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PHYSICS (563 journals)            First | 1 2 3 4 5 6 | Last

Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 1)
Science Foundation in China     Full-text available via subscription   (Followers: 2)
Scientific Reports     Open Access   (Followers: 10)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 17)
Sensor Letters     Full-text available via subscription   (Followers: 1)
Sensors and Actuators A: Physical     Hybrid Journal   (Followers: 62)
Services Computing, IEEE Transactions on     Hybrid Journal   (Followers: 3)
Shock and Vibration     Hybrid Journal   (Followers: 7)
Shock Waves     Hybrid Journal   (Followers: 4)
Small     Hybrid Journal   (Followers: 10)
Software Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 23)
Solid State Physics     Full-text available via subscription  
Solid-State Circuits Magazine, IEEE     Hybrid Journal   (Followers: 4)
South African Journal for Research in Sport, Physical Education and Recreation     Full-text available via subscription   (Followers: 4)
Space Research Journal     Open Access   (Followers: 2)
Space Weather     Full-text available via subscription   (Followers: 3)
Spectral Analysis Review     Open Access  
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy     Hybrid Journal   (Followers: 8)
Spectrochimica Acta Part B: Atomic Spectroscopy     Hybrid Journal   (Followers: 7)
Spectroscopy     Hybrid Journal   (Followers: 3)
Spectroscopy Letters: An International Journal for Rapid Communication     Hybrid Journal   (Followers: 3)
Sri Lankan Journal of Physics     Open Access  
Strain     Hybrid Journal   (Followers: 2)
Strength of Materials     Hybrid Journal   (Followers: 5)
Strength, Fracture and Complexity     Hybrid Journal   (Followers: 1)
Structural Dynamics     Open Access  
Studies In Applied Mathematics     Hybrid Journal   (Followers: 1)
Superconductor Science and Technology     Hybrid Journal   (Followers: 1)
Surface Engineering     Hybrid Journal   (Followers: 3)
Surface Review and Letters     Hybrid Journal   (Followers: 1)
Surface Science Reports     Full-text available via subscription   (Followers: 14)
Surface Science Spectra     Hybrid Journal  
Surface Topography : Metrology and Properties     Full-text available via subscription  
Synchrotron Radiation News     Hybrid Journal   (Followers: 2)
Synthetic Metals     Hybrid Journal   (Followers: 3)
Technical Physics     Hybrid Journal  
Technical Physics Letters     Hybrid Journal  
Tectonics     Full-text available via subscription   (Followers: 9)
The Astronomy and Astrophysics Review     Hybrid Journal   (Followers: 2)
The Chemical Physics of Solid Surfaces     Full-text available via subscription  
The European Physical Journal H     Hybrid Journal   (Followers: 1)
The European Physical Journal Plus     Open Access  
The International Journal of Multiphysics     Full-text available via subscription   (Followers: 2)
The Physics of Metals and Metallography     Hybrid Journal   (Followers: 4)
The Physics Teacher     Full-text available via subscription   (Followers: 5)
Theoretical and Computational Fluid Dynamics     Hybrid Journal   (Followers: 7)
Theoretical and Mathematical Physics     Hybrid Journal   (Followers: 4)
Topological Quantum Matter     Open Access  
Transport Theory and Statistical Physics     Hybrid Journal   (Followers: 3)
Tribology International     Hybrid Journal   (Followers: 32)
Tribology Letters     Hybrid Journal   (Followers: 5)
Tribotest     Hybrid Journal   (Followers: 1)
Turkish Journal of Physics     Open Access  
Ultrasonics     Hybrid Journal   (Followers: 4)
Ultrasonics Sonochemistry     Hybrid Journal   (Followers: 2)
Ultrasound in Medicine & Biology     Full-text available via subscription   (Followers: 6)
Universal Journal of Physics and Application     Open Access  
Western Journal of Communication     Hybrid Journal   (Followers: 5)
Women & Performance: a journal of feminist theory     Hybrid Journal   (Followers: 3)
Women in Engineering Magazine, IEEE     Full-text available via subscription   (Followers: 8)
World Journal of Condensed Matter Physics     Open Access  
X-Acoustics: Imaging and Sensing : Photoacoustics, Thermoacoustics, Magnetoacoustics     Open Access  
Zeitschrift für angewandte Mathematik und Physik     Hybrid Journal   (Followers: 1)

  First | 1 2 3 4 5 6 | Last

Journal Cover   Ultrasound in Medicine & Biology
  [SJR: 0.939]   [H-I: 91]   [8 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0301-5629
   Published by Elsevier Homepage  [2588 journals]
  • Hemodynamic Effects of Proximal Supra-aortic Artery Stenosis on Anterior
           Cerebral Artery
    • Abstract: Publication date: Available online 29 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Nicolás López-Hernández , Alejandro García-Escrivá , Federico Ballenilla , Jose Ignacio Gallego-Leon
      Alternating flow in the anterior cerebral artery is a rare finding, associated with innominate artery stenosis. We present a series of four patients with this finding on transcranial color coded sonography, under basal conditions. In all of these patients, vascular studies detected an ipsilateral proximal stenosis, three in the innominate artery and, for the first time, one at the left common carotid artery origin. Successful angioplasties with stenting were performed, resulting for the first time in the normalization of orthograde flow in all cases. We conclude that an early systolic hemodynamic compromise in the first segment of the anterior cerebral artery, in the form of alternating flow, is an indirect indicator of ipsilateral proximal stenosis in the supra-aortic arteries, either in the innominate artery or at the origin of the left common carotid artery.


      PubDate: 2015-02-06T01:04:43Z
       
  • In Memoriam: Hector Lopez, 1947–2014
    • Abstract: Publication date: Available online 31 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Ernest Joseph Feleppa



      PubDate: 2015-02-06T01:04:43Z
       
  • Investigation into the Mechanisms of Tissue Atomization by High-Intensity
           Focused Ultrasound
    • Abstract: Publication date: Available online 3 February 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Julianna C. Simon , Oleg A. Sapozhnikov , Yak-Nam Wang , Vera A. Khokhlova , Lawrence A. Crum , Michael R. Bailey
      Ultrasonic atomization, or the emission of a fog of droplets, was recently proposed to explain tissue fractionation in boiling histotripsy. However, even though liquid atomization has been studied extensively, the mechanisms underlying tissue atomization remain unclear. In the work described here, high-speed photography and overpressure were used to evaluate the role of bubbles in tissue atomization. As static pressure increased, the degree of fractionation decreased, and the ex vivo tissue became thermally denatured. The effect of surface wetness on atomization was also evaluated in vivo and in tissue-mimicking gels, where surface wetness was found to enhance atomization by forming surface instabilities that augment cavitation. In addition, experimental results indicated that wetting collagenous tissues, such as the liver capsule, allowed atomization to breach such barriers. These results highlight the importance of bubbles and surface instabilities in atomization and could be used to enhance boiling histotripsy for transition to clinical use.


      PubDate: 2015-02-06T01:04:43Z
       
  • Bas-Relief Map Using Texture Analysis with Application to Live Enhancement
           of Ultrasound Images
    • Abstract: Publication date: Available online 29 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Huarui Du , Rui Ma , Xiaoying Wang , Jue Zhang , Jing Fang
      For ultrasound imaging, speckle is one of the most important factors in the degradation of contrast resolution because it masks meaningful texture and has the potential to interfere with diagnosis. It is expected that researchers would explore appropriate ways to reduce the speckle noise, to find the edges of structures and enhance weak borders between different organs in ultrasound imaging. Inspired by the principle of differential interference contrast microscopy, a “bas-relief map” is proposed that depicts the texture structure of ultrasound images. Based on a bas-relief map, an adaptive bas-relief filter was developed for ultrafast despeckling. Subsequently, an edge map was introduced to enhance the edges of images in real time. The holistic bas-relief map approach has been used experimentally with synthetic phantoms and digital ultrasound B-scan images of liver, kidney and gallbladder. Based on the visual inspection and the performance metrics of the despeckled images, it was found that the bas-relief map approach is capable of effectively reducing the speckle while significantly enhancing contrast and tissue boundaries for ultrasonic images, and its speckle reduction ability is comparable to that of Kuan, Lee and Frost filters. Meanwhile, the proposed technique could preserve more intra-region details compared with the popular speckle reducing anisotropic diffusion technique and more effectively enhance edges. In addition, the adaptive bas-relief filter was much less time consuming than the Kuan, Lee and Frost filter and speckle reducing anisotropic diffusion techniques. The bas-relief map strategy is effective for speckle reduction and live enhancement of ultrasound images, and can provide a valuable tool for clinical diagnosis.


