US lexicon as associated findings. This review suggests practical guidelines for breast US elastography in consensus with the Korean Breast Elastography Study Group, which was formed in August 2013 to perform a multicenter prospective study on the use of elastography for US breast screening. This article is focused on the role of elastography in combination with B-mode US for the evaluation of breast masses. Practical tips for adequate data acquisition and the interpretation of elastography results are also presented.

Performance of real-time strain elastography, transient elastography, and aspartate-to-platelet ratio index in the assessment of fibrosis in chronic hepatitis C.

PubMed

Ferraioli, Giovanna; Tinelli, Carmine; Malfitano, Antonello; Dal Bello, Barbara; Filice, Gaetano; Filice, Carlo; Above, Elisabetta; Barbarini, Giorgio; Brunetti, Enrico; Calderon, Willy; Di Gregorio, Marta; Lissandrin, Raffaella; Ludovisi, Serena; Maiocchi, Laura; Michelone, Giuseppe; Mondelli, Mario; Patruno, Savino F A; Perretti, Alessandro; Poma, Gianluigi; Sacchi, Paolo; Zaramella, Marco; Zicchetti, Mabel

2012-07-01

The purpose of this article is to evaluate the diagnostic performance of transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index in assessing fibrosis in patients with chronic hepatitis C by using histologic Metavir scores as reference standard. Consecutive patients with chronic hepatitis C scheduled for liver biopsy were enrolled. Liver biopsy was performed on the same day as transient elastography and real-time strain elastography. Transient elastography and real-time strain elastography were performed in the same patient encounter by a single investigator using a medical device based on elastometry and an ultrasound machine, respectively. Diagnostic performance was assessed by using receiver operating characteristic curves and area under the receiver operating characteristic curve (AUC) analysis. One hundred thirty patients (91 men and 39 women) were analyzed. The cutoff values for transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index were 6.9 kPa, 1.82, and 0.37, respectively, for fibrosis score of 2 or higher; 7.3 kPa, 1.86, and 0.70, respectively, for fibrosis score of 3 or higher; and 9.3 kPa, 2.33, and 0.70, respectively, for fibrosis score of 4. AUC values of transient elastography, real-time strain elastography, aspartate-to-platelet ratio index were 0.88, 0.74, and 0.86, respectively, for fibrosis score of 2 or higher; 0.95, 0.80, and 0.89, respectively, for fibrosis score of 3 or higher; and 0.97, 0.80, and 0.84, respectively, for fibrosis score of 4. A combination of the three methods, when two of three were in agreement, showed AUC curves of 0.93, 0.95, and 0.95 for fibrosis scores of 2 or higher, 3 or higher, and 4, respectively. Transient elastography, real-time strain elastography, and aspartate-to-platelet ratio index values were correlated with histologic stages of fibrosis. Transient elastography offered excellent diagnostic performance in assessing severe fibrosis and cirrhosis. Real-time elastography does not yet have the potential to substitute for transient elastography in the assessment of liver fibrosis.

High-resolution analysis of the mechanical behavior of tissue

NASA Astrophysics Data System (ADS)

Hudnut, Alexa W.; Armani, Andrea M.

2017-06-01

The mechanical behavior and properties of biomaterials, such as tissue, have been directly and indirectly connected to numerous malignant physiological states. For example, an increase in the Young's Modulus of tissue can be indicative of cancer. Due to the heterogeneity of biomaterials, it is extremely important to perform these measurements using whole or unprocessed tissue because the tissue matrix contains important information about the intercellular interactions and the structure. Thus, developing high-resolution approaches that can accurately measure the elasticity of unprocessed tissue samples is of great interest. Unfortunately, conventional elastography methods such as atomic force microscopy, compression testing, and ultrasound elastography either require sample processing or have poor resolution. In the present work, we demonstrate the characterization of unprocessed salmon muscle using an optical polarimetric elastography system. We compare the results of compression testing within different samples of salmon skeletal muscle with different numbers of collagen membranes to characterize differences in heterogeneity. Using the intrinsic collagen membranes as markers, we determine the resolution of the system when testing biomaterials. The device reproducibly measures the stiffness of the tissues at variable strains. By analyzing the amount of energy lost by the sample during compression, collagen membranes that are 500 μm in size are detected.

Elastography in clinical practice.

PubMed

Barr, Richard G

2014-11-01

Elastography is a new technique that evaluates tissue stiffness. There are two elastography methods, strain and shear wave elastography. Both techniques are being used to evaluate a wide range of applications in medical imaging. Elastography of breast masses and prostates have been shown to have high accuracy for characterizing masses and can significantly decrease the need for biopsies. Shear wave elastography has been shown to be able to detect and grade liver fibrosis and may decrease the need for liver biopsy. Evaluation of other organs is still preliminary. This article reviews the principles of elastography and its potential clinical applications. Copyright © 2014 Elsevier Inc. All rights reserved.

Sonoelastography in the musculoskeletal system: Current role and future directions.

PubMed

Winn, Naomi; Lalam, Radhesh; Cassar-Pullicino, Victor

2016-11-28

Ultrasound is an essential modality within musculoskeletal imaging, with the recent addition of elastography. The elastic properties of tissues are different from the acoustic impedance used to create B mode imaging and the flow properties used within Doppler imaging, hence elastography provides a different form of tissue assessment. The current role of ultrasound elastography in the musculoskeletal system will be reviewed, in particular with reference to muscles, tendons, ligaments, joints and soft tissue tumours. The different ultrasound elastography methods currently available will be described, in particular strain elastography and shear wave elastography. Future directions of ultrasound elastography in the musculoskeletal system will also be discussed.

Elastography in Chronic Liver Disease: Modalities, Techniques, Limitations, and Future Directions

PubMed Central

Srinivasa Babu, Aparna; Wells, Michael L.; Teytelboym, Oleg M.; Mackey, Justin E.; Miller, Frank H.; Yeh, Benjamin M.; Ehman, Richard L.

2016-01-01

Chronic liver disease has multiple causes, many of which are increasing in prevalence. The final common pathway of chronic liver disease is tissue destruction and attempted regeneration, a pathway that triggers fibrosis and eventual cirrhosis. Assessment of fibrosis is important not only for diagnosis but also for management, prognostic evaluation, and follow-up of patients with chronic liver disease. Although liver biopsy has traditionally been considered the reference standard for assessment of liver fibrosis, noninvasive techniques are the emerging focus in this field. Ultrasound-based elastography and magnetic resonance (MR) elastography are gaining popularity as the modalities of choice for quantifying hepatic fibrosis. These techniques have been proven superior to conventional cross-sectional imaging for evaluation of fibrosis, especially in the precirrhotic stages. Moreover, elastography has added utility in the follow-up of previously diagnosed fibrosis, the assessment of treatment response, evaluation for the presence of portal hypertension (spleen elastography), and evaluation of patients with unexplained portal hypertension. In this article, a brief overview is provided of chronic liver disease and the tools used for its diagnosis. Ultrasound-based elastography and MR elastography are explored in depth, including a brief glimpse into the evolution of elastography. Elastography is based on the principle of measuring tissue response to a known mechanical stimulus. Specific elastographic techniques used to exploit this principle include MR elastography and ultrasonography-based static or quasistatic strain imaging, one-dimensional transient elastography, point shear-wave elastography, and supersonic shear-wave elastography. The advantages, limitations, and pitfalls of each modality are emphasized. ©RSNA, 2016 PMID:27689833

What we need to know when performing and interpreting US elastography

PubMed Central

Park, So Hyun; Kim, So Yeon; Suh, Chong Hyun; Lee, Seung Soo; Kim, Kyoung Won; Lee, So Jung; Lee, Moon-Gyu

2016-01-01

According to the increasing need for accurate staging of hepatic fibrosis, the ultrasound (US) elastography techniques have evolved significantly over the past two decades. Currently, US elastography is increasingly used in clinical practice. Previously published studies have demonstrated the excellent diagnostic performance of US elastography for the detection and staging of liver fibrosis. Although US elastography may seem easy to perform and interpret, there are many technical and clinical factors which can affect the results of US elastography. Therefore, clinicians who are involved with US elastography should be aware of these factors. The purpose of this article is to present a brief overview of US techniques with the relevant technology, the clinical indications, diagnostic performance, and technical and biological factors which should be considered in order to avoid misinterpretation of US elastography results. PMID:27729637

A novel 3D-printed mechanical actuator using centrifugal force for magnetic resonance elastography.

PubMed

Neumann, Wiebke; Schad, Lothar R; Zollner, Frank G

2017-07-01

Magnetic resonance elastography (MRE) is a technique for the quantification of tissue stiffness during MR examinations. It requires consistent methods for mechanical shear wave induction to the region of interest in the human body to reliably quantify elastic properties of soft tissues. This work proposes a novel 3D-printed mechanical actuator using the principle of centrifugal force for wave induction. The driver consists of a 3D-printed turbine vibrator powered by compressed air (located inside the scanner room) and an active driver controlling the pressure of inflowing air (placed outside the scanner room). The generated force of the proposed actuator increases for higher actuation frequencies as opposed to conventionally used air cushions. There, the displacement amplitude decreases with increasing actuation frequency resulting in a smaller signal-to-noise ratio. An initial phantom study is presented which demonstrates the feasibility of the actuator for MRE. The wave-actuation frequency was regulated in a range between 15 Hz and 60 Hz for force measurements and proved sufficiently stable (± 0.3 Hz) for any given nominal frequency. The generated forces depend on the weight of the eccentric unbalance within the turbine and ranged between 0.67 N to 2.70 N (for 15 Hz) and 3.09 N to 7.77 N (for 60 Hz). Therefore, the generated force of the presented actuator increases with rotational speed of the turbine and offers an elegant solution for sufficiently large wave actuation at higher frequencies. In future work, we will investigate an optimal ratio of the weight of unbalance to the size of turbine for appropriately large but tolerable wave actuation for a given nominal frequency.

Relationship between isometric contraction intensity and muscle hardness assessed by ultrasound strain elastography.

PubMed

Inami, Takayuki; Tsujimura, Toru; Shimizu, Takuya; Watanabe, Takemasa; Lau, Wing Yin; Nosaka, Kazunori

2017-05-01

Ultrasound elastography is used to assess muscle hardness or stiffness; however, no previous studies have validated muscle hardness measures using ultrasound strain elastography (SE). This study investigated the relationship between plantar flexor isometric contraction intensity and gastrocnemius hardness assessed by SE. We hypothesised that the muscle would become harder linearly with an increase in the contraction intensity of the plantar flexors. Fifteen young women (20.1 ± 0.8 years) performed isometric contractions of the ankle plantar flexors at four different intensities (25, 50, 75, 100% of maximal voluntary contraction force: MVC) at 0° plantar flexion. Using SE images, the strain ratio (SR) between the muscle and an acoustic coupler (elastic modulus 22.6 kPa) placed over the skin was calculated (muscle/coupler); pennation angle and muscle thickness were measured for the resting and contracting conditions. SR decreased with increasing contraction intensity from rest (1.28 ± 0.20) to 25% (0.99 ± 0.21), 50% (0.61 ± 0.15), 75% (0.34 ± 0.1) and 100% MVC (0.20 ± 0.05). SR decreased linearly (P < 0.05) with increasing MVC from rest to 75% MVC, but levelled off from 75 and 100% MVC. SR was negatively correlated with pennation angle (r = -0.80, P < 0.01) and muscle thickness ( r= -0.78,  P< 0.01). SR appears to represent muscle hardness changes in response to contraction intensity changes, in the assumption that the gastrocnemius muscle contraction intensity is proportional to the plantar flexion intensity. We concluded that gastrocnemius muscle hardness changes could be validly assessed by SR, and the force-hardness relationship was not linear.

Performance of Shear Wave Elastography for Differentiation of Benign and Malignant Solid Breast Masses

PubMed Central

Song, Yi-Jiang; Deng, Zhu-Jun; Gao, Jian; Xie, Yan; Yin, Tian-Sheng; Ying, Li; Tang, Kai-Fu

2013-01-01

Objectives To perform a meta-analysis assessing the ability of shear wave elastography (SWE) to identify malignant breast masses. Methods PubMed, the Cochrane Library, and the ISI Web of Knowledge were searched for studies evaluating the accuracy of SWE for identifying malignant breast masses. The diagnostic accuracy of SWE was evaluated according to sensitivity, specificity, and hierarchical summary receiver operating characteristic (HSROC) curves. An analysis was also performed according to the SWE mode used: supersonic shear imaging (SSI) and the acoustic radiation force impulse (ARFI) technique. The clinical utility of SWE for identifying malignant breast masses was evaluated using analysis of Fagan plot. Results A total of 9 studies, including 1888 women and 2000 breast masses, were analyzed. Summary sensitivities and specificities were 0.91 (95% confidence interval [CI], 0.88–0.94) and 0.82 (95% CI, 0.75–0.87) by SSI and 0.89 (95% CI, 0.81–0.94) and 0.91 (95% CI, 0.84–0.95) by ARFI, respectively. The HSROCs for SSI and ARFI were 0.92 (95% CI, 0.90–0.94) and 0.96 (95% CI, 0.93–0.97), respectively. SSI and ARFI were both very informative, with probabilities of 83% and 91%, respectively, for correctly differentiating between benign and malignant breast masses following a “positive” measurement (over the threshold value) and probabilities of disease as low as 10% and 11%, respectively, following a “negative” measurement (below the threshold value) when the pre-test probability was 50%. Conclusions SWE could be used as a good identification tool for the classification of breast masses. PMID:24204613

Effect of depth on shear-wave elastography estimated in the internal and external cervical os during pregnancy

PubMed Central

Hernandez-Andrade, Edgar; Aurioles-Garibay, Alma; Garcia, Maynor; Korzeniewski, Steven J.; Schwartz, Alyse G.; Ahn, Hyunyoung; Martinez-Varea, Alicia; Yeo, Lami; Chaiworapongsa, Tinnakorn; Hassan, Sonia S.; Romero, Roberto

2014-01-01

Aim To investigate the effect of depth on cervical shear-wave elastography. Methods Shear-wave elastography was applied to estimate the velocity of propagation of the acoustic force impulse (shear-wave) in the cervix of 154 pregnant women at 11-36 weeks of gestation. Shear-wave speed (SWS) was evaluated in cross-sectional views of the internal and external cervical os in five regions of interest: anterior, posterior, lateral right, lateral left, and endocervix. Distance from the center of the US transducer to the center of the each region of interest was registered. Results In all regions, SWS decreased significantly with gestational age (p=0.006). In the internal os SWS was similar among the anterior, posterior and lateral regions, and lower in the endocervix. In the external os, the endocervix and anterior regions showed similar SWS values, lower than those from the posterior and lateral regions. In the endocervix, these differences remained significant after adjustment for depth, gestational age and cervical length. SWS estimations in all regions of the internal os were higher than those of the external os, suggesting denser tissue. Conclusion Depth from the ultrasound probe to different regions in the cervix did not significantly affect the SWS estimations. PMID:25029081

Efficacy of ultrasound elastography in detecting active myositis in children: can it replace MRI?

PubMed

Berko, Netanel S; Hay, Arielle; Sterba, Yonit; Wahezi, Dawn; Levin, Terry L

2015-09-01

Juvenile idiopathic inflammatory myopathy is a rare yet potentially debilitating condition. MRI is used both for diagnosis and to assess response to treatment. No study has evaluated the performance of US elastography in the diagnosis of this condition in children. To assess the performance of compression-strain US elastography in detecting active myositis in children with clinically confirmed juvenile idiopathic inflammatory myopathy and to compare its efficacy to MRI. Children with juvenile idiopathic inflammatory myopathy underwent non-contrast MR imaging as well as compression-strain US elastography of the quadriceps muscles. Imaging findings from both modalities were compared to each other as well as to the clinical determination of active disease based on physical examination and laboratory data. Active myositis on MR was defined as increased muscle signal on T2-weighted images. Elastography images were defined as normal or abnormal based on a previously published numerical scale of muscle elastography in normal children. Muscle echogenicity was graded as normal or abnormal based on gray-scale sonographic images. Twenty-one studies were conducted in 18 pediatric patients (15 female, 3 male; age range 3-19 years). Active myositis was present on MRI in ten cases. There was a significant association between abnormal MRI and clinically active disease (P = 0.012). US elastography was abnormal in 4 of 10 cases with abnormal MRI and in 4 of 11 cases with normal MRI. There was no association between abnormal elastography and either MRI (P > 0.999) or clinically active disease (P > 0.999). Muscle echogenicity was normal in 11 patients; all 11 had normal elastography. Of the ten patients with increased muscle echogenicity, eight had abnormal elastography. There was a significant association between muscle echogenicity and US elastography (P < 0.001). The positive and negative predictive values for elastography in the determination of active myositis were 75% and 31%, respectively, with a sensitivity of 40% and specificity of 67%. Compression-strain US elastography does not accurately detect active myositis in children with juvenile idiopathic inflammatory myopathy and cannot replace MRI as the imaging standard for detecting myositis in these children. The association between abnormal US elastography and increased muscle echogenicity suggests that elastography is capable of detecting muscle derangement in patients with myositis; however further studies are required to determine the clinical significance of these findings.

The Feasibility of Classifying Breast Masses Using a Computer-Assisted Diagnosis (CAD) System Based on Ultrasound Elastography and BI-RADS Lexicon.

PubMed

Fleury, Eduardo F C; Gianini, Ana Claudia; Marcomini, Karem; Oliveira, Vilmar

2018-01-01

To determine the applicability of a computer-aided diagnostic system strain elastography system for the classification of breast masses diagnosed by ultrasound and scored using the criteria proposed by the breast imaging and reporting data system ultrasound lexicon and to determine the diagnostic accuracy and interobserver variability. This prospective study was conducted between March 1, 2016, and May 30, 2016. A total of 83 breast masses subjected to percutaneous biopsy were included. Ultrasound elastography images before biopsy were interpreted by 3 radiologists with and without the aid of computer-aided diagnostic system for strain elastography. The parameters evaluated by each radiologist results were sensitivity, specificity, and diagnostic accuracy, with and without computer-aided diagnostic system for strain elastography. Interobserver variability was assessed using a weighted κ test and an intraclass correlation coefficient. The areas under the receiver operating characteristic curves were also calculated. The areas under the receiver operating characteristic curve were 0.835, 0.801, and 0.765 for readers 1, 2, and 3, respectively, without computer-aided diagnostic system for strain elastography, and 0.900, 0.926, and 0.868, respectively, with computer-aided diagnostic system for strain elastography. The intraclass correlation coefficient between the 3 readers was 0.6713 without computer-aided diagnostic system for strain elastography and 0.811 with computer-aided diagnostic system for strain elastography. The proposed computer-aided diagnostic system for strain elastography system has the potential to improve the diagnostic performance of radiologists in breast examination using ultrasound associated with elastography.

Ultrasound Imaging Techniques for Spatiotemporal Characterization of Composition, Microstructure, and Mechanical Properties in Tissue Engineering.

PubMed

Deng, Cheri X; Hong, Xiaowei; Stegemann, Jan P

2016-08-01

Ultrasound techniques are increasingly being used to quantitatively characterize both native and engineered tissues. This review provides an overview and selected examples of the main techniques used in these applications. Grayscale imaging has been used to characterize extracellular matrix deposition, and quantitative ultrasound imaging based on the integrated backscatter coefficient has been applied to estimating cell concentrations and matrix morphology in tissue engineering. Spectral analysis has been employed to characterize the concentration and spatial distribution of mineral particles in a construct, as well as to monitor mineral deposition by cells over time. Ultrasound techniques have also been used to measure the mechanical properties of native and engineered tissues. Conventional ultrasound elasticity imaging and acoustic radiation force imaging have been applied to detect regions of altered stiffness within tissues. Sonorheometry and monitoring of steady-state excitation and recovery have been used to characterize viscoelastic properties of tissue using a single transducer to both deform and image the sample. Dual-mode ultrasound elastography uses separate ultrasound transducers to produce a more potent deformation force to microscale characterization of viscoelasticity of hydrogel constructs. These ultrasound-based techniques have high potential to impact the field of tissue engineering as they are further developed and their range of applications expands.

[Elastography as an additional tool in breast sonography. Technical principles and clinical applications].

PubMed

Rjosk-Dendorfer, D; Reichelt, A; Clevert, D-A

2014-03-01

In recent years the use of elastography in addition to sonography has become a routine clinical tool for the characterization of breast masses. Whereas free hand compression elastography results in qualitative imaging of tissue stiffness due to induced compression, shear wave elastography displays quantitative information of tissue displacement. Recent studies have investigated the use of elastography in addition to sonography and improvement of specificity in differentiating benign from malignant breast masses could be shown. Therefore, additional use of elastography could help to reduce the number of unnecessary biopsies in benign breast lesions especially in category IV lesions of the ultrasound breast imaging reporting data system (US-BI-RADS).

Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 2, Diagnostic Performance, Confounders, and Future Directions

PubMed Central

Tang, An; Cloutier, Guy; Szeverenyi, Nikolaus M.; Sirlin, Claude B.

2016-01-01

OBJECTIVE The purpose of the article is to review the diagnostic performance of ultrasound and MR elastography techniques for detection and staging of liver fibrosis, the main current clinical applications of elastography in the abdomen. CONCLUSION Technical and instrument-related factors and biologic and patient-related factors may constitute potential confounders of stiffness measurements for assessment of liver fibrosis. Future developments may expand the scope of elastography for monitoring liver fibrosis and predict complications of chronic liver disease. PMID:25905762

WE-AB-202-09: Feasibility and Quantitative Analysis of 4DCT-Based High Precision Lung Elastography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasse, K; Neylon, J; Low, D

2016-06-15

Purpose: The purpose of this project is to derive high precision elastography measurements from 4DCT lung scans to facilitate the implementation of elastography in a radiotherapy context. Methods: 4DCT scans of the lungs were acquired, and breathing stages were subsequently registered to each other using an optical flow DIR algorithm. The displacement of each voxel gleaned from the registration was taken to be the ground-truth deformation. These vectors, along with the 4DCT source datasets, were used to generate a GPU-based biomechanical simulation that acted as a forward model to solve the inverse elasticity problem. The lung surface displacements were appliedmore » as boundary constraints for the model-guided lung tissue elastography, while the inner voxels were allowed to deform according to the linear elastic forces within the model. A biomechanically-based anisotropic convergence magnification technique was applied to the inner voxels in order to amplify the subtleties of the interior deformation. Solving the inverse elasticity problem was accomplished by modifying the tissue elasticity and iteratively deforming the biomechanical model. Convergence occurred when each voxel was within 0.5 mm of the ground-truth deformation and 1 kPa of the ground-truth elasticity distribution. To analyze the feasibility of the model-guided approach, we present the results for regions of low ventilation, specifically, the apex. Results: The maximum apical boundary expansion was observed to be between 2 and 6 mm. Simulating this expansion within an apical lung model, it was observed that 100% of voxels converged within 0.5 mm of ground-truth deformation, while 91.8% converged within 1 kPa of the ground-truth elasticity distribution. A mean elasticity error of 0.6 kPa illustrates the high precision of our technique. Conclusion: By utilizing 4DCT lung data coupled with a biomechanical model, high precision lung elastography can be accurately performed, even in low ventilation regions of the lungs. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144087.« less

Endoscopic Ultrasound Elastography: Current Clinical Use in Pancreas.

PubMed

Mondal, Utpal; Henkes, Nichole; Patel, Sandeep; Rosenkranz, Laura

2016-08-01

Elastography is a newer technique for the assessment of tissue elasticity using ultrasound. Cancerous tissue is known to be stiffer (hence, less elastic) than corresponding healthy tissue, and as a result, could be identified in an elasticity-based imaging. Ultrasound elastography has been used in the breast, thyroid, and cervix to differentiate malignant from benign neoplasms and to guide or avoid unnecessary biopsies. In the liver, elastography has enabled a noninvasive and reliable estimate of fibrosis. Endoscopic ultrasound has become a robust diagnostic and therapeutic tool for the management of pancreatic diseases. The addition of elastography to endoscopic ultrasound enabled further characterization of pancreas lesions, and several European and Asian studies have reported encouraging results. The current clinical role of endoscopic ultrasound elastography in the management of pancreas disorders and related literature are reviewed.

Technical Failure of MR Elastography Examinations of the Liver: Experience from a Large Single-Center Study.

PubMed

Wagner, Mathilde; Corcuera-Solano, Idoia; Lo, Grace; Esses, Steven; Liao, Joseph; Besa, Cecilia; Chen, Nelson; Abraham, Ginu; Fung, Maggie; Babb, James S; Ehman, Richard L; Taouli, Bachir

2017-08-01

Purpose To assess the determinants of technical failure of magnetic resonance (MR) elastography of the liver in a large single-center study. Materials and Methods This retrospective study was approved by the institutional review board. Seven hundred eighty-one MR elastography examinations performed in 691 consecutive patients (mean age, 58 years; male patients, 434 [62.8%]) in a single center between June 2013 and August 2014 were retrospectively evaluated. MR elastography was performed at 3.0 T (n = 443) or 1.5 T (n = 338) by using a gradient-recalled-echo pulse sequence. MR elastography and anatomic image analysis were performed by two observers. Additional observers measured liver T2* and fat fraction. Technical failure was defined as no pixel value with a confidence index higher than 95% and/or no apparent shear waves imaged. Logistic regression analysis was performed to assess potential predictive factors of technical failure of MR elastography. Results The technical failure rate of MR elastography at 1.5 T was 3.5% (12 of 338), while it was higher, 15.3% (68 of 443), at 3.0 T. On the basis of univariate analysis, body mass index, liver iron deposition, massive ascites, use of 3.0 T, presence of cirrhosis, and alcoholic liver disease were all significantly associated with failure of MR elastography (P < .004); but on the basis of multivariable analysis, only body mass index, liver iron deposition, massive ascites, and use of 3.0 T were significantly associated with failure of MR elastography (P < .004). Conclusion The technical failure rate of MR elastography with a gradient-recalled-echo pulse sequence was low at 1.5 T but substantially higher at 3.0 T. Massive ascites, iron deposition, and high body mass index were additional independent factors associated with failure of MR elastography of the liver with a two-dimensional gradient-recalled-echo pulse sequence. © RSNA, 2017.

Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study.

PubMed

Seo, Mirinae; Ahn, Hye Shin; Park, Sung Hee; Lee, Jong Beum; Choi, Byung Ihn; Sohn, Yu-Mee; Shin, So Youn

2018-01-01

To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography. Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC). The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P < .001). Combined strain and shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031). These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality. © 2017 by the American Institute of Ultrasound in Medicine.

Impedance-controlled ultrasound probe

NASA Astrophysics Data System (ADS)

Gilbertson, Matthew W.; Anthony, Brian W.

2011-03-01

An actuated hand-held impedance-controlled ultrasound probe has been developed. The controller maintains a prescribed contact state (force and velocity) between the probe and a patient's body. The device will enhance the diagnostic capability of free-hand elastography and swept-force compound imaging, and also make it easier for a technician to acquire repeatable (i.e. directly comparable) images over time. The mechanical system consists of an ultrasound probe, ball-screw-driven linear actuator, and a force/torque sensor. The feedback controller commands the motor to rotate the ball-screw to translate the ultrasound probe in order to maintain a desired contact force. It was found that users of the device, with the control system engaged, maintain a constant contact force with 15 times less variation than without the controller engaged. The system was used to determine the elastic properties of soft tissue.

Elastography using multi-stream GPU: an application to online tracked ultrasound elastography, in-vivo and the da Vinci Surgical System.

PubMed

Deshmukh, Nishikant P; Kang, Hyun Jae; Billings, Seth D; Taylor, Russell H; Hager, Gregory D; Boctor, Emad M

2014-01-01

A system for real-time ultrasound (US) elastography will advance interventions for the diagnosis and treatment of cancer by advancing methods such as thermal monitoring of tissue ablation. A multi-stream graphics processing unit (GPU) based accelerated normalized cross-correlation (NCC) elastography, with a maximum frame rate of 78 frames per second, is presented in this paper. A study of NCC window size is undertaken to determine the effect on frame rate and the quality of output elastography images. This paper also presents a novel system for Online Tracked Ultrasound Elastography (O-TRuE), which extends prior work on an offline method. By tracking the US probe with an electromagnetic (EM) tracker, the system selects in-plane radio frequency (RF) data frames for generating high quality elastograms. A novel method for evaluating the quality of an elastography output stream is presented, suggesting that O-TRuE generates more stable elastograms than generated by untracked, free-hand palpation. Since EM tracking cannot be used in all systems, an integration of real-time elastography and the da Vinci Surgical System is presented and evaluated for elastography stream quality based on our metric. The da Vinci surgical robot is outfitted with a laparoscopic US probe, and palpation motions are autonomously generated by customized software. It is found that a stable output stream can be achieved, which is affected by both the frequency and amplitude of palpation. The GPU framework is validated using data from in-vivo pig liver ablation; the generated elastography images identify the ablated region, outlined more clearly than in the corresponding B-mode US images.

Elastography Using Multi-Stream GPU: An Application to Online Tracked Ultrasound Elastography, In-Vivo and the da Vinci Surgical System

PubMed Central

Deshmukh, Nishikant P.; Kang, Hyun Jae; Billings, Seth D.; Taylor, Russell H.; Hager, Gregory D.; Boctor, Emad M.

2014-01-01

A system for real-time ultrasound (US) elastography will advance interventions for the diagnosis and treatment of cancer by advancing methods such as thermal monitoring of tissue ablation. A multi-stream graphics processing unit (GPU) based accelerated normalized cross-correlation (NCC) elastography, with a maximum frame rate of 78 frames per second, is presented in this paper. A study of NCC window size is undertaken to determine the effect on frame rate and the quality of output elastography images. This paper also presents a novel system for Online Tracked Ultrasound Elastography (O-TRuE), which extends prior work on an offline method. By tracking the US probe with an electromagnetic (EM) tracker, the system selects in-plane radio frequency (RF) data frames for generating high quality elastograms. A novel method for evaluating the quality of an elastography output stream is presented, suggesting that O-TRuE generates more stable elastograms than generated by untracked, free-hand palpation. Since EM tracking cannot be used in all systems, an integration of real-time elastography and the da Vinci Surgical System is presented and evaluated for elastography stream quality based on our metric. The da Vinci surgical robot is outfitted with a laparoscopic US probe, and palpation motions are autonomously generated by customized software. It is found that a stable output stream can be achieved, which is affected by both the frequency and amplitude of palpation. The GPU framework is validated using data from in-vivo pig liver ablation; the generated elastography images identify the ablated region, outlined more clearly than in the corresponding B-mode US images. PMID:25541954

Use of Ultrasound Elastography in the Assessment of the Musculoskeletal System.

PubMed

Paluch, Łukasz; Nawrocka-Laskus, Ewa; Wieczorek, Janusz; Mruk, Bartosz; Frel, Małgorzata; Walecki, Jerzy

2016-01-01

This article presents possible applications of ultrasound elastography in musculoskeletal imaging based on the available literature, as well as the possibility of extending indications for the use of elastography in the future. Ultrasound elastography (EUS) is a new method that shows structural changes in tissues following application of physical stress. Elastography techniques have been widely used to assess muscles and tendons in vitro since the early parts of the twentieth century. Only recently with the advent of new technology and creation of highly specialized ultrasound devices, has elastography gained widespread use in numerous applications. The authors performed a search of the Medline/PubMed databases for original research and reviewed publications on the application of ultrasound elastography for musculoskeletal imaging. All publications demonstrate possible uses of ultrasound elastography in examinations of the musculoskeletal system. The most widely studied areas include the muscles, tendons and rheumatic diseases. There are also reports on the employment in vessel imaging. The main limitation of elastography as a technique is above all the variability of applied pressure during imaging, which is operator-dependent. It would therefore be reasonable to provide clear guidelines on the technique applied, as well as clear indications for performing the test. It is important to develop methods for creating artifact-free, closed-loop, compression-decompression cycles. The main advantages include cost-effectiveness, short duration of the study, non-invasive nature of the procedure, as well as a potentially broader clinical availability. There are no clear guidelines with regard to indications as well as examination techniques. Ultrasound elastography is a new and still poorly researched method. We conclude, however, that it can be widely used in the examinations of musculoskeletal system. Therefore, it is necessary to conduct large, multi-center studies to determine the methodology, indications and technique of examination.

Magnetic resonance elastography using an air ball-actuator.

PubMed

Numano, Tomokazu; Kawabata, Yoshihiko; Mizuhara, Kazuyuki; Washio, Toshikatsu; Nitta, Naotaka; Homma, Kazuhiro

2013-07-01

The purpose of this study was to develop a new technique for a powerful compact MR elastography (MRE) actuator based on a pneumatic ball-vibrator. This is a compact actuator that generates powerful centrifugal force vibrations via high speed revolutions of an internal ball using compressed air. This equipment is easy to handle due to its simple principles and structure. Vibration frequency and centrifugal force are freely adjustable via air pressure changes (air flow volume), and replacement of the internal ball. In order to achieve MRI compatibility, all parts were constructed from non-ferromagnetic materials. Vibration amplitudes (displacements) were measured optically by a laser displacement sensor. From a bench test of displacement, even though the vibration frequency increased, the amount of displacement did not decrease. An essential step in MRE is the generation of mechanical waves within tissue via an actuator, and MRE sequences are synchronized to several phase offsets of vibration. In this system, the phase offset was detected by a four-channel optical-fiber sensor, and it was used as an MRI trigger signal. In an agarose gel phantom experiment, this actuator was used to make an MR elastogram. This study shows that the use of a ball actuator for MRE is feasible. Copyright © 2013 Elsevier Inc. All rights reserved.

Acoustic radiation force impulse tissue characterization of the anterior talofibular ligament: A promising non-invasive approach in ankle imaging.

PubMed

Hotfiel, Thilo; Heiss, Rafael; Janka, Rolf; Forst, Raimund; Raithel, Martine; Lutter, Christoph; Gelse, Kolja; Pachowsky, Milena; Golditz, Tobias

2018-06-09

The anterior talofibular ligament (ATFL) is the most frequently injured ligament during inversion strains of the ankle. The purpose of this study was to evaluate the feasibility of acoustic radiation force impulse (ARFI) elastography and to determine the in vivo mechanical properties of the ATFL in healthy athletes. Fifty-one healthy athletes (32 female, 28 male; 29 ±2 years) were recruited from the medical and sports faculty. ARFI values, represented as shear wave velocities (SWV) as well as conventional ultrasound were obtained for the ATFL in neutral ankle position. A clinical assessment was performed in which the American Orthopaedic Foot & Ankle Society (AOFAS) Ankle-Hindfoot Score and the functional ankle ability measure (FAAM) were collected. Interobserver and intraobserver reliability (repeated sessions and repeated days) were assessed using an intra class correlation coefficient (ICC) and typical error (TE) calculation in absolute (TE) and relative units as coefficient of the variation (CV). SWV values of the ATFL had an average velocity of 1.79±0.34 m/s for all participants, with an average of 1.72±0.36 m/s for females and 1.85±0.31 m/s for males. The interobserver and intraobserver reliability revealed an ICC of 0.902 and 0.933 (TE of 0.67 (CV: 5.2 % and 0.51 m/s (CV: 3.83 %), respectively. FAAM and AOFAS revealed the best possible scores. ARFI seems to be a valuable diagnostic modality and represents a promising imaging marker for the assessment and monitoring of ankle ligaments in the context of acute and chronic ankle instabilities; ARFI could also be used to investigate loading or sport dependent adaptions.

Correlation between acoustic radiation force impulse (ARFI)-based tissue elasticity measurements and perfusion parameters acquired by perfusion CT in cirrhotic livers: a proof of principle.

PubMed

Esser, Michael; Bitzer, Michael; Kolb, Manuel; Fritz, Jan; Kurucay, Mustafa; Ruff, Christer; Horger, Marius

2018-06-13

To investigate whether liver stiffness measured by acoustic radiation force impulse (ARFI) sonoelastography always correlates with the liver perfusion parameters quantified by perfusion CT in patients with known liver cirrhosis. Sonoelastography and perfusion CT were performed in 50 patients (mean age 65.5; range 45-87 years) with liver cirrhosis, who were classified according to Child-Pugh into class A (30/50, 60%), B (17/50, 34%), and C (3/50, 6%). For standardized ARFI measurements in the left liver lobe at a depth of 4 cm, a convex 6-MHz probe was used. CT examinations were performed using 80 kV, 100 mAs, and 50 ml of iodinated contrast agent injected at 5 ml/s. Using standardized region-of-interest measurements, we quantified arterial, portal venous, and total liver perfusion. There was a significant linear correlation between tissue stiffness and arterial liver perfusion (p = 0.015), and also when limiting the analysis to patients with histology (p = 0.019). In addition, there was a positive correlation between the total blood supply (arterial + portal-venous liver perfusion) to the liver and tissue stiffness (p = 0.001; with histology, p = 0.027). Shear wave velocity increased with higher Child-Pugh stages (p = 0.013). The degree of tissue stiffness in cirrhotic livers correlates expectedly-even if only moderately-with the magnitude of arterial liver perfusion and total liver perfusion. As such, liver elastography remains the leading imaging tool in assessing liver fibrosis.

MR-guided transcranial brain HIFU in small animal models

PubMed Central

Larrat, Benoît; Pernot, Mathieu; Aubry, Jean-François; Dervishi, Elvis; Sinkus, Ralph; Seilhean, Danielle; Marie, Yannick; Boch, Anne-Laure; Fink, Mathias; Tanter, Mickaël

2010-01-01

Recent studies have demonstrated the feasibility of transcranial High Intensity Focused Ultrasound (HIFU) therapy in the brain using adaptive focusing techniques. However, the complexity of the procedures imposes to provide an accurate targeting, monitoring and control of this emerging therapeutic modality in order to ensure the safety of the treatment and avoid potential damaging effects of ultrasound on healthy tissues. For these purposes, a complete workflow and setup for HIFU treatment under Magnetic Resonance (MR) guidance is proposed and implemented in rats. For the first time, tissue displacements induced by the acoustic radiation force are detected in vivo in brain tissues and measured quantitatively using motion-sensitive MR sequences. Such a valuable target control prior to treatment assesses the quality of the focusing pattern in situ and enables to estimate the acoustic intensity at focus. This MR-Acoustic radiation force imaging is then correlated with conventional MR-Thermometry sequences which are used to follow the temperature changes during the HIFU therapeutic session. Last, pre and post treatment Magnetic Resonance Elastography (MRE) datasets are acquired and evaluated as a new potential way to non invasively control the stiffness changes due to the presence of thermal necrosis. As a proof of concept, MRguided HIFU is performed in vitro in turkey breast samples and in vivo in transcranial rat brain experiments. The experiments are conducted using a dedicated MR compatible HIFU setup in a high field MRI scanner (7T). Results obtained on rats confirmed that both the MR localization of the US focal point and the pre and post HIFU measurement of the tissue stiffness, together with temperature control during HIFU are feasible and valuable techniques for an efficient monitoring of HIFU in the brain. Brain elasticity appears to be more sensitive to the presence of oedema than to tissue necrosis. PMID:20019400

Acoustic radiation force impulse elastography in evaluation of triple-negative breast cancer: A preliminary experience.

PubMed

Wan, Jing; Wu, Rong; Yao, Minghua; Xu, Guang; Liu, Hui; Pu, Huan; Xiang, Lihua; Zhang, Shupin

2018-05-19

To assess the elastographic features of triple-negative breast cancers and evaluate the diagnostic value of acoustic radiation force impulse imaging (ARFI) for the characterization of triple-negative breast cancers. This study analyzed data from 234 women with breast cancer. Patients were categorized into three groups; 1) triple-negative breast cancers (n = 48); 2) ER-positive tumors (n = 128) and 3) HER2-positive tumors (n = 58). Mean tumor stiffness was evaluated by virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ) and quantified as both qualitative scores (1-5) and shear wave velocity (SWV) (m/s). The relationship between mean SWV and tumor parameters, including tumor size, tumor type, histologic grade and lymph node status, were investigated using multiple linear regression. Triple-negative tumor were more likely to have a large invasive size (p = 0.002), high histological grade (p < 0.001), lymph node involvement (p = 0.022) and strong ki-67 expression (p < 0.001). The highest mean SWV value were recorded in triple-negative tumors (7.36 m/s±1.83), followed by HER2+ tumors (6.65 m/s±2.26) and ER+ tumors (6.60 m/s±2.35) (p = 0.122). Triple-negative tumors were also associated with increased stiffness than ER+ tumors and HER2+ tumors (p = 0.016), as measured by qualitative VTI scores. Tumor size was independently associated with mean SWV value on adjusted regression (p < 0.001). Triple-negative breast cancer is associated with high stiffness scores and SWV in ARFI. The latter may be considered a useful complementary tool in evaluation of triple-negative breast cancer.

Model-based elastography: a survey of approaches to the inverse elasticity problem

PubMed Central

Doyley, M M

2012-01-01

Elastography is emerging as an imaging modality that can distinguish normal versus diseased tissues via their biomechanical properties. This article reviews current approaches to elastography in three areas — quasi-static, harmonic, and transient — and describes inversion schemes for each elastographic imaging approach. Approaches include: first-order approximation methods; direct and iterative inversion schemes for linear elastic; isotropic materials; and advanced reconstruction methods for recovering parameters that characterize complex mechanical behavior. The paper’s objective is to document efforts to develop elastography within the framework of solving an inverse problem, so that elastography may provide reliable estimates of shear modulus and other mechanical parameters. We discuss issues that must be addressed if model-based elastography is to become the prevailing approach to quasi-static, harmonic, and transient elastography: (1) developing practical techniques to transform the ill-posed problem with a well-posed one; (2) devising better forward models to capture the transient behavior of soft tissue; and (3) developing better test procedures to evaluate the performance of modulus elastograms. PMID:22222839

Current status of musculoskeletal application of shear wave elastography.

PubMed

Ryu, JeongAh; Jeong, Woo Kyoung

2017-07-01

Ultrasonography (US) is a very powerful diagnostic modality for the musculoskeletal system due to the ability to perform real-time dynamic high-resolution examinations with the Doppler technique. In addition to acquiring morphologic data, we can now obtain biomechanical information by quantifying the elasticity of the musculoskeletal structures with US elastography. The earlier diagnosis of degeneration and the ability to perform follow-up evaluations of healing and the effects of treatment are possible. US elastography enables a transition from US-based inspection to US-based palpation in order to diagnose the characteristics of tissue. Shear wave elastography is considered the most suitable type of US elastography for the musculoskeletal system. It is widely used for tendons, ligaments, and muscles. It is important to understand practice guidelines in order to enhance reproducibility. Incorporating viscoelasticity and overcoming inconsistencies among manufacturers are future tasks for improving the capabilities of US elastography.

Current status of musculoskeletal application of shear wave elastography

PubMed Central

2017-01-01

Ultrasonography (US) is a very powerful diagnostic modality for the musculoskeletal system due to the ability to perform real-time dynamic high-resolution examinations with the Doppler technique. In addition to acquiring morphologic data, we can now obtain biomechanical information by quantifying the elasticity of the musculoskeletal structures with US elastography. The earlier diagnosis of degeneration and the ability to perform follow-up evaluations of healing and the effects of treatment are possible. US elastography enables a transition from US-based inspection to US-based palpation in order to diagnose the characteristics of tissue. Shear wave elastography is considered the most suitable type of US elastography for the musculoskeletal system. It is widely used for tendons, ligaments, and muscles. It is important to understand practice guidelines in order to enhance reproducibility. Incorporating viscoelasticity and overcoming inconsistencies among manufacturers are future tasks for improving the capabilities of US elastography. PMID:28292005

Strain Elastography - How To Do It?

PubMed Central

Dietrich, Christoph F.; Barr, Richard G.; Farrokh, André; Dighe, Manjiri; Hocke, Michael; Jenssen, Christian; Dong, Yi; Saftoiu, Adrian; Havre, Roald Flesland

2017-01-01

Tissue stiffness assessed by palpation for diagnosing pathology has been used for thousands of years. Ultrasound elastography has been developed more recently to display similar information on tissue stiffness as an image. There are two main types of ultrasound elastography, strain and shear wave. Strain elastography is a qualitative technique and provides information on the relative stiffness between one tissue and another. Shear wave elastography is a quantitative method and provides an estimated value of the tissue stiffness that can be expressed in either the shear wave speed through the tissues in meters/second, or converted to the Young’s modulus making some assumptions and expressed in kPa. Each technique has its advantages and disadvantages and they are often complimentary to each other in clinical practice. This article reviews the principles, technique, and interpretation of strain elastography in various organs. It describes how to optimize technique, while pitfalls and artifacts are also discussed. PMID:29226273

Mechanics of ultrasound elastography

PubMed Central

Li, Guo-Yang

2017-01-01

Ultrasound elastography enables in vivo measurement of the mechanical properties of living soft tissues in a non-destructive and non-invasive manner and has attracted considerable interest for clinical use in recent years. Continuum mechanics plays an essential role in understanding and improving ultrasound-based elastography methods and is the main focus of this review. In particular, the mechanics theories involved in both static and dynamic elastography methods are surveyed. They may help understand the challenges in and opportunities for the practical applications of various ultrasound elastography methods to characterize the linear elastic, viscoelastic, anisotropic elastic and hyperelastic properties of both bulk and thin-walled soft materials, especially the in vivo characterization of biological soft tissues. PMID:28413350

Characterization of focal breast lesions by means of elastography.

PubMed

Fischer, T; Sack, I; Thomas, A

2013-09-01

The modern method of sonoelastography of the breast is used for differentiating focal lesions. This review gives an overview of the different techniques available and discusses their roles in the routine clinical setting. The presented techniques include compression or vibration elastography as well as shear wave elastography. Descriptions of the methods are supplemented by a discussion of the clinical role of each technique based on the most recent literature. We discuss by outlining two recent experimental approaches - MRI and tomosynthesis elastography. Currently available data suggest that elastography is an important supplementary tool for the differentiation of breast tumors under routine clinical conditions. The specificity improves with the immediate availability of additional diagnostic information using real-time techniques and/or the calculation of strain ratios (SR). Elastography is especially helpful in women with involuted breasts for differentiating BI-RADS-US 3 and 4 lesions and for evaluating very small cancers without the typical imaging features of malignancy. Here, elastography techniques are highly specific, while the sensitivity decreases compared to B-mode ultrasound. SR calculation is especially helpful in women who have a high risk of breast cancer and high pretest likelihood. B-mode ultrasound is still the first-line method for the initial evaluation of the breast. If suspicious findings are detected, elastography with or without SR calculation is the most crucial supplementary tool. © Georg Thieme Verlag KG Stuttgart · New York.

Diagnostic Performance of MR Elastography and Vibration-controlled Transient Elastography in the Detection of Hepatic Fibrosis in Patients with Severe to Morbid Obesity

PubMed Central

Chen, Jun; Yin, Meng; Talwalkar, Jayant A.; Oudry, Jennifer; Glaser, Kevin J.; Smyrk, Thomas C.; Miette, Véronique; Sandrin, Laurent

2017-01-01

Purpose To evaluate the diagnostic performance and examination success rate of magnetic resonance (MR) elastography and vibration-controlled transient elastography (VCTE) in the detection of hepatic fibrosis in patients with severe to morbid obesity. Materials and Methods This prospective and HIPAA-compliant study was approved by the institutional review board. A total of 111 patients (71 women, 40 men) participated. Written informed consent was obtained from all patients. Patients underwent MR elastography with two readers and VCTE with three observers to acquire liver stiffness measurements for liver fibrosis assessment. The results were compared with those from liver biopsy. Each pathology specimen was evaluated by two hepatopathologists according to the METAVIR scoring system or Brunt classification when appropriate. All imaging observers were blinded to the biopsy results, and all hepatopathologists were blinded to the imaging results. Examination success rate, interobserver agreement, and diagnostic accuracy for fibrosis detection were assessed. Results In this obese patient population (mean body mass index = 40.3 kg/m2; 95% confidence interval [CI]: 38.7 kg/m2, 41.8 kg/m2]), the examination success rate was 95.8% (92 of 96 patients) for MR elastography and 81.3% (78 of 96 patients) or 88.5% (85 of 96 patients) for VCTE. Interobserver agreement was higher with MR elastography than with biopsy (intraclass correlation coefficient, 0.95 vs 0.89). In patients with successful MR elastography and VCTE examinations (excluding unreliable VCTE examinations), both MR elastography and VCTE had excellent diagnostic accuracy in the detection of clinically significant hepatic fibrosis (stage F2–F4) (mean area under the curve: 0.93 [95% CI: 0.85, 0.97] vs 0.91 [95% CI: 0.83, 0.96]; P = .551). Conclusion In this obese patient population, both MR elastography and VCTE had excellent diagnostic performance for assessing hepatic fibrosis; MR elastography was more technically reliable than VCTE and had a higher interobserver agreement than liver biopsy. © RSNA, 2016 Online supplemental material is available for this article. An earlier incorrect version of this article appeared online. This article was corrected on January 25, 2017. PMID:27861111

Ultrafast imaging of cell elasticity with optical microelastography

PubMed Central

Grasland-Mongrain, Pol; Zorgani, Ali; Nakagawa, Shoma; Bernard, Simon; Paim, Lia Gomes; Fitzharris, Greg; Catheline, Stefan

2018-01-01

Elasticity is a fundamental cellular property that is related to the anatomy, functionality, and pathological state of cells and tissues. However, current techniques based on cell deformation, atomic force microscopy, or Brillouin scattering are rather slow and do not always accurately represent cell elasticity. Here, we have developed an alternative technique by applying shear wave elastography to the micrometer scale. Elastic waves were mechanically induced in live mammalian oocytes using a vibrating micropipette. These audible frequency waves were observed optically at 200,000 frames per second and tracked with an optical flow algorithm. Whole-cell elasticity was then mapped using an elastography method inspired by the seismology field. Using this approach we show that the elasticity of mouse oocytes is decreased when the oocyte cytoskeleton is disrupted with cytochalasin B. The technique is fast (less than 1 ms for data acquisition), precise (spatial resolution of a few micrometers), able to map internal cell structures, and robust and thus represents a tractable option for interrogating biomechanical properties of diverse cell types. PMID:29339488

Computationally-efficient optical coherence elastography to assess degenerative osteoarthritis based on ultrasound-induced fringe washout (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tong, Minh Q.; Hasan, M. Monirul; Gregory, Patrick D.; Shah, Jasmine; Park, B. Hyle; Hirota, Koji; Liu, Junze; Choi, Andy; Low, Karen; Nam, Jin

2017-02-01

We demonstrate a computationally-efficient optical coherence elastography (OCE) method based on fringe washout. By introducing ultrasound in alternating depth profile, we can obtain information on the mechanical properties of a sample within acquisition of a single image. This can be achieved by simply comparing the intensity in adjacent depth profiles in order to quantify the degree of fringe washout. Phantom agar samples with various densities were measured and quantified by our OCE technique, the correlation to Young's modulus measurement by atomic force micrscopy (AFM) were observed. Knee cartilage samples of monoiodo acetate-induced arthiritis (MIA) rat models were utilized to replicate cartilage damages where our proposed OCE technique along with intensity and birefringence analyses and AFM measurements were applied. The results indicate that our OCE technique shows a correlation to the techniques as polarization-sensitive OCT, AFM Young's modulus measurements and histology were promising. Our OCE is applicable to any of existing OCT systems and demonstrated to be computationally-efficient.

New Imaging Methods for Non-invasive Assessment of Mechanical, Structural, and Biochemical Properties of Human Achilles Tendon: A Mini Review

PubMed Central

Fouré, Alexandre

2016-01-01

The mechanical properties of tendon play a fundamental role to passively transmit forces from muscle to bone, withstand sudden stretches, and act as a mechanical buffer allowing the muscle to work more efficiently. The use of non-invasive imaging methods for the assessment of human tendon's mechanical, structural, and biochemical properties in vivo is relatively young in sports medicine, clinical practice, and basic science. Non-invasive assessment of the tendon properties may enhance the diagnosis of tendon injury and the characterization of recovery treatments. While ultrasonographic imaging is the most popular tool to assess the tendon's structural and indirectly, mechanical properties, ultrasonographic elastography, and ultra-high field magnetic resonance imaging (UHF MRI) have recently emerged as potentially powerful techniques to explore tendon tissues. This paper highlights some methodological cautions associated with conventional ultrasonography and perspectives for in vivo human Achilles tendon assessment using ultrasonographic elastography and UHF MRI. PMID:27512376

Shear Wave Elastography May Add a New Dimension to Ultrasound Evaluation of Thyroid Nodules: Case Series with Comparative Evaluation

PubMed Central

Slapa, Rafal Z.; Piwowonski, Antoni; Jakubowski, Wieslaw S.; Bierca, Jacek; Szopinski, Kazimierz T.; Slowinska-Srzednicka, Jadwiga; Migda, Bartosz; Mlosek, R. Krzysztof

2012-01-01

Although elastography can enhance the differential diagnosis of thyroid nodules, its diagnostic performance is not ideal at present. Further improvements in the technique and creation of robust diagnostic criteria are necessary. The purpose of this study was to compare the usefulness of strain elastography and a new generation of elasticity imaging called supersonic shear wave elastography (SSWE) in differential evaluation of thyroid nodules. Six thyroid nodules in 4 patients were studied. SSWE yielded 1 true-positive and 5 true-negative results. Strain elastography yielded 5 false-positive results and 1 false-negative result. A novel finding appreciated with SSWE, were punctate foci of increased stiffness corresponding to microcalcifications in 4 nodules, some not visible on B-mode ultrasound, as opposed to soft, colloid-inspissated areas visible on B-mode ultrasound in 2 nodules. This preliminary paper indicates that SSWE may outperform strain elastography in differentiation of thyroid nodules with regard to their stiffness. SSWE showed the possibility of differentiation of high echogenic foci into microcalcifications and inspissated colloid, adding a new dimension to thyroid elastography. Further multicenter large-scale studies of thyroid nodules evaluating different elastographic methods are warranted. PMID:22685685

Liver elastography, comments on EFSUMB elastography guidelines 2013

PubMed Central

Cui, Xin-Wu; Friedrich-Rust, Mireen; Molo, Chiara De; Ignee, Andre; Schreiber-Dietrich, Dagmar; Dietrich, Christoph F

2013-01-01

Recently the European Federation of Societies for Ultrasound in Medicine and Biology Guidelines and Recommendations have been published assessing the clinical use of ultrasound elastography. The document is intended to form a reference and to guide clinical users in a practical way. They give practical advice for the use and interpretation. Liver disease forms the largest section, reflecting published experience to date including evidence from meta-analyses with shear wave and strain elastography. In this review comments and illustrations on the guidelines are given. PMID:24151351

Radiologic evaluation of nonalcoholic fatty liver disease

PubMed Central

Lee, Seung Soo; Park, Seong Ho

2014-01-01

Nonalcoholic fatty liver disease (NAFLD) is a frequent cause of chronic liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH)-related liver cirrhosis. Although liver biopsy is still the gold standard for the diagnosis of NAFLD, especially for the diagnosis of NASH, imaging methods have been increasingly accepted as noninvasive alternatives to liver biopsy. Ultrasonography is a well-established and cost-effective imaging technique for the diagnosis of hepatic steatosis, especially for screening a large population at risk of NAFLD. Ultrasonography has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis, operator-dependent, and rather qualitative. Computed tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation hazard. However, computed tomography may be effective in specific clinical situations, such as evaluation of donor candidates for hepatic transplantation. Magnetic resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice, especially for longitudinal follow-up of patients with NAFLD. Ultrasound elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple steatosis. This article will review current imaging methods used to evaluate hepatic steatosis, including the diagnostic accuracy, limitations, and practical applicability of each method. It will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD. PMID:24966609

An ultrasound transient elastography system with coded excitation.

PubMed

Diao, Xianfen; Zhu, Jing; He, Xiaonian; Chen, Xin; Zhang, Xinyu; Chen, Siping; Liu, Weixiang

2017-06-28

Ultrasound transient elastography technology has found its place in elastography because it is safe and easy to operate. However, it's application in deep tissue is limited. The aim of this study is to design an ultrasound transient elastography system with coded excitation to obtain greater detection depth. The ultrasound transient elastography system requires tissue vibration to be strictly synchronous with ultrasound detection. Therefore, an ultrasound transient elastography system with coded excitation was designed. A central component of this transient elastography system was an arbitrary waveform generator with multi-channel signals output function. This arbitrary waveform generator was used to produce the tissue vibration signal, the ultrasound detection signal and the synchronous triggering signal of the radio frequency data acquisition system. The arbitrary waveform generator can produce different forms of vibration waveform to induce different shear wave propagation in the tissue. Moreover, it can achieve either traditional pulse-echo detection or a phase-modulated or a frequency-modulated coded excitation. A 7-chip Barker code and traditional pulse-echo detection were programmed on the designed ultrasound transient elastography system to detect the shear wave in the phantom excited by the mechanical vibrator. Then an elasticity QA phantom and sixteen in vitro rat livers were used for performance evaluation of the two detection pulses. The elasticity QA phantom's results show that our system is effective, and the rat liver results show the detection depth can be increased more than 1 cm. In addition, the SNR (signal-to-noise ratio) is increased by 15 dB using the 7-chip Barker coded excitation. Applying 7-chip Barker coded excitation technique to the ultrasound transient elastography can increase the detection depth and SNR. Using coded excitation technology to assess the human liver, especially in obese patients, may be a good choice.

Elastography methods applicable to the eye

NASA Astrophysics Data System (ADS)

Khan, Altaf A.; Cortina, Soledad M.; Chamon, Wallace; Royston, Thomas J.

2014-02-01

Elastography is the mapping of tissues and cells by their respective mechanical properties, such as elasticity and viscosity. Our interest primarily lies in the human eye. Combining Scanning Laser Doppler Vibrometry (SLDV) with geometrically focused mechanical vibratory excitations of the cornea, it is possible to reconstruct these mechanical properties of the cornea. Experiments were conducted on phantom corneas as well as excised donor human corneas to test feasibility and derive a method of modeling. Finite element analysis was used to recreate the phantom studies and corroborate with the experimental data. Results are in close agreement. To further expand the study, lamb eyes were used in MR Elastography studies. 3D wave reconstruction was created and elastography maps were obtained. With MR Elastography, it would be possible to noninvasively measure mechanical properties of anatomical features not visible to SLDV, such as the lens and retina. Future plans include creating a more robust finite element model, improving the SLDV method for in-vivo application, and continuing experiments with MR Elastography.

Ultrasound elastography of the lower uterine segment in women with a previous cesarean section: Comparison of in-/ex-vivo elastography versus tensile-stress-strain-rupture analysis.

PubMed

Seliger, Gregor; Chaoui, Katharina; Lautenschläger, Christine; Jenderka, Klaus-Vitold; Kunze, Christian; Hiller, Grit Gesine Ruth; Tchirikov, Michael

2018-06-01

The purpose of this study was to assess, if the biomechanical properties of the lower uterine segment (LUS) in women with a previous cesarean section (CS) can be determined by ultrasound (US) elastography. The first aim was to establish an ex-vivo LUS tensile-stress-strain-rupture(break point) analysis with the possibility of simultaneously using US elastography. The second aim was to investigate the relationship between measurement results of LUS stiffness using US elastography in-/ex-vivo with results of tensile-stress-strain-rupture analysis, and to compare different US elastography LUS-stiffness-measurement methods ex-vivo. An explorative experimental, in-/ex-vivo US study of women with previous CS was conducted. LUS elasticity was measured by point Shear Wave Elastography (pSWE) and bidimensional Shear-Wave-Elastography (2D-SWE) first in-vivo during preoperative examination within 24 h before repeat CS (including resection of the thinnest part of the LUS = uterine scar area during CS), second within 1 h after operation during the ex-vivo experiment, followed by tensile-stress-strain-rupture analysis. Pearson's correlation coefficient and scatter plots, Bland-Altman plots and paired T-tests, were used. Thirty three women were included in the study; elastography measurements n = 1412. The feasibility of ex-vivo assessment of LUS by quantitative US elastography using pSWE and 2D-SWE to detect stiffness of LUS was demonstrated. The strongest correlation with tensile-stress-strain analysis was found in the US elastography examination carried out with 2D-SWE (0.78, p < 0.001, 95%CI [0.48, 0.92]). The laboratory experiment illustrated that, the break point - as a surrogate marker for the risk of rupture of the LUS after CS - is linearly dependent on the thickness of the LUS in the scar area (Coefficient of correlation: 0.79, p < 0.001, 95%CI [0.55, 0.91]). Two extremely stiff LUS-specimens (outlier or extreme values) rupture even at less stroke/strain than would be expected by their thickness. This study confirms that US elastography can help in determining viscoelastic properties of the LUS in women with a previous CS. The data from our small series are promising. However whether individual extreme values of high stiffness and consecutive restricted biomechanical resilience can explain the phenomenon of rupture during TOLAC in cases of LUS with adequate thickness remains a question which prospective trials have to analyze before US elastography can be introduced into clinical practice. Copyright © 2018 Elsevier B.V. All rights reserved.

Reliability and validity of quantifying absolute muscle hardness using ultrasound elastography.

PubMed

Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

2012-01-01

Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young's moduli of seven tissue-mimicking materials (in vitro; Young's modulus range, 20-80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young's modulus ratio of two reference materials, one hard and one soft (Young's moduli of 7 and 30 kPa, respectively), the Young's moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young's moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young's moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified.

Elastography in the differential diagnosis of thyroid nodules in Hashimoto thyroiditis.

PubMed

Şahin, Mustafa; Çakal, Erman; Özbek, Mustafa; Güngünes, Aşkin; Arslan, Müyesser Sayki; Akkaymak, Esra Tutal; Uçan, Bekir; Ünsal, Ilknur Öztürk; Bozkurt, Nujen Çolak; Delibaşi, Tuncay

2014-08-01

Elastography is a method which assesses the risk of the malignancy and provides information about the degree of hardness in tissue. Hashimoto's thyroiditis, autoimmune lymphocytic infiltration and fibrosis, is considered to be a very common disease that is able to change the hardness of the tissue. The diagnostic value of elastography of this group of patients has not previously been reported. In our study, we aimed to determine the diagnostic value of elastography in 283 patients (255 female, 28 male) with Hashimoto's thyroiditis. Elastography score and index were measured with real-time ultrasound elastography (Hitachi(®) EUB 7000 HV machine with using 13 MHz linear transducer). The outcome of this measure shows that malignant nodules were with higher elastography scores (ES) and strain indexes (SI) values. ES ≥3 were observed in 16/20 malignant and 130/263 benign nodules, respectively. The area under the curve (AUC) for the elasto score (AUC) was 0.72 (p = 0.001), and AUC for the strain index was 0.77 (p < 0.0001). Accordingly, our study suggests that strain index reflects malignancy better than the elasto score. We conclude that elastography score is ≥3 providing 80 % sensitivity and 50 %, six specificity for diagnosing malignancy. For strain index, we found that 2.45 (72.2 % sensitivity and 70 % specificity) is a cut-off point. We have detected a lower cut-off point for SI in Hashimoto patients although sensitivity and specificity decreases in Hashimoto in this population.

Reliability and Validity of Quantifying Absolute Muscle Hardness Using Ultrasound Elastography

PubMed Central

Chino, Kentaro; Akagi, Ryota; Dohi, Michiko; Fukashiro, Senshi; Takahashi, Hideyuki

2012-01-01

Muscle hardness is a mechanical property that represents transverse muscle stiffness. A quantitative method that uses ultrasound elastography for quantifying absolute human muscle hardness has been previously devised; however, its reliability and validity have not been completely verified. This study aimed to verify the reliability and validity of this quantitative method. The Young’s moduli of seven tissue-mimicking materials (in vitro; Young’s modulus range, 20–80 kPa; increments of 10 kPa) and the human medial gastrocnemius muscle (in vivo) were quantified using ultrasound elastography. On the basis of the strain/Young’s modulus ratio of two reference materials, one hard and one soft (Young’s moduli of 7 and 30 kPa, respectively), the Young’s moduli of the tissue-mimicking materials and medial gastrocnemius muscle were calculated. The intra- and inter-investigator reliability of the method was confirmed on the basis of acceptably low coefficient of variations (≤6.9%) and substantially high intraclass correlation coefficients (≥0.77) obtained from all measurements. The correlation coefficient between the Young’s moduli of the tissue-mimicking materials obtained using a mechanical method and ultrasound elastography was 0.996, which was equivalent to values previously obtained using magnetic resonance elastography. The Young’s moduli of the medial gastrocnemius muscle obtained using ultrasound elastography were within the range of values previously obtained using magnetic resonance elastography. The reliability and validity of the quantitative method for measuring absolute muscle hardness using ultrasound elastography were thus verified. PMID:23029231

Pulmonary ultrasound elastography: a feasibility study with phantoms and ex-vivo tissue

NASA Astrophysics Data System (ADS)

Nguyen, Man Minh; Xie, Hua; Paluch, Kamila; Stanton, Douglas; Ramachandran, Bharat

2013-03-01

Elastography has become widely used for minimally invasive diagnosis in many tumors as seen with breast, liver and prostate. Among different modalities, ultrasound-based elastography stands out due to its advantages including being safe, real-time, and relatively low-cost. While lung cancer is the leading cause of cancer mortality among both men and women, the use of ultrasound elastography for lung cancer diagnosis has hardly been investigated due to the limitations of ultrasound in air. In this work, we investigate the use of static-compression based endobronchial ultrasound elastography by a 3D trans-oesophageal echocardiography (TEE) transducer for lung cancer diagnosis. A water-filled balloon was designed to 1) improve the visualization of endobronchial ultrasound and 2) to induce compression via pumping motion inside the trachea and bronchiole. In a phantom study, we have successfully generated strain images indicating the stiffness difference between the gelatin background and agar inclusion. A similar strain ratio was confirmed with Philips ultrasound strain-based elastography product. For ex-vivo porcine lung study, different tissue ablation methods including chemical injection, Radio Frequency (RF) ablation, and direct heating were implemented to achieve tumor-mimicking tissue. Stiff ablated lung tissues were obtained and detected with our proposed method. These results suggest the feasibility of pulmonary elastography to differentiate stiff tumor tissue from normal tissue.

High resolution SAW elastography for ex-vivo porcine skin specimen

NASA Astrophysics Data System (ADS)

Zhou, Kanheng; Feng, Kairui; Wang, Mingkai; Jamera, Tanatswa; Li, Chunhui; Huang, Zhihong

2018-02-01

Surface acoustic wave (SAW) elastography has been proven to be a non-invasive, non-destructive method for accurately characterizing tissue elastic properties. Current SAW elastography technique tracks generated surface acoustic wave impulse point by point which are a few millimeters away. Thus, reconstructed elastography has low lateral resolution. To improve the lateral resolution of current SAW elastography, a new method was proposed in this research. A M-B scan mode, high spatial resolution phase sensitive optical coherence tomography (PhS-OCT) system was employed to track the ultrasonically induced SAW impulse. Ex-vivo porcine skin specimen was tested using this proposed method. A 2D fast Fourier transform based algorithm was applied to process the acquired data for estimating the surface acoustic wave dispersion curve and its corresponding penetration depth. Then, the ex-vivo porcine skin elastogram was established by relating the surface acoustic wave dispersion curve and its corresponding penetration depth. The result from the proposed method shows higher lateral resolution than that from current SAW elastography technique, and the approximated skin elastogram could also distinguish the different layers in the skin specimen, i.e. epidermis, dermis and fat layer. This proposed SAW elastography technique may have a large potential to be widely applied in clinical use for skin disease diagnosis and treatment monitoring.

Elastography for the differentiation of benign and malignant liver lesions: a meta-analysis.

PubMed

Ma, Xuelei; Zhan, Wenli; Zhang, Binglan; Wei, Benling; Wu, Xin; Zhou, Min; Liu, Lei; Li, Ping

2014-05-01

The objective of this paper was to evaluate the overall accuracy of elastography in the diagnosis of benign and malignant liver lesions by liver biopsy as the gold standard. Literature databases were searched. The studies which were related to evaluate the diagnostic value of elastography for differentiation in benign and malignant liver lesions in English or Chinese were included. The summary receiver operating characteristic (SROC) curve was performed, and the areas under the curve (AUC) were also calculated to present the accuracy of the elastography for the diagnosis of benign and malignant liver lesions. Six studies which included a total of 448 liver lesions in 384 patients were analyzed. The summary sensitivity and specificity of elastography for the differentiation of malignant liver lesions were 85% (95% CI, 80 to 89%) and 84% (95% CI, 80 to 88%), respectively. And the summary diagnostic odds ratio was 46.33 (95% CI, 15.22 to 141.02), and the SROC was 0.9328. Elastography has a high sensitivity and specificity differentiation for benign and malignant liver lesions. As a non-invasive method, it is promising to be applied to clinical practice. To estimate elastography objectively, a large, prospective, international, and multi-center study is still needed.

Comparison of strain and shear wave elastography for qualitative and quantitative assessment of breast masses in the same population.

PubMed

Kim, Hyo Jin; Kim, Sun Mi; Kim, Bohyoung; La Yun, Bo; Jang, Mijung; Ko, Yousun; Lee, Soo Hyun; Jeong, Heeyeong; Chang, Jung Min; Cho, Nariya

2018-04-18

We investigated addition of strain and shear wave elastography to conventional ultrasonography for the qualitative and quantitative assessment of breast masses; cut-off points were determined for strain ratio, elasticity ratio, and visual score for differentiating between benign and malignant masses. In all, 108 masses from 94 patients were evaluated with strain and shear wave elastography and scored for suspicion of malignancy, visual score, strain ratio, and elasticity ratio. The diagnostic performance between ultrasonography alone and ultrasonography combined with either type of elastography was compared; cut-off points were determined for strain ratio, elasticity ratio, and visual score. Of the 108 masses, 44 were malignant and 64 were benign. The areas under the curves were significantly higher for strain and shear wave elastography-supplemented ultrasonography (0.839 and 0.826, respectively; P = 0.656) than for ultrasonography alone (0.764; P = 0.018 and 0.035, respectively). The diagnostic performances of strain and elasticity ratios were similar when differentiating benign from malignant masses. Cut-off values for strain ratio, elasticity ratio, and visual scores for strain and shear wave elastography were 2.93, 4, 3, and 2, respectively. Both forms of elastography similarly improved the diagnostic performance of conventional ultrasonography in the qualitative and quantitative assessment of breast masses.

Spin-echo Echo-planar Imaging MR Elastography versus Gradient-echo MR Elastography for Assessment of Liver Stiffness in Children and Young Adults Suspected of Having Liver Disease.

PubMed

Serai, Suraj D; Dillman, Jonathan R; Trout, Andrew T

2017-03-01

Purpose To compare two-dimensional (2D) gradient-recalled echo (GRE) and 2D spin-echo (SE) echo-planar imaging (EPI) magnetic resonance (MR) elastography for measurement of hepatic stiffness in pediatric and young adult patients suspected of having liver disease. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 58 patients underwent both 2D GRE and 2D SE-EPI MR elastography at 1.5 T during separate breath holds. Liver stiffness (mean of means; in kilopascals) was measured by five blinded reviewers. Pooled mean liver stiffness and region-of-interest (ROI) size were compared by using paired t tests. Intraclass correlation coefficients (ICCs) were used to assess agreement between techniques. Respiratory motion artifacts were compared across sequences by using the Fisher exact test. Results Mean patient age was 14.7 years ± 5.2 (standard deviation; age range, 0.7-20.5 years), and 55.2% (32 of 58) of patients were male. Mean liver stiffness was 2.92 kPa ± 1.29 measured at GRE MR elastography and 2.76 kPa ± 1.39 at SE-EPI MR elastography (n = 290; P = .15). Mean ROI sizes were 8495 mm 2 ± 4482 for 2D GRE MR elastography and 15 176 mm 2 ± 7609 for 2D SE-EPI MR elastography (n = 290; P < .001). Agreement was excellent for measured stiffness between five reviewers for both 2D GRE (ICC, 0.97; 95% confidence interval: 0.95, 0.98) and 2D SE-EPI (ICC, 0.98; 95% confidence interval: 0.96, 0.99). Mean ICC (n = 5) for agreement between 2D GRE and 2D SE-EPI MR elastography was 0.93 (range, 0.91-0.95). Moderate or severe breathing artifacts were observed on 27.5% (16 of 58) of 2D GRE images versus 0% 2D SE-EPI images (P < .001). Conclusion There is excellent agreement on measured hepatic stiffness between 2D GRE and 2D SE-EPI MR elastography across multiple reviewers. SE-EPI MR elastography allowed for stiffness measurement across larger areas of the liver and can be performed in a single breath hold. © RSNA, 2016.

Quantitative shear wave ultrasound elastography: initial experience in solid breast masses

PubMed Central

2010-01-01

Introduction Shear wave elastography is a new method of obtaining quantitative tissue elasticity data during breast ultrasound examinations. The aims of this study were (1) to determine the reproducibility of shear wave elastography (2) to correlate the elasticity values of a series of solid breast masses with histological findings and (3) to compare shear wave elastography with greyscale ultrasound for benign/malignant classification. Methods Using the Aixplorer® ultrasound system (SuperSonic Imagine, Aix en Provence, France), 53 solid breast lesions were identified in 52 consecutive patients. Two orthogonal elastography images were obtained of each lesion. Observers noted the mean elasticity values in regions of interest (ROI) placed over the stiffest areas on the two elastography images and a mean value was calculated for each lesion. A sub-set of 15 patients had two elastography images obtained by an additional operator. Reproducibility of observations was assessed between (1) two observers analysing the same pair of images and (2) findings from two pairs of images of the same lesion taken by two different operators. All lesions were subjected to percutaneous biopsy. Elastography measurements were correlated with histology results. After preliminary experience with 10 patients a mean elasticity cut off value of 50 kilopascals (kPa) was selected for benign/malignant differentiation. Greyscale images were classified according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS). BI-RADS categories 1-3 were taken as benign while BI-RADS categories 4 and 5 were classified as malignant. Results Twenty-three benign lesions and 30 cancers were diagnosed on histology. Measurement of mean elasticity yielded an intraclass correlation coefficient of 0.99 for two observers assessing the same pairs of elastography images. Analysis of images taken by two independent operators gave an intraclass correlation coefficient of 0.80. Shear wave elastography versus greyscale BI-RADS performance figures were sensitivity: 97% vs 87%, specificity: 83% vs 78%, positive predictive value (PPV): 88% vs 84%, negative predictive value (NPV): 95% vs 82% and accuracy: 91% vs 83% respectively. These differences were not statistically significant. Conclusions Shear wave elastography gives quantitative and reproducible information on solid breast lesions with diagnostic accuracy at least as good as greyscale ultrasound with BI-RADS classification. PMID:21122101

Quantitative shear wave ultrasound elastography: initial experience in solid breast masses.

PubMed

Evans, Andrew; Whelehan, Patsy; Thomson, Kim; McLean, Denis; Brauer, Katrin; Purdie, Colin; Jordan, Lee; Baker, Lee; Thompson, Alastair

2010-01-01

Shear wave elastography is a new method of obtaining quantitative tissue elasticity data during breast ultrasound examinations. The aims of this study were (1) to determine the reproducibility of shear wave elastography (2) to correlate the elasticity values of a series of solid breast masses with histological findings and (3) to compare shear wave elastography with greyscale ultrasound for benign/malignant classification. Using the Aixplorer® ultrasound system (SuperSonic Imagine, Aix en Provence, France), 53 solid breast lesions were identified in 52 consecutive patients. Two orthogonal elastography images were obtained of each lesion. Observers noted the mean elasticity values in regions of interest (ROI) placed over the stiffest areas on the two elastography images and a mean value was calculated for each lesion. A sub-set of 15 patients had two elastography images obtained by an additional operator. Reproducibility of observations was assessed between (1) two observers analysing the same pair of images and (2) findings from two pairs of images of the same lesion taken by two different operators. All lesions were subjected to percutaneous biopsy. Elastography measurements were correlated with histology results. After preliminary experience with 10 patients a mean elasticity cut off value of 50 kilopascals (kPa) was selected for benign/malignant differentiation. Greyscale images were classified according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS). BI-RADS categories 1-3 were taken as benign while BI-RADS categories 4 and 5 were classified as malignant. Twenty-three benign lesions and 30 cancers were diagnosed on histology. Measurement of mean elasticity yielded an intraclass correlation coefficient of 0.99 for two observers assessing the same pairs of elastography images. Analysis of images taken by two independent operators gave an intraclass correlation coefficient of 0.80. Shear wave elastography versus greyscale BI-RADS performance figures were sensitivity: 97% vs 87%, specificity: 83% vs 78%, positive predictive value (PPV): 88% vs 84%, negative predictive value (NPV): 95% vs 82% and accuracy: 91% vs 83% respectively. These differences were not statistically significant. Shear wave elastography gives quantitative and reproducible information on solid breast lesions with diagnostic accuracy at least as good as greyscale ultrasound with BI-RADS classification.

Analysis of shear wave propagation derived from MR elastography in 3D thigh skeletal muscle using subject specific finite element model.

PubMed

Dao, Tien Tuan; Pouletaut, Philippe; Charleux, Fabrice; Tho, Marie-Christine Ho Ba; Bensamoun, Sabine

2014-01-01

The purpose of this study was to develop a subject specific finite element model derived from MRI images to numerically analyze the MRE (magnetic resonance elastography) shear wave propagation within skeletal thigh muscles. A sagittal T2 CUBE MRI sequence was performed on the 20-cm thigh segment of a healthy male subject. Skin, adipose tissue, femoral bone and 11 muscles were manually segmented in order to have 3D smoothed solid and meshed models. These tissues were modeled with different constitutive laws. A transient modal dynamics analysis was applied to simulate the shear wave propagation within the thigh tissues. The effects of MRE experimental parameters (frequency, force) and the muscle material properties (shear modulus: C10) were analyzed through the simulated shear wave displacement within the vastus medialis muscle. The results showed a plausible range of frequencies (from 90Hz to 120 Hz), which could be used for MRE muscle protocol. The wave amplitude increased with the level of the force, revealing the importance of the boundary condition. Moreover, different shear displacement patterns were obtained as a function of the muscle mechanical properties. The present study is the first to analyze the shear wave propagation in skeletal muscles using a 3D subject specific finite element model. This study could be of great value to assist the experimenters in the set-up of MRE protocols.

Prediction of Esophageal Varices in Patients with Cirrhosis: Usefulness of Three-dimensional MR Elastography with Echo-planar Imaging Technique

PubMed Central

Shin, Sung Ui; Yu, Mi Hye; Yoon, Jeong Hee; Han, Joon Koo; Choi, Byung-Ihn; Glaser, Kevin J.; Ehman, Richard L.

2014-01-01

Purpose To determine the diagnostic performance of magnetic resonance (MR) elastography in comparison to spleen length and dynamic contrast material–enhanced (DCE) MR imaging in association with esophageal varices in patients with liver cirrhosis by using endoscopy as the reference standard. Materials and Methods This retrospective study received institutional review board approval, and informed consent was waived. One hundred thirty-nine patients with liver cirrhosis who underwent liver DCE MR imaging, including MR elastography, were included. Hepatic stiffness (HS) and spleen stiffness (SS) values assessed with MR elastography, as well as spleen length, were correlated with the presence of esophageal varices and high-risk varices by using Spearman correlation analysis. The diagnostic performance of MR elastography was compared with that of DCE MR imaging and combined assessment of MR elastography and DCE MR imaging by using receiver operating characteristic analysis. MR elastography reproducibility was assessed prospectively, with informed consent, in another 15 patients by using intraclass correlation coefficients. Results There were significant positive linear correlations between HS, SS, and spleen length and the grade of esophageal varices (r = 0.46, r = 0.48, and r = 0.36, respectively; all P < .0001). HS and SS values (>4.81 kPa and >7.60 kPa, respectively) showed better performance than did spleen length in the association with esophageal varices (P = .0306 and P = .0064, respectively). Diagnostic performance of HS and SS in predicting high-risk varices was comparable to that of DCE MR imaging (P = .1282 and P = .1371, respectively). When MR elastography and DCE MR imaging were combined, sensitivity improved significantly (P = .0004). MR elastography was highly reproducible (intraclass correlation coefficient > 0.9). Conclusion HS and SS are associated with esophageal varices and showed better performance than did spleen length in assessing the presence of esophageal varices. MR elastography is comparable to DCE MR imaging in predicting the presence of esophageal varices and high-risk varices, but, when assessed in combination, sensitivity is higher. © RSNA, 2014 Online supplemental material is available for this article. PMID:24620910

Advanced MRI Methods for Assessment of Chronic Liver Disease

PubMed Central

Taouli, Bachir; Ehman, Richard L.; Reeder, Scott B.

2010-01-01

MRI plays an increasingly important role for assessment of patients with chronic liver disease. MRI has numerous advantages, including lack of ionizing radiation and the possibility of performing multiparametric imaging. With recent advances in technology, advanced MRI methods such as diffusion-, perfusion-weighted MRI, MR elastography, chemical shift based fat-water separation and MR spectroscopy can now be applied to liver imaging. We will review the respective roles of these techniques for assessment of chronic liver disease. PMID:19542391

Transient elastography for the assessment of chronic liver disease: Ready for the clinic?

PubMed Central

Cobbold, JFL; Morin, S; Taylor-Robinson, SD

2007-01-01

Transient elastography is a recently developed non-invasive technique for the assessment of hepatic fibrosis. The technique has been subject to rigorous evaluation in a number of studies in patients with chronic liver disease of varying aetiology. Transient elastography has been compared with histological assessment of percutaneous liver biopsy, with high sensitivity and specificity for the diagnosis of cirrhosis, and has also been used to assess pre-cirrhotic disease. However, the cut-off values between different histological stages vary substantially in different studies, patient groups and aetiology of liver disease. More recent studies have examined the possible place of transient elastography in clinical practice, including risk stratification for the development of complications of cirrhosis. This review describes the technique of transient elastography and discusses the interpretation of recent studies, emphasizing its applicability in the clinical setting. PMID:17828808

Lumbar annulus fibrosus biomechanical characterization in healthy children by ultrasound shear wave elastography.

PubMed

Vergari, Claudio; Dubois, Guillaume; Vialle, Raphael; Gennisson, Jean-Luc; Tanter, Mickael; Dubousset, Jean; Rouch, Philippe; Skalli, Wafa

2016-04-01

Intervertebral disc (IVD) is key to spine biomechanics, and it is often involved in the cascade leading to spinal deformities such as idiopathic scoliosis, especially during the growth spurt. Recent progress in elastography techniques allows access to non-invasive measurement of cervical IVD in adults; the aim of this study was to determine the feasibility and reliability of shear wave elastography in healthy children lumbar IVD. Elastography measurements were performed in 31 healthy children (6-17 years old), in the annulus fibrosus and in the transverse plane of L5-S1 or L4-L5 IVD. Reliability was determined by three experienced operators repeating measurements. Average shear wave speed in IVD was 2.9 ± 0.5 m/s; no significant correlations were observed with sex, age or body morphology. Intra-operator repeatability was 5.0 % while inter-operator reproducibility was 6.2 %. Intraclass correlation coefficient was higher than 0.9 for each operator. Feasibility and reliability of IVD shear wave elastography were demonstrated. The measurement protocol is compatible with clinical routine and the results show the method's potential to give an insight into spine deformity progression and early detection. • Intervertebral disc mechanical properties are key to spine biomechanics • Feasibility of shear wave elastography in children lumbar disc was assessed • Measurement was fast and reliable • Elastography could represent a novel biomarker for spine pathologies.

Ultrasound elastography of the prostate: state of the art.

PubMed

Correas, J-M; Tissier, A-M; Khairoune, A; Khoury, G; Eiss, D; Hélénon, O

2013-05-01

Prostate cancer is the cancer exhibiting the highest incidence rate and it appears as the second cause of cancer death in men, after lung cancer. Prostate cancer is difficult to detect, and the treatment efficacy remains limited despite the increase use of biological tests (prostate-specific antigen [PSA] dosage), the development of new imaging modalities, and the use of invasive procedures such as biopsy. Ultrasound elastography is a novel imaging technique capable of mapping tissue stiffness of the prostate. It is known that prostatic cancer tissue is often harder than healthy tissue (information used by digital rectal examination [DRE]). Two elastography techniques have been developed based on different principles: first, quasi-static (or strain) technique, and second, shear wave technique. The tissue stiffness information provided by US elastography should improve the detection of prostate cancer and provide guidance for biopsy. Prostate elastography provides high sensitivity for detecting prostate cancer and shows high negative predictive values, ensuring that few cancers will be missed. US elastography should become an additional method of imaging the prostate, complementing the conventional transrectal ultrasound and MRI. This technique requires significant training (especially for quasi-static elastography) to become familiar with acquisition process, acquisition technique, characteristics and limitations, and to achieve correct diagnoses. Copyright © 2013 Éditions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.

Mapping tissue shear modulus on Thiel soft-embalmed mouse skin with shear wave optical coherence elastography

NASA Astrophysics Data System (ADS)

Song, Shaozhen; Joy, Joyce; Wang, Ruikang K.; Huang, Zhihong

2015-03-01

A quantitative measurement of the mechanical properties of biological tissue is a useful assessment of its physiologic conditions, which may aid medical diagnosis and treatment of, e.g., scleroderma and skin cancer. Traditional elastography techniques such as magnetic resonance elastography and ultrasound elastography have limited scope of application on skin due to insufficient spatial resolution. Recently, dynamic / transient elastography are attracting more applications with the advantage of non-destructive measurements, and revealing the absolute moduli values of tissue mechanical properties. Shear wave optical coherence elastography (SW-OCE) is a novel transient elastography method, which lays emphasis on the propagation of dynamic mechanical waves. In this study, high speed shear wave imaging technique was applied to a range of soft-embalmed mouse skin, where 3 kHz shear waves were launched with a piezoelectric actuator as an external excitation. The shear wave velocity was estimated from the shear wave images, and used to recover a shear modulus map in the same OCT imaging range. Results revealed significant difference in shear modulus and structure in compliance with gender, and images on fresh mouse skin are also compared. Thiel embalming technique is also proven to present the ability to furthest preserve the mechanical property of biological tissue. The experiment results suggest that SW-OCE is an effective technique for quantitative estimation of skin tissue biomechanical status.

Correlates of mammographic density in B-mode ultrasound and real time elastography.

PubMed

Jud, Sebastian Michael; Häberle, Lothar; Fasching, Peter A; Heusinger, Katharina; Hack, Carolin; Faschingbauer, Florian; Uder, Michael; Wittenberg, Thomas; Wagner, Florian; Meier-Meitinger, Martina; Schulz-Wendtland, Rüdiger; Beckmann, Matthias W; Adamietz, Boris R

2012-07-01

The aim of our study involved the assessment of B-mode imaging and elastography with regard to their ability to predict mammographic density (MD) without X-rays. Women, who underwent routine mammography, were prospectively examined with additional B-mode ultrasound and elastography. MD was assessed quantitatively with a computer-assisted method (Madena). The B-mode and elastography images were assessed by histograms with equally sized gray-level intervals. Regression models were built and cross validated to examine the ability to predict MD. The results of this study showed that B-mode imaging and elastography were able to predict MD. B-mode seemed to give a more accurate prediction. R for B-mode image and elastography were 0.67 and 0.44, respectively. Areas in the B-mode images that correlated with mammographic dense areas were either dark gray or of intermediate gray levels. Concerning elastography only the gray levels that represent extremely stiff tissue correlated positively with MD. In conclusion, ultrasound seems to be able to predict MD. Easy and cheap utilization of regular breast ultrasound machines encourages the use of ultrasound in larger case-control studies to validate this method as a breast cancer risk predictor. Furthermore, the application of ultrasound for breast tissue characterization could enable comprehensive research concerning breast cancer risk and breast density in young and pregnant women.

Ultrasound Shear Wave Elastography for Liver Disease. A Critical Appraisal of the Many Actors on the Stage.

PubMed

Piscaglia, F; Salvatore, V; Mulazzani, L; Cantisani, V; Schiavone, C

2016-02-01

In the last 12 - 18 months nearly all ultrasound manufacturers have arrived to implement ultrasound shear wave elastography modality in their equipment for the assessment of chronic liver disease; the few remaining players are expected to follow in 2016.When all manufacturers rush to a new technology at the same time, it is evident that the clinical demand for this information is of utmost value. Around 1990, there was similar demand for color Doppler ultrasound; high demand for contrast-enhanced ultrasonography was evident at the beginning of this century, and around 2010 demand increased for strain elastography. However, some issues regarding the new shear wave ultrasound technologies must be noted to avoid misuse of the resulting information for clinical decisions. As new articles are expected to appear in 2016 reporting the findings of the new technologies from various companies, we felt that the beginning of this year was the right time to present an appraisal of these issues. We likewise expect that in the meantime EFSUMB will release a new update of the existing guidelines 1 2.The first ultrasound elastography method became available 13 years ago in the form of transient elastography with Fibroscan(®) 3. It was the first technique providing non-invasive quantitive information about the stiffness of the liver and hence regarding the amount of fibrosis in chronic liver disease 3. The innovation was enormous, since a non-invasive modality was finally available to provide findings otherwise achievable only by liver biopsy. In fact, prior to ultrasound elastography, a combination of conventional and Doppler ultrasound parameters were utilized to inform the physician about the presence of cirrhosis and portal hypertension 4. However, skilled operators were required, reproducibility and diagnostic accuracy were suboptimal, and it was not possible to differentiate the pre-cirrhotic stages of fibrosis. All these limitations were substantially improved by transient elastography, performed with Fibroscan(®), a technology dedicated exclusively to liver elastography. Since then, more than 1300 articles dealing with transient elastography have been listed in PubMed, some describing results with more than 10,000 patients 5. The technique has been tested in nearly all liver disease etiologies, with histology as the reference standard. Meta-analysis of data, available in many etiologies 6, showed good performance and reproducibility as well as some situations limiting reliability 5. Thresholds for the different fibrosis stages (F0 to F4) have been provided by many large-scale studies utilizing histology as the reference standard 7. Transient elastography tracks the velocity of shear waves generated by the gentle hit of a piston on the skin, with the resulting compression wave traveling in the liver along its longitudinal axis. The measurement is made in a 4 cm long section of the liver, thus able to average slightly inhomogeneous fibrotic deposition.In 2008 a new modality became available, Acoustic Radiation Force Impulse (ARFI) quantification, and classified by EFSUMB 1 as point shear wave elastography (pSWE), since the speed of the shear wave (perpendicular to the longitudinal axis) is measured in a small region (a "point", few millimeters) at a freely-choosen depth within 8 cm from the skin. This technology was the first to be implemented in a conventional ultrasound scanner by Siemens(®) 8. Several articles have been published regarding this technology, most with the best reference standards 9, some including findings on more than 1000 hepatitis C patients 10 or reporting meta-analysis of data 11. Although the correlation between Siemens pSWE and transient elastography appeared high 12 13, the calculated thresholds for the different fibrosis stages and the stiffness ranges between the two techniques are not superimposable.Interestingly, pSWE appears to provide greater applicability than transient elastography for measuring both liver 13 and spleen stiffness, which is a new application of elastography 14, of interest for the prediction of the degree of portal hypertension 15 16.Nowadays other companies have started producing equipment with pSWE technology, but only very few articles have been published so far, for instance describing the use of Philips(®) equipment, which was the second to provide pSWE. These articles show preliminary good results also in comparison with TE 17 18. Not enough evidence is currently available in the literature about the elastographic performance of the products most recently introduced to the market. Furthermore, with some products the shear wave velocities generated by a single ultrasound acoustic push pulse can be measured in a bidimensional area (a box in the range of 2 - 3 cm per side) rather than in a single small point, producing a so-called bidimensional 2D-SWE 1. The stiffness is depicted in color within the area and refreshing of the measurement occurs every 1 - 2 seconds. Once the best image is acquired, the operator chooses a Region Of Interest (ROI) within the color box, where the mean stiffness is then calculated. 2D-SWE can be performed as a "one shot" technique or as a semi-"real-time" technique for a few seconds (at about 1 frame per second) in order to obtain a stable elastogram. With either technique, there should be no motion/breathing during image acquisition. A bidimensional averaged area should overcome the limitation of pSWE to inadvertently investigate small regions of greater or lesser stiffness than average. A shear wave quality indicator could be useful to provide real-time feedback and optimize placement of the sampling ROIs, a technology recently presented by Toshiba(®), but which is still awaiting validation in the literature.Supersonic Imagine by Aixplorer(®) which works with a different modality of insonation and video analysis compared to the the previously-mentioned three techniques (i. e., transient elastography, pSWE and 2D-SWE), leading to a bidimensional assessment of liver stiffness in real time up to 5 Hz and in larger regions; thus this technique is also termed real-time 2 D SWE. It has been available on the market for a few years 19 20, and many articles have been published showing stiffness values quite similar to those of Fibroscan(®) 21; likewise, defined thresholds based on histological findings have appeared in several articles 19 20 21.After this brief summary of the technological state of the art we would like to mention the following critical issues that we believe every user should note prior to providing liver stiffness reports. · The thresholds obtained from the "oldest" techniques for the various fibrosis stages based on hundreds of patients with histology as reference standard cannot be straightforwardly applied to the new ultrasound elastography techniques, even if based on the same principle (e. g. pSWE). In fact, the different manufacturers apply proprietary patented calculation modes, which might result in slightly to moderately different values. It should be kept in mind that the range for intermediate fibrosis stages (F1 to F3) is quite narrow, in the order of 2 - 3 kilopascal (over a total range spanning 2 to 75 kPa with Fibroscan), so that slightly different differences in outputs could shift the assessment of patients from one stage to another. Comparative studies using phantoms and healthy volunteers, as well as patients, are eagerly awaited. In fact, the equipment might not produce linear correlations of measurements at different degrees of severity of fibrosis. As a theoretical example, some equipment might well correlate in their values with an older technique, such as transient elastography, at low levels of liver fibrosis, but not as well in cases of more advanced fibrosis or vice versa. Consequentely, when elastography data are included in a report, the equipment utilized for the measurement should be clearly specified, and conclusions about the fibrosis stage should be withheld if an insufficient number of comparative studies with solid reference standards are available for that specific equipment.. · Future studies using histology as a reference might be biased in comparison to previous studies, since nowadays fewer patients with chronic hepatitis C or hepatitis B undergo biopsy. In fact, due to wide availability of effective drugs as well as the use of established elastography methods for patients with viral hepatitis, most cases submitted to biopsy today have uncertain etiology or inconsistent and inconclusive clinical data. Therefore, extrapolated thresholds from such inhomogeneous populations applied to more ordinary patients with viral hepatitis might become problematic in the future, although no better solution is currently anticipated. This situation might lead to the adoption of a standard validated elastographic method as reference, but this has to be agreed-upon at an international level.. · Ultrasound elastography embedded in conventional scanners usually allows the choice of where to place the ROI within the color stiffness box and whether to confirm or exclude each single measurement when determining the final value. Thus, the operator has a greater potential to influence the final findings than with Fibroscan®, where these choices are not available. This has to be kept in mind to avoid the possibility that an operator could, even inadvertently, tend to confirm an assumption about that specific patient or to confirm the patient's expectations.. · Quality criteria for the new technologies following transient elastography are absent (depending on the manufacturer) or have not been satisfactorily defined, so that the information potentially inserted in a report cannot currently be judged for its reliability by the clinician.. (ABSTRACT TRUNCATED) © Georg Thieme Verlag KG Stuttgart · New York.

Development of an Anthropomorphic Breast Phantom for Combined PET, B-Mode Ultrasound and Elastographic Imaging

NASA Astrophysics Data System (ADS)

Dang, Jun; Frisch, Benjamin; Lasaygues, Philippe; Zhang, Dachun; Tavernier, Stefaan; Felix, Nicolas; Lecoq, Paul; Auffray, Etiennette; Varela, Joao; Mensah, Serge; Wan, Mingxi

2011-06-01

Combining the advantages of different imaging modalities leads to improved clinical results. For example, ultrasound provides good real-time structural information without any radiation and PET provides sensitive functional information. For the ongoing ClearPEM-Sonic project combining ultrasound and PET for breast imaging, we developed a dual-modality PET/Ultrasound (US) phantom. The phantom reproduces the acoustic and elastic properties of human breast tissue and allows labeling the different tissues in the phantom with different concentrations of FDG. The phantom was imaged with a whole-body PET/CT and with the Supersonic Imagine Aixplorer system. This system allows both B-mode US and shear wave elastographic imaging. US elastography is a new imaging method for displaying the tissue elasticity distribution. It was shown to be useful in breast imaging. We also tested the phantom with static elastography. A 6D magnetic positioning system allows fusing the images obtained with the two modalities. ClearPEM-Sonic is a project of the Crystal Clear Collaboration and the European Centre for Research on Medical Imaging (CERIMED).

Shear-wave elastography of the breast: value of a quality measure and comparison with strain elastography.

PubMed

Barr, Richard G; Zhang, Zheng

2015-04-01

To determine whether addition of quality measure (QM) of shear-wave (SW) velocity (Vs) estimation can increase SW elastography sensitivity for breast cancer. With written informed consent, this institutional review board-approved, HIPAA-compliant study included 143 women (mean age, 48.5 years ± 8.7) scheduled for breast biopsy. Mean lesion size was 16.4 mm ± 11.8; 95 (66%) lesions were benign; 48 (34%), malignant. If more than one lesion was present, lesion with highest Breast Imaging Reporting and Data System (BI-RADS) category was chosen. If there were more than one with highest BI-RADS category, a lesion was randomly selected. Conventional ultrasonography (US), strain elastography, and SW elastography were performed with QM. QM assesses SW quality to provide accurate Vs. Lesions were evaluated for Vs and QM (high or low). Lesions with Vs of less than 4.5 m/sec were classified benign; lesions with Vs of 4.5 m/sec or greater, malignant. Results were correlated with pathologic findings. Vs data with or without incorporating QM were used to determine SW elastography diagnostic performance. Binomial proportions and exact 95% confidence intervals (CIs) were calculated. In 95 benign lesions, 13 (14%) had no SW elastography signal; 77 (81%), Vs of less than 4.5 m/sec; and five (5%), Vs of 4.5 m/sec or greater. In 48 malignant lesions, eight (17%) had no SW elastography signal; 20 (42%), Vs of less than 4.5 m/sec; and 20 (42%), V of 4.5 m/sec or greater. QM was low in 17 of 20 (85%) malignant lesions with Vs of less than 4.5 m/sec. Without QM, using Vs of 4.5 m/sec or greater as test positive, SW elastography had lesion-level sensitivity of 50% (95% CI: 34%, 66%); specificity, 94% (95% CI: 86%, 98%); positive predictive value (PPV), 80% (95% CI: 59%, 93%); and negative predictive value (NPV), 79% (95% CI: 70%, 87%). Using QM where additional lesions with both low Vs and low QM were treated as test positive, SW elastography had lesion-level sensitivity of 93% (95% CI: 80%, 98%); specificity, 89% (95% CI: 80%, 95%); PPV, 80% (95% CI: 66%, 91%); and NPV, 96% (95% CI: 89%, 99%). Addition of QM can improve SW elastography sensitivity, with no significant change in specificity. © RSNA, 2014 Online supplemental material is available for this article.

Real time endoscopic ultrasound elastography and strain ratio in the diagnosis of solid pancreatic lesions.

PubMed

Okasha, Hussein; Elkholy, Shaimaa; El-Sayed, Ramy; Wifi, Mohamed-Naguib; El-Nady, Mohamed; El-Nabawi, Walid; El-Dayem, Waleed A; Radwan, Mohamed I; Farag, Ali; El-Sherif, Yahya; Al-Gemeie, Emad; Salman, Ahmed; El-Sherbiny, Mohamed; El-Mazny, Ahmed; Mahdy, Reem E

2017-08-28

To evaluate the accuracy of the elastography score combined to the strain ratio in the diagnosis of solid pancreatic lesions (SPL). A total of 172 patients with SPL identified by endoscopic ultrasound were enrolled in the study to evaluate the efficacy of elastography and strain ratio in differentiating malignant from benign lesions. The semi quantitative score of elastography was represented by the strain ratio method. Two areas were selected, area (A) representing the region of interest and area (B) representing the normal area. Area (B) was then divided by area (A). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated by comparing diagnoses made by elastography, strain ratio and final diagnoses. SPL were shown to be benign in 49 patients and malignant in 123 patients. Elastography alone had a sensitivity of 99%, a specificity of 63%, and an accuracy of 88%, a PPV of 87% and an NPV of 96%. The best cut-off level of strain ratio to obtain the maximal area under the curve was 7.8 with a sensitivity of 92%, specificity of 77%, PPV of 91%, NPV of 80% and an accuracy of 88%. Another estimated cut off strain ratio level of 3.8 had a higher sensitivity of 99% and NPV of 96%, but with less specificity, PPV and accuracy 53%, 84% and 86%, respectively. Adding both elastography to strain ratio resulted in a sensitivity of 98%, specificity of 77%, PPV of 91%, NPV of 95% and accuracy of 92% for the diagnosis of SPL. Combining elastography to strain ratio increases the accuracy of the differentiation of benign from malignant SPL.

Real time endoscopic ultrasound elastography and strain ratio in the diagnosis of solid pancreatic lesions

PubMed Central

Okasha, Hussein; Elkholy, Shaimaa; El-Sayed, Ramy; Wifi, Mohamed-Naguib; El-Nady, Mohamed; El-Nabawi, Walid; El-Dayem, Waleed A; Radwan, Mohamed I; Farag, Ali; El-sherif, Yahya; Al-Gemeie, Emad; Salman, Ahmed; El-Sherbiny, Mohamed; El-Mazny, Ahmed; Mahdy, Reem E

2017-01-01

AIM To evaluate the accuracy of the elastography score combined to the strain ratio in the diagnosis of solid pancreatic lesions (SPL). METHODS A total of 172 patients with SPL identified by endoscopic ultrasound were enrolled in the study to evaluate the efficacy of elastography and strain ratio in differentiating malignant from benign lesions. The semi quantitative score of elastography was represented by the strain ratio method. Two areas were selected, area (A) representing the region of interest and area (B) representing the normal area. Area (B) was then divided by area (A). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated by comparing diagnoses made by elastography, strain ratio and final diagnoses. RESULTS SPL were shown to be benign in 49 patients and malignant in 123 patients. Elastography alone had a sensitivity of 99%, a specificity of 63%, and an accuracy of 88%, a PPV of 87% and an NPV of 96%. The best cut-off level of strain ratio to obtain the maximal area under the curve was 7.8 with a sensitivity of 92%, specificity of 77%, PPV of 91%, NPV of 80% and an accuracy of 88%. Another estimated cut off strain ratio level of 3.8 had a higher sensitivity of 99% and NPV of 96%, but with less specificity, PPV and accuracy 53%, 84% and 86%, respectively. Adding both elastography to strain ratio resulted in a sensitivity of 98%, specificity of 77%, PPV of 91%, NPV of 95% and accuracy of 92% for the diagnosis of SPL. CONCLUSION Combining elastography to strain ratio increases the accuracy of the differentiation of benign from malignant SPL. PMID:28932088

A soft patellar tendon on ultrasound elastography is associated with pain and functional deficit in volleyball players.

PubMed

Ooi, Chin Chin; Richards, Paula J; Maffulli, Nicola; Ede, David; Schneider, Michal E; Connell, David; Morrissey, Dylan; Malliaras, Peter

2016-05-01

To investigate the diagnostic performance of grey scale Ultrasound (US), power Doppler (PD) and US elastography for diagnosing painful patellar tendinopathy, and to establish their relationship with Victorian Institute of Sport Assessment-Patella (VISA-P) scores in a group of volleyball players with and without symptoms of patellar tendinopathy. Cross-sectional study. Thirty-five volleyball players (70 patellar tendons) were recruited during a national university volleyball competition. Players were imaged with conventional US followed by elastography. The clinical findings of painful patellar tendons were used as the reference standard for diagnosing patellar tendinopathy. In addition, all participants completed the VISA-P questionnaires. Of the 70 patellar tendons, 40 (57.1%) were clinically painful. The diagnostic accuracy of grey scale US, PD and elastography were 60%, 50%, 62.9%, respectively, with sensitivity/specificity of 72.5%/43.3%, 12.5%/100%, and 70%/53.3%, respectively. Combined US elastography and grey scale imaging achieved 82.5% sensitivity, 33.3% specificity and 61.4% accuracy while routine combination technique of PD and grey scale imaging revealed 72.5% sensitivity, 43.3% specificity and 60.0% accuracy. Tendons in players categorized as soft on elastography had statistically significantly greater AP thickness (p<0.001) and lower VISA-P scores (p=0.004) than those categorized as hard. There was no significant association between grey scale US abnormalities (hypoechogenicities and/or fusiform swelling) and VISA-P scores (p=0.098). Soft tendon properties depicted by US elastography may be more related to patellar tendon symptoms compared to grey scale US abnormalities. The supplementation of US elastography to conventional US may enhance the sensitivity for diagnosing patellar tendinopathy in routine clinical practice. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Optical coherence elastography – OCT at work in tissue biomechanics [Invited

PubMed Central

Larin, Kirill V.; Sampson, David D.

2017-01-01

Optical coherence elastography (OCE), as the use of OCT to perform elastography has come to be known, began in 1998, around ten years after the rest of the field of elastography – the use of imaging to deduce mechanical properties of tissues. After a slow start, the maturation of OCT technology in the early to mid 2000s has underpinned a recent acceleration in the field. With more than 20 papers published in 2015, and more than 25 in 2016, OCE is growing fast, but still small compared to the companion fields of cell mechanics research methods, and medical elastography. In this review, we describe the early developments in OCE, and the factors that led to the current acceleration. Much of our attention is on the key recent advances, with a strong emphasis on future prospects, which are exceptionally bright. PMID:28271011

Experimental Validation of Displacement Underestimation in ARFI Ultrasound

PubMed Central

Czernuszewicz, Tomasz J.; Streeter, Jason E.; Dayton, Paul A.; Gallippi, Caterina M.

2014-01-01

Acoustic radiation force impulse (ARFI) imaging is an elastography technique that uses ultrasonic pulses to both displace and track tissue motion. Previous modeling studies have shown that ARFI displacements are susceptible to underestimation due to lateral and elevational shearing that occurs within the tracking resolution cell. In this study, optical tracking was utilized to experimentally measure the displacement underestimation achieved by acoustic tracking using a clinical ultrasound system. Three optically translucent phantoms of varying stiffness were created, embedded with sub-wavelength diameter microspheres, and ARFI excitation pulses with F/1.5 or F/3 lateral focal configurations were transmitted from a standard linear array to induce phantom motion. Displacements were tracked using confocal optical and acoustic methods. As predicted by earlier FEM studies, significant acoustic displacement underestimation was observed for both excitation focal configurations; the maximum underestimation error was 35% of the optically measured displacement for the F/1.5 excitation pulse in the softest phantom. Using higher F/#, less tightly focused beams in the lateral dimension improved accuracy of displacements by approximately 10 percentage points. This work experimentally demonstrates limitations of ARFI implemented on a clinical scanner using a standard linear array and sets up a framework for future displacement tracking validation studies. PMID:23858054

Ultrasound elastography in the early diagnosis of plantar fasciitis.

PubMed

Lee, So-Yeon; Park, Hee Jin; Kwag, Hyon Joo; Hong, Hyun-Pyo; Park, Hae-Won; Lee, Yong-Rae; Yoon, Kyung Jae; Lee, Yong-Taek

2014-01-01

The purpose of this study was to investigate whether ultrasound (US) elastography is useful for the early diagnosis of plantar fasciitis. We retrospectively reviewed US elastography findings of 18 feet with a clinical history and physical examination highly suggestive of plantar fasciitis but with normal findings on conventional US imaging as well as 18 asymptomatic feet. Softening of the plantar fascia was significantly greater in the patient than in the control group [Reviewers 1 and 2: 89% (16/18) vs. 50% (9/18), P=.027, respectively]. US elastography is useful for the early diagnosis of plantar fasciitis. Copyright © 2014 Elsevier Inc. All rights reserved.

Two-dimensional Shear Wave Elastography on Conventional Ultrasound Scanners with Time Aligned Sequential Tracking (TAST) and Comb-push Ultrasound Shear Elastography (CUSE)

PubMed Central

Song, Pengfei; Macdonald, Michael C.; Behler, Russell H.; Lanning, Justin D.; Wang, Michael H.; Urban, Matthew W.; Manduca, Armando; Zhao, Heng; Callstrom, Matthew R.; Alizad, Azra; Greenleaf, James F.; Chen, Shigao

2014-01-01

Two-dimensional (2D) shear wave elastography presents 2D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2D shear wave elastography on conventional ultrasound scanners, however, is challenging due to the low tracking pulse-repetition-frequency (PRF) of these systems. While some clinical and research platforms support software beamforming and plane wave imaging with high PRF, the majority of current clinical ultrasound systems do not have the software beamforming capability, which presents a critical challenge for translating the 2D shear wave elastography technique from laboratory to clinical scanners. To address this challenge, this paper presents a Time Aligned Sequential Tracking (TAST) method for shear wave tracking on conventional ultrasound scanners. TAST takes advantage of the parallel beamforming capability of conventional systems and realizes high PRF shear wave tracking by sequentially firing tracking vectors and aligning shear wave data in the temporal direction. The Comb-push Ultrasound Shear Elastography (CUSE) technique was used to simultaneously produce multiple shear wave sources within the field-of-view (FOV) to enhance shear wave signal-to-noise-ratio (SNR) and facilitate robust reconstructions of 2D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner (the General Electric LOGIQ E9). A phantom study showed that the shear wave speed measurements from the LOGIQ E9 were in good agreement to the values measured from other 2D shear wave imaging technologies. An inclusion phantom study showed that the LOGIQ E9 had comparable performance to the Aixplorer (Supersonic Imagine) in terms of bias and precision in measuring different sized inclusions. Finally, in vivo case analysis of a breast with a malignant mass, and a liver from a healthy subject demonstrated the feasibility of using the LOGIQ E9 for in vivo 2D shear wave elastography. These promising results indicate that the proposed technique can enable the implementation of 2D shear wave elastography on conventional ultrasound scanners and potentially facilitate wider clinical applications with shear wave elastography. PMID:25643079

Transient and 2-Dimensional Shear-Wave Elastography Provide Comparable Assessment of Alcoholic Liver Fibrosis and Cirrhosis.

PubMed

Thiele, Maja; Detlefsen, Sönke; Sevelsted Møller, Linda; Madsen, Bjørn Stæhr; Fuglsang Hansen, Janne; Fialla, Annette Dam; Trebicka, Jonel; Krag, Aleksander

2016-01-01

Alcohol abuse causes half of all deaths from cirrhosis in the West, but few tools are available for noninvasive diagnosis of alcoholic liver disease. We evaluated 2 elastography techniques for diagnosis of alcoholic fibrosis and cirrhosis; liver biopsy with Ishak score and collagen-proportionate area were used as reference. We performed a prospective study of 199 consecutive patients with ongoing or prior alcohol abuse, but without known liver disease. One group of patients had a high pretest probability of cirrhosis because they were identified at hospital liver clinics (in Southern Denmark). The second, lower-risk group, was recruited from municipal alcohol rehabilitation centers and the Danish national public health portal. All subjects underwent same-day transient elastography (FibroScan), 2-dimensional shear wave elastography (Supersonic Aixplorer), and liver biopsy after an overnight fast. Transient elastography and 2-dimensional shear wave elastography identified subjects in each group with significant fibrosis (Ishak score ≥3) and cirrhosis (Ishak score ≥5) with high accuracy (area under the curve ≥0.92). There was no difference in diagnostic accuracy between techniques. The cutoff values for optimal identification of significant fibrosis by transient elastography and 2-dimensional shear wave elastography were 9.6 kPa and 10.2 kPa, and for cirrhosis 19.7 kPa and 16.4 kPa. Negative predictive values were high for both groups, but the positive predictive value for cirrhosis was >66% in the high-risk group vs approximately 50% in the low-risk group. Evidence of alcohol-induced damage to cholangiocytes, but not ongoing alcohol abuse, affected liver stiffness. The collagen-proportionate area correlated with Ishak grades and accurately identified individuals with significant fibrosis and cirrhosis. In a prospective study of individuals at risk for liver fibrosis due to alcohol consumption, we found elastography to be an excellent tool for diagnosing liver fibrosis and for excluding (ruling out rather than ruling in) cirrhosis. Copyright © 2016 AGA Institute. Published by Elsevier Inc. All rights reserved.

Sonographic Elastography of Mastitis.

PubMed

Sousaris, Nicholas; Barr, Richard G

2016-08-01

Sonographic elastography has been shown to be a useful imaging modality in characterizing breast lesions as benign or malignant. However, in preliminary research, mastitis has given false-positive findings on both strain and shear wave elastography. In this article, we review the findings in mastitis with and without abscess formation on both strain and shear wave elastography. The elastographic findings in all cases were suggestive of a malignancy according to published thresholds. In cases of mastitis with abscess formation, there is a characteristic appearance, with a central very soft area (abscess cavity) and a very stiff outer rim (edema and inflammation). This appearance should raise the suspicion of mastitis with abscess formation, since these findings are rare in breast cancers.

Automated 3D ultrasound elastography of the breast: a phantom validation study

NASA Astrophysics Data System (ADS)

Hendriks, Gijs A. G. M.; Holländer, Branislav; Menssen, Jan; Milkowski, Andy; Hansen, Hendrik H. G.; de Korte, Chris L.

2016-04-01

In breast cancer screening, the automated breast volume scanner (ABVS) was introduced as an alternative for mammography since the latter technique is less suitable for women with dense breasts. Although clinical studies show promising results, clinicians report two disadvantages: long acquisition times (>90 s) introducing breathing artefacts, and high recall rates due to detection of many small lesions of uncertain malignant potential. Technical improvements for faster image acquisition and better discrimination between benign and malignant lesions are thus required. Therefore, the aim of this study was to investigate if 3D ultrasound elastography using plane-wave imaging is feasible. Strain images of a breast elastography phantom were acquired by an ABVS-mimicking device that allowed axial and elevational movement of the attached transducer. Pre- and post-deformation volumes were acquired with different constant speeds (between 1.25 and 40.0 mm s-1) and by three protocols: Go-Go (pre- and post-volumes with identical start and end positions), Go-Return (similar to Go-Go with opposite scanning directions) and Control (pre- and post-volumes acquired per position, this protocol can be seen as reference). Afterwards, 2D and 3D cross-correlation and strain algorithms were applied to the acquired volumes and the results were compared. The Go-Go protocol was shown to be superior with better strain image quality (CNRe and SNRe) than Go-Return and to be similar as Control. This can be attributed to applying opposite mechanical forces to the phantom during the Go-Return protocol, leading to out-of-plane motion. This motion was partly compensated by using 3D cross-correlation. However, the quality was still inferior to Go-Go. Since these results were obtained in a phantom study with controlled deformations, the effect of possible uncontrolled in vivo tissue motion artefacts has to be addressed in future studies. In conclusion, it seems feasible to implement 3D ultrasound quasi-static elastography on an ABVS-like system and to reduce scan times within one breath-hold (~10 s) by plane-wave acquisitions.

Analisys of pectoralis major tendon in weightlifting athletes using ultrasonography and elastography.

PubMed

Pochini, Alberto de Castro; Ferretti, Mario; Kawakami, Eduardo Felipe Kin Ito; Fernandes, Artur da Rocha Corrêa; Yamada, Andre Fukunishi; Oliveira, Gabriela Clemente de; Cohen, Moisés; Andreoli, Carlos Vicente; Ejnisman, Benno

2015-01-01

To evaluate tendinopathy of the pectoralis major muscle in weightlifting athletes using ultrasound and elastography. This study included 20 patients, 10 with rupture of the pectoralis major muscle and 10 control patients. We evaluated pectoralis major muscle contralateral tendon with ultrasonographic and elastography examinations. The ultrasonographic examinations were performed using a high-resolution B mode ultrasound device. The elastography evaluation was classified into three patterns: (A), if stiff (more than 50% area with blue staining); (B), if intermediate (more than 50% green); and (C), if softened (more than 50% red). Patients' mean age was 33±5.3 years. The presence of tendinous injury measured by ultrasound had a significant different (p=0.0055), because 80% of cases had tendinous injury versus 10% in the Control Group. No significant differences were seen between groups related with change in elastography (p=0.1409). Long-term bodybuilders had ultrasound image with more tendinous injury than those in Control Group. There was no statistical significance regarding change in tendon elasticity compared with Control Group.

Effect of bone-soft tissue friction on ultrasound axial shear strain elastography

NASA Astrophysics Data System (ADS)

Tang, Songyuan; Chaudhry, Anuj; Kim, Namhee; Reddy, J. N.; Righetti, Raffaella

2017-08-01

Bone-soft tissue friction is an important factor affecting several musculoskeletal disorders, frictional syndromes and the ability of a bone fracture to heal. However, this parameter is difficult to determine using non-invasive imaging modalities, especially in clinical settings. Ultrasound axial shear strain elastography is a non-invasive imaging modality that has been used in the recent past to estimate the bonding between different tissue layers. As most elastography methods, axial shear strain elastography is primarily used in soft tissues. More recently, this technique has been proposed to assess the bone-soft tissue interface. In this paper, we investigate the effect of a variation in bone-soft tissue friction coefficient in the resulting axial shear strain elastograms. Finite element poroelastic models of bone specimens exhibiting different bone-soft tissue friction coefficients were created and mechanically analyzed. These models were then imported to an ultrasound elastography simulation module to assess the presence of axial shear strain patterns. In vitro experiments were performed to corroborate selected simulation results. The results of this study show that the normalized axial shear strain estimated at the bone-soft tissue interface is statistically correlated to the bone-soft tissue coefficient of friction. This information may prove useful to better interpret ultrasound elastography results obtained in bone-related applications and, possibly, monitor bone healing.

Considering Angle Selection When Using Ultrasound Electrode Displacement Elastography to Evaluate Radiofrequency Ablation of Tissues

PubMed Central

Li, Qiang; Chen, Pin-Yu; Wang, Chiao-Yin; Liu, Hao-Li; Teng, Jianfu

2014-01-01

Percutaneous radiofrequency ablation (RFA) is a minimally invasive treatment to thermally destroy tumors. Ultrasound-based electrode-displacement elastography is an emerging technique for evaluating the region of RFA-induced lesions. The angle between the imaging probe and the RFA electrode can influence electrode-displacement elastography when visualizing the ablation zone. We explored the angle effect on electrode-displacement elastography to measure the ablation zone. Phantoms embedded with meatballs were fabricated and then ablated using an RFA system to simulate RFA-induced lesions. For each phantom, a commercial ultrasound scanner with a 7.5 MHz linear probe was used to acquire raw image data at different angles, ranging from 30° to 90° at increments of 10°, to construct electrode-displacement images and facilitate comparisons with tissue section images. The results revealed that the ablation regions detected using electrode-displacement elastography were highly correlated with those from tissue section images when the angle was between 30° and 60°. However, the boundaries of lesions were difficult to distinguish, when the angle was larger than 60°. The experimental findings suggest that angle selection should be considered to achieve reliable electrode-displacement elastography to describe ablation zones. PMID:24971347

Effect of bone-soft tissue friction on ultrasound axial shear strain elastography.

PubMed

Tang, Songyuan; Chaudhry, Anuj; Kim, Namhee; Reddy, J N; Righetti, Raffaella

2017-07-12

Bone-soft tissue friction is an important factor affecting several musculoskeletal disorders, frictional syndromes and the ability of a bone fracture to heal. However, this parameter is difficult to determine using non-invasive imaging modalities, especially in clinical settings. Ultrasound axial shear strain elastography is a non-invasive imaging modality that has been used in the recent past to estimate the bonding between different tissue layers. As most elastography methods, axial shear strain elastography is primarily used in soft tissues. More recently, this technique has been proposed to assess the bone-soft tissue interface. In this paper, we investigate the effect of a variation in bone-soft tissue friction coefficient in the resulting axial shear strain elastograms. Finite element poroelastic models of bone specimens exhibiting different bone-soft tissue friction coefficients were created and mechanically analyzed. These models were then imported to an ultrasound elastography simulation module to assess the presence of axial shear strain patterns. In vitro experiments were performed to corroborate selected simulation results. The results of this study show that the normalized axial shear strain estimated at the bone-soft tissue interface is statistically correlated to the bone-soft tissue coefficient of friction. This information may prove useful to better interpret ultrasound elastography results obtained in bone-related applications and, possibly, monitor bone healing.

System for robot-assisted real-time laparoscopic ultrasound elastography

NASA Astrophysics Data System (ADS)

Billings, Seth; Deshmukh, Nishikant; Kang, Hyun Jae; Taylor, Russell; Boctor, Emad M.

2012-02-01

Surgical robots provide many advantages for surgery, including minimal invasiveness, precise motion, high dexterity, and crisp stereovision. One limitation of current robotic procedures, compared to open surgery, is the loss of haptic information for such purposes as palpation, which can be very important in minimally invasive tumor resection. Numerous studies have reported the use of real-time ultrasound elastography, in conjunction with conventional B-mode ultrasound, to differentiate malignant from benign lesions. Several groups (including our own) have reported integration of ultrasound with the da Vinci robot, and ultrasound elastography is a very promising image guidance method for robotassisted procedures that will further enable the role of robots in interventions where precise knowledge of sub-surface anatomical features is crucial. We present a novel robot-assisted real-time ultrasound elastography system for minimally invasive robot-assisted interventions. Our system combines a da Vinci surgical robot with a non-clinical experimental software interface, a robotically articulated laparoscopic ultrasound probe, and our GPU-based elastography system. Elasticity and B-mode ultrasound images are displayed as picture-in-picture overlays in the da Vinci console. Our system minimizes dependence on human performance factors by incorporating computer-assisted motion control that automatically generates the tissue palpation required for elastography imaging, while leaving high-level control in the hands of the user. In addition to ensuring consistent strain imaging, the elastography assistance mode avoids the cognitive burden of tedious manual palpation. Preliminary tests of the system with an elasticity phantom demonstrate the ability to differentiate simulated lesions of varied stiffness and to clearly delineate lesion boundaries.

