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Ultrasound in Medicine & Biology

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ISSN (Print) 0301-5629
Published by Elsevier

[2565 journals]

Management of Thyroid Follicular Proliferation: An Ultrasound-Based Malignancy Score to Opt for Surgical or Conservative Treatment
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Giovanni Pompili , Silvia Tresoldi , Alessandra Primolevo , Loredana De Pasquale , Giovanni Di Leo , Gianpaolo Cornalba
  This study was conducted to evaluate whether ultrasound characteristics of thyroid nodules with a known cytologic diagnosis of “follicular pattern” (indicative of follicular hyperplasia, follicular adenoma or follicular carcinoma) can be used to define a nodule malignancy score to limit surgery to selected, higher-risk cases. In pre-operative ultrasound results of patients diagnosed with a “follicular pattern” on cytology who subsequently underwent surgery, each nodule feature was given a score from 0 (most likely benign) to 2 (most likely malignant), resulting in a total score ranging from 0 to 11. The total nodule score (total malignancy score) was then compared with the definitive histologic diagnosis. According to our results, surgery is advisable in patients with score ≥4 (79% of carcinomas), ultrasound follow-up seems to be appropriate for patients with a score of 3 (21% of carcinomas) and no action is recommended for patients with score <3 (only benign nodules).
  
  PubDate: 2013-06-07T09:47:11Z
Liver Stiffness Measurements by Means of Supersonic Shear Imaging in Patients without Known Liver Pathology
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Roxana Sirli , Simona Bota , Ioan Sporea , Ana Jurchis , Alina Popescu , Oana Gradinaru-Tascău , Milana Szilaski
  We used supersonic shear imaging to determine the liver stiffness (LS) values of 82 patients without known liver pathology and studied the factors that influence these measurements. Five LS measurements were made in each subject, and the median value, expressed in kilopascals, was calculated. Reliable LS measurements were obtained in 84.5% of patients. Higher body mass index and older age were associated with failure to obtain reliable measurements. The mean value of LS measurements determined by SSI in our cohort of patients without known liver pathology was 6 ± 1.4 kPa. The mean LS measurements determined by SSI for men were significantly higher than those for women; body mass index did not significantly influence SSI measurements. Thus, 6 kPa is the mean SSI value in patients without known liver pathology, with higher values being obtained in men.
  
  PubDate: 2013-06-07T09:47:11Z
Creating Brain Lesions with Low-Intensity Focused Ultrasound with Microbubbles: A Rat Study at Half a Megahertz
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Yuexi Huang , Natalia I. Vykhodtseva , Kullervo Hynynen
  Low-intensity focused ultrasound was applied with microbubbles (Definity, Lantheus Medical Imaging, North Billerica, MA, USA; 0.02 mL/kg) to produce brain lesions in 50 rats at 558 kHz. Burst sonications (burst length: 10 ms; pulse repetition frequency: 1 Hz; total exposure: 5 min; acoustic power: 0.47–1.3 W) generated ischemic or hemorrhagic lesions at the focal volume revealed by both magnetic resonance imaging and histology. Shorter burst time (2 ms) or shorter sonication time (1 min) reduced the probability of lesion production. Longer pulses (200 ms, 500 ms and continuous wave) caused significant near-field damage. Using microbubbles with focused ultrasound significantly reduced acoustic power levels and, therefore, avoided skull heating issues and potentially can extend the treatable volume of transcranial focused ultrasound to brain tissues close to the skull.
  
  PubDate: 2013-06-07T09:47:11Z
Abdominal Aortic Aneurysm Imaging with 3-D Ultrasound: 3-D-Based Maximum Diameter Measurement and Volume Quantification
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): A. Long , L. Rouet , A. Debreuve , R. Ardon , C. Barbe , J.P. Becquemin , E. Allaire
  The clinical reliability of 3-D ultrasound imaging (3-DUS) in quantification of abdominal aortic aneurysm (AAA) was evaluated. B-mode and 3-DUS images of AAAs were acquired for 42 patients. AAAs were segmented. A 3-D-based maximum diameter (Max3-D) and partial volume (Vol30) were defined and quantified. Comparisons between 2-D (Max2-D) and 3-D diameters and between orthogonal acquisitions were performed. Intra- and inter-observer reproducibility was evaluated. Intra- and inter-observer coefficients of repeatability (CRs) were less than 5.18 mm for Max3-D. Intra-observer and inter-observer CRs were respectively less than 6.16 and 8.71 mL for Vol30. The mean of normalized errors of Vol30 was around 7%. Correlation between Max2-D and Max3-D was 0.988 (p < 0.0001). Max3-D and Vol30 were not influenced by a probe rotation of 90°. Use of 3-DUS to quantify AAA is a new approach in clinical practice. The present study proposed and evaluated dedicated parameters. Their reproducibility makes the technique clinically reliable.
  
  PubDate: 2013-06-07T09:47:11Z
Design and Evaluation of a Wearable Self-Applied Therapeutic Ultrasound Device for Chronic Myofascial Pain
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): George K. Lewis Jr. , Matthew D. Langer , Charles R. Henderson Jr. , Ralph Ortiz
  Ultrasound therapy for pain and healing is a versatile treatment modality for musculoskeletal conditions that is used daily in rehabilitation clinics around the world. Our group designed and constructed a wearable, battery-operated, low-intensity therapeutic ultrasound (LITUS) device that patients could self-apply and operate during daily activity for up to 6 h. Thirty patients with chronic trapezius myofascial pain evaluated the LITUS system in a double-blind, placebo-controlled, 10-d study under institutional review board approval. While continuing their prescribed medication regimen, patients with the active device reported on average 1.94× reduction in pain and 1.58× improvement in health relative to placebo devices after 1 h of treatment. Both of these results were statistically significant (p < 0.05) for the first 2 d of the study. Male patients reported the majority of benefit, and there is a sex-treatment confound in the sample. The study indicates that wearable, long-duration LITUS technology improves mobile access to drug-free pain relief.
  
  PubDate: 2013-06-07T09:47:11Z
Three-Dimensional HDlive Rendering Images of the Fetal Heart
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Toshiyuki Hata , Masato Mashima , Megumi Ito , Emiko Uketa , Nobuhiro Mori , Mari Ishimura
  Our objective is to describe our experience with reconstruction of normal fetal cardiac structures and congenital heart anomalies using the 3-D HDlive rendering mode with spatiotemporal image correlation (STIC). Four normal fetuses and three fetuses with congenital heart anomalies (Ebstein’s anomaly, hypoplastic left heart syndrome and tetralogy of Fallot) at 25–35 wk of gestation were studied using the 3-D HDlive rendering mode with STIC. In normal fetuses, the natural appearance of the dynamic motion of the foramen ovale flap and both atrioventricular valves was clearly visualized in real time in the four-chamber view. Moreover, new, realistic sensations of each leaflet of atrioventricular valves and semilunar valves of the pulmonary artery were obtained in the en face view of both atrioventricular valves and great vessels. In the case of Ebstein’s anomaly, the procedure rendered the natural and anatomically realistic appearance of significantly low attachment of the tricuspid valve and atrialized portion of the right ventricle. In hypoplastic left heart syndrome, thickened tricuspid and dysplastic pulmonary valves were clearly revealed. In tetralogy of Fallot, an overriding aorta and ventricular septal defect were realistically depicted. The 3-D HDlive rendering mode with STIC provides entirely new visual experiences for obstetricians and pediatric cardiologists owing to the anatomically realistic depiction of normal and abnormal fetal cardiac structures of the beating heart.
  
