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  Subjects -> PHYSICS (Total: 736 journals)
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Physics of the Solid State     Hybrid Journal   (3 followers)
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Physics Procedia     Partially Free   (1 follower)
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Plasma Physics and Controlled Fusion     Partially Free   (2 followers)
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Pramana     Open Access   (8 followers)
Preview     Hybrid Journal  
Proceedings of the National Academy of Sciences, India Section A     Hybrid Journal   (3 followers)
Progress in Low Temperature Physics     Full-text available via subscription  
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Radiation Effects and Defects in Solids     Hybrid Journal   (1 follower)
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Rheologica Acta     Hybrid Journal   (3 followers)
Russian Journal of Mathematical Physics     Hybrid Journal   (1 follower)
Russian Journal of Nondestructive Testing     Hybrid Journal  
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  First | 1 2 3 4 5 6 7 | Last

Ultrasound in Medicine & Biology    [8 followers]  Follow    
  Full-text available via subscription Subscription journal
     ISSN (Print) 0301-5629
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.864]   [H-I: 85]
  • Heterogeneous Echogenicity of the Thyroid Parenchyma Does Not Influence
           the Detection of Multi-focality in Papillary Thyroid Carcinoma on
           Preoperative Ultrasound Staging
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Sun Jin Herh , Eun-Kyung Kim , Ji Min Sung , Jung Hyun Yoon , Hee Jung Moon , Jin Young Kwak
      Heterogeneous echogenicity and micro-nodulations of diffuse thyroid disease on ultrasonography (US) might influence the diagnostic performance of pre-operative US staging, especially the detection of multi-focality. This study was designed to determine whether heterogeneous echogenicity of the thyroid parenchyma influences the diagnostic performance of US in the detection of multi-focality in papillary thyroid carcinoma. Between December 2010 and April 2011, 811 patients underwent pre-operative staging US for papillary thyroid carcinoma and surgery. Twelve radiologists performed the pre-operative US for T and N staging. Underlying parenchymal echogenicity and unilateral and bilateral multi-focality of the thyroid nodules were also evaluated. Patients were divided into two groups on the basis of the underlying echogenicity of the thyroid gland. To evaluate the diagnostic accuracy of US with respect to underlying echogenicity, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated and compared between the two groups. Among the 811 patients included, US revealed underlying heterogeneous echogenicity of the thyroid parenchyma in 204 (25.2%) and underlying homogeneous echogenicity of the thyroid parenchyma in 607 (74.8%). There were no significant differences between the two groups in the diagnostic performance of pre-operative staging US in predicting unilateral multi-focality and bilaterality. Underlying heterogeneous echogenicity in a thyroid gland with Hashimoto's thyroiditis does not significantly influence the detection of multi-focality in papillary thyroid cancer on pre-operative US staging.


      PubDate: 2014-04-02T05:05:27Z
       
  • Reproducibility Study of Fetal 3-D Volumetry in the First Trimester:
           Effect of Fetal Size and Rotational Angle of VOCAL Software
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Ioannis Papastefanou , Dimitra Kappou , Athena P. Souka , Athanasios Pilalis , Charalambos Chrelias , Charalambos Siristatidis , Dimitrios Kassanos
      Intra- and inter-observer reproducibility of fetal volume measurement by 3-D ultrasound scan (using VOCAL [Virtual Organ Computer-Aided Analysis] software) in 27 fetuses at 7 to 13 wk was studied. For intra-observer variability, the mean difference (MD) and 95% limits of agreement (95% LOA) at 12°, 18° and 30° were MD12 = 0.097, 95% LOA12 = –0.87 to +1.06; MD18 = 0.07, 95% LOA18 = –1.31 to +1.45; and MD30 = –0.07, 95% LOA30 = –1.55 to +1.41. The standard deviation of the differences (SDDIF) increased with crown-rump length at 12° (p = 0.0016), 18° (p = 0.0011) and 30° (p = 0.02). For inter-observer variability, MD12 = 0.15, 95% LOA12 = –1.65 to +1.95; MD18 = 0.042, 95% LOA18 = –1.79 to +1.87; and MD30 = 0.19, 95% LOA30 = –1.24 to +1.62. SDDIF increased with crown-rump length at 18° (p = 0.0084) and 30° (p = 0.0073). The accuracy of fetal volume measurement was not influenced by rotational angle or fetal size. Precision deteriorated for wider rotational angles and larger fetuses.


      PubDate: 2014-04-02T05:05:27Z
       
  • Preperitoneal Fat Tissue May Be Associated with Arterial Stiffness in
           Obese Adolescents
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Bülent Hacıhamdioğlu , Gönül Öçal , Merih Berberoğlu , Zeynep Şıklar , Suat Fitöz , Ercan Tutar , Gökhan Nergisoğlu , Şenay Savaş Erdeve , Emine Çamtosun
      Vascular aging is a chronic process, and many negative effects of obesity in this process have been well defined. We assessed arterial stiffness in obese adolescents and evaluated the relationship between intra-abdominal fat distribution and arterial stiffness. Arterial stiffness parameters and pulse wave velocity (PWV) were evaluated in 61 obese adolescents and 58 healthy controls. Carotid-femoral PWV was calculated by arterial tonometry. Additionally, all obese children were evaluated for metabolic syndrome and insulin resistance. Intra-abdominal fat distribution, including subcutaneous, preperitoneal and visceral fat thicknesses, was assessed by ultrasonography. PWVs of obese children were significantly higher than those of healthy controls (5.0 ± 0.7 m/s vs. 4.7 ± 0.5 m/s). Parameters affecting PWV were evaluated by regression analysis. The independent variable in the regression analysis model was PWV, and the dependent variables were age, metabolic syndrome, body mass index and Homeostasis Model Assessment—Insulin Resistance, as well as subcutaneous, preperitoneal and visceral fat tissue thicknesses measured by ultrasonography. The only parameter associated with PWV was preperitoneal fat tissue thickness. Vascular changes related to obesity may begin in adolescence, as illustrated by the increased PWV. Preperitoneal fat tissue may be related to arterial stiffness. Intra-abdominal fat distributions obtained by ultrasonography may provide clinicians with valuable information needed to determine cardiovascular disease risk factors in obese adolescents.