      PubDate: 2015-02-06T01:04:43Z
       
  • Quantifying Activation of Perfluorocarbon-Based Phase-Change Contrast
           Agents Using Simultaneous Acoustic and Optical Observation
    • Abstract: Publication date: Available online 2 February 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Sinan Li , Shengtao Lin , Yi Cheng , Terry O. Matsunaga , Robert J. Eckersley , Meng-Xing Tang
      Phase-change contrast agents in the form of nanoscale droplets can be activated into microbubbles by ultrasound, extending the contrast beyond the vasculature. This article describes simultaneous optical and acoustical measurements for quantifying the ultrasound activation of phase-change contrast agents over a range of concentrations. In experiments, decafluorobutane-based nanodroplets of different dilutions were sonicated with a high-pressure activation pulse and two low-pressure interrogation pulses immediately before and after the activation pulse. The differences between the pre- and post-interrogation signals were calculated to quantify the acoustic power scattered by the microbubbles activated over a range of droplet concentrations. Optical observation occurred simultaneously with the acoustic measurement, and the pre- and post-microscopy images were processed to generate an independent quantitative indicator of the activated microbubble concentration. Both optical and acoustic measurements revealed linear relationships to the droplet concentration at a low concentration range <108/mL when measured at body temperature. Further increases in droplet concentration resulted in saturation of the acoustic interrogation signal. Compared with body temperature, room temperature was found to produce much fewer and larger bubbles after ultrasound droplet activation.


      PubDate: 2015-02-06T01:04:43Z
       
  • Prenatal Exposure to Ultrasound Affects Learning and Memory in Young Rats
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Ping Li , Pei-jun Wang , Wei Zhang
      Prenatal exposure to ultrasound may cause cognitive impairments in experimental animals; however, the exact mechanisms remain unknown. In this study, we exposed pregnant rats (or sham-exposed controls) to different intensities of ultrasound repeatedly on days 6, 12 and 18 of pregnancy for 4 min (3.5 MHz, spatial peak time average intensity = 7.6 mW/cm2, mechanical index = 0.1, thermal index bone = 0.1: 4-min group) or 20 min (3.5 MHz, spatial peak time average intensity = 106 mW/cm2, mechanical index = 1.4, thermal index bone = 1.0: 20-min group). The Morris water maze was used to assess learning and memory function in pups at 2 mo of age. Noticeable deficits in behavior occurred in the group exposed to ultrasound for 20 min. Using real-time polymerase chain reaction and Western blot, we also determined that both the mRNA and protein expression levels of hippocampal N-methyl-D-aspartate (NMDA) receptor units 1 (NR1) and 2B (NR2B) and brain-derived neurotrophic factor (BDNF) were significantly lower in pups exposed to ultrasound for 20 min than in controls. Furthermore, the morphology of the synapses in the hippocampus was partially damaged. Compared with the control group, the 4-min group had better spatial learning and memory abilities, as well as higher mRNA and protein levels of NR1, NR2B and BDNF. Our study suggests that high-intensity ultrasound irradiation can decrease learning and memory abilities by reducing the expression of NR1, NR2B and BDNF in the hippocampal regions and damaging the structure of synapses. In contrast, low-intensity ultrasound irradiation can enhance the learning and memory abilities of the offspring rats by increasing the expression of NR1, NR2B and BDNF receptor in the hippocampal regions.


      PubDate: 2015-01-30T00:19:25Z
       
  • Multifrequency Time-Harmonic Elastography for the Measurement of Liver
           Viscoelasticity in Large Tissue Windows
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Heiko Tzschätzsch , Selcan Ipek-Ugay , Manh Nguyen Trong , Jing Guo , Jonathan Eggers , Enno Gentz , Thomas Fischer , Michael Schultz , Jürgen Braun , Ingolf Sack
      Elastography of the liver for the non-invasive diagnosis of hepatic fibrosis is an established method. However, investigations of obese patients or patients with ascites are often limited by small and superficial elastographic windows. Therefore, multifrequency time-harmonic elastography (THE) based on time-resolved A-line ultrasound has recently been developed for measuring liver viscoelasticity in wide soft tissue windows and at greater depths. In this study, THE was integrated into a clinical B-mode scanner connected to a dedicated actuator bed driven by superimposed vibrations of 30- to 60-Hz frequencies. The resulting shear waves in the liver were captured along multiple profiles 7 to 14 cm in width and automatically processed for reconstruction of mean efficient shear wave speed and shear wave dispersion slope. This new modality was tested in healthy volunteers and 22 patients with clinically proven cirrhosis. Patients could be separated from controls by higher shear wave speeds (3.11 ± 0.64 m/s, 2.14–4.81 m/s, vs. 1.74 ± 0.10 m/s, 1.60–1.91 m/s) without significant degradation of data by high body mass index or ascites. Furthermore, the wave speed dispersion slope was significantly (p = 0.0025) lower in controls (5.2 ± 1.8 m/s/kHz) than in patients (39.1 ± 32.2 m/s/kHz). In conclusion, THE is useful for the diagnosis of cirrhosis in large tissue windows.


      PubDate: 2015-01-30T00:19:25Z
       
  • Acoustic Radiation Force Impulse Elastography of the Liver in Healthy
           Patients: Test Location, Reference Range and Influence of Gender and Body
           Mass Index
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Li-Ying Liao , Kuan-Liang Kuo , Huei-Shin Chiang , Chong-Zong Lin , Yi-Ping Lin , Chih-Lin Lin
      The objective of this study was to evaluate the best test location and study factors associated with acoustic radiation force impulse (ARFI) elastography measurements in healthy individuals. When ARFI elastography was performed on 68 healthy patients after controlling for all known test condition factors except segmental location, the median shear wave velocities (SWVs) derived from five valid measurements in the area between S5 and S8 in patients in the supine position had a significantly lower mean and the narrowest 95% confidence interval, followed by those for the S8 supine and S8 semidecubitus locations (p = 0.045). Analysis of mean SWVs revealed similar, although statistically insignificant, findings (p = 0.078). Male patients had significantly higher median SWVs (p = 0.0073) and mean SWVs (p = 0.0043) than female patients. Patients with body mass indexes >22 had significantly lower median SWVs (p = 0.0033) and mean SWVs (p = 0.0008) than those with body mass indexes ≤22. S5/8 supine was the better test location for ARFI. The reference ranges for median and mean SWV were 0.81–1.27 and 0.82–1.27 m/s, respectively. Gender and body mass index, but not age, were the significant factors associated with ARFI SWV values.


      PubDate: 2015-01-30T00:19:25Z
       
  • Influence of Temperature-Dependent Thermal Parameters on Temperature
           Elevation of Tissue Exposed to High-Intensity Focused Ultrasound:
           Numerical Simulation
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Sitaramanjaneya Reddy Guntur , Min Joo Choi
      High-intensity focused ultrasound (HIFU) has been used successfully as a non-invasive modality in treating solid tumors. The temperature rise HIFU irradiation causes in a tissue depends on the thermal properties of the tissue. This study was motivated by our observation that the thermal properties of a tissue vary significantly with temperature (Guntur SR, Lee KI, Paeng DG, Coleman AJ, Choi MJ. Ultrasound Med Biol 2013;39:1771–1784). This research investigated how significantly the alteration of tissue thermal parameters, in the ranges of values measured at 25°C–90°C, affects prediction of the temperature elevation of tissue under the same HIFU exposure. The numerical simulation was performed by coupling a non-linear Khokhlov–Zabolotskaya–Kuznetsov equation with a bio-heat transfer function. In the conventional method of prediction, the thermal parameters were set as constants measured at room temperature (25°C). This study compared the conventional prediction with those predicted with different thermal parameters measured at the various temperatures up to 90°C. The results indicated that the conventional method significantly overestimated the rise in focal temperature in the liver tissue exposed to a clinical HIFU field, compared with the prediction made using thermal parameters measured at temperatures that cause thermal denaturation. This finding suggests that temperature-dependent thermal parameters should be considered in predicting the temperature rise in a tissue to avoid use of an insufficient thermal dose in treatment planning for HIFU surgery.


      PubDate: 2015-01-30T00:19:25Z
       
  • Non-invasive Ultrasound to Identify Eosinophil Granule Proteins in
           Eosinophilic Esophagitis
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Hedieh Saffari , Anne Kennedy , Kathryn A. Peterson , Gerald J. Gleich , Leonard F. Pease III
      Although traditional microbubble contrast agents are bright, the high contrast of gas bubbles and air–water interfaces in the upper gastrointestinal tract renders these agents less useful for diagnosing diseases such as eosinophilic esophagitis, a disease characterized by patchy infiltration of eosinophils into the esophagus. Here we report a first-in-class ultrasound contrast enhancement agent composed of echogenic insulin particles, which are labeled with molecular recognition elements to diagnose eosinophil-associated diseases. We prepared solid echogenic insulin particles, tethered antibodies to eosinophil granule major basic protein 1 (MBP-1) to their surfaces and experimentally evaluated binding of these agents to MBP-1 on ex vivo non-human primate esophagi. We found that insulin particles can be readily observed by ultrasound and bind to MBP-1-coated esophagi within minutes. Our results suggest the potential of this new class of solid contrast agents to image, diagnose and improve management of eosinophilic esophagitis.