  PubDate: 2013-06-07T09:47:11Z
Second Harmonic and Subharmonic for Non-linear Wideband Contrast Imaging Using a Capacitive Micromachined Ultrasonic Transducer Array
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Anthony Novell , Jean-Michel Escoffre , Ayache Bouakaz
  When insonified with suitable ultrasound excitation, contrast microbubbles generate various non-linear scattered components, such as the second harmonic (2H) and the subharmonic (SH). In this study, we exploit the wide frequency bandwidth of capacitive micromachined ultrasonic transducers (CMUTs) to enhance the response from ultrasound contrast agents by selective imaging of both the 2H and SH components simultaneously. To this end, contrast images using the pulse inversion method were recorded with a 64-element CMUT linear array connected to an open scanner. In comparison to imaging at 2H alone, the wideband imaging including both the 2H and SH contributions provided up to 130% and 180% increases in the signal-to-noise and contrast-to-tissue ratios, respectively. The wide-frequency band of CMUTs offers new opportunities for improved ultrasound contrast agent imaging.
  
  PubDate: 2013-06-07T09:47:11Z
Comparative Study of Standing Wave Reduction Methods Using Random Modulation for Transcranial Ultrasonication
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Hiroshi Furuhata , Osamu Saito
  Various transcranial sonotherapeutic technologies have risks related to standing waves in the skull. In this study, we present a comparative study on standing waves using four different activation methods: sinusoidal (SIN), frequency modulation by noise (FMN), periodic selection of random frequency (PSRF), and random switching of both inverse carriers (RSBIC). The standing wave was produced and monitored by the schlieren method using a flat plane and a human skull. The minimum ratio RSW, which is defined by the ratio of the mean of the difference between local maximal value and local minimal value of amplitude to the average value of the amplitude, was 36% for SIN, 24% for FMN, 13% for PSRF, and 4%for RSBIC for the flat reflective plate, and it was 25% for SIN, 11% for FMN, 13% for PSRF, and 5% for RSBIC for the inner surface of the human skull. This study is expected to have a role in the development of safer therapeutic equipment.
  
  PubDate: 2013-06-07T09:47:11Z
Arthroscopic Ultrasound Technique for Simultaneous Quantitative Assessment of Articular Cartilage and Subchondral Bone: An In Vitro and In Vivo Feasibility Study
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): J. Liukkonen , J. Hirvasniemi , A. Joukainen , P. Penttilä , T. Virén , S. Saarakkala , H. Kröger , J.S. Jurvelin , J. Töyräs
  Traditional arthroscopic examination is subjective and poorly reproducible. Recently, we introduced an arthroscopic ultrasound method for quantitative diagnostics of cartilage lesions. Here we describe our investigation of the feasibility of ultrasound arthroscopy for simultaneous measurements of articular cartilage and subchondral bone. Human osteochondral samples (n = 13) were imaged using a clinical 9-MHz ultrasound system. Ultrasound reflection coefficients (R, IRC), the ultrasound roughness index (URI) and the apparent integrated backscattering coefficient (AIB) were determined for both tissues. Mechanical testing, histologic analyses and micro-scale computed tomography imaging were the reference methods. Ultrasound arthroscopies were conducted on two patients. The ultrasound reflection coefficient correlated with the Mankin score and Young's modulus of cartilage ( r > 0.56, p < 0.05). Ultrasound parameters (R, IRC, AIB) for subchondral bone correlated with the bone surface/volume ratio ( r > 0.70, p < 0.05) and trabecular thickness ( r > 0.59, p < 0.05). Furthermore, R and subchondral bone mineral density were significantly correlated ( r > 0.65, p < 0.05). Arthroscopic ultrasound examination provided diagnostically valuable information on cartilage and subchondral bone in vivo.
  
  PubDate: 2013-06-07T09:47:11Z
Left Ventricular Longitudinal Strain and Strain Rate Measured by 2-D Speckle Tracking Echocardiography in Neonates During Whole-Body Hypothermia
- Abstract: Publication date: Available online 4 June 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Christoph Czernik , Stefanie Rhode , Sven Helfer , Gerd Schmalisch , Christoph Bührer
  The purpose of the study was to assess changes in cardiac performance in newborn infants with hypoxic-ischemic encephalopathy during therapeutic hypothermia and rewarming with two-dimensional speckle tracking echocardiography. For eight asphyxiated neonates (median birth weight (range): 3038 (2725–3253) g; umbilical artery pH: 6.9 (6.8–7.18) undergoing whole-body hypothermia (33–34°C), left ventricular longitudinal strain and strain rate, as well as heart rate, cardiac output and left ventricular fractional shortening, were determined at four points in time: the start (T1) and end of hypothermia (T2), immediately after rewarming (T3) and the age of 5 to 7 d (T4). Mean (standard deviation) heart rate increased from 93 (12) beats/min at T1 to 133 (12) beats/min at T4 (p < 0.001). Cardiac output was low during hypothermia (T1: 207 [43] mL/kg/min, T2: 240 [70] mL/kg/min) and increased significantly (p < 0.001) afterward (T3: 329 [70] mL/kg/min, T4: 388 [78] mL/kg/min). Left ventricular fractional shortening remained unchanged. Left ventricular global longitudinal peak systolic strain did not differ significantly between hypothermia and rewarming, whereas the systolic strain rate increased from −1.1 (0.3) s-1 at T1 to −1.8 (0.26) s-1 at T4 (p = 0.001). Hypothermia affects peak systolic strain rate, heart rate and cardiac output, with complete recovery after rewarming, whereas peak systolic strain and fractional shortening remain stable.
  
  PubDate: 2013-06-07T09:47:11Z
Axial and Radial Waveforms in Common Carotid Artery: An Advanced Method for Studying Arterial Elastic Properties in Ultrasound Imaging
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Heikki Yli-Ollila , T. Laitinen , M. Weckström , T.M. Laitinen
  Our objective was to develop a method for studying the biomechanics of the common carotid artery (CCA) by evaluating both radial and less known axial distension of the arterial wall. We developed software capable of tracking the movements of different arterial wall layers from ultrasound recordings of CCA, and we then calculated several indices of arterial stiffness. The wide spectrum of arterial stiffness indices defined from one measurement is a unique feature of our method. The motion-tracking algorithm is based on 2-D cross-correlation enhanced with luminance optimizations. The repeatability and reproducibility of the motion tracking were evaluated by performing 10-s ultrasound recordings of left CCA twice to 19 healthy volunteers (11 women, 8 men, age 41.3 ± 14.3 y). The method revealed a biphasic axial movement of the CCA and demonstrated that the indices of arterial stiffness defined from radial movement of carotid artery are reproducible (Cronbach’s α, 0.59–0.97) as well as the indices from axial movement are reproducible (Cronbach’s α, −0.68 to 0.93). The good reproducibility of the motion tracking is evidence that this method of studying arterial elastic properties is adequate for in vivo studies.
  
  PubDate: 2013-06-03T12:44:39Z
Classification of Breast Tumors Using Elastographic and B-mode Features: Comparison of Automatic Selection of Representative Slice and Physician-Selected Slice of Images
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Woo Kyung Moon , Shao-Chien Chang , Jung Min Chang , Nariya Cho , Chiun-Sheng Huang , Jen-Wei Kuo , Ruey-Feng Chang
  Inter-observer variability and image quality are two key factors that can affect the diagnostic performance of elastography and B-mode ultrasound for breast tumor characterization. The purpose of this study is to use an image quantification method that automatically chooses a representative slice and then segments the tumor contour to evaluate the diagnostic features for tumor characterization. First, the representative slice is selected based on either the stiffness inside the tumor (the signal-to-noise ratio on the elastogram [SNRe]) or the contrast between the tumor and the surrounding normal tissue (the contrast-to-noise ratio on the elastogram [CNRe]). Next, the level set method is used to segment the tumor contour. Finally, the B-mode and elastographic features related to the segmented tumor are extracted for tumor characterization. The performance of the representative slice selected using the proposed methods is compared to that of the physician-selected slice in 151 biopsy-proven lesions (89 benign and 62 malignant). The diagnostic accuracies using elastographic features are 82.1% (124/151) for the slice with the maximum CNRe value, 82.1% (124/151) for the slice with the maximum SNRe value and 82.8% (125/151) for the physician-selected slice, whereas the diagnostic accuracies using B-mode features are 80.8% (122/151) for the slice with the maximum CNRe value, 87.4% (132/151) for the slice with the maximum SNRe value and 84.1% (127/151) for the physician-selected slice. When using both the B-mode and elastographic features to characterize the tumor, the accuracy of diagnosis is 86.1% (130/151) for the slice with the maximum CNRe value, 90.1% (136/151) for the slice with the maximum SNRe value and 89.4% (135/151) for the physician-selected slice. Our results show that the representative slice selected by SNRe and CNRe could be used to reduce the observer variability and to increase the diagnostic performance by the B-mode and elastographic features.
  