Endoscopic ultrasound elastography: Current status and future perspectives

PubMed Central

Cui, Xin-Wu; Chang, Jian-Min; Kan, Quan-Cheng; Chiorean, Liliana; Ignee, Andre; Dietrich, Christoph F

2015-01-01

Elastography is a new ultrasound modality that provides images and measurements related to tissue stiffness. Endoscopic ultrasound (EUS) has played an important role in the diagnosis and management of numerous abdominal and mediastinal diseases. Elastography by means of EUS examination can assess the elasticity of tumors in the proximity of the digestive tract that are hard to reach with conventional transcutaneous ultrasound probes, such as pancreatic masses and mediastinal or abdominal lymph nodes, thus improving the diagnostic yield of the procedure. Results from previous studies have promised benefits for EUS elastography in the differential diagnosis of lymph nodes, as well as for assessing masses with pancreatic or gastrointestinal (GI) tract locations. It is important to mention that EUS elastography is not considered a modality that can replace biopsy. However, it may be a useful adjunct, improving the accuracy of EUS-fine needle aspiration biopsy (EUS-FNAB) by selecting the most suspicious area to be targeted. Even more, it may be useful for guiding further clinical management when EUS-FNAB is negative or inconclusive. In the present paper we will discuss the current knowledge of EUS elastography, including the technical aspects, along with its applications in the differential diagnosis between benign and malignant solid pancreatic masses and lymph nodes, as well as its aid in the differentiation between normal pancreatic tissues and chronic pancreatitis. Moreover, the emergent indication and future perspectives are summarized, such as the benefit of EUS elastography in EUS-guided fine needle aspiration biopsy, and its uses for characterization of lesions in liver, biliary tract, adrenal glands and GI tract. PMID:26715804

[Real-time elastography in the diagnosis of prostate cancer: personal experience].

PubMed

Romagnoli, Andrea; Autieri, Gaspare; Centrella, Danilo; Gastaldi, Christian; Pedaci, Giuseppe; Rivolta, Lorenzo; Pozzi, Emilio; Anghileri, Alessio; Cerabino, Maurizio; Bianchi, Carlo Maria; Roggia, Alberto

2010-01-01

Prostate cancer is the most common cancer in men. In the future, a significant further increase in the incidence of prostate cancer is expected. The indication to perform a prostate biopsy is digital rectal examination suspicious for prostate cancer, total prostate specific antigen (PSA) value, free PSA/total PSA ratio, PSA density and PSA velocity, and an evidence of hypoechoic area at transrectal ultrasound scan. Unfortunately the specificity and sensibility are still poor. The aim of this retrospective study is to evaluate the specificity and sensibility of real time elastography versus ultrasound transrectal B-mode scan. We retrospectively evaluated 108 pts. having undergone TRUS-guided transrectal prostate biopsy (10 samples). The indication for biopsy is: digital rectal examination, total prostate specific antigen (PSA) value, PSA ratio, PSA density and PSA velocity suspicious for prostate cancer, and/or an evidence of hypoechoic area at transrectal ultrasound scan, and/or hard area at real-time elastography. The mean age of patients is 66.8 years, mean PSA 6.5 ng/mL, and mean ratio 16.5%. We compared the histopathological findings of needle prostate biopsies with the results of transrectal ultrasound and transrectal real-time elastography. 32/108 (29.6%) pts. were positive for prostate cancer (mean Gleason score 7.08), mean PSA 14 ng/mL and mean ratio 9.5%. Transrectal ultrasound scan shows a sensibility of 69% and specificity of 68%. Transrectal ultrasound scan shows a VPP of 51.4%. Transrectal ultrasound scan shows a VPN of 80.9%. Real-time elastography shows a sensibility of 56% and specificity of 85.7%. Real-time elastography shows a VPP of 60.1%. Real-time elastography shows a VPN of 83%. Elastography has a significantly higher specificity for the detection of prostate cancer than the conventionally used examinations including DRE and TRUS. It is a useful real-time diagnostic method because it is not invasive, and simultaneous evaluation is possible while performing TRUS.

Diagnostic performance of quantitative shear wave elastography in the evaluation of solid breast masses: determination of the most discriminatory parameter.

PubMed

Au, Frederick Wing-Fai; Ghai, Sandeep; Moshonov, Hadas; Kahn, Harriette; Brennan, Cressida; Dua, Hemi; Crystal, Pavel

2014-09-01

The purpose of this article is to assess the diagnostic performance of quantitative shear wave elastography in the evaluation of solid breast masses and to determine the most discriminatory parameter. B-mode ultrasound and shear wave elastography were performed before core biopsy of 123 masses in 112 women. The diagnostic performance of ultrasound and quantitative shear wave elastography parameters (mean elasticity, maximum elasticity, and elasticity ratio) were compared. The added effect of shear wave elastography on the performance of ultrasound was determined. The mean elasticity, maximum elasticity, and elasticity ratio were 24.8 kPa, 30.3 kPa, and 1.90, respectively, for 79 benign masses and 130.7 kPa, 154.9 kPa, and 11.52, respectively, for 44 malignant masses (p < 0.001). The optimal cutoff value for each parameter was determined to be 42.5 kPa, 46.7 kPa, and 3.56, respectively. The AUC of each shear wave elastography parameter was higher than that of ultrasound (p < 0.001); the AUC value for the elasticity ratio (0.943) was the highest. By adding shear wave elastography parameters to the evaluation of BI-RADS category 4a masses, about 90% of masses could be downgraded to BI-RADS category 3. The numbers of downgraded masses were 40 of 44 (91%) for mean elasticity, 39 of 44 (89%) for maximum elasticity, and 42 of 44 (95%) for elasticity ratio. The numbers of correctly downgraded masses were 39 of 40 (98%) for mean elasticity, 38 of 39 (97%) for maximum elasticity, and 41 of 42 (98%) for elasticity ratio. There was improvement in the diagnostic performance of ultrasound of mass assessment with shear wave elastography parameters added to BI-RADS category 4a masses compared with ultrasound alone. Combined ultrasound and elasticity ratio had the highest improvement, from 35.44% to 87.34% for specificity, from 45.74% to 80.77% for positive predictive value, and from 57.72% to 90.24% for accuracy (p < 0.0001). The AUC of combined ultrasound and elasticity ratio (0.914) was the highest compared with the other combined parameters. There was a statistically significant difference in the values of the quantitative shear wave elastography parameters of benign and malignant solid breast masses. By adding shear wave elastography parameters to BI-RADS category 4a masses, we found that about 90% of them could be correctly downgraded to BI-RADS category 3, thereby avoiding biopsy. Elasticity ratio (cutoff, 3.56) appeared to be the most discriminatory parameter.

Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Hsieh, Bao-Yu; Song, Shaozhen; Nguyen, Thu-Mai; Yoon, Soon Joon; Shen, Tueng; Wang, Ruikang; O'Donnell, Matthew

2016-03-01

Phase-sensitive optical coherence tomography (PhS-OCT) can be utilized for quantitative shear-wave elastography using speckle tracking. However, current approaches cannot directly reconstruct elastic properties in speckle-less or speckle-free regions, for example within the crystalline lens in ophthalmology. Investigating the elasticity of the crystalline lens could improve understanding and help manage presbyopia-related pathologies that change biomechanical properties. We propose to reconstruct the elastic properties in speckle-less regions by sequentially launching shear waves with moving acoustic radiation force (mARF), and then detecting the displacement at a specific speckle-generating position, or limited set of positions, with PhS-OCT. A linear ultrasound array (with a center frequency of 5 MHz) interfaced with a programmable imaging system was designed to launch shear waves by mARF. Acoustic sources were electronically translated to launch shear waves at laterally shifted positions, where displacements were detected by speckle tracking images produced by PhS-OCT operating in M-B mode with a 125-kHz A-line rate. Local displacements were calculated and stitched together sequentially based on the distance between the acoustic source and the detection beam. Shear wave speed, and the associated elasticity map, were then reconstructed based on a time-of-flight algorithm. In this study, moving-source shear wave elasticity imaging (SWEI) can highlight a stiff inclusion within an otherwise homogeneous phantom but with a CNR increased by 3.15 dB compared to a similar image reconstructed with moving-detector SWEI. Partial speckle-free phantoms were also investigated to demonstrate that the moving-source sequence could reconstruct the elastic properties of speckle-free regions. Results show that harder inclusions within the speckle-free region can be detected, suggesting that this imaging method may be able to detect the elastic properties of the crystalline lens.

Towards the Early Detection of Breast Cancer in Young Women

DTIC Science & Technology

2005-10-01

T. Shiina, and F. Tranquart. Progress in Freehand Elastography of the Breast . IEICE Transactions on Information and Systems, E85D (1):5–14, 2002. [3...Meaney, Naomi R. Miller, Tsuyoshi Shiina, and Francois Tranquart. Progress in freehand elastography of the breast . IEICE Transactions on Information...solution of the non-linear inverse elasticity problem 28 [26] Liew HL and Pinsky PM. Recovery of shear modulus in elastography using an adjoint method

The emergence of optical elastography in biomedicine

NASA Astrophysics Data System (ADS)

Kennedy, Brendan F.; Wijesinghe, Philip; Sampson, David D.

2017-04-01

Optical elastography, the use of optics to characterize and map the mechanical properties of biological tissue, involves measuring the deformation of tissue in response to a load. Such measurements may be used to form an image of a mechanical property, often elastic modulus, with the resulting mechanical contrast complementary to the more familiar optical contrast. Optical elastography is experiencing new impetus in response to developments in the closely related fields of cell mechanics and medical imaging, aided by advances in photonics technology, and through probing the microscale between that of cells and whole tissues. Two techniques -- optical coherence elastography and Brillouin microscopy -- have recently shown particular promise for medical applications, such as in ophthalmology and oncology, and as new techniques in cell mechanics.

Breast elastography: Identification of benign and malignant cancer based on absolute elastic modulus measurement using vibro-elastography

NASA Astrophysics Data System (ADS)

Arroyo, Junior; Saavedra, Ana Cecilia; Guerrero, Jorge; Montenegro, Pilar; Aguilar, Jorge; Pinto, Joseph A.; Lobo, Julio; Salcudean, Tim; Lavarello, Roberto; Castañeda, Benjamín.

2018-03-01

Breast cancer is a public health problem with 1.7 million new cases per year worldwide and with several limitations in the state-of-art screening techniques. Ultrasound elastography involves a set of techniques intended to facilitate the noninvasive diagnosis of cancer. Among these, Vibro-elastography is an ultrasound-based technique that employs external mechanical excitation to infer the elastic properties of soft tissue. In this paper, we evaluate the Vibro-elastography performance in the differentiation of benign and malignant breast lesions. For this study, a group of 18 women with clinically confirmed tumors or suspected malignant breast lesions were invited to participate. For each volunteer, an elastogram was obtained, and the mean elasticity of the lesion and the adjacent healthy tissue were calculated. After the acquisition, the volunteers underwent core-needle biopsy. The histopathological results allowed to validate the Vibro-elastography diagnosis, which ranged from benign to malignant lesions. Results indicate that the mean elasticity value of the benign lesions, malignant lesions and healthy breast tissue were 39.4 +/- 12 KPa, 55.4 +/- 7.02 KPa and 23.91 +/- 4.57 kPa, respectively. The classification between benign and malignant breast cancer was performed using Support Vector Machine based on the measured lesion stiffness. A ROC curve permitted to quantify the accuracy of the differentiation and to define a suitable cutoff value of stiffness, obtaining an AUC of 0.90 and a cutoff value of 44.75 KPa. The results obtained suggest that Vibro-elastography allows differentiating between benign and malignant lesions. Furthermore, the elasticity values obtained for benign, malignant and healthy tissue are consistent with previous reports.

Establishing ultrasound based transient elastography cutoffs for different stages of hepatic fibrosis and cirrhosis in Egyptian chronic hepatitis C patients.

PubMed

Elsharkawy, Aisha; Alboraie, Mohamed; Fouad, Rabab; Asem, Noha; Abdo, Mahmoud; Elmakhzangy, Hesham; Mehrez, Mai; Khattab, Hany; Esmat, Gamal

2017-12-01

Transient elastography is widely used to assess fibrosis stage in chronic hepatitis C (CHC). We aimed to establish and validate different transient elastography cut-off values for significant fibrosis and cirrhosis in CHC genotype 4 patients. The data of 100 treatment-naive CHC patients (training set) and 652 patients (validation set) were analysed. The patients were subjected to routine pretreatment laboratory investigations, liver biopsy and histopathological staging of hepatic fibrosis according to the METAVIR scoring system. Transient elastography was performed before and in the same week as liver biopsy using FibroScan (Echosens, Paris, France). Transient elastography results were correlated to different stages of hepatic fibrosis in both the training and validation sets. ROC curves were constructed. In the training set, the best transient elastography cut-off values for significant hepatic fibrosis (≥F2 METAVIR), advanced hepatic fibrosis (≥F3 METAVIR) and cirrhosis (F4 METAVIR) were 7.1, 9 and 12.2 kPa, with sensitivities of 87%, 87.5% and 90.9% and specificities of 100%, 99.9% and 99.9%, respectively. The application of these cut-offs in the validation set showed sensitivities of 85.5%, 82.8% and 92% and specificities of 86%, 89.4% and 99.01% for significant hepatic fibrosis, advanced hepatic fibrosis and cirrhosis, respectively. Transient elastography performs well for significant hepatic fibrosis, advanced hepatic fibrosis and cirrhosis, with validated cut-offs of 7.1, 9 and 12.2 kPa, respectively, in genotype 4 CHC patients. Copyright © 2017 Pan-Arab Association of Gastroenterology. Published by Elsevier B.V. All rights reserved.

Efficacy of an artificial neural network-based approach to endoscopic ultrasound elastography in diagnosis of focal pancreatic masses.

PubMed

Săftoiu, Adrian; Vilmann, Peter; Gorunescu, Florin; Janssen, Jan; Hocke, Michael; Larsen, Michael; Iglesias-Garcia, Julio; Arcidiacono, Paolo; Will, Uwe; Giovannini, Marc; Dietrich, Cristoph F; Havre, Roald; Gheorghe, Cristian; McKay, Colin; Gheonea, Dan Ionuţ; Ciurea, Tudorel

2012-01-01

By using strain assessment, real-time endoscopic ultrasound (EUS) elastography provides additional information about a lesion's characteristics in the pancreas. We assessed the accuracy of real-time EUS elastography in focal pancreatic lesions using computer-aided diagnosis by artificial neural network analysis. We performed a prospective, blinded, multicentric study at of 258 patients (774 recordings from EUS elastography) who were diagnosed with chronic pancreatitis (n = 47) or pancreatic adenocarcinoma (n = 211) from 13 tertiary academic medical centers in Europe (the European EUS Elastography Multicentric Study Group). We used postprocessing software analysis to compute individual frames of elastography movies recorded by retrieving hue histogram data from a dynamic sequence of EUS elastography into a numeric matrix. The data then were analyzed in an extended neural network analysis, to automatically differentiate benign from malignant patterns. The neural computing approach had 91.14% training accuracy (95% confidence interval [CI], 89.87%-92.42%) and 84.27% testing accuracy (95% CI, 83.09%-85.44%). These results were obtained using the 10-fold cross-validation technique. The statistical analysis of the classification process showed a sensitivity of 87.59%, a specificity of 82.94%, a positive predictive value of 96.25%, and a negative predictive value of 57.22%. Moreover, the corresponding area under the receiver operating characteristic curve was 0.94 (95% CI, 0.91%-0.97%), which was significantly higher than the values obtained by simple mean hue histogram analysis, for which the area under the receiver operating characteristic was 0.85. Use of the artificial intelligence methodology via artificial neural networks supports the medical decision process, providing fast and accurate diagnoses. Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.

The potential role of elastography in differentiating between endometrial polyps and submucosal fibroids: a preliminary study

PubMed Central

2015-01-01

Endometrial polyps and submucosal fibroids are common causes of abnormal uterine bleeding (AUB) and less commonly infertility. The prevalence of such intrauterine lesions increases with age during the reproductive years, and usually decreases after menopause. The first-line imaging examination in the diagnosis of endometrial polyps as well as submucosal fibroidsis ultrasound, but its accuracy is not obvious. Elastography is an ultrasound-based imaging modality that is used to assess the stiffness of examined tissues. Considering the fact that endometrial polyps derive from soft endometrial tissue and submucosal fibroids are made of hard muscle tissue, elastography seems a perfect tool to differentiate between such lesions. I present two groups of patients with AUB and intrauterine lesions suspected on ultrasound. In the first group of patients, elastography showed that the stiffness of the lesion was similar to the endometrium and softer than the myometrium. During hysteroscopies endometrial polyps were removed. In the second group of patients, elastography showed that the stiffness of the lesion was similar to the myometrium and harder than the endometrium. During hysteroscopies submucosal fibroids were removed. In both groups, the diagnosis was confirmed by the pathological examination in all cases. It was demonstrated that with the use of elastography it is possible to assess the stiffness of intrauterine lesions, which may be useful in differentiating between endometrial polyps and submucosal fibroids. PMID:26327901

The potential role of elastography in differentiating between endometrial polyps and submucosal fibroids: a preliminary study.

PubMed

Woźniak, Sławomir

2015-06-01

Endometrial polyps and submucosal fibroids are common causes of abnormal uterine bleeding (AUB) and less commonly infertility. The prevalence of such intrauterine lesions increases with age during the reproductive years, and usually decreases after menopause. The first-line imaging examination in the diagnosis of endometrial polyps as well as submucosal fibroidsis ultrasound, but its accuracy is not obvious. Elastography is an ultrasound-based imaging modality that is used to assess the stiffness of examined tissues. Considering the fact that endometrial polyps derive from soft endometrial tissue and submucosal fibroids are made of hard muscle tissue, elastography seems a perfect tool to differentiate between such lesions. I present two groups of patients with AUB and intrauterine lesions suspected on ultrasound. In the first group of patients, elastography showed that the stiffness of the lesion was similar to the endometrium and softer than the myometrium. During hysteroscopies endometrial polyps were removed. In the second group of patients, elastography showed that the stiffness of the lesion was similar to the myometrium and harder than the endometrium. During hysteroscopies submucosal fibroids were removed. In both groups, the diagnosis was confirmed by the pathological examination in all cases. It was demonstrated that with the use of elastography it is possible to assess the stiffness of intrauterine lesions, which may be useful in differentiating between endometrial polyps and submucosal fibroids.

Repeatability of shear wave elastography in liver fibrosis phantoms—Evaluation of five different systems

PubMed Central

2018-01-01

This study aimed to assess and validate the repeatability and agreement of quantitative elastography of novel shear wave methods on four individual tissue-mimicking liver fibrosis phantoms with different known Young’s modulus. We used GE Logiq E9 2D-SWE, Philips iU22 ARFI (pSWE), Samsung TS80A SWE (pSWE), Hitachi Ascendus (SWM) and Transient Elastography (TE). Two individual investigators performed all measurements non-continued and in parallel. The methods were evaluated for inter- and intraobserver variability by intraclass correlation, coefficient of variation and limits of agreement using the median elastography value. All systems used in this study provided high repeatability in quantitative measurements in a liver fibrosis phantom and excellent inter- and intraclass correlations. All four elastography platforms showed excellent intra-and interobserver agreement (interclass correlation 0.981–1.000 and intraclass correlation 0.987–1.000) and no significant difference in mean elasticity measurements for all systems, except for TE on phantom 4. All four liver fibrosis phantoms could be differentiated by quantitative elastography, by all platforms (p<0.001). In the Bland-Altman analysis the differences in measurements were larger for the phantoms with higher Young’s modulus. All platforms had a coefficient of variation in the range 0.00–0.21 for all four phantoms, equivalent to low variance and high repeatability. PMID:29293527

[Differential diagnostic value of real-time tissue elastography and three dimensional ultrasound imaging in breast lumps].

PubMed

Li, M H; Liu, Y; Liu, L S; Li, P X; Chen, Q

2016-05-24

To investigate the real-time tissue elastography and 3D contrast-enhanced ultrasonography(CEUS) in breast lumps differential diagnostic value. A total of 126 patients (180 lumps) with breast mass were retrospectively analyzed from December 2012 to December 2014 in Tumor Hospital Affiliated To Xinjiang Medical University.All patients were divided into three groups by using stratified random method.Each group was detected by real-time tissue elastography, 3D CEUS and two joint inspection.Each group of 42 cases (60 lumps) was confirmed by the pathological results as gold standard.Diagnostic sensitivity, specificity and coincidence rate of different methods were compared. The benign masses of ultrasound contrast showed the punctate, linear and nodular enhancement, and the border of enhancement was smooth.The malignant tumors were mainly dominated by uneven and high enhancement. There was no statistical difference in sensitivity, specificity and coincidence rate between elastography group and 3D CEUS group (64.7% vs 73.5%, 69.2% vs 76.9%, 66.7% vs 75.0%, all P>0.05). The sensitivity, specificity and coincidence rate of two joint inspection group were higher than those of elastography group and 3D CEUS group, the differences were statistically significant (97.1%, 92.3% and 98.3% , all P<0.05). 3D CEUS combined with real-time tissue elastography is of high value in the diagnosis of breast masses.

Tissue elasticity of in vivo skeletal muscles measured in the transverse and longitudinal planes using shear wave elastography.

PubMed

Chino, Kentaro; Kawakami, Yasuo; Takahashi, Hideyuki

2017-07-01

The aim of the present study was to measure in vivo skeletal muscle elasticity in the transverse and longitudinal planes using shear wave elastography and then to compare the image stability, measurement values and measurement repeatability between these imaging planes. Thirty-one healthy males participated in this study. Tissue elasticity (shear wave velocity) of the medial gastrocnemius, rectus femoris, biceps brachii and rectus abdominis was measured in both the transverse and longitudinal planes using shear wave elastography. Image stability was evaluated by the standard deviation of the colour distribution in the shear wave elastography image. Measurement repeatability was assessed by the coefficient of variance obtained from three measurement values. Image stability of all tested muscles was significantly higher in the longitudinal plane (P<0·001), but measurement repeatability did not differ significantly between the imaging planes (P>0·05), except in the biceps brachii (P = 0·001). Measurement values of the medial gastrocnemius, rectus femoris and biceps brachii were significantly different between the imaging planes (P<0·001). Image stability and measurement values of shear wave elastography images varied with imaging plane, which indicates that imaging plane should be considered when measuring skeletal muscle tissue elasticity by shear wave elastography. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Synergistic advances in diagnostic and therapeutic medical ultrasound

NASA Astrophysics Data System (ADS)

Lizzi, Frederic L.

2003-04-01

Significant advances are more fully exploiting ultrasound's potential for noninvasive diagnosis and treatment. Therapeutic systems employ intense focused beams to thermally kill cancer cells in, e.g., prostate; to stop bleeding; and to treat specific diseases (e.g., glaucoma). Diagnostic ultrasound techniques can quantitatively image an increasingly broad spectrum of physical tissue attributes. An exciting aspect of this progress is the emerging synergy between these modalities. Advanced diagnostic techniques may contribute at several stages in therapy. For example, treatment planning for small ocular tumors uses 50-MHz, 3-D ultrasonic images with 0.05-mm resolution. Thermal simulations employ these images to evaluate desired and undesired effects using exposure stategies with specially designed treatment beams. Therapy beam positioning can use diagnostic elastography to sense tissue motion induced by radiation pressure from high-intensity treatment beams. Therapy monitoring can sense lesion formation using elastography motion sensing (to detect the increased stiffness in lesions); harmonic imaging (to sense altered nonlinear properties); and spectrum analysis images (depicting changes in the sizes, concentration, and configuration of sub-resolution structures.) Experience from these applications will greatly expand the knowledge of acoustic phenomena in living tissues and should lead to further advances in medical ultrasound.

Development of novel imaging probe for optical/acoustic radiation imaging (OARI).

PubMed

Ejofodomi, O'tega A; Zderic, Vesna; Zara, Jason M

2013-11-01

Optical/acoustic radiation imaging (OARI) is a novel imaging modality being developed to interrogate the optical and mechanical properties of soft tissues. OARI uses acoustic radiation force to generate displacement in soft tissue. Optical images before and after the application of the force are used to generate displacement maps that provide information about the mechanical properties of the tissue under interrogation. Since the images are optical images, they also represent the optical properties of the tissue as well. In this paper, the authors present the first imaging probe that uses acoustic radiation force in conjunction with optical coherence tomography (OCT) to provide information about the optical and mechanical properties of tissues to assist in the diagnosis and staging of epithelial cancers, and in particular bladder cancer. The OARI prototype probe consisted of an OCT probe encased in a plastic sheath, a miniaturized transducer glued to a plastic holder, both of which were encased in a 10 cm stainless steel tube with an inner diameter of 10 mm. The transducer delivered an acoustic intensity of 18 W/cm(2) and the OCT probe had a spatial resolution of approximately 10-20 μm. The tube was filled with deionized water for acoustic coupling and covered by a low density polyethylene cap. The OARI probe was characterized and tested on bladder wall phantoms. The phantoms possessed Young's moduli ranging from 10.2 to 12 kPa, mass density of 1.05 g/cm(3), acoustic attenuation coefficient of 0.66 dB/cm MHz, speed of sound of 1591 m/s, and optical scattering coefficient of 1.80 mm(-1). Finite element model (FEM) theoretical simulations were performed to assess the performance of the OARI probe. The authors obtained displacements of 9.4, 8.7, and 3.4 μm for the 3%, 4%, and 5% bladder wall phantoms, respectively. This shows that the probe is capable of generating optical images, and also has the ability to generate and track displacements in tissue. This will provide information about the optical and mechanical properties of the tissue to assist in epithelial cancer detection. The corresponding theoretical FEM displacement was 5.8, 5.4, and 5.0 μm for the 3%, 4%, and 5% phantoms, respectively. Deviation between OARI displacement and FEM displacement is due to the resolution of the crosscorrelation algorithm used to track the displacement. To the authors' knowledge, this is the first probe that successfully combines OCT with a source of acoustic radiation force. The OARI probe has the ability to provide information about the mechanical and optical properties of phantoms and soft tissue. This could prove useful in early epithelial cancer detection. Because the probe is 10 mm in diameter, it is currently only useful for skin and oral applications. The probe would have to be reduced in size to make it applicable for cancer detection in other internal sites. Future work will focus on utilizing phase-sensitive optical coherence elastography to obtain the resulting OARI displacements, improving the resolution of the probe, and enable physicians to better evaluate the mechanical properties of soft tissues.

Analisys of pectoralis major tendon in weightlifting athletes using ultrasonography and elastography

PubMed Central

Pochini, Alberto de Castro; Ferretti, Mario; Kawakami, Eduardo Felipe Kin Ito; Fernandes, Artur da Rocha Corrêa; Yamada, Andre Fukunishi; de Oliveira, Gabriela Clemente; Cohen, Moisés; Andreoli, Carlos Vicente; Ejnisman, Benno

2015-01-01

ABSTRACT Objective To evaluate tendinopathy of the pectoralis major muscle in weightlifting athletes using ultrasound and elastography. Methods This study included 20 patients, 10 with rupture of the pectoralis major muscle and 10 control patients. We evaluated pectoralis major muscle contralateral tendon with ultrasonographic and elastography examinations. The ultrasonographic examinations were performed using a high-resolution B mode ultrasound device. The elastography evaluation was classified into three patterns: (A), if stiff (more than 50% area with blue staining); (B), if intermediate (more than 50% green); and (C), if softened (more than 50% red). Results Patients’ mean age was 33±5.3 years. The presence of tendinous injury measured by ultrasound had a significant different (p=0.0055), because 80% of cases had tendinous injury versus 10% in the Control Group. No significant differences were seen between groups related with change in elastography (p=0.1409). Conclusion Long-term bodybuilders had ultrasound image with more tendinous injury than those in Control Group. There was no statistical significance regarding change in tendon elasticity compared with Control Group. PMID:26761551

The role of ultrasound elastographic techniques in chronic liver disease: current status and future perspectives.

PubMed

Piscaglia, Fabio; Marinelli, Sara; Bota, Simona; Serra, Carla; Venerandi, Laura; Leoni, Simona; Salvatore, Veronica

2014-03-01

This review illustrates the state of the art clinical applications and the future perspectives of ultrasound elastographic methods for the evaluation of chronic liver diseases, including the most widely used and validated technique, transient elastography, followed by shear wave elastography and strain imaging elastography. Liver ultrasound elastography allows the non-invasive evaluation of liver stiffness, providing information regarding the stage of fibrosis, comparable to liver biopsy which is still considered the gold standard; in this way, it can help physicians in managing patients, including the decision as to when to start antiviral treatment. The characterization of focal liver lesions and the prognostic role of the elastographic technique in the prediction of complications of cirrhosis are still under investigation. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

A first demonstration of audio-frequency optical coherence elastography of tissue

NASA Astrophysics Data System (ADS)

Adie, Steven G.; Alexandrov, Sergey A.; Armstrong, Julian J.; Kennedy, Brendan F.; Sampson, David D.

2008-12-01

Optical elastography is aimed at using the visco-elastic properties of soft tissue as a contrast mechanism, and could be particularly suitable for high-resolution differentiation of tumour from surrounding normal tissue. We present a new approach to measure the effect of an applied stimulus in the kilohertz frequency range that is based on optical coherence tomography. We describe the approach and present the first in vivo optical coherence elastography measurements in human skin at audio excitation frequencies.

Assessing Age-Related Changes in the Biomechanical Properties of Rabbit Lens Using a Coaligned Ultrasound and Optical Coherence Elastography System

PubMed Central

Wu, Chen; Han, Zhaolong; Wang, Shang; Li, Jiasong; Singh, Manmohan; Liu, Chih-hao; Aglyamov, Salavat; Emelianov, Stanislav; Manns, Fabrice; Larin, Kirill V.

2015-01-01

Purpose. To evaluate the capability of a novel, coaligned focused ultrasound and phase-sensitive optical coherence elastography (US-OCE) system to assess age-related changes in biomechanical properties of the crystalline lens in situ. Methods. Low-amplitude elastic deformations in young and mature rabbit lenses were measured by an US-OCE system consisting of a spectral-domain optical coherence tomography (OCT) system coaligned with a focused ultrasound system used to produce a transient force on the lens surface. Uniaxial compressional tests were used to validate the OCE data. Results. The OCE measurements showed that the maximum displacements of the young rabbit lenses were significantly larger than those of the mature lenses, indicating a gradual increase of the lens stiffness with age. Temporal analyses of the displacements also demonstrate a similar trend of elastic properties in these lenses. The stress-strain measurements using uniaxial mechanical tests confirmed the results obtained by the US-OCE system. Conclusions. The results demonstrate that the US-OCE system can be used for noninvasive analysis and quantification of lens biomechanical properties in situ and possibly in vivo. PMID:25613945

Modeling and measurement of tissue elastic moduli using optical coherence elastography

NASA Astrophysics Data System (ADS)

Liang, Xing; Oldenburg, Amy L.; Crecea, Vasilica; Kalyanam, Sureshkumar; Insana, Michael F.; Boppart, Stephen A.

2008-02-01

Mechanical forces play crucial roles in tissue growth, patterning and development. To understand the role of mechanical stimuli, biomechanical properties are of great importance, as well as our ability to measure biomechanical properties of developing and engineered tissues. To enable these measurements, a novel non-invasive, micron-scale and high-speed Optical Coherence Elastography (OCE) system has been developed utilizing a titanium:sapphire based spectral-domain Optical Coherence Tomography (OCT) system and a mechanical wave driver. This system provides axial resolution of 3 microns, transverse resolution of 13 microns, and an acquisition rate as high as 25,000 lines per second. External lowfrequency vibrations are applied to the samples in the system. Step and sinusoidal steady-state responses are obtained to first characterize the OCE system and then characterize samples. Experimental results of M-mode OCE on silicone phantoms and human breast tissues are obtained, which correspond to biomechanical models developed for this analysis. Quantified results from the OCE system correspond directly with results from an indentation method from a commercial. With micron-scale resolution and a high-speed acquisition rate, our OCE system also has the potential to rapidly measure dynamic 3-D tissue biomechanical properties.

A haptic sensor-actor-system based on ultrasound elastography and electrorheological fluids for virtual reality applications in medicine.

PubMed

Khaled, W; Ermert, H; Bruhns, O; Boese, H; Baumann, M; Monkman, G J; Egersdoerfer, S; Meier, A; Klein, D; Freimuth, H

2003-01-01

Mechanical properties of biological tissue represent important diagnostic information and are of histological relevance (hard lesions, "nodes" in organs: tumors; calcifications in vessels: arteriosclerosis). The problem is, that such information is usually obtained by digital palpation only, which is limited with respect to sensitivity. It requires intuitive assessment and does not allow quantitative documentation. A suitable sensor is required for quantitative detection of mechanical tissue properties. On the other hand, there is also some need for a realistic mechanical display of those tissue properties. Suitable actuator arrays with high spatial resolution and real-time capabilities are required operating in a haptic sensor actuator system with different applications. The sensor system uses real time ultrasonic elastography whereas the tactile actuator is based on electrorheological fluids. Due to their small size the actuator array elements have to be manufactured by micro-mechanical production methods. In order to supply the actuator elements with individual high voltages a sophisticated switching and control concept have been designed. This haptic system has the potential of inducing real time substantial forces, using a compact lightweight mechanism which can be applied to numerous areas including intraoperative navigation, telemedicine, teaching, space and telecommunication.

Reproducibility of shear wave elastography (SWE) in patients with chronic liver disease

PubMed Central

Salomone Megna, Angelo; Ragucci, Monica; De Luca, Massimo; Marino Marsilia, Giuseppina; Nardone, Gerardo; Coccoli, Pietro; Prinster, Anna; Mannelli, Lorenzo; Vergara, Emilia; Monti, Serena; Liuzzi, Raffaele; Incoronato, Mariarosaria

2017-01-01

The presence of significant fibrosis is an indicator for liver disease staging and prognosis. The aim of the study was to determine reproducibility of real-time shear wave elastography using a hepatic biopsy as the reference standard to identify patients with chronic liver disease. Forty patients with chronic liver disease and 12 normal subjects received shear wave elastography performed by skilled operators. Interoperator reproducibility was studied in 29 patients. Fibrosis was evaluated using the Metavir score. The median and range shear wave elastography values in chronic liver disease subjects were 6.15 kPa and 3.14–16.7 kPa and were 4.49 kPa and 2.92–7.32 kPa in normal subjects, respectively. With respect to fibrosis detected by liver biopsy, shear wave elastography did not change significantly between F0 and F1 (p = 0.334), F1 and F2 (p = 0.611), or F3 and F4 (0.327); a significant difference was observed between the F0-F2 and F3-F4 groups (p = 0.002). SWE also correlated with inflammatory activity (Rs = 0.443, p = 0.0023) and ALT levels (Rs = 0.287, p = 0.0804). Age, sex and body mass index did not affect shear wave elastography measurements. Using receiver operator characteristic curves, two threshold values for shear wave elastography were identified: 5.62 kPa for patients with fibrosis (≥F2; sensitivity 80%, specificity 69.4%, and accuracy 77%) and 7.04 kPa for patients with severe fibrosis (≥F3; sensitivity 88.9%, specificity 81%, and accuracy 89%). Overall interobserver agreement was excellent and was analysed using an interclass correlation coefficient (0.94; CI 0.87–0.97).This study shows that shear wave elastography executed by skilled operators can be performed on almost all chronic liver disease patients with high reproducibility. It is not influenced by age, sex or body mass index, identifies severely fibrotic patients and is also related to inflammatory activity. PMID:29023554

Comb-push Ultrasound Shear Elastography (CUSE) with Various Ultrasound Push Beams

PubMed Central

Song, Pengfei; Urban, Matthew W.; Manduca, Armando; Zhao, Heng; Greenleaf, James F.; Chen, Shigao

2013-01-01

Comb-push Ultrasound Shear Elastography (CUSE) has recently been shown to be a fast and accurate two-dimensional (2D) elasticity imaging technique that can provide a full field-of- view (FOV) shear wave speed map with only one rapid data acquisition. The initial version of CUSE was termed U-CUSE because unfocused ultrasound push beams were used. In this paper, we present two new versions of CUSE – Focused CUSE (F-CUSE) and Marching CUSE (M-CUSE), which use focused ultrasound push beams to improve acoustic radiation force penetration and produce stronger shear waves in deep tissues (e.g. kidney and liver). F-CUSE divides transducer elements into several subgroups which transmit multiple focused ultrasound beams simultaneously. M-CUSE uses more elements for each focused push beam and laterally marches the push beams. Both F-CUSE and M-CUSE can generate comb-shaped shear wave fields that have shear wave motion at each imaging pixel location so that a full FOV 2D shear wave speed map can be reconstructed with only one data acquisition. Homogeneous phantom experiments showed that U-CUSE, F-CUSE and M-CUSE can all produce smooth shear wave speed maps with accurate shear wave speed estimates. An inclusion phantom experiment showed that all CUSE methods could provide good contrast between the inclusion and background with sharp boundaries while F-CUSE and M-CUSE require shorter push durations to achieve shear wave speed maps with comparable SNR to U-CUSE. A more challenging inclusion phantom experiment with a very stiff and deep inclusion shows that better shear wave penetration could be gained by using F-CUSE and M-CUSE. Finally, a shallow inclusion experiment showed that good preservations of inclusion shapes could be achieved by both U-CUSE and F-CUSE in the near field. Safety measurements showed that all safety parameters are below FDA regulatory limits for all CUSE methods. These promising results suggest that, using various push beams, CUSE is capable of reconstructing a 2D full FOV shear elasticity map using only one push-detection data acquisition in a wide range of depths for soft tissue elasticity imaging. PMID:23591479

Comb-push ultrasound shear elastography (CUSE) with various ultrasound push beams.

PubMed

Song, Pengfei; Urban, Matthew W; Manduca, Armando; Zhao, Heng; Greenleaf, James F; Chen, Shigao

2013-08-01

Comb-push ultrasound shear elastography (CUSE) has recently been shown to be a fast and accurate 2-D elasticity imaging technique that can provide a full field-of-view (FOV) shear wave speed map with only one rapid data acquisition. The initial version of CUSE was termed U-CUSE because unfocused ultrasound push beams were used. In this paper, we present two new versions of CUSE-focused CUSE (F-CUSE) and marching CUSE (M-CUSE), which use focused ultrasound push beams to improve acoustic radiation force penetration and produce stronger shear waves in deep tissues (e.g., kidney and liver). F-CUSE divides transducer elements into several subgroups which transmit multiple focused ultrasound beams simultaneously. M-CUSE uses more elements for each focused push beam and laterally marches the push beams. Both F-CUSE and M-CUSE can generate comb-shaped shear wave fields that have shear wave motion at each imaging pixel location so that a full FOV 2-D shear wave speed map can be reconstructed with only one data acquisition. Homogeneous phantom experiments showed that U-CUSE, F-CUSE, and M-CUSE can all produce smooth shear wave speed maps with accurate shear wave speed estimates. An inclusion phantom experiment showed that all CUSE methods could provide good contrast between the inclusion and background with sharp boundaries while F-CUSE and M-CUSE require shorter push durations to achieve shear wave speed maps with comparable SNR to U-CUSE. A more challenging inclusion phantom experiment with a very stiff and deep inclusion shows that better shear wave penetration could be gained by using F-CUSE and M-CUSE. Finally, a shallow inclusion experiment showed that good preservations of inclusion shapes could be achieved by both U-CUSE and F-CUSE in the near field. Safety measurements showed that all safety parameters are below FDA regulatory limits for all CUSE methods. These promising results suggest that, using various push beams, CUSE is capable of reconstructing a 2-D full FOV shear elasticity map using only one push-detection data acquisition in a wide range of depths for soft tissue elasticity imaging.

[Shear waves elastography of the placenta in pregnant baboon].

PubMed

Quarello, E; Lacoste, R; Mancini, J; Melot-Dusseau, S; Gorincour, G

2015-03-01

To evaluate tissue characteristics of the placenta by transabdominal ShearWave Elastography in pregnant baboon. For 9 months (03/2013-12/2013) two operators (EQ, GG) performed ultrasound of the placenta during pregnancy pregnant baboons station partner primatology project. The identification of the placenta was performed previously in 2D ultrasound. The elastography method was then activated. Three measurements were carried out by operator for each placenta. The intraclass correlation coefficients within and between observers were calculated for the objective assessment (elastography) of placental maturity. During the study period, 21 pregnant baboons were included and ultrasounds were performed between 1 and 3 times each. The measurements have been carried out by two operators in 100% of cases. The intra- and inter-observer ICC for single values are respectively 0.657 - 95% CI (0.548 to 0.752) and 0.458 - 95% CI (0.167 to 0.675). The intra- and inter-observer ICC for average values are respectively 0.852 - 95% CI (0.784 to 0.901) and 0.628 - 95% CI (0.286 to 0.806). The study by transabdominal ShearWave Elastography of placenta's pregnant baboons is possible. The intra- and inter-operator reproducibility of this method is good using the average of three measurements. The objective study via elastography ShearWave of the degree of placental maturity seems not yet be used in clinical practice. Studies of larger cohorts are needed. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Optical coherence tomography detection of shear wave propagation in inhomogeneous tissue equivalent phantoms and ex-vivo carotid artery samples

PubMed Central

Razani, Marjan; Luk, Timothy W.H.; Mariampillai, Adrian; Siegler, Peter; Kiehl, Tim-Rasmus; Kolios, Michael C.; Yang, Victor X.D.

2014-01-01

In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) in an inhomogeneous phantom and carotid artery samples based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a piezoelectric transducer transmitting sine-wave bursts of 400 μs duration, applying acoustic radiation force (ARF) to inhomogeneous phantoms and carotid artery samples, synchronized with a swept-source OCT (SS-OCT) imaging system. The phantoms were composed of gelatin and titanium dioxide whereas the carotid artery samples were embedded in gel. Differential OCT phase maps, measured with and without the ARF, detected the microscopic displacement generated by shear wave propagation in these phantoms and samples of different stiffness. We present the technique for calculating tissue mechanical properties by propagating shear waves in inhomogeneous tissue equivalent phantoms and carotid artery samples using the ARF of an ultrasound transducer, and measuring the shear wave speed and its associated properties in the different layers with OCT phase maps. This method lays the foundation for future in-vitro and in-vivo studies of mechanical property measurements of biological tissues such as vascular tissues, where normal and pathological structures may exhibit significant contrast in the shear modulus. PMID:24688822

Instrument for determining the complex shear modulus of soft-tissue-like materials from 10 to 300 Hz

PubMed Central

Madsen, E L; Frank, G R; Hobson, M A; Lin-Gibson, S; Hall, T J; Jiang, J; Stiles, T A

2010-01-01

Accurate determination of the complex shear modulus of soft tissues and soft-tissue-like materials in the 10–300 Hz frequency range is very important to researchers in MR elastography and acoustic radiation force impulse (ARFI) imaging. A variety of instruments for making such measurements has been reported, but none of them is easily reproduced, and none have been tested to conform to causality via the Kramers–Kronig (K-K) relations. A promising linear oscillation instrument described in a previous brief report operates between 20 and 160 Hz, but results were not tested for conformity to the K-K relations. We have produced a similar instrument with our own version of the electronic components and have also accounted for instrumental effects on the data reduction, which is not addressed in the previous report. The improved instrument has been shown to conform to an accurate approximation of the K-K relations over the 10–300 Hz range. The K-K approximation is based on the Weichert mechanical circuit model. We also found that the sample thickness must be small enough to obtain agreement with a calibrated commercial rheometer. A complete description of the improved instrument is given, facilitating replication in other labs. PMID:18758002

Measurement of mechanical properties of homogeneous tissue with ultrasonically induced shear waves

NASA Astrophysics Data System (ADS)

Greenleaf, James F.; Chen, Shigao

2007-03-01

Fundamental mechanical properties of tissue are altered by many diseases. Regional and systemic diseases can cause changes in tissue properties. Liver stiffness is caused by cirrhosis and fibrosis. Vascular wall stiffness and tone are altered by smoking, diabetes and other diseases. Measurement of tissue mechanical properties has historically been done with palpation. However palpation is subjective, relative, and not quantitative or reproducible. Elastography in which strain is measured due to stress application gives a qualitative estimate of Young's modulus at low frequency. We have developed a method that takes advantage of the fact that the wave equation is local and shear wave propagation depends only on storage and loss moduli in addition to density, which does not vary much in soft tissues. Our method is called shearwave dispersion ultrasonic velocity measurement (SDUV). The method uses ultrasonic radiation force to produce repeated motion in tissue that induces shear waves to propagate. The shear wave propagation speed is measured with pulse echo ultrasound as a function of frequency of the shear wave. The resulting velocity dispersion curve is fit with a Voight model to determine the elastic and viscous moduli of the tissue. Results indicate accurate and precise measurements are possible using this "noninvasive biopsy" method. Measurements in beef along and across the fibers are consistent with the literature values.

A Freehand Ultrasound Elastography System with Tracking for In-vivo Applications

PubMed Central

Foroughi, Pezhman; Kang, Hyun-Jae; Carnegie, Daniel A.; van Vledder, Mark G.; Choti, Michael A.; Hager, Gregory D.; Boctor, Emad M.

2012-01-01

Ultrasound transducers are commonly tracked in modern ultrasound navigation/guidance systems. In this paper, we demonstrate the advantages of incorporating tracking information into ultrasound elastography for clinical applications. First, we address a common limitation of freehand palpation: speckle decorrelation due to out-of-plane probe motion. We show that by automatically selecting pairs of radio frequency (RF) frames with minimal lateral and out-of-plane motions combined with a fast and robust displacement estimation technique greatly improves in-vivo elastography results. We also use tracking information and image quality measure to fuse multiple images with similar strain that are taken roughly from the same location to obtain a high quality elastography image. Finally, we show that tracking information can be used to give the user partial control over the rate of compression. Our methods are tested on tissue mimicking phantom and experiments have been conducted on intra-operative data acquired during animal and human experiments involving liver ablation. Our results suggest that in challenging clinical conditions, our proposed method produces reliable strain images and eliminates the need for a manual search through the ultrasound data in order to find RF pairs suitable for elastography. PMID:23257351

Full skin quantitative optical coherence elastography achieved by combining vibration and surface acoustic wave methods

NASA Astrophysics Data System (ADS)

Li, Chunhui; Guan, Guangying; Huang, Zhihong; Wang, Ruikang K.; Nabi, Ghulam

2015-03-01

By combining with the phase sensitive optical coherence tomography (PhS-OCT), vibration and surface acoustic wave (SAW) methods have been reported to provide elastography of skin tissue respectively. However, neither of these two methods can provide the elastography in full skin depth in current systems. This paper presents a feasibility study on an optical coherence elastography method which combines both vibration and SAW in order to give the quantitative mechanical properties of skin tissue with full depth range, including epidermis, dermis and subcutaneous fat. Experiments are carried out on layered tissue mimicking phantoms and in vivo human forearm and palm skin. A ring actuator generates vibration while a line actuator were used to excited SAWs. A PhS-OCT system is employed to provide the ultrahigh sensitive measurement of the generated waves. The experimental results demonstrate that by the combination of vibration and SAW method the full skin bulk mechanical properties can be quantitatively measured and further the elastography can be obtained with a sensing depth from ~0mm to ~4mm. This method is promising to apply in clinics where the quantitative elasticity of localized skin diseases is needed to aid the diagnosis and treatment.

Shear wave velocity imaging using transient electrode perturbation: phantom and ex vivo validation.

PubMed

DeWall, Ryan J; Varghese, Tomy; Madsen, Ernest L

2011-03-01

This paper presents a new shear wave velocity imaging technique to monitor radio-frequency and microwave ablation procedures, coined electrode vibration elastography. A piezoelectric actuator attached to an ablation needle is transiently vibrated to generate shear waves that are tracked at high frame rates. The time-to-peak algorithm is used to reconstruct the shear wave velocity and thereby the shear modulus variations. The feasibility of electrode vibration elastography is demonstrated using finite element models and ultrasound simulations, tissue-mimicking phantoms simulating fully (phantom 1) and partially ablated (phantom 2) regions, and an ex vivo bovine liver ablation experiment. In phantom experiments, good boundary delineation was observed. Shear wave velocity estimates were within 7% of mechanical measurements in phantom 1 and within 17% in phantom 2. Good boundary delineation was also demonstrated in the ex vivo experiment. The shear wave velocity estimates inside the ablated region were higher than mechanical testing estimates, but estimates in the untreated tissue were within 20% of mechanical measurements. A comparison of electrode vibration elastography and electrode displacement elastography showed the complementary information that they can provide. Electrode vibration elastography shows promise as an imaging modality that provides ablation boundary delineation and quantitative information during ablation procedures.

Application of Elastography for the Noninvasive Assessment of Biomechanics in Engineered Biomaterials and Tissues

PubMed Central

Kim, Woong; Ferguson, Virginia L.; Borden, Mark; Neu, Corey P.

2016-01-01

The elastic properties of engineered biomaterials and tissues impact their post-implantation repair potential and structural integrity, and are critical to help regulate cell fate and gene expression. The measurement of properties (e.g., stiffness or shear modulus) can be attained using elastography, which exploits noninvasive imaging modalities to provide functional information of a material indicative of the regeneration state. In this review, we outline the current leading elastography methodologies available to characterize the properties of biomaterials and tissues suitable for repair and mechanobiology research. We describe methods utilizing magnetic resonance, ultrasound, and optical coherent elastography, highlighting their potential for longitudinal monitoring of implanted materials in vivo, in addition to spatiotemporal limits of each method for probing changes in cell-laden constructs. Micro-elastography methods now allow acquisitions at length scales approaching 5–100 μm in two and three dimensions. Many of the methods introduced in this review are therefore capable of longitudinal monitoring in biomaterials and tissues approaching the cellular scale. However, critical factors such as anisotropy, heterogeneity and viscoelasity—inherent in many soft tissues—are often not fully described and therefore require further advancements and future developments. PMID:26790865

Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Zorgani, Ali; Lescanne, Maxime; Boccara, Claude; Fink, Mathias; Catheline, Stefan

2016-12-01

Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography.

PubMed

Nguyen, Thu-Mai; Zorgani, Ali; Lescanne, Maxime; Boccara, Claude; Fink, Mathias; Catheline, Stefan

2016-12-01

Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

Usefulness of elastography in predicting the outcome of Foley catheter labour induction.

PubMed

Wozniak, Slawomir; Czuczwar, Piotr; Szkodziak, Piotr; Paszkowski, Tomasz

2015-06-01

Incorrect selection of women for labour induction may increase the risk of caesarean section and other postpartum and neonatal complications. It has been recently shown that elastography of the uterine cervix holds the potential to predict the outcome of pharmacological labour induction. There are no data on the usefulness of elastography in predicting the outcome of mechanical induction of labour. To assess the usefulness of elastographic cervical assessment in predicting the success of Foley catheter labour induction. This prospective observational study included 39 pregnant women at term with an unfavourable cervix (Bishop score ≤ 6) suitable for Foley catheter labour induction. Before labour induction the following data were recorded: Bishop score, cervical length (measured by ultrasound) and the stiffness of cervical internal os, canal and external os assessed by elastography (elastography index - EI). Statistical relationships between pre-interventional assessment of the cervix and outcome of Foley catheter labour induction (successful induction, time to delivery and route of delivery) were analysed. EI's of internal cervical os and cervical canal were significantly lower (softer) in women with successful labour induction and vaginal delivery, while EI's of the external cervical os, Bishop score and cervix length were not significantly different. Time to vaginal delivery was significantly correlated with the EI's of internal cervical os, cervical canal and Bishop score, but not with EI's of the external cervical os and cervix length. Elastography has the potential to predict the outcome of Foley catheter labour induction. © 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.

Shear wave induced resonance elastography of spherical masses with polarized torsional waves

NASA Astrophysics Data System (ADS)

Hadj Henni, Anis; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

2012-03-01

Shear wave induced resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an invitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary invivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection.

Shear wave induced resonance elastography of spherical masses with polarized torsional waves.

PubMed

Henni, Anis Hadj; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

2012-03-26

Shear Wave Induced Resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an in vitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary in vivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection.

Shear Wave Velocity Imaging Using Transient Electrode Perturbation: Phantom and ex vivo Validation

PubMed Central

Varghese, Tomy; Madsen, Ernest L.

2011-01-01

This paper presents a new shear wave velocity imaging technique to monitor radio-frequency and microwave ablation procedures, coined electrode vibration elastography. A piezoelectric actuator attached to an ablation needle is transiently vibrated to generate shear waves that are tracked at high frame rates. The time-to-peak algorithm is used to reconstruct the shear wave velocity and thereby the shear modulus variations. The feasibility of electrode vibration elastography is demonstrated using finite element models and ultrasound simulations, tissue-mimicking phantoms simulating fully (phantom 1) and partially ablated (phantom 2) regions, and an ex vivo bovine liver ablation experiment. In phantom experiments, good boundary delineation was observed. Shear wave velocity estimates were within 7% of mechanical measurements in phantom 1 and within 17% in phantom 2. Good boundary delineation was also demonstrated in the ex vivo experiment. The shear wave velocity estimates inside the ablated region were higher than mechanical testing estimates, but estimates in the untreated tissue were within 20% of mechanical measurements. A comparison of electrode vibration elastography and electrode displacement elastography showed the complementary information that they can provide. Electrode vibration elastography shows promise as an imaging modality that provides ablation boundary delineation and quantitative information during ablation procedures. PMID:21075719

A novel shape similarity based elastography system for prostate cancer assessment

NASA Astrophysics Data System (ADS)

Wang, Haisu; Mousavi, Seyed Reza; Samani, Abbas

2012-03-01

Prostate cancer is the second common cancer among men worldwide and remains the second leading cancer-related cause of death in mature men. The disease can be cured if it is detected at early stage. This implies that prostate cancer detection at early stage is very critical for desirable treatment outcome. Conventional techniques of prostate cancer screening and detection, such as Digital Rectal Examination (DRE), Prostate-Specific Antigen (PSA) and Trans Rectal Ultra-Sonography (TRUS), are known to have low sensitivity and specificity. Elastography is an imaging technique that uses tissue stiffness as contrast mechanism. As the association between the degree of prostate tissue stiffness alteration and its pathology is well established, elastography can potentially detect prostate cancer with a high degree of sensitivity and specificity. In this paper, we present a novel elastography technique which, unlike other elastography techniques, does not require displacement data acquisition system. This technique requires the prostate's pre-compression and postcompression transrectal ultrasound images. The conceptual foundation of reconstructing the prostate's normal and pathological tissues elastic moduli is to determine these moduli such that the similarity between calculated and observed shape features of the post compression prostate image is maximized. Results indicate that this technique is highly accurate and robust.

Copolymer-in-oil phantom materials for elastography.

PubMed

Oudry, J; Bastard, C; Miette, V; Willinger, R; Sandrin, L

2009-07-01

Phantoms that mimic mechanical and acoustic properties of soft biological tissues are essential to elasticity imaging investigation and to elastography device characterization. Several materials including agar/gelatin, polyvinyl alcohol and polyacrylamide gels have been used successfully in the past to produce tissue phantoms, as reported in the literature. However, it is difficult to find a phantom material with a wide range of stiffness, good stability over time and high resistance to rupture. We aim at developing and testing a new copolymer-in-oil phantom material for elastography. The phantom is composed of a mixture of copolymer, mineral oil and additives for acoustic scattering. The mechanical properties of phantoms were evaluated with a mechanical test instrument and an ultrasound-based elastography technique. The acoustic properties were investigated using a through-transmission water-substituting method. We showed that copolymer-in-oil phantoms are stable over time. Their mechanical and acoustic properties mimic those of most soft tissues: the Young's modulus ranges from 2.2-150 kPa, the attenuation coefficient from 0.4-4.0 dB.cm(-1) and the ultrasound speed from 1420-1464 m/s. Their density is equal to 0.90 +/- 0.04 g/cm3. The results suggest that copolymer-in-oil phantoms are attractive materials for elastography.

Advanced imaging techniques for small bowel Crohn's disease: what does the future hold?

PubMed

Pita, Inês; Magro, Fernando

2018-01-01

Treatment of Crohn's disease (CD) is intrinsically reliant on imaging techniques, due to the preponderance of small bowel disease and its transmural pattern of inflammation. Ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) are the most widely employed imaging methods and have excellent diagnostic accuracy in most instances. Some limitations persist, perhaps the most clinically relevant being the distinction between inflammatory and fibrotic strictures. In this regard, several methodologies have recently been tested in animal models and human patients, namely US strain elastography, shear wave elastography, contrast-enhanced US, magnetization transfer MRI and contrast dynamics in standard MRI. Technical advances in each of the imaging methods may expand their indications. The addition of oral contrast to abdominal US appears to substantially improve its diagnostic capabilities compared to standard US. Ionizing dose-reduction methods in CT can decrease concern about cumulative radiation exposure in CD patients and diffusion-weighted MRI may reduce the need for gadolinium contrast. Clinical indexes of disease activity and severity are also increasingly relying on imaging scores, such as the recently developed Lémann Index. In this review we summarize some of the recent advances in small bowel CD imaging and how they might affect clinical practice in the near future.

Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography

NASA Astrophysics Data System (ADS)

Zhu, Jiang; Miao, Yusi; Qi, Li; Qu, Yueqiao; He, Youmin; Yang, Qiang; Chen, Zhongping

2017-05-01

Shear wave measurements for the determination of tissue elastic properties have been used in clinical diagnosis and soft tissue assessment. A shear wave propagates as a transverse wave where vibration is perpendicular to the wave propagation direction. Previous transverse shear wave measurements could detect the shear modulus in the lateral region of the force; however, they could not provide the elastic information in the axial region of the force. In this study, we report the imaging and quantification of longitudinal shear wave propagation using optical coherence tomography to measure the elastic properties along the force direction. The experimental validation and finite element simulations show that the longitudinal shear wave propagates along the vibration direction as a plane wave in the near field of a planar source. The wave velocity measurement can quantify the shear moduli in a homogeneous phantom and a side-by-side phantom. Combining the transverse shear wave and longitudinal shear wave measurements, this system has great potential to detect the directionally dependent elastic properties in tissues without a change in the force direction.

A novel breast software phantom for biomechanical modeling of elastography.

PubMed

Bhatti, Syeda Naema; Sridhar-Keralapura, Mallika

2012-04-01

In developing breast imaging technologies, testing is done with phantoms. Physical phantoms are normally used but their size, shape, composition, and detail cannot be modified readily. These difficulties can be avoided by creating a software breast phantom. Researchers have created software breast phantoms using geometric and/or mathematical methods for applications like image fusion. The authors report a 3D software breast phantom that was built using a mechanical design tool, to investigate the biomechanics of elastography using finite element modeling (FEM). The authors propose this phantom as an intermediate assessment tool for elastography simulation; for use after testing with commonly used phantoms and before clinical testing. The authors design the phantom to be flexible in both, the breast geometry and biomechanical parameters, to make it a useful tool for elastography simulation. The authors develop the 3D software phantom using a mechanical design tool based on illustrations of normal breast anatomy. The software phantom does not use geometric primitives or imaging data. The authors discuss how to create this phantom and how to modify it. The authors demonstrate a typical elastography experiment of applying a static stress to the top surface of the breast just above a simulated tumor and calculate normal strains in 3D and in 2D with plane strain approximations with linear solvers. In particular, they investigate contrast transfer efficiency (CTE) by designing a parametric study based on location, shape, and stiffness of simulated tumors. The authors also compare their findings to a commonly used elastography phantom. The 3D breast software phantom is flexible in shape, size, and location of tumors, glandular to fatty content, and the ductal structure. Residual modulus, maps, and profiles, served as a guide to optimize meshing of this geometrically nonlinear phantom for biomechanical modeling of elastography. At best, low residues (around 1-5 KPa) were found within the phantom while errors were elevated (around 10-30 KPa) at tumor and lobule boundaries. From our FEM analysis, the breast phantom generated a superior CTE in both 2D and in 3D over the block phantom. It also showed differences in CTE values and strain contrast for deep and shallow tumors and showed significant change in CTE when 3D modeling was used. These changes were not significant in the block phantom. Both phantoms, however, showed worsened CTE values for increased input tumor-background modulus contrast. Block phantoms serve as a starting tool but a next level phantom, like the proposed breast phantom, will serve as a valuable intermediate for elastography simulation before clinical testing. Further, given the CTE metrics for the breast phantom are superior to the block phantom, and vary for tumor shape, location, and stiffness, these phantoms would enhance the study of elastography contrast. Further, the use of 2D phantoms with plane strain approximations overestimates the CTE value when compared to the true CTE achieved with 3D models. Thus, the use of 3D phantoms, like the breast phantom, with no approximations, will assist in more accurate estimation of modulus, especially valuable for 3D elastography systems.

A novel high amplitude piezoceramic actuator for applications in magnetic resonance elastography: a compliant mechanical amplifier approach

NASA Astrophysics Data System (ADS)

Arani, Arvin; Eskandari, Amiraslan; Ouyang, Puren; Chopra, Rajiv

2017-08-01

Piezoceramic actuators are capable of precise positioning with high force, but suffer from limited displacement range, which has hindered their application in the field of magnetic resonance elastography (MRE). The objective of this study was to investigate the feasibility of using a mechanical amplifier in combination with a piezoceramic actuator for the application of endorectal prostate MRE. A five-bar symmetric structure was designed in ANSYS® and manufactured out of brass. Laser vibrometer measurements were used to characterize the amplitude of the CMA actuator while attached to masses in the 0-325 g range and over operating frequencies of 90-500 Hz. The response of the CMA was investigated while mechanically coupled to a balloon type endorectal coil. The resonant frequency of the prototype CMA actuator was predicted within 10% error using ANSYS simulations. The amplification ratio of the CMA actuator was measured to be 10 with the laser vibrometer and 7.6 ± 1.7 (max: 9.2, min: 6.5) using MRE, at a vibration frequency of 200 Hz. Laser vibrometer data also showed that the CMA actuator’s performance did not change whether it was connected to an empty or inflated endorectal. The feasibility of performing endorectal prostate MRE with a CMA actuator was successfully demonstrated in a human volunteer.