      PubDate: 2015-01-30T00:19:25Z
       
  • Quantitative Ultrasound Assessment of the Facet Joint in the Lumbar Spine:
           A Feasibility Study
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Da Liu , Ying Huang , Dan Tian , Jing Yin
      This study was designed to determine the feasibility and accuracy of a sonographic approach to assessment of facet joints of the lumbar spine in healthy populations. Five facet joints (L1–S1) on each side of 30 volunteers, for a total of 300 facet joints, were examined and evaluated by sonography and computed tomography. Parameters of the facet joints (height and width) were established to assess the facet joint in the parasagittal and transverse planes on all volunteers. Differences between means of continuous variables including age, height, weight, body surface area, body mass index and joint parameters were evaluated with Student's t-test. Stepwise multiple regression analysis was used to evaluate the associations between the mean values of facet joint parameters and age, height, body surface area and body mass index. In general, sonography revealed that facet joints had a clear and smooth border. There were no significant differences in width and height between the left and right facet joints at the same level by sonography. Stepwise multiple regression analysis revealed that body mass index and age (p < 0.05) were the only independent factors modulating height of the facet joint. Facet joint width was independently influenced by age (p < 0.01). There were no significant differences between ultrasound and computed tomography in mean measurements of height (1.23 ± 0.15 vs. 1.25 ± 0.07, p > 0.05) and width (0.17 ± 0.08 vs. 0.18 ± 0.07, p > 0.05) of the facet joint, respectively. In this article, we describe a feasible, accurate and simple technique for identification and depiction of facet joints of the lumbar spine in healthy populations.


      PubDate: 2015-01-30T00:19:25Z
       
  • Improved Correlation between Carotid and Coronary Atherosclerosis SYNTAX
           Score Using Automated Ultrasound Carotid Bulb Plaque IMT Measurement
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Nobutaka Ikeda , Ajay Gupta , Nilanjan Dey , Soumyo Bose , Shoaib Shafique , Tadashi Arak , Elisa Cuadrado Godia , Luca Saba , John R. Laird , Andrew Nicolaides , Jasjit S. Suri
      Described here is a detailed novel pilot study on whether the SYNTAX (Synergy between percutaneous coronary intervention with TAXUS and cardiac surgery) score, a measure of coronary artery disease complexity, could be better predicted with carotid intima–media thickness (cIMT) measures using automated IMT all along the common carotid and bulb plaque compared with manual IMT determined by sonographers. Three hundred seventy consecutive patients who underwent carotid ultrasound and coronary angiography were analyzed. SYNTAX score was determined from coronary angiograms by two experienced interventional cardiologists. Unlike most methods of cIMT measurement commonly used by sonographers, our method involves a computerized automated cIMT measurement all along the carotid artery that includes the bulb region and the region proximal to the bulb (under the class of AtheroEdge systems from AtheroPoint, Roseville, CA, USA). In this study, the correlation between automated cIMT that includes bulb plaque and SYNTAX score was found to be 0.467 (p < 0.0001), compared with 0.391 (p < 0.0001) for the correlation between the sonographer's IMT reading and SYNTAX score. The correlation between the automated cIMT and the sonographer's IMT was 0.882. When compared against the radiologist's manual tracings, automated cIMT system performance had a lumen–intima error of 0.007818 ± 0.0071 mm, media–adventitia error of 0.0179 ± 0.0125 mm and automated cIMT error of 0.0099 ± 0.00988 mm. The precision of automated cIMT against the manual radiologist's reading was 98.86%. This current automated algorithm revealed a significantly stronger correlation between cIMT and coronary SYNTAX score as compared with the sonographer's cIMT measurements with multiple cardiovascular risk factors. We benchmarked our correlation between the automated cIMT that includes bulb plaque and SYNTAX score against a previously published (Ikeda et al. 2013) AtheroEdgeLink (AtheroPoint) correlation between the automated cIMT that does not include bulb plaque and SYNTAX score and had an improvement of 44.58%. By sampling cIMT in the bulb region, the automated cIMT technique improves the degree of correlation between coronary artery disease lesion complexity and carotid atherosclerosis characteristics.


      PubDate: 2015-01-30T00:19:25Z
       
  • Quantitative Sonography of Basal Cell Carcinoma
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Hanna Piotrzkowska-Wroblewska , Jerzy Litniewski , Elzbieta Szymanska , Andrzej Nowicki
      A 30-MHz ultrasonic scanner was used to collect B-scan images together with appropriate radiofrequency echoes from diseased and healthy skin regions of patients with diagnosed basal cell carcinoma and pre-cancerous lesions (actinic keratosis). Radiofrequency data were processed to obtain the attenuation coefficient and statistics of the backscattered echo signal determination (K-distribution and effective density of scatterers [EDS]). The attenuation coefficient was significantly higher for patients with basal cell carcinoma than for healthy patients. Also, the pre-cancerous skin lesions had increased attenuation. The averaged EDS values for cancer lesions were significantly lower than those for pre-cancerous lesions and healthy skin. The successful differentiation between the tissue groups examined suggests the potential value of the attenuation coefficient and EDS for carcinoma characterization.


      PubDate: 2015-01-30T00:19:25Z
       
  • Semi-automated Tracking and Continuous Monitoring of Inferior Vena Cava
           Diameter in Simulated and Experimental Ultrasound Imaging
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Luca Mesin , Paolo Pasquero , Stefano Albani , Massimo Porta , Silvestro Roatta
      Assessment of respirophasic fluctuations in the diameter of the inferior vena cava (IVC) is detrimentally affected by its concomitant displacements. This study was aimed at presenting and validating a method to compensate for IVC movement artifacts while continuously measuring IVC diameter in an automated fashion (with minimal interaction with the user) from a longitudinal B-mode ultrasound clip. Performance was tested on both experimental ultrasound clips collected from four healthy patients and simulations, implementing rigid IVC displacements and pulsation. Compared with traditional M-mode measurements, the new approach systematically reduced errors in caval index assessment (range over maximum diameter value) to an extent depending on individual vessel geometry, IVC movement and choice of the M-line (the line along which the diameter is computed). In experimental recordings, this approach identified both the cardiac and respiratory components of IVC movement and pulsatility and evidenced the spatial dependence of IVC pulsatility. IVC tracking appears to be a promising approach to reduce movement artifacts and to improve the reliability of IVC diameter monitoring.


      PubDate: 2015-01-30T00:19:25Z
       
  • GPU-Based Minimum Variance Beamformer for Synthetic Aperture Imaging of
           the Eye
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Billy Y.S. Yiu , Alfred C.H. Yu
      Minimum variance (MV) beamforming has emerged as an adaptive apodization approach to bolster the quality of images generated from synthetic aperture ultrasound imaging methods that are based on unfocused transmission principles. In this article, we describe a new high-speed, pixel-based MV beamforming framework for synthetic aperture imaging to form entire frames of adaptively apodized images at real-time throughputs and document its performance in swine eye imaging case examples. Our framework is based on parallel computing principles, and its real-time operational feasibility was realized on a six-GPU (graphics processing unit) platform with 3,072 computing cores. This framework was used to form images with synthetic aperture imaging data acquired from swine eyes (based on virtual point-source emissions). Results indicate that MV-apodized image formation with video-range processing throughput (>20 fps) can be realized for practical aperture sizes (128 channels) and frames with λ/2 pixel spacing. Also, in a corneal wound detection experiment, MV-apodized images generated using our framework revealed apparent contrast enhancement of the wound site (10.8 dB with respect to synthetic aperture images formed with fixed apodization). These findings indicate that GPU-based MV beamforming can, in real time, potentially enhance image quality when performing synthetic aperture imaging that uses unfocused firings.


      PubDate: 2015-01-30T00:19:25Z
       
  • Delivery of Molecules to the Lymph Node via Lymphatic Vessels Using
           Ultrasound and Nano/Microbubbles
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Shigeki Kato , Yuko Shirai , Hiroyuki Kanzaki , Maya Sakamoto , Shiro Mori , Tetsuya Kodama
      Lymph node (LN) dissection is the primary option for head and neck cancer when imaging modalities and biopsy confirm metastasis to the sentinel LN. However, there are no effective alternative treatments to dissection for LN metastasis. Here, we describe a novel drug delivery system combining nano/microbubbles (NMBs) with ultrasound (US) that exhibits considerable potential for the delivery of exogenous molecules into LNs through the lymphatic vessels. A solution containing fluorophores (as a model of a therapeutic molecule) and NMBs was injected into the subiliac LNs of MXH10/Mo-lpr/lpr mice, which develop systemic swelling of LNs (up to 13 mm in diameter, similar to human LNs). It was found that the NMBs were delivered to the entire area of the proper axillary LN (proper-ALN) via the lymphatic channels and that these were retained there for more than 8 min. Furthermore, exposure to US in the presence of NMBs enhanced the delivery of fluorophores into the lymphocytes near the lymphatic channels, compared with exposure to US in the absence of NMBs. It is proposed that a system using US and NMBs to deliver therapeutic drugs via lymphatic vessels can serve as a new treatment method for LN metastasis.


