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Sample records for force impulse elastography

  1. Assessment of liver fibrosis with 2-D shear wave elastography in comparison to transient elastography and acoustic radiation force impulse imaging in patients with chronic liver disease.

    PubMed

    Gerber, Ludmila; Kasper, Daniela; Fitting, Daniel; Knop, Viola; Vermehren, Annika; Sprinzl, Kathrin; Hansmann, Martin L; Herrmann, Eva; Bojunga, Joerg; Albert, Joerg; Sarrazin, Christoph; Zeuzem, Stefan; Friedrich-Rust, Mireen

    2015-09-01

    Two-dimensional shear wave elastography (2-D SWE) is an ultrasound-based elastography method integrated into a conventional ultrasound machine. It can evaluate larger regions of interest and, therefore, might be better at determining the overall fibrosis distribution. The aim of this prospective study was to compare 2-D SWE with the two best evaluated liver elastography methods, transient elastography and acoustic radiation force impulse (point SWE using acoustic radiation force impulse) imaging, in the same population group. The study included 132 patients with chronic hepatopathies, in which liver stiffness was evaluated using transient elastography, acoustic radiation force impulse imaging and 2-D SWE. The reference methods were liver biopsy for the assessment of liver fibrosis (n = 101) and magnetic resonance imaging/computed tomography for the diagnosis of liver cirrhosis (n = 31). No significant difference in diagnostic accuracy, assessed as the area under the receiver operating characteristic curve (AUROC), was found between the three elastography methods (2-D SWE, transient elastography, acoustic radiation force impulse imaging) for the diagnosis of significant and advanced fibrosis and liver cirrhosis in the "per protocol" (AUROCs for fibrosis stages ≥2: 0.90, 0.95 and 0.91; for fibrosis stage [F] ≥3: 0.93, 0.95 and 0.94; for F = 4: 0.92, 0.96 and 0.92) and "intention to diagnose" cohort (AUROCs for F ≥2: 0.87, 0.92 and 0.91; for F ≥3: 0.91, 0.93 and 0.94; for F = 4: 0.88, 0.90 and 0.89). Therefore, 2-D SWE, ARFI imaging and transient elastography seem to be comparably good methods for non-invasive assessment of liver fibrosis. PMID:26116161

  2. Acoustic Radiation Force Impulse Elastography in the Diagnosis of Thyroid Nodules: Useful or Not Useful?

    PubMed

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

    2015-10-01

    The goal of this study is to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) elastography for differentiating benign from malignant thyroid nodules. One hundred and seventy-four pathologically proven thyroid nodules (139 benign, 35 malignant) in 154 patients (mean age: 49.2 ± 12.1 y; range: 16-72 y) were included in this study. Conventional ultrasound (US) and ARFI elastography using virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ) were performed to examine the thyroid nodules. Two blinded readers with different amounts of experience independently scored the likelihood of malignancy on the basis of a five-point scale in three different image-reading sets. The diagnostic performances among different image-reading sets and between the two readers were compared. The diagnostic specificity of both readers improved significantly after reading the VTI images or both VTI and VTQ images (all p < 0.05). After review of the results of both VTI and VTQ, the numbers of correctly diagnosed nodules increased in nodules <1.0 cm for both readers and in both nodular goiter and papillary thyroid carcinoma for the junior reader (p < 0.05). The nodules with definite diagnoses (i.e., confidence levels including definite benign and definite malignant cases) increased after review of VTI and VTQ images versus conventional US for the senior reader (p < 0.05). In conclusion, adding ARFI elastography improves the specificity in diagnosing malignant thyroid nodules compared with conventional US on its own. ARFI elastography particularly facilitates the specific diagnosis for thyroid nodules smaller than 1.0 cm. ARFI elastography is also able to increase the diagnostic confidence of the readers. PMID:26119458

  3. Assessment of Placental Stiffness Using Acoustic Radiation Force Impulse Elastography in Pregnant Women with Fetal Anomalies

    PubMed Central

    Göya, Cemil; Tunç, Senem; Teke, Memik; Hattapoğlu, Salih

    2016-01-01

    Objective We aimed to evaluate placental stiffness measured by acoustic radiation force impulse (ARFI) elastography in pregnant women in the second trimester with a normal fetus versus those with structural anomalies and non-structural findings. Materials and Methods Forty pregnant women carrying a fetus with structural anomalies diagnosed sonographically at 18–28 weeks of gestation comprised the study group. The control group consisted of 34 healthy pregnant women with a sonographically normal fetus at a similar gestational age. Placental shear wave velocity (SWV) was measured by ARFI elastography and compared between the two groups. Structural anomalies and non-structural findings were scored based on sonographic markers. Placental stiffness measurements were compared among fetus anomaly categories. Doppler parameters of umbilical and uterine arteries were compared with placental SWV measurements. Results All placental SWV measurements, including minimum SWV, maximum SWV, and mean SWV were significantly higher in the study group than the control group ([0.86 ± 0.2, 0.74 ± 0.1; p < 0.001], [1.89 ± 0.7, 1.59 ± 0.5; p = 0.04], and [1.26 ± 0.4, 1.09 ± 0.2; p = 0.01]), respectively. Conclusion Placental stiffness evaluated by ARFI elastography during the second trimester in pregnant women with fetuses with congenital structural anomalies is higher than that of pregnant women with normal fetuses. PMID:26957906

  4. Acoustic radiation force impulse induced strain elastography and point shear wave elastography for evaluation of thyroid nodules

    PubMed Central

    Huang, Xian; Guo, Le-Hang; Xu, Hui-Xiong; Gong, Xue-Hao; Liu, Bo-Ji; Xu, Jun-Mei; Zhang, Yi-Feng; Li, Xiao-Long; Li, Dan-Dan; Qu, Shen; Fang, Lin

    2015-01-01

    The aim of the study was to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) induced strain elastography (SE), point shear wave elastography (p-SWE), and their combined use in differentiating thyroid nodules. This retrospective study included 155 thyroid nodules (94 benign and 61 malignant) in 136 patients. Ultrasound, ARFI-induced SE and p-SWE were performed on each nodule. Receiver operating characteristic curve (ROC) analyses were performed to assess the diagnostic efficacy of ARFI-induced SE, p-SWE and their combined use to distinguish benign from malignant thyroid nodules with histological results used as the reference standard. The areas under the ROC for ARFI-induced SE, p-SWE, and their combined use were 0.828, 0.829, and 0.840, respectively (both P > 0.05). The specificity of ARFI-induced SE was higher than that of p-SWE as well as their combined use (both P < 0.05). The combination of the two methods significantly improved the diagnostic sensitivity and NPV compared with either ARFI-induced SE or p-SWE alone (both P < 0.05). For nodules ≤ 10 mm, the combination of the two methods significantly improved the diagnostic sensitivity only. For nodules > 10 mm, there were no significant differences in sensitivity and NPV among the three methods in differentiating thyroid nodules (all P > 0.05). In conclusions, ARFI-induced SE and p-SWE are both valuable tools for detecting malignant thyroid nodules. The combined use of ARFI-induced SE and p-SWE improves the diagnostic sensitivity and NPV significantly whereas ARFI-induced SE alone achieves the highest specificity. PMID:26379890

  5. Acoustic Radiation Force Impulse Elastography for Focal Hepatic Tumors: Usefulness for Differentiating Hemangiomas from Malignant Tumors

    PubMed Central

    Kim, Ji Eun; Bae, Kyung Soo; Han, Joon Koo; Choi, Byung Ihn

    2013-01-01

    Objective The purpose of this study is to investigate whether acoustic radiation force impulse (ARFI) elastography with ARFI quantification and ARFI 2-dimensional (2D) imaging is useful for differentiating hepatic hemangiomas from malignant hepatic tumors. Materials and Methods One-hundred-and-one tumors in 74 patients were included in this study: 28 hemangiomas, 26 hepatocellular carcinomas (HCCs), three cholangiocarcinomas (CCCs), 20 colon cancer metastases and 24 other metastases. B-mode ultrasound, ARFI 2D imaging, and ARFI quantification were performed in all tumors. Shear wave velocities (SWVs) of the tumors and the adjacent liver and their SWV differences were compared among the tumor groups. The ARFI 2D images were compared with B-mode images regarding the stiffness, conspicuity and size of the tumors. Results The mean SWV of the hemangiomas was significantly lower than the malignant hepatic tumor groups: hemangiomas, 1.80 ± 0.57 m/sec; HCCs, 2.66 ± 0.94 m/sec; CCCs, 3.27 ± 0.64 m/sec; colon cancer metastases, 3.70 ± 0.61 m/sec; and other metastases, 2.82 ± 0.96 m/sec (p < 0.05). The area under the receiver operating characteristics curve of SWV for differentiating hemangiomas from malignant tumors was 0.86, with a sensitivity of 96.4% and a specificity of 65.8% at a cut-off value of 2.73 m/sec (p < 0.05). In the ARFI 2D images, the malignant tumors except HCCs were stiffer and more conspicuous as compared with the hemangiomas (p < 0.05). Conclusion ARFI elastography with ARFI quantification and ARFI 2D imaging may be useful for differentiating hepatic hemangiomas from malignant hepatic tumors. PMID:24043967

  6. Factors Influencing the Diagnostic Accuracy of Acoustic Radiation Force Impulse Elastography in Patients with Chronic Hepatitis B

    PubMed Central

    Park, Mi Sung; Kim, Sun Wook; Yoon, Ki Tae; Kim, Seung Up; Park, Soo Young; Tak, Won Young; Kweon, Young Oh; Cho, Mong; Kim, Beom Kyung; Park, Jun Yong; Kim, Do Young; Ahn, Sang Hoon; Han, Kwang-Hyub

    2016-01-01

    Background/Aims To determine factors predictive of discordance in staging liver fibrosis using liver biopsy (LB) and acoustic radiation force impulse (ARFI) elastography in patients with chronic hepatitis B (CHB). Methods Consecutive patients with CHB who underwent LB and ARFI elastography on the same day from November 2010 to March 2013 were prospectively recruited from three tertiary hospitals. Results We analyzed 105 patients (median age of 47 years). The F0–1, F2, F3, and F4 fibrosis stages were identified in 27 (25.7%), 27 (25.7%), 21 (20.0%), and 30 (28.6%) patients, respectively. The areas under the receiver operating characteristics curves for ARFI elastography in assessing ≥F2, ≥F3, and F4 was 0.814, 0.848, and 0.752, respectively. The discordance of at least one stage between LB and ARFI was observed in 68 patients (64.8%) and of at least two stages in 16 patients (15.2%). In a multivariate analysis, advanced fibrosis stage (F3–4) was the only factor that was negatively correlated with one-stage discordance (p=0.042). Moreover, advanced fibrosis stage was negatively (p=0.016) correlated and body mass index (BMI) was positively (p=0.006) correlated with two-stage discordance. Conclusions Advanced fibrosis stage (F3–4) was a predictor of nondiscordance between LB and ARFI elastography; BMI also influenced the accuracy of ARFI elastography. PMID:26087790

  7. Acoustic radiation force impulse elastography for hepatocellular carcinoma-associated radiofrequency ablation

    PubMed Central

    Kwon, Hee-Jin; Kang, Myong-Jin; Cho, Jin-Han; Oh, Jong-Young; Nam, Kyung-Jin; Han, Sang-Yeong; Lee, Sung Wook

    2011-01-01

    AIM: To evaluate the potential usefulness of acoustic radiation force impulse (ARFI) images for evaluation of hepatocellular carcinomas (HCC)-associated radiofrequency ablation. METHODS: From January 2010 to June 2010, a total of 38 patients with HCC including recurred HCCs after RFA underwent ARFI elastography. The brightness of tumor was checked and the shear wave velocity was measured for the quantification of stiffness. According to the brightness, the tumors were classified as brighter, same color and darker compared with adjacent parenchyma. Using the same methods, 8 patients with recurred HCCs after RFA state were evaluated about the brightness compared with adjacent RFA ablation area. RESULTS: In the 38 patients with HCCs, 20 (52.6%) were brighter than surrounding cirrhotic parenchyma. Another 13 (34.2%) were darker. The others (5 cases, 13.2%) were seen as the same color as the adjacent liver parenchyma. Post-RFA lesions were darker than previous tumor and surrounding parenchyma in all 38 cases. However, recurred HCCs were brighter than the treated site in all 8 cases. CONCLUSION: Using ARFI technique is helpful for differential diagnosis in order to detect recurred HCCs more easily in patients with confusing status. PMID:21528062

  8. The diagnosis value of acoustic radiation force impulse (ARFI) elastography for thyroid malignancy without highly suspicious features on conventional ultrasound

    PubMed Central

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

    2015-01-01

    Objective: The aim of this study was to evaluate the potential diagnostic performance of acoustic radiation force impulse (ARFI) elastography in identifying malignancy in nodules that do not appear highly suspicious on conventional ultrasound (US). Methods: 330 pathologically confirmed thyroid nodules (40 malignant and 290 benign; mean size, 22.0±11.6 mm) not suspicious of malignancy on conventional US in 330 patients (mean age 52.8±11.7 years) underwent ARFI elastography before surgery. ARFI elastography included qualitative ARFI-induced strain elastography (SE) and quantitative point shear wave elastography (p-SWE). ARFI-induced SE image was assessed by SE score, while p-SWE was denoted with shear wave velocity (SWV, m/s). The diagnostic performance of four criteria sets was evaluated: criteria set 1 (ARFI-induced SE), criteria set 2 (p-SWE), criteria set 3 (either set 1 or 2), criteria set 4 (both set 1 and 2). Receiver operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance. Results: SE score ≥4 was more frequently found in malignant nodules (32/40) than in benign nodules (30/290, P<0.001). The mean SWV of malignant nodules (3.64±2.23 m/s) was significantly higher than that of benign nodules (2.02±0.69 m/s) (P<0.001). ARFI-induced SE (set 1) had a sensitivity of 80.0% (32/40) and a specificity of 89.7% (260/290) with a cut-off point of SE score ≥4; p-SWE (set 2) had a sensitivity of 80.0% (32/40) and a specificity of 57.9% (168/290) with a cut-off point of SWV ≥2.15 m/s. When ARFI-induced SE and p-SWE were combined, set 3 had the highest sensitivity (92.5%, 37/40) while set 4 had the highest specificity (95.2%, 276/290). Conclusion: ARFI elastography can be used for differential diagnosis of malignant thyroid nodules without highly suspicious features on US. The combination of ARFI-induced SE and p-SWE leads to improved sensitivity and specificity. PMID:26629025

  9. 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

  10. Acoustic Radiation Force Impulse Elastography: A Useful Tool for Differential Diagnosis of Thyroid Nodules and Recommending Fine-Needle Aspiration

    PubMed Central

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

    2015-01-01

    Abstract To investigate the diagnostic performance of combined use of conventional ultrasound (US) and elastography, including conventional strain elastography such as elasticity imaging (EI) and acoustic radiation force impulse (ARFI) elastography, and to evaluate their usefulness in recommending fine-needle aspiration (FNA). A total of 556 pathologically proven thyroid nodules were evaluated by US, EI, and ARFI examinations in this study. Three blinded readers scored the likelihood of malignancy for 4 datasets (ie, US alone, US and EI, US and virtual touch tissue imaging [VTI], and US and virtual touch tissue quantification [VTQ]). The diagnostic performances of 4 datasets in differentiating malignant from benign thyroid nodules were evaluated. The decision-making changes for FNA recommendation in the indeterminate nodules or the probably benign nodules on conventional US were evaluated after review of elastography. The diagnostic performance in terms of area under the ROC curve did not show any change after adding EI, VTI, or VTQ for analysis; and no differences were found among different readers; however, the specificity and positive predictive value (PPV) improved significantly after adding VTI or VTQ for analysis in the senior reader. For the indeterminate nodules on US that were pathologically benign, VTQ made correct decision-making changes from FNA biopsy to follow-up in a mean of 82.6% nodules, which was significantly higher than those achieved by EI (46.8%) and VTI (54.4%) (both P < 0.05). With regard to the probably benign nodules on US that were pathologically malignant, EI made the highest correct decision-making change from follow-up to FNA biopsy in a mean of 62.6% nodules (compared with 41.5% on VTQ, P < 0.05). The results indicated that ARFI increases the specificity and PPV in diagnosing thyroid nodules. US combined VTQ might be helpful in reducing unnecessary FNA for indeterminate nodules on US whereas US combined EI is useful to detect

  11. A Novel Model to Predict Esophageal Varices in Patients with Compensated Cirrhosis Using Acoustic Radiation Force Impulse Elastography

    PubMed Central

    Park, Yehyun; Kim, Seung Up; Park, Soo Young; Kim, Beom Kyung; Park, Jun Yong; Kim, Do Young; Ahn, Sang Hoon; Tak, Won Young; Kweon, Young Oh; Han, Kwang-Hyub

    2015-01-01

    Background & Aims Few noninvasive methods can accurately identify esophageal varices (EVs) in patients with compensated cirrhosis. We developed and validated a novel, acoustic radiation force impulse (ARFI) elastography-based prediction model for high-risk EVs (HEVs) in patients with compensated cirrhosis. Methods A total of 143 patients with compensated cirrhosis between February, 2010 and February, 2013 (training set) and 148 between June, 2010 and May, 2013 (validation set) who underwent ARFI elastography and endoscopy were prospectively recruited. Independent predictors of HEVs were used to construct a prediction model. Results Based on multivariate analysis, we developed two new statistical models, a varices risk score and ARFI-spleen diameter-to-platelet ratio score (ASPS), the latter of which was calculated as ARFI velocity × spleen diameter/platelet count. The area under receiver operating characteristic curve (AUROC) of the varices risk score and ASPS to predict HEVs were 0.935 (95% confidence interval [CI] 0.882–0.970) and 0.946 (95% CI 0.895–0.977), respectively. When ASPS, a simpler model with a higher AUROC, was applied in the validation set, acceptable diagnostic accuracy for HEVs was observed (AUROC = 0.814 [95% CI 0.743–0.885]). To detect HEVs, a negative predictive value of 98.3% was achieved at ASPS <2.83, whereas a positive predictive value of 100% was achieved at ASPS >5.28. Conclusions ASPS, a novel noninvasive ARFI-based prediction model, can accurately identify HEVs in patients with compensated cirrhosis. ASPS <2.83 may safely rule out the presence of HEVs, whereas patients with ASPS >5.28 should be considered for endoscopic examinations or appropriate prophylactic treatment. PMID:25826654

  12. 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.

  13. Kidney Shear Wave Speed Values in Subjects with and without Renal Pathology and Inter-Operator Reproducibility of Acoustic Radiation Force Impulse Elastography (ARFI) - Preliminary Results

    PubMed Central

    Bob, Flaviu; Bota, Simona; Sporea, Ioan; Sirli, Roxana; Petrica, Ligia; Schiller, Adalbert

    2014-01-01

    Aim to assess the inter-operator reproducibility of kidney shear wave speed, evaluated by means of Acoustic Radiation Force Impulse (ARFI) elastography, and the factors which influence it. Methods Our prospective pilot study included 107 subjects with or without kidney pathology in which kidney shear wave speed was evaluated by means of ARFI elastography. Intraclass correlation coefficient (ICC) was used to assess ARFI elastography reproducibility. Results A strong agreement was obtained between kidney shear wave speed measurements obtained by the two operators: ICC = 0.71 (right kidney) and 0.69 (left kidney). Smaller ICCs were obtained in “healthy subjects”, as compared to patients with kidney diseases (0.68 vs. 0.75), in women as compared with men (0.59 vs. 0.78), in subjects younger than 50 years as compared with those aged at least 50 years (0.63 vs. 0.71), in obese as compared with normal weight and overweight subjects (0.36 vs. 0.66 and 0.78) and in case of measurements depth <4 cm or >6 cm as compared with those performed at a depth of 4–6 cm from the skin (0.32 and 0.60 vs. 0.81). Conclusion ARFI elastography is a reproducible method for kidney shear wave speed assessment. PMID:25426849

  14. Differentiation of benign and malignant focal liver lesions: value of virtual touch tissue quantification of acoustic radiation force impulse elastography.

    PubMed

    Guo, Le-Hang; Wang, Shu-Jun; Xu, Hui-Xiong; Sun, Li-Ping; Zhang, Yi-Feng; Xu, Jun-Mei; Wu, Jian; Fu, Hui-Jun; Xu, Xiao-Hong

    2015-03-01

    The purpose of this study was to investigate the value of virtual tissue quantification (VTQ) of acoustic radiation force impulse elastography for the differential diagnosis of benign and malignant focal liver lesions (FLLs). Thus, a total of 134 FLLs in 134 patients were included. VTQ measurement was performed for each lesion in which the shear wave velocity (SWV) was measured. The difference in SWV and SWV ratio of FLL to surrounding liver between malignant and benign FLLs was evaluated, and the cutoff value was investigated. Receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic performance. A total of 134 lesions including 55 (41.0%) malignant FLLs and 79 (59.0%) benign ones were analyzed. The SWV of malignant and benign FLLs was 2.95 ± 1.00 m/s and 1.69 ± 0.89 m/s, respectively. Significant difference in SWV was presented between malignant and benign FLLs (p < 0.001). The SWV ratio of each FLL to the surrounding liver parenchyma was 1.83 ± 1.32 for malignant and 1.26 ± 0.78 for benign FLLs (p < 0.001). The area under the ROC curve in distinguishing malignant from benign lesions was 0.824 for SWV and 0.660 for SWV ratio. The cutoff value for differential diagnosis was 2.13 m/s for SWV and 1.37 for SWV ratio. The associated sensitivity and specificity were 83.3 and 77.9% for SWV and 59.6 and 77.3% for SWV ratio, respectively. In conclusion, VTQ provides quantitative stiffness information of FLLs and is helpful in the differential diagnosis between malignant and benign FLLs, particularly for the patients who are not candidates for contrast-enhanced imaging such as CT, MRI or contrast-enhanced ultrasound. PMID:25691297

  15. Acoustic Radiation Force Impulse Elastography: A Useful Tool for Differential Diagnosis of Thyroid Nodules and Recommending Fine-Needle Aspiration: A Diagnostic Accuracy Study.

    PubMed

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

    2015-10-01

    To investigate the diagnostic performance of combined use of conventional ultrasound (US) and elastography, including conventional strain elastography such as elasticity imaging (EI) and acoustic radiation force impulse (ARFI) elastography, and to evaluate their usefulness in recommending fine-needle aspiration (FNA).A total of 556 pathologically proven thyroid nodules were evaluated by US, EI, and ARFI examinations in this study. Three blinded readers scored the likelihood of malignancy for 4 datasets (ie, US alone, US and EI, US and virtual touch tissue imaging [VTI], and US and virtual touch tissue quantification [VTQ]). The diagnostic performances of 4 datasets in differentiating malignant from benign thyroid nodules were evaluated. The decision-making changes for FNA recommendation in the indeterminate nodules or the probably benign nodules on conventional US were evaluated after review of elastography.The diagnostic performance in terms of area under the ROC curve did not show any change after adding EI, VTI, or VTQ for analysis; and no differences were found among different readers; however, the specificity and positive predictive value (PPV) improved significantly after adding VTI or VTQ for analysis in the senior reader. For the indeterminate nodules on US that were pathologically benign, VTQ made correct decision-making changes from FNA biopsy to follow-up in a mean of 82.6% nodules, which was significantly higher than those achieved by EI (46.8%) and VTI (54.4%) (both P < 0.05). With regard to the probably benign nodules on US that were pathologically malignant, EI made the highest correct decision-making change from follow-up to FNA biopsy in a mean of 62.6% nodules (compared with 41.5% on VTQ, P < 0.05).The results indicated that ARFI increases the specificity and PPV in diagnosing thyroid nodules. US combined VTQ might be helpful in reducing unnecessary FNA for indeterminate nodules on US whereas US combined EI is useful to detect the false negative

  16. Head-to-Head Comparison between Collagen Proportionate Area and Acoustic Radiation Force Impulse Elastography in Liver Fibrosis Quantification in Chronic Hepatitis C

    PubMed Central

    Chen, Sheng-Hung; Peng, Cheng-Yuan; Lai, Hsueh-Chou; Chang, I-Ping; Lee, Chiung-Ju; Su, Wen-Pang; Lin, Chia-Hsin; Kao, Jung-Ta; Chuang, Po-Heng

    2015-01-01

    Background The aim of this study was to compare the diagnostic performances of the collagen proportionate area (CPA) and liver stiffness measurement (LSM) for liver fibrosis quantification in chronic hepatitis C (CHC). Methods A total of 137 eligible consecutive Taiwanese patients (74 women and 63 men; age 21–80 years; median age 54 years), with CHC underwent LSM by using acoustic radiation force impulse (ARFI) elastography and an immediate percutaneous liver biopsy for METAVIR scoring. Liver tissue sections were stained using picrosirius red. Areas of the stained collagen and the tissue parenchyma were calculated in pixels. The ratio between the two areas was expressed as a CPA percentage. The result of LSM was presented as shear wave velocity (SWV). Results METAVIR fibrosis (F) stages were dichotomized using the CPA (%) and SWV (m/s), and the optimal cut-off values were 7.47 and 1.59 for F1 versus F2–4; 12.56 and 1.73 for F1, 2 versus F3, 4; 15.32 and 1.96 for F1–3 versus F4. To dichotomize F1 versus F2–4, the areas under receiver operating characteristic curves for the CPA was 0.9349 (95% confidence interval: 0.8943–0.9755) and for SWV was 0.8434 (0.7762–0.9105) (CPA versus SWV, P = 0.0063). For F1, 2 versus F3, 4, the CPA was 0.9436 (0.9091–0.9781); SWV was 0.8997 (0.8444–0.9551) (P = 0.1587). For F1–3 versus F4, the CPA was 0.8647 (0.7944–0.9349); SWV was 0.9036 (0.8499–0.9573) (P = 0.2585). The CPA could be predicted in a linear regression formula by using SWV and platelet count (R2 = 0.524). Conclusions The CPA and ARFI elastography are promising tools for liver fibrosis evaluation. The CPA was superior to ARFI elastography in the diagnosis of significant fibrosis (≥ F2). The CPA may be independent of severe necroinflammation, which may augment liver stiffness. PMID:26461105

  17. A Risk Model for Predicting Central Lymph Node Metastasis of Papillary Thyroid Microcarcinoma Including Conventional Ultrasound and Acoustic Radiation Force Impulse Elastography.

    PubMed

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

    2016-01-01

    The aim of this prospective study was to propose a new rating system using a risk model including conventional ultrasound (US) and acoustic radiation force impulse (ARFI) elastography for predicting central lymph node metastasis (LNM) in patients with papillary thyroid microcarcinoma (PTMC).A total of 252 patients with PTMCs were enrolled, who were preoperatively evaluated by US and ARFI elastography including virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ). Risk factors of independent variables for central LNM were analyzed by univariate and multivariate analyses. A multivariate analysis was performed to create a predicting model and rating system.Of the 252 patients, 72 (28.6%) had central LNMs. Multivariate analysis revealed that rare internal flow (odds ratio [OR]: 4.454), multiple suspicious foci on US (OR: 5.136), capsule involvement (OR: 20.632), and VTI area ratio (VAR) > 1 (OR: 5.621) were independent risk factors for central LNM. The final predicting model was obtained and the risk score (RS) was defined as 1.5 × (if rare internal flow) + 1.6 × (if multiple suspicious foci on US) + 1.7 × (if VAR > 1) + 3.0 × (if capsule involvement). The rating system was divided into 5 stages. Stage I, <1.5; Stage II, 1.5 to 3.0; Stage III, 3.1 to 4.7; Stage IV, 4.8 to 6.3; and Stage V, 6.4 to 7.8. The risk rates of central LNM were 3.4% (2/59) in Stage I, 13.3% (13/98) in Stage II, 54.2% (39/72) in Stage III, 72.2% (13/18) in Stage IV, and 100% (5/5) in Stage V (P < 0.001).The results indicated that rare internal flow, multiple suspicious foci, capsule involvement on US, and VAR > 1 on ARFI elastography are the risk factors for predicting central LNM. The risk model developed in the study clearly predicts the risk of central LNM in patients with PTMC and thus has a potential to avoid unnecessary central compartment node dissection. PMID:26817907

  18. Investigation of the effects of myocardial anisotropy for shear wave elastography using impulsive force and harmonic vibration

    NASA Astrophysics Data System (ADS)

    Urban, Matthew W.; Qiang, Bo; Song, Pengfei; Nenadic, Ivan Z.; Chen, Shigao; Greenleaf, James F.

    2016-01-01

    The myocardium is known to be an anisotropic medium where the muscle fiber orientation changes through the thickness of the wall. Shear wave elastography methods use propagating waves which are measured by ultrasound or magnetic resonance imaging (MRI) techniques to characterize the mechanical properties of various tissues. Ultrasound- or MR-based methods have been used and the excitation frequency ranges for these various methods cover a large range from 24-500 Hz. Some of the ultrasound-based methods have been shown to be able to estimate the fiber direction. We constructed a model with layers of elastic, transversely isotropic materials that were oriented at different angles to simulate the heart wall in systole and diastole. We investigated the effect of frequency on the wave propagation and the estimation of fiber direction and wave speeds in the different layers of the assembled models. We found that waves propagating at low frequencies such as 30 or 50 Hz showed low sensitivity to the fiber direction but also had substantial bias in estimating the wave speeds in the layers. Using waves with higher frequency content (>200 Hz) allowed for more accurate fiber direction and wave speed estimation. These results have particular relevance for MR- and ultrasound-based elastography applications in the heart.

  19. Acoustic Radiation Force Impulse (ARFI) and Transient Elastography (TE) for evaluation of liver fibrosis in HIV-HCV co-infected patients

    PubMed Central

    2014-01-01

    Background Transient elastography (TE) is widely used for non-invasive assessment of liver fibrosis in HIV-HCV co-infected patients. TE, however, cannot determine liver morphology. Acoustic radiation force impulse (ARFI) imaging is a novel procedure enabling assessment of liver fibrosis during a conventional ultrasonographic examination. This study evaluated the correlation between liver fibrosis measurements by TE and ARFI. Methods Each of 46 HIV-HCV patients underwent both ARFI and TE within 6 months. Patients were evaluated by the “equivalent METAVIR” scoring system, using previously established cut-off values. Agreements between the ARFI and TE scores were estimated by Kappa coefficients, with Kappa values ≥0.40, ≥0.60, and ≥0.80 defined as moderate, good and very good agreement, respectively. Results ARFI and TE yielded "Equivalent Metavir" fibrosis scores of F1 in 26 and 31 patients, respectively; F2 in nine and seven, respectively; F3 in three and two, respectively; and F4 in eight and six, respectively. The two methods showed very good agreement in predicting overall stages [Kappa = 0.82] and for F ≥3 [Kappa = 0.80] and moderate agreement in predicting significant fibrosis F ≥2 [Kappa = 0.50]. Morphologic ultrasound analysis concomitant to ARFI detected two hepatocarcinomas. Conclusions ARFI showed promising results in the non-invasive assessment of liver fibrosis in HIV-HCV patients, with liver fibrosis staging similar to that of TE. Moreover, ARFI can assess morphology and fibrosis during the same session. PMID:25041708

  20. Evaluation of Transient Elastography, Acoustic Radiation Force Impulse Imaging (ARFI), and Enhanced Liver Function (ELF) Score for Detection of Fibrosis in Morbidly Obese Patients

    PubMed Central

    Karlas, Thomas; Dietrich, Arne; Peter, Veronica; Wittekind, Christian; Lichtinghagen, Ralf; Garnov, Nikita; Linder, Nicolas; Schaudinn, Alexander; Busse, Harald; Prettin, Christiane; Keim, Volker; Tröltzsch, Michael; Schütz, Tatjana; Wiegand, Johannes

    2015-01-01

    Background Liver fibrosis induced by non-alcoholic fatty liver disease causes peri-interventional complications in morbidly obese patients. We determined the performance of transient elastography (TE), acoustic radiation force impulse (ARFI) imaging, and enhanced liver fibrosis (ELF) score for fibrosis detection in bariatric patients. Patients and Methods 41 patients (median BMI 47 kg/m2) underwent 14-day low-energy diets to improve conditions prior to bariatric surgery (day 0). TE (M and XL probe), ARFI, and ELF score were performed on days -15 and -1 and compared with intraoperative liver biopsies (NAS staging). Results Valid TE and ARFI results at day -15 and -1 were obtained in 49%/88% and 51%/90% of cases, respectively. High skin-to-liver-capsule distances correlated with invalid TE measurements. Fibrosis of liver biopsies was staged as F1 and F3 in n = 40 and n = 1 individuals. However, variations (median/range at d-15/-1) of TE (4.6/2.6–75 and 6.7/2.9–21.3 kPa) and ARFI (2.1/0.7–3.7 and 2.0/0.7–3.8 m/s) were high and associated with overestimation of fibrosis. The ELF score correctly classified 87.5% of patients. Conclusion In bariatric patients, performance of TE and ARFI was poor and did not improve after weight loss. The ELF score correctly classified the majority of cases and should be further evaluated. PMID:26528818

  1. Acoustic Radiation Force Impulse Elastography for the Non-Invasive Evaluation of Hepatic Fibrosis in Non-Alcoholic Fatty Liver Disease Patients: A Systematic Review & Meta-Analysis

    PubMed Central

    Liu, Haixia; Fu, Jing; Hong, Ruixia; Liu, Li; Li, Fang

    2015-01-01

    Background In order to better monitor non-alcoholic fatty liver disease (NAFLD) patients at higher risk for HCC, there is a need for non-invasive diagnostic approaches to screen for the presence of advanced fibrosis in these patients. The aim of this systematic review and meta-analysis will be to evaluate the diagnostic efficacy of ARFI elastography in detecting hepatic fibrosis in NAFLD patients. Methods Relevant studies were identified from systematic searches of several major electronic databases (PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials). The primary outcomes were the summary sensitivity, summary specificity, the diagnostic odds ratio, and the summary receiver operating characteristic curve (SROC) of ARFI elastography in detecting significant fibrosis (defined as 4>F≥2) in NAFLD patients. Study quality was assessed using the Quality Assessment of Studies of Diagnostic Accuracy included in Systematic Review (QUADAS-2). Results The summary sensitivity and specificity of ARFI in detecting significant fibrosis were 80.2% (95% confidence interval (CI): 0.758–0.842; p = 0.0000) and 85.2% (95% CI: 0.808–0.890), p = 0.1617), respectively. The pooled diagnostic odds ratio of ARFI in detecting significant fibrosis was 30.13 (95% CI: 12.08–75; chi-squared = 14.59, p = 0.0237). The area under the SROC curve (AUC) was 0.898 (standard error (SE): 0.031) with a Q* index of 0.830 (SE: 0.033). Conclusions ARFI elastography appears to be modestly accurate in detecting significant fibrosis in NAFLD patients. Future studies in this field should provide head-to-head comparisons of ARFI elastography versus other elastographic imaging modalities in NAFLD patients. PMID:26131717

  2. Acoustic radiation force impulse of the liver

    PubMed Central

    D’Onofrio, Mirko; Crosara, Stefano; De Robertis, Riccardo; Canestrini, Stefano; Demozzi, Emanuele; Gallotti, Anna; Pozzi Mucelli, Roberto

    2013-01-01

    Acoustic radiation force impulse (ARFI) imaging is a new and promising ultrasound-based diagnostic technique that, evaluating the wave propagation speed, allows the assessment of the tissue stiffness. ARFI is implemented in the ultrasound scanner. By short-duration acoustic radiation forces (less than 1 ms), localized displacements are generated in a selected region of interest not requiring any external compression so reducing the operator dependency. The generated wave scan provides qualitative or quantitative (wave velocity values) responses. Several non-invasive methods for assessing the staging of fibrosis are used, in order to avoid liver biopsy. Liver function tests and transient elastography are non-invasive, sensitive and accurate tools for the assessment of liver fibrosis and for the discrimination between cirrhotic and non-cirrhotic liver. Many published studies analyse ARFI performance and feasibility in studying diffuse liver diseases and compare them to other diagnostic imaging modalities such as conventional ultrasonography and transient elastography. Solid focal liver lesions, both benign and malignant, are common findings during abdominal examinations. The accurate characterization and differential diagnosis are important aims of all the imaging modalities available today. Only few papers describe the application of ARFI technology in the study of solid focal liver lesions, with different results. In the present study, the existing literature, to the best of our knowledge, about ARFI application on diffuse and focal liver pathology has been evaluated and results and statistical analyses have been compared, bringing to the conclusion that ARFI can be used in the study of the liver with similar accuracy as transient elastography in diagnosing significant fibrosis or cirrhosis and has got some advantages in respect to transient elastography since it does not require separate equipment, better displays anatomical structures and measurements can be

  3. Lorentz force megahertz optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Wu, Chen; Singh, Manmohan; Han, Zhaolong; Raghunathan, Raksha; Liu, Chih-Hao; Li, Jiasong; Schill, Alexander; Larin, Kirill V.

    2016-03-01

    Optical Coherence Elastography (OCE) is a rapidly developing technique for assessing tissue biomechanical properties. This study demonstrates the first use of the Lorentz force to induce elastic waves within tissue to quantify the elasticity of tissue in combination with a phase-sensitive OCE system at ~1.5 million A-scans per second. The feasibility of this technique was tested on tissue-mimicking agar phantoms of various concentrations. The results as assessed by OCE were in good agreement with standard mechanical testing of the samples. After the preliminary experiments, the stiffness of porcine liver was examined. The results demonstrate that Lorentz force MHz OCE can be applied to study the elasticity of biological tissue effectively and has the potential for clinical applications due to rapid excitation and imaging.

  4. [Radiology Update Ultrasound Elastography – Quintessence for the Primary Care Physician].

    PubMed

    Franckenberg, Sabine; Gubler, Christoph; Frauenfelder, Thomas; Rominger, Marga

    2016-02-01

    Ultrasound elastography visualizes and measures elasticity of tissue. Depending on the methods there are four types of elastography: strain elastography (SE), transient elastography (TE), acoustic radiation force impulse imaging (ARFI) and shear wave elastography (SWE). Due to the fact that pathological changes in the tissue in most of the cases mean a lower elasticity, ultrasound elastography is able to diagnose diseases such as liver fibrosis, liver cirrhosis, to help in the diagnosis of suspicious lesions in mamma, prostate and thyroid gland. So far, ultrasound elastography is not yet able to replace other standardized diagnostic tools but can add valuable diagnostic information. PMID:26837322

  5. Testicular microlithiasis and preliminary experience of acoustic radiation force impulse imaging

    PubMed Central

    Osther, Palle Jørn Sloth; Rafaelsen, Søren Rafael

    2016-01-01

    Background Elastography of the testis can be used as a part of multiparametric examination of the scrotum. Purpose To determine the testicular stiffness using acoustic radiation force impulse imaging (ARFI) technique in men with testicular microlithiasis (TML). Material and Methods In 2013, 12 patients with diagnosed testicular microlithiasis in 2008 (mean age, 51 years; age range, 25–76 years) underwent a 5-year follow-up B-mode ultrasonography with three ARFI elastography measurements of each testis. We used a Siemens Acuson S3000 machine. Results No malignancy was found at the 5-year follow-up B-mode and elastography in 2013. However, we found an increase in TML; in the previous ultrasonography in 2008, eight men had bilateral TML, whereas in 2013, 10 men were diagnosed with bilateral TML. The mean elasticity of testicles with TML was 0.82 m/s (interquartile range [IQR], 0.72–0.88 m/s; range, 65–1.08 m/s). Conclusion Elastography velocity of testis with TML seems to be in the same velocity range as in men with normal testis tissue. PMID:27504193

  6. 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

  7. Elastography for Muscle Biomechanics: Toward the Estimation of Individual Muscle Force.

    PubMed

    Hug, François; Tucker, Kylie; Gennisson, Jean-Luc; Tanter, Mickaël; Nordez, Antoine

    2015-07-01

    Estimation of individual muscle force remains one of the main challenges in biomechanics. This review presents a series of experiments that used ultrasound shear wave elastography to support the hypothesis that muscle stiffness is linearly related to both active and passive muscle forces. Examples of studies that used measurement of muscle stiffness to estimate changes in muscle force are presented. PMID:25906424

  8. Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

    SciTech Connect

    Qi, Wenjuan; Li, Rui; Ma, Teng; Kirk Shung, K.; Zhou, Qifa; Chen, Zhongping

    2014-03-24

    We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.

  9. Breast Elastography: How We Do It.

    PubMed

    Gkali, Christina A; Chalazonitis, Athanasios N; Feida, Eleni; Sotiropoulou, Maria; Giannos, Aris; Tsigginou, Alexandra; Dimitrakakis, Constantine

    2015-12-01

    In recent years, the use of elastography in addition to sonography has become a routine clinical tool for the characterization of breast masses. Studies have investigated the improvement of specificity in differentiating benign from malignant breast masses. Therefore, additional use of elastography could help reduce the number of unnecessary biopsies in benign breast lesions especially in category IV lesions of the ultrasound breast imaging reporting data system. Ultrasound elastography is a cheap, readily available, useful, quick, noninvasive method, but it needs specific training as well as acknowledging technical and pathological factors, which may influence it. Both strain and acoustic radiation force impulse (ARFI) methods have been evaluated in breast lesions. Whereas strain elastography results in qualitative imaging of tissue stiffness due to induced compression, ARFI elastography displays quantitative and qualitative information of tissue displacement. A standardized imaging protocol is essential for an adequate and effective examination, also helping reduce the dependence from operators. Furthermore, knowledge of pitfalls that can be encountered when ultrasound elastography is performed may help avoid erroneous image interpretation. In this article, we describe a practical examination protocol for both strain and ARFI elastography and demonstrate the elastographic imaging findings in benign and malignant breast lesions. Short video clips displaying the technique are included as supplementary material. PMID:26327432

  10. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Bradway, David Pierson

    This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal

  11. Magnetic force Optical Coherence Elastography at 1.5 million a-lines per second

    NASA Astrophysics Data System (ADS)

    Wu, Chen; Han, Zhaolong; Singh, Manmohan; Liu, Chih-Hao; Li, Jiasong; Schill, Alexander; Raghunathan, Raksha; Larin, Kirill V.

    2016-03-01

    Optical Coherence Elastography (OCE) has been widely used to characterize tissue elasticity. In this paper we introduce a new excitation method using magnetic force to induce shear waves in phantoms and tissues. The shear waves were imaged using an Optical Coherence Tomography system with an A-scan rate of ~1.5 million a-lines per second and the speed of the waves were used to quantify elasticity of different concentrations of agar sampled and porcine liver. The OCE results acquired from this magnetic force excitation were compared with the mechanical compressional tests for validation. The results showed that magnetic force OCE and mechanical testing results were in good agreement, demonstrating the ability of magnetic force OCE to accurately quantify the Young's modulus of tissue.

  12. Weakly nonlinear analysis of impulsively-forced Faraday waves.

    PubMed

    Catllá, Anne; Porter, Jeff; Silber, Mary

    2005-11-01

    Parametrically-excited surface waves, forced by a repeating sequence of delta-function impulses, are considered within the framework of the Zhang-Viñals model [W. Zhang and J. Viñals, J. Fluid Mech. 336, 301 (1997)]. With impulsive forcing, the linear stability analysis can be carried out exactly and leads to an implicit equation for the neutral stability curves. As noted previously [J. Bechhoefer and B. Johnson, Am. J. Phys. 64, 1482 (1996)], in the simplest case of N=2 equally-spaced impulses per period (which alternate up and down) there are only subharmonic modes of instability. The familiar situation of alternating subharmonic and harmonic resonance tongues emerges only if an asymmetry in the spacing between the impulses is introduced. We extend the linear analysis for N=2 impulses per period to the weakly nonlinear regime, where we determine the leading order nonlinear saturation of one-dimensional standing waves as a function of forcing strength. Specifically, an analytic expression for the cubic Landau coefficient in the bifurcation equation is derived as a function of the dimensionless spacing between the two impulses and the fluid parameters that appear in the Zhang-Viñals model. As the capillary parameter is varied, one finds a parameter regime of wave amplitude suppression, which is due to a familiar 1:2 spatiotemporal resonance between the subharmonic mode of instability and a damped harmonic mode. This resonance occurs for impulsive forcing even when harmonic resonance tongues are absent from the neutral stability curves. The strength of this resonance feature can be tuned by varying the spacing between the impulses. This finding is interpreted in terms of a recent symmetry-based analysis of multifrequency forced Faraday waves [J. Porter, C. M. Topaz, and M. Silber, Phys. Lett. 93, 034502 (2004); C. M. Topaz, J. Porter, and M. Silber, Phys. Rev. E 70, 066206 (2004)]. PMID:16383732

  13. Impulsive Enzymes: A New Force in Mechanobiology

    PubMed Central

    Butler, Peter J.; Dey, Krishna K.; Sen, Ayusman

    2015-01-01

    We review studies that quantify newly discovered forces from single enzymatic reactions. These forces arise from the conversion of chemical energy to kinetic energy, which can be harnessed to direct diffusion of the enzyme up a concentration gradient of substrate, a novel phenomenon of molecular chemotaxis. When immobilized, enzymes can move fluid around them and perform directional pumping in microfluidic chambers. Because of the extensive array of enzymes in biological cells, we also develop three new hypotheses: that enzymatic self diffusion can assist in organizing signaling pathways in cells, can assist in pumping of fluid in cells, and can impose biologically significant forces on organelles, which will be manifested as stochastic motion not explained by thermal forces or myosin II. Such mechanochemical phenomena open up new directions in research in mechanobiology in which all enzymes, in addition to their primary function as catalysts for reactions, may have secondary functions as initiators of mechanosensitive transduction pathways. PMID:26019728

  14. Acoustic Radiation Force Impulse (ARFI) Imaging: a Review

    PubMed Central

    Nightingale, Kathy

    2012-01-01

    Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. PMID:22545033

  15. Multi-frame elastography using a handheld force-controlled ultrasound probe.

    PubMed

    Kuzmin, Andrey; Zakrzewski, Aaron M; Anthony, Brian W; Lempitsky, Victor

    2015-08-01

    We propose a new method for strain field estimation in quasi-static ultrasound elastography based on matching RF data frames of compressed tissues. The method benefits from using a handheld force-controlled ultrasound probe, which provides the contact force magnitude and therefore improves repeatability of displacement field estimation. The displacement field is estimated in a two-phase manner using triplets of RF data frames consisting of a pre-compression image and two post-compression images obtained with lower and higher compression ratios. First, a reliable displacement field estimate is calculated for the first post-compression frame. Second, we use this displacement estimate to warp the second post-compression frame while using linear elasticity to obtain an initial approximation. Final displacement estimation is refined using the warped image. The two-phase displacement estimation allows for higher compression ratios, thus increasing the practical resolution of the strain estimates. The strain field is computed from a displacement field using a smoothness- regularized energy functional, which takes into consideration local displacement estimation quality. The minimization is performed using an efficient primal-dual hybrid gradient algorithm, which can leverage the architecture of a graphical processing unit. The method is quantitatively evaluated using finite element simulations. We compute strain estimates for tissue-mimicking phantoms with known elastic properties and finally perform a qualitative validation using in vivo patient data. PMID:26276958

  16. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    PubMed Central

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O’Donnell, Matthew

    2015-01-01

    Abstract. Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6). PMID:25554970

  17. Acoustic radiation force impulse imaging for assessing liver fibrosis in alcoholic liver disease

    PubMed Central

    Kiani, Anita; Brun, Vanessa; Lainé, Fabrice; Turlin, Bruno; Morcet, Jeff; Michalak, Sophie; Le Gruyer, Antonia; Legros, Ludivine; Bardou-Jacquet, Edouard; Gandon, Yves; Moirand, Romain

    2016-01-01

    AIM: To evaluate the performance of elastography by ultrasound with acoustic radiation force impulse (ARFI) in determining fibrosis stage in patients with alcoholic liver disease (ALD) undergoing alcoholic detoxification in relation to biopsy. METHODS: Eighty-three patients with ALD undergoing detoxification were prospectively enrolled. Each patient underwent ARFI imaging and a liver biopsy on the same day. Fibrosis was staged according to the METAVIR scoring system. The median of 10 valid ARFI measurements was calculated for each patient. RESULTS: Sixty-nine males and thirteen females (one patient excluded due to insufficient biopsy size) were assessed with a mean alcohol consumption of 132.4 ± 128.8 standard drinks per week and mean cumulative year duration of 17.6 ± 9.5 years. Sensitivity and specificity were respectively 82.4% (0.70-0.95) and 83.3% (0.73-0.94) (AUROC = 0.87) for F ≥ 2 with a cut-off value of 1.63m/s; 82.4% (0.64-1.00) and 78.5% (0.69-0.89) (AUROC = 0.86) for F ≥ 3 with a cut-off value of 1.84m/s; and 92.3% (0.78-1.00] and 81.6% (0.72-0.90) (AUROC = 0.89) for F = 4 with a cut-off value of 1.94 m/s. CONCLUSION: ARFI is an accurate, non-invasive and easy method for assessing liver fibrosis in patients with ALD undergoing alcoholic detoxification. PMID:27239119

  18. The performance of acoustic radiation force impulse imaging in predicting liver fibrosis in chronic liver diseases.

    PubMed

    Lin, Yi-Hung; Yeh, Ming-Lun; Huang, Ching-I; Yang, Jeng-Fu; Liang, Po-Cheng; Huang, Chung-Feng; Dai, Chia-Yen; Lin, Zu-Yau; Chen, Shinn-Cherng; Huang, Jee-Fu; Yu, Ming-Lung; Chuang, Wan-Long

    2016-07-01

    Sonography-based noninvasive liver fibrosis assessment is promising in the prediction of treatment efficacy and prognosis in chronic liver disease (CLD) patients. Acoustic radiation force impulse imaging (ARFI) is a newly-developed transient elastography (TE) method integrated into a conventional ultrasound machine. The study aimed to assess the performance of ARFI imaging in the diagnosis of liver fibrosis in Taiwanese CLD patients. We also aimed to search for the optimal cut-off values in different fibrosis stages. A total of 60 CLD patients (40 males; mean age, 51.8±11 years) were consecutively included. They received standard ARFI measurement within 2 weeks at the time of liver biopsy. There were eight patients with Metavir fibrosis stage 0 (F0), 16 patients with F1, 20 patients with F2, eight patients with F3, and eight patients with F4, respectively. The mean values among patient with F0, F1, F2, F3, and F4 were 1.17±0.13, 1.30±0.17, 1.31±0.24, 2.01±0.45, and 2.69±0.91, respectively (p<0.001). The optimal cut-off ARFI value for significant fibrosis (F≥2) was 1.53 with the accuracy of 0.733, while it was 1.66 for advanced fibrosis (F≥3) with the accuracy of 0.957. Our study demonstrated that ARFI imaging is competent for fibrosis diagnosis, particularly in CLD patients with advanced fibrosis. PMID:27450025

  19. Interval oscillation criteria for second-order forced impulsive delay differential equations with damping term.

    PubMed

    Thandapani, Ethiraju; Kannan, Manju; Pinelas, Sandra

    2016-01-01

    In this paper, we present some sufficient conditions for the oscillation of all solutions of a second order forced impulsive delay differential equation with damping term. Three factors-impulse, delay and damping that affect the interval qualitative properties of solutions of equations are taken into account together. The results obtained in this paper extend and generalize some of the the known results for forced impulsive differential equations. An example is provided to illustrate the main result. PMID:27218008

  20. Transient Elastography for Assessment of Liver Fibrosis and Steatosis: An Evidence-Based Analysis

    PubMed Central

    Brener, S

    2015-01-01

    Background Liver fibrosis is a sign of advanced liver disease and is often an indication for treatment. The current standard for diagnosing liver fibrosis and steatosis is biopsy, but noninvasive alternatives are available; one of the most common is transient elastography (FibroScan). Objectives The objective of this analysis was to assess the diagnostic accuracy and clinical utility of transient elastography alone for liver fibrosis and with controlled attenuation parameter (CAP) for steatosis in patients with hepatitis C virus, hepatitis B virus, nonalcoholic fatty liver disease, alcoholic liver disease, or cholestatic diseases. The analysis also aimed to compare the diagnostic accuracy of transient elastography with two alternative noninvasive technologies: FibroTest and acoustic force radiation impulse (ARFI). Data Sources Ovid MEDLINE, Ovid MEDLINE In-Process, Ovid Embase, and all EBM databases were searched for all studies published prior to October 2, 2014. Review Methods An overview of reviews was conducted using a systematic search and assessment approach. The results of the included systematic reviews were summarized, analyzed, and reported for outcomes related to diagnostic accuracy and clinical utility as a measure of impact on diagnoses, therapeutic decisions, and patient outcomes. Results Fourteen systematic reviews were included, summarizing more than 150 studies. The reviews demonstrated that transient elastography (with or without CAP) has good diagnostic accuracy compared to biopsy for the assessment of liver fibrosis and steatosis. Acoustic force radiation impulse and FibroTest were not superior to transient elastography. Limitations None of the included systematic reviews reported on the clinical utility of transient elastography. Conclusions Transient elastography (with or without CAP) offers a noninvasive alternative to biopsy for the assessment of liver fibrosis and steatosis, given its comparable diagnostic accuracy. PMID:26664664

  1. Acoustic Radiation Force Impulse (ARFI) Imaging-Based Needle Visualization

    PubMed Central

    Rotemberg, Veronica; Palmeri, Mark; Rosenzweig, Stephen; Grant, Stuart; Macleod, David; Nightingale, Kathryn

    2011-01-01

    Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARFI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18, 21 and 25 gauge needles between 0–4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10° and 35° from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm off set in elevation from the transducer imaging plane and on-axis angled needles between 10°–35° above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications. PMID:21608445

  2. Prediction of Renal Allograft Acute Rejection Using a Novel Non-Invasive Model Based on Acoustic Radiation Force Impulse.

    PubMed

    Yang, Cheng; Jin, Yunjie; Wu, Shengdi; Li, Long; Hu, Mushuang; Xu, Ming; Rong, Ruiming; Zhu, Tongyu; He, Wanyuan

    2016-09-01

    Point shear wave elastography based on acoustic radiation force impulse is a novel technology used to quantify tissue stiffness by measuring shear wave speed. A total of 115 kidney transplantation recipients were consecutively enrolled in this prospective study. The patients were subdivided into two groups using 1 mo post-transplantation as the cutoff time for determining the development of acute rejection (AR). Shear wave speed was significantly higher in the AR group than in the non-AR group. We created a model called SEV, comprising shear wave speed, estimated glomerular filtration rate and kidney volume change, that could successfully discriminate patients with or without AR. The area under the receiver operating characteristic curve of SEV was 0.89, which was higher than values for other variables; it was even better in patients within 1 mo post-transplantation (0.954), but was lower than the estimated glomerular filtration rate in patients after 1 mo post-transplantation. Therefore, the SEV model may predict AR after renal transplantation with a high degree of accuracy, and it may be more useful in the early post-operative stage after renal transplantation. PMID:27267289

  3. Identifying Vulnerable Plaques with Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Joshua Ryan

    The rupture of arterial plaques is the most common cause of ischemic complications including stroke, the fourth leading cause of death and number one cause of long term disability in the United States. Unfortunately, because conventional diagnostic tools fail to identify plaques that confer the highest risk, often a disabling stroke and/or sudden death is the first sign of disease. A diagnostic method capable of characterizing plaque vulnerability would likely enhance the predictive ability and ultimately the treatment of stroke before the onset of clinical events. This dissertation evaluates the hypothesis that Acoustic Radiation Force Impulse (ARFI) imaging can noninvasively identify lipid regions, that have been shown to increase a plaque's propensity to rupture, within carotid artery plaques in vivo. The work detailed herein describes development efforts and results from simulations and experiments that were performed to evaluate this hypothesis. To first demonstrate feasibility and evaluate potential safety concerns, finite- element method simulations are used to model the response of carotid artery plaques to an acoustic radiation force excitation. Lipid pool visualization is shown to vary as a function of lipid pool geometry and stiffness. A comparison of the resulting Von Mises stresses indicates that stresses induced by an ARFI excitation are three orders of magnitude lower than those induced by blood pressure. This thesis also presents the development of a novel pulse inversion harmonic tracking method to reduce clutter-imposed errors in ultrasound-based tissue displacement estimates. This method is validated in phantoms and was found to reduce bias and jitter displacement errors for a marked improvement in image quality in vivo. Lastly, this dissertation presents results from a preliminary in vivo study that compares ARFI imaging derived plaque stiffness with spatially registered composition determined by a Magnetic Resonance Imaging (MRI) gold standard

  4. Acoustic Radiation Force Impulse Measurement in Renal Transplantation

    PubMed Central

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-01-01

    Abstract Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = −0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW <3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥3.5 g/kg. No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  5. Liver reserve function assessment by acoustic radiation force impulse imaging

    PubMed Central

    Sun, Xiao-Lan; Liang, Li-Wei; Cao, Hui; Men, Qiong; Hou, Ke-Zhu; Chen, Zhen; Zhao, Ya-E

    2015-01-01

    AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors. METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy. RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively

  6. Impulsive events in the evolution of a forced nonlinear system

    SciTech Connect

    Longcope, D.W.; Sudan, R.N. )

    1992-03-16

    Long-time numerical solutions of a low-dimensional model of the reduced MHD equations show that, when this system is driven quasistatically, the response is punctuated by impulsive events. The statistics of these events indicate a Poisson process; the frequency of these events scales as {Delta}{ital E}{sub {ital M}}{sup {minus}1}, where {Delta}{ital E}{sub {ital M}} is the energy released in one event.

  7. Internal waves generated by unsteady impulsive forcing - numerical simulations

    NASA Astrophysics Data System (ADS)

    Paoletti, Matthew; Shipley, Kara; Brandt, Alan

    2014-11-01

    Numerical simulations of the generation of internal waves by an unsteady impulse are presented. While extensive work has examined the generation of internal waves by steady flow, such as winds over mountains, or periodic flow, an example being tidal flow over bathymetry, internal waves can also be generated by transient events like those produced by local instabilities. The studies presented here focus on the generation of internal waves by the release of a patch of miscible fluid of constant density into a stably stratified water column. The fluid descends owing to its initial momentum, spreads in the lateral direction, and vertically displaces the isopycnals, leading to the generation of internal waves. The transfer of energy from the impulse to the internal wave field is characterized by the energy flux of the radiated internal waves. While the impulse is initially axisymmetric, the effects of the three-dimensional nature of the turbulent evolution are examined by comparing the results of two-dimensional and three-dimensional numerical simulations. Supported by the Office of Navel Research.

  8. Quantitative optical coherence elastography based on fiber-optic probe with integrated Fabry-Perot force sensor

    NASA Astrophysics Data System (ADS)

    Qiu, Yi; Wang, Yahui; Xu, Yiqing; Chandra, Namas; Haorah, James; Hubbi, Basil; Pfister, Bryan J.; Liu, Xuan

    2016-03-01

    Optical coherence tomography (OCT) is a versatile imaging technique and has great potential in tissue characterization for breast cancer diagnosis and surgical guidance. In addition to structural difference, cancerous breast tissue is usually stiffer compared to normal adipose breast tissue. However, previous studies on compression optical coherence elastography (OCE) are qualitative rather than quantitative. It is challenging to identify the cancerous status of tissue based on qualitative OCE results obtained from different measurement sessions or from different patients. Therefore, it is critical to develop technique that integrates structural imaging and force sensing, for quantitative elasticity characterization of breast tissue. In this work, we demonstrate a quantitative OCE (qOCE) microsurgery device which simultaneously quantifies force exerted to tissue and measures the resultant tissue deformation. The qOCE system is based on a spectral domain OCT engine operated at 1300 nm and a probe with an integrated Febry-Perot (FP) interferometric cavity at its distal end. The FP cavity is formed by the cleaved end of the lead-in fiber and the end surface of a GRIN lens which allows light to incident into tissue for structural imaging. The force exerted to tissue is quantified by the change of FP cavity length which is interrogated by a fiber-optic common-paths phase resolved OCT system with sub-nanometer sensitivity. Simultaneously, image of the tissue structure is acquired from photons returned from tissue through the GRIN lens. Tissue deformation is obtained through Doppler analysis. Tissue elasticity can be quantified by comparing the force exerted and tissue deformation.

  9. 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.

  10. Miniature probe for mechanical properties of vascular lesions using acoustic radiation force optical coherence elastography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Qu, Yueqiao; Ma, Teng; He, Youmin; Yu, Mingyue; Li, Rui; Zhu, Jiang; Dai, Cuixia; Piao, Zhonglie; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

    2016-03-01

    Changes in tissue biomechanical properties often signify the onset and progression of diseases, such as in determining the vulnerability of atherosclerotic plaques. Acoustic radiation force optical coherence elastography (ARF-OCE) has been used in the detection of tissue elasticity to obtain high-resolution elasticity maps. We have developed a probe-based ARF-OCE technology that utilizes a miniature 10 MHz ring ultrasonic transducer for excitation and Doppler optical coherence tomography (OCT) for detection. The transducer has a small hole in the center for the OCT light to propagate through. This allows for a confocal stress field and light detection within a small region for high sensitivity and localized excitation. This device is a front-facing probe that is only 3.5 mm in diameter and it is the smallest ARF-OCE catheter to the best of our knowledge. We have tested the feasibility of the probe by measuring the point displacement of an agarose tissue-mimicking phantom using different ARF excitation voltages. Small displacement values ranging from 30 nm to 90 nm have been detected and are shown to be directly proportional to the excitation voltage as expected. We are currently working on obtaining 2D images using a scanning mechanism. We will be testing to capture 2D elastograms of phantoms to further verify feasibility, and eventually characterize the mechanical properties of cardiovascular tissue. With its high portability and sensitivity, this novel technology can be applied to the diagnosis and characterization of vulnerable atherosclerotic plaques.

  11. 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

  12. Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results.