  PubDate: 2013-06-03T12:44:39Z
Masthead
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  
  PubDate: 2013-06-03T12:44:39Z
Acoustic Waves in Medical Imaging and Diagnostics
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Armen P. Sarvazyan , Matthew W. Urban , James F. Greenleaf
  Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term ultrasonography, or its abbreviated version sonography, meant an imaging modality based on the use of ultrasonic compressional bulk waves. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities and frequencies that have been used in different imaging applications is presented. We discuss the potential for future shear wave imaging applications.
  
  PubDate: 2013-06-03T12:44:39Z
Ultrasound-Based Diagnosis for Solid Thyroid Nodules with the Largest Diameter <5 mm
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Dong Wook Kim , Yoo Jin Lee , Jae Wook Eom , Soo Jin Jung , Tae Kwun Ha , Taewoo Kang
  This study was aimed at assessing the efficacy of using an ultrasound (US)-based classification system to diagnose solid thyroid nodules with the largest diameter <5 mm (i.e., small solid nodules). For 406 small solid nodules in 365 patients who underwent thyroid US and US-guided fine-needle aspiration, each thyroid nodule was prospectively classified into one of five diagnostic categories: benign, probably benign, borderline, possibly malignant and malignant. Of 406 nodules, 145 were surgically removed: 95 papillary thyroid carcinomas, 1 follicular thyroid carcinoma, 1 poorly differentiated carcinoma, 3 pseudonodules related to thyroiditis and 45 nodular hyperplasias. On the basis of the histopathologic results, the diagnostic accuracies of US diagnosis and cytologic diagnosis were similar, but the sensitivity of US diagnosis was higher than that of cytologic diagnosis, and the specificity and positive predictive values of US diagnosis were lower those of cytologic diagnosis. An US-based classification system may be helpful for the diagnosis and management of small solid nodules.
  
  PubDate: 2013-06-03T12:44:39Z
Contents
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  
  PubDate: 2013-06-03T12:44:39Z
Editorial Advisory Board
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  
  PubDate: 2013-06-03T12:44:39Z
Introduction of a New Index of Cervical Consistency with Transvaginal B-mode Ultrasonography
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Hiroe M.-Hyodo , Hironobu Hyodo , Kohzo Aisaka
  Changes in the length and consistency of the uterine cervix during pregnancy are known to precede pre-term labor. However, cervical consistency has not been studied in depth because its objective evaluation requires special equipment. Our aim was to define a new index to evaluate cervical consistency simply and easily using B-mode ultrasonography. The cervical length–consistency index (CLCI) is defined as the ratio of the length of the cervix stretched during compression to that before compression. CLCI increases as pregnancy progresses. The CLCI values that corresponded to digital examination results of firm, medium and soft were 112.0 ± 10.0, 124.1 ± 22.4 and 153.2 ± 35.7, respectively, thus confirming the existence of a significant relationship between the index and consistency. The CLCI may be useful in predicting pre-term labor and should therefore be investigated further in larger cohorts.
  
  PubDate: 2013-06-03T12:44:39Z
Calendar
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  
  PubDate: 2013-06-03T12:44:39Z
Ultrasound Elastographic Evaluation in the Diagnosis of Carpal Tunnel Syndrome: Initial Findings
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Gunes Orman , Serkan Ozben , Nergiz Huseyinoglu , Mahmut Duymus , Keziban Gunce Orman
  The purpose of this study was to investigate ultrasound (US)- and US elastography-detected changes in the median nerve of patients with carpal tunnel syndrome (CTS). Seventy-four wrists of 41 female patients with CTS (mean age, 47.73 ± 11.45 y) and 45 wrists of 24 asymptomatic female controls (mean age, 42.83 ± 10.66 y) were examined with US and US elastography. Electromyography results confirmed the diagnosis of CTS in the patients. The mean median nerve perimeter (MN-P = 15.26 ± 2.18 mm) and median nerve cross-sectional area (MN-CSA = 11.81 ± 4.05 mm²) of patients with CTS were higher than those of controls (12.08 ± 1.54 mm and 7.76 ± 1.40 mm², respectively) (p < 0.05). Mean tissue strain was lower in the patients with CTS (0.094 ± 0.045 than in the controls (0.145 ± 0.068) (p < 0.05). The most sensitive cut-off value for tissue strain was 0.0635, and the most specific was 0.19. US and US elastography, in addition to electromyography, proved to be beneficial in the diagnosis of CTS. US elastography is a new technique that may well find a place in the diagnosis of nerve entrapment syndromes.
  
  PubDate: 2013-06-03T12:44:39Z
Mechanotransduction of Ultrasound is Frequency Dependent Below the Cavitation Threshold
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Tobias M. Louw , Gaurav Budhiraja , Hendrik J. Viljoen , Anuradha Subramanian
  This study provides evidence that low-intensity ultrasound directly affects nuclear processes, and the magnitude of the effect varies with frequency. In particular, we show that the transcriptional induction of first load-inducible genes, which is independent of new protein synthesis, is frequency dependent. Bovine chondrocytes were exposed to low-intensity (below the cavitational threshold) ultrasound at 2, 5 and 8 MHz. Ultrasound elevated the expression of early response genes c-Fos, c-Jun and c-Myc, maximized at 5 MHz. The phosphorylated ERK inhibitor PD98059 abrogated any increase in c-series gene expression, suggesting that signaling occurs via the MAPPK/ERK pathway. However, phosphorylated ERK levels did not change with ultrasound frequency, indicating that processes downstream of ERK phosphorylation (such as nuclear transport and chromatin reorganization) respond to ultrasound with frequency dependence. A quantitative, biphasic mathematical model based on Biot theory predicted that cytoplasmic and nuclear stress is maximized at 5.2 ± 0.8 MHz for a chondrocyte, confirming experimental measurements.
  
  PubDate: 2013-06-03T12:44:39Z
Enhanced Intracellular Delivery of a Model Drug Using Microbubbles Produced by a Microfluidic Device
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Adam J. Dixon , Ali H. Dhanaliwala , Johnny L. Chen , John A. Hossack
  Focal drug delivery to a vessel wall facilitated by intravascular ultrasound and microbubbles holds promise as a potential therapy for atherosclerosis. Conventional methods of microbubble administration result in rapid clearance from the bloodstream and significant drug loss. To address these limitations, we evaluated whether drug delivery could be achieved with transiently stable microbubbles produced in real time and in close proximity to the therapeutic site. Rat aortic smooth muscle cells were placed in a flow chamber designed to simulate physiological flow conditions. A flow-focusing microfluidic device produced 8 μm diameter monodisperse microbubbles within the flow chamber, and ultrasound was applied to enhance uptake of a surrogate drug (calcein). Acoustic pressures up to 300 kPa and flow rates up to 18 mL/s were investigated. Microbubbles generated by the flow-focusing microfluidic device were stabilized with a polyethylene glycol-40 stearate shell and had either a perfluorobutane (PFB) or nitrogen gas core. The gas core composition affected stability, with PFB and nitrogen microbubbles exhibiting half-lives of 40.7 and 18.2 s, respectively. Calcein uptake was observed at lower acoustic pressures with nitrogen microbubbles (100 kPa) than with PFB microbubbles (200 kPa) (p < 0.05, n > 3). In addition, delivery was observed at all flow rates, with maximal delivery (>70% of cells) occurring at a flow rate of 9 mL/s. These results demonstrate the potential of transiently stable microbubbles produced in real time and in close proximity to the intended therapeutic site for enhancing localized drug delivery.
  