      PubDate: 2014-04-02T05:05:27Z
       
  • Carotid Wall Elastography to Assess Midterm Vascular Dysfunction Secondary
           to Intrauterine Growth Restriction: Feasibility and Comparison with
           Standardized Intima-Media Thickness
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Roch L. Maurice , Laurence Vaujois , Nagib Dahdah , Najat Chibab , Anika Maurice , Anne-Monique Nuyt , Émile Lévy , Jean-Luc Bigras
      Several studies have suggested that intrauterine growth restriction (IUGR) increases the risk of cardiovascular disease and early atherosclerosis. Early detection of arteriopathy is essential to early intervention. Although arterial intima-media thickness (IMT) is considered an index of subclinical atherosclerosis in the adult, its validity in pediatric patients may be limited. We have recently introduced a novel imaging-based biomarker (ImBioMark) to assess intrinsic mechanical features of the arterial wall from B-mode ultrasound data. The aim of the work described here was to evaluate the potential of ImBioMark in investigation of cardiovascular health status at the level of the common carotid artery (CCA) in adolescents born after IUGR. We also compared ImBioMark results with automated IMT measurements, a well-established biomarker used in clinical practice and research. The potential sequelae of IUGR on the CCA were examined in a group of adolescents in comparison with healthy controls. Patients with IUGR (n = 7) were 13.85 ± 0.46 y old; the healthy controls (n = 7) were 14.58 ± 0.80 y old (p = 0.058). Cine loops of the CCA B-mode data were digitally recorded, and the arterial elastic modulus was estimated a posteriori with ImBioMark. IMT of the CCA was automatically calculated using QLAB software (Philips, Andover, MA, USA). All patients had been evaluated in utero in our fetal echocardiographic laboratory. ImBioMark detected a significant increase in CCA stiffness in patients with IUGR as compared with healthy controls: elastic modulus = 90.74 ± 11.86 versus 61.30 ± 15.94 kPa, respectively (p = 0.002). There was, however, no significant difference between patients with IUGR and controls in IMT (0.483 ± 0.067 versus 0.476 ± 0.051 mm, respectively, p = 0.831). The impact of IUGR on CCA wall dynamics was confirmed by ImBioMark. The apparent limitation of IMT measurement in this cohort may be the result of geometric arterial changes, that is, the expected thickening, below the level of detection at this age. As early detection of vascular modulation is essential to early intervention in a population at risk, we now intend to extend ImBioMark to investigate larger pathologic cohorts with various degrees of arteriopathy.


      PubDate: 2014-04-02T05:05:27Z
       
  • Diagnostic Performance of Ultrasound and Ultrasound Elastography with
           Respect to Physician Experience
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Su Yeon Ko , Eun-Kyung Kim , Ji Min Sung , Hee Jung Moon , Jin Young Kwak
      The aim of this study was to compare the diagnostic performance of gray-scale ultrasound (US), elastography and a combination of gray-scale ultrasound and elastography (US-E) in differentiating benign and malignant thyroid nodules with respect to the level of physician experience. Three hundred fifty-eight patients with 367 thyroid nodules who underwent both gray-scale US and elastography, from November 2011 to January 2012, were included in this study. The diagnostic performance of US performed by experienced and less experienced physicians was compared. Comparisons of the diagnostic performance of US, elastography and US-E were evaluated for each group separately. Of 367 nodules, 121 were malignant and 246 were benign. When we compared the diagnostic performance of the experienced and less experienced physician groups, specificity was statistically higher in the experienced physician group for both US alone (p = 0.001) and US-E (p = 0.048). However, the experienced and less experienced physician groups did not differ significantly on other measures of diagnostic performance, regardless of modality. For the experienced physicians, the specificity and positive predictive value US were 88.0% and 76.8%, respectively; both of them were significantly higher than the corresponding values for US-E. For the less experienced physicians, specificity was significantly higher on elastography (93.8%) than on US (71.4%) (p < 0.001). However, diagnostic performance did not differ significantly between US and US-E for the less experienced physicians. Experienced physicians had superior specificity compared with less experienced physicians. The diagnostic performance of elastography and US-E was inferior compared with that of US alone, irrespective of the level of experience of the physician.


      PubDate: 2014-04-02T05:05:27Z
       
  • Editorial Advisory Board
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5




      PubDate: 2014-04-02T05:05:27Z
       
  • Contents
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5




      PubDate: 2014-04-02T05:05:27Z
       
  • Ultrasonographic Measurement of the Respiratory Variation in the Inferior
           Vena Cava Diameter Is Predictive of Fluid Responsiveness in Critically Ill
           Patients: Systematic Review and Meta-analysis
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Zhongheng Zhang , Xiao Xu , Sheng Ye , Lei Xu
      Respiratory variation in the inferior vena cava (ΔIVC) has been extensively studied with respect to its value in predicting fluid responsiveness, but the results are conflicting. This systematic review was aimed at investigating the diagnostic accuracy of ΔIVC in predicting fluid responsiveness. Databases including Medline, Embase, Scopus and Web of Knowledge were searched from inception to May 2013. Studies exploring the diagnostic performance of ΔIVC in predicting fluid responsiveness were included. To allow for more between- and within-study variance, a hierarchical summary receiver operating characteristic model was used to pool the results. Subgroup analyses were performed for patients on mechanical ventilation, spontaneously breathing patients and those challenged with colloids and crystalloids. A total of 8 studies involving 235 patients were eligible for analysis. Cutoff values of ΔIVC varied across studies, ranging from 12% to 40%. The pooled sensitivity and specificity in the overall population were 0.76 (95% confidence interval [CI]: 0.61–0.86) and 0.86 (95% CI: 0.69–0.95), respectively. The pooled diagnostic odds ratio (DOR) was 20.2 (95% CI: 6.1–67.1). The diagnostic performance of ΔIVC appeared to be better in patients on mechanical ventilation than in spontaneously breathing patients (DOR: 30.8 vs. 13.2). The pooled area under the receiver operating characteristic curve was 0.84 (95% CI: 0.79–0.89). Our study indicates that ΔIVC measured with point-of-care ultrasonography is of great value in predicting fluid responsiveness, particularly in patients on controlled mechanical ventilation and those resuscitated with colloids.


      PubDate: 2014-04-02T05:05:27Z
       
  • Masthead
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5




      PubDate: 2014-04-02T05:05:27Z
       
  • Endovascular Shear Strain Elastography for the Detection and
           Characterization of the Severity of Atherosclerotic Plaques: In Vitro
           Validation and In Vivo Evaluation
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Younes Majdouline , Jacques Ohayon , Zahra Keshavarz-Motamed , Marie-Hélène Roy Cardinal , Damien Garcia , Louise Allard , Sophie Lerouge , Frédéric Arsenault , Gilles Soulez , Guy Cloutier
      This work explores the potential of shear strain elastograms to identify vulnerable atherosclerotic plaques. The Lagrangian speckle model estimator (LSME) elasticity imaging method was further developed to estimate shear strain elasticity (SSE). Three polyvinyl alcohol cryogel vessel phantoms were imaged with an intravascular ultrasound (IVUS) scanner. The estimated SSE maps were validated against finite-element results. Atherosclerosis was induced in carotid arteries of eight Sinclair mini-pigs using a combination of surgical techniques, diabetes and a high-fat diet. IVUS images were acquired in vivo in 14 plaques before euthanasia and histology. All plaques were characterized by high magnitudes in SSE maps that correlated with American Heart Association atherosclerosis stage classifications (r = 0.97, p < 0.001): the worse the plaque condition the higher was the absolute value of SSE, i.e. SSE (e.g., mean SSE was 3.70 ± 0.40% in Type V plaques, whereas it was reduced to 0.11 ± 0.01% in normal walls). This study indicates the feasibility of using SSE to highlight atherosclerotic plaque vulnerability characteristics.


      PubDate: 2014-04-02T05:05:27Z
       
  • Stellate Masses and Histologic Grades in Breast Cancer
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Chin-Yuan Chang , Shou-Jen Kuo , Hwa-Koon Wu , Yu-Len Huang , Dar-Ren Chen
      Breast masses with a radiologic stellate pattern often transform into malignancies, but their tendency to be of low histologic grade yields a better survival rate compared with tumors with other patterns on mammography screening. This study was designed to investigate the correlation of histologic grade with stellate features extracted from the coronal plane of 3-D ultrasound images. A pre-processing method was proposed to facilitate the extraction of stellate features. Extracted features were statistically measured to derive a set of indices that quantitatively represent the stellate pattern. These indices then went through a selection procedure to build proper decision trees. The splitting rules of decision trees indicated that stellate tumors are associated with low grade. A set of indices from the low grade-associated rules has the potential to represent the stellate feature. Further investigation of the hypoechoic region of peripheral tissue is essential to establishment of a complete discriminating model for tumor grades.


      PubDate: 2014-04-02T05:05:27Z
       
  • Modeling of Errors in Nakagami Imaging: Illustration on Breast Mass
           Characterization
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Aymeric Larrue , J. Alison Noble
      Nakagami imaging is an attractive tissue characterization method, as the parameter estimated at each location is related to properties of the tissues. The application to clinical ultrasound images is problematic, as the estimation of the parameters is disturbed by the presence of complex structures. We propose to consider separately the different aspects potentially affecting the value of the Nakagami parameters and quantify their effects on the estimation. This framework is applied to the classification of breast masses. Quantitative parameters are computed on two groups of ultrasound images of benign and malignant tumors. A statistical analysis of the result indicated that the previously observed difference between average values of the Nakagami parameters is explained mostly by estimation errors. In the future, new methods for reliable computation of Nakagami parameters need to be developed, and factors of error should be considered in studies using Nakagami parameters.


      PubDate: 2014-04-02T05:05:27Z
       
  • In Vivo Lateral Blood Flow Velocity Measurement Using Speckle Size
           Estimation
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Tiantian Xu , Mohsen Hozan , Gregory R. Bashford
      In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is “smeared”) if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator.


      PubDate: 2014-04-02T05:05:27Z
       
  • Estimation of Urinary Flow Velocity in Models of Obstructed and
           Unobstructed Urethras by Decorrelation of Ultrasound Radiofrequency
           Signals
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Muhammad Arif , Tim Idzenga , Ron van Mastrigt , Chris L. de Korte
      The feasibility of estimating urinary flow velocity from the decorrelation of radiofrequency (RF) signals was investigated in soft tissue-mimicking models of obstructed and unobstructed urethras. The decorrelation was studied in the near field, focal zone and far field of the ultrasound beam. Furthermore, the effect of beam width was investigated. The results of this study suggest that it is feasible to estimate flow velocity in models of the urethra by quantifying the decorrelation of RF ultrasound signals. The decorrelation slope increased more rapidly and more linearly with increasing velocity in the focal zone than in the near and far field. A preliminary example of an in vivo measurement in a healthy volunteer illustrated that this method has potential for clinical use in the future.


      PubDate: 2014-04-02T05:05:27Z
       
  • High-Intensity Focused Ultrasound Treatment of Late-Stage Pancreatic Body
           Carcinoma: Optimal Tumor Depth for Safe Ablation
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Hui-Yu Ge , Li-Ying Miao , Liu-Lin Xiong , Fang Yan , Cui-Shan Zheng , Jin-Rui Wang , Jian-Wen Jia , Li-Gang Cui , Wen Chen
      Objective criteria are currently not available for assessing the extent of ablation by high-intensity focused ultrasound (HIFU). A retrospective review was conducted in Chinese patients with late-stage pancreatic body carcinoma treated with 1 h/d intermittent HIFU at a single center. Clinical and procedure-related characteristics were examined in relation to tumor posterior depth. Clinically, tumor ablation was negatively correlated with posterior tumor depth, with a 1-cm increase in depth decreasing ablation by 30.7%. At a computed tomography (CT)-determined 7-cm posterior tumor depth (considered the critical value for the procedure), ablation sensitivity and specificity were 77.8% and 72.7%, respectively. Tumor ablation >30% in patients with a CT-determined posterior tumor depth ≤7 cm was 9.333 times better than that in patients with a CT-determined posterior tumor depth >7 cm. Adverse effects did not affect the efficacy of HIFU. Tumors with posterior depths <7 cm may effectively be treated with HIFU-induced ablation with minimal adverse events.


      PubDate: 2014-04-02T05:05:27Z
       
  • Magnetic Resonance Imaging for the Exploitation of Bubble-Enhanced Heating
           by High-Intensity Focused Ultrasound: A Feasibility Study in ex Vivo
           Liver
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Delphine Elbes , Quentin Denost , Benjamin Robert , Max O. Köhler , Mickaël Tanter , Quesson Bruno
      Bubble-enhanced heating (BEH) may be exploited to improve the heating efficiency of high-intensity focused ultrasound in liver and to protect tissues located beyond the focal point. The objectives of this study, performed in ex vivo pig liver, were (i) to develop a method to determine the acoustic power threshold for induction of BEH from displacement images measured by magnetic resonance acoustic radiation force imaging (MR-ARFI), and (ii) to compare temperature distribution with MR thermometry for HIFU protocols with and without BEH. The acoustic threshold for generation of BEH was determined in ex vivo pig liver from MR-ARFI calibration curves of local tissue displacement resulting from sonication at different powers. Temperature distributions (MR thermometry) resulting from “conventional” sonications (20 W, 30 s) were compared with those from “composite” sonications performed at identical parameters, but after a HIFU burst pulse (0.5 s, acoustic power over the threshold for induction of BEH). Displacement images (MR-ARFI) were acquired between sonications to measure potential modifications of local tissue displacement associated with modifications of tissue acoustic characteristics induced by the burst HIFU pulse. The acoustic threshold for induction of BEH corresponded to a displacement amplitude of approximately 50 μm in ex vivo liver. The displacement and temperature images of the composite group exhibited a nearly spherical pattern, shifted approximately 4 mm toward the transducer, in contrast to elliptical shapes centered on the natural focal position for the conventional group. The gains in maximum temperature and displacement values were 1.5 and 2, and the full widths at half-maximum of the displacement data were 1.7 and 2.2 times larger than in the conventional group in directions perpendicular to ultrasound propagation axes. Combination of MR-ARFI and MR thermometry for calibration and exploitation of BEH appears to increase the efficiency and safety of HIFU treatment.


      PubDate: 2014-04-02T05:05:27Z
       
  • Application of High-Intensity Focused Ultrasound to the Study of Mild
           Traumatic Brain Injury
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Joseph T. McCabe , Chantal Moratz , Yunbo Liu , Ellen Burton , Amy Morgan , Craig Budinich , Dennell Lowe , John Rosenberger , HuaZhen Chen , Jiong Liu , Matthew Myers
      Though intrinsically of much higher frequency than open-field blast overpressures, high-intensity focused ultrasound (HIFU) pulse trains can be frequency modulated to produce a radiation pressure having a similar form. In this study, 1.5-MHz HIFU pulse trains of 1-ms duration were applied to intact skulls of mice in vivo and resulted in blood-brain barrier disruption and immune responses (astrocyte reactivity and microglial activation). Analyses of variance indicated that 24 h after HIFU exposure, staining density for glial fibrillary acidic protein was elevated in the parietal and temporal regions of the cerebral cortex, corpus callosum and hippocampus, and staining density for the microglial marker, ionized calcium binding adaptor molecule, was elevated 2 and 24 h after exposure in the corpus callosum and hippocampus (all statistical test results, p < 0.05). HIFU shows promise for the study of some bio-effect aspects of blast-related, non-impact mild traumatic brain injuries in animals.