Optical Coherence Elastography

NASA Astrophysics Data System (ADS)

Kennedy, Brendan F.; Kennedy, Kelsey M.; Oldenburg, Amy L.; Adie, Steven G.; Boppart, Stephen A.; Sampson, David D.

The mechanical properties of tissue are pivotal in its function and behavior, and are often modified by disease. From the nano- to the macro-scale, many tools have been developed to measure tissue mechanical properties, both to understand the contribution of mechanics in the origin of disease and to improve diagnosis. Optical coherence elastography is applicable to the intermediate scale, between that of cells and whole organs, which is critical in the progression of many diseases and not widely studied to date. In optical coherence elastography, a mechanical load is imparted to a tissue and the resulting deformation is measured using optical coherence tomography. The deformation is used to deduce a mechanical parameter, e.g., Young's modulus, which is mapped into an image, known as an elastogram. In this chapter, we review the development of optical coherence elastography and report on the latest developments. We provide a focus on the underlying principles and assumptions, techniques to measure deformation, loading mechanisms, imaging probes and modeling, including the inverse elasticity problem.

Quantitative photoacoustic elastography of Young's modulus in humans

NASA Astrophysics Data System (ADS)

Hai, Pengfei; Zhou, Yong; Gong, Lei; Wang, Lihong V.

2017-03-01

Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.

Comparison Between Neck and Shoulder Stiffness Determined by Shear Wave Ultrasound Elastography and a Muscle Hardness Meter.

PubMed

Akagi, Ryota; Kusama, Saki

2015-08-01

The goals of this study were to compare neck and shoulder stiffness values determined by shear wave ultrasound elastography with those obtained with a muscle hardness meter and to verify the correspondence between objective and subjective stiffness in the neck and shoulder. Twenty-four young men and women participated in the study. Their neck and shoulder stiffness was determined at six sites. Before the start of the measurements, patients rated their present subjective symptoms of neck and shoulder stiffness on a 6-point verbal scale. At all measurement sites, the correlation coefficients between the values of muscle hardness indices determined by the muscle hardness meter and shear wave ultrasound elastography were not significant. Furthermore, individuals' subjective neck and shoulder stiffness did not correspond to their objective symptoms. These results suggest that the use of shear wave ultrasound elastography is essential to more precisely assess neck and shoulder stiffness. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Chronic musculoskeletal pain: ultrasound guided pain control.

PubMed

Chiou, Hong-Jen; Chou, Yi-Hong; Wang, Hsin-Kai; Lai, Yi-Chen

2014-09-01

The review demonstrates the unique advantages of ultrasonography in pain control. Several imaging modalities can be used to guide pain control, such as computed tomography, magnetic resonance imaging, and radiography. Ultrasonography has unique advantages over these other modalities in terms of its non-ionizing radiation, real-time imaging, portability, and cost-effectiveness. Ultrasonography with color Doppler and elastography can provide safer guidance to avoid blood vessels and the nerve trunk when using steroid or xylocaine infusions to encase the nerve trunk. This review focuses on the control of chronic pain in the upper limbs, lower limbs, and trunk. Copyright © 2014. Published by Elsevier B.V.

4-D ultrafast shear-wave imaging.

PubMed

Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael

2015-06-01

Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE.

The link between tissue elasticity and thermal dose in vivo

NASA Astrophysics Data System (ADS)

Sapin-de Brosses, Emilie; Pernot, Mathieu; Tanter, Mickaël

2011-12-01

The objective of this study was to investigate in vivo the relationship between stiffness and thermal dose. For this purpose, shear wave elastography (SWE)—a novel ultrasound-based technique for real-time mapping of the stiffness of biological soft tissues—is performed in temperature-controlled experiments. Experiments were conducted on nine anesthetized rats. Their right leg was put in a thermo-regulated waterbath. The right leg of each animal was heated at one particular temperature between 38 °C and 48.5 °C for 15 min to 3 h. Shear waves were generated in the muscle using the acoustic radiation force induced by a linear ultrasonic probe. The shear wave propagation was imaged in real time by the probe using an ultrafast scanner prototype (10 000 frames s-1). The local tissue stiffness was derived from the shear wave speed. Two optical fiber sensors were inserted into the muscle to measure in situ the temperature. Stiffness was found to increase strongly during the experiments. When expressed as a function of the thermal dose, the stiffness curves were found to be the same for all experiments. A thermal dose threshold was found at 202 min for an eightfold stiffness increase. Finally, the time-temperature relationship was established for different stiffness ratios. The slope of the time-temperature relationship based on stiffness measurements was found identical to the one obtained for cell death in the seminal paper on the thermal dose by Sapareto and Dewey in 1984 (Int. J. Radiat. Oncol. Biol. Phys. 10 787-800). The present results highlight the stiffness increase as a good indicator of thermal necrosis. SWE imaging can be used in vivo for necrosis threshold determination in thermal therapy.

Endoscopic ultrasound: Elastographic lymph node evaluation.

PubMed

Dietrich, Christoph F; Jenssen, Christian; Arcidiacono, Paolo G; Cui, Xin-Wu; Giovannini, Marc; Hocke, Michael; Iglesias-Garcia, Julio; Saftoiu, Adrian; Sun, Siyu; Chiorean, Liliana

2015-01-01

Different imaging techniques can bring different information which will contribute to the final diagnosis and further management of the patients. Even from the time of Hippocrates, palpation has been used in order to detect and characterize a body mass. The so-called virtual palpation has now become a reality due to elastography, which is a recently developed technique. Elastography has already been proving its added value as a complementary imaging method, helpful to better characterize and differentiate between benign and malignant masses. The current applications of elastography in lymph nodes (LNs) assessment by endoscopic ultrasonography will be further discussed in this paper, with a review of the literature and future perspectives.

Muscle ultrasound elastography and MRI in preschool children with Duchenne muscular dystrophy.

PubMed

Pichiecchio, Anna; Alessandrino, Francesco; Bortolotto, Chandra; Cerica, Alessandra; Rosti, Cristina; Raciti, Maria Vittoria; Rossi, Marta; Berardinelli, Angela; Baranello, Giovanni; Bastianello, Stefano; Calliada, Fabrizio

2018-06-01

The aim of this study was to determine muscle tissue elasticity, measured with shear-wave elastography, in selected lower limb muscles of patients affected by Duchenne muscular dystrophy (DMD) and to correlate the values obtained with those recorded in healthy children and with muscle magnetic resonance imaging (MRI) data from the same DMD children, specifically the pattern on T1-weighted (w) and short-tau inversion recovery (STIR) sequences. Five preschool DMD children and five age-matched healthy children were studied with shear-wave elastography. In the DMD children, muscle stiffness was moderately higher compared with the muscle stiffness in HC, in the rectus femoris, vastus lateralis, adductor magnus and gluteus maximus muscles. On muscle MRI T1-w images showed fatty replacement in 3/5 patients at the level of the GM, while thigh and leg muscles were affected in 2/5; hyperintensity on STIR images was identified in 4/5 patients. No significant correlation was observed between stiffness values and MRI scoring. Our study demonstrated that lower limb muscles of preschool DMD patients show fatty replacement and patchy edema on muscle MRI and increased stiffness on shear-wave elastography. In conclusion, although further studies in larger cohorts are needed, shear-wave elastography could be considered a useful non-invasive tool to easily monitor muscle changes in early stages of the disease. Copyright © 2018 Elsevier B.V. All rights reserved.

[Renal elastography].

PubMed

Correas, Jean-Michel; Anglicheau, Dany; Gennisson, Jean-Luc; Tanter, Mickael

2016-04-01

Renal elastography has become available with the development of noninvasive quantitative techniques (including shear-wave elastography), following the rapidly growing field of diagnosis and quantification of liver fibrosis, which has a demonstrated major clinical impact. Ultrasound or even magnetic resonance techniques are leaving the pure research area to reach the routine clinical use. With the increased incidence of chronic kidney disease and its specific morbidity and mortality, the noninvasive diagnosis of renal fibrosis can be of critical value. However, it is difficult to simply extend the application from one organ to the other due to a large number of anatomical and technical issues. Indeed, the kidney exhibits various features that make stiffness assessment more complex, such as the presence of various tissue types (cortex, medulla), high spatial orientation (anisotropy), local blood flow, fatty sinus with variable volume and echotexture, perirenal space with variable fatty content, and the variable depth of the organ. Furthermore, the stiffness changes of the renal parenchyma are not exclusively related to fibrosis, as renal perfusion or hydronephrosis will impact the local elasticity. Renal elastography might be able to diagnose acute or chronic obstruction, or to renal tumor or pseudotumor characterization. Today, renal elastography appears as a promising application that still requires optimization and validation, which is the contrary for liver stiffness assessment. Copyright © 2016 Association Société de néphrologie. Published by Elsevier SAS. All rights reserved.

Differences in liver stiffness values obtained with new ultrasound elastography machines and Fibroscan: A comparative study.

PubMed

Piscaglia, Fabio; Salvatore, Veronica; Mulazzani, Lorenzo; Cantisani, Vito; Colecchia, Antonio; Di Donato, Roberto; Felicani, Cristina; Ferrarini, Alessia; Gamal, Nesrine; Grasso, Valentina; Marasco, Giovanni; Mazzotta, Elena; Ravaioli, Federico; Ruggieri, Giacomo; Serio, Ilaria; Sitouok Nkamgho, Joules Fabrice; Serra, Carla; Festi, Davide; Schiavone, Cosima; Bolondi, Luigi

2017-07-01

Whether Fibroscan thresholds can be immediately adopted for none, some or all other shear wave elastography techniques has not been tested. The aim of the present study was to test the concordance of the findings obtained from 7 of the most recent ultrasound elastography machines with respect to Fibroscan. Sixteen hepatitis C virus-related patients with fibrosis ≥2 and having reliable results at Fibroscan were investigated in two intercostal spaces using 7 different elastography machines. Coefficients of both precision (an index of data dispersion) and accuracy (an index of bias correction factors expressing different magnitudes of changes in comparison to the reference) were calculated. Median stiffness values differed among the different machines as did coefficients of both precision (range 0.54-0.72) and accuracy (range 0.28-0.87). When the average of the measurements of two intercostal spaces was considered, coefficients of precision significantly increased with all machines (range 0.72-0.90) whereas of accuracy improved more scatteredly and by a smaller degree (range 0.40-0.99). The present results showed only moderate concordance of the majority of elastography machines with the Fibroscan results, preventing the possibility of the immediate universal adoption of Fibroscan thresholds for defining liver fibrosis staging for all new machines. Copyright © 2017 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Accuracy of localization of prostate lesions using manual palpation and ultrasound elastography

NASA Astrophysics Data System (ADS)

Kut, Carmen; Schneider, Caitlin; Carter-Monroe, Naima; Su, Li-Ming; Boctor, Emad; Taylor, Russell

2009-02-01

Purpose: To compare the accuracy of detecting tumor location and size in the prostate using both manual palpation and ultrasound elastography (UE). Methods: Tumors in the prostate were simulated using both synthetic and ex vivo tissue phantoms. 25 participants were asked to provide the presence, size and depth of these simulated lesions using manual palpation and UE. Ultrasound images were captured using a laparoscopic ultrasound probe, fitted with a Gore-Tetrad transducer with frequency of 7.5 MHz and a RF capture depth of 4-5 cm. A MATLAB GUI application was employed to process the RF data for ex vivo phantoms, and to generate UE images using a cross-correlation algorithm. Ultrasonix software was used to provide real time elastography during laparoscopic palpation of the synthetic phantoms. Statistical analyses were performed based on a two-tailed, student t-test with α = 0.05. Results: UE displays both a higher accuracy and specificity in tumor detection (sensitivity = 84%, specificity = 74%). Tumor diameters and depths are better estimated using ultrasound elastography when compared with manual palpation. Conclusions: Our results indicate that UE has strong potential in assisting surgeons to intra-operatively evaluate the tumor depth and size. We have also demonstrated that ultrasound elastography can be implemented in a laparoscopic environment, in which manual palpation would not be feasible. With further work, this application can provide accurate and clinically relevant information for surgeons during prostate resection.

Effect of Compression Garments on the Development of Delayed-Onset Muscle Soreness: A Multimodal Approach Using Contrast-Enhanced Ultrasound and Acoustic Radiation Force Impulse Elastography.

PubMed

Heiss, Rafael; Kellermann, Marion; Swoboda, Bernd; Grim, Casper; Lutter, Christoph; May, Matthias S; Wuest, Wolfgang; Uder, Michael; Nagel, Armin M; Hotfiel, Thilo

2018-06-12

Study Design Controlled laboratory study with repeated measures. Background Delayed-onset muscle soreness (DOMS) is one of the most common reasons for impaired muscle performance in sports. However, little consensus exists regarding which treatments may be most effective and the underlying mechanisms are poorly understood. Objectives To investigate the influence of compression garments on the development of DOMS, focusing on changes in muscle perfusion and muscle stiffness. Methods Muscle perfusion and stiffness, calf circumference, muscle soreness, passive ankle dorsiflexion, and creatine kinase levels were assessed on participants before (baseline) a DOMS-inducing eccentric calf exercise intervention and 60 h later (follow-up). After DOMS induction, a sports compression garment (18-21 mmHg) was worn on one randomized calf until follow-up. The contralateral calf served as an internal control. Muscle perfusion was assessed using contrast-enhanced ultrasound (peak enhancement [PE] and wash-in area under the curve [WiAUC]), while muscle stiffness was assessed using acoustic radiation force impulse (shear wave velocities [SWV]). An MRI scan of both lower legs was also performed during the follow-up testing session to characterize the extent of exercise-induced muscle damage. Comparisons were made between limbs and over time. Results SWV values of the medial gastrocnemius showed a significant interaction between time and limb (p=0.006) with the non-compressed muscle demonstrating lower muscle stiffness values at follow-up compared to baseline or the compressed muscle. No significant differences in soleus muscle stiffness were noted between limb or over time, as was the case for muscle perfusion metrics (PE and WiAUC) for the medial gastrocnemius and soleus muscles. Further, compression had no significant effect on passive ankle dorsiflexion, muscle soreness, calf circumference, or injury severity per MRI. Conclusion Continuous wearing of compression garments during the inflammation phase of DOMS may play an important role in regulating muscle stiffness; however, they have no significant effects on intramuscular perfusion or other common clinical assessments. J Orthop Sports Phys Ther, Epub 12 Jun 2018. doi:10.2519/jospt.2018.8038.

Comparison of acoustic radiation force impulse imaging (ARFI) to liver biopsy histologic scores in the evaluation of chronic liver disease: A pilot study.

PubMed

Haque, Mazhar; Robinson, Charlotte; Owen, David; Yoshida, Eric M; Harris, Alison

2010-01-01

Acoustic Radiation Force Impulse Imaging (ARFI) is a novel non invasive technique studying the localized mechanical properties of tissue by utilising short, high intensity acoustic pulses (shear wave pulses) to assess the mechanical response (tissue displacement), providing a measure of tissue elasticity. The aim of this study is to investigate the feasibility of ARFI imaging as a non-invasive method for the assessment of liver fibrosis compared to liver biopsy scores. A prospective blind comparison study of ARFI elastography (Virtual Touch Imaging., ACUSON S2000 Ultrasound Unit, Siemens, Mountain View CA) in a consecutive series of patients who underwent liver biopsy for assessment of fibrosis in chronic liver disease. ARFI shear-wave propagation velocity was measured in meters per second. Mean ARFI velocities were compared with both Batts-Ludwig (F0 to F4) and Modified Ishak scores (F0 to F4) for fibrosis in liver biopsy findings. Twenty-one patients with chronic liver disease (Hepatitis C (HCV) =16, Hepatitis B (HBV) = 1, both HCV and HBV = 1 Alcoholic liver disease (ALD) = 1, others = 2) underwent ARFI and liver biopsy on the same day. The Spearman correlation coefficients between the median values of the ARFI measurements and the histological fibrosis stage of the Modified Ishak score and Batts-Lud- (3) wig score were both highly significant (p < 0.01) with rho = 0.69 and rho = 0.72 respectively. The median ARFI (total 180 replications; minimum 5, maximum 10 measurements per patients) velocities for our study population range from 0.92 to 4.17 m/sec. Areas under the receiver operating characteristic curve for the accuracy of ARFI imaging was 1.00 and 0.35, for the diagnosis of moderate fibrosis (histologic fibrosis stage, F (3) 2) and 0.85 and 0.85 respectively for Ishak and Batts-Ludwig score, for the diagnosis of cirrhosis. ARFI imaging has a strong correlation with the fibrosis stage of both Batts-Ludwig and shak score in chronic liver disease. It.s accuracy in prediction of severe fibrosis and cirrhosis is maximal in comparison with earlier stages.

Liver fibrosis in non-alcoholic fatty liver disease - diagnostic challenge with prognostic significance

PubMed Central

Stål, Per

2015-01-01

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the Western world, with a prevalence of 20%. In a subgroup of patients, inflammation, ballooning degeneration of hepatocytes and a varying degree of fibrosis may develop, a condition named non-alcoholic steatohepatitis. Advanced liver fibrosis (stage F3) and cirrhosis (stage F4) are histologic features that most accurately predict increased mortality in both liver-related and cardiovascular diseases. Patients with advanced fibrosis or cirrhosis are at risk for complications such as hepatocellular carcinoma and esophageal varices and should therefore be included in surveillance programs. However, liver disease and fibrosis are often unrecognized in patients with NAFLD, possibly leading to a delayed diagnosis of complications. The early diagnosis of advanced fibrosis in NAFLD is therefore crucial, and it can be accomplished using serum biomarkers (e.g., the NAFLD Fibrosis Score, Fib-4 Index or BARD) or non-invasive imaging techniques (transient elastography or acoustic radiation force impulse imaging). The screening of risk groups, such as patients with obesity and/or type 2 diabetes mellitus, for NAFLD development with these non-invasive methods may detect advanced fibrosis at an early stage. Additionally, patients with a low risk for advanced fibrosis can be identified, and the need for liver biopsies can be minimized. This review focuses on the diagnostic challenge and prognostic impact of advanced liver fibrosis in NAFLD. PMID:26494963

Liver fibrosis in non-alcoholic fatty liver disease - diagnostic challenge with prognostic significance.

PubMed

Stål, Per

2015-10-21

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the Western world, with a prevalence of 20%. In a subgroup of patients, inflammation, ballooning degeneration of hepatocytes and a varying degree of fibrosis may develop, a condition named non-alcoholic steatohepatitis. Advanced liver fibrosis (stage F3) and cirrhosis (stage F4) are histologic features that most accurately predict increased mortality in both liver-related and cardiovascular diseases. Patients with advanced fibrosis or cirrhosis are at risk for complications such as hepatocellular carcinoma and esophageal varices and should therefore be included in surveillance programs. However, liver disease and fibrosis are often unrecognized in patients with NAFLD, possibly leading to a delayed diagnosis of complications. The early diagnosis of advanced fibrosis in NAFLD is therefore crucial, and it can be accomplished using serum biomarkers (e.g., the NAFLD Fibrosis Score, Fib-4 Index or BARD) or non-invasive imaging techniques (transient elastography or acoustic radiation force impulse imaging). The screening of risk groups, such as patients with obesity and/or type 2 diabetes mellitus, for NAFLD development with these non-invasive methods may detect advanced fibrosis at an early stage. Additionally, patients with a low risk for advanced fibrosis can be identified, and the need for liver biopsies can be minimized. This review focuses on the diagnostic challenge and prognostic impact of advanced liver fibrosis in NAFLD.

Development of an intravascular ultrasound elastography based on a dual-element transducer

NASA Astrophysics Data System (ADS)

Shih, Cho-Chiang; Chen, Pei-Yu; Ma, Teng; Zhou, Qifa; Shung, K. Kirk; Huang, Chih-Chung

2018-04-01

The ability to measure the elastic properties of plaques and vessels would be useful in clinical diagnoses, particularly for detecting a vulnerable plaque. This study demonstrates the feasibility of the combination of intravascular ultrasound (IVUS) and acoustic radiation force elasticity imaging for detecting the distribution of stiffness within atherosclerotic arteries ex vivo. A dual-frequency IVUS transducer with two elements was used to induce the propagation of the shear wave (by the 8.5 MHz pushing element) which could be simultaneously monitored by the 31 MHz imaging element. The wave-amplitude image and the wave-velocity image were reconstructed by measuring the peak displacement and wave velocity of shear wave propagation, respectively. System performance was verified using gelatin phantoms. The phantom results demonstrate that the stiffness differences of shear modulus of 1.6 kPa can be distinguished through the wave-amplitude and wave-velocity images. The stiffness distributions of the atherosclerotic aorta from a rabbit were obtained, for which the values of peak displacement and the shear wave velocity were 3.7 ± 1.2 µm and 0.38 ± 0.19 m s-1 for the lipid-rich plaques, and 1.0 ± 0.2 µm and 3.45 ± 0.45 m s-1 for the arterial walls, respectively. These results indicate that IVUS elasticity imaging can be used to distinguish the elastic properties of plaques and vessels.

MR-ARFI-based method for the quantitative measurement of tissue elasticity: application for monitoring HIFU therapy

NASA Astrophysics Data System (ADS)

Vappou, Jonathan; Bour, Pierre; Marquet, Fabrice; Ozenne, Valery; Quesson, Bruno

2018-05-01

Monitoring thermal therapies through medical imaging is essential in order to ensure that they are safe, efficient and reliable. In this paper, we propose a new approach, halfway between MR acoustic radiation force imaging (MR-ARFI) and MR elastography (MRE), allowing for the quantitative measurement of the elastic modulus of tissue in a highly localized manner. It relies on the simulation of the MR-ARFI profile, which depends on tissue biomechanical properties, and on the identification of tissue elasticity through the fitting of experimental displacement images measured using rapid MR-ARFI. This method was specifically developed to monitor MR-guided high intensity focused ultrasound (MRgHIFU) therapy. Elasticity changes were followed during HIFU ablations (N  =  6) performed ex vivo in porcine muscle samples, and were compared to temperature changes measured by MR-thermometry. Shear modulus was found to increase consistently and steadily a few seconds after the heating started, and such changes were found to be irreversible. The shear modulus was found to increase from 1.49  ±  0.48 kPa (before ablation) to 3.69  ±  0.93 kPa (after ablation and cooling). Thanks to its ability to perform quantitative elasticity measurements in a highly localized manner around the focal spot, this method proved to be particularly attractive for monitoring HIFU ablations.

Transient Elastography vs. Aspartate Aminotransferase to Platelet Ratio Index in Hepatitis C: A Meta-Analysis.

PubMed

Mattos, A Z; Mattos, A A

Many different non-invasive methods have been studied with the purpose of staging liver fibrosis. The objective of this study was verifying if transient elastography is superior to aspartate aminotransferase to platelet ratio index for staging fibrosis in patients with chronic hepatitis C. A systematic review with meta-analysis of studies which evaluated both non-invasive tests and used biopsy as the reference standard was performed. A random-effects model was used, anticipating heterogeneity among studies. Diagnostic odds ratio was the main effect measure, and summary receiver operating characteristic curves were created. A sensitivity analysis was planned, in which the meta-analysis would be repeated excluding each study at a time. Eight studies were included in the meta-analysis. Regarding the prediction of significant fibrosis, transient elastography and aspartate aminotransferase to platelet ratio index had diagnostic odds ratios of 11.70 (95% confidence interval = 7.13-19.21) and 8.56 (95% confidence interval = 4.90-14.94) respectively. Concerning the prediction of cirrhosis, transient elastography and aspartate aminotransferase to platelet ratio index had diagnostic odds ratios of 66.49 (95% confidence interval = 23.71-186.48) and 7.47 (95% confidence interval = 4.88-11.43) respectively. In conclusion, there was no evidence of significant superiority of transient elastography over aspartate aminotransferase to platelet ratio index regarding the prediction of significant fibrosis, but the former proved to be better than the latter concerning prediction of cirrhosis.

Validity of measurement of shear modulus by ultrasound shear wave elastography in human pennate muscle.

PubMed

Miyamoto, Naokazu; Hirata, Kosuke; Kanehisa, Hiroaki; Yoshitake, Yasuhide

2015-01-01

Ultrasound shear wave elastography is becoming a valuable tool for measuring mechanical properties of individual muscles. Since ultrasound shear wave elastography measures shear modulus along the principal axis of the probe (i.e., along the transverse axis of the imaging plane), the measured shear modulus most accurately represents the mechanical property of the muscle along the fascicle direction when the probe's principal axis is parallel to the fascicle direction in the plane of the ultrasound image. However, it is unclear how the measured shear modulus is affected by the probe angle relative to the fascicle direction in the same plane. The purpose of the present study was therefore to examine whether the angle between the principal axis of the probe and the fascicle direction in the same plane affects the measured shear modulus. Shear modulus in seven specially-designed tissue-mimicking phantoms, and in eleven human in-vivo biceps brachii and medial gastrocnemius were determined by using ultrasound shear wave elastography. The probe was positioned parallel or 20° obliquely to the fascicle across the B-mode images. The reproducibility of shear modulus measurements was high for both parallel and oblique conditions. Although there was a significant effect of the probe angle relative to the fascicle on the shear modulus in human experiment, the magnitude was negligibly small. These findings indicate that the ultrasound shear wave elastography is a valid tool for evaluating the mechanical property of pennate muscles along the fascicle direction.

Transient elastography with the XL probe rapidly identifies patients with nonhepatic ascites.

PubMed

Kohlhaas, Anna; Durango, Esteban; Millonig, Gunda; Bastard, Cecile; Sandrin, Laurent; Golriz, Mohammad; Mehrabi, Arianeb; Büchler, Markus W; Seitz, Helmut Karl; Mueller, Sebastian

2012-01-01

In contrast with other elastographic techniques, ascites is considered an exclusion criterion for assessment of fibrosis stage by transient elastography. However, a normal liver stiffness could rule out hepatic causes of ascites at an early stage. The aim of the present study was to determine whether liver stiffness can be generally determined by transient elastography through an ascites layer, to determine whether the ascites-mediated increase in intra-abdominal pressure affects liver stiffness, and to provide initial data from a pilot cohort of patients with various causes of ascites. Using the XL probe in an artificial ascites model, we demonstrated (copolymer phantoms surrounded by water) that a transient elastography-generated shear wave allows accurate determination of phantom stiffness up to a water lamella of 20 mm. We next showed in an animal ascites model that increased intra-abdominal pressure does not affect liver stiffness. Liver stiffness was then determined in 24 consecutive patients with ascites due to hepatic (n = 18) or nonhepatic (n = 6) causes. The cause of ascites was eventually clarified using routine clinical, imaging, laboratory, and other tools. Valid (75%) or acceptable (25%) liver stiffness data could be obtained in 23 patients (95.8%) with ascites up to an ascites lamella of 39 mm. The six patients (25%) with nonhepatic causes of ascites (eg, pancreatitis, peritoneal carcinomatosis) had a significantly lower liver stiffness (<8 kPa) as compared with the remaining patients with hepatic ascites (>30 kPa). Mean liver stiffness was 5.4 kPa ± 1.3 versus 66.2 ± 13.3 kPa. In conclusion, the presence of ascites and increased intra-abdominal pressure does not alter underlying liver stiffness as determined by transient elastography. We suggest that, using the XL probe, transient elastography can be used first-line to identify patients with nonhepatic ascites at an early stage.

Transient elastography with the XL probe rapidly identifies patients with nonhepatic ascites

PubMed Central

Kohlhaas, Anna; Durango, Esteban; Millonig, Gunda; Bastard, Cecile; Sandrin, Laurent; Golriz, Mohammad; Mehrabi, Arianeb; Büchler, Markus W; Seitz, Helmut Karl; Mueller, Sebastian

2012-01-01

Background In contrast with other elastographic techniques, ascites is considered an exclusion criterion for assessment of fibrosis stage by transient elastography. However, a normal liver stiffness could rule out hepatic causes of ascites at an early stage. The aim of the present study was to determine whether liver stiffness can be generally determined by transient elastography through an ascites layer, to determine whether the ascites-mediated increase in intra-abdominal pressure affects liver stiffness, and to provide initial data from a pilot cohort of patients with various causes of ascites. Methods and results Using the XL probe in an artificial ascites model, we demonstrated (copolymer phantoms surrounded by water) that a transient elastography-generated shear wave allows accurate determination of phantom stiffness up to a water lamella of 20 mm. We next showed in an animal ascites model that increased intra-abdominal pressure does not affect liver stiffness. Liver stiffness was then determined in 24 consecutive patients with ascites due to hepatic (n = 18) or nonhepatic (n = 6) causes. The cause of ascites was eventually clarified using routine clinical, imaging, laboratory, and other tools. Valid (75%) or acceptable (25%) liver stiffness data could be obtained in 23 patients (95.8%) with ascites up to an ascites lamella of 39 mm. The six patients (25%) with nonhepatic causes of ascites (eg, pancreatitis, peritoneal carcinomatosis) had a significantly lower liver stiffness (<8 kPa) as compared with the remaining patients with hepatic ascites (>30 kPa). Mean liver stiffness was 5.4 kPa ± 1.3 versus 66.2 ± 13.3 kPa. Conclusion In conclusion, the presence of ascites and increased intra-abdominal pressure does not alter underlying liver stiffness as determined by transient elastography. We suggest that, using the XL probe, transient elastography can be used first-line to identify patients with nonhepatic ascites at an early stage. PMID:24367229

Imaging of idle breast implants with ultrasound-strain elastography- A first experimental study to establish criteria for accurate imaging of idle implants via ultrasound-strain elastography.

PubMed

Kuehlmann, Britta; Prantl, Lukas; Michael Jung, Ernst

2016-01-01

To investigate whether there are fundamental sonographic and elastographic criteria to precisely assess different surfaces and fillings of idle breast implants and to determine their most distinctive parameters. This was a comparative study of different unused breast implant materials, neighter in animals nor in humans. This knowledge should be transferred in vivo to develop an objective measurement tool. Nine idle breast implants-silicone and polyurethane (PU)-were examined in an experimental study by using ultrasound B-mode with tissue harmonic imaging (THI), speckle reduction imaging (SRI, level 0-4), cross-beam (CB, low, medium, high), photopic and the colour coded ultrasound-strain elastography with a multifrequency probe (9-15 MHz).Using a standardised protocol the implants' centre as well as the edge were analysed by one experienced examiner. Two independent readers performed analysis and evaluation. For image interpretation a score was created (score 0:inadequate image, score 5:best image quality). The highest score result for the centre was achieved by using ultrasound with B-mode in addition with CB level medium, SRI level 2, THI and photopic (mean:3.22±SD:1.56), but without any statistic significant difference (t-value = 0.71). With elastography the implants' edge in general was represented without disruptive artefacts (3.89±0.60) with statistic significant difference (t-value = 5.29). Implants filled with inner cohesive silicone gel II° showed best imaging conditions for their centre via ultrasound (5±0) as well as for their edge via elastography (4.50±0.71). Ultrasound-strain elastography and high resolution ultrasound represent a valuable measurement tool to evaluate different properties of idle breast implants. These modified ultrasound examinations could be an additional help for clinical investigations and be correlated with Baker's Classification.

Feasibility of a transient elastography technique for in vitro arterial elasticity assessment.

PubMed

Brum, J; Balay, G; Bia, D; Armentano, R L; Negreira, C

2010-01-01

The early detection of biomechanical modifications in the arterial wall could be used as a predictor factor for various diseases, for example hypertension or atherosclerosis. In this work a transient elastography technique is used for the in vitro evaluation of the arterial wall elasticity. The obtained Young modulus is compared with the one obtained by a more classical approach: pressure-diameter relationships. As a sample an arterial phantom made of PolyVinyl Alcohol (PVA) gel was used. Diameter variation due to pressure variation inside the phantom was recorded by means of ultrasound. Through both techniques similar Young modulus estimations are obtained showing in this way the feasibility of applying transient elastography for the arterial wall elasticity assessment.

Comparison of two ways of altering carpal tunnel pressure with ultrasound surface wave elastography.

PubMed

Cheng, Yu-Shiuan; Zhou, Boran; Kubo, Kazutoshi; An, Kai-Nan; Moran, Steven L; Amadio, Peter C; Zhang, Xiaoming; Zhao, Chunfeng

2018-06-06

Higher carpal tunnel pressure is related to the development of carpal tunnel syndrome. Currently, the measurement of carpal tunnel pressure is invasive and therefore, a noninvasive technique is needed. We previously demonstrated that speed of wave propagation through a tendon in the carpal tunnel measured by ultrasound elastography could be used as an indicator of carpal tunnel pressure in a cadaveric model, in which a balloon had to be inserted into the carpal tunnel to adjust the carpal tunnel pressure. However, the method for adjusting the carpal tunnel pressure in the cadaveric model is not applicable for the in vivo model. The objective of this study was to utilize a different technique to adjust carpal tunnel pressure via pressing the palm and to validate it with ultrasound surface wave elastography in a human cadaveric model. The outcome was also compared with a previous balloon insertion technique. Results showed that wave speed of intra-carpal tunnel tendon and the ratio of wave speed of intra-and outer-carpal tunnel tendons increased linearly with carpal tunnel pressure. Moreover, wave speed of intra carpal tunnel tendon via both ways of altering carpal tunnel pressure showed similar results with high correlation. Therefore, it was concluded that the technique of pressing the palm can be used to adjust carpal tunnel pressure, and pressure changes can be detected via ultrasound surface wave elastography in an ex vivo model. Future studies will utilize this technique in vivo to validate the usefulness of ultrasound surface wave elastography for measuring carpal tunnel pressure. Copyright © 2018 Elsevier Ltd. All rights reserved.

Diagnostic potential of real-time elastography (RTE) and shear wave elastography (SWE) to differentiate benign and malignant thyroid nodules: A systematic review and meta-analysis.

PubMed

Hu, Xiangdong; Liu, Yujiang; Qian, Linxue

2017-10-01

Real-time elastography (RTE) and shear wave elastography (SWE) are noninvasive and easily available imaging techniques that measure the tissue strain, and it has been reported that the sensitivity and the specificity of elastography were better in differentiating between benign and malignant thyroid nodules than conventional technologies. Relevant articles were searched in multiple databases; the comparison of elasticity index (EI) was conducted with the Review Manager 5.0. Forest plots of the sensitivity and specificity and SROC curve of RTE and SWE were performed with STATA 10.0 software. In addition, sensitivity analysis and bias analysis of the studies were conducted to examine the quality of articles; and to estimate possible publication bias, funnel plot was used and the Egger test was conducted. Finally 22 articles which eventually satisfied the inclusion criteria were included in this study. After eliminating the inefficient, benign and malignant nodules were 2106 and 613, respectively. The meta-analysis suggested that the difference of EI between benign and malignant nodules was statistically significant (SMD = 2.11, 95% CI [1.67, 2.55], P < .00001). The overall sensitivities of RTE and SWE were roughly comparable, whereas the difference of specificities between these 2 methods was statistically significant. In addition, statistically significant difference of AUC between RTE and SWE was observed between RTE and SWE (P < .01). The specificity of RTE was statistically higher than that of SWE; which suggests that compared with SWE, RTE may be more accurate on differentiating benign and malignant thyroid nodules.

Value of the Strain Ratio on Ultrasonic Elastography for Differentiation of Benign and Malignant Soft Tissue Tumors.

PubMed

Hahn, Seok; Lee, Young Han; Lee, Seung Hyun; Suh, Jin-Suck

2017-01-01

The purpose of this study was to evaluate whether the strain ratio provides additional value to conventional visual elasticity scores in the differentiation of benign and malignant soft tissue tumors by ultrasonic elastography. The Institutional Review Board approved the protocol of this retrospective review. Seventy-three patients who underwent elastography and had a soft tissue mass pathologically confirmed by ultrasound-guided core biopsy or surgical excision were enrolled from April 2012 through October 2014. On elastography, elasticity scores were determined with a 5-point visual scale, and the strain ratio to adjacent soft tissue at the same depth was calculated. Tumors were divided into benign and malignant groups according to the pathologic diagnoses. Elasticity scores and strain ratios were compared between benign and malignant groups, and diagnostic performance was evaluated by receiver operating characteristic curves. Of the 73 patients, 40 had benign tumors, and 33 had malignant tumors. Strain ratios (P = .003) and elasticity scores (P = .048) were significantly different between pathologic results. The areas under the receiver operating characteristic curves were 0.700 (95% confidence interval, 0.581-0.802) for the strain ratio and 0.623 (95% confidence interval, 0.515-0.746) for elastography. The strain ratios of malignant soft tissue tumors were lower than those of benign tumors and showed better diagnostic performance than did elasticity scores. The strain ratio can be used as a diagnostic indicator to predict the malignant potential of soft tissue tumors. © 2016 by the American Institute of Ultrasound in Medicine.

Diagnostic potential of real-time elastography (RTE) and shear wave elastography (SWE) to differentiate benign and malignant thyroid nodules

PubMed Central

Hu, Xiangdong; Liu, Yujiang; Qian, Linxue

2017-01-01

Abstract Background: Real-time elastography (RTE) and shear wave elastography (SWE) are noninvasive and easily available imaging techniques that measure the tissue strain, and it has been reported that the sensitivity and the specificity of elastography were better in differentiating between benign and malignant thyroid nodules than conventional technologies. Methods: Relevant articles were searched in multiple databases; the comparison of elasticity index (EI) was conducted with the Review Manager 5.0. Forest plots of the sensitivity and specificity and SROC curve of RTE and SWE were performed with STATA 10.0 software. In addition, sensitivity analysis and bias analysis of the studies were conducted to examine the quality of articles; and to estimate possible publication bias, funnel plot was used and the Egger test was conducted. Results: Finally 22 articles which eventually satisfied the inclusion criteria were included in this study. After eliminating the inefficient, benign and malignant nodules were 2106 and 613, respectively. The meta-analysis suggested that the difference of EI between benign and malignant nodules was statistically significant (SMD = 2.11, 95% CI [1.67, 2.55], P < .00001). The overall sensitivities of RTE and SWE were roughly comparable, whereas the difference of specificities between these 2 methods was statistically significant. In addition, statistically significant difference of AUC between RTE and SWE was observed between RTE and SWE (P < .01). Conclusion: The specificity of RTE was statistically higher than that of SWE; which suggests that compared with SWE, RTE may be more accurate on differentiating benign and malignant thyroid nodules. PMID:29068996

In vivo time-harmonic multifrequency elastography of the human liver

NASA Astrophysics Data System (ADS)

Tzschätzsch, Heiko; Ipek-Ugay, Selcan; Guo, Jing; Streitberger, Kaspar-Josche; Gentz, Enno; Fischer, Thomas; Klaua, Robert; Schultz, Michael; Braun, Jürgen; Sack, Ingolf

2014-04-01

Elastography is capable of noninvasively detecting hepatic fibrosis by imposing mechanical stress and measuring the viscoelastic response in the liver. Magnetic resonance elastography (MRE) relies on time-harmonic vibrations, while most dynamic ultrasound elastography methods employ transient stimulation methods. This study attempts to benefit from the advantages of time-harmonic tissue stimulation, i.e. relative insensitivity to obesity and ascites and mechanical approachability of the entire liver, and the advantages of ultrasound, i.e. time efficiency, low costs, and wide availability, by introducing in vivo time-harmonic elastography (THE) of the human liver using ultrasound and a broad range of harmonic stimulation frequencies. THE employs continuous harmonic shear vibrations at 7 frequencies from 30 to 60 Hz in a single examination and determines the elasticity and the viscosity of the liver from the dispersion of the shear wave speed within the applied frequency range. The feasibility of the method is demonstrated in the livers of eight healthy volunteers and a patient with cirrhosis. Multifrequency MRE at the same drive frequencies was used as elastographic reference method. Similar values of shear modulus and shear viscosity according the Kelvin-Voigt model were obtained by MRE and THE, indicating that the new method is suitable for in vivo quantification of the shear viscoelastic properties of the liver, however, in real-time and at a fraction of the costs of MRE. In conclusion, THE may provide a useful tool for fast assessment of the viscoelastic properties of the liver at low costs and without limitations in obesity, ascites or hemochromatosis.

Feasibility of transient elastography versus real-time two-dimensional shear wave elastography in difficult-to-scan patients.

PubMed

Staugaard, Benjamin; Christensen, Peer Brehm; Mössner, Belinda; Hansen, Janne Fuglsang; Madsen, Bjørn Stæhr; Søholm, Jacob; Krag, Aleksander; Thiele, Maja

2016-11-01

Transient elastography (TE) is hampered in some patients by failures and unreliable results. We hypothesized that real time two-dimensional shear wave elastography (2D-SWE), the FibroScan XL probe, and repeated TE exams, could be used to obtain reliable liver stiffness measurements in patients with an invalid TE examination. We reviewed 1975 patients with 5764 TE exams performed between 2007 and 2014, to identify failures and unreliable exams. Fifty-four patients with an invalid TE at their latest appointment entered a comparative feasibility study of TE vs. 2D-SWE. The initial TE exam was successful in 93% (1835/1975) of patients. Success rate increased from 89% to 96% when the XL probe became available (OR: 1.07, 95% CI 1.06-1.09). Likewise, re-examining those with a failed or unreliable TE led to a reliable TE in 96% of patients. Combining availability of the XL probe with TE re-examination resulted in a 99.5% success rate on a per-patient level. When comparing the feasibility of TE vs. 2D-SWE, 96% (52/54) of patients obtained a reliable TE, while 2D-SWE was reliable in 63% (34/54, p < 0.001). The odds of a successful 2D-SWE exam decreased with higher skin-capsule distance (OR = 0.77, 95% CI 0.67-0.98). Transient elastography can be accomplished in nearly all patients by use of the FibroScan XL probe and repeated examinations. In difficult-to-scan patients, the feasibility of TE is superior to 2D-SWE.

Comparison of shear wave velocities on ultrasound elastography between different machines, transducers, and acquisition depths: a phantom study.

PubMed

Shin, Hyun Joo; Kim, Myung-Joon; Kim, Ha Yan; Roh, Yun Ho; Lee, Mi-Jung

2016-10-01

To investigate consistency in shear wave velocities (SWVs) on ultrasound elastography using different machines, transducers and acquisition depths. The SWVs were measured using an elasticity phantom with a Young's modulus of 16.9 kPa, with three recently introduced ultrasound elastography machines (A, B and C from different vendors) and two transducers (low and high frequencies) at four depths (2, 3, 4 and 5 cm). Mean SWVs from 15 measurements and coefficient of variations (CVs) were compared between three machines, two transducers and four acquisition depths. The SWVs using the high frequency transducer were not acquired at 5 cm depth in machine B, and a high frequency transducer was not available in machine C. The mean SWVs in the three machines were different (p ≤ 0.002). The CVs were 0-0.09 in three machines. The mean SWVs between the two transducers were different (p < 0.001) except at 4 and 5 cm depths in machine A. The SWVs were affected by the acquisition depths in all conditions (p < 0.001). There is considerable difference in SWVs on ultrasound elastography depending on different machines, transducers and acquisition depths. Caution is needed when using the cutoff values of SWVs in different conditions. • The shear wave velocities (SWVs) are different between different ultrasound elastography machines • The SWVs are also different between different transducers and acquisition depths • Caution is needed when using the cutoff SWVs measured under different conditions.

Comparison of Two Different Ultrasound Devices Using Strain Elastography Technology in the Diagnosis of Breast Lesions Related to the Histologic Results.

PubMed

Farrokh, André; Schaefer, Fritz; Degenhardt, Friedrich; Maass, Nicolai

2018-05-01

This study was conducted to provide evidence that elastograms of two different devices and different manufacturers using the same technical approach provide the same diagnoses. A total of 110 breast lesions were prospectively analysed by two experts in ultrasound, using the strain elastography function from two different manufacturers (Hitachi HI-RTE, Hitachi Medical Systems, Wiesbaden, Germany; and Siemens eSie Touch, Siemens Medical Systems, Erlangen, Germany). Results were compared with the histopathologic results. Applying the Bowker test of symmetry, no statistically significant difference between the two elastography functions of these two devices was found (p = 0.120). The Cohen's kappa of k = 0.591 showed moderate strength of agreement between the two elastograms. The two examiners yielded moderate strength of agreement analysing the elastograms (Hitachi HI-RTE, k = 0.478; Siemens eSie Touch, k = 0.441). In conclusion, evidence is provided that elastograms of the same lesion generated by two different ultrasound devices equipped with a strain elastography function do not significantly differ. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Accuracy of real-time shear wave elastography in the assessment of normal liver tissue in the guinea pig (cavia porcellus).

PubMed

Glińska-Suchocka, K; Kubiak, K; Spużak, J; Jankowski, M; Borusewicz, P

2017-03-28

Shear wave elastography is a novel technique enabling real-time measurement of the elasticity of liver tissue. The color map is superimposed on the classic ultrasound image of the assessed tissue, which enables a precise evaluation of the stiffness of the liver tissue. The aim of the study was to assess the stiffness of normal liver tissue in the guinea pig using shear wave elastography. The study was carried out on 36 guinea pigs using the SuperSonic Imagine Aixplorer scanner, and a 1 to 6 MH convex SC6-1 transducer. An ultrasound guided Try-Cut liver core needle biopsy was carried out in all the studied animals and the collected samples were examined to exclude pathological lesions. The mean liver tissue stiffness ranged from 0.89 to 5.40 kPa. We found that shear wave elastography is an easy, non-invasive technique that can be used to assess the stiffness of liver tissue. The obtained results can be used in future studies to assess the types and changes of liver tissue in the course of various types of liver disease.

Prostate Cancer Detection and Diagnosis: The Role of MR and its Comparison to other Diagnostic Modalities – A Radiologist's Perspective

PubMed Central

Penzkofer, Tobias; Tempany-Afdhal, Clare M.

2013-01-01

It is now universally recognized that many prostate cancers are over-diagnosed and over-treated. The European Randomized Study of Screening for Prostate Cancer (ERSPC) from 2009 evidenced that, to save one man from death of prostate cancer, over 1,400 men had to be screened, and 48 had to undergo treatment. Detection of prostate cancer is traditionally based upon digital rectal examination (DRE) and measuring serum prostate specific antigen (PSA), followed by ultrasound guided biopsy. The primary role of imaging for the detection and diagnosis of prostate cancer has been transrectal ultrasound (TRUS) guidance during biopsy. MRI has traditionally been used primarily for staging disease in men with biopsy proven cancer. It is has a well-established role in detecting T3 disease, planning radiation therapy, especially 3D conformal or intensity modulated external beam radiation therapy (IMRT), and planning and guiding interstitial seed implant or brachytherapy. New advances have now established prostate MRI can accurately characterize focal lesions within the gland, an ability that has led to new opportunities for improved cancer detection and guidance for biopsy. There are two new approaches to prostate biopsy are under investigation both use pre-biopsy MRI to define potential targets for sampling and then the biopsy is performed either with direct real-time MR guidance (in-bore) or MR fusion/registration with TRUS images (out-of-bore). In-bore or out-of-bore MRI-guided prostate biopsies have the advantage of using the MR target definition for accurate localization and sampling of targets or suspicious lesions. The out-of-bore method uses combined MRI/TRUS with fusion software that provided target localization and increases the sampling accuracy for TRUS-guided biopsies by integrating prostate MRI information with TRUS. Newer parameters for each imaging modality such as sonoelastography or shear wave elastography (SWE), contrast enhanced US (CEUS) and MRI-elastography, show promise to further enrich data sets. PMID:24000133

Effectiveness of the Benign and Malignant Diagnosis of Mediastinal and Hilar Lymph Nodes by Endobronchial Ultrasound Elastography.

PubMed

Huang, Haidong; Huang, Zhiang; Wang, Qin; Wang, Xinan; Dong, Yuchao; Zhang, Wei; Zarogoulidis, Paul; Man, Yan-Gao; Schmidt, Wolfgang Hohenforst; Bai, Chong

2017-01-01

Background and Objectives: Endobronchial ultrasound elastography is a new technique for describing the stiffness of tissue during endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). The aims of this study were to investigate the diagnostic value of Endobronchial ultrasound (EBUS) elastography for distinguishing the difference between benign and malignant lymph nodes among mediastinal and hilar lymph node. Materials and Methods: From June 2015 to August 2015, 47 patients confirmed of mediastinal and hilar lymph node enlargement through examination of Computed tomography (CT) were enrolled, and a total of 78 lymph nodes were evaluated by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). EBUS-guided elastography of lymph nodes was performed prior to EBUS-TBNA. A convex probe EBUS was used with a new EBUS processor to assess elastographic patterns that were classified based on color distribution as follows: Type 1, predominantly non-blue (green, yellow and red); Type 2, part blue, part non-blue (green, yellow and red); Type 3, predominantly blue. Pathological determination of malignant or benign lymph nodes was used as the gold standard for this study. The elastographic patterns were compared with the final pathologic results from EBUS-TBNA. Results: On pathological evaluation of the lymph nodes, 45 were benign and 33 were malignant. The lymph nodes that were classified as Type 1 on endobronchial ultrasound elastography were benign in 26/27 (96.3%) and malignant in 1/27 (3.7%); for Type 2 lymph nodes, 15/20 (75.0%) were benign and 5/20 (25.0%) were malignant; Type 3 lymph nodes were benign in 4/31 (12.9%) and malignant in 27/31 (87.1%). In classifying Type 1 as 'benign' and Type 3 as 'malignant,' the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy rates were 96.43%, 86.67%, 87.10%, 96.30%, 91.38%, respectively. Conclusion: EBUS elastography of mediastinal and hilar lymph nodes is a noninvasive technique that can be performed reliably and may be helpful in the prediction of benign and malignant lymph nodes among mediastinal and hilar lymph node during EBUS-TBNA.

Aerosol Radiative Forcing over North India during Pre-Monsoon Season using WRF-Chem

NASA Astrophysics Data System (ADS)

Misra, A.; Kumar, K.; Michael, M.; Tripathi, S. N.

2013-12-01

Study of aerosols is important for a fair understanding of the Earth climate system. This requires knowledge of the physical, chemical, optical, and morphological properties of aerosols. Aerosol radiative forcing provides information on the effect of aerosols on the Earth radiation budget. Radiative forcing estimates using model data provide an opportunity to examine the contribution of individual aerosol species to overall radiative forcing. We have used Weather Research and Forecast with Online Chemistry (WRF-Chem) derived aerosol concentration data to compute aerosol radiative forcing over north India during pre-monsoon season of 2008, 2009, and 2010. WRF-Chem derived mass concentrations are converted to number concentrations using standard procedure. Optical Properties of Aerosol and Cloud (OPAC) software package is used to compute extinction and scattering coefficients, and asymmetry parameter. Computations are performed at different altitudes and the obtained values are integrated to get the column optical properties. Santa Barbara Discrete Ordinate Radiative Transfer (SBDART) model is used to calculate the radiative forcing at surface and top-of-atmosphere. Higher values of aerosol radiative forcing are observed over desert region in western Indian state of Rajasthan, and Punjab of Pakistan. Contribution of individual aerosol species to atmospheric radiative forcing is also assessed. Dust radiative forcing is high over western India. Radiative forcing due to BC and water-soluble (WASO) aerosols are higher over north-west Indian states of Punjab and Haryana, and the Indo-Gangetic Basin. A pool of high WASO optical depth and radiative forcing is observed over the Indo-Bangladesh border. The findings of aerosol optical depth and radiative forcing are consistent with the geography and prevailing aerosol climatology of various regions. Heating rate profiles due to total aerosols and only due to BC have been evaluated at selected stations in north India. They show variation between various stations and seasons.

Age-related changes in pancreatic elasticity: When should we be concerned about their effect on strain elastography?

PubMed

Chantarojanasiri, Tanyaporn; Hirooka, Yoshiki; Kawashima, Hiroki; Ohno, Eizaburo; Sugimoto, Hiroyuki; Hayashi, Daijuro; Kuwahara, Takamichi; Yamamura, Takeshi; Funasaka, Kohei; Nakamura, Masanao; Miyahara, Ryoji; Ishigami, Masatoshi; Watanabe, Osamu; Hashimoto, Senju; Goto, Hidemi

2016-07-01

Ultrasound strain elastography is one of the useful methods for evaluating pancreatic lesions. During aging, several pancreatic parenchymal changes occur that may interfere with the interpretation of the ultrasound images. We studied age-related changes in pancreatic elasticity using transabdominal ultrasound strain elastography in subjects without known pancreatic disease. This study was conducted at Nagoya University Hospital, which is an academic medical center, and included 102 subjects (66 women and 39 men) aged 20-85years (mean 58.6±17.5) who underwent transabdominal ultrasonography for screening and follow-up for non-pancreatic diseases. Strain elastography of the pancreas was performed, and the results were subjected to quantitative strain histogram analysis. The correlations of age with four elastographic parameters (Mean, Standard deviation, Skewness, and Kurtosis) and other findings, including hyperechoic pancreas, hyperechoic liver, and diabetes, were evaluated. There was a significant correlation between increasing age and elastographic parameters such as the Mean (P=0.004), Skewness (P=0.007), and Kurtosis (P=0.03), and these differences became significant after the age of 40. The prevalence of hyperechoic pancreas increased with age (P<0.001), and the Means were lower in those with hyperechoic pancreas (P=0.004) and a higher body mass index (BMI, P=0.008). No significant correlations with diabetes, hyperechoic liver, or elastographic parameters were demonstrated. Strain elastography demonstrated elastographic changes in the pancreas with aging that included a decreasing Mean and increasing Skewness and Kurtosis after the age of 40. The prevalence of pancreatic hyperechogenicity increased, and the pancreatic hyperechogenicity was significantly negatively correlated with the Mean. Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation into the visual perceptive ability of anaesthetists during ultrasound-guided interscalene and femoral blocks conducted on soft embalmed cadavers: a randomised single-blind study.

PubMed

Mustafa, A; Seeley, J; Munirama, S; Columb, M; McKendrick, M; Schwab, A; Corner, G; Eisma, R; Mcleod, G

2018-04-01

Errors may occur during regional anaesthesia whilst searching for nerves, needle tips, and test doses. Poor visual search impacts on decision making, clinical intervention, and patient safety. We conducted a randomised single-blind study in a single university hospital. Twenty trainees and two consultants examined the paired B-mode and fused B-mode and elastography video recordings of 24 interscalene and 24 femoral blocks conducted on two soft embalmed cadavers. Perineural injection was randomised equally to 0.25, 0.5, and 1.0 ml volumes. Tissue displacement perceived on both imaging modalities was defined as 'target' or 'distractor'. Our primary objective was to test the anaesthetists' perception of the number and proportion of targets and distractors on B-mode and fused elastography videos collected during femoral and sciatic nerve block on soft embalmed cadavers. Our secondary objectives were to determine the differences between novices and experts, and between test-dose volumes, and to measure the area and brightness of spread and strain patterns. All anaesthetists recognised perineural spread using 0.25 ml volumes. Distractor patterns were recognised in 133 (12%) of B-mode and in 403 (38%) of fused B-mode and elastography patterns; P<0.001. With elastography, novice recognition improved from 12 to 37% (P<0.001), and consultant recognition increased from 24 to 53%; P<0.001. Distractor recognition improved from 8 to 31% using 0.25 ml volumes (P<0.001), and from 15 to 45% using 1 ml volumes (P<0.001). Visual search improved with fusion elastography, increased volume, and consultants. A need exists to investigate image search strategies. Copyright © 2018 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

The potential of high intensity focused ultrasound (HIFU) combine phase-sensitive optical coherence tomography (PhS-OCT) for diseases diagnosis, treatment and monitoring

NASA Astrophysics Data System (ADS)

Zhou, Kanheng; Wang, Yan; Feng, Kairui; Li, Chunhui; Huang, Zhihong

2018-02-01

HIFU is a truly noninvasive, acoustic therapeutic technique that utilizes high intensity acoustic field in the focus to kill the targeted tissue for disease treatment purpose. The mechanical properties of targeted tissue changes before and after treatment, and this change can be accurately detected by shear wave elastography. Hence, shear wave elastography is usually used for monitoring HIFU treatment asynchronously. To improve the low spatial resolution in ultrasound shear wave elastography, and to perform diseases diagnosis, treatment and monitoring in the same system, a new setup that combines HIFU and PhS-OCT system was proposed in this study. This proposed setup could do 1) HIFU treatment when the transducer works at high energy level, 2) ultrasound induced shear wave optical coherence elastography for HIFU treatment asynchronous monitoring when the transducer works at low energy level. Ex-vivo bovine liver tissue was treated at the same energy level for different time (0s, 1s, 5s, 9s) in this research. Elastography was performed on the lesion area of the sample after HIFU treatment, and the elastogram was reconstructed by the time of flight time method. The elastogram results clearly show the boundary of HIFU lesion area and surrounding normal tissue, even for 1s treatment time. And the average elasticity of the lesion grows linearly as the treatment time increases. Combined with OCT needle probe, the proposed method has a large potential not only to be used for superficial diseases treatment, but also to be used for high-precision-demanded diseases treatment, e.g. nervous disease treatment.

Interobserver variability of ultrasound elastography and the ultrasound BI-RADS lexicon of breast lesions.

PubMed

Park, Chang Suk; Kim, Sung Hun; Jung, Na Young; Choi, Jae Jung; Kang, Bong Joo; Jung, Hyun Seouk

2015-03-01

Elastographpy is a newly developed noninvasive imaging technique that uses ultrasound (US) to evaluate tissue stiffness. The interpretation of the same elastographic images may be variable according to reviewers. Because breast lesions are usually reported according to American College of Radiology Breast Imaging and Data System (ACR BI-RADS) lexicons and final category, we tried to compare observer variability between lexicons and final categorization of US BI-RADS and the elasticity score of US elastography. From April 2009 to February 2010, 1356 breast lesions in 1330 patients underwent ultrasound-guided core biopsy. Among them, 63 breast lesions in 55 patients (mean age, 45.7 years; range, 21-79 years) underwent both conventional ultrasound and elastography and were included in this study. Two radiologists independently performed conventional ultrasound and elastography, and another three observers reviewed conventional ultrasound images and elastography videos. Observers independently recorded the elasticity score for a 5-point scoring system proposed by Itoh et al., BI-RADS lexicons and final category using ultrasound BI-RADS. The histopathologic results were obtained and used as the reference standard. Interobserver variability was evaluated. Of the 63 lesions, 42 (66.7 %) were benign, and 21 (33.3 %) were malignant. The highest value of concordance among all variables was achieved for the elasticity score (k = 0.59), followed by shape (k = 0.54), final category (k = 0.48), posterior acoustic features (k = 0.44), echogenecity and orientation (k = 0.43). The least concordances were margin (k = 0.26), lesion boundary (k = 0.29) and calcification (k = 0.3). Elasticity score showed a higher level of interobserver agreement for the diagnosis of breast lesions than BI-RADS lexicons and final category.

Prospective comparison of magnetic resonance imaging to transient elastography and serum markers for liver fibrosis detection.

PubMed

Dyvorne, Hadrien A; Jajamovich, Guido H; Bane, Octavia; Fiel, M Isabel; Chou, Hsin; Schiano, Thomas D; Dieterich, Douglas; Babb, James S; Friedman, Scott L; Taouli, Bachir

2016-05-01

Establishing accurate non-invasive methods of liver fibrosis quantification remains a major unmet need. Here, we assessed the diagnostic value of a multiparametric magnetic resonance imaging (MRI) protocol including diffusion-weighted imaging (DWI), dynamic contrast-enhanced (DCE)-MRI and magnetic resonance elastography (MRE) in comparison with transient elastography (TE) and blood tests [including ELF (Enhanced Liver Fibrosis) and APRI] for liver fibrosis detection. In this single centre cross-sectional study, we prospectively enrolled 60 subjects with liver disease who underwent multiparametric MRI (DWI, DCE-MRI and MRE), TE and blood tests. Correlation was assessed between non-invasive modalities and histopathologic findings including stage, grade and collagen content, while accounting for covariates such as age, sex, BMI, HCV status and MRI-derived fat and iron content. ROC curve analysis evaluated the performance of each technique for detection of moderate-to-advanced liver fibrosis (F2-F4) and advanced fibrosis (F3-F4). Magnetic resonance elastography provided the strongest correlation with fibrosis stage (r = 0.66, P < 0.001), inflammation grade (r = 0.52, P < 0.001) and collagen content (r = 0.53, P = 0.036). For detection of moderate-to-advanced fibrosis (F2-F4), AUCs were 0.78, 0.82, 0.72, 0.79, 0.71 for MRE, TE, DCE-MRI, DWI and APRI, respectively. For detection of advanced fibrosis (F3-F4), AUCs were 0.94, 0.77, 0.79, 0.79 and 0.70, respectively. Magnetic resonance elastography provides the highest correlation with histopathologic markers and yields high diagnostic performance for detection of advanced liver fibrosis and cirrhosis, compared to DWI, DCE-MRI, TE and serum markers. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Doppler ultrasonography combined with transient elastography improves the non-invasive assessment of fibrosis in patients with chronic liver diseases.

