bluuebunny/crossref_metadata_2025 huggingface dataset:
A methodology for sensitivity analysis in inverse problems—application to a palaeoclimate study
Authors: Bhattacharya Sourabh
Published: March 2007

We present a methodology for implementing sensitivity analysis in the case of inverse problems. This is motivated by a problem in palaeoclimatology, where interest lies in reconstruction of past climates from fossil data. In such situations fossil data are modelled as functions of climate variables, since in general ecological terms, variations in climate drive variations in fossil. However, prediction of climate variables are of interest, indicating the inverse nature of the problem.

Technically, given a data set {xi,yi};i = 1, … ,n, and a probability distributionp(yi | xi, θ), where θ is the set of model parameters, the problem is ‘inverse’ if, given a new observedy, prediction of the corresponding unknownxis required. On the other hand, the more usual forward problem considers prediction ofyfor givenx. Sensitivity analysis in forward problems is about examining if the results are robust with respect to changes of the prior on θ. This has received a lot of attention in the statistical literature. However, in the case of inverse problems, a prior onxis required, in addition to the prior on θ. This complicates sensitivity analysis, at least operationally, and, to our knowledge, there exists no work in the literature that addresses this. In this paper, we propose a new methodology for sensitivity analysis in inverse problems, and discuss its application to a real, complex, palaeoclimate problem. Copyright © 2007 John Wiley & Sons, Ltd.
Overturning of top profile of the Koyna Dam during severe ground motion
Authors: Saini S. S. , Krishna Jai
Published: March 2007

The Koyna Dam in India was subjected to a severe earthquake on 11 December 1967 with its epicentre very close to the dam site. During this earthquake, higher non‐overflow monoliths of the dam suffered significant damage. In the highest non‐overflow monolith, a horizontal crack occurred at the level where there was an abrupt change in the downstream slope. The dynamic behaviour of the top profile of this monolith of the dam above the crack has been investigated treating it as a rigid body. The study shows that the overturning of the cracked portion of the dam will not occur due to the severest anticipated ground motion at the site. However, to prevent the seepage of water and as a permanent remedial measure, strengthening of the dam is necessary but no emergency measures need be taken.
Simulation of artificial earthquakes
Authors: Rodolfo Saragoni G. , Hart Gary C.
Published: March 2007

A procedure is developed for the simulation of artificial earthquake accelerograms, The time variation of amplitude and frequency content is preserved in the simulation procedure. Sixteen artificial earthquake accelerograms are simulated and compared with a target accelerogram. The time variation of amplitude and frequency content for 26 historical earthquake accelerograms is characterized.
Inelastic dynamic analysis of tall buildings
Authors: Meyer Christian
Published: March 2007

The importance of inelastic action of frame structures subjected to strong ground motions has been recognized by engineers for many years. However, the dynamic analysis of buildings undergoing inelastic deformations requires the solution of many theoretical problems, as well as the development of computer software which makes such analyses economically feasible in a design office–in spite of the extraordinary amount of computation involved. In this paper, some of the principal theoretical problems are briefly described. These are the load‐deformation relationship, yield capacity reduction, ductility, P– δ effect, viscous damping, panel zone distortions, numerical integration techniques, energy analysis and the effect of non‐structural elements. Special consideration is given to questions associated with the practical implementation of this theory. These questions arose during the development of a computer program, called NLDYN, capable of analysing the non‐linear dynamic behaviour of tall buildings in an engineering office environment. The capabilities of this computer program are illustrated with the results of the analysis of a 60 storey office building currently under construction in downtown Los Angeles.
Looking at the evidence: What variations in practice might indicate
Authors: Datta Lois‐ellin
Published: March 2007

This chapter presents the findings from a review of the practice of evaluation in federal agencies as an attempt to inform policies on method choice. The author explores whether federal agencies differ in their approaches to evaluation design and the factors that influence these differences. The nature of the programs, agency culture, evaluator training and experience, and the politics of methodology all emerge as possible context‐appropriate influences on method choice.
Pragmatic support for policies on methodology
Authors: Julnes George , Rog Debra J.
Published: March 2007

This final chapter summarizes the areas of consensus in the debate on method choice, including considering the nature of the primary evaluation questions, the nature of the phenomenon being evaluated, the constraints on the evaluation, and ethical issues. Pragmatic suggestions based on these areas as well as areas still in contention are offered.
Temporal accuracy analysis of phase change convection simulations using the JFNK‐SIMPLE algorithm
Authors: Evans Katherine J. , Knoll Dana A.
Published: March 2007

The incompressible Navier–Stokes and energy conservation equations with phase change effects are applied to two benchmark problems: (1) non‐dimensional freezing with convection; and (2) pure gallium melting. Using a Jacobian‐free Newton–Krylov (JFNK) fully implicit solution method preconditioned with the SIMPLE (Numerical Heat Transfer and Fluid Flow. Hemisphere: New York, 1980) algorithm using centred discretization in space and three‐level discretization in time converges with second‐order accuracy for these problems. In the case of non‐dimensional freezing, the temporal accuracy is sensitive to the choice of velocity attenuation parameter. By comparing to solutions with first‐order backward Euler discretization in time, it is shown that the second‐order accuracy in time is required to resolve the fine‐scale convection structure during early gallium melting. Qualitative discrepancies develop over time for both the first‐order temporal discretized simulation using the JFNK‐SIMPLE algorithm that converges the nonlinearities and a SIMPLE‐based algorithm that converges to a more common mass balance condition. The discrepancies in the JFNK‐SIMPLE simulations using only first‐order rather than second‐order accurate temporal discretization for a given time step size appear to be offset in time. Copyright © 2007 John Wiley & Sons, Ltd.
The violation of objectivity in Laplace formulations of the Navier–Stokes equations
Authors: Limache A. , Idelsohn S. , Rossi R. , Oñate E.
Published: March 2007

The Navier–Stokes equations written in Laplace form are often the starting point of many numerical methods for the simulation of viscous flows. Imposing the natural boundary conditions of the Laplace form or neglecting the viscous contributions on free surfaces are traditionally considered reasonable and harmless assumptions. With these boundary conditions any formulation derived from integral methods (like finite elements or finite volumes) recovers the pure Laplacian aspect of the strong form of the equations. This approach has also the advantage of being convenient in terms of computational effort and, as a consequence, it is used extensively. However, we have recently discovered that these resulting Laplacian formulations violate a basic axiom of continuum mechanics: the principle of objectivity. In the present article we give an accurate account about these topics. We also show that unexpected differences may sometimes arise between Laplace discretizations and divergence discretizations. Copyright © 2007 John Wiley & Sons, Ltd.
Gender‐related differences in neonatal imitation
Authors: Nagy Emese , Kompagne Hajnalka , Orvos Hajnalka , Pal Attila
Published: March 2007

Socio‐emotional behaviour is in part sex‐related in humans, although the contribution of the biological and socio‐cultural factors is not yet known. This study explores sex‐related differences during the earliest communicative exchange, the neonatal imitation in 43 newborn infants (3–96 hours old) using an index finger extension imitative gesture. Results showed that although the experimenter presented comparable stimuli to both sexes, and the total number of movements was similar in boys and girls, girls showed more fine motor movements, a higher number of specific imitative gestures, responded faster during the imitation and showed a higher baseline heart rate during the experiment. Newborn girls, with their faster and more accurate imitative abilities, may create a more responsive and interactive social environment, which in turn may lead to differences in socio‐emotional and cognitive development between girls and boys. Copyright © 2007 John Wiley & Sons, Ltd.
Biological roles of carboxymethyl‐chitin associated for the growth factor production
Authors: Kariya Hiroyuki , Kiyohara Ai , Masuda Shingo , Yoshihara Yusuke , Ueno Masaru , Hashimoto Masahito , Suda Yasuo
Published: March 2007

Many techniques to restore cartilage defection have been tried. However, the development is still under way because of problems, including loosening of artificial joint, degenerative change of compensated tissue, risk of viral transmission via allograft/autograft, and cost of therapeutic materials for repair. In the previous research, we found that complementing cartilage defective part with carboxymethyl‐chitin (CM‐chitin)/β‐tricalcium phosphate composite induced regeneration of cartilage in rabbits in vivo, and it is presumable that CM‐chitin plays a key role in chondrogenesis causing the regeneration of cartilage. However, the induction mechanism of chondrogenesis with CM‐chitin is still unclear. In this study, we investigated the cell responses to CM‐chitin by using peritoneal exudate cell (PEC) in mice and found that CM‐chitin induced the expression of inflammatory cytokines and growth factors, both of which are both considered to correlate with chondrogenesis. After intraperitoneal injection CM‐chitin showed enhanced expressions of mRNA of interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), keratinocyte‐derived chemokine, tumor necrosis factor‐α, and transforming growth factor‐β1 (TGF‐β1) in PEC as observed by reverse transcriptase polymerase chain reaction. Productions of TGF‐β1 protein were confirmed by enzyme linked immunosorbant assay. It was also shown that mononuclear cells in PEC were responsible for the TGF‐β1 production. These results suggest that CM‐chitin is an inductor of inflammatory cytokines and growth factors and may contribute to regeneration of cartilage. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Stent material surface and glucose activate mononuclear cells of control, type 1 and type 2 diabetes subjects
Authors: Harrison Moira , Siddiq Amer , Guildford Anna , Bone Adrian , Santin Matteo
Published: March 2007

In stent restenosis (ISR) has been described as an unaccomplished tissue healing and its rate is particularly high in diabetic patients. Evidence has been collected which relates the formation of ISR proteoglycan‐rich neointimal tissue to the accumulation and protracted activation of macrophages around the stent metal struts. Here, the in vitro activation of mononuclear cells adhering to stainless steel (a material of choice in stent manufacturing) from control and diabetic (types 1 and 2) subjects was assessed in the presence of different glucose levels. The results showed that cells from the control and type 1 diabetes groups produced significantly higher levels of TGF‐β1 when adhering on stainless steel (p = 0.04 and p = 0.01), but a significant PDGF‐BB secretion was observed only in control subjects. When tested at physiological glucose concentration, the effect of the stainless steel on control cells was more pronounced. The present study shows that mononuclear cells adhering onto stainless steel secrete growth factors relevant to ISR. Cells from diabetic subjects seem to secrete relatively higher levels of PDGF under hyperglycaemic conditions regardless of the substrate exposed thus offering an explanation for the higher incidence of restenosis in these patients. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Effect of soluble zinc on differentiation of osteoprogenitor cells
Authors: Popp Jenni R. , Love Brian J. , Goldstein Aaron S.
Published: March 2007