      PubDate: 2014-04-02T05:05:27Z
       
  • Sonoporation-Induced Depolarization of Plasma Membrane Potential: Analysis
           of Heterogeneous Impact
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Peng Qin , Lin Xu , Yaxin Hu , Wenjing Zhong , Ping Cai , Lianfang Du , Lifang Jin , Alfred C.H. Yu
      Disrupting plasma membrane integrity would inevitably promote anomalous ion fluxes across the membrane and thereby upset the trans-membranous potential. In this article, we report new findings on how sonoporation as a physical membrane perforation strategy would lead to different forms of plasma membrane potential disruption. Our investigation was conducted with a customized fluorescence imaging platform that enabled live monitoring of plasma membrane potential in relation to individual sonoporation events triggered on HeLa cervical cancer cells. Sonovue microbubbles were used as sonoporation agents (added at a 4:3 cell-to-bubble ratio), and they were activated by 1-MHz pulsed ultrasound with 0.35-MPa peak negative pressure, 20-cycle pulse duration, 20-Hz pulse repetition frequency and 1-s total exposure duration. Results indicate that the plasma membrane potential response was heterogeneous among sonoporated cells: (i) membrane potential of irreversibly sonoporated cells was permanently depolarized; (ii) reversibly sonoporated cells exhibited either transient or sustained membrane depolarization; (iii) intact cells adjacent to sonoporated ones underwent transitory membrane depolarization. These findings effectively serve to substantiate the causal relationship between sonoporation and plasma membrane potential.


      PubDate: 2014-04-02T05:05:27Z
       
  • Involvement of Mitochondrial and Reactive Oxygen Species in the
           Sonodynamic Toxicity of Chlorin e6 in Human Leukemia K562 Cells
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Yixiang Li , Pan Wang , Xiaobing Wang , Xiaomin Su , Quanhong Liu
      It is well accepted that sonodynamic therapy (SDT) exerts cytotoxicity and anti-tumor activity in many human tumors through the induction of cell apoptosis. The aim of the work described here was to study the effect of chlorin e6 (Ce6)-mediated SDT on human chronic myelogenous leukemia K562 cells. Our results indicate that Ce6-mediated SDT can suppress the viability of K562 cells. SDT caused apoptosis as analyzed by annexin V-phycoerythrin/7-amino-actinomycin D staining as well as cleavage of caspase 3 and the polypeptide poly(ADP-ribose) polymerase. After SDT exposure, loss of mitochondrial membrane potential, translocation of Bax from cytoplasm to mitochondria and activation of caspase 9 indicated that the mitochondrial-related apoptotic pathway might be activated. This process was accompanied by rapid generation of reactive oxygen species (ROS). Scavenging of ROS significantly blocked caspase-3 expression and the killing effect of SDT on K562 cells. Stress-activated protein kinases c-jun NH2-terminal kinase (JNK) and the p38 mitogen-activated protein kinase were activated after SDT treatment. Together, these findings indicate that Ce6-mediated SDT triggers mitochondria- and caspase-dependent apoptosis; oxidative injury may play a vital role in apoptotic signaling cascades.


      PubDate: 2014-04-02T05:05:27Z
       
  • Thermal Safety Simulations of Transient Temperature Rise during Acoustic
           Radiation Force-Based Ultrasound Elastography
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Yunbo Liu , Bruce A. Herman , Joshua E. Soneson , Gerald R. Harris
      Ultrasound transient elastography is a new diagnostic imaging technique that uses acoustic radiation force to produce motion in solid tissue via a high-intensity, long-duration “push” beam. In our previous work, we developed analytical models for calculating transient temperature rise, both in soft tissue and at a bone/soft tissue interface, during a single acoustic radiation force impulse (ARFI) imaging frame. The present study expands on these temperature rise calculations, providing applicable range assessment and error analysis for a single ARFI frame. Furthermore, a “virtual source” approach is described for temperature and thermal dose calculation under multiple ARFI frames. By use of this method, the effect of inter-frame cooling duration on temperature prediction is analyzed, and a thermal buildup phenomenon is revealed. Thermal safety assessment indicates that the thermal dose values, especially at the absorptive bone/soft tissue interface, could approach recommended dose thresholds if the cooling interval of multiple-frame ARFI elastography is too short.


      PubDate: 2014-04-02T05:05:27Z
       
  • Modeling of Femoral Neck Cortical Bone for the Numerical Simulation of
           Ultrasound Propagation
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Quentin Grimal , Daniel Rohrbach , Julien Grondin , Reinhard Barkmann , Claus-C. Glüer , Kay Raum , Pascal Laugier
      Quantitative ultrasound assessment of the cortical compartment of the femur neck (FN) is investigated with the goal of achieving enhanced fracture risk prediction. Measurements at the FN are influenced by bone size, shape and material properties. The work described here was aimed at determining which FN material properties have a significant impact on ultrasound propagation around 0.5 MHz and assessing the relevancy of different models. A methodology for the modeling of ultrasound propagation in the FN, with a focus on the modeling of bone elastic properties based on scanning acoustic microscopy data, is introduced. It is found that the first-arriving ultrasound signal measured in through-transmission at the FN is not influenced by trabecular bone properties or by the heterogeneities of the cortical bone mineralized matrix. In contrast, the signal is sensitive to variations in cortical porosity, which can, to a certain extent, be accounted for by effective properties calculated with the Mori-Tanaka method.


      PubDate: 2014-04-02T05:05:27Z
       
  • Evaluation of the Specific Adsorption of Biotinylated Microbubbles Using a
           Quartz Crystal Microbalance
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5
      Author(s): Takashige Muramoto , Ryosuke Shimoya , Kenji Yoshida , Yoshiaki Watanabe
      Specific adsorption of biotinylated microbubbles to streptavidin was evaluated by measuring the resonant frequency of an AT-cut quartz crystal microbalance (QCM). Streptavidin was fixed via self-assembled monolayers coated onto the QCM electrode. The resonant frequency of the QCM decreased as a result of specific adsorption of the biotinylated microbubbles, compared with the results for microbubbles containing no biotin. Additionally, there was significant evidence indicating that the frequency shift was caused by the internal gas of the microbubble, as well as the mass of the outer-shell material surrounding the gas. These results suggest that the QCM measurement system can be used effectively to evaluate the specific adsorption of targeted microbubbles.


      PubDate: 2014-04-02T05:05:27Z
       
  • Calendar
    • Abstract: Publication date: May 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 5




      PubDate: 2014-04-02T05:05:27Z
       
  • High-Frequency Intra-operative Ultrasound-Guided Surgery of Superficial
           Intra-cerebral Lesions via a Single-Burr-Hole Approach
    • Abstract: Publication date: Available online 27 March 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Jan-Karl Burkhardt , Carlo Serra , Marian C. Neidert , Christoph M. Woernle , Jorn Fierstra , Luca Regli , Oliver Bozinov
      The study described here examined the feasibility of using high-frequency intra-operative ultrasound (hfioUS) guidance to resect superficial intra-cerebral lesions through a single burr hole. A cohort of 23 consecutive patients with a total of 24 intra-cerebral lesions (9 intra-cerebral metastases, 8 gliomas, 4 infections, 2 lymphomas and 1 cavernoma) were studied. All lesions could be localized and successfully resected, biopsied or aspirated, and histopathological diagnoses were obtained in all cases. The mean operating time was 59.6 ± 23.9 min. The mean cross-sectional lesion size was 6.4 ± 7.6 cm2, and the mean cortex surface-to-lesion distance was 0.6 ± 0.8 cm. Our results illustrate the feasibility of identifying and resecting superficial intra-cerebral lesions under hfioUS guidance via a single-burr-hole approach. We were able to achieve short resection times with no post-operative complications in all patients, favorable conditions under which to start adjuvant therapy when indicated.


      PubDate: 2014-03-28T07:21:09Z
       
  • The Combination of Intralymphatic Chemotherapy with Ultrasound and
           Nano-/Microbubbles Is Efficient in the Treatment of Experimental Tumors in
           Mouse Lymph Nodes
    • Abstract: Publication date: Available online 20 March 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Takuma Sato , Shiro Mori , Yoichi Arai , Tetsuya Kodama
      Intravenous chemotherapy is a therapeutic option for the treatment of lymph node metastasis, but the drugs often have difficulty accessing the lymphatic system. The aim of this study was to determine whether the combination of intralymphatic chemotherapy with ultrasound and nano-/microbubbles is active against tumors in mouse lymph nodes. Intralymphatic chemotherapy in mice with lymph nodes containing tumors was found to have a marked anti-tumor effect, compared with intravenous administration, and the addition of ultrasound combined with nano-/microbubbles enhanced the effect of the anti-cancer drug, but only when the drug was administered intralymphatically. Furthermore, decreases in the volumes and blood vessel densities of tumor-bearing lymph nodes are reliable measures of therapeutic effect, confirmed by histopathological evaluation. The main conclusion is that combining ultrasound with nano-/microbubbles and intralymphatic chemotherapy improves drug delivery to the lymphatic system and has a more potent anti-tumor effect.


      PubDate: 2014-03-23T07:13:30Z
       
  • Shock Waves and DNA-Cationic Lipid Assemblies: A Synergistic Approach to
           Express Exogenous Genes in Human Cells
    • Abstract: Publication date: Available online 15 March 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Blanca Millán-Chiu , Giselle Camacho , Alfredo Varela-Echavarría , Elisa Tamariz , Francisco Fernández , Luz M. López-Marín , Achim M. Loske
      Cationic lipid/DNA complexes (lipoplexes) represent a powerful tool for cell transfection; however, their use is still limited by important concerns, including toxicity and poor internalization into deep tissues. In this work, we investigated the use of shock wave-induced acoustic cavitation in vitro for the transfection of lipoplexes in human embryo kidney 293 cells. We selected shock waves with the ability to internalize 10-kDa fluorescein isothiocyanate-dextran into cells while maintaining survival rates above 50%. Cell transfection was tested using the green fluorescent protein-encoding plasmid pCX::GFPGPI2. Confocal microscopy and fluorescence-assisted cell sorting analyses revealed successful transfection after treatments ranging from 1 to 3 min using 60 to 180 shock waves at peak amplitudes of 12.3 ± 1.5 MPa. Interestingly, the combination of shock waves and lipoplexes induced a 3.1- and 3.8-fold increase in the expression of the reporter gene compared with the use of lipoplexes or shock waves alone, respectively. These results indicate that cationic DNA assembly and shock waves act in a synergistic manner to promote transfection of human cells, revealing a potential approach for non-invasive site-specific gene therapy.


      PubDate: 2014-03-18T07:10:44Z
       
  • High-Intensity Focused Ultrasound-Induced, Localized Mild Hyperthermia to
           Enhance Anti-cancer Efficacy of Systemic Doxorubicin: An Experimental
           Study
    • Abstract: Publication date: Available online 15 March 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Sun Young Chae , Young-sun Kim , Min Jung Park , Jehoon Yang , Hajan Park , Mi-Sun Namgung , Hyunchul Rhim , Hyo Keun Lim
      The aim of this study was to evaluate the enhancement of the efficacy of systemic doxorubicin by pulsed high-intensity focused ultrasound (HIFU)-induced, localized mild hyperthermia. For the in vitro study, the intranuclear uptake of doxorubicin by squamous cell carcinoma (SCC)-7 cells incubated at different temperatures was compared. For the in vivo study, mice with SCC-7 tumors were assigned to either the control, conventional hyperthermia, HIFU hyperthermia, doxorubicin-alone, conventional hyperthermia + doxorubicin or HIFU hyperthermia + doxorubicin group. Conventional hyperthermia was induced by immersing the tumor in warm water (42.5°C), and HIFU hyperthermia was induced by HIFU after optimizing the parameters with direct temperature measurements (frequency = 1 MHz, pulse repetition frequency = 5 Hz, power = 12 W, duty cycle = 50%). In the in vitro study, fluorescence was more intense at 42°C than at 37°C and was time dependent. In the in vivo study, tumor growth in the HIFU hyperthermia + doxorubicin group was most prominently suppressed with the highest apoptotic index compared with all other groups (p < 0.05). Pulsed HIFU-induced localized mild hyperthermia enhanced the anti-cancer efficacy of systemic doxorubicin more than conventional mild hyperthermia.


      PubDate: 2014-03-18T07:10:44Z
       
  • Erratum
    • Abstract: Publication date: Available online 11 March 2014
      Source:Ultrasound in Medicine & Biology




      PubDate: 2014-03-13T07:21:20Z
       
  • Albumin Acts Like Transforming Growth Factor β1 in Microbubble-Based
           Drug Delivery
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Yueh-Hsun Chuang , Yu-Hsin Wang , Tien-Kuei Chang , Ching-Jung Lin , Pai-Chi Li
      Unlike lipid-shelled microbubbles (MBs), albumin-shelled microbubbles (MBs) have not been reported to be actively targeted to cells without the assistance of antibodies. Recent studies indicate that the albumin molecule is similar to transforming growth factor β (TGF-β) both structurally and functionally. The TGF-β superfamily is important during early tumor outgrowth, with an elevated TGF-β being tumor suppressive; at later stages, this switches to malignant conversion and progression, including breast cancer. TGF-β receptors I and II play crucial roles in both the binding and endocytosis of albumin. However, until now, no specific albumin receptor has been found. On the basis of the above-mentioned information, we hypothesized that non-antibody-conjugated albumin-shelled MBs can be used to deliver drugs to breast cancer cells. We also studied the possible roles of TGF-β1 and radiation force in the behavior of cells and albumin-shelled MBs. The results indicate that albumin-shelled MBs loaded with paclitaxel (PTX) induce breast cancer cell apoptosis without the specific targeting produced by an antibody. Applying either an acoustic radiation force or cavitation alone to cells with PTX-loaded albumin MBs increased the apoptosis rate to 23.2% and 26.3% (p < 0.05), respectively. We also found that albumin-shelled MBs can enter MDA-MB-231 breast cancer cells and remain there for at least 24 h, even in the presence of PTX loading. Confocal micrographs revealed that 70.5% of the breast cancer cells took up albumin-shelled MBs spontaneously after 1 d of incubation. Applying an acoustic radiation force further increased the percentage to 91.9% in our experiments. However, this process could be blocked by TGF-β1, even with subsequent exposure to the radiation force. From these results, we conclude that TGF-β1 receptors are involved in the endocytotic process by which albumin-shelled MBs enter breast cancer cells. The acoustic radiation force increases the contact rate between albumin-shelled MBs and tumor cells. Combining a radiation force and cavitation yields an apoptosis rate of 31.3%. This in vitro study found that non-antibody-conjugated albumin-shelled MBs provide a useful method of drug delivery. Further in vivo studies of the roles of albumin MBs and TGF-β in different stages of cancer are necessary.