    PubMed

    Shih, Cho-Chiang; Lai, Ting-Yu; Huang, Chih-Chung

    2016-08-01

    The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI-IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm(2), as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm(2) was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI-IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the

  13. [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. PMID:26976058

  14. The role of impulse parameters in force variability

    NASA Technical Reports Server (NTRS)

    Carlton, L. G.; Newell, K. M.

    1986-01-01

    One of the principle limitations of the human motor system is the ability to produce consistent motor responses. When asked to repeatedly make the same movement, performance outcomes are characterized by a considerable amount of variability. This occurs whether variability is expressed in terms of kinetics or kinematics. Variability in performance is of considerable importance because for tasks requiring accuracy it is a critical variable in determining the skill of the performer. What has long been sought is a description of the parameter or parameters that determine the degree of variability. Two general experimental protocals were used. One protocal is to use dynamic actions and record variability in kinematic parameters such as spatial or temporal error. A second strategy was to use isometric actions and record kinetic variables such as peak force produced. What might be the important force related factors affecting variability is examined and an experimental approach to examine the influence of each of these variables is provided.

  15. Flexural waves induced by electro-impulse deicing forces

    NASA Technical Reports Server (NTRS)

    Gien, P. H.

    1990-01-01

    The generation, reflection and propagation of flexural waves created by electroimpulsive deicing forces are demonstrated both experimentally and analytically in a thin circular plate and a thin semicylindrical shell. Analytical prediction of these waves with finite element models shows good correlation with acceleration and displacement measurements at discrete points on the structures studied. However, sensitivity to spurious flexural waves resulting from the spatial discretization of the structures is shown to be significant. Consideration is also given to composite structures as an extension of these studies.

  16. Bubble mass center and fluid feedback force fluctuations activated by constant lateral impulse with variable thrust

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Long, Y. T.

    1995-01-01

    Sloshing dynamics within a partially filled rotating dewar of superfluid helium 2 are investigated in response to constant lateral impulse with variable thrust. The study, including how the rotating bubble of superfluid helium 2 reacts to the constant impulse with variable time period of thrust action in microgravity, how amplitudes of bubble mass center fluctuates with growth and decay of disturbances, and how fluid feedback forces fluctuates in activating on the rotating dewar through the dynamics of sloshing waves are investigated. The numerical computation of sloshing dynamics is based on the non-inertial frame spacecraft bound coordinate with lateral impulses actuating on the rotating dewar in both inertial and non-inertial frames of thrust. Results of the simulations are illustrated.

  17. Unexpectedly Strong Lorentz-Force Impulse Observed During a Solar Eruption

    NASA Astrophysics Data System (ADS)

    Sun, Xudong; Fisher, George H.; Torok, Tibor; Hoeksema, Jon Todd; Li, Yan; CGEM Team

    2016-05-01

    For fast coronal mass ejections (CMEs), the acceleration phase takes place in the low corona; the momentum process is presumably dominated by the Lorentz force. Using ultra-high-cadence vector magnetic data from the Helioseismic and Magnetic Imager (HMI) and numerical simulations, we show that the observed fast-evolving photospheric field can be used to characterize the impulse of the Lorentz force during a CME. While the peak Lorentz force concurs with the maximum ejecta acceleration, the observed total force impulse surprisingly exceeds the CME momentum by over an order of magnitude. We conjecture that most of the Lorentz force impulse is "trapped" in the thin layer of the photosphere above the HMI line-formation height and is counter-balanced by gravity. This implies a consequent upward plasma motion which we coin "gentle photospheric upwelling". The unexpected effect dominates the momentum processes, but is negligible for the energy budget, suggesting a complex coupling between different layers of the solar atmosphere during CMEs.

  18. Introduction to ultrasound elastography.

    PubMed

    Nowicki, Andrzej; Dobruch-Sobczak, Katarzyna

    2016-06-01

    For centuries tissue palpation has been an important diagnostic tool. During palpation, tumors are felt as tissues harder than the surrounding tissues. The significance of palpation is related to the relationship between mechanical properties of different tissue lesions. The assessment of tissue stiffness through palpation is based on the fact that mechanical properties of tissues are changing as a result of various diseases. A higher tissue stiffness translates into a higher elasticity modulus. In the 90's, ultrasonography was extended by the option of examining the stiffness of tissue by estimating the difference in backscattering of ultrasound in compressed and non-compressed tissue. This modality is referred to as the static, compression elastography and is based on tracking the deformation of tissue subjected to the slowly varying compression through the recording of the backscattered echoes. The displacement is estimated using the methods of cross-correlation between consecutive ultrasonic lines of examined tissue, so calculating the degree of similarity of ultrasonic echoes acquired from tissue before and after the compression was applied. The next step in the development of ultrasound palpation was to apply the local remote tissue compression by using the acoustic radiation force generated through the special beam forming of the ultrasonic beam probing the tissue. The acoustic radiation force causes a slight deformation the tissue thereby forming a shear wave propagating in the tissue at different speeds dependent on the stiffness of the tissue. Shear wave elastography, carries great hopes in the field of quantitative imaging of tissue lesions. This article describes the physical basis of both elastographic methods: compression elastography and shear wave elastography. PMID:27446596

  19. Introduction to ultrasound elastography

    PubMed Central

    Dobruch-Sobczak, Katarzyna

    2016-01-01

    For centuries tissue palpation has been an important diagnostic tool. During palpation, tumors are felt as tissues harder than the surrounding tissues. The significance of palpation is related to the relationship between mechanical properties of different tissue lesions. The assessment of tissue stiffness through palpation is based on the fact that mechanical properties of tissues are changing as a result of various diseases. A higher tissue stiffness translates into a higher elasticity modulus. In the 90's, ultrasonography was extended by the option of examining the stiffness of tissue by estimating the difference in backscattering of ultrasound in compressed and non-compressed tissue. This modality is referred to as the static, compression elastography and is based on tracking the deformation of tissue subjected to the slowly varying compression through the recording of the backscattered echoes. The displacement is estimated using the methods of cross-correlation between consecutive ultrasonic lines of examined tissue, so calculating the degree of similarity of ultrasonic echoes acquired from tissue before and after the compression was applied. The next step in the development of ultrasound palpation was to apply the local remote tissue compression by using the acoustic radiation force generated through the special beam forming of the ultrasonic beam probing the tissue. The acoustic radiation force causes a slight deformation the tissue thereby forming a shear wave propagating in the tissue at different speeds dependent on the stiffness of the tissue. Shear wave elastography, carries great hopes in the field of quantitative imaging of tissue lesions. This article describes the physical basis of both elastographic methods: compression elastography and shear wave elastography. PMID:27446596

  20. Dynamical relations for left ventricular ejection - Flow rate, momentum, force and impulse

    NASA Technical Reports Server (NTRS)

    Back, L. H.; Selzer, R. H.; Gordon, D. G.; Ledbetter, D. C.; Crawford, D. W.

    1984-01-01

    An investigation was carried out to quantitatively evaluate left ventricular volume flow rate, momentum, force and impulse derived from application of conservation principles for mass and momentum of blood within the ventricle during the ejection phase. An automated digital image processing system was developed and applied to left ventricular angiograms which are computer processed and analyzed frame by frame to determine the dynamical relations by numerical methods. The initial experience with force and impulse has indicated that neither quantity seemed to be a sensitive indicator of coronary artery disease as evaluated by qualitative angiography for the particular patient group studied. Utilization of the dynamical relations in evaluating human left ventricular performance requires improved means of measurement and interpretation of clinical studies.

  1. Image quality, tissue heating, and frame rate trade-offs in acoustic radiation force impulse imaging.

    PubMed

    Bouchard, Richard R; Dahl, Jeremy J; Hsu, Stephen J; Palmeri, Mark L; Trahey, Gregg E

    2009-01-01

    The real-time application of acoustic radiation force impulse (ARFI) imaging requires both short acquisition times for a single ARFI image and repeated acquisition of these frames. Due to the high energy of pulses required to generate appreciable radiation force, however, repeated acquisitions could result in substantial transducer face and tissue heating. We describe and evaluate several novel beam sequencing schemes which, along with parallel-receive acquisition, are designed to reduce acquisition time and heating. These techniques reduce the total number of radiation force impulses needed to generate an image and minimize the time between successive impulses. We present qualitative and quantitative analyses of the trade-offs in image quality resulting from the acquisition schemes. Results indicate that these techniques yield a significant improvement in frame rate with only moderate decreases in image quality. Tissue and transducer face heating resulting from these schemes is assessed through finite element method modeling and thermocouple measurements. Results indicate that heating issues can be mitigated by employing ARFI acquisition sequences that utilize the highest track-to-excitation ratio possible. PMID:19213633

  2. 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

  3. 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

  4. Using MBL To Verify Newton's Second Law and the Impulse-Momentum Relationship with an Arbitrary Changing Force.

    ERIC Educational Resources Information Center

    Trumper, Ricardo; Gelbman, Moshe

    2002-01-01

    Uses microcomputer-based laboratories (MBL) to teach Newton's second law and the impulse-momentum relationship with a high degree of precision and accuracy while applying forces that change in an arbitrary way. (YDS)

  5. Non-contact quantification of laser micro-impulse in water by atomic force microscopy and its application for biomechanics

    NASA Astrophysics Data System (ADS)

    Hosokawa, Yoichiroh

    2011-12-01

    We developed a local force measurement system of a femtosecond laser-induced impulsive force, which is due to shock and stress waves generated by focusing an intense femtosecond laser into water with a highly numerical aperture objective lens. In this system, the force localized in micron-sized region was detected by bending movement of a cantilever of atomic force microscope (AFM). Here we calculated the bending movement of the AFM cantilever when the femtosecond laser is focused in water at the vicinity of the cantilever and the impulsive force is loaded on the cantilever. From the result, a method to estimate the total of the impulsive force at the laser focal point was suggested and applied to estimate intercellular adhesion strength.

  6. 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.

  7. Acoustic Radiation Force Impulse Imaging: A New Tool for the Diagnosis of Papillary Thyroid Microcarcinoma

    PubMed Central

    Zhang, Yi-Feng; Xu, Jun-Mei; Zhang, Jing; Liu, Lin-Na; Xu, Xiao-Hong

    2014-01-01

    Purpose. To evaluate the diagnostic performance of ARFI imaging in differentiating between benign and malignant thyroid nodules <1 cm. Materials and Methods. 173 pathologically proven thyroid nodules (77 benign, 96 malignant) in 157 patients were included in this study. Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of conventional ultrasound (US) and ARFI imaging in papillary thyroid microcarcinoma (PTMC). The independent risk factors for predicting PTMC were evaluated. Results. The mean SWV value of benign and malignant thyroid nodules were 2.57 ± 0.79 m/s (range: 0.90–4.92 m/s) and 3.88 ± 2.24 m/s (range: 1.49–9.00 m/s) (P = 0.000). Az for VTI elastography score was higher than that for hypoechoic, absence of halo sign, and type III vascularity (P < 0.05). The optimal cut-offs for VTI elastography score and SWV were score 4 and 3.10 m/s. Gender, hypoechoic, taller than wide, VTI elastography score ≥ 4, and SWV > 3.10 m/s had been found to be independent risk factors for predicting PTMC. Conclusion. ARFI elastography can provide elasticity information of PTMC quantitatively (VTQ) and directly reflects the overall elastic properties (VTI). Gender, hypoechogenicity, taller than wide, VTI elastography score ≥ 4, and SWV > 3.10 m/s are independent risk factors for predicting PTMC. ARFI elastography seems to be a new tool for the diagnosis of PTMC. PMID:25045673

  8. Ultrasound elastography: principles, techniques, and clinical applications.

    PubMed

    Dewall, Ryan J

    2013-01-01

    Ultrasound elastography is an emerging set of imaging modalities used to image tissue elasticity and are often referred to as virtual palpation. These techniques have proven effective in detecting and assessing many different pathologies, because tissue mechanical changes often correlate with tissue pathological changes. This article reviews the principles of ultrasound elastography, many of the ultrasound-based techniques, and popular clinical applications. Originally, elastography was a technique that imaged tissue strain by comparing pre- and postcompression ultrasound images. However, new techniques have been developed that use different excitation methods such as external vibration or acoustic radiation force. Some techniques track transient phenomena such as shear waves to quantitatively measure tissue elasticity. Clinical use of elastography is increasing, with applications including lesion detection and classification, fibrosis staging, treatment monitoring, vascular imaging, and musculoskeletal applications. PMID:23510006

  9. Analysis of Dragonfly Take-off Mechanism: Initial Impulse Generated by Aerodynamic Forces

    NASA Astrophysics Data System (ADS)

    Zhu, Ruijie; Bode-Oke, Ayodeji; Ren, Yan; Dong, Haibo; Flow Simulation Research Team

    2013-11-01

    Take-off is a critical part of insect flight due to not only that every single flight initiates from take-off, but also that the take-off period, despite its short duration, accounts for a relatively large fraction of the total energy consumption. Thus, studying the mechanism of insect take-off will help to improve the design of Micro Air Vehicles (MAVs) in two major properties, the success rate and the energy efficiency of take-off. In this work, we study 20 cases in which dragonflies (species including Pachydiplax longipennis, Epitheca Cynosura, Epitheca princeps etc.) take off from designed platform. By high-speed photogrammetry, 3-d reconstruction and numerical simulation, we explore how dragonflies coordinate different body parts to help take-off. We evaluate how aerodynamic forces generated by wing flapping create the initial impulse, and how these forces help save energy consumption. Supported by NSF CBET-1343154.

  10. On the Evolution of Pulsatile Flow Subject to a Transverse Impulse Body Force

    NASA Astrophysics Data System (ADS)

    di Labbio, Giuseppe; Keshavarz-Motamed, Zahra; Kadem, Lyes

    2014-11-01

    In the event of an unexpected abrupt traffic stop or car accident, automotive passengers will experience an abrupt body deceleration. This may lead to tearing or dissection of the aortic wall known as Blunt Traumatic Aortic Rupture (BTAR). BTAR is the second leading cause of death in automotive accidents and, although quite frequent, the mechanisms leading to BTAR are still not clearly identified, particularly the contribution of the flow field. As such, this work is intended to provide a fundamental framework for the investigation of the flow contribution to BTAR. In this fundamental study, pulsatile flow in a three-dimensional, straight pipe of circular cross-section is subjected to a unidirectional, transverse, impulse body force applied on a strictly bounded volume of fluid. These models were simulated using the Computational Fluid Dynamics (CFD) software FLUENT. The evolution of fluid field characteristics was investigated during and after the application of the force. The application of the force significantly modified the flow field. The force induces a transverse pressure gradient causing the development of secondary flow structures that dissipate the energy added by the acceleration. Once the force ceases to act, these structures are carried downstream and gradually dissipate their excess energy.

  11. Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force

    NASA Astrophysics Data System (ADS)

    Nightingale, Kathryn R.; Palmeri, Mark L.; Congdon, Amy N.; Frinkely, Kristin D.; Trahey, Gregg E.

    2001-05-01

    Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.

  12. On the clinical characterization of impulse and suction force contributions by the diastolic left ventricular vortex

    NASA Astrophysics Data System (ADS)

    Martinez-Legazpi, Pablo; Alhama, Marta; Benito, Yolanda; Bermejo, Javier; Yotti, Raquel; Perez-David, Esther; Barrio, Alicia; Perez-Del-Villar, Candelas; Gonzalez-Mansilla, Ana; Fernandez-Aviles, Francisco; Del Alamo, Juan C.

    2012-11-01

    One of the fluid-dynamic mechanisms that characterize the diastolic phase of the cardiac cycle is the formation of a left ventricular (LV) vortex ring that has been proposed to improve LV filling. However, direct clinical quantification of the contribution of this vortex to LV filling is elusive. In this clinical study, we considered 20 patients with dilated cardiomyopathy (DCM) and 40 healthy volunteers. We have developed and validated a method that derives two-dimensional maps of the LV flow from standard color-Doppler sequences. This study employs the new imaging modality in combination with a vortex identification method and a panel method in order to isolate and estimate the direct contribution of the LV vortex to fluid impulse and suction force during filling in the healthy and diseased populations. Funded by NIH Grant R21HL108268.

  13. An optimal two-input approach for impulse measurements in the nanoN·s range produced by contact forces

    NASA Astrophysics Data System (ADS)

    Benedetti, M.; Bortoluzzi, D.; Baglivo, L.; Vitale, S.

    2011-07-01

    The performances of an optimal two-input filter technique for measuring impulses, caused by contact forces, in the nanoN·s range have been investigated. The instrument is based on a sensing element (proof mass) suspended by a simple pendulum. The impulse is exerted to the proof mass and is measured by applying the optimal filter to the measured signal of the resulting swing motion of the pendulum. Since the contact forces cause the mass to rest out of the pendulum equilibrium before the application of an unknown impulse, the resulting swing motion is also affected by such an undesired and unknown input. As a consequence, the pendulum initial position must be included as an additional input of the optimal filter. Main objectives of this article are to: (a) present the mathematical formulation of the two-input optimal filter, (b) apply this formulation to a harmonic oscillator initially set out of the equilibrium position and subjected to an impulse, (c) analyze the performances of the filtering technique in terms of an achievable measurement accuracy taking into account the effect of noise, sampling frequency, width of the sampling window and an unknown instant of an impulse application.

  14. The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization.

    PubMed

    Allen, Jason D; Ham, Katherine L; Dumont, Douglas M; Sileshi, Bantayehu; Trahey, Gregg E; Dahl, Jeremy J

    2011-08-01

    Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50-69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability. PMID:21447606

  15. Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.

    PubMed

    Park, Jinhyoung; Lee, Jungwoo; Lau, Sien Ting; Lee, Changyang; Huang, Ying; Lien, Ching-Ling; Kirk Shung, K

    2012-04-01

    Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2-10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells. This article thus presents a high-frequency coded excitation ARFI technique, with the ultimate goal of displaying elastic characteristics of cellular structures. Tissue mimicking phantoms and zebrafish embryos are imaged with a 100-MHz lithium niobate (LiNbO₃) transducer, by cross-correlating tracked RF echoes with the reference. The phantom results show that the contrast of ARFI image (14 dB) with coded excitation is better than that of the conventional ARFI image (9 dB). The depths of penetration are 2.6 and 2.2 mm, respectively. The stiffness data of the zebrafish demonstrate that the envelope is harder than the embryo region. The temporal displacement change at the embryo and the chorion is as large as 36 and 3.6 μm. Consequently, this high-frequency ARFI approach may serve as a remote palpation imaging tool that reveals viscoelastic properties of small biological samples. PMID:22101757

  16. Optical tracking of acoustic radiation force impulse-induced dynamics in a tissue-mimicking phantom

    PubMed Central

    Bouchard, Richard R.; Palmeri, Mark L.; Pinton, Gianmarco F.; Trahey, Gregg E.; Streeter, Jason E.; Dayton, Paul A.

    2009-01-01

    Optical tracking was utilized to investigate the acoustic radiation force impulse (ARFI)-induced response, generated by a 5-MHz piston transducer, in a translucent tissue-mimicking phantom. Suspended 10-μm microspheres were tracked axially and laterally at multiple locations throughout the field of view of an optical microscope with 0.5-μm displacement resolution, in both dimensions, and at frame rates of up to 36 kHz. Induced dynamics were successfully captured before, during, and after the ARFI excitation at depths of up to 4.8 mm from the phantom’s proximal boundary. Results are presented for tracked axial and lateral displacements resulting from on-axis and off-axis (i.e., shear wave) acquisitions; these results are compared to matched finite element method modeling and independent ultrasonically based empirical results and yielded reasonable agreement in most cases. A shear wave reflection, generated by the proximal boundary, consistently produced an artifact in tracked displacement data later in time (i.e., after the initial ARFI-induced displacement peak). This tracking method provides high-frame-rate, two-dimensional tracking data and thus could prove useful in the investigation of complex ARFI-induced dynamics in controlled experimental settings. PMID:19894849

  17. Vortex force generation of an impulsively started wing at high angle of attack

    NASA Astrophysics Data System (ADS)

    Fu, Xiang; Wang, Fuxin; Liu, Hong; Qin, Suyang; Xiang, Yang

    2015-11-01

    A wing at high angle of attack (AoA) impulsively started from rest is a fundamental motion employed by insects during flight. Previous studies have almost solely focused on the lift enhancement by the leading-edge vortex (LEV). However, the influences of the starting vortex and secondary vortex on both the lift and drag generation have been less studied. In this paper, the vorticity fields for three AoAs of 45°, 58.5° and 72° are obtained numerically. The roles of the LEV, starting vortex and secondary vortex in generating the lift and drag are quantitatively studied using the vorticity moment theory. It is revealed that the LEV provides positive lift whereas the starting vortex and secondary vortex provide negative lift during the whole motion. The negative lift produced by the starting vortex or secondary vortex is not trivial and cannot be ignored. Regarding the drag, the LEV reduces the total drag whereas the starting vortex, the secondary vortex increases the total drag. As the AoA increases, the drag resulting from the starting vortex increases quickly and comprises almost all the total drag for the AoA of 72°. The relations between the motion of the vortical structures and the forces are also investigated. Financial support from the State Key Development Program of Basic Research of China (2014CB744802) is gratefully acknowledged.

  18. Endobronchial ultrasound elastography

    PubMed Central

    Dietrich, Christoph F.; Jenssen, Christian; Herth, Felix J. F.

    2016-01-01

    Elastographic techniques have recently become available as advanced diagnostic tools for tissue characterization. Strain elastography is a real-time technique used with transcutaneous ultrasound (US) and endoscopic US. Convincing evidence is available demonstrating a significant value of strain elastography for the discrimination of benign and malignant lymph nodes (LNs). This paper reviews preliminary data demonstrating the feasibility of performing real-time elastography during endobronchial US (EBUS) and a potential application of this technique for selection of LNs for EBUS-guided transbronchial needle aspiration in patients with lung cancer and extrathoracic malignancies. PMID:27503154

  19. The utility of acoustic radiation force impulse imaging in diagnosing acute appendicitis and staging its severity

    PubMed Central

    Göya, Cemil; Hamidi, Cihad; Okur, Mehmet Hanifi; İçer, Mustafa; Oğuz, Abdullah; Hattapoğlu, Salih; Çetinçakmak, Mehmet Güli; Teke, Memik

    2014-01-01

    PURPOSE The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) imaging to diagnose acute appendicitis. METHODS Abdominal ultrasonography (US) and ARFI imaging were performed in 53 patients that presented with right lower quadrant pain, and the results were compared with those obtained in 52 healthy subjects. Qualitative evaluation of the patients was conducted by Virtual Touch™ tissue imaging (VTI), while quantitative evaluation was performed by Virtual Touch™ tissue quantification (VTQ) measuring the shear wave velocity (SWV). The severity of appendix inflammation was observed and rated using ARFI imaging in patients diagnosed with acute appendicitis. Alvarado scores were determined for all patients presenting with right lower quadrant pain. All patients diagnosed with appendicitis received appendectomies. The sensitivity and specificity of ARFI imaging relative to US was determined upon confirming the diagnosis of acute appendicitis via histopathological analysis. RESULTS The Alvarado score had a sensitivity and specificity of 70.8% and 20%, respectively, in detecting acute appendicitis. Abdominal US had 83.3% sensitivity and 80% specificity, while ARFI imaging had 100% sensitivity and 98% specificity, in diagnosing acute appendicitis. The median SWV value was 1.11 m/s (range, 0.6–1.56 m/s) for healthy appendix and 3.07 m/s (range, 1.37–4.78 m/s) for acute appendicitis. CONCLUSION ARFI imaging may be useful in guiding the clinical management of acute appendicitis, by helping its diagnosis and determining the severity of appendix inflammation. PMID:25323836

  20. In vivo study of transverse carpal ligament stiffness using acoustic radiation force impulse (ARFI) imaging.

    PubMed

    Shen, Zhilei Liu; Vince, D Geoffrey; Li, Zong-Ming

    2013-01-01

    The transverse carpal ligament (TCL) forms the volar boundary of the carpal tunnel and may provide mechanical constraint to the median nerve, leading to carpal tunnel syndrome. Therefore, the mechanical properties of the TCL are essential to better understand the etiology of carpal tunnel syndrome. The purpose of this study was to investigate the in vivo TCL stiffness using acoustic radiation force impulse (ARFI) imaging. The shear wave velocity (SWV) of the TCL was measured using Virtual Touch IQ(TM) software in 15 healthy, male subjects. The skin and the thenar muscles were also examined as reference tissues. In addition, the effects of measurement location and ultrasound transducer compression on the SWV were studied. The SWV of the TCL was dependent on the tissue location, with greater SWV values within the muscle-attached region than those outside of the muscle-attached region. The SWV of the TCL was significantly smaller without compression (5.21 ± 1.08 m/s) than with compression (6.62 ± 1.18 m/s). The SWV measurements of the skin and the thenar muscles were also affected by transducer compression, but to different extents than the SWV of the TCL. Therefore to standardize the ARFI imaging procedure, it is recommended that a layer of ultrasound gel be maintained to minimize the effects of tissue compression. This study demonstrated the feasibility of ARFI imaging for assessing the stiffness characteristics of the TCL in vivo, which has the potential to identify pathomechanical changes of the tissue. PMID:23861919

  1. Acoustic Radiation Force Impulse Measurement in Renal Transplantation: A Prospective, Longitudinal Study With Protocol Biopsies.

    PubMed

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-09-01

    Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = -0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW < 3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥ 3.5 g/kg.No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  2. Breast Lesions Evaluated by Color-Coded Acoustic Radiation Force Impulse (ARFI) Imaging.

    PubMed

    Zhou, JianQiao; Yang, ZhiFang; Zhan, WeiWei; Zhang, JingWen; Hu, Na; Dong, YiJie; Wang, YingYing

    2016-07-01

    The goal of our study was to investigate the value of color-coded Virtual Touch tissue imaging (VTI) using acoustic radiation force impulse (ARFI) technology in the characterization of breast lesions and to compare it with conventional ultrasound (US). Conventional US and color-coded VTI were performed in 196 solid breast lesions in 196 consecutive women (age range 17-91 y; mean 48.17 ± 14.46 y). A four-point scale VTI score was assigned for each lesion according to the color pattern both in the lesion and in the surrounding breast tissue. The mean VTI score was significantly higher for malignant lesions (3.80 ± 0.66, range 1-4) than for benign ones (2.02 ± 1.20, range 1-4) (p < 0.001), and the optimal cut-off value was between score 3 and score 4. The area under the receiver operating characteristic (ROC) curve for combined conventional US and VTI (0.945) was significantly higher than that for conventional US (0.902) and for VTI (0.871) (p = 0.0021 and p < 0.001, respectively). It was concluded that color-coded VTI with the proposed four-point scale score system combined with conventional US might have the potential to aid in the characterization of benign and malignant breast lesions. PMID:27131841

  3. Tracked ultrasound elastography (TRUE)

    NASA Astrophysics Data System (ADS)

    Foroughi, Pezhman

    Medical ultrasound research has experienced a renaissance in the past decade leading to innovations in flow mapping, elasticity and thermal imaging, measurement of optical properties, beamforming, and image enhancement. In this thesis, we focus on ultrasound elastography, an emerging imaging modality with great potential to become a part of several ultrasound diagnostic applications. Elastography images the stiffness of soft tissue by applying a mechanical stimulus and estimating the disturbance created by this stimulus. In freehand elastography, soft tissue is palpated by hand using the ultrasound transducer. The elastography image is generated by comparing the pre- and post-compression images to form a displacement map which is then differentiated to produce the final strain map. To achieve the best result in freehand elastography, the sonographer must compress and decompress the tissue uniformly in a specific direction with adequate compression. This can be a difficult task even for trained users. A small rotational or out-of-plane motion in the collected ultrasound frames can render them unusable for elastography. This has made freehand elastography highly qualitative and user-dependent. We tackle this issue by incorporating the extra information from a position sensor attached to the ultrasound transducer. Our aim is to show that the localization information of ultrasound images may be utilized to improve the quality and reliability of freehand elastography. For this purpose, we have developed a frame selection scheme that finds pairs of images with optimal compression and minimal lateral and out-of-plane displacement. Relying on the localization information, our algorithm merges multiple strain images computed from the selected frame pairs. This method is applicable to both 2D and 3D elastography. Our 3D elastography does not require for the transducer to be held still during the acquisition of each volume. Instead, the sonographer freely palpates the tissue

  4. Influence of Food Intake on 2-D Shear Wave Elastography Assessment of Liver Stiffness in Healthy Subjects.

    PubMed

    Gersak, Mariana M; Badea, Radu; Lenghel, Lavinia M; Vasilescu, Dan; Botar-Jid, Carolina; Dudea, Sorin M

    2016-06-01

    Transient elastography and Acoustic Radiation Force Impulse imaging are useful non-invasive methods for liver stiffness estimation, although both are influenced by food intake. The aim of the work described here was to identify liver stiffness variation after a standardized meal using 2-D shear wave elastography. Liver stiffness was estimated in 31 apparently healthy subjects, under fasting conditions and after a standardized meal (20, 40, 60, 80, 100 and 120 min after food intake). In most of the cases, liver stiffness values increased between 20 and 40 min after the meal (p < 0.05) and then significantly decreased between 60 and 80 min (p < 0.05). At 120 min after food intake, liver stiffness values were significantly lower compared with liver stiffness values under fasting conditions (p < 0.05). Gender, but not body mass index, had an important role in liver stiffness variation after food intake (p < 0.01). In conclusion, to avoid the influence of food intake on liver stiffness estimation, 2-D shear wave elastography should be performed only under fasting conditions. PMID:26947447

  5. Age and gender effects on the proximal propagation of an impulsive force along the adult human upper extremity

    PubMed Central

    Lee, Yunju; Ashton-Miller, James A.

    2013-01-01

    We tested the null hypotheses that neither age, gender nor muscle pre-cocontraction state affect the latencies of changes in upper extremity kinematics or elbow muscle activity following an impulsive force to the hand. Thirty eight healthy young and older adult volunteers lay prone on an apparatus with shoulders flexed 75 degrees and arms slightly flexed. The non-dominant hand was subjected to three trials of impulsive loading with arm muscles precontracted to 25, 50 or 75% of maximum pre-cocontraction levels. Limb kinematic data and upper extremity electromyographic (EMG) activity were acquired. The results showed that pre-cocontraction muscle level (p < 0.001) and gender (p < 0.05 for wrist and shoulder) affected joint displacement onset times and age affected EMG onset times (p < 0.05). The peak applied force (F1) occurred a mean (± SD) 27 (± 2) msec after impact. The latencies for the wrist, elbow and shoulder displacements were 21 ± 3 msec, 29 ± 5 msec and 34 ± 7 msec, respectively. Because the latencies for elbow flexion and lateral triceps EMG were 23 ± 5 msec and 84 ± 8 msec, respectively, muscle pre-activation rather than stretch reflexes prevent arm buckling under impulsive end loads. PMID:23979475

  6. Single- and Multiple- Track Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, CNR, and Resolution

    PubMed Central

    Hollender, Peter J.; Rosenzweig, Stephen J.; Nightingale, Kathryn R.; Trahey, Gregg E.

    2014-01-01

    Acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple track location SWEI (MTL-SWEI), denoted single track location SWEI (STL-SWEI) offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image inclusions of different sizes and contrasts. STL-SWEI is shown to have significantly higher CNR than MTL-SWEI, allowing for operation at higher resolution. ARFI and STL-SWEI perform similarly in the larger inclusions, with STL-SWEI providing better visualization of small targets ≤2.5 mm in diameter. The processing of each modality introduces different trade-offs between smoothness and resolution of edges and structures; these are discussed in detail. PMID:25701531

  7. Primary biliary cirrhosis degree assessment by acoustic radiation force impulse imaging and hepatic fibrosis indicators

    PubMed Central

    Zhang, Hai-Chun; Hu, Rong-Fei; Zhu, Ting; Tong, Ling; Zhang, Qiu-Qin

    2016-01-01

    AIM: To evaluate the assessment of primary biliary cirrhosis degree by acoustic radiation force impulse imaging (ARFI) and hepatic fibrosis indicators. METHODS: One hundred and twenty patients who developed liver cirrhosis secondary to primary biliary cirrhosis were selected as the observation group, with the degree of patient liver cirrhosis graded by Child-Pugh (CP) score. Sixty healthy individuals were selected as the control group. The four indicators of hepatic fibrosis were detected in all research objects, including hyaluronic acid (HA), laminin (LN), type III collagen (PC III), and type IV collagen (IV-C). The liver parenchyma hardness value (LS) was then measured by ARFI technique. LS and the four indicators of liver fibrosis (HA, LN, PC III, and IV-C) were observed in different grade CP scores. The diagnostic value of LS and the four indicators of liver fibrosis in determining liver cirrhosis degree with PBC, whether used alone or in combination, were analyzed by receiver operating characteristic (ROC) curve. RESULTS: LS and the four indicators of liver fibrosis within the three classes (A, B, and C) of CP scores in the observation group were higher than in the control group, with C class > B class > A class; the differences were statistically significant (P < 0.01). Although AUC values of LS within the three classes of CP scores were higher than in the four indicators of liver fibrosis, sensitivity and specificity were unstable. The ROC curves of LS combined with the four indicators of liver fibrosis revealed that: AUC and sensitivity in all indicators combined in the A class of CP score were higher than in LS alone, albeit with slightly decreased specificity; AUC and specificity in all indicators combined in the B class of CP score were higher than in LS alone, with unchanged sensitivity; AUC values (0.967), sensitivity (97.4%), and specificity (90%) of all indicators combined in the C class of CP score were higher than in LS alone (0.936, 92.1%, 83

  8. Kinetics of respiratory and circulatory responses to step, impulse, sinusoidal and ramp forcings of exercise load in humans.

    PubMed

    Miyamoto, Y

    1992-01-01

    Transient responses of minute ventilation (VE), oxygen consumption (VO2), carbon dioxide output (VCO2), cardiac output (Q) and heart rate (HR) to step, impulse, sinusoidal and ramp changes in exercise load were studied in healthy human subjects at the moderate load range. Exercise was performed in the upright position using a bicycle ergometer. The transient responses to step and impulse forcings fitted essentially to a second-order model consisting of a fast and a slow component, while the responses to sinusoidal and ramp forcings fitted to a first-order model. No significant asymmetry was observed between the on- and off-responses to step forcing. On the contrary, the mean response time (MRT = pure time delay + time constant) of variables to ascending ramp forcing was prolonged, while the MRT to descending ramp was shortened with decreasing ramp slope. The on- and off asymmetry of the MRT was observed in VE, VO2 and VCO2 and, to a lesser extent, also in HR and Q. A non-linear blood flow model, which simulates changes in the wash-in and wash-out time of metabolic substances into and from the chemoreceptor, has been proposed as a likely explanation for the asymmetrical responses. It was concluded that the regulatory system of respiration and circulation might be essentially non-linear in its operation, despite the fact that the cardiorespiratory responses during exercise seemed to fit linear models. PMID:1599881

  9. Texture generation in compressional photoacoustic elastography

    NASA Astrophysics Data System (ADS)

    Schmid, J. W.; Zabihian, B.; Widlak, T.; Glatz, T.; Liu, M.; Drexler, W.; Scherzer, O.

    2015-03-01

    Elastography is implemented by applying a mechanical force to a specimen and visualizing the resulting displacement. As a basis of elastographic imaging typically ultrasound, optical coherence tomography or magnetic resonance imaging are used. Photoacoustics has not been viewed as a primary imaging modality for elastography, but only as a complementary method to enhance the contrast in ultrasound elastography. The reason is that photoacoustics is considered speckle free [3], which hinders application of speckle tracking algorithms. However, while conventional ultrasound only uses a single frequency, photoacoustics utilizes a broad frequency spectrum. We are therefore able to generate artificial texture by using a frequency band limited part of the recorded data. In this work we try to assess the applicability of this technique to photoacoustic tomography. We use Agar phantoms with predefined Young's moduli and laterally apply a 50μm static compression. Pre- and post compression data are recorded via a Fabry Pérot interferometer planar sensor setup and reconstructed via a non-uniform-FFT reconstruction algorithm. A displacement vector field, between pre- and post compressed data is then determined via optical flow algorithms. While the implementation of texture generation during post processing reduces image quality overall, it turns out that it improves the detection of moving patterns and is therefore better suited for elastography.

  10. 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. PMID:27353071

  11. Elastography to assess the effect of varicoceles on testes: a prospective controlled study.

    PubMed

    Dede, O; Teke, M; Daggulli, M; Utangaç, M; Baş, O; Penbegül, N

    2016-04-01

    Varicoceles are the most common and treatable cause of male infertility. The pathophysiology of varicoceles primarily includes elevated temperature, adrenal hormone reflux, gonadotoxic metabolite reflux, altered testicular blood flow, antisperm antibody formation and oxidative stress. The diagnosis of a varicocele is mainly clinical. However, a Doppler ultrasound is used to obtain clinical data and to more accurately measure testicular size. Acoustic radiation force impulse (ARFI) is an additional technique to simultaneously show different areas with different densities in a colour-coded image and a B-mode or greyscale image. This can be used for structural analysis of testicular tissue and has become an additional method for detecting pathologic tissue alterations. We enrolled 30 patients who had clinically diagnosed with left varicoceles and male infertility (Group 1). All patients were evaluated by history taking, physical examination, a spermiogram and an endocrine profile. Thirty control patients (Group 2) were randomly chosen from patients who had applied to an andrology clinic for infertility; their physical examinations and laboratory results showed normal findings. Mean elastography results were significantly different between the groups, and significantly lower in patients who had varicoceles. The relationship between hormonal profiles and elastography parameters was calculated as statistically significant negative correlations between FSH and elasticity. Additionally, a negative correlation was determined between varicocele grade and elasticity of testes. In conclusion, our prospective study showed that ARFI imaging may be more useful than palpation for determining early damage of testicular structure by varicoceles. PMID:26011193

  12. Crawling wave optical coherence elastography.

    PubMed

    Meemon, Panomsak; Yao, Jianing; Chu, Ying-Ju; Zvietcovich, Fernando; Parker, Kevin J; Rolland, Jannick P

    2016-03-01

    Elastography is a technique that measures and maps the local elastic property of biological tissues. Aiming for detection of micron-scale inclusions, various optical elastography, especially optical coherence elastography (OCE), techniques have been investigated over the past decade. The challenges of current optical elastography methods include the decrease in elastographic resolution as compared with its parent imaging resolution, the detection sensitivity and accuracy, and the cost of the overall system. Here we report for the first time, we believe, on an elastography technique-crawling wave optical coherence elastography (CRW-OCE)-which significantly lowers the requirements on the imaging speed and opens the path to high-resolution and high-sensitivity OCE at relatively low cost. Methods of crawling wave excitation, data acquisition, and crawling wave tracking are presented. PMID:26974061

  13. Impulse variability in isometric tasks.

    PubMed

    Carlton, L G; Kim, K H; Liu, Y T; Newell, K M

    1993-03-01

    An isometric elbow flexion task was used in two experiments that examined the influence of force-production characteristics on impulse variability. Impulse size was held constant while peak force, time to peak force, rate of force, and, hence, the shape of the criterion force-time curve were manipulated. The results indicated that changes in the force-time curve under conditions of equal impulse bring about systematic changes in impulse variability, and this effect is more pronounced for larger impulse conditions. The inability of existing functions to account for the peak force variability findings led to the generation of a new predicted force variability function. The proposed function accounts for changes in the standard deviation and coefficient of variation of peak force, impulse, and rate of force over a range of force-time conditions. PMID:12730039

  14. 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.

  15. Increased plantar force and impulse in American football players with high arch compared to normal arch

    PubMed Central

    Carson, Daniel W.; Myer, Gregory D.; Hewett, Timothy E.; Heidt, Robert S.; Ford, Kevin R.

    2014-01-01

    Background Risk of overuse injury among athletes is high due in part to repeated loading of the lower extremities. Compared to individuals with normal arch (NA) structure, those with high (HA) or low arch (LA) may be at increased risk of specific overuse injuries, including stress fractures. A high medial longitudinal arch may result in decreased shock absorbing properties due to increased rigidity in foot mechanics. While the effect of arch structure on dynamic function has been examined in straight line walking and running, the relationship between the two during multi-directional movements remains unstudied. Objective The purpose of this study was to determine if differences in plantar loading in football players occur during both walking and pivoting movements. Method Plantar loading was examined in 9 regions of the foot for 26 participants (16 NA, 10 HA). Results High arch athletes demonstrated increased maximum force in the lateral rear foot and medial forefoot, and force time integral in the medial forefoot while walking. HA athletes also demonstrated increased maximum force in the medial rear foot and medial and central forefoot during rapid pivoting. Conclusions The current findings demonstrate that loading patterns differ between football players with high and normal arch structure, which could possibly influence injury risk in this population. PMID:23141809

  16. Small airway dysfunction by impulse oscillometry in asthmatic patients with normal forced expiratory volume in the 1st second values.

    PubMed

    Pisi, Roberta; Tzani, Panagiota; Aiello, Marina; Martinelli, Enrico; Marangio, Emilio; Nicolini, Gabriele; Olivieri, Dario; Chetta, Alfredo

    2013-01-01

    Small airways are relevant to the pathophysiology of asthma. We investigated whether in asthmatic patients with normal forced expiratory volume in the 1st second (FEV(1)) values, impulse oscillometry system (IOS), as a measure of small airway function, contributed additional information to spirometry either at baseline or after bronchodilator, and whether it was related to the disease control. The fall in resistance from 5 to 20 Hz (R5-R20) and reactance at 5 Hz (X5) by IOS and spirometry measures of small airway function (forced expiratory flow at 25-75% [FEF(25-75)] and forced vital capacity/slow inspiratory vital capacity [FVC/SVC]) at baseline and after 400 micrograms of salbutamol were prospectively measured in 33 asthmatic patients (18 women; age range, 18-66 years). Disease control was assessed by the Asthma Control Test (ACT). R5-R20 but not X5 values were significantly related to FEF(25-75) and FVC/SVC values (p < 0.05 for both correlations). When the bronchodilator response was assessed, no correlation was found among IOS and spirometry changes. ACT scores were related to R5-R20, FEF(25-75), and FVC/SVC values (p < 0.01 for all correlations). In asthmatic patients with normal FEV(1) values, R5-R20 values were related to spirometry measures of small airway function. However, when the bronchodilator response was assessed, IOS and spirometry provided quite different results. Moreover, small airway dysfunction, as assessed by IOS and spirometry, was associated with poor disease control and history of asthma exacerbations. The results of this study confirm the value of IOS, as an investigative tool, and suggest that in asthmatic patients with normal FEV(1) values and poor disease control, small airway function should be investigated. PMID:23406931

  17. 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

    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

  18. Real-time ultrasound elastography

    NASA Astrophysics Data System (ADS)

    Bae, Unmin; Kim, Yongmin

    2007-03-01

    Ultrasound elastography can provide tissue stiffness information that is complementary to the anatomy and blood flow information offered by conventional ultrasound machines, but it is computationally challenging due to many time-consuming modules and a large amount of data. To facilitate real-time implementations of ultrasound elastography, we have developed new methods that can significantly reduce the computational burden of common processing components in ultrasound elastography, such as the crosscorrelation analysis and spatial filtering applied to displacement and strain estimates. Using the new correlation-based search algorithm, the computational requirement of correlation-based search does not increase with the correlation window size. For typical parameters used in ultrasound elastography, the computation in correlation-based search can be reduced by a factor of more than 30. Median filtering is often performed to suppress the spike-like noise that results from correlation-based search. For fast median filtering, we have developed a method that efficiently finds a new median value utilizing the sort result of the previous pixel. With careful mapping of the new algorithms on digital signal processors, our work has led to development of a clinical ultrasound machine supporting real-time elastography. Our methods can help real-time implementations of various applications including ultrasound elastography, which could lead to increased use of ultrasound elastography in the clinic.

  19. A scanning-mode 2D shear wave imaging (s2D-SWI) system for ultrasound elastography.

    PubMed

    Qiu, Weibao; Wang, Congzhi; Li, Yongchuan; Zhou, Juan; Yang, Ge; Xiao, Yang; Feng, Ge; Jin, Qiaofeng; Mu, Peitian; Qian, Ming; Zheng, Hairong

    2015-09-01

    Ultrasound elastography is widely used for the non-invasive measurement of tissue elasticity properties. Shear wave imaging (SWI) is a quantitative method for assessing tissue stiffness. SWI has been demonstrated to be less operator dependent than quasi-static elastography, and has the ability to acquire quantitative elasticity information in contrast with acoustic radiation force impulse (ARFI) imaging. However, traditional SWI implementations cannot acquire two dimensional (2D) quantitative images of the tissue elasticity distribution. This study proposes and evaluates a scanning-mode 2D SWI (s2D-SWI) system. The hardware and image processing algorithms are presented in detail. Programmable devices are used to support flexible control of the system and the image processing algorithms. An analytic signal based cross-correlation method and a Radon transformation based shear wave speed determination method are proposed, which can be implemented using parallel computation. Imaging of tissue mimicking phantoms, and in vitro, and in vivo imaging test are conducted to demonstrate the performance of the proposed system. The s2D-SWI system represents a new choice for the quantitative mapping of tissue elasticity, and has great potential for implementation in commercial ultrasound scanners. PMID:26025508

  20. Evaluation of Stiffness of the Spastic Lower Extremity Muscles in Early Spinal Cord Injury by Acoustic Radiation Force Impulse Imaging

    PubMed Central

    Cho, Kang Hee

    2015-01-01

    Objective To investigate intrinsic viscoelastic changes using shear wave velocities (SWVs) of spastic lower extremity muscles in patients with early spinal cord injury (SCI) via acoustic radiation force impulse (ARFI) imaging and to evaluate correlation between the SWV values and spasticity. Methods Eighteen patients with SCI within 3 months and 10 healthy adults participated. We applied the ARFI technique to measure SWV of gastrocnemius muscle (GCM) and long head of biceps femoris muscle. Spasticity of ankle and knee joint was assessed by original Ashworth Scale. Results Ten patients with SCI had spasticity. Patients with spasticity had significantly faster SWV for GCM and biceps femoris muscle than those without spasticity (Mann-Whitney U test, p=0.007 and p=0.008) and normal control (p=0.011 and p=0.037, respectively). The SWV values of GCM correlated with the ankle spasticity (Spearman rank teat, p=0.026). There was significant correlation between the SWV values for long head of biceps femoris muscle and knee spasticity (Spearman rank teat, p=0.022). Conclusion ARFI demonstrated a difference in muscle stiffness in the GCM between patients with spastic SCI and those without spasticity. This finding suggested that stiffness of muscles increased in spastic lower extremity of early SCI patients. ARFI imaging is a valuable tool for noninvasive assessment of the stiffness of the spastic muscle and has the potential to identify pathomechanical changes of the tissue associated with SCI. PMID:26161345

  1. Renal elasticity quantification by acoustic radiation force impulse applied to the evaluation of kidney diseases: a review.

    PubMed

    Zaffanello, Marco; Piacentini, Giorgio; Bruno, Costanza; Brugnara, Milena; Fanos, Vassilios

    2015-04-01

    For centuries, clinicians have used palpation to evaluate abdominal organs. After exploring almost all the different methods of interaction between x-rays, ultrasound, and magnetic fields on tissues, recent interest has focused on the evaluation of their mechanical properties.Acoustic radiation force impulse (ARFI) is a recent, established ultrasound-based diagnostic technique that allows physicians to obtain a measure of the elastic properties of an organ. Shear wave velocity, obtained by the ARFI technique, depends on the elasticity of tissues.To date, there are studies on the ARFI technique applied to normal kidneys, chronic kidney diseases, and kidney transplants. Mechanical properties of the kidney, such as stiffness and deformity, depend on various conditions that alter its histology, in particular the amount of fibrosis in the renal parenchyma; urinary pressure and renal blood perfusion may be other important contributing factors. Unfortunately, the ARFI technique applied to native renal pathologies is still limited, and not all studies are comparable because they used different methods. Therefore, the results reported in recent literature encourage further improvement of this method and the drawing up of standardized guidelines of investigation. PMID:25738649

  2. Noninvasive In Vivo Characterization of Human Carotid Plaques with Acoustic Radiation Force Impulse (ARFI) Ultrasound: Comparison with Histology Following Endarterectomy

    PubMed Central

    Czernuszewicz, Tomasz J.; Homeister, Jonathon W.; Caughey, Melissa C.; Farber, Mark A.; Fulton, Joseph J.; Ford, Peter F.; Marston, William A.; Vallabhaneni, Raghuveer; Nichols, Timothy C.; Gallippi, Caterina M.

    2014-01-01

    Ischemic stroke from thromboembolic sources is linked to carotid artery atherosclerotic disease with a trend toward medical management in asymptomatic patients. Extent of disease is currently diagnosed by noninvasive imaging techniques that measure luminal stenosis, but it has been suggested that a better biomarker for determining risk of future thromboembolic events is plaque morphology and composition. Specifically, plaques that are composed of mechanically-soft lipid/necrotic regions covered by thin fibrous caps are the most vulnerable to rupture. An ultrasound technique that noninvasively interrogates the mechanical properties of soft tissue, called acoustic radiation force impulse (ARFI) imaging, has been developed as a new modality for atherosclerotic plaque characterization using phantoms and atherosclerotic pigs, but the technique has yet to be validated in vivo in humans. In this preliminary study, in vivo ARFI imaging is presented in a case-study format from four patients undergoing clinically-indicated carotid endarterectomy and compared to histology. In two type Va plaques, characterized by lipid/necrotic cores covered by fibrous caps, mean ARFI displacements in focal regions were high relative to the surrounding plaque material, suggesting soft features covered by stiffer layers within the plaques. In two type Vb plaques, characterized by heavy calcification, mean ARFI peak displacements were low relative to the surrounding plaque and arterial wall, suggesting stiff tissue. This pilot study demonstrates the feasibility and challenges of transcutaneous ARFI for characterizing the material and structural composition of carotid atherosclerotic plaques via mechanical properties, in humans, in vivo. PMID:25619778

  3. Ultrasound Elastography in Breast Cancer Diagnosis.

    PubMed

    Carlsen, J; Ewertsen, C; Sletting, S; Vejborg, I; Schäfer, F K W; Cosgrove, D; Bachmann Nielsen, M

    2015-12-01

    Ultrasound elastography is an established method for characterization of focal lesions in the breast. Different techniques and analyses of the images may be used for the characterization. This article addresses the use of ultrasound elastography in breast cancer diagnosis. In the first part of the article the techniques behind both strain- and shear-wave-elastography are explained and followed by a section on how to obtain adequate elastography images and measurements. In the second part of the article the application of elastography as an adjunct to B-mode ultrasound in clinical practice is described, and the potential diagnostic gains and limitations of elastography are discussed. PMID:26274379

  4. Upper limb dynamic responses to impulsive forces for selected assembly workers.

    PubMed

    Sesto, Mary E; Radwin, Robert G; Block, Walter F; Best, Thomas M

    2006-02-01

    This study evaluated the upper limb, dynamic, mechanical response parameters for 14 male assembly workers recruited from selected jobs based on power tool use. It was hypothesized that the type of power tool operation would affect stiffness, effective mass, and damping of the upper extremity; and workers with symptoms and positive physical examination findings would have different mechanical responses than asymptomatic workers without physical examination findings. Participants included operators who regularly used torque reaction power hand tools, such as nutrunners and screwdrivers, and nontorque reaction power hand tools, such as riveters. The mechanical parameters of the upper limb were characterized from the loading response of an apparatus having known dynamic properties while worker grasps an oscillating handle in free vibration. In addition, all workers underwent a physical examination, magnetic resonance imaging, and completed a symptom survey. Workers were categorized as controls or cases based on reported forearm symptoms and physical exam findings. A total of seven workers were categorized as cases and had less average mechanical stiffness (46%, p > 0.01), damping (74%, p > 0.01), and effective mass (59%, p > 0.05) than the seven workers categorized as controls. Magnetic resonance imaging (MRI) findings suggestive of muscle edema were observed for two workers classified as cases and who regularly used torque reaction power tools. No MRI enhancement was observed in the seven subjects who did not regularly use torque reaction power tools. The ergonomic consequences of less stiffness, effective mass, and damping in symptomatic workers may include reduced capacity to react against rapidly building torque reaction forces encountered when operating power hand tools. PMID:16361220

  5. Acoustic Radiation Force Impulse Imaging (ARFI) on an IVUS Circular Array

    PubMed Central

    Patel, Vivek; Dahl, Jeremy; Bradway, David; Doherty, Joshua; Lee, Seung Yun; Smith, Stephen

    2014-01-01

    Our long-term goal is the detection and characterization of vulnerable plaque in the coronary arteries of the heart using IVUS catheters. Vulnerable plaque, characterized by a thin fibrous cap and a soft, lipid-rich, necrotic core is a pre-cursor to heart attack and stroke. Early detection of such plaques may potentially alter the course of treatment of the patient in order to prevent ischemic events. We have previously described the characterization of carotid plaques using external linear arrays operating at 9 MHz. In addition, we previously modified circular array IVUS catheters by short-circuiting several neighboring elements to produce fixed beam-widths for intra-vascular hyperthermia applications. In this paper we modified Volcano Visions 8.2 French, 9 MHz catheters and Volcano Platinum 3.5 French, 20 MHz catheters by short circuiting portions of the array for ARFI applications. The catheters had an effective transmit aperture size of 2 mm and 1.5 mm respectively. The catheters were connected to a Verasonics scanner and driven with pushing pulses of 180 V p-p to acquire ARFI data from a soft gel phantom with a Young’s modulus of 2.9 kPa. The dynamic response of the tissue-mimicking material demonstrates a typical ARFI motion of 1–2 microns as the gel phantom displaces away and recovers back to its normal position. The hardware modifications applied to our IVUS catheters mimic potential beamforming modifications that could be implemented on IVUS scanners. Our results demonstrate that the generation of radiation force from IVUS catheters and the development of intra-vascular ARFI may be feasible. PMID:24554291

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

    SciTech Connect

    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 in 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

  7. 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

  8. Spectroscopic optical coherence elastography

    PubMed Central

    Adie, Steven G.; Liang, Xing; Kennedy, Brendan F.; John, Renu; Sampson, David D.; Boppart, Stephen A.

    2010-01-01

    We present an optical technique to image the frequency-dependent complex mechanical response of a viscoelastic sample. Three-dimensional hyperspectral data, comprising two-dimensional B-mode images and a third dimension corresponding to vibration frequency, were acquired from samples undergoing external mechanical excitation in the audio-frequency range. We describe the optical coherence tomography (OCT) signal when vibration is applied to a sample and detail the processing and acquisition techniques used to extract the local complex mechanical response from three-dimensional data that, due to a wide range of vibration frequencies, possess a wide range of sample velocities. We demonstrate frequency-dependent contrast of the displacement amplitude and phase of a silicone phantom containing inclusions of higher stiffness. Measurements of an ex vivo tumor margin demonstrate distinct spectra between adipose and tumor regions, and images of displacement amplitude and phase demonstrated spatially-resolved contrast. Contrast was also observed in displacement amplitude and phase images of a rat muscle sample. These results represent the first demonstration of mechanical spectroscopy based on B-mode OCT imaging. Spectroscopic optical coherence elastography (S-OCE) provides a high-resolution imaging capability for the detection of tissue pathologies that are characterized by a frequency-dependent viscoelastic response. PMID:21164898

  9. Spectroscopic optical coherence elastography.

    PubMed

    Adie, Steven G; Liang, Xing; Kennedy, Brendan F; John, Renu; Sampson, David D; Boppart, Stephen A

    2010-12-01

    We present an optical technique to image the frequency-dependent complex mechanical response of a viscoelastic sample. Three-dimensional hyperspectral data, comprising two-dimensional B-mode images and a third dimension corresponding to vibration frequency, were acquired from samples undergoing external mechanical excitation in the audio-frequency range. We describe the optical coherence tomography (OCT) signal when vibration is applied to a sample and detail the processing and acquisition techniques used to extract the local complex mechanical response from three-dimensional data that, due to a wide range of vibration frequencies, possess a wide range of sample velocities. We demonstrate frequency-dependent contrast of the displacement amplitude and phase of a silicone phantom containing inclusions of higher stiffness. Measurements of an ex vivo tumor margin demonstrate distinct spectra between adipose and tumor regions, and images of displacement amplitude and phase demonstrated spatially-resolved contrast. Contrast was also observed in displacement amplitude and phase images of a rat muscle sample. These results represent the first demonstration of mechanical spectroscopy based on B-mode OCT imaging. Spectroscopic optical coherence elastography (S-OCE) provides a high-resolution imaging capability for the detection of tissue pathologies that are characterized by a frequency-dependent viscoelastic response. PMID:21164898

  10. Damping models in elastography

    NASA Astrophysics Data System (ADS)

    McGarry, Matthew D. J.; Berger, Hans-Uwe; Van Houten, Elijah E. W.

    2007-03-01

    Current optimization based Elastography reconstruction algorithms encounter difficulties when the motion approaches resonant conditions, where the model does a poor job of approximating the real behavior of the material. Model accuracy can be improved through the addition of damping effects. These effects occur in-vivo due to the complex interaction between microstructural elements of the tissue; however reconstruction models are typically formulated at larger scales where the structure can be treated as a continuum. Attenuation behavior in an elastic continuum can be described as a mixture of inertial and viscoelastic damping effects. In order to develop a continuum damping model appropriate for human tissue, the behavior of each aspect of this proportional, or Rayleigh damping needs to be characterized. In this paper we investigate the nature of these various damping representations with a goal of best describing in-vivo behavior of actual tissue in order to improve the accuracy and performance of optimization based elastographic reconstruction. Inertial damping effects are modelled using a complex density, where the imaginary part is equivalent to a damping coefficient, and the effects of viscoelasticity are modelled through the use of complex shear moduli, where the real and imaginary parts represent the storage and loss moduli respectively. The investigation is carried out through a combination of theoretical analysis, numerical experiment, investigation of gelatine phantoms and comparison with other continua such as porous media models.

  11. Magnetic Resonance Elastography

    PubMed Central

    Litwiller, Daniel V.; Mariappan, Yogesh K.; Ehman, Richard L.

    2015-01-01

    Often compared to the practice of manual palpation, magnetic resonance elastography is an emerging technology for quantitatively assessing the mechanical properties of tissue as a basis for characterizing disease. The potential of MRE as a diagnostic tool is rooted in the fact that normal and diseased tissues often differ significantly in terms of their intrinsic mechanical properties. MRE uses magnetic resonance imaging (MRI) in conjunction with the application of mechanical shear waves to probe tissue mechanics. This process can be broken down into three essential steps: inducing shear waves in the tissue,imaging the propagating shear waves with MRI, andanalyzing the wave data to generate quantitative images of tissue stiffness MRE has emerged as a safe, reliable and noninvasive method for staging hepatic liver fibrosis, and is now used in some locations as an alternative to biopsy. MRE is also being used in the ongoing investigations of numerous other organs and tissues, including, for example, the spleen, kidney, pancreas, brain, heart, breast, skeletal muscle, prostate, vasculature, lung, spinal cord, eye, bone, and cartilage. In the article that follows, some fundamental techniques and applications of MRE are summarized. PMID:26361467

  12. Spectral estimators in elastography.

    PubMed

    Konofagou, E E; Varghese, T; Ophir, J

    2000-03-01

    Like velocity, strain induces a time delay and a time scaling to the received signal. Elastography typically uses time delay techniques to indirectly (i.e. via the displacement estimate) measure tissue strain induced by an applied compression, and considers time scaling as a source of distortion. More recently, we have shown that the time scaling factor can also be spectrally estimated and used as a direct measure of strain. Strain causes a Doppler-like frequency shift and a change in bandwidth of the bandpass power spectrum of the echo signal. Two frequency shift strain estimators are described that have been proven to be more robust but less precise when compared to time delay estimators, both in simulations and experiments. The increased robustness is due to the insensitivity of the spectral techniques to phase decorrelation noise. In this paper we discuss and compare the theoretical and experimental findings obtained with traditional time delay estimators and with the newly proposed spectral methods. PMID:10829698

  13. Instantaneous Impulses.

    ERIC Educational Resources Information Center

    Erlichson, Herman

    2000-01-01

    Describes an experiment that extends Newton's instantaneous-impulse method of orbital analysis to a graphical method of orbit determination. Discusses the experiment's usefulness for teaching both horizontal projectile motion and instantaneous impulse. (WRM)

  14. Ultrasound Elastography Used for Preventive Non-Invasive Screening in Early Detection of Liver Fibrosis

    PubMed Central

    Bert, Florian; Stahmeyer, Jona T.; Rossol, Siegbert

    2016-01-01

    Background Early discovery of liver fibrosis is becoming more popular because of enhanced incidence of hepatocellular carcinoma. Ultrasound-based liver elastography is a method used to approve suspected liver fibrosis or cirrhosis. We assessed the clinical usefulness of acoustic radiation force impulse shear wave elasticity imaging (ARFI-SWEI) as a preventive screening method to uncover fibrosis. Methods We screened 382 patients by native routine sonography for abnormal liver results and divided them into six groups: group 1: normal liver, groups 2-4: fatty liver grade I-III, group 5: liver cirrhosis, and group 6: inhomogenic liver tissue. Then ARFI-SWEI was performed and the results were compared with published shear wave velocity cut-off values that were predictive of each fibrosis stage (F0-4). A control group consisted of 20 healthy volunteers. Results The part of liver fibrosis ≥ F2 was in groups 1-4: 20-32%, group 5: 100%, and group 6: 91%. Main causes for fibrosis stage ≥ F2 were (non)-alcoholic steatohepatitis, chronic viral or autoimmune hepatitis and chronic heart failure. Conclusions Screening of the liver tissue in b-mode ultrasound can underestimate possible liver fibrosis; by using ARFI-SWEI, liver fibrosis can be uncovered early. It is a suitable preventive method comparable to colonoscopy for colon cancer. PMID:27540438

  15. Magnetic resonance acoustic radiation force imaging

    PubMed Central

    McDannold, Nathan; Maier, Stephan E.

    2008-01-01

    Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery. PMID:18777934

  16. Force balance in the take-off of a pierid butterfly: relative importance and timing of leg impulsion and aerodynamic forces.

    PubMed

    Bimbard, Gaëlle; Kolomenskiy, Dmitry; Bouteleux, Olivier; Casas, Jérôme; Godoy-Diana, Ramiro

    2013-09-15

    Up to now, the take-off stage has remained an elusive phase of insect flight that was relatively poorly explored compared with other maneuvers. An overall assessment of the different mechanisms involved in force production during take-off has never been explored. Focusing on the first downstroke, we have addressed this problem from a force balance perspective in butterflies taking off from the ground. In order to determine whether the sole aerodynamic wing force could explain the observed motion of the insect, we have firstly compared a simple analytical model of the wing force with the acceleration of the insect's center of mass estimated from video tracking of the wing and body motions. Secondly, wing kinematics were also used for numerical simulations of the aerodynamic flow field. Similar wing aerodynamic forces were obtained by the two methods. However, neither are sufficient, nor is the inclusion of the ground effect, to predict faithfully the body acceleration. We have to resort to the leg forces to obtain a model that best fits the data. We show that the median and hind legs display an active extension responsible for the initiation of the upward motion of the insect's body, occurring before the onset of the wing downstroke. We estimate that legs generate, at various times, an upward force that can be much larger than all other forces applied to the insect's body. The relative timing of leg and wing forces explains the large variability of trajectories observed during the maneuvers. PMID:23788714

  17. Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 1, Principles and Techniques

    PubMed Central

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

    2016-01-01

    Objective The purpose of this article is to provide an overview of ultrasound and magnetic resonance elastography, including a glossary of relevant terminology, a classification of elastography techniques, and a discussion of their respective strengths and limitations. Conclusion Elastography is an emerging technique for the non-invasive assessment of mechanical tissue properties. These techniques report metrics related to tissue stiffness such as shear wave speed, magnitude of the complex shear modulus, and Young’s modulus. PMID:25905647

  18. Primary Non-Hodgkin Lymphoma of the Breast: Ultrasonography, Elastography, Digital Mammography, Contrast-Enhanced Digital Mammography, and Pathology Findings.

    PubMed

    Gkali, Christina An; Chalazonitis, Athanasios N; Feida, Eleni; Giannos, Aris; Sotiropoulou, Maria; Dimitrakakis, Constantine; Loutradis, Dimitrios

    2015-12-01

    Lymphomas constitute approximately 0.15% of malignant mammary neoplasms. Less than 0.5% of all malignant lymphomas involve the breast primarily. Primary non-Hodgkin breast lymphoma is usually right sided. The combined therapy approach, with chemotherapy and radiotherapy, is the most successful treatment. Mastectomy offers no benefit in the treatment of primary non-Hodgkin breast lymphoma. To the author's knowledge, this is the first published case of primary non-Hodgkin breast lymphoma reported with conventional ultrasonography, elastography (both freehand and acoustic radiation force impulse imaging), digital mammography, contrast-enhanced digital mammography, and pathology findings. A 45-year-old woman presented with a lump in the right breast for 2 months. There was no evidence of systemic lymphoma or leukemia when the breast lesion was detected. Imaging findings were negative for lymphoma. Ipsilateral lymph nodes were not palpable. The mass was resected, and histopathology findings were diagnostic of non-Hodgkin lymphoma. Immunohistochemistry was confirmatory of non-Hodgkin lymphoma, diffuse large cell type of B-cell lineage. Although primary and secondary lymphomas of the breast are rare entities, they should be considered in the differential diagnosis of breast malignancies. PMID:25831151

  19. Combined acoustic radiation force impulse, aminotransferase to platelet ratio index and Forns index assessment for hepatic fibrosis grading in hepatitis B

    PubMed Central

    Dong, Chang-Feng; Xiao, Jia; Shan, Ling-Bo; Li, Han-Ying; Xiong, Yong-Jia; Yang, Gui-Lin; Liu, Jing; Yao, Si-Min; Li, Sha-Xi; Le, Xiao-Hua; Yuan, Jing; Zhou, Bo-Ping; Tipoe, George L; Liu, Ying-Xia

    2016-01-01

    AIM: To investigate the combined diagnostic accuracy of acoustic radiation force impulse (ARFI), aspartate aminotransferase to platelet ratio index (APRI) and Forns index for a non-invasive assessment of liver fibrosis in patients with chronic hepatitis B (CHB). METHODS: In this prospective study, 206 patients had CHB with liver fibrosis stages F0-F4 classified by METAVIR and 40 were healthy volunteers were measured by ARFI, APRI and Forns index separately or combined as indicated. RESULTS: ARFI, APRI or Forns index demonstrated a significant correlation with the histological stage (all P < 0.001). According to the AUROC of ARFI and APRI for evaluating fibrotic stages more than F2, ARFI showed an enhanced diagnostic accuracy than APRI (P < 0.05). The combined measurement of ARFI and APRI exhibited better accuracy than ARFI alone when evaluating ≥ F2 fibrotic stage (Z = 2.77, P = 0.006). Combination of ARFI, APRI and Forns index did not obviously improve the diagnostic accuracy compared to the combination of ARFI and APRI (Z = 0.958, P = 0.338). CONCLUSION: ARFI + APRI showed enhanced diagnostic accuracy than ARFI or APRI alone for significant liver fibrosis and ARFI + APRI + Forns index shows the same effect with ARFI + APRI. PMID:27190578

  20. Acoustic Radiation Force Impulse Technology in the Differential Diagnosis of Solid Breast Masses with Different Sizes: Which Features Are Most Efficient?

    PubMed Central

    Bai, Min; Zhang, Hui-Ping; Xing, Jin-Fang; Shi, Qiu-Sheng; Gu, Ji-Ying; Li, Fan; Chen, Hui-Li; Zhang, Xue-Mei; Fang, Yun; Du, Lian-Fang

    2015-01-01

    Purpose. To evaluate diagnostic performance of acoustic radiation force impulse (ARFI) technology for solid breast masses with different sizes and determine which features are most efficient. Materials and Methods. 271 solid breast masses in 242 women were examined with ARFI, and their shear wave velocities (SWVs), Virtual Touch tissue imaging (VTI) patterns, and area ratios (ARs) were measured and compared with their histopathological outcomes. Receiver operating characteristic curves (ROC) were calculated to assess diagnostic performance of ARFI for small masses (6–14 mm) and big masses (15–30 mm). Results. SWV of mass was shown to be positively associated with mass size (P < 0.001). For small masses, area under ROC (Az) of AR was larger than that of SWV (P < 0.001) and VTI pattern (P < 0.001); no significant difference was found between Az of SWV and that of VTI pattern (P = 0.906). For big masses, Az of VTI pattern was less than that of SWV (P = 0.008) and AR (P = 0.002); no significant difference was identified between Az of SWV and that of AR (P = 0.584). Conclusions. For big masses, SWV and AR are both efficient measures; nevertheless, for small masses, AR seems to be the best feature. PMID:26258138

  1. Assessment of the Stiffness of Major Salivary Glands in Primary Sjögren's Syndrome through Quantitative Acoustic Radiation Force Impulse Imaging.

    PubMed

    Zhang, Shanshan; Zhu, Jiaan; Zhang, Xia; He, Jing; Li, Jianguo

    2016-03-01

    The purpose of the study described here was to evaluate salivary gland stiffness in primary Sjögren's syndrome (pSS) via acoustic radiation force impulse imaging, including Virtual Touch tissue quantification (VTQ) and Virtual Touch tissue imaging quantification (VTIQ). Twenty-one patients with pSS and 11 healthy patients were included, and the paired parotid and submandibular glands of all of the patients were examined using VTQ and VTIQ. Differences between the two groups were compared with independent and paired t-tests. The VTQ value for the parotid in the pSS group was significantly higher than that obtained for the control group (1.33 ± 0.22 and 1.18 ± 0.04 m/s, respectively, p < 0.01). The VTIQ values for the parotid and submandibular gland were both significantly higher in the pSS group than in the control group (p < 0.05). In the pSS group, a positive correlation was observed between the VTQ and VTIQ results for the parotid and submandibular glands. In summary, the stiffness of the major salivary glands in patients with pSS was increased compared with that of patients with normal glands. This finding indicates that VTQ and VTIQ imaging may be valuable adjuncts to gray-scale ultrasonography for the clinical diagnosis of pSS. PMID:26715188

  2. A single-degree-of-freedom dynamic model predicts the range of human responses to impulsive forces produced by power hand tools.

    PubMed

    Lin, Jia-Hua; Radwin, Robert G; Richard, Terry G

    2003-12-01

    The human operator is modelled as a single-degree-of-freedom dynamic mechanical system for predicting the response to impulsive torque reaction forces produced by rotating spindle power hand tools such as nutrunners or screwdrivers. The model uses mass, spring and damping elements to represent the standing operator supporting the tool in the hand. It was hypothesized that these mechanical elements are affected by work location and vary among individuals. These elements were ascertained by measuring the resulting frequency and amplitude of a freely oscillating defined mechanical system when externally loaded using maximal effort to oppose its motion. Twenty-five subjects (13 female, 12 male) participated in the full factorial experiment that measured the effects of gender, vertical and horizontal work location for various tool shapes (in-line, pistol, right angle), and orientations (horizontal and vertical). The mean operator stiffness decreased from 1721 to 1195 N/m when the horizontal work location increased from 30 to 90 cm in front of the ankles for a pistol-grip handle used on a vertical surface. Males had greater mass moment of inertia of (0.0099 kg m2) than females (0.0072 kg m2) for an in-line handle used on a horizontal surface. Internal validation by independently measuring apparatus torque found that the model satisfactorily explained the measured operator dynamics with an average error of 2.86%. Group variance reflects the range of operator capacities to react against power hand tool generated forces for the sample group and therefore it may also be useful for understanding the range of capacities among a group of operators performing similar tasks. PMID:14614938

  3. Ultrasound elastography for musculoskeletal applications

    PubMed Central

    Drakonaki, E E; Allen, G M; Wilson, D J

    2012-01-01

    Ultrasound elastography (EUS) is a method to assess the mechanical properties of tissue, by applying stress and detecting tissue displacement using ultrasound. There are several EUS techniques used in clinical practice; strain (compression) EUS is the most common technique that allows real-time visualisation of the elastographic map on the screen. There is increasing evidence that EUS can be used to measure the mechanical properties of musculoskeletal tissue in clinical practice, with the future potential for early diagnosis to both guide and monitor therapy. This review describes the various EUS techniques available for clinical use, presents the published evidence on musculoskeletal applications of EUS and discusses the technical issues, limitations and future perspectives of this method in the assessment of the musculoskeletal system. PMID:23091287

  4. Magnetic resonance elastography of abdomen.

    PubMed

    Venkatesh, Sudhakar Kundapur; Ehman, Richard L

    2015-04-01

    Many diseases cause substantial changes in the mechanical properties of tissue, and this provides motivation for developing methods to noninvasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate noninvasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed. PMID:25488346

  5. Quantitative photoacoustic elastography in humans

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We report quantitative photoacoustic elastography (QPAE) capable of measuring Young's modulus of biological tissue in vivo in humans. By combining conventional PAE 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 demonstrate the feasibility of QPAE in agar phantoms with different concentrations. The measured Young's modulus values fit well with both the empirical expectation based on the agar concentrations and those measured in an independent standard compression test. Next, QPAE was applied to quantify the Young's modulus of skeletal muscle in vivo in humans, showing a linear relationship between muscle stiffness and loading. The results demonstrated the capability of QPAE to assess the absolute elasticity of biological tissue noninvasively in vivo in humans, indicating its potential for tissue biomechanics studies and clinical applications.

  6. Magnetic Resonance Elastography of Abdomen

    PubMed Central

    Venkatesh, Sudhakar K.; Ehman, Richard L.

    2015-01-01

    Many diseases cause substantial changes in the mechanical properties of tissue and this provides motivation for developing methods to non-invasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate non-invasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed. PMID:25488346

  7. Relativistic impulse dynamics.

    PubMed

    Swanson, Stanley M

    2011-08-01

    Classical electrodynamics has some annoying rough edges. The self-energy of charges is infinite without a cutoff. The calculation of relativistic trajectories is difficult because of retardation and an average radiation reaction term. By reconceptuallizing electrodynamics in terms of exchanges of impulses rather than describing it by forces and potentials, we eliminate these problems. A fully relativistic theory using photonlike null impulses is developed. Numerical calculations for a two-body, one-impulse-in-transit model are discussed. A simple relationship between center-of-mass scattering angle and angular momentum was found. It reproduces the Rutherford cross section at low velocities and agrees with the leading term of relativistic distinguishable-particle quantum cross sections (Møller, Mott) when the distance of closest approach is larger than the Compton wavelength of the particle. Magnetism emerges as a consequence of viewing retarded and advanced interactions from the vantage point of an instantaneous radius vector. Radiation reaction becomes the local conservation of energy-momentum between the radiating particle and the emitted impulse. A net action is defined that could be used in developing quantum dynamics without potentials. A reinterpretation of Newton's laws extends them to relativistic motion. PMID:21929132

  8. 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.

  9. Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation.

    PubMed

    Palmeri, Mark L; Glass, Tyler J; Miller, Zachary A; Rosenzweig, Stephen J; Buck, Andrew; Polascik, Thomas J; Gupta, Rajan T; Brown, Alison F; Madden, John; Nightingale, Kathryn R

    2016-06-01

    Overly aggressive prostate cancer (PCa) treatment adversely affects patients and places an unnecessary burden on our health care system. The inability to identify and grade clinically significant PCa lesions is a factor contributing to excessively aggressive PCa treatment, such as radical prostatectomy, instead of more focal, prostate-sparing procedures such as cryotherapy and high-dose radiation therapy. We have performed 3-D in vivo B-mode and acoustic radiation force impulse (ARFI) imaging using a mechanically rotated, side-fire endorectal imaging array to identify regions suspicious for PCa in 29 patients being treated with radical prostatectomies for biopsy-confirmed PCa. Whole-mount histopathology analyses were performed to identify regions of clinically significant/insignificant PCa lesions, atrophy and benign prostatic hyperplasia. Regions of suspicion for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location. These regions of suspicion were compared with histopathology identified lesions using a nearest-neighbor regional localization approach. Of all clinically significant lesions identified on histopathology, 71.4% were also identified using ARFI imaging, including 79.3% of posterior and 33.3% of anterior lesions. Among the ARFI-identified lesions, 79.3% corresponded to clinically significant PCa lesions, with these lesions having higher indices of suspicion than clinically insignificant PCa. ARFI imaging had greater sensitivity for posterior versus anterior lesions because of greater displacement signal-to-noise ratio and finer spatial sampling. Atrophy and benign prostatic hyperplasia can cause appreciable prostate anatomy distortion and heterogeneity that confounds ARFI PCa lesion identification; however, in general, ARFI regions of suspicion did not coincide with these benign pathologies. PMID:26947445

  10. Ultrasound elastography for imaging tendons and muscles

    PubMed Central

    2012-01-01

    Ultrasound elastography is a recently developed ultrasound-based method which allows the qualitative or quantitative evaluation of the mechanical properties of tissue. Strain (compression) ultrasound elastography is the commonest technique performed by applying mild compression with the hand-held transducer to create real-time strain distribution maps, which are color-coded and superimposed on the B-mode images. There is increasing evidence that ultrasound elastography can be used in the investigation of muscle, tendon and soft tissue disease in the clinical practice, as a supplementary tool to conventional ultrasound examination. Based on preliminary data, potential clinical applications include early diagnosis, staging, and guiding interventions musculotendinous and neuromuscular disease as well as monitoring disease during rehabilitation. Ultrasound elastography could also be used for research into the biomechanics and pathophysiology of musculotendinous disease. Despite the great interest in the technique, there is still limited evidence in the literature and there are several technical issues which limit the reproducibility of the method, including differences in quantification methods, artefacts, limitations and variation in the application of the technique by different users. This review presents the published evidence on musculoskeletal applications of strain elastography, discusses the technical issues and future perspectives of this method and emphasizes the need for standardization and further research. PMID:26673318

  11. Recognition Memory in Reflective and Impulsive Preschool Children

    ERIC Educational Resources Information Center

    Siegel, Alexander W.; And Others

    1973-01-01

    Eight reflective and eight impulsive preschool children were tested in a forced-choice recognition memory task. Reflective children made more correct recognition choices than did impulsive children under all experimental conditions. (ST)

  12. JSUM ultrasound elastography practice guidelines: breast.

    PubMed

    Nakashima, Kazutaka; Shiina, Tsuyoshi; Sakurai, Masaru; Enokido, Katsutoshi; Endo, Tokiko; Tsunoda, Hiroko; Takada, Etsuo; Umemoto, Takeshi; Ueno, Ei

    2013-10-01

    Ten years have passed since the first elastography application: Real-time Tissue Elastography™. Now there are several elastography applications in existence. The Quality Control Research Team of The Japan Association of Breast and Thyroid Sonology (JABTS) and the Breast Elasticity Imaging Terminology and Diagnostic Criteria Subcommittee, Terminology and Diagnostic Criteria Committee of the Japan Society of Ultrasonics in Medicine (JSUM) have advocated breast elastography classifications for exact knowledge and good clinical use. We suggest two types of classifications: the technical classification and the classification for interpretation. The technical classification has been created to use vibration energy and to make images, and also shows how to obtain a good elastic image. The classification for interpretation has been prepared on the basis of interpretation of evidence in this decade. Finally, we describe the character and specificity of each vender equipment. We expect the present guidelines to be useful for many physicians and examiners throughout the world. PMID:27277451

  13. Ultrasound-based transient elastography compared to magnetic resonance elastography in soft tissue-mimicking gels.

    PubMed

    Oudry, Jennifer; Vappou, Jonathan; Choquet, Philippe; Willinger, Rémy; Sandrin, Laurent; Constantinesco, André

    2009-11-21

    Ultrasound-based transient elastography (TE) and magnetic resonance elastography (MRE) are increasingly used methods for the clinical evaluation of soft tissue mechanical properties and their alteration under diseased conditions. This study proposes a comparison between magnetic resonance elastography (MRE) and ultrasound-based transient elastography (TE). Both methods were tested on the same soft tissue-mimicking gels in a common frequency range in order to allow for direct quantitative comparison. For the four gels tested, relatively good agreement was found between the shear moduli measured by both methods, with an averaged relative difference of 23%. This study demonstrates that under the assumption of homogeneous media that are significantly more elastic than viscous, quantitative results obtained by both methods are comparable. PMID:19887718

  14. Sonographic Elastography of the Thyroid Gland

    PubMed Central

    Menzilcioglu, Mehmet Sait; Duymus, Mahmut; Avcu, Serhat

    2016-01-01

    Summary Thyroid gland disorders include benign and malignant thyroid nodules and diffuse thyroid disorders. The incidence of malignant thyroid nodules is low and the prognosis is good. The diagnosis of thyroid cancer and diffuse parenchymal disorders is generally based on clinical manifestations and histopathological evaluation. Ultrasonography has its place in the diagnostics and follow-up of thyroid disorders. Ultrasonographic elastography is a new, developing method that shows increase in clinical practice. In this study, we aimed to review the data on thyroid ultrasound elastography. PMID:27103947

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

    SciTech Connect

    Fu, Ji; Li, Faxin

    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 the 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.

  16. MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW

    PubMed Central

    Mariappan, Yogesh K; Glaser, Kevin J; Ehman, Richard L

    2011-01-01

    Magnetic Resonance Elastography (MRE) is a rapidly developing technology for quantitatively assessing the mechanical properties of tissue. The technology can be considered to be an imaging-based counterpart to palpation, commonly used by physicians to diagnose and characterize diseases. The success of palpation as a diagnostic method is based on the fact that the mechanical properties of tissues are often dramatically affected by the presence of disease processes such as cancer, inflammation, and fibrosis. MRE obtains information about the stiffness of tissue by assessing the propagation of mechanical waves through the tissue with a special magnetic resonance imaging (MRI) technique. The technique essentially involves three steps: generating shear waves in the tissue,acquiring MR images depicting the propagation of the induced shear waves andprocessing the images of the shear waves to generate quantitative maps of tissue stiffness, called elastograms. MRE is already being used clinically for the assessment of patients with chronic liver diseases and is emerging as a safe, reliable and noninvasive alternative to liver biopsy for staging hepatic fibrosis. MRE is also being investigated for application to pathologies of other organs including the brain, breast, blood vessels, heart, kidneys, lungs and skeletal muscle. The purpose of this review article is to introduce this technology to clinical anatomists and to summarize some of the current clinical applications that are being pursued. PMID:20544947

  17. B-Mode and Acoustic Radiation Force Impulse (ARFI) Imaging of Prostate Zonal Anatomy: Comparison with 3T T2-Weighted MR Imaging

    PubMed Central

    Palmeri, Mark L.; Miller, Zachary A.; Glass, Tyler J.; Garcia-Reyes, Kirema; Gupta, Rajan T.; Rosenzweig, Stephen J.; Kauffman, Christopher; Polascik, Thomas J.; Buck, Andrew; Kulbacki, Evan; Madden, John; Lipman, Samantha L.; Rouze, Ned C.; Nightingale, Kathryn R.

    2015-01-01

    Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R2 = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and −10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R2 = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (−28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management. PMID:25060914

  18. B-mode and acoustic radiation force impulse (ARFI) imaging of prostate zonal anatomy: comparison with 3T T2-weighted MR imaging.

    PubMed

    Palmeri, Mark L; Miller, Zachary A; Glass, Tyler J; Garcia-Reyes, Kirema; Gupta, Rajan T; Rosenzweig, Stephen J; Kauffman, Christopher; Polascik, Thomas J; Buck, Andrew; Kulbacki, Evan; Madden, John; Lipman, Samantha L; Rouze, Ned C; Nightingale, Kathryn R

    2015-01-01

    Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R(2) = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and -10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R(2) = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (-28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management. PMID:25060914

  19. Impulse Control of Turbulence

    NASA Astrophysics Data System (ADS)

    Menaldi, Jose-Luis; Sritharan, S. S.

    2000-11-01

    Impulse control corresponds to forcing the fluid at strategic times where the optimal instances of time as well as the strengths of the control are to be determined by control theory of Navier-Stokes equation. This subject can also be exactly rephrased as an optimal weather prediction problem where the initial data is updated at strategic times (in current variational data assimilation literature in meteorology one obtains the optimal initial data just once). The underlying mathematical structure is precisely resolved with very elegant explanations using infinite dimensional free boundary problems where the boundaries of the free boundary correspond to optimal instances.

  20. Maximum likelihood estimation of shear wave speed in transient elastography.

    PubMed

    Audière, Stéphane; Angelini, Elsa D; Sandrin, Laurent; Charbit, Maurice

    2014-06-01

    Ultrasonic transient elastography (TE), enables to assess, under active mechanical constraints, the elasticity of the liver, which correlates with hepatic fibrosis stages. This technique is routinely used in clinical practice to assess noninvasively liver stiffness. The Fibroscan system used in this work generates a shear wave via an impulse stress applied on the surface of the skin and records a temporal series of radio-frequency (RF) lines using a single-element ultrasound probe. A shear wave propagation map (SWPM) is generated as a 2-D map of the displacements along depth and time, derived from the correlations of the sequential 1-D RF lines, assuming that the direction of propagation (DOP) of the shear wave coincides with the ultrasound beam axis (UBA). Under the assumption of pure elastic tissue, elasticity is proportional to the shear wave speed. This paper introduces a novel approach to the processing of the SWPM, deriving the maximum likelihood estimate of the shear wave speed when comparing the observed displacements and the estimates provided by the Green's functions. A simple parametric model is used to interface Green's theoretical values of noisy measures provided by the SWPM, taking into account depth-varying attenuation and time-delay. The proposed method was evaluated on numerical simulations using a finite element method simulator and on physical phantoms. Evaluation on this test database reported very high agreements of shear wave speed measures when DOP and UBA coincide. PMID:24835213

  1. 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

  2. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  3. ANTHROPOMORPHIC BREAST PHANTOMS FOR TESTING ELASTOGRAPHY SYSTEMS

    PubMed Central

    Madsen, Ernest L.; Hobson, Maritza A.; Frank, Gary R.; Shi, Hairong; Jiang, Jingfeng; Hall, Timothy J.; Varghese, Tomy; Doyley, Marvin M.; Weaver, John B.

    2006-01-01

    Two equivalent anthropomorphic breast phantoms were constructed, one for use in ultrasound elastography and the other in magnetic resonance (MR) elastography. A complete description of the manufacturing methods is provided. The materials used were oil-in-gelatin dispersions, where the volume percent oil differentiates the materials, primarily according to Young’s moduli. Values of Young’s moduli are in agreement with in vitro ranges for the corresponding normal and abnormal breast tissues. Ultrasound and nuclear magnetic resonance (NMR) properties are reasonably well represented. Phantoms of the type described promise to aid researchers who are developing hardware and software for elastography. Examples of ultrasound and MR elastograms of the phantoms are included to demonstrate the utility of the phantoms. Also, the level of stability of elastic properties of the component materials is quantified over a 15-month period. Such phantoms can serve as performance-assessing intermediaries between simple phantoms (consisting, for example, of homogeneous cylindrical inclusions in a homogeneous background) and a full-scale clinical trial. Thus, premature clinical trials may be avoided. PMID:16785008

  4. Anthropomorphic breast phantoms for testing elastography systems.

    PubMed

    Madsen, Ernest L; Hobson, Maritza A; Frank, Gary R; Shi, Hairong; Jiang, Jingfeng; Hall, Timothy J; Varghese, Tomy; Doyley, Marvin M; Weaver, John B

    2006-06-01

    Two equivalent anthropomorphic breast phantoms were constructed, one for use in ultrasound elastography and the other in magnetic resonance (MR) elastography. A complete description of the manufacturing methods is provided. The materials used were oil-in-gelatin dispersions, where the volume percent oil differentiates the materials, primarily according to Young's moduli. Values of Young's moduli are in agreement with in vitro ranges for the corresponding normal and abnormal breast tissues. Ultrasound and nuclear magnetic resonance (NMR) properties are reasonably well represented. Phantoms of the type described promise to aid researchers who are developing hardware and software for elastography. Examples of ultrasound and MR elastograms of the phantoms are included to demonstrate the utility of the phantoms. Also, the level of stability of elastic properties of the component materials is quantified over a 15-month period. Such phantoms can serve as performance-assessing intermediaries between simple phantoms (consisting, for example, of homogeneous cylindrical inclusions in a homogeneous background) and a full-scale clinical trial. Thus, premature clinical trials may be avoided. PMID:16785008

  5. 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

  6. 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. PMID:25020066

  7. 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. PMID:26825864

  8. Specific Impulse and Mass Flow Rate Error

    NASA Technical Reports Server (NTRS)

    Gregory, Don A.

    2005-01-01

    Specific impulse is defined in words in many ways. Very early in any text on rocket propulsion a phrase similar to .specific impulse is the thrust force per unit propellant weight flow per second. will be found.(2) It is only after seeing the mathematics written down does the definition mean something physically to scientists and engineers responsible for either measuring it or using someone.s value for it.

  9. Wide-range dynamic magnetic resonance elastography.

    PubMed

    Riek, Kerstin; Klatt, Dieter; Nuzha, Hassan; Mueller, Susanne; Neumann, Ulf; Sack, Ingolf; Braun, Jürgen

    2011-04-29

    Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100 Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10-20 times higher than those used in human MRE. The dispersion of the complex shear modulus (G(⁎)) prevents direct comparison of elastography data at different frequency bands and, consequently, frequency-independent viscoelastic models that fit to G(*) over a wide dynamic range have to be employed. This study presents data of G(*) of samples of agarose gel, liver, brain, and muscle measured by high-resolution MRE in a 7T-animal scanner at 200-800 Hz vibration frequency. Material constants μ and α according to the springpot model and related to shear elasticity and slope of the G(*)-dispersion were determined. Both μ and α of calf brain and bovine liver were found to be similar, while a sample of fibrotic human liver (METAVIR score of 3) displayed about fifteen times higher shear elasticity, similar to μ of bovine muscle measured in muscle fiber direction. α was the highest in fibrotic liver, followed by normal brain and liver, while muscle had the lowest α-values of all biological samples investigated in this study. As expected, the least G(*)-dispersion was seen in soft gel. The proposed technique of wide-range dynamic MRE can provide baseline data for both human MRE and high-dynamic MRE for better understanding tissue mechanics of different tissue structures. PMID:21295305

  10. Passive in vivo elastography from skeletal muscle noise

    SciTech Connect

    Sabra, Karim G.; Conti, Stephane; Roux, Philippe; Kuperman, W. A.

    2007-05-07

    Measuring the in vivo elastic properties of muscles (e.g., stiffness) provides a means for diagnosing and monitoring muscular activity. The authors demonstrated a passive in vivo elastography technique without an active external radiation source. This technique instead uses cross correlations of contracting skeletal muscle noise recorded with skin-mounted sensors. Each passive sensor becomes a virtual in vivo shear wave source. The results point to a low-cost, noninvasive technique for monitoring biomechanical in vivo muscle properties. The efficacy of the passive elastography technique originates from the high density of cross paths between all sensor pairs, potentially achieving the same sensitivity obtained from active elastography methods.

  11. Genetics of impulsive behaviour

    PubMed Central

    Bevilacqua, Laura; Goldman, David

    2013-01-01

    Impulsivity, defined as the tendency to act without foresight, comprises a multitude of constructs and is associated with a variety of psychiatric disorders. Dissecting different aspects of impulsive behaviour and relating these to specific neurobiological circuits would improve our understanding of the etiology of complex behaviours for which impulsivity is key, and advance genetic studies in this behavioural domain. In this review, we will discuss the heritability of some impulsivity constructs and their possible use as endophenotypes (heritable, disease-associated intermediate phenotypes). Several functional genetic variants associated with impulsive behaviour have been identified by the candidate gene approach and re-sequencing, and whole genome strategies can be implemented for discovery of novel rare and common alleles influencing impulsivity. Via deep sequencing an uncommon HTR2B stop codon, common in one population, was discovered, with implications for understanding impulsive behaviour in both humans and rodents and for future gene discovery. PMID:23440466

  12. Behavioral components of impulsivity.

    PubMed

    Stahl, Christoph; Voss, Andreas; Schmitz, Florian; Nuszbaum, Mandy; Tüscher, Oliver; Lieb, Klaus; Klauer, Karl Christoph

    2014-04-01

    Acting in accord with long-term goals requires control of interfering impulses, the success of which depends on several different processes. Using a structural-equation modeling approach, we investigated 5 behavioral components of impulsivity: the control of stimulus interference, proactive interference, and response interference, as well as decisional and motivational impulsivity. Results support the existence of 5 correlated but separable components of impulsive behavior. The present study is the 1st to demonstrate the separability of stimulus and response interference. It also supports the notion that control of response-related interference is not a unitary construct: Response-selection demands were separable from those of withholding or stopping. Relations between behavioral impulsivity components and self-report measures of impulsivity were largely absent. We conclude that as the construct of impulsivity has been extended to describe an increasingly diverse set of phenomena and processes, it has become too broad to be helpful in guiding future research. PMID:23957282

  13. Impulsive action: emotional impulses and their control

    PubMed Central

    Frijda, Nico H.; Ridderinkhof, K. Richard; Rietveld, Erik

    2014-01-01

    This paper presents a novel theoretical view on impulsive action, integrating thus far separate perspectives on non-reflective action, motivation, emotion regulation, and impulse control. We frame impulsive action in terms of directedness of the individual organism toward, away, or against other givens – toward future states and away from one’s present state. First, appraisal of a perceived or thought-of event or object on occasion, rapidly and without premonition or conscious deliberation, triggers a motive to modify one’s relation to that event or object. Situational specifics of the event as perceived and appraised motivate and guide selection of readiness for a particular kind of purposive action. Second, perception of complex situations can give rise to multiple appraisals, multiple motives, and multiple simultaneous changes in action readiness. Multiple states of action readiness may interact in generating action, by reinforcing or attenuating each other, thereby yielding impulse control. We show how emotion control can itself result from a motive state or state of action readiness. Our view links impulsive action mechanistically to states of action readiness, which is the central feature of what distinguishes one kind of emotion from another. It thus provides a novel theoretical perspective to the somewhat fragmented literature on impulsive action. PMID:24917835

  14. Use of a Rayleigh damping model in elastography.

    PubMed

    McGarry, Matthew D J; Van Houten, Elijah E W

    2008-08-01

    A Rayleigh damping model applied to magnetic resonance elastography incorporates attenuation behavior proportionally related to both elastic and inertial forces, and allows two damping parameters to be extracted from an MRI motion dataset. Under time-harmonic conditions, the model can be implemented by the use of complex shear modulus and density, whereas viscoelastic damping models commonly used in elastography consist of only a complex shear modulus, and model only a single damping effect. Simulation studies reveal that the differences between damped elastic behavior resulting from a purely complex shear modulus (CSM damping) and from a purely complex density (CD damping) become larger as the overall level of damping present (indicated by the damping ratio) increases. A plot of results generated from the finite element (FE) model indicate the relative motion differences estimated for a range of damping ratios and CSM/CD damping combinations increase with damping ratio, and can be up to 15% at a damping ratio of 50% and therefore using the correct model for a Rayleigh damped material becomes increasingly important as damping levels increase. Resonance-related effects cause values from this plot to vary by as much as 3% as parameters such as wave speed, frequency, and problem size are altered. These motion differences can be compared to expected noise levels to estimate the parameter resolution achievable by a reconstruction algorithm. An optimization-based global property reconstruction algorithm was developed, and used for testing Rayleigh damping parameter reconstructions with gaussian noise added to the simulated motion input data. The coherent motion errors resulting from altering the combination of the two damping parameters are large enough to allow accurate determination of both of the Rayleigh damping parameters with incoherent noise levels comparable to MR measurements. The accuracy achieved by the global reconstructions was significantly better than

  15. Liver ultrasound elastography: More than staging the disease

    PubMed Central

    Gherlan, George S

    2015-01-01

    Ultrasound elastography is perhaps the most important breakthrough in the evolution of ultrasonography in the last 15 years. Since transient elastography was introduced, many other methods have been developed and became more and more widely available. The value of ultrasound elastography in staging a chronic liver disease has been established by numerous studies. There have been many studies that have shown that using liver elastography it is possible to predict the presence of the complications of cirrhosis: portal hypertension, presence of esophageal varices (and even their risk of bleeding) and hepatocellular carcinoma. It has been shown that liver elastography can predict the progression of liver fibrosis and also the survival (hepatic events - free) of the patients with chronic liver diseases. These are the real quests of the clinicians, this is the ultimate scope of any medical investigation - to predict the outcome of a patient and to help making therapeutic decisions. I brought together only a small amount of the data that has already been written on this subject to support my affirmation that liver ultrasound elastography is more than a tool for staging the liver disease, but it is also comparable to a crystal ball which in the hands of a skilled clinician can reveal the future of the patient and can help to improve this future. PMID:26140079

  16. Liver ultrasound elastography: More than staging the disease.

    PubMed

    Gherlan, George S

    2015-06-28

    Ultrasound elastography is perhaps the most important breakthrough in the evolution of ultrasonography in the last 15 years. Since transient elastography was introduced, many other methods have been developed and became more and more widely available. The value of ultrasound elastography in staging a chronic liver disease has been established by numerous studies. There have been many studies that have shown that using liver elastography it is possible to predict the presence of the complications of cirrhosis: portal hypertension, presence of esophageal varices (and even their risk of bleeding) and hepatocellular carcinoma. It has been shown that liver elastography can predict the progression of liver fibrosis and also the survival (hepatic events - free) of the patients with chronic liver diseases. These are the real quests of the clinicians, this is the ultimate scope of any medical investigation - to predict the outcome of a patient and to help making therapeutic decisions. I brought together only a small amount of the data that has already been written on this subject to support my affirmation that liver ultrasound elastography is more than a tool for staging the liver disease, but it is also comparable to a crystal ball which in the hands of a skilled clinician can reveal the future of the patient and can help to improve this future. PMID:26140079

  17. Demonstration of concurrent tensile testing and magnetic resonance elastography.

    PubMed

    Brinker, Spencer; Klatt, Dieter

    2016-10-01

    Magnetic Resonance Elastography (MRE) is a technique used to measure the mechanical properties of soft tissues and has already shown its diagnostic potential for pathologies involving fibrogenesis and neurodegeneration. Experimental investigation of loading during MRE is fairly unexplored and may help to better understand changing mechanical properties in relation to organ function. Tensile testing is a common technique for examining mechanical properties of materials and is used as the simultaneous comparison method with MRE in this study. 3D MRE data was acquired during quasistatic uniaxial tensile loading of an Ecoflex 0010 cylindrical specimen. Individual MRE scans at 1.5, 2.0, and 2.5kHz where performed on engineering strain increments of 20% from 0% to 140% while tensile reaction force was recorded using a load cell attached to an adjustable elongation slide. Tensile stress-strain relation resembled the Fung hyperelastic strain energy model. We observe that the MRE shear storage modulus is related to the state of tensile deformation. This study demonstrates the feasibility of simultaneous tensile testing during MRE and the new design can potentially be used for MRE calibration using pre-tension. PMID:27429072

  18. Elastography: A New Ultrasound and MRI Procedure

    SciTech Connect

    Pavan, Theo Z.; Vieira, Silvio L.; Carneiro, Antonio A. O.

    2008-08-11

    Elastography is an imaging technique whereby local tissue strains are estimated from small displacements of internal tissue structure. These displacements are generated from a weak, quasi-static or dynamic stress field. Displacement evaluation through ultrasound is based on time delay estimation between speckle patterns of echo maps acquired for different levels of tissue deformation. A classical model of deformation is applying a quasi-static compression on a sample during echoes acquisition. The elastogram map corresponds to the spatial derivation of the displacement map. By magnetic resonance, the displacement is evaluated from a map of phase acquired using a sequence gradient echo synchronized with a mechanical end sinusoidal excitation. The map of shear elastic modulus is obtained from the phase map.

  19. Overhauser-enhanced magnetic resonance elastography.

    PubMed

    Salameh, Najat; Sarracanie, Mathieu; Armstrong, Brandon D; Rosen, Matthew S; Comment, Arnaud

    2016-05-01

    Magnetic resonance elastography (MRE) is a powerful technique to assess the mechanical properties of living tissue. However, it suffers from reduced sensitivity in regions with short T2 and T2 * such as in tissue with high concentrations of paramagnetic iron, or in regions surrounding implanted devices. In this work, we exploit the longer T2 * attainable at ultra-low magnetic fields in combination with Overhauser dynamic nuclear polarization (DNP) to enable rapid MRE at 0.0065 T. A 3D balanced steady-state free precession based MRE sequence with undersampling and fractional encoding was implemented on a 0.0065 T MRI scanner. A custom-built RF coil for DNP and a programmable vibration system for elastography were developed. Displacement fields and stiffness maps were reconstructed from data recorded in a polyvinyl alcohol gel phantom loaded with stable nitroxide radicals. A DNP enhancement of 25 was achieved during the MRE sequence, allowing the acquisition of 3D Overhauser-enhanced MRE (OMRE) images with (1.5 × 2.7 × 9) mm(3) resolution over eight temporal steps and 11 slices in 6 minutes. In conclusion, OMRE at ultra-low magnetic field can be used to detect mechanical waves over short acquisition times. This new modality shows promise to broaden the scope of conventional MRE applications, and may extend the utility of low-cost, portable MRI systems to detect elasticity changes in patients with implanted devices or iron overload. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26915977

  20. Dealing with Impulsivity.

    ERIC Educational Resources Information Center

    Neidhardt, Janet

    1987-01-01

    A mother recounts her neurologically impaired son's struggles and progress in combating impulsivity in his work and social habits. Now 23 years old, employed full-time, and off medication, the son is still impulsive, has problems with social skills, but has improved his self-image through a photography hobby. (CB)

  1. Tendon motion and strain patterns evaluated with two-dimensional ultrasound elastography.

    PubMed

    Chernak, Laura A; Thelen, Darryl G

    2012-10-11

    The purpose of this study was to evaluate the use of 2D ultrasound elastography to assess tendon tissue motion and strain under axial loading conditions. Four porcine flexor tendons were cyclically loaded to 4% peak strain using a servo hydraulic test system. An ultrasound transducer was positioned to image a longitudinal cross-section of the tendon during loading. Ultrasound radiofrequency (RF) data were collected at 63 frames per second simultaneously with applied force and crosshead displacement. A grid of nodes was manually positioned on an ultrasound image of the unloaded tendon. Small kernels (2×1 mm) centered at each node were then cross-correlated with search regions centered at corresponding nodal locations in the subsequent frame. Frame-to-frame nodal displacements were defined as the values that maximized the normalized cross-correlations. This process was repeated across all frames in the loading cycle, providing a measurement of the 2D trajectories of tissue motion throughout the loading cycle. The high resolution displacement measures along the RF beam direction were spatially differentiated to estimate the transverse (relative to tendon fibers) tissue strains. The nodal displacements obtained using this method were very repeatable, with average along-fiber trajectories that were highly correlated (average r=0.99) with the prescribed crosshead displacements. The elastography transverse strains were also repeatable and were consistent with average transverse strains estimated via changes in tendon width. The apparent Poisson's ratios (0.82-1.64) exceeded the incompressibility limit, but are comparable to values found for tendon in prior experimental and computational studies. The results demonstrate that 2D ultrasound elastography is a promising approach for noninvasively assessing localized tissue motion and strain patterns. PMID:22939179

  2. Tendon motion and strain patterns evaluated with two-dimensional ultrasound elastography

    PubMed Central

    Chernak, Laura A.; Thelen, Darryl G.

    2012-01-01

    The purpose of this study was to evaluate the use of 2D ultrasound elastography to assess tendon tissue motion and strains under axial loading conditions. Four porcine flexor tendons were cyclically loaded to 4% peak strain using a servo hydraulic test system. An ultrasound transducer was positioned to image a longitudinal cross-section of the tendon during loading. Ultrasound radiofrequency (RF) data were collected at 63 frames per second simultaneously with applied force and crosshead displacement. A grid of nodes was manually positioned on an ultrasound image of the unloaded tendon. Small kernels (2 × 1 mm) centered at each node were then cross-correlated with search regions centered at corresponding nodal locations in the subsequent frame. Frame-to-frame nodal displacements were defined as the values that maximized the normalized cross-correlations. This process was repeated across all frames in the loading cycle, providing a measurement of the 2D trajectories of tissue motion through out the loading cycle. The high resolution displacement measures along the RF beam direction were spatially differentiated to estimate the transverse (relative to tend on fibers) tissue strains. The nodal displacements obtained using this method were very repeatable, with average along-fiber trajectories that were highly correlated (r2>0.98) with the prescribed crosshead displacements. The elastography transverse strains were also repeatable and were consistent with average transverse strains estimated via changes in tendon width. The apparent Poisson’s ratios (0.82-1.64) exceeded the incompressibility limit, but are comparable to values found for tendon in prior experimental and computational studies. The results demonstrate that 2D ultrasound elastography is a promising approach for noninvasively assessing localized tissue motion and strain patterns. PMID:22939179

  3. Impulsiveness in professional fighters.

    PubMed

    Banks, Sarah J; Mayer, Brittany; Obuchowski, Nancy; Shin, Wanyong; Lowe, Mark; Phillips, Michael; Modic, Michael; Bernick, Charles

    2014-01-01

    Sports involving repeated head trauma are associated with risk of neurodegenerative disorders such as chronic traumatic encephalopathy (CTE). Among the behavioral manifestations of CTE is increased impulsiveness. Here, the authors investigate the relationship between impulsiveness and exposure to head trauma in a large group of active professional fighters. Fighters tended to report less impulsiveness than did non-fighting control respondents. Overall, greater fight exposure was associated with higher levels of a specific form of impulsiveness, although there were differences between mixed martial arts fighters and boxers. Fight exposure was associated with reduction in volume of certain brain structures, and these changes were also associated with impulsiveness patterns. Longitudinal studies of professional fighters are important to understand the risk for neuropsychiatric problems. PMID:24515676

  4. Breast Lesions: Quantitative Diagnosis Using Ultrasound Shear Wave Elastography-A Systematic Review and Meta-Analysis.

    PubMed

    Liu, Baoxian; Zheng, Yanling; Huang, Guangliang; Lin, Manxia; Shan, Quanyuan; Lu, Ying; Tian, Wenshuo; Xie, Xiaoyan

    2016-04-01

    The aim of this meta-analysis was to estimate the diagnostic performance of shear wave elastography (SWE) in differentiating malignant from benign breast lesions. A literature search of PubMed, Web of Science and Scopus up to November 2014 was conducted. A summary receiver operating characteristic curve was constructed, and pooled weighted estimates of sensitivity and specificity were calculated using a bivariate mixed-effects regression model. Thirty-three studies, which included a total of 5838 lesions (2093 malignant, 3745 benign) from 5397 patients, were finally analyzed. Summary sensitivity and specificity were 0.886 (95% confidence interval [CI], 0.858-0.909) and 0.866 (95% CI, 0.833-0.894), respectively. The pooled diagnostic odds ratio was 50.410 (95% CI, 34.972-72.664). And the area under the receiver operating characteristic curve of SWE was 0.94 (95% CI, 0.91-0.96). No publication bias existed among these studies (p = 0.245). In the subgroup analysis, sensitivity and specificity were 0.862 (95% CI, 0.811-0.901) and 0.875 (95% CI, 0.793-0.928) among 1552 lesions from 1429 patients in the 12 studies using acoustic radiation force impulse imaging and 0.897 (95% CI, 0.863-0.923) and 0.863 (95% CI, 0.831-0.889) among another 4436 lesions from 4097 patients in the 21 studies using supersonic shear imaging. When analysis confined to 9 studies evaluated the diagnostic performance of combination SWE and conventional ultrasound, the area under the curve was 0.96 (95% CI, 0.94-0.97), yielding a sensitivity of 0.971 (95% CI, 0.941-0.986) and specificity of 0.801 (95% CI, 0.733-0.856). SWE seems to be a good quantitative method for differentiating breast lesions, with promise for integration into routine imaging protocols. PMID:26778289

  5. Critical comparison of elastography methods to assess chronic liver disease.

    PubMed

    Friedrich-Rust, Mireen; Poynard, Thierry; Castera, Laurent

    2016-07-01

    Staging of liver fibrosis and diagnosis, or exclusion, of early compensated liver cirrhosis are important in the treatment decisions and surveillance of patients with chronic liver disease. Good diagnostic accuracy, increased availability and the possibility to perform follow-up examinations led to the implementation of noninvasive methods into clinical practice. Noninvasive tests are increasingly included in national and international guidelines, leaving liver biopsy reserved for patients with unexplained discordance or suspected additional aetiologies of liver disease. In addition to staging of liver fibrosis, data on the prognostic value of these methods have increased in the past few years and are of great importance for patient care. This Review focuses on elastography methods for noninvasive assessment of liver fibrosis, disease severity and prognosis. Although liver elastography started with transient elastography, at present all large ultrasonography companies offer an elastography technique integrated in their machines. The goal of this Review is to summarize the methodological problems of noninvasive tests in general, in addition to providing an overview on currently available techniques and latest developments in liver elastography. PMID:27273167

  6. Subzone based multi-frequency magnetic resonance elastography using a Rayleigh damped material model.

    PubMed

    Petrov, Andrii; Chase, Geoffrey; Sellier, Mathieu; Latta, Peter; Gruwel, Marco; McGarry, Matthew; Van Houten, Elijah

    2012-01-01

    MR Elastography (MRE) is a relatively novel imaging technique using conventional MRI methods to assess the mechanical properties of tissues. In time-harmonic MRE, a Rayleigh, or proportional, Damping (RD) model incorporates attenuation behavior proportionally related to both elastic and inertial forces, thus providing a more sophisticated description of the elastic energy dissipation occurring in the biological tissue. The overall damping ratio can be extracted from the combined effect of these two components, while an additional measure, called Rayleigh Composition, can be calculated by the ratio between the two components. Thus, RD elastography is capable of not only reconstructing the viscoelastic properties of the material, but also providing additional information about damping behavior and structure. A 3D subzone based reconstruction algorithm using a RD material model has been developed and optimized to reconstruct the viscoelastic properties, damping behavior and elastic energy attenuation mechanism of tissue-simulating damping phantoms across multiple frequencies. Results have shown that all three iterative reconstructed parameters are in relatively close agreement for both the tofu and gelatin materials in both phantom configurations across the frequency range. Preliminary results from in-vivo healthy brain are also presented and discussed. PMID:23365922

  7. Model-based registration of ex vivo and in vivo MRI of the prostate using elastography.

    PubMed

    Nir, Guy; Sahebjavaher, Ramin S; Kozlowski, Piotr; Chang, Silvia D; Sinkus, Ralph

    2013-06-01

    Registration of histopathology to in vivo magnetic resonance imaging (MRI) of the prostate is an important task that can be used to optimize in vivo imaging for cancer detection. Such registration is challenging due to the change in volume and deformation of the prostate during excision and fixation. One approach towards this problem involves the use of an ex vivo MRI of the excised prostate specimen, followed by in vivo to ex vivo MRI registration of the prostate. We propose a novel registration method that uses a patient-specific biomechanical model acquired using magnetic resonance elastography to deform the in vivo volume and match it to the surface of the ex vivo specimen. The forces that drive the deformations are derived from a region-based energy, with the elastic potential used for regularization. The incorporation of elastography data into the registration framework allows inhomogeneous elasticity to be assigned to the in vivo volume. We show that such inhomogeneity improves the registration results by providing a physical regularization of the deformation map. The method is demonstrated and evaluated on six clinical cases. PMID:23475353

  8. Usefulness of strain elastography of the musculoskeletal system

    PubMed Central

    2016-01-01

    Ultrasound elastography is a widely used technique for assessing the mechanical characteristics of tissues. Although there are several ultrasound elastography techniques, strain elastography (SE) is currently the most widely used technique for visualizing an elastographic map in real time. Among its various indications, SE is especially useful in evaluating the musculoskeletal system. In this article, we review the SE techniques for clinical practice and describe the images produced by these techniques in the context of the musculoskeletal system. SE provides information about tissue stiffness and allows real-time visualization of the image; however, SE cannot completely replace gray-scale, color, or power Doppler ultrasonography. SE can increase diagnostic accuracy and may be useful for the follow-up of benign lesions. PMID:26810195

  9. Dynamic programming on a tree for ultrasound elastography

    NASA Astrophysics Data System (ADS)

    Shams, Roozbeh; Boily, Mathieu; Martineau, Paul A.; Rivaz, Hassan

    2016-04-01

    Ultrasound Elastography is an emerging imaging technique that allows estimation of the mechanical characteristics of tissue. Two issues that need to be addressed before widespread use of elastography in clinical environments are real time constraints and deteriorating effects of signal decorrelation between pre- and post-compression images. Previous work has used Dynamic Programming (DP) to estimate tissue deformation. However, in case of large signal decorrelation, DP can fail. In this paper we, have proposed a novel solution to this problem by solving DP on a tree instead of a single Radio-Frequency line. Formulation of DP on a tree allows exploiting significantly more information, and as such, is more robust and accurate. Our results on phantom and in-vivo human data show that DP on tree significantly outperforms traditional DP in ultrasound elastography.

  10. Comparative Lightcraft Impulse Measurements

    NASA Astrophysics Data System (ADS)

    Mead, Franklin B., Jr.; Larson, C. W.; Kalliomaa, Wayne M.

    2001-11-01

    The impulse coupling coefficients, cm, of two radically different laser propulsion thruster concepts (lightcrafts), each 10 cm in diameter, have been measured under equal conditions using two different test stands. Lightcraft one is of toroidal shape and was provided by the U.S. Air Force Research Laboratory (AFRL). A lightcraft of this shape and size has been used in free flight experiments at White Sands Missile Range, NM. Lightcraft two is bell (e.g., a paraboloid) shaped. With this type of lightcraft, the DLR previously conducted preliminary performance experiments, including vertical wire-bound flights in the laboratory. Both test stands were of the pendulum type. Test stand one was provided by the AFRL, and was a "rigid" pendulum, allowing motion in only one degree of freedom. The second test stand, a DLR design, suspended the lightcraft by thin wires and corresponded to a nearly perfect pendulum in the mathematical sense. All experiments employed the DLR electric-beam sustained, pulsed, CO(2) laser with pulse energies up to 400 J. The laser was operated with two configurations: 1) a stable resonator (flat beam profile); and, 2) an unstable resonator (ring shaped beam profile). All experiments were carried out in the open laboratory environment. Propellant, therefore, was either the surrounding air alone, or Delrin as an added solid propellant. For lightcraft one the cm value increased by a factor of three (450 N/MW) by adding Delrin. With lightcraft two, a comparable cm value of 590 N/MW was obtained. This corresponded to a Delrin loss of 60-SO ug/J. Results of cm as a function of the laser pulse energy for the various experimental conditions will be presented.

  11. 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

  12. Endoscopic ultrasound elastography: Current status and future perspectives.

    PubMed

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

    2015-12-21

    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

  13. Quantitative micro-elastography: imaging of tissue elasticity using compression optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Kennedy, Kelsey M.; Chin, Lixin; McLaughlin, Robert A.; Latham, Bruce; Saunders, Christobel M.; Sampson, David D.; Kennedy, Brendan F.

    2015-10-01

    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.

  14. 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

  15. Impulsivity and methamphetamine use.

    PubMed

    Semple, Shirley J; Zians, Jim; Grant, Igor; Patterson, Thomas L

    2005-09-01

    The purpose of this study was to explore the relationship between methamphetamine (meth) use and impulsivity in a sample of 385 HIV-negative heterosexually identified meth users. Participants who scored highest on a self-report measure of impulsivity were compared with those who scored lower in terms of background characteristics, meth use patterns, use of alcohol and other illicit drugs, sexual risk behavior, and psychiatric health variables. Methamphetamine users in the high impulsivity group were younger, less educated, used larger quantities of meth, were more likely to be binge users, had a larger number of sexual partners, engaged in more unprotected vaginal and oral sex, and scored higher on the Beck Depression Inventory as compared with those in the low impulsivity group. In a logistic regression analysis, Beck depression was the factor that best distinguished between meth users who scored high and those who scored low on impulsivity. Neurophysiological pathways that may underlie the relationship between impulsivity and meth use are discussed. PMID:16135337

  16. Tomographic elastography of contracting skeletal muscles from their natural vibrations

    NASA Astrophysics Data System (ADS)

    Sabra, Karim G.; Archer, Akibi

    2009-11-01

    Conventional elastography techniques require an external mechanical or radiation excitation to measure noninvasively the viscoelastic properties of skeletal muscles and thus monitor human motor functions. We developed instead a passive elastography technique using only an array of skin-mounted accelerometers to record the low-frequency vibrations of the biceps brachii muscle naturally generated during voluntary contractions and to determine their two-dimensional directionality. Cross-correlating these recordings provided travel-times measurements of these muscle vibrations between multiple sensor pairs. Travel-time tomographic inversions yielded spatial variations of their propagation velocity during isometric elbow flexions which indicated a nonuniform longitudinal stiffening of the biceps.

  17. General review of magnetic resonance elastography

    PubMed Central

    Low, Gavin; Kruse, Scott A; Lomas, David J

    2016-01-01

    Magnetic resonance elastography (MRE) is an innovative imaging technique for the non-invasive quantification of the biomechanical properties of soft tissues via the direct visualization of propagating shear waves in vivo using a modified phase-contrast magnetic resonance imaging (MRI) sequence. Fundamentally, MRE employs the same physical property that physicians utilize when performing manual palpation - that healthy and diseased tissues can be differentiated on the basis of widely differing mechanical stiffness. By performing “virtual palpation”, MRE is able to provide information that is beyond the capabilities of conventional morphologic imaging modalities. In an era of increasing adoption of multi-parametric imaging approaches for solving complex problems, MRE can be seamlessly incorporated into a standard MRI examination to provide a rapid, reliable and comprehensive imaging evaluation at a single patient appointment. Originally described by the Mayo Clinic in 1995, the technique represents the most accurate non-invasive method for the detection and staging of liver fibrosis and is currently performed in more than 100 centers worldwide. In this general review, the mechanical properties of soft tissues, principles of MRE, clinical applications of MRE in the liver and beyond, and limitations and future directions of this discipline -are discussed. Selected diagrams and images are provided for illustration. PMID:26834944

  18. Vibration safety limits for magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Ehman, E. C.; Rossman, P. J.; Kruse, S. A.; Sahakian, A. V.; Glaser, K. J.

    2008-02-01

    Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within a tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to audit the vibration amplitude of exposure for our IRB-approved human MRE studies, to compare these values to a conservative regulatory standard for vibrational exposure and to evaluate the applicability and implications of this standard for MRE. MRE displacement data were examined from 29 MRE exams, including the liver, brain, kidney, breast and skeletal muscle. Vibrational acceleration limits from a European Union directive limiting occupational exposure to whole-body and extremity vibrations (EU 2002/44/EC) were adjusted for time and frequency of exposure, converted to maximum displacement values and compared to the measured in vivo displacements. The results indicate that the vibrational amplitudes used in MRE studies are below the EU whole-body vibration limit, and the EU guidelines represent a useful standard that could be readily accepted by Institutional Review Boards to define standards for vibrational exposures for MRE studies in humans.

  19. General review of magnetic resonance elastography.

    PubMed

    Low, Gavin; Kruse, Scott A; Lomas, David J

    2016-01-28

    Magnetic resonance elastography (MRE) is an innovative imaging technique for the non-invasive quantification of the biomechanical properties of soft tissues via the direct visualization of propagating shear waves in vivo using a modified phase-contrast magnetic resonance imaging (MRI) sequence. Fundamentally, MRE employs the same physical property that physicians utilize when performing manual palpation - that healthy and diseased tissues can be differentiated on the basis of widely differing mechanical stiffness. By performing "virtual palpation", MRE is able to provide information that is beyond the capabilities of conventional morphologic imaging modalities. In an era of increasing adoption of multi-parametric imaging approaches for solving complex problems, MRE can be seamlessly incorporated into a standard MRI examination to provide a rapid, reliable and comprehensive imaging evaluation at a single patient appointment. Originally described by the Mayo Clinic in 1995, the technique represents the most accurate non-invasive method for the detection and staging of liver fibrosis and is currently performed in more than 100 centers worldwide. In this general review, the mechanical properties of soft tissues, principles of MRE, clinical applications of MRE in the liver and beyond, and limitations and future directions of this discipline -are discussed. Selected diagrams and images are provided for illustration. PMID:26834944

  20. Magnetic resonance elastography hardware design: a survey.

    PubMed

    Tse, Z T H; Janssen, H; Hamed, A; Ristic, M; Young, I; Lamperth, M

    2009-05-01

    Magnetic resonance elastography (MRE) is an emerging technique capable of measuring the shear modulus of tissue. A suspected tumour can be identified by comparing its properties with those of tissues surrounding it; this can be achieved even in deep-lying areas as long as mechanical excitation is possible. This would allow non-invasive methods for cancer-related diagnosis in areas not accessible with conventional palpation. An actuating mechanism is required to generate the necessary tissue displacements directly on the patient in the scanner and three different approaches, in terms of actuator action and position, exist to derive stiffness measurements. However, the magnetic resonance (MR) environment places considerable constraints on the design of such devices, such as the possibility of mutual interference between electrical components, the scanner field, and radio frequency pulses, and the physical space restrictions of the scanner bore. This paper presents a review of the current solutions that have been developed for MRE devices giving particular consideration to the design criteria including the required vibration frequency and amplitude in different applications, the issue of MR compatibility, actuation principles, design complexity, and scanner synchronization issues. The future challenges in this field are also described. PMID:19499839

  1. Compression-sensitive magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

    2013-08-01

    Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus.

  2. Wideband MR elastography for viscoelasticity model identification.

    PubMed

    Yasar, Temel K; Royston, Thomas J; Magin, Richard L

    2013-08-01

    The growing clinical use of MR elastography requires the development of new quantitative standards for measuring tissue stiffness. Here, we examine a soft tissue mimicking phantom material (Ecoflex) over a wide frequency range (200 Hz to 7.75 kHz). The recorded data are fit to a cohort of viscoelastic models of varying complexity (integer and fractional order). This was accomplished using multiple sample sizes by employing geometric focusing of the shear wave front to compensate for the changes in wavelength and attenuation over this broad range of frequencies. The simple axisymmetric geometry and shear wave front of this experiment allows us to calculate the frequency-dependent complex-valued shear modulus of the material. The data were fit to several common models of linear viscoelasticity, including those with fractional derivative operators, and we identified the best possible matches over both a limited frequency band (often used in clinical studies) and over the entire frequency span considered. In addition to demonstrating the superior capability of the fractional order viscoelastic models, this study highlights the advantages of measuring the complex-valued shear modulus over as wide a range of frequencies as possible. PMID:23001852

  3. Compression-sensitive magnetic resonance elastography.

    PubMed

    Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

    2013-08-01

    Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus. PMID:23852144

  4. Scatter-based magnetic resonance elastography

    NASA Astrophysics Data System (ADS)

    Papazoglou, Sebastian; Xu, Chao; Hamhaber, Uwe; Siebert, Eberhard; Bohner, Georg; Klingebiel, Randolf; Braun, Jürgen; Sack, Ingolf

    2009-04-01

    Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 ± 0.1 and 1.7 ± 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations.

  5. Magnetic Resonance Elastography: Inversions in Bounded Media

    PubMed Central

    Kolipaka, Arunark; McGee, Kiaran P.; Manduca, Armando; Romano, Anthony J.; Glaser, Kevin J.; Araoz, Philip A.; Ehman, Richard L.