      PubDate: 2015-01-30T00:19:25Z
       
  • Measurement of Quantitative Viscoelasticity of Bovine Corneas Based on
           Lamb Wave Dispersion Properties
    • Abstract: Publication date: Available online 28 January 2015
      Source:Ultrasound in Medicine & Biology
      Author(s): Xinyu Zhang , Yin Yin , Yanrong Guo , Ning Fan , Haoming Lin , Fulong Liu , Xianfen Diao , Changfeng Dong , Xin Chen , Tianfu Wang , Siping Chen
      The viscoelastic properties of the human cornea can provide valuable information for clinical applications such as the early detection of corneal diseases, better management of corneal surgery and treatment and more accurate measurement of intra-ocular pressure. However, few techniques are capable of quantitatively and non-destructively assessing corneal biomechanics in vivo. The cornea can be regarded as a thin plate in which the vibration induced by an external vibrator propagates as a Lamb wave, the properties of which depend on the thickness and biomechanics of the tissue. In this study, pulses of ultrasound radiation force with a repetition frequency of 100 or 200 Hz were applied to the apex of corneas, and the linear-array transducer of a SonixRP system was used to track the tissue motion in the radial direction. Shear elasticity and viscosity were estimated from the phase velocities of the A0 Lamb waves. To assess the effectiveness of the method, some of the corneas were subjected to collagen cross-linking treatment, and the changes in mechanical properties were validated with a tensile test. The results indicated that the shear modulus was 137 ± 37 kPa and the shear viscosity was 3.01 ± 2.45 mPa·s for the group of untreated corneas and 1145 ± 267 kPa and was 0.16 ± 0.11 mPa·s for the treated group, respectively, implying a significant increase in elasticity and a significant decrease in viscosity after collagen cross-linking treatment. This result is in agreement with the results of the mechanical tensile test and with reports in the literature. This initial investigation illustrated the ability of this ultrasound-based method, which uses the velocity dispersion of low-frequency A0 Lamb waves, to quantitatively assess both the elasticity and viscosity of corneas. Future studies could discover ways to optimize this system and to determine the feasibility of using this method in clinical situations.


      PubDate: 2015-01-30T00:19:25Z
       
  • Global and Regional Left Ventricular Strain Indices in Post-Myocardial
           Infarction Patients with Ventricular Arrhythmias and Moderately Abnormal
           Ejection Fraction
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Bich Lien Nguyen , Lidia Capotosto , Alessandro Persi , Attilio Placanica , Asim Rafique , Gianfranco Piccirillo , Carlo Gaudio , Eli S. Gang , Robert J. Siegel , Antonio Vitarelli
      The aim of the study described here was to compare myocardial strains in ischemic heart patients with and without sustained ventricular tachycardia (VT) and moderately abnormal left ventricular ejection fraction (LVEF) to investigate which index could better predict VT on the basis of the analysis of global and regional left ventricular (LV) dysfunction. We studied 467 patients with previous myocardial infarction and LVEF >35%. Fifty-one patients had documented VT, and 416 patients presented with no VT. LV volumes and score index were obtained by 2-D echocardiography. Longitudinal, radial and circumferential strains were determined. Strains of the infarct, border and remote zones were also obtained. There were no differences in standard LV 2-D parameters between patients with and those without VT. Receiver operating characteristic values were −12.7% for global longitudinal strain (area under the curve [AUC] = 0.72), −4.8% for posterior-inferior wall circumferential strain (AUC = 0.80), 61 ms for LV mechanical dispersion (AUC = 0.84), −10.1% for longitudinal strain of the border zone (AUC = 0.86) and −9.2% for circumferential strain of the border zone (AUC = 0.89). In patients with previous myocardial infarction and moderately abnormal LVEF, peri-infarct circumferential strain was the strongest predictor of documented ventricular arrhythmias among all strain quantitative indices. Additionally, strain values from posterior-inferior wall infarctions had a higher association with arrhythmic events compared with global strain.


      PubDate: 2015-01-16T23:01:53Z
       
  • Using Critical Care Chest Ultrasonic Examination in Emergency
           Consultation: A Pilot Study
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Xiaoting Wang , Dawei Liu , Huaiwu He , Wei Du , Hongmin Zhang , Ye Liu , Wenzhao Chai , Qing Zhang , Xiang Zhou
      The purpose of this study was to investigate the effects of critical care chest ultrasonic examination (CCUE) by intensivist on the diagnosis and treatment decisions in emergent consultation for patients who may have a problem-need transfer to an intensive care unit (ICU). A total of 130 patients who required emergent consultation in the ordinary wards were included in this study. Patients were randomly divided into conventional group (n = 63) and CCUE group (n = 67, added CCUE). The two groups showed no significant differences in general clinical information or final diagnosis (p > 0.05). The CCUE group had a shorter time to preliminary diagnosis, final diagnosis, treatment response and X-ray/computed tomography examination; a delay in ICU transfer and ICU stay days (3.9 ± 1.2 vs. 5.4 ± 1.9 d, p < 0.05) and a higher diagnostic accuracy than the conventional group (p < 0.001). In conclusion, CCUE could help early diagnosis and therapy for the patient who may need to transfer to the ICU and reduce the ICU stay for in-hospital patients in emergent consultation.


      PubDate: 2015-01-16T23:01:53Z
       
  • Diagnosis of Thyroid Nodules Using Virtual Touch Tissue Quantification
           Value and Anteroposterior/Transverse Diameter Ratio
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Tao Li , Pei Zhou , Xuming Zhang , Mingyue Ding , Ming Yuchi , Yiyong Li
      This paper proposes an effective approach to differential diagnosis of thyroid nodules using a hierarchical classification model based on the Virtual Touch tissue quantification (VTQ) value and anteroposterior/transverse diameter (A/T) ratio. One hundred twenty nodules (92 benign, 28 malignant) were analyzed using this approach by combining the quantitative elastic characteristic with the conventional sonographic feature. First, nodules were classified as benign (VTQ values <2.27 m/s), malignant (VTQ values >2.73 m/s) and indeterminate (2.27 m/s ≤ VTQ values ≤2.73 m/s) using two cutoff points selected on the basis of receiver operating characteristic analysis. Second, the indeterminate nodules were separated into malignant and benign nodules using an A/T ratio ≥1. The advantage of this approach was that it could alleviate the limitation of an overlap in VTQ values between benign and malignant nodules. According to the pathologic results, the accuracy of this approach was 95%. The proposed approach may potentially improve diagnostic accuracy.


      PubDate: 2015-01-16T23:01:53Z
       
  • Ultrasound of the Pleurae and Lungs
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Christoph F. Dietrich , Gebhard Mathis , Xin-Wu Cui , Andre Ignee , Michael Hocke , Tim O. Hirche
      The value of ultrasound techniques in examination of the pleurae and lungs has been underestimated over recent decades. One explanation for this is the assumption that the ventilated lungs and the bones of the rib cage constitute impermeable obstacles to ultrasound. However, a variety of pathologies of the chest wall, pleurae and lungs result in altered tissue composition, providing substantially increased access and visibility for ultrasound examination. It is a great benefit that the pleurae and lungs can be non-invasively imaged repeatedly without discomfort or radiation exposure for the patient. Ultrasound is thus particularly valuable in follow-up of disease, differential diagnosis and detection of complications. Diagnostic and therapeutic interventions in patients with pathologic pleural and pulmonary findings can tolerably be performed under real-time ultrasound guidance. In this article, an updated overview is given presenting not only the benefits and indications, but also the limitations of pleural and pulmonary ultrasound.


      PubDate: 2015-01-16T23:01:53Z
       
  • Masthead
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2




      PubDate: 2015-01-16T23:01:53Z
       
  • Editorial Advisory Board
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2




      PubDate: 2015-01-16T23:01:53Z
       
  • Contents
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2




      PubDate: 2015-01-16T23:01:53Z
       
  • Role of Shear Wave Sonoelastography in Differentiation Between Focal
           Breast Lesions
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Katarzyna Dobruch-Sobczak , Andrzej Nowicki
      Our goal in this study was to evaluate the relevance of shear wave sonoelastography (SWE) in the differential diagnosis of masses in the breast with respect to ultrasound (US). US and SWE were performed (Aixplorer System, SuperSonic Imagine, Aix en Provence, France) in 76 women (aged 24 to 85) with 84 lesions (43 malignant, 41 benign). The study included BI-RADS-US (Breast Imaging Reporting and Data System for Ultrsound) category 3–5 lesions. In elastograms, the following values were calculated: mean elasticity in lesions (E av.l) and in fat tissue (E av.f.) and maximal (E max.adj.) and mean (E av.adj.) elasticity in lesions and adjacent tissues. The sensitivity and specificity of the BI-RADS category 4a/4b cutoff value were 97.7% and 90.2%. For an E av.adj. of 68.5 kPa, the cutoff sensitivity was 86.1% and the specificity was 87.8%, and for an E max.adj. of 124.1 kPa, 74.4% and 92.7%, respectively. For BI-RADS-US category 3 lesions, E av.l, E max.adj. and E av.adj. were below cutoff levels. On the basis of our findings, E av.adj. had lower sensitivity and specificity compared with US. E max.adj. improved the specificity of breast US with loss of sensitivity.