      PubDate: 2014-03-03T07:21:15Z
       
  • The Delayed Onset of Subharmonic and Ultraharmonic Emissions from a
           Phospholipid-Shelled Microbubble Contrast Agent
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Himanshu Shekhar , Ivy Awuor , Keri Thomas , Joshua J. Rychak , Marvin M. Doyley
      Characterizing the non-linear response of microbubble contrast agents is important for their efficacious use in imaging and therapy. In this article, we report that the subharmonic and ultraharmonic response of lipid-shelled microbubble contrast agents exhibits a strong temporal dependence. We characterized non-linear emissions from Targestar-p microbubbles (Targeson Inc., San Diego, CA, USA) periodically for 60 min, at 10 MHz excitation frequency. The results revealed a considerable increase in the subharmonic and ultraharmonic response (nearly 12–15 and 5–8 dB) after 5–10 min of agent preparation. However, the fundamental and the harmonic response remained almost unchanged in this period. During the next 50 min, the subharmonic, fundamental, ultraharmonic, and harmonic responses decreased steadily by 2–5 dB. The temporal changes in the non-linear behavior of the agent appeared to be primarily mediated by gas-exchange through the microbubble shell; temperature and prior acoustic excitation based mechanisms were ruled out. Further, there was no measurable change in the agent size distribution by static diffusion. We envisage that these findings will help obtain reproducible measurements from agent characterization, non-linear imaging, and fluid-pressure sensing. These findings also suggest the possibility for improving non-linear imaging by careful design of ultrasound contrast agents.


      PubDate: 2014-03-03T07:21:15Z
       
  • Masthead
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4




      PubDate: 2014-03-03T07:21:15Z
       
  • Mouse Liver Dispersion for the Diagnosis of Early-Stage Fatty Liver
           Disease: A 70-Sample Study
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Christopher T. Barry , Zaegyoo Hah , Alexander Partin , Robert A. Mooney , Kuang-Hsiang Chuang , Alicia Augustine , Anthony Almudevar , Wenqing Cao , Deborah J. Rubens , Kevin J. Parker
      The accumulation of fat droplets within the liver is an important marker of liver disease. This study assesses gradations of steatosis in mouse livers using crawling waves, which are interfering patterns of shear waves introduced into the liver by external sources. The crawling waves are detected by Doppler ultrasound imaging techniques, and these are analyzed to estimate the shear wave speed as a function of frequency between 200 and 360 Hz. In a study of 70 mice with progressive increases in steatosis from 0% to >60%, increases in steatosis are found to increase the dispersion, or frequency dependence, of shear wave speed. This finding confirms an earlier, smaller study and points to the potential of a scoring system for steatosis based on shear wave dispersion.


      PubDate: 2014-03-03T07:21:15Z
       
  • Comparison of Fractional Wave Equations for Power Law Attenuation in
           Ultrasound and Elastography
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Sverre Holm , Sven Peter Näsholm
      A set of wave equations with fractional loss operators in time and space are analyzed. The fractional Szabo equation, the power law wave equation and the causal fractional Laplacian wave equation are all found to be low-frequency approximations of the fractional Kelvin-Voigt wave equation and the more general fractional Zener wave equation. The latter two equations are based on fractional constitutive equations, whereas the former wave equations have been derived from the desire to model power law attenuation in applications like medical ultrasound. This has consequences for use in modeling and simulation, especially for applications that do not satisfy the low-frequency approximation, such as shear wave elastography. In such applications, the wave equations based on constitutive equations are the viable ones.


      PubDate: 2014-03-03T07:21:15Z
       
  • Calendar
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4




      PubDate: 2014-03-03T07:21:15Z
       
  • Elasticity Estimates from Images of Crawling Waves Generated by Miniature
           Surface Sources
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Alexander Partin , Zaegyoo Hah , Christopher T. Barry , Deborah J. Rubens , Kevin J. Parker
      We describe a surface-based approach to the generation of shear wave interference patterns, called crawling waves (CrW), within a medium and derive local estimates of biomechanical properties of tissue. In previous experiments, elongated bars operating as vibration sources were used to generate CrW propagation in samples. In the present study, however, a pair of miniature circular vibration sources was applied to the overlying skin to generate the CrW within the medium. The shape and position of the miniature sources make this configuration more applicable for in vivo implementation. A modified ultrasound imaging system is used to display the CrW propagation. A shear speed mapping algorithm is developed using a detailed analysis of the CrW. The proposed setup is applied to several biomaterials including a homogeneous phantom, an inhomogeneous phantom and an ex vivo human liver. The data are analyzed using the mapping algorithm to reveal the biomechanical properties of the biomaterials.


      PubDate: 2014-03-03T07:21:15Z
       
  • The Gaussian Shear Wave in a Dispersive Medium
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Kevin J. Parker , Natalie Baddour
      In “imaging the biomechanical properties of tissues,” a number of approaches analyze shear wave propagation initiated by a short radiation force push. Unfortunately, it has been experimentally observed that the displacement-versus-time curves for lossy tissues are rapidly damped and distorted in ways that can confound simple tracking approaches. This article addresses the propagation, decay and distortion of pulses in lossy and dispersive media, to derive closed-form analytic expressions for the propagating pulses. The theory identifies key terms that drive the distortion and broadening of the pulse. Furthermore, the approach taken is not dependent on any particular viscoelastic model of tissue, but instead takes a general first-order approach to dispersion. Examples with a Gaussian beam pattern and realistic dispersion parameters are given along with general guidelines for identifying the features of the distorting wave that are the most compact.


      PubDate: 2014-03-03T07:21:15Z
       
  • Ultrasound-Stimulated Drug Delivery for Treatment of Residual Disease
           after Incomplete Resection of Head and Neck Cancer
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Anna G. Sorace , Melissa Korb , Jason M. Warram , Heidi Umphrey , Kurt R. Zinn , Eben Rosenthal , Kenneth Hoyt
      Microbubbles triggered with localized ultrasound (US) can improve tumor drug delivery and retention. Termed US-stimulated drug delivery, this strategy was applied to head and neck cancer (HNC) in a post-surgical tumor resection model. Luciferase-positive HNC squamous cell carcinoma (SCC) was implanted in the flanks of nude athymic mice (N = 24) that underwent various degrees of surgical tumor resection (0%, 50% or 100%). After surgery, animals received adjuvant therapy with cetuximab-IRDye alone, or cetuximab-IRDye in combination with US-stimulated drug delivery or saline injections (control) on days 4, 7 and 10. Tumor drug delivery was assessed on days 0, 4, 7, 10, 14 and 17 with an in vivo fluorescence imaging system, and tumor viability was evaluated at the same times with in vivo bioluminescence imaging. Tumor caliper measurements occurred two times per week for 24 d. Optical imaging revealed that in the 50% tumor resection group, US-stimulated drug delivery resulted in a significant increase in cetuximab delivery compared with administration of drug alone on day 10 (day of peak fluorescence) (p = 0.03). Tumor viability decreased in all groups that received cetuximab-IRDye in combination with US-stimulated drug delivery, compared with the group that received only the drug. After various degrees of surgical resection, this novel study reports positive improvements in drug uptake in the residual cancer cells when drug delivery is stimulated with US.