Amorphous calcium phosphates (ACPs) are attractive fillers for osseous defects and are stabilized through the incorporation of transition metals such as zirconium and zinc. As ACP converts in solution to hydroxyapatite (HAP) in a manner marked by a transient release of calcium and phosphate ions, it is capable of stimulating osteoblastic differentiation. Zinc is known to retard ACP conversion to HAP, and—when incorporated into ceramic biomaterials—has been shown to stimulate osteoblastic differentiation. Because zinc deficiency in vivo is marked by skeletal defects, we postulated that zinc ions released from ACP and other minerals could stimulate proliferation and osteoblastic differentiation of progenitor cells. To test this hypothesis, rat bone marrow stromal cells were cultured in osteogenic medium containing basal (3 × 10−6 M) or supplemented Zn2+ concentrations (1 × 10−5 and 4 × 10−5 M) for up to 3 weeks. No significant effects of zinc concentration on cell number, alkaline phosphatase activity, total protein content, collagen synthesis, or matrix mineralization were found. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Category IV indications for therapeutic apheresis—ASFA fourth special issue
Authors: Shaz Beth H. , Linenberger Michael L. , Bandarenko Nicholas , Winters Jeffrey L. , Kim Haewon C. , Marques Marisa B. , Sarode Ravindra , Schwartz Joseph , Weinstein Robert , Wirk Ashka , Szczepiorkowski Zbigniew M.
Published: March 2007

The American Society for Apheresis (ASFA) Committee on Clinical Applications systematically and critically reviews published information on the use of therapeutic apheresis in clinical practice. On the basis of this review, selected diseases are assigned one of five categories (category I, II, III, IV, and P). The diseases, which were classified as category IV indications, and the rationale for such assignment are reviewed in this article. The diseases assigned to category I, II, III, and newly created category P are discussed in a separate article in this issue. J. Clin. Apheresis, 2007 © 2007 Wiley‐Liss, Inc.
Prenatal sonographic findings of Klippel‐Trénaunay‐Weber syndrome
Authors: Chen Chih‐Ping , Lin Shuan‐Pei , Chang Tung‐Yao , Lee Hung‐Chang , Hung Han‐Yang , Lin Hsiang‐Yu , Huang Jian‐Pei , Wang Wayseen
Published: March 2007

We describe the prenatal sonographic findings in a case of Klippel‐Trénaunay‐Weber syndrome including fetal ascites and subcutaneous cystic lesions associated with a relatively low level of maternal serum alpha‐fetoprotein and a relatively high level of maternal serum β‐human chorionic gonadotrophin. Klippel‐Trénaunay‐Weber syndrome may present prenatally with fetal ascites and an abnormal maternal serum screening result in addition to fetal limb hypertrophy and subcutaneous cystic lesions. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Real‐time 3‐dimensional echocardiographic features of fetal cardiac tumor
Authors: Hata Toshiyuki , Yan Fang , Dai Shu‐Yan , Kanenishi Kenji , Yanagihara Toshihiro
Published: March 2007

We present a case of fetal cardiac tumors diagnosed using conventional 2‐dimensional (2D) fetal echocardiography and real‐time 3‐dimensional (3D) echocardiography. Conventional 2D echocardiography revealed multiple cardiac tumors involving the right atrium, interventricular septum, and right and left ventricles. Real‐time 3D echocardiography with instantaneous volume rendering showed the cardiac tumors in motion. The advantages and disadvantages of real‐time 3D fetal echocardiography are discussed. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Protein‐losing gastropathy with hypertrophic gastric folds: Endosonographic findings
Authors: Tsurumaru Daisuke , Masunari Satoru , Utsunomiya Takashi , Takano Heihachirou , Matsuura Shuji , Nishihara Yunosuke , Yao Takashi , Irie Hiroyuki , Honda Hiroshi
Published: March 2007

We present a case of protein‐losing gastropathy with hypertrophic gastric folds. A 38‐year‐old man was hospitalized for severe epigastric pain suggestive of hypoproteinemia. Endoscopic and radiologic examination revealed enlarged gastric folds on the greater curvature of the stomach. Endoscopic sonography revealed marked thickening of the second layer on the greater curvature of the stomach. Endoscopic mucosal resection was performed, and the diagnosis was hypertrophic gastritis. After prednisolone treatment, hypoproteinemia and the enlarged gastric folds of the stomach resolved. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2008
Effects of altitude on spleen volume: Sonographic assessment
Authors: Sonmez Guner , Ozturk Ersin , Basekim C. Cinar , Mutlu Hakan , Kilic Selim , Onem Yalcin , Kizilkaya Esref
Published: March 2007

Purpose.

To use sonography to determine changes that may arise in splenic volume in humans from regions of lower altitude who begin to live in regions of higher altitude.

Materials and Methods.

The study was conducted in the Turkish province of Ağrı, at an altitude of 1750 m and included 108 healthy, nonsmoking, disease‐free volunteers who had moved from regions at an altitude lower than 500 m. Length, width, and thickness of the spleen were measured using sonography. Splenic volume was calculated using the following standard ellipsoid formula: length × width × thickness × 0.523. Sonographic assessments were repeated at 3 and 6 months along with other blood tests, including hemoglobin, hematocrit, and platelet levels.

Results.