      PubDate: 2015-01-16T23:01:53Z
       
  • Musculoskeletal Ultrasound Ian Beggs, editor. Lippincott Williams
           &amp; Wilkins, Philadelphia, PA, USA, 2014, 339 pages. ISBN:
           978-1-4511-4498-7
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Joseph Fournier



      PubDate: 2015-01-16T23:01:53Z
       
  • Calendar
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2




      PubDate: 2015-01-16T23:01:53Z
       
  • Reliability of Superficial Male Pelvic Floor Structural Measurements Using
           Linear-Array Transperineal Sonography
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Shawn C. Roll , Manku Rana , Susan M. Sigward , Moheb S. Yani , Daniel J. Kirages , Jason J. Kutch
      This study evaluated reliability of measures for superficial structures of the male pelvic floor (PF) obtained via transperineal sonography. Two embalmed cadavers were dissected to identify positioning of muscles on and around the bulb of the penis and to confirm the PF protocol. Cross-sectional area (CSA) and linear thickness of the bulb of the penis, urethra, bulbospongiosus (BS) muscles, and ischiocavernosus (IC) muscles were measured on 38 transverse images from 20 male patients by three raters with varied study knowledge and sonographic experience. Intra- and inter-rater reliability were calculated with two-way, mixed effects intra-class correlation coefficients. Measures of the bulb of the penis had the best reliability. CSA of all muscles and sagittal thickness of the BS near the central tendon had good reliability. Reliability varied for rater-identified thickest muscle region and measures of the urethra. Our study suggests that structures of the male PF can be reliably evaluated using a transperineal sonographic approach.


      PubDate: 2015-01-16T23:01:53Z
       
  • Pennation Angle Does Not Influence the Age-Related Differences in Echo
           Intensity of the Medial Gastrocnemius
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Eric D. Ryan , Joseph G. Rosenberg , Michael J. Scharville , Eric J. Sobolewski , Andrew J. Tweedell , Craig R. Kleinberg
      The reflection of an ultrasound (US) wave is strongest when the propagation direction of the wave is perpendicular to muscle fascicles. Thus, it is possible that muscle echo intensity (EI), a gray-scale US measure of muscle quality, may be influenced by the angulation of muscle fascicles. Therefore, the purpose of this study was to determine if age-related differences in muscle EI values are influenced by differences in pennation angle (PA). Medial gastrocnemius EI and PA were examined using panoramic US imaging in 24 young (19.8 ± 1.7 y) and 21 older (69.3 ± 3.3 y) men. The young men had lower EI values (young = 74.1 ± 6.3 a.u., older = 89.1 ± 8.8 a.u.) and a greater PA (young = 20.0 ± 2.9°; older = 17.2 ± 2.5°) compared with the older men (p < 0.01). In addition, there was a negative relationship (r = –0.473, p < 0.01) between PA and EI with both groups combined, but no significant relationship when the young (r = –0.334, p = 0.111) and older (r = –0.147, p = 0.525) men were examined separately. An analysis of covariance revealed that muscle EI values remained different (p < 0.01) between age groups after adjustment for differences in PA. Thus, after statistically adjusting the mean EI values for the differences in PA, there were still significant age-related differences in EI. These findings may provide further support that the age-related changes in muscle EI values reflect changes in tissue composition (i.e., increase in intramuscular fat and/or connective tissue) commonly reported in older adults.


      PubDate: 2015-01-16T23:01:53Z
       
  • The Role of Viscosity Estimation for Oil-in-gelatin Phantom in Shear Wave
           Based Ultrasound Elastography
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Ying Zhu , Changfeng Dong , Yin Yin , Xin Chen , Yanrong Guo , Yi Zheng , Yuanyuan Shen , Tianfu Wang , Xinyu Zhang , Siping Chen
      Shear wave based ultrasound elastography utilizes mechanical excitation or acoustic radiation force to induce shear waves in deep tissue. The tissue response is monitored to obtain elasticity information about the tissue. During the past two decades, tissue elasticity has been extensively studied and has been used in clinical disease diagnosis. However, biological soft tissues are viscoelastic in nature. Therefore, they should be simultaneously characterized in terms of elasticity and viscosity. In this study, two shear wave-based elasticity imaging methods, shear wave dispersion ultrasound vibrometry (SDUV) and acoustic radiation force impulsive (ARFI) imaging, were compared. The discrepancy between the measurements obtained by the two methods was analyzed, and the role of viscosity was investigated. To this end, four types of gelatin phantoms containing 0%, 20%, 30% and 40% castor oil were fabricated to mimic different viscosities of soft tissue. For the SDUV method, the shear elasticity μ1 was 3.90 ± 0.27 kPa, 4.49 ± 0.16 kPa, 2.41 ± 0.33 kPa and 1.31 ± 0.09 kPa; and the shear viscosity μ2 was 1.82 ± 0.31 Pa•s, 2.41 ± 0.35 Pa•s, 2.65 ± 0.13 Pa•s and 2.89 ± 0.14 Pa•s for 0%, 20%, 30% and 40% oil, respectively in both cases. For the ARFI measurements, the shear elasticity μ was 7.30 ± 0.20 kPa, 8.20 ± 0.31 kPa, 7.42 ± 0.21 kPa and 5.90 ± 0.36 kPa for 0%, 20%, 30% and 40% oil, respectively. The SDUV results demonstrated that the elasticity first increased from 0% to 20% oil and then decreased for the 30% and 40% oil. The viscosity decreased consistently as the concentration of castor oil increased from 0% to 40%. The elasticity measured by ARFI showed the same trend as that of the SDUV but exceeded the results measured by SDUV. To clearly validate the impact of viscosity on the elasticity estimation, an independent measurement of the elasticity and viscosity by dynamic mechanical analysis (DMA) was conducted on these four types of gelatin phantoms and then compared with SDUV and ARFI results. The shear elasticities obtained by DMA (3.44 ± 0.31 kPa, 4.29 ± 0.13 kPa, 2.05 ± 0.29 kPa and 1.06 ± 0.18 kPa for 0%, 20%, 30% and 40% oil, respectively) were lower than those by SDUV, whereas the shear viscosities obtained by DMA (2.52 ± 0.32 Pa·s, 3.18 ± 0.12 Pa·s, 3.98 ± 0.19 Pa·s and 4.90 ± 0.20 Pa·s for 0%, 20%, 30% and 40% oil, respectively) were greater than those obtained by SDUV. However, the DMA results showed that the trend in the elasticity and viscosity data was the same as that obtained from the SDUV and ARFI. The SDUV results demonstrated that adding castor oil changed the viscoelastic properties of the phantoms and resulted in increased dispersion of the shear waves. Viscosity can provide important and independent information about the inner state of the phantoms, in addition to the elasticity. Because the ARFI method ignores the dispersion of the shear waves, namely viscosity, it may bias the estimation of the true elasticity. This study sheds further light on the significance of the viscosity measurements in shear wave based elasticity imaging methods.


      PubDate: 2015-01-16T23:01:53Z
       
  • Quantification of Elastic Heterogeneity Using Contourlet-Based Texture
           Analysis in Shear-Wave Elastography for Breast Tumor Classification
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Qi Zhang , Yang Xiao , Shuai Chen , Congzhi Wang , Hairong Zheng
      Ultrasound shear-wave elastography (SWE) has become a valuable tool for diagnosis of breast tumors. The purpose of this study was to quantify the elastic heterogeneity of breast tumors in SWE by using contourlet-based texture features and evaluating their diagnostic performance for classification of benign and malignant breast tumors, with pathologic results as the gold standard. A total of 161 breast tumors in 125 women who underwent B-mode and SWE ultrasonography before biopsy were included. Five quantitative texture features in SWE images were extracted from the directional subbands after the contourlet transform, including the mean (T mean), maximum (T max), median (T med), third quartile (T qt), and standard deviation (T sd) of the subbands. Diagnostic performance of the texture features and the classic features was compared using the area under the receiver operating characteristic curve (AUC) and the leave-one-out cross validation with Fisher classifier. The feature T mean achieved the highest AUC (0.968) among all features and it yielded a sensitivity of 89.1%, a specificity of 94.3% and an accuracy of 92.5% for differentiation between benign and malignant tumors via the leave-one-out cross validation. Compared with the best classic feature, i.e., the maximum elasticity, T mean improved the AUC, sensitivity, specificity and accuracy by 3.5%, 12.7%, 2.8% and 6.2%, respectively. The T med, T qt and T sd were also superior to the classic features in terms of the AUC and accuracy. The results demonstrated that the contourlet-based texture features captured the tumor's elastic heterogeneity and improved diagnostic performance contrasted with the classic features.


      PubDate: 2015-01-16T23:01:53Z
       
  • Validity of Ultrasound Prediction Equations for Total and Regional
           Muscularity in Middle-aged and Older Men and Women
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Takashi Abe , Jeremy P. Loenneke , Kaelin C. Young , Robert S. Thiebaud , Vinayak K. Nahar , Kaitlyn M. Hollaway , Caitlin D. Stover , M. Allison Ford , Martha A. Bass , Mark Loftin
      To test the validity of published equations, 79 Caucasian adults (40 men and 39 women) aged 50–78 y had muscle thickness (MT) measured by ultrasound at nine sites of the body. Fat-free mass (FFM), lean soft tissue mass (LM) and total muscle mass (TMM) were estimated from MT using equations previously published in the literature. Appendicular LM (aLM) was estimated using dual-energy X-ray absorptiometry (DXA) and this method served as the reference criterion. There were strong correlations (range r = 0.85–0.94) between DXA-derived aLM and estimated FFM, leg LM or TMM. Total error between DXA-derived aLM and TMM (∼2 kg) was lower compared with the three other selected equations (6–10 kg). A Bland-Altman plot revealed that there was no systematic bias between aLM and TMM; however, the other three equations included systematic error. Our results suggest that an ultrasound equation for TMM is appropriate and useful for evaluating skeletal muscle mass in the body.