PubMed

Alempijevic, Tamara; Zec, Simon; Nikolic, Vladimir; Veljkovic, Aleksandar; Stojanovic, Zoran; Matovic, Vera; Milosavljevic, Tomica

2017-01-31

Accurate clinical assessment of liver fibrosis is essential and the aim of our study was to compare and combine hemodynamic Doppler ultrasonography, liver stiffness by transient elastography, and non-invasive serum biomarkers with the degree of fibrosis confirmed by liver biopsy, and thereby to determine the value of combining non-invasive method in the prediction significant liver fibrosis. We included 102 patients with chronic liver disease of various etiology. Each patient was evaluated using Doppler ultrasonography measurements of the velocity and flow pattern at portal trunk, hepatic and splenic artery, serum fibrosis biomarkers, and transient elastography. These parameters were then input into a multilayer perceptron artificial neural network with two hidden layers, and used to create models for predicting significant fibrosis. According to METAVIR score, clinically significant fibrosis (≥F2) was detected in 57.8% of patients. A model based only on Doppler parameters (hepatic artery diameter, hepatic artery systolic and diastolic velocity, splenic artery systolic velocity and splenic artery Resistance Index), predicted significant liver fibrosis with a sensitivity and specificity of75.0% and 60.0%. The addition of unrelated non-invasive tests improved the diagnostic accuracy of Doppler examination. The best model for prediction of significant fibrosis was obtained by combining Doppler parameters, non-invasive markers (APRI, ASPRI, and FIB-4) and transient elastography, with a sensitivity and specificity of 88.9% and 100%. Doppler parameters alone predict the presence of ≥F2 fibrosis with fair accuracy. Better prediction rates are achieved by combining Doppler variables with non-invasive markers and liver stiffness by transient elastography.

Five-dimensional ultrasound system for soft tissue visualization.

PubMed

Deshmukh, Nishikant P; Caban, Jesus J; Taylor, Russell H; Hager, Gregory D; Boctor, Emad M

2015-12-01

A five-dimensional ultrasound (US) system is proposed as a real-time pipeline involving fusion of 3D B-mode data with the 3D ultrasound elastography (USE) data as well as visualization of these fused data and a real-time update capability over time for each consecutive scan. 3D B-mode data assist in visualizing the anatomy of the target organ, and 3D elastography data adds strain information. We investigate the feasibility of such a system and show that an end-to-end real-time system, from acquisition to visualization, can be developed. We present a system that consists of (a) a real-time 3D elastography algorithm based on a normalized cross-correlation (NCC) computation on a GPU; (b) real-time 3D B-mode acquisition and network transfer; (c) scan conversion of 3D elastography and B-mode volumes (if acquired by 4D wobbler probe); and (d) visualization software that fuses, visualizes, and updates 3D B-mode and 3D elastography data in real time. We achieved a speed improvement of 4.45-fold for the threaded version of the NCC-based 3D USE versus the non-threaded version. The maximum speed was 79 volumes/s for 3D scan conversion. In a phantom, we validated the dimensions of a 2.2-cm-diameter sphere scan-converted to B-mode volume. Also, we validated the 5D US system visualization transfer function and detected 1- and 2-cm spherical objects (phantom lesion). Finally, we applied the system to a phantom consisting of three lesions to delineate the lesions from the surrounding background regions of the phantom. A 5D US system is achievable with real-time performance. We can distinguish between hard and soft areas in a phantom using the transfer functions.

Value of ultrasound shear wave elastography in the diagnosis of adenomyosis.

PubMed

Acar, S; Millar, E; Mitkova, M; Mitkov, V

2016-11-01

The aim of the study was to assess the accuracy of ultrasound shear wave elastography in the diagnosis of adenomyosis. One hundred and fifty three patients were examined. Ninety-seven patients were with suspected adenomyosis and 56 patients were with unremarkable myometrium. Adenomyosis was confirmed in 39 cases (A subgroup) and excluded in 14 cases (B subgroup) in the main group based on morphological examination. All patients underwent ultrasound examination using an Aixplorer (Supersonic Imagine, France) scanner with application of shear wave elastography during transvaginal scanning. Retrospective analysis of the elastography criteria against the findings from morphological/histological examination was performed. The following values of Young's modulus were found in subgroup A (adenomyosis): Emean - 72.7 (22.6-274.2) kPa (median, 5-95th percentiles), Emax - 94.8 (29.3-300.0) kPa, SD - 9.9 (2.6-26.3) kPa; in subgroup B (non adenomyosis) - 28.3 (12.7-59.5) kPa, 33.6 (16.0-80.8) kPa, 3.0 (1.4-15.6) kPa; in the control group - 24.4 (17.9-32.4) kPa, 29.8 (21.6-40.8) kPa, 2.3 (1.3-6.1) kPa, respectively (P < 0.05 for all comparison with subgroup В and the control group). The Emean cut-off value for adenomyosis diagnosis was 34.6 kPa. The sensitivity, specificity, positive predictive value, negative predictive value and area under curve (AUC) were 89.7%, 92.9%, 97.2%, 76.5% and 0.908. The Emax cut-off value was 45.4 kPa (89.7%, 92.9%, 97.2%, 76.5% and 0.907, respectively). This study showed a significant increase of the myometrial stiffness estimated with shear wave elastography use in patients with adenomyosis.

Shear-wave elastography of the testis in the healthy man - determination of standard values.

PubMed

Trottmann, M; Marcon, J; D'Anastasi, M; Bruce, M F; Stief, C G; Reiser, M F; Buchner, A; Clevert, D A

2016-01-01

Real-time shear-wave elastography (SWE) is a newly developed technique for the sonographic quantification of tissue elasticity, which already is used in the assessment of breast and thyroid lesions. Due to limited overlying tissue, the testes are ideally suited for assessment using shear wave elastography. To our knowledge, no published data exist on real-time SWE of the testes. Sixty six male volunteers (mean age 51.86±18.82, range 20-86) with no known testicular pathology underwent normal B-mode sonography and multi-frame shear-wave elastography of both testes using the Aixplorer ® ultrasound system (SuperSonic Imagine, Aix en Provence, France). Three measurements were performed for each testis; one in the upper pole, in the middle portion and in the lower pole respectively. The results were statistically evaluated using multivariate analysis. Mean shear-wave velocity values were similar in the inferior and superior part of the testicle (1.15 m/s) and were significantly lower in the centre (0.90 m/s). These values were age-independent. Testicular stiffness was significantly lower in the upper pole than in the rest of the testis with increasing volume (p = 0.007). Real-time shear-wave elastography proved to be feasible in the assessment of testicular stiffness. It is important to consider the measurement region as standard values differ between the centre and the testicular periphery. Further studies with more subjects may be required to define the normal range of values for each age group. Useful clinical applications could include the diagnostic work-up of patients with scrotal masses or male infertility.

[The diagnostic value of ultrasonic elastography and ultrasonography comprehensive score in cervical lesions].

PubMed

Lu, R; Xiao, Y

2017-07-18

Objective: To evaluate the clinical value of ultrasonic elastography and ultrasonography comprehensive scoring method in the diagnosis of cervical lesions. Methods: A total of 116 patients were selected from the Department of Gynecology of the first hospital affiliated with Central South University from March 2014 to September 2015.All of the lesions were preoperatively examined by Doppler Ultrasound and elastography.The elasticity score was determined by a 5-point scoring method. Calculation of the strain ratio was based on a comparison of the average strain measured in the lesion with the adjacent tissue of the same depth, size, and shape.All these ultrasonic parameters were quantified, added, and arrived at ultrasonography comprehensive scores.To use surgical pathology as the gold standard, the sensitivity, specificity, accuracy of Doppler Ultrasound, elasticity score and strain ratio methods and ultrasonography comprehensive scoring method were comparatively analyzed. Results: (1) The sensitivity, specificity, and accuracy of Doppler Ultrasound in diagnosing cervical lesions were 82.89% (63/76), 85.0% (34/40), and 83.62% (97/116), respectively.(2) The sensitivity, specificity, and accuracy of the elasticity score method were 77.63% (59/76), 82.5% (33/40), and 79.31% (92/116), respectively; the sensitivity, specificity, and accuracy of the strain ratio measure method were 84.21% (64/76), 87.5% (35/40), and 85.34% (99/116), respectively.(3) The sensitivity, specificity, and accuracy of ultrasonography comprehensive scoring method were 90.79% (69/76), 92.5% (37/40), and 91.38% (106/116), respectively. Conclusion: (1) It was obvious that ultrasonic elastography had certain diagnostic value in cervical lesions. Strain ratio measurement can be more objective than elasticity score method.(2) The combined application of ultrasonography comprehensive scoring method, ultrasonic elastography and conventional sonography was more accurate than single parameter.

Force approach to radiation reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

López, Gustavo V., E-mail: gulopez@udgserv.cencar.udg.mx

The difficulty of the usual approach to deal with the radiation reaction is pointed out, and under the condition that the radiation force must be a function of the external force and is zero whenever the external force be zero, a new and straightforward approach to radiation reaction force and damping is proposed. Starting from the Larmor formula for the power radiated by an accelerated charged particle, written in terms of the applied force instead of the acceleration, an expression for the radiation force is established in general, and applied to the examples for the linear and circular motion ofmore » a charged particle. This expression is quadratic in the magnitude of the applied force, inversely proportional to the speed of the charged particle, and directed opposite to the velocity vector. This force approach may contribute to the solution of the very old problem of incorporating the radiation reaction to the motion of the charged particles, and future experiments may tell us whether or not this approach point is in the right direction.« less

Evaluation of posterior porcine sclera elasticity in situ as a function of IOP

NASA Astrophysics Data System (ADS)

Nair, Achuth; Wu, Chen; Singh, Manmohan; Liu, Chih Hao; Raghunathan, Raksha; Nguyen, Jennifer; Goh, Megan; Aglyamov, Salavat; Larin, Kirill V.

2018-02-01

The biomechanical properties of the sclera could provide key information regarding the progression and etiology of ocular diseases. For example, an elevated intraocular pressure is one of the most common risk factors for glaucoma and can cause pathological deformations in the tissues of the posterior eye, such as the sclera, potentially damaging these vital tissues. Previous work has evaluated scleral biomechanical response to global displacements with techniques such as inflation testing. However, these methods cannot provide localized biomechanical assessments. In this pilot work, we induce low amplitude (< 10 μm) elastic waves using acoustic radiation force in posterior scleral tissue of fresh porcine eyes (n=2) in situ. The wave propagation induced using an ultrasound transducer was detected across an 8 mm region using a phase-sensitive optical coherence elastography system (PhS-OCE). The elastographic measurements were taken at various artificially controlled intraocular pressures (IOP). The IOP was pre-cycled before being set to 10 mmHg for the first measurement. Subsequent measurements were taken at 20 mmHg and 30 mmHg for each sample. The results show an increase in the stiffness of the sclera as a function of IOP. Furthermore, we observed a variation in the elasticity based on direction, suggesting that the sclera has anisotropic biomechanical properties. Our results show that OCE is an effective method for evaluating the mechanical properties of the sclera, and reveals a new area for our future work.

Ultrasound elastography in diagnosis and follow-up for patients with sialolithiasis.

PubMed

Reichel, Christoph A; Vincek, Teresa; Gellrich, Donata; Schrötzlmair, Florian; Clevert, Dirk; Zengel, Pamela

2018-05-03

This study aims to answer whether acoustic radiation force impulse imaging (ARFI) can reasonably be employed in initial examination and follow-up during therapy in patients with sialolithiasis, one of the most common non-malignant disorders of the salivary glands. Mechanical tissue properties of affected and contralateral healthy salivary glands were analyzed by ARFI in 129 patients with sialolithiasis. In different subgroup analyses, ARFI shear wave velocity values were compared between healthy and diseased submandibular or parotid glands, salivary glands with calculi exhibiting different sizes, as well as before and after therapy. The patients' symptoms were evaluated by a standardized questionnaire. The t-test (2 groups) or the One-way ANOVA test (>2 groups) was used for the estimation of stochastic probability in intergroup comparisons. Submandibular or parotid glands affected by sialolithiasis were found to exhibit significant lower ARFI values as compared to the healthy contralateral glands in the same individuals. ARFI values in submandibular glands with a single calculus of more than 5 mm in diameter or with multiple calculi as well as in parotid glands with calculi exhibiting diameters of more than 5 mm were significantly higher as compared to the respective healthy contralateral glands. No significant differences in ARFI values of affected salivary glands were detected between patients with low or high symptom perception. ARFI provides an easy, quick and reliable diagnostic tool for the objective assessment of disease severity and progression in patients with sialolithiasis that can simply be implemented in pre-existing ultrasound protocols.

A New Clinical HIFU System (Teleson II)

NASA Astrophysics Data System (ADS)

Ma, Yixin; Symonds-Tayler, Richard; Rivens, Ian H.; ter Haar, Gail R.

2007-05-01

Previous clinical trials with our first prototype HIFU system (Teleson I) for the treatment of liver tumors, demonstrated a major challenge to be treatment of those tumors located behind the ribs. We have designed a new multi-element transducer for rib sparing. Initial simulation and experimental results (using a single channel power amplifier) are very encouraging. A new clinical HIFU system which can drive the multi-element transducer and control each channel independently is being designed and constructed. This second version of a clinical prototype HIFU system consists of a 3D motorised gantry, a multi-channel signal generator, a multi-channel power amplifier, a user interface PC, an embedded controller and auxiliary circuits for real-time interleaving/synchronization control and a to-be-implemented safety monitoring and data logging unit. For multi-element transducers, each element can be individually switched on and off for rib sparing, and phase and amplitude modulated for potential phased array applications. The multi-channel power amplifier can be switched on/off very rapidly at required intervals to interleave with ultrasound B-Scan imaging for HIFU monitoring or radiation force elastography imaging via a dedicated interleaving/timing module. The gantry movement can also be synchronised with power amplifier on/off and phase/amplitude updating for lesion generation under a wide variety of conditions including single lesions, lesion arrays and lesions "tracks" created whilst translating the active transducer. Results from testing the system using excised tissue will be presented.

Quantitative analysis of retina layer elasticity based on automatic 3D segmentation (Conference Presentation)

NASA Astrophysics Data System (ADS)

He, Youmin; Qu, Yueqiao; Zhang, Yi; Ma, Teng; Zhu, Jiang; Miao, Yusi; Humayun, Mark; Zhou, Qifa; Chen, Zhongping

2017-02-01

Age-related macular degeneration (AMD) is an eye condition that is considered to be one of the leading causes of blindness among people over 50. Recent studies suggest that the mechanical properties in retina layers are affected during the early onset of disease. Therefore, it is necessary to identify such changes in the individual layers of the retina so as to provide useful information for disease diagnosis. In this study, we propose using an acoustic radiation force optical coherence elastography (ARF-OCE) system to dynamically excite the porcine retina and detect the vibrational displacement with phase resolved Doppler optical coherence tomography. Due to the vibrational mechanism of the tissue response, the image quality is compromised during elastogram acquisition. In order to properly analyze the images, all signals, including the trigger and control signals for excitation, as well as detection and scanning signals, are synchronized within the OCE software and are kept consistent between frames, making it possible for easy phase unwrapping and elasticity analysis. In addition, a combination of segmentation algorithms is used to accommodate the compromised image quality. An automatic 3D segmentation method has been developed to isolate and measure the relative elasticity of every individual retinal layer. Two different segmentation schemes based on random walker and dynamic programming are implemented. The algorithm has been validated using a 3D region of the porcine retina, where individual layers have been isolated and analyzed using statistical methods. The errors compared to manual segmentation will be calculated.

Time Harmonic Elastography Reveals Sensitivity of Liver Stiffness to Water Ingestion.

PubMed

Ipek-Ugay, Selcan; Tzschätzsch, Heiko; Hudert, Christian; Marticorena Garcia, Stephan Rodrigo; Fischer, Thomas; Braun, Jürgen; Althoff, Christian; Sack, Ingolf

2016-06-01

The aim of the study was to test the sensitivity of liver stiffness (LS) measured by time harmonic elastography in large tissue windows to water uptake and post-prandial effects. Each subject gave written informed consent to participate in this institutional review board-approved prospective study. LS was measured by time harmonic elastography in 10 healthy volunteers pre- and post-prandially, as well as before, directly after and 2 h after drinking water. The LS-time function during water intake was measured in 14 scans over 3 h in five volunteers. LS increased by 10% (p = 0.0015) post-prandially and by 11% (p = 0.0024) after pure water ingestion, and decreased to normal values after 2 h. LS was lower after overnight fasting than after 2-h fasting (3%, p = 0.04). Over the time course, LS increased to post-water peak values 15 min after drinking 0.25 L water and remained unaffected by further ingestion of water. In conclusion, our study indicates that LS measured by time harmonic elastography represents an effective-medium property sensitive to physiologic changes in vascular load of the liver. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Transurethral prostate magnetic resonance elastography: prospective imaging requirements.

PubMed

Arani, Arvin; Plewes, Donald; Chopra, Rajiv

2011-02-01

Tissue stiffness is known to undergo alterations when affected by prostate cancer and may serve as an indicator of the disease. Stiffness measurements can be made with magnetic resonance elastography performed using a transurethral actuator to generate shear waves in the prostate gland. The goal of this study was to help determine the imaging requirements of transurethral magnetic resonance elastography and to evaluate whether the spatial and stiffness resolution of this technique overlapped with the requirements for prostate cancer detection. Through the use of prostate-mimicking gelatin phantoms, frequencies of at least 400 Hz were necessary to obtain accurate stiffness measurements of 10 mm diameter inclusions, but the detection of inclusions with diameters as small as 4.75 mm was possible at 200 Hz. The shear wave attenuation coefficient was measured in vivo in the canine prostate gland, and was used to predict the detectable penetration depth of shear waves in prostate tissue. These results suggested that frequencies below 200 Hz could propagate to the prostate boundary with a signal to noise ratio (SNR) of 60 and an actuator capable of producing 60 μm displacements. These requirements are achievable with current imaging and actuator technologies, and motivate further investigation of magnetic resonance elastography for the targeting of prostate cancer. Copyright © 2010 Wiley-Liss, Inc.

Ultrasound Elastography for Estimation of Regional Strain of Multilayered Hydrogels and Tissue-Engineered Cartilage

PubMed Central

Chung, Chen-Yuan; Heebner, Joseph; Baskaran, Harihara; Welter, Jean F.; Mansour, Joseph M.

2015-01-01

Tissue-engineered (TE) cartilage constructs tend to develop inhomogeneously, thus, to predict the mechanical performance of the tissue, conventional biomechanical testing, which yields average material properties, is of limited value. Rather, techniques for evaluating regional and depth-dependent properties of TE cartilage, preferably non-destructively, are required. The purpose of this study was to build upon our previous results and to investigate the feasibility of using ultrasound elastography to non-destructively assess the depth-dependent biomechanical characteristics of TE cartilage while in a sterile bioreactor. As a proof-of-concept, and to standardize an assessment protocol, a well-characterized three-layered hydrogel construct was used as a surrogate for TE cartilage, and was studied under controlled incremental compressions. The strain field of the construct predicted by elastography was then validated by comparison with a poroelastic finite-element analysis (FEA). On average, the differences between the strains predicted by elastography and the FEA were within 10%. Subsequently engineered cartilage tissue was evaluated in the same test fixture. Results from these examinations showed internal regions where the local strain was 1–2 orders of magnitude greater than that near the surface. These studies document the feasibility of using ultrasound to evaluate the mechanical behaviors of maturing TE constructs in a sterile environment. PMID:26077987

Elastography methods for the non-invasive assessment of portal hypertension.

PubMed

Roccarina, Davide; Rosselli, Matteo; Genesca, Joan; Tsochatzis, Emmanuel A

2018-02-01

The gold standard to assess the presence and severity of portal hypertension remains the hepatic vein pressure gradient, however the recent development of non-invasive assessment using elastography techniques offers valuable alternatives. In this review, we discuss the diagnostic accuracy and utility of such techniques in patients with portal hypertension due to cirrhosis. Areas covered: A literature search focused on liver and spleen stiffness measurement with different elastographic techniques for the assessment of the presence and severity of portal hypertension and oesophageal varices in people with chronic liver disease. The combination of elastography with parameters such as platelet count and spleen size is also discussed. Expert commentary: Non-invasive assessment of liver fibrosis and portal hypertension is a validated tool for the diagnosis and follow-up of patients. Baveno VI recommended the combination of transient elastography and platelet count for ruling out varices needing treatment in patients with compensated advanced chronic liver disease. Assessment of aetiology specific cut-offs for ruling in and ruling out clinically significant portal hypertension is an unmet clinical need. The incorporation of spleen stiffness measurements in non-invasive algorithms using validated software and improved measuring scales might enhance the non-invasive diagnosis of portal hypertension in the next 5 years.

Quantitative micro-elastography: imaging of tissue elasticity using compression optical coherence elastography

PubMed Central

Kennedy, Kelsey M.; Chin, Lixin; McLaughlin, Robert A.; Latham, Bruce; Saunders, Christobel M.; Sampson, David D.; Kennedy, Brendan F.

2015-01-01

Probing the mechanical properties of tissue on the microscale could aid in the identification of diseased tissues that are inadequately detected using palpation or current clinical imaging modalities, with potential to guide medical procedures such as the excision of breast tumours. Compression optical coherence elastography (OCE) maps tissue strain with microscale spatial resolution and can delineate microstructural features within breast tissues. However, without a measure of the locally applied stress, strain provides only a qualitative indication of mechanical properties. To overcome this limitation, we present quantitative micro-elastography, which combines compression OCE with a compliant stress sensor to image tissue elasticity. The sensor consists of a layer of translucent silicone with well-characterized stress-strain behaviour. The measured strain in the sensor is used to estimate the two-dimensional stress distribution applied to the sample surface. Elasticity is determined by dividing the stress by the strain in the sample. We show that quantification of elasticity can improve the ability of compression OCE to distinguish between tissues, thereby extending the potential for inter-sample comparison and longitudinal studies of tissue elasticity. We validate the technique using tissue-mimicking phantoms and demonstrate the ability to map elasticity of freshly excised malignant and benign human breast tissues. PMID:26503225

Novel applications of the temporal kernel method: Historical and future radiative forcing

NASA Astrophysics Data System (ADS)

Portmann, R. W.; Larson, E.; Solomon, S.; Murphy, D. M.

2017-12-01

We present a new estimate of the historical radiative forcing derived from the observed global mean surface temperature and a model derived kernel function. Current estimates of historical radiative forcing are usually derived from climate models. Despite large variability in these models, the multi-model mean tends to do a reasonable job of representing the Earth system and climate. One method of diagnosing the transient radiative forcing in these models requires model output of top of the atmosphere radiative imbalance and global mean temperature anomaly. It is difficult to apply this method to historical observations due to the lack of TOA radiative measurements before CERES. We apply the temporal kernel method (TKM) of calculating radiative forcing to the historical global mean temperature anomaly. This novel approach is compared against the current regression based methods using model outputs and shown to produce consistent forcing estimates giving confidence in the forcing derived from the historical temperature record. The derived TKM radiative forcing provides an estimate of the forcing time series that the average climate model needs to produce the observed temperature record. This forcing time series is found to be in good overall agreement with previous estimates but includes significant differences that will be discussed. The historical anthropogenic aerosol forcing is estimated as a residual from the TKM and found to be consistent with earlier moderate forcing estimates. In addition, this method is applied to future temperature projections to estimate the radiative forcing required to achieve those temperature goals, such as those set in the Paris agreement.

The Radiative Forcing Model Intercomparison Project (RFMIP): Assessment and characterization of forcing to enable feedback studies

NASA Astrophysics Data System (ADS)

Pincus, R.; Stevens, B. B.; Forster, P.; Collins, W.; Ramaswamy, V.

2014-12-01

The Radiative Forcing Model Intercomparison Project (RFMIP): Assessment and characterization of forcing to enable feedback studies An enormous amount of attention has been paid to the diversity of responses in the CMIP and other multi-model ensembles. This diversity is normally interpreted as a distribution in climate sensitivity driven by some distribution of feedback mechanisms. Identification of these feedbacks relies on precise identification of the forcing to which each model is subject, including distinguishing true error from model diversity. The Radiative Forcing Model Intercomparison Project (RFMIP) aims to disentangle the role of forcing from model sensitivity as determinants of varying climate model response by carefully characterizing the radiative forcing to which such models are subject and by coordinating experiments in which it is specified. RFMIP consists of four activities: 1) An assessment of accuracy in flux and forcing calculations for greenhouse gases under past, present, and future climates, using off-line radiative transfer calculations in specified atmospheres with climate model parameterizations and reference models 2) Characterization and assessment of model-specific historical forcing by anthropogenic aerosols, based on coordinated diagnostic output from climate models and off-line radiative transfer calculations with reference models 3) Characterization of model-specific effective radiative forcing, including contributions of model climatology and rapid adjustments, using coordinated climate model integrations and off-line radiative transfer calculations with a single fast model 4) Assessment of climate model response to precisely-characterized radiative forcing over the historical record, including efforts to infer true historical forcing from patterns of response, by direct specification of non-greenhouse-gas forcing in a series of coordinated climate model integrations This talk discusses the rationale for RFMIP, provides an overview of the four activities, and presents preliminary motivating results.

Non-invasive structural and biomechanical imaging of the developing embryos (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Jitao; Wu, Chen; Raghunathan, Raksha; Larin, Kirill V.; Scarcelli, Giuliano

2017-02-01

Embryos undergo dramatic changes in size, shape, and mechanical properties during development, which is regulated by both genetic and environmental factors. Quantifying mechanical properties of different embryonic tissues may represent good metrics for the embryonic health and proper development. Alternations and structure coupled with biomechanical information may provide a way for early diagnosis and drug treatment of various congenital diseases. Many methods have been developed to determine the mechanical properties of the embryo, such as atomic force microscopy (AFM), ultrasound elastography (UE), and optical coherent elastography (OCE). However, AFM is invasive and time-consuming. While UE and OCE are both non-invasive methods, the spatial resolutions are limited to mm to sub-mm, which is not enough to observe the details inside the embryo. Brillouin microscopy can potentially enable non-invasive measurement of the mechanical properties of a sample by measuring the spectra of acoustically induced light scattering therein. It has fast speed ( 0.1 second per point) and high resolution (sub-micron), and thus has been widely investigated for biomedical application, such as single cell and tissue. In this work, we utilized this technique to characterize the mechanical property of an embryo. A 2D elasticity imaging of the whole body of an E8 embryo was acquired by a Brillouin microscopy, and the stiffness changes between different organs (such as brain, heart, and spine) were shown. The elasticity maps were correlated with structural information provided by OCT.

Mechanical characterization of the mouse diaphragm with optical coherence elastography reveals fibrosis-related change of direction-dependent muscle tissue stiffness

NASA Astrophysics Data System (ADS)

Wang, Shang; Loehr, James A.; Larina, Irina V.; Rodney, George G.; Larin, Kirill V.

2016-03-01

The diaphragm, composed of skeletal muscle, plays an important role in respiration through its dynamic contraction. Genetic and molecular studies of the biomechanics of mouse diaphragm can provide great insights into an improved understanding and potential treatment of the disorders that lead to diaphragm dysfunction (i.e. muscular dystrophy). However, due to the small tissue size, mechanical assessment of mouse diaphragm tissue under its proper physiological conditions has been challenging. Here, we present the application of noncontact optical coherence elastography (OCE) for quantitative elastic characterization of ex vivo mouse diaphragm. Phase-sensitive optical coherence tomography was combined with a focused air-puff system to capture and measure the elastic wave propagation from tissue surface. Experiments were performed on wildtype and dystrophic mouse diaphragm tissues containing different levels of fibrosis. The OCE measurements of elastic wave propagation were conducted along both the longitudinal and transverse axis of the muscle fibers. Cross-correlation of the temporal displacement profiles from different spatial locations was utilized to obtain the propagation time delay, which was used to calculate the wave group velocity and to further quantify the tissue Young's modulus. Prior to and after OCE assessment, peak tetanic force was measured to monitor viability of the tissue during the elasticity measurements. Our experimental results indicate a positive correlation between fibrosis level and tissue stiffness, suggesting this elastic-wave-based OCE method could be a useful tool to monitor mechanical properties of skeletal muscle under physiological and pathological conditions.

Assessment and characterization of in situ rotator cuff biomechanics

NASA Astrophysics Data System (ADS)

Trent, Erika A.; Bailey, Lane; Mefleh, Fuad N.; Raikar, Vipul P.; Shanley, Ellen; Thigpen, Charles A.; Dean, Delphine; Kwartowitz, David M.

2013-03-01

Rotator cuff disease is a degenerative disorder that is a common, costly, and often debilitating, ranging in severity from partial thickness tear, which may cause pain, to total rupture, leading to loss in function. Currently, clinical diagnosis and determination of disease extent relies primarily on subjective assessment of pain, range of motion, and possibly X-ray or ultrasound images. The final treatment plan however is at the discretion of the clinician, who often bases their decision on personal experiences, and not quantitative standards. The use of ultrasound for the assessment of tissue biomechanics is established, such as in ultrasound elastography, where soft tissue biomechanics are measured. Few studies have investigated the use of ultrasound elastography in the characterization of musculoskeletal biomechanics. To assess tissue biomechanics we have developed a device, which measures the force applied to the underlying musculotendentious tissue while simultaneously obtaining the related ultrasound images. In this work, the musculotendinous region of the infraspinatus of twenty asymptomatic male organized baseball players was examined to access the variability in tissue properties within a single patient and across a normal population. Elastic moduli at percent strains less than 15 were significantly different than those above 15 percent strain within the normal population. No significant difference in tissue properties was demonstrated within a single patient. This analysis demonstrated elastic moduli are variable across individuals and incidence. Therefore threshold elastic moduli will likely be a function of variation in local-tissue moduli as opposed to a specific global value.

Evaluation of Liver and Spleen Stiffness with Acoustic Radiation Force Impulse Quantification Elastography for Diagnosing Clinically Significant Portal Hypertension.

PubMed

Attia, D; Schoenemeier, B; Rodt, T; Negm, A A; Lenzen, H; Lankisch, T O; Manns, M; Gebel, M; Potthoff, A

2015-12-01

Hepatic vein pressure gradient (HVPG) is the gold standard for diagnosing clinically significant portal hypertension (CSPH). The aim of this study was to investigate-in comparison to HVPG-the ability to diagnose CSPH by liver and spleen stiffness measurements obtained by acoustic radiation force impulse (ARFI) imaging. A total of 78 patients (mean age: 53 ± 13 years, 62 % male) with chronic liver disease were enrolled in this study. Each patient received liver (LSM) and spleen (SSM) stiffness measurements by ARFI, an HVPG measurement and a transjugular liver biopsy on the same day. Patients were classified according to their HVPG into three different groups: HVPG < 10 mmHg, HVPG ≥ 10-< 12 mmHg and HVPG ≥ 12 mmHg. LSM, SSM were significantly higher in patients with HVPG ≥ 10 - < 12 in comparison to HVPG < 10 mmHg (p < 0.001 and p < 0.001, respectively), and in patients with HVPG ≥ 12 mmHg in comparison to ≥ 10 - < 12 mmHg (p < 0.001 and p < 0.001, respectively). LSM and SSM were able to diagnose HVPG ≥ 10 mmHg and HVPG ≥ 12 mmHg with high diagnostic performance (AUC LSM: 0.93 and 0.87, respectively; AUC SSM: 0.97 and 0.95, respectively). The AUC of SSM in predicting esophageal varices (EVs) plus HVPG ≥ 10 mmHg and EVs plus HVPG ≥ 12 mmHg were higher compared to LSM in both groups of patients (SSM: 0.90 and 0.93 vs. LSM: 0.84 and 0.88, respectively). No significant difference between both AUCs was detected in the different HVPG groups. In the multivariate -analysis SSM remained a factor predicting HVPG (HVPG > 10 mmHg p = 0.007; HVPG ≥ 12 mmHg p = 0.003). LSM and SSM by ARFI are noninvasive diagnostic tools that may help in diagnosing CSPH. LSM and SSM could be used as a guiding noninvasive screening tool in patients with esophageal varices requiring endoscopic evaluation. © Georg Thieme Verlag KG Stuttgart · New York.

Acoustic radiation force control: Pulsating spherical carriers.

PubMed

Rajabi, Majid; Mojahed, Alireza

2018-02-01

The interaction between harmonic plane progressive acoustic beams and a pulsating spherical radiator is studied. The acoustic radiation force function exerted on the spherical body is derived as a function of the incident wave pressure and the monopole vibration characteristics (i.e., amplitude and phase) of the body. Two distinct strategies are presented in order to alter the radiation force effects (i.e., pushing and pulling states) by changing its magnitude and direction. In the first strategy, an incident wave field with known amplitude and phase is considered. It is analytically shown that the zero- radiation force state (i.e., radiation force function cancellation) is achievable for specific pulsation characteristics belong to a frequency-dependent straight line equation in the plane of real-imaginary components (i.e., Nyquist Plane) of prescribed surface displacement. It is illustrated that these characteristic lines divide the mentioned displacement plane into two regions of positive (i.e., pushing) and negative (i.e., pulling) radiation forces. In the second strategy, the zero, negative and positive states of radiation force are obtained through adjusting the incident wave field characteristics (i.e., amplitude and phase) which insonifies the radiator with prescribed pulsation characteristics. It is proved that zero radiation force state occurs for incident wave pressure characteristics belong to specific frequency-dependent circles in Nyquist plane of incident wave pressure. These characteristic circles divide the Nyquist plane into two distinct regions corresponding to positive (out of circles) and negative (in the circles) values of radiation force function. It is analytically shown that the maximum amplitude of negative radiation force is exactly equal to the amplitude of the (positive) radiation force exerted upon the sphere in the passive state, by the same incident field. The developed concepts are much more deepened by considering the required power supply for distinct cases of zero, negative and positive radiation force states along with the frequency dependent asymmetry index. In addition, considering the effect of phase difference between the incident wave field and the pulsating object, and its possible variation with respect to spatial position of object, some practical points about the spatial average of generated radiation force, the optimal state of operation, the stability of zero radiation force states and the possibly of precise motion control are discussed. This work would extend the novel concept of smart carriers to and may be helpful for robust single-beam acoustic handling techniques. Furthermore, the shown capability of precise motion control may be considered as a new way toward smart acoustic driven micro-mechanisms and micro-machines. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetic Resonance Elastography Demonstrating Low Brain Stiffness in a Patient with Low-Pressure Hydrocephalus: Case Report.

PubMed

Olivero, William C; Wszalek, Tracey; Wang, Huan; Farahvar, Arash; Rieth, Sandra M; Johnson, Curtis L

2016-01-01

The authors describe the case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus that responded to negative pressure drainage. A magnetic resonance elastography scan performed 3 weeks later demonstrated very low brain tissue stiffness (high brain tissue compliance). An analysis of the importance of this finding in understanding this rare condition is discussed. © 2016 S. Karger AG, Basel.

Development of an Automated Modality-Independent Elastographic Image Analysis System for Tumor Screening

DTIC Science & Technology

2006-02-01

further develop modality-independent elastography as a system that is able to reproducibly detect regions of increased stiffness within the breast based...tested on a tissue-like polymer phantom. elastography , breast cancer screening, image processing 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...is a map of the breast (or other tissue of interest) that reflects material inhomogeneity, such as in the case of a tumor mass that disrupts the

Magnetic resonance elastography (MRE) in cancer: Technique, analysis, and applications

PubMed Central

Pepin, Kay M.; Ehman, Richard L.; McGee, Kiaran P.

2015-01-01

Tissue mechanical properties are significantly altered with the development of cancer. Magnetic resonance elastography (MRE) is a noninvasive technique capable of quantifying tissue mechanical properties in vivo. This review describes the basic principles of MRE and introduces some of the many promising MRE methods that have been developed for the detection and characterization of cancer, evaluation of response to therapy, and investigation of the underlying mechanical mechanisms associated with malignancy. PMID:26592944

Improved measurement of vibration amplitude in dynamic optical coherence elastography

PubMed Central

Kennedy, Brendan F.; Wojtkowski, Maciej; Szkulmowski, Maciej; Kennedy, Kelsey M.; Karnowski, Karol; Sampson, David D.

2012-01-01

Abstract: Optical coherence elastography employs optical coherence tomography (OCT) to measure the displacement of tissues under load and, thus, maps the resulting strain into an image, known as an elastogram. We present a new improved method to measure vibration amplitude in dynamic optical coherence elastography. The tissue vibration amplitude caused by sinusoidal loading is measured from the spread of the Doppler spectrum, which is extracted using joint spectral and time domain signal processing. At low OCT signal-to-noise ratio (SNR), the method provides more accurate vibration amplitude measurements than the currently used phase-sensitive method. For measurements performed on a mirror at OCT SNR = 5 dB, our method introduces <3% error, compared to >20% using the phase-sensitive method. We present elastograms of a tissue-mimicking phantom and excised porcine tissue that demonstrate improvements, including a 50% increase in the depth range of reliable vibration amplitude measurement. PMID:23243565

Host model uncertainties in aerosol radiative forcing estimates: results from the AeroCom prescribed intercomparison study

NASA Astrophysics Data System (ADS)

Stier, P.; Schutgens, N. A. J.; Bian, H.; Boucher, O.; Chin, M.; Ghan, S.; Huneeus, N.; Kinne, S.; Lin, G.; Myhre, G.; Penner, J. E.; Randles, C.; Samset, B.; Schulz, M.; Yu, H.; Zhou, C.

2012-09-01

Simulated multi-model "diversity" in aerosol direct radiative forcing estimates is often perceived as measure of aerosol uncertainty. However, current models used for aerosol radiative forcing calculations vary considerably in model components relevant for forcing calculations and the associated "host-model uncertainties" are generally convoluted with the actual aerosol uncertainty. In this AeroCom Prescribed intercomparison study we systematically isolate and quantify host model uncertainties on aerosol forcing experiments through prescription of identical aerosol radiative properties in nine participating models. Even with prescribed aerosol radiative properties, simulated clear-sky and all-sky aerosol radiative forcings show significant diversity. For a purely scattering case with globally constant optical depth of 0.2, the global-mean all-sky top-of-atmosphere radiative forcing is -4.51 W m-2 and the inter-model standard deviation is 0.70 W m-2, corresponding to a relative standard deviation of 15%. For a case with partially absorbing aerosol with an aerosol optical depth of 0.2 and single scattering albedo of 0.8, the forcing changes to 1.26 W m-2, and the standard deviation increases to 1.21 W m-2, corresponding to a significant relative standard deviation of 96%. However, the top-of-atmosphere forcing variability owing to absorption is low, with relative standard deviations of 9% clear-sky and 12% all-sky. Scaling the forcing standard deviation for a purely scattering case to match the sulfate radiative forcing in the AeroCom Direct Effect experiment, demonstrates that host model uncertainties could explain about half of the overall sulfate forcing diversity of 0.13 W m-2 in the AeroCom Direct Radiative Effect experiment. Host model errors in aerosol radiative forcing are largest in regions of uncertain host model components, such as stratocumulus cloud decks or areas with poorly constrained surface albedos, such as sea ice. Our results demonstrate that host model uncertainties are an important component of aerosol forcing uncertainty that require further attention.

Greenhouse Effect, Radiative Forcing and Climate Sensitivity

NASA Astrophysics Data System (ADS)

Ponater, Michael; Dietmüller, Simone; Sausen, Robert

Temperature conditions and climate on Earth are controlled by the balance between absorbed solar radiation and outgoing terrestrial radiation. The greenhouse effect is a synonym for the trapping of infrared radiation by radiatively active atmospheric constituents. It generally causes a warming of the planet's surface, compared to the case without atmosphere. Perturbing the radiation balance of the planet, e.g., by anthropogenic greenhouse gas emissions, induces climate change. Individual contributions to a total climate impact are usually quantified and ranked in terms of their respective radiative forcing. This method involves some limitations, because the effect of the external forcing is modified by radiative feedbacks. Here the current concept of radiative forcing and potential improvements are explained.

Radiation Force Caused by Scattering, Absorption, and Emission of Light by Nonspherical Particles

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

2001-01-01

General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.

Dynamic acoustic radiation force acting on cylindrical shells: theory and simulations.

PubMed

Mitri, F G; Fatemi, M

2005-05-01

An object placed in an acoustic field is known to experience a force due to the transfer of momentum from the wave to the object itself. This force is known to be steady when the incident field is considered to be continuous with constant amplitude. One may define the dynamic (oscillatory) radiation force for a continuous wave-field whose intensity varies slowly with time. This paper extends the theory of the dynamic acoustic radiation force resulting from an amplitude-modulated progressive plane wave-field incident on solid cylinders to the case of solid cylindrical shells with particular emphasis on their thickness and contents of their hollow regions. A new factor corresponding to the dynamic radiation force is defined as Y(d) and stands for the dynamic radiation force per unit energy density and unit cross sectional surface. The results of numerical calculations are presented, indicating the ways in which the form of the dynamic radiation force function curves are affected by variations in the material mechanical parameters and by changes in the interior fluid inside the shell's hollow region. It was shown that the dynamic radiation force function Y(d) deviates from the static radiation force function for progressive waves Y(p) when the modulation frequency increases. These results indicate that the theory presented here is broader than the existing theory on cylinders.

Experimental study of acoustic radiation force of an ultrasound beam on absorbing and scattering objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikolaeva, Anastasiia V., E-mail: niko200707@mail.ru; Kryzhanovsky, Maxim A.; Tsysar, Sergey A.

Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of anmore » obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter.« less

Relationship of liver stiffness and controlled attenuation parameter measured by transient elastography with diabetes mellitus in patients with chronic liver disease.

PubMed

Ahn, Jem Ma; Paik, Yong-Han; Kim, So Hyun; Lee, Jun Hee; Cho, Ju Yeon; Sohn, Won; Gwak, Geum-Youn; Choi, Moon Seok; Lee, Joon Hyeok; Koh, Kwang Cheol; Paik, Seung Woon; Yoo, Byung Chul

2014-08-01

High prevalence of diabetes mellitus in patients with liver cirrhosis has been reported in many studies. The aim of our study was to evaluate the relationship of hepatic fibrosis and steatosis assessed by transient elastography with diabetes in patients with chronic liver disease. The study population consisted of 979 chronic liver disease patients. Liver fibrosis and steatosis were assessed by liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) on transient elastography. Diabetes was diagnosed in 165 (16.9%) of 979 patients. The prevalence of diabetes had significant difference among the etiologies of chronic liver disease. Higher degrees of liver fibrosis and steatosis, assessed by LSM and CAP score, showed higher prevalence of diabetes (F0/1 [14%], F2/3 [18%], F4 [31%], P<0.001; S0/1 [15%], S2 [17%], S3 [26%], P=0.021). Multivariate analysis showed that the independent predictive risk factors for diabetes were hypertension (OR, 1.98; P=0.001), LSM F4 (OR, 1.86; P=0.010), male gender (OR, 1.60; P=0.027), and age>50 yr (OR, 1.52; P=0.046). The degree of hepatic fibrosis but not steatosis assessed by transient elastography has significant relationship with the prevalence of diabetes in patients with chronic liver disease.

Attenuation measuring ultrasound shearwave elastography and in vivo application in post-transplant liver patients

NASA Astrophysics Data System (ADS)

Nenadic, Ivan Z.; Qiang, Bo; Urban, Matthew W.; Zhao, Heng; Sanchez, William; Greenleaf, James F.; Chen, Shigao

2017-01-01

Ultrasound and magnetic resonance elastography techniques are used to assess mechanical properties of soft tissues. Tissue stiffness is related to various pathologies such as fibrosis, loss of compliance, and cancer. One way to perform elastography is measuring shear wave velocity of propagating waves in tissue induced by intrinsic motion or an external source of vibration, and relating the shear wave velocity to tissue elasticity. All tissues are inherently viscoelastic and ignoring viscosity biases the velocity-based estimates of elasticity and ignores a potentially important parameter of tissue health. We present attenuation measuring ultrasound shearwave elastography (AMUSE), a technique that independently measures both shear wave velocity and attenuation in tissue and therefore allows characterization of viscoelasticity without using a rheological model. The theoretical basis for AMUSE is first derived and validated in finite element simulations. AMUSE is validated against the traditional methods for assessing shear wave velocity (phase gradient) and attenuation (amplitude decay) in tissue mimicking phantoms and excised tissue. The results agreed within one standard deviation. AMUSE was used to measure shear wave velocity and attenuation in 15 transplanted livers in patients with potential acute rejection, and the results were compared with the biopsy findings in a preliminary study. The comparison showed excellent agreement and suggests that AMUSE can be used to separate transplanted livers with acute rejection from livers with no rejection.

The use of real-time elastography in the assessment of gallbladder polyps: preliminary observations.

PubMed

Teber, Mehmet Akif; Tan, Sinan; Dönmez, Uğur; İpek, Ali; Uçar, Ali Erkan; Yıldırım, Halil; Aslan, Ahmet; Arslan, Halil

2014-12-01

Gallbladder polyps often have a benign nature. Current guidelines suggest surgical removal of polyps greater than 10 mm. However, the accuracy of the size criteria is limited because neoplasia can be found in gallbladder polyps less than 10 mm. The aim of this study was to evaluate the feasibility of real time elastography for gallbladder polyps and to demonstrate the elasticity properties of the polyps. Fifty-three polypoid lesions of the gallbladder were prospectively examined with real-time elastography. Of these patients, 52 had a diagnosis of benign gallbladder polyps and one patient was accepted as a gallbladder carcinoma due to its clinical and radiological findings. B-mode and real-time elastographic images were simultaneously presented as a two-panel image, and the elastogram was displayed in a color scale that ranged from red (greatest strain, softest component), to green (average strain, intermediate component), to blue (no strain, hardest component). The mean size for benign gallbladder polyps was 7.2 +/- 3 mm (range, 5-21 mm). All benign gallbladder polyps on consecutive real-time elastographic images appeared as having a high-strain elastographic pattern. Only one patient who was accepted with gallbladder carcinoma had a gallbladder polyp with low elasticity properties. Our study showed that real time elastography of gallbladder polyps is feasible. This novel approach may be useful for the characterization of polypoid lesions of the gallbladder.

An Investigation of the Immediate Effect of Static Stretching on the Morphology and Stiffness of Achilles Tendon in Dominant and Non-Dominant Legs

PubMed Central

Chiu, Tsz-chun Roxy; Ngo, Hiu-ching; Lau, Lai-wa; Leung, King-wah; Lo, Man-him; Yu, Ho-fai; Ying, Michael

2016-01-01

Aims This study was undertaken to investigate the immediate effect of static stretching on normal Achilles tendon morphology and stiffness, and the different effect on dominant and non-dominant legs; and to evaluate inter-operator and intra-operator reliability of using shear-wave elastography in measuring Achilles tendon stiffness. Methods 20 healthy subjects (13 males, 7 females) were included in the study. Thickness, cross-sectional area and stiffness of Achilles tendons in both legs were measured before and after 5-min static stretching using grey-scale ultrasound and shear-wave elastography. Inter-operator and intra-operator reliability of tendon stiffness measurements of six operators were evaluated. Results Result showed that there was no significant change in the thickness and cross-sectional area of Achilles tendon after static stretching in both dominant and non-dominant legs (p > 0.05). Tendon stiffness showed a significant increase in non-dominant leg (p < 0.05) but not in dominant leg (p > 0.05). The inter-operator reliability of shear-wave elastography measurements was 0.749 and the intra-operator reliability ranged from 0.751 to 0.941. Conclusion Shear-wave elastography is a useful and non-invasive imaging tool to assess the immediate stiffness change of Achilles tendon in response to static stretching with high intra-operator and inter-operator reliability. PMID:27120097

Differentiating benign from malignant solid breast masses: value of shear wave elastography according to lesion stiffness combined with greyscale ultrasound according to BI-RADS classification.

PubMed

Evans, A; Whelehan, P; Thomson, K; Brauer, K; Jordan, L; Purdie, C; McLean, D; Baker, L; Vinnicombe, S; Thompson, A

2012-07-10

The aim of this study was to assess the performance of shear wave elastography combined with BI-RADS classification of greyscale ultrasound images for benign/malignant differentiation in a large group of patients. One hundred and seventy-five consecutive patients with solid breast masses on routine ultrasonography undergoing percutaneous biopsy had the greyscale findings classified according to the American College of Radiology BI-RADS. The mean elasticity values from four shear wave images were obtained. For mean elasticity vs greyscale BI-RADS, the performance results against histology were sensitivity: 95% vs 95%, specificity: 77% vs 69%, Positive Predictive Value (PPV): 88% vs 84%, Negative Predictive Value (NPV): 90% vs 91%, and accuracy: 89% vs 86% (all P>0.05). The results for the combination (positive result from either modality counted as malignant) were sensitivity 100%, specificity 61%, PPV 82%, NPV 100%, and accuracy 86%. The combination of BI-RADS greyscale and shear wave elastography yielded superior sensitivity to BI-RADS alone (P=0.03) or shear wave alone (P=0.03). The NPV was superior in combination compared with either alone (BI-RADS P=0.01 and shear wave P=0.02). Together, BI-RADS assessment of greyscale ultrasound images and shear wave ultrasound elastography are extremely sensitive for detection of malignancy.

Differentiating benign from malignant solid breast masses: value of shear wave elastography according to lesion stiffness combined with greyscale ultrasound according to BI-RADS classification

PubMed Central

Evans, A; Whelehan, P; Thomson, K; Brauer, K; Jordan, L; Purdie, C; McLean, D; Baker, L; Vinnicombe, S; Thompson, A

2012-01-01

Background: The aim of this study was to assess the performance of shear wave elastography combined with BI-RADS classification of greyscale ultrasound images for benign/malignant differentiation in a large group of patients. Methods: One hundred and seventy-five consecutive patients with solid breast masses on routine ultrasonography undergoing percutaneous biopsy had the greyscale findings classified according to the American College of Radiology BI-RADS. The mean elasticity values from four shear wave images were obtained. Results: For mean elasticity vs greyscale BI-RADS, the performance results against histology were sensitivity: 95% vs 95%, specificity: 77% vs 69%, Positive Predictive Value (PPV): 88% vs 84%, Negative Predictive Value (NPV): 90% vs 91%, and accuracy: 89% vs 86% (all P>0.05). The results for the combination (positive result from either modality counted as malignant) were sensitivity 100%, specificity 61%, PPV 82%, NPV 100%, and accuracy 86%. The combination of BI-RADS greyscale and shear wave elastography yielded superior sensitivity to BI-RADS alone (P=0.03) or shear wave alone (P=0.03). The NPV was superior in combination compared with either alone (BI-RADS P=0.01 and shear wave P=0.02). Conclusion: Together, BI-RADS assessment of greyscale ultrasound images and shear wave ultrasound elastography are extremely sensitive for detection of malignancy. PMID:22691969

The Potential Radiative Forcing of Global Land Use and Land Cover Change Activities

NASA Astrophysics Data System (ADS)

Ward, D. S.; Mahowald, N. M.; Kloster, S.

2014-12-01

Given the expected increase in pressure on land resources over the next century, there is a need to understand the total impacts of activities associated with land use and land cover change (LULCC). Here we quantify these impacts using the radiative forcing metric, including forcings from changes in long-lived greenhouse gases, tropospheric ozone, aerosol effects, and land surface albedo. We estimate radiative forcings from the different agents for historical LULCC and for six future projections using simulations from the National Center for Atmospheric Research Community Land Model and Community Atmosphere Models and additional offline analyses. When all forcing agents are considered together we show that 45% (+30%, -20%) of the present-day (2010) anthropogenic radiative forcing can be attributed to LULCC. Changes in the emission of non-CO2 greenhouse gases and aerosols from LULCC enhance the total LULCC radiative forcing by a factor of 2 to 3 with respect to the forcing from CO2 alone. In contrast, the non-CO2 forcings from fossil fuel burning are roughly neutral, due largely to the negative (cooling) impact of aerosols from these sources. We partition the global LULCC radiative forcing into three major sources: direct modification of land cover (e.g. deforestation), agricultural activities, and fire regime changes. Contributions from deforestation and agriculture are roughly equal in the present day, while changes to wildfire activity impose a small negative forcing globally. In 2100, deforestation activities comprise the majority of the LULCC radiative forcing for all projections except one (Representative Concentration Pathway (RCP) 4.5). This suggests that realistic scenarios of future forest area change are essential for projecting the contribution of LULCC to climate change. However, the commonly used RCP land cover change projections all include decreases in global deforestation rates over the next 85 years. To place an upper bound on the potential radiative forcing from LULCC we create a 'worst-case scenario" in which all arable land is converted to agriculture by the year 2100. This scenario leads to a total radiative forcing of 4.3 Wm-2 (+/- 1 Wm-2) suggesting that well thought-out land policy is needed to minimize future increases in global anthropogenic radiative forcing.

The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing.

PubMed

Stuber, Nicola; Forster, Piers; Rädel, Gaby; Shine, Keith

2006-06-15

Air traffic condensation trails, or contrails, are believed to have a net atmospheric warming effect, although one that is currently small compared to that induced by other sources of human emissions. However, the comparably large growth rate of air traffic requires an improved understanding of the resulting impact of aircraft radiative forcing on climate. Contrails have an effect on the Earth's energy balance similar to that of high thin ice clouds. Their trapping of outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) is partly compensated by their reflection of incoming solar radiation (negative radiative forcing). On average, the longwave effect dominates and the net contrail radiative forcing is believed to be positive. Over daily and annual timescales, varying levels of air traffic, meteorological conditions, and solar insolation influence the net forcing effect of contrails. Here we determine the factors most important for contrail climate forcing using a sophisticated radiative transfer model for a site in southeast England, located in the entrance to the North Atlantic flight corridor. We find that night-time flights during winter (December to February) are responsible for most of the contrail radiative forcing. Night flights account for only 25 per cent of daily air traffic, but contribute 60 to 80 per cent of the contrail forcing. Further, winter flights account for only 22 per cent of annual air traffic, but contribute half of the annual mean forcing. These results suggest that flight rescheduling could help to minimize the climate impact of aviation.

Liver fibrosis diagnosis by blood test and elastography in chronic hepatitis C: agreement or combination?

PubMed

Calès, P; Boursier, J; Lebigot, J; de Ledinghen, V; Aubé, C; Hubert, I; Oberti, F

2017-04-01

In chronic hepatitis C, the European Association for the Study of the Liver and the Asociacion Latinoamericana para el Estudio del Higado recommend performing transient elastography plus a blood test to diagnose significant fibrosis; test concordance confirms the diagnosis. To validate this rule and improve it by combining a blood test, FibroMeter (virus second generation, Echosens, Paris, France) and transient elastography (constitutive tests) into a single combined test, as suggested by the American Association for the Study of Liver Diseases and the Infectious Diseases Society of America. A total of 1199 patients were included in an exploratory set (HCV, n = 679) or in two validation sets (HCV ± HIV, HBV, n = 520). Accuracy was mainly evaluated by correct diagnosis rate for severe fibrosis (pathological Metavir F ≥ 3, primary outcome) by classical test scores or a fibrosis classification, reflecting Metavir staging, as a function of test concordance. Score accuracy: there were no significant differences between the blood test (75.7%), elastography (79.1%) and the combined test (79.4%) (P = 0.066); the score accuracy of each test was significantly (P < 0.001) decreased in discordant vs. concordant tests. Classification accuracy: combined test accuracy (91.7%) was significantly (P < 0.001) increased vs. the blood test (84.1%) and elastography (88.2%); accuracy of each constitutive test was significantly (P < 0.001) decreased in discordant vs. concordant tests but not with combined test: 89.0 vs. 92.7% (P = 0.118). Multivariate analysis for accuracy showed an interaction between concordance and fibrosis level: in the 1% of patients with full classification discordance and severe fibrosis, non-invasive tests were unreliable. The advantage of combined test classification was confirmed in the validation sets. The concordance recommendation is validated. A combined test, expressed in classification instead of score, improves this rule and validates the recommendation of a combined test, avoiding 99% of biopsies, and offering precise staging. © 2017 John Wiley & Sons Ltd.

Application of Modified Spin-Echo–based Sequences for Hepatic MR Elastography: Evaluation, Comparison with the Conventional Gradient-Echo Sequence, and Preliminary Clinical Experience

PubMed Central

Mariappan, Yogesh K.; Dzyubak, Bogdan; Glaser, Kevin J.; Venkatesh, Sudhakar K.; Sirlin, Claude B.; Hooker, Jonathan; McGee, Kiaran P.

2017-01-01

Purpose To (a) evaluate modified spin-echo (SE) magnetic resonance (MR) elastographic sequences for acquiring MR images with improved signal-to-noise ratio (SNR) in patients in whom the standard gradient-echo (GRE) MR elastographic sequence yields low hepatic signal intensity and (b) compare the stiffness values obtained with these sequences with those obtained with the conventional GRE sequence. Materials and Methods This HIPAA-compliant retrospective study was approved by the institutional review board; the requirement to obtain informed consent was waived. Data obtained with modified SE and SE echo-planar imaging (EPI) MR elastographic pulse sequences with short echo times were compared with those obtained with the conventional GRE MR elastographic sequence in two patient cohorts, one that exhibited adequate liver signal intensity and one that exhibited low liver signal intensity. Shear stiffness values obtained with the three sequences in 130 patients with successful GRE-based examinations were retrospectively tested for statistical equivalence by using a 5% margin. In 47 patients in whom GRE examinations were considered to have failed because of low SNR, the SNR and confidence level with the SE-based sequences were compared with those with the GRE sequence. Results The results of this study helped confirm the equivalence of SE MR elastography and SE-EPI MR elastography to GRE MR elastography (P = .0212 and P = .0001, respectively). The SE and SE-EPI MR elastographic sequences provided substantially improved SNR and stiffness inversion confidence level in 47 patients in whom GRE MR elastography had failed. Conclusion Modified SE-based MR elastographic sequences provide higher SNR MR elastographic data and reliable stiffness measurements; thus, they enable quantification of stiffness in patients in whom the conventional GRE MR elastographic sequence failed owing to low signal intensity. The equivalence of the three sequences indicates that the current diagnostic thresholds are applicable to SE MR elastographic sequences for assessing liver fibrosis. © RSNA, 2016 PMID:27509543

Real-Time Shear Wave versus Transient Elastography for Predicting Fibrosis: Applicability, and Impact of Inflammation and Steatosis. A Non-Invasive Comparison.

PubMed

Poynard, Thierry; Pham, Tam; Perazzo, Hugo; Munteanu, Mona; Luckina, Elena; Elaribi, Djamel; Ngo, Yen; Bonyhay, Luminita; Seurat, Noemie; Legroux, Muriel; Ngo, An; Deckmyn, Olivier; Thabut, Dominique; Ratziu, Vlad; Lucidarme, Olivier

2016-01-01

Real-time shear wave elastography (2D-SWE) is a two-dimensional transient elastography and a competitor as a biomarker of liver fibrosis in comparison with the standard reference transient elastography by M probe (TE-M). The aims were to compare several criteria of applicability, and to assess inflammation and steatosis impact on elasticity values, two unmet needs. We took FibroTest as the fibrosis reference and ActiTest and SteatoTest as quantitative estimates of inflammation and steatosis. After standardization of estimates, analyses used curve fitting, quantitative Lin concordance coefficient [LCC], and multivariate logistic regression. A total of 2,251 consecutive patients were included. We validated the predetermined 0.2 kPa cut-off as a too low minimal elasticity value identifying not-reliable 2D-SWE results (LCC with FibroTest = 0.0281[-0.119;0.175]. Other criteria, elasticity CV, body mass index and depth of measures were not sufficiently discriminant. The applicability of 2D-SWE (95%CI) 89.6%(88.2-90.8), was significantly higher than that of TE, 85.6%(84.0-87.0; P<0.0001). In patients with non-advanced fibrosis (METAVIR F0F1F2), elasticity values estimated by 2D-SWE was less impacted by inflammation and steatosis than elasticity value estimated by TE-M: LCC (95%CI) 0.039 (0.021;0.058) vs 0.090 (0.068;0.112;P<0.01) and 0.105 (0.068;0.141) vs 0.192 (0.153;0.230; P<0.01) respectively. The three analyses methods gave similar results. Elasticity results including very low minimal signal in the region of interest should be considered not reliable. 2D-SWE had a higher applicability than TE, the reference elastography, with less impact of inflammation and steatosis especially in patients with non-advanced fibrosis, as presumed by blood tests. ClinicalTrials.gov NCT01927133.

Dynamic Elastography in Diagnostics of Liver Fibrosis in Patients After Liver Transplantation Due to Cirrhosis in the Course of Hepatitis C.

PubMed

Mikołajczyk-Korniak, N; Tronina, O; Ślubowska, K; Perkowska-Ptasińska, A; Pacholczyk, M; Bączkowska, T; Durlik, M

2016-06-01

Assessment of the dynamics and degree of liver fibrosis in patients after liver transplantation is a basic element in the process of determining transplant survival prognosis. It allows planning and early initiation of prophylaxis or treatment, which translates into increased chances of preventing cirrhosis and of long-term optimal function of the graft. The aim of this study was to compare the results of biopsy and dynamic elastography in diagnostics of transplanted liver fibrosis, as well as determination of the stiffness cut-off point for assessment of significant fibrosis. The study included 36 patients who had undergone liver transplantation due to cirrhosis in the course of hepatitis C virus (HVC) infection. Fibrosis was assessed in bioptates according to the METAVIR score (F0-F4). Elastography was performed using FibroScan; receiver operating characteristic curve analysis was used to identify the cut-off point for significant fibrosis (≥F2). The median stiffness in kPa for the whole group F0-F4 was 6.3 (range 3.4-29.9); for ≥F2 it was 6.9 (3.4-29.9), whereas for F0-F1 it was 4.4 (3.5-8.0). It was demonstrated that the value of 4.7 kPa in elastography is a statistically significant cut-off point for differentiation between the groups F0-F1 and F2-F4 (sensitivity: 93%, specificity: 57%, positive predictive value: 90%, negative predictive value: 66%), area under the receiver operating characteristic curve: 0.746 (95% confidence interval: 0.53-0.95, P < .05). Elastography is a promising tool for noninvasive assessment of significant liver fibrosis in patients after transplantation due to cirrhosis in the course of hepatitis C; it allows reduction in the number of biopsies performed. Copyright © 2016 Elsevier Inc. All rights reserved.

