bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Socrates to Teach Psychology
Authors: Dillon James J.
Published: March 2013

A cursory reading of most college mission statements can take one’s breath away in their lofty, humanistic sweep. The same is true for many course goals for Introductory Psychology. An analysis of 150 Introductory Psychology syllabi revealed that nearly 88% of courses attempt to achieve at least four of five humanistic outcomes. Students are expected to attain rich theoretical understanding, engage in critical and higher order thinking, change deep-seated attitudes, apply concepts to everyday life, and grow personally. At the end of the semester, however, many psychology instructors wonder about the extent to which these goals have actually been achieved and how much their students have learned, particularly when courses are structured around the “big textbook” and delivered in the traditional lecture format. This article presents a lively and accessible course outline for using Platonic dialogues and the ancient figure of Socrates to teach modern psychology. Socrates is among the world’s most engaging and effective teachers. He is also regarded as one of the founding figures of humanistic psychology who would have had serious problems with the didactic teaching methods and sterile textbooks of today’s college classrooms. The article shows how encountering Socrates and engaging Plato’s dialogues can help professors achieve many of the laudable humanistic goals they have for their students.
The Adult Reading History Questionnaire (ARHQ) in Icelandic
Authors: Bjornsdottir Gyda , Halldorsson Jonas G. , Steinberg Stacy , Hansdottir Ingunn , Kristjansson Kristleifur , Stefansson Hreinn , Stefansson Kari
Published: March 2013

This article describes psychometric testing of an Icelandic adaptation of the Adult Reading History Questionnaire (ARHQ), designed to detect a history of reading difficulties indicative of dyslexia. Tested in a large and diverse sample of 2,187 adults, the Icelandic adaptation demonstrated internal consistency reliability (Cronbach’s alpha = .92) and test–retest reliability ( r = .93). Validity was established by comparing scores of adults who as children received ICD-10 diagnoses of specific reading disorder (F81.0; n = 419) to those of adults defined as nondyslexics ( n = 679). ROC curve analysis resulted in an area under the curve of .92 (95% CI = .90, .93, p < .001) and a cutoff score of .43 with sensitivity of 84.5% and specificity of 83.7%. An exploratory factor analysis ( n = 2,187) suggested three subscales, Dyslexia Symptoms, Current Reading, and Memory, the mean scores of which differed significantly among diagnosed dyslexics, relatives of dyslexics, and population controls. Our results support the applicability of the ARHQ in Icelandic as a self-report screening tool for adult dyslexia in Iceland.
A Longitudinal Study of Preservice Music Teacher Development
Authors: Miksza Peter , Berg Margaret H.
Published: March 2013

The purpose of this study was to investigate the development of preservice music teachers’ concerns using Fuller and Bown’s model. Participants were 8 instrumental teachers who participated in the previous Berg and Miksza (2010) study. Data sources included goals essays, journals, a midterm growth plan, and teaching observation reports with accompanying lesson plans that were collected over a 1.5-year period. The participants expressed less concern for self-survival and more concern for making an impact on students as time progressed from their junior-level practicum experience to the end of student teaching. Concerns regarding basic competencies and professionalism ultimately gave way to specific contextual aspects of the participants’ teaching placements and more nuanced instructional issues. Results indicated that the focus of the participants’ concerns also was greatly affected by their teaching context. Implications for music teacher preparation as well as extensions of Fuller and Bown’s model are discussed.
In(visible) Bruges by Martin McDonagh
Authors: Melnikova Irina
Published: March 2013

This paper examines the ways in which In Bruges by Martin McDonagh constitutes the cinematic Bruges. It explores the peculiarities of the narrative and the ways intertextual references are made to the artworks associated with the cultural history of Bruges (Flemish painting, Georges Rodenbach’s novel Le Carillonneur) and the references to the texts which bear no relation to the history of Bruges (films on Venice, other cinematic texts, literary texts by McDonagh). The exploration of these narrative devices reveals that the interfusion of different discourses revitalizes and changes the ‘Bruges myth’ which occurs in a hypertextual dialogue with the ‘Venetian myth’. The analysis of hypertextual dialogue shows the essential difference between the two textual cities. Instead of the excess of the visible, typical of representations of Venice, the film introduces the principle of the limitation of the visible as the main feature of Bruges. This inspires the conclusion connected to the model of travelling which In Bruges proposes.
Holocaust literature and historiography in Anne Michaels’ Fugitive Pieces
Authors: Nesfield Victoria , Smith Philip
Published: March 2013

This paper examines Anne Michaels’ Fugitive Pieces (2007) in the context of Holocaust literature and historiography. It begins with an introduction to the genre of Holocaust literature and the problematic nature of ‘survivor’ testimony. Michaels’ work is then contextualized within this body of literature. The essay goes on to examine the means through which Michaels approaches the act of writing history, specifically the recording of history through alternative means to the hegemonic historiography utilized by the Nazis.
Surrealism’s ‘found object’: The enigmatic Mexico of Artaud and Breton
Authors: Nicholson Melanie
Published: March 2013