      PubDate: 2015-01-16T23:01:53Z
       
  • Measurement of the Doppler Power of Flowing Blood Using Ultrasound Doppler
           Devices
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Chih-Chung Huang , Hung-Lung Chou , Pay-Yu Chen
      Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser–receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and echogenicity of flowing blood were compared with those obtained in several previous studies.


      PubDate: 2015-01-16T23:01:53Z
       
  • An Ultrasound-Driven Kinematic Model for Deformation of the Infarcted
           Mouse Left Ventricle Incorporating a Near-Incompressibility Constraint
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Dan Lin , Brent A. French , Yaqin Xu , John A. Hossack , Jeffrey W. Holmes
      Mathematical models of varying complexity have proved useful in fitting and interpreting regional cardiac displacements obtained from imaging methods such as ultrasound speckle tracking or MRI tagging. Simpler models, such as the classic thick-walled cylinder model of the left ventricle (LV), can be solved quickly and are easy to implement, but they ignore regional geometric variations and are difficult to adapt to the study of regional pathologies like myocardial infarctions. Complex, anatomically accurate finite-element models work well, but are computationally intensive and require specialized expertise to implement. We developed a kinematic model that offers a compromise between these two traditional approaches, assuming only that displacements in the left ventricle are polynomial functions of initial position and that the myocardium is nearly incompressible, while allowing myocardial motion to vary spatially as would be expected in an ischemic or dyssynchronous LV. Model parameters were determined using an objective function with adjustable weights to account for confidence in individual displacement components and desired strength of the incompressibility constraint. The model accurately represented the motion of both normal and infarcted mouse LVs during the cardiac cycle, with normalized root mean square errors in predicted deformed positions of 8.2 ± 2.3% and 7.4 ± 2.1% for normal and infarcted hearts, respectively.


      PubDate: 2015-01-16T23:01:53Z
       
  • Validation of a Computer-Aided Diagnosis System for the Automatic
           Identification of Carotid Atherosclerosis
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Lilla Bonanno , Silvia Marino , Placido Bramanti , Fabrizio Sottile
      Carotid atherosclerosis represents one of the most important causes of brain stroke. The degree of carotid stenosis is, up to now, considered one of the most important features for determining the risk of brain stroke. Ultrasound (US) is a non-invasive, relatively inexpensive, portable technique, which has an excellent temporal resolution. Computer-aided diagnosis (CAD) has become one of the major research fields in medical and diagnostic imaging. We studied US images of 44 patients, 22 patients with and 22 without carotid artery stenosis, by using US examination and applying a CAD system, an automatic prototype software to detect carotid plaques. We obtained 287 regions: 60 were classified as plaques, with an average signal echogenicity of 244.1 ± 20.0 and 227 were classified as non-plaques, with an average signal echogenicity of 193.8 ± 38.6 compared with the opinion of an expert neurologist (golden test). The receiver operating characteristic (ROC) analysis revealed a highly significant area under the ROC curve difference from 0.5 (null hypothesis) in the discrimination between plaques and non-plaques; the diagnostic accuracy was 89% (95% CI: 0.85–0.92), with an appropriate cut-off value of 236.8, sensitivity was 83% and specificity reached a value of 85%. The experimental results showed that the proposed method is feasible and has a good agreement with the expert neurologist. Without the need of any user-interaction, this method generates a detection out-put that may be useful in second opinion.


      PubDate: 2015-01-16T23:01:53Z
       
  • Fully Automated Carotid Plaque Segmentation in Combined Contrast-Enhanced
           and B-Mode Ultrasound
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Zeynettin Akkus , Diego D.B. Carvalho , Stijn C.H. van den Oord , Arend F.L. Schinkel , Wiro J. Niessen , Nico de Jong , Antonius F.W. van der Steen , Stefan Klein , Johan G. Bosch
      Carotid plaque segmentation in B-mode ultrasound (BMUS) and contrast-enhanced ultrasound (CEUS) is crucial to the assessment of plaque morphology and composition, which are linked to plaque vulnerability. Segmentation in BMUS is challenging because of noise, artifacts and echo-lucent plaques. CEUS allows better delineation of the lumen but contains artifacts and lacks tissue information. We describe a method that exploits the combined information from simultaneously acquired BMUS and CEUS images. Our method consists of non-rigid motion estimation, vessel detection, lumen–intima segmentation and media–adventitia segmentation. The evaluation was performed in training (n = 20 carotids) and test (n = 28) data sets by comparison with manually obtained ground truth. The average root-mean-square errors in the training and test data sets were comparable for media–adventitia (411 ± 224 and 393 ± 239 μm) and for lumen–intima (362 ± 192 and 388 ± 200 μm), and were comparable to inter-observer variability. To the best of our knowledge, this is the first method to perform fully automatic carotid plaque segmentation using combined BMUS and CEUS.


      PubDate: 2015-01-16T23:01:53Z
       
  • A Theoretical Study of Inertial Cavitation from Acoustic Radiation Force
           Impulse Imaging and Implications for the Mechanical Index1
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Charles C. Church , Cecille Labuda , Kathryn Nightingale
      The mechanical index (MI) attempts to quantify the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a non-thermal mechanism. The current formulation of the MI implicitly assumes that the acoustic field is generated using the short pulse durations appropriate to B-mode imaging. However, acoustic radiation force impulse (ARFI) imaging employs high-intensity pulses up to several hundred acoustic periods long. The effect of increased pulse durations on the thresholds for inertial cavitation was studied computationally in water, urine, blood, cardiac and skeletal muscle, brain, kidney, liver and skin. The results indicate that, although the effect of pulse duration on cavitation thresholds in the three liquids can be considerable, reducing them by, for example, 6%–24% at 1 MHz, the effect on tissue is minor. More importantly, the frequency dependence of the MI appears to be unnecessarily conservative; that is, the magnitude of the exponent on frequency could be increased to 0.75. Comparison of these theoretical results with experimental measurements suggests that some tissues do not contain the pre-existing, optimally sized bubbles assumed for the MI. This means that in these tissues, the MI is not necessarily a strong predictor of the probability of an adverse biological effect.


      PubDate: 2015-01-16T23:01:53Z
       
  • Subharmonic, Non-linear Fundamental and Ultraharmonic Imaging of
           Microbubble Contrast at High Frequencies
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Verya Daeichin , Johan G. Bosch , Andrew Needles , F. Stuart Foster , Antonius van der Steen , Nico de Jong
      There is increasing use of ultrasound contrast agent in high-frequency ultrasound imaging. However, conventional contrast detection methods perform poorly at high frequencies. We performed systematic in vitro comparisons of subharmonic, non-linear fundamental and ultraharmonic imaging for different depths and ultrasound contrast agent concentrations (Vevo 2100 system with MS250 probe and MicroMarker ultrasound contrast agent, VisualSonics, Toronto, ON, Canada). We investigated 4-, 6- and 10-cycle bursts at three power levels with the following pulse sequences: B-mode, amplitude modulation, pulse inversion and combined pulse inversion/amplitude modulation. The contrast-to-tissue (CTR) and contrast-to-artifact (CAR) ratios were calculated. At a depth of 8 mm, subharmonic pulse-inversion imaging performed the best (CTR = 26 dB, CAR = 18 dB) and at 16 mm, non-linear amplitude modulation imaging was the best contrast imaging method (CTR = 10 dB). Ultraharmonic imaging did not result in acceptable CTRs and CARs. The best candidates from the in vitro study were tested in vivo in chicken embryo and mouse models, and the results were in a good agreement with the in vitro findings.


      PubDate: 2015-01-16T23:01:53Z
       
  • Electrophysiological Changes Correlated with Temperature Increases Induced
           by High-Intensity Focused Ultrasound Ablation
    • Abstract: Publication date: February 2015
      Source:Ultrasound in Medicine & Biology, Volume 41, Issue 2
      Author(s): Ziqi Wu , Ronald E. Kumon , Jacob I. Laughner , Igor R. Efimov , Cheri X. Deng
      To gain better understanding of the detailed mechanisms of high-intensity focused ultrasound (HIFU) ablation for cardiac arrhythmias, we investigated how the cellular electrophysiological (EP) changes were correlated with temperature increases and thermal dose (cumulative equivalent minutes [CEM 43 ]) during HIFU application using Langendorff-perfused rabbit hearts. Employing voltage-sensitive dye di-4-ANEPPS, we measured the EP and temperature during HIFU using simultaneous optical mapping and infrared imaging. Both action potential amplitude (APA) and action potential duration at 50% repolarization (APD50) decreased with temperature increases, and APD50 was more thermally sensitive than APA. EP and tissue changes were irreversible when HIFU-induced temperature increased above 52.3 ± 1.4°C and log10(CEM 43 ) above 2.16 ± 0.51 (n = 5), but were reversible when temperature was below 50.1 ± 0.8°C and log10(CEM 43 ) below –0.9 ± 0.3 (n = 9). EP and temperature/thermal dose changes were spatially correlated with HIFU-induced tissue necrosis surrounded by a transition zone.