The mean ± SD splenic volume was 299 ± 97 cm3 (range, 116–574 cm3). At 3 and 6 months, the splenic volumes decreased significantly compared to their initial values (p < 0.05). An increase in hemoglobin, hematocrit, and platelet count was observed in all subjects.

Conclusion.

Our data show that splenic volume in healthy individuals who begins to live at high altitudes decreases gradually. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Accuracy of sonography for detecting renal stone: Comparison with CT
Authors: Ulusan Serife , Koc Zafer , Tokmak Naime
Published: March 2007

Purpose.

To determine the diagnostic accuracy values of sonography in the detection of renal stones using noncontrast CT as the gold standard. In addition, we correlated the accuracy of sonography with stone size, the kidney affected (right versus left), and body mass index (BMI).

Methods.

Fifty patients underwent 2 separate sonographic examinations performed by 2 radiologists. CT scans were evaluated by another 2 radiologists, and the diagnosis was made by consensus. We compared the sonograms and CT scans and the sonographic detection of stones in the left and right kidneys. All sonographic findings were correlated with the BMI groups.

Results.

The sensitivity of sonography for any stone in a patient was 52–57% for the right kidney (radiologist 1 and 2) and 32–39% for the left kidney (radiologist 1 and 2). The overall accuracy of sonography in detecting a stone in the right kidney by radiologists 1 and 2 was 67% and 77%, respectively. The corresponding accuracy values for the left kidney were 53% and 54%, respectively.

Conclusion.

Sonography is of limited value for detecting renal stones. The sonographic detection of a renal stone is dependent on the side of the kidney involved but is independent of BMI. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Juvenile hormone mediates sexual dimorphism in horned beetles
Authors: Shelby J. Andrew , Madewell Richard , Moczek Armin P.
Published: March 2007

The causes and consequences of sexual dimorphism are major themes in biology. Here we explore the endocrine regulation of sexual dimorphism in horned beetles. Specifically, we explore the role of juvenile hormone (JH) in regulating horn expression in females of two species with regular sexual dimorphism for pronotal horns (females have much shorter horns than males) and a third species with a rare reversed sexual dimorphism for both pronotal and head horns (females have much larger horns in both body regions compared with males). Applications of the JH analog methoprene caused females of the two more typical species to grow significantly shorter pronotal horns than control females, whereas no consistent effect on pronotal horn development was detected in the third, sex‐reversed species. Instead, females in this species showed an unexpected and significant increase in head horn expression in response to methoprene treatment. Lastly, horn shape was also affected in females of one of the regularly sexually dimorphic species, but in the opposite direction than horn lenght. Although methoprene exerted a feminizing effect on female horn length in this species, it significantly masculinized horn shape by inducing a peculiar shape change observed naturally only in males. Our results suggest that JH influences both overall size and shape of female horns, but does so flexibly and as a function of species, sex and horn location. We use our results to review current models on the role of endocrine mechanisms in development and evolution of horned beetle diversity. J. Exp. Zool. (Mol. Dev. Evol.) 308B:417–427, 2007. © 2007 Wiley‐Liss, Inc.
Analysis of myocardial motion based on velocity measurements with a black blood prepared segmented gradient‐echo sequence: Methodology and applications to normal volunteers and patients
Authors: Hennig Juergen , Schneider Britta , Peschl Simone , Markl Michael , Laubenberger Thomas Krause Jörg
Published: March 2007

The paper describes a strategy for measuring and characterizing myocardial motion in terms of velocity parameters derived from measurements with a segmented black blood prepared phase contrast gradient echo sequence. The characteristic parameters are calculated by transforming the velocities measured on a pixel‐by‐pixel basis across the left ventricle from the laboratory frame of reference into a cylindrical coordinate system, in which the motion velocities within the short axis plane are represented in polar coordinates and which is located at the center of the myocardium and moving with it over the ECG cycle. First results in a study with 12 healthy volunteers gave highly consistent values for the radial (expansion/ compression) as well as the rotational velocities. Except for one volunteer, motion at the R wave of the ECG starts with clockwise rotation, followed by contraction and expansion accompanied by counterclockwise rotation. First examinations of patients with global and focal disease demonstrate the potential to detect disturbances in the local as well as the overall motion patterns.
Accuracy of arterial pulse‐wave velocity measurement using MR
Authors: Bolster Bradley D. , Atalar Ergin , Hardy Christopher J. , McVeigh Elliot R.
Published: March 2007

The performance of a one‐dimensional MR technique for the estimation of pulse‐wave velocity in the aorta was evaluated. An expression for the error in this estimate was formulated and verified both by simulation and by experiment. On the basis of this formulation, guidelines for increasing the efficiency of the acquisition were established. The technique was further validated by comparison with pulse‐wave velocity measurements made with a pressure catheter. All data were acquired from a latex tube driven by a pulsatile flow system. MR measurements of pulse‐wave velocity in the tube were found to be very reproducible in the presence of white noise. Measurements by other techniques were in good agreement, falling within 2 SD of the mean. Because of its sensitivity and spatial resolution, this technique shows promise for making spatially resolved estimates of vessel distensibility. This would allow assessment of diseases, such as atherosclerosis, that cause local changes in the material properties of the vasculature.
Systematic assessment and evaluation of sliding interleaved ky (SLINKY) acquisition for 3D MRA
Authors: Liu Kecheng , Lee Donald H. , Rutt Brian K.
Published: March 2007