This article explores the paradoxical relationship of European surrealism to Mexico in the 1930s and 1940s. I argue that while Mexico’s historical circumstances in this period created a cultural atmosphere largely hostile to surrealism, its geography, racial mestizaje, and cultural traditions transformed the country into an ideal ‘found object’ for European surrealists. Rather than revealing itself to be the site of authentic existence sought by the surrealists, however, Mexico acted as a Rorschach image in which the surrealists revealed more about themselves than about the object of their fascination. In order to make sense of this complicated relationship, I examine several provocative texts by Antonin Artaud and André Breton (both of whom spent time in Mexico in the late 1930s) in the context of their reception by Mexican writers, who remained largely resistant to the magnetic pull of surrealism.
Researching, teaching and professional development
Authors: Notten Ton
Published: March 2013

Continuing adult education requires continuous education of the educators themselves - a highly self-referential issue. This article focuses on educating a group of ‘urban educators’ in the western part of the Netherlands who have been involved in broad urban educational programmes: school, parental education and participation, living environment, vocational preparation and the like. These contexts refer to plural and mutually connected ambitions: the necessity for more research in the broad field of urban renewal and its manifold domains; more focus on supporting the professionalisation of mid-career students engaged in Master of Public Administration (MPA) programmes, and in urban education (UrbEd) in particular, in order to build research, reflection and innovation into the course. Universities involved in professional education can make a major contribution to meeting this challenge when they arrange fruitful connections with a Research Centre like ‘Growing up in the City’.
Wavelet-Based Speckle Noise Reduction in Ultrasound B-Scan Images
Authors: Rakotomamonjy Alain , Deforge Philippe , Marché Pierre
Published: March 2013

Speckle noise is known to be signal-dependent in ultrasound imaging. Hence, separating noise from signal becomes a difficult task. This paper describes a wavelet-based method for reducing speckle noise. We derive from the model of the displayed ultrasound image the optimal wavelet-domain filter, in the least mean-square sense. Simulations on synthetic data have been carried out in order to assess the performance of the proposed filter with regards to the classical wavelet shrinkage scheme, while phantom and tissue images have been used for testing it on real data. The results show that the filter effectively reduces the speckle noise while preserving resolvable details.
Axial Strain Imaging Using a Local Estimation of the Scaling Factor from RF Ultrasound Signals
Authors: Brusseau Elisabeth , Perrey Christian , Delachartre Philippe , Vogt Michael , Vray Didier , Ermert Helmut
Published: March 2013

The main signal-processing techniques used in elastography compute strains as the displacement derivative. They perform well for very low deformations, but suffer rapidly from decorrelation noise. Aiming to increase the range of accurate strain measurements, we developed an adaptive method based on the estimation of strains as local scaling factors. Its adaptability makes this method appropriate for computing scaling factors resulting from larger strains or a wide spread of strain variations. First, segments corresponding to the same part of tissue are adaptively selected in the rest and stressed state echo signals. Then, local scaling factors are estimated by iteratively varying their values until reaching the zero of the phase of the complex cross-correlation function.

Results from simulation and from experimental data are presented. They show how this adaptive method can track various local deformations and its accuracy for strain up to 7%.
Theoretical Bounds on the Estimation of Transverse Displacement, Transverse Strain and Poisson's Ratio in Elastography
Authors: Konofagou Elisa E. , Varghese Tomy , Ophir Jonathan
Published: March 2013

The Cramér-Rao Lower Bounds (CRLB) are derived for the displacement and strain estimation in directions orthogonal to the ultrasonic beam axis, using a previously-described recorrelation method of axial, lateral and elevational motion estimation. We also compare it to the lateral tracking method that involves the sole use of the axial signal in the transverse direction. Our theoretical results, verified with simulations and phantom experiments, show that elastography is capable of measuring axial and transverse strain at up to 10% axially applied compression. Finally, we predict the performance of the estimation of the Poisson's ratio using decoupled axial and lateral estimates that result from the recorrelation method.
Modified Weighting Method for Forward-Looking Ring-Annular Arrays
Authors: Crowe J.R. , Hamilton J.D. , Stephens D.N. , Wang Y. , O'Donnell M.
Published: March 2013

Side-looking Intravascular Ultrasound Systems (IVUS) systems provide high resolution cross-sectional images of vascular structure. However, blood velocity estimation is hampered by the orthogonality of the primary blood flow direction to the imaging plane, and do not image in front of the catheter. A forward-looking aperture would improve the ability to guide interventions and allow Doppler processing for improved blood speed estimates; however, catheter-based systems delivered over a guide wire limit forward-looking array geometry to annular variations. Unfortunately, the imaging characteristics of annular arrays are inferior to a full aperture disk. A modified weighting method for a practical synthetic phased, ring-annular array is presented that achieves a transmit-receive aperture and on-axis performance comparable to a full aperture disk array.
Near-Field Diffraction Tomography
Authors: Mensah Serge , Ferriere Robert
Published: March 2013