      PubDate: 2015-01-16T23:01:53Z
       
  • Meshless Bubble Filter Using Ultrasound for Extracorporeal Circulation and
           its Effect on Blood
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Koji Mino , Masato Imura , Daisuke Koyama , Masayoshi Omori , Shigeki Kawarabata , Masafumi Sato , Yoshiaki Watanabe
      A bubble filter with no mesh structure for extracorporeal circulation using ultrasound was developed. Hemolysis was evaluated by measuring free hemoglobin (FHb). FHb in 120 mL of bovine blood was measured in acoustic standing-wave fields. With a sound pressure amplitude of 60 kPa at driving frequencies of 1 MHz, 500 kHz and 27 kHz for 15 min. FHb values were 641.6, 2575 and 8903 mg/dL, respectively. Thus, hemolysis was inhibited with higher driving frequencies when the same sound pressure amplitude was applied. An ultrasound bubble filter with a resonance frequency of 1 MHz was designed. The filtering characteristics of the flowing microbubbles were investigated with a circulation system using bovine blood with a flow rate of 5.0 L/min. Approximately 99.1% of microbubbles were filtered with 250 kPa and a flow of 5.0 L/min. Hemolysis decreased as the sound pressure decreased; FHb values were 225.8 and 490.7 mg/dL when using 150 and 200 kPa, respectively.


      PubDate: 2014-12-24T21:18:15Z
       
  • Diagnostic Ultrasound Imaging: Inside Out (Second Edition) Thomas L.
           Szabo. Academic Press, Kidlington, Oxford, UK, 2014. 832 pages. ISBN
           number 978 012 396487 8.
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Christian Kollmann



      PubDate: 2014-12-24T21:18:15Z
       
  • Treatment of Microvascular Micro-embolization Using Microbubbles and
           Long-Tone-Burst Ultrasound: An in Vivo Study
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): John J. Pacella , Judith Brands , Frederick G. Schnatz , John J. Black , Xucai Chen , Flordeliza S. Villanueva
      Despite epicardial coronary artery reperfusion by percutaneous coronary intervention, distal micro-embolization into the coronary microcirculation limits myocardial salvage during acute myocardial infarction. Thrombolysis using ultrasound and microbubbles (sonothrombolysis) is an approach that induces microbubble oscillations to cause clot disruption and restore perfusion. We sought to determine whether this technique could restore impaired tissue perfusion caused by thrombotic microvascular obstruction. In 16 rats, an imaging transducer was placed on the biceps femoris muscle, perpendicular to a single-element 1-MHz treatment transducer. Ultrasound contrast perfusion imaging was performed at baseline and after micro-embolization. Therapeutic ultrasound (5000 cycles, pulse repetition frequency = 0.33 Hz, 1.5 MPa) was delivered to nine rats for two 10-min sessions during intra-arterial infusion of lipid-encapsulated microbubbles; seven control rats received no ultrasound–microbubble therapy. Ultrasound contrast perfusion imaging was repeated after each treatment or control period, and microvascular volume was measured as peak video intensity. There was a 90% decrease in video intensity after micro-embolization (from 8.6 ± 4.8 to 0.7 ± 0.8 dB, p < 0.01). The first and second ultrasound–microbubble sessions were respectively followed by video intensity increases of 5.8 ± 5.1 and 8.7 ± 5.7 dB (p < 0.01, compared with micro-embolization). The first and second control sessions, respectively, resulted in no significant increase in video intensity (2.4 ± 2.3 and 3.6 ± 4.9) compared with micro-embolization (0.6 ± 0.7 dB). We have developed an in vivo model that simulates the distal thrombotic microvascular obstruction that occurs after primary percutaneous coronary intervention. Long-pulse-length ultrasound with microbubbles has a therapeutic effect on microvascular perfusion and may be a valuable adjunct to reperfusion therapy for acute myocardial infarction.


      PubDate: 2014-12-24T21:18:15Z
       
  • Strokes and TIAs during and after Carotid Artery Doppler: Cause or
           Coincidence'
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Vasileios Papavasileiou , Haralampos Milionis , Lorenz Hirt , Patrik Michel
      The aim of the present study was to explore the prevalence of acute cerebrovascular symptoms temporally related to carotid Doppler examination (DEx), in order to increase the awareness and recording of such events and to discuss possible mechanisms. All adult patients who complained of acute onset neurologic symptoms during or shortly after a carotid DEx, between 01/2003 and 12/2011 in the University Hospital of Lausanne were prospectively collected. We identified four consecutive patients with acute onset neurologic symptoms during or shortly after a carotid DEx among approximately 13,500 patients who underwent carotid DEx in our facility during the nine-year period (0.015% of all examined carotids). Clinical data, imaging reports and CTA (CT angiography) or/and ultrasound images are presented for each patient. Ischemic cerebrovascular events during or immediately after cervical Doppler could be due to chance or to several physical factors. They should be promptly recognized by Doppler personnel and properly treated, but do not put into question the overwhelming benefits of Doppler in cerebrovascular patients.


      PubDate: 2014-12-24T21:18:15Z
       
  • Near Real-Time Robust Non-rigid Registration of Volumetric Ultrasound
           Images for Neurosurgery
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Hassan Rivaz , D. Louis Collins
      Ultrasound images are acquired before and after the resection of brain tumors to help the surgeon to localize the tumor and its extent and to minimize the amount of residual tumor after the resection. Because the brain undergoes large deformation between these two acquisitions, deformable image-based registration of these data sets is of substantial clinical importance. In this work, we present an algorithm for non-rigid registration of ultrasound images (RESOUND) that models the deformation with free-form cubic B-splines. We formulate a regularized cost function that uses normalized cross-correlation as the similarity metric. To optimize the cost function, we calculate its analytic derivative and use the stochastic gradient descent technique to achieve near real-time performance. We further propose a robust technique to minimize the effect of non-corresponding regions such as the resected tumor and possible hemorrhage in the post-resection image. Using manually labeled corresponding landmarks in the pre- and post-resection ultrasound volumes, we illustrate that our registration algorithm reduces the mean target registration error from an initial value of 3.7 to 1.5 mm. We also compare RESOUND with the previous work of Mercier et al. (2013) and illustrate that it has three important advantages: (i) it is fully automatic and does not require a manual segmentation of the tumor, (ii) it produces smaller registration errors and (iii) it is about 30 times faster. The clinical data set is available online on the BITE database website.


      PubDate: 2014-12-24T21:18:15Z
       
  • Changes in Backscattered Ultrasonic Envelope Statistics as a Function of
           Thrombus Age: An in Vitro Study
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Jui Fang , Chin-Kuo Chen , Ju-Yi Peng , Chung-Hsin Hsu , Yung-Ming Jeng , Yu-Hsin Lee , Jen-Jen Lin , Po-Hsiang Tsui
      It is necessary to determine the age of thrombi in planning clinical treatment for thrombolysis. Ultrasound imaging can potentially be used to evaluate thrombus age in real time. The backscattered signals from thrombi may contain useful information regarding their age. On the basis of the randomness of ultrasound backscattering, this study explored changes in backscattered US statistics as a function of thrombus age. Porcine blood samples were used for the in vitro induction of fresh thrombi (day 0) with hematocrits ranging from 0%–40% and aged thrombi (days 0–8) with a hematocrit of 40%. Each thrombus was imaged using a pulse-echo ultrasound scanner equipped with a 7.5-MHz linear array transducer to acquire raw backscattered signals for B-mode and Nakagami imaging, by which the backscattered statistics were visualized. Hematoxylin and eosin staining and scanning electron microscopy were used to observe the histology of fresh and aged thrombi. The results indicated that a decrease in the number of red blood cells in the thrombus caused by the aging effect was observed in the in vitro model, indicating that the proposed model could simulate the structural changes in the thrombus during aging. Compared with fresh thrombi with various hematocrits, the aged thrombi exhibited a trend toward more substantial decreases in the Nakagami parameter with increasing thrombus age (the Nakagami parameter decreased from 1.1 to 0.6 as thrombus age increased from day 0 to day 8), indicating that thrombus aging causes the backscattered statistics to follow a pre-Rayleigh distribution to a high degree. This finding may be applied to the determination of thrombus age using conventional ultrasound imaging in the future.