    2009-01-01

    Magnetic resonance elastography (MRE) is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, MRE inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates and spherical shells using geometry-specific equations of motion. MRE and finite element modeling (FEM) of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from FEM and MRE data and a linear correlation of r2 ≥ 0.99 was observed between the stiffness values obtained using MRE and FEM data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. PMID:19780146

  6. DYNAMIC OPTICAL COHERENCE ELASTOGRAPHY: A REVIEW

    PubMed Central

    LIANG, XING; CRECEA, VASILICA; BOPPART, STEPHEN A.

    2012-01-01

    With the development of optical coherence tomography, the application optical coherence elastography (OCE) has gained more and more attention in biomechanics for its unique features including micron-scale resolution, real-time processing, and non-invasive imaging. In this review, one group of OCE techniques, namely dynamic OCE, are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor, external dynamic OCE measurement of in vivo human skin, and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE. These techniques overcame some of the major drawbacks of traditional static OCE, and broadened the OCE application fields. Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics, results of biomechanical properties were obtained from biological tissues. The results suggest potential diagnostic and therapeutic clinical applications. Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems. PMID:22448192

  7. Synthetic aperture elastography: a GPU based approach

    NASA Astrophysics Data System (ADS)

    Verma, Prashant; Doyley, Marvin M.

    2014-03-01

    Synthetic aperture (SA) ultrasound imaging system produces highly accurate axial and lateral displacement estimates; however, low frame rates and large data volumes can hamper its clinical use. This paper describes a real-time SA imaging based ultrasound elastography system that we have recently developed to overcome this limitation. In this system, we implemented both beamforming and 2D cross-correlation echo tracking on Nvidia GTX 480 graphics processing unit (GPU). We used one thread per pixel for beamforming; whereas, one block per pixel was used for echo tracking. We compared the quality of elastograms computed with our real-time system relative to those computed using our standard single threaded elastographic imaging methodology. In all studies, we used conventional measures of image quality such as elastographic signal to noise ratio (SNRe). Specifically, SNRe of axial and lateral strain elastograms computed with real-time system were 36 dB and 23 dB, respectively, which was numerically equal to those computed with our standard approach. We achieved a frame rate of 6 frames per second using our GPU based approach for 16 transmits and kernel size of 60 × 60 pixels, which is 400 times faster than that achieved using our standard protocol.

  8. Wideband MR elastography for viscoelasticity model identification

    PubMed Central

    Yasar, Temel K.; Royston, Thomas J.; Magin, Richard L.

    2012-01-01

    The growing clinical use of MR Elastography (MRE) requires the development of new quantitative standards for measuring tissue stiffness. Here, we examine a soft tissue mimicking phantom material (Ecoflex) over a wide frequency range (200 Hz to 7.75 kHz). The recorded data are fit to a cohort of viscoelastic models of varying complexity (integer and fractional order). This was accomplished using multiple sample sizes by employing geometric focusing of the shear wave front to compensate for the changes in wavelength and attenuation over this broad range of frequencies. The simple axisymmetric geometry and shear wave front of this experiment allows us to calculate the frequency-dependent complex-valued shear modulus of the material. The data were fit to several common models of linear viscoelasticity, including those with fractional derivative operators, and we identified the best possible matches over both a limited frequency band (often used in clinical studies) and over the entire frequency span considered. In addition to demonstrating the superior capability of the fractional order viscoelastic models, this study highlights the advantages of measuring the complex-valued shear modulus over as wide a range of frequencies as possible. PMID:23001852

  9. Angular Impulse and Balance Regulation During the Golf Swing.

    PubMed

    Peterson, Travis J; Wilcox, Rand R; McNitt-Gray, Jill L

    2016-08-01

    Our aim was to determine how skilled players regulate linear and angular impulse while maintaining balance during the golf swing. Eleven highly-skilled golf players performed swings with a 6-iron and driver. Components contributing to linear and angular impulse generated by the rear and target legs (resultant horizontal reaction force [RFh], RFh-angle, and moment arm) were quantified and compared across the group and within a player (α = .05). Net angular impulse generated by both the rear and target legs was greater for the driver than the 6-iron. Mechanisms used to regulate angular impulse generation between clubs varied across players and required coordination between the legs. Increases in net angular impulse with a driver involved increases in target leg RFh. Rear leg RFh-angle was maintained between clubs whereas target leg RFh became more aligned with the target line. Net linear impulse perpendicular to the target line remained near zero, preserving balance, while net linear impulse along the target line decreased in magnitude. These results indicate that the net angular impulse was regulated between clubs by coordinating force generation of the rear and target legs while sustaining balance throughout the task. PMID:26958870

  10. Optically measured explosive impulse

    NASA Astrophysics Data System (ADS)

    Biss, Matthew M.; McNesby, Kevin L.

    2014-06-01

    An experimental technique is investigated to optically measure the explosive impulse produced by laboratory-scale spherical charges detonated in air. Explosive impulse has historically been calculated from temporal pressure measurements obtained via piezoelectric transducers. The presented technique instead combines schlieren flow visualization and high-speed digital imaging to optically measure explosive impulse. Prior to an explosive event, schlieren system calibration is performed using known light-ray refractions and resulting digital image intensities. Explosive charges are detonated in the test section of a schlieren system and imaged by a high-speed digital camera in pseudo-streak mode. Spatiotemporal schlieren intensity maps are converted using an Abel deconvolution, Rankine-Hugoniot jump equations, ideal gas law, triangular temperature decay profile, and Schardin's standard photometric technique to yield spatiotemporal pressure maps. Temporal integration of individual pixel pressure profiles over the positive pressure duration of the shock wave yields the explosive impulse generated for a given radial standoff. Calculated explosive impulses are shown to exhibit good agreement between optically derived values and pencil gage pressure transducers.

  11. 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. PMID:19427100

  12. Impulse-Momentum Diagrams

    NASA Astrophysics Data System (ADS)

    Rosengrant, David

    2011-01-01

    Multiple representations are a valuable tool to help students learn and understand physics concepts. Furthermore, representations help students learn how to think and act like real scientists.2 These representations include: pictures, free-body diagrams,3 energy bar charts,4 electrical circuits, and, more recently, computer simulations and animations.5 However, instructors have limited choices when they want to help their students understand impulse and momentum. One of the only available options is the impulse-momentum bar chart.6 The bar charts can effectively show the magnitude of the momentum as well as help students understand conservation of momentum, but they do not easily show the actual direction. This paper highlights a new representation instructors can use to help their students with momentum and impulse—the impulse-momentum diagram (IMD).

  13. Ultrasound elastography using empirical mode decomposition analysis.

    PubMed

    Sadeghi, Sajjad; Behnam, Hamid; Tavakkoli, Jahan

    2014-01-01

    Ultrasound elastography is a non-invasive method which images the elasticity of soft-tissues. To make an image, pre and after a small compression, ultrasound radio frequency (RF) signals are acquired and the time delays between them are estimated. The first differentiation of displacement estimations is called elastogram. In this study, we are going to make an elastogram using the processing method named empirical mode decomposition (EMD). EMD is an analytic technique which decomposes a complicated signal to a collection of simple signals called intrinsic mode functions (IMFs). The idea of paper is using these IMFs instead of primary RF signals. To implement the algorithms two different datasets selected. The first one was data from a sandwich structure of normal and cooked tissue. The second dataset consisted of around 180 frames acquired from a malignant breast tumor. For displacement estimating, two different methods, cross-correlation and wavelet transform, were used too and for evaluating the quality, two conventional parameters, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) calculated for each image. Results show that in both methods after using EMD the quality improves. In first dataset and cross correlation technique CNR and SNR improve about 16 dB and 9 dB respectively. In same dataset by using wavelet technique, the parameters show 14 dB and 10 dB improvement respectively. In second dataset (breast tumor data) CNR and SNR in cross correlation method improve 18 dB and 7 dB and in wavelet technique improve 17 dB and 6 dB respectively. PMID:24696805

  14. 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

  15. Quantitative optical coherence elastography based on fiber-optic probe for in situ measurement of tissue mechanical properties.

    PubMed

    Qiu, Yi; Wang, Yahui; Xu, Yiqing; Chandra, Namas; Haorah, James; Hubbi, Basil; Pfister, Bryan J; Liu, Xuan

    2016-02-01

    We developed a miniature quantitative optical coherence elastography (qOCE) instrument with an integrated Fabry-Perot force sensor, for in situ elasticity measurement of biological tissue. The technique has great potential for biomechanics modeling and clinical diagnosis. We designed the fiber-optic qOCE probe that was used to exert a compressive force to deform tissue at 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 quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation corresponding to the external stimulus. Simultaneous measurement of force and displacement allowed us to extract Young's modulus of biological tissue. We experimentally calibrated our qOCE instrument, and validated its effectiveness on tissue mimicking phantoms and biological tissues. PMID:26977372

  16. Quantitative optical coherence elastography based on fiber-optic probe for in situ measurement of tissue mechanical properties

    PubMed Central

    Qiu, Yi; Wang, Yahui; Xu, Yiqing; Chandra, Namas; Haorah, James; Hubbi, Basil; Pfister, Bryan J.; Liu, Xuan

    2016-01-01

    We developed a miniature quantitative optical coherence elastography (qOCE) instrument with an integrated Fabry-Perot force sensor, for in situ elasticity measurement of biological tissue. The technique has great potential for biomechanics modeling and clinical diagnosis. We designed the fiber-optic qOCE probe that was used to exert a compressive force to deform tissue at 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 quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation corresponding to the external stimulus. Simultaneous measurement of force and displacement allowed us to extract Young’s modulus of biological tissue. We experimentally calibrated our qOCE instrument, and validated its effectiveness on tissue mimicking phantoms and biological tissues. PMID:26977372

  17. Ballistic impulse gauge

    DOEpatents

    Ault, Stanley K.

    1993-01-01

    A gauge for detecting the impulse generated in sample materials by X-rays or other impulse producing mechanisms utilizes a pair of flat annular springs to support a plunger relative to a housing which may itself be supported by a pair of flat annular springs in a second housing. The plunger has a mounting plate mounted on one end and at the other, a position or velocity transducer is mounted. The annular springs consist of an outer ring and an inner ring with at least three arcuate members connecting the outer ring with the inner ring.

  18. Ballistic impulse gauge

    DOEpatents

    Ault, S.K.

    1993-12-21

    A gauge for detecting the impulse generated in sample materials by X-rays or other impulse producing mechanisms utilizes a pair of flat annular springs to support a plunger relative to a housing which may itself be supported by a pair of flat annular springs in a second housing. The plunger has a mounting plate mounted on one end and at the other, a position or velocity transducer is mounted. The annular springs consist of an outer ring and an inner ring with at least three arcuate members connecting the outer ring with the inner ring. 4 figures.

  19. Noninvasive 3D elasticity mapping using phase-stabilized optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Singh, Manmohan; Li, Jiasong; Wang, Shang; Twa, Michael; Larin, Kirill V.

    2015-03-01

    We demonstrate a novel method for noninvasive elasticity mapping in three dimensions using phase stabilized swept source optical coherence elastography (PhS-SSOCE). By calculating the velocity in all radial directions from the origin of the induced shear wave, a volumetric elasticity map of the sample was generated. Due to the submicrometer spatial sensitivity of PhS-SSOCE, the loading force and the induced deformation amplitude can be minimal, thus preserving the structure and function of delicate tissues such as the cornea and sclera of the eye. Tissue mimicking agar phantoms were utilized for proof of concept testing and the results show that this method can noninvasively provide a three dimensional estimation of sample elasticity.

  20. Feasibility of optical coherence elastography measurements of shear wave propagation in homogeneous tissue equivalent phantoms

    PubMed Central

    Razani, Marjan; Mariampillai, Adrian; Sun, Cuiru; Luk, Timothy W. H.; Yang, Victor X. D.; Kolios, Michael C.

    2012-01-01

    In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a 20 MHz piezoelectric transducer (circular element 8.5 mm diameter) transmitting sine-wave bursts of 400 μs, synchronized with the OCT swept source wavelength sweep. The acoustic radiation force (ARF) was applied to two gelatin phantoms (differing in gelatin concentration by weight, 8% vs. 14%). Differential OCT phase maps, measured with and without the ARF, demonstrate microscopic displacement generated by shear wave propagation in these phantoms of different stiffness. We present preliminary results of OCT derived shear wave propagation velocity and modulus, and compare these results to rheometer measurements. The results demonstrate the feasibility of shear wave OCE (SW-OCE) for high-resolution microscopic homogeneous tissue mechanical property characterization. PMID:22567590

  1. Feasibility of optical coherence elastography measurements of shear wave propagation in homogeneous tissue equivalent phantoms.

    PubMed

    Razani, Marjan; Mariampillai, Adrian; Sun, Cuiru; Luk, Timothy W H; Yang, Victor X D; Kolios, Michael C

    2012-05-01

    In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a 20 MHz piezoelectric transducer (circular element 8.5 mm diameter) transmitting sine-wave bursts of 400 μs, synchronized with the OCT swept source wavelength sweep. The acoustic radiation force (ARF) was applied to two gelatin phantoms (differing in gelatin concentration by weight, 8% vs. 14%). Differential OCT phase maps, measured with and without the ARF, demonstrate microscopic displacement generated by shear wave propagation in these phantoms of different stiffness. We present preliminary results of OCT derived shear wave propagation velocity and modulus, and compare these results to rheometer measurements. The results demonstrate the feasibility of shear wave OCE (SW-OCE) for high-resolution microscopic homogeneous tissue mechanical property characterization. PMID:22567590

  2. Elastography in the differential diagnosis of thyroid nodules.

    PubMed

    Çakal, Erman; Şahin, Mustafa; Ünsal, İlknur Öztürk; Güngüneş, Aşkın; Akkaymak, Esra; Özkaya, Evrim Çakır; Bozkurt, Nujen Çolak; Özbek, Mustafa; Delibaşı, Tuncay

    2015-07-01

    Despite the publication of a recent meta-analysis of elastography in thyroid nodules, further work is necessary on this issue in different populations. In this study, we aimed to evaluate the clinical value of elastography on nodular goiters in mild iodine-deficient regions without excluding patients according to nodule characteristics. This prospective study was conducted between April 2010 and December 2011 in Yıldırım Beyazıt Dıskapı Research Hospital Endocrinology outpatient clinic. Five hundred twenty-eight nodular goiter patients who underwent thyroid fine-needle aspiration biopsy were included in our study. Elastography scores and indexes were measured with real-time ultrasound elastography (Hitachi® EUB 7000 HV machine with 13 MHz linear transducer). There were 471 females and 57 males and their ages ranged from 45 years to 78 years. A total of 601 nodules were evaluated in these patients. The area under the curve (AUC) for the elasto score was 0.91 (p < 0.0001) and AUC for the strain index (SI) was 0.96 (p < 0.0001). We suggest that the SI reflects malignancy better than the elasto score. We conclude that elastography scores greater than 3 have 76% sensitivity and 96% specificity for diagnosing malignancy. For SI, we conclude that 3.75 (83% sensitivity and 95% specificity) is the cutoff point. Elasto score and SI measurements of thyroid nodules in our population are efficient and increase the diagnostic performance of the sonography. PMID:25161183

  3. Walking Through the Impulse-Momentum Theorem

    NASA Astrophysics Data System (ADS)

    Haugland, Ole Anton

    2013-02-01

    Modern force platforms are handy tools for investigating forces during human motion. Earlier they were very expensive and were mostly used in research laboratories. But now even platforms that can measure in two directions are quite affordable. In this work we used the PASCO 2-Axis Force Platform. The analysis of the data can serve as a nice illustration of qualitative or quantitative use of the impulse-momentum theorem p - p0 = ∫t0t Fdt = I. The most common use of force platforms is to study the force from the base during the push-off period of a vertical jump. I think this is an activity of great value, and I would recommend it. The use of force platforms in teaching is well documented in research literature.1-4

  4. Impulse radar studfinder

    DOEpatents

    McEwan, T.E.

    1995-10-10

    An impulse radar studfinder propagates electromagnetic pulses and detects reflected pulses from a fixed range. Unmodulated pulses, about 200 ps wide, are emitted. A large number of reflected pulses are sampled and averaged. Background reflections are subtracted. Reflections from wall studs or other hidden objects are detected and displayed using light emitting diodes. 9 figs.

  5. Impulse radar studfinder

    DOEpatents

    McEwan, Thomas E.

    1995-01-01

    An impulse radar studfinder propagates electromagnetic pulses and detects reflected pulses from a fixed range. Unmodulated pulses, about 200 ps wide, are emitted. A large number of reflected pulses are sampled and averaged. Background reflections are subtracted. Reflections from wall studs or other hidden objects are detected and displayed using light emitting diodes.

  6. Prostate clinical study of a full inversion unconstrained ultrasound elastography technique

    NASA Astrophysics Data System (ADS)

    Mousavi, S. Reza; Sadeghi-Naini, Ali; Czarnota, Gregory J.; Samani, Abbas

    2014-03-01

    Prostate cancer detection at early stages is crucial for desirable treatment outcome. Among available imaging modalities, ultrasound (US) elastography is being developed as an effective clinical tool for prostate cancer diagnosis. Current clinical US elastography systems utilise strain imaging where tissue strain images are generated to approximate the tissue elastic modulus distribution. While strain images can be generated in real-time fashion, they lack the accuracy necessary for having desirable sensitivity and specificity. To improve strain imaging, full inversion based elastography techniques were proposed. Among these techniques, a constrained elastography technique was developed which showed promising results as long as the tumor and prostate geometry can be obtained accurately from the imaging modality used in conjunction with the elastography system. This requirement is not easy to fulfill, especially with US imaging. To address this issue, we present an unconstrained full inversion prostate elastography method in conjunction with US imaging where knowledge of tissue geometry is not necessary. One of the reasons that full inversion elastography techniques have not been routinely used in the clinic is lack of clinical validation studies. To our knowledge, no quasistatic full inversion based prostate US elastography technique has been applied in vivo before. In this work, the proposed method was applied to clinical prostate data and reconstructed elasticity images were compared to corresponding annotated histopathology images which is the first quasi-static full inversion based prostate US elastography technique applied successfully in vivo. Results demonstrated a good potential for clinical utility of the proposed method.

  7. 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

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

    PubMed

    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

  9. Annoyance of helicopter impulsive noise

    NASA Technical Reports Server (NTRS)

    Dambra, F.; Damongeot, A.

    1978-01-01

    Psychoacoustic studies of helicopter impulsive noise were conducted in order to qualify additional annoyance due to this feature and to develop physical impulsiveness descriptors to develop impulsivity correction methods. The currently proposed descriptors and methods of impulsiveness correction are compared using a multilinear regression analysis technique. It is shown that the presently recommended descriptor and correction method provides the best correlation with the subjective evaluations of real helicopter impulsive noises. The equipment necessary for data processing in order to apply the correction method is discussed.

  10. Micropower impulse radar imaging

    SciTech Connect

    Hall, M.S.

    1995-11-01

    From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

  11. Magnetic hyperthermia dosimetry by biomechanical properties revealed in magnetomotive optical coherence elastography (MM-OCE) (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Huang, Pin-Chieh; Marjanovic, Marina; Spillman, Darold R.; Odintsov, Boris M.; Boppart, Stephen A.

    2016-03-01

    Magnetic nanoparticles (MNPs) have been utilized in magnetic hyperthermia to treat solid tumors. Under an appropriate AC magnetic field, energy can be transferred to the MNPs to heat up the intended tissue target while sparing non-targeted healthy tissue. However, a sensitive monitoring technique for the dose of MNP thermal therapy is desirable in order to prevent over-treatment and collateral injury. Typical hyperthermia dosimetry often relies on changes in imaging properties or temperature measurements based on the thermal distribution. Alternative dosimetric indicators can include the biomechanical properties of the tissue, reflecting the changes due to protein denaturation, coagulation, and tissue dehydration during hyperthermia treatments. Tissue stiffness can be probed by elastography modalities including MRI, ultrasound imaging, and optical coherence elastography (OCE), with OCE showing the highest displacement sensitivity (tens of nanometers). Magnetomotive optical coherence elastography (MM-OCE) is one type of OCE that utilizes MNPs as internal force transducers to probe the tissue stiffness. Therefore, we examined the feasibility of evaluating the hyperthermia dose based on the elasticity changes revealed by MM-OCE. Superparamagnetic MNPs were applied to ex vivo tissue specimens for both magnetic hyperthermia and MM-OCE experiments, where temperature and elastic modulus were obtained. A correlation between temperature rise and measured stiffness was observed. In addition, we found that with repetitive sequential treatments, tissue stiffness increased, while temperature rise remained relatively constant. These results potentially suggest that MM-OCE could indicate the irreversible changes the tissue undergoes during thermal therapy, which supports the idea for MM-OCE-based hyperthermia dosage control in future applications.

  12. Application of OCT elastography for diagnosis of thyroid hydatoncus

    NASA Astrophysics Data System (ADS)

    Li, Zhifang; Lin, Xiaona; Li, Hui; Chen, Wei R.

    2014-02-01

    In this study, we presented a method combining optical coherence tomography with wavelet differentiation method to quantify the elastic properties of tissue. Based on the optimized kernel size for 2D normalized cross-correlation, the wavelet differentiation method was used to estimate the tissue strains. The influences of the dilation parameter of wavelet on calculations of axial strain had been investigated. Experimental results suggest that the dilation parameter of 8 was selected in strain calculation for best quality of axial strain images. The method based on wavelet differentiation shows great potential for optical coherence tomography elastography. In addition, elastic properties images of thyroid with suspected cysts were depicted to distinguish benign lesions qualitatively. Thus, elastic properties imaging based on optical coherence elastography shows great promise for the detailed characterization of lesions and preliminary diagnosis of human thyroid diseases.

  13. Editorial: A New Spin on Magnetic Resonance Elastography.

    PubMed

    Kishore, Rekha; Loomba, Rohit; Sterling, Richard K

    2016-06-01

    The development of hepatic fibrosis is the hallmark of liver disease progression. Identifying fibrosis across the spectrum, from early stages to cirrhosis has become a major unmet need. Newer imaging techniques that measure liver elastography (stiffness) as a surrogate of fibrosis seem to outperform serum tests. The current study compares two-dimensional (2D) gradient-recalled echo magnetic resonance elastography (MRE) to three-dimensional (3D) spin-echo echo-planar imaging MRE. 3D-SE-EPI MRE was able to image more liver volume in less time with fewer technical failures. The current study demonstrates that 3D-SE-EPI MRE appears marginally superior to 2D-GRE and may evolve into the new gold standard. PMID:27249983

  14. Optical coherence elastography for tissue characterization: a review

    PubMed Central

    Wang, Shang; Larin, Kirill V.

    2015-01-01

    Optical coherence elastography (OCE) represents the frontier of optical elasticity imaging techniques and focuses on the micro-scale assessment of tissue biomechanics in 3D that is hard to achieve with traditional elastographic methods. Benefit from the advancement of optical coherence tomography, and driven by the increasing requirements in nondestructive biomechanical characterization, this emerging technique recently has experienced a rapid development. In this paper, we start with the description of the mechanical contrast that has been employed by OCE and review the state-of-the-art techniques based on the reported applications and discuss the current technical challenges, emphasizing the unique role of OCE in tissue mechanical characterization. The position of OCE among other elastography techniques. PMID:25412100

  15. 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.

  16. Comb-push Ultrasound Shear Elastography (CUSE) for Evaluation of Thyroid Nodules: Preliminary In vivo Results

    PubMed Central

    Mehrmohammadi, Mohammad; Song, Pengfei; Meixner, Duane D.; Fazzio, Robert T.; Chen, Shigao; Greenleaf, James F.; Fatemi, Mostafa; Alizad, Azra

    2014-01-01

    In clinical practice, an overwhelming majority of biopsied thyroid nodules are benign. Therefore, there is a need for a complementary and noninvasive imaging tool to provide clinically relevant diagnostic information about thyroid nodules to reduce the rate of unnecessary biopsies. The goal of this study was to evaluate the feasibility of utilizing Comb-push Ultrasound Shear Elastography (CUSE) to measure the mechanical properties (i.e., stiffness) of thyroid nodules and use this information to help classify nodules as benign or malignant. CUSE is a fast and robust 2D shear elastography technique in which multiple laterally distributed acoustic radiation force beams are utilized simultaneously to produce shear waves. Unlike other shear elasticity imaging modalities, CUSE does not suffer from limited field of view (FOV) due to shear wave attenuation and can provide a large FOV at high frame rates. To evaluate the utility of CUSE in thyroid imaging, a preliminary study was performed on a group of 5 healthy volunteers and 10 patients with ultrasound (US)-detected thyroid nodules prior to fine needle aspiration biopsy (FNAB). The measured shear wave speeds in normal thyroid tissue and thyroid nodules were converted to Young's modulus (E), indicating a measure of tissue stiffness. Our results indicate an increase in E for thyroid nodules compared to normal thyroid tissue. This increase was significantly higher in malignant nodules compared to benign. The Young's modulus in normal thyroid tissue, benign and malignant nodules were found to be 23.2±8.29 kPa, 91.2±34.8 kPa, and 173.0±17.1 kPa, respectively. Results of this study suggest the utility of CUSE in differentiating between benign and malignant thyroid nodules. PMID:25122532

  17. Shear Wave Elastography and Cervical Lymph Nodes: Predicting Malignancy.

    PubMed

    Azizi, Ghobad; Keller, James M; Mayo, Michelle L; Piper, Kelé; Puett, David; Earp, Karly M; Malchoff, Carl D

    2016-06-01

    This prospective study evaluates the accuracy of virtual touch imaging quantification (VTIQ), a non-invasive shear wave elastography method for measuring cervical lymph nodes (LN) stiffness in differentiating benign from malignant LN. The study evaluated 270 LN in 236 patients with both conventional B-mode ultrasound and VTIQ shear wave elastography before fine-needle aspiration biopsy (FNAB). LN stiffness was measured as shear wave velocity (SWV) in m/s. Surgical resection was advised for FNAB results that were not clearly benign. Surgical pathology confirmed 54 malignant LN. The receiver operating curve (ROC) identified a single cut-off value of 2.93 m/s as the maximum SWV for predicting a malignant cervical LN. The sensitivity and specificity were 92.59% and 75.46%, respectively. Positive predictive value (PPV) was 48.54% and negative predictive value (NPV) was 97.60%. LN stiffness measured by VTIQ-generated shear wave elastography is an independent predictor of malignancy. PMID:26976785

  18. Spatial Angular Compounding for Elastography without the Incompressibility Assumption

    PubMed Central

    Rao, Min; Varghese, Tomy

    2007-01-01

    Spatial-angular compounding is a new technique that enables the reduction of noise artifacts in ultrasound elastography. Previous results using spatial angular compounding, however, were based on the use of the tissue incompressibility assumption. Compounded elastograms were obtained from a spatially-weighted average of local strain estimated from radiofrequency echo signals acquired at different insonification angles. In this paper, we present a new method for reducing the noise artifacts in the axial strain elastogram utilizing a least-squares approach on the angular displacement estimates that does not use the incompressibility assumption. This method produces axial strain elastograms with higher image quality, compared to noncompounded axial strain elastograms, and is referred to as the least-squares angular-compounding approach for elastography. To distinguish between these two angular compounding methods, the spatial-angular compounding with angular weighting based on the tissue incompressibility assumption is referred to as weighted compounding. In this paper, we compare the performance of the two angular-compounding techniques for elastography using beam steering on a linear-array transducer. Quantitative experimental results demonstrate that least-squares compounding provides comparable but smaller improvements in both the elastographic signal-to-noise ratio and the contrast-to-noise ratio, as compared to the weighted-compounding method. Ultrasound simulation results suggest that the least-squares compounding method performs better and provide accurate and robust results when compared to the weighted compounding method, in the case where the incompressibility assumption does not hold. PMID:16761786

  19. Dissociated neural substrates underlying impulsive choice and impulsive action.

    PubMed

    Wang, Qiang; Chen, Chunhui; Cai, Ying; Li, Siyao; Zhao, Xiao; Zheng, Li; Zhang, Hanqi; Liu, Jing; Chen, Chuansheng; Xue, Gui

    2016-07-01

    There is a growing consensus that impulsivity is a multifaceted construct that comprises several components such as impulsive choice and impulsive action. Although impulsive choice and impulsive action have been shown to be the common characteristics of some impulsivity-related psychiatric disorders, surprisingly few studies have directly compared their neural correlates and addressed the question whether they involve common or distinct neural correlates. We addressed this important empirical gap using an individual differences approach that could characterize the functional relevance of neural networks in behaviors. A large sample (n=227) of college students was tested with the delay discounting and stop-signal tasks, and their performances were correlated with the neuroanatomical (gray matter volume, GMV) and functional (resting-state functional connectivity, RSFC) measures, using multivariate pattern analysis (MVPA) and 10-fold cross-validation. Behavioral results showed no significant correlation between impulsive choice measured by discounting rate (k) and impulsive action measured by stop signal reaction time (SSRT). The GMVs in the right frontal pole (FP) and left middle frontal gyrus (MFG) were predictive of k, but not SSRT. In contrast, the GMVs in the right inferior frontal gyrus (IFG), supplementary motor area (SMA), and anterior cingulate cortex (ACC) could predict individuals' SSRT, but not k. RSFC analysis using the FP and right IFG as seed regions revealed two distinct networks that correspond well to the "waiting" and "stopping" systems, respectively. Furthermore, the RSFC between the FP and ventromedial prefrontal cortex (VMPFC) was predictive of k, whereas the RSFC between the IFG and pre-SMA was predictive of SSRT. These results demonstrate clearly neural dissociations between impulsive choice and impulsive action, provide new insights into the nature of impulsivity, and have implications for impulsivity-related disorders. PMID:27083527

  20. Development of a training phantom for compression breast elastography-comparison of various elastography systems and numerical simulations.

    PubMed

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

    2015-10-01

    The elastic properties of tissue are related to tissue composition and pathological changes. It has been observed that many pathological processes increase the elastic modulus of soft tissue compared to normal. Ultrasound compression elastography is a method of characterization of elastic properties that has been the focus of many research efforts in the last two decades. In medical radiology, compression elastography is provided as an additional tool with ultrasound B-mode in the existing scanners, and the combined features of elastography and echography act as a promising diagnostic method in breast cancer detection. However, the full capability of the ultrasound elastography technique together with B-mode has not been utilized by novice radiologists due to the nonavailability of suitable, appropriately designed tissue-mimicking phantoms. Since different commercially available ultrasound elastographic scanners follow their own unique protocols, training novice radiologists is becoming cumbersome. The main focus of this work is to develop a tissue-like agar-based phantom, which mimics breast tissue with common abnormal lesions like fibroadenoma and invasive ductal carcinoma in a clinically perceived way and compares the sonographic and elastographic appearances using different commercially available systems. In addition, the developed phantoms are simulated using the finite-element method, and ideal strain images are generated. Strain images from experiment and simulation are compared based on image contrast parameters, namely contrast transfer efficiency (CTE) and observed strain, and they are in good agreement. The strain image contrast of malignant inclusions is significantly improved compared to benign inclusions, and the trend of CTE is similar for all elastographic scanners under investigation. PMID:26697511

  1. Prospective Comparison of Liver Stiffness Measurements between Two Point Shear Wave Elastography Methods: Virtual Touch Quantification and Elastography Point Quantification

    PubMed Central

    Yoo, Hyunsuk; Yoon, Jeong Hee; Lee, Dong Ho; Chang, Won; Han, Joon Koo

    2016-01-01

    Objective To prospectively compare technical success rate and reliable measurements of virtual touch quantification (VTQ) elastography and elastography point quantification (ElastPQ), and to correlate liver stiffness (LS) measurements obtained by the two elastography techniques. Materials and Methods Our study included 85 patients, 80 of whom were previously diagnosed with chronic liver disease. The technical success rate and reliable measurements of the two kinds of point shear wave elastography (pSWE) techniques were compared by χ2 analysis. LS values measured using the two techniques were compared and correlated via Wilcoxon signed-rank test, Spearman correlation coefficient, and 95% Bland-Altman limit of agreement. The intraobserver reproducibility of ElastPQ was determined by 95% Bland-Altman limit of agreement and intraclass correlation coefficient (ICC). Results The two pSWE techniques showed similar technical success rate (98.8% for VTQ vs. 95.3% for ElastPQ, p = 0.823) and reliable LS measurements (95.3% for VTQ vs. 90.6% for ElastPQ, p = 0.509). The mean LS measurements obtained by VTQ (1.71 ± 0.47 m/s) and ElastPQ (1.66 ± 0.41 m/s) were not significantly different (p = 0.209). The LS measurements obtained by the two techniques showed strong correlation (r = 0.820); in addition, the 95% limit of agreement of the two methods was 27.5% of the mean. Finally, the ICC of repeat ElastPQ measurements was 0.991. Conclusion Virtual touch quantification and ElastPQ showed similar technical success rate and reliable measurements, with strongly correlated LS measurements. However, the two methods are not interchangeable due to the large limit of agreement. PMID:27587964

  2. Impulsive Action but Not Impulsive Choice Determines Problem Gambling Severity

    PubMed Central

    Brevers, Damien; Cleeremans, Axel; Verbruggen, Frederick; Bechara, Antoine; Kornreich, Charles; Verbanck, Paul; Noël, Xavier

    2012-01-01

    Background Impulsivity is a hallmark of problem gambling. However, impulsivity is not a unitary construct and this study investigated the relationship between problem gambling severity and two facets of impulsivity: impulsive action (impaired ability to withhold a motor response) and impulsive choice (abnormal aversion for the delay of reward). Methods The recruitment includes 65 problem gamblers and 35 normal control participants. On the basis of DSM-IV-TR criteria, two groups of gamblers were distinguished: problem gamblers (n = 38) and pathological gamblers (n = 27) with similar durations of gambling practice. Impulsive action was assessed using a response inhibition task (the stop-signal task). Impulsive choice was estimated with the delay-discounting task. Possible confounds (e.g., IQ, mood, ADHD symptoms) were recorded. Results Both problem and pathological gamblers discounted reward at a higher rate than their controls, but only pathological gamblers showed abnormally low performance on the most demanding condition of the stop-signal task. None of the potential confounds covaried with these results. Conclusions These results suggest that, whereas abnormal impulsive choice characterizes all problem gamblers, pathological gamblers' impairments in impulsive action may represent an important developmental pathway of pathological gambling. PMID:23209796

  3. Fine Needle Elastography (FNE) device for biomechanically determining local variations of tissue mechanical properties.

    PubMed

    Wickramaratne, Dayan; Wilkinson, Paul; Rao, JianYu; Ragavendra, Nagesh; Sharma, Shivani; Gimzewski, James K

    2015-01-01

    Diseased tissues exhibit changes in mechanical properties and thus possess clinical diagnostic significance. We report the design and development of a Fine Needle Elastography (FNE) prototype device integrated with Fine Needle Aspiration Cytology (FNAC) needle that allows for quantitative and sensitive assessment of tissues and materials based on local variations in elastic, friction, and cutting forces on needle insertion. A piezoelectric force-sensor at the base of FNA needle measures the forces opposing needle penetration with micrometer scale resolution. Measurement precision (±5 μm) and axial resolution (~20 μm) of FNE device was tested using control mm size gelatin matrices and unripe pear in assessing needle penetration resistance, force heterogeneity and optimization of needle penetration velocity. Further, we demonstrated the usefulness of FNE in quantitative, biomechanical differentiation of simulated thyroid tumor nodules in an ultrasound neck phantom. Fluid or solid nodules were probed in the phantom study coupled with ultrasound guidance. Our data shows significantly higher force variations (1-D force heterogeneity; HF,a=6.5 mN, HF,q=8.25 mN and stiffness heterogeneity; HS,a=0.0274 kN/m, HS,q=0.0395 kN/m) in solid nodules compared either to fluid nodules or to regions corresponding to healthy thyroid tissue within the ultrasound phantom. The results suggest future applications of in vivo FNE biopsies based on force heterogeneity to diagnose thyroid tumors in areas where ultrasound instrumentation or access to a qualified pathologist for FNAC are unavailable, as well as an ancillary diagnostic tool in thyroid cancer management. PMID:25468668

  4. Thin film eddy current impulse deicer

    NASA Technical Reports Server (NTRS)

    Smith, Samuel O.; Zieve, Peter B.

    1990-01-01

    Two new styles of electrical impulse deicers has been developed and tested in NASA's Icing Research Tunnel. With the Eddy Current Repulsion Deicing Boot (EDB), a thin and flexible spiral coil is encapsulated between two thicknesses of elastomer. The coil, made by an industrial printed circuit board manufacturer, is bonded to the aluminum aircraft leading edge. A capacitor bank is discharged through the coil. Induced eddy currents repel the coil from the aluminum aircraft structure and shed accumulated ice. A second configuration, the Eddy Current Repulsion Deicing-Strip (EDS) uses an outer metal erosion strip fastened over the coil. Opposite flowing eddy currents repel the strip and create the impulse deicing force. The outer strip serves as a surface for the collection and shedding of ice and does not require any structural properties. The EDS is suitable for composite aircraft structures. Both systems successfully dispelled over 95 percent of the accumulated ice from airfoils over the range of the FAA icing envelope.

  5. 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

  6. 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. PMID:25541954

  7. Impulsive phase transport

    NASA Technical Reports Server (NTRS)

    Canfield, Richard C.; Bely-Dubau, Francoise; Brown, John C.; Dulk, George A.; Emslie, A. Gordon; Enome, Shinzo; Gabriel, Alan H.; Kundu, Mukul R.; Melrose, Donald; Neidig, Donald F.

    1986-01-01

    The transport of nonthermal electrons is explored. The thick-target electron beam model, in which electrons are presumed to be accelerated in the corona and typically thermalized primarily in the chromosphere and photosphere, is supported by observations throughout the electromagnetic spectrum. At the highest energies, the anisotropy of gamma-ray emission above 10 MeV clearly indicates that these photons are emitted by anisotropically-directed particles. The timing of this high-energy gamma-radiation with respect to lower-energy hard X-radiation implies that the energetic particles have short life-times. For collisional energy loss, this means that they are stopped in the chromosphere or below. Stereoscopic (two-spacecraft) observations at hard X-ray energies (up to 350 keV) imply that these lower-energy (but certainly nonthermal) electrons are also stopped deep in the chromosphere. Hard X-ray images show that, in spatially resolved flares whose radiation consists of impulsive bursts, the impulsive phase starts with X-radiation that comes mostly from the foot-points of coronal loops whose coronal component is outlined by microwaves.

  8. Transient Elastography in Clinical Detection of Liver Cirrhosis: A Systematic Review and Meta-analysis

    PubMed Central

    Geng, Xiao-Xia; Huang, Ren-Gang; Lin, Jian-Mei; Jiang, Nan; Yang, Xing-Xiang

    2016-01-01

    Background/Aims: Transient elastography is a noninvasive method for measuring liver fibrosis. This meta-analysis assesses the diagnostic performance of transient elastography of detecting liver cirrhosis in patients with liver disease. Patients and Methods: We searched MEDLINE, Cochrane, EMBASE databases until Jan 31, 2015, using the following search terms: elastography and liver cirrhosis. Included studies assessed patients with a diagnosis of liver cirrhosis, with an index test of transient elastography, and with the reference standard being a histopathological exam by liver biopsy. Sensitivity analysis and assessment of risk of bias and publication bias were performed. Results: Fifty-seven studies were included in the meta-analysis with a total of 10,504 patients. The pooled estimate for the sensitivity of transient elastography for detecting liver fibrosis was 81% and the specificity was 88%. The imputed diagnostic odds ratio (DOR) was 26.08 and the area under the receiver-operating characteristic (AUROC) curve was 0.931. Conclusion: Our findings indicate that transient elastography shows good sensitivity, specificity and a high accuracy for detecting liver cirrhosis. Transient elastography can be used as an additional method for the clinical diagnosis of liver fibrosis and cirrhosis. PMID:27488324

  9. Teaching about Impulse and Momentum

    ERIC Educational Resources Information Center

    Franklin, Bill

    2004-01-01

    This American Association of Physics Teachers/Physics Teaching Resource Agents (APPT/PTRA) spiral-bound manual features labs and demos physics teachers can use to give students hands-on opportunities to learn about impulse and momentum. "Make-and-take activities" include AAPT Apparatus Contest winners "An Air Impulse Rocket," "A Fan Driven…

  10. 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.

  11. Dynamic and quantitative assessment of blood coagulation using optical coherence elastography.

    PubMed

    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

  12. 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

  13. 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

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

    PubMed Central

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

    2016-01-01

    Summary 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

  15. Nonsputtering impulse magnetron discharge

    SciTech Connect

    Khodachenko, G. V.; Mozgrin, D. V.; Fetisov, I. K.; Stepanova, T. V.

    2012-01-15

    Experiments with quasi-steady high-current discharges in crossed E Multiplication-Sign B fields in various gases (Ar, N{sub 2}, H{sub 2}, and SF{sub 6}) and gas mixtures (Ar/SF{sub 6} and Ar/O{sub 2}) at pressures from 10{sup -3} to 5 Torr in discharge systems with different configurations of electric and magnetic fields revealed a specific type of stable low-voltage discharge that does not transform into an arc. This type of discharge came to be known as a high-current diffuse discharge and, later, a nonsputtering impulse magnetron discharge. This paper presents results from experimental studies of the plasma parameters (the electron temperature, the plasma density, and the temperature of ions and atoms of the plasma-forming gas) of a high-current low-pressure diffuse discharge in crossed E Multiplication-Sign B fields.

  16. Recent Insights into the Neurobiology of Impulsivity

    PubMed Central

    Mitchell, Marci R.; Potenza, Marc N.

    2014-01-01

    Impulsivity is associated with various psychopathologies, and elevated impulsivity is typically disadvantageous. This manuscript reviews recent investigations into the neurobiology of impulsivity using human imaging techniques and animal models. Both human imaging and preclinical pharmacological manipulations have yielded important insights into the neurobiological underpinnings of impulsivity. A more thorough understanding of the complex neurobiology underlying aspects of impulsivity may provide insight into new treatment options that target elevated impulsivity and psychopathologies such as addictions. PMID:25431750

  17. Real-time quasi-static ultrasound elastography

    PubMed Central

    Treece, Graham; Lindop, Joel; Chen, Lujie; Housden, James; Prager, Richard; Gee, Andrew

    2011-01-01

    Ultrasound elastography is a technique used for clinical imaging of tissue stiffness with a conventional ultrasound machine. It was first proposed two decades ago, but active research continues in this area to the present day. Numerous clinical applications have been investigated, mostly related to cancer imaging, and though these have yet to prove conclusive, the technique has seen increasing commercial and clinical interest. This paper presents a review of the most widely adopted, non-quantitative, techniques focusing on technical innovations rather than clinical applications. The review is not intended to be exhaustive, concentrating instead on placing the various techniques in context according to the authors' perspective of the field. PMID:22866230

  18. Impulse and Frequency Response of a Moving Coil Galvanometer.

    ERIC Educational Resources Information Center

    McNeill, D. J.

    1985-01-01

    Describes an undergraduate laboratory experiment in which a moving coil galvanometer is studied and the electromotive force generated by the swinging coil provides the impulse response information in a form suitable for digitizing and inputing to a microcomputer. Background information and analysis of typical data are included. (JN)

  19. Feasibility of monitoring HIFU prostate cancer therapy using elastography

    NASA Astrophysics Data System (ADS)

    Souchon, Remi; Chapelon, Jean Y.; Bertrand, Michel J.; Kallel, Faouzi; Ophir, Jonathan

    2001-05-01

    The objective of this study is to investigate the feasibility of elastographic monitoring of High Intensity Focused Ultrasound (HIFU) therapy of prostate cancer. Elastography is an imaging technique based on strain estimation in soft tissues under quasi-static compression. Since pathological tissues and HIFU-induced lesions exhibit different elastic properties than normal tissues, elastography is potentially able to achieve these goals. An ultrasound scanner was connected to a PC to acquire RF images. This setup is compatible with a HIFU device used for prostate cancer therapy by transrectal route. The therapy transducer and the biplane-imaging probe are covered with a balloon filled with a coupling liquid. Compression of the prostate is applied by inflating the balloon, while imaging sector scans of the prostate. In-vivo elastograms of the prostate were acquired before HIFU treatment. Problems inherent to in-vivo acquisitions are reported, such as undesired tangential displacements during the radial compression. This study shows the potential for in-vivo elastogram acquisition of HIFU-induced lesions in the human prostate.

  20. Predicting prognostic factors of breast cancer using shear wave elastography.

    PubMed

    Choi, Woo Jung; Kim, Hak Hee; Cha, Joo Hee; Shin, Hee Jung; Kim, Hyunji; Chae, Eun Young; Hong, Min Ji

    2014-02-01

    The purpose of the study described here was to investigate the correlation between histologic factors, including immunohistochemical factors, related to the prognosis of breast cancer and shear wave elastography (SWE) measurements. One hundred twenty-two breast cancers from 116 women were subjected to sonoelastography. Of the SWE features, mean and maximum elasticity and SWE ratio were extracted. The SWE ratio was calculated as the ratio of the stiffness of a portion of the lesion to that of a similar region of interest in fatty tissue. High ratios indicate stiffer lesions. The Mann-Whitney U-test, Kruskal-Wallis test and receiver operating characteristic (ROC) curve were used for statistical analysis. Estrogen receptor negativity, progesterone receptor negativity, p53 positivity, Ki-67 positivity, high nuclear grade, high histologic grade and large tumor (invasive) size were associated with a significantly high SWE ratio (p < 0.05). ROC curve analysis yielded SWE ratio cutoff values of 2.74-3.69 for significant immunohistochemical factors and 4.21 for the basal-like subtype by maximizing specificity while ensuring more than 80% sensitivity. Breast cancers with aggressive histologic features had high SWE ratios. Shear wave elastography may provide useful information for determining prognosis. PMID:24268451

  1. Ultrasound elastography: enabling technology for image guided laparoscopic prostatectomy

    NASA Astrophysics Data System (ADS)

    Fleming, Ioana N.; Rivaz, Hassan; Macura, Katarzyna; Su, Li-Ming; Hamper, Ulrike; Lagoda, Gwen A.; Burnett, Arthur L., II; Lotan, Tamara; Taylor, Russell H.; Hager, Gregory D.; Boctor, Emad M.

    2009-02-01

    Radical prostatectomy using the laparoscopic and robot-assisted approach lacks tactile feedback. Without palpation, the surgeon needs an affordable imaging technology which can be easily incorporated into the laparoscopic surgical procedure, allowing for precise real time intraoperative tumor localization that will guide the extent of surgical resection. Ultrasound elastography (USE) is a novel ultrasound imaging technology that can detect differences in tissue density or stiffness based on tissue deformation. USE was evaluated here as an enabling technology for image guided laparoscopic prostatectomy. USE using a 2D Dynamic Programming (DP) algorithm was applied on data from ex vivo human prostate specimens. It proved consistent in identification of lesions; hard and soft, malignant and benign, located in the prostate's central gland or in the peripheral zone. We noticed the 2D DP method was able to generate low-noise elastograms using two frames belonging to the same compression or relaxation part of the palpation excitation, even at compression rates up to 10%. Good preliminary results were validated by pathology findings, and also by in vivo and ex vivo MR imaging. We also evaluated the use of ultrasound elastography for imaging cavernous nerves; here we present data from animal model experiments.

  2. Shear wave elastography using phase sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Song, Shaozhen; Huang, Zhihong; Nguyen, Thu-Mai; Wong, Emily Y.; Arnal, Bastien; O'Donnell, Matthew; Wang, Ruikang K.

    2014-03-01

    Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that are ideal for imaging the cornea and lens. Quantifying the biomechanical properties of these tissues could add clinically valuable information. Thus, we propose a dynamic elastography method combining OCT detection and a mechanical actuator to map the shear modulus of soft tissues. We used a piezoelectric actuator driven in the kHz range and we used phase-sensitive OCT (PhS-OCT) to track the resulting shear waves at an equivalent frame rate of 47 kHz. We mapped the shear wave speed of anesthetized mice cornea using monochromatic excitations. We found a significant difference between a group of knock-out (3.92 +/- 0.35 m/s, N=4) and wild-type mice (5.04 +/- 0.51 m/s, N=3). These preliminary results demonstrate the feasibility of using PhS-OCT to perform in vivo shear wave elastography of the cornea. We then implemented a shear pulse compression approach on ex vivo human cornea. For that purpose, frequency- modulated excitations were used and the resulting displacement field was digitally compressed in a short broadband pulse with a 7 dB gain in signal-to-noise ratio (SNR).

  3. Rheological assessment of a polymeric spherical structure using a three-dimensional shear wave scattering model in dynamic spectroscopy elastography.

    PubMed

    Montagnon, Emmanuel; Hadj-Henni, Anis; Schmitt, Cédric; Cloutier, Guy

    2014-02-01

    With the purpose of assessing localized rheological behavior of pathological tissues using ultrasound dynamic elastography, an analytical shear wave scattering model was used in an inverse problem framework. The proposed method was adopted to estimate the complex shear modulus of viscoelastic spheres from 200 to 450 Hz. The inverse problem was formulated and solved in the frequency domain, allowing assessment of the complex viscoelastic shear modulus at discrete frequencies. A representative rheological model of the spherical obstacle was determined by comparing storage and loss modulus behaviors with Kelvin-Voigt, Maxwell, Zener, and Jeffrey models. The proposed inversion method was validated by using an external vibrating source and acoustic radiation force. The estimation of viscoelastic properties of three-dimensional spheres made softer or harder than surrounding tissues did not require a priori rheological assumptions. The proposed method is intended to be applied in the context of breast cancer imaging. PMID:24474134

  4. Modification of impulse generation during piqué turns with increased rotational demands.

    PubMed

    Zaferiou, Antonia M; Wilcox, Rand R; McNitt-Gray, Jill L

    2016-06-01

    During initiation of a piqué turn, a dancer generates impulse to achieve the desired lateral translation and whole-body rotation. The goal of this study was to determine how individuals regulate impulse generation when initiating piqué turns with increased rotational demands. Skilled dancers (n=10) performed single (∼360°) and double (∼720°) piqué turns from a stationary position. Linear and angular impulse generated by the push and turn legs were quantified using ground reaction forces and compared across turn conditions as a group and within a dancer using probability-based statistical methods. The results indicate that as the rotation demands of the piqué turn increased, the net angular impulse generated increased whereas net lateral impulse decreased. Early during turn initiation, the free moment contributed to angular impulse generation. Later during turn initiation, horizontal reaction forces were controlled to generate angular impulse. As rotational demands increased, the moment applied increased primarily from redirection of the horizontal reaction force (RFh) at the push leg and a combination of RFh magnitude and moment arm increases at the turn leg. RFh at each leg were coordinated to limit unwanted net linear impulse. Knowledge of observed subject-specific mechanisms is important to inform the design of turning performance training tools. PMID:27038006

  5. Microwave emission from lead zirconate titanate induced by impulsive mechanical load

    NASA Astrophysics Data System (ADS)

    Aman, A.; Majcherek, S.; Hirsch, S.; Schmidt, B.

    2015-10-01

    This paper focuses on microwave emission from Lead zirconate titanate Pb [ZrxTi1-x] O3 (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression and restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.

  6. WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 2: breast.

    PubMed

    Barr, Richard G; Nakashima, Kazutaka; Amy, Dominique; Cosgrove, David; Farrokh, Andre; Schafer, Fritz; Bamber, Jeffrey C; Castera, Laurent; Choi, Byung Ihn; Chou, Yi-Hong; Dietrich, Christoph F; Ding, Hong; Ferraioli, Giovanna; Filice, Carlo; Friedrich-Rust, Mireen; Hall, Timothy J; Nightingale, Kathryn R; Palmeri, Mark L; Shiina, Tsuyoshi; Suzuki, Shinichi; Sporea, Ioan; Wilson, Stephanie; Kudo, Masatoshi

    2015-05-01

    The breast section of these Guidelines and Recommendations for Elastography produced under the auspices of the World Federation of Ultrasound in Medicine and Biology (WFUMB) assesses the clinically used applications of all forms of elastography used in breast imaging. The literature on various breast elastography techniques is reviewed, and recommendations are made on evidence-based results. Practical advice is given on how to perform and interpret breast elastography for optimal results, with emphasis placed on avoiding pitfalls. Artifacts are reviewed, and the clinical utility of some artifacts is discussed. Both strain and shear wave techniques have been shown to be highly accurate in characterizing breast lesions as benign or malignant. The relationship between the various techniques is discussed, and recommended interpretation based on a BI-RADS-like malignancy probability scale is provided. This document is intended to be used as a reference and to guide clinical users in a practical way. PMID:25795620

  7. Can Hybrid Learning Theory Be Used to Teach Working Sonographers Breast Elastography?

    PubMed Central

    Mitchell, Carol; Hall, Timothy J.; Baker, Sara; Burke, Megan; Knauf, Laura; Willey, Bridgett

    2016-01-01

    Hybrid learning is a combination of on-line learning and face-to-face sessions. This research sought to answer the question of “Can Hybrid Learning be Utilized To Teach Working Sonographers to perform breast Elastography?” We designed a hybrid course entitled “Breast Elastography for Working Sonographers.” This course consisted of four on-line training modules, each complete with a post-test and one face-to-face session. After the face-to-face session lectures, participants were interviewed and observed performing elastography on a breast phantom. Our results indicate that this is a successful method for teaching working sonographers breast elastography, in this setting.

  8. WFUMB guidelines and recommendations for clinical use of ultrasound elastography: Part 3: liver.

    PubMed

    Ferraioli, Giovanna; Filice, Carlo; Castera, Laurent; Choi, Byung Ihn; Sporea, Ioan; Wilson, Stephanie R; Cosgrove, David; Dietrich, Christoph F; Amy, Dominique; Bamber, Jeffrey C; Barr, Richard; Chou, Yi-Hong; Ding, Hong; Farrokh, Andre; Friedrich-Rust, Mireen; Hall, Timothy J; Nakashima, Kazutaka; Nightingale, Kathryn R; Palmeri, Mark L; Schafer, Fritz; Shiina, Tsuyoshi; Suzuki, Shinichi; Kudo, Masatoshi

    2015-05-01

    The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced these guidelines for the use of elastography techniques in liver disease. For each available technique, the reproducibility, results, and limitations are analyzed, and recommendations are given. Finally, recommendations based on the international literature and the findings of the WFUMB expert group are established as answers to common questions. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of liver diseases. PMID:25800942

  9. Cross-Validation of Magnetic Resonance Elastography and Ultrasound-Based Transient Elastography: A Preliminary Phantom Study

    PubMed Central

    Chen, Jun; Glaser, Kevin J; Miette, Véronique; Sandrin, Laurent; Ehman, Richard L

    2010-01-01

    Purpose To cross-validate two recent noninvasive elastographic techniques, Ultrasound-based Transient Elastography (UTE) and Magnetic Resonance Elastography (MRE). As potential alternatives to liver biopsy, UTE and MRE are undergoing clinical investigations for liver fibrosis diagnosis and liver disease management around the world. These two techniques use tissue stiffness as a marker for disease state and it is important to do a cross-validation study of both elastographic techniques to determine the consistency with which the two techniques can measure the mechanical properties of materials. Materials and Methods In this paper, 19 well-characterized phantoms with a range of stiffness values were measured by two clinical devices (a Fibroscan and a MRE system based respectively on the UTE and MRE techniques) successively with the operators double-blinded. Results Statistical analysis showed that the correlation coefficient was r2=0.93 between MRE and UTE, and there was no evidence of a systematic difference between them within the range of stiffnesses examined. Conclusion These two noninvasive methods, MRE and UTE, provide clinicians with important new options for improving patient care regarding liver diseases in terms of the diagnosis, prognosis, and monitoring of fibrosis progression, as well for evaluating the efficacy of treatment. PMID:19856447

  10. Comparison of Diagnostic Accuracy of Real-Time Elastography and Shear Wave Elastography in Differentiation Malignant From Benign Thyroid Nodules.

    PubMed

    Tian, Wuguo; Hao, Shuai; Gao, Bo; Jiang, Yan; Zhang, Shu; Guo, Lingji; Gu, Lingji; Luo, Donglin

    2015-12-01

    Thyroid nodules are relatively more prevalent in iodine-deficiency area, and the incidence increased sharply in the past decade in these areas. Workup of malignant from benign nodules in clinic was the main problem for managing thyroid nodules.An overall search for the articles about the diagnostic performance of real-time elastography (RTE) and shear wave elastography (SWE) before April 2015 in the databases of PubMed, Embase, and Google scholar. The pooled sensitivity, specificity, and summary receiver operating characteristic (SROC) curve were obtained from individual studies with a random-effects model. Subgroup and meta-regression analysis were also performed.Fifty-six studies involved in 2621 malignant nodules and 7380 benign nodules were contained in our meta-analysis. The pooled sensitivity and specificity of RTE was 83.0% and 81.2%, which is higher than SWE (sensitivity: 78.7%, specificity: 80.5%). The areas under the SROC curve of RTE and SWE were 0.885 and 0.842 respectively. RTE had higher diagnostic value for Caucasians than Asians. Stran ratio (SR) assessment had higher diagnostic performance than elasticity score (ES) system. Similarly, it had higher diagnostic value when malignant nodules were more than 50.In summary, the results revealed that RTE had higher diagnostic performance than SWE in differentiating malignant from benign nodules. However, future international multicenter studies in the region of thyroid risk need to further assess the diagnostic performance of RTE. PMID:26717367

  11. 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

  12. 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.

  13. Three-dimensional mapping of corneal elasticity using optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Singh, Manmohan; Li, Jiasong; Wang, Shang; Vantipalli, Srilatha; Twa, Michael; Larin, Kirill V.

    2015-03-01

    We demonstrate a novel method for noninvasive quantification of tissue biomechanical properties in 3D using phase-stabilized swept source optical coherence elastography (PhS-SSOCE). A focused air-pulse delivery system induces an elastic wave, which is then recorded by the PhS-SSOCE system. By calculating the velocity in all radial directions and imaging depths from the origin of the stimulation, a volumetric elasticity map was generated. Utilizing the high spatial sensitivity of PhS-SSOCE, the force applied on the surface of the cornea and subsequent induced deformation amplitude was minimal, thus preserving the structure and function of delicate ocular tissues such as the cornea and sclera. The results show that this noninvasive method for elasticity assessment can provide a volumetric mapping of elasticity and can differentiate untreated and UV-induced collagen cross-linked (CXL) corneas. As expected, the elastic wave velocity and subsequent Young's modulus was significantly higher in the CXL cornea as compared to the untreated cornea, indicating a substantial increase in corneal stiffness after the CXL treatment.

  14. Origin of the sinus impulse.

    PubMed

    Schuessler, R B; Boineau, J P; Bromberg, B I

    1996-03-01

    It was generally accepted that the site of normal impulse origin within the atria was a single static focus within the sinus node. This review will examine how this model of impulse origin came about and has evolved. Early on, conflicting data suggested that the sinus node focus was not static and changed with interventions that changed heart rate, such as vagal stimulation. Furthermore, even with removal of the sinus node, a normal atrial rhythm was generated. High-resolution mapping in humans and dogs showed that the initiation of the impulse was dynamic and could be multicentric, with more than one focus initiating a single beat. Shifts in the site of origin correlated with changes in rate and were consistent with P wave changes routinely observed in the standard ECG. These studies suggested multiple pacemakers were responsible for impulse initiation. However, it was not clear how these widespread pacemakers were coordinated to function synchronously. Recent canine data suggest that the node may be partially insulated from the surrounding atrium, resulting in multicentric origin starting from a single site within the node. What has evolved is a model of impulse origin with a sinus node having discrete exit sites and a dominant pacemaker within the node that can shift to other nodal sites. Complex and changing conduction out of the node, coupled with extranodal pacemakers, which can assume dominance over the node, combine with the autonomic nervous system to control heart rate and the pattern of impulse origin within the atria. PMID:8867301

  15. 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

  16. Dopamine-agonists and impulsivity in Parkinson's disease: impulsive choices vs. impulsive actions.

    PubMed

    Antonelli, Francesca; Ko, Ji Hyun; Miyasaki, Janis; Lang, Anthony E; Houle, Sylvain; Valzania, Franco; Ray, Nicola J; Strafella, Antonio P

    2014-06-01

    The control of impulse behavior is a multidimensional concept subdivided into separate subcomponents, which are thought to represent different underlying mechanisms due to either disinhibitory processes or poor decision-making. In patients with Parkinson's disease (PD), dopamine-agonist (DA) therapy has been associated with increased impulsive behavior. However, the relationship among these different components in the disease and the role of DA is not well understood. In this imaging study, we investigated in PD patients the effects of DA medication on patterns of brain activation during tasks testing impulsive choices and actions. Following overnight withdrawal of antiparkinsonian medication, PD patients were studied with a H2 ((15)) O PET before and after administration of DA (1 mg of pramipexole), while they were performing the delay discounting task (DDT) and the GoNoGo Task (GNG). We observed that pramipexole augmented impulsivity during DDT, depending on reward magnitude and activated the medial prefrontal cortex and posterior cingulate cortex and deactivated ventral striatum. In contrast, the effect of pramipexole during the GNG task was not significant on behavioral performance and involved different areas (i.e., lateral prefrontal cortex). A voxel-based correlation analysis revealed a significant negative correlation between the discounting value (k) and the activation of medial prefrontal cortex and posterior cingulate suggesting that more impulsive patients had less activation in those cortical areas. Here we report how these different subcomponents of inhibition/impulsivity are differentially sensitive to DA treatment with pramipexole influencing mainly the neural network underlying impulsive choices but not impulsive action. PMID:24038587

  17. Muscle contraction: the step-size distance and the impulse-time per ATP.

    PubMed

    Worthington, C R; Elliott, G F

    1996-02-01

    We derive the step-size distance, and the impulse time per ATP split, from a consideration of Hill's energy rate equation coupled with the enthalpy available per ATP split. This definition of step-size distance is model-independent, and is calculated to have a maximum of 17 A at no load and to reduce to zero at isometric tension, since it will depend on the velocity of shortening. We revisit a derivation of Hill's force-velocity equation depending on impulsive forces working against frictional forces and show that this gives a physical meaning to Hill's constants a and b. This is particularly elegant for Hill's constant b, which is directly related to the impulse time; the value of this impulse time is 1/2 ms. The question that muscle contraction may involve overlapping interactions is considered. However, we find that the step-size distance is not dependent on the possibility of overlapping interactions. PMID:8852761

  18. IPD -The Use of Impulse Plasma in Surface Engineering

    NASA Astrophysics Data System (ADS)

    Zdunek, Krzysztof

    2008-10-01

    It is evident that impulse plasma ensures both the highest level of nonequilibrity and highest level of vapour ionisation. These conditions seemed to be especially suitable for synthetizing the phases with high energetic barrier of nucleation process. In our methods, called by us as the Impulse Plasma Deposition (IPD) the impulse plasma is generated and accelerated in a coaxial accelerator. The only source of electric energy in the plasma process is condenser battery charged to the voltage of order of kVs. During the discharge of condensers individual plasmoids are being accelerated in the coaxial generator by the Ampere force to the speed of the order of 10^4 ms-1 and directed to the non-heated substrate. The most characteristic feature of the is that the synthesis proceeds in the impulse plasma itself, with the participation of ions. The crystallization on ions (ionization degree of the impulse plasma is equal to 100%) makes individual plasmoids to be strongly enriched rather in clusters or particles agglomerates with dimensions of order of single nms than the atoms. Because of the very short life time of plasmoids (approx. 10-4 sec each) the surface coalescence of particles delivered to the substrate has a limited character. As a consequence the material of the layer has nanocrystalline, globular morphology.