We propose an algorithm that deals with broadband ultrasonic signals acquired in the near-field domain using probes close to the skin. This technique is designed for diffraction tomography of compact support objects interrogated by spherical waves (small transducers). It is an approximate inversion procedure in the Born approximation based on elliptical backprojection. Near-field imaging is enhanced by reducing the geometrical distortion observed on standard tomography. Numerical tests based on finite difference time domain (FDTD) simulations of data scattered by a tissue-like phantom are given.
Elastographic Imaging Using a Handheld Compressor
Authors: Varghese T. , Zagzebski J.A. , Frank G. , Madsen E.L.
Published: March 2013

Elastography is an emerging imaging modality that allows noninvasive imaging of tissue stiffness changes and stiffness values associated with pathology or as a result of therapy. However, many currently-used systems for elastography rely on a fixed geometry transducer and compressor system for imaging. This configuration is disadvantageous for imaging difficult-to-reach regions that are currently accessible with conventional ultrasound. In this paper, we describe a handheld, portable stepper motor controlled system for elastography. This system may reduce motion and jitter errors that are prevalent in completely ‘freehand elastography’ that employs hand-induced compressions using the transducer. The latter also requires collection of large amounts of data and use of strain estimation algorithms that may not be sensitive to phase changes or use additional preprocessing to minimize decorrelation effects. The stepper motor controlled handheld system provides controlled compressions and synchronized data acquisition. Our technique yields elastograms of a low-contrast phantom that have contrast levels and contrast-to-noise ratios that are comparable to those obtained with a fixed geometry system.
Circular Antenna for Breast Ultrasonic Diffraction Tomography
Authors: Lasaygues P. , Tanne D. , Mensah S. , Lefebvre J.P.
Published: March 2013

Compared to echography, which exploits only the reflected field, ultrasonic diffraction tomography improves image resolution by combining the total diffracted field. For breast cancer imaging, this improvement reinforces contrast between various breast tissues and structures by eliminating some interference phenomena such as speckle and then allowing parameterization of the images. Our work concerns the development of an experimental set-up for fast acquisition of the diffracted field and construction of two-dimensional tomographic images. For this purpose, we developed a multichannel ultrasound circular antenna with eight focused transducers.
Tissue-Mimicking Oil-in-Gelatin Dispersions for Use in Heterogeneous Elastography Phantoms
Authors: Madsen E.L. , Frank G.R. , Krouskop T.A. , Varghese T. , Kallel F. , Ophir J.
Published: March 2013

A ten-month study is presented of materials for use in heterogeneous elastography phantoms. The materials consist of gelatin with or without a suspension of microscopic safflower oil droplets. The highest volume percent of oil in the materials is 50%. Thimerosal acts as a preservative. The greater the safflower oil concentration, the lower the Young's modulus. Elastographic data for heterogeneous phantoms, in which the only variable is safflower oil concentration, demonstrate stability of inclusion geometry and elastic strain contrast. Young's modulus ratios (elastic contrasts) producible in a heterogeneous phantom are as high as 2.7. The phantoms are particularly useful for ultrasound elastography. They can also be employed in MR elastography, although the highest achievable ratio of longitudinal to transverse relaxation times is considerably less than is the case for soft tissues.
Microwave-Induced Thermal Imaging of Tissue Dielectric Properties
Authors: Shi Y. , Witte R.S. , Milas S.M. , Neiss J.H. , Chen X.C. , Cain C.A. , O'Donnell M.
Published: March 2013

A new imaging method, microwave-induced thermal imaging (MITI), was developed to differentiate tissue based on thermal and dielectric properties. Image contrast depends on temporal strain in tissue, which was determined by one-dimensional speckle tracking using a phase-sensitive, correlation-based technique. The underlying mechanisms were analyzed and experimental results on biologic tissue agreed well with theoretical predictions. Because of its strong contrast between water-bearing and lipid-bearing tissue, the technique may enhance existing intravascular ultrasound (IVUS) imaging systems to identify vulnerable arterial plaque.
Differences in the Compressive Stress-Strain Response of Infiltrating Ductal Carcinomas with and without Lobular Features — Implications for Mammography and Elastography
Authors: Krouskop Thomas A. , Younes Pamela S. , Srinivasan Seshadri , Wheeler Thomas , Ophir Jonathan
Published: March 2013

In a previous study, it was noted that in some cases when compressive strains greater than about 5% were applied to tumors removed from the breast, there was an abrupt and irreversible change in the tissue stiffness. The data from that study were further analyzed and infiltrating ductal carcinomas with and without lobular features were selected for additional testing to explore their behavior under compressive strains from 0–10%. Fresh tumor samples were tested using a servo-hydraulic Instron testing machine to apply ramp type displacement loads to the samples. The results show that when strains greater than 5% are applied to the tumor tissue without lobular features, there is an irreversible decrease in the stiffness of the tissue while no such change is noted in the other tumor tissue. The implications for this behavior in making mammographic and elastographic images of the breast were then explored using finite element simulations to determine under what compression conditions could the critical strain threshold be reached in the tumor tissue.
A Scalable Architecture for Real-Time Synthetic-Focus Imaging
Authors: Richard William D.
Published: March 2013

A scalable architecture for forming real-time synthetic focus images is described and the design of a 256-channel system using currently-available technology is presented as an example implementation of the architecture. The parallelism of the system scales directly with the number of array elements and the image computation rate for a given image size (in pixels) stays constant as the number of array elements is increased. The system leverages earlier work in the real-time generation of the required time-of-flight surfaces and allows either real-time image generation or iterative adaptive image generation from a single complete data set.
Two Dimensional Arrays for Real Time 3D Intravascular Ultrasound
Authors: Light Edward D. , Smith Stephen W.
Published: March 2013

We have previously described 2D arrays operating at up to 10.0 MHz consisting of several thousand elements for transthoracic cardiac imaging and over a hundred elements for intracardiac imaging using 7 Fr to 12 Fr catheters. We have begun to explore forward viewing real time 3D phased array intravascular ultrasound, which may require imaging depths of a few centimeters to look down the axis of a vessel to view vulnerable atherosclerotic plaque. We used a noncoaxial based cable technology that allowed 100 signal wires to be placed inside a 4.8 French IVUS lumen with an inner diameter of 1.3 mm. We pursued two different fabrication technologies for the building of the transducers. Each transducer was constructed in the forward viewing configuration to allow simultaneous real time B-scans, C-scans and volumetric rendering of vessels and vascular stents distal to the catheter tip. In order to obtain the desired penetration depth, each transducer was constructed to operate at 10.0 MHz. The first method included an ordered array of 11 × 11 = 121 elements. In order to conform to the round aperture of the IVUS lumen, the corners were cut off, resulting in a total of 97 signal channels. Real time images include a 4 mm diameter vessel in a tissue mimicking phantom, an expanded stent and a stent in an excised sheep aorta. The second method is based upon a laser dicing technique that cuts the individual elements in a random pattern. This resulted in 61 signal channels. Real time 3D images of the AIUM test object were made with this transducer.
Influence of Bright Intramural Echoes on Estimates of Ultrasonic Attenuation from Backscattered Ultrasound in Excised Myocardium
Authors: Baldwin Steven L. , Yang Min , Marutyan Karen R. , Wallace Kirk D. , Holland Mark R. , Miller James G.
Published: March 2013

The purpose of this study was to quantitate the influence of bright intramural echoes on estimates of myocardial attenuation from analyses of backscattered ultrasound. To achieve this, M-mode image-based measurements of the inherent anisotropic properties of myocardial attenuation were performed on rotating myocardial specimens. The approach was to use a commercially-available ultrasonic imaging system to acquire M-mode images of 24 excised cylindrical specimens from six formalin-fixed lamb hearts for data analysis using a video signal analysis technique. As a control, through-transmission rf-based measurements were performed concurrently using a pair of focused, single-element ultrasonic transducers. We devised an objective approach to compensate M-mode results for the presence of bright intramural echoes that makes use of the rotational symmetry of the measurements. A comparison of the uncompensated and compensated estimates of attenuation shows that the effect of bright intramural echoes under the conditions of this study increases the average error in M-mode results by approximately 240% compared with that observed when such effects are minimized by compensation. For both uncompensated and compensated M-mode results, increased temporal averaging shows only a modest reduction in average error. These data suggest that for measurements of attenuation from backscattered ultrasound using M-mode images, the effects of bright intramural echoes can be a significant source of error despite increased temporal averaging and therefore may require compensation.
3-D Correlation-Based Speckle Tracking
Authors: Chen X. , Xie H. , Erkamp R. , Kim K. , Jia C. , Rubin J. M. , O'Donnell M.
Published: March 2013

Widely-used 1-D/2-D speckle tracking techniques in elasticity imaging often experience significant speckle decorrelation in applications involving large elevational motion (i.e., out of plane motion). The problem is more pronounced for cardiac strain rate imaging (SRI) since it is very difficult to confine cardiac motion to a single image plane. Here, we present a 3-D correlation-based speckle tracking algorithm. Conceptually, 3-D speckle tracking is just an extension of 2-D phase-sensitive correlation-based speckle tracking. However, due to its high computational cost, optimization schemes, such as dynamic programming, decimation and two-path processing, are introduced to reduce the computational burden. To evaluate the proposed approach, a 3-D bar phantom under uniaxial compression was simulated for benchmark tests. A more sophisticated 3-D simulation of the left ventricle of the heart was also made to test the applicability of 3-D speckle tracking in cardiac SRI. Results from both simulations clearly demonstrated the feasibility of 3-D correlation-based speckle tracking. With the ability to follow 3-D speckle in 3-D space, 3-D speckle tracking outperforms lower-dimensional speckle tracking by minimizing decorrelation caused by pure elevational translation. In other words, 3-D tracking can push toward solely deformation-limited, decorrelation-optimized speckle tracking. Hardware implementation of the proposed 3-D speckle tracking algorithm using field programmable gate arrays (FPGA) is also discussed.
Real-Time Excitation-Enhanced Ultrasound Contrast Imaging
Authors: Forsberg Flemming , Shi William T. , Knauer Michael K. , Hall Anne L. , Vecchio Chris , Bernardi Richard
Published: March 2013

