bluuebunny/crossref_metadata_2025 huggingface dataset:
Validating in utero electroporation for the rapid analysis of gene regulatory elements in the murine telencephalon
Authors: Langevin Lisa Marie , Mattar Pierre , Scardigli Raffaella , Roussigné Myriam , Logan Cairine , Blader Patrick , Schuurmans Carol
Published: March 2007

With the ultimate goal of understanding how genetic modules have evolved in the telencephalon, we set out to modernize the functional analysis of cross‐species cis‐regulatory elements in mouse. In utero electroporation is rapidly replacing transgenesis as the method of choice for gain‐ and loss‐of‐function studies in the murine telencephalon, but the application of this technique to the analysis of transcriptional regulation has yet to be fully explored and exploited. To empirically define the developmental stages required to target specific populations of neurons in the dorsal telencephalon, or pallium, which gives rise to the neocortex in mouse, we performed a temporal and spatial analysis of the migratory properties of electroporated versus birth‐dated cells. Next, we compared the activities of two known Ngn2 enhancers via transgenesis and in utero electroporation, demonstrating that the latter technique more faithfully reports the endogenous telencephalic expression pattern observed in an Ngn2lacZ knock‐in line. Finally, we used this approach to test the telencephalic activities of a series of deletion constructs comprised of the zebrafish ER81 upstream regulatory region, allowing us to identify a previously uncharacterized enhancer that displays cross‐species activity in the murine piriform cortex and lateral neocortex, yet not in more medial domains of the forebrain. Taken together, our data supports the contention that in utero technology can be exploited to rapidly examine the architecture and evolution of pallial‐specific cis‐regulatory elements. Developmental Dynamics 236:1273–1286, 2007. © 2007 Wiley‐Liss, Inc.
Nr2e3 and Nrl can reprogram retinal precursors to the rod fate in Xenopus retina
Authors: McIlvain Vera A. , Knox Barry E.
Published: March 2007

Transformation of undifferentiated progenitors into specific cell types is largely dependent on temporal and spatial expression of a complex network of transcription factors. Here, we examined whether neural retina leucine zipper (Nrl) and photoreceptor‐specific nuclear receptor Nr2e3 transcription factors contribute to cell fate determination. We cloned the Xenopus Nr2e3 gene and showed that its temporal and spatial expression is similar to its mammalian ortholog. We tested its in vivo function by misexpressing these transcription factors in Xenopus eye primordia, demonstrating that either human Nr2e3 or Nrl directed photoreceptor precursors to become rods at the expense of cones. Furthermore, overexpression of Xenopus Nrl dramatically increased the number of lens fibers, whereas human Nrl did not, suggesting evolutionary divergence of function of the Nrl gene family. Misexpression of Nrl and Nr2e3 together were more effective than either transcription factor alone in directing precursors to the rod fate. Developmental Dynamics 236:1970–1979, 2007. © 2007 Wiley‐Liss, Inc.
Macrophage migration inhibitory factor is essential for allergic asthma but not for Th2 differentiation
Authors: Magalhães Elizabeth S. , Mourao‐Sa Diego S. , Vieira‐de‐Abreu Adriana , Figueiredo Rodrigo T. , Pires Ana L. , Farias‐Filho Francisco A. , Fonseca Bruna P. F. , Viola João P. B. , Metz Christine , Martins Marco A. , Castro‐Faria‐Neto Hugo C. , Bozza Patrícia T. , Bozza Marcelo T.
Published: March 2007

Macrophage migration inhibitory factor (MIF) is increased in asthmatic patients and plays a critical role in the pathogenesis of asthma. We show here that mice lacking MIF failed to develop airway hyper‐responsiveness (AHR), