Ultrasound in medicine & biology

Publications in this journal

• Article: Determination of the Interfacial Rheological Properties of a Poly(DL-lactic acid)-Encapsulated Contrast Agent Using In Vitro Attenuation and Scattering.

  Shirshendu Paul, Daniel Russakow, Tyler Rodgers, Kausik Sarkar, Michael Cochran, Margaret A Wheatley
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 05/2013;
• Article: Assessment of the Fundamental Flexural Guided Wave in Cortical Bone by an Ultrasonic Axial-Transmission Array Transducer.

  Vantte Kilappa, Kailiang Xu, Petro Moilanen, Erkki Heikkola, Dean Ta, Jussi Timonen
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Ultrasound Elastographic Evaluation in the Diagnosis of Carpal Tunnel Syndrome: Initial Findings.

  Gunes Orman, Serkan Ozben, Nergiz Huseyinoglu, Mahmut Duymus, Keziban Gunce Orman
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Effects of Biophysical Parameters in Enhancing Radiation Responses of Prostate Tumors with Ultrasound-Stimulated Microbubbles.

  Hyunjung Christina Kim, Azza Al-Mahrouki, Alborz Gorjizadeh, Raffi Karshafian, Gregory J Czarnota
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  ABSTRACT: We show here that ultrasound-stimulated microbubbles can enhance cell death within tumors when combined with radiation. The aim of this study was to investigate how different ultrasound parameters, different microbubble concentrations and different radiation doses interact to enhance cell death. Prostate xenograft tumors (PC-3) in severe combined immunodeficiency mice were subjected to ultrasound treatment at various peak negative pressures (250, 570 and 750 kPa) at a center frequency of 500 kHz, different microbubble concentrations (8, 80 and 1000 μL/kg) and different radiation doses (0, 2 and 8 Gy). Twenty-four hours after treatment, tumors were excised and assessed for cell death. Histologic analyses revealed that increases in radiation dose, microbubble concentration and ultrasound pressure promoted apoptotic cell death and disruption within tumors by as much as 21%, 30% and 43%, respectively. Comparable increases in ceramide, a cell death mediator, were identified using immunohistochemistry. We also show here that even clinically used microbubble concentrations combined with ultrasound can induce significant enhancement of cell death.
  Ultrasound in medicine & biology 04/2013;
• Article: Enhanced Intracellular Delivery of a Model Drug Using Microbubbles Produced by a Microfluidic Device.

  Adam J Dixon, Ali H Dhanaliwala, Johnny L Chen, John A Hossack
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Acoustic Waves in Medical Imaging and Diagnostics.

  Armen P Sarvazyan, Matthew W Urban, James F Greenleaf
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: 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.

  J Van der Ende, Clara A Vázquez Antona, Julio Erdmenger Orellana, Angel Romero Cárdenas, Francisco Javier Roldan, Jesús Vargas Barrón
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Quantitative Contrast-Enhanced Ultrasound Comparison Between Inflammatory and Fibrotic Lesions in Patients With Crohn's Disease.

  Kim Nylund, Radovan Jirik, Martin Mezl, Sabine Leh, Trygve Hausken, Frank Pfeffer, Svein Odegaard, Torfinn Taxt, Odd Helge Gilja
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Ultrasound Improves the Uptake and Distribution of Liposomal Doxorubicin in Prostate Cancer Xenografts.

  Siv Eggen, Mercy Afadzi, Esben A Nilssen, Solveig Bjærum Haugstad, Bjørn Angelsen, Catharina de L Davies
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Electronic Beam Steering Used With a Toroidal HIFU Transducer Substantially Increases the Coagulated Volume.

  Jeremy Vincenot, David Melodelima, Françoise Chavrier, Alexandre Vignot, Anthony Kocot, Jean-Yves Chapelon
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  ABSTRACT: 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 cm(3) 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Non-invasive Assessment of Liver Fibrosis in a Rat Model: Shear Wave Elasticity Imaging Versus Real-Time Elastography.

  Sen-Hao Lin, Hong Ding, Feng Mao, Li-Yun Xue, Wei-Wei Lv, Hong-Guang Zhu, Bei-Jian Huang, Wen-Ping Wang
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  ABSTRACT: 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 (Vs) and liver fibrosis (LF) index, respectively. Correlations between Vs 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 Vs 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 Vs, 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). Vs 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 Vs or the LF index and the severity of liver fibrosis in rats. Vs is more accurate than the LF index in predicting liver fibrosis in rats. However, severe inflammatory activity may reduce the accuracy of both techniques.
  Ultrasound in medicine & biology 04/2013;
• Article: Axial and Radial Waveforms in Common Carotid Artery: An Advanced Method for Studying Arterial Elastic Properties in Ultrasound Imaging.

  Heikki Yli-Ollila, T Laitinen, M Weckström, T M Laitinen
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Microbubble-Enhanced Ultrasound Liberation of mRNA Biomarkers In Vitro.

  Alex Forbrich, Robert Paproski, Mary Hitt, Roger Zemp
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  ABSTRACT: Blood-borne biomarkers have great potential in diagnostic medicine, but low concentrations, inability to determine their source and lack of a patient baseline have limited their success in both research and clinical medicine. D'Souza et al. previously demonstrated that ultrasound-induced sonoporation can be used to liberate protein biomarkers from a colorectal cancer into the surrounding serum, overcoming many of the limitations of blood-borne biomarkers. In this study we build on D'Souza's work, extending this technique to nucleic acids, specifically mammaglobin mRNA-a potential diagnostic biomarker for breast cancer metastases. Furthermore, we propose to use ultrasound contrast agents, lipid-stabilized microbubbles, to enhance the effects of sonoporation and further amplify the biomarker levels. We demonstrate that microbubbles can enhance mammaglobin mRNA levels by two to three orders of magnitude greater than background levels and one to two orders of magnitude greater than ultrasound alone.
  Ultrasound in medicine & biology 04/2013;
• Article: Evidence for Trapped Surface Bubbles as the Cause for the Twinkling Artifact in Ultrasound Imaging.

  Wei Lu, Oleg A Sapozhnikov, Michael R Bailey, Peter J Kaczkowski, Lawrence A Crum
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Acoustic Radiation Force Impulse Imaging for Reactive and Malignant/Metastatic Cervical Lymph Nodes.

  Takashi Fujiwara, Junko Tomokuni, Ken Iwanaga, Susumu Ooba, Tomoyuki Haji
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Accuracy of Real-Time Single- and Multi-Beat 3-D Speckle Tracking Echocardiography In Vitro.

  Johannes Just Hjertaas, Henrik Fosså, Grete Lunestad Dybdahl, Renate Grüner, Per Lunde, Knut Matre
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Liver Fibrosis Assessment Using Transient Elastography Guided with Real-time B-mode Ultrasound Imaging: A Feasibility Study.

  Tak-Man Mak, Yan-Ping Huang, Yong-Ping Zheng
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  ABSTRACT: 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/m(2); 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.
  Ultrasound in medicine & biology 04/2013;
• Article: Pre-clinical Study of in Vivo Magnetic Resonance-Guided Bubble-Enhanced Heating in Pig Liver.

  Delphine Elbes, Quentin Denost, Christophe Laurent, Hervé Trillaud, Anne Rullier, Bruno Quesson
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  ABSTRACT: Bubble-enhanced heating (BEH) can be exploited to increase heating efficiency in treatment of liver tumors with non-invasive high-intensity focused ultrasound (HIFU). The objectives of this study were: (i) to demonstrate the feasibility of increasing the heating efficiency of sonication exploiting BEH in pig liver in vivo using a clinical platform; (ii) to determine the acoustic threshold for such effects with real-time, motion-compensated magnetic resonance-guided thermometry; and (iii) to compare the heating patterns and thermal lesion characteristics resulting from continuous sonication and sonication including a burst pulse. The threshold acoustic power for generation of BEH in pig liver in vivo was determined using sonication of 0.5-s duration ("burst pulse") under real-time magnetic resonance thermometry. In a second step, experimental sonication composed of a burst pulse followed by continuous sonication (14.5 s) was compared with conventional sonication (15 s) of identical energy (1.8 kJ). Modification of the heating pattern at the targeted region located at a liver depth between 20 and 25 mm required 600-800 acoustic watts. The experimental group exhibited near-spherical heating with 40% mean enhancement of the maximal temperature rise as compared with the conventional sonication group, a mean shift of 7 ± 3.3 mm toward the transducer and reduction of the post-focal temperature increase. Magnetic resonance thermometry can be exploited to control acoustic BEH in vivo in the liver. By use of experimental sonication, more efficient heating can be achieved while protecting tissues located beyond the focal point.
  Ultrasound in medicine & biology 04/2013;
• Article: Characterization of the Ultrasound Beam Produced by the MIST Therapy, Wound Healing System.

  K Keltie, C A Reay, D R Bousfield, H Cole, B Ward, C P Oates, A J Sims
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;
• Article: The Value of High-Frequency Ultrasonographic Imaging for Quantifying Trigger Digits: A Correlative Study with Clinical Findings in Patients with Different Severity Grading.

  Chen-Hao Chiang, Li-Chieh Kuo, Yao-Lung Kuo, Kuo-Chen Wu, Chung-Jung Shao, Tai-Chang Chern, I-Ming Jou
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  ABSTRACT: 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.
  Ultrasound in medicine & biology 04/2013;