A new nonlinear contrast specific imaging modality, excitation-enhanced imaging (EEI) has been implemented on commercially-available scanners for real-time imaging. This novel technique employs two acoustic fields: a low-frequency, high-intensity ultrasound field (the excitation field) to actively condition contrast microbubbles, and a second lower-intensity regular imaging field applied shortly afterwards to detect enhanced contrast scattering. A Logiq 9 scanner (GE Healthcare, Milwaukee, WI) with a 3.5C curved linear array and an AN2300 digital ultrasound engine (Analogic Corporation, Peabody, MA) with a P4-2 phased array transducer (Philips Medical Systems, Bothell, WA) were modified to perform EEI on a vector-by-vector basis in fundamental and pulse inversion harmonic grayscale modes. Ultrasound contrast microbubbles within an 8 mm vessel embedded in a tissue-mimicking flow phantom (ATS Laboratories, Bridgeport, CT) were imaged in vitro. While video intensities of scattered signals from the surrounding tissue were unchanged, video intensities of echoes from contrast bubbles within the vessel were markedly enhanced. The maximum enhancement achieved was 10.4 dB in harmonic mode (mean enhancement: 6.3 dB; p=0.0007). In conclusion, EEI may improve the sensitivity of ultrasound contrast imaging, but further work is required to assess the in vivo potential of this new technique.
Catheter Ultrasound Phased-Array Transducers for Thermal Ablation: A Feasibility Study
Authors: Gentry Kenneth L. , Sachedina Nasheer , Smith Stephen W.
Published: March 2013

The feasibility of catheter single-element ultrasound transducers for cardiac ablation has been shown previously. We describe the design and testing of catheter-sized linear phased arrays transducers for ultrasound ablation. One array has 86 PZT-4 elements operating at 8 MHz and 5 MHz. The overall array size is 14.9 mm by 3.1 mm (10 Fr). The other array has 50 PZT-5 elements operating at 4 MHz and is 17 mm by 3.1 mm (10 Fr). In order to produce the intensity needed to create lesions in heart tissue, we modified a real-time, 3D scanner to produce 100 Vpp 256-cycle transmit pulses at a pulse repetition frequency of 14.1 kHz. This made it possible for the PZT-4 and PZT-5 transducers to produce ISPTA of 3.26 W/cm2 and 142 W/cm2, respectively. When driving the transducers at high duty factor, the transmit circuitry in the scanner was damaged. A mechanically-focused transducer with the same dimensions as the PZT-4 transducer was built. When transmitting continuously at 9 MHz, it produced an ISPTA of 29.3 W/cm2. This created a lesion 5 mm across and 5 mm deep in beef tissue while raising the focal temperature 23°C. Ablation is within the capabilities of a catheter phased array transducer integrated into a diagnostic ultrasound scanner.
Real-Time 3D Laparoscopic Ultrasonography
Authors: Light Edward D. , Idriss Salim F. , Sullivan Kathryn F. , Wolf Patrick D. , Smith Stephen W.
Published: March 2013

We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 times 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm × 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the −6 dB bandwidth ranges from 15% to 30%. The 50 Ω insertion loss, including Gore MicroFlat cabling, is −81.2 dB. The second transducer is a 7 MHz, 36 times 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the −6 dB bandwidth ranges from 18% to 33%. The 50 Ω insertion loss is −79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parasternal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.
Dual-Mode Ultrasound Phased Arrays for Image-Guided Surgery
Authors: Ebbini Emad S. , Yao Hui , Shrestha Ajay
Published: March 2013

A 64-element, 1 MHz prototype dual-mode array (DMUA) with therapeutic and imaging capabilities is described. Simulation and experimental results for the characterization of the therapeutic operating field (ThxOF) and imaging field-of-view (IxFOV) for a DMUA are given. In addition, some of the special considerations for imaging with DMUAs are given and illustrated experimentally using wire-target arrays and commercial, quality-assurance phantoms. These results demonstrate what is potentially the most powerful advantage of the use of DMUAs in image-guided surgery; namely, inherent registration between the imaging and therapeutic coordinate systems. We also present imaging results before and after discrete and volumetric HIFU-induced lesions in freshly-excised tissues. DMUA images consistently show changes in echogenicity after lesion formation with shape and extent reflecting the actual shape of the lesion. While changes in echogenicity cannot be used as an indicator of irreversible HIFU-induced tissue damage, they provide important feedback on the location and extent of the expected lesion. Thus, together with the self-registration property of DMUAs, lesion images can be expected to provide immediate and spatially-accurate feedback on the tissue response to the therapeutic HIFU beams. Based on the results provided here, the imaging capabilities of DMUAs can add unique features to other forms of image guidance, e.g. MRI, CT and diagnostic ultrasound.
Application of Three Scattering Models to Characterization of Solid Tumors in Mice
Authors: Oelze Michael L. , O'Brien William D.
Published: March 2013