  PubDate: 2013-06-03T12:44:39Z
Determination of the Interfacial Rheological Properties of a Poly(DL-lactic acid)-Encapsulated Contrast Agent Using In Vitro Attenuation and Scattering
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Shirshendu Paul , Daniel Russakow , Tyler Rodgers , Kausik Sarkar , Michael Cochran , Margaret A. Wheatley
  The stabilizing encapsulation of a microbubble-based ultrasound contrast agent (UCA) critically affects its acoustic properties. Polymers, which behave differently from materials commonly used (i.e., lipids or proteins) for monolayer encapsulation, have the potential for better stability and improved control of encapsulation properties. Air-filled microbubbles coated with poly(DL-lactic acid) (PLA) are characterized here using in vitro acoustic experiments and several models of encapsulation. The interfacial rheological properties of the encapsulation are determined according to each model using attenuation of ultrasound through a suspension of microbubbles. Then the model predictions are compared with scattered non-linear (sub- and second harmonic) responses. For this microbubble population (average diameter, 1.9 μm), the peak in attenuation measurement indicates a weighted-average resonance frequency of 2.5–3 MHz, which, in contrast to other encapsulated microbubbles, is lower than the resonance frequency of a free bubble of similar size (diameter, 1.9 μm). This apparently contradictory result stems from the extremely low surface dilational elasticity (around 0.01–0.07 N/m) and the reduced surface tension of the poly(DL-lactic acid) encapsulation, as well as the polydispersity of the bubble population. All models considered here are shown to behave similarly even in the non-linear regime because of the low surface dilational elasticity value. Pressure-dependent scattering measurements at two different excitation frequencies (2.25 and 3 MHz) revealed strongly non-linear behavior with 25–30 dB and 5–20 dB enhancements in fundamental and second-harmonic responses, respectively, for a contrast agent concentration of 1.33 μg/mL in the suspension. Sub-harmonic responses are registered above a relatively low generation threshold of 100–150 kPa, with up to 20 dB enhancement beyond that pressure. Numerical predictions from all models show good agreement with the experimentally measured fundamental response, but not with the experimental second-harmonic response. The characteristic features of sub-harmonic responses and the steady response beyond the threshold are matched well by model predictions. However, prediction of the threshold value depends on estimated properties and size distribution. The variation in size distribution from sample to sample leads to variation in estimates of encapsulation properties: the lowest estimated value for surface dilational viscosity better predicts the sub-harmonic threshold.
  
  PubDate: 2013-06-03T12:44:39Z
Ultrasound Improves the Uptake and Distribution of Liposomal Doxorubicin in Prostate Cancer Xenografts
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Siv Eggen , Mercy Afadzi , Esben A. Nilssen , Solveig Bjærum Haugstad , Bjørn Angelsen , Catharina de L. Davies
  Combining liposomally encapsulated cytotoxic drugs with ultrasound exposure has improved the therapeutic response to cancer in animal models; however, little is known about the underlying mechanisms. This study focused on investigating the effect of ultrasound exposures (1 MHz and 300 kHz) on the delivery and distribution of liposomal doxorubicin in mice with prostate cancer xenografts. The mice were exposed to ultrasound 24 h after liposome administration to study the effect on release of doxorubicin and its penetration through the extracellular matrix. Optical imaging methods were used to examine the effects at both microscopic subcellular and macroscopic tissue levels. Confocal laser scanning microscopy revealed that ultrasound-exposed tumors had increased levels of released doxorubicin compared with unexposed control tumors and that the distribution of liposomes and doxorubicin through the tumor tissue was improved. Whole-animal optical imaging revealed that liposomes were taken up by both abdominal organs and tumors.
  
  PubDate: 2013-06-03T12:44:39Z
Characterization of the Ultrasound Beam Produced by the MIST Therapy, Wound Healing System
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): K. Keltie , C.A. Reay , D.R. Bousfield , H. Cole , B. Ward , C.P. Oates , A.J. Sims
  The MIST Therapy wound healing device (Celleration, Eden Prairie, MN, USA), which uses low-frequency ultrasound to deliver an atomized saline spray to acute wounds, was evaluated in a laboratory environment. The output of the MIST device was characterized by its frequency, transmission in the presence and absence of the saline spray and intensity. When measured up to 500 mm away from the transducer tip, the transmission of 39.5 kHz ultrasound was not significantly attenuated by the saline itself. In the absence of the saline spray, the acoustic intensity range of the MIST device was calculated to be 429–188 mW cm−2 across the manufacturer-specified treatment range (12.5–20 mm). Because of the acoustic impedance mismatch between air and soft tissue, the MIST Therapy device would deliver only 0.1% of this incident intensity into the wound site.
  
  PubDate: 2013-06-03T12:44:39Z
Electronic Beam Steering Used with a Toroidal HIFU Transducer Substantially Increases the Coagulated Volume
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Jeremy Vincenot , David Melodelima , Françoise Chavrier , Alexandre Vignot , Anthony Kocot , Jean-Yves Chapelon
  Treatment with high-intensity focused ultrasound is well established but requires extended treatment time. A device composed of 256 elements arranged on a toroidal transducer was developed to increase the coagulated volume. When all the elements are working in phase for 40 s, a volume of 6–8 cm3 can be ablated. However, the mechanical juxtaposition of single lesions is still necessary for treating one tumor with a diameter of 2 cm. The objective of this study was to combine this toroidal transducer geometry with electronic beam steering to ablate tumors with adequate normal tissue margins and without any mechanical displacement of the high-intensity focused ultrasound device. In vitro tests demonstrated that the coagulated volume obtained from 130 s of total exposure has an average diameter of 41.4 ± 4.0 mm and an average length of 53.3 ± 6.1 mm. This single lesion can be used to treat various size of metastasis, located at depths in the liver ranging 5–45 mm.
  
  PubDate: 2013-06-03T12:44:39Z
Assessment of the Fundamental Flexural Guided Wave in Cortical Bone by an Ultrasonic Axial-Transmission Array Transducer
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Vantte Kilappa , Kailiang Xu , Petro Moilanen , Erkki Heikkola , Dean Ta , Jussi Timonen
  The fundamental flexural guided wave (FFGW), as modeled, for example, by the A0 Lamb mode, is a clinically useful indicator of cortical bone thickness. In the work described in this article, we tested so-called multiridge-based analysis, based on the crazy climber algorithm and short-time Fourier transform, for assessment of the FFGW component recorded by a clinical array transducer featuring a limited number of elements. Methods included numerical finite-element simulations and experiments in bone phantoms and human radius specimens (n = 41). The proposed approach enabled extraction of the FFGW component and determination of its group velocity. This group velocity was in good agreement with theoretical predictions and possessed reasonable sensitivity to cortical width (r 2 = 0.51, p < 0.001) in the in vitro experiments. It is expected that the proposed approach enables related clinical application. Further work is still needed to analyze in more detail the challenges related to the impact of the overlying soft tissue.
  
  PubDate: 2013-06-03T12:44:39Z
Left Ventricular Longitudinal Strain Measured by Speckle Tracking as a Predictor of the Decrease in Left Ventricular Deformation in Children with Congenital Stenosis of the Aorta or Coarctation of the Aorta
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): J. Van der Ende , Clara A. Vázquez Antona , Julio Erdmenger Orellana , Ángel Romero Cárdenas , Francisco Javier Roldan , Jesús Vargas Barrón
  Children born with a left ventricular outflow tract obstruction (LVOTO) can present with symptoms of left ventricular (LV) failure while ejection fraction (EF) is normal. A more sensitive parameter of systolic function might be obtained with speckle tracking echocardiography, which describes ventricular longitudinal deformation in strain values. It is presumed that despite a normal or only slight decrease in ejection fraction, patients with a LVOTO demonstrate aberrations in the longitudinal deformation of the left ventricle. In addition, it is expected that after a successful intervention, longitudinal deformation returns to normal values. Standard trans-thoracic echocardiography was performed on 33 consecutive patients with a LVOTO, either an isolated aortic coarctation (AoCo) or an isolated aortic stenosis (AoSt). Before intervention a significant decrease in strain values was observed compared with the control group (N = 40), with an additional decrease in strain values in the first week after intervention (N = 16). Strain values recovered after a mean follow-up period of 42 wk (N = 9), though normal values were never reached. In addition, patients with an AoCo had a smaller decrease in strain values compared with patients with AoSt. All strain values were measured with a concomitant ejection fraction between normal limits. It is concluded that patients with a congenital LVOTO have decreased ventricular systolic function measured as strain values, whereas their ejection fraction is within the normal range. Therefore, as ejection fraction may not be an accurate measure, speckle tracking-based strain may be significant in the identification of subtle changes in longitudinal deformation and may create opportunities for patients to benefit from early treatment for heart failure.
  
  PubDate: 2013-06-03T12:44:39Z
Non-invasive Assessment of Liver Fibrosis in a Rat Model: Shear Wave Elasticity Imaging Versus Real-Time Elastography
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Sen-hao Lin , Hong Ding , Feng Mao , Li-Yun Xue , Wei-wei Lv , Hong-Guang Zhu , Bei-Jian Huang , Wen-Ping Wang
  The purpose of this study was to investigate the diagnostic value of shear wave elasticity imaging (SWEI) and real-time elastography (RTE) in liver fibrosis induced by dimethylnitrosamine (DMN) and to compare the accuracy of these methods. Seventy male Wistar rats given a single intra-peritoneal injection of DMN and 10 control rats given a saline injection underwent SWEI and RTE to determine their shear wave velocity (V s) and liver fibrosis (LF) index, respectively. Correlations between V s or the LF index and histologic stage of liver fibrosis (S0–S4) were analyzed, and the diagnostic values of the techniques were assessed using a receiver operating characteristic curve. A positive correlation was found between V s and stage of liver fibrosis (r = 0.947, p < 0.001) and between LF index and stage (S) of liver fibrosis (r = 0.662, p < 0.001). For V s, the areas under the receiver operating characteristic curve for the diagnosis of fibrosis, S ≥ S1, S ≥ S2, S ≥ S3 and S = S4, were 0.983, 0.995, 0.999 and 0.964, respectively; for the LF index, the values were 0.871, 0.887, 0.761 and 0.839, respectively (all p < 0.001). V s and the LF index values in rats with severe inflammatory activity were significantly higher than those in controls (p < 0.001). In conclusion, positive correlations exist between V s or the LF index and the severity of liver fibrosis in rats. V s is more accurate than the LF index in predicting liver fibrosis in rats. However, severe inflammatory activity may reduce the accuracy of both techniques.
  
  PubDate: 2013-06-03T12:44:39Z
Quantitative Contrast-Enhanced Ultrasound Comparison Between Inflammatory and Fibrotic Lesions in Patients with Crohn's Disease
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Kim Nylund , Radovan Jirik , Martin Mezl , Sabine Leh , Trygve Hausken , Frank Pfeffer , Svein Ødegaard , Torfinn Taxt , Odd Helge Gilja
  The aim of this study was to determine whether there are differences in absolute blood flow between patients with Crohn's disease with inflammation or fibrosis using contrast-enhanced ultrasound. Eighteen patients with fibrotic disease and 19 patients with inflammation were examined. Video sequences of contrast data were analyzed using a pharmacokinetic model to extract the arterial input and tissue residue functions with a custom software, enabling calculation of the absolute values for mean transit time, blood volume and flow. Feasibility of the examination was 89%. The fibrosis group had lower blood volume (0.9 vs. 3.4 mL per 100 mL tissue; p = 0.001) and flow (22.6 vs. 45.3 mL/min per 100 mL tissue; p = 0.003) compared with the inflammation group. There was no significant difference in mean transit time (3.9 vs. 5.5 s). In conclusion, absolute perfusion measurement in the gastrointestinal wall using contrast-enhanced ultrasound is feasible. There seems to be reduced blood volume and blood flow in patients with fibrotic disease.
  
  PubDate: 2013-06-03T12:44:39Z
Acoustic Radiation Force Impulse Imaging for Reactive and Malignant/Metastatic Cervical Lymph Nodes
- Abstract: Publication date: July 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 7
  Author(s): Takashi Fujiwara , Junko Tomokuni , Ken Iwanaga , Susumu Ooba , Tomoyuki Haji
  The aim of this study was to compare lymph node stiffness using acoustic radiation force impulse (ARFI) imaging in patients with cervical lymph node swelling. Forty-two cervical lymph nodes (reactive, n = 22; metastatic, n = 20) from 19 patients (13 men, 6 women; mean age, 63.68 ± 14.9 y; range, 23–85 y) were examined between September 2011 and March 2012. The shear wave velocity (SWV, m/s) of each lymph node was evaluated by ARFI imaging. SWV of reactive lymph nodes was 1.52 ± 0.48 m/s, and that of metastatic/malignant lymph nodes was 2.46 ± 0.75 m/s. A SWV > 1.9 m/s was very useful metastatic lymph node classification, with 95.0% specificity, 81.8% sensitivity and 88.0% overall accuracy. The area under the receiver operating characteristic curve was 0.923 (95% confidence interval, 0.842–1.000). ARFI imaging can be useful in the differentiation of reactive and malignant/metastatic cervical lymph nodes.
  
  PubDate: 2013-06-03T12:44:39Z
Influence of Shell Composition on the Resonance Frequency of Microbubble Contrast Agents
- Abstract: Publication date: Available online 15 May 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Stephen Dicker , Michał Mleczko , Monica Siepmann , Nicole Wallace , Youhan Sunny , Christopher R. Bawiec , Georg Schmitz , Peter Lewin , Steven P. Wrenn
  The effect of variations in microbubble shell composition on microbubble resonance frequency is revealed through experiment. These variations are achieved by altering the mole fraction and molecular weight of functionalized polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell and measuring the microbubble resonance frequency. The resonance frequency is measured via a chirp pulse and identified as the frequency at which the pressure amplitude loss of the ultrasound wave is the greatest as a result of passing through a population of microbubbles. For the shell compositions used herein, we find that PEG molecular weight has little to no influence on resonance frequency at an overall PEG mole fraction (0.01) corresponding to a mushroom regime and influences the resonance frequency markedly at overall PEG mole fractions (0.050–0.100) corresponding to a brush regime. Specifically, the measured resonance frequency was found to be 8.4, 4.9, 3.3 and 1.4 MHz at PEG molecular weights of 1000, 2000, 3000 and 5000 g/mol, respectively, at an overall PEG mole fraction of 0.075. At an overall PEG mole fraction of just 0.01, on the other hand, resonance frequency exhibited no systematic variation, with values ranging from 5.7 to 4.9 MHz. Experimental results were analyzed using the Sarkar bubble dynamics model. With the dilatational viscosity held constant (10–8 N·s/m) and the elastic modulus used as a fitting parameter, model fits to the pressure amplitude loss data resulted in elastic modulus values of 2.2, 2.4, 1.6 and 1.8 N/m for PEG molecular weights of 1000, 2000, 3000 and 5000 g/mol, respectively, at an overall PEG mole fraction of 0.010 and 4.2, 1.4, 0.5 and 0.0 N/m, respectively, at an overall PEG mole fraction of 0.075. These results are consistent with theory, which predicts that the elastic modulus is constant in the mushroom regime and decreases with PEG molecular weight to the inverse 3/5 power in the brush regime. Additionally, these results are consistent with inertial cavitation studies, which revealed that increasing PEG molecular weight has little to no effect on inethe rtial cavitation threshold in the mushroom regime, but that increasing PEG molecular weight decreases inertial cavitation markedly in the brush regime. We conclude that the design and synthesis of microbubbles with a prescribed resonance frequency is attainable by tuning PEG composition and molecular weight.
  