  19. Parametric imaging of viscoelasticity using optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Wijesinghe, Philip; McLaughlin, Robert A.; Sampson, David D.; Kennedy, Brendan F.

    2015-03-01

    We demonstrate imaging of soft tissue viscoelasticity using optical coherence elastography. Viscoelastic creep deformation is induced in tissue using step-like compressive loading and the resulting time-varying deformation is measured using phase-sensitive optical coherence tomography. From a series of co-located B-scans, we estimate the local strain rate as a function of time, and parameterize it using a four-parameter Kelvin-Voigt model of viscoelastic creep. The estimated viscoelastic strain and time constant are used to visualize viscoelastic creep in 2D, dual-parameter viscoelastograms. We demonstrate our technique on six silicone tissue-simulating phantoms spanning a range of viscoelastic parameters. As an example in soft tissue, we report viscoelastic contrast between muscle and connective tissue in fresh, ex vivo rat gastrocnemius muscle and mouse abdominal transection. Imaging viscoelastic creep deformation has the potential to provide complementary contrast to existing imaging modalities, and may provide greater insight into disease pathology.

  20. Single shot line-field optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Liu, Chih-Hao; Schill, Alexander; Singh, Manmohan; Wu, Chen; Li, Jiasong; Han, Zhaolong; Raghunathan, Raksha; Kazemi, Tina; Nair, Achuth; Hsu, Thomas; Larin, Kirill V.

    2016-03-01

    Elastic wave imaging optical coherence elastography (EWI-OCE) is an emerging technique that can quantify local biomechanical properties of tissues. However, long acquisition times make this technique unfeasible for clinical use. Here, we demonstrate a noncontact single shot line-field OCE technique using a line-field interferometer and an air-pulse delivery system. The spatial-temporal elastic wave propagation profile was acquired in a single shot and used to quantify the elastic wave group velocity in tissue. Results on tissue-mimicking phantoms and chicken breast muscle agreed well with mechanical compression testing, demonstrating that the presented method can effectively reduce the OCE acquisition time to a few milliseconds in biological application.

  1. Dynamic spectral-domain optical coherence elastography for tissue characterization.

    PubMed

    Liang, Xing; Adie, Steven G; John, Renu; Boppart, Stephen A

    2010-06-21

    A dynamic spectral-domain optical coherence elastography (OCE) imaging technique is reported. In this technique, audio-frequency compressive vibrations are generated by a piezoelectric stack as external excitation, and strain rates in the sample are calculated and mapped quantitatively using phase-sensitive spectral-domain optical coherence tomography. At different driving frequencies, this technique provides contrast between sample regions with different mechanical properties, and thus is used to mechanically characterize tissue. We present images of a three-layer silicone tissue phantom and rat tumor tissue ex vivo, based on quantitative strain rate. Both acquisition speed and processing speed are improved dramatically compared with previous OCE imaging techniques. With high resolution, high acquisition speed, and the ability to characterize the mechanical properties of tissue, this OCE technique has potential use in non-destructive volumetric imaging and clinical applications. PMID:20588552

  2. A new shear wave imaging system for ultrasound elastography.

    PubMed

    Qiu, Weibao; Wang, Congzhi; Xiao, Yang; Qian, Ming; Zheng, Hairong

    2015-08-01

    Ultrasound elastography is able to provide a non-invasive measurement of tissue elasticity properties. Shear wave imaging (SWI) technique is a quantitative method for tissue stiffness assessment. However, traditional SWI implementations cannot acquire 2D quantitative images of tissue elasticity distribution. In this study, a new shear wave imaging system is proposed and evaluated. Detailed delineation of hardware and image processing algorithms are presented. Programmable devices are selected to support flexible control of the system and the image processing algorithms. Analytic signal based cross-correlation method and a Radon transform based shear wave speed determination method are proposed with parallel computation ability. Tissue mimicking phantom imaging, and in vitro imaging measurements are conducted to demonstrate the performance of the proposed system. The system has the ability to provide a new choice for quantitative mapping of the tissue elasticity, and has good potential to be implemented into commercial ultrasound scanner. PMID:26737133

  3. Quantitative Elastography for Cervical Stiffness Assessment during Pregnancy

    PubMed Central

    Fruscalzo, A.; Londero, A. P.; Fröhlich, C.; Möllmann, U.; Schmitz, R.

    2014-01-01

    Aim. Feasibility and reliability of tissue Doppler imaging-(TDI-) based elastography for cervical quantitative stiffness assessment during all three trimesters of pregnancy were evaluated. Materials and Methods. Prospective case-control study including seventy-four patients collected between the 12th and 42nd weeks of gestation. The tissue strain (TS) was measured by two independent operators as natural strain. Intra- and interoperator intraclass correlation coefficient (ICC) agreements were evaluated. Results. TS measurement was always feasible and exhibited a high performance in terms of reliability (intraoperator ICC-agreement = 0.93; interoperator ICC agreement = 0.89 and 0.93 for a single measurement and for the average of two measurements, resp.). Cervical TS showed also a significant correlation with gestational age, cervical length, and parity. Conclusions. TS measurement during pregnancy demonstrated high feasibility and reliability. Furthermore, TS significantly correlated with gestational age, cervical length, and parity. PMID:24734246

  4. Dynamic spectral-domain optical coherence elastography for tissue characterization

    PubMed Central

    Liang, Xing; Adie, Steven G.; John, Renu; Boppart, Stephen A.

    2010-01-01

    A dynamic spectral-domain optical coherence elastography (OCE) imaging technique is reported. In this technique, audio-frequency compressive vibrations are generated by a piezoelectric stack as external excitation, and strain rates in the sample are calculated and mapped quantitatively using phase-sensitive spectral-domain optical coherence tomography. At different driving frequencies, this technique provides contrast between sample regions with different mechanical properties, and thus is used to mechanically characterize tissue. We present images of a three-layer silicone tissue phantom and rat tumor tissue ex vivo, based on quantitative strain rate. Both acquisition speed and processing speed are improved dramatically compared with previous OCE imaging techniques. With high resolution, high acquisition speed, and the ability to characterize the mechanical properties of tissue, this OCE technique has potential use in non-destructive volumetric imaging and clinical applications. PMID:20588552

  5. Diagnostic Value of Elastography in the Diagnosis of Intermetatarsal Neuroma.

    PubMed

    Ormeci, Tugrul; Güler, Olcay; Malkoc, Melih; Keskinbora, Mert; Güngören, Fatma Zeynep; Mahirogulları, Mahir

    2016-01-01

    The objective of the present study was to characterize the ultrasound and elastographic properties of intermetatarsal neuroma (interdigital neuroma) and their contribution to diagnosis. Eighteen patients with metatarsalgia, who had presented to an orthopedic clinic from April 2013 to February 2015, were diagnosed with 25 intermetatarsal neuromas (11 unilateral [61.11%], 7 bilateral [38.89%]). These patients underwent evaluation with ultrasonography and simultaneous ultrasound strain elastography to assess the elastographic properties of the tissues in the intermetatarsal space. The intermetatarsal neuroma diagnosis was confirmed by histopathologic inspection. The lesion contours, localization, dimensions, and vascularization were evaluated before surgical excision. The elasticity and strain ratio values were compared between the neuroma and adjacent healthy intermetatarsal space. Of the 25 intermetatarsal neuromas, 1 (4%) was not detected by ultrasonography (incidence of detection of 96%). The mean neuroma width was 6.35 (range 3.7 to 13) mm in the coronal plane, and the mean elasticity and strain ratio values were 3.44 (range 1.1 to 5.1) and 9.47 (range 2.3 to 19.3), respectively. The elasticity and strain ratio values were significantly greater in the presence of an interdigital neuroma than in the adjacent healthy intermetatarsal spaces (Z = -3.964, p = .0001 and Z = -3.927, p = .0001, respectively). The diagnostic cutoff values were calculated as 2.52 for elasticity and 6.1 for the strain ratio. Four neuromas (16%) were not demarcated, and the elasticity and strain ratio values for these were lower than those for neuromas with demarcated contours but were greater than those for healthy intermetatarsal spaces (p < .006 and p < .005, respectively). Patients with clinically suspected intermetatarsal neuromas that do not show demarcation and with smaller lesions might benefit from the use of ultrasound elastography for diagnosis. PMID:26964696

  6. Swept-source anatomic optical coherence elastography of porcine trachea

    NASA Astrophysics Data System (ADS)

    Bu, Ruofei; Price, Hillel; Mitran, Sorin; Zdanski, Carlton; Oldenburg, Amy L.

    2016-02-01

    Quantitative endoscopic imaging is at the vanguard of novel techniques in the assessment upper airway obstruction. Anatomic optical coherence tomography (aOCT) has the potential to provide the geometry of the airway lumen with high-resolution and in 4 dimensions. By coupling aOCT with measurements of pressure, optical coherence elastography (OCE) can be performed to characterize airway wall stiffness. This can aid in identifying regions of dynamic collapse as well as informing computational fluid dynamics modeling to aid in surgical decision-making. Toward this end, here we report on an anatomic optical coherence tomography (aOCT) system powered by a wavelength-swept laser source. The system employs a fiber-optic catheter with outer diameter of 0.82 mm deployed via the bore of a commercial, flexible bronchoscope. Helical scans are performed to measure the airway geometry and to quantify the cross-sectional-area (CSA) of the airway. We report on a preliminary validation of aOCT for elastography, in which aOCT-derived CSA was obtained as a function of pressure to estimate airway wall compliance. Experiments performed on a Latex rubber tube resulted in a compliance measurement of 0.68+/-0.02 mm2/cmH2O, with R2=0.98 over the pressure range from 10 to 40 cmH2O. Next, ex vivo porcine trachea was studied, resulting in a measured compliance from 1.06+/-0.12 to 3.34+/-0.44 mm2/cmH2O, (R2>0.81). The linearity of the data confirms the elastic nature of the airway. The compliance values are within the same order-of-magnitude as previous measurements of human upper airways, suggesting that this system is capable of assessing airway wall compliance in future human studies.

  7. Noncontact depth-resolved micro-scale corneal elastography

    NASA Astrophysics Data System (ADS)

    Wang, Shang; Larin, Kirill V.

    2015-03-01

    Noninvasive high-resolution depth-resolved measurement of corneal biomechanics is of great clinical significance for improving the diagnosis and optimizing the treatment of various degenerated ocular diseases. Here, we report a micro-scale optical coherence elastography (OCE) method that enables noncontact assessment of the depthwise elasticity distribution in the cornea. The OCE system combines a focused air-puff device with phase-sensitive optical coherence tomography (OCT). Low-pressure short-duration air stream is used to load the cornea with the localized displacement at micron level. The phase-resolved OCT detection with nano-scale sensitivity probes the induced corneal deformation at various locations within a scanning line, providing the ultra-fast imaging of the corneal lamb wave propagation. With spectral analysis, the amplitude spectra and the phase spectra are available for the estimation of the frequency range of the lamb wave and the quantification of the wave propagation, respectively. Curved propagation paths following the top and bottom corneal boundaries are selected inside the cornea for measuring the phase velocity of the lamb wave at the major frequency components over the whole depths. Our pilot experiments on ex vivo rabbit eyes indicate the distinct stiffness of different layers in the cornea, including the epithelium, the anterior stroma, the posterior stroma, and the innermost region, which demonstrates the feasibility of this micro-scale OCE method for noncontact depth-resolved corneal elastography. Also, the quantification of the lamb wave dispersion in the cornea could lead to the measurement of the elastic modulus, suggesting the potential of this method for quantitative monitoring of the corneal biomechanics.

  8. Ultrasonic elastography using sector scan imaging and a radial compression.

    PubMed

    Souchon, Rémi; Soualmi, Lahbib; Bertrand, Michel; Chapelon, Jean-Yves; Kallel, Faouzi; Ophir, Jonathan

    2002-05-01

    Elastography is an imaging technique based on strain estimation in soft tissues under quasi-static compression. The stress is usually created by a compression plate, and the target is imaged by an ultrasonic linear array. This configuration is used for breast elastography, and has been investigated both theoretically and experimentally. Phenomena such as strain decay with tissue depth and strain concentrations have been reported. However in some in vivo situations, like prostate or blood vessels imaging, this set-up cannot be used. We propose a device to acquire in vivo elastograms of the prostate. The compression is applied by inflating a balloon that covers a transrectal sector probe. The 1D algorithm used to calculate the radial strain fails if the center of the imaging probe does not correspond to the center of the compressor. Therefore, experimental elastograms are calculated with a 2D algorithm that accounts for tangential displacements of the tissue. In this article, in order to gain a better understanding of the image formation process, the use of ultrasonic sector scans to image the radial compression of a target is investigated. Elastograms of homogeneous phantoms are presented, and compared with simulated images. Both show a strain decay with tissue depth. Then experimental and simulated elastograms of a phantom that contains a hard inclusion are presented, showing that strain concentrations occur as well. A method to compensate for strain decay and therefore to increase the contrast of the strain elastograms is proposed. It is expected that such information will help to interpret and possibly improve the elastograms obtained via radial compression. PMID:12160060

  9. Magnetic Resonance Elastography of Liver Tumors- Preliminary Results

    PubMed Central

    Venkatesh, Sudhakar K; Yin, Meng; Glockner, James F; Takahashi, Naoki; Araoz, Philip A; Talwalkar, Jayant A; Ehman, Richard L

    2010-01-01

    Aim To evaluate the potential value of magnetic resonance elastography (MRE) for characterizing solid liver tumors. Materials and Methods Forty-four liver tumors (metastases-14, hepatocellular carcinoma- 12, hemangioma-9, cholangiocarcinoma-5, focal nodular hyperplasia-3, and hepatic adenoma-1) were evaluated with MRE. MRE was performed on a 1.5 T scanner with a modified phase-contrast, gradient echo sequence to collect axial wave images sensitized along the through-plane motion direction. The tumors were identified in T2-, T1-weighted and gadolinium enhanced T1-weighted images and the MRE images were obtained through the tumor. A stiffness map (elastogram) was generated by an automated process using an inversion algorithm. The mean shear stiffness of the tumor was calculated using a manually specified region of interest placed over the tumor in the stiffness map. The stiffness value of non-tumor bearing hepatic parenchyma was also calculated. Statistical analysis was performed on the stiffness values for differentiation between normal liver, fibrotic liver, benign tumors and malignant tumors. Results Malignant liver tumors had significantly higher mean shear stiffness than benign tumors, fibrotic liver and normal liver (10.1kPa vs. 2.7kpa (p<0.001), vs. 5.9kPa (p<0.001) and vs. 2.3kPa (p<0.001) respectively). Fibrotic livers had stiffness values overlapping both the benign and malignant tumors. Cut-off values of 5kPa accurately differentiate malignant tumors from benign tumors and normal liver parenchyma in this preliminary investigation. Conclusions MR elastography is a promising, non-invasive technique for assessing solid liver tumors. MRE may provide new, quantitative tissue characterization parameters for differentiating benign and malignant liver tumors. PMID:18492904

  10. A class of kernel based real-time elastography algorithms.

    PubMed

    Kibria, Md Golam; Hasan, Md Kamrul

    2015-08-01

    In this paper, a novel real-time kernel-based and gradient-based Phase Root Seeking (PRS) algorithm for ultrasound elastography is proposed. The signal-to-noise ratio of the strain image resulting from this method is improved by minimizing the cross-correlation discrepancy between the pre- and post-compression radio frequency signals with an adaptive temporal stretching method and employing built-in smoothing through an exponentially weighted neighborhood kernel in the displacement calculation. Unlike conventional PRS algorithms, displacement due to tissue compression is estimated from the root of the weighted average of the zero-lag cross-correlation phases of the pair of corresponding analytic pre- and post-compression windows in the neighborhood kernel. In addition to the proposed one, the other time- and frequency-domain elastography algorithms (Ara et al., 2013; Hussain et al., 2012; Hasan et al., 2012) proposed by our group are also implemented in real-time using Java where the computations are serially executed or parallely executed in multiple processors with efficient memory management. Simulation results using finite element modeling simulation phantom show that the proposed method significantly improves the strain image quality in terms of elastographic signal-to-noise ratio (SNRe), elastographic contrast-to-noise ratio (CNRe) and mean structural similarity (MSSIM) for strains as high as 4% as compared to other reported techniques in the literature. Strain images obtained for the experimental phantom as well as in vivo breast data of malignant or benign masses also show the efficacy of our proposed method over the other reported techniques in the literature. PMID:25929595

  11. Evaluation of cervical stiffness during pregnancy using semiquantitative ultrasound elastography

    PubMed Central

    Hernandez-Andrade, Edgar; Hassan, Sonia S; Ahn, Hyunyoung; Korzeniewski, Steven J.; Yeo, Lami; Chaiworapongsa, Tinnakorn; Romero, Roberto

    2014-01-01

    Objective To evaluate cervical stiffness during pregnancy using ultrasound-derived elastography, a method used to estimate the average tissue displacement (strain) on a defined region of interest when oscillatory compression is applied. Methods Strain was calculated in two regions of interest, the endocervical canal and the entire cervix, from three anatomical planes of the cervix: mid-sagittal in the plane used for cervical length measurement, and in cross-sectional planes located at the internal and external cervical os. Associations between strain values, method of ascertainment and patient characteristics were assessed using linear mixed models to account for within-subject correlation. Inter-rater agreement in defining the degree of cervical stiffness was evaluated in 120 regions of interest acquired by two operators in 20 patients. Results A total of 1557 strain estimations were performed in 262 patients at 8-40 weeks of gestation. Adjusting for other sources of variation, 1) cervical tissue strain estimates obtained in the endocervical canal were on average 33% greater than those obtained in the entire cervix; 2) measures obtained in the cross-sectional plane of the external cervical os and sagittal plane were 45% and 13% greater compared to those measured in the cross-sectional plane of the internal cervical os, respectively; 3) mean strain rate was 14% and 5% greater among multiparous women with and without a history of preterm delivery compared to nulliparous women, respectively, and was on average 13% greater among women with a cervical length between 25-30mm compared to those with a cervical length >30mm; and 4) cervical tissue strain was more strongly associated with cervical length than with gestational age. Conclusion Semiquantitative elastography can be employed to evaluate changes in cervical stiffness during pregnancy. PMID:23151941

  12. The physics of spinal manipulation: work-energy and impulse-momentum principles.

    PubMed

    Herzog, W

    1993-01-01

    The purpose of this article was to illustrate that the work-energy and impulse-momentum relations are derived from Newton's second law, and, thus, will give identical results to F = ma for any force system analysis. It should be noted that using the work-energy or the impulse-momentum approach requires that all external forces acting on a system are considered. Furthermore, it must be emphasized that any force acting internal to the system (e.g., muscular forces in the system "chiropractor") do not enter these equations. PMID:8423425

  13. An Experimental Study of the Potential Biological Effects Associated with 2-D Shear Wave Elastography on the Neonatal Brain.

    PubMed

    Li, Changtian; Zhang, Changsheng; Li, Junlai; Cao, Xiaolin; Song, Danfei

    2016-07-01

    2-D Shear wave elastography (SWE) imaging is widely used in clinical practice, and some researchers have applied this technique in the evaluation of neonatal brains. However, the immediate and long-term impacts of dynamic radiation force exposure on the neonatal central nervous system remain unknown. In this study, we exposed neonatal mice to 2-D SWE scanning for 10 min, 20 min and 30 min under diagnostic mode (mechanical index [MI]: 1.3; thermal index [TI]: 0.5), respectively. For the control group, the neonatal mice were sham irradiated for 30 min with the machine powered off. Their brains were collected and analyzed using histologic staining and western blot analysis at 24 h and 3 mo after the 2-D SWE scanning. The Morris water maze (MWM) test was used to assess learning and memory function of the mice at 3 mo of age. The results indicated that using 2-D SWE in evaluating brains of neonatal mice does not cause detectable histologic changes, nor does it have long-term effects on their learning and memory abilities. However, the PI3 K/AKT/mTOR pathway was disturbed when the 2-D SWE scanning lasted for more than 30 min, and the expression of p-PKCa was suppressed by 10 min or more in 2-D SWE scanning. Although these injuries may be self-repaired as the mice grow, more attention should be paid to the scanning duration when applying 2-D-SWE elastography in the assessment of neonatal brains. PMID:27112914

  14. Towards intraoperative monitoring of ablation using tracked 3D ultrasound elastography and internal palpation

    NASA Astrophysics Data System (ADS)

    Foroughi, Pezhman; Burgner, Jessica; Choti, Michael A.; Webster, Robert J., III; Hager, Gregory D.; Boctor, Emad M.

    2012-03-01

    B-mode ultrasound is widely used in liver ablation. However, the necrosis zone is typically not visible under b-mode ultrasound, since ablation does not necessarily change the acoustic properties of the tissue. In contrast, the change in tissue stiffness makes elastography ideal for monitoring ablation. Tissue palpation for elastography is typically applied at the imaging probe, by indenting it slightly into the tissue surface. However, in this paper we propose an alternate approach, where palpation is applied by a surgical instrument located inside the tissue. In our approach, the ablation needle is placed inside a steerable device called an active cannula and inserted into the tissue. A controlled motion is applied to the center of the ablation zone via the active cannula. Since the type and direction of motion is known, displacement can then be computed from two frames with the desired motion. The elastography results show the ablated region around the needle. While internal palpation provides excellent local contrast, freehand palpation from outside of the tissue via the transducer can provide a more global view of the region of the interest. For this purpose, we used a tracked 3D transducer to generate volumetric elastography images covering the ablated region. The tracking information is employed to improve the elastography results by selecting volume pairs suitable for elastography. This is an extension of our 2D frame selection technique which can cope with uncertainties associated with intra-operative elastography. In our experiments with phantom and ex-vivo tissue, we were able to generate high-quality images depicting the boundaries of the hard lesions.

  15. Fluid-orbit coupling calculation for flight analysis of impulsively driven laser vehicle

    NASA Astrophysics Data System (ADS)

    Takahashi, Masayuki; Ohnishi, Naofumi

    2013-08-01

    Using a fluid-orbit coupling simulator, we numerically solve the three-dimensional Navier-Stokes equations with exchanging information of six-degree-of-freedom reactions for predicting impulsive flight motions of a laser propulsion vehicle driven by blast waves. By feedback of angular and translational velocities into the flowfield, pressure and viscous drags induced by the unsteady vehicle motion are introduced to provide precise motion analysis. In the impulsive-motion estimation of the laser-boosted vehicle, restoring forces and moments are underestimated if the vehicle motion effect is modeled using aerodynamic coefficients of steady flow. Also, a simple model using impulse data examined by experiments for predicting the impulsive motion is compared with our coupling approach which can reproduce instantaneous acceleration resulting from the interaction between the vehicle and the blast wave. Velocity overshoot is generated by evaluating sharp thrust through the coupling calculation, and the flight height becomes 6% larger than conventional prediction using the impulse data.

  16. Two-dimensional shear-wave elastography on conventional ultrasound scanners with time-aligned sequential tracking (TAST) and comb-push ultrasound shear elastography (CUSE).

    PubMed

    Song, Pengfei; Macdonald, Michael; Behler, Russell; Lanning, Justin; Wang, Michael; Urban, Matthew; Manduca, Armando; Zhao, Heng; Callstrom, Matthew; Alizad, Azra; Greenleaf, James; Chen, Shigao

    2015-02-01

    Two-dimensional shear-wave elastography presents 2-D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2-D shear-wave elastography on conventional ultrasound scanners, however, is challenging because of the low tracking pulse-repetition-frequency (PRF) of these systems. Although 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 2-D 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 SNR and facilitate robust reconstructions of 2-D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner. A phantom study showed that the shear-wave speed measurements from the conventional ultrasound scanner were in good agreement with the values measured from other 2-D shear wave imaging technologies. An inclusion phantom study showed that the conventional ultrasound scanner had comparable performance to a state-of-the-art shear-wave imaging system 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 conventional ultrasound

  17. Voxel-level reproducibility assessment of modality independent elastography in a pre-clinical murine model

    NASA Astrophysics Data System (ADS)

    Flint, Katelyn M.; Weis, Jared A.; Yankeelov, Thomas E.; Miga, Michael I.

    2015-03-01

    Changes in tissue mechanical properties, measured non-invasively by elastography methods, have been shown to be an important diagnostic tool, particularly for cancer. Tissue elasticity information, tracked over the course of therapy, may be an important prognostic indicator of tumor response to treatment. While many elastography techniques exist, this work reports on the use of a novel form of elastography that uses image texture to reconstruct elastic property distributions in tissue (i.e., a modality independent elastography (MIE) method) within the context of a pre-clinical breast cancer system.1,2 The elasticity results have previously shown good correlation with independent mechanical testing.1 Furthermore, MIE has been successfully utilized to localize and characterize lesions in both phantom experiments and simulation experiments with clinical data.2,3 However, the reproducibility of this method has not been characterized in previous work. The goal of this study is to evaluate voxel-level reproducibility of MIE in a pre-clinical model of breast cancer. Bland-Altman analysis of co-registered repeat MIE scans in this preliminary study showed a reproducibility index of 24.7% (scaled to a percent of maximum stiffness) at the voxel level. As opposed to many reports in the magnetic resonance elastography (MRE) literature that speak to reproducibility measures of the bulk organ, these results establish MIE reproducibility at the voxel level; i.e., the reproducibility of locally-defined mechanical property measurements throughout the tumor volume.

  18. 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

  19. 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. PMID:26327901

  20. Reflection-Impulsivity and Wholist-Analytic: Two Fledglings...or is R-I a cuckoo?

    ERIC Educational Resources Information Center

    Jones, Anne Elizabeth

    1997-01-01

    Considers the theoretical validity of two approaches to cognitive style. Wholist-Analytic maintains that cognitive processes depend on the interaction of two opposing forces, destructive and constructive. Reflection-Impulsivity characterizes learners according to their reflective or impulsive responses to solution hypotheses. Evaluates these…

  1. Children's Help Seeking and Impulsivity

    ERIC Educational Resources Information Center

    Puustinen, Minna; Kokkonen, Marja; Tolvanen, Asko; Pulkkinen, Lea

    2004-01-01

    The aim of the present study was to analyze the relationship between students' (100 children aged 8 to 12) help-seeking behavior and impulsivity. Help-seeking behavior was evaluated using a naturalistic experimental paradigm in which children were placed in a problem-solving situation and had the opportunity to seek help from the experimenter, if…

  2. Commentary on Hyperkinetic Impulse Disorder

    ERIC Educational Resources Information Center

    Barkley, Russell A.

    2011-01-01

    Dr. Goldstein continues the laudable practice of reprinting articles of historical significance in the history of ADHD with this selective reprinting of material from the original article by Maurice Laufer, Eric Denhoff, and Gerald Solomons on hyperkinetic impulsive disorder (HID) in children. This article on HID is among the first articles to…

  3. Characteristics of Impulsive Suicide Attempts and Attempters.

    ERIC Educational Resources Information Center

    Simon, Thomas R.; Swann, Alan C.; Powell, Kenneth E.; Potter, Lloyd B.; Kresnow, Marcie-jo; O'Carroll, Patrick W.

    2002-01-01

    Examined impulsive suicide attempts within a population-based, case-control study of nearly lethal suicide attempts among adolescents and young adults. Impulsive attempts were more likely among those who had been in a physical fight and less likely among those who were depressed. Findings suggest inadequate control of aggressive impulses as a…

  4. A STUDY OF METHODS OF CONTROLLING IMPULSES.

    ERIC Educational Resources Information Center

    WHITESIDE, RAY

    THE PERSON LESS ABLE TO CONTROL HIS IMPULSES IS ALSO APT TO EXHIBIT SOCIALLY DISVALUED BEHAVIOR. VOCATIONAL AND ACADEMIC FAILURE IS A PARTIAL CONSEQUENCE OF IMPULSIVENESS AND LACK OF SELF-CONTROL. TO INVESTIGATE IMPULSE CONTROL, TWO INSTRUMENTS BELIEVED TO MEASURE ATTRIBUTES OF OPPOSITE POLES OF THIS CONCEPT (SEQUENTIAL TESTS OF EDUCATIONAL…

  5. Adolescent Impulsivity: Findings from a Community Sample

    ERIC Educational Resources Information Center

    d'Acremont, Mathieu; Van der Linden, Martial

    2005-01-01

    Impulsivity is central to several psychopathological states in adolescence. However, there is little consensus concerning the definition of impulsivity and its core dimensions. In response to this lack of consensus, Whiteside and Lynam (2001, "Pers. Individ. Differ." 30, 669-689) have developed the UPPS Impulsive Behavior Scale, which is able to…

  6. An automatic differentiation-based gradient method for inversion of the shear wave equation in magnetic resonance elastography: specific application in fibrous soft tissues.

    PubMed

    Chatelin, Simon; Charpentier, Isabelle; Corbin, Nadège; Meylheuc, Laurence; Vappou, Jonathan

    2016-07-01

    Quantitative and accurate measurement of in vivo mechanical properties using dynamic elastography has been the scope of many research efforts over the past two decades. Most of the shear-wave-based inverse approaches for magnetic resonance elastography (MRE) make the assumption of isotropic viscoelasticity. In this paper, we propose a quantitative gradient method for inversion of the shear wave equation in anisotropic media derived from a full waveform description using analytical viscoelastic Green formalism and automatic differentiation. The abilities and performances of the proposed identification method are first evaluated on numerical phantoms calculated in a transversely isotropic medium, and subsequently on experimental MRE data measured on an isotropic hydrogel phantom, on an anisotropic cryogel phantom and on an ex vivo fibrous muscle. The experiments are carried out by coupling circular shear wave profiles generated by acoustic radiation force and MRE acquisition of the wave front. Shear modulus values obtained by our MRE method are compared to those obtained by rheometry in the isotropic hydrogel phantom, and are found to be in good agreement despite non-overlapping frequency ranges. Both the cryogel and the ex vivo muscle are found to be anisotropic. Stiffness values in the longitudinal direction are found to be 1.8 times and 1.9 times higher than those in the transverse direction for the cryogel and the muscle, respectively. The proposed method shows great perspectives and substantial benefits for the in vivo quantitative investigation of complex mechanical properties in fibrous soft tissues. PMID:27300107

  7. An automatic differentiation-based gradient method for inversion of the shear wave equation in magnetic resonance elastography: specific application in fibrous soft tissues

    NASA Astrophysics Data System (ADS)

    Chatelin, Simon; Charpentier, Isabelle; Corbin, Nadège; Meylheuc, Laurence; Vappou, Jonathan

    2016-07-01

    Quantitative and accurate measurement of in vivo mechanical properties using dynamic elastography has been the scope of many research efforts over the past two decades. Most of the shear-wave-based inverse approaches for magnetic resonance elastography (MRE) make the assumption of isotropic viscoelasticity. In this paper, we propose a quantitative gradient method for inversion of the shear wave equation in anisotropic media derived from a full waveform description using analytical viscoelastic Green formalism and automatic differentiation. The abilities and performances of the proposed identification method are first evaluated on numerical phantoms calculated in a transversely isotropic medium, and subsequently on experimental MRE data measured on an isotropic hydrogel phantom, on an anisotropic cryogel phantom and on an ex vivo fibrous muscle. The experiments are carried out by coupling circular shear wave profiles generated by acoustic radiation force and MRE acquisition of the wave front. Shear modulus values obtained by our MRE method are compared to those obtained by rheometry in the isotropic hydrogel phantom, and are found to be in good agreement despite non-overlapping frequency ranges. Both the cryogel and the ex vivo muscle are found to be anisotropic. Stiffness values in the longitudinal direction are found to be 1.8 times and 1.9 times higher than those in the transverse direction for the cryogel and the muscle, respectively. The proposed method shows great perspectives and substantial benefits for the in vivo quantitative investigation of complex mechanical properties in fibrous soft tissues.

  8. Optical coherence micro-elastography: mechanical-contrast imaging of tissue microstructure.

    PubMed

    Kennedy, Brendan F; McLaughlin, Robert A; Kennedy, Kelsey M; Chin, Lixin; Curatolo, Andrea; Tien, Alan; Latham, Bruce; Saunders, Christobel M; Sampson, David D

    2014-07-01

    We present optical coherence micro-elastography, an improved form of compression optical coherence elastography. We demonstrate the capacity of this technique to produce en face images, closely corresponding with histology, that reveal micro-scale mechanical contrast in human breast and lymph node tissues. We use phase-sensitive, three-dimensional optical coherence tomography (OCT) to probe the nanometer-to-micrometer-scale axial displacements in tissues induced by compressive loading. Optical coherence micro-elastography incorporates common-path interferometry, weighted averaging of the complex OCT signal and weighted least-squares regression. Using three-dimensional phase unwrapping, we have increased the maximum detectable strain eleven-fold over no unwrapping and the minimum detectable strain is 2.6 με. We demonstrate the potential of mechanical over optical contrast for visualizing micro-scale tissue structures in human breast cancer pathology and lymph node morphology. PMID:25071952

  9. A comparison study of optical coherence elastography and laser Michelson vibrometry

    NASA Astrophysics Data System (ADS)

    Li, Jiasong; Liu, Chih-Hao; Schill, Alexander; Singh, Manmohan; Kistenev, Yury V.; Larin, Kirill V.

    2016-03-01

    Quantitative elastography is a power technique to detect and analyze the changes in biomedical properties of tissues in normal and pathological states. In this study, two noncontact elastography techniques, laser Michelson vibrometry (LMV) and optical coherence elastography (OCE), were utilized to quantify the Young's modulus of tissue-mimicking agar phantoms of various concentrations. Low-amplitude (micrometer scale) elastic waves were induced by a focused air-pulse delivery system and imaged by the respective systems. The Young's modulus as assessed by both elastographic techniques was similar and was compared to the stiffness as measured by uniaxial mechanical testing. The results show that both techniques accurately quantified the elasticity. OCE can provide absolute elastic wave temporal profile, depth-resolved measurement and superior displacement sensitivity compared to LMV, but LMV is significantly cheaper (10X) and easier to implement than OCE.

  10. Value of ultrasound elastography in the diagnosis of native kidney fibrosis.

    PubMed

    Peride, Ileana; Rădulescu, Daniela; Niculae, Andrei; Ene, Vladimir; Bratu, Ovidiu Gabriel; Checheriță, Ionel Alexandru

    2016-09-01

    In the last decade, ultrasound elastography, an already widely used technique in the diagnosis of hepatic fibrosis, has raised the attention of nephrologists as a potential valuable noninvasive tool for the diagnosis of renal fibrosis. Due to renal deep location and anatomic complexity, the shear wave techniques are the most appropriate elastography methods for exploring native kidneys. Recent research offers promising results, but further larger studies are required for a better standardization of this method and also for establishing reference values of normal kidney elasticity. This article reviews the studies conducted for exploring the native kidney, highlighting the advantages and limitations of ultrasound elastography for assessing fibrosis development in chronic kidney diseases. PMID:27622414

  11. 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.

  12. Magnetomotive optical coherence elastography (MM-OCE) for thermal therapy dosimetry (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Huang, Pin-Chieh; Marjanovic, Marina; Spillman, Darold R.; Odintsov, Boris M.; Boppart, Stephen A.

    2016-03-01

    Biomechanical properties of tissues have been utilized for disease detection, diagnosis, and progression, however they have not been extensively utilized for therapy dosimetry. Magnetic hyperthermia aims to kill cells and ablate tumors using magnetic nanoparticles (MNPs) either injected in or targeted to tumors. Upon application of an appropriate AC magnetic field, MNPs can heat target tissue while sparing non-targeted healthy tissue. However, a sensitive monitoring technique for the dose of magnetic hyperthermia is needed to prevent over-treatment and collateral injury. During hyperthermia treatments, the viscoelastic properties of tissues are altered due to protein denaturation, coagulation, and tissue dehydration, making these properties candidates for dosimetry. Magnetomotive optical coherence elastography (MM-OCE) utilizes MNPs as internal force transducers to probe the biomechanical properties of tissues. Therefore, we aim to evaluate the hyperthermia dose based on the elastic changes revealed by MM-OCE. In this study, MNPs embedded in tissues were utilized for both hyperthermia and MM-OCE measurements. Tissue temperature and elastic modulus were obtained, where the elastic modulus was extracted from the resonance frequency detected by MM-OCE. Results showed a correlation between stiffness and temperature change following treatment. To investigate the thermal-dose-dependent changes, intervals of hyperthermia treatment were repeatedly performed on the same tissue sequentially, interspersed with MM-OCE. With increasing times of treatment, tissue stiffness increased, while temperature rise remained relatively constant. These results suggest that MM-OCE may potentially identify reversible and irreversible tissue changes during thermal therapy, supporting the use of MM-OCE for dosimetric control of hyperthermia in future applications.

  13. Generating Shear Waves in the Human Brain for Ultrasound Elastography: A new Approach

    NASA Astrophysics Data System (ADS)

    Nicolas, Emmanuel; Callé, Samuel; Remenieras, Jean-Pierre

    One of the challenges of brain elastography is the generation of the shear waves inside the brain. The generation system has to bypass the body's natural protection while keeping a good level of comfort for the patient. We propose a shear wave inducing system for brain ultrasound elastography. In this paper we will validate this system in vitro on a tissue mimicking phantom by doing shear wave velocity measurements. The system proves to work well on phantoms and to be comfortable for the patient. Further work will include measurements in vivo.

  14. Correlation of Strain Elastography with Conventional Sonography and FNAC/Biopsy

    PubMed Central

    Sardessai, Sanjay; Furtado, Renny; Sardessai, Mahesh

    2016-01-01

    Introduction Elastography is a new promising technique that can be especially helpful when used as an adjunct to conventional B-mode ultrasound in evaluating breast lesions. Aim To evaluate the diagnostic performance of four interpretation criteria for elastography and to compare the diagnostic performance of sonoelastography with that of conventional sonography in characterising breast lesions as benign or malignant with FNAC/biopsy correlation. Materials and Methods One hundred breast lesions were prospectively evaluated by ultrasound as well as by strain elastography followed by FNAC/ biopsy correlation. The criteria used were Elastography Score, Strain Ratio, Distance Ratio and Area Ratio. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated for each modality. The best cut-off point was calculated for each of the interpretation criteria using the MedCalc version 10.1 software. The diagnostic performance of the interpretation criteria was compared with that of conventional sonography by the area under the receiver operating characteristic curve using SPSS software. Results The elastography score was found to have the best performance among the 4 criteria used with a sensitivity and specificity of 100% and 82.66%, respectively at the best cut-off point between 3 and 4. At a best cut-off point for conventional sonography between BI-RADS categories 4A and 4B, the sensitivity and specificity were found to be 96% and 92% respectively. The area under the curve value was slightly greater for conventional sonography (0.980) than for the elastography score (0.913) using receiver operating characteristic curve analysis. Conclusion While all interpretation criteria were able to differentiate benign and malignant lesions with statistical significance, the elastography score was found to be the most accurate. While conventional ultrasound remains the primary modality for the characterization of breast masses

  15. Review of ultrasonography of malignant neck nodes: greyscale, Doppler, contrast enhancement and elastography.

    PubMed

    Ying, M; Bhatia, K S S; Lee, Y P; Yuen, H Y; Ahuja, A T

    2013-01-01

    Assessment of neck lymph nodes is essential in patients with head and neck cancers for predicting the patient's prognosis and selecting the appropriate treatment. Ultrasonography is a useful imaging tool in the assessment of neck lymph nodes. Greyscale ultrasonography assesses the size, distribution, and internal architecture of lymph nodes. Doppler ultrasonography evaluates the intranodal vascular pattern and resistance of lymph nodes. Contrast-enhanced ultrasonography provides information on lymph node parenchymal perfusion. Elastography allows qualitative and quantitative assessment of lymph node stiffness. This article reviews the value of greyscale, Doppler and contrast-enhanced ultrasonography as well as elastography in the assessment of malignant nodes in the neck. PMID:24434158

  16. Rescaled Local Interaction Simulation Approach for Shear Wave Propagation Modelling in Magnetic Resonance Elastography.

    PubMed

    Hashemiyan, Z; Packo, P; Staszewski, W J; Uhl, T

    2016-01-01

    Properties of soft biological tissues are increasingly used in medical diagnosis to detect various abnormalities, for example, in liver fibrosis or breast tumors. It is well known that mechanical stiffness of human organs can be obtained from organ responses to shear stress waves through Magnetic Resonance Elastography. The Local Interaction Simulation Approach is proposed for effective modelling of shear wave propagation in soft tissues. The results are validated using experimental data from Magnetic Resonance Elastography. These results show the potential of the method for shear wave propagation modelling in soft tissues. The major advantage of the proposed approach is a significant reduction of computational effort. PMID:26884808

  17. Rescaled Local Interaction Simulation Approach for Shear Wave Propagation Modelling in Magnetic Resonance Elastography

    PubMed Central

    Packo, P.; Staszewski, W. J.; Uhl, T.

    2016-01-01

    Properties of soft biological tissues are increasingly used in medical diagnosis to detect various abnormalities, for example, in liver fibrosis or breast tumors. It is well known that mechanical stiffness of human organs can be obtained from organ responses to shear stress waves through Magnetic Resonance Elastography. The Local Interaction Simulation Approach is proposed for effective modelling of shear wave propagation in soft tissues. The results are validated using experimental data from Magnetic Resonance Elastography. These results show the potential of the method for shear wave propagation modelling in soft tissues. The major advantage of the proposed approach is a significant reduction of computational effort. PMID:26884808

  18. Periodic components of hand acceleration/deceleration impulses during telemanipulation

    SciTech Connect

    Draper, J.V.; Handel, S.

    1994-01-01

    Responsiveness is the ability of a telemanipulator to recreate user trajectories and impedance in time and space. For trajectory production, a key determinant of responsiveness is the ability of the system to accept user inputs, which are forces on the master handle generated by user hand acceleration/deceleration (a/d) impulses, and translate them into slave arm acceleration/deceleration. This paper presents observations of master controller a/d impulses during completion of a simple target acquisition task. Power spectral density functions (PSDF`s) calculated from hand controller a/d impulses were used to assess impulse waveform. The relative contributions of frequency intervals ranging up to 25 Hz for three spatially different versions of the task were used to determine which frequencies were most important. The highest relative power was observed in frequencies between 1 Hz and 6 Hz. The key frequencies related to task difficulty were in the range from 2 Hz to 8 Hz. the results provide clues to the source of the performance inhibition.

  19. Regulation of angular impulse during two forward translating tasks.

    PubMed

    Mathiyakom, Witaya; McNitt-Gray, Jill L; Wilcox, Rand R

    2007-05-01

    Angular impulse generation is dependent on the position of the total body center of mass (CoM) relative to the ground reaction force (GRF) vector during contact with the environment. The purpose of this study was to determine how backward angular impulse was regulated during two forward translating tasks. Control of the relative angle between the CoM and the GRF was hypothesized to be mediated by altering trunk-leg coordination. Eight highly skilled athletes performed a series of standing reverse somersaults and reverse timers. Sagittal plane kinematics, GRF, and electromyograms of lower extremity muscles were acquired during the take-off phase of both tasks. The magnitude of the backward angular impulse generated during the push interval of both tasks was mediated by redirecting the GRF relative to the CoM. During the reverse timer, backward angular impulse generated during the early part of the take-off phase was negated by limiting backward trunk rotation and redirecting the GRF during the push interval. Biarticular muscles crossing the knee and hip coordinated the control of GRF direction and CoM trajectory via modulation of trunk-leg coordination. PMID:17603134

  20. Application of a discretized vortex impulse framework to fish maneuvering

    NASA Astrophysics Data System (ADS)

    Mendelson, Leah; Techet, Alexandra

    2015-11-01

    In studies of biological propulsion, metrics for quantitative analysis of the vortex wake, including circulation, impulse, and their time derivatives, are a valuable indicator of performance. To better utilize volumetric PIV data in this type of analysis, a discretized method of deriving vortex impulse relying only on velocity data is developed. The impulse formulation is based on the geometry and distribution of circulation along the vortex core line, which can be detected using critical points in the velocity field. This analysis method is then applied to time-resolved velocity data of a turning giant danio (Devario aequipinnatus) and a jumping archer fish (Toxotes microlepis) obtained using Synthetic Aperture PIV (SAPIV). In the case of the danio, the vortex force vector derived from the impulse derivative shows good agreement with the kinematics of the fish tail during the turning maneuver. With the archer fish, the model is used to explore the relationship between the number of tail beats prior to the jump and the jump height.

  1. Digital image correlation-based optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Sun, Cuiru; Standish, Beau; Vuong, Barry; Wen, Xiao-Yan; Yang, Victor

    2013-12-01

    Optical coherence elastography (OCE) provides deformation or material properties, mapping of soft tissue. We aim to develop a robust speckle tracking OCE technique with improved resolution and accuracy. A digital image correlation (DIC)-based OCE technique was developed by combining an advanced DIC algorithm with optical coherence tomography (OCT). System calibration and measurement error evaluation demonstrated that this DIC-based OCE technique had a resolution of ˜0.6 μm displacement and <0.5% strain measurement in the axial scan direction. The measured displacement ranged from 0.6 to 150 μm, obtained via phantom imaging. The capability of the DIC-based OCE technique, for differentiation of stiffness, was evaluated by imaging a candle gel phantom with an irregularly shaped stiff inclusion. OCE imaging of a chicken breast sample differentiated the fat, membrane, and muscle layers. Strain elastograms of an aneurysm sample showed heterogeneity of the tissue and clear contrast between the adventitia and media. These promising results demonstrated the capability of the DIC-based OCE for the characterization of the various components of the tissue sample. Further improvement of the system will be conducted to make this OCE technique a practical tool for measuring and differentiating material properties of soft tissue.

  2. The simulation of magnetic resonance elastography through atherosclerosis.

    PubMed

    Thomas-Seale, L E J; Hollis, L; Klatt, D; Sack, I; Roberts, N; Pankaj, P; Hoskins, P R

    2016-06-14

    The clinical diagnosis of atherosclerosis via the measurement of stenosis size is widely acknowledged as an imperfect criterion. The vulnerability of an atherosclerotic plaque to rupture is associated with its mechanical properties. The potential to image these mechanical properties using magnetic resonance elastography (MRE) was investigated through synthetic datasets. An image of the steady state wave propagation, equivalent to the first harmonic, can be extracted directly from finite element analysis. Inversion of this displacement data yields a map of the shear modulus, known as an elastogram. The variation of plaque composition, stenosis size, Gaussian noise, filter thresholds and excitation frequency were explored. A decreasing mean shear modulus with an increasing lipid composition was identified through all stenosis sizes. However the inversion algorithm showed sensitivity to parameter variation leading to artefacts which disrupted both the elastograms and quantitative trends. As noise was increased up to a realistic level, the contrast was maintained between the fully fibrous and lipid plaques but lost between the interim compositions. Although incorporating a Butterworth filter improved the performance of the algorithm, restrictive filter thresholds resulted in a reduction of the sensitivity of the algorithm to composition and noise variation. Increasing the excitation frequency improved the techniques ability to image the magnitude of the shear modulus and identify a contrast between compositions. In conclusion, whilst the technique has the potential to image the shear modulus of atherosclerotic plaques, future research will require the integration of a heterogeneous inversion algorithm. PMID:27130475

  3. Analysis of elastography methods using mathematical and ex vivo data

    NASA Astrophysics Data System (ADS)

    Byram, Brett C.; Wahl, Michael R.; Holmes, David R., III; Lerman, Amir; Robb, Richard A.

    2003-05-01

    Intravascular ultrasound (IVUS) currently has a limited ability to characterize endovascular anatomic properties. IVUS elastography enhances the ability to characterize the biomechanical properties of arterial walls. A mathematical phantom generator was developed based on the characteristics of 30MHz, 64 element IVUS catheter images from excised canine femoral arteries. The difference between high and low-pressure intra-arterial images was modeled using phase shifts. The increase in phase shift occurred randomly, generally at every three pixels in our images. Using mathematical phantoms, different methods for calculating elastograms were quantitatively analyzed. Specifically, the effect of standard cross correlation versus cross correlation of the integral of the inflection characteristics for a given set of data, and the effect of an algorithm utilizing a non-constant kernel, were assessed. The specific methods found to be most accurate on the mathematical phantom data were then applied to ex vivo canine data of a scarred and a healthy artery. The algorithm detected significant differences between these two sets of arterial data. It will be necessary to obtain and analyze several more sets of canine arterial data in order to determine the accuracy and reproducibility of the algorithm.

  4. Dynamic viscoelastic models of human skin using optical elastography

    PubMed Central

    Kearney, Steven P.; Khan, Altaf; Dai, Zoujun; Royston, Thomas J.

    2015-01-01

    A novel technique for measuring in vivo human skin viscoelastic properties using optical elastography has been developed. The technique uses geometrically focused surface (GFS) waves that allow for wide bandwidth measurements of the wave field. An analytical solution for the case of a radiating annular disk surface source was fit to experimentally measured GFS waves, enabling an estimate of the frequency-dependent surface wavenumber, which can then be related to the dynamic shear modulus. Several viscoelastic models were then fit to the dynamic shear modulus dispersion curve. Viscoelastic models were evaluated based on their overall quality of fit and variability amongst healthy volunteers. An Ecoflex phantom was used to validate the procedure and results by comparison to similar studies using the same type of phantom. For skin results, it was found that the “α” parameters from the fractional models had the least variability, with coefficients of variability of 0.15, and 0.16. The best fitting models were the standard linear solid, and the fractional Voigt, with a mean fit correlation coefficient, R2, of 0.93, 0.89, respectively. This study has demonstrated the efficacy of this new method, and with larger studies the viscoelastic skin models could be used to identify various skin diseases and their response to treatment. PMID:26305137

  5. Nonlinear elastic behavior of phantom materials for elastography.

    PubMed

    Pavan, Theo Z; Madsen, Ernest L; Frank, Gary R; Adilton O Carneiro, Antonio; Hall, Timothy J

    2010-05-01

    The development of phantom materials for elasticity imaging is reported in this paper. These materials were specifically designed to provide nonlinear stress/strain relationship that can be controlled independently of the small strain shear modulus of the material. The materials are mixtures of agar and gelatin gels. Oil droplet dispersions in these materials provide further control of the small strain shear modulus and the nonlinear parameter of the material. Since these materials are mostly water, they are assumed to be incompressible under typical experimental conditions in elasticity imaging. The Veronda-Westman model for strain energy density provided a good fit to all materials used in this study. Materials with a constant gelatin concentration (3.0% dry weight) but varying agar concentration (0.6-2.8% dry weight) demonstrated the same power law relationship between elastic modulus and agar concentration found for pure agar (1.89 +/- 0.02), consistent with percolation theory, and provided a consistent nonlinearity parameter of 4.5 +/- 0.3. The insights provided by this study will form the basis for stable elastography phantoms with stiffness and nonlinear stress/strain relationships in the background that differ from those in the target. PMID:20400811

  6. Digital image correlation-based optical coherence elastography.

    PubMed

    Sun, Cuiru; Standish, Beau; Vuong, Barry; Wen, Xiao-Yan; Yang, Victor

    2013-12-01

    Optical coherence elastography (OCE) provides deformation or material properties, mapping of soft tissue. We aim to develop a robust speckle tracking OCE technique with improved resolution and accuracy. A digital image correlation (DIC)-based OCE technique was developed by combining an advanced DIC algorithm with optical coherence tomography (OCT). System calibration and measurement error evaluation demonstrated that this DIC-based OCE technique had a resolution of ~0.6 μm displacement and <0.5% strain measurement in the axial scan direction. The measured displacement ranged from 0.6 to 150 μm, obtained via phantom imaging. The capability of the DIC-based OCE technique, for differentiation of stiffness, was evaluated by imaging a candle gel phantom with an irregularly shaped stiff inclusion. OCE imaging of a chicken breast sample differentiated the fat, membrane, and muscle layers. Strain elastograms of an aneurysm sample showed heterogeneity of the tissue and clear contrast between the adventitia and media. These promising results demonstrated the capability of the DIC-based OCE for the characterization of the various components of the tissue sample. Further improvement of the system will be conducted to make this OCE technique a practical tool for measuring and differentiating material properties of soft tissue. PMID:24346855

  7. Ultrasound elastography assessment of bone/soft tissue interface

    NASA Astrophysics Data System (ADS)

    Parmar, Biren J.; Yang, Xu; Chaudhry, Anuj; Shafeeq Shajudeen, Peer; Nair, Sanjay P.; Weiner, Bradley K.; Tasciotti, Ennio; Krouskop, Thomas A.; Righetti, Raffaella

    2016-01-01

    We report on the use of elastographic imaging techniques to assess the bone/soft tissue interface, a region that has not been previously investigated but may provide important information about fracture and bone healing. The performance of axial strain elastograms and axial shear strain elastograms at the bone/soft tissue interface was studied ex vivo on intact and fractured canine and ovine tibias. Selected ex vivo results were corroborated on intact sheep tibias in vivo. The elastography results were statistically analyzed using elastographic image quality tools. The results of this study demonstrate distinct patterns in the distribution of the normalized local axial strains and axial shear strains at the bone/soft tissue interface with respect to the background soft tissue. They also show that the relative strength and distribution of the elastographic parameters change in the presence of a fracture and depend on the degree of misalignment between the fracture fragments. Thus, elastographic imaging modalities might be used in the future to obtain information regarding the integrity of bones and to assess the severity of fractures, alignment of bone fragments as well as to follow bone healing.

  8. Dynamic viscoelastic models of human skin using optical elastography.

    PubMed

    Kearney, Steven P; Khan, Altaf; Dai, Zoujun; Royston, Thomas J

    2015-09-01

    A novel technique for measuring in vivo human skin viscoelastic properties using optical elastography has been developed. The technique uses geometrically focused surface (GFS) waves that allow for wide bandwidth measurements of the wave field. An analytical solution for the case of a radiating annular disk surface source was fit to experimentally measured GFS waves, enabling an estimate of the frequency-dependent surface wavenumber, which can then be related to the dynamic shear modulus. Several viscoelastic models were then fit to the dynamic shear modulus dispersion curve. Viscoelastic models were evaluated based on their overall quality of fit and variability amongst healthy volunteers. An Ecoflex phantom was used to validate the procedure and results by comparison to similar studies using the same type of phantom. For skin results, it was found that the 'α' parameters from the fractional models had the least variability, with coefficients of variability of 0.15, and 0.16. The best fitting models were the standard linear solid, and the fractional Voigt, with a mean fit correlation coefficient, R(2), of 0.93, 0.89, respectively. This study has demonstrated the efficacy of this new method, and with larger studies the viscoelastic skin models could be used to identify various skin diseases and their response to treatment. PMID:26305137

  9. Feasibility of skin surface elastography by tracking skin surface topography

    NASA Astrophysics Data System (ADS)

    Coutts, Louise V.; Miller, Naomi R.; Harland, Christopher C.; Bamber, Jeffrey C.

    2013-12-01

    Recent advances have led to a multitude of image modalities being used for visualization of tissue stiffness. High-resolution images of tissue stiffness are desirable, as they have the potential to provide useful diagnostic information. A noncontact optical imaging method has the attractions of low cost, simplicity, and utility when skin contact is undesirable. However, previous optical techniques have required the application of paint or ink to the surface of the skin and so have required contact. Therefore, the present study assessed the feasibility of tracking skin surface topography to produce elastograms. The study showed, by analyzing a variety of silicone skin surface replicas from various body sites of subjects of different ages, that skin surface elastography by tracking surface topography would be feasible. The study further showed that the quality of the strain images can be optimized by measuring skin line pattern frequency. Skin samples with high skin line frequency will achieve best spatial resolution, in the order of 1 mm, comparable to contact techniques reported previously. A mechanically inhomogeneous silicone replica was then imaged, illustrating the technique's ability to detect strain contrast. Finally, the feasibility of implementing the technique in vivo was illustrated using a single pigmented skin lesion.

  10. Cross-vendor validation of liver magnetic resonance elastography

    PubMed Central

    Serai, Suraj D.; Yin, Meng; Wang, Hui; Ehman, Richard L.; Podberesky, Daniel J.

    2015-01-01

    Purpose To evaluate and validate the reproducibility of MR Elastography (MRE) derived liver stiffness values on two different MR vendor platforms performed on the same subject on the same day. Methods This investigation was approved by the hospital IRB. MRE exams were performed twice in identical fashion in eight volunteers and in five clinical patients on two different 1.5T MR scanners – once on a Philips MR scanner and immediately afterward in back-to-back fashion on a General Electric MR scanner, or vice versa. All scan parameters were kept identical on the two platforms to the best extent possible. After the MRE magnitude and phase images were obtained, the data was converted into quantitative images displaying the stiffness of the liver parenchyma. Mean liver stiffness values between the two platforms were compared using interclass correlation with a p-value < 0.05 considered statistically significant. Results Interclass correlation coefficient (ICC) value of 0.994 was obtained for 13 subjects with p-value <0.001 indicating a significantly positive correlation. Conclusion As MRE gains in acceptance and as its availability becomes more widespread, it is important to ascertain and confirm that liver stiffness values obtained on different MRE vendor platforms are consistent and reproducible. In this small pilot investigation, we demonstrate that liver stiffness measurement with MRE is reproducible and has very good consistency across two vendor platforms. PMID:25476489

  11. Transient elastography in Canada: Current state and future directions

    PubMed Central

    Aljawad, Mohammed; Sirpal, Sanjeev; Yoshida, Eric M; Chandok, Natasha

    2015-01-01

    BACKGROUND: Transient elastography (TE) is a safe and effective technology to noninvasively assess hepatic fibrosis in patients with numerous liver conditions. TE is not readily available to all Canadians, and data regarding how this technology is incorporated into clinical practice are lacking. OBJECTIVE: To describe TE practices in Canada, and to identify strategies to optimize access and usage. METHODS: All Canadian centres with TE devices were invited to complete a survey after obtaining purchasing data from the national distributor of the device. Descriptive statistics were generated. RESULTS: Forty-two devices were available in Canada as of January 2015. Seventy-one percent are used in academic settings, 74% are hospital based and 26% are in private clinics. The test is performed by trained nurses in 48% of centres, physicians in 19%, technicians in 9.5% and by any member of the health care team in 19%. Nineteen percent of centres provide satellite clinics to perform the test. While the majority of the centres perform the test at no additional cost to patients, 29% charge a variable fee. CONCLUSION: In Canada, most TE devices are used in academic and/or hospital-based settings, thus limiting access to this technology to many patients. A sizeable minority of centres mandate patients pay variable out-of-pocket fees. Satellite clinics offered by some centres could increase access, but are not widespread. The lack of uniformity with TE practices in Canada suggests that a national policy is needed. PMID:26069895

  12. Method for optical coherence elastography of the cornea

    NASA Astrophysics Data System (ADS)

    Ford, Matthew R.; Dupps, William J.; Rollins, Andrew M.; Roy, Abhijit Sinha; Hu, Zhilin

    2011-01-01

    The material properties of the cornea are important determinants of corneal shape and refractive power. Corneal ectatic diseases, such as keratoconus, are characterized by material property abnormalities, are associated with progressive thinning and distortion of the cornea, and represent a leading indication for corneal transplantation. We describe a corneal elastography technique based on optical coherence tomography (OCT) imaging, in which displacement of intracorneal optical features is tracked with a 2-D cross-correlation algorithm as a step toward nondestructive estimation of local and directional corneal material properties. Phantom experiments are performed to measure the effects of image noise and out-of-plane displacement on effectiveness of displacement tracking and demonstrated accuracy within the tolerance of a micromechanical translation stage. Tissue experiments demonstrate the ability to produce 2-D maps of heterogeneous intracorneal displacement with OCT. The ability of a nondestructive optical method to assess tissue under in situ mechanical conditions with physiologic-range stress levels provides a framework for in vivo quantification of 3-D corneal elastic and viscoelastic resistance, including analogs of shear deformation and Poisson's ratio that may be relevant in the early diagnosis of corneal ectatic disease.