Two mouse models of mammary cancer (a carcinoma and sarcoma) were examined using quantitative ultrasound (QUS) and three models for ultrasound backscattering. The first model that was examined was the spherical Gaussian model (SGM). The second model was the fluid-filled sphere model (FFSM) and was hypothesized to model scattering from cell nuclei with the cell cytoplasm acting as background. The third model, called the new cell model (NCM), was constructed to model backscattering from cell nuclei and cytoskeleton. The average scatterer diameters (ASDs) were estimated from regions-of-interest (ROIs) inside the tumors using all three models and then compared. The ultrasound analysis bandwidth used in the study was 16 to 27 MHz. QUS images of the tumors utilizing the ASD estimates from the three models were constructed. The ASDs were 30.3 ± 3.06 μm and 25.2 ± 4.01 μm with the SGM, 47.3 ± 7.99 μm and 47.7 ± 7.01 μm with the FFSM and 41.2 ± 1.39 μm and 34.4 ± 5.95 μm with the NCM for the carcinoma and sarcoma, respectively. statistically significant differences between the ASD estimates from the carcinomas and sarcomas were observed using the SGM and NCM but not with the FFSM.
Waveform Design for Ultrasonic Pulse-Inversion Fundamental Imaging
Authors: Li Pai-Chi , Shen Che-Chou , Huang Sheng-Wen
Published: March 2013

Pulse-inversion (PI) fundamental imaging exhibits significantly better contrast detection than linear and second-harmonic imaging. PI fundamental imaging involves two firings with inverted waveforms. When the returning echoes from the two firings are summed, the residual signal related to tissue is limited to even-order harmonics, whereas for microbubbles, the fundamental signal is not completely canceled due to the echo under compression differing from that under rarefaction. The efficacy of PI fundamental imaging has been reported previously. In this study, we investigated the performance of PI fundamental imaging using both simulations and in vitro experiments with various transmit waveforms, including coded excitation and asymmetrical waveforms (i.e., asymmetrical between compression and rarefaction). For coded excitation, a longer waveform was found to increase the similarity in the responses to positive and negative pulses, thus lowering the contrast between microbubbles and tissue. In addition, imperfect pulse compression also decreases the contrast because it increases the residue fundamental signal emanating from tissue. Using asymmetrical waveforms noticeably increased the residual microbubble signal in the fundamental band but the nonzero DC component that is inherent in such waveforms also increases the tissue fundamental signal. The combination of these two effects decreases the contrast. From these results, it is concluded that the use of coded excitation is undesirable in PI fundamental imaging and that the waveforms should contain no DC component. Furthermore, the transmit waveform needs to be appropriately windowed in order to reduce spectral leakage. Therefore, a Gaussian pulse with the pulse length determined by the signal-to-noise ratio of the imaging system is generally optimal for PI fundamental imaging.
Frame Rate Considerations for Real-Time Abdominal Acoustic Radiation Force Impulse Imaging
Authors: Fahey Brian J. , Palmeri Mark L. , Trahey Gregg E.
Published: March 2013

With the advent of real-time Acoustic Radiation Force Impulse (ARFI) imaging, elevated frame rates are both desirable and relevant from a clinical perspective. However, fundamental limitations on frame rates are imposed by thermal safety concerns related to incident radiation force pulses. Abdominal ARFI imaging utilizes a curvilinear scanning geometry that results in markedly different tissue heating patterns than those previously studied for linear arrays or mechanically-translated concave transducers. Finite Element Method (FEM) models were used to simulate these tissue heating patterns and to analyze the impact of tissue heating on frame rates available for abdominal ARFI imaging. A perfusion model was implemented to account for cooling effects due to blood flow and frame rate limitations were evaluated in the presence of normal, reduced and negligible tissue perfusions. Conventional ARFI acquisition techniques were also compared to ARFI imaging with parallel receive tracking in terms of thermal efficiency. Additionally, thermocouple measurements of transducer face temperature increases were acquired to assess the frame rate limitations imposed by cumulative heating of the imaging array. Frame rates sufficient for many abdominal imaging applications were found to be safely achievable utilizing available ARFI imaging techniques.
Nonlinear Pulse Compression in Pulse-Inversion Fundamental Imaging
Authors: Cheng Yun-Chien , Shen Che-Chou , Li Pai-Chi
Published: March 2013

Coded excitation can be applied in ultrasound contrast agent imaging to enhance the signal-to-noise ratio with minimal destruction of the microbubbles. Although the axial resolution is usually compromised by the requirement for a long coded transmit waveforms, this can be restored by using a compression filter to compress the received echo. However, nonlinear responses from microbubbles may cause difficulties in pulse compression and result in severe range side-lobe artifacts, particularly in pulse-inversion-based (PI) fundamental imaging. The efficacy of pulse compression in nonlinear contrast imaging was evaluated by investigating several factors relevant to PI fundamental generation using both in-vitro experiments and simulations. The results indicate that the acoustic pressure and the bubble size can alter the nonlinear characteristics of microbubbles and change the performance of the compression filter. When nonlinear responses from contrast agents are enhanced by using a higher acoustic pressure or when more microbubbles are near the resonance size of the transmit frequency, higher range side lobes are produced in both linear imaging and PI fundamental imaging. On the other hand, contrast detection in PI fundamental imaging significantly depends on the magnitude of the nonlinear responses of the bubbles and thus the resultant contrast-to-tissue ratio (CTR) still increases with acoustic pressure and the nonlinear resonance of microbubbles. It should be noted, however, that the CTR in PI fundamental imaging after compression is consistently lower than that before compression due to obvious side-lobe artifacts. Therefore, the use of coded excitation is not beneficial in PI fundamental contrast detection.
Characterization of Anisotropic Myocardial Backscatter Using Spectral Slope, Intercept and Midband Fit Parameters
Authors: Yang Min , Krueger Todd M. , Miller James G. , Holland Mark R.
Published: March 2013