  PubDate: 2013-05-18T09:31:25Z
Sonographic and Pathologic Image Analysis of Pure Mucinous Carcinoma of the Breast
- Abstract: Publication date: Available online 15 May 2013
  Source:Ultrasound in Medicine & Biology
  Author(s): Setsuko Kaoku , Eiichi Konishi , Yasuhisa Fujimoto , Eriko Tohno , Tsuyoshi Shiina , Kengo Kondo , Sanae Yamazaki , Mariko Kajihara , Nobuhiko Shinkura , Akio Yanagisawa
  The aims of this study were to elucidate sonographic and histologic features of pure mucinous carcinoma (P-MC) of the breast using quantitative analysis and to evaluate the relationship between quantitative analysis and visual qualitative assessment. Eleven P-MCs (nine patients) were evaluated qualitatively and quantitatively. Three experts assessed these sonographic images using the Breast Imaging Reporting and Data System (BI-RADS) lexicon. For assessment of internal echoes and posterior echoes, quantitative measures were determined using ImageJ software. Histologic thin sections were stained for classification into separate parts of the tumor (stroma, mucin and cancer cells) and were digitized. Internal echoes were isoechoic in 7 of 11 (63.6%) tumors and hypoechoic in 4 of 11 (36.4%); all P-MCs were “enhanced” in qualitative evaluation. As internal echoes increased, the proportion of stroma increased and that of mucin decreased. The high level of internal echoes is correlated with reflection and back-scattering, which are caused mainly by the interface between mucin and stroma.
  
  PubDate: 2013-05-18T09:31:25Z
Editorial Advisory Board
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  
  PubDate: 2013-05-06T08:12:46Z
Masthead
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  
  PubDate: 2013-05-06T08:12:46Z
Inter- and Intra-Operator Reliability and Repeatability of Shear Wave Elastography in the Liver: A Study in Healthy Volunteers
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): John M. Hudson , Laurent Milot , Craig Parry , Ross Williams , Peter N. Burns
  This study assessed the reproducibility of shear wave elastography (SWE) in the liver of healthy volunteers. Intra- and inter-operator reliability and repeatability were quantified in three different liver segments in a sample of 15 subjects, scanned during four independent sessions (two scans on day 1, two scans 1 wk later) by two operators. A total of 1440 measurements were made. Reproducibility was assessed using the intra-class correlation coefficient (ICC) and a repeated measures analysis of variance. The shear wave speed was measured and used to estimate Young's modulus using the Supersonics Imagine Aixplorer. The median Young's modulus measured through the inter-costal space was 5.55 ± 0.74 kPa. The intra-operator reliability was better for same-day evaluations (ICC = 0.91) than the inter-operator reliability (ICC = 0.78). Intra-observer agreement decreased when scans were repeated on a different day. Inter-session repeatability was between 3.3% and 9.9% for intra-day repeated scans, compared with to 6.5%–12% for inter-day repeated scans. No significant difference was observed in subjects with a body mass index greater or less than 25 kg/m2.
  
  PubDate: 2013-05-06T08:12:46Z
Correlation Between Subclinical Median Neuropathy and the Cross-Sectional Area of the Median Nerve at the Wrist
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Po-Hsien Su , Wen-Shiang Chen , Tyng-Guey Wang , Huey-Wen Liang
  Although subclinical median neuropathy is not uncommon, its correlation with sonographic changes to the median nerve at the wrist has not been studied. We included 62 subjects (with 107 wrists) who reported experiencing no hand numbness. All subjects underwent nerve conduction studies (NCS) and sonography for median nerve at the pisiform level. The cross-sectional area (CSA), perimeter, long axis and short axis of median nerve were obtained off-line by manual tracing with a mouse and computed by one algorithm written in MatLab. Eighteen wrists met the inclusion criteria of subclinical median neuropathy. The CSA, perimeter and long axis of the median nerve were significantly different between normal and abnormal NCS wrists. Mixed model analysis showed that subclinical neuropathy was associated with enlarged CSA, but the other demographic variables (gender, age and body mass index and occupational categories) were not. Our findings support the use of both patient symptoms and NCS to define normal subjects during further studies. In addition, enlarged CSA within asymptomatic individuals should raise concern for subclinical median neuropathy.
  
  PubDate: 2013-05-06T08:12:46Z
The Value of High-Frequency Ultrasonographic Imaging for Quantifying Trigger Digits: A Correlative Study with Clinical Findings in Patients with Different Severity Grading
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Chen-Hao Chiang , Li-Chieh Kuo , Yao-Lung Kuo , Kuo-Chen Wu , Chung-Jung Shao , Tai-Chang Chern , I-Ming Jou
  Trigger digit is recognized as thickening and constriction of the flexor tendon sheath at the base of digits. This study investigates the correlation between the severity grading of trigger digits and clinical findings from high-frequency ultrasonography. We measured and compared thicknesses, areas and pathological changes of the flexor digit tendons among total, contracture and noncontracture trigger digits and noninvolved contralateral digits. Forty-seven patients with 55 idiopathic trigger digits (36 contracture and 19 noncontracture) and 55 noninvolved contralateral digits were examined using high-frequency ultrasonography. The thickness of the flexor tendons was measured in a longitudinal plane at the A1 pulley: Inlet (metacarpal head–neck junction), Outlet (proximal phalangeal base–shaft junction) and Interpulley (middle of Inlet and Outlet). The cross-sectional and extratendinous tissue areas of the flexor tendons in a transverse plane at the point of Interpulley were measured. Pathological changes including irregular internal echotextures, fluid collection, dominant A1 pulley and abnormal metacarpophalangeal joint were analyzed. All thicknesses and areas of total and contracture trigger digits were significantly greater than those of noninvolved contralateral digits (p < 0.05), whereas no significant difference was observed in noncontracture trigger digits. The pathological changes were all significantly different from noninvolved contralateral digits in total, contracture and noncontracture trigger digits (p < 0.05). In contracture and noncontracture trigger digits, there were significant differences only in the thickness of the Inlet and the pathological change of the dominant A1 pulley (p < 0.05). In conclusion, the results of the ultrasonographic measurements and findings provided evidence of Notta's node and correlated with clinical findings and severity grades.
  