  13. Tissue characterization using magnetic resonance elastography: preliminary results*

    NASA Astrophysics Data System (ADS)

    Kruse, S. A.; Smith, J. A.; Lawrence, A. J.; Dresner, M. A.; Manduca, A.; Greenleaf, J. F.; Ehman, R. L.; Kruse, S. A.; Smith, J. A.; Lawrence, A. J.; Dresner, M. A.; Manduca, A.; Greenleaf, J. F.

    2000-06-01

    The well-documented effectiveness of palpation as a diagnostic technique for detecting cancer and other diseases has provided motivation for developing imaging techniques for non-invasively evaluating the mechanical properties of tissue. A recently described approach for elasticity imaging, using propagating acoustic shear waves and phase-contrast MRI, has been called magnetic resonance elastography (MRE). The purpose of this work was to conduct preliminary studies to define methods for using MRE as a tool for addressing the paucity of quantitative tissue mechanical property data in the literature. Fresh animal liver and kidney tissue specimens were evaluated with MRE at multiple shear wave frequencies. The influence of specimen temperature and orientation on measurements of stiffness was studied in skeletal muscle. The results demonstrated that all of the materials tested (liver, kidney, muscle and tissue-simulating gel) exhibit systematic dependence of shear stiffness on shear rate. These data are consistent with a viscoelastic model of tissue mechanical properties, allowing calculation of two independent tissue properties from multiple-frequency MRE data: shear modulus and shear viscosity. The shear stiffness of tissue can be substantially affected by specimen temperature. The results also demonstrated evidence of shear anisotropy in skeletal muscle but not liver tissue. The measured shear stiffness in skeletal muscle was found to depend on both the direction of propagation and polarization of the shear waves.

  14. Emotion Regulation and Impulsivity in Young Adults

    PubMed Central

    Schreiber, Liana R.N.; Grant, Jon E.; Odlaug, Brian L.

    2012-01-01

    Past research has linked both emotion regulation and impulsivity with the development and maintenance of addictions. However, no research has investigated the relationship between emotion regulation and impulsivity within young adults. In the present study, we analyzed 194 young adults (27.8% female; 21.3 ± 3.32 years old; 91.8% single; 85.1% Caucasian), grouping them as low, average, or high emotionally dysregulated, and compared self-reported impulsivity, impulsive behaviors (such as alcohol and substance use and gambling) and cognitive impulsivity. We hypothesized that those with high levels of emotion dysregulation would score higher on self-reported and cognitive impulsivity, and report more impulsive behaviors. Analysis indicated that compared to low, the high emotion dysregulation group scored significantly higher on two self-report measures of impulsivity, harm avoidance, and cognitive reasoning. No significant differences were found between groups in impulsive behaviors and cognitive impulsivity. Overall, this study highlights the relationship between emotion dysregulation and impulsivity, suggesting that emotion regulation may be an important factor to consider when assessing individuals at a higher risk for developing an addiction. PMID:22385661

  15. A Neurogenetic Approach to Impulsivity

    PubMed Central

    Congdon, Eliza; Canli, Turhan

    2008-01-01

    Impulsivity is a complex and multidimensional trait that is of interest to both personality psychologists and to clinicians. For investigators seeking the biological basis of personality traits, the use of neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) revolutionized personality psychology in less than a decade. Now, another revolution is under way, and it originates from molecular biology. Specifically, new findings in molecular genetics, the detailed mapping and the study of the function of genes, have shown that individual differences in personality traits can be related to individual differences within specific genes. In this article, we will review the current state of the field with respect to the neural and genetic basis of trait impulsivity. PMID:19012655

  16. Microwave emission from lead zirconate titanate induced by impulsive mechanical load

    SciTech Connect

    Aman, A.; Majcherek, S.; Hirsch, S.; Schmidt, B.

    2015-10-28

    This paper focuses on microwave emission from Lead zirconate titanate Pb [Zr{sub x}Ti{sub 1−x}] O{sub 3} (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression and restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.

  17. Passive elastography: shear-wave tomography from physiological-noise correlation in soft tissues.

    PubMed

    Gallot, Thomas; Catheline, Stefan; Roux, Philippe; Brum, Javier; Benech, Nicolas; Negreira, Carlos

    2011-06-01

    Inspired by seismic-noise correlation and time reversal, a shear-wave tomography of soft tissues using an ultrafast ultrasonic scanner is presented here. Free from the need for controlled shear-wave sources, this passive elastography is based on Green's function retrieval and takes advantage of the permanent physiological noise of the human body. PMID:21693392

  18. 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.

  19. The Avaibility of Strain Elastography in a Hydatid Cyst – Interobserver Study

    PubMed Central

    Duymuş, Mahmut; Menzilcioğlu, Mehmet Sait; Gök, Mustafa; Erdem, Ahmet; Avcu, Serhat; Kırış, Adem

    2016-01-01

    Summary Background To differentiate the hydatid cyst (HC) types by ultrasound elastography using two different sizes (4 mm and 8 mm) of the region of interest (ROI) and asking two different radiologists (interobserver) for their opinion. Material/Methods Patients with HC were evaluated by USG elastography. The statistical anayses were performed using Strain index (SI) which is the unit of strain elastography. Results A total of 26 out of 33 patients were female, and 7 were male. The mean age was 38.85±17.62 (range from 10 to 72 years). Type I: 6, Type 2: 6, Type III: 6, Type IV: 11, Type V: 4. There was no significant difference in HC SI (regardless of types) between O1 and O2, and 4-mm and 8-mm ROI (p>0.05). There was no statistically significant difference between SI of HC types of interobservers (O1–O2) and ROI sizes (4–8 mm) (p>0.05 for all parameters). The highest correlation between HC types and ROI sizes was in ROI size of 4 mm. Conclusions The correlation between SI and types was reliable in standard-applied 4-mm ROI. There was no statistically significant difference between interobservers in SI values. Thus, elastography tecnhnique is objective for HC but not appropriate to differentiate the types. PMID:27429674

  20. Evaluation of levator ani with no defect on elastography in women with POP

    PubMed Central

    Xie, Meng; Zhang, Xuyin; Liu, Jia; Ding, Jingxin; Ren, Yunyun; Hua, Keqin

    2015-01-01

    Objective: It is difficult to evaluate the function of levator ani with no defect encountered in routine practice. Elastography is a new adjunct to real-time ultrasound imaging that overlays traditional B-mode imaging with a color graphic representation of tissue elasticity. The aim of this study is to specifically evaluate the function of levator ani with no defect by ES (elastography). Methods: This was a prospective, observational study. All patients were examined by MRI and the cases with levator ani defect were excluded. The included cases underwent conventional translabial ultrasound, and then ultrasound ES. A little levator ani were biopsied for immunohistochemistry check in the patients who underwent surgery. Results: Of the 52 cases with no levator ani defects, 22 had an elastography score of 1, 20 had a score of 2, 8 had a score of 3 and 2 had a score of 4 in levator ani. Cases of ES1 and ES2 were more than ES3 and ES4 (P = 0.004). The immunohistochemistry check indicated that 12 patients who underwent surgery showed weak expression and the other 4 patients showed moderate expression of collagen type I in levator ani, compared with 2 controls showing strong expressions. Conclusions: Elastography can assess the change of elasticity function of levator ani though the structure has no defect which was detected by MRI and conventional ultrasound. And probably the change of function of levator ani was earlier than structure abnormity in POP. PMID:26309719

  1. 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.

  2. 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.

  3. 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

  4. Intracardiac Myocardial Elastography in canines and humans in vivo

    PubMed Central

    Grondin, Julien; Wan, Elaine; Gambhir, Alok; Garan, Hasan; Konofagou, Elisa E.

    2014-01-01

    Intracardiac echocardiography (ICE) is a useful imaging modality which is used during radiofrequency (RF) ablation procedures to help identify anatomical structures. Utilizing ICE in adjunct with myocardial elastography (ME) can provide additional information on the mechanical properties of cardiac tissue and provide information on mechanical changes due to ablation. The objective of this study was to demonstrate that ICE can be used at high frame rate using a diverging beam transmit sequence to image myocardial strain and differentiate myocardial tissue properties before, during and after ablation for a clinical ablation procedure. In this feasibility study, three normal canines and eight patients with atrial fibrillation (AF) were studied in vivo. A 5.8-MHz ICE transducer was used to image the heart with a diverging beam transmit method achieving 1200 frames per second (fps). Cumulative axial displacement estimation was performed using 1-D cross-correlation with a window size of 2.7mm and 95% overlap. Axial cumulative strains were estimated in left atrium (LA) and right atrium (RA) using a least-squares estimator with a kernel of 2mm on the axial displacements. In the canine case, radial thickening was detected in the lateral wall and in the interatrial septum during LA emptying. For AF patients, mean absolute strain in the ablated region was lower (6.7±3.1%) than before the ablation (17.4±9.3%) in LA at end LA emptying. In the cavotricuspid isthmus (CTI) region, mean absolute strain magnitude at end RA emptying was found to be higher during ablation (43.0±18.1%) compared to after ablation (33.7±15.8%). Myocardial strains in the LA of an AF patient were approximately 2.6 times lower in the ablated region than before ablation. This initial feasibility may suggest ME as a new imaging modality to be used in adjunct with ICE in RF ablation guidance and lesion monitoring. PMID:25643083

  5. Validation of Shear Wave Elastography in Skeletal Muscle

    PubMed Central

    Eby, Sarah F.; Song, Pengfei; Chen, Shigao; Chen, Qingshan; Greenleaf, James F.; An, Kai-Nan

    2013-01-01

    Skeletal muscle is a very dynamic tissue, thus accurate quantification of skeletal muscle stiffness throughout its functional range is crucial to improve the physical functioning and independence following pathology. Shear wave elastography (SWE) is an ultrasound-based technique that characterizes tissue mechanical properties based on the propagation of remotely induced shear waves. The objective of this study is to validate SWE throughout the functional range of motion of skeletal muscle for three ultrasound transducer orientations. We hypothesized that combining traditional materials testing (MTS) techniques with SWE measurements will show increased stiffness measures with increasing tensile load, and will correlate well with each other for trials in which the transducer is parallel to underlying muscle fibers. To evaluate this hypothesis, we monitored the deformation throughout tensile loading of four porcine brachialis whole-muscle tissue specimens, while simultaneously making SWE measurements of the same specimen. We used regression to examine the correlation between Young's modulus from MTS and shear modulus from SWE for each of the transducer orientations. We applied a generalized linear model to account for repeated testing. Model parameters were estimated via generalized estimating equations. The regression coefficient was 0.1944, with a 95% confidence interval of (0.1463 – 0.2425) for parallel transducer trials. Shear waves did not propagate well for both the 45° and perpendicular transducer orientations. Both parallel SWE and MTS showed increased stiffness with increasing tensile load. This study provides the necessary first step for additional studies that can evaluate the distribution of stiffness throughout muscle. PMID:23953670

  6. Effect of off-frequency sampling in magnetic resonance elastography.

    PubMed

    Johnson, Curtis L; Chen, Danchin D; Olivero, William C; Sutton, Bradley P; Georgiadis, John G

    2012-02-01

    In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results were compared with numerical simulations to quantify these effects. It is known that off-frequency encoding alone results in a scaling of wave amplitude, and it is shown here that off-frequency sampling can result in two main effects: (1) errors in the overall shear stiffness estimate of the material on the global scale and (2) local variations appearing as stiffer and softer structures in the material. For small differences in frequency, it was found that measured global stiffness of the brain could theoretically vary by up to 12.5% relative to actual stiffness with local variations of up to 3.7% of the mean stiffness. It was demonstrated that performing MRE experiments at a frequency other than that of tissue vibration can lead to artifacts in the MRE stiffness images, and this mismatch could explain some of the large-scale scatter of stiffness data or lack of repeatability reported in the brain MRE literature. PMID:22055750

  7. Elastography Study of Hamstring Behaviors during Passive Stretching

    PubMed Central

    Le Sant, Guillaume; Ates, Filiz; Brasseur, Jean-Louis; Nordez, Antoine

    2015-01-01

    Introduction The mechanical properties of hamstring muscles are usually inferred from global passive torque/angle relationships, in combination with adjoining tissues crossing the joint investigated. Shear modulus measurement provides an estimate of changes in muscle-tendon stiffness and passive tension. This study aimed to assess the passive individual behavior of each hamstring muscle in different stretching positions using shear wave elastography. Methods/Results The muscle shear modulus of each hamstring muscle was measured during a standardized slow passive knee extension (PKE, 80% of maximal range of motion) on eighteen healthy male volunteers. Firstly, we assessed the reliability of the measurements. Results were good for semitendinosus (ST, CV: 8.9%-13.4%), semimembranosus (SM, CV: 10.3%-11.2%) and biceps femoris long-head (BF-lh, CV: 8.6%-13.3%), but not for biceps femoris short-head (BF-sh, CV: 20.3%-44.9%). Secondly, we investigated each reliable muscle in three stretch positions: 70°, 90° and 110° of hip flexion. The results showed different values of shear modulus for the same amount of perceived stretch, with the highest measurements in the high-flexed hip situation. Moreover, individual muscles displayed different values, with values increasing or BF-lh, SM and ST, respectively. The inter-subject variability was 35.3% for ST, 27.4% for SM and 30.2% for BF-lh. Conclusion This study showed that the hip needs to be high-flexed to efficiently tension the hamstrings, and reports a higher muscle-tendon stress tolerance at 110° of hip angle. In addition muscles have different passive behaviors, and future works will clarify if it can be linked with rate of injury. PMID:26418862

  8. Magnetic Resonance Elastography as a Method to Estimate Myocardial Contractility

    PubMed Central

    Kolipaka, Arunark; Aggarwal, Shivani R.; McGee, Kiaran P.; Anavekar, Nandan; Manduca, Armando; Ehman, Richard L.; Araoz, Philip A.

    2012-01-01

    Purpose To determine whether increasing epinephrine infusion in an in-vivo pig model is associated with an increase in end-systolic magnetic resonance elastography (MRE)-derived effective stiffness. Methods Finite element modeling (FEM) was performed to determine range of myocardial wall thicknesses that could be used for analysis. Then MRE was performed on 5-pigs to measure the end-systolic effective stiffness with epinephrine infusion. Epinephrine was continuously infused intravenously in each pig to increase the heart-rate in increments of 20%. For each such increase end-systolic effective stiffness was measured using MRE. In each pig, Student’s t-test was used to compare effective end-systolic stiffness at baseline and at initial infusion of epinephrine. Least-square linear regression was performed to determine the correlation between normalized end-systolic effective stiffness and increase in heart-rate with epinephrine infusion. Results FEM showed that phase gradient inversion could be performed on wall thickness ~≥1.5cm. In pigs, effective end-systolic stiffness significantly increased from baseline to the first infusion in all pigs (p=0.047). A linear correlation was found between normalized effective end-systolic stiffness and percent increase in heart-rate by epinephrine infusion with R2 ranging from 0.86–0.99 in 4-pigs. In one of the pigs the R2 value was 0.1. A linear correlation with R2=0.58 was found between normalized effective end-systolic stiffness and percent increase in heart-rate when pooling data points from all pigs. Conclusion Noninvasive MRE-derived end-systolic effective myocardial stiffness may be a surrogate for myocardial contractility. PMID:22334349

  9. Detection of dermal systemic sclerosis using noncontact optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Liu, Chih-Hao; Du, Yong; Singh, Manmohan; Li, Jiasong; Wu, Chen; Han, Zhaolong; Raghunathan, Raksha; Hsu, Thomas; Noorani, Shezaan; Hicks, M. John; Mohan, Chandra; Larin, Kirill V.

    2016-03-01

    Systemic sclerosis (SSc) is a connective tissue disease that results in excessive accumulation of collagen in the skin and internal organs. Overall, SSc is a rare disorder, but has a high mortality, particularly in last decade of life. To improve the survival rate, an accurate and early diagnosis is crucial. Currently, the modified Rodnan skin score (mRSS) is the gold standard for evaluating SSc progression based on clinical palpation at 17 sites on the body. However, this procedure can be time consuming, and the assessed score may be biased by the experience of the clinician, causing inter- and intraobserver variabilities. Moreover, the instrinsic elasticity of skin may further bias the mRSS assessment in the early stages of SSc, such as oedematous. To overcome these limitations, there is a need for a rapid, accurate, and objective assessment technique. Optical coherence elastography (OCE) is a novel, rapidly emerging technique, which can assess mechanical contrast in tissues with micrometer spatial resolution. In this work, we demonstrate the first use of OCE to assess the mechanical properties of control and SSc-like diseased skin non-invasively. A focused air-pulse induced an elastic wave in the skin, which was detected by a home-built OCE system. The elastic wave propagated significantly faster in SSc skin compared to healthy skin. The Young's modulus of the SSc skin was significantly higher than that of normal skin (P<0.05). Thus, OCE was able to objectively differentiate healthy and fibrotic skin completely noninvasively and is a promising and potentially useful new technology for quantifying skin involvement in SSc.

  10. Influence of corneal hydration on optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Twa, Michael D.; Vantipalli, Srilatha; Singh, Manmohan; Li, Jiasong; Larin, Kirill V.

    2016-03-01

    Corneal biomechanical properties are influenced by several factors, including intraocular pressure, corneal thickness, and viscoelastic responses. Corneal thickness is directly proportional to tissue hydration and can influence corneal stiffness, but there is no consensus on the magnitude or direction of this effect. We evaluated the influence of corneal hydration on dynamic surface deformation responses using optical coherence elastography (OCE). Fresh rabbit eyes (n=10) were prepared by removing the corneal epithelium and dropping with 0.9% saline every 5 minutes for 1 hour, followed by 20% dextran solution every 5 minutes for one hour. Corneal thickness was determined from structural OCT imaging and OCE measurements were performed at baseline and every 20 minutes thereafter. Micron-scale deformations were induced at the apex of the corneal tissue using a spatially-focused (150μm) short-duration (<1ms) air-pulse delivery system. These dynamic tissue responses were measured non-invasively with a phase-stabilized swept source OCT system. The tissue surface deformation response (Relaxation Rate: RR) was quantified as the time constant, over which stimulated tissue recovered from the maximum deformation amplitude. Elastic wave group velocity (GV) was also quantified and correlated with change in corneal thickness due to hydration process. Corneal thickness rapidly increased and remained constant following epithelium removal and changed little thereafter. Likewise, corneal stiffness changed little over the first hour and then decreased sharply after Dextran application (thickness: -46% [-315/682 μm] RR: - 24% [-0.7/2.88 ms-1]; GV: -19% [-0.6/3.2 m/s]). Corneal thickness and corneal stiffness (RR) were well correlated (R2 = .66). Corneal biomechanical properties are highly correlated with tissue hydration over a wide range of corneal thickness and these changes in corneal stiffness are quantifiable using OCE.

  11. Rapid Vaporization of Thin Conductors Used for Impulse Metalworking

    NASA Astrophysics Data System (ADS)

    Vivek, Anupam

    Forming, cutting and welding of metal by impulse has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can be used with much lighter and more agile equipment because large static forces do not need to be resisted. Impulse metalworking is commonly implemented using explosives or electromagnetic actuators. Explosives have limitations such as space requirements, handling and storage restrictions and ability to scale down the process. The application of electromagnetic forming is limited at high energies and large numbers of operations by the availability of long-lived electromagnetic coils (or actuators, as they are sometimes referred to). Here low-cost, disposable actuators have been suggested as one method to treat this issue. Forming, cutting and welding of metal by impulse has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can be used with much lighter and more agile equipment because large static forces do not need to be resisted. Impulse metalworking is commonly implemented using explosives or electromagnetic actuators. Explosives have limitations such as space requirements, handling and storage restrictions and ability to scale down the process. The application of electromagnetic forming is limited at high energies and large numbers of operations by the availability of long-lived electromagnetic coils (or actuators, as they are sometimes referred to). Here low-cost, disposable actuators have been suggested as one method to treat this issue. Applications including cutting, forming, axisymmetric joining and collision welding are demonstrated and discussed. From analysis of the data from these applications, it was seen that degree of confinement has a great effect on effective geometries of a vaporizing foil. With less confinement, thicker foils were found to be more efficient whereas thinner foils

  12. Co-focused ultrasound and optical coherence elastography system for the study of age-related changes of biomechanical properties of crystalline lens in rabbit eyes

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    In this study, we utilize a confocal ultrasound and phase-sensitive optical coherence elastography (OCE) system to assess age-related changes in biomechanical properties of the crystalline lens in intact rabbit eyes in situ. Lowamplitude elastic deformations, induced on the surface of the lens by localized acoustic radiation force, were measured using phase-sensitive OCT. The results demonstrate that the displacements induced in young rabbit lenses are significantly larger than those in the mature lenses. Temporal analyses of the elastic waves are also demonstrated significant difference between young and old lenses, indicating that the stiffness of lens increases with the age. These results demonstrate possibility of OCE for completely noninvasive analysis and quantification of lens biomechanical properties, which could be used in many clinical and basic science applications such as surgeries and studies on lens physiology and function.

  13. Robust stochastic resonance: Signal detection and adaptation in impulsive noise

    NASA Astrophysics Data System (ADS)

    Kosko, Bart; Mitaim, Sanya

    2001-11-01

    Stochastic resonance (SR) occurs when noise improves a system performance measure such as a spectral signal-to-noise ratio or a cross-correlation measure. All SR studies have assumed that the forcing noise has finite variance. Most have further assumed that the noise is Gaussian. We show that SR still occurs for the more general case of impulsive or infinite-variance noise. The SR effect fades as the noise grows more impulsive. We study this fading effect on the family of symmetric α-stable bell curves that includes the Gaussian bell curve as a special case. These bell curves have thicker tails as the parameter α falls from 2 (the Gaussian case) to 1 (the Cauchy case) to even lower values. Thicker tails create more frequent and more violent noise impulses. The main feedback and feedforward models in the SR literature show this fading SR effect for periodic forcing signals when we plot either the signal-to-noise ratio or a signal correlation measure against the dispersion of the α-stable noise. Linear regression shows that an exponential law γopt(α)=cAα describes this relation between the impulsive index α and the SR-optimal noise dispersion γopt. The results show that SR is robust against noise ``outliers.'' So SR may be more widespread in nature than previously believed. Such robustness also favors the use of SR in engineering systems. We further show that an adaptive system can learn the optimal noise dispersion for two standard SR models (the quartic bistable model and the FitzHugh-Nagumo neuron model) for the signal-to-noise ratio performance measure. This also favors practical applications of SR and suggests that evolution may have tuned the noise-sensitive parameters of biological systems.

  14. Multiple Modes of Impulsivity in Parkinson's Disease

    PubMed Central

    Nombela, Cristina; Rittman, Timothy; Robbins, Trevor W.; Rowe, James B.

    2014-01-01

    Cognitive problems are a major factor determining quality of life of patients with Parkinson's disease. These include deficits in inhibitory control, ranging from subclinical alterations in decision-making to severe impulse control disorders. Based on preclinical studies, we proposed that Parkinson's disease does not cause a unified disorder of inhibitory control, but rather a set of impulsivity factors with distinct psychological profiles, anatomy and pharmacology. We assessed a broad set of measures of the cognitive, behavioural and temperamental/trait aspects of impulsivity. Sixty adults, including 30 idiopathic Parkinson's disease patients (Hoehn and Yahr stage I–III) and 30 healthy controls, completed a neuropsychological battery, objective behavioural measures and self-report questionnaires. Univariate analyses of variance confirmed group differences in nine out of eleven metrics. We then used factor analysis (principal components method) to identify the structure of impulsivity in Parkinson's disease. Four principal factors were identified, consistent with four different mechanisms of impulsivity, explaining 60% of variance. The factors were related to (1) tests of response conflict, interference and self assessment of impulsive behaviours on the Barrett Impulsivity Scale, (2) tests of motor inhibitory control, and the self-report behavioural approach system, (3) time estimation and delay aversion, and (4) reflection in hypothetical scenarios including temporal discounting. The different test profiles of these four factors were consistent with human and comparative studies of the pharmacology and functional anatomy of impulsivity. Relationships between each factor and clinical and demographic features were examined by regression against factor loadings. Levodopa dose equivalent was associated only with factors (2) and (3). The results confirm that impulsivity is common in Parkinson's disease, even in the absence of impulse control disorders, and that it is

  15. Cotton buds, momentum, and impulse

    NASA Astrophysics Data System (ADS)

    van den Berg, Ed; Nuñez, Jover; Guirit, Alfredo; van Huis, Cor

    2000-01-01

    Here is a simple experiment demonstrating impulse and momentum that was picked up from a Japanese presenter at a physics teacher conference held in Cebu City. We have not been able to trace the experiment farther and have never seen it in print. After student-author Nuñez demonstrated it during an exam on conducting demonstrations, we converted the qualitative idea into a quanitative experiment and even discovered some possibilities for student research. The lab is also suitable as homework, since it uses universally available "equipment" — cotton buds (swabs), drinking straws, and a ruler.

  16. Impulsively started incompressible turbulent jet

    SciTech Connect

    Witze, P O

    1980-10-01

    Hot-film anemometer measurements are presented for the centerline velocity of a suddenly started jet of air. The tip penetration of the jet is shown to be proportional to the square-root of time. A theoretical model is developed that assumes the transient jet can be characterized as a spherical vortex interacting with a steady-state jet. The model demonstrates that the ratio of nozzle radius to jet velocity defines a time constant that uniquely characterizes the behavior and similarity of impulsively started incompressible turbulent jets.

  17. Sphere-Wall Impact Experiments with Piezoelectric Force Sensors

    SciTech Connect

    Sinko, John E.; Lassiter, Jonathan S.

    2008-04-28

    Measurement of impulse imparted to a target from {mu}s-timescale laser ablation events is often performed with piezoelectric force sensors. For pulsed laser ablation with a target resting on the force sensors, an effect can occur for a vertical thrust stand in an exhaust-up configuration that results in measurement of about twice the actual imparted impulse. A CO{sub 2} laser operating at 10.6 {mu}m wavelength, 300 ns pulse length, and up to 20 J pulse energy single shots was used to ablate samples of PCTFE. Force sensor measurements of the imparted impulse were compared to tests with a ballistic pendulum over a variety of fluences. The theoretical impulse delivered by the impacts of 6 mm diameter spheres of aluminum, steel, POM, and PTFE on the force sensor were studied, and the coefficients of restitution were measured for the targets. Practical issues for measurement of ablation-imparted impulse with piezoelectric sensors are discussed.

  18. Impulsive synchronization of networked nonlinear dynamical systems

    NASA Astrophysics Data System (ADS)

    Jiang, Haibo; Bi, Qinsheng

    2010-06-01

    In this Letter, we investigate the problem of impulsive synchronization of networked multi-agent systems, where each agent can be modeled as an identical nonlinear dynamical system. Firstly, an impulsive control protocol is designed for network with fixed topology based on the local information of agents. Then sufficient conditions are given to guarantee the synchronization of the networked nonlinear dynamical system by using algebraic graph theory and impulsive control theory. Furthermore, how to select the discrete instants and impulsive constants is discussed. The case that the topologies of the networks are switching is also considered. Numerical simulations show the effectiveness of our theoretical results.

  19. Impaired Decisional Impulsivity in Pathological Videogamers

    PubMed Central

    Irvine, Michael A.; Worbe, Yulia; Bolton, Sorcha; Harrison, Neil A.; Bullmore, Edward T.; Voon, Valerie

    2013-01-01

    Background Pathological gaming is an emerging and poorly understood problem. Impulsivity is commonly impaired in disorders of behavioural and substance addiction, hence we sought to systematically investigate the different subtypes of decisional and motor impulsivity in a well-defined pathological gaming cohort. Methods Fifty-two pathological gaming subjects and age-, gender- and IQ-matched healthy volunteers were tested on decisional impulsivity (Information Sampling Task testing reflection impulsivity and delay discounting questionnaire testing impulsive choice), and motor impulsivity (Stop Signal Task testing motor response inhibition, and the premature responding task). We used stringent diagnostic criteria highlighting functional impairment. Results In the Information Sampling Task, pathological gaming participants sampled less evidence prior to making a decision and scored fewer points compared with healthy volunteers. Gaming severity was also negatively correlated with evidence gathered and positively correlated with sampling error and points acquired. In the delay discounting task, pathological gamers made more impulsive choices, preferring smaller immediate over larger delayed rewards. Pathological gamers made more premature responses related to comorbid nicotine use. Greater number of hours played also correlated with a Motivational Index. Greater frequency of role playing games was associated with impaired motor response inhibition and strategy games with faster Go reaction time. Conclusions We show that pathological gaming is associated with impaired decisional impulsivity with negative consequences in task performance. Decisional impulsivity may be a potential target in therapeutic management. PMID:24146789

  20. The annoyance of impulsive helicopter noise

    NASA Technical Reports Server (NTRS)

    Karamcheti, K.

    1981-01-01

    A total of 96 impulsive and non-impulsive sounds were rated for annoyance by 10 subjects. The signals had the same amplitude spectrum with a maximum frequency of 4.75 kHz. By changing the phase of the spectral components different levels of impulsivity were obtained. The signals had coefficients of impulsivity of 10,8, 7,9, and -0.2 respectively. Further, signals had intensity levels 89 and 95 dBA, pulse repetition rates 10 and 20 Hz, and half the signals had pink noise added at a level 12 dBA lower than the level of the sound. The significant results were: The four females and six male subjects rated the impulsive sounds respectively 3.7 dB less annoying and 2.6 dB more annoying than the non-impulsive sounds. Overall, impulsivity had no effect. The hish pulse repetition rate increased annoyance by 2.2 dB. Addition of pink noise increased annoyance of the non-impulsive sounds 1.2 dB, but decreased the annoyance of the impulsive sounds 0.5 dB.

  1. Impulsivity and the Sexes: Measurement and Structural Invariance of the UPPS-P Impulsive Behavior Scale

    ERIC Educational Resources Information Center

    Cyders, Melissa A.

    2013-01-01

    Before it is possible to test whether men and women differ in impulsivity, it is necessary to evaluate whether impulsivity measures are invariant across sex. The UPPS-P Impulsive Behavior Scale (negative urgency, lack of premeditation, lack of perseverance, and sensation seeking, with added subscale of positive urgency) is one measure of five…

  2. Impulsive model for reactive collisions

    NASA Technical Reports Server (NTRS)

    Marron, M. T.; Bernstein, R. B.

    1972-01-01

    A simple classical mechanical model of the reactive scattering of a structureless atom A and a quasi-diatomic BC is developed which takes full advantage of energy, linear and angular momentum conservation relations but introduces a minimum of further assumptions. These are as follows: (1) the vibrational degree of freedom of the reactant (BC) and product (AB) molecules is suppressed, so the change in vibrational energy is simply a parameter; (2) straight-line trajectories are assumed outside of a reaction shell; (3) within this zone, momentum transfer occurs impulsively (essentially instantaneously) following mass transfer; (4) the impulse, which may be either positive or negative, is directed along the BC axis, which may, however, assume all orientations with respect to the incident relative velocity. The model yields differential and total cross sections and product rotational energy distributions for a given collision exoergicity Q, or for any known distribution over Q. Numerical results are presented for several prototype reactions whose dynamics have been well-studied.

  3. 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.

  4. Spatial mapping of the biomechanical properties of rabbit cornea after cross-linking using optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Li, Jiasong; Singh, Manmohan; Vantipalli, Srilatha; Han, Zhaolong; Twa, Michael D.; Larin, Kirill V.

    2015-03-01

    Keratoconus, a structural degeneration of the cornea, is often treated with UV-induced collagen cross-linking (CXL) to increase tissue resistance to further deformation and degeneration. Optimal treatment would be customized to the individual and consider pre-existing biomechanical properties as well as the effects induced by CXL. This requires the capability to noninvasively measure corneal mechanical properties. In this study, we demonstrate the use of phase-stabilized swept source optical coherence elastography (PhS-SSOCE) to assess the relaxation rate of a deformation which was induced by a focused air-pulse in tissue-mimicking gelatin phantoms of various concentration and partially cross-linked rabbit corneas. The temporal relaxation process was utilized to estimate the Young's modulus from a newly developed model based elasticity reconstruction method. Due to the high spatial sensitivity of PhS-SSOCE, the deformation was only a few microns. The results show that the relaxation process was successfully used to differentiate the untreated (UT) and CXL region of the cornea. The results also indicate that the CXL regions had faster relaxation rates and greater Young's moduli than the UT regions. Therefore, this method can be used to spatially assess the stiffness of the cornea. This non-contact and noninvasive measurement technique utilizes minimal force for excitation and can be potentially used to study the biomechanical properties of ocular and other sensitive tissues.

  5. Reliability and validity of measures of impulsive choice and impulsive action in smokers trying to quit.

    PubMed

    McCarthy, Danielle E; Bold, Krysten W; Minami, Haruka; Yeh, Vivian M; Rutten, Emily; Nadkarni, Shruti G; Chapman, Gretchen B

    2016-04-01

    Cross-sectional research suggests that smokers are more impulsive than are nonsmokers, but few studies have examined relations between impulsiveness and later success in quitting smoking. The purpose of this study was to investigate the reliability and predictive validity of facets of impulsiveness in adult smokers trying to quit. Baseline behavioral measures of impulsive choice (assessed with a delay discounting task) and impulsive action (assessed with a measure of behavioral disinhibition) were used as predictors of smoking cessation success over 12 weeks. The sample included 116 adult (18 years old or older) daily smokers from central New Jersey. Impulsive choice, impulsive action, and self-reported impulsiveness were not significantly related to one another at baseline. Impulsive choice had high test-retest reliability from pre- to postquit, whereas impulsive action was less stable. Test-retest reliability from prequit to 3 weeks' postquit was moderated by achievement of 7-day abstinence. Baseline impulsive action was significantly negatively related to quitting for at least 1 day in the first 2 weeks of a quit attempt and of prolonged abstinence (no relapse over the next 10 weeks). Baseline impulsive choice was robustly associated with biochemically verified 7-day point-prevalence abstinence 12 weeks' postquit, such that those with lower delay discounting were more likely to achieve abstinence. Facets of impulsiveness appear to function largely independently in adult smokers, as indicated by their lack of intercorrelation, differential stability, and differential relations with abstinence. Impulsive action may impede initial quitting, whereas impulsive choice may be an obstacle to maintaining lasting abstinence. (PsycINFO Database Record PMID:26751623

  6. Reliability and Validity of Measures of Impulsive Choice and Impulsive Action in Smokers Trying to Quit

    PubMed Central

    McCarthy, Danielle E.; Bold, Krysten W.; Minami, Haruka; Yeh, Vivian M.; Rutten, Emily; Nadkarni, Shruti G.; Chapman, Gretchen B.

    2016-01-01

    Cross-sectional research suggests that smokers are more impulsive than are non-smokers, but few studies have examined relations between impulsiveness and later success in quitting smoking. The purpose of this study was to investigate the reliability and predictive validity of facets of impulsiveness in adult smokers trying to quit. Baseline behavioral measures of impulsive choice (assessed with a delay discounting task) and impulsive action (assessed with a measure of behavioral disinhibition) were used as predictors of smoking cessation success over 12 weeks. The sample included 116 adult (18 years old or older) daily smokers from central New Jersey. Impulsive choice, impulsive action, and self-reported impulsiveness were not significantly related to one another at baseline. Impulsive choice had high test-retest reliability from pre- to post-quit, whereas impulsive action was less stable. Test-retest reliability from pre-quit to three weeks post-quit was moderated by achievement of seven-day abstinence. Baseline impulsive action was significantly negatively related to quitting for at least one day in the first two weeks of a quit attempt and of prolonged abstinence (no relapse over the next 10 weeks). Baseline impulsive choice was robustly associated with biochemically verified seven-day point-prevalence abstinence 12 weeks post-quit, such that those with lower delay discounting were more likely to achieve abstinence. Facets of impulsiveness appear to function largely independently in adult smokers, as indicated by their lack of inter-correlation, differential stability, and differential relations with abstinence. Impulsive action may impede initial quitting, whereas impulsive choice may be an obstacle to maintaining lasting abstinence. PMID:26751623

  7. Intracardiac myocardial elastography in canines and humans in vivo.

    PubMed

    Grondin, Julien; Wan, Elaine; Gambhir, Alok; Garan, Hasan; Konofagou, Elisa

    2015-02-01

    Intracardiac echocardiography (ICE) is a useful imaging modality which is used during RF ablation procedures to identify anatomical structures. Utilizing ICE in conjunction with myocardial elastography (ME) can provide additional information on the mechanical properties of cardiac tissue and provide information on mechanical changes caused by ablation. The objective of this study was to demonstrate that ICE can be used at high frame rate using a diverging beam transmit sequence to image myocardial strain and differentiate myocardial tissue properties before, during, and after ablation for a clinical ablation procedure. In this feasibility study, three normal canines and eight patients with atrial fibrillation (AF) were studied in vivo. A 5.8-MHz ICE transducer was used to image the heart with a diverging beam transmit method achieving 1200 frames per second (fps). Cumulative axial displacement estimation was performed using 1-D cross-correlation with a window size of 2.7 mm and 95% overlap. Axial cumulative strains were estimated in the left atrium (LA) and right atrium (RA) using a least-squares estimator with a kernel of 2 mm on the axial displacements. In the canine case, radial thickening was detected in the lateral wall and in the interatrial septum during LA emptying. For AF patients, the mean absolute strain in the ablated region was lower (6.7 ± 3.1%) than before the ablation (17.4 ± 9.3%) in LA at the end of the LA emptying phase. In the cavotricuspid isthmus (CTI) region, mean absolute strain magnitude at the end of the RA emptying phase was found to be higher during ablation (43.0 ± 18.1%) compared with after ablation (33.7 ± 15.8%). Myocardial strains in the LA of an AF patient were approximately 2.6 times lower in the ablated region than before ablation. This initial feasibility indicates that ME can be used as a new imaging modality in conjunction with ICE in RF ablation guidance and lesion monitoring. PMID:25643083

  8. In vivo study of myocardial elastography under graded ischemia conditions

    NASA Astrophysics Data System (ADS)

    Lee, Wei-Ning; Provost, Jean; Fujikura, Kana; Wang, Jie; Konofagou, Elisa E.

    2011-02-01

    The capability of currently available echocardiography-based strain estimation techniques to fully map myocardial abnormality at early stages of myocardial ischemia is yet to be investigated. In this study, myocardial elastography (ME), a radio-frequency (RF)-based strain imaging technique that maps the full 2D transmural angle-independent strain tensor in standard echocardiographic views at both high spatial and temporal resolution is presented. The objectives were to (1) evaluate the performance of ME on mapping the onset, extent and progression of myocardial ischemia at graded coronary constriction levels (from partial to complete coronary flow reduction), and (2) validate the accuracy of the strain estimates against sonomicrometry (SM) measurements. A non-survival canine ischemic model (n = 5) was performed by gradually constricting the left anterior descending (LAD) coronary blood flow from 0% (baseline blood flow) to 100% (zero blood flow) at 20% increments. An open-architecture ultrasound system was used to acquire RF echocardiograms in a standard full short-axis view at the frame rate of 211 fps, at least twice higher than what is typically used in conventional echocardiographic systems, using a previously developed, fully automated composite technique. Myocardial deformation was estimated by ME and validated against sonomicrometry. ME estimates and maps transmural (1) 2D displacements using RF cross-correlation and recorrelation; and (2) 2D polar (radial and circumferential) strains, derived from 2D (i.e. both lateral and axial) displacement components, at high accuracy. Full-view strain images were shown and found to reliably depict decreased myocardial function in the region at risk at increased levels of coronary flow reduction. The ME radial strain was deemed to be a more sensitive, quantitative, regional measure of myocardial ischemia as a result of coronary flow reduction when compared to the conventional wall motion score index and ejection fraction

  9. Temporal Preparation, Response Inhibition and Impulsivity

    ERIC Educational Resources Information Center

    Correa, Angel; Trivino, Monica; Perez-Duenas, Carolina; Acosta, Alberto; Lupianez, Juan

    2010-01-01

    Temporal preparation and impulsivity involve overlapping neural structures (prefrontal cortex) and cognitive functions (response inhibition and time perception), however, their interrelations had not been investigated. We studied such interrelations by comparing the performance of groups with low vs. high non-clinical trait impulsivity during a…

  10. Solar Impulse's Solar-Powered Plane

    ScienceCinema

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2014-01-07

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  11. Impulsivity, School Context, and School Misconduct

    ERIC Educational Resources Information Center

    Vogel, Matt; Barton, Michael S.

    2013-01-01

    Impulsivity holds a central place in the explanations of adolescent delinquency. Recent research suggests that neighborhood characteristics, particularly SES (socioeconomic status), perceived supervision, and collective efficacy, moderate the association between impulsivity and delinquency. However, findings to date have been equivocal, and the…

  12. Hyperkinetic Impulse Disorder in Children's Behavior Problems

    ERIC Educational Resources Information Center

    Laufer, Maurice W.; Denhoff, Eric; Solomons, Gerald

    2011-01-01

    A very common cause of children's behavior disorder disturbance is an entity described as the hyperkinetic impulse disorder. This is characterized by hyperactivity, short attention span and poor powers of concentration, irritability, impulsiveness, variability, and poor schoolwork. The existence of this complexity may lead to many psychological…

  13. Solar Impulse's Solar-Powered Plane

    SciTech Connect

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2013-07-08

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  14. High-intensity drying processes: Impulse drying

    SciTech Connect

    Orloff, D.I.

    1989-05-01

    Impulse drying is an innovative process for drying paper that holds great promise for reducing the energy consumed during manufacture of paper and similar web products. Impulse drying occurs when a wet paper web passes through a press nip where one of the rolls is heated to a very high temperature. Steam generated by contact with the hot roll expands and displaces water from the sheet in a very efficient manner. The energy required for water removal is much lower than that required for conventional evaporative drying. Tests have been completed that elucidate the unique displacement mechanism of water removal in the impulse drying process. A pilot roll press has been designed, installed and used to examine impulse drying under conditions that simulate commercial press conditions. The results of this earlier work have been reported in three previous reports. During this report period October, 1987 to September, 1988, the pilot press was equipped with a second impulse drying roll to facilitate studies of surface uniformity in impulse dried paper. Studies have also been completed which examine the origins of sheet delamination that has been been encountered during impulse drying of certain heavyweight paper grades, and which investigate approaches to prevent delamination in these grades. Finally, an experimental plan has been formalized to examine impulse drying of lightweight grades which are candidates for early commercialization. 7 refs., 30 figs., 3 tabs.

  15. Impulsivity and Psychoeducational Intervention in Hyperactive Children.

    ERIC Educational Resources Information Center

    Brown, Ronald T.

    1980-01-01

    Two psychoeducational procedures were investigated for their effects on impulsivity in 120 hyperactive children in two groups: those receiving stimulant drug therapy and those not receiving stimulant drug therapy. Results indicated that the use of psychoeducational treatment approaches are of value in altering the impulsive responses of…

  16. Covert Suicidal Impulses in Maternally Deprived Children.

    ERIC Educational Resources Information Center

    Kliman, Gilbert; Lubin, Harriet

    This paper discusses the development of suicidal impulses in children who have lost their mothers due to abandonment or death. The paper is based on two psychoanalytic case studies, in which the children were in therapy when the first suicidal impulses emerged. A pattern is described in which bereaved children's intense wishes to have their…

  17. Anatomy of a SAR impulse response.

    SciTech Connect

    Doerry, Armin Walter

    2007-08-01

    A principal measure of Synthetic Aperture Radar (SAR) image quality is the manifestation in the SAR image of a spatial impulse, that is, the SAR's Impulse Response (IPR). IPR requirements direct certain design decisions in a SAR. Anomalies in the IPR can point to specific anomalous behavior in the radar's hardware and/or software.

  18. 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

  19. Helicopter impulsive noise - Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1986-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  20. Impulse position control algorithms for nonlinear systems

    NASA Astrophysics Data System (ADS)

    Sesekin, A. N.; Nepp, A. N.

    2015-11-01

    The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of such regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.

  1. Impulse position control algorithms for nonlinear systems

    SciTech Connect

    Sesekin, A. N.; Nepp, A. N.

    2015-11-30

    The article is devoted to the formalization and description of impulse-sliding regime in nonlinear dynamical systems that arise in the application of impulse position controls of a special kind. The concept of trajectory impulse-sliding regime formalized as some limiting network element Euler polygons generated by a discrete approximation of the impulse position control This paper differs from the previously published papers in that it uses a definition of solutions of systems with impulse controls, it based on the closure of the set of smooth solutions in the space of functions of bounded variation. The need for the study of such regimes is the fact that they often arise when parry disturbances acting on technical or economic control system.

  2. Helicopter impulsive noise - Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1986-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory/experiment are suggested.

  3. Helicopter impulsive noise: Theoretical and experimental status

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Yu, Y. H.

    1983-01-01

    The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanism is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanism of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.

  4. Conversion of Impulse Voltage Generator Into Steep Wave Impulse Test-Equipment

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed Zaid; Tanwar, Surender Singh; Dayama, Ravindra; Choudhary, Rahul Raj; Mangal, Ravindra

    This paper demonstrates the alternative measures to generate the Steep wave impulse by using Impulse Voltage Generator (IVG) for high voltage testing of porcelain insulators. The modification of IVG by incorporating compensation of resistor, inductor, and capacitor has been achieved and further performance of the modified system has been analyzed by applying the generated lightning impulse and analyzing the electrical characteristics of impulse waves under standard lightning and fast rise multiple lightning waveform to determine the effect to improve rise time. The advantageous results have been received and being reported such as increase in overshoot compensation, increase in capacitive and inductive load ranges. Such further reduces the duration of oscillations of standard impulse voltages. The reduction in oscillation duration of steep front impulse voltages may be utilized in up gradation of Impulse Voltage Generator System. Stray capacitance could further be added in order to get the minimized difference of measurement between simulation and the field establishment.

  5. Response of a seat-passenger system to impulsive loading.

    NASA Technical Reports Server (NTRS)

    Collins, J. A.; Turnbow, J. W.

    1972-01-01

    This paper presents a summary of a study of the dynamic response of an aircraft seat-passenger system to impulsive loading typical of aircraft crash situations. A brief description of the computer model SIMULA is presented, and selected data from 305 separate cases which have been studied are discussed. Maximum system forces, displacements, velocities, and accelerations are presented as functions of velocity change, aircraft deceleration, crash pulse shape, passenger weight, and seat belt slack. Data from both single and coupled parameter studies are included. A correlation of SIMULA results with experimentally obtained data is made.

  6. Solar impulsive energetic electron events

    NASA Astrophysics Data System (ADS)

    Wang, Linghua

    The Sun is capable of accelerating ions from ~ tens of keV up to tens of GeV and electrons from ~ tens of eV up to hundreds of MeVs in transient events such as flares and fast coronal mass ejections (CMEs). The energized particles escaping into the interplanetary medium are referred to as Solar Energetic Particle (SEP) events. The great majority of SEP events are impulsive SEP events that are dominated by ~1-100 keV electrons and ~MeV/nucleon ion emissions, with enhanced 3 He/ 4 He ratios up to 10 4 times the coronal values (also called electron/ 3 He-rich SEP events). This thesis is focused on solar impulsive energetic electron events, the electron part of impulsive SEP events, using electron observations from the 3-D Plasma and Energetic Particle instrument (3DP) on the WIND spacecraft near the Earth. First, I present the first comprehensive statistical study of solar energetic electron events over almost one solar cycle. I find that the occurrence rate of solar electron events shows a strong solar-cycle variation; after correction for the background effect, the estimated occurrence frequency exhibits a good power-law distribution, and the estimated occurrence rate near the Earth is ~1000/year at solar maximum and ~30/year at solar minimum for the instrumental sensitivity (~2.9×10^-4 (cm 2 s str eV) -1 for the 40 keV channel) of WIND/3DP, about one order of magnitude larger than the observed occurrence rate. Solar energetic electron events have a one-to-one association with type III radio bursts and a poor association with flares, but a close association with 3 He- rich ion emissions. These 3 He-rich electron events also have a poor association with flares but a close (~ 60%) association with west-limb CMEs. Then I present two case studies: one investigating the temporal relationship between solar impulsive electrons and type III radio emissions, and the second studying the temporal relationship between solar impulsive electrons and 3 He- rich ions. For both

  7. Ground Reaction Forces of the Lead and Trail Limbs when Stepping Over an Obstacle

    PubMed Central

    Bovonsunthonchai, Sunee; Khobkhun, Fuengfa; Vachalathiti, Roongtiwa

    2015-01-01

    Background Precise force generation and absorption during stepping over different obstacles need to be quantified for task accomplishment. This study aimed to quantify how the lead limb (LL) and trail limb (TL) generate and absorb forces while stepping over obstacle of various heights. Material/Methods Thirteen healthy young women participated in the study. Force data were collected from 2 force plates when participants stepped over obstacles. Two limbs (right LL and left TL) and 4 conditions of stepping (no obstacle, stepping over 5 cm, 20 cm, and 30 cm obstacle heights) were tested for main effect and interaction effect by 2-way ANOVA. Paired t-test and 1-way repeated-measure ANOVA were used to compare differences of variables between limbs and among stepping conditions, respectively. The main effects on the limb were found in first peak vertical force, minimum vertical force, propulsive peak force, and propulsive impulse. Results Significant main effects of condition were found in time to minimum force, time to the second peak force, time to propulsive peak force, first peak vertical force, braking peak force, propulsive peak force, vertical impulse, braking impulse, and propulsive impulse. Interaction effects of limb and condition were found in first peak vertical force, propulsive peak force, braking impulse, and propulsive impulse. Conclusions Adaptations of force generation in the LL and TL were found to involve adaptability to altered external environment during stepping in healthy young adults. PMID:26169293

  8. Cardiopulmonary effects of high-impulse noise exposure.

    PubMed

    Dodd, K T; Mundie, T G; Lagutchik, M S; Morris, J R

    1997-10-01

    In high-energy impulse noise environments, the biomechanical coupling process between the external forces and the pathophysiology of cardiopulmonary injury is not well understood. A 12-in-diameter compressed air-driven shock tube with reflector plate was used to induce three levels of pulmonary contusion injury in a large animal model. Twenty-one anesthetized sheep were exposed to the various levels of impulse noise generated by the shock tube, with six additional sheep serving as a control group. Pathologic evaluations, performed 3 hours after exposure, showed pulmonary contusion ranging from minor petechial changes on the surface of the lung parenchyma to diffuse ecchymoses affecting as much as 60% of the lung. The gross pathologic observations of injury produced by exposure to the impulse noise produced by the shock tube were similar to those reported for blunt impact trauma or exposure to chemical or grain-dust explosions. The extent of lung injury (lung injury index) was quantitatively assessed. A semilogarithmic relationship between the lung injury index and the measured peak pressure was demonstrated. A significant linear correlation was demonstrated between lung injury index and lung weight-to-body weight ratio. Significant cardiopulmonary changes were also observed as a result of exposure to high-impulse noise. Although in most cases the degree of change was related to the severity of the injury, significant cardiopulmonary function changes were also observed in the absence of significant grossly observable pulmonary injury. Cardiac injury was indicated by decreased cardiac output and hypotension at all levels of injury and might be the result of myocardial contusion or air emboli. Pulmonary injury was demonstrated by respiratory acidosis, increases in lung resistance, and decreases in lung compliance and lung volume. Arterial PO2 appeared to be the most sensitive parameter of injury and was decreased for all measurement intervals for all exposure groups

  9. Osteochondral Tissue Cell Viability Is Affected by Total Impulse during Impaction Grafting

    PubMed Central

    Balash, Paul; Kang, Richard W.; Schwenke, Thorsten; Cole, Brian J.; Wimmer, Markus A.

    2010-01-01

    Objective: Osteochondral graft transplantation has garnered significant attention because of its ability to replace the lesion with true hyaline cartilage. However, surgical impaction of the graft to anchor it into the defect site can be traumatic and lead to cell death and cartilage degeneration. This study aimed to test the hypothesis that increasing impulse magnitude during impaction of osteochondral plugs has a direct effect on loss of cell viability. Design: In this controlled laboratory study, the impaction force was kept constant while the impulse was varied. Ninety-six osteochondral plugs were extracted from the trochlea of bovine stifle joints and were randomly assigned into 3 experimental and 1 (nonimpacted) control group. The transferred impulse of the experimental groups reflected the median and the lower and upper quartiles of preceding clinical measurements. Data were obtained at day 0, day 4, and day 8; at each point, cell viability was assessed using the Live/Dead staining kit and histological assessments were performed to visualize matrix structural changes. Results: After impaction, cartilage samples stayed intact and did not show any histological signs of matrix disruption. As expected, higher impulse magnitudes introduced more cell death; however, this relationship was lost at day 8 after impaction. Conclusion: Impulse magnitude has a direct effect on cell viability of the graft. Because impulse magnitude is mostly governed by the press-fit characteristics of the recipient site, this study aids in the definition of optimal insertion conditions for osteochondral grafts. PMID:26069558

  10. Liver fibrosis grading using multiresolution histogram information in real-time elastography

    NASA Astrophysics Data System (ADS)

    Albouy-Kissi, A.; Sarry, L.; Massoulier, S.; Bonny, C.; Randl, K.; Abergel, A.

    2010-03-01

    Despites many limitations, liver biopsy remains the gold standard method for grading and staging liver biopsy. Several modalities have been developed for a non invasive assessment of liver diseases. Real-time elastography may constitute a true alternative to liver biopsy by providing an image of tissular elasticity distribution correlated to the fibrosis grade. In this paper, we investigate a new approach for the assessment of liver fibrosis by the classification of fibrosis morphometry. Multiresolution histogram, based on a combination of intensity and texture features, has been tested as feature space. Thus, the ability of such multiresolution histograms to discriminate fibrosis grade has been proven. The results have been tested on seventeen patients that underwent a real time elastography and FibroScan examination.

  11. Magnetic resonance elastography detected with a SQUID in microtesla magnetic fields

    NASA Astrophysics Data System (ADS)

    Kelso, Nathan; Koski, Kristie; Reimer, Jeffrey

    2005-03-01

    We have used a SQUID-based microtesla magnetic resonance imaging (MRI) system to perform magnetic resonance elastography (MRE) experiments in a measurement field of 132 microtesla. Magnetic resonance elastography is based on MRI and measures three-dimensional displacement and strain fields in a sample. With appropriate data processing this allows for a quantitative map of the physical response of a material to an applied deformation. In the past, MRE experiments using conventional (1.5 tesla and above) MRI systems have demonstrated that MRE may be used as a non-invasive method for measuring stiffness of human tissues, which may aid in the detection and diagnosis of breast cancer and other cancers. Our MRE experiment consists of applying a small axial deformation to a cylindrical sample of 0.5% agarose gel. For samples approximately 30 mm in height, we were able to measure displacements on the order of 500 micrometers. Supported by USDOE.

  12. Pediatric Cardiac Shear Wave Elastography for Quantitative Assessment of Myocardial Stiffness: A Pilot Study in Healthy Controls.

    PubMed

    Song, Pengfei; Bi, Xiaojun; Mellema, Daniel C; Manduca, Armando; Urban, Matthew W; Pellikka, Patricia A; Chen, Shigao; Greenleaf, James F

    2016-08-01

    The long-term goal of this study is to assess chemotherapy-induced cardiotoxicity for pediatric cancer patients using cardiac ultrasound shear wave (SW) elastography. This pilot study aimed to systematically investigate the feasibility of using cardiac SW elastography in children and provide myocardial stiffness control data for cancer patients. Twenty healthy volunteers (ages 5-18) were recruited. A novel cardiac SW elastography sequence with pulse-inversion harmonic imaging and time-aligned sequential tracking was developed for this study. Cardiac SW elastography produces and detects transient SWs propagating in the myocardium in late-diastole, which can be used to quantify myocardial stiffness. The parasternal long-axis (L-A) and short-axis (S-A) views of the interventricular septum (IVS) were feasible for pediatric cardiac SW elastography. The L-A and S-A views of the basal and mid IVS provided better success rates than those of the apical IVS. Success rates decreased with increased body mass index (BMI), but did not differ with age or gender. Two-dimensional SW speed measurements were 1.26, 1.22, 1.71 and 1.67 m/s for L-A base, L-A mid, S-A base and S-A mid IVS, respectively. All S-A SW speed values were significantly higher (p < 0.01) than L-A values due to myocardial anisotropy. No SW speed difference was observed for different ages and genders. This pilot study demonstrated, for the first time, the feasibility of using cardiac SW elastography to measure quantitative myocardial stiffness in children, and established control SW speed values for using SW elastography to assess chemo-induced cardiotoxicity for pediatric cancer patients. The results showed that the myocardial anisotropy needs to be accounted for when comparing SW speed from different imaging axes. PMID:27140522

  13. Theoretical analysis of the electrical aspects of the basic electro-impulse problem in aircraft de-icing applications

    NASA Technical Reports Server (NTRS)

    Henderson, R. A.; Schrag, R. L.

    1986-01-01

    A summary of modeling the electrical system aspects of a coil and metal target configuration resembling a practical electro-impulse deicing (EIDI) installation, and a simple circuit for providing energy to the coil, was presented. The model was developed in sufficient theoretical detail to allow the generation of computer algorithms for the current in the coil, the magnetic induction on both surfaces of the target, the force between the coil and target, and the impulse delivered to the target. These algorithms were applied to a specific prototype EIDI test system for which the current, magnetic fields near the target surfaces, and impulse were previously measured.

  14. Detection and Measurement of Stones With Ultrasound Strain Elastography: A Phantom Study.

    PubMed

    Li, Qian; Chen, Lei; Halpern, Elkan F; Samir, Anthony E

    2015-12-01

    The sonoelastographic appearances of stones in a phantom were evaluated in this study. Ten stones were embedded into a tissue-mimicking meat phantom. The stone axial (vertical) and transverse (horizontal) dimensions measured by an electronic digital caliper, gray-scale ultrasound, and strain elastography (SE) were compared in 5 groups with stones embedded at different depths. In this study, physically measured axial and transverse stone dimensions were 1.17 to 6.86 and 1.30 to 11.15 mm, respectively. Strain elastography showed a characteristic 3-layer pattern associated with stones, comprising a superficial transition region, a hard region, and a deep transition region. As SE data were available in group 5, only data of groups 1 to 4 were analyzed. Compared with physical measurements, measurement mean errors of SE horizontal and SE vertical dimensions ranged from -0.20 to 0.42 mm and from -1.28 to -0.05 mm, respectively, in the 4 groups. Paired t testing demonstrated a significant horizontal dimension measurement error difference between B mode and SE method in group 4 (0.44 vs -0.20 mm, P < 0.05; F = 1.18, P > 0.05), but not in the other groups. Strain elastography horizontal dimension measurement error was not statistically correlated with stone size in the 4 groups. Strain elastography vertical dimension measurement error significantly correlated with stone size only in group 4 (P < 0.05). Preliminary results indicate that stone horizontal and vertical dimensions can be measured using SE in a soft tissue phantom, including when shadowing precludes measurement of vertical dimension on conventional 2-dimensional ultrasound. These results provide substantial motivation to further investigate SE as a modality to image stones in clinical practice. PMID:26656990

  15. 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.

  16. In vivo time-harmonic multifrequency elastography of the human liver.

    PubMed

    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. PMID:24614751

  17. Ultrasound elastography using carotid artery pulsation in the differential diagnosis of sonographically indeterminate thyroid nodules.

    PubMed

    Choi, Woo Jung; Park, Jeong Seon; Koo, Hye Ryoung; Kim, Soo-Yeon; Chung, Min Sung; Tae, Kyung

    2015-02-01

    OBJECTIVE. The purpose of this study was to evaluate the diagnostic performance of gray-scale ultrasound and a new method of thyroid ultrasound elastography using carotid artery pulsation in the differential diagnosis of sonographically indeterminate thyroid nodules. MATERIALS AND METHODS. A total of 102 thyroid nodules with indeterminate gray-scale ultrasound features from 102 patients (20 males and 82 females; age range, 16-74 years; mean age, 51 years) were included. The gray-scale ultrasound images of each nodule were reviewed and assigned a score from 1 (low) to 5 (high) according to the possibility of malignancy. Ultrasound elastography was performed using carotid pulsation as the compression source. The elasticity contrast index (ECI), which quantifies local strain contrast within a nodule, was automatically calculated. The radiologist reassessed the scores after concurrently reviewing gray-scale ultrasound and elastography. ROC curve analysis was used to evaluate the diagnostic performances of each dataset and to compare the AUC (Az) values of gray-scale ultrasound score alone, ECI alone, and a combined assessment. RESULTS. Significantly more malignant thyroid nodules were hypoechoic than benign nodules (p = 0.014). The ECI was significantly higher in malignant nodules than in benign thyroid nodules. The Az values of each dataset were 0.755 (95% CI, 0.660-0.835) for gray-scale ultrasound score, 0.835 (0.748-0.901) for ECI, and 0.853 (0.769-0.915) for a combined assessment. The Az value for a combined assessment of the gray-scale ultrasound score and the ECI was significantly higher than that for the gray-scale ultrasound score alone (p = 0.022). CONCLUSION. Combined assessment with gray-scale ultrasound and elastography using carotid artery pulsation is helpful for characterizing sonographically indeterminate thyroid nodules as benign or malignant. PMID:25615763

  18. Religiosity and Impulsivity in Mental Health

    PubMed Central

    Caribé, André C.; Rocha, Marlos Fernando Vasconcelos; Junior, Davi Félix Martins; Studart, Paula; Quarantini, Lucas C.; Guerreiro, Nicolau; Miranda-Scippa, Ângela

    2015-01-01

    Abstract Our aim is to evaluate the relationship between religiosity and impulsivity in patients with mental illness who had attempted suicide and in healthy individuals. This is a cross-sectional study that included 61 healthy individuals and 93 patients. The instruments used were a sociodemographic data questionnaire, the Mini International Neuropsychiatric Interview, the Barratt Impulsiveness Scale, and the Duke University Religion Index. The healthy individuals presented higher scores in the religiosity domains (organizational, p = 0.028; non-organizational, p = 0.000; intrinsic, p = 0.000). The patients presented higher scores in the impulsivity dimensions (attentional, p = 0.000; motor, p = 0.000; absence of planning, p = 0.000). In the patient group, intrinsic religiosity had a significant inverse relationship with total impulsivity (p = 0.023), attentional (p = 0.010), and absence of planning (p = 0.007), even after controlling for sociodemographic variables. Healthy individuals were more religious and less impulsive than patients. The relationship between religiosity, impulsiveness, and mental illness could be bidirectional; that is, just as mental illness might impair religious involvement, religiosity could diminish the expression of mental illness and impulsive behaviors. PMID:26020819

  19. Impulsive and non-impulsive suicide attempts in patients treated for alcohol dependence

    PubMed Central

    Wojnar, Marcin; Ilgen, Mark A.; Czyz, Ewa; Strobbe, Stephen; Klimkiewicz, Anna; Jakubczyk, Andrzej; Glass, Jennifer; Brower, Kirk J.