Value of ultrasound shear wave elastography in the diagnosis of adenomyosis

PubMed Central

Millar, E; Mitkova, M; Mitkov, V

2016-01-01

Background The aim of the study was to assess the accuracy of ultrasound shear wave elastography in the diagnosis of adenomyosis. Methods One hundred and fifty three patients were examined. Ninety-seven patients were with suspected adenomyosis and 56 patients were with unremarkable myometrium. Adenomyosis was confirmed in 39 cases (A subgroup) and excluded in 14 cases (B subgroup) in the main group based on morphological examination. All patients underwent ultrasound examination using an Aixplorer (Supersonic Imagine, France) scanner with application of shear wave elastography during transvaginal scanning. Retrospective analysis of the elastography criteria against the findings from morphological/histological examination was performed. Results The following values of Young’s modulus were found in subgroup A (adenomyosis): Emean – 72.7 (22.6–274.2) kPa (median, 5–95th percentiles), Emax – 94.8 (29.3–300.0) kPa, SD – 9.9 (2.6–26.3) kPa; in subgroup B (non adenomyosis) – 28.3 (12.7–59.5) kPa, 33.6 (16.0–80.8) kPa, 3.0 (1.4–15.6) kPa; in the control group – 24.4 (17.9–32.4) kPa, 29.8 (21.6–40.8) kPa, 2.3 (1.3–6.1) kPa, respectively (P < 0.05 for all comparison with subgroup В and the control group). The Emean cut-off value for adenomyosis diagnosis was 34.6 kPa. The sensitivity, specificity, positive predictive value, negative predictive value and area under curve (AUC) were 89.7%, 92.9%, 97.2%, 76.5% and 0.908. The Emax cut-off value was 45.4 kPa (89.7%, 92.9%, 97.2%, 76.5% and 0.907, respectively). Conclusion This study showed a significant increase of the myometrial stiffness estimated with shear wave elastography use in patients with adenomyosis. PMID:27847535

EUS elastography (strain ratio) and fractal-based quantitative analysis for the diagnosis of solid pancreatic lesions.

PubMed

Carrara, Silvia; Di Leo, Milena; Grizzi, Fabio; Correale, Loredana; Rahal, Daoud; Anderloni, Andrea; Auriemma, Francesco; Fugazza, Alessandro; Preatoni, Paoletta; Maselli, Roberta; Hassan, Cesare; Finati, Elena; Mangiavillano, Benedetto; Repici, Alessandro

2018-06-01

EUS elastography is useful in characterizing solid pancreatic lesions (SPLs), and fractal analysis-based technology has been used to evaluate geometric complexity in oncology. The aim of this study was to evaluate EUS elastography (strain ratio) and fractal analysis for the characterization of SPLs. Consecutive patients with SPLs were prospectively enrolled between December 2015 and February 2017. Elastographic evaluation included parenchymal strain ratio (pSR) and wall strain ratio (wSR) and was performed with a new compact US processor. Elastographic images were analyzed using a computer program to determine the 3-dimensional histogram fractal dimension. A composite cytology/histology/clinical reference standard was used to assess sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating curve. Overall, 102 SPLs from 100 patients were studied. At final diagnosis, 69 (68%) were malignant and 33 benign. At elastography, both pSR and wSR appeared to be significantly higher in malignant as compared with benign SPLs (pSR, 24.5 vs 6.4 [P < .001]; wSR, 56.6 vs 15.3 [P < .001]). When the best cut-off levels of pSR and wSR at 9.10 and 16.2, respectively, were used, sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating curve were 88.4%, 78.8%, 89.7%, 76.9%, and 86.7% and 91.3%, 69.7%, 86.5%, 80%, and 85.7%, respectively. Fractal analysis showed a significant statistical difference (P = .0087) between the mean surface fractal dimension of malignant lesions (D = 2.66 ± .01) versus neuroendocrine tumor (D = 2.73 ± .03) and a statistical difference for all 3 channels red, green, and blue (P < .0001). EUS elastography with pSR and fractal-based analysis are useful in characterizing SPLs. (Clinical trial registration number: NCT02855151.). Copyright © 2018 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.

Host model uncertainties in aerosol radiative forcing estimates: results from the AeroCom Prescribed intercomparison study

NASA Astrophysics Data System (ADS)

Stier, P.; Schutgens, N. A. J.; Bellouin, N.; Bian, H.; Boucher, O.; Chin, M.; Ghan, S.; Huneeus, N.; Kinne, S.; Lin, G.; Ma, X.; Myhre, G.; Penner, J. E.; Randles, C. A.; Samset, B.; Schulz, M.; Takemura, T.; Yu, F.; Yu, H.; Zhou, C.

2013-03-01

Simulated multi-model "diversity" in aerosol direct radiative forcing estimates is often perceived as a measure of aerosol uncertainty. However, current models used for aerosol radiative forcing calculations vary considerably in model components relevant for forcing calculations and the associated "host-model uncertainties" are generally convoluted with the actual aerosol uncertainty. In this AeroCom Prescribed intercomparison study we systematically isolate and quantify host model uncertainties on aerosol forcing experiments through prescription of identical aerosol radiative properties in twelve participating models. Even with prescribed aerosol radiative properties, simulated clear-sky and all-sky aerosol radiative forcings show significant diversity. For a purely scattering case with globally constant optical depth of 0.2, the global-mean all-sky top-of-atmosphere radiative forcing is -4.47 Wm-2 and the inter-model standard deviation is 0.55 Wm-2, corresponding to a relative standard deviation of 12%. For a case with partially absorbing aerosol with an aerosol optical depth of 0.2 and single scattering albedo of 0.8, the forcing changes to 1.04 Wm-2, and the standard deviation increases to 1.01 W-2, corresponding to a significant relative standard deviation of 97%. However, the top-of-atmosphere forcing variability owing to absorption (subtracting the scattering case from the case with scattering and absorption) is low, with absolute (relative) standard deviations of 0.45 Wm-2 (8%) clear-sky and 0.62 Wm-2 (11%) all-sky. Scaling the forcing standard deviation for a purely scattering case to match the sulfate radiative forcing in the AeroCom Direct Effect experiment demonstrates that host model uncertainties could explain about 36% of the overall sulfate forcing diversity of 0.11 Wm-2 in the AeroCom Direct Radiative Effect experiment. Host model errors in aerosol radiative forcing are largest in regions of uncertain host model components, such as stratocumulus cloud decks or areas with poorly constrained surface albedos, such as sea ice. Our results demonstrate that host model uncertainties are an important component of aerosol forcing uncertainty that require further attention.

SOURCE ATTRIBUTION OF RADIATIVE FORCING FROM SHORT LIVED CLIMATE FORCING AGENTS

EPA Science Inventory

The immediate project result is quantification of the pre-industrial to present forcing for anthropogenic emissions, the radiative effects of natural emissions, and spatial distribution of the radiative forcing efficiency for key aerosol and O3 precursors (i.e., mW/m^2<...

Radiation force on absorbing targets and power measurements of a high intensity focused ultrasound (HIFU) source

NASA Astrophysics Data System (ADS)

Qian, Zuwen; Zhu, Zhemin; Ye, Shigong; Jiang, Wenhua; Zhu, Houqing; Yu, Jinshen

2010-10-01

Based on the analytic expressions for the radiated field of a circular concave piston given by Hasegawa et al., an integral for calculation of the radiation force on a plane absorbing target in a spherically focused field is derived. A general relation between acoustic power P and normal radiation force F n is obtained under the condition of kr ≫ 1. Numerical computation is carried out by using the symbolic computation program for practically focused sources and absorbing circular targets. The results show that, for a given source, there is a range of target positions where the radiation force is independent of the target’s position under the assumption that the contribution of the acoustic field behind the target to the radiation force can be neglected. The experiments are carried out and confirm that there is a range of target positions where the measured radiation force is basically independent of the target’s position even at high acoustic power (up to 700 W). It is believed that when the radiation force method is used to measure the acoustic power radiated from a focused source, the size of the target must be selected in such a way that no observable sound can be found in the region behind the target.

Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves.

PubMed

Johnson, Kennita A; Vormohr, Hannah R; Doinikov, Alexander A; Bouakaz, Ayache; Shields, C Wyatt; López, Gabriel P; Dayton, Paul A

2016-05-01

Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.

Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves

NASA Astrophysics Data System (ADS)

Johnson, Kennita A.; Vormohr, Hannah R.; Doinikov, Alexander A.; Bouakaz, Ayache; Shields, C. Wyatt; López, Gabriel P.; Dayton, Paul A.

2016-05-01

Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.

Real-Time Palpation Imaging for Improved Detection and Discrimination of Breast Abnormalities

DTIC Science & Technology

2005-07-01

contrasts are also in the range of elastic contrasts in terms of shear storage moduli for 85 Hz shear waves in in vivo MR breast elastography (Sinkus et al... elastography ) may aid the differentiation of benign and malignant solid breast masses .(4-19) This research is based on the fact that benign and malignant...on 445 breast masses of which 42 were discarded based on our exclusion criteria leaving 403 (157 malignant-39.0%; 246 benign-61.0%) lesions as

Radiative forcing over the conterminous United States due to contemporary land cover land use change and sensitivity to snow and interannual albedo variability

USGS Publications Warehouse

Barnes, Christopher A.; Roy, David P.

2010-01-01

Satellite-derived land cover land use (LCLU), snow and albedo data, and incoming surface solar radiation reanalysis data were used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 58 ecoregions covering 69% of the conterminous United States. A net positive surface radiative forcing (i.e., warming) of 0.029 Wm−2 due to LCLU albedo change from 1973 to 2000 was estimated. The forcings for individual ecoregions were similar in magnitude to current global forcing estimates, with the most negative forcing (as low as −0.367 Wm−2) due to the transition to forest and the most positive forcing (up to 0.337 Wm−2) due to the conversion to grass/shrub. Snow exacerbated both negative and positive forcing for LCLU transitions between snow-hiding and snow-revealing LCLU classes. The surface radiative forcing estimates were highly sensitive to snow-free interannual albedo variability that had a percent average monthly variation from 1.6% to 4.3% across the ecoregions. The results described in this paper enhance our understanding of contemporary LCLU change on surface radiative forcing and suggest that future forcing estimates should model snow and interannual albedo variation.

MR elastography to measure the effects of cancer and pathology fixation on prostate biomechanics, and comparison with T 1, T 2 and ADC

NASA Astrophysics Data System (ADS)

McGrath, Deirdre M.; Lee, Jenny; Foltz, Warren D.; Samavati, Navid; van der Kwast, Theo; Jewett, Michael A. S.; Chung, Peter; Ménard, Cynthia; Brock, Kristy K.

2017-02-01

MRI is under evaluation for image-guided intervention for prostate cancer. The sensitivity and specificity of MRI parameters is determined via correlation with the gold-standard of histopathology. Whole-mount histopathology of prostatectomy specimens can be digitally registered to in vivo imaging for correlation. When biomechanical-based deformable registration is employed to account for deformation during histopathology processing, the ex vivo biomechanical properties are required. However, these properties are altered by pathology fixation, and vary with disease. Hence, this study employs magnetic resonance elastography (MRE) to measure ex vivo prostate biomechanical properties before and after fixation. A quasi-static MRE method was employed to measure high resolution maps of Young’s modulus (E) before and after fixation of canine prostate and prostatectomy specimens (n  =  4) from prostate cancer patients who had previously received radiation therapy. For comparison, T 1, T 2 and apparent diffusion coefficient (ADC) were measured in parallel. E (kPa) varied across clinical anatomy and for histopathology-identified tumor: peripheral zone: 99(±22), central gland: 48(±37), tumor: 85(±53), and increased consistently with fixation (factor of 11  ±  5 p  <  0.02). T 2 decreased consistently with fixation, while changes in T 1 and ADC were more complex and inconsistent. The biomechanics of the clinical prostate specimens varied greatly with fixation, and to a lesser extent with disease and anatomy. The data obtained will improve the precision of prostate pathology correlation, leading to more accurate disease detection and targeting.

The Radiative Forcing Model Intercomparison Project (RFMIP): Experimental protocol for CMIP6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pincus, Robert; Forster, Piers M.; Stevens, Bjorn

The phrasing of the first of three questions motivating CMIP6 – “How does the Earth system respond to forcing?” – suggests that forcing is always well-known, yet the radiative forcing to which this question refers has historically been uncertain in coordinated experiments even as understanding of how best to infer radiative forcing has evolved. The Radiative Forcing Model Intercomparison Project (RFMIP) endorsed by CMIP6 seeks to provide a foundation for answering the question through three related activities: (i) accurate characterization of the effective radiative forcing relative to a near-preindustrial baseline and careful diagnosis of the components of this forcing; (ii) assessment ofmore » the absolute accuracy of clear-sky radiative transfer parameterizations against reference models on the global scales relevant for climate modeling; and (iii) identification of robust model responses to tightly specified aerosol radiative forcing from 1850 to present. Complete characterization of effective radiative forcing can be accomplished with 180 years (Tier 1) of atmosphere-only simulation using a sea-surface temperature and sea ice concentration climatology derived from the host model's preindustrial control simulation. Assessment of parameterization error requires trivial amounts of computation but the development of small amounts of infrastructure: new, spectrally detailed diagnostic output requested as two snapshots at present-day and preindustrial conditions, and results from the model's radiation code applied to specified atmospheric conditions. In conclusion, the search for robust responses to aerosol changes relies on the CMIP6 specification of anthropogenic aerosol properties; models using this specification can contribute to RFMIP with no additional simulation, while those using a full aerosol model are requested to perform at least one and up to four 165-year coupled ocean–atmosphere simulations at Tier 1.« less

The Radiative Forcing Model Intercomparison Project (RFMIP): Experimental protocol for CMIP6

DOE PAGES

Pincus, Robert; Forster, Piers M.; Stevens, Bjorn

2016-09-27

The phrasing of the first of three questions motivating CMIP6 – “How does the Earth system respond to forcing?” – suggests that forcing is always well-known, yet the radiative forcing to which this question refers has historically been uncertain in coordinated experiments even as understanding of how best to infer radiative forcing has evolved. The Radiative Forcing Model Intercomparison Project (RFMIP) endorsed by CMIP6 seeks to provide a foundation for answering the question through three related activities: (i) accurate characterization of the effective radiative forcing relative to a near-preindustrial baseline and careful diagnosis of the components of this forcing; (ii) assessment ofmore » the absolute accuracy of clear-sky radiative transfer parameterizations against reference models on the global scales relevant for climate modeling; and (iii) identification of robust model responses to tightly specified aerosol radiative forcing from 1850 to present. Complete characterization of effective radiative forcing can be accomplished with 180 years (Tier 1) of atmosphere-only simulation using a sea-surface temperature and sea ice concentration climatology derived from the host model's preindustrial control simulation. Assessment of parameterization error requires trivial amounts of computation but the development of small amounts of infrastructure: new, spectrally detailed diagnostic output requested as two snapshots at present-day and preindustrial conditions, and results from the model's radiation code applied to specified atmospheric conditions. In conclusion, the search for robust responses to aerosol changes relies on the CMIP6 specification of anthropogenic aerosol properties; models using this specification can contribute to RFMIP with no additional simulation, while those using a full aerosol model are requested to perform at least one and up to four 165-year coupled ocean–atmosphere simulations at Tier 1.« less

[Radiative and hygienic certification in Armed Forces, problems of its implementation and ways of perfection].

PubMed

Rusakov, V N; Cherkashin, A V; Shishkanov, A P; Ian'shin, L A; Gracheva, T N

2010-12-01

Radiative and hygienic passportization is one of the most actual pattern of socio and hygienic monitoring in Armed Forces. Radiative and hygienic passport is the main document which characterizes the safety control in military unit and uses the sources of ionizing radiation. Sanitary and epidemiologic institutions were imputed to control the formation of radiative and hygienic passports, analysis and generalization of its data, formation of conclusions about the condition of radiation security in the military units. According to radiative and hygienic passportization, which took place in 2009, the radiation security in the Armed Forces and organizations is satisfactory, but there are some problems of providing of radiation security of personnel under the professional and medical radiation. The salvation of its problems requires the effective work of official functionary of radiac object and institutions of state sanitary and epidemiological supervision in Armed Forces of Russian Federation.

Using level set based inversion of arrival times to recover shear wave speed in transient elastography and supersonic imaging

NASA Astrophysics Data System (ADS)

McLaughlin, Joyce; Renzi, Daniel

2006-04-01

Transient elastography and supersonic imaging are promising new techniques for characterizing the elasticity of soft tissues. Using this method, an 'ultrafast imaging' system (up to 10 000 frames s-1) follows in real time the propagation of a low-frequency shear wave. The displacement of the propagating shear wave is measured as a function of time and space. Here we develop a fast level set based algorithm for finding the shear wave speed from the interior positions of the propagating front. We compare the performance of level curve methods developed here and our previously developed (McLaughlin J and Renzi D 2006 Shear wave speed recovery in transient elastography and supersonic imaging using propagating fronts Inverse Problems 22 681-706) distance methods. We give reconstruction examples from synthetic data and from data obtained from a phantom experiment accomplished by Mathias Fink's group (the Laboratoire Ondes et Acoustique, ESPCI, Université Paris VII).

Optical coherence elastography in ophthalmology

NASA Astrophysics Data System (ADS)

Kirby, Mitchell A.; Pelivanov, Ivan; Song, Shaozhen; Ambrozinski, Łukasz; Yoon, Soon Joon; Gao, Liang; Li, David; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

2017-12-01

Optical coherence elastography (OCE) can provide clinically valuable information based on local measurements of tissue stiffness. Improved light sources and scanning methods in optical coherence tomography (OCT) have led to rapid growth in systems for high-resolution, quantitative elastography using imaged displacements and strains within soft tissue to infer local mechanical properties. We describe in some detail the physical processes underlying tissue mechanical response based on static and dynamic displacement methods. Namely, the assumptions commonly used to interpret displacement and strain measurements in terms of tissue elasticity for static OCE and propagating wave modes in dynamic OCE are discussed with the ultimate focus on OCT system design for ophthalmic applications. Practical OCT motion-tracking methods used to map tissue elasticity are also presented to fully describe technical developments in OCE, particularly noting those focused on the anterior segment of the eye. Clinical issues and future directions are discussed in the hope that OCE techniques will rapidly move forward to translational studies and clinical applications.

Non-invasive assessment of liver fibrosis by transient elastography in post transfusional iron overload.

PubMed

Mirault, Tristan; Lucidarme, Damien; Turlin, Bruno; Vandevenne, Philippe; Gosset, Pierre; Ernst, Olivier; Rose, Christian

2008-04-01

Liver fibrosis, assessed by biopsy, is the main complication of post transfusional liver iron overload. Transient elastography (TE) is a new, non invasive method able to measure liver stiffness (LS) caused by fibrosis. We prospectively evaluated the predictive value of LS measurement for liver fibrosis evaluation in 15 chronically transfused patients and compared these results with the METAVIR histological fibrosis stage from liver biopsies. Mean TE values significantly differed in patients with severe fibrosis (METAVIR F3, F4): 9.1 (+/-3.7 SD) kPa from those with mild or no fibrosis (METAVIR F0, F1, F2): 5.9 (+/-1.8 SD) kPa (P = 0.046). TE value above 6.25 kPa (Se = 80%; Sp = 70%; AUROC = 0.820) identified patients at risk for severe fibrosis (Negative Predictive Value 88%; Positive Predictive Value 57%). Transient elastography appears to be a reliable tool to evaluate liver fibrosis in post-transfusional iron overload.

Cardiac elastography: detecting pathological changes in myocardium tissues

NASA Astrophysics Data System (ADS)

Konofagou, Elisa E.; Harrigan, Timothy; Solomon, Scott

2003-05-01

Estimation of the mechanical properties of the cardiac muscle has been shown to play a crucial role in the detection of cardiovascular disease. Elastography was recently shown feasible on RF cardiac data in vivo. In this paper, the role of elastography in the detection of ischemia/infarct is explored with simulations and in vivo experiments. In finite-element simulations of a portion of the cardiac muscle containing an infarcted region, the cardiac cycle was simulated with successive compressive and tensile strains ranging between -30% and 20%. The incremental elastic modulus was also mapped uisng adaptive methods. We then demonstrated this technique utilizing envelope-detected sonographic data (Hewlett-Packard Sonos 5500) in a patient with a known myocardial infarction. In cine-loop and M-Mode elastograms from both normal and infarcted regions in simulations and experiments, the infarcted region was identifed by the up to one order of magnitude lower incremental axial displacements and strains, and higher modulus. Information on motion, deformation and mechanical property should constitute a unique tool for noninvasive cardiac diagnosis.

Vibration-synchronized magnetic resonance imaging for the detection of myocardial elasticity changes.

PubMed

Elgeti, Thomas; Tzschätzsch, Heiko; Hirsch, Sebastian; Krefting, Dagmar; Klatt, Dieter; Niendorf, Thoralf; Braun, Jürgen; Sack, Ingolf

2012-04-01

Vibration synchronized magnetic resonance imaging of harmonically oscillating tissue interfaces is proposed for cardiac magnetic resonance elastography. The new approach exploits cardiac triggered cine imaging synchronized with extrinsic harmonic stimulation (f = 22.83 Hz) to display oscillatory tissue deformations in magnitude images. Oscillations are analyzed by intensity threshold-based image processing to track wave amplitude variations over the cardiac cycle. In agreement to literature data, results in 10 volunteers showed that endocardial wave amplitudes during systole (0.13 ± 0.07 mm) were significantly lower than during diastole (0.34 ± 0.14 mm, P < 0.001). Wave amplitudes were found to decrease 117 ± 40 ms before myocardial contraction and to increase 75 ± 31 ms before myocardial relaxation. Vibration synchronized magnetic resonance imaging improves the temporal resolution of magnetic resonance elastography as it overcomes the use of extra motion encoding gradients, is less sensitive to susceptibility artifacts, and does not suffer from dynamic range constraints frequently encountered in phase-based magnetic resonance elastography. Copyright © 2012 Wiley Periodicals, Inc.

Shear wave pulse compression for dynamic elastography using phase-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Huang, Zhihong; Wang, Ruikang K.; O'Donnell, Matthew

2014-01-01

Assessing the biomechanical properties of soft tissue provides clinically valuable information to supplement conventional structural imaging. In the previous studies, we introduced a dynamic elastography technique based on phase-sensitive optical coherence tomography (PhS-OCT) to characterize submillimetric structures such as skin layers or ocular tissues. Here, we propose to implement a pulse compression technique for shear wave elastography. We performed shear wave pulse compression in tissue-mimicking phantoms. Using a mechanical actuator to generate broadband frequency-modulated vibrations (1 to 5 kHz), induced displacements were detected at an equivalent frame rate of 47 kHz using a PhS-OCT. The recorded signal was digitally compressed to a broadband pulse. Stiffness maps were then reconstructed from spatially localized estimates of the local shear wave speed. We demonstrate that a simple pulse compression scheme can increase shear wave detection signal-to-noise ratio (>12 dB gain) and reduce artifacts in reconstructing stiffness maps of heterogeneous media.

Roles of production, consumption and trade in global and regional aerosol radiative forcing

NASA Astrophysics Data System (ADS)

Lin, J.; Tong, D.; Davis, S. J.; Ni, R.; Tan, X.; Pan, D.; Zhao, H.; Lu, Z.; Streets, D. G.; Feng, T.; Zhang, Q.; Yan, Y.; Hu, Y.; Li, J.; Liu, Z.; Jiang, X.; Geng, G.; He, K.; Huang, Y.; Guan, D.

2016-12-01

Anthropogenic aerosols exert strong radiative forcing on the climate system. Prevailing view regards aerosol radiative forcing as a result of emissions from regions' economic production, with China and other developing regions having the largest contributions to radiative forcing at present. However, economic production is driven by global demand for computation, and international trade allows for separation of regions consuming goods and services from regions where goods and related aerosol pollution are produced. It has recently been recognized that regions' consumption and trade have profoundly altered the spatial distribution of aerosol emissions and pollution. Building upon our previous work, this study quantifies for the first time the roles of trade and consumption in aerosol climate forcing attributed to different regions. We contrast the direct radiative forcing of aerosols related to regions' consumption of goods and services against the forcing due to emissions produced in each region. Aerosols assessed include black carbon, primary organic aerosol, and secondary inorganic aerosols including sulfate, nitrate and ammonium. We find that global aerosol radiative forcing due to emissions produced in East Asia is much stronger than the forcing related to goods and services ultimately consumed in that region because of its large net export of emissions-intensive goods. The opposite is true for net importers like Western Europe and North America: global radiative forcing related to consumption is much greater than the forcing due to emissions produced in these regions. Overall, trade is associated with a shift of radiative forcing from net importing to net exporting regions. Compared to greenhouse gases such as carbon dioxide, the short atmospheric lifetimes of aerosols cause large localized differences in radiative forcing. International efforts to reduce emissions in the exporting countries will help alleviate trade-related climate and health impacts of aerosols while lowering global emissions associated with global consumption. Ref: Lin et al., China's international trade and air pollution in the United States, PNAS, 2014 Lin et al., Global climate forcing of aerosols embodied in international trade, Nature Geoscience, 2016

Shear-wave elastography - virtual touch tissue quantification of fetal placentas with a single umbilical artery.

PubMed

Arslan, Harun; Tolunay, Harun Egemen; Cim, Numan; Boza, Barış; Yavuz, Alpaslan; İlik, İbrahim; Sahin, Hanim Guler; Yildizhan, Recep

2018-02-25

In this study, we aimed to evaluate the elasticities of fetal placentas with a single umbilical artery using the Virtual Touch Tissue Quantification (VTTQ) technique. Pregnant women with fetuses with a single umbilical artery (SUA) and pregnant women with fetuses having three vessel cord (3VC) at 18-22 weeks of gestation were enrolled in the research. The placentas were evaluated and divided into three equal parts as the inner 1/3 of the placenta (fetal edge), the outer 1/3 of the placenta (maternal edge) and the central 1/3 of the placenta (central part). Shear-wave velocity (SWV) measurements were used in the elastographic evaluation of placentas by VTTQ. Forty pregnant women were included in the study (n = 20 SUA, n = 20 three vessel cord pregnant women). The placental Acoustic Radiation Force Impulse (VTTQ) of the placenta regarding SWV measurement values of the fetal edge of the placenta in the fetuses with SUA and the control group were 0.876 and 0.957 m/sec, respectively. A significant statistical difference was found between the groups regarding the measurement of the stiffness of fetal placenta (p = 0.021). There was no significant difference between the measured stiffness values of the central or outer region of the placentas. In this study, we found lower SWV scores for the fetal edge of the placenta with SUA. This finding may reflect tissue elasticity level, and we hope that the use of the VTTQ technique may contribute to predicting the pregnancy-related morbidities of fetuses with SUA in the future.

Intercomparison of Models Representing Direct Shortwave Radiative Forcing by Sulfate Aerosols

NASA Technical Reports Server (NTRS)

Boucher, O.; Schwartz, S. E.; Ackerman, T. P.; Anderson, T. L.; Bergstrom, B.; Bonnel, B.; Dahlback, A.; Fouquart, Y.; Chylek, P.; Fu, Q.;

Performance of 2-D shear wave elastography in liver fibrosis assessment compared with serologic tests and transient elastography in clinical routine.

PubMed

Bota, Simona; Paternostro, Rafael; Etschmaier, Alexandra; Schwarzer, Remy; Salzl, Petra; Mandorfer, Mattias; Kienbacher, Christian; Ferlitsch, Monika; Reiberger, Thomas; Trauner, Michael; Peck-Radosavljevic, Markus; Ferlitsch, Arnulf

2015-09-01

Liver stiffness values assessed with 2-D shear wave elastography (SWE), transient elastography (TE) and simple serologic tests were compared with respect to non-invasive assessment in a cohort of 127 consecutive patients with chronic liver diseases. The rate of reliable liver stiffness measurements was significantly higher with 2-D SWE than with TE: 99.2% versus 74.8%, p < 0.0001 (different reliability criteria used, according to current recommendations). In univariate analysis, liver stiffness measured with 2-D SWE correlated best with fibrosis stage estimated with TE (r = 0.699, p < 0.0001), followed by Forns score (r = 0.534, p < 0.0001) and King's score (r = 0.512, p < 0.0001). However, in multivariate analysis, only 2-D SWE-measured values remained correlated with fibrosis stage (p < 0.0001). The optimal 2-D SWE cutoff values for predicting significant fibrosis were 8.03 kPa for fibrosis stage ≥2 (area under the receiver operating characteristic curve = 0.832) and 13.1 kPa for fibrosis stage 4 (area under the receiver operating characteristic curve = 0.915), respectively. In conclusion, 2-D SWE can be used to obtain reliable liver stiffness measurements in almost all patients and performs very well in predicting the presence of liver cirrhosis. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Extensor indicis proprius tendon transfer using shear wave elastography.

PubMed

Lamouille, J; Müller, C; Aubry, S; Bensamoun, S; Raffoul, W; Durand, S

2017-06-01

The means for judging optimal tension during tendon transfers are approximate and not very quantifiable. The purpose of this study was to demonstrate the feasibility of quantitatively assessing muscular mechanical properties intraoperatively using ultrasound elastography (shear wave elastography [SWE]) during extensor indicis proprius (EIP) transfer. We report two cases of EIP transfer for post-traumatic rupture of the extensor pollicis longus muscle. Ultrasound acquisitions measured the elasticity modulus of the EIP muscle at different stages: rest, active extension, active extension against resistance, EIP section, distal passive traction of the tendon, after tendon transfer at rest and then during active extension. A preliminary analysis was conducted of the distribution of values for this modulus at the various transfer steps. Different shear wave velocity and elasticity modulus values were observed at the various transfer steps. The tension applied during the transfer seemed close to the resting tension if a traditional protocol were followed. The elasticity modulus varied by a factor of 37 between the active extension against resistance step (565.1 kPa) and after the tendon section (15.3 kPa). The elasticity modulus values were distributed in the same way for each patient. The therapeutic benefit of SWE elastography was studied for the first time in tendon transfers. Quantitative data on the elasticity modulus during this test may make it an effective means of improving intraoperative adjustments. Copyright © 2017 SFCM. Published by Elsevier Masson SAS. All rights reserved.

3D Myocardial Elastography In Vivo.

PubMed

Papadacci, Clement; Bunting, Ethan A; Wan, Elaine Y; Nauleau, Pierre; Konofagou, Elisa E

2017-02-01

Strain evaluation is of major interest in clinical cardiology as it can quantify the cardiac function. Myocardial elastography, a radio-frequency (RF)-based cross-correlation method, has been developed to evaluate the local strain distribution in the heart in vivo. However, inhomogeneities such as RF ablation lesions or infarction require a three-dimensional approach to be measured accurately. In addition, acquisitions at high volume rate are essential to evaluate the cardiac strain in three dimensions. Conventional focused transmit schemes using 2D matrix arrays, trade off sufficient volume rate for beam density or sector size to image rapid moving structure such as the heart, which lowers accuracy and precision in the strain estimation. In this study, we developed 3D myocardial elastography at high volume rates using diverging wave transmits to evaluate the local axial strain distribution in three dimensions in three open-chest canines before and after radio-frequency ablation. Acquisitions were performed with a 2.5 MHz 2D matrix array fully programmable used to emit 2000 diverging waves at 2000 volumes/s. Incremental displacements and strains enabled the visualization of rapid events during the QRS complex along with the different phases of the cardiac cycle in entire volumes. Cumulative displacement and strain volumes depict high contrast between non-ablated and ablated myocardium at the lesion location, mapping the tissue coagulation. 3D myocardial strain elastography could thus become an important technique to measure the regional strain distribution in three dimensions in humans.

Quantitative assessment of the mechanical properties of prostate tissue with optical coherence elastography

NASA Astrophysics Data System (ADS)

Ling, Yuting; Li, Chunhui; Zhou, Kanheng; Guan, Guangying; Lang, Stephen; McGloin, David; Nabi, Ghulam; Huang, Zhihong

2018-02-01

Prostate cancer (PCa) is a heterogeneous disease with multifocal origin. In current clinical care, the Gleason scoring system is the well-established diagnosis by microscopic evaluation of the tissue from trans-rectal ultrasound (TRUS) guided biopsies. Nevertheless, the sensitivity and specificity in detecting PCa can range from 40 to 50% for conventional TRUS B-mode imaging. Tissue elasticity is associated with the disease progression and elastography technique has recently shown promise in aiding PCa diagnosis. However, many cancer foci in the prostate gland has very small size less than 1 mm and those detected by medical elastography were larger than 2 mm. Hereby, we introduce optical coherence elastography (OCE) to quantify the prostate stiffness with high resolution in the magnitude of 10 µm. Following our feasibility study of 10 patients reported previously, we recruited 60 more patients undergoing 12-core TRUS guided biopsies for suspected PCa with a total of 720 biopsies. The stiffness of cancer tissue was approximately 57.63% higher than that of benign ones. Using histology as reference standard and cut-off threshold of 600kPa, the data analysis showed sensitivity and specificity of 89.6% and 99.8% respectively. The method also demonstrated potential in characterising different grades of PCa based on the change of tissue morphology and quantitative mechanical properties. In conclusion, quantitative OCE can be a reliable technique to identify PCa lesion and differentiate indolent from aggressive cancer.

Acoustic Radiation Force of a Quasi-Gaussian Beam on an Elastic Sphere in a Fluid.

PubMed

Nikolaeva, A V; Sapozhnikov, O A; Bailey, M R

2016-09-01

Acoustic radiation force has many applications. One of the related technologies is the ability to noninvasively expel stones from the kidney. To optimize the procedure it is important to develop theoretical approaches that can provide rapid calculations of the radiation force depending in stone size and elastic properties, together with ultrasound beam diameter, intensity, and frequency. We hypothesize that the radiation force nonmonotonically depends on the ratio between the acoustic beam width and stone diameter because of coupling between the acoustic wave in the fluid and shear waves in the stone. Testing this hypothesis by considering a spherical stone and a quasi-Gaussian beam was performed in the current work. The calculation of the radiation force was conducted for elastic spheres of two types. Dependence of the magnitude of the radiation force on the beam diameter at various fixed values of stone diameters was modeled. In addition to using real material properties, speed of shear wave in the stone was varied to reveal the importance of shear waves in the stone. It was found that the radiation force reaches its maximum at the beamwidth comparable to the stone diameter; the gain in the force magnitude can reach 40% in comparison with the case of a narrow beam.

Black carbon radiative forcing at TOA decreased during aging.

PubMed

Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao

2016-12-05

During aging processing, black carbon (also called soot) particles may tend to be mixed with other aerosols, and highly influence their radiative forcing. In this study, freshly emitted soot particles were simulated as fractal aggregates composed of small spherical primary monomers. After aging in the atmosphere, soot monomers were coated by a thinly layer of sulfate as thinly coated soot particles. These soot particles were entirely embedded into large sulfate particle by further aging, and becoming heavily coated soot particles. In clear-sky conditions, black carbon radiative forcing with different aging states were investigated for the bottom and top of atmosphere (BOA and TOA). The simulations showed that black carbon radiative forcing increased at BOA and decreased at TOA after their aging processes. Thinly and heavily coated states increased up to ~12% and ~35% black carbon radiative forcing at BOA, and black carbon radiative forcing at TOA can reach to ~20% and ~100% smaller for thinly and heavily coated states than those of freshly emitted states, respectively. The effect of aging states of black carbon radiative forcing was varied with surface albedo, aerosol optical depth and solar zenith angles. These findings would be helpful for the assessments of climate change.

Resonant acoustic spectroscopy of soft tissues using embedded magnetomotive nanotransducers and optical coherence tomography

PubMed Central

Oldenburg, Amy L

2010-01-01

We present a new method for performing dynamic elastography of soft tissue samples. By sensing nanoscale displacements with optical coherence tomography, a chirped, modulated force is applied to acquire the mechanical spectrum of a tissue sample within a few seconds. This modulated force is applied via magnetic nanoparticles, named ‘nanotransducers’, which are diffused into the tissue, and which contribute negligible inertia to the soft tissue mechanical system. Using this novel system, we observed that excised tissues exhibit mechanical resonance modes which are well described by a linear damped harmonic oscillator. Results are validated by using cylindrical tissue phantoms of agarose in which resonant frequencies (30–400 Hz) are consistent with longitudinal modes and the sample boundary conditions. We furthermore show that the Young’s modulus can be computed from their measured resonance frequencies, analogous to resonant ultrasound spectroscopy for stiff material analysis. Using this new technique, named magnetomotive resonant acoustic spectroscopy (MRAS), we monitored the relative stiffening of an excised rat liver during a chemical fixation process. PMID:20124653

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, Fred G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2012-12-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at higher and lower sun elevation, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as sun elevation increases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, F. G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2013-03-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Key drivers of ozone change and its radiative forcing over the 21st century

NASA Astrophysics Data System (ADS)

Iglesias-Suarez, Fernando; Kinnison, Douglas E.; Rap, Alexandru; Maycock, Amanda C.; Wild, Oliver; Young, Paul J.

2018-05-01

Over the 21st century changes in both tropospheric and stratospheric ozone are likely to have important consequences for the Earth's radiative balance. In this study, we investigate the radiative forcing from future ozone changes using the Community Earth System Model (CESM1), with the Whole Atmosphere Community Climate Model (WACCM), and including fully coupled radiation and chemistry schemes. Using year 2100 conditions from the Representative Concentration Pathway 8.5 (RCP8.5) scenario, we quantify the individual contributions to ozone radiative forcing of (1) climate change, (2) reduced concentrations of ozone depleting substances (ODSs), and (3) methane increases. We calculate future ozone radiative forcings and their standard error (SE; associated with inter-annual variability of ozone) relative to year 2000 of (1) 33 ± 104 m Wm-2, (2) 163 ± 109 m Wm-2, and (3) 238 ± 113 m Wm-2 due to climate change, ODSs, and methane, respectively. Our best estimate of net ozone forcing in this set of simulations is 430 ± 130 m Wm-2 relative to year 2000 and 760 ± 230 m Wm-2 relative to year 1750, with the 95 % confidence interval given by ±30 %. We find that the overall long-term tropospheric ozone forcing from methane chemistry-climate feedbacks related to OH and methane lifetime is relatively small (46 m Wm-2). Ozone radiative forcing associated with climate change and stratospheric ozone recovery are robust with regard to background climate conditions, even though the ozone response is sensitive to both changes in atmospheric composition and climate. Changes in stratospheric-produced ozone account for ˜ 50 % of the overall radiative forcing for the 2000-2100 period in this set of simulations, highlighting the key role of the stratosphere in determining future ozone radiative forcing.

Negative radiation forces and the asymmetry of scattered radiation: spheres in Bessel beams

NASA Astrophysics Data System (ADS)

Marston, Philip L.; Zhang, Likun

2011-11-01

The discovery that acoustical and optical, radiation forces computed on spheres placed on the axis of acoustical and optical Bessel beams may be opposite the direction of beam propagation makes it appropriate to reexamine the relationship between radiation forces and the asymmetry of the scattered radiation. For all of the previously identified acoustical cases in which the force was negative and the scattering pattern was also computed, it was found that the backscattering was suppressed and the forward scattering relatively enhanced (see e.g.). In the present research the acoustic radiation force on an arbitrary isotropic sphere is related to the asymmetry in the scattering and the extinction introduced by the sphere for the case of a helical Bessel beam of arbitrary order. The analysis confirms that conditions are more favorable for generating negative forces when the asymmetry is such that the backscattering is suppressed relative to the forward scattering. It is also found, however, that absorption of power by the sphere gives rise to a positive force contribution, a term which has been neglected in the corresponding optical analysis.

Strong enhancement of dispersion forces from microwave radiation

NASA Astrophysics Data System (ADS)

Sernelius, B. E.

2002-11-01

We have studied non-thermal effects of microwave radiation on the forces between objects. This is the first step in a study of possible effects of microwave radiation from cellular phones on biological tissue. We have used a simplified model for human blood cells in blood. We find for the normal radiation level of cellular phones an enhancement of the attractive force with ten orders of magnitude as compared to the corresponding effect at thermal radiation.

Audio frequency in vivo optical coherence elastography

NASA Astrophysics Data System (ADS)

Adie, Steven G.; Kennedy, Brendan F.; Armstrong, Julian J.; Alexandrov, Sergey A.; Sampson, David D.

2009-05-01

We present a new approach to optical coherence elastography (OCE), which probes the local elastic properties of tissue by using optical coherence tomography to measure the effect of an applied stimulus in the audio frequency range. We describe the approach, based on analysis of the Bessel frequency spectrum of the interferometric signal detected from scatterers undergoing periodic motion in response to an applied stimulus. We present quantitative results of sub-micron excitation at 820 Hz in a layered phantom and the first such measurements in human skin in vivo.

Quantitative assessment of hyaline cartilage elasticity during optical clearing using optical coherence elastography

NASA Astrophysics Data System (ADS)

Liu, Chih-Hao; Singh, Manmohan; Li, Jiasong; Han, Zhaolong; Wu, Chen; Wang, Shang; Idugboe, Rita; Raghunathan, Raksha; Zakharov, Valery P.; Sobol, Emil N.; Tuchin, Valery V.; Twa, Michael; Larin, Kirill V.

2015-03-01

We report the first study on using optical coherence elastography (OCE) to quantitatively monitor the elasticity change of the hyaline cartilage during the optical clearing administrated by glucose solution. The measurement of the elasticity is verified using uniaxial compression test, demonstrating the feasibility of using OCE to quantify the Young's modulus of the cartilage tissue. As the results, we found that the stiffness of the hyaline cartilage increases during the optical clearing of the tissue. This study might be potentially useful for the early detection of osteoarthritis disease.

Dynamic measurement of local displacements within curing resin-based dental composite using optical coherence elastography

NASA Astrophysics Data System (ADS)

Tomlins, Peter H.; Rahman, Mohammed Wahidur; Donnan, Robert S.

2016-04-01

This study aimed to determine the feasibility of using optical coherence elastography to measure internal displacements during the curing phase of a light-activated, resin-based composite material. Displacement vectors were spatially mapped over time within a commercial dental composite. Measurements revealed that the orientation of cure-induced displacement vectors varied spatially in a complex manner; however, each vector showed a systematic evolution with time. Precision of individual displacements was estimated to be ˜1 to 2 μm, enabling submicrometer time-varying displacements to be detected.

The role of viscosity estimation for oil-in-gelatin phantom in shear wave based ultrasound elastography.

PubMed

Zhu, Ying; Dong, Changfeng; Yin, Yin; Chen, Xin; Guo, Yanrong; Zheng, Yi; Shen, Yuanyuan; Wang, Tianfu; Zhang, Xinyu; Chen, Siping

2015-02-01

Shear wave based ultrasound elastography utilizes mechanical excitation or acoustic radiation force to induce shear waves in deep tissue. The tissue response is monitored to obtain elasticity information about the tissue. During the past two decades, tissue elasticity has been extensively studied and has been used in clinical disease diagnosis. However, biological soft tissues are viscoelastic in nature. Therefore, they should be simultaneously characterized in terms of elasticity and viscosity. In this study, two shear wave-based elasticity imaging methods, shear wave dispersion ultrasound vibrometry (SDUV) and acoustic radiation force impulsive (ARFI) imaging, were compared. The discrepancy between the measurements obtained by the two methods was analyzed, and the role of viscosity was investigated. To this end, four types of gelatin phantoms containing 0%, 20%, 30% and 40% castor oil were fabricated to mimic different viscosities of soft tissue. For the SDUV method, the shear elasticity μ1 was 3.90 ± 0.27 kPa, 4.49 ± 0.16 kPa, 2.41 ± 0.33 kPa and 1.31 ± 0.09 kPa; and the shear viscosity μ2 was 1.82 ± 0.31 Pa•s, 2.41 ± 0.35 Pa•s, 2.65 ± 0.13 Pa•s and 2.89 ± 0.14 Pa•s for 0%, 20%, 30% and 40% oil, respectively in both cases. For the ARFI measurements, the shear elasticity μ was 7.30 ± 0.20 kPa, 8.20 ± 0.31 kPa, 7.42 ± 0.21 kPa and 5.90 ± 0.36 kPa for 0%, 20%, 30% and 40% oil, respectively. The SDUV results demonstrated that the elasticity first increased from 0% to 20% oil and then decreased for the 30% and 40% oil. The viscosity decreased consistently as the concentration of castor oil increased from 0% to 40%. The elasticity measured by ARFI showed the same trend as that of the SDUV but exceeded the results measured by SDUV. To clearly validate the impact of viscosity on the elasticity estimation, an independent measurement of the elasticity and viscosity by dynamic mechanical analysis (DMA) was conducted on these four types of gelatin phantoms and then compared with SDUV and ARFI results. The shear elasticities obtained by DMA (3.44 ± 0.31 kPa, 4.29 ± 0.13 kPa, 2.05 ± 0.29 kPa and 1.06 ± 0.18 kPa for 0%, 20%, 30% and 40% oil, respectively) were lower than those by SDUV, whereas the shear viscosities obtained by DMA (2.52 ± 0.32 Pa·s, 3.18 ± 0.12 Pa·s, 3.98 ± 0.19 Pa·s and 4.90 ± 0.20 Pa·s for 0%, 20%, 30% and 40% oil, respectively) were greater than those obtained by SDUV. However, the DMA results showed that the trend in the elasticity and viscosity data was the same as that obtained from the SDUV and ARFI. The SDUV results demonstrated that adding castor oil changed the viscoelastic properties of the phantoms and resulted in increased dispersion of the shear waves. Viscosity can provide important and independent information about the inner state of the phantoms, in addition to the elasticity. Because the ARFI method ignores the dispersion of the shear waves, namely viscosity, it may bias the estimation of the true elasticity. This study sheds further light on the significance of the viscosity measurements in shear wave based elasticity imaging methods. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Variability of the contrail radiative forcing due to crystal shape

NASA Astrophysics Data System (ADS)

Markowicz, K. M.; Witek, M. L.

2011-12-01

The aim of this study is to examine the influence of particles' shape and particles' optical properties on the contrail radiative forcing. Contrail optical properties in the shortwave and longwave range are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single scattering albedo and the asymmetry parameter in a transition range (3-7μm). We compare optical properties defined following simple 10 crystals habits randomly oriented: hexagonal plates, hexagonal columns with different aspect ratio, and spherical. There are substantial differences in single scattering properties between ten crystal models investigated here (e.g. hexagonal columns and plates with different aspect ratios, spherical particles). The single scattering albedo and the asymmetry parameter both vary up to 0.1 between various crystal shapes. Radiative forcing calculations were performed using a model which includes an interface between the state-of-the-art radiative transfer model Fu-Liou and databases containing optical properties of the atmosphere and surface reflectance and emissivity. This interface allows to determine radiative fluxes in the atmosphere and to estimate the contrail radiative forcing for clear- and all-sky (including natural clouds) conditions for various crystal shapes. The Fu-Liou code is fast and therefore it is suitable for computing radiative forcing on a global scale. At the same time it has sufficiently good accuracy for such global applications. A noticeable weakness of the Fu-Liou code is that it does not take into account the 3D radiative effects, e.g. cloud shading and horizontal. Radiative transfer model calculations were performed at horizontal resolution of 5x5 degree and time resolution of 20 min during day and 3 h during night. In order to calculate a geographic distribution of the global and annual mean contrail radiative forcing, the contrail cover must be determined. Two cases are discussed here: a 1% homogeneous contrail cover and the contrail cover provided by Rädel and Shine (2008). In the second distribution case, a more realistic contrail cover is taken into account. This model combines the AERO2K flight inventory with meteorological data and normalizes it with respect to the contrail cover derived from satellite observations. Simulations performed by the Fu-Liou model show significant variability of the shortwave, longwave, and net radiative forcing with crystal shape. The nonspherical crystals have smaller net forcing in contrary to spherical particles. The differences in net radiative forcing between optical models reach up to 50%. The hexagonal column and hexagonal plate particles show the smallest net radiative forcing while the largest forcing is obtained for the spheres. The global and annual mean shortwave, longwave, and net contrail radiative forcing, average over all crystal models and assuming an optical depth of 0.3 at visible wavelengths, is -5.7, 16.8, and 11.1 mW/m2, respectively. A ratio of the radiative forcings' standard deviation to the mean value, derived using 10 different ice particle models, is about 0.2 for the shortwave, 0.14 for the longwave, and 0.23 for the net radiation.

First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning using Satellite Data

NASA Technical Reports Server (NTRS)

Chistopher, Sundar A.; Kliche, Donna V.; Chou, Joyce; Welch, Ronald M.

1996-01-01

Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning Using Satellite Data

NASA Technical Reports Server (NTRS)

Christopher, Sundar A.; Kliche, Donna A.; Chou, Joyce; Welch, Ronald M.

1996-01-01

Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

Variation in Rising Limb of Colorado River Snowmelt Runoff Hydrograph Controlled by Dust Radiative Forcing in Snow

NASA Astrophysics Data System (ADS)

Painter, Thomas H.; Skiles, S. McKenzie; Deems, Jeffrey S.; Brandt, W. Tyler; Dozier, Jeff

2018-01-01

Common practice and conventional wisdom hold that fluctuations in air temperature control interannual variability in snowmelt and subsequent river runoff. However, recent observations in the Upper Colorado River Basin confirm that net solar radiation and by extension radiative forcing by dust deposited on snow cover exerts the primary forcing on snowmelt. We show that the variation in the shape of the rising limb of the annual hydrograph is controlled by variability in dust radiative forcing and surprisingly is independent of variations in winter and spring air temperatures. These observations suggest that hydroclimatic modeling must be improved to account for aerosol forcings of the water cycle. Anthropogenic climate change will likely reduce total snow accumulations and cause snowmelt runoff to occur earlier. However, dust radiative forcing of snowmelt is likely consuming important adaptive capacity that would allow human and natural systems to be more resilient to changing hydroclimatic conditions.

Direct Aerosol Radiative Forcing: Calculations and Measurements from the Tropospheric

NASA Technical Reports Server (NTRS)

Russell, P. B.; Hignett, P.; Stowe, L. L.; Livingston, J. M.; Kinne, S.; Wong, J.; Chan, K. Roland (Technical Monitor)

1997-01-01

Radiative forcing is defined as the change in the net (downwelling minus upwelling) radiative flux at a given level in the atmosphere. This net flux is the radiative power density available to drive climatic processes in the earth-atmosphere system below that level. Recent research shows that radiative forcing by aerosol particles is a major source of uncertainty in climate predictions. To reduce those uncertainties, TARFOX was designed to determine direct (cloud-free) radiative forcing by the aerosols in one of the world's major industrial pollution plumes--that flowing from the east coast of the US over the Atlantic Ocean. TARFOX measured a variety of aerosol radiative effects (including direct forcing) while simultaneously measuring the chemical, physical, and optical properties of the aerosol particles causing those effects. The resulting data sets permit a wide variety of tests of the consistency, or closure, among the measurements and the models that link them. Because climate predictions use the same or similar model components, closure tests help to assess and reduce prediction uncertainties. In this work we use the TARFOX-determined aerosol, gas, and surface properties to compute radiative forcing for a variety of aerosol episodes, with inadvisable optical depths ranging from 0.07 to 0.6. We calculate forcing by several techniques with varying degrees of sophistication, in part to test the range of applicability of simplified techniques--which are often the only ones feasible in climate predictions by general circulation models (GCMs). We then compare computed forcing to that determined from: (1) Upwelling and downwelling fluxes (0.3-0.7 mm and 0.7-3.0 mm) measured by radiometers on the UK MRF C-130. and (2) Daily average cloud-free absorbed solar and emitted thermal radiative flux at the top of the atmosphere derived from the AVHRR radiometer on the NOAA- 14 satellite. The calculations and measurements all yield aerosol direct radiative forcing in the range -50 to -190 W sq m per unit inadvisable optical depth. The magnitudes are about 15 to 100 times larger than the global-average direct forcing expected for the global-average sulfate aerosol optical depth of 0.04. The reasons for the larger forcing in TARFOX include the relatively large optical depths and the focus on cloud-free, daytime conditions over the dark ocean surface. These are the conditions that produce the actual major radiative forcing events that contribute to any global-average climate effect. Detailed comparisons of calculated and measured forcings for specific events are used for more refined tests of closure.

Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

NASA Technical Reports Server (NTRS)

Rajiyah, Harindra (Inventor); Hedeen, Robert A. (Inventor); Pla, Frederic G. (Inventor); Renshaw, Anthony A. (Inventor)

1995-01-01

A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

Radiation Forces and Torques without Stress (Tensors)

ERIC Educational Resources Information Center

Bohren, Craig F.

2011-01-01

To understand radiation forces and torques or to calculate them does not require invoking photon or electromagnetic field momentum transfer or stress tensors. According to continuum electromagnetic theory, forces and torques exerted by radiation are a consequence of electric and magnetic fields acting on charges and currents that the fields induce…

Radiative forcing over the conterminous United States due to contemporary land cover land use albedo change

USGS Publications Warehouse

Barnes, Christopher; Roy, David P.

2008-01-01

Recently available satellite land cover land use (LCLU) and albedo data are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 36 ecoregions covering 43% of the conterminous United States (CONUS). Moderate Resolution Imaging Spectroradiometer (MODIS) snow-free broadband albedo values are derived from Landsat LCLU classification maps located using a stratified random sampling methodology to estimate ecoregion estimates of LCLU induced albedo change and surface radiative forcing. The results illustrate that radiative forcing due to LCLU change may be disguised when spatially and temporally explicit data sets are not used. The radiative forcing due to contemporary LCLU albedo change varies geographically in sign and magnitude, with the most positive forcings (up to 0.284 Wm−2) due to conversion of agriculture to other LCLU types, and the most negative forcings (as low as −0.247 Wm−2) due to forest loss. For the 36 ecoregions considered a small net positive forcing (i.e., warming) of 0.012 Wm−2 is estimated.

Magnetic resonance elastography of the brain: A comparison between pigs and humans.

PubMed

Weickenmeier, Johannes; Kurt, Mehmet; Ozkaya, Efe; Wintermark, Max; Pauly, Kim Butts; Kuhl, Ellen

2018-01-01

Magnetic resonance elastography holds promise as a non-invasive, easy-to-use, in vivo biomarker for neurodegenerative diseases. Throughout the past decade, pigs have gained increased popularity as large animal models for human neurodegeneration. However, the volume of a pig brain is an order of magnitude smaller than the human brain, its skull is 40% thicker, and its head is about twice as big. This raises the question to which extent established vibration devices, actuation frequencies, and analysis tools for humans translate to large animal studies in pigs. Here we explored the feasibility of using human brain magnetic resonance elastography to characterize the dynamic properties of the porcine brain. In contrast to humans, where vibration devices induce an anterior-posterior displacement recorded in transverse sections, the porcine anatomy requires a dorsal-ventral displacement recorded in coronal sections. Within these settings, we applied a wide range of actuation frequencies, from 40Hz to 90Hz, and recorded the storage and loss moduli for human and porcine brains. Strikingly, we found that optimal actuation frequencies for humans translate one-to-one to pigs and reliably generate shear waves for elastographic post-processing. In a direct comparison, human and porcine storage and loss moduli followed similar trends and increased with increasing frequency. When translating these frequency-dependent storage and loss moduli into the frequency-independent stiffnesses and viscosities of a standard linear solid model, we found human values of μ 1 =1.3kPa, μ 2 =2.1kPa, and η=0.025kPas and porcine values of μ 1 =2.0kPa, μ 2 =4.9kPa, and η=0.046kPas. These results suggest that living human brain is softer and less viscous than dead porcine brain. Our study compares, for the first time, magnetic resonance elastography in human and porcine brains, and paves the way towards systematic interspecies comparison studies and ex vivo validation of magnetic resonance elastography as a whole. Copyright © 2017 Elsevier Ltd. All rights reserved.

Real-Time Shear Wave versus Transient Elastography for Predicting Fibrosis: Applicability, and Impact of Inflammation and Steatosis. A Non-Invasive Comparison

PubMed Central

Poynard, Thierry; Pham, Tam; Perazzo, Hugo; Munteanu, Mona; Luckina, Elena; Elaribi, Djamel; Ngo, Yen; Bonyhay, Luminita; Seurat, Noemie; Legroux, Muriel; Ngo, An; Deckmyn, Olivier; Thabut, Dominique; Ratziu, Vlad; Lucidarme, Olivier

2016-01-01

Background and Aims Real-time shear wave elastography (2D-SWE) is a two-dimensional transient elastography and a competitor as a biomarker of liver fibrosis in comparison with the standard reference transient elastography by M probe (TE-M). The aims were to compare several criteria of applicability, and to assess inflammation and steatosis impact on elasticity values, two unmet needs. Methods We took FibroTest as the fibrosis reference and ActiTest and SteatoTest as quantitative estimates of inflammation and steatosis. After standardization of estimates, analyses used curve fitting, quantitative Lin concordance coefficient [LCC], and multivariate logistic regression. Results A total of 2,251 consecutive patients were included. We validated the predetermined 0.2 kPa cut-off as a too low minimal elasticity value identifying not-reliable 2D-SWE results (LCC with FibroTest = 0.0281[-0.119;0.175]. Other criteria, elasticity CV, body mass index and depth of measures were not sufficiently discriminant. The applicability of 2D-SWE (95%CI) 89.6%(88.2–90.8), was significantly higher than that of TE, 85.6%(84.0–87.0; P<0.0001). In patients with non-advanced fibrosis (METAVIR F0F1F2), elasticity values estimated by 2D-SWE was less impacted by inflammation and steatosis than elasticity value estimated by TE-M: LCC (95%CI) 0.039 (0.021;0.058) vs 0.090 (0.068;0.112;P<0.01) and 0.105 (0.068;0.141) vs 0.192 (0.153;0.230; P<0.01) respectively. The three analyses methods gave similar results. Conclusions Elasticity results including very low minimal signal in the region of interest should be considered not reliable. 2D-SWE had a higher applicability than TE, the reference elastography, with less impact of inflammation and steatosis especially in patients with non-advanced fibrosis, as presumed by blood tests. Trial Registration ClinicalTrials.gov NCT01927133 PMID:27706177

Shear-wave elastography of the liver and spleen identifies clinically significant portal hypertension: A prospective multicentre study.

PubMed

Jansen, Christian; Bogs, Christopher; Verlinden, Wim; Thiele, Maja; Möller, Philipp; Görtzen, Jan; Lehmann, Jennifer; Vanwolleghem, Thomas; Vonghia, Luisa; Praktiknjo, Michael; Chang, Johannes; Krag, Aleksander; Strassburg, Christian P; Francque, Sven; Trebicka, Jonel

2017-03-01

Clinically significant portal hypertension (CSPH) is associated with severe complications and decompensation of cirrhosis. Liver stiffness measured either by transient elastography (TE) or Shear-wave elastography (SWE) and spleen stiffness by TE might be helpful in the diagnosis of CSPH. We recently showed the algorithm to rule-out CSPH using sequential liver- (L-SWE) and spleen-Shear-wave elastography (S-SWE). This study investigated the diagnostic value of S-SWE for diagnosis of CSPH. One hundred and fifty-eight cirrhotic patients with pressure gradient measurements were included into this prospective multicentre study. L-SWE was measured in 155 patients, S-SWE in 112 patients, and both in 109 patients. Liver-shear-wave elastography and S-SWE correlated with clinical events and decompensation. SWE of liver and spleen revealed strong correlations with the pressure gradient and to differentiate between patients with and without CSPH. The best cut-off values were 24.6 kPa:L-SWE and 26.3 kPa:S-SWE. L-SWE ≤16.0 kPa and S-SWE ≤21.7 kPa were able to rule-out CSPH. Cut-off values of L-SWE >29.5 kPa and S-SWE >35.6 kPa were able to rule-in CSPH (specificity >92%). Patients with a L-SWE >38.0 kPa had likely CSPH. In patients with L-SWE ≤38.0 kPa, a S-SWE >27.9 kPa ruled in CSPH. This algorithm has a sensitivity of 89.2% and a specificity of 91.4% to rule-in CSPH. Patients not fulfilling these criteria may undergo HVPG measurement. Liver and spleen SWE correlate with portal pressure and can both be used as a non-invasive method to investigate CSPH. Even though external validation is still missing, these algorithms to rule-out and rule-in CSPH using sequential SWE of liver and spleen might change the clinical practice. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Real-Time Elastography Visualization and Histopathological Characterization of Rabbit Atherosclerotic Carotid Arteries.

PubMed

Wang, ZhenZhen; Liu, NaNa; Zhang, LiFeng; Li, XiaoYing; Han, XueSong; Peng, YanQing; Dang, MeiZheng; Sun, LiTao; Tian, JiaWei

2016-01-01

To evaluate the feasibility of non-invasive vascular real-time elastography imaging (RTE) in visualizing the composition of rabbit carotid atherosclerotic plaque as determined by histopathology, a rabbit model of accelerated carotid atherosclerosis was used. Thirty rabbits were randomly divided into two groups of 15 rabbits each. The first group was fed a cholesterol-rich diet and received balloon-induced injury the left common carotid artery endothelium, whereas the second group only received a cholesterol-rich diet. The rabbits were all examined in vivo with HITACHI non-invasive vascular real-time elastography (Hi-RTE) at baseline and 12 wk, and results from the elastography were compared with American Heart Association histologic classifications. Hi-RTE and the American Heart Association histologic classifications had good agreement, with weighted Cohen's kappa (95% confidence internal) of 0.785 (0.649-0.920). Strains of segmented plaques that were stained in different colors were statistically different (p < 0.0001). The sensitivity and specificity of elastograms for detecting a lipid core were 95.5% and 61.5%, respectively, and the area under the receiver operating characteristic curve was 0.789, with a 95% confidence interval of 0.679 to 0.876. This study is the first to indicate the feasibility of utilizing Hi-RTE in visualizing normal and atherosclerotic rabbit carotid arteries non-invasively. This affordable and reliable method can be widely applied in research of both animal and human peripheral artery atherosclerosis. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Ultrasound Elastography of the Neonatal Brain: Preliminary Study.