The specific myocardial structural components that contribute to the observed level of backscatter from the heart and its dependence on the angle of insonification have not been completely identified. The objectives of this study were to measure the anisotropy of backscatter from myocardium using the approach first introduced by Lizzi et al. [ J Acoust Soc Am 73, 1366–1373 (1983)] and to use the extracted spectral parameters (spectral slope, intercept and midband fit) to characterize changes in the apparent scatterer size, spatial concentration and acoustic impedance properties as functions of the angle of insonification. Backscatter measurements were performed in vitro on eight cylindrical formalin-fixed lamb myocardial specimens using a 5 MHz focused transducer. The backscattered spectral data as a function of angle of insonification relative to the myocardial fiber direction were analyzed over the frequency range of 4 to 6 MHz. The spectral parameters describing features of backscatter were determined by applying a linear fit to attenuation-compensated normalized spectra. Results show that values of the spectral slope do not exhibit a significant dependence on the angle of insonification within uncertainties; however, the zero-frequency intercept showed clear anisotropy and was found to be a maximum for insonification perpendicular to the predominant myofiber orientation and a minimum for parallel insonification. A comparison of midband fit values at 5 MHz with attenuation-compensated integrated backscatter values showed excellent agreement for all angles of insonification. These data suggest that measurements of spectral slope, intercept, and midband fit can provide insights regarding aspects of tissue microstructure underlying the observed anisotropy of myocardial scattering properties. Measurements of the slope parameter suggest a very modest change in effective scatterer size with angle of insonification. However, the observed anisotropy in intercept and midband fit and apparent absence of anisotropy in the spectral slope suggests an angle of insonification dependence of acoustic concentration, the combination of effective spatial scatterer concentration and acoustic impedance properties, without a significant contribution from changes in effective scatterer size.
Intracardiac Echocardiography and Acoustic Radiation Force Impulse Imaging of a Dynamic Ex Vivo Ovine Heart Model
Authors: Hsu Stephen J. , Hubert Julia L. , Smith Stephen W. , Trahey Gregg E.
Published: March 2013

Intracardiac echocardiography (ICE) has demonstrated utility in providing high-resolution cardiac ultrasound images for guidance of numerous catheter-based interventions, including radiofrequency ablations (RFA). However, the training of interventionalists and refinement of procedures involving intracardiac catheters is costly and time consuming due to necessary clinical and animal studies. As a result, research and development of ICE for other purposes is gradual and deliberate. Intracardiac acoustic radiation force impulse (ARFI) imaging has been demonstrated to be a suitable modality to monitor the progress of RFA procedures; however, a clinical protocol has been slow to develop due to the expense and demands of clinical experiments. We report on the development and use of an ex vivo heart model to evaluate ICE and intracardiac ARFI imaging.

The ability of this model to provide clinically-relevant intracardiac imaging angles was investigated by inserting an intracardiac probe into the heart and imaging it from various positions and orientations. ARFI images of all four chambers also were formed. RFAs were also performed to create stiffer lesions within the right and left ventricles. Upon completion of the ablation, ARFI imaging was used to visualize the lesion and compared with images taken from pathology. The results show the ovine heart model to be a suitable apparatus for recreating several clinically-relevant intracardiac viewing angles of the heart. Also, the results indicate the potential of the heart model to be a valuable tool in the future development and refinement of a clinical protocol for intracardiac ARFI imaging based guidance and assessment of cardiac radiofrequency ablations.
Real-Time 3D Imaging Methods using 2D Phased Arrays Based on Synthetic Focusing Techniques
Authors: Kim Jung-Jun , Song Tai-Kyong
Published: March 2013

A fast 3D ultrasound imaging technique using a 2D phased array transducer based on the synthetic focusing method for nondestructive testing or medical imaging is proposed. In the proposed method, each column of a 2D array is fired successively to produce transverse fan beams focused at a fixed depth along a given longitudinal direction and the resulting pulse echoes are received at all elements of a 2D array used. After firing all column arrays, a frame of high-resolution image along a given longitudinal direction is obtained with dynamic focusing employed in the longitudinal direction on receive and in the transverse direction on both transmit and receive. The volume rate of the proposed method can be increased much higher than that of the conventional 2D array imaging by employing an efficient sparse array technique. A simple modification to the proposed method can further increase the volume scan rate significantly. The proposed methods are verified through computer simulations.
Characterization of Malignant Focal Liver Lesions with Contrast-Enhanced 40 MHz Ultrasound Imaging in Hepatitis B Virus X Transgenic Mice: A Feasibility Study
Authors: Liao Ai-Ho , Cheng Ya-Chien , Weng Chien-Hsiu , Tsai Ting-Fen , Lin Wei-Hsiang , Yeh Shiou-Hwei , Yeh Wen-Chun , Li Pai-Chi
Published: March 2013