      PubDate: 2014-03-03T07:21:15Z
       
  • Physical Models of Tissue in Shear Fields11This article is dedicated to
           our friend and colleague, Robert C. Waag.
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Edwin L. Carstensen , Kevin J. Parker
      This review considers three general classes of physical as opposed to phenomenological models of the shear elasticity of tissues. The first is simple viscoelasticity. This model has a special role in elastography because it is the language in which experimental and clinical data are communicated. The second class of models involves acoustic relaxation, in which the medium contains inner time-dependent systems that are driven through the external bulk medium. Hysteresis, the phenomenon characterizing the third class of models, involves losses that are related to strain rather than time rate of change of strain. In contrast to the vast efforts given to tissue characterization through their bulk moduli over the last half-century, similar research using low-frequency shear data is in its infancy. Rather than a neat summary of existing facts, this essay is a framework for hypothesis generation—guessing what physical mechanisms give tissues their shear properties.


      PubDate: 2014-03-03T07:21:15Z
       
  • Editorial Advisory Board
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4




      PubDate: 2014-03-03T07:21:15Z
       
  • Contents
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4




      PubDate: 2014-03-03T07:21:15Z
       
  • Introduction to the Festschrift for Robert C. Waag
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Frederick W. Kremkau



      PubDate: 2014-03-03T07:21:15Z
       
  • Can Contrast-Enhanced Ultrasound Distinguish Malignant from Reactive Lymph
           Nodes in Patients with Head and Neck Cancers'
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Cristina Dudau , Shema Hameed , Daren Gibson , Senthil Muthu , Ann Sandison , Rob J. Eckersley , Peter Clarke , David O. Cosgrove , Adrian K. Lim
      The purpose of this study was to investigate the utility of contrast-enhanced ultrasound in differentiating benign from malignant cervical lymph nodes in patients with squamous cell carcinoma of the head and neck. A consecutive series of 17 patients with known head and neck malignancy scheduled for neck surgery and lymph node clearance were recruited for contrast-enhanced ultrasound evaluation. Sonographic signal intensity as a function of time, comparing features of time to peak, time to arrival and time to wash-out, was quantified. The selected node was removed surgically and submitted for histology. Contrast-enhanced ultrasound examination had 100% sensitivity and 85.7% specificity for lymph node involvement. Functional analysis revealed contrast peaks significantly earlier in the malignant nodes (mean ± standard deviation) of 24.14 ± 2.7 s compared with 29.33 ± 3.4 s (p = 0.0128). Contrast-enhanced ultrasound holds promise in the detection and characterization of metastatic nodes that would not be diagnosed as abnormal on the basis of conventional ultrasound criteria.


      PubDate: 2014-03-03T07:21:15Z
       
  • Effects of Vascularity and Differentiation of Hepatocellular Carcinoma on
           Tumor and Liver Stiffness: In Vivo and in Vitro Studies
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Wenwu Ling , Qiang Lu , Changli Lu , Jierong Quan , Lin Ma , Jiawu Li , Du He , Jianping Liu , Jiaying Yang , Tianfu Wen , Hong Wu , Hongguang Zhu , Yan Luo
      Tissue stiffness has been found to be a useful predictor of malignancy in various cancers. However, data on the stiffness of hepatocellular carcinomas (HCCs) and their background livers are contradictory. The aim of this study was to investigate the effects of vascularity and histologic differentiation on HCC stiffness. Elastography point quantification (ElastPQ), a new shear wave-based elastography method, was used to measure liver stiffness in vivo in 99 patients with pathology-proven HCC. Lesion vascularity was assessed using contrast-enhanced ultrasound, computed tomography and/or magnetic resonance imaging. The association of HCC vascularity and differentiation with liver stiffness was determined. In addition, in vitro stiffness of 20 of the 99 surgical HCC specimens was mechanically measured and compared with in vivo measurements. We found that in vivo stiffness was significantly higher than in vitro stiffness in both HCCs and their background livers (p < 0.0001). Moreover, significantly higher stiffness was observed in hyper-vascular and poorly differentiated lesions than in hypo-vascular (p = 0.0352) and moderately to well-differentiated lesions (p = 0.0139). These in vivo and in vitro studies reveal that shear wave-based ultrasound elasticity quantification can effectively measure in vivo liver stiffness.


      PubDate: 2014-03-03T07:21:15Z
       
  • Measuring Absolute Blood Pressure Using Microbubbles
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Charles Tremblay-Darveau , Ross Williams , Peter N. Burns
      Gas microbubbles are highly compressible, which makes them very efficient sound scatterers. As another consequence of their high compressibility, the radii of the microbubbles are affected by the pressure of the fluid around them, which changes their resonance frequency. Although the pressures present within the human body cause only minor variations in the radii of uncoated microbubbles (∼0.2% per 10 mmHg) and, therefore, very small variations in the resonance frequency (∼1 kHz per 10 mmHg), it was found in the work described here, through both simulations and in vitro measurements, that large changes in resonance frequency can occur in phospholipid-coated microbubbles for small blood pressure variations because of the exotic buckling dynamics of phospholipid monolayers (up to 240 kHz per 10 mmHg). This method should allow non-invasive measurement of the gauge blood pressure in deep blood vessels as long as the microbubble physical properties are well controlled.


      PubDate: 2014-03-03T07:21:15Z
       
  • Detection of Hepatic Hemodynamics in Normal Rhesus Monkeys Using
           High-Frequency Ultrasound
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Hong Wang , Pengfei Han , Xiaorong Sun , Jiandan Cai , Xin Fan , Yan Luo
      The rhesus monkey liver disease model provides useful information for hepatic research, as studies of hepatic hemodynamics in humans are rare. A 3-9 MHz high-frequency linear transducer (iU22, Philips Medical Systems, Royal Philips Electronics, The Netherlands) was used to obtain ultrasonograms of the livers of 28 normal rhesus monkeys (16 males, 12 females). Diameters of the portal vein and proper hepatic artery; maximum velocity of the portal vein; and peak-systolic and end-diastolic velocity and resistive index of the proper hepatic artery were also assessed. The portal vein and proper hepatic artery were 0.584 ± 0.123 and 0.151 ± 0.052 cm in diameter, respectively. The maximum velocity of the portal vein was 40.2 ± 13.7 cm/s. Peak systolic velocity and resistive index of the proper hepatic artery were 72.2 ± 25.4 cm/s and 0.67 ± 0.10, respectively. We found that high-frequency Doppler ultrasonography can be used to obtain clear portal vein and proper hepatic artery ultrasonograms and to measure the hemodynamic parameters of the portal vein and proper hepatic artery in rhesus monkeys. It is thus an effective method for studying changes in hepatic hemodynamics and has interesting technical and therapeutic implications. Our results provide useful information and establish normal reference values for future studies of adult healthy rhesus monkeys.