PubMed

Kim, Hyun Gi; Park, Moon Sung; Lee, Jung-Dong; Park, Seon Young

2017-07-01

To determine the ultrasound elasticity of the brain in neonates METHODS: Strain elastography was performed in 21 healthy neonates (mean gestational age [GA], 34 weeks; range, 28-40 weeks). Elastographic scores were assigned to the following structures on a 5-point color scale (1-5): ventricle, periventricular white matter, caudate, subcortical, cortical gray matter, and subdural space. Three elastographic images were evaluated in each patient, and median elastographic scores were calculated. The scores were compared between regions and were correlated with the corrected GA. Interobserver agreements for assignment of elastographic scores were analyzed. The ventricle and subdural space showed an elasticity score of 1 in all patients. The cortical gray matter (median, 3.0; first-third quartiles, 2.33-3.33) showed higher elasticity compared to the periventricular white mater (4.0; 3.00-4.00; P < .001), caudate (4.3; 3.67-4.67; P < .001), and subcortical white matter (4.0; 4.00-4.00; P < .001). The caudate showed lower elasticity compared to periventricular white matter (P = .004). The periventricular white matter showed higher elasticity compared to subcortical white matter (P = .009). There was a positive trend between the corrected GA and cortical gray matter elastographic score (γ = 0.376; P = .093). Interobserver agreement was moderate to almost perfect (κ = 0.53-0.89). Neonatal intracranial regions showed different elasticity, which could be accessed by strain elastography. These normal findings should prompt future studies investigating the use of ultrasound elastography in the neonatal brain. © 2017 by the American Institute of Ultrasound in Medicine.

Quantitative US Elastography Can Be Used to Quantify Mechanical and Histologic Tendon Healing in a Rabbit Model of Achilles Tendon Transection.

PubMed

Yamamoto, Yohei; Yamaguchi, Satoshi; Sasho, Takahisa; Fukawa, Taisuke; Akatsu, Yorikazu; Akagi, Ryuichiro; Yamaguchi, Tadashi; Takahashi, Kenji; Nagashima, Kengo; Takahashi, Kazuhisa

2017-05-01

Purpose To determine the time-dependent change in strain ratios (SRs) at the healing site of an Achilles tendon rupture in a rabbit model of tendon transection and to assess the correlation between SRs and the mechanical and histologic properties of the healing tissue. Materials and Methods Experimental methods were approved by the institutional animal care and use committee. The Achilles tendons of 24 New Zealand white rabbits (48 limbs) were surgically transected. The SRs of Achilles tendons were calculated by using compression-based quantitative ultrasonographic elastography measurements obtained 2, 4, 8, and 12 weeks after transection. After in vivo elastography, the left Achilles tendon was harvested for mechanical testing of ultimate load, ultimate stress, elastic modulus, and linear stiffness, and the right tendons were harvested for tissue histologic analysis with the Bonar scale. Time-dependent changes in SRs, mechanical parameters, and Bonar scale scores were evaluated by using repeated-measures analysis of variance. The correlation between SRs and each measured variable was evaluated by using the Spearman rank correlation coefficient. Results Mean SRs and Bonar scale values decreased as a function of time after transection, whereas mechanical parameters increased (P < .001). SR correlated with ultimate stress (ρ = 0.68, P <.001,) elastic modulus (ρ = 0.74, P <.001), and the Bonar scale (ρ = 0.87, P <.001). Conclusion Quantitative elastography could be a useful method with which to evaluate mechanical and histologic properties of the healing tendon. © RSNA, 2017 Online supplemental material is available for this article.

Visualizing ex vivo radiofrequency and microwave ablation zones using electrode vibration elastography

PubMed Central

DeWall, Ryan J.; Varghese, Tomy; Brace, Chris L.

2012-01-01

Purpose: Electrode vibration elastography is a new shear wave imaging technique that can be used to visualize thermal ablation zones. Prior work has shown the ability of electrode vibration elastography to delineate radiofrequency ablations; however, there has been no previous study of delineation of microwave ablations or radiological–pathological correlations using multiple observers. Methods: Radiofrequency and microwave ablations were formed in ex vivo bovine liver tissue. Their visualization was compared on shear wave velocity and maximum displacement images. Ablation dimensions were compared to gross pathology. Elastographic imaging and gross pathology overlap and interobserver variability were quantified using similarity measures. Results: Elastographic imaging correlated with gross pathology. Correlation of area estimates was better in radiofrequency than in microwave ablations, with Pearson coefficients of 0.79 and 0.54 on shear wave velocity images and 0.90 and 0.70 on maximum displacement images for radiofrequency and microwave ablations, respectively. The absolute relative difference in area between elastographic imaging and gross pathology was 18.9% and 22.9% on shear wave velocity images and 16.0% and 23.1% on maximum displacement images for radiofrequency and microwave ablations, respectively. Conclusions: Statistically significant radiological–pathological correlation was observed in this study, but correlation coefficients were lower than other modulus imaging techniques, most notably in microwave ablations. Observers provided similar delineations for most thermal ablations. These results suggest that electrode vibration elastography is capable of imaging thermal ablations, but refinement of the technique may be necessary before it can be used to monitor thermal ablation procedures clinically. PMID:23127063

Non-invasive assessment of liver fibrosis: Between prediction/prevention of outcomes and cost-effectiveness.

PubMed

Stasi, Cristina; Milani, Stefano

2016-01-28

The assessment of the fibrotic evolution of chronic hepatitis has always been a challenge for the clinical hepatologist. Over the past decade, various non-invasive methods have been proposed to detect the presence of fibrosis, including the elastometric measure of stiffness, panels of clinical and biochemical parameters, and combinations of both methods. The aim of this review is to analyse the most recent data on non-invasive techniques for the evaluation of hepatic fibrosis with particular attention to cost-effectiveness. We searched for relevant studies published in English using the PubMed database from 2009 to the present. A large number of studies have suggested that elastography and serum markers are useful techniques for diagnosing severe fibrosis and cirrhosis and for excluding significant fibrosis in hepatitis C virus patients. In addition, hepatic stiffness may also help to prognosticate treatment response to antiviral therapy. It has also been shown that magnetic resonance elastography has a high accuracy for staging and differentiating liver fibrosis. Finally, studies have shown that non-invasive methods are becoming increasingly precise in either positively identifying or excluding liver fibrosis, thus reducing the need for liver biopsy. However, both serum markers and transient elastography still have "grey area" values of lower accuracy. In this case, liver biopsy is still required to properly assess liver fibrosis. Recently, the guidelines produced by the World Health Organization have suggested that the AST-to-platelet ratio index or FIB-4 test could be utilised for the evaluation of liver fibrosis rather than other, more expensive non-invasive tests, such as elastography or FibroTest.

Non-invasive assessment of liver fibrosis: Between prediction/prevention of outcomes and cost-effectiveness

PubMed Central

Stasi, Cristina; Milani, Stefano

2016-01-01

The assessment of the fibrotic evolution of chronic hepatitis has always been a challenge for the clinical hepatologist. Over the past decade, various non-invasive methods have been proposed to detect the presence of fibrosis, including the elastometric measure of stiffness, panels of clinical and biochemical parameters, and combinations of both methods. The aim of this review is to analyse the most recent data on non-invasive techniques for the evaluation of hepatic fibrosis with particular attention to cost-effectiveness. We searched for relevant studies published in English using the PubMed database from 2009 to the present. A large number of studies have suggested that elastography and serum markers are useful techniques for diagnosing severe fibrosis and cirrhosis and for excluding significant fibrosis in hepatitis C virus patients. In addition, hepatic stiffness may also help to prognosticate treatment response to antiviral therapy. It has also been shown that magnetic resonance elastography has a high accuracy for staging and differentiating liver fibrosis. Finally, studies have shown that non-invasive methods are becoming increasingly precise in either positively identifying or excluding liver fibrosis, thus reducing the need for liver biopsy. However, both serum markers and transient elastography still have “grey area” values of lower accuracy. In this case, liver biopsy is still required to properly assess liver fibrosis. Recently, the guidelines produced by the World Health Organization have suggested that the AST-to-platelet ratio index or FIB-4 test could be utilised for the evaluation of liver fibrosis rather than other, more expensive non-invasive tests, such as elastography or FibroTest. PMID:26819535

[Proposal for the systematization of the elastographic study of mammary lesions through ultrasound scan].

PubMed

Fleury, Eduardo de Faria Castro; Fleury, Jose Carlos Vendramini; Oliveira, Vilmar Marques de; Rinaldi, Jose Francisco; Piato, Sebastiao; Roveda Junior, Decio

2009-01-01

Proposal of systematization for the elastographic study in the ultrasound routine. Evaluation was made of 308 patients forwarded to the breast intervention service in the CTC-Genesis from May 1, 2007 to March 1, 2008 to perform percutaneous breast biopsy. Prior to the percutaneous biopsy, an ultrasound study and an elastography were performed. Lesions were primarily analyzed and classified according to the Bi-Rads lexicon criteria by the conventional ultrasound scan (B mode). The elastography was then performed and analyzed in accordance with the systematization proposed by the authors, using images obtained during compression and after decompression of the area of interest. Lesions were classified following the system developed by the authors using a four-point scale, where scores (1) and (2) were considered benign, score (3) probably benign and score (4) suspicion of malignancy. Results obtained by the two methods were compared with the histological results using the areas within the ROC (receiver operator curves) curves. The area within the curve for elastography was of 0.952 with a confidence interval between 0.910 and 0.966, error of 0.023, and of 0.867 with a confidence interval between 0.823 and 0.903, error of 0.0333 for the ultrasound. When the areas were compared, a difference between the curves of 0.026 was observed, which was statistically significant. This work shows the systematization of the elastographic study using information obtained during compression and after decompression of the ultrasound scan sample, thus showing that elastography might enhance the assessment of risk of malignancy for lesions characterized by the ultrasound.

High speed all optical shear wave imaging optical coherence elastography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Song, Shaozhen; Hsieh, Bao-Yu; Wei, Wei; Shen, Tueng; O'Donnell, Matthew; Wang, Ruikang K.

2016-03-01

Optical Coherence Elastography (OCE) is a non-invasive testing modality that maps the mechanical property of soft tissues with high sensitivity and spatial resolution using phase-sensitive optical coherence tomography (PhS-OCT). Shear wave OCE (SW-OCE) is a leading technique that relies on the speed of propagating shear waves to provide a quantitative elastography. Previous shear wave imaging OCT techniques are based on repeated M-B scans, which have several drawbacks such as long acquisition time and repeated wave stimulations. Recent developments of Fourier domain mode-locked high-speed swept-source OCT system has enabled enough speed to perform KHz B-scan rate OCT imaging. Here we propose ultra-high speed, single shot shear wave imaging to capture single-shot transient shear wave propagation to perform SW-OCE. The frame rate of shear wave imaging is 16 kHz, at A-line rate of ~1.62 MHz, which allows the detection of high-frequency shear wave of up to 8 kHz. The shear wave is generated photothermal-acoustically, by ultra-violet pulsed laser, which requires no contact to OCE subjects, while launching high frequency shear waves that carries rich localized elasticity information. The image acquisition and processing can be performed at video-rate, which enables real-time 3D elastography. SW-OCE measurements are demonstrated on tissue-mimicking phantoms and porcine ocular tissue. This approach opens up the feasibility to perform real-time 3D SW-OCE in clinical applications, to obtain high-resolution localized quantitative measurement of tissue biomechanical property.

Measuring shear-wave speed with point shear-wave elastography and MR elastography: a phantom study

PubMed Central

Kishimoto, Riwa; Suga, Mikio; Koyama, Atsuhisa; Omatsu, Tokuhiko; Tachibana, Yasuhiko; Ebner, Daniel K; Obata, Takayuki

2017-01-01

Objectives To compare shear-wave speed (SWS) measured by ultrasound-based point shear-wave elastography (pSWE) and MR elastography (MRE) on phantoms with a known shear modulus, and to assess method validity and variability. Methods 5 homogeneous phantoms of different stiffnesses were made. Shear modulus was measured by a rheometer, and this value was used as the standard. 10 SWS measurements were obtained at 4 different depths with 1.0–4.5 MHz convex (4C1) and 4.0–9.0 MHz linear (9L4) transducers using pSWE. MRE was carried out once per phantom, and SWSs at 5 different depths were obtained. These SWSs were then compared with those from a rheometer using linear regression analyses. Results SWSs obtained with both pSWE as well as MRE had a strong correlation with those obtained by a rheometer (R2>0.97). The relative difference in SWS between the procedures was from −25.2% to 25.6% for all phantoms, and from −8.1% to 6.9% when the softest and hardest phantoms were excluded. Depth dependency was noted in the 9L4 transducer of pSWE and MRE. Conclusions SWSs from pSWE and MRE showed a good correlation with a rheometer-determined SWS. Although based on phantom studies, SWSs obtained with these methods are not always equivalent, the measurement can be thought of as reliable and these SWSs were reasonably close to each other for the middle range of stiffness within the measurable range. PMID:28057657

Satellite-derived aerosol radiative forcing from the 2004 British Columbia wildfires

USGS Publications Warehouse

Guo, Song; Leighton, H.

2008-01-01

The British Columbia wildfires of 2004 was one of the largest wildfire events in the last ten years in Canada. Both the shortwave and longwave smoke aerosol radiative forcing at the top-of-atmosphere (TOA) are investigated using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES) instruments. Relationships between the radiative forcing fluxes (??F) and wildfire aerosol optical thickness (AOT) at 0.55 ??m (??0.55) are deduced for both noontime instantaneous forcing and diurnally averaged forcing. The noontime averaged instantaneous shortwave and longwave smoke aerosol radiative forcing at the TOA are 45.8??27.5 W m-2 and -12.6??6.9 W m-2, respectively for a selected study area between 62??N and 68??N in latitude and 125??W and 145??W in longitude over three mainly clear-sky days (23-25 June). The derived diurnally averaged smoke aerosol shortwave radiative forcing is 19.9??12.1 W m-2 for a mean ??0.55 of 1.88??0.71 over the same time period. The derived ??F-?? relationship can be implemented in the radiation scheme used in regional climate models to assess the effect of wildfire aerosols.

Arterial waveguide model for shear wave elastography: implementation and in vitro validation

NASA Astrophysics Data System (ADS)

Vaziri Astaneh, Ali; Urban, Matthew W.; Aquino, Wilkins; Greenleaf, James F.; Guddati, Murthy N.

2017-07-01

Arterial stiffness is found to be an early indicator of many cardiovascular diseases. Among various techniques, shear wave elastography has emerged as a promising tool for estimating local arterial stiffness through the observed dispersion of guided waves. In this paper, we develop efficient models for the computational simulation of guided wave dispersion in arterial walls. The models are capable of considering fluid-loaded tubes, immersed in fluid or embedded in a solid, which are encountered in in vitro/ex vivo, and in vivo experiments. The proposed methods are based on judiciously combining Fourier transformation and finite element discretization, leading to a significant reduction in computational cost while fully capturing complex 3D wave propagation. The developed methods are implemented in open-source code, and verified by comparing them with significantly more expensive, fully 3D finite element models. We also validate the models using the shear wave elastography of tissue-mimicking phantoms. The computational efficiency of the developed methods indicates the possibility of being able to estimate arterial stiffness in real time, which would be beneficial in clinical settings.

Reliable protocol for shear wave elastography of lower limb muscles at rest and during passive stretching.

PubMed

Dubois, Guillaume; Kheireddine, Walid; Vergari, Claudio; Bonneau, Dominique; Thoreux, Patricia; Rouch, Philippe; Tanter, Mickael; Gennisson, Jean-Luc; Skalli, Wafa

2015-09-01

Development of shear wave elastography gave access to non-invasive muscle stiffness assessment in vivo. The aim of the present study was to define a measurement protocol to be used in clinical routine for quantifying the shear modulus of lower limb muscles. Four positions were defined to evaluate shear modulus in 10 healthy subjects: parallel to the fibers, in the anterior and posterior aspects of the lower limb, at rest and during passive stretching. Reliability was first evaluated on two muscles by three operators; these measurements were repeated six times. Then, measurement reliability was compared in 11 muscles by two operators; these measurements were repeated three times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. Position did not significantly influence reliability. Shear wave elastography appeared to be an appropriate and reliable tool to evaluate the shear modulus of lower limb muscles with the proposed protocol. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Ultrahigh resolution optical coherence elastography using a Bessel beam for extended depth of field

NASA Astrophysics Data System (ADS)

Curatolo, Andrea; Villiger, Martin; Lorenser, Dirk; Wijesinghe, Philip; Fritz, Alexander; Kennedy, Brendan F.; Sampson, David D.

2016-03-01

Visualizing stiffness within the local tissue environment at the cellular and sub-cellular level promises to provide insight into the genesis and progression of disease. In this paper, we propose ultrahigh-resolution optical coherence elastography, and demonstrate three-dimensional imaging of local axial strain of tissues undergoing compressive loading. The technique employs a dual-arm extended focus optical coherence microscope to measure tissue displacement under compression. The system uses a broad bandwidth supercontinuum source for ultrahigh axial resolution, Bessel beam illumination and Gaussian beam detection, maintaining sub-2 μm transverse resolution over nearly 100 μm depth of field, and spectral-domain detection allowing high displacement sensitivity. The system produces strain elastograms with a record resolution (x,y,z) of 2×2×15 μm. We benchmark the advances in terms of resolution and strain sensitivity by imaging a suitable inclusion phantom. We also demonstrate this performance on freshly excised mouse aorta and reveal the mechanical heterogeneity of vascular smooth muscle cells and elastin sheets, otherwise unresolved in a typical, lower resolution optical coherence elastography system.

Ultrasound elastography to determine the layered mechanical properties of articular cartilage and the importance of such structural characteristics under load.

PubMed

McCredie, Alexandra J; Stride, Eleanor; Saffari, Nader

2009-01-01

Articular cartilage is an important load bearing surface in joints. Prone to damage and with limited self-repair ability, it is of interest to tissue engineers. Tissue implant design requires full mechanical characterisation of healthy native tissue. A layered organisation of reinforcing collagen fibrils exists in healthy articular cartilage and is believed to be important for correct tissue function. However, the effect of this on the local depth-dependent elasticity is poorly characterised. In this study, quasi-static ultrasound elastography is used both to compare the depth-dependent elastic properties of cartilage structures with two different fibril arrangements and to monitor changes in the elastic properties of engineered samples during development. Results show global and local elastic properties of the native tissues and highlight the differences caused by fibril architecture. At increasing culture periods, results from the engineered tissue demonstrate an increase in elastic stiffness and the time taken to reach equilibrium under a quasi-static displacement. The study suggests suitability of ultrasound elastography for design and monitoring engineered articular cartilage.

Real-time 1-D/2-D transient elastography on a standard ultrasound scanner using mechanically induced vibration.

PubMed

Azar, Reza Zahiri; Dickie, Kris; Pelissier, Laurent

2012-10-01

Transient elastography has been well established in the literature as a means of assessing the elasticity of soft tissue. In this technique, tissue elasticity is estimated from the study of the propagation of the transient shear waves induced by an external or internal source of vibration. Previous studies have focused mainly on custom single-element transducers and ultrafast scanners which are not available in a typical clinical setup. In this work, we report the design and implementation of a transient elastography system on a standard ultrasound scanner that enables quantitative assessment of tissue elasticity in real-time. Two new custom imaging modes are introduced that enable the system to image the axial component of the transient shear wave, in response to an externally induced vibration, in both 1-D and 2-D. Elasticity reconstruction algorithms that estimate the tissue elasticity from these transient waves are also presented. Simulation results are provided to show the advantages and limitations of the proposed system. The performance of the system is also validated experimentally using a commercial elasticity phantom.

Second harmonic generation efficiency affected by radiation force of a high-energy laser beam through stress within a mounted potassium dihydrogen phosphate crystal

NASA Astrophysics Data System (ADS)

Su, Ruifeng; Zhu, Mingzhi; Huang, Zhan; Wang, Baoxu; Wu, Wenkai

2018-01-01

Influence of radiation force of a high-energy laser beam on the second harmonic generation (SHG) efficiency through stress within a mounted potassium dihydrogen phosphate (KDP) crystal is studied, as well as an active method of improving the SHG efficiency by controlling the stress is proposed. At first, the model for studying the influence of the radiation force on the SHG efficiency is established, where the radiation force is theoretically analyzed, the stress caused by the radiation force is theoretically analyzed and numerically calculated using the finite-element method, and the influence of the stress on the SHG efficiency is theoretically analyzed. Then, a method of improving the SHG efficiency by controlling the stress through adjusting the structural parameters of the mounting set of the KDP crystal is examined. It demonstrates that the radiation force causes stress within the KDP crystal and further militates against the SHG efficiency; however, the SHG efficiency could be improved by controlling the stress through adjusting the structural parameters of the mounting set of the KDP crystal.

Negative radiation forces on spheres illuminated by acoustic Bessel beams.

NASA Astrophysics Data System (ADS)

Marston, Philip L.; Thiessen, David B.

2007-11-01

An analytical solution for the scattering of an acoustic Bessel beam by a sphere centered on the beam has made it possible to explore the way the acoustic radiation force on elastic and fluid spheres depends on beam and material parameters. Situations have been previously noted where, even in the absence of absorption, the radiation force of the beam on the sphere is opposite the direction of beam propagation [1]. In extensions of that work, conditions have been identified for such a force reversal on solid spheres and elastic shells. Negative radiation forces may be useful for manipulation of objects in reduced gravity and of biological cells (with single beam acoustic tweezers). The finite element method (FEM) has been used to evaluate the total acoustic field in the region near the sphere. This makes it possible to evaluate the radiation force from numerical integration of an appropriate projection of the Brillouin radiation stress tensor. FEM and analytical results agree for plane wave and Bessel beam illumination. 1. P. L. Marston, J. Acoust. Soc. Am. 120, 3518-3524 (2006).

Observationally constrained estimates of carbonaceous aerosol radiative forcing.

PubMed

Chung, Chul E; Ramanathan, V; Decremer, Damien

2012-07-17

Carbonaceous aerosols (CA) emitted by fossil and biomass fuels consist of black carbon (BC), a strong absorber of solar radiation, and organic matter (OM). OM scatters as well as absorbs solar radiation. The absorbing component of OM, which is ignored in most climate models, is referred to as brown carbon (BrC). Model estimates of the global CA radiative forcing range from 0 to 0.7 Wm(-2), to be compared with the Intergovernmental Panel on Climate Change's estimate for the pre-Industrial to the present net radiative forcing of about 1.6 Wm(-2). This study provides a model-independent, observationally based estimate of the CA direct radiative forcing. Ground-based aerosol network data is integrated with field data and satellite-based aerosol observations to provide a decadal (2001 through 2009) global view of the CA optical properties and direct radiative forcing. The estimated global CA direct radiative effect is about 0.75 Wm(-2) (0.5 to 1.0). This study identifies the global importance of BrC, which is shown to contribute about 20% to 550-nm CA solar absorption globally. Because of the inclusion of BrC, the net effect of OM is close to zero and the CA forcing is nearly equal to that of BC. The CA direct radiative forcing is estimated to be about 0.65 (0.5 to about 0.8) Wm(-2), thus comparable to or exceeding that by methane. Caused in part by BrC absorption, CAs have a net warming effect even over open biomass-burning regions in Africa and the Amazon.

Observationally constrained estimates of carbonaceous aerosol radiative forcing

PubMed Central

Chung, Chul E.; Ramanathan, V.; Decremer, Damien

2012-01-01

Carbonaceous aerosols (CA) emitted by fossil and biomass fuels consist of black carbon (BC), a strong absorber of solar radiation, and organic matter (OM). OM scatters as well as absorbs solar radiation. The absorbing component of OM, which is ignored in most climate models, is referred to as brown carbon (BrC). Model estimates of the global CA radiative forcing range from 0 to 0.7 Wm-2, to be compared with the Intergovernmental Panel on Climate Change’s estimate for the pre-Industrial to the present net radiative forcing of about 1.6 Wm-2. This study provides a model-independent, observationally based estimate of the CA direct radiative forcing. Ground-based aerosol network data is integrated with field data and satellite-based aerosol observations to provide a decadal (2001 through 2009) global view of the CA optical properties and direct radiative forcing. The estimated global CA direct radiative effect is about 0.75 Wm-2 (0.5 to 1.0). This study identifies the global importance of BrC, which is shown to contribute about 20% to 550-nm CA solar absorption globally. Because of the inclusion of BrC, the net effect of OM is close to zero and the CA forcing is nearly equal to that of BC. The CA direct radiative forcing is estimated to be about 0.65 (0.5 to about 0.8) Wm-2, thus comparable to or exceeding that by methane. Caused in part by BrC absorption, CAs have a net warming effect even over open biomass-burning regions in Africa and the Amazon. PMID:22753522

Measurement of time-varying displacement fields in cell culture for traction force optical coherence microscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Mulligan, Jeffrey A.; Adie, Steven G.

2017-02-01

Mechanobiology is an emerging field which seeks to link mechanical forces and properties to the behaviors of cells and tissues in cancer, stem cell growth, and other processes. Traction force microscopy (TFM) is an imaging technique that enables the study of traction forces exerted by cells on their environment to migrate as well as sense and manipulate their surroundings. To date, TFM research has been performed using incoherent imaging modalities and, until recently, has been largely confined to the study of cell-induced tractions within two-dimensions using highly artificial and controlled environments. As the field of mechanobiology advances, and demand grows for research in physiologically relevant 3D culture and in vivo models, TFM will require imaging modalities that support such settings. Optical coherence microscopy (OCM) is an interferometric imaging modality which enables 3D cellular resolution imaging in highly scattering environments. Moreover, optical coherence elastography (OCE) enables the measurement of tissue mechanical properties. OCE relies on the principle of measuring material deformations in response to artificially applied stress. By extension, similar techniques can enable the measurement of cell-induced deformations, imaged with OCM. We propose traction force optical coherence microscopy (TF-OCM) as a natural extension and partner to existing OCM and OCE methods. We report the first use of OCM data and digital image correlation to track temporally varying displacement fields exhibited within a 3D culture setting. These results mark the first steps toward the realization of TF-OCM in 2D and 3D settings, bolstering OCM as a platform for advancing research in mechanobiology.

Accuracy of the Enhanced Liver Fibrosis Test vs FibroTest, Elastography, and Indirect Markers in Detection of Advanced Fibrosis in Patients With Alcoholic Liver Disease.

PubMed

Thiele, Maja; Madsen, Bjørn Stæhr; Hansen, Janne Fuglsang; Detlefsen, Sönke; Antonsen, Steen; Krag, Aleksander

2018-04-01

Alcohol is the leading cause of cirrhosis and liver-related mortality, but we lack serum markers to detect compensated disease. We compared the accuracy of the Enhanced Liver Fibrosis test (ELF), the FibroTest, liver stiffness measurements (made by transient elastography and 2-dimensional shear-wave elastography), and 6 indirect marker tests in detection of advanced liver fibrosis (Kleiner stage ≥F3). We performed a prospective study of 10 liver fibrosis markers (patented and not), all performed on the same day. Patients were recruited from primary centers (municipal alcohol rehabilitation, n = 128; 6% with advanced fibrosis) and secondary health care centers (hospital outpatient clinics, n = 161; 36% with advanced fibrosis) in the Region of Southern Denmark from 2013 through 2016. Biopsy-verified fibrosis stage was used as the reference standard. The primary aim was to validate ELF in detection of advanced fibrosis in patients with alcoholic liver disease recruited from primary and secondary health care centers, using the literature-based cutoff value of 10.5. Secondary aims were to assess the diagnostic accuracy of ELF for significant fibrosis and cirrhosis and to determine whether combinations of fibrosis markers increase diagnostic yield. The ELF identified patients with advanced liver fibrosis with an area under the receiver operating characteristic curve (AUROC) of 0.92 (95% confidence interval 0.89-0.96); findings did not differ significantly between patients from primary vs secondary care (P = .917). ELF more accurately identified patients with advanced liver fibrosis than indirect marker tests, but ELF and FibroTest had comparable diagnostic accuracies (AUROC of FibroTest, 0.90) (P = .209 for comparison with ELF). Results from the ELF and FibroTest did not differ significantly from those of liver stiffness measurement in intention-to-diagnose analyses (AUROC for transient elastography, 0.90), but did differ in the per-protocol analysis (AUROC for transient elastography, 0.97) (P = .521 and .004 for comparison with ELF). Adding a serum marker to transient elastography analysis did not increase accuracy. For patients in primary care, ELF values below 10.5 and FibroTest values below 0.58 had negative predictive values for advanced liver fibrosis of 98% and 94%, respectively. In a prospective, direct comparison of tests, ELF and FibroTest identified advanced liver fibrosis in alcoholic patients from primary and secondary care with high diagnostic accuracy (AUROC values of 0.90 or higher using biopsy as reference). Advanced fibrosis can be ruled out in primary health care patients based on an ELF value below 10.5 or a FibroTest value below 0.58. Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.

Accurate Satellite-Derived Estimates of Tropospheric Ozone Radiative Forcing

NASA Technical Reports Server (NTRS)

Joiner, Joanna; Schoeberl, Mark R.; Vasilkov, Alexander P.; Oreopoulos, Lazaros; Platnick, Steven; Livesey, Nathaniel J.; Levelt, Pieternel F.

2008-01-01

Estimates of the radiative forcing due to anthropogenically-produced tropospheric O3 are derived primarily from models. Here, we use tropospheric ozone and cloud data from several instruments in the A-train constellation of satellites as well as information from the GEOS-5 Data Assimilation System to accurately estimate the instantaneous radiative forcing from tropospheric O3 for January and July 2005. We improve upon previous estimates of tropospheric ozone mixing ratios from a residual approach using the NASA Earth Observing System (EOS) Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) by incorporating cloud pressure information from OMI. Since we cannot distinguish between natural and anthropogenic sources with the satellite data, our estimates reflect the total forcing due to tropospheric O3. We focus specifically on the magnitude and spatial structure of the cloud effect on both the shortand long-wave radiative forcing. The estimates presented here can be used to validate present day O3 radiative forcing produced by models.

Estimation of Asian Dust Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements

NASA Technical Reports Server (NTRS)

Su, Jing; Huang, Jianping; Fu, Qiang; Minnis, Patrick; Ge, Jinming; Bi, Jianrong

2008-01-01

The impact of Asian dust on cloud radiative forcing during 2003-2006 is studied by using the Earth's Radiant Energy Budget Scanner (CERES) data and the Fu-Liou radiative transfer model. Analysis of satellite data shows that the dust aerosol significantly reduced the cloud cooling effect at TOA. In dust contaminated cloudy regions, the 4-year mean values of the instantaneous shortwave, longwave and net cloud radiative forcing are -138.9, 69.1, and -69.7 Wm(sup -2), which are 57.0, 74.2, and 46.3%, respectively, of the corresponding values in more pristine cloudy regions. The satellite-retrieved cloud properties are significantly different in the dusty regions and can influence the radiative forcing indirectly. The contributions to the cloud radiation forcing by the dust direct, indirect and semi-direct effects are estimated using combined satellite observations and Fu-Liou model simulation. The 4-year mean value of combination of indirect and semi-direct shortwave radiative forcing (SWRF) is 82.2 Wm(sup -2), which is 78.4% of the total dust effect. The direct effect is only 22.7 Wm(sup -2), which is 21.6% of the total effect. Because both first and second indirect effects enhance cloud cooling, the aerosol-induced cloud warming is mainly the result of the semi-direct effect of dust.

Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up.

PubMed

Lacourpaille, Lilian; Gross, Raphaël; Hug, François; Guével, Arnaud; Péréon, Yann; Magot, Armelle; Hogrel, Jean-Yves; Nordez, Antoine

2017-03-01

The present study aimed to assess the ability of muscle stiffness (shear modulus) and response to electrically-induced muscle contraction to detect changes in muscle properties over a 12-month period in children with Duchenne muscular dystrophy (DMD). Ten children with DMD and nine age-matched healthy male controls participated in two experimental sessions (T 0 and T +12months ) separated by 12.4 ± 0.9 months. Two contractions of the biceps brachii were electrically-induced during which an ultrasound probe was placed over the muscle. The resting shear modulus was measured using elastography from six muscles. Evoked maximal torque was increased at T +12months in controls (+11.2 ± 7.6%, P <0.001) but was not modified in children with DMD (P = 0.222). Electromechanical delay (+12.9 ± 11.3%, P <0.001) and its force transmission component (+10.1 ± 21.6%, P = 0.003) were significantly longer at T +12months than T 0 for children with DMD. The results revealed an increase in muscle stiffness at T +12months in children with DMD for tibialis anterior (+75.1 ± 93.5%, P= 0.043), gastrocnemius medialis (+144.8 ± 180.6%, P= 0.050) and triceps brachii (+35.5 ± 32.2%, P= 0.005). This 12-month follow-up study demonstrates that electromechanical delay and elastography may help detect subtle muscle impairments in patients with DMD. These sensitive outcomes may improve the follow-up of innovative therapeutic interventions within the field of DMD. Copyright © 2017 Elsevier B.V. All rights reserved.

Orbit Stability of OSIRIS-REx in the Vicinity of Bennu Using a High-Fidelity Solar Radiation Model

NASA Technical Reports Server (NTRS)

Williams, Trevor W.; Hughes, Kyle M.; Mashiku, Alinda K.; Longuski, James M.

2015-01-01

Solar radiation pressure is one of the largest perturbing forces on the OSIRISRex trajectory as it orbits the asteroid Bennu. In this work, we investigate how forces due to solar radiation perturb the OSIRIS-REx trajectory in a high-fidelity model. The model accounts for Bennu's non-spherical gravity field, third-body gravity forces from the Sun and Jupiter, as well as solar radiation forces acting on a simplified spacecraft model. Such high-fidelity simulations indicate significant solar radiation pressure perturbations from the nominal orbit. Modifications to the initial design of the nominal orbit are found using a variation of parameters approach that reduce the perturbation in eccentricity by a factor of one-half.

Acoustic radiation force on an air bubble and soft fluid spheres in ideal liquids: example of a high-order Bessel beam of quasi-standing waves.

PubMed

Mitri, F G

2009-04-01

The partial wave series for the scattering of a high-order Bessel beam (HOBB) of acoustic quasi-standing waves by an air bubble and fluid spheres immersed in water and centered on the axis of the beam is applied to the calculation of the acoustic radiation force. A HOBB refers to a type of beam having an axial amplitude null and an azimuthal phase gradient. Radiation force examples obtained through numerical evaluation of the radiation force function are computed for an air bubble, a hexane, a red blood and mercury fluid spheres in water. The examples were selected to illustrate conditions having progressive, standing and quasi-standing waves with appropriate selection of the waves' amplitude ratio. An especially noteworthy result is the lack of a specific vibrational mode contribution to the radiation force determined by appropriate selection of the HOBB parameters.

The Dependence of Cloud-SST Feedback on Circulation Regime and Timescale

NASA Astrophysics Data System (ADS)

Middlemas, E.; Clement, A. C.; Medeiros, B.

2017-12-01

Studies suggest cloud radiative feedback amplifies internal variability of Pacific sea surface temperature (SST) on interannual-and-longer timescales, though only a few modeling studies have tested the quantitative importance of this feedback (Bellomo et al. 2014b, Brown et al. 2016, Radel et al. 2016 Burgman et al. 2017). We prescribe clouds from a previous control run in the radiation module in Community Atmospheric Model (CAM5-slab), a method called "cloud-locking". By comparing this run to a control run, in which cloud radiative forcing can feedback on the climate system, we isolate the effect of cloud radiative forcing on SST variability. Cloud-locking prevents clouds from radiatively interacting with atmospheric circulation, water vapor, and SST, while maintaining a similar mean state to the control. On all timescales, cloud radiative forcing's influence on SST variance is modulated by the circulation regime. Cloud radiative forcing amplifies SST variance in subsiding regimes and dampens SST variance in convecting regimes. In this particular model, a tug of war between latent heat flux and cloud radiative forcing determines the variance of SST, and the winner depends on the timescale. On decadal-and-longer timescales, cloud radiative forcing plays a relatively larger role than on interannual-and-shorter timescales, while latent heat flux plays a smaller role. On longer timescales, the absence of cloud radiative feedback changes SST variance in a zonally asymmetric pattern in the Pacific Ocean that resembles an IPO-like pattern. We also present an analysis of cloud feedback's role on Pacific SST variability among preindustrial control CMIP5 models to test the model robustness of our results. Our results suggest that circulation plays a crucial role in cloud-SST feedbacks across the globe and cloud radiative feedbacks cannot be ignored when studying SST variability on decadal-and-longer timescales.

On the contribution of circumferential resonance modes in acoustic radiation force experienced by cylindrical shells

NASA Astrophysics Data System (ADS)

Rajabi, Majid; Behzad, Mehdi

2014-10-01

A body insonified by a constant (time-varying) intensity sound field is known to experience a steady (oscillatory) force that is called the steady-state (dynamic) acoustic radiation force. Using the classical resonance scattering theorem (RST) which suggests the scattered field as a superposition of a resonance field and a background (non-resonance) component, we show that the radiation force acting on a cylindrical shell may be synthesized as a composition of three components: background part, resonance part and their interaction. The background component reveals the pure geometrical reflection effects and illustrates a regular behavior with respect to frequency, while the others demonstrate a singular behavior near the resonance frequencies. The results illustrate that the resonance effects associated to partial waves can be isolated by the subtraction of the background component from the total (steady-state or dynamic) radiation force function (i.e., residue component). In the case of steady-state radiation force, the components are exerted on the body as static forces. For the case of oscillatory amplitude excitation, the components are exerted at the modulation frequency with frequency-dependant phase shifts. The results demonstrate the dominant contribution of the non-resonance component of dynamic radiation force at high frequencies with respect to the residue component, which offers the potential application of ultrasound stimulated vibro-acoustic spectroscopy technique in low frequency resonance spectroscopy purposes. Furthermore, the proposed formulation may be useful essentially due to its intrinsic value in physical acoustics. In addition, it may unveil the contribution of resonance modes in the dynamic radiation force experienced by the cylindrical objects and its underlying physics.

Unbinding of targeted ultrasound contrast agent microbubbles by secondary acoustic forces.

PubMed

Garbin, Valeria; Overvelde, Marlies; Dollet, Benjamin; de Jong, Nico; Lohse, Detlef; Versluis, Michel

2011-10-07

Targeted molecular imaging with ultrasound contrast agent microbubbles is achieved by incorporating targeting ligands on the bubble coating and allows for specific imaging of tissues affected by diseases. Improved understanding of the interplay between the acoustic forces acting on the bubbles during insonation with ultrasound and other forces (e.g. shear due to blood flow, binding of targeting ligands to receptors on cell membranes) can help improve the efficacy of this technique. This work focuses on the effects of the secondary acoustic radiation force, which causes bubbles to attract each other and may affect the adhesion of targeted bubbles. First, we examine the translational dynamics of ultrasound contrast agent microbubbles in contact with (but not adherent to) a semi-rigid membrane due to the secondary acoustic radiation force. An equation of motion that effectively accounts for the proximity of the membrane is developed, and the predictions of the model are compared with experimental data extracted from optical recordings at 15 million frames per second. A time-averaged model is also proposed and validated. In the second part of the paper, initial results on the translation due to the secondary acoustic radiation force of targeted, adherent bubbles are presented. Adherent bubbles are also found to move due to secondary acoustic radiation force, and a restoring force is observed that brings them back to their initial positions. For increasing magnitude of the secondary acoustic radiation force, a threshold is reached above which the adhesion of targeted microbubbles is disrupted. This points to the fact that secondary acoustic radiation forces can cause adherent bubbles to detach and alter the spatial distribution of targeted contrast agents bound to tissues during activation with ultrasound. While the details of the rupture of intermolecular bonds remain elusive, this work motivates the use of the secondary acoustic radiation force to measure the strength of adhesion of targeted microbubbles.

The effect of radiation pressure on spatial distribution of dust inside H II regions

NASA Astrophysics Data System (ADS)

Ishiki, Shohei; Okamoto, Takashi; Inoue, Akio K.

2018-02-01

We investigate the impact of radiation pressure on spatial dust distribution inside H II regions using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. In order to investigate grain-size effects as well, we introduce two additional fluid components describing large and small dust grains in the simulations. Relative velocity between dust and gas strongly depends on the drag force. We include collisional drag force and coulomb drag force. We find that, in a compact H II region, a dust cavity region is formed by radiation pressure. Resulting dust cavity sizes (˜0.2 pc) agree with observational estimates reasonably well. Since dust inside an H II region is strongly charged, relative velocity between dust and gas is mainly determined by the coulomb drag force. Strength of the coulomb drag force is about 2 order of magnitude larger than that of the collisional drag force. In addition, in a cloud of mass 105 M⊙, we find that the radiation pressure changes the grain-size distribution inside H II regions. Since large (0.1 μm) dust grains are accelerated more efficiently than small (0.01 μm) grains, the large-to-small grain mass ratio becomes smaller by an order of magnitude compared with the initial one. Resulting dust-size distributions depend on the luminosity of the radiation source. The large and small grain segregation becomes weaker when we assume stronger radiation source, since dust grain charges become larger under stronger radiation and hence coulomb drag force becomes stronger.

Radiative Forcing Due to Enhancements in Tropospheric Ozone and Carbonaceous Aerosols Caused by Asian Fires During Spring 2008

NASA Technical Reports Server (NTRS)

Natarajan, Murali; Pierce, R. Bradley; Lenzen, Allen J.; Al-Saadi, Jassim A.; Soja, Amber J.; Charlock, Thomas P.; Rose, Fred G.; Winker, David M.; Worden, John R.

2012-01-01

Simulations of tropospheric ozone and carbonaceous aerosol distributions, conducted with the Real-time Air Quality Modeling System (RAQMS), are used to study the effects of major outbreaks of fires that occurred in three regions of Asia, namely Thailand, Kazakhstan, and Siberia, during spring 2008. RAQMS is a global scale meteorological and chemical modeling system. Results from these simulations, averaged over April 2008, indicate that tropospheric ozone column increases by more than 10 Dobson units (DU) near the Thailand region, and by lesser amounts in the other regions due to the fires. Widespread increases in the optical depths of organic and black carbon aerosols are also noted. We have used an off-line radiative transfer model to evaluate the direct radiative forcing due to the fire-induced changes in atmospheric composition. For clear sky, the monthly averaged radiative forcing at the top of the atmosphere (TOA) is mostly negative with peak values less than -12 W/sq m occurring near the fire regions. The negative forcing represents the increased outgoing shortwave radiation caused by scattering due to carbonaceous aerosols. At high latitudes, the radiative forcing is positive due to the presence of absorbing aerosols over regions of high surface albedo. Regions of positive forcing at TOA are more pronounced under total sky conditions. The monthly averaged radiative forcing at the surface is mostly negative, and peak values of less than -30 W/sq m occur near the fire regions. Persistently large negative forcing at the surface could alter the surface energy budget and potentially weaken the hydrological cycle.

Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models

NASA Technical Reports Server (NTRS)

Cess, R. D.; Zhang, M.-H.; Potter, G. L.; Gates, W. L.; Taylor, K. E.; Barker, H. W.; Colman, R. A.; Fraser, J. R.; McAvaney, B. J.; Dazlich, D. A.;

Measuring the radiation force of megahertz ultrasound acting on a solid spherical scatterer

NASA Astrophysics Data System (ADS)

Nikolaeva, A. V.; Tsysar, S. A.; Sapozhnikov, O. A.

2016-01-01

The paper considers the problem of precise measurement of the acoustic radiation force of an ultrasonic beam on targets in the form of solid spherical scatterers. Using known analytic relations, a numerical model is developed to perform calculations for different sizes of spherical scatterers and arbitrary frequencies of the incident acoustic wave. A novel method is proposed for measuring the radiation force, which is based on the principle of acoustic echolocation. The radiation force is measured experimentally in a wide range of incident wave intensities using two chosen methods differing in the way the location of the target is controlled.

Radiative Forcing by Contrails

NASA Technical Reports Server (NTRS)

Meerkoetter, R.; Schumann, U.; Doelling, D. R.; Nakajima, T.; Tsushima, Y.

1999-01-01

A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmospheres The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 W/m(exp 2)a daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.

Recent technological advancements in cardiac ultrasound imaging.

PubMed

Dave, Jaydev K; Mc Donald, Maureen E; Mehrotra, Praveen; Kohut, Andrew R; Eisenbrey, John R; Forsberg, Flemming

2018-03-01

About 92.1 million Americans suffer from at least one type of cardiovascular disease. Worldwide, cardiovascular diseases are the number one cause of death (about 31% of all global deaths). Recent technological advancements in cardiac ultrasound imaging are expected to aid in the clinical diagnosis of many cardiovascular diseases. This article provides an overview of such recent technological advancements, specifically focusing on tissue Doppler imaging, strain imaging, contrast echocardiography, 3D echocardiography, point-of-care echocardiography, 3D volumetric flow assessments, and elastography. With these advancements ultrasound imaging is rapidly changing the domain of cardiac imaging. The advantages offered by ultrasound imaging include real-time imaging, imaging at patient bed-side, cost-effectiveness and ionizing-radiation-free imaging. Along with these advantages, the steps taken towards standardization of ultrasound based quantitative markers, reviewed here, will play a major role in addressing the healthcare burden associated with cardiovascular diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

MR elastography of the liver at 3.0 T in diagnosing liver fibrosis grades; preliminary clinical experience.

PubMed

Yoshimitsu, Kengo; Mitsufuji, Toshimichi; Shinagawa, Yoshinobu; Fujimitsu, Ritsuko; Morita, Ayako; Urakawa, Hiroshi; Hayashi, Hiroyuki; Takano, Koichi

2016-03-01

To clarify the usefulness of 3.0-T MR elastography (MRE) in diagnosing the histological grades of liver fibrosis using preliminary clinical data. Between November 2012 and March 2014, MRE was applied to all patients who underwent liver MR study at a 3.0-T clinical unit. Among them, those who had pathological evaluation of liver tissue within 3 months from MR examinations were retrospectively recruited, and the liver stiffness measured by MRE was correlated with histological results. Institutional review board approved this study, waiving informed consent. There were 70 patients who met the inclusion criteria. Liver stiffness showed significant correlation with the pathological grades of liver fibrosis (rho = 0.89, p < 0.0001, Spearman's rank correlation). Areas under the receiver operating characteristic curve were 0.93, 0.95, 0.99 and 0.95 for fibrosis score greater than or equal to F1, F2, F3 and F4, with cut-off values of 3.13, 3.85, 4.28 and 5.38 kPa, respectively. Multivariate analysis suggested that grades of necroinflammation also affected liver stiffness, but to a significantly lesser degree as compared to fibrosis. 3.0-T clinical MRE was suggested to be sufficiently useful in assessing the grades of liver fibrosis. MR elastography may help clinicians assess patients with chronic liver diseases. Usefulness of 3.0-T MR elastography has rarely been reported. Measured liver stiffness correlated well with the histological grades of liver fibrosis. Measured liver stiffness was also affected by necroinflammation, but to a lesser degree. 3.0-T MRE could be a non-invasive alternative to liver biopsy.

Placental elastography in a murine intrauterine growth restriction model.

PubMed

Quibel, T; Deloison, B; Chammings, F; Chalouhi, G E; Siauve, N; Alison, M; Bessières, B; Gennisson, J L; Clément, O; Salomon, L J

2015-11-01

To compare placental elasticity in normal versus intrauterine growth restriction (IUGR) murine pregnancies using shear wave elastography (SWE). Intrauterine growth restriction was created by ligation of the left uterine artery of Sprague-Dawley rats on E17. Ultrasonography (US) and elastography were performed 2 days later on exteriorized horns after laparotomy. Biparietal diameter (BPD) and abdominal diameter (AD) were measured and compared in each horn. Placental elasticity of each placenta was compared in the right and left horns, respectively, using the Young's modulus, which increases with increasing stiffness of the tissue. Two hundred seventeen feto-placental units from 18 rats were included. Fetuses in the left ligated horn had smaller biometric measurements than those in the right horn (6.7 vs 7.2 mm, p < 0.001, and 9.2 vs 11.2 mm, p < 0.001 for BPD and AD, respectively). Mean fetal weight was lower in the pups from the left than the right horn (1.65 vs 2.11 g; p < 0.001). Mean (SD) Young's modulus was higher for placentas from the left than the right horn (11.7 ± 1.5 kPa vs 8.01 ± 3.8 kPa, respectively; p < 0.001), indicating increased stiffness in placentas from the left than the right horn. There was an inverse relationship between fetal weight and placental elasticity (r = 0.42; p < 0.001). Shear wave elastography may be used to provide quantitative elasticity measurements of the placenta. In our model, placentas from IUGR fetuses demonstrated greater stiffness, which correlated with the degree of fetal growth restriction. © 2015 John Wiley & Sons, Ltd.

Multiresolution MR elastography using nonlinear inversion

PubMed Central

McGarry, M. D. J.; Van Houten, E. E. W.; Johnson, C. L.; Georgiadis, J. G.; Sutton, B. P.; Weaver, J. B.; Paulsen, K. D.

2012-01-01

Purpose: Nonlinear inversion (NLI) in MR elastography requires discretization of the displacement field for a finite element (FE) solution of the “forward problem”, and discretization of the unknown mechanical property field for the iterative solution of the “inverse problem”. The resolution requirements for these two discretizations are different: the forward problem requires sufficient resolution of the displacement FE mesh to ensure convergence, whereas lowering the mechanical property resolution in the inverse problem stabilizes the mechanical property estimates in the presence of measurement noise. Previous NLI implementations use the same FE mesh to support the displacement and property fields, requiring a trade-off between the competing resolution requirements. Methods: This work implements and evaluates multiresolution FE meshes for NLI elastography, allowing independent discretizations of the displacements and each mechanical property parameter to be estimated. The displacement resolution can then be selected to ensure mesh convergence, and the resolution of the property meshes can be independently manipulated to control the stability of the inversion. Results: Phantom experiments indicate that eight nodes per wavelength (NPW) are sufficient for accurate mechanical property recovery, whereas mechanical property estimation from 50 Hz in vivo brain data stabilizes once the displacement resolution reaches 1.7 mm (approximately 19 NPW). Viscoelastic mechanical property estimates of in vivo brain tissue show that subsampling the loss modulus while holding the storage modulus resolution constant does not substantially alter the storage modulus images. Controlling the ratio of the number of measurements to unknown mechanical properties by subsampling the mechanical property distributions (relative to the data resolution) improves the repeatability of the property estimates, at a cost of modestly decreased spatial resolution. Conclusions: Multiresolution NLI elastography provides a more flexible framework for mechanical property estimation compared to previous single mesh implementations. PMID:23039674

Passive optical coherence elastography using a time-reversal approach (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Zorgani, Ali; Fink, Mathias; Catheline, Stefan; Boccara, A. Claude

2017-02-01

Background and motivation - Conventional Optical Coherence Elastography (OCE) methods consist in launching controlled shear waves in tissues, and measuring their propagation speed using an ultrafast imaging system. However, the use of external shear sources limits transfer to clinical practice, especially for ophthalmic applications. Here, we propose a totally passive OCE method for ocular tissues based on time-reversal of the natural vibrations. Methods - Experiments were first conducted on a tissue-mimicking phantom containing a stiff inclusion. Pulsatile motions were reproduced by stimulating the phantom surface with two piezoelectric actuators excited asynchronously at low frequencies (50-500 Hz). The resulting random displacements were tracked at 190 frames/sec using spectral-domain optical coherence tomography (SD-OCT), with a 10x5µm² resolution over a 3x2mm² field-of-view (lateral x depth). The shear wavefield was numerically refocused (i.e. time-reversed) at each pixel using noise-correlation algorithms. The focal spot size yields the shear wavelength. Results were validated by comparison with shear wave speed measurements obtained from conventional active OCE. In vivo tests were then conducted on anesthetized rats. Results - The stiff inclusion of the phantom was delineated on the wavelength map with a wavelength ratio between the inclusion and the background (1.6) consistent with the speed ratio (1.7). This validates the wavelength measurements. In vivo, natural shear waves were detected in the eye and wavelength maps of the anterior segment showed a clear elastic contrast between the cornea, the sclera and the iris. Conclusion - We validated the time-reversal approach for passive elastography using SD-OCT imaging at low frame-rate. This method could accelerate the clinical transfer of ocular elastography.

Thyroid nodule classification using ultrasound elastography via linear discriminant analysis.

PubMed

Luo, Si; Kim, Eung-Hun; Dighe, Manjiri; Kim, Yongmin

2011-05-01

The non-surgical diagnosis of thyroid nodules is currently made via a fine needle aspiration (FNA) biopsy. It is estimated that somewhere between 250,000 and 300,000 thyroid FNA biopsies are performed in the United States annually. However, a large percentage (approximately 70%) of these biopsies turn out to be benign. Since the aggressive FNA management of thyroid nodules is costly, quantitative risk assessment and stratification of a nodule's malignancy is of value in triage and more appropriate healthcare resources utilization. In this paper, we introduce a new method for classifying the thyroid nodules based on the ultrasound (US) elastography features. Unlike approaches to assess the stiffness of a thyroid nodule by visually inspecting the pseudo-color pattern in the strain image, we use a classification algorithm to stratify the nodule by using the power spectrum of strain rate waveform extracted from the US elastography image sequence. Pulsation from the carotid artery was used to compress the thyroid nodules. Ultrasound data previously acquired from 98 thyroid nodules were used in this retrospective study to evaluate our classification algorithm. A classifier was developed based on the linear discriminant analysis (LDA) and used to differentiate the thyroid nodules into two types: (I) no FNA (observation-only) and (II) FNA. Using our method, 62 nodules were classified as type I, all of which were benign, while 36 nodules were classified as Type-II, 16 malignant and 20 benign, resulting in a sensitivity of 100% and specificity of 75.6% in detecting malignant thyroid nodules. This indicates that our triage method based on US elastography has the potential to substantially reduce the number of FNA biopsies (63.3%) by detecting benign nodules and managing them via follow-up observations rather than an FNA biopsy. Published by Elsevier B.V.

Assessment of the accuracy of an ultrasound elastography liver scanning system using a PVA-cryogel phantom with optimal acoustic and mechanical properties

NASA Astrophysics Data System (ADS)

Cournane, S.; Cannon, L.; Browne, J. E.; Fagan, A. J.

2010-10-01

The accuracy of a transient elastography liver-scanning ultrasound system was assessed using a novel application of PVA-cryogel as a tissue-mimicking material with acoustic and shear elasticity properties optimized to best represent those of liver tissue. Although the liver-scanning system has been shown to offer a safer alternative for diagnosing liver cirrhosis through stiffness measurement, as compared to the liver needle biopsy exam, the scanner's accuracy has not been fully established. Young's elastic modulus values of 5-6 wt% PVA-cryogel phantoms, also containing glycerol and 0.3 µm Al2O3 and 3 µm Al2O3, were measured using a 'gold standard' mechanical testing technique and transient elastography. The mechanically measured values and acoustic velocities of the phantoms ranged between 1.6 and 16.1 kPa and 1540 and 1570 m s-1, respectively, mimicking those observed in liver tissue. The values reported by the transient elastography system overestimated Young's elastic modulus values representative of the progressive stages of liver fibrosis by up to 32%. These results were attributed to the relative rather than absolute nature of the measurement arising from the single-point acoustic velocity calibration of the system, rendering the measurements critically dependent on the speed of sound of the sample under investigation. Given the wide range of acoustic velocities which exist in the liver, spanning healthy tissue to cirrhotic pathology, coupled with the system's assumption that the liver is approximately elastic when it is rather highly viscoelastic, care should be exercised when interpreting the results from this system in patient groups.

Magnetic resonance elastography of the lung parenchyma in an in situ porcine model with a noninvasive mechanical driver: correlation of shear stiffness with trans-respiratory system pressures.

PubMed

Mariappan, Yogesh K; Kolipaka, Arunark; Manduca, Armando; Hubmayr, Rolf D; Ehman, Richard L; Araoz, Philip; McGee, Kiaran P

2012-01-01

Quantification of the mechanical properties of lung parenchyma is an active field of research due to the association of this metric with normal function, disease initiation and progression. A phase contrast MRI-based elasticity imaging technique known as magnetic resonance elastography is being investigated as a method for measuring the shear stiffness of lung parenchyma. Previous experiments performed with small animals using invasive drivers in direct contact with the lungs have indicated that the quantification of lung shear modulus with (1) H based magnetic resonance elastography is feasible. This technique has been extended to an in situ porcine model with a noninvasive mechanical driver placed on the chest wall. This approach was tested to measure the change in parenchymal stiffness as a function of airway opening pressure (P(ao) ) in 10 adult pigs. In all animals, shear stiffness was successfully quantified at four different P(ao) values. Mean (±STD error of mean) pulmonary parenchyma density corrected stiffness values were calculated to be 1.48 (±0.09), 1.68 (±0.10), 2.05 (±0.13), and 2.23 (±0.17) kPa for P(ao) values of 5, 10, 15, and 20 cm H2O, respectively. Shear stiffness increased with increasing P(ao) , in agreement with the literature. It is concluded that in an in situ porcine lung shear stiffness can be quantitated with (1) H magnetic resonance elastography using a noninvasive mechanical driver and that it is feasible to measure the change in shear stiffness due to change in P(ao) . Copyright © 2011 Wiley-Liss, Inc.

Measurement of real-time tissue elastography in a phantom model and comparison with transient elastography in pediatric patients with liver diseases.

PubMed

Schenk, Jens-Peter; Alzen, Gerhard; Klingmüller, Volker; Teufel, Ulrike; El Sakka, Saroa; Engelmann, Guido; Selmi, Buket

2014-01-01

We aimed to determine the comparability of real-time tissue elastography (RTE) and transient elastography (TE) in pediatric patients with liver diseases. RTE was performed on the Elasticity QA Phantom Model 049 (Computerized Imaging Reference Systems Company Inc., Norfolk, Virginia, USA), which has five areas with different levels of stiffness. RTE measurements of relative stiffness (MEAN [mean value of tissue elasticity], AREA [% of blue color-coded stiffer tissue]) in the phantom were compared with the phantom stiffness specified in kPa (measurement unit of TE). RTE and TE were performed on 147 pediatric patients with various liver diseases. A total of 109 measurements were valid. The participants had following diseases: metabolic liver disease (n=25), cystic fibrosis (n=20), hepatopathy of unknown origin (n=11), autoimmune hepatitis (n=12), Wilson's disease (n=11), and various liver parenchyma alterations (n=30). Correlations between RTE and TE measurements in the patients were calculated. In addition, RTE was performed on a control group (n=30), and the RTE values between the patient and control groups were compared. The RTE parameters showed good correlation in the phantom model with phantom stiffness (MEAN/kPa, r=-0.97; AREA/kPa, r=0.98). However, the correlation of RTE and TE was weak in the patient group (MEAN/kPa, r=-0.23; AREA/kPa, r=0.24). A significant difference was observed between the patient and control groups (MEAN, P = 5.32 e-7; AREA, P = 1.62 e-6). In the phantom model, RTE was correlated with kPa, confirming the presumed comparability of the methods. However, there was no direct correlation between RTE and TE in patients with defined liver diseases under real clinical conditions.

Reference Values for Shear Wave Elastography of Neck and Shoulder Muscles in Healthy Individuals.

PubMed

Ewertsen, Caroline; Carlsen, Jonathan; Perveez, Mohammed Aftab; Schytz, Henrik

2018-01-01

to establish reference values for ultrasound shear-wave elastography for pericranial muscles in healthy individuals (m. trapezius, m. splenius capitis, m. semispinalis capitis, m. sternocleidomastoideus and m. masseter). Also to evaluate day-to-day variations in the shear-wave speeds and evaluate the effect of the pennation of the muscle fibers, ie scanning parallel or perpendicularly to the fibers. 10 healthy individuals (5 males and 5 females) had their pericranial muscles examined with shear-wave elastography in two orthogonal planes on two different days for their dominant and non-dominant side. Mean shear wave speeds from 5 ROI's in each muscle, for each scan plane for the dominant and non-dominant side for the two days were calculated. The effect of the different parameters - muscle pennation, gender, dominant vs non-dominant side and day was evaluated. The effect of scan plane in relation to muscle pennation was statistically significant (p<0.0001). The mean shear-wave speed when scanning parallel to the muscle fibers was significantly higher than the mean shear-wave speed when scanning perpendicularly to the fibers. The day-to-day variation was statistically significant (p=0.0258), but not clinically relevant. Shear-wave speeds differed significantly between muscles. Mean shear wave speeds (m/s) for the muscles in the parallel plane were: for masseter 2.45 (SD:+/-0.25), semispinal 3.36 (SD:+/-0.75), splenius 3.04 (SD:+/-0.65), sternocleidomastoid 2.75 (SD:+/-0.23), trapezius 3.20 (SD:+/-0.27) and trapezius lateral 3.87 (SD:+/-3.87). The shear wave speed variation depended on the direction of scanning. Shear wave elastography may be a method to evaluate muscle stiffness in patients suffering from chronic neck pain.