  PubDate: 2013-05-06T08:12:46Z
Liver Fibrosis Assessment Using Transient Elastography Guided with Real-Time B-mode Ultrasound Imaging: A Feasibility Study
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Tak-Man Mak , Yan-Ping Huang , Yong-Ping Zheng
  Liver fibrosis is a kind of chronic damage of the liver and can lead to cirrhosis, one of the top 10 causes of death in the Western world. However, there is still a lack of noninvasive methods for diagnosing liver fibrosis. Fibroscan (Echosens, Paris, France), a device based on A-mode transient elastography, has shown promising results. In this study, a transient elastography system with real-time B-mode imaging for non-invasive liver fibrosis assessment, named Liverscan, was developed; its performance was tested and compared with that of the Fibroscan. A specific measurement probe was designed and fabricated with a B-mode ultrasound transducer fixed along the axis of a mechanical vibrator. It was integrated with the Liverscan to measure liver stiffness based on the shear wave propagation in liver tissues. The system was validated by mechanical indentation test using custom-made agar-gelatin phantoms with different stiffness. To further test its feasibility, in vivo measurements were conducted in 67 volunteers (age, 34 ± 3 years; body mass index, 21.3 ± 2.8 kg/m2; Mean ± SD., 34 male and 33 female), including 20 patients with various liver diseases, and 28 (19 male and 9 female) being tested by both Liverscan and Fibroscan. A significant linear correlation between the stiffness measured by the mechanical indentation test and that by the Liverscan (r = 0.973; p < 0.001) was obtained. The in vivo liver stiffness measured by Liverscan was also correlated with that by Fibroscan significantly (r = 0.886; p < 0.001). There was a significant difference in liver stiffness between the 20 patients and the other healthy subjects (14.1 ± 3.4 kPa vs. 10.5 ± 2.1 kPa; p = 0.001). The intra- and inter-observer tests indicated that the measurements were repeatable with intra-class correlation coefficients being 0.987 (p < 0.001) and 0.988 (p < 0.001), respectively. This study demonstrated that Liverscan with a specifically designed probe was able to measure and differentiate liver of different stiffness using the established measurement protocol under the guidance of real-time B-mode ultrasound imaging.
  
  PubDate: 2013-05-06T08:12:46Z
Sonographic Elastography Improves the Sensitivity and Specificity of Axilla Sampling in Breast Cancer: A Prospective Study
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Wan-Chen Tsai , Christopher Kwang-Jane Lin , Hung-Kuang Wei , Ben-Long Yu , Chen-Fang Hung , Skye Hongiun Cheng , Chii-Ming Chen
  We describe a study to determine whether elastography of axillary lymph nodes (LNs) combined with B-mode ultrasound (US) is capable of differentiating the benign from the metastatic state in patients with breast cancer. B-mode US, elastography and fine-needle aspiration of 90 axillary lymph nodes from 89 female patients with breast cancer are described in this report. Five elastographic patterns were observed as defined by the percentages of high elasticity according to pattern of distribution and degree of hardness of the target LNs. B-mode US and elastography scores were combined to give the final scores. Sensitivity and specificity were 80% and 88%, respectively, for B-mode US alone, 86% and 90% for elastography alone and 84% and 98% for the combined assessment to differentiate the benign from the malignant state. The combination of B-mode US and elastography is capable of identifying metastatic axillary LNs from benign enlargement in patients with breast cancer.
  
  PubDate: 2013-05-06T08:12:46Z
Contents
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  
  PubDate: 2013-05-06T08:12:46Z
Quantitative Shear Wave Elastography in the Evaluation of Metastatic Cervical Lymph Nodes
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Young Jun Choi , Jeong Hyun Lee , Hyun Kyung Lim , Sang Yoon Kim , Myung Woul Han , Kyung-Ja Cho , Jung Hwan Baek
  Our aim was to compare the diagnostic performance of shear wave elastography (SWE) with that of gray-scale ultrasound (US) in differentiating metastatic from benign lymph nodes in patients with head and neck malignancies. Maximum shear elasticity modulus (maxSM) was measured on SWE. The reference standard was pathologic diagnosis after surgery. We examined 67 lymph nodes (34 metastatic, 33 benign) from 15 patients (8 men and 7 women; mean age, 54.2 years). The maxSM value was significantly higher for metastatic than benign lymph nodes (41.06 ± 36.34 kPa vs. 14.22 ± 4.19 kPa, p < 0.0001) at a cutoff level of 19.44 kPa. Accuracy, sensitivity and specificity were 94, 91 and 97%, respectively, for SWE, and 91, 88 and 94%, respectively, for gray-scale US. Multiple regression analysis showed that the maxSM value (r = 0.882) and gray-scale US criteria (r = 0.837) were independent variables. SWE may be a valuable quantitative reproducible method for characterizing cervical lymph nodes.
  
  PubDate: 2013-05-06T08:12:46Z
Developmental Impact and Lesion Maturation of Histotripsy-Mediated Non-Invasive Tissue Ablation in a Fetal Sheep Model
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Yohan Kim , Carlen G. Fifer , Sarah K. Gelehrter , Gabe E. Owens , Deborah R. Berman , Eli Vlaisavljevich , Steven P. Allen , Maria F. Ladino-Torres , Zhen Xu
  Non-invasive histotripsy therapy has previously been used to achieve precise fetal tissue ablation in a sheep model. To further assess the clinical viability of the technique, this study investigated potential effects of histotripsy therapy during the remaining gestation and its local impact on fetal development. Five ewes (six lambs) at 95–107 d of gestation were treated and allowed to complete the full gestation period of 150 d. A 1-MHz focused transducer was used to treat the fetal kidney and liver with 5-μs pulses at 500-Hz repetition rates and 10- to 16-MPa peak negative pressures; ultrasound imaging provided real-time treatment guidance. The lambs were euthanized after delivery and treated organs were harvested. Samples were examined by magnetic resonance imaging and histopathologic analysis. These data were compared with results from four other ewes (four lambs) that underwent similar treatments but were sacrificed immediately after the procedure. The sheep tolerated the treatment well, and acute lesion samples displayed well-defined ablated regions characterized by the presence of fractionated tissue and hemorrhage. All fetuses that were allowed to continue gestation survived and were delivered at full term. The lambs were healthy on delivery, with no signs of external injury. A minor indentation was observed in each of the treated kidneys with minimal presence of fibrous tissue, while no discernible signs of lesions were detected in treated livers. In a sheep model, histotripsy-mediated fetal tissue ablation caused no acute or pregnancy-related complications, supporting the potential safety and effectiveness of histotripsy therapy as a tool in fetal intervention procedures.
  
  PubDate: 2013-05-06T08:12:46Z
Evidence for Trapped Surface Bubbles as the Cause for the Twinkling Artifact in Ultrasound Imaging
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Wei Lu , Oleg A. Sapozhnikov , Michael R. Bailey , Peter J. Kaczkowski , Lawrence A. Crum
  The mechanism of the twinkling artifact (TA) that occurs during Doppler ultrasound imaging of kidney stones was investigated. The TA expresses itself in Doppler images as time-varying color. To define the TA quantitatively, beam-forming and Doppler processing were performed on raw per channel radio-frequency data collected when imaging human kidney stones in vitro. Suppression of twinkling by an ensemble of computer-generated replicas of a single radio frequency signal demonstrated that the TA arises from variability among the acoustic signals and not from electronic signal capture or processing. This variability was found to be random, and its suppression by elevated static pressure and return when the pressure was released suggest that the presence of bubbles on the stone surface is the mechanism that gives rise to the TA.
  
  PubDate: 2013-05-06T08:12:46Z
Impact of Microbubble-Enhanced Ultrasound on Liver Ethanol Ablation
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Qing Liu , Hongzhi Zhao , Shengzheng Wu , Xiaochen Zhao , Yu Zhong , Lu Li , Zheng Liu
  Ethanol ablation (EA) is a safe and effective method for treating small liver cancer. However, the ethanol is rapidly washed out by blood perfusion, preventing its accumulation within tumors. Microbubble-enhanced ultrasound (MEUS) is capable of disrupting tumor and liver circulation. We hypothesized that this disruption could be used to enhance EA of normal liver tissue. We treated surgically exposed rabbit liver with a combination of MEUS and EA. The controls were treated with only MEUS or 0.05 mL EA. MEUS treatment was administered with a high-pressure-amplitude, pulsed therapeutic ultrasound device and intra-venous injection of microbubbles. Therapeutic ultrasound was delivered at an acoustic pressure of 4.3 MPa and a duty cycle of 0.22%. Contrast-enhanced ultrasound was performed to estimate liver blood perfusion. Livers were harvested for necrotic volume measurements 48 h after treatment. Contrast-enhanced ultrasound demonstrated that liver perfusion was temporally arrested, with a significant peak intensity decline from −46.9 ± 3.8 to −64.0 ± 3.3 dB, after MEUS treatment. The mean volume ablated in MEUS + EA-treated livers (3.3 ± 2.3 cm3) was more than 10 times larger than that in livers treated only with EA (0.3 ± 0.2 cm3). The volume of liver ablated by MEUS treatment alone was minor, scattered and immeasurable. These results indicate that MEUS disruption of the liver circulation can greatly promote EA of liver.
  