      PubDate: 2014-12-24T21:18:15Z
       
  • Effect of Biological Characteristics of Different Types of Uterine
           Fibroids, as Assessed with T2-Weighted Magnetic Resonance Imaging, on
           Ultrasound-Guided High-Intensity Focused Ultrasound Ablation
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Wen-Peng Zhao , Jin-Yun Chen , Wen-Zhi Chen
      The aims of this study were to assess the effects of the biological characteristics of different types of uterine fibroids, as assessed with T2-weighted magnetic resonance imaging (MRI), on ultrasound-guided high-intensity focused ultrasound (USgHIFU) ablation. Thirty-five patients with 39 symptomatic uterine fibroids who underwent myomectomy or hysterectomy were enrolled. Before surgery, the uterine fibroids were subdivided into hypo-intense, iso-intense, heterogeneous hyper-intense and homogeneous hyper-intense categories based on signal intensity on T2-weighted MRI. Tissue density and moisture content were determined in post-operative samples and normal uterine tissue, the isolated uterine fibroids were subjected to USgHIFU, and the extent of ablation was measured using triphenyltetrazolium chloride. Hematoxylin and eosin staining and sirius red staining were undertaken to investigate the organizational structure of the uterine fibroids. Estrogen and progesterone receptor expression was assayed via immunohistochemical staining. The mean diameter of uterine fibroids was 6.9 ± 2.8 cm. For all uterine fibroids, the average density and moisture content were 10.7 ± 0.7 mg/mL and 75.7 ± 2.4%, respectively; and for the homogeneous hyper-intense fibroids, 10.3 ± 0.5 mg/mL and 76.6 ± 2.3%. The latter subgroup had lower density and higher moisture content compared with the other subgroups. After USgHIFU treatment, the extent of ablation of the hyper-intense fibroids was 102.7 ± 42.1 mm2, which was significantly less than those of the hypo-intense and heterogeneous hyper-intense fibroids. Hematoxylin and eosin staining and sirius red staining revealed that the homogeneous hyper-intense fibroids had sparse collagen fibers and abundant cells. Immunohistochemistry results revealed that estrogen and progesterone receptors were highly expressed in the homogeneous hyper-intense fibroids. This study revealed that lower density, higher moisture content, sparse collagen fibers, abundant cells and overexpression of estrogen and progesterone receptors are important biological characteristics that resulted in poor efficacy in the treatment of homogeneous hyper-intense fibroids.


      PubDate: 2014-12-24T21:18:15Z
       
  • Mammographic and Sonographic Features of Triple-Negative Invasive
           Carcinoma of No Special Type
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Hyun Kyung Jung , Kyunghwa Han , Yeo Jin Lee , Hee Jung Moon , Eun-Kyung Kim , Min Jung Kim
      The aim of this study was to compare the mammography, ultrasound (US) and histologic features of triple-negative (TN) invasive carcinoma of no special type (NST) to non-TN invasive carcinoma of NST. The second aim was to assess whether the distinct imaging characteristics of TN breast cancer would persist after controlling for the histologic features. A total of 344 invasive carcinomas of NST in 337 patients from January 2007 to February 2008 were included in this study. Two radiologists retrospectively reviewed the mammography and US findings using the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) lexicon and our institution's criteria. On mammography, TN invasive carcinoma of NST most commonly presented as a mass with round shape and non-spiculated margin. On US, it was more likely to have internal hypoechogenicity, an abrupt boundary and posterior acoustic enhancement. TNBC lacked major suspicious imaging findings such as an irregular shape, spiculated margin and calcification.


      PubDate: 2014-12-24T21:18:15Z
       
  • Defining the Optimal Age for Focal Lesioning in a Rat Model
           of Transcranial HIFU
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Yanrong Zhang , Jean-François Aubry , Junfeng Zhang , Yi Wang , Jack Roy , Jaime F. Mata , Wilson Miller , Erik Dumont , Mingxing Xie , Kevin Lee , Zhiyi Zuo , Max Wintermark
      This study aimed at determining the optimal age group for high-intensity focused ultrasound (HIFU) experiments for producing lesions in rats. Younger rats have thinner skulls, allowing for the acoustic waves to propagate easily through the skull without causing burns of the skin and brain surface. Younger rats however, have a smaller brain that can make HIFU focusing in the brain parenchyma challenging because of the focus size. In this study, we conducted transcranial HIFU sonications in rat pups of different ages (from 9 to 43 d) with a 1.5MHz MR compatible transducer. The electric power was selected to always reach a target temperature of at least 50°C in the parenchyma. The thickness of the skull and of the brain parenchyma was measured using T2-weighted MR imaging. Results showed that the thickness of the brain parenchyma increased quickly from P9 to P12, reaching 8.5 mm at P16, and then increasing gradually along with age. The skull thickness increased gradually from P9 to P26, and then more quickly after P30. The ratio between brain parenchyma thickness and skull thickness decreased gradually with age. For the pups at 30 d, the temperature in the brain tissue adjacent to the skull increased to 48.9°C, and those from the rodents older than 33 d reached 60°C or higher, which can produce undesired irreversible damage in this location. We conclude that young rats aged 16–26 d are optimal for experiments producing transcranial HIFU lesions in rats with an intact skull.


      PubDate: 2014-12-24T21:18:15Z
       
  • Hepatic Angiomyolipomas: Ultrasonic Characteristics of 25 Patients from a
           Single Center
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Baohua Wang , Zhengdu Ye , Yan Chen , Qiyu Zhao , Min Huang , Fen Chen , Yanyuan Li , Tian'an Jiang
      Twenty-five pathologically proven hepatic angiomyolipomas (AMLs) were included in the study. Ultrasonic features of hepatic AMLs were reviewed. Three types of echogenicity were observed on ultrasound examination: (i) strong hyper-echogenicity, (ii) moderate hyper-echogenicity and (iii) hypo-echogenicity. Vascular signals within tumors could be detected in 22 (88.00%) tumors as multiple punctiform, filiform or dendriform signals by color Doppler flow imaging. Based on the enhancement patterns in the arterial, portal and late phases, the features of hepatic AMLs on contrast-enhanced ultrasound were divided into four subtypes: (i) “fast in slow out” (68.00%, n = 17); (ii) “fast in same out” (16%, n = 4); (iii) “fast in fast out” (12.00%, n = 3); and (iv) “fast in uneven out” (4.00%, n = 1). Contrast-enhanced ultrasound diagnosed 22 (88.00%) tumors as benign tumors and 13 (52.00%) as hepatic AMLs. Four cases were misdiagnosed as hepatic hemangioma, five cases as focal nodular hyperplasia (total = 36.00%). The rate of correct diagnosis of hepatic AMLs increased significantly from 24.00% for ultrasound alone to 52.00% for contrast-enhanced ultrasound. Therefore, information obtained from ultrasound, color Doppler flow imaging and contrast-enhanced ultrasound should be combined to improve diagnosis.


      PubDate: 2014-12-24T21:18:15Z
       
  • User-Guided Segmentation of Preterm Neonate Ventricular System from 3-D
           Ultrasound Images Using Convex Optimization
    • Abstract: Publication date: Available online 23 December 2014
      Source:Ultrasound in Medicine & Biology
      Author(s): Wu Qiu , Jing Yuan , Jessica Kishimoto , Jonathan McLeod , Yimin Chen , Sandrine de Ribaupierre , Aaron Fenster
      A three-dimensional (3-D) ultrasound (US) system has been developed to monitor the intracranial ventricular system of preterm neonates with intraventricular hemorrhage (IVH) and the resultant dilation of the ventricles (ventriculomegaly). To measure ventricular volume from 3-D US images, a semi-automatic convex optimization-based approach is proposed for segmentation of the cerebral ventricular system in preterm neonates with IVH from 3-D US images. The proposed semi-automatic segmentation method makes use of the convex optimization technique supervised by user-initialized information. Experiments using 58 patient 3-D US images reveal that our proposed approach yielded a mean Dice similarity coefficient of 78.2% compared with the surfaces that were manually contoured, suggesting good agreement between these two segmentations. Additional metrics, the mean absolute distance of 0.65 mm and the maximum absolute distance of 3.2 mm, indicated small distance errors for a voxel spacing of 0.22 × 0.22 × 0.22 mm3. The Pearson correlation coefficient (r = 0.97, p < 0.001) indicated a significant correlation of algorithm-generated ventricular system volume (VSV) with the manually generated VSV. The calculated minimal detectable difference in ventricular volume change indicated that the proposed segmentation approach with 3-D US images is capable of detecting a VSV difference of 6.5 cm3 with 95% confidence, suggesting that this approach might be used for monitoring IVH patients' ventricular changes using 3-D US imaging. The mean segmentation times of the graphics processing unit (GPU)- and central processing unit-implemented algorithms were 50 ± 2 and 205 ± 5 s for one 3-D US image, respectively, in addition to 120 ± 10 s for initialization, less than the approximately 35 min required by manual segmentation. In addition, repeatability experiments indicated that the intra-observer variability ranges from 6.5% to 7.5%, and the inter-observer variability is 8.5% in terms of the coefficient of variation of the Dice similarity coefficient. The intra-class correlation coefficient for ventricular system volume measurements for each independent observer ranged from 0.988 to 0.996 and was 0.945 for three different observers. The coefficient of variation and intra-class correlation coefficient revealed that the intra- and inter-observer variability of the proposed approach introduced by the user initialization was small, indicating good reproducibility, independent of different users.


      PubDate: 2014-12-24T21:18:15Z
       
 
 
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