Real-time shear wave elastography may predict autoimmune thyroid disease.

PubMed

Vlad, Mihaela; Golu, Ioana; Bota, Simona; Vlad, Adrian; Timar, Bogdan; Timar, Romulus; Sporea, Ioan

2015-05-01

To evaluate and compare the values of the elasticity index as measured by shear wave elastography in healthy subjects and in patients with autoimmune thyroid disease, in order to establish if this investigation can predict the occurrence of autoimmune thyroid disease. A total of 104 cases were included in the study group: 91 women (87.5%), out of which 52 (50%) with autoimmune thyroid disease diagnosed by specific tests and 52 (50%) healthy volunteers, matched for age and gender. For all the subjects, three measurements were performed on each thyroid lobe and a mean value was calculated. The data were expressed in kPa. The investigation was performed with an Aixplorer system (SuperSonic Imagine, France), using a linear high-resolution 15-4 MHz transducer. The mean value for the elasticity index was similar in the right and the left thyroid lobes, both in normal subjects and in patients with autoimmune thyroid disease: 19.6 ± 6.6 vs. 19.5 ± 6.8 kPa, p = 0.92, and 26.6 ± 10.0 vs. 25.8 ± 11.7 kPa, p = 0.71, respectively. This parameter was significantly higher in patients with autoimmune thyroid disease than in controls (p < 0.001). For a cut-off value of 22.3 kPa, which resulted in the highest sum of sensitivity and specificity, the elasticity index assessed by shear wave elastography had a sensitivity of 59.6% and a specificity of 76.9% (AUROC = 0.71; p < 0.001) for predicting the presence of autoimmune thyroid disease. Quantitative elasticity index measured by shear wave elastography was significantly higher in autoimmune thyroid disease than in normal thyroid parenchyma and may predict the presence of autoimmune thyroid disease.

Assessment of biopsy‐proven liver fibrosis by two‐dimensional shear wave elastography: An individual patient data‐based meta‐analysis

PubMed Central

de Lédinghen, Victor; Cassinotto, Christophe; Chu, Winnie C.‐W.; Leung, Vivian Y.‐F.; Ferraioli, Giovanna; Filice, Carlo; Castera, Laurent; Vilgrain, Valérie; Ronot, Maxime; Dumortier, Jérôme; Guibal, Aymeric; Pol, Stanislas; Trebicka, Jonel; Jansen, Christian; Strassburg, Christian; Zheng, Rongqin; Zheng, Jian; Francque, Sven; Vanwolleghem, Thomas; Vonghia, Luisa; Manesis, Emanuel K.; Zoumpoulis, Pavlos; Sporea, Ioan; Thiele, Maja; Krag, Aleksander; Cohen‐Bacrie, Claude; Criton, Aline; Gay, Joel; Deffieux, Thomas; Friedrich‐Rust, Mireen

2017-01-01

Two‐dimensional shear wave elastography (2D‐SWE) has proven to be efficient for the evaluation of liver fibrosis in small to moderate‐sized clinical trials. We aimed at running a larger‐scale meta‐analysis of individual data. Centers which have worked with Aixplorer ultrasound equipment were contacted to share their data. Retrospective statistical analysis used direct and paired receiver operating characteristic and area under the receiver operating characteristic curve (AUROC) analyses, accounting for random effects. Data on both 2D‐SWE and liver biopsy were available for 1,134 patients from 13 sites, as well as on successful transient elastography in 665 patients. Most patients had chronic hepatitis C (n = 379), hepatitis B (n = 400), or nonalcoholic fatty liver disease (n = 156). AUROCs of 2D‐SWE in patients with hepatitis C, hepatitis B, and nonalcoholic fatty liver disease were 86.3%, 90.6%, and 85.5% for diagnosing significant fibrosis and 92.9%, 95.5%, and 91.7% for diagnosing cirrhosis, respectively. The AUROC of 2D‐SWE was 0.022‐0.084 (95% confidence interval) larger than the AUROC of transient elastography for diagnosing significant fibrosis (P = 0.001) and 0.003‐0.034 for diagnosing cirrhosis (P = 0.022) in all patients. This difference was strongest in hepatitis B patients. Conclusion: 2D‐SWE has good to excellent performance for the noninvasive staging of liver fibrosis in patients with hepatitis B; further prospective studies are needed for head‐to‐head comparison between 2D‐SWE and other imaging modalities to establish disease‐specific appropriate cutoff points for assessment of fibrosis stage. (Hepatology 2018;67:260‐272). PMID:28370257

Revisiting the Cramér Rao Lower Bound for Elastography: Predicting the Performance of Axial, Lateral and Polar Strain Elastograms.

PubMed

Verma, Prashant; Doyley, Marvin M

2017-09-01

We derived the Cramér Rao lower bound for 2-D estimators employed in quasi-static elastography. To illustrate the theory, we modeled the 2-D point spread function as a sinc-modulated sine pulse in the axial direction and as a sinc function in the lateral direction. We compared theoretical predictions of the variance incurred in displacements and strains when quasi-static elastography was performed under varying conditions (different scanning methods, different configuration of conventional linear array imaging and different-size kernels) with those measured from simulated or experimentally acquired data. We performed studies to illustrate the application of the derived expressions when performing vascular elastography with plane wave and compounded plane wave imaging. Standard deviations in lateral displacements were an order higher than those in axial. Additionally, the derived expressions predicted that peak performance should occur when 2% strain is applied, the same order of magnitude as observed in simulations (1%) and experiments (1%-2%). We assessed how different configurations of conventional linear array imaging (number of active reception and transmission elements) influenced the quality of axial and lateral strain elastograms. The theoretical expressions predicted that 2-D echo tracking should be performed with wide kernels, but the length of the kernels should be selected using knowledge of the magnitude of the applied strain: specifically, longer kernels for small strains (<5%) and shorter kernels for larger strains. Although the general trends of theoretical predictions and experimental observations were similar, biases incurred during beamforming and subsample displacement estimation produced noticeable differences. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Combination of two-dimensional shear wave elastography with ultrasound breast imaging reporting and data system in the diagnosis of breast lesions: a new method to increase the diagnostic performance.

PubMed

Li, Dan-Dan; Xu, Hui-Xiong; Guo, Le-Hang; Bo, Xiao-Wan; Li, Xiao-Long; Wu, Rong; Xu, Jun-Mei; Zhang, Yi-Feng; Zhang, Kun

2016-09-01

To evaluate the diagnostic performance of a new method of combined two-dimensional shear wave elastography (i.e. virtual touch imaging quantification, VTIQ) and ultrasound (US) Breast Imaging Reporting and Data System (BI-RADS) in the differential diagnosis of breast lesions. From September 2014 to December 2014, 276 patients with 296 pathologically proven breast lesions were enrolled in this study. The conventional US images were interpreted by two independent readers. The diagnosis performances of BI-RADS and combined BI-RADS and VTIQ were evaluated, including the area under the receiver operating characteristic curve (AUROC), sensitivity and specificity. Observer consistency was also evaluated. Pathologically, 212 breast lesions were benign and 84 were malignant. Compared with BI-RADS alone, the AUROCs and specificities of the combined method for both readers increased significantly (AUROC: 0.862 vs. 0.693 in reader 1, 0.861 vs. 0.730 in reader 2; specificity: 91.5 % vs. 38.7 % in reader 1, 94.8 % vs. 47.2 % in reader 2; all P < .05). The Kappa value between the two readers for BI-RADS assessment was 0.614, and 0.796 for the combined method. The combined VTIQ and BI-RADS had a better diagnostic performance in the diagnosis of breast lesions in comparison with BI-RADS alone. • Combination of conventional ultrasound and elastography distinguishes breast cancers more effectively. • Combination of conventional ultrasound and elastography increases observer consistency. • BI-RADS weights more than the 2D-SWE with an increase in malignancy probability.

Diagnostic value of commercially available shear-wave elastography for breast cancers: integration into BI-RADS classification with subcategories of category 4.

PubMed

Youk, Ji Hyun; Gweon, Hye Mi; Son, Eun Ju; Han, Kyung Hwa; Kim, Jeong-Ah

2013-10-01

To evaluate the diagnostic performance of shear-wave elastography (SWE) for breast cancer and to determine whether the integration of SWE into BI-RADS with subcategories of category 4 improves the diagnostic performance. A total of 389 breast masses (malignant 120, benign 269) in 324 women who underwent SWE before ultrasound-guided core biopsy or surgery were included. The qualitative SWE feature was assessed using a four-colour overlay pattern. Quantitative elasticity values including the lesion-to-fat elasticity ratio (Eratio) were measured. Diagnostic performance of B-mode ultrasound, SWE, or their combined studies was compared using the area under the ROC curve (AUC). AUC of Eratio (0.952) was the highest among elasticity values (mean, maximum, and minimum elasticity, 0.949, 0.939, and 0.928; P = 0.04) and AUC of colour pattern was 0.947. AUC of combined studies was significantly higher than for a single study (P < 0.0001). When adding SWE to category 4 lesions, lesions were dichotomised according to % of malignancy: 2.1 % vs. 43.2 % (category 4a) and 0 % vs. 100 % (category 4b) for Eratio and 2.4 % vs. 25.8 % (category 4a) for colour pattern (P < 0.05). Shear-wave elastography showed a good diagnostic performance. Adding SWE features to BI-RADS improved the diagnostic performance and may be helpful to stratify category 4 lesions. • Quantitative and qualitative shear-wave elastography provides further diagnostic information during breast ultrasound. • The elasticity ratio (E ratio ) showed the best diagnostic performance in SWE. • E ratio and four-colour overlay pattern significantly differed between benign and malignant lesions. • SWE features allowed further stratification of BI-RADS category 4 lesions.

Real time elastography - a non-invasive diagnostic method of small hepatocellular carcinoma in cirrhosis.

PubMed

Gheorghe, Liana; Iacob, Speranta; Iacob, Razvan; Dumbrava, Mona; Becheanu, Gabriel; Herlea, Vlad; Gheorghe, Cristian; Lupescu, Ioana; Popescu, Irinel

2009-12-01

Small nodules (under 3 cm) detected on ultrasound (US) in cirrhotics represent the most challenging category for noninvasive diagnosis of hepatocellular carcinoma (HCC). To evaluate real-time sonoelastography as a noninvasive tool for the diagnosis of small HCC nodules in cirrhotic patients. 42 cirrhotic patients with 58 nodules (1-3 cm) were evaluated with real-time elastography (Hitachi EUB-6500); the mean intensity of colors red, blue, green were measured using a semi-quantitative method. Analysis of histograms for each color of the sonoelastography images was performed for quantifying the elasticity of nodule tissue in comparison with the cirrhotic liver tissue. AUROC curves were constructed to define the best cut-off points to distinguish malignant features of the nodules. Univariate and multivariate logistic regression analysis was performed. 595 sonoelastography images from 42 patients (25 men; 17 women) were analyzed. The mean age was 56.4 +/- 0.7 years and 69% patients were in Child-Pugh class A, 19% class B, 11% class C. For the mean intensity of green color AUROC=0.81, a cut-off value under 108.7 being diagnostic for HCC with a Sp=91.1%, Se=50%, PPV=92.1%, NPV=47.1%. Mean intensity of blue color proved to be an excellent diagnostic tool for HCC (AUROC=0.94); for a cut-off value greater than 128.9, Sp=92.2%, Se=78.9%, PPV=95.4%, NPV=68%. Independent predictive factors of HCC for a small nodule in cirrhotic patients were: blue color over 128.9 at sonoelastography and hypervascular appearance at Doppler US. US elastography is a promising method for the non-invasive diagnosis of early HCC. Blue color at elastography and hypervascular aspects are independent predictors of HCC.

Regional Attribution of Ozone Production and Associated Radiative Forcing: a Step to Crediting NOx Emission Reductions

NASA Astrophysics Data System (ADS)

Naik, V.; Mauzerall, D. L.; Horowitz, L.; Schwarzkopf, D.; Ramaswamy, V.; Oppenheimer, M.

2004-12-01

The global distribution of tropospheric ozone (O3) depends on the location of emissions of its precursors in addition to chemical and dynamical factors. The global picture of O3 forcing is, therefore, a sum of regional forcings arising from emissions of precursors from different sources. The Kyoto Protocol does not include ozone as a greenhouse gas, and emission reductions of ozone precursors made under Kyoto or any similar agreement would presently receive no credit. In this study, we quantitatively estimate the contribution of emissions of nitrogen oxides (NOx), the primary limiting O3 precursor in the non-urban atmosphere, from specific countries and regions of the world to global O3 concentration distributions. We then estimate radiative forcing resulting from the regional perturbations of NOx emissions. This analysis is intended as an early step towards incorporating O3 into the Kyoto Protocol or any successor agreement. Under such a system countries could obtain credit for improvements in local air quality that result in reductions of O3 concentrations because of the associated reductions in radiative forcing. We use the global chemistry transport model, MOZART-2, to simulate the global O3 distribution for base year 1990 and perturbations to this distribution caused by a 10% percent reduction in the base emissions of NOx from the United States, Europe, East Asia, India, South America, and Africa. We calculate the radiative forcing for the simulated base and perturbed O3 distributions using the GFDL radiative transfer model. The difference between the radiative forcing from O3 for the base and perturbed distributions provides an estimate of the marginal radiative forcing from a region's emissions of NOx. We will present a quantitative analysis of the magnitude, spatial, and temporal distribution of radiative forcing resulting from marginal changes in the NOx emissions from each region.

A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51)

NASA Astrophysics Data System (ADS)

Dietmüller, Simone; Jöckel, Patrick; Tost, Holger; Kunze, Markus; Gellhorn, Catrin; Brinkop, Sabine; Frömming, Christine; Ponater, Michael; Steil, Benedikt; Lauer, Axel; Hendricks, Johannes

2016-06-01

The Modular Earth Submodel System (MESSy) provides an interface to couple submodels to a base model via a highly flexible data management facility (Jöckel et al., 2010). In the present paper we present the four new radiation related submodels RAD, AEROPT, CLOUDOPT, and ORBIT. The submodel RAD (including the shortwave radiation scheme RAD_FUBRAD) simulates the radiative transfer, the submodel AEROPT calculates the aerosol optical properties, the submodel CLOUDOPT calculates the cloud optical properties, and the submodel ORBIT is responsible for Earth orbit calculations. These submodels are coupled via the standard MESSy infrastructure and are largely based on the original radiation scheme of the general circulation model ECHAM5, however, expanded with additional features. These features comprise, among others, user-friendly and flexibly controllable (by namelists) online radiative forcing calculations by multiple diagnostic calls of the radiation routines. With this, it is now possible to calculate radiative forcing (instantaneous as well as stratosphere adjusted) of various greenhouse gases simultaneously in only one simulation, as well as the radiative forcing of cloud perturbations. Examples of online radiative forcing calculations in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model are presented.

Subresolution Displacements in Finite Difference Simulations of Ultrasound Propagation and Imaging.

PubMed

Pinton, Gianmarco F

2017-03-01

Time domain finite difference simulations are used extensively to simulate wave propagation. They approximate the wave field on a discrete domain with a grid spacing that is typically on the order of a tenth of a wavelength. The smallest displacements that can be modeled by this type of simulation are thus limited to discrete values that are integer multiples of the grid spacing. This paper presents a method to represent continuous and subresolution displacements by varying the impedance of individual elements in a multielement scatterer. It is demonstrated that this method removes the limitations imposed by the discrete grid spacing by generating a continuum of displacements as measured by the backscattered signal. The method is first validated on an ideal perfect correlation case with a single scatterer. It is subsequently applied to a more complex case with a field of scatterers that model an acoustic radiation force-induced displacement used in ultrasound elasticity imaging. A custom finite difference simulation tool is used to simulate propagation from ultrasound imaging pulses in the scatterer field. These simulated transmit-receive events are then beamformed into images, which are tracked with a correlation-based algorithm to determine the displacement. A linear predictive model is developed to analytically describe the relationship between element impedance and backscattered phase shift. The error between model and simulation is λ/ 1364 , where λ is the acoustical wavelength. An iterative method is also presented that reduces the simulation error to λ/ 5556 over one iteration. The proposed technique therefore offers a computationally efficient method to model continuous subresolution displacements of a scattering medium in ultrasound imaging. This method has applications that include ultrasound elastography, blood flow, and motion tracking. This method also extends generally to finite difference simulations of wave propagation, such as electromagnetic or seismic waves.

Micromechanical Resonator Driven by Radiation Pressure Force.

PubMed

Boales, Joseph A; Mateen, Farrukh; Mohanty, Pritiraj

2017-11-22

Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects. In this Letter, we demonstrate direct actuation of a radio-frequency micromechanical plate-type resonator by the radiation pressure force generated by a standard laser diode at room temperature. Using two independent methods, the magnitude of the resonator's response to forcing by radiation pressure is found to be proportional to the intensity of the incident light.

Case Studies of the Vertical Structure of the Direct Shortwave Aerosol Radiative Forcing During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Hobbs, P. V.; Hartley, W. S.; Bergstrom, R. W.; Browell, E. V.; Russell, P. B.

2000-01-01

The vertical structure of aerosol-induced radiative flux changes in the Earth's troposphere affects local heating rates and thereby convective processes, the formation and lifetime of clouds, and hence the distribution of chemical constituents. We present observationally based estimates of the vertical structure of direct shortwave aerosol radiative forcing for two case studies from the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) which took place on the U.S. east coast in July 1996. The aerosol radiative forcings are computed using the Fu-Liou broadband radiative transfer model. The aerosol optical properties used in the radiative transfer simulations are calculated from independent vertically resolved estimates of the complex aerosol indices of refraction in two to three distinct vertical layers, using profiles of in situ particle size distributions measured aboard the University of Washington research aircraft. Aerosol single-scattering albedos at 450 nm thus determined range from 0.9 to 0.985, while the asymmetry factor varies from 0.6 to 0.8. The instantaneous shortwave aerosol radiative forcings derived from the optical properties of the aerosols are of the order of -36 Wm(exp -2) at the top of the atmosphere and about -56 Wm(exp -2) at the surface for both case studies.

Radiative Energy Loss by Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Ahern, Sean C.; Norbury, John W.; Tripathi, R. K.

2002-01-01

Interactions between galactic cosmic rays and matter are a primary focus of the NASA radiation problem. The electromagnetic forces involved are for the most part well documented. Building on previous research, this study investigated the relative importance of the weak forces that occur when a cosmic ray impinges on different types of materials. For the familiar electromagnetic case, it is known that energy lost in the form of radiation is more significant than that lost via contact collisions the rate at which the energy is lost is also well understood. Similar results were derived for the weak force case. It was found that radiation is also the dominant mode of energy loss in weak force interactions and that weak force effects are indeed relatively weak compared to electromagnetic effects.

Experimental measurement of interparticle acoustic radiation force in the Rayleigh limit

NASA Astrophysics Data System (ADS)

Mohapatra, Abhishek Ray; Sepehrirahnama, Shahrokh; Lim, Kian-Meng

2018-05-01

Acoustophoresis is a form of contact-free particle manipulation in microfluidic devices. The precision of manipulation can be enhanced with better understanding of the acoustic radiation force. In this paper we present the measurements of interparticle radiation force between a pair of polystyrene beads in the Rayleigh limit. The study is conducted for three different sizes of beads and the experimental results are of the same order of magnitude when compared with theoretical predictions. However, the experimental values are larger than the theoretical values. The trend of a decrease in the magnitude of the interparticle radiation force with decreasing particle size and increasing center-to-center distance between the particles is also observed experimentally. The experiments are conducted in the specific scenario where the pair of beads are in close proximity, but not in contact with each other, and the beads are approaching the pressure nodal plane with the center-to-center line aligned perpendicular to the incident wave. This scenario minimizes the presence of the primary radiation force, allowing accurate measurement of the interparticle force. The attractive nature of the interparticle force is observed, consistent with theoretical predictions.

Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties

NASA Technical Reports Server (NTRS)

Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua

1999-01-01

Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol optical thickness at the wavelength of 865-nm is taken from the SeaWIFS archive. It is found that the nominal optical thickness over oceans ranges from 0.1 to 0.2. Using a maritime aerosol model and the radiances measured at the various SeaWiFS channels, the Angstrom exponent is determined to be 0.2174, the single-scattering albedo to be 0.995, and the asymmetry factor to be 0.786. The radiative transfer model has eight bands in the visible and ultraviolet spectral regions and three bands in the near infrared. It includes the absorption due to aerosols, water vapor, carbon dioxide, and oxygen, and the scattering due to aerosols and gases (Rayleigh scattering). The radiative forcing is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol radiative forcing is large and changes significantly with seasons near the continents with large-scale forest fires and desert dust. Averaged over oceans and the four months, the aerosol radiative forcing is approximately 7 W/sq m at the top of the atmosphere. This large radiative forcing is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.

Viscoelastic Property Measurement in Thin Tissue Constructs Using Ultrasound

PubMed Central

Liu, Dalong; Ebbini, Emad S.

2010-01-01

We present a dual-element concave ultrasound transducer system for generating and tracking of localized tissue displacements in thin tissue constructs on rigid substrates. The system is comprised of a highly focused PZT-4 5-MHz acoustic radiation force (ARF) transducer and a confocal 25-MHz polyvinylidene fluoride imaging transducer. This allows for the generation of measurable displacements in tissue samples on rigid substrates with thickness values down to 500 µm. Impulse-like and longer duration sine-modulated ARF pulses are possible with intermittent M-mode data acquisition for displacement tracking. The operations of the ARF and imaging transducers are strictly synchronized using an integrated system for arbitrary waveform generation and data capture with a shared timebase. This allows for virtually jitter-free pulse-echo data well suited for correlation-based speckle tracking. With this technique we could faithfully capture the entire dynamics of the tissue axial deformation at pulse-repetition frequency values up to 10 kHz. Spatio-temporal maps of tissue displacements in response to a variety of modulated ARF beams were produced in tissue-mimicking elastography phantoms on rigid substrates. The frequency response was measured for phantoms with different modulus and thickness values. The frequency response exhibited resonant behavior with the resonance frequency being inversely proportional to the sample thickness. This resonant behavior can be used in obtaining high-contrast imaging using magnitude and phase response to sinusoidally modulated ARF beams. Furthermore, a second order forced harmonic oscillator (FHO) model was shown to capture this resonant behavior. Based on the FHO model, we used the extended Kalman filter (EKF) for tracking the apparent modulus and viscosity of samples subjected to dc and sinusoidally modulated ARF. The results show that the stiffness (apparent modulus) term in the FHO is largely time-invariant and can be estimated robustly using the EKF. On the other hand, the damping (apparent viscosity) is time varying. These findings were confirmed by comparing the magnitude response of the FHO (with parameters obtained using the EKF) with the measured ones for different thin tissue constructs. PMID:18334343

Host Model Uncertainty in Aerosol Radiative Forcing Estimates - The AeroCom Prescribed Experiment

NASA Astrophysics Data System (ADS)

Stier, P.; Kinne, S.; Bellouin, N.; Myhre, G.; Takemura, T.; Yu, H.; Randles, C.; Chung, C. E.

2012-04-01

Anthropogenic and natural aerosol radiative effects are recognized to affect global and regional climate. However, even for the case of identical aerosol emissions, the simulated direct aerosol radiative forcings show significant diversity among the AeroCom models (Schulz et al., 2006). Our analysis of aerosol absorption in the AeroCom models indicates a larger diversity in the translation from given aerosol radiative properties (absorption optical depth) to actual atmospheric absorption than in the translation of a given atmospheric burden of black carbon to the radiative properties (absorption optical depth). The large diversity is caused by differences in the simulated cloud fields, radiative transfer, the relative vertical distribution of aerosols and clouds, and the effective surface albedo. This indicates that differences in host model (GCM or CTM hosting the aerosol module) parameterizations contribute significantly to the simulated diversity of aerosol radiative forcing. The magnitude of these host model effects in global aerosol model and satellites retrieved aerosol radiative forcing estimates cannot be estimated from the diagnostics of the "standard" AeroCom forcing experiments. To quantify the contribution of differences in the host models to the simulated aerosol radiative forcing and absorption we conduct the AeroCom Prescribed experiment, a simple aerosol model and satellite retrieval intercomparison with prescribed highly idealised aerosol fields. Quality checks, such as diagnostic output of the 3D aerosol fields as implemented in each model, ensure the comparability of the aerosol implementation in the participating models. The simulated forcing variability among the models and retrievals is a direct measure of the contribution of host model assumptions to the uncertainty in the assessment of the aerosol radiative effects. We will present the results from the AeroCom prescribed experiment with focus on the attribution to the simulated variability to parametric and structural model uncertainties. This work will help to prioritise areas for future model improvements and ultimately lead to uncertainty reduction.

Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

EPA Science Inventory

Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary...

Radiative flux and forcing parameterization error in aerosol-free clear skies.

PubMed

Pincus, Robert; Mlawer, Eli J; Oreopoulos, Lazaros; Ackerman, Andrew S; Baek, Sunghye; Brath, Manfred; Buehler, Stefan A; Cady-Pereira, Karen E; Cole, Jason N S; Dufresne, Jean-Louis; Kelley, Maxwell; Li, Jiangnan; Manners, James; Paynter, David J; Roehrig, Romain; Sekiguchi, Miho; Schwarzkopf, Daniel M

2015-07-16

Radiation parameterizations in GCMs are more accurate than their predecessorsErrors in estimates of 4 ×CO 2 forcing are large, especially for solar radiationErrors depend on atmospheric state, so global mean error is unknown.

Radiative forcing perturbation due to observed increases in tropospheric ozone at Hohenpeissenberg

NASA Technical Reports Server (NTRS)

Wang, Wei-Chyung; Bojkov, Rumen D.; Zhuang, Yi-Cheng

1994-01-01

The effect on surface temperature due to changes in atmospheric O3 depends highly on the latitude where the change occurs. Previous sensitivity calculations indicate that ozone changes in the upper troposphere and lower stratosphere are more effective in causing surface temperature change (Wang et al., 1980). Long term ground-based observations show that tropospheric ozone, especially at the tropopause region, has been increasing at middle and high latitudes in the Northern Hemisphere (NATO, 1988; Quadrennial Ozone Symposium, 1992). These increases will enhance the greenhouse effect and increase the radiative forcing to the troposphere-surface system, which is opposite to the negative radiative forcing calculated from the observed stratospheric ozone depletion recently reported in WMO (1992). We used more than two thousands regularly measured ozonesondes providing reliable vertical O3 distribution at Hohenpeissenberg (47N; 11E) for the 1967-1990 to study the instantaneous solar and longwave radiative forcing the two decades 1971-1990 and compare the forcing with those caused by increasing CO2, CH4, N2O, and CFCs. Calculations are also made to compare the O3 radiative forcing between stratospheric depletion and tropospheric increase. Results indicate that the O3 changes will induce a positive radiative forcing dominated by tropospheric O3 increase and the magnitude of the forcing is comparable to that due to CO2 increases during the two decades. The significant implications of the tropospheric O3 increase to the global climate are discussed.

Modelling the effects of the radiation reaction force on the interaction of thin foils with ultra-intense laser fields

NASA Astrophysics Data System (ADS)

Duff, M. J.; Capdessus, R.; Del Sorbo, D.; Ridgers, C. P.; King, M.; McKenna, P.

2018-06-01

The effects of the radiation reaction (RR) force on thin foils undergoing radiation pressure acceleration (RPA) are investigated. Using QED-particle-in-cell simulations, the influence of the RR force on the collective electron dynamics within the target can be examined. The magnitude of the RR force is found to be strongly dependent on the target thickness, leading to effects which can be observed on a macroscopic scale, such as changes to the distribution of the emitted radiation and the target dynamics. This suggests that such parameters may be controlled in experiments at multi-PW laser facilities. In addition, the effects of the RR force are characterized in terms of an average radiation emission angle. We present an analytical model which, for the first time, describes the effect of the RR force on the collective electron dynamics within the ‘light-sail’ regime of RPA. The predictions of this model can be tested in future experiments with ultra-high intensity lasers interacting with solid targets.

Climatic Effects of 1950-2050 Changes in US Anthropogenic Aerosols. Part 1; Aerosol Trends and Radiative Forcing

NASA Technical Reports Server (NTRS)

Leibensperger, E. M.; Mickley, L. J.; Jacob, D. J.; Chen, W.-T.; Seinfeld, J. H.; Nenes, A.; Adams, P. J.; Streets, D. G.; Kumar, N.; Rind, D.

2012-01-01

We calculate decadal aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950-2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980-2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970-1990, with values over the eastern US (east of 100 deg W) of -2.0Wm(exp-2 for direct forcing including contributions from sulfate (-2.0Wm-2), nitrate (-0.2Wm(exp-2), organic carbon (-0.2Wm(exp-2), and black carbon (+0.4Wm(exp-2). The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50 %. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8Wm(exp-2) direct and 1.0Wm(exp-2 indirect), mainly reflecting decreases in SO2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3Wm(exp-2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide) suggests that a US emission control strategy focused on BC would have only limited climate benefit.

Radiative Forcing Over Ocean by Ship Wakes

NASA Technical Reports Server (NTRS)

Gatebe, Charles K.; Wilcox, E.; Poudyal, R.; Wang, J.

2011-01-01

Changes in surface albedo represent one of the main forcing agents that can counteract, to some extent, the positive forcing from increasing greenhouse gas concentrations. Here, we report on enhanced ocean reflectance from ship wakes over the Pacific Ocean near the California coast, where we determined, based on airborne radiation measurements that ship wakes can increase reflected sunlight by more than 100%. We assessed the importance of this increase to climate forcing, where we estimated the global radiative forcing of ship wakes to be -0.00014 plus or minus 53% Watts per square meter assuming a global distribution of 32331 ships of size of greater than or equal to 100000 gross tonnage. The forcing is smaller than the forcing of aircraft contrails (-0.007 to +0.02 Watts per square meter), but considering that the global shipping fleet has rapidly grown in the last five decades and this trend is likely to continue because of the need of more inter-continental transportation as a result of economic globalization, we argue that the radiative forcing of wakes is expected to be increasingly important especially in harbors and coastal regions.

Optical coherence elastography for cellular-scale stiffness imaging of mouse aorta

NASA Astrophysics Data System (ADS)

Wijesinghe, Philip; Johansen, Niloufer J.; Curatolo, Andrea; Sampson, David D.; Ganss, Ruth; Kennedy, Brendan F.

2017-04-01

We have developed a high-resolution optical coherence elastography system capable of estimating Young's modulus in tissue volumes with an isotropic resolution of 15 μm over a 1 mm lateral field of view and a 100 μm axial depth of field. We demonstrate our technique on healthy and hypertensive, freshly excised and intact mouse aortas. Our technique has the capacity to delineate the individual mechanics of elastic lamellae and vascular smooth muscle. Further, we observe global and regional vascular stiffening in hypertensive aortas, and note the presence of local micro-mechanical signatures, characteristic of fibrous and lipid-rich regions.

Breast magnetic resonance elastography: a review of clinical work and future perspectives.

PubMed

Bohte, A E; Nelissen, J L; Runge, J H; Holub, O; Lambert, S A; de Graaf, L; Kolkman, S; van der Meij, S; Stoker, J; Strijkers, G J; Nederveen, A J; Sinkus, R

2018-05-30

This review on magnetic resonance elastography (MRE) of the breast provides an overview of available literature and describes current developments in the field of breast MRE, including new transducer technology for data acquisition and multi-frequency-derived power-law behaviour of tissue. Moreover, we discuss the future potential of breast MRE, which goes beyond its original application as an additional tool in differentiating benign from malignant breast lesions. These areas of ongoing and future research include MRE for pre-operative tumour delineation, staging, monitoring and predicting response to treatment, as well as prediction of the metastatic potential of primary tumours. Copyright © 2018 John Wiley & Sons, Ltd.

Brain palpation from physiological vibrations using MRI.

PubMed

Zorgani, Ali; Souchon, Rémi; Dinh, Au-Hoang; Chapelon, Jean-Yves; Ménager, Jean-Michel; Lounis, Samir; Rouvière, Olivier; Catheline, Stefan

2015-10-20

We present a magnetic resonance elastography approach for tissue characterization that is inspired by seismic noise correlation and time reversal. The idea consists of extracting the elasticity from the natural shear waves in living tissues that are caused by cardiac motion, blood pulsatility, and any muscle activity. In contrast to other magnetic resonance elastography techniques, this noise-based approach is, thus, passive and broadband and does not need any synchronization with sources. The experimental demonstration is conducted in a calibrated phantom and in vivo in the brain of two healthy volunteers. Potential applications of this "brain palpation" approach for characterizing brain anomalies and diseases are foreseen.

Shear-wave elastography in breast ultrasonography: the state of the art

PubMed Central

2017-01-01

Shear-wave elastography (SWE) is a recently developed ultrasound technique that can visualize and measure tissue elasticity. In breast ultrasonography, SWE has been shown to be useful for differentiating benign breast lesions from malignant breast lesions, and it has been suggested that SWE enhances the diagnostic performance of ultrasonography, potentially improving the specificity of conventional ultrasonography using the Breast Imaging Reporting and Data System criteria. More recently, not only has SWE been proven useful for the diagnosis of breast cancer, but has also been shown to provide valuable information that can be used as a preoperative predictor of the prognosis or response to chemotherapy. PMID:28513127

Review of MR Elastography Applications and Recent Developments

PubMed Central

Glaser, Kevin J.; Manduca, Armando; Ehman, Richard L.

2012-01-01

The technique of MR elastography (MRE) has emerged as a useful modality for quantitatively imaging the mechanical properties of soft tissues in vivo. Recently, MRE has been introduced as a clinical tool for evaluating chronic liver disease, but many other potential applications are being explored. These applications include measuring tissue changes associated with diseases of the liver, breast, brain, heart, and skeletal muscle including both focal lesions (e.g., hepatic, breast, and brain tumors) and diffuse diseases (e.g., fibrosis and multiple sclerosis). The purpose of this review article is to summarize some of the recent developments of MRE and to highlight some emerging applications. PMID:22987755

Maximizing the endosonography: The role of contrast harmonics, elastography and confocal endomicroscopy.

PubMed

Seicean, Andrada; Mosteanu, Ofelia; Seicean, Radu

2017-01-07

New technologies in endoscopic ultrasound (EUS) evaluation have been developed because of the need to improve the EUS and EUS-fine needle aspiration (EUS-FNA) diagnostic rate. This paper reviews the principle, indications, main literature results, limitations and future expectations for each of the methods presented. Contrast-enhanced harmonic EUS uses a low mechanical index and highlights slow-flow vascularization. This technique is useful for differentiating solid and cystic pancreatic lesions and assessing biliary neoplasms, submucosal neoplasms and lymph nodes. It is also useful for the discrimination of pancreatic masses based on their qualitative patterns; however, the quantitative assessment needs to be improved. The detection of small solid lesions is better, and the EUS-FNA guidance needs further research. The differentiation of cystic lesions of the pancreas and the identification of the associated malignancy features represent the main indications. Elastography is used to assess tissue hardness based on the measurement of elasticity. Despite its low negative predictive value, elastography might rule out the diagnosis of malignancy for pancreatic masses. Needle confocal laser endomicroscopy offers useful information about cystic lesions of the pancreas and is still under evaluation for use with solid pancreatic lesions of lymph nodes.

Magnetomotive optical coherence elastography for relating lung structure and function in cystic fibrosis

NASA Astrophysics Data System (ADS)

Chhetri, Raghav K.; Carpenter, Jerome; Superfine, Richard; Randell, Scott H.; Oldenburg, Amy L.

2010-02-01

Cystic fibrosis (CF) is a genetic defect in the cystic fibrosis transmembrane conductance regulator protein and is the most common life-limiting genetic condition affecting the Caucasian population. It is an autosomal recessive, monogenic inherited disorder characterized by failure of airway host defense against bacterial infection, which results in bronchiectasis, the breakdown of airway wall extracellular matrix (ECM). In this study, we show that the in vitro models consisting of human tracheo-bronchial-epithelial (hBE) cells grown on porous supports with embedded magnetic nanoparticles (MNPs) at an air-liquid interface are suitable for long term, non-invasive assessment of ECM remodeling using magnetomotive optical coherence elastography (MMOCE). The morphology of ex vivo CF and normal lung tissues using OCT and correlative study with histology is also examined. We also demonstrate a quantitative measure of normal and CF airway elasticity using MMOCE. The improved understanding of pathologic changes in CF lung structure and function and the novel method of longitudinal in vitro ECM assessment demonstrated in this study may lead to new in vivo imaging and elastography methods to monitor disease progression and treatment in cystic fibrosis.

Automatic Generation of Boundary Conditions Using Demons Nonrigid Image Registration for Use in 3-D Modality-Independent Elastography

PubMed Central

Ou, Jao J.; Ong, Rowena E.; Miga, Michael I.

2013-01-01

Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm and are often determined by time-consuming point correspondence methods requiring manual user input. This study presents a novel method of automatically generating boundary conditions by nonrigidly registering two image sets with a demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray-computed tomography image data with known boundary conditions. These preliminary results produced boundary conditions with an accuracy of up to 80% compared to the known conditions. Demons-based boundary conditions were utilized within a 3-D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Two phantom experiments were then conducted to further test the accuracy of the demons boundary conditions and the MIE reconstruction arising from the use of these conditions. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method. PMID:21690002

Automatic generation of boundary conditions using demons nonrigid image registration for use in 3-D modality-independent elastography.

PubMed

Pheiffer, Thomas S; Ou, Jao J; Ong, Rowena E; Miga, Michael I

2011-09-01

Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm and are often determined by time-consuming point correspondence methods requiring manual user input. This study presents a novel method of automatically generating boundary conditions by nonrigidly registering two image sets with a demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray-computed tomography image data with known boundary conditions. These preliminary results produced boundary conditions with an accuracy of up to 80% compared to the known conditions. Demons-based boundary conditions were utilized within a 3-D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Two phantom experiments were then conducted to further test the accuracy of the demons boundary conditions and the MIE reconstruction arising from the use of these conditions. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method.

Real-time elastography in the evaluation of diffuse thyroid disease: a study based on elastography histogram parameters.

PubMed

Yoon, Jung Hyun; Yoo, Jaeheung; Kim, Eun-Kyung; Moon, Hee Jung; Lee, Hye Sun; Seo, Jae Young; Park, Hye Young; Park, Woon-Ju; Kwak, Jin Young

2014-09-01

The purpose of this study was to evaluate the diagnostic performance of quantitative histogram parameters using real-time tissue elastography (RTE) in the diagnosis of patients with diffuse thyroid disease. One hundred and sixteen patients (mean age, 43.7 ± 10.97 y) who had undergone pre-operative staging ultrasonography and RTE were included. For each patient, 11 parameters were obtained from RTE images, from which the "elastic index" was calculated. Diagnostic performance of the elastic index and that of the 11 parameters on RTE were calculated and compared. Of the 116 patients, 31 had diffuse thyroid disease and 85 had normal thyroid parenchyma. Area under the receiver operating characteristic curve (A(z)) of MEAN (average relative value) elasticity was high (0.737), without significant differences from other elasticity values. Diagnostic performance of the elastic index was higher than the MEAN, A(z) = 0.753, without significance (p = 0.802). In conclusion, RTE using the elastic index was found to have good diagnostic performance and may be useful in the diagnosis and management of patients with diffuse thyroid disease. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Application of Eshelby's Solution to Elastography for Diagnosis of Breast Cancer.

PubMed

Shin, Bonghun; Gopaul, Darindra; Fienberg, Samantha; Kwon, Hyock Ju

2016-03-01

Eshelby's solution is the analytical method that can derive the elastic field within and around an ellipsoidal inclusion embedded in a matrix. Since breast tumor can be regarded as an elastic inclusion with different elastic properties from those of surrounding matrix when the deformation is small, we applied Eshelby's solution to predict the stress and strain fields in the breast containing a suspicious lesion. The results were used to investigate the effectiveness of strain ratio (SR) from elastography in representing modulus ratio (MR) that may be the meaningful indicator of the malignancy of the lesion. This study showed that SR significantly underestimates MR and is varied with the shape and the modulus of the lesion. Based on the results from Eshelby's solution and finite element analysis (FEA), we proposed a surface regression model as a polynomial function that can predict the MR of the lesion to the matrix. The model has been applied to gelatin-based phantoms and clinical ultrasound images of human breasts containing different types of lesions. The results suggest the potential of the proposed method to improve the diagnostic performance of breast cancer using elastography. © The Author(s) 2015.

Preliminary Comparison of Multi-scale and Multi-model Direct Inversion Algorithms for 3T MR Elastography.

PubMed

Yoshimitsu, Kengo; Shinagawa, Yoshinobu; Mitsufuji, Toshimichi; Mutoh, Emi; Urakawa, Hiroshi; Sakamoto, Keiko; Fujimitsu, Ritsuko; Takano, Koichi

2017-01-10

To elucidate whether any differences are present in the stiffness map obtained with a multiscale direct inversion algorithm (MSDI) vs that with a multimodel direct inversion algorithm (MMDI), both qualitatively and quantitatively. The MR elastography (MRE) data of 37 consecutive patients who underwent liver MR elastography between September and October 2014 were retrospectively analyzed by using both MSDI and MMDI. Two radiologists qualitatively assessed the stiffness maps for the image quality in consensus, and the measured liver stiffness and measurable areas were quantitatively compared between MSDI and MMDI. MMDI provided a stiffness map of better image quality, with comparable or slightly less artifacts. Measurable areas by MMDI (43.7 ± 17.8 cm 2 ) was larger than that by MSDI (37.5 ± 14.7 cm 2 ) (P < 0.05). Liver stiffness measured by MMDI (4.51 ± 2.32 kPa) was slightly (7%), but significantly less than that by MSDI (4.86 ± 2.44 kPa) (P < 0.05). MMDI can provide stiffness map of better image quality, and slightly lower stiffness values as compared to MSDI at 3T MRE, which radiologists should be aware of.

Improving arrival time identification in transient elastography

NASA Astrophysics Data System (ADS)

Klein, Jens; McLaughlin, Joyce; Renzi, Daniel

2012-04-01

In this paper, we improve the first step in the arrival time algorithm used for shear wave speed recovery in transient elastography. In transient elastography, a shear wave is initiated at the boundary and the interior displacement of the propagating shear wave is imaged with an ultrasound ultra-fast imaging system. The first step in the arrival time algorithm finds the arrival times of the shear wave by cross correlating displacement time traces (the time history of the displacement at a single point) with a reference time trace located near the shear wave source. The second step finds the shear wave speed from the arrival times. In performing the first step, we observe that the wave pulse decorrelates as it travels through the medium, which leads to inaccurate estimates of the arrival times and ultimately to blurring and artifacts in the shear wave speed image. In particular, wave ‘spreading’ accounts for much of this decorrelation. Here we remove most of the decorrelation by allowing the reference wave pulse to spread during the cross correlation. This dramatically improves the images obtained from arrival time identification. We illustrate the improvement of this method on phantom and in vivo data obtained from the laboratory of Mathias Fink at ESPCI, Paris.

Is real-time elastography helpful to differentiate acute from subacute deep venous thrombosis? A preliminary study.

PubMed

Aslan, Ahmet; Barutca, Hakan; Ayaz, Ercan; Aslan, Mine; Kocaaslan, Cemal; Inan, Ibrahim; Sahin, Sinan; Yıkılmaz, Ali

2018-02-01

To detect and characterize changes in stiffness of thrombus in patients with acute and subacute deep venous thrombosis (DVT) by using real-time elastography (RTE). Fifty-eight patients with acute or subacute DVT were prospectively evaluated by B-mode sonography (US), color Doppler US (CDUS), and RTE. Two radiologists evaluated the thrombus echogenicity, compressibility, and recanalization of the affected vein, and thrombus stiffness in consensus. The thrombi were classified into 3 groups as soft, intermediate, and hard on RTE images. The final study group consisted of 30 patients with acute DVT, among whom 10 were women (33%), and 19 patients with subacute DVT, among whom 6 were women (32%). The presence of hypoechoic thrombus, incompressible vein, and absence of recanalization on US and CDUS were significantly associated with acute DVT (P < .001 for all variables). The differences in elasticity pattern of the thrombi between acute and subacute DVT were not significant (P = .202). Venous thrombus hardens with age; however, elastography pattern on RTE, in its present form, may not be able to differentiate acute DVT from subacute DVT. © 2017 Wiley Periodicals, Inc.

Modeling of Soft Poroelastic Tissue in Time-Harmonic MR Elastography

PubMed Central

Perriñez, Phillip R.; Kennedy, Francis E.; Van Houten, Elijah E. W.; Weaver, John B.; Paulsen, Keith D.

2010-01-01

Elastography is an emerging imaging technique that focuses on assessing the resistance to deformation of soft biological tissues in vivo. Magnetic resonance elastography (MRE) uses measured displacement fields resulting from low-amplitude, low-frequency (10 Hz–1 kHz) time-harmonic vibration to recover images of the elastic property distribution of tissues including breast, liver, muscle, prostate, and brain. While many soft tissues display complex time-dependent behavior not described by linear elasticity, the models most commonly employed in MRE parameter reconstructions are based on elastic assumptions. Further, elasticity models fail to include the interstitial fluid phase present in vivo. Alternative continuum models, such as consolidation theory, are able to represent tissue and other materials comprising two distinct phases, generally consisting of a porous elastic solid and penetrating fluid. MRE reconstructions of simulated elastic and poroelastic phantoms were performed to investigate the limitations of current-elasticity-based methods in producing accurate elastic parameter estimates in poroelastic media. The results indicate that linearly elastic reconstructions of fluid-saturated porous media at amplitudes and frequencies relevant to steady-state MRE can yield misleading effective property distributions resulting from the complex interaction between their solid and fluid phases. PMID:19272864

Noninvasive scoring system for significant inflammation related to chronic hepatitis B

NASA Astrophysics Data System (ADS)

Hong, Mei-Zhu; Ye, Linglong; Jin, Li-Xin; Ren, Yan-Dan; Yu, Xiao-Fang; Liu, Xiao-Bin; Zhang, Ru-Mian; Fang, Kuangnan; Pan, Jin-Shui

2017-03-01

Although a liver stiffness measurement-based model can precisely predict significant intrahepatic inflammation, transient elastography is not commonly available in a primary care center. Additionally, high body mass index and bilirubinemia have notable effects on the accuracy of transient elastography. The present study aimed to create a noninvasive scoring system for the prediction of intrahepatic inflammatory activity related to chronic hepatitis B, without the aid of transient elastography. A total of 396 patients with chronic hepatitis B were enrolled in the present study. Liver biopsies were performed, liver histology was scored using the Scheuer scoring system, and serum markers and liver function were investigated. Inflammatory activity scoring models were constructed for both hepatitis B envelope antigen (+) and hepatitis B envelope antigen (-) patients. The sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve were 86.00%, 84.80%, 62.32%, 95.39%, and 0.9219, respectively, in the hepatitis B envelope antigen (+) group and 91.89%, 89.86%, 70.83%, 97.64%, and 0.9691, respectively, in the hepatitis B envelope antigen (-) group. Significant inflammation related to chronic hepatitis B can be predicted with satisfactory accuracy by using our logistic regression-based scoring system.

Diagnosis of hyperfunctional thyroid nodules: impact of US-elastography.

PubMed

Ruhlmann, M; Stebner, V; Görges, R; Farahati, J; Simon, D; Bockisch, A; Rosenbaum-Krumme, S; Nagarajah, J

2014-01-01

Several studies described the ultrasound based real-time elastography (USE) having a high sensitivity, specificity and negative predictive value in the diagnosis of suspicious thyroid nodules. Recently published studies called these results into question. Until now the usefulness of USE in the diagnosis of scintigraphically hyperfunctional thyroid nodules is not examined. This study included 135 hyperfunctional thyroid nodules of 102 consecutive patients. The following attributes of the nodules were analyzed: stiffness with the USE using scores of Rago or Asteria and ultrasound criteria using TIRADS. 94 of the examined thyroid nodules (70%) were rated as hard (suspicious for malignancy) and 41 nodules (30%) as soft (not suspicious) with a specificity of 30%. The scoring systems of Rago and Asteria showed no significant difference. Applying the TIRADS criteria 44 nodules (33%) have a higher risk for malignancy (33 nodules TIRADS 4a, 11 nodules TIRADS 4b). Combining USE and TIRADS 32 nodules (24%) are categorized as suspicious (intersection of hard nodules that are categorized as TIRADS 4a or 4b). Ultrasound based real-time elastography cannot identify scintigraphically hyperfunctional thyroid nodules as benign nodules reliably. Its accuracy in the assessment of at least "hot" thyroid nodules is to be questioned.

[IMPORTANCE OF SHEAR WAVE ELASTOGRAPHY OF LIVERS IN PRACTICALLY HEALTHY PREGNANT WOMEN].

PubMed

Sariyeva, E; Salahova, S; Bayramov, N

2017-01-01

Pulse-wave elastography (SWE) that is one of the mostly used methods in the recent years holds important place in assessment of liver fibrosis. However there is no exact information on the results of liver elastography in healthy pregnant women in the world literature. The aim of the study was to investigate theSWE parameters of liver elastography in practically healthy pregnant women. The subject of the research was 50 practically healthy pregnant women within 18-45 years old (mean age 27.7±0.7). The pregnant women with genital and extragenital diseases were not included to the research. The research work was executed in the II Department of Obstetrics and Gynecology of Azerbaijan Medical University. SWE of liver in pregnant women was conducted in the I Department of Surgical Diseases of Azerbaijan Medical University through Supersonic Aixplorer Multi Wave device presented by the Scientific Development Foundation under the President of the Azerbaijan Republic. The obtained tissue hardness indicators are assessed under METAVIR scale. The results of the research showed that the measures of liver in practically healthy pregnant women are normal, edges flat, its echogenicity mainly normal, echostructure of its parenchyma homogenous, hardness was F0-F1 (normal) under METAVIR scale, fibrosis not observed. The obtained results were processed by variational (power average, percentile distribution) and correlation (ρ-Spearman) analyzes using the statistical package SPSS-20. A statistical study of the distribution of liver density in healthy women showed that the average density was 4,43±0,01 with 95% confidence interval (4,23 - 4,63). The histogram of distribution of liver density in practically healthy women belongs to the family of normal distributions with coefficients of variation coefficient (16.3%), asymmetry (-0.861±0.337) and excess (-0.068±0.662). Correlation analysis in healthy women did not reveal a reliable relationship between age and liver density (ρ=0.082, p=0.571), but a significant inverse correlation was found between the body mass index (BMI) and liver density (ρ=-0.317; p=0.025). Easy application, non-invasiveness, maximum exactness within the real time, repeatedly application of procedure and no risk to fetus by Shear Wave elastography of liver allow applying this method in pregnant women. Study of liver elasticity in pregnant women allows assessing the grades of hepatic fibrosis and differentiating liver disease.

The contribution of China’s emissions to global climate forcing

NASA Astrophysics Data System (ADS)

Li, Bengang; Gasser, Thomas; Ciais, Philippe; Piao, Shilong; Tao, Shu; Balkanski, Yves; Hauglustaine, Didier; Boisier, Juan-Pablo; Chen, Zhuo; Huang, Mengtian; Li, Laurent Zhaoxin; Li, Yue; Liu, Hongyan; Liu, Junfeng; Peng, Shushi; Shen, Zehao; Sun, Zhenzhong; Wang, Rong; Wang, Tao; Yin, Guodong; Yin, Yi; Zeng, Hui; Zeng, Zhenzhong; Zhou, Feng

2016-03-01

Knowledge of the contribution that individual countries have made to global radiative forcing is important to the implementation of the agreement on “common but differentiated responsibilities” reached by the United Nations Framework Convention on Climate Change. Over the past three decades, China has experienced rapid economic development, accompanied by increased emission of greenhouse gases, ozone precursors and aerosols, but the magnitude of the associated radiative forcing has remained unclear. Here we use a global coupled biogeochemistry-climate model and a chemistry and transport model to quantify China’s present-day contribution to global radiative forcing due to well-mixed greenhouse gases, short-lived atmospheric climate forcers and land-use-induced regional surface albedo changes. We find that China contributes 10% ± 4% of the current global radiative forcing. China’s relative contribution to the positive (warming) component of global radiative forcing, mainly induced by well-mixed greenhouse gases and black carbon aerosols, is 12% ± 2%. Its relative contribution to the negative (cooling) component is 15% ± 6%, dominated by the effect of sulfate and nitrate aerosols. China’s strongest contributions are 0.16 ± 0.02 watts per square metre for CO2 from fossil fuel burning, 0.13 ± 0.05 watts per square metre for CH4, -0.11 ± 0.05 watts per square metre for sulfate aerosols, and 0.09 ± 0.06 watts per square metre for black carbon aerosols. China’s eventual goal of improving air quality will result in changes in radiative forcing in the coming years: a reduction of sulfur dioxide emissions would drive a faster future warming, unless offset by larger reductions of radiative forcing from well-mixed greenhouse gases and black carbon.

The contribution of China's emissions to global climate forcing.

PubMed

Li, Bengang; Gasser, Thomas; Ciais, Philippe; Piao, Shilong; Tao, Shu; Balkanski, Yves; Hauglustaine, Didier; Boisier, Juan-Pablo; Chen, Zhuo; Huang, Mengtian; Li, Laurent Zhaoxin; Li, Yue; Liu, Hongyan; Liu, Junfeng; Peng, Shushi; Shen, Zehao; Sun, Zhenzhong; Wang, Rong; Wang, Tao; Yin, Guodong; Yin, Yi; Zeng, Hui; Zeng, Zhenzhong; Zhou, Feng

2016-03-17

Knowledge of the contribution that individual countries have made to global radiative forcing is important to the implementation of the agreement on "common but differentiated responsibilities" reached by the United Nations Framework Convention on Climate Change. Over the past three decades, China has experienced rapid economic development, accompanied by increased emission of greenhouse gases, ozone precursors and aerosols, but the magnitude of the associated radiative forcing has remained unclear. Here we use a global coupled biogeochemistry-climate model and a chemistry and transport model to quantify China's present-day contribution to global radiative forcing due to well-mixed greenhouse gases, short-lived atmospheric climate forcers and land-use-induced regional surface albedo changes. We find that China contributes 10% ± 4% of the current global radiative forcing. China's relative contribution to the positive (warming) component of global radiative forcing, mainly induced by well-mixed greenhouse gases and black carbon aerosols, is 12% ± 2%. Its relative contribution to the negative (cooling) component is 15% ± 6%, dominated by the effect of sulfate and nitrate aerosols. China's strongest contributions are 0.16 ± 0.02 watts per square metre for CO2 from fossil fuel burning, 0.13 ± 0.05 watts per square metre for CH4, -0.11 ± 0.05 watts per square metre for sulfate aerosols, and 0.09 ± 0.06 watts per square metre for black carbon aerosols. China's eventual goal of improving air quality will result in changes in radiative forcing in the coming years: a reduction of sulfur dioxide emissions would drive a faster future warming, unless offset by larger reductions of radiative forcing from well-mixed greenhouse gases and black carbon.

Aerosol Direct Radiative Forcing and Forcing Efficiencies at Surface from the shortwave Irradiance Measurements in Abu Dhabi, UAE

NASA Astrophysics Data System (ADS)

Beegum S, N.; Ben Romdhane, H.; Ghedira, H.

2013-12-01

Atmospheric aerosols are known to affect the radiation balance of the Earth-Atmospheric system directly by scattering and absorbing the solar and terrestrial radiation, and indirectly by affecting the lifetime and albedo of the clouds. Continuous and simultaneous measurements of short wave global irradiance in combination with synchronous spectral aerosol optical depth (AOD) measurements (from 340 nm to 1640 nm in 8 channels), for a period of 1 year from June 2012 to May 2013, were used for the determination of the surface direct aerosol radiative forcing and forcing efficiencies under cloud free conditions in Abu Dhabi (24.42°N, 54.61o E, 7m MSL), a coastal location in United Arab Emirates (UAE) in the Arabian Peninsula. The Rotating Shadow band Pyranometer (RSP, LI-COR) was used for the irradiance measurements (in the spectral region 400-1100 nm), whereas the AOD measurements were carried out using CIMEL Sunphotometer (CE 318-2, under AERONET program). The differential method, which is neither sensitive to calibration uncertainties nor model assumptions, has been employed for estimating forcing efficiencies from the changes in the measured fluxes. The forcing efficiency, which quantifies the net change in irradiance per unit change in AOD, is an appropriate parameter for the characterization of the aerosol radiative effects even if the microphysical and optical properties of the aerosols are not completely understood. The corresponding forcing values were estimated from the forcing efficiencies. The estimated radiative forcing and forcing efficiencies exhibited strong monthly variations. The forcing efficiencies (absolute magnitudes) were highest during March, and showed continuous decrease thereafter to reach the lowest value during September. In contrast, the forcing followed a slightly different pattern of variability, with the highest solar dimming during April ( -60 W m-2) and the minimum during February ( -20 W m-2). The results indicate that the aerosol microphysics as well as the types of aerosol undergo significant seasonal variations.

Absorption, scattering, and radiation force efficiencies in the longitudinal wave scattering by a small viscoelastic particle in an isotropic solid.

PubMed

Lopes, J H; Leão-Neto, J P; Silva, G T

2017-11-01

Analytical expressions of the absorption, scattering, and elastic radiation force efficiency factors are derived for the longitudinal plane wave scattering by a small viscoelastic particle in a lossless solid matrix. The particle is assumed to be much smaller than the incident wavelength, i.e., the so-called long-wavelength (Rayleigh) approximation. The efficiencies are dimensionless quantities that represent the absorbed and scattering powers and the elastic radiation force on the particle. In the quadrupole approximation, they are expressed in terms of contrast functions (bulk and shear moduli, and density) between the particle and solid matrix. The results for a high-density polyethylene particle embedded in an aluminum matrix agree with those obtained with the partial wave expansion method. Additionally, the connection between the elastic radiation force and forward scattering function is established through the optical theorem. The present results should be useful for ultrasound characterization of particulate composites, and the development of implanted devices activated by radiation force.

Atmospheric response and feedback to radiative forcing from biomass burning in tropical South America

Treesearch

Yongqiang Liu

2005-01-01

Simulations are performed to understand the importance of smoke from biomass burning in tropical South America to regional radiation and climate. The National Center for Atmospheric Research (NCAR) regional climate model coupled with the NCAR column radiative model is used to estimate smoke direct radiative forcing and consequent atmospheric perturbations during a...

Theoretical and Experimental Investigation of Particle Trapping via Acoustic Bubbles

NASA Astrophysics Data System (ADS)

Chen, Yun; Fang, Zecong; Merritt, Brett; Saadat-Moghaddam, Darius; Strack, Dillon; Xu, Jie; Lee, Sungyon

2014-11-01

One important application of lab-on-a-chip devices is the trapping and sorting of micro-objects, with acoustic bubbles emerging as an effective, non-contact method. Acoustically actuated bubbles are known to exert a secondary radiation force on micro-particles and trap them, when this radiation force exceeds the drag force that acts to keep the particles in motion. In this study, we theoretically evaluate the magnitudes of these two forces for varying actuation frequencies and voltages. In particular, the secondary radiation force is calculated directly from bubble oscillation shapes that have been experimentally measured for varying acoustic parameters. Finally, based on the force estimates, we predict the threshold voltage and frequency for trapping and compare them to the experimental results.

Cloud Radiation Forcings and Feedbacks: General Circulation Model Tests and Observational Validation

NASA Technical Reports Server (NTRS)

Lee,Wan-Ho; Iacobellis, Sam F.; Somerville, Richard C. J.

1997-01-01

Using an atmospheric general circulation model (the National Center for Atmospheric Research Community Climate Model: CCM2), the effects on climate sensitivity of several different cloud radiation parameterizations have been investigated. In addition to the original cloud radiation scheme of CCM2, four parameterizations incorporating prognostic cloud water were tested: one version with prescribed cloud radiative properties and three other versions with interactive cloud radiative properties. The authors' numerical experiments employ perpetual July integrations driven by globally constant sea surface temperature forcings of two degrees, both positive and negative. A diagnostic radiation calculation has been applied to investigate the partial contributions of high, middle, and low cloud to the total cloud radiative forcing, as well as the contributions of water vapor, temperature, and cloud to the net climate feedback. The high cloud net radiative forcing is positive, and the middle and low cloud net radiative forcings are negative. The total net cloud forcing is negative in all of the model versions. The effect of interactive cloud radiative properties on global climate sensitivity is significant. The net cloud radiative feedbacks consist of quite different shortwave and longwave components between the schemes with interactive cloud radiative properties and the schemes with specified properties. The increase in cloud water content in the warmer climate leads to optically thicker middle- and low-level clouds and in turn to negative shortwave feedbacks for the interactive radiative schemes, while the decrease in cloud amount simply produces a positive shortwave feedback for the schemes with a specified cloud water path. For the longwave feedbacks, the decrease in high effective cloudiness for the schemes without interactive radiative properties leads to a negative feedback, while for the other cases, the longwave feedback is positive. These cloud radiation parameterizations are empirically validated by using a single-column diagnostic model. together with measurements from the Atmospheric Radiation Measurement program and from the Tropical Ocean Global Atmosphere Combined Ocean-Atmosphere Response Experiment. The inclusion of prognostic cloud water produces a notable improvement in the realism of the parameterizations, as judged by these observations. Furthermore, the observational evidence suggests that deriving cloud radiative properties from cloud water content and microphysical characteristics is a promising route to further improvement.