    2009-01-01

    Background Suicidal behavior has been recognized as an increasing problem among alcohol-dependent subjects. The aim of the study was to identify correlates of impulsive and non-impulsive suicide attempts among a treated population of alcohol-dependent patients. Methods A total of 154 patients with alcohol dependence consecutively admitted for addiction treatment participated in the study. Suicidal behavior was assessed together with severity of alcohol dependence, childhood abuse, impulsivity, and family history. A stop-signal procedure was used as a behavioral measure of impulsivity. Results and conclusions Lifetime suicide attempts were reported by 43% of patients in alcohol treatment; of which 62% were impulsive. Compared to patients without a suicide attempt, those with a non-impulsive attempt were more likely to have a history of sexual abuse (OR = 7.17), a family history of suicide (OR = 4.09), and higher scores on a personality measure of impulsiveness (OR = 2.27). The only significant factor that distinguished patients with impulsive suicide attempts from patients without a suicide attempt and from patients with a non-impulsive suicide attempt was a higher level of behavioral impulsivity (OR = 1.84 – 2.42). Limitations Retrospective self-report of suicide attempts and family history. Lack of diagnostic measure. PMID:18835498

  20. Norepinephrine and impulsivity: Effects of acute yohimbine

    PubMed Central

    Swann, Alan C.; Lijffijt, Marijn; Lane, Scott D.; Cox, Blake; Steinberg, Joel L.; Moeller, F. Gerard

    2013-01-01

    Rationale Rapid-response impulsivity, characterized by inability to withhold response to a stimulus until it is adequately appraised, is associated with risky behavior and may be increased in a state-dependent manner by norepinephrine. Objective We assessed effects of yohimbine, which increases norepinephrine release by blocking alpha-2 noradrenergic receptors, on plasma catecholamine metabolites, blood pressure, subjective symptoms, and laboratory-measured rapid-response impulsivity. Methods Subjects were twenty-three healthy controls recruited from the community, with normal physical examination and ECG, and negative history for hypertension, cardiovascular illness, and Axis I or II disorder. Blood pressure, pulse, and behavioral measures were obtained before and periodically after 0.4 mg/kg oral yohimbine or placebo in a randomized, counterbalanced design. Metabolites of norepinephrine (3-methoxy-4-hydroxyphenylglycol, MHPG; vanillylmandelic acid, VMA) and dopamine (homovanillic acid, HVA) were measured by high pressure liquid chromatography with electrochemical detection. Rapid-response impulsivity was measured by commission errors and reaction times on the Immediate Memory Task (IMT), a continuous performance test designed to measure impulsivity and attention. Results Yohimbine increased plasma MHPG and VMA but not HVA. Yohimbine increased systolic and diastolic blood pressure and pulse rate. On the IMT, yohimbine increased impulsive errors and impulsive response bias and accelerated reaction times. Yohimbine-associated increase in plasma MHPG correlated with increased impulsive response rates. Time courses varied; effects on blood pressure generally preceded those on metabolites and test performance. Conclusions These effects are consistent with increased rapid-response impulsivity after pharmacological noradrenergic stimulation in healthy controls. Labile noradrenergic responses, or increased sensitivity to norepinephrine, may increase risk for impulsive

  1. Psychosocial predictors of impulsivity in alcohol-dependent patients.

    PubMed

    Jakubczyk, Andrzej; Klimkiewicz, Anna; Mika, Katarzyna; Bugaj, Marcin; Konopa, Aleksandra; Podgórska, Anna; Brower, Kirk J; Wojnar, Marcin

    2013-01-01

    Impulsivity is an important risk factor of severe course of alcohol dependence. However, the significance of environmental determinants of impulsivity has been underestimated. The aim of this study was to identify psychosocial factors increasing the level of impulsivity in alcoholics. Levels of impulsivity were measured in 304 alcohol-dependent patients. The stop-signal task was used to assess behavioral impulsivity, and the Barratt Impulsiveness Scale, to measure global and cognitive impulsivity. Correlations between impulsivity and psychosocial variables were examined. A significant association between level of impulsivity and severity of psychopathological symptoms was observed. Patients who reported childhood sexual or physical abuse, lower social support, and more severe course of alcohol dependence were more impulsive, especially in the cognitive domain. When entered into a linear regression analysis model, severity of alcohol dependence, psychopathology, and childhood physical abuse remained significant. These results suggest that psychosocial variables are important factors associated with high levels of impulsivity in alcohol-dependent patients. PMID:23274294

  2. Ultrasound Elastography for Estimation of Regional Strain of Multilayered Hydrogels and Tissue-Engineered Cartilage.

    PubMed

    Chung, Chen-Yuan; Heebner, Joseph; Baskaran, Harihara; Welter, Jean F; Mansour, Joseph M

    2015-12-01

    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

  3. 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. PMID:26971462

  4. Object detection in ultrasound elastography for use in HIFU treatment of cancer

    NASA Astrophysics Data System (ADS)

    Huang, Alex; Mankani, Soumya; Choo, Chang

    2014-03-01

    High intensity focused ultrasound (HIFU), has applications in treating various cancers, such as prostate, liver and breast cancer. In order for HIFU to be effective and efficient it needs to be guided by an imaging modality. While there are several options for guiding HIFU treatment, one of the most promising is ultrasound elastography. Current commercial devices use Brightness-Mode (B-mode) imaging or MRI, and are manual processes. Ultrasound elastography, allows complete automation of HIFU treatment due to the enhanced image, that elastography provides. The elastic image provides more information and less noise. To show that segmentation was possible on elastic images, nine algorithms were implemented in matlab and used on three distinct images for object detection. The three images used, have varying properties regarding object intensity and placement, as well as different noise patterns. Using PSNR, to gauge the effectiveness of each algorithm, it was shown that segmentation was possible on all images using different algorithms. The bilateral-shock-bilateral algorithm proved to be an overall effective algorithm in every situation with a PSNR of 83.87db on the phantom image. The segmentation results clearly highlight any object in the images. Future work includes fine tuning the algorithm with different phantom images and in-vivo images to distinguish between noise and desired object.

  5. Optimization of a surface wave elastography method through diffraction and guided waves effects characterization

    NASA Astrophysics Data System (ADS)

    Grinspan, G. A.; Aguiar, S.; Benech, N.

    2016-04-01

    Soft biological tissue elasticity is a parameter whose reliable measure is relevant to many applications in fields as diverse as medicine and the agrifood industry. The ultrasonic elastography methods are often unviable to be applied to provide such solutions. In this way, the surface wave elastography (SWE) appears as a viable alternative, due its low cost, easy to use, non-invasive-destructive character as well as its ability to provide in vivo estimates. Previous studies have described a good correlation between the overall behavior of ultrasonic elastography and SWE, although the latter overestimates the elasticity values compared to the first. It has been suggested that this is due to the influence of certain physical effects related to the exclusive use of low frequency waves, as well as by characteristics of the experimental setup and/or medium. In this work we confirm the influence of such effects and discuss different strategies to make independent the estimations thereof. This allows achieving a good agreement between the ultrasonic reference method and SWE. Thus, SWE becomes a reliable method to estimate soft biological tissue elasticity.

  6. Thyroid Nodules and Shear Wave Elastography: A New Tool in Thyroid Cancer Detection.

    PubMed

    Azizi, Ghobad; Keller, James M; Mayo, Michelle L; Piper, Kelé; Puett, David; Earp, Karly M; Malchoff, Carl D

    2015-11-01

    This study determines the performance of virtual touch imaging quantification (VTIQ), a non-invasive shear wave elastography method for measuring thyroid nodule (TN) stiffness, in distinguishing benign from malignant TNs. This prospective study evaluates 707 TNs in 676 patients with fine-needle aspiration biopsy (FNAB). Before FNAB, both conventional B-mode ultrasound and shear wave elastography were performed. Surgical resection was recommended for FNAB results that were not clearly benign. Surgical pathology confirmed 82 malignant TNs. The receiver operating curve identified a single cut-off of 3.54 m/s as the maximum shear wave velocity (SWV) for predicting thyroid cancer (TC). The sensitivity and specificity were 79.27% and 71.52%, respectively. Positive predictive value (PPV) was 26.75% and negative predictive value (NPV) was 96.34%. Compared with B-mode US features for predicting malignancy, SWV ≥3.54 m/s has a higher sensitivity, specificity, PPV and NPV. TN stiffness measured by VTIQ-generated shear wave elastography is an independent predictor of TC. PMID:26277203

  7. The Shear Wave Velocity on Elastography Correlates with the Clinical Symptoms and Histopathological Features of Keloids

    PubMed Central

    Yamawaki, Satoko; Yoshikawa, Katsuhiro; Katayama, Yasuhiro; Enoshiri, Tatsuki; Naitoh, Motoko; Suzuki, Shigehiko

    2015-01-01

    Background: Keloids present as red, painful lesions causing serious functional and cosmetic problems; however, there is no consensus regarding tools for objectively evaluating keloids. To demonstrate the utility of shear wave elastography in keloids, we investigated the correlations between clinical symptoms, ultrasound shear wave velocity, and histopathological findings. Methods: Three patients with keloids containing both red hypertrophic and mature areas were evaluated using the shear wave velocity and histopathological findings. Results: The results indicate that the shear wave velocity is high in active hypertrophic areas and low in mature areas. The areas with high elastography values exhibited numerous fibrillar collagenous matrices forming a whorled pattern with hyalinized tissue on hematoxylin-eosin staining corresponding with metachromasia on toluidine blue staining. In the mature area, the collagen fibers were oriented parallel to each other without metachromasia. Conclusions: Shear wave elastography provides quantitative estimates of tissue stiffness that correlate with the clinical symptoms and histopathological findings of the keloid lesions and can be used to assess the activity of keloids. PMID:26301153

  8. Nondestructive inspection for internal defects of rail based on photoacoustic elastography

    NASA Astrophysics Data System (ADS)

    Sun, Mingjian; Fu, Ying; Liu, Ting; Cheng, Xingzhen; Leng, Guanji; Feng, Naizhang

    2015-11-01

    Laser ultrasonic technique is used for the nondestructive testing technology of surface damage, but ignores the density variation in the sample. Photoacoustic elastography is adopted to obtain more rail information (such as the internal defects, the variation of sample's interior density) of the sample by collecting Rayleigh wave on rail surface and shear wave within the rail. In this paper, it is proved that the internal defects and the variation of density can be detected by photoacoustic elastography, using finite element analysis (FEA). We first use FEA to simulate the ultrasound excitation on the steel material surface excited by the laser source. Two cases of sample are modeled and analyzed, one is with defects of different depth and the other is with different density. Then, an isotropic model using ANSYS is employed and shear wave propagation is modeled. The preliminary results successfully recapitulate the trend of the change of shear wave's velocities, which shows that the defects can enhance the amplitude of shear wave. In addition, the velocities of shear wave would increase when the density of the sample enlarges. Results from computer simulations demonstrate the effectiveness of photoacoustic elastography with application to quantitative analysis for the structures of sample.

  9. Two-impulse reorientation of asymmetric spacecraft

    NASA Technical Reports Server (NTRS)

    Martz, C. W.

    1979-01-01

    An investigation conducted to determine minimum maneuver costs for attitude reorientation of spacecraft of all possible inertial distribution over a wide range of maneuver angles by use of a two impulse coning method of reorientation is reported. Maneuver cost, proportional to the product of fuel consumed (total impulse) and time expended during a maneuver is discussed. Assumptions included external impulsive control torques, rigid body spacecraft rest-to-rest maneuvers, and no disturbance torques. Results are presented in terms of average cost and standard deviation for various maneuver ranges. Costs of individual reorientations are calculated with the computer program included.

  10. [Impulse control disorders in Parkinson's disease].

    PubMed

    Joutsa, Juho; Kaasinen, Valtteri

    2013-01-01

    Of the patients having Parkinson's disease, up to third encounters some degree of impulse control problems and one out of seven suffers from true impulse control disorders such as pathological gambling, hypersexuality, compulsive shopping and binge eating. Dopaminergic drugs used in anti-Parkinson therapy, especially dopamine agonists, increase the risk of these disorders. Impulse control disorders are associated with a relatively more active dopamine-mediated neurotransmission of the mesolimbic and mesocortical system. Discontinuation of dopamine agonist medication can thus be considered as the first line treatment of these disorders. PMID:24397147

  11. Impulsively generated fast coronal pulsations

    NASA Technical Reports Server (NTRS)

    Edwin, P. M.; Roberts, B.

    1986-01-01

    Rapid oscillations in the corona are discussed from a theoretical standpoint, developing some previous work on ducted, fast magnetoacoustic waves in an inhomogeneous medium. In the theory, impulsively (e.g., flare) generated mhd (magnetohydrodynamic) waves are ducted by regions of low Alfven speed (high density) such as coronal loops. Wave propagation in such ducts is strongly dispersive and closely akin to the behavior of Love waves in seismology, Pekeris waves in oceanography and guided waves in fiber optics. Such flare-generated magnetoacoustic waves possess distinctive temporal signatures consisting of periodic, quasi-periodic and decay phases. The quasi-periodic phase possesses the strongest amplitudes and the shortest time scales. Time scales are typically of the order of a second for inhomogeneities (coronal loop width) of 1000 km and Alfven speeds of 1000/kms, and pulse duration times are of tens of seconds. Quasi-periodic signatures have been observed in radio wavelengths for over a decade and more recently by SMM. It is hoped that the theoretical ideas outlined may be successfully related to these observations and thus aid the interpretation of oscillatory signatures recorded by SMM. Such signatures may also provide a diagnostic of coronal conditions. New aspects of the ducted mhd waves, for example their behavior in smoothly varying as opposed to tube-like inhomogeneities, are currently under investigation. The theory is not restricted to loops but applied equally to open field regions.

  12. Toric focusing for radiation force applications using a toric lens coupled to a spherically focused transducer.

    PubMed

    Arnal, Bastien; Nguyen, Thu-Mai; O'Donnell, Matthew

    2014-12-01

    Dynamic elastography using radiation force requires that an ultrasound field be focused during hundreds of microseconds at a pressure of several megapascals. Here, we address the importance of the focal geometry. Although there is usually no control of the elevational focal width in generating a tissue mechanical response, we propose a tunable approach to adapt the focus geometry that can significantly improve radiation force efficiency. Several thin, in-house-made polydimethylsiloxane lenses were designed to modify the focal spot of a spherical transducer. They exhibited low absorption and the focal spot widths were extended up to 8-fold in the elevation direction. Radiation force experiments demonstrated an 8-fold increase in tissue displacements using the same pressure level in a tissue-mimicking phantom with a similar shear wave spectrum, meaning it does not affect elastography resolution. Our results demonstrate that larger tissue responses can be obtained for a given pressure level, or that similar response can be reached at a much lower mechanical index (MI). We envision that this work will impact 3-D elastography using 2-D phased arrays, where such shaping can be achieved electronically with the potential for adaptive optimization. PMID:25474778

  13. Examining impulse-variability in overarm throwing.

    PubMed

    Urbin, M A; Stodden, David; Boros, Rhonda; Shannon, David

    2012-01-01

    The purpose of this study was to examine variability in overarm throwing velocity and spatial output error at various percentages of maximum to test the prediction of an inverted-U function as predicted by impulse-variability theory and a speed-accuracy trade-off as predicted by Fitts' Law Thirty subjects (16 skilled, 14 unskilled) were instructed to throw a tennis ball at seven percentages of their maximum velocity (40-100%) in random order (9 trials per condition) at a target 30 feet away. Throwing velocity was measured with a radar gun and interpreted as an index of overall systemic power output. Within-subject throwing velocity variability was examined using within-subjects repeated-measures ANOVAs (7 repeated conditions) with built-in polynomial contrasts. Spatial error was analyzed using mixed model regression. Results indicated a quadratic fit with variability in throwing velocity increasing from 40% up to 60%, where it peaked, and then decreasing at each subsequent interval to maximum (p < .001, η2 = .555). There was no linear relationship between speed and accuracy. Overall, these data support the notion of an inverted-U function in overarm throwing velocity variability as both skilled and unskilled subjects approach maximum effort. However, these data do not support the notion of a speed-accuracy trade-off. The consistent demonstration of an inverted-U function associated with systemic power output variability indicates an enhanced capability to regulate aspects of force production and relative timing between segments as individuals approach maximum effort, even in a complex ballistic skill. PMID:22402218

  14. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  15. Electro-impulse de-icing electrodynamic solution by discrete elements

    NASA Technical Reports Server (NTRS)

    Bernhart, W. D.; Schrag, R. L.

    1988-01-01

    This paper describes a technique for analyzing the electrodynamic phenomena associated with electro-impulse deicing. The analysis is done in the time domain and utilizes a discrete element formulation concept expressed in state variable form. Calculated results include coil current, eddy currents in the target (aircraft leading edge skin), pressure distribution on the target, and total force and impulse on the target. Typical results are presented and described. Some comparisons are made between calculated and experimental results, and also between calculated values from other theoretical approaches. Application to the problem of a nonrigid target is treated briefly.

  16. Impulsive Social Influence Increases Impulsive Choices on a Temporal Discounting Task in Young Adults

    PubMed Central

    Gilman, Jodi M.; Curran, Max T.; Calderon, Vanessa; Stoeckel, Luke E.; Evins, A. Eden

    2014-01-01

    Adolescents and young adults who affiliate with friends who engage in impulsive behavior are more likely to engage in impulsive behaviors themselves, and those who associate with prosocial (i.e. more prudent, future oriented) peers are more likely to engage in prosocial behavior. However, it is difficult to disentangle the contribution of peer influence vs. peer selection (i.e., whether individuals choose friends with similar traits) when interpreting social behaviors. In this study, we combined a novel social manipulation with a well-validated delay discounting task assessing impulsive behavior to create a social influence delay discounting task, in which participants were exposed to both impulsive (smaller, sooner or SS payment) and non-impulsive (larger, later or LL payment) choices from their peers. Young adults in this sample, n = 51, aged 18–25 had a higher rate of SS choices after exposure to impulsive peer influence than after exposure to non-impulsive peer influence. Interestingly, in highly susceptible individuals, the rate of non-impulsive choices did not increase after exposure to non-impulsive influence. There was a positive correlation between self-reported suggestibility and degree of peer influence on SS choices. These results suggest that, in young adults, SS choices appear to be influenced by the choices of same-aged peers, especially for individuals who are highly susceptible to influence. PMID:24988440

  17. Multi-impulsivity of Japanese patients with eating disorders: primary and secondary impulsivity.

    PubMed

    Nagata, T; Kawarada, Y; Kiriike, N; Iketani, T

    2000-07-17

    Several studies have noted that multi-impulsive bulimia nervosa tends to be refractory to treatment. However, it is not known whether these impulsivities are an expression of more fundamental psychopathology or simply the consequence of chaotic eating behaviors. Studies of the temporal relationship between the onset of eating disorder and the occurrence of impulsive behaviors will facilitate a better understanding of these issues. Subjects consisted of 60 patients with anorexia nervosa restricting type (AN-R), 62 patients with anorexia nervosa binge-eating/purging type (AN-BP), 114 patients with bulimia nervosa purging type (BN) and 66 control subjects. Impulsive behaviors and childhood traumatic experiences were assessed by self-report questionnaire. Multi-impulsivity (defined by at least three of the following: heavy regular alcohol drinking; suicide attempt; self-mutilation; repeated shoplifting of items other than food; sexual relationships with persons not well known to the subject) was found in 2% of AN-R, 11% of AN-BP, 18% of BN and 2% of control subjects. Eighty percent of BN patients with multi-impulsivity had a history of suicide attempts or self-mutilation history prior to the onset of bulimia nervosa. In BN patients, there tended to be a relationship between childhood parental loss or borderline personality disorder and multi-impulsivity. In conclusion, primary impulsivity (chronological prior occurrence of impulsive behaviors) does exist even in a very different culture, although the number of patients of this type is very limited. PMID:10889288

  18. Numerical vorticity creation based on impulse conservation.

    PubMed Central

    Summers, D M; Chorin, A J

    1996-01-01

    The problem of creating solenoidal vortex elements to satisfy no-slip boundary conditions in Lagrangian numerical vortex methods is solved through the use of impulse elements at walls and their subsequent conversion to vortex loops. The algorithm is not uniquely defined, due to the gauge freedom in the definition of impulse; the numerically optimal choice of gauge remains to be determined. Two different choices are discussed, and an application to flow past a sphere is sketched. PMID:11607636

  19. Impulse noise generator--design and operation.

    PubMed

    Brinkmann, H

    1991-01-01

    In the seventies PFANDER (Pfander, 1975) proposed a screening test with an impulse noise simulator to check the particular responsivity of soldiers on vulnerability of the inner ear concerning the impulse noise-induced hearing loss. According to a system developed at the University of Oldenburg (Germany) (Klug & Radek, 1987), we have constructed an impulse noise generator designed for our specific requirements that will be presented. The simulator consists of an electrical ignited impulse noise spark gap which is supplied by a 3.5 kV high voltage source. At a distance of 1.10 m from the center of the impulse noise spark gap a peak pressure level of 155 dB with a C-Duration (Pfander, 1975) of .2 msec and with the main energy in the frequency range from 1 kHz to 2 kHz was good reproducible. It would be preferable to shift the impulse noise spectrum to lower frequencies but experimental effort has failed so far. PMID:1842469

  20. Enhanced awakening probability of repetitive impulse sounds.

    PubMed

    Vos, Joos; Houben, Mark M J

    2013-09-01

    In the present study relations between the level of impulse sounds and the observed proportion of behaviorally confirmed awakening reactions were determined. The sounds (shooting sounds, bangs produced by door slamming or by container transshipment, aircraft landings) were presented by means of loudspeakers in the bedrooms of 50 volunteers. The fragments for the impulse sounds consisted of single or multiple events. The sounds were presented during a 6-h period that started 75 min after the subjects wanted to sleep. In order to take account of habituation, each subject participated during 18 nights. At equal indoor A-weighted sound exposure levels, the proportion of awakening for the single impulse sounds was equal to that for the aircraft sounds. The proportion of awakening induced by the multiple impulse sounds, however, was significantly higher. For obtaining the same rate of awakening, the sound level of each of the successive impulses in a fragment had to be about 15-25 dB lower than the level of one single impulse. This level difference was largely independent of the degree of habituation. Various explanations for the enhanced awakening probability are discussed. PMID:23967934

  1. Ground vibration test results of a JetStar airplane using impulsive sine excitation

    NASA Technical Reports Server (NTRS)

    Kehoe, Michael W.; Voracek, David F.

    1989-01-01

    Structural excitation is important for both ground vibration and flight flutter testing. The structural responses caused by this excitation are analyzed to determine frequency, damping, and mode shape information. Many excitation waveforms have been used throughout the years. The use of impulsive sine (sin omega t)/omega t as an excitation waveform for ground vibration testing and the advantages of using this waveform for flight flutter testing are discussed. The ground vibration test results of a modified JetStar airplane using impulsive sine as an excitation waveform are compared with the test results of the same airplane using multiple-input random excitation. The results indicated that the structure was sufficiently excited using the impulsive sine waveform. Comparisons of input force spectrums, mode shape plots, and frequency and damping values for the two methods of excitation are presented.

  2. "Impulsive" suicide attempts: What do we really mean?

    PubMed

    May, Alexis M; Klonsky, E David

    2016-07-01

    Suicide attempts are often regarded as impulsive acts. However, there is little consensus regarding the definition or clinical characteristics of an "impulsive" attempt. To clarify this issue, we examined 3 indicators of the impulsivity of an attempt: (a) preparation, (b) time contemplating the attempt, and (c) self-report that impulsivity motivated the attempt. We examined relationships among the indicators and their relationship to trait impulsivity and characteristics of the suicide attempt. Adult participants (N = 205) with a history of suicide attempts were administered validated interviews and questionnaires. In general, the 3 attempt impulsivity indicators correlated only moderately with each other and not at all with trait impulsivity or with important characteristics of the attempt (e.g., lethality, preattempt communication, motivations). However, there were 2 exceptions. First, intent to die was inversely related to the 3 attempt impulsivity indicators (rs ranged from -.17 to .45) such that more impulsive attempts were associated with lower intent. Second, self-report that the attempt was motivated by impulsivity was related to 3 facets of trait impulsivity (rs ranged from .16 to .41). These findings suggest that individuals endorsing trait impulsivity are likely to describe their attempts as motivated by impulsivity, regardless of the presence of preparation or prolonged contemplation. Overall, study results suggest that the common conception of a unidimensional impulsive attempt may be inaccurate and that the emphasis on general impulsivity in prevention guidelines should be tempered. Implications for suicide risk assessment and prevention are discussed. (PsycINFO Database Record PMID:26653582

  3. Effects of nerve impulses on threshold of frog sciatic nerve fibres.

    PubMed Central

    Raymond, S A

    1979-01-01

    persists for at least as long as an absolute superexcitability (with threshold below the resting level) can be measured in the same fibre at rest. 7. The duration of the superexcitable phase interpreted as a relative change in excitability was roughly the same regardless of the level of depression. 8. The magnitude of the oscillation in threshold was give to ten times larger than the grey region (the range of stimuli for which response is probabilistic). It is concluded that at regions of low conduction safety such as axonal branches, where weak forces can influence whether an impulse will pass, such pronounced and long-lasting after-effects of firing can be expected to modulate conduction of nerve impulses. PMID:313985

  4. Relations between Reflection-Impulsivity and Behavioral Impulsivity in Preschool Children.

    ERIC Educational Resources Information Center

    Victor, James B.; And Others

    1985-01-01

    Reflection-impulsivity was studied in preschoolers to clarify underlying behavioral dimensions, sex differences, and contribution of activity level, mental age, and socioeconomic status. Analyses replicate a previous finding that dimension of behavioral impulsivity characterizes children with long response latency and high error scores, not…

  5. Impulsive corporal punishment by mothers and antisocial behavior and impulsiveness of children.

    PubMed

    Straus, M A; Mouradian, V E

    1998-01-01

    This study tested the hypothesis that corporal punishment (CP), such as spanking or slapping a child for purposes of correcting misbehavior, is associated with antisocial behavior (ASB) and impulsiveness by the child. The data were obtained through interviews with a probability sample of 933 mothers of children age 2-14 in two small American cities. Analyses of variance found that the more CP experienced by the child, the greater the tendency for the child to engage in ASB and to act impulsively. These relationships hold even after controlling for family socioeconomic status, the age and sex of the child, nurturance by the mother, and the level of noncorporal interventions by the mother. There were also significant interaction effects of CP with impulsiveness by the mother. When CP was carried out impulsively, it was most strongly related to child impulsiveness and ASB; when CP was done when the mother was under control, the relationship to child behavior problems was reduced but still present. In view of the fact that there is a high risk of losing control when engaged in CP, even by parents who are not usually impulsive, and the fact that impulsive CP is so strongly associated with child behavior problems, the results of this study suggest that CP is an important risk factor for children developing a pattern of impulsive and antisocial behavior which, in turn, may contribute to the level of violence and other crime in society. PMID:9768466

  6. Impulse-driven Micromechanism Capsule

    NASA Astrophysics Data System (ADS)

    Ito, Takahiro; Ishimori, Shohei; Hayashi, Teru

    We have developed a traveling small capsule, which has a smooth outer surface and is driven by inertia force and friction force. Measuring only 7 mm in diameter and 12 mm in length, it is sufficiently small to be placed in the human gullet or intestines. The capsule contains a small magnet and a coil, and an electric pulse drives the magnet to move the capsule. We performed an experimental investigation on making our capsule travel on a plastic material, which has similar elasticity characteristics to the living body. We also showed that it can travel on the surface of a pig's intestine. Our capsule may be useful for medical treatments such as inspection, drug delivery and operation.

  7. Entrainment and the cranial rhythmic impulse.

    PubMed

    McPartland, J M; Mein, E A

    1997-01-01

    Entrainment is the integration or harmonization of oscillators. All organisms pulsate with myriad electrical and mechanical rhythms. Many of these rhythms emanate from synchronized pulsating cells (eg, pacemaker cells, cortical neurons). The cranial rhythmic impulse is an oscillation recognized by many bodywork practitioners, but the functional origin of this impulse remains uncertain. We propose that the cranial rhythmic impulse is the palpable perception of entrainment, a harmonic frequency that incorporates the rhythms of multiple biological oscillators. It is derived primarily from signals between the sympathetic and parasympathetic nervous systems. Entrainment also arises between organisms. The harmonizing of coupled oscillators into a single, dominant frequency is called frequency-selective entrainment. We propose that this phenomenon is the modus operandi of practitioners who use the cranial rhythmic impulse in craniosacral treatment. Dominant entrainment is enhanced by "centering," a technique practiced by many healers, for example, practitioners of Chinese, Tibetan, and Ayurvedic medicine. We explore the connections between centering, the cranial rhythmic impulse, and craniosacral treatment. PMID:8997803

  8. Impulsivity, Frontal Lobes and Risk for Addiction

    PubMed Central

    Crews, Fulton Timm; Boettiger, Charlotte Ann

    2009-01-01

    Alcohol and substance abuse disorders involve continued use of substances despite negative consequences, i.e. loss of behavioral control of drug use. The frontal cortical areas of brain oversee behavioral control through executive functions. Executive functions include abstract thinking, motivation, planning, attention to tasks and inhibition of impulsive responses. Impulsiveness generally refers to premature, unduly risky, poorly conceived actions. Dysfunctional impulsivity includes deficits in attention, lack of reflection and/or insensitivity to consequences, all of which occur in addiction (Evenden, 1999; (de Wit, 2009). Binge drinking models indicate chronic alcohol damages corticolimbic brain regions (Crews et al., 2000) causing reversal learning deficits indicative of loss of executive function (Obernier et al., 2002b). Genetics and adolescent age are risk factors for alcoholism that coincide with sensitivity to alcohol induced neurotoxicity. Cortical degeneration from alcohol abuse may increase impulsivity contributing to the development, persistence and severity of alcohol use disorders. Interestingly, abstinence results in bursts of neurogenesis and brain regrowth (Crews and Nixon, 2009). Treatments for alcoholism, including naltrexone pharmacotherapy and psychotherapy may work through improving executive functions. This review will examine the relationships between impulsivity and executive function behaviors to changes in cortical structure during alcohol dependence and recovery. PMID:19410598

  9. An H∞ Strategy for Strain Estimation in Ultrasound Elastography Using Biomechanical Modeling Constraint

    PubMed Central

    Yuan, Jinwei; Lu, Minhua; Chen, Siping; Liu, Huafeng

    2013-01-01

    The purpose of ultrasound elastography is to identify lesions by reconstructing the hardness characteristics of tissue reconstructed from ultrasound data. Conventional quasi-static ultrasound elastography is easily applied to obtain axial strain components along the compression direction, with the results inverted to represent the distribution of tissue hardness under the assumption of constant internal stresses. However, previous works of quasi-static ultrasound elastography have found it difficult to obtain the lateral and shear strain components, due to the poor lateral resolution of conventional ultrasound probes. The physical nature of the strain field is a continuous vector field, which should be fully described by the axial, lateral, and shear strain components, and the clinical value of lateral and shear strain components of deformed tissue is gradually being recognized by both engineers and clinicians. Therefore, a biomechanical-model-constrained filtering framework is proposed here for recovering a full displacement field at a high spatial resolution from the noisy ultrasound data. In our implementation, after the biomechanical model constraint is integrated into the state-space equation, both the axial and lateral displacement components can be recovered at a high spatial resolution from the noisy displacement measurements using a robust filter, which only requires knowledge of the worst-case noise levels in the measurements. All of the strain components can then be calculated by applying a gradient operator to the recovered displacement field. Numerical experiments on synthetic data demonstrated the robustness and effectiveness of our approach, and experiments on phantom data and in-vivo clinical data also produced satisfying results. PMID:24058460

  10. 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.

  11. Thrust measurements of a complete axisymmetric scramjet in an impulse facility

    NASA Technical Reports Server (NTRS)

    Paull, A.; Stalker, R. J.; Mee, D.

    1995-01-01

    This paper describes tests which were conducted in the hypersonic impulse facility T4 on a fully integrated axisymmetric scramjet configuration. In these tests the net force on the scramjet vehicle was measured using a deconvolution force balance. This measurement technique and its application to a complex model such as the scramjet are discussed. Results are presented for the scramjet's aerodynamic drag and the net force on the scramjet when fuel is injected into the combustion chambers. It is shown that a scramjet using a hydrogen-silane fuel produces greater thrust than its aerodynamic drag at flight speeds equivalent to 260 m/s.

  12. Measurement of real-time tissue elastography in a phantom model and comparison with transient elastography in pediatric patients with liver diseases

    PubMed Central

    Schenk, Jens-Peter; Alzen, Gerhard; Klingmüller, Volker; Teufel, Ulrike; Sakka, Saroa El; Engelmann, Guido; Selmi, Buket

    2014-01-01

    PURPOSE We aimed to determine the comparability of real-time tissue elastography (RTE) and transient elastography (TE) in pediatric patients with liver diseases. MATERIALS AND METHODS 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. RESULTS 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). CONCLUSION 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. PMID:24317333

  13. Performance of 2-D ultrasound shear wave elastography in liver fibrosis detection using magnetic resonance elastography as the reference standard: A pilot study

    PubMed Central

    Song, Pengfei; Mellema, Daniel C.; Sheedy, Shannon P.; Meixner, Duane D.; Karshen, Ryan M.; Urban, Matthew W.; Manduca, Armando; Sanchez, William; Callstrom, Matthew R.; Greenleaf, James F.; Chen, Shigao

    2015-01-01

    Objective To investigate the correlation between 2-D ultrasound shear wave elastography (SWE) and magnetic resonance elastography (MRE) in liver stiffness measurement and the diagnostic performance of 2-D SWE for liver fibrosis when imaging from different intercostal spaces and using MRE as the reference standard. Methods 2-D SWE was performed on 47 patients (22 females and 25 males, age 19–77) using the GE LOGIQ E9 scanner. Each of the 47 patients had same day MRE obtained for clinical purposes. The study was HIPAA-compliant and approved by the institutional review board. Informed consent was obtained from each subject. 2-D SWE measurements were acquired from the 9th, 8th, and 7th intercostal spaces. Correlation with MRE was calculated at each intercostal space and multiple intercostal spaces combined. The performance of 2-D SWE in diagnosing liver fibrosis was evaluated with receiver operating characteristic (ROC) curve analysis using MRE as the standard. Results The highest correlation between 2-D SWE and MRE was from the 8th and 7th intercostal spaces (r = 0.68 – 0.76). The range of the areas under the ROC curve for separating normal or inflamed livers from fibrotic livers using MRE as the clinical reference were 0.84 – 0.92 when using 8th and 7th intercostal spaces individually, and 0.89 –0.9 when combined. Conclusion The results suggest that 2-D SWE and MRE are well correlated when SWE is performed at the 8th and 7th intercostal spaces. The 9th intercostal space is less reliable for diagnosing fibrosis using 2-D SWE. Combining measurements from multiple intercostal spaces does not significantly improve 2-D SWE performance for the detection of fibrosis. PMID:26782164

  14. Elastography Assessment of Liver Fibrosis: Society of Radiologists in Ultrasound Consensus Conference Statement.

    PubMed

    Barr, Richard G; Ferraioli, Giovanna; Palmeri, Mark L; Goodman, Zachary D; Garcia-Tsao, Guadalupe; Rubin, Jonathan; Garra, Brian; Myers, Robert P; Wilson, Stephanie R; Rubens, Deborah; Levine, Deborah

    2015-09-01

    The Society of Radiologists in Ultrasound convened a panel of specialists from radiology, hepatology, pathology, and basic science and physics to arrive at a consensus regarding the use of elastography in the assessment of liver fibrosis in chronic liver disease. The panel met in Denver, Colo, on October 21-22, 2014, and drafted this consensus statement. The recommendations in this statement are based on analysis of current literature and common practice strategies and are thought to represent a reasonable approach to the noninvasive assessment of diffuse liver fibrosis. PMID:26079489

  15. Evaluation of robust wave image processing methods for magnetic resonance elastography.

    PubMed

    Li, Bing Nan; Shan, Xiang; Xiang, Kui; An, Ning; Xu, Jinzhang; Huang, Weimin; Kobayashi, Etsuko

    2014-11-01

    Magnetic resonance elastography (MRE) is a promising modality for in vivo quantification and visualization of soft tissue elasticity. It involves three stages of processes for (1) external excitation, (2) wave imaging and (3) elasticity reconstruction. One of the important issues to be addressed in MRE is wave image processing and enhancement. In this study we approach it from three different ways including phase unwrapping, directional filtering and noise suppression. The relevant solutions were addressed briefly. Some of them were implemented and evaluated on both simulated and experimental MRE datasets. The results confirm that wave image enhancement is indispensable before carrying out MRE elasticity reconstruction. PMID:25222934

  16. Noninvasive assessment of alcoholic liver disease using unidimensional transient elastography (Fibroscan®)

    PubMed Central

    Lupsor-Platon, Monica; Badea, Radu

    2015-01-01

    Unidimensional transient elastography (TE) is a noninvasive technique, which has been increasingly used in the assessment of diffuse liver diseases. This paper focuses on reviewing the existing data on the use of TE in the diagnosis of fibrosis and in monitoring disease progression in alcoholic liver disease, on the factors that may influence the result of fibrosis prediction, and last but not least, on its potential use in assessing the steatosis degree. Therefore, this field is far from being exhausted and deserves more attention. Further studies are required, on large groups of biopsied patients, in order to find answers to all the remaining questions in this field. PMID:26576080

  17. Assessment of the Cervix in Pregnant Women Using Shear Wave Elastography: A Feasibility Study.

    PubMed

    Muller, Marie; Aït-Belkacem, Dora; Hessabi, Mahdieh; Gennisson, Jean-Luc; Grangé, Gilles; Goffinet, François; Lecarpentier, Edouard; Cabrol, Dominique; Tanter, Mickaël; Tsatsaris, Vassilis

    2015-11-01

    The quantitative assessment of the cervix is crucial for the estimation of pre-term delivery risk and the prediction of the success of labor induction. We conducted a cross-sectional study using shear wave elastography based on the supersonic shear imaging technique. The shear wave speed (SWS) of the lower anterior part of the cervix was quantified over an 8-mm region of interest in 157 pregnant women. Cervical SWS is slightly but significantly reduced in patients diagnosed with pre-term labor and in patients who actually delivered pre-term. PMID:26278635

  18. Ultrasound elastography in the head and neck. Part I. Basic principles and practical aspects

    PubMed Central

    Bhatia, Kunwar S.S.; Lee, Yolanda Y.P.; Yuen, Edmund H.Y.

    2013-01-01

    Abstract Ultrasound elastography (USE) is a rapidly developing field of imaging that measures and displays tissue elasticity or stiffness properties using ultrasound. In recent years, real-time USE modes have appeared on commercially available clinical ultrasound machines, stimulating an explosion of research into potential oncologic and non-oncologic clinical applications of USE. Preliminary evidence suggests that USE can differentiate benign and malignant conditions accurately in several different tissues. This article presents an overview of the basic principles of different USE technologies that are currently under investigation in the head and neck region. In addition, more practical aspects pertaining to the optimal performance of USE at this site are discussed. PMID:23876352

  19. Noninvasive assessment of alcoholic liver disease using unidimensional transient elastography (Fibroscan(®)).

    PubMed

    Lupsor-Platon, Monica; Badea, Radu

    2015-11-14

    Unidimensional transient elastography (TE) is a noninvasive technique, which has been increasingly used in the assessment of diffuse liver diseases. This paper focuses on reviewing the existing data on the use of TE in the diagnosis of fibrosis and in monitoring disease progression in alcoholic liver disease, on the factors that may influence the result of fibrosis prediction, and last but not least, on its potential use in assessing the steatosis degree. Therefore, this field is far from being exhausted and deserves more attention. Further studies are required, on large groups of biopsied patients, in order to find answers to all the remaining questions in this field. PMID:26576080

  20. Magnetomotive optical coherence elastography using magnetic particles to induce mechanical waves

    PubMed Central

    Ahmad, Adeel; Kim, Jongsik; Sobh, Nahil A.; Shemonski, Nathan D.; Boppart, Stephen A.

    2014-01-01

    Magnetic particles are versatile imaging agents that have found wide spread applicability in diagnostic, therapeutic, and rheology applications. In this study, we demonstrate that mechanical waves generated by a localized inclusion of magnetic nanoparticles can be used for assessment of the tissue viscoelastic properties using magnetomotive optical coherence elastography. We show these capabilities in tissue mimicking elastic and viscoelastic phantoms and in biological tissues by measuring the shear wave speed under magnetomotive excitation. Furthermore, we demonstrate the extraction of the complex shear modulus by measuring the shear wave speed at different frequencies and fitting to a Kelvin-Voigt model. PMID:25071969

  1. Development of a Soft Tissue Elastography Robotic Arm (STiERA).

    PubMed

    Dargar, Saurabh; Akyildiz, Ali Cagdas; De, Suvranu

    2016-01-01

    High fidelity surgical simulations must rely upon accurate soft tissue models to ensure realism of the simulations. Simulating multi-layer tissue becomes increasingly complex due to the specific mechanical properties of each individual layer. We have developed a Soft Tissue Elastography Robotic Arm (STiERA) system capable of identifying layer specific properties of multi-layer constructs while maintaining the integrity of each layer. The system was validated using tissue mimicking agar gel phantoms and showed great promise by identifying the layer specific properties with accuracy of greater than 80% when compared to known ground truth values from a commercial material testing system. PMID:27046557

  2. 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.

  3. 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.

  4. Spatial characterization of corneal biomechanical properties with optical coherence elastography after UV cross-linking.

    PubMed

    Twa, Michael D; Li, Jiasong; Vantipalli, Srilatha; Singh, Manmohan; Aglyamov, Salavat; Emelianov, Stanislav; Larin, Kirill V

    2014-05-01

    Corneal collagen cross-linking (CXL) is a clinical treatment for keratoconus that structurally reinforces degenerating ocular tissue, thereby limiting disease progression. Clinical outcomes would benefit from noninvasive methods to assess tissue material properties in affected individuals. Regional variations in tissue properties were quantified before and after CXL in rabbit eyes using optical coherence elastography (OCE) imaging. Low-amplitude (<1µm) elastic waves were generated using micro air-pulse stimulation and the resulting wave amplitude and speed were measured using phase-stabilized swept-source OCE. OCE imaging following CXL treatment demonstrates increased corneal stiffness through faster elastic wave propagation speeds and lower wave amplitudes. PMID:24877005

  5. Auto-programmable impulse neural circuits

    NASA Technical Reports Server (NTRS)

    Watula, D.; Meador, J.

    1990-01-01

    Impulse neural networks use pulse trains to communicate neuron activation levels. Impulse neural circuits emulate natural neurons at a more detailed level than that typically employed by contemporary neural network implementation methods. An impulse neural circuit which realizes short term memory dynamics is presented. The operation of that circuit is then characterized in terms of pulse frequency modulated signals. Both fixed and programmable synapse circuits for realizing long term memory are also described. The implementation of a simple and useful unsupervised learning law is then presented. The implementation of a differential Hebbian learning rule for a specific mean-frequency signal interpretation is shown to have a straightforward implementation using digital combinational logic with a variation of a previously developed programmable synapse circuit. This circuit is expected to be exploited for simple and straightforward implementation of future auto-adaptive neural circuits.

  6. [Impulse galvanization in postoperative urination disorders].

    PubMed

    Kölbl, H; Riss, P

    1988-03-01

    In this study we examined the therapeutic effect of impulse-galvanization in patients with voiding difficulties after anterior vaginal repair. Patients (n = 56/79) revealing residual urine until the sixth postoperative day were studied. Considering the onset of the first spontaneous micturition and the lack of residual urine no significant difference was found in the group undergoing impulse-galvanization (n = 19) compared to a group without therapy (n = 37). By adjuvant treatment with alpha-sympathicolytics, spasmolytics or tranquilizers patients with impulse-galvanization and the comparative group were found to be without residual urine 11.2 and 13 days after surgery, respectively (p less than 0.001). PMID:3259522

  7. Ion acceleration in impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Steinacker, Jurgen; Jaekel, Uwe; Schlickeiser, Reinhard

    1993-01-01

    Nonrelativistic spectra of protons and ions accelerated in impulsive solar flares are derived using more realistic turbulence power spectra. The calculation is based on a particle transport equation extracted from a second step acceleration model containing stochastic acceleration. The turbulence model is generalized to waves with a small angle to the magnetic field vector and to turbulence power spectra with spectral indices s smaller than 2. Due to the occurrence of impulsive flares at low coronal heights, Coulomb losses at the dense coronal plasma and diffusive particle escape are taken into account. The ion spectra show deviations from long-duration spectra near the Coulomb barrier, where the losses become maximal. The Z-squared/A-dependence of the Coulomb losses leads to spectral variations for different ions. We present a method to estimate the turbulence parameters and injection conditions of the flare particles using ion ratios like Fe/O of impulsive flares.

  8. Estimating Thruster Impulses From IMU and Doppler Data

    NASA Technical Reports Server (NTRS)

    Lisano, Michael E.; Kruizinga, Gerhard L.

    2009-01-01

    A computer program implements a thrust impulse measurement (TIM) filter, which processes data on changes in velocity and attitude of a spacecraft to estimate the small impulsive forces and torques exerted by the thrusters of the spacecraft reaction control system (RCS). The velocity-change data are obtained from line-of-sight-velocity data from Doppler measurements made from the Earth. The attitude-change data are the telemetered from an inertial measurement unit (IMU) aboard the spacecraft. The TIM filter estimates the threeaxis thrust vector for each RCS thruster, thereby enabling reduction of cumulative navigation error attributable to inaccurate prediction of thrust vectors. The filter has been augmented with a simple mathematical model to compensate for large temperature fluctuations in the spacecraft thruster catalyst bed in order to estimate thrust more accurately at deadbanding cold-firing levels. Also, rigorous consider-covariance estimation is applied in the TIM to account for the expected uncertainty in the moment of inertia and the location of the center of gravity of the spacecraft. The TIM filter was built with, and depends upon, a sigma-point consider-filter algorithm implemented in a Python-language computer program.

  9. Using Dual Process Models to Examine Impulsivity Throughout Neural Maturation.

    PubMed

    Leshem, Rotem

    2016-01-01

    The multivariate construct of impulsivity is examined through neural systems and connections that comprise the executive functioning system. It is proposed that cognitive and behavioral components of impulsivity can be divided into two distinct groups, mediated by (1) the cognitive control system: deficits in top-down cognitive control processes referred to as action/cognitive impulsivity and (2) the socioemotional system: related to bottom-up affective/motivational processes referred to as affective impulsivity. Examination of impulsivity from a developmental viewpoint can guide future research, potentially enabling the selection of more effective interventions for impulsive individuals, based on the cognitive components requiring improvement. PMID:27186976

  10. Intensity impulse response of SDM links.

    PubMed

    Mecozzi, Antonio; Antonelli, Cristian; Shtaif, Mark

    2015-03-01

    We study the response of space-division multiplexed fiber links to an excitation by a short impulse of the optical intensity. We show that, in the presence of full mixing, the intensity impulse response is Gaussian, confirming recently reported experimental observations, and relate its variance to the mean square of the mode dispersion vector of the link τ(->). The good agreement between our theory and the previously published experiments provides solid foundations to the random coupling model of SDM fiber links, and provides a tool for efficient design of MIMO-DSP receivers. PMID:25836803

  11. Lewis rats have greater response impulsivity than Fischer rats.

    PubMed

    Hamilton, Kristen R; Potenza, Marc N; Grunberg, Neil E

    2014-11-01

    Impulsivity, a tendency toward immediate action without consideration of future consequences, is associated with a wide array of problematic behaviors. Response impulsivity, a type of behaviorally-assessed impulsivity characterized by behavioral disinhibition, is also associated with health risk behaviors. Response impulsivity is distinct from choice impulsivity, which is characterized by intolerance for delay. Lewis rats have higher levels of choice impulsivity than Fischer rats (Anderson & Woolverton, 2005; Madden et al., 2008; Stein et al., 2012). However, no studies have examined whether Lewis and Fischer rats have different levels of response impulsivity. The present research examined response impulsivity in the two rat strains. Subjects were 16 male Lewis and Fischer rats. Rats' response impulsivity was measured using the Five Choice Serial Reaction Time Task (5-CSRTT). In addition, their locomotor activity was measured in locomotor activity chambers. Lewis rats had more premature responses than Fischer rats during the 5-CSRTT assessment [F(1, 14)=5.34, p<0.05], indicating higher levels of response impulsivity. Locomotor activity did not differ between rat strain groups [F(1, 14)=3.05, p=.10], suggesting that overall movement did not account for group differences in response impulsivity on the 5-CSRTT. It can be concluded from this research that Lewis rats have higher levels of response impulsivity than Fischer rats, and therefore provide a valid rat model of individual differences in impulsivity. PMID:24613059

  12. Recent Translational Findings on Impulsivity in Relation to Drug Abuse

    PubMed Central

    Weafer, Jessica; Mitchell, Suzanne H.

    2015-01-01

    Impulsive behavior is strongly implicated in drug abuse, as both a cause and a consequence of drug use. To understand how impulsive behaviors lead to and result from drug use, translational evidence from both human and non-human animal studies is needed. Here, we review recent (2009 or later) studies that have investigated two major components of impulsive behavior, inhibitory control and impulsive choice, across preclinical and clinical studies. We concentrate on the stop-signal task as the measure of inhibitory control and delay discounting as the measure of impulsive choice. Consistent with previous reports, recent studies show greater impulsive behavior in drug users compared with non-users. Additionally, new evidence supports the prospective role of impulsive behavior in drug abuse, and has begun to identify the neurobiological mechanisms underlying impulsive behavior. We focus on the commonalities and differences in findings between preclinical and clinical studies, and suggest future directions for translational research. PMID:25678985

  13. The use of 2D ultrasound elastography for measuring tendon motion and strain.

    PubMed

    Chernak Slane, Laura; Thelen, Darryl G

    2014-02-01

    The goal of the current study was to investigate the fidelity of a 2D ultrasound elastography method for the measurement of tendon motion and strain. Ultrasound phantoms and ex vivo porcine flexor tendons were cyclically stretched to 4% strain while cine ultrasound radiofrequency (RF) data and video data were simultaneously collected. 2D ultrasound elastography was used to estimate tissue motion and strain from RF data, and surface tissue motion and strain were separately estimated using digital image correlation (DIC). There were strong correlations (R(2)>0.97) between DIC and RF measurements of phantom displacement and strain, and good agreement in estimates of peak phantom strain (DIC: 3.5±0.2%; RF: 3.7±0.1%). For tendon, elastographic estimates of displacement profiles also correlated well with DIC measurements (R(2)>0.92), and exhibited similar estimated peak tendon strain (DIC: 2.6±1.4%; RF: 2.2±1.3%). Elastographic tracking with B-Mode images tended to under-predict peak strain for both the phantom and tendon. This study demonstrates the capacity to use quantitative elastographic techniques to measure tendon displacement and strain within an ultrasound image window. The approach may be extendible to in vivo use on humans, which would allow for the non-invasive analysis of tendon deformation in both normal and pathological states. PMID:24388164

  14. Monitoring Cartilage Tissue Engineering Using Magnetic Resonance Spectroscopy, Imaging, and Elastography

    PubMed Central

    Klatt, Dieter; Magin, Richard L.

    2013-01-01

    A key technical challenge in cartilage tissue engineering is the development of a noninvasive method for monitoring the composition, structure, and function of the tissue at different growth stages. Due to its noninvasive, three-dimensional imaging capabilities and the breadth of available contrast mechanisms, magnetic resonance imaging (MRI) techniques can be expected to play a leading role in assessing engineered cartilage. In this review, we describe the new MR-based tools (spectroscopy, imaging, and elastography) that can provide quantitative biomarkers for cartilage tissue development both in vitro and in vivo. Magnetic resonance spectroscopy can identify the changing molecular structure and alternations in the conformation of major macromolecules (collagen and proteoglycans) using parameters such as chemical shift, relaxation rates, and magnetic spin couplings. MRI provides high-resolution images whose contrast reflects developing tissue microstructure and porosity through changes in local relaxation times and the apparent diffusion coefficient. Magnetic resonance elastography uses low-frequency mechanical vibrations in conjunction with MRI to measure soft tissue mechanical properties (shear modulus and viscosity). When combined, these three techniques provide a noninvasive, multiscale window for characterizing cartilage tissue growth at all stages of tissue development, from the initial cell seeding of scaffolds to the development of the extracellular matrix during construct incubation, and finally, to the postimplantation assessment of tissue integration in animals and patients. PMID:23574498

  15. Patient-specific Deformation Modelling via Elastography: Application to Image-guided Prostate Interventions.

    PubMed

    Wang, Yi; Ni, Dong; Qin, Jing; Xu, Ming; Xie, Xiaoyan; Heng, Pheng-Ann

    2016-01-01

    Image-guided prostate interventions often require the registration of preoperative magnetic resonance (MR) images to real-time transrectal ultrasound (TRUS) images to provide high-quality guidance. One of the main challenges for registering MR images to TRUS images is how to estimate the TRUS-probe-induced prostate deformation that occurs during TRUS imaging. The combined statistical and biomechanical modeling approach shows promise for the adequate estimation of prostate deformation. However, the right setting of the biomechanical parameters is very crucial for realistic deformation modeling. We propose a patient-specific deformation model equipped with personalized biomechanical parameters obtained from shear wave elastography to reliably predict the prostate deformation during image-guided interventions. Using data acquired from a prostate phantom and twelve patients with suspected prostate cancer, we compared the prostate deformation model with and without patient-specific biomechanical parameters in terms of deformation estimation accuracy. The results show that the patient-specific deformation model possesses favorable model ability, and outperforms the model without patient-specific biomechanical parameters. The employment of the patient-specific biomechanical parameters obtained from elastography for deformation modeling shows promise for providing more precise deformation estimation in applications that use computer-assisted image-guided intervention systems. PMID:27272239

  16. Effect of Calcifications on Breast Ultrasound Shear Wave Elastography: An Investigational Study

    PubMed Central

    Gregory, Adriana; Mehrmohammadi, Mohammad; Denis, Max; Bayat, Mahdi; Stan, Daniela L.; Fatemi, Mostafa; Alizad, Azra

    2015-01-01

    Purpose To investigate the effects of macrocalcifications and clustered microcalcifications associated with benign breast masses on shear wave elastography (SWE). Methods SuperSonic Imagine (SSI) and comb-push ultrasound shear elastography (CUSE) were performed on three sets of phantoms to investigate how calcifications of different sizes and distributions influence measured elasticity. To demonstrate the effect in vivo, three female patients with benign breast masses associated with mammographically-identified calcifications were evaluated by CUSE. Results Apparent maximum elasticity (Emax) estimates resulting from individual macrocalcifications (with diameters of 2mm, 3mm, 5mm, 6mm, 9mm, 11mm, and 15mm) showed values over 50 kPa for all cases, which represents more than 100% increase over background (~21kPa). We considered a 2cm-diameter circular region of interest for all phantom experiments. Mean elasticity (Emean) values varied from 26 kPa to 73 kPa, depending on the macrocalcification size. Highly dense clusters of microcalcifications showed higher Emax values than clusters of microcalcification with low concentrations, but the difference in Emean values was not significant. Conclusions Our results demonstrate that the presence of large isolated macrocalcifications and highly concentrated clusters of microcalcifications can introduce areas with apparent high elasticity in SWE. Considering that benign breast masses normally have significantly lower elasticity values than malignant tumors, such areas with high elasticity appearing due to presence of calcification in benign breast masses may lead to misdiagnosis. PMID:26368939

  17. VISUALIZING THE STRESS DISTRIBUTION WITHIN VASCULAR TISSUES USING INTRAVASCULAR ULTRASOUND ELASTOGRAPHY: A PRELIMINARY INVESTIGATION

    PubMed Central

    Richards, Michael S.; Perucchio, Renato; Doyley, Marvin M.

    2015-01-01

    A methodology for computing the stress distribution of vascular tissue using finite element-based, intravascular ultrasound (IVUS) reconstruction elastography is described. This information could help cardiologists detect life-threatening atherosclerotic plaques and predict their propensity to rupture. The calculation of vessel stresses requires the measurement of strain from the ultrasound images, a calibrating pressure measurement and additional model assumptions. In this work, we conducted simulation studies to investigate the effect of varying the model assumptions, specifically Poisson’s ratio and the outer boundary conditions, on the resulting stress fields. In both simulation and phantom studies, we created vessel geometries with two fibrous cap thicknesses to determine if we could detect a difference in peak stress (spatially) between the two. The results revealed that (i) Poisson’s ratios had negligible impact on the accuracy of stress elastograms, (ii) the outer boundary condition assumption had the greatest effect on the resulting modulus and stress distributions and (iii) in simulation and in phantom experiments, our stress imaging technique was able to detect an increased peak stress for the vessel geometry with the smaller cap thickness. This work is a first step toward understanding and creating a robust stress measurement technique for evaluating atherosclerotic plaques using IVUS elastography. PMID:25837424

  18. Assessment of Diffuse Thyroid Disease by Strain Ratio in Ultrasound Elastography.

    PubMed

    Yang, Zhi; Zhang, Haixian; Wang, Kun; Cui, Guanghe; Fu, Fengkui

    2015-11-01

    The goal of this study was to explore the value of strain ratio from real-time elastography in the semi-quantitative assessment of diffuse thyroid disease. Fifty-one patients with primary hyperthyroidism, 70 with Hashimoto's thyroiditis, 8 with subacute thyroiditis and 43 with normal healthy thyroids were recruited to measure the strain ratio (SR) of thyroid tissue and sternocleidomastoid muscle (on the same side of the thyroid). SR values of all groups were subjected to statistical analysis. The SRs (mean ± standard deviation) of patients with hyperthyroidism, Hashimoto's thyroiditis and subacute thyroiditis were 2.30 ± 1.08, 7.04 ± 7.74 and 24.09 ± 13.56, respectively. The SR of the control group was 1.76 ± 0.54. SR values ranked in ascending order were control group < hyperthyroidism group < Hashimoto's thyroiditis group < subacute thyroiditis group. There were statistically significant (p < 0.05) differences in thyroid hardness between groups with different diffuse thyroid diseases. SR values of the hyperthyroidism and control groups did not statistically differ (p > 0.05). It is feasible to assess diffuse thyroid disease with strain ratios obtained with ultrasound elastography. PMID:26306430

  19. Continuous Shear Wave Elastography: a New Method to Measure in-vivo Viscoelastic Properties of Tendons

    PubMed Central

    Cortes, Daniel H.; Suydam, Stephen M.; Silbernagel, Karin Grävare; Buchanan, Thomas S.; Elliott, Dawn M.

    2015-01-01

    Viscoelastic mechanical properties are frequently altered after tendon injuries and during recovery. Therefore, non-invasive measurements of shear viscoelastic properties may help evaluate tendon recovery and compare the effectiveness of different therapies. The objectives of this study are to present an elastography method to measure localized viscoelastic properties of tendon and to present initial results in healthy and injured human Achilles and semitendinosus tendons. The technique used an external actuator to generate the shear waves in the tendon at different frequencies and plane wave imaging to measure shear wave displacements. For each of the excitation frequencies, maps of direction specific wave speeds were calculated using Local Frequency Estimation. Maps of viscoelastic properties were obtained using a pixel wise curve-fit of wave speed and frequency. The method was validated by comparing measurements of wave speed in agarose gels to those obtained using magnetic resonance elastography. Measurements in human healthy Achilles tendons revealed a pronounced increase in wave speed as function of frequency that highlights the importance of tendon viscoelasticity. Additionally, the viscoelastic properties of the Achilles tendon were larger than those reported for other tissues. Measurements in a tendinopathic Achilles tendon showed that it is feasible to quantify local viscoeasltic properties. Similarly, measurement in the semitendinosus tendon showed a substantial differences in viscoelastic properties between the healthy and contralateral tendons. Consequently, this technique has the potential of evaluating localized changes in tendon viscoelastic properties due to injury and during recovery in a clinical setting. PMID:25796414

  20. 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.