Contrast-enhanced ultrasound (CEUS) imaging has been a reliable clinical method of detecting three vascular contrast phases and characterizing focal liver lesions. Previous results were all from human (i.e., clinical studies). The main purpose of this study was to extend this to small animals and to investigate the feasibility of using CEUS in preclinical research. Specifically, high-frequency (40 MHz) ultrasound liver imaging with albumin-shelled microbubbles was employed to detect the three vascular contrast phases and characterize focal liver lesions that developed in thirteen Hepatitis B virus X (HBx) transgenic mice at around 14 to 16 months of age. Previous studies indicated that 90–100% incidence of hepatocellular carcinoma (HCC) was observed in HBx transgenic male mice. After injecting the contrast agent, the time-intensity curves (TICs) of focal liver lesions, vessels in focal liver lesions and surrounding liver parenchyma tissues were measured for 30 minutes. The peak of mean intensity relative to the baseline increased 7.36 dB (p<0.02). On the other hand, the mean contrast between the focal liver lesion and the liver parenchyma increased by 7.74 (p<0.05) dB, thus allowing clear detection of the lesion margin. Histopathology investigations confirmed the development of the lesion in these mice. In addition, guidelines of European Federation of Societies for Ultrasound in Medicine and Biology were followed as an attempt to characterize features of the TICs in mice. The arterial phase was defined as 2 to 60 seconds post contrast injection, and the parenchyma phase was defined as the time period from 10 to 30 minutes post contrast injection. Comparing the imaging with the pathology results, the sensitivity, specificity and accuracy of CEUS for the detection of malignant focal liver lesion in HBx transgenic mice were 91%, 100% and 92%. These results demonstrated that high-frequency CEUS imaging potentially can be used for detecting the three vascular contrast phases of malignant focal liver lesions and characterizing malignant focal liver lesions in mice. Thus can be a valuable tool in preclinical research.
Correlations among Acoustic, Texture and Morphological Features for Breast Ultrasound CAD
Authors: Yang Hsin-Chia , Chang Chen-Han , Huang Sheng-Wen , Chou Yi-Hong , Li Pai-Chi
Published: March 2013

Acoustic, textural and morphological features of the breast in ultrasound imaging were extracted for computer-aided diagnosis. In addition, correlations among different categories of features were analyzed. Clinical data from 14 patients (7 malignant and 7 benign samples) were acquired. A custom-made experimental apparatus was used for simultaneous data acquisition of B-mode ultrasound and limited-angle tomography images. Textural features were extracted from B-mode images, including five parameters derived from the gray-level concurrence matrix and five parameters derived from a nonseparable wavelet transform. Morphological features were also extracted from B-mode images, including the depth-to-width ratio and normalized radial gradient. Acoustic features were estimated using limited-angle tomography, including the sound velocity and attenuation coefficient. Generally, the correlation coefficients for features within the textural feature group were relatively high (0.48–0.79), whereas those between different feature categories were relatively low (0.17–0.40). This suggests that combining different sets of features would improve the computer-aided diagnosis of breast cancer.
Contrast Harmonic Detection with Chirp Excitation in 3f0 Transmit Phasing
Authors: Shen Che-Chou , Wang Hong-Wei , Chiu Yi-Yuan
Published: March 2013

The method of third harmonic (3 f0) transmit phasing is capable of providing effective tissue background suppression for contrast-to-tissue ratio (CTR) improvement in harmonic imaging. With the additional 3 f0 transmit signal to generate both the frequency-sum and the frequency-difference components of harmonic signal, the tissue suppression is achieved when the two components are opposite in phase and mutually cancel out. One major problem in 3 f0 transmit phasing is the limited signal-to-noise ratio (SNR) due to the constraint on transmit amplitude. Chirp excitation can be applied in contrast harmonic imaging to enhance the SNR with minimal destruction of the microbubbles. In this paper, the effect of chirp waveform in combination with the 3 f0 transmit phasing was studied using both in-vitro experiments and simulations. Our results indicate that, though the chirp transmit pulse can increase the SNR of harmonic imaging in 3 f0 transmit phasing (3 dB, p<0.001), it suffers from degraded tissue harmonic suppression and thus provides less CTR improvement as compared to a conventional pulse. The spectral mismatch between the frequency-sum and the frequency-difference components of tissue harmonic signal is particularly evident in the off-center region of second harmonic band, leading to significant residue tissue background. Consequently, with the chirp waveform, the improvement of CTR decreases from 9.5 dB to 5.9 dB (p<0.0006) and thus a tradeoff exists between the SNR improvement and the CTR improvement in 3 f0 transmit phasing.