  PubDate: 2013-05-06T08:12:46Z
High-Frame-Rate Ultrasound Color-Encoded Speckle Imaging of Complex Flow Dynamics
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Billy Y.S. Yiu , Alfred C.H. Yu
  Realization of flow imaging at high frame rates is essential to the visualization of complex flow patterns with fast-changing spatiotemporal dynamics. In this study, we present an experimental demonstration of a novel ultrasound-based high-frame-rate flow visualization technique called color-encoded speckle imaging (CESI), which depicts flow information in a hybrid form comprising flow speckle pattern and color-encoded velocity mapping. This technique works by integrating two key principles: (i) using broad-view data acquisition schemes like plane wave compounding to obtain image data at frame rates well beyond the video display range and (ii) deriving and displaying both flow speckles and velocity estimates from the acquired broad-view image data. CESI was realized on a channel-domain ultrasound imaging research platform, and its performance was evaluated in the context of monitoring complex flow dynamics inside a carotid bifurcation flow phantom with 25% eccentric stenosis at the inlet of the internal carotid artery. Results show that, using an imaging frame rate of 2000 frames per second (based on plane wave compounding with five steering angles), CESI can effectively render flow acceleration and deceleration with visual continuity. It is also effective in depicting how stenosis-related flow disturbance events, such as flow jet formation and post-stenotic flow recirculation, evolve spatiotemporally over a pulse cycle. We anticipate that CESI can represent a rational approach to rendering flow information in ultrasound-based vascular diagnoses.
  
  PubDate: 2013-05-06T08:12:46Z
Accuracy of Real-Time Single- and Multi-Beat 3-D Speckle Tracking Echocardiography In Vitro
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Johannes Just Hjertaas , Henrik Fosså , Grete Lunestad Dybdahl , Renate Grüner , Per Lunde , Knut Matre
  With little data published on the accuracy of cardiac 3-D strain measurements, we investigated the agreement between 3-D echocardiography and sonomicrometry in an in vitro model with a polyvinyl alcohol phantom. A cardiac scanner with a 3-D probe was used to acquire recordings at 15 different stroke volumes at a heart rate of 60 beats/min, and eight different stroke volumes at a heart rate of 120 beats/min. Sonomicrometry was used as a reference, monitoring longitudinal, circumferential and radial lengths. Both single- and multi-beat acquisitions were recorded. Strain values were compared with sonomicrometer strain using linear correlation coefficients and Bland–Altman analysis. Multi-beat acquisition showed good agreement, whereas real-time images showed less agreement. The best correlation was obtained for a heart rate 60 of beats/min at a volume rate 36.6 volumes/s.
  
  PubDate: 2013-05-06T08:12:46Z
Extended-Field-of-View Three-Dimensional Transesophageal Echocardiography Using Image-Based X-Ray Probe Tracking
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): R. James Housden , YingLiang Ma , Aruna Arujuna , Niels Nijhof , Pascal Cathier , Geert Gijsbers , Roland Bullens , Jaswinder Gill , C. Aldo Rinaldi , Victoria Parish , Kawal S. Rhode
  The use of ultrasound imaging for guidance of cardiac interventional procedures is limited by the small field of view of the ultrasound volume. A larger view can be created by image-based registration of several partially overlapping volumes, but automatic registration is likely to fail unless the registration is initialized close to the volumes' correct alignment. In this article, we use X-ray images to track a transesophageal ultrasound probe and thereby provide initial position information for the registration of the ultrasound volumes. The tracking is possible using multiple X-rays or just a single X-ray for each probe position. We test the method in a phantom experiment and find that with at least 50% overlap, 88% of volume pairs are correctly registered when tracked using three X-rays and 86% when using single X-rays. Excluding failed registrations with errors greater than 10 mm, the average registration accuracy is 2.92 mm between ultrasound volumes and 4.75 mm for locating an ultrasound volume in X-ray space. We conclude that the accuracy and robustness of the registrations are sufficient to provide useful images for interventional guidance.
  
  PubDate: 2013-05-06T08:12:46Z
Combination of High-Resolution Ultrasound-Guided Perivascular Regional Anesthesia of the Internal Carotid Artery and Intermediate Cervical Plexus Block for Carotid Surgery
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Thomas Rössel , Stephan Kersting , Axel R. Heller , Thea Koch
  All previously documented regional anesthesia procedures for carotid artery surgery routinely require additional local infiltration or systemic supplementation with opioids to achieve satisfactory analgesia because of the complex innervation of the surgical site. Here, we report a reliable ultrasound-guided anesthesia method for carotid artery surgery. High-resolution ultrasound-guided regional anesthesia using a 12.5-MHz linear ultrasound transducer was performed in 34 patients undergoing carotid endarterectomy. Anesthesia consisted of perivascular regional anesthesia of the internal carotid artery and intermediate cervical plexus block. The internal carotid artery and the nerves of the superficial cervical plexus were identified, and a needle was placed dorsal to the internal carotid artery and directed cranially to the carotid bifurcation under ultrasound visualization. After careful aspiration, local anesthetic was spread around the internal carotid artery and the carotid bifurcation. In the second step, local anesthetic was injected below the sternocleidomastoid muscle along the previously identified nerves of the intermediate cervical plexus. The necessity for intra-operative supplementation and the conversion rate to general anesthesia were recorded. Ultrasonic visualization of the region of interest was possible in all cases. Needle direction was successful in all cases. Three to five milliliters of 0.5% ropivacaine produced satisfactory spread around the carotid bifurcation. For intermediate cervical plexus block, 10 to 20 mL of 0.5% ropivacaine produced sufficient intra-operative analgesia. Conversion to general anesthesia because of an incomplete block was not necessary. Five cases required additional local infiltration with 1% prilocaine (2–6 mL) by the surgeon. Visualization with high-resolution ultrasound yields safe and accurate performance of the block. Because of the low rate of intra-operative supplementation, we conclude that the described ultrasound-guided perivascular anesthesia technique is effective for carotid artery surgery.
  
  PubDate: 2013-05-06T08:12:46Z
Phyllodes Tumors of the Breast: Ultrasonographic Findings and Diagnostic Performance of Ultrasound-Guided Core Needle Biopsy
- Abstract: Publication date: June 2013
  Source:Ultrasound in Medicine & Biology, Volume 39, Issue 6
  Author(s): Inyoung Youn , Seon Hyeong Choi , Hee Jung Moon , Min Jung Kim , Eun-Kyung Kim
  We evaluated ultrasonography (US) findings between benign and malignant phyllodes tumors and analyzed diagnostic performance of US-guided core needle biopsy (CNB) for phyllodes tumors. Surgically removed phyllodes tumors of 168 women were divided into two groups according to the benign and malignant (including borderline tumor) groups and 116 were benign and 52 were malignant. On US, the complex cystic echogenicity (p = 0.021), presence of cleft (p = 0.005) and higher final US assessment (p = 0.008) were more frequent in the malignant group. The sensitivity of CNB including fibroepithelial tumors was 67.9% (114/168) and the concordant rate between CNB and surgical excision was 82.1% (32/39) and 5.8% (3/52) in the benign and malignant group. Our results suggested that the US findings of complex cystic echogenicity, cleft, higher final US assessment were more frequent in malignant phyllodes tumors. The sensitivity of CNB was 67.9% (114/168) and malignant phyllodes tumors were rarely diagnosed as malignant by US-guided CNB.
  
  PubDate: 2013-05-06T08:12:46Z