  1. High-Resolution Mechanical Imaging of Glioblastoma by Multifrequency Magnetic Resonance Elastography

    PubMed Central

    Freimann, Florian Baptist; Bayerl, Simon; Guo, Jing; Arlt, Felix; Wuerfel, Jens; Braun, Jürgen; Hoffmann, Karl-Titus; Sack, Ingolf

    2014-01-01

    Objective To generate high-resolution maps of the viscoelastic properties of human brain parenchyma for presurgical quantitative assessment in glioblastoma (GB). Methods Twenty-two GB patients underwent routine presurgical work-up supplemented by additional multifrequency magnetic resonance elastography. Two three-dimensional viscoelastic parameter maps, magnitude |G*|, and phase angle φ of the complex shear modulus were reconstructed by inversion of full wave field data in 2-mm isotropic resolution at seven harmonic drive frequencies ranging from 30 to 60 Hz. Results Mechanical brain maps confirmed that GB are composed of stiff and soft compartments, resulting in high intratumor heterogeneity. GB could be easily differentiated from healthy reference tissue by their reduced viscous behavior quantified by φ (0.37±0.08 vs. 0.58±0.07). |G*|, which in solids more relates to the material's stiffness, was significantly reduced in GB with a mean value of 1.32±0.26 kPa compared to 1.54±0.27 kPa in healthy tissue (P = 0.001). However, some GB (5 of 22) showed increased stiffness. Conclusion GB are generally less viscous and softer than healthy brain parenchyma. Unrelated to the morphology-based contrast of standard magnetic resonance imaging, elastography provides an entirely new neuroradiological marker and contrast related to the biomechanical properties of tumors. PMID:25338072

  2. 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

  3. Virtual Touch Tissue Imaging Quantification Shear Wave Elastography: Prospective Assessment of Cervical Lymph Nodes.

    PubMed

    Cheng, Kai Lun; Choi, Young Jun; Shim, Woo Hyun; Lee, Jeong Hyun; Baek, Jung Hwan

    2016-02-01

    The goal of this study was to prospectively evaluate the diagnostic performance of Virtual Touch tissue imaging quantification (VTIQ) shear wave elastography in the discrimination of benign and malignant cervical lymph nodes in routine clinical practice. Shear wave velocity was analyzed using VTIQ in 100 patients with 100 histologically proven cervical lymph nodes. Diagnostic performance was evaluated using receiver operating characteristic curve analysis and leave-one-out cross-validation. Agreement between measurements was assessed with intra-class correlation coefficients. The mean shear wave velocity was significantly higher in metastatic lymphadenopathy (4.46 ± 1.46 m/s) than in benign lymphadenopathy (2.71 ± 0.85 m/s) (p < 0.001) at a cutoff level of 3.34 m/s. The cross-validated accuracy, sensitivity and specificity were 77%, 78.9% and 74.4%, respectively. Agreement of measurements with VTIQ was excellent (intra-class correlation coefficient = 0.961). VTIQ shear wave elastography may be a feasible quantitative imaging method for differentiating benign and malignant cervical lymph nodes. PMID:26553206

  4. Patient-specific Deformation Modelling via Elastography: Application to Image-guided Prostate Interventions

    PubMed Central

    Wang, Yi; Ni, Dong; Qin, Jing; Xu, Ming; Xie, Xiaoyan; Heng, Pheng-Ann

    2016-01-01

    Image-guided prostate interventions often require the registration of preoperative magnetic resonance (MR) images to real-time transrectal ultrasound (TRUS) images to provide high-quality guidance. One of the main challenges for registering MR images to TRUS images is how to estimate the TRUS-probe-induced prostate deformation that occurs during TRUS imaging. The combined statistical and biomechanical modeling approach shows promise for the adequate estimation of prostate deformation. However, the right setting of the biomechanical parameters is very crucial for realistic deformation modeling. We propose a patient-specific deformation model equipped with personalized biomechanical parameters obtained from shear wave elastography to reliably predict the prostate deformation during image-guided interventions. Using data acquired from a prostate phantom and twelve patients with suspected prostate cancer, we compared the prostate deformation model with and without patient-specific biomechanical parameters in terms of deformation estimation accuracy. The results show that the patient-specific deformation model possesses favorable model ability, and outperforms the model without patient-specific biomechanical parameters. The employment of the patient-specific biomechanical parameters obtained from elastography for deformation modeling shows promise for providing more precise deformation estimation in applications that use computer-assisted image-guided intervention systems. PMID:27272239

  5. 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.

  6. Revealing anisotropic properties of cornea at different intraocular pressures using optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Li, Jiasong; Singh, Manmohan; Han, Zhaolong; Wu, Chen; Nair, Achuth; Aglyamov, Salavat R.; Twa, Michael D.; Larin, Kirill V.

    2016-03-01

    In this study we have evaluated the elastic anisotropy of porcine corneas with increasing intraocular pressures (IOPs) using a noncontact optical coherence elastography (OCE) technique. A focused air-pulse induced low amplitude (<=10 μm) elastic waves in fresh porcine corneas (n=9) in situ in the whole eye-globe configuration. A phase-stabilized swept source optical coherence elastography (PhS-SSOCE) system imaged the propagation of the elastic wave in different stepped radial directions. A closed-loop feedback system was utilized to artificially manipulate the IOP, and OCE measurements were repeated while the IOP was increased in 5 mmHg increments from 15 to 30 mmHg. The OCE measurements demonstrated that the elastic anisotropy of the cornea became more pronounced at higher IOPs, and that there were distinct radial angles of higher and lower stiffness. The presented noncontact OCE method was capable of detecting and assessing the corneal elastic anisotropy as a function of IOP. Due to the noninvasive nature and small amplitude of the elastic wave, this method may be able to provide additional information about corneal health and integrity in vivo.

  7. Noncontact depth-resolved micro-scale optical coherence elastography of the cornea

    PubMed Central

    Wang, Shang; Larin, Kirill V.

    2014-01-01

    High-resolution elastographic assessment of the cornea can greatly assist clinical diagnosis and treatment of various ocular diseases. Here, we report on the first noncontact depth-resolved micro-scale optical coherence elastography of the cornea achieved using shear wave imaging optical coherence tomography (SWI-OCT) combined with the spectral analysis of the corneal Lamb wave propagation. This imaging method relies on a focused air-puff device to load the cornea with highly-localized low-pressure short-duration air stream and applies phase-resolved OCT detection to capture the low-amplitude deformation with nano-scale sensitivity. The SWI-OCT system is used here to image the corneal Lamb wave propagation with the frame rate the same as the OCT A-line acquisition speed. Based on the spectral analysis of the corneal temporal deformation profiles, the phase velocity of the Lamb wave is obtained at different depths for the major frequency components, which shows the depthwise distribution of the corneal stiffness related to its structural features. Our pilot experiments on ex vivo rabbit eyes demonstrate the feasibility of this method in depth-resolved micro-scale elastography of the cornea. The assessment of the Lamb wave dispersion is also presented, suggesting the potential for the quantitative measurement of corneal viscoelasticity. PMID:25426312

  8. Modeling transversely isotropic, viscoelastic, incompressible tissue-like materials with application in ultrasound shear wave elastography

    NASA Astrophysics Data System (ADS)

    Qiang, Bo; Brigham, John C.; Aristizabal, Sara; Greenleaf, James F.; Zhang, Xiaoming; Urban, Matthew W.

    2015-02-01

    In this paper, we propose a method to model the shear wave propagation in transversely isotropic, viscoelastic and incompressible media. The targeted application is ultrasound-based shear wave elastography for viscoelasticity measurements in anisotropic tissues such as the kidney and skeletal muscles. The proposed model predicts that if the viscoelastic parameters both across and along fiber directions can be characterized as a Voigt material, then the spatial phase velocity at any angle is also governed by a Voigt material model. Further, with the aid of Taylor expansions, it is shown that the spatial group velocity at any angle is close to a Voigt type for weakly attenuative materials within a certain bandwidth. The model is implemented in a finite element code by a time domain explicit integration scheme and shear wave simulations are conducted. The results of the simulations are analyzed to extract the shear wave elasticity and viscosity for both the spatial phase and group velocities. The estimated values match well with theoretical predictions. The proposed theory is further verified by an ex vivo tissue experiment measured in a porcine skeletal muscle by an ultrasound shear wave elastography method. The applicability of the Taylor expansion to analyze the spatial velocities is also discussed. We demonstrate that the approximations from the Taylor expansions are subject to errors when the viscosities across or along the fiber directions are large or the maximum frequency considered is beyond the bandwidth defined by radii of convergence of the Taylor expansions.

  9. Isovolumetric elasticity alteration in the human heart detected by in vivo time-harmonic elastography.

    PubMed

    Tzschätzsch, Heiko; Hättasch, Robert; Knebel, Fabian; Klaua, Robert; Schultz, Michael; Jenderka, Klaus-Vitold; Braun, Jürgen; Sack, Ingolf

    2013-12-01

    Time harmonic elastography (THE) has recently been introduced for measurement of the periodic alteration in myocardial shear modulus based on externally induced low-frequency acoustic vibrations produced by a loudspeaker. In this study, we propose further developments of cardiac THE toward a clinical modality including integration of the vibration source into the patient bed and automated parameter extraction from harmonic shear wave amplitudes, wall motion profiles and synchronized electrocardiographic records. This method has enabled us to evaluate the delay between wall motion and wave amplitude alteration for the measurement of isovolumetric times of elasticity alteration during contraction (τ(C)) and relaxation (τ(R)) in a group of 32 healthy volunteers. On average, the wave amplitudes changed between systole and diastole by a factor of 1.7 ± 0.3, with a τ(C) of 137 ± 61 ms and a τ(R) of 68 ± 73 ms, which agrees with results obtained with the more time-consuming and expensive cardiac magnetic resonance elastography. Furthermore, because of the high sampling rate, elasto-morphometric parameters such as transition times and the area of wave amplitude-cardiac motion cycles can be processed in an automated way for the future clinical detection of myocardial relaxation abnormalities. PMID:24035628

  10. Corneal elastic anisotropy and hysteresis as a function of IOP assessed by optical coherence elastography

    NASA Astrophysics Data System (ADS)

    Li, Jiasong; Singh, Manmohan; Han, Zhaolong; Wu, Chen; Raghunathan, Raksha; Liu, Chih-Hao; Nair, Achuth; Noorani, Shezaan; Aglyamov, Salavat R.; Twa, Michael D.; Larin, Kirill V.

    2016-03-01

    The mechanical anisotropic properties of the cornea can be an important indicator for determining the onset and severity of different diseases and can be used to assess the efficacy of various therapeutic interventions, such as cross-linking and LASIK surgery. In this work, we introduce a noncontact method of assessing corneal mechanical anisotropy as a function of intraocular pressure (IOP) using optical coherence elastography (OCE). A focused air-pulse induced low amplitude (<10 μm) elastic waves in fresh porcine corneas in the whole eye-globe configuration in situ. A phase-stabilized swept source optical coherence elastography (PhS-SSOCE) system imaged the elastic wave propagation at stepped radial angles, and the OCE measurements were repeated as the IOP was cycled. The elastic wave velocity was then quantified to determine the mechanical anisotropy and hysteresis of the cornea. The results show that the elastic anisotropy at the corneal of the apex of the cornea becomes more pronounced at higher IOPs, and that there are distinct radial angles of higher and lower stiffness. Due to the noncontact nature and small amplitude of the elastic wave, this method may be useful for characterizing the elastic anisotropy of ocular and other tissues in vivo completely noninvasively.

  11. Shear wave pulse compression for dynamic elastography using phase-sensitive optical coherence tomography

    PubMed Central

    Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Huang, Zhihong; Wang, Ruikang K.; O’Donnell, Matthew

    2014-01-01

    Abstract. 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. PMID:24441876

  12. The Use of 2D Ultrasound Elastography for Measuring Tendon Motion and Strain

    PubMed Central

    Slane, Laura Chernak; Thelen, Darryl G.

    2014-01-01

    The goal of the current study was to investigate the fidelity of a 2D ultrasound elastography method for the measurement of tendon motion and strain. Ultrasound phantoms and ex vivo porcine flexor tendons were cyclically stretched to 4% strain while cine ultrasound radiofrequency (RF) data and video data were simultaneously collected. 2D ultrasound elastography was used to estimate tissue motion and strain from RF data, and surface tissue motion and strain were separately estimated using digital image correlation (DIC). There were strong correlations (R2 > 0.97) between DIC and RF measurements of phantom displacement and strain, and good agreement in estimates of peak phantom strain (DIC: 3.5 ± 0.2%; RF: 3.7 ± 0.1%). For tendon, elastographic estimates of displacement profiles also correlated well with DIC measurements (R2 > 0.92), and exhibited similar estimated peak tendon strain (DIC: 2.6 ± 1.4%; RF: 2.2 ± 1.3%). Elastographic tracking with B-Mode images tended to under-predict peak strain for both the phantom and tendon. This study demonstrates the capacity to use quantitative elastographic techniques to measure tendon displacement and strain within an ultrasound image window. The approach may be extendible to in vivo use on humans, which would allow for the non-invasive analysis of tendon deformation in both normal and pathological states. PMID:24388164

  13. Visualizing the stress distribution within vascular tissues using intravascular ultrasound elastography: a preliminary investigation.

    PubMed

    Richards, Michael S; Perucchio, Renato; Doyley, Marvin M

    2015-06-01

    A methodology for computing the stress distribution of vascular tissue using finite element-based, intravascular ultrasound (IVUS) reconstruction elastography is described. This information could help cardiologists detect life-threatening atherosclerotic plaques and predict their propensity to rupture. The calculation of vessel stresses requires the measurement of strain from the ultrasound images, a calibrating pressure measurement and additional model assumptions. In this work, we conducted simulation studies to investigate the effect of varying the model assumptions, specifically Poisson's ratio and the outer boundary conditions, on the resulting stress fields. In both simulation and phantom studies, we created vessel geometries with two fibrous cap thicknesses to determine if we could detect a difference in peak stress (spatially) between the two. The results revealed that (i) Poisson's ratios had negligible impact on the accuracy of stress elastograms, (ii) the outer boundary condition assumption had the greatest effect on the resulting modulus and stress distributions and (iii) in simulation and in phantom experiments, our stress imaging technique was able to detect an increased peak stress for the vessel geometry with the smaller cap thickness. This work is a first step toward understanding and creating a robust stress measurement technique for evaluating atherosclerotic plaques using IVUS elastography. PMID:25837424

  14. 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.

  15. Tabletop magnetic resonance elastography for the measurement of viscoelastic parameters of small tissue samples

    NASA Astrophysics Data System (ADS)

    Ipek-Ugay, Selcan; Drießle, Toni; Ledwig, Michael; Guo, Jing; Hirsch, Sebastian; Sack, Ingolf; Braun, Jürgen

    2015-02-01

    We demonstrate the feasibility of low-cost tabletop MR elastography (MRE) for quantifying the complex shear modulus G∗ of small soft biological tissue samples as provided by pathologists. The MRE system was developed based on a tabletop MRI scanner equipped with a 0.5 T permanent magnet and a tissue sample holder mounted to a loudspeaker. A spin echo sequence was enhanced with motion-encoding gradients of 250 mT/m amplitude synchronized to acoustic vibration frequencies. Shear wave images suitable for elastography were acquired between vibration frequencies of 0.5 and 1 kHz in agarose, ultrasound gel, porcine liver, porcine skeletal muscle, and bovine heart with a spatial resolution of 234 μm pixel edge length. The measured frequency dependence of G∗ agreed well with previous work based on high-field MR systems. The ratio between loss and storage moduli was highest in liver and ultrasound gel, followed by muscle tissue and agarose gel while ultrasound gel and liver showed similarly low storage moduli compared to the other samples. The shear wave to noise ratio is an important imaging criteria for MRE and was about 4.2 times lower for the preliminary setup of the 0.5 T tabletop system compared to a 7 T animal scanner. In the future, the new tabletop MRE system may serve as a low cost device for preclinical research on the correlation of viscoelastic parameters with histopathology of biological samples.

  16. Tabletop magnetic resonance elastography for the measurement of viscoelastic parameters of small tissue samples.

    PubMed

    Ipek-Ugay, Selcan; Drießle, Toni; Ledwig, Michael; Guo, Jing; Hirsch, Sebastian; Sack, Ingolf; Braun, Jürgen

    2015-02-01

    We demonstrate the feasibility of low-cost tabletop MR elastography (MRE) for quantifying the complex shear modulus G(∗) of small soft biological tissue samples as provided by pathologists. The MRE system was developed based on a tabletop MRI scanner equipped with a 0.5 T permanent magnet and a tissue sample holder mounted to a loudspeaker. A spin echo sequence was enhanced with motion-encoding gradients of 250 mT/m amplitude synchronized to acoustic vibration frequencies. Shear wave images suitable for elastography were acquired between vibration frequencies of 0.5 and 1 kHz in agarose, ultrasound gel, porcine liver, porcine skeletal muscle, and bovine heart with a spatial resolution of 234 μm pixel edge length. The measured frequency dependence of G(∗) agreed well with previous work based on high-field MR systems. The ratio between loss and storage moduli was highest in liver and ultrasound gel, followed by muscle tissue and agarose gel while ultrasound gel and liver showed similarly low storage moduli compared to the other samples. The shear wave to noise ratio is an important imaging criteria for MRE and was about 4.2 times lower for the preliminary setup of the 0.5 T tabletop system compared to a 7 T animal scanner. In the future, the new tabletop MRE system may serve as a low cost device for preclinical research on the correlation of viscoelastic parameters with histopathology of biological samples. PMID:25554945

  17. Quantitative methods for reconstructing tissue biomechanical properties in optical coherence elastography: a comparison study

    PubMed Central

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Wu, Chen; Liu, Chih-hao; Wang, Shang; Idugboe, Rita; Raghunathan, Raksha; Sudheendran, Narendran; Aglyamov, Salavat R.; Twa, Michael D.; Larin, Kirill V.

    2015-01-01

    We present a systematic analysis of the accuracy of five different methods for extracting the biomechanical properties of soft samples using optical coherence elastography (OCE). OCE is an emerging noninvasive technique, which allows assessing biomechanical properties of tissues with a micrometer spatial resolution. However, in order to accurately extract biomechanical properties from OCE measurements, application of proper mechanical model is required. In this study, we utilize tissue-mimicking phantoms with controlled elastic properties and investigate the feasibilities of four available methods for reconstructing elasticity (Young’s modulus) based on OCE measurements of an air-pulse induced elastic wave. The approaches are based on the shear wave equation (SWE), the surface wave equation (SuWE), Rayleigh-Lamb frequency equation (RLFE), and finite element method (FEM), Elasticity values were compared with uniaxial mechanical testing. The results show that the RLFE and the FEM are more robust in quantitatively assessing elasticity than the other simplified models. This study provides a foundation and reference for reconstructing the biomechanical properties of tissues from OCE data, which is important for the further development of noninvasive elastography methods. PMID:25860076

  18. Noncontact phase-sensitive dynamic optical coherence elastography at megahertz rate

    NASA Astrophysics Data System (ADS)

    Singh, Manmohan; Wu, Chen; Liu, Chih-Hao; Li, Jiasong; Schill, Alexander; Nair, Achuth; Kistenev, Yury V.; Larin, Kirill V.

    2016-03-01

    Dynamic optical coherence elastography (OCE) techniques have shown great promise at quantitatively obtaining the biomechanical properties of tissue. However, the majority of these techniques have required multiple temporal OCT acquisitions (M-B mode) and corresponding excitations, which lead to clinically unfeasible acquisition times and potential tissue damage. Furthermore, the large data sets and extended laser exposures hinder their translation to the clinic, where patient discomfort and safety are critical criteria. In this work we demonstrate noncontact true kilohertz frame-rate dynamic optical coherence elastography by directly imaging a focused air-pulse induced elastic wave with a home-built phase-sensitive OCE system based on a 4X buffered Fourier Domain Mode Locked swept source laser with an A-scan rate of ~1.5 MHz. The elastic wave was imaged at a frame rate of ~7.3 kHz using only a single excitation. In contrast to previous techniques, successive B-scans were acquired over the measurement region (B-M mode) in this work. The feasibility of this method was validated by quantifying the elasticity of tissue-mimicking agar phantoms as well as porcine corneas ex vivo at different intraocular pressures. The results demonstrate that this method can acquire a depth-resolved elastogram in milliseconds. The reduced data set enabled a rapid elasticity assessment, and the ultra-fast acquisition speed allowed for a clinically safe laser exposure to the cornea.

  19. Modeling Transversely Isotropic, Viscoelastic, Incompressible Tissue-like Materials with Application in Ultrasound Shear Wave Elastography

    PubMed Central

    Qiang, Bo; Brigham, John C.; Aristizabal, Sara; Greenleaf, James F.; Zhang, Xiaoming; Urban, Matthew W.

    2015-01-01

    In this paper, we propose a method to model the shear wave propagation in transversely isotropic, viscoelastic and incompressible media. The targeted application is ultrasound-based shear wave elastography for viscoelasticity measurements in anisotropic tissues such as the kidney and skeletal muscles. The proposed model predicts that if the viscoelastic parameters both across and along fiber directions can be characterized as a Voigt material, then the spatial phase velocity at any angle is also governed by a Voigt material model. Further, with the aid of Taylor expansions, it is shown that the spatial group velocity at any angle is close to a Voigt type for weakly attenuative materials within a certain bandwidth. The model is implemented in a finite element code by a time domain explicit integration scheme and shear wave simulations are conducted. The results of the simulations are analyzed to extract the shear wave elasticity and viscosity for both the spatial phase and group velocities. The estimated values match well with theoretical predictions. The proposed theory is further verified by an ex vivo tissue experiment measured in a porcine skeletal muscle by an ultrasound shear wave elastography method. The applicability of the Taylor expansion to analyze the spatial velocities is also discussed. We demonstrate that the approximations from the Taylor expansions are subject to errors when the viscosities across or along the fiber directions are large or the maximum frequency considered is beyond the bandwidth defined by radii of convergence of the Taylor expansions. PMID:25591921

  20. Arbitration between controlled and impulsive choices

    PubMed Central

    Economides, M.; Guitart-Masip, M.; Kurth-Nelson, Z.; Dolan, R.J.

    2015-01-01

    The impulse to act for immediate reward often conflicts with more deliberate evaluations that support long-term benefit. The neural architecture that negotiates this conflict remains unclear. One account proposes a single neural circuit that evaluates both immediate and delayed outcomes, while another outlines separate impulsive and patient systems that compete for behavioral control. Here we designed a task in which a complex payout structure divorces the immediate value of acting from the overall long-term value, within the same outcome modality. Using model-based fMRI in humans, we demonstrate separate neural representations of immediate and long-term values, with the former tracked in the anterior caudate (AC) and the latter in the ventromedial prefrontal cortex (vmPFC). Crucially, when subjects' choices were compatible with long-run consequences, value signals in AC were down-weighted and those in vmPFC were enhanced, while the opposite occurred when choice was impulsive. Thus, our data implicate a trade-off in value representation between AC and vmPFC as underlying controlled versus impulsive choice. PMID:25573670

  1. How Many Impulsivities? A Discounting Perspective

    ERIC Educational Resources Information Center

    Green, Leonard; Myerson, Joel

    2013-01-01

    People discount the value of delayed and uncertain outcomes, and how steeply individuals discount is thought to reflect how impulsive they are. From this perspective, steep discounting of delayed outcomes (which fails to maximize long-term welfare) and shallow discounting of probabilistic outcomes (which fails to adequately take risk into account)…

  2. GABRA2 Genotype, Impulsivity, and Body Mass

    PubMed Central

    Bauer, Lance O.; Yang, Bao-Zhu; Houston, Rebecca J.; Kranzler, Henry R.; Gelernter, Joel

    2013-01-01

    Background The goal of this study was to test a hypothesis associating impulsivity with an elevated body mass index (BMI). Methods To this end, we examined associations of BMI with putative genetic, neurophysiological, psychiatric, and psychological indicators of impulsivity in 78 women and 74 men formerly dependent on alcohol or drugs. A second analysis was designed to test the replicability of the genetic findings in an independent sample of 109 women and 111 men with a similar history of substance dependence. Results The results of the first analysis showed that BMI was positively correlated with Total and Nonplanning Scale Scores on the Barratt Impulsiveness Scale and the number of childhood symptoms of Attention-Deficit/Hyperactivity Disorder in women. It was also positively correlated, in women, with a GABRA2 variant previously implicated as a risk factor for substance dependence and an objective electroencephalographic feature previously associated with GABRA2 and relapse risk. The second analysis confirmed that the correlation between BMI and the substance-dependence-associated GABRA2 genotype was reliable and sex-specific. Conclusions We conclude that an elevated BMI is associated with genetic, neurophysiological, psychiatric, and psychological indicators of impulsivity. The sex difference may be explained by greater opportunities to eat and overeat, a preference for higher calorie foods, a longer duration of alcohol/drug abstinence, or previous pregnancies in women. PMID:22882390

  3. High-intensity drying processes: Impulse drying

    SciTech Connect

    Orloff, D.I.

    1990-09-01

    Impulse drying is an innovative process for drying paper that holds great promise for reducing the energy consumed during the manufacture of paper and similar web products. Impulse drying occurs when a wet paper web passes through a press nip in which one of the rolls is heated to a high temperature. A steam layer adjacent to the heated surface grows and displaces water from the sheet in a very efficient manner. The energy required for water removal is very much less than that required for conventional evaporative drying. Hence, it has been projected that wide commercialization of impulse drying would result in at least a 10% industry-wide energy saving. This report covers work completed between October, 1988 and September, 1989. During this period, pilot press trails demonstrated that newsprint as well as linerboard experience delamination. Hence, the major focus of the research was the resolution of the delamination problem. In order to document potential process improvements, measurement methods were developed to quantify sheet delamination. Using these methods, low thermal diffusivity ceramic roll surfaces were shown to extend the range of impulse drying operating conditions while avoiding sheet delamination. As compared to steel surfaces, ceramics were found to provide significantly higher water volume without inducing sheet delamination. 46 figs., 4 tabs.

  4. Impulse noise trauma during army weapon firing.

    PubMed

    Munjal, K R; Singh, V P

    1997-04-01

    A 100 infanty personnel firing modern weapons such as the Anti Tank Guided Missile, 106mm Recoiless Gun (RCL), 84mm Rocket Launcher (RL) and 81mm Mortar were studied for the effect of impulse noise on the ear and the evolution of the Temporary Threshold Shift (TTS), Recovery Time (RT) and Permanent Threshold Shift (PTS) was traced. PMID:23119288

  5. Signal processing in impulsive electromagnetic interference

    NASA Astrophysics Data System (ADS)

    Zabin, Serena M.

    1993-06-01

    Statistical signal processing functions such as signal detection, estimation, and identification play a key role in the development of effective communications, radar, and sonar systems. For example, advanced statistical methods are emerging as being particularly important in digital communications systems operating in channels corrupted by interference from such phenomena as multiple-access noise, intentional jamming, and impulsive noise sources. Conventional demodulation methods, such as coherent matched filtering, often suffer serious performance degradation when subject to interference of these types; however, this degradation can frequently be eliminated through the use of more sophisticated signal processing techniques. During this reporting period, the focus of our work has been on the problem of obtaining optimum and efficient identification and detection procedures for impulsive channels. Of particular interest is the Middleton Class A noise model, which is a widely-accepted statistical-physical model for impulsive interference superimposed on a Gaussian background. The model has two basic parameters that can be adjusted to fit a wide variety of impulsive noise phenomena occurring in practice.

  6. Impulse Plasma In Surface Engineering - a review

    NASA Astrophysics Data System (ADS)

    Zdunek, K.; Nowakowska-Langier, K.; Chodun, R.; Okrasa, S.; Rabinski, M.; Dora, J.; Domanowski, P.; Halarowicz, J.

    2014-11-01

    The article describes the view of the plasma surface engineering, assuming the role of non-thermal energy effects in the synthesis of materials and coatings deposition. In the following study it was underlined that the vapor excitation through the application of an electric field during coatings deposition gives new possibilities for coatings formation. As an example the IPD method was chosen. During the IPD (Impulse Plasma Deposition) the impulse plasma is generated in the coaxial accelerator by strong periodic electrical pulses. The impulse plasma is distributed in the form of energetic plasma pockets. Due to the almost completely ionization of gas, the nucleation of new phases takes place on ions directly in the plasma itself. As a result the coatings of metastable materials with nano-amorphous structure and excellent adhesion to the non-heated intentionally substrates could be deposited. Recently the novel way of impulse plasma generation during the coatings deposition was proposed and developed by our group. An efficient tool for plasma process control, the plasma forming gas injection to the interelectrode space was used. Periodic changing the gas pressure results in increasing both the degree of dispersion and the dynamics of the plasma pulses. The advantage of the new technique in deposition of coatings with exceptionally good properties has been demonstrated in the industrial scale not only in the case of the IPD method but also in the case of very well known magnetron sputtering method.

  7. Impulse Control Disorders - The Continuum Hypothesis.

    PubMed

    Stenberg, Georg

    2016-01-01

    The group Parkinson Inside Out is composed of health professionals and academic researchers who have been diagnosed with Parkinson's Disease. In our discussions we try to make use of both our inside perspective as patients, and our outside perspective as professionals. In this paper, we apply the two perspectives to the Impulse Control Disorders. These impulsive behaviour patterns are thought to be relatively uncommon side effects of some of the medication used in dopamine replacement therapy. The phenomenon is usually described as relatively rare (<15%), and mainly confined to patients with special vulnerabilities. In contrast, we propose that having some problems with controlling impulses is a very common experience for patients undergoing dopamine replacement therapy. They result from difficulties in decision making engendered by variations in dopamine accessibility in the reward centre of the brain. Only in a minority do the consequences grow to the damaging proportions of a disorder, but most patients are probably affected to some degree. Seeing, and measuring, decision difficulties as a continuous dimension, rather than as a discrete category, brings increased possibilities for early detection and continuous monitoring. With reliable measures of the propensity for impulsive decision making, it may become possible to both reap the benefits and avoid the dangers of the dopamine agonists. We point to ways of empirically testing our continuity hypothesis. PMID:27031861

  8. Fluctuations of a spherical gravitational impulsive wave.

    NASA Astrophysics Data System (ADS)

    Hortaçsu, M.

    1993-02-01

    It is shown that quantum fluctuations, in particular vacuum polarization, vanish in the background of a spherical impulsive wave solution of the Einstein field equations, recently found by Nutku and Penrose. The calculation is done in first-order perturbation theory but arguments are given why it should persist to all orders.

  9. Ultrahigh Specific Impulse Nuclear Thermal Propulsion

    SciTech Connect

    Anne Charmeau; Brandon Cunningham; Samim Anghaie

    2009-02-09

    Research on nuclear thermal propulsion systems (NTP) have been in forefront of the space nuclear power and propulsion due to their design simplicity and their promise for providing very high thrust at reasonably high specific impulse. During NERVA-ROVER program in late 1950's till early 1970's, the United States developed and ground tested about 18 NTP systems without ever deploying them into space. The NERVA-ROVER program included development and testing of NTP systems with very high thrust (~250,000 lbf) and relatively high specific impulse (~850 s). High thrust to weight ratio in NTP systems is an indicator of high acceleration that could be achieved with these systems. The specific impulse in the lowest mass propellant, hydrogen, is a function of square root of absolute temperature in the NTP thrust chamber. Therefor optimizing design performance of NTP systems would require achieving the highest possible hydrogen temperature at reasonably high thrust to weight ratio. High hydrogen exit temperature produces high specific impulse that is a diret measure of propellant usage efficiency.

  10. The Relationship among Spontaneity, Impulsivity, and Creativity

    ERIC Educational Resources Information Center

    Kipper, David A.; Green, Doreen J.; Prorak, Amanda

    2010-01-01

    The present study was designed to investigate two characteristics of spontaneity, its relationship to creativity and to impulsivity. We hypothesized a positive relationship between spontaneity and creativity, consistent with Moreno, 1953 "canon of spontaneity-creativity." We also predicted a negative relationship between spontaneity and…

  11. Designing a Stochastic Adaptive Impulsive Observer for Stochastic Linear and Nonlinear Impulsive Systems

    SciTech Connect

    Ayati, Moosa; Alwan, Mohamad; Liu Xinzhi; Khaloozadeh, Hamid

    2011-11-30

    State observation (estimation) is a very important issue in system analysis and control. This paper develops a new observer called Stochastic Adaptive Impulsive Observer (SAIO) for the state estimation of impulsive systems. The proposed observer is applicable to linear and nonlinear stochastic impulsive systems. In addition, the effect of parametric uncertainty is considered and unknown parameters of the system are estimated by suitable adaptation laws. Impulsive system theory, particularly stochastic Lyapunov-like function, is used to analyze the stability and convergence of the state estimations. The main advantages of the proposed observer are: 1) it gives continuous estimation from discrete time measurements of the system output, and 2) it is useful for state estimation when continuous measurements are impossible or expensive. Simulation results show the effectiveness of the proposed observer and we believe that it has many applications in control and estimation theories.

  12. The flare kernel in the impulsive phase

    NASA Technical Reports Server (NTRS)

    Dejager, C.

    1986-01-01

    The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.

  13. Entropic forces in Brownian motion

    NASA Astrophysics Data System (ADS)

    Roos, Nico

    2014-12-01

    Interest in the concept of entropic forces has risen considerably since Verlinde proposed in 2011 to interpret the force in Newton's second law and gravity as entropic forces. Brownian motion—the motion of a small particle (pollen) driven by random impulses from the surrounding molecules—may be the first example of a stochastic process in which such forces are expected to emerge. In this article, it is shown that at least two types of entropic force can be identified in three-dimensional Brownian motion. This analysis yields simple derivations of known results of Brownian motion, Hooke's law, and—applying an external (non-radial) force—Curie's law and the Langevin-Debye equation.

  14. Dissemination of Weak Waves in Granular Materials Under Short-Term Impulse Loads

    NASA Astrophysics Data System (ADS)

    Bobriakov, A. P.; Kosykh, V. P.; Revuzhenko, A. F.; Kazantsev, A. A.; Ivushkina, N. V.

    2016-04-01

    The results of experiments with dry high-silica sand are presented. Multiple point impacts have been revealed to improve waveguide properties of the material because a conductive channel, containing force “chains”, is formed there. Quasistatic alternating shears condition the change in the particle packing; destroy “chains”, and deteriorate the channel conductivity. Further multiple impulse loads lead to restoration of the “chains” and conductivity of the channel.

  15. Exploring the relationship between worry and impulsivity in military recruits: the role of mindfulness and self-compassion as potential mediators.

    PubMed

    Mantzios, Michail

    2014-12-01

    When military recruits cannot tolerate the stressful environment in the military, they typically become more impulsive. Impulsivity serves to avoid the stress, or, in other words, to release the pressure and cope. Becoming more impulsive, however, is related to damaging behaviours and unsuccessful coping. This research explored the relationship between worry and impulsivity in armed forces, and the possibility of mindfulness and self-compassion mediating this relationship. Participants (n = 166), who were in the second week of their basic military training, completed questionnaires in mindfulness, self-compassion, worry and impulsivity. Results indicated that worry related positively to impulsivity. Further, the negative relationship of worry with mindfulness and self-compassion mediated the relationship between worry and impulsivity. Findings support the notion that lacking mindfulness and self-compassion, in excessive worriers, may lead to impulsivity. This research concluded that mindfulness and self-compassion may assist military personnel who are exposed to highly stressful environments. Alternative explanations and future directions are discussed. PMID:25476964

  16. Measuring Impulsivity in Adolescents with Serious Substance and Conduct Problems

    ERIC Educational Resources Information Center

    Thompson, Laetitia L.; Whitmore, Elizabeth A.; Raymond, Kristen M.; Crowley, Thomas J.

    2006-01-01

    Adolescents with substance use and conduct disorders have high rates of aggression and attention deficit hyperactivity disorder (ADHD), all of which have been characterized in part by impulsivity. Developing measures that capture impulsivity behaviorally and correlate with self-reported impulsivity has been difficult. One promising behavioral…

  17. Sample controllability of impulsive differential systems with random coefficients

    NASA Astrophysics Data System (ADS)

    Zhang, Shuorui; Sun, Jitao

    2016-07-01

    In this paper, we investigate the controllability of impulsive differential systems with random coefficients. Impulsive differential systems with random coefficients are a different stochastic model from stochastic differential equations. Sufficient conditions of sample controllability for impulsive differential systems with random coefficients are obtained by using random Sadovskii's fixed-point theorem. Finally, an example is given to illustrate our results.

  18. Teaching Emotional Intelligence to Impulsive-Aggressive Youth.

    ERIC Educational Resources Information Center

    Henley, Martin; Long, Nicholas J.

    1999-01-01

    Describes complex issues involved in helping impulsive-aggressive youth who are devoid of emotional intelligence. Reviews anatomy of impulsivity and the irrational beliefs used as defense mechanisms by impulsive-aggressive students. Discusses two alternative intervention strategies, Life Space Crisis Intervention techniques and the Self Control…

  19. Stability analysis of impulsive functional systems of fractional order

    NASA Astrophysics Data System (ADS)

    Stamova, Ivanka; Stamov, Gani

    2014-03-01

    In this paper, a class of impulsive fractional functional differential systems is investigated. Sufficient conditions for stability of the zero solution are proved, extending the corresponding theory of impulsive functional differential equations. The investigations are carried out by using the comparison principle, coupled with the Lyapunov function method. We apply our results to an impulsive single species model of Lotka-Volterra type.

  20. 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.

  1. A versatile and experimentally validated finite element model to assess the accuracy of shear wave elastography in a bounded viscoelastic medium.

    PubMed

    Caenen, Annette; Shcherbakova, Darya; Verhegghe, Benedict; Papadacci, Clément; Pernot, Mathieu; Segers, Patrick; Swillens, Abigaïl

    2015-03-01

    The feasibility of shear wave elastography (SWE) in arteries for cardiovascular risk assessment remains to be investigated as the artery's thin wall and intricate material properties induce complex shear wave (SW) propagation phenomena. To better understand the SW physics in bounded media, we proposed an in vitro validated finite element model capable of simulating SW propagation, with full flexibility at the level of the tissue's geometry, material properties, and acoustic radiation force. This computer model was presented in a relatively basic set-up, a homogeneous slab of gelatin-agar material (4.35 mm thick), allowing validation of the numerical settings according to actual SWE measurements. The resulting tissue velocity waveforms and SW propagation speed matched well with the measurement: 4.46 m/s (simulation) versus 4.63 ± 0.07 m/s (experiment). Further, we identified the impact of geometrical and material parameters on the SW propagation characteristics. As expected, phantom thickness was a determining factor of dispersion. Adding viscoelasticity to the model augmented the estimated wave speed to 4.58 m/s, an even better match with the experimental determined value. This study demonstrated that finite element modeling can be a powerful tool to gain insight into SWE mechanics and will in future work be advanced to more clinically relevant settings. PMID:25768813

  2. 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

  3. Is impulsivity a common trait in bipolar and unipolar disorders?

    PubMed Central

    Henna, Elaine; Hatch, John P; Nicoletti, Mark; Swann, Alan C; Zunta-Soares, Giovana; Soares, Jair C

    2012-01-01

    Objectives Impulsivity is increased in bipolar and unipolar disorders during episodes and is associated with substance abuse disorders and suicide risk. Impulsivity between episodes predisposes to relapses and poor therapeutic compliance. However, there is little information about impulsivity during euthymia in mood disorders. We sought to investigate trait impulsivity in euthymic bipolar and unipolar disorder patients, comparing them to healthy individuals and unaffected relatives of bipolar disorder patients. Methods Impulsivity was evaluated by the Barratt Impulsiveness Scale (BIS-11A) in 54 bipolar disorder patients, 25 unipolar disorder patients, 136 healthy volunteers, and 14 unaffected relatives. The BIS-11A mean scores for all four groups were compared through the Games–Howell test for all possible pairwise combinations. Additionally, we compared impulsivity in bipolar and unipolar disorder patients with and without history of suicide attempt and substance abuse disorder. Results Bipolar and unipolar disorder patients scored significantly higher than the healthy controls and unaffected relatives on all measures of the BIS-11A except for attentional impulsivity. On the attentional impulsivity measures there were no differences among the unaffected relatives and the bipolar and unipolar disorder groups, but all three of these groups scored higher than the healthy participant group. There was no difference in impulsivity between bipolar and unipolar disorder subjects with and without suicide attempt. However, impulsivity was higher among bipolar and unipolar disorder subjects with past substance use disorder compared to patients without such a history. Conclusions Questionnaire-measured impulsivity appears to be relatively independent of mood state in bipolar and unipolar disorder patients; it remains elevated in euthymia and is higher in individuals with past substance abuse. Elevated attentional and lower non-planning impulsivity in unaffected relatives of

  4. The Stomach-Derived Hormone Ghrelin Increases Impulsive Behavior.

    PubMed

    Anderberg, Rozita H; Hansson, Caroline; Fenander, Maya; Richard, Jennifer E; Dickson, Suzanne L; Nissbrandt, Hans; Bergquist, Filip; Skibicka, Karolina P

    2016-04-01

    Impulsivity, defined as impaired decision making, is associated with many psychiatric and behavioral disorders, such as attention-deficit/hyperactivity disorder as well as eating disorders. Recent data indicate that there is a strong positive correlation between food reward behavior and impulsivity, but the mechanisms behind this relationship remain unknown. Here we hypothesize that ghrelin, an orexigenic hormone produced by the stomach and known to increase food reward behavior, also increases impulsivity. In order to assess the impact of ghrelin on impulsivity, rats were trained in three complementary tests of impulsive behavior and choice: differential reinforcement of low rate (DRL), go/no-go, and delay discounting. Ghrelin injection into the lateral ventricle increased impulsive behavior, as indicated by reduced efficiency of performance in the DRL test, and increased lever pressing during the no-go periods of the go/no-go test. Central ghrelin stimulation also increased impulsive choice, as evidenced by the reduced choice for large rewards when delivered with a delay in the delay discounting test. In order to determine whether signaling at the central ghrelin receptors is necessary for maintenance of normal levels of impulsive behavior, DRL performance was assessed following ghrelin receptor blockade with central infusion of a ghrelin receptor antagonist. Central ghrelin receptor blockade reduced impulsive behavior, as reflected by increased efficiency of performance in the DRL task. To further investigate the neurobiological substrate underlying the impulsivity effect of ghrelin, we microinjected ghrelin into the ventral tegmental area, an area harboring dopaminergic cell bodies. Ghrelin receptor stimulation within the VTA was sufficient to increase impulsive behavior. We further evaluated the impact of ghrelin on dopamine-related gene expression and dopamine turnover in brain areas key in impulsive behavior control. This study provides the first

  5. Correlations between the disintegration of melt and the measured impulses in steam explosions

    SciTech Connect

    Froehlich, G.; Linca, A.; Schindler, M.

    1995-09-01

    To find our correlations in steam explosions (melt water interactions) between the measured impulses and the disintegration of the melt, experiments were performed in three configurations i.e. stratified, entrapment and jet experiments. Linear correlations were detected between the impulse and the total surface of the fragments. Theoretical considerations point out that a linear correlation assumes superheating of a water layer around the fragments of a constant thickness during the fragmentation process to a constant temperature (here the homogeneous nucleation temperature of water was assumed) and a constant expansion velocity of the steam in the main expansion time. The correlation constant does not depend on melt temperature and trigger pressure, but it depends on the configuration of the experiment or of a scenario of an accident. Further research is required concerning the correlation constant. For analysing steam explosion accidents the explosivity is introduced. The explosivity is a mass specific impulse. The explosivity is linear correlated with the degree of fragmentation. Knowing the degree of fragmentation with proper correlation constant the explosivity can be calculated and from the explosivity combined with the total mass of fragments the impulse is obtained which can be used to an estimation of the maximum force.

  6. Ejection of ferrofluid grains from a ferrofluid using nonlinear acoustic impulses

    NASA Astrophysics Data System (ADS)

    Manciu, Felicia S.; Manciu, Marian; Sen, Surajit

    2000-03-01

    We consider a model study of a dilute ferrofluid in a container with a flat base and an open top surface with monodisperse ferrofluid grains that form a stable colloid in water or oil. The grains are assumed to be under the influence of a strong, uniform, external magnetic field. It is well known that due to the influence of the field, such a system forms chains of ferrofluid grains between the base and the surface of the liquid. The phase-separated system is then subjected to non-linear acoustic impulses at its base. We show that for impulses of any magnitude, it is possible to generate non-dispersive bundles of energy through the chains. By carrying out detailed dynamical simulations of impulse propagation in the chains, we show that for appropriate impulse magnitudes, the ferrofluid grains in each of the chains, which are in the vicinity of the surface, will overcome the force due to surface tension and eject into air. Ferrofluid grains carry a coating of the host liquid, which can be colored for water-based ferrofluids and hence the system may potentially be used to design a nozzle-free inkjet printer. For ferrofluid grains of typical diameter of about 100 Angstroms, the proposed system could lead one to develop inkjet printers with dot sizes that are less than 200 Angstroms and hence to a printing system of unparalleled resolution. [1] S. Sen, M. Manciu and F.S. Manciu, Appl. Phys. Lett. 75, 1479 (1999).

  7. New Combined Parameter of Liver and Splenic Stiffness as Determined by Elastography in Healthy Volunteers

    PubMed Central

    Kassym, Laura; Nounou, Mohammed A.; Zhumadilova, Zauresh; Dajani, Asad I.; Barkibayeva, Nurgul; Myssayev, Ayan; Rakhypbekov, Tolebay; Abuhammour, Adnan M.

    2016-01-01

    Background: The diagnosis of chronic liver disease (CLD) leading to fibrosis, cirrhosis, and portal hypertension had witnessed dramatic changes after the introduction of noninvasive figure accessible tools over the past few years. Imaging techniques that are based on evaluation of the liver stiffness was particularly useful in this respect. Acoustic radiation force impulse (ARFI) emerged as an interesting figure tool with reliable repute and high precision. Aims: To evaluate liver stiffness measurement (LSM) and splenic stiffness measurement (SSM) in healthy volunteers as concluded by the ARFI technique and to out a numeric calculated ratio that may reflect their correlation in the otherwise healthy liver. Patients and Methods: A ratio (splenic stiffness/liver stiffness in kPa) was determined in 207 consenting healthy subjects and was investigated with respect to age, gender, ethnic origin, body mass index (BMI), liver and spleen sizes healthy volunteers, alanine aminotransferase (ALT), aspartate aminotransferase (AST), platelet count (PLT), APRI, and FIB-4 scores. Results: Data from this work led to computing an index of 4.72 (3.42–7.33) in healthy persons on an average. Females had a higher index than males 6.37 vs 4.92, P=0.002. There was not any significant difference of the ratio in different age groups; ethnic origins; any correlation between SSM/LSM ratio and BMI; liver and spleen sizes; or ALT, AST, PLT, APRI, and FIB-4 scores. Conclusions: A quantifiable numeric relationship between splenic and liver stiffness in the healthy subjects could be computed to a parameter expressed as SSM/LSM ratio. We believe that this ratio can be a useful reference tool for further researches in CLD. PMID:27488328

  8. Narcissism predicts impulsive buying: phenotypic and genetic evidence.

    PubMed

    Cai, Huajian; Shi, Yuanyuan; Fang, Xiang; Luo, Yu L L

    2015-01-01

    Impulsive buying makes billions of dollars for retail businesses every year, particularly in an era of thriving e-commerce. Narcissism, characterized by impulsivity and materialism, may serve as a potential antecedent to impulsive buying. To test this hypothesis, two studies examined the relationship between narcissism and impulsive buying. In Study 1, we surveyed an online sample and found that while adaptive narcissism was not correlated with impulsive buying, maladaptive narcissism was significantly predictive of the impulsive buying tendency. By investigating 304 twin pairs, Study 2 showed that global narcissism and its two components, adaptive and maladaptive narcissism, as well as the impulsive buying tendency were heritable. The study found, moreover, that the connections between global narcissism and impulsive buying, and between maladaptive narcissism and impulsive buying were genetically based. These findings not only establish a link between narcissism and impulsive buying but also help to identify the origins of the link. The present studies deepen our understanding of narcissism, impulsive buying, and their interrelationship. PMID:26217251

  9. Narcissism predicts impulsive buying: phenotypic and genetic evidence

    PubMed Central

    Cai, Huajian; Shi, Yuanyuan; Fang, Xiang; Luo, Yu L. L.

    2015-01-01

    Impulsive buying makes billions of dollars for retail businesses every year, particularly in an era of thriving e-commerce. Narcissism, characterized by impulsivity and materialism, may serve as a potential antecedent to impulsive buying. To test this hypothesis, two studies examined the relationship between narcissism and impulsive buying. In Study 1, we surveyed an online sample and found that while adaptive narcissism was not correlated with impulsive buying, maladaptive narcissism was significantly predictive of the impulsive buying tendency. By investigating 304 twin pairs, Study 2 showed that global narcissism and its two components, adaptive and maladaptive narcissism, as well as the impulsive buying tendency were heritable. The study found, moreover, that the connections between global narcissism and impulsive buying, and between maladaptive narcissism and impulsive buying were genetically based. These findings not only establish a link between narcissism and impulsive buying but also help to identify the origins of the link. The present studies deepen our understanding of narcissism, impulsive buying, and their interrelationship. PMID:26217251

  10. Barratt Impulsivity and Neural Regulation of Physiological Arousal

    PubMed Central

    Zhang, Sheng; Hu, Sien; Hu, Jianping; Wu, Po-Lun; Chao, Herta H.; Li, Chiang-shan R.

    2015-01-01

    Background Theories of personality have posited an increased arousal response to external stimulation in impulsive individuals. However, there is a dearth of studies addressing the neural basis of this association. Methods We recorded skin conductance in 26 individuals who were assessed with Barratt Impulsivity Scale (BIS-11) and performed a stop signal task during functional magnetic resonance imaging. Imaging data were processed and modeled with Statistical Parametric Mapping. We used linear regressions to examine correlations between impulsivity and skin conductance response (SCR) to salient events, identify the neural substrates of arousal regulation, and examine the relationship between the regulatory mechanism and impulsivity. Results Across subjects, higher impulsivity is associated with greater SCR to stop trials. Activity of the ventromedial prefrontal cortex (vmPFC) negatively correlated to and Granger caused skin conductance time course. Furthermore, higher impulsivity is associated with a lesser strength of Granger causality of vmPFC activity on skin conductance, consistent with diminished control of physiological arousal to external stimulation. When men (n = 14) and women (n = 12) were examined separately, however, there was evidence suggesting association between impulsivity and vmPFC regulation of arousal only in women. Conclusions Together, these findings confirmed the link between Barratt impulsivity and heightened arousal to salient stimuli in both genders and suggested the neural bases of altered regulation of arousal in impulsive women. More research is needed to explore the neural processes of arousal regulation in impulsive individuals and in clinical conditions that implicate poor impulse control. PMID:26079873

  11. Impulsive Choice Predicts Poor Working Memory in Male Rats

    PubMed Central

    Renda, C. Renee; Stein, Jeffrey S.; Madden, Gregory J.

    2014-01-01

    A number of maladaptive behaviors and poor health outcomes (e.g., substance abuse, obesity) correlate with impulsive choice, which describes the tendency to prefer smaller, immediate rewards in lieu of larger, delayed rewards. Working memory deficits are often reported in those diagnosed with the same maladaptive behaviors. Human studies suggest that impulsive choice is associated with working memory ability but, to date, only one study has explored the association between working memory and impulsive choice in rats and no relation was reported. The current study reevaluated the association between working memory and impulsive choice in 19 male Long-Evans rats. Psychophysical adjusting procedures were used to quantify working memory (titrating-delay match-to-position procedure) and impulsive choice (adjusting delay procedure). Rats were partitioned into low- and high-impulsive groups based on performance in the impulsive choice task. Low-impulsive rats performed significantly better in the working memory assessment. Across all rats, impulsive choice was negatively correlated with working memory performance. These findings support the hypothesis that prefrontal cortex function, specifically, working memory, is related to impulsive choice. Future research might profitably examine the experimental variables designed to influence working memory to evaluate the effects of these variables on impulsive choice and maladaptive behaviors with which it is correlated. PMID:24732895

  12. Relative rates of growth of annoyance of impulsive and non-impulsive noises.

    PubMed

    Fidell, Sanford; Silvati, Laura; Pearsons, Karl

    2002-01-01

    Twenty-nine people judged the relative annoyance of five variable level signals and 29 impulsive and non-impulsive fixed-level signals in an adaptive paired comparison study. Signals were presented for judgment as heard indoors in a facility capable of accurately reproducing the very low-frequency content of sonic booms. When the annoyance of sonic booms unaccompanied by rattle was compared with that of sounds containing more higher-frequency energy (an aircraft flyover and an octave band of noise centered at 1 kHz), the relative rate of growth of annoyance, as expressed in C-weighted SEL units, was nearly 2:1. In other words, to maintain subjective equality of annoyance, each increase in level of sonic booms had to be matched by nearly twice the increase in level of an aircraft flyover or an octave band of noise centered at 1 kHz. Relative rates of growth of annoyance of sonic booms accompanied by rattle and of non-impulsive sounds, including both low- (63-Hz octave band of noise) and high-frequency energy (1-kHz octave band of noise and an aircraft flyover), were closer to 1:1. Relative rates of growth of annoyance for sonic booms unaccompanied by rattle and low-frequency sounds (63 Hz) were also about 1:1. These differences in relative rates of growth of annoyance of impulsive and non-impulsive sounds are as plausibly attributed to their relative low-frequency content as to impulsiveness per se. It may therefore be more useful for some purposes to express the annoyance of impulsive signals and other environmental noises containing substantial low-frequency energy in terms of effective (duration-corrected) loudness level rather than commonplace ASEL or CSEL. PMID:11837963

  13. Multidimensional Examination of Impulsivity in Relation to Disordered Gambling

    PubMed Central

    MacKillop, James; Miller, Joshua D.; Fortune, Erica; Maples, Jessica; Lance, Charles E.; Campbell, W. Keith; Goodie, Adam S.

    2014-01-01

    Impulsivity has been consistently associated with pathological gambling (PG), but the diversity of definitions and measures of impulsivity has led to ambiguity with regard to which indices are independently relevant. Toward clarifying this relationship, the current study examined indices from an array of commonly-used impulsivity measures in relation to PG severity in an adult community sample of frequent gamblers (N = 353). These included both survey assessments and behavioral tasks. Using a factor analytic approach, four latent factors were identified among 19 indices and were designated reward sensitivity, punishment sensitivity, delay discounting, and cognitive impulsivity. All four latent variables were positively and independently related to PG severity, albeit at a trend level for cognitive impulsivity in a combined model. These findings reveal four generally independent domains of impulsivity that are related to PG severity, clarify which assessment measures aggregate in each domain, and illustrate the importance of measurement specificity in studying impulsivity in relation to PG and other psychiatric disorders. PMID:24708148

  14. Subjective field study of response to impulsive helicopter noise

    NASA Technical Reports Server (NTRS)

    Powell, C. A.

    1981-01-01

    Subjects, located outdoors and indoors, judged the noisiness and other subjective noise characteristics of flyovers of two helicopters and a propeller driven airplane as part of a study of the effects of impulsiveness on the subjective response to helicopter noise. In the first experiment, the impulsive characteristics of one helicopter was controlled by varying the main rotor speed while maintaining a constant airspeed in level flight. The second experiment which utilized only the helicopters, included descent and level flight operations. The more impulsive helicopter was consistently judged less noisy than the less impulsive helicopter at equal effective perceived noise levels (EPNL). The ability of EPNL to predict noisiness was not improved by the addition of either of two proposed impulse corrections. A subjective measure of impulsiveness, however, which was not significantly related to the proposed impulse corrections, was found to improve the predictive ability of EPNL.

  15. [Anti-impulsivity drugs and their mechanisms of action].

    PubMed

    Ohmura, Yu; Tsutsui-Kimura, Iku; Yoshioka, Mitsuhiro

    2014-04-01

    Higher impulsivity could be a risk factor for drug addiction, criminal involvement, and suicide. Moreover, poor inhibitory control is observed in several psychiatric disorders such as attention-deficit/hyperactivity disorder, schizophrenia, and bipolar disorder. Thus it is preferred that clinical drugs have anti-impulsive effects in addition to the therapeutic effects on the primary disease. At least it is better to use clinical drugs that do not increase impulsivity. We have developed a 3-choice serial reaction time task and examined the effects of clinical drugs on impulsivity in rats using the task. We have found several anti-impulsive drugs (lithium, tandospirone, and milnacipran) and elucidated the mechanism of action in some of these drugs. For example, we demonstrated that milnacipran enhanced the control of impulsive action by activating D1-like receptors in the infralimbic cortex. In this review, we introduce recent advances in this field and suggest future directions to develop anti-impulsive drugs. PMID:25080806

  16. Adaptive impulsive cluster synchronization in community network with nonidentical nodes

    NASA Astrophysics Data System (ADS)

    Gong, Xiaoli; Gan, Luyining; Wu, Zhaoyan

    2016-07-01

    In this paper, cluster synchronization in community network with nonidentical nodes is investigated. Through introducing proper adaptive strategy into impulsive control scheme, adaptive impulsive controllers are designed for achieving the cluster synchronization. In this adaptive impulsive control scheme, for any given networks, the impulsive gains can adjust themselves to proper values according to the proposed adaptive strategy when the impulsive intervals are fixed. The impulsive instants can be estimated by solving a sequence of maximum value problems when the impulsive gains are fixed. Both community networks without and with coupling delay are considered. Based on the Lyapunov function method and mathematical analysis technique, two synchronization criteria are derived. Several numerical examples are performed to verify the effectiveness of the derived theoretical results.

  17. Multidimensional examination of impulsivity in relation to disordered gambling.

    PubMed

    Mackillop, James; Miller, Joshua D; Fortune, Erica; Maples, Jessica; Lance, Charles E; Campbell, W Keith; Goodie, Adam S

    2014-04-01

    Impulsivity has been consistently associated with pathological gambling (PG), but the diversity of definitions and measures of impulsivity has led to ambiguity with regard to which indices are independently relevant. Toward clarifying this relationship, the current study examined indices from an array of commonly used impulsivity measures in relation to PG severity in an adult community sample of frequent gamblers (N = 353). These included both survey assessments and behavioral tasks. Using a factor analytic approach, 4 latent factors were identified among 19 indices and were designated reward sensitivity, punishment sensitivity, delay discounting, and cognitive impulsivity. All 4 latent variables were positively and independently related to PG severity, albeit at a trend level for cognitive impulsivity in a combined model. These findings reveal 4 generally independent domains of impulsivity that are related to PG severity, clarify which assessment measures aggregate in each domain, and illustrate the importance of measurement specificity in studying impulsivity in relation to PG and other psychiatric disorders. PMID:24708148

  18. Papillary thyroid microcarcinoma co-exists with Hashimoto's thyroiditis: Is strain elastography still useful?

    PubMed

    Li, Yi; Wang, Yan; Wu, Qiong; Hu, Bing

    2016-05-01

    To study the performance of strain elastography in differentiating papillary thyroid microcarcinoma (PTMC) combined with Hashimoto's thyroiditis (HT), conventional ultrasound scan (US) and strain elastography (SE) were performed on 558 nodules smaller than 10mm by one examiner before surgeries. Serum concentrations of thyroid peroxidase antibody (TPO-Ab) (normal range: 0-60U/ml) were measured. Continuous variables were analyzed by independent t test. Receiver operating characteristics (ROC) curve analysis was applied to calculate the cut-off values of strain ratio (SR) and elastography score (ES). The comparison of AUCs is performed by Z test. 482 nodules were diagnosed as PTMC and there were 181 nodules co-existed with HT. SR measurements were lower in PTMC co-existed with HT when comparing to those without HT. (7.292±6.581 vs 11.319±13.155, p<0.000). Taking the data from all of the 558 nodules, the best cut-off of diagnosing PTMC was SR>2.58. When taking the data from 181 PTMC with HT, the best cut-off was SR>2.10. The diagnostic value of SR>2.1 were higher than ES>3, conventional US and combining US and SE (z=3.595, 4.876, 4.420, p<0.001), but cut-off of SR>2.1 did not show significant enhancement of diagnostic value compared to SR>2.58 (z=0.439, p=0.8903>0.001) in PTMC with HT. There is a negative relation between SR and titer of TPO-Ab (r=-0.650, p<0.0001). PTMC with high TPO-Ab (>1000) titer presented lower SR (5.972±4.118 vs 8.379±9.172, p=0.009). Although SR measurements were lower in nodules co-existed with HT when comparing those without HT, using a regular ES and cut-off of SR measurement would not influence the diagnosing performance. SE is still very useful for diagnosing PTMC with HT. PTMC with high TPO-Ab titer might require a lower cut-off of SR. PMID:26945905

  19. A bifurcation giving birth to order in an impulsively driven complex system

    NASA Astrophysics Data System (ADS)

    Seshadri, Akshay; Sujith, R. I.

    2016-08-01

    Nonlinear oscillations lie at the heart of numerous complex systems. Impulsive forcing arises naturally in many scenarios, and we endeavour to study nonlinear oscillators subject to such forcing. We model these kicked oscillatory systems as a piecewise smooth dynamical system, whereby their dynamics can be investigated. We investigate the problem of pattern formation in a turbulent combustion system and apply this formalism with the aim of explaining the observed dynamics. We identify that the transition of this system from low amplitude chaotic oscillations to large amplitude periodic oscillations is the result of a discontinuity induced bifurcation. Further, we provide an explanation for the occurrence of intermittent oscillations in the system.

  20. A bifurcation giving birth to order in an impulsively driven complex system.

    PubMed

    Seshadri, Akshay; Sujith, R I

    2016-08-01

    Nonlinear oscillations lie at the heart of numerous complex systems. Impulsive forcing arises naturally in many scenarios, and we endeavour to study nonlinear oscillators subject to such forcing. We model these kicked oscillatory systems as a piecewise smooth dynamical system, whereby their dynamics can be investigated. We investigate the problem of pattern formation in a turbulent combustion system and apply this formalism with the aim of explaining the observed dynamics. We identify that the transition of this system from low amplitude chaotic oscillations to large amplitude periodic oscillations is the result of a discontinuity induced bifurcation. Further, we provide an explanation for the occurrence of intermittent oscillations in the system. PMID:27586599