In comparison with the conventional three‐dimensional multiple overlapped thin slab acquisition (MOTSA) for magnetic resonance angiography (MRA), we have developed a novel sliding interleaved ky (SLINKY) acquisition technique, which can eliminate the slab boundary artifact (SBA) or venetian blind artifact without any a priori knowledge of blood flow. This work addresses the systematic assessment and evaluation of the SLINKY technique and verifies the advantages of SLINKY in the following several aspects: (a) scan time efficiency; (b) signal‐to‐noise ratio (SNR), and signal‐difference‐to‐noise ratio (SDNR); (c) sensitivity to flow velocity range; (d) sensitivity to flow direction; (e) signal loss in slow/reversal flow regions; and (f) reconstruction efficiency and feasibility. Both phantom and in vivo experiments verify the clinical significance of the technique. The new MRA images acquired with this imaging technique in 31 volunteer/patient examinations show highly reliable mapping of vascular morphology without the SBA and reduction of signal voids in complex/slow flow regions.
Improved clinical echo‐planar MRI using spatial‐spectral excitation
Authors: Schick Fritz , Forster Jürgen , Machann Jürgen , Kuntz Reinhard , Claussen Claus D.
Published: March 2007

Echo‐planar imaging (EPI) is markedly susceptible to B0 field distortions and to frequency differences caused by chemical shift, because the phase of the signals is accumulating during the acquisition train. Thus, only water proton signals are usually recorded after frequency‐selective suppression of the fat portions of magnetization. Otherwise, a shifted signal frequency from fat results in ghosting artifacts. In this article, a technique is presented working with spatial‐spectral excitation for highly selective water or fat EPI. The proposed method allows recording in multislice operation on EPI scanners without irregular gradient or RF pulse shapes. Examples of gradient‐echo and spin‐echo EPI using spatial‐spectral excitation by series of two to eight single slice‐selective RF pulses are demonstrated. The method is not sensitive to misadjustments or inhomogeneities of the B1 field, but sufficient homogeneity of the static magnetic field B0 is required. Especially the quality of diffusion‐weighted echo‐planar images can be markedly improved by the new technique compared to conventional EPI, because artifacts from undesired chemical shift components are completely avoided.
Hybrid ordered phase encoding (HOPE): An improved approach for respiratory artifact reduction
Authors: Jhooti Permi , Wiesmann Frank , Taylor Andrew M. , Gatehouse Peter D. , Yang Guang Z. , Keegan Jennifer , Pennell Dudley J. , Firmin David N.
Published: March 2007

Respiration causes continuous change in cardiac position, which leads to image degradation. Phase‐encode reordering methods are often used to reduce these artifacts. An improved method for suppressing motion artifacts by reordering the acquisition of k space has been developed that is less sensitive to change of breathing patterns and bulk movement. We describe the theory behind the new approach and compare its results with those of existing methods by use of a phantom with simulated and actual acquired breathing patterns. The comparison was also made in vivo; cardiac scans were performed in 15 subjects with image planes that are known to be particularly susceptible to respiratory artifact. A significant improvement in image quality was achieved compared with conventional nonreordered and existing reordering methods.
Reduction of field of view in MRI using a surface‐spoiling local gradient insert
Authors: Wiesler David G. , Wen Han , Wolff Steven D. , Balaban Robert S.
Published: March 2007

Herein is presented a method for suppressing the magnetic resonance signal to a controlled depth by applying a spatially heterogeneous spoiler field between the slice‐select and readout pulses. Eliminating the signal from near‐surface regions allows one to shrink the field of view without introducing aliasing artifacts, thereby decreasing imaging time over a smaller defined volume. A unique planar magnetic gradient coil was constructed to generate the spoiler field. Phantom and human subject studies showed that the signal can be suppressed to controlled distances of up to 90 mm from the coil, with modest requirements on power supplies, pulse sequences, and materials, and with no increase in imaging time.
A simple method for the correction of endorectal surface coil inhomogeneity in prostate imaging
Authors: Liney Gary P. , Turnbull Lindsay W. , Knowles Adrian J.
Published: March 2007

A simple method is described that corrects for the intensity inhomogeneity experienced when using endorectal surface coils in prostate imaging. The method uses a series of proton‐density‐weighted images, which are acquired to demonstrate the sensitivity profile of the coil and used to correct T2‐weighted images acquired in the same plane. The results demonstrate improved image uniformity and visualization of prostatic anatomy.
MRI evaluation of right ventricular pressure overload in chronic obstructive pulmonary disease
Authors: Marcus J. Tim , Noordegraaf Anton Vonk , De Vries Peter M. J. M. , Van Rossum Albert C. , Roseboom Bea , Heethaar Robert M. , Postmus Pieter E.
Published: March 2007