      PubDate: 2014-03-03T07:21:15Z
       
  • Relative Blood Flow Changes Measured Using Calibrated Frequency-Weighted
           Doppler Power at Different Hematocrit Levels
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Sean Wallace , Nicola Logallo , Kashif W. Faiz , Christian Lund , Rainer Brucher , David Russell
      In theory, the power of a trans-cranial Doppler signal may be used to measure changes in blood flow and vessel diameter in addition to velocity. In this study, a flow index (FI) of relative changes in blood flow was derived from frequency-weighted Doppler power signals. The FI, plotted against velocity, was calibrated to the zero intercept with absent flow to reduce the effects of non-uniform vessel insonation. An area index was also calculated. FIs were compared with actual flow in four silicone tubes of different diameter at increasing flow rates and increasing hematocrit (Hct) in a closed-loop phantom model. FI values were strongly correlated with actual flow, at constant Hct, but varied substantially with changes in Hct. Percentage changes in area indexes, relative to the 4-mm tube, were strongly correlated with tube cross-sectional area. The implications of these results for in vivo use are discussed.


      PubDate: 2014-03-03T07:21:15Z
       
  • Axial Transmission Method for Long Bone Fracture Evaluation by Ultrasonic
           Guided Waves: Simulation, Phantom and in Vitro Experiments
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Kailiang Xu , Dean Ta , Runxin He , Yi-Xian Qin , Weiqi Wang
      Mode conversion occurs when the ultrasonic guided waves encounter fractures. The aim of this study was to investigate the feasibility of fracture assessment in long cortical bone using guided-mode conversion. Mode conversion behavior between the fundamental modes S0 and A0 was analyzed. The expressions proposed for modal velocity were used to identify the original and converted modes. Simulations and phantom experiments were performed using 1.0-mm-thick steel plates with a notch width of 0.5 mm and notch depths of 0.2, 0.4, 0.6 and 0.8 mm. Furthermore, in vitro experiments were carried out on nine ovine tibias with 1.0-mm-wide partial transverse gap break and cortical thickness varying from 2.10 to 3.88 mm. The study confirmed that mode conversion gradually becomes observable as fracture depth increases. Energy percentages of the converted modes correlated strongly with fracture depth, as illustrated by the frequency-sweeping experiments on steel phantoms (100–1100 kHz, r 2 = 0.97, p < 0.0069) and the fixed-frequency experiments on nine ovine tibias (250 kHz, r 2 = 0.97, p < 0.0056). The approaches described, including mode excitation, velocity expressions and energy percentage criteria, may also contribute to ultrasonic monitoring of long bone fracture healing.


      PubDate: 2014-03-03T07:21:15Z
       
  • Phase Grouping-Based Needle Segmentation in 3-D Trans-rectal
           Ultrasound-Guided Prostate Trans-perineal Therapy
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Wu Qiu , Ming Yuchi , Mingyue Ding
      A robust and efficient needle segmentation method used to localize and track the needle in 3-D trans-rectal ultrasound (TRUS)-guided prostate therapy is proposed. The algorithmic procedure begins by cropping the 3-D US image containing a needle; then all voxels in the cropped 3-D image are grouped into different line support regions (LSRs) based on the outer product of the adjacent voxels' gradient vector. Two different needle axis extraction methods in the candidate LSR are presented: least-squares fitting and 3-D randomized Hough transform. Subsequent local optimization refines the position of the needle axis. Finally, the needle endpoint is localized by finding an intensity drop along the needle axis. The proposed methods were validated with 3-D TRUS tissue-mimicking agar phantom images, chicken breast phantom images and patient images obtained during prostate cryotherapy. The results of the in vivo test indicate that our method can localize the needle accurately and robustly with a needle endpoint localization accuracy <1.43 mm and detection accuracy >84%, which are favorable for 3-D TRUS-guided prostate trans-perineal therapy.


      PubDate: 2014-03-03T07:21:15Z
       
  • Model-Based Correction of Tissue Compression for Tracked Ultrasound in
           Soft Tissue Image-Guided Surgery
    • Abstract: Publication date: April 2014
      Source:Ultrasound in Medicine & Biology, Volume 40, Issue 4
      Author(s): Thomas S. Pheiffer , Reid C. Thompson , Daniel C. Rucker , Amber L. Simpson , Michael I. Miga
      Acquisition of ultrasound data negatively affects image registration accuracy during image-guided therapy because of tissue compression by the probe. We present a novel compression correction method that models sub-surface tissue displacement resulting from application of a tracked probe to the tissue surface. Patient landmarks are first used to register the probe pose to pre-operative imaging. The ultrasound probe geometry is used to provide boundary conditions to a biomechanical model of the tissue. The deformation field solution of the model is inverted to non-rigidly transform the ultrasound images to an estimation of the tissue geometry before compression. Experimental results with gel phantoms indicated that the proposed method reduced the tumor margin modified Hausdorff distance (MHD) from 5.0 ± 1.6 to 1.9 ± 0.6 mm, and reduced tumor centroid alignment error from 7.6 ± 2.6 to 2.0 ± 0.9 mm. The method was applied to a clinical case and reduced the tumor margin MHD error from 5.4 ± 0.1 to 2.6 ± 0.1 mm and the centroid alignment error from 7.2 ± 0.2 to 3.5 ± 0.4 mm.


      PubDate: 2014-03-03T07:21:15Z
       
  • Reverberation Clutter from Subcutaneous Tissue Layers: Simulation and
           in Vivo Demonstrations
    • Abstract: Publication date: Available online 14 February 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Jeremy J. Dahl , Niral M. Sheth
      The degradation of ultrasonic image quality is typically attributed to aberration and reverberation. Although the sources and impact of aberration are well understood, very little is known about the source and impact of image degradation caused by reverberation. Reverberation is typically associated with multiple reflections at two interfaces along the same propagation path, as with the arterial wall or a metal sphere. However, the reverberation that results in image degradation includes more complex interaction between the propagating wave and the tissue. Simulations of wave propagation in realistic and simplified models of the abdominal wall are used to illustrate the characteristics of coherent and diffuse clutter generated by reverberation. In the realistic models, diffuse reverberation clutter is divided into that originating from the tissue interfaces and that originating from sub-resolution diffuse scatterers. In the simplified models, the magnitude of the reverberation clutter is observed as angle and density of the connective tissue are altered. The results suggest that multi-path scattering from the connective tissue/fat interfaces is a dominant component of reverberation clutter. Diffuse reverberation clutter is maximal when the connective tissue is near normal to the beam direction and increases with the density of connective tissue layers at these large angles. The presence of a thick fascial or fibrous layer at the distal boundary of the abdominal wall magnifies the amount of reverberation clutter. The simulations also illustrate that compression of the abdominal layer, a technique often used to mitigate clutter in overweight and obese patients, increases the decay of reverberation clutter with depth. In addition, rotation of the transducer or steering of the beam with respect to highly reflecting boundaries can reduce coherent clutter and transform it to diffuse clutter, which can be further reduced using coherence-based beamforming techniques. In vivo images of the human bladder illustrate some of the reverberation effects observed in simulation.


      PubDate: 2014-02-16T07:20:09Z
       
 
 
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