In chronic obstructive pulmonary disease (COPD), the development of pulmonary hypertension is common. This study was performed to assess the signs of right ventricular (RV) pressure overload and RV failure in COPD. In 8 COPD patients without primary cardiac disease, RV wall thickness, mass, and end‐diastolic volume were measured by cardiac‐triggered cine MRI. MR phase‐contrast velocity quantification was used to measure stroke volume and the patterns of flow into and out of the RV. Data of patients were tested versus those of a control group matched for age (n = 8). Results showed that the RV wall thickness was increased (.6 ± 0.1 vs 0.4 ± 0.1 cm, P < .001). RV mass was increased (67 ± 11 vs 57 ± 5 g, P < .005). RV stroke volume was decreased (57 ± 13 vs 71 ± 13 ml, P < .01), but RV ejection fraction was not different. In the main pulmonary artery flow, the quotient of acceleration time divided by ejection time was decreased (33 ± 5% vs 38 ± 4%, P < .05), which is indicative of pulmonary hypertension. In conclusion, this MRI protocol provides a tool to assess the effects of RV pressure overload in COPD before heart failure has become manifest.
Comparison of fast spiral, echo planar, and fast low‐angle shot MRI for cardiac volumetry at .5T
Authors: Wiesmann Frank , Gatehouse Peter D. , Panting Jonathan R. , Taylor Andrew M. , Firmin David N. , Pennell Dudley J.
Published: March 2007

The application of fast imaging is necessary to reduce the scanning time for cardiac volumetric MRI. Fast spiral, echo planar imaging (EPI), and fast low‐angle shot (FLASH) imaging are rapid MRI techniques that allow image acquisition within a fraction of a second. Performed as a multi‐shot technique, breath‐hold imaging with high temporal and spatial resolution is feasible. This study evaluated the accuracy of interleaved spiral, EPI, and FLASH imaging for measuring ventricular volume and mass at .5T. Breath‐hold short‐axis cines in parallel planes covering both ventricles were acquired in 16 volunteers with all three fast methods, as well as with conventional gradient‐echo imaging for comparison. All fast techniques showed good agreement with conventional imaging. Despite its lower temporal resolution, FLASH imaging yielded higher image quality than EPI and spiral, making FLASH more reliable and suggesting that at .5T, it is the method of choice for rapid cardiac volumetric imaging.
MRI in focal liver disease: A comparison of small and ultra‐small superparamagnetic iron oxide as hepatic contrast agents
Authors: Mergo Patricia J. , Engelken John D. , Helmberger T. , Ros Pablo R.
Published: March 2007

The purpose of this study was to compare small and ultrasmall superparamagnetic iron oxide particles (SPIO and USPIO, respectively) as MR contrast agents for the evaluation of focal hepatic disease. In two different patient groups (SPIO [n = 53], USPIO [n = 27]), with focal liver disease (metastases, hepatocellular carcinoma [HCC], hepatocellular adenoma [HCA], and focal nodular hyperplasia [FNH]), spin‐echo T1‐ and T2‐weighted images (T1WI, T2WI) were obtained at 1.0T, before and after intravenous contrast administration. The percentage signal‐to‐noise ratio (SNR) change and lesion‐to‐liver contrast (LLC) were measured and statistically compared. The liver decreased in signal intensity (SI) after SPIO administration (−28%) and increased after USPIO administration (+16%) on T1WI. On T2WI, the liver decreased in SI on postcontrast images with both agents (−78% SPIO, −73% USPIO). This difference was not statistically significantly different (P ⩽ .07). Both SPIO and USPIO provided >500% improvement in LLC on T2WI. On T1WI, LLC was increased in metastases (120%) and HCC (325%) with SPIO. Post‐USPIO, LLC was increased on T1WI only in metastases (>500%). Both SPIO and USPIO show excellent hepatic uptake, presumed secondary to reticuloendothelial activity, based on the degree of %SI change seen in the liver after administration of contrast on T2WI. However, USPIO preparations exhibit blood pool activity that may aid in further characterization of focal liver lesions, as is evidenced by their greater T1 effect in the liver and in some focal liver lesions.
Comparison of multishot turbo spin echo and HASTE sequences for T2‐weighted MRI of liver lesions
Authors: Yu Jeong‐Sik , Kim Ki Whang , Kim Young Hwan , Jeong Eun‐Kee , Chien Daisy
Published: March 2007

The purpose of this study was to compare the relative usefulness of multishot turbo spin echo (TSE) and half‐Fourier single‐shot turbo spin echo (HASTE) for determination of optimal breath‐hold fast T2‐weighted technique in terms of lesion detection, lesion‐to‐liver contrast‐to‐noise ratio (CNR), and image quality. The images of TSE with and without fat suppression (FS) and of HASTE with and without FS were retrospectively reviewed for 49 patients with 128 lesions. Without FS, TSE and HASTE images allowed depiction of focal hepatic masses (112 of 128, sensitivity = 87.5%) at the same rate. TSE with FS depicted more focal lesions (115 of 128, 89.8%) than HASTE with FS (109 of 128, 85.2%), but the difference was not statistically significant (P > .05). The CNR of each lesion on HASTE sequences was greater (P < .01) than that on TSE sequences. The CNR of hemangioma was distinct from that of solid tumors and cystic lesions in all sequences, and the range of CNR in each group of pathologies overlapped less and were well separated in the HASTE sequences. HASTE sequences produced better image quality with fewer artifacts (P < .0001). The results of this study suggest that HASTE sequences allow differentiation between solid tumors, hemangiomas, and cystic lesions in terms of CNR, producing fewer image artifacts, with acceptable sensitivity in lesion detection.
Quantification of white matter and gray matter volumes from three‐dimensional magnetic resonance volume studies using fuzzy classifiers
Authors: Herndon R. Craig , Lancaster Jack L. , Giedd Jay N. , Fox Peter T.
Published: March 2007

We accurately measured white matter (WM) and gray matter (GM) from three‐dimensional (3D) volume studies, using a fuzzy classification technique. The new segmentation method is a modification of a recently published method developed for T1 parametric images. 3D MR images were transformed into pseudo forms of T1 parametric images and segmented into WM and GM voxel fraction images with a set of standardized fuzzy classifiers. This segmentation method was validated with synthesized 3D MR images as phantoms. These phantoms were developed from cryosectioned human brain images located in the superior, middle, and inferior regions of the cerebrum. Phantom volume measurements revealed that, generally, the difference between measured and actual volumes was less than 3% for 1.5‐mm simulated brain slices. The average cerebral GM/WM ratio calculated from 3D MR studies in four subjects was 1.77, which compared favorably with the estimate of 1.67 derived from anatomical data. Results indicate that this is an accurate and rapid method for quantifying WM and GM from T1‐weighted 3D volume studies.
Simultaneous gradient‐echo/spin‐echo EPI of graded ischemia in human skeletal muscle
Authors: Donahue Kathleen M. , Van Kylen Joel , Guven Safak , El‐Bershawi Ahmed , Luh Wen‐Ming , Bandettini Peter A. , Cox Robert W. , Hyde James S. , Kissebah Ahmed H.
Published: March 2007

The goal of this study was to evaluate the usefulness of blood oxygenation level‐dependent (BOLD) methodologies to provide temporal and spatial information about skeletal muscle perfusion. A simultaneous gradient echo (GE) and spin‐echo (SE) imaging sequence (GE/SE) with alternating TE was used to acquire images of leg skeletal muscle throughout a stepped reactive hyperemia paradigm. The change in both the GE and SE relaxation rates (ΔR2*, ΔR2) measured during ischemia and reactive hyperemia scaled with the duration of cuff inflation (the ischemic period) plateaued for cuff inflations lasting longer than 120 seconds and were greater in soleus muscle than in gastrocnemius. The ratio ΔR2*/ΔR2 was found to be less during the reactive hyperemia period relative to ischemia. Considering that a greater proportion of capillary vessels are perfused during reactive hyperemia than during ischemia, this finding suggests that magnetic susceptibility methodologies, with their dependence on compartment size, may provide a measure of the relative distribution of small and large vessels in skeletal muscle.
Gradient coil design considerations for iron core interventional magnets
Authors: Ersahin Atila , Bronskill Michael J. , Henkelman R. Mark , Collick Bruce , Hinks R. Scott
Published: March 2007

The requirements for access and imaging performance compete in the design of open‐concept MR magnets and gradient coils. We conducted a theoretical and experimental investigation of gradient coil design using both solid and laminated pole piece construction to determine whether adequate eddy current control can be obtained without shielded gradient coils while maintaining good patient access and high gradient performance. Eddy currents, gradient characteristics, gradient efficiency, and magnet openness are compared and contrasted for various construction options based on a compact, .27 T iron yoke magnet. The resulting pole pieces and gradient coils have high efficiency for an interventional open‐configuration magnet while taking up minimal space between the poles for improved patient access.
Determination of gradient magnetic field‐induced acoustic noise associated with the use of echo planar and three‐dimensional, fast spin echo techniques
Authors: Shellock Frank G. , Ziarati Mokhtar , Atkinson Dennis , Chen Dar‐Yeong
Published: March 2007

The purpose of this study was to assess gradient magnetic‐field‐induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three‐dimensional fast spin echo (3D‐FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field‐strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D‐FSE pulse sequences. Parameters were selected to produce “worst case” acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A‐weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D‐FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.
Combined MRI and CFD analysis of fully developed steady and pulsatile laminar flow through a bend
Authors: Weston S. J. , Wood N. B. , Tabor G. , Gosman A. D. , Firmin D. N.
Published: March 2007

A combined MR and computational fluid dynamics (CFD) study is made of flow in a simple phantom laboratory flow rig consisting of a 180° bend with straight entry and exit sections. The aim was to investigate the potential of the use of MRI‐linked CFD simulations for in vivo use. To this end, the experiment was set up for both steady and pulsatile laminar flow conditions, with Reynolds and Dean numbers and Womersley pulsatility parameter representative of resting flow in the human aorta. The geometrical images of the pipe and the velocity images at entry to the bend were used as boundary conditions for CFD simulations of the flow. The CFD results for both steady and pulsatile cases compared favorably with velocity images obtained at exit from the bend. Additional information such as pressure and wall shear stress, which either could not be measured adequately via MRI, or could not be measured at all, was also extracted from the simulation. Overall, the results were sufficiently promising to justify persuing subsequent in vivo studies.
Lipomatous hypertrophy of the atrial septum: Diagnosis with fat suppressed MR imaging
Authors: Mortele Koenraad J. , Merge Patricia J. , Williams Willie F.
Published: March 2007

We present a case of a 50‐year‐old female evaluated for a 1‐year history of numbness of the first and second toe of the right foot. Echocardiography performed in order to exclude cardiovascular compromise revealed a granular mass originating from the posterior part of the interatrial septum. On subsequent magnetic resonance imaging (MRI) with fat suppression sequences, the final diagnosis of lipomatous hypertrophy of the interatrial septum, a benign and under‐recognized condition characterized by septal accumulation of fatty tissue, was made. Although no previous reports have focused on this, tailored cardiac MR with fat suppression sequences proved to be an excellent noninvasive method in assessing an accurate diagnosis and in differentiating lipomatous hypertrophy of the atrial septum from other cardiac neoplasms.
Primary carcinoid of the duodenum: Detection and characterization by magnetic resonance imaging
Authors: Whitfill Charlene Hu , Siegelman Evan S. , Rosato Ernest F. , Furth Emma E.
Published: March 2007

We report a rare case of a primary small bowel carcinoid in which high‐resolution MRI was able to detect a 1‐cm primary duodenal neoplasm. This case illustrates that breath‐hold contrast‐enhanced MRI is capable of evaluating disease of the small bowel.
Three‐dimensional triple‐quantum‐filtered 23Na imaging of the dog head in vivo
Authors: Kalyanapuram Roopa , Seshan Viswanathan , Bansal Navin
Published: March 2007

Multiple‐quantum (MQ)‐filtered 23Na NMR has been proposed as a means to partially discriminate between intracellular and extracellular sodium. However, low signal‐to‐noise ratio (SNR) has been a major obstacle to MQ‐filtered 23Na imaging becoming an important technique for biological and clinical applications. We compared the various MQ‐filtered 23Na imaging pulse sequences to select the optimum sequence that provides the best SNR. The results of phantom experiments show that the gradient‐echo MQ‐filtered 23Na imaging sequence produces the best SNR. We also report, for the first time, three‐dimensional single‐quantum (SQ) and triple‐quantum (TQ)‐filtered 23Na images of the live dog brain and demonstrate the sensitivity of these images to ischemia produced by euthanizing the animal. The SQ images showed a 10% to 15% decrease in signal intensity from the brain postmortem, whereas the TQ‐filtered images showed a 40% to 50% increase. These changes in signal intensities are consistent with the influx of Na+ into the cells upon death. The feasibility of obtaining TQ‐filtered 23Na images of in situ dog brain encourages us to apply this technique to humans.
In vivo 1H MRS of normal breast and breast tumors using a dedicated double breast coil
Authors: Gribbestad Ingrid S. , Singstad Trond E. , Nilsen Gunnar , Fjøsne Hans E. , Engan Terje , Haugen Olav A. , Rinck Peter A.
Published: March 2007

Image‐guided localized proton MR spectroscopy (MRS) of normal breasts and breast tumors (ductal and undifferentiated carcinomas) was performed using a dedicated double breast coil. In vivo 1H MR spectra from 10 normal volunteers showed signals from water and lipids only, even in breasts with small contribution of fatty breast tissue. In the spectra from 6 of the 12 examined patients, an intense signal assigned to choline compounds was detected. The signal was also detected at lower levels in the remaining patients. This study shows that in vivo 1H MRI/MRS examinations of breast tumors can be performed within an examination time of 45 to 60 minutes. Signals from breast tumor metabolites may be detected using in vivo 1H MRS.
Hyperreactio luteinalis in a normal pregnancy: Sonographic and MRI findings
Authors: Ghossain Michel A. , Buy Jean‐Noël , Ruiz Alain , Jacob Denis , Sciot Catherine , Hugol Danièle , Vadrot Dominique
Published: March 2007

A case of hyperreactio luteinalis in an otherwise normal pregnancy is reported. Ascites was present, but no peritoneal implants or adenopathy were seen. Findings that would have suggested the correct diagnosis are the symmetrical and bilateral pattern of the mass, as well as the rather uniform size of the loculi, which were 1 to 3 cm in diameter.
T2‐weighted breath‐hold MRI of the liver at 1.0 T: Comparison of turbo spin‐echo and HASTE sequences with and without fat suppression
Authors: Kim Tae Kyoung , Lee Hyun Joo , Jang Hyun‐Jung , Kim Ah Young , Han Joon Koo , Choi Byung Ihn
Published: March 2007

To compare the clinical usefulness of T2‐weighted breath‐hold sequences for imaging the liver, 33 patients with 97 focal hepatic lesions were studied with a 1.0‐T scanner by using T2‐weighted breath‐hold turbo spin‐echo (SE) sequences and T2‐weighted breath‐hold half‐Fourier single‐shot turbo SE (HASTE) sequences with and without fat suppression. Images were quantitatively analyzed for liver signal‐to‐noise ratio (SNR) and lesion‐to‐liver contrast‐to‐noise ratios (CNR). Qualitative analysis was performed for lesion conspicuity, motion artifacts, and anatomic sharpness of extrahepatic structures. Breath‐hold turbo SE imaging with fat suppression showed the highest CNR for cystic lesions and the best lesion conspicuity for cystic and solid lesions among the four sequences. For solid lesions, there was no significant difference of lesion‐to‐liver CNR between them. HASTE sequence was superior to turbo SE sequences in terms of motion artifacts; however, the usefulness for evaluating focal hepatic lesions was limited compared with turbo SE sequence with fat suppression. Addition of fat suppression was not helpful for HASTE imaging because of decreased lesion conspicuity and extrahepatic details without the advantage of reducing motion artifacts. This study suggests that turbo SE sequence with fat suppression is most useful for breath‐hold T2‐weighted liver imaging at 1.0 T. Addition of imaging without fat suppression can be considered for evaluating extrahepatic structures. HASTE sequence may have a role for imaging uncooperative patients due to absence of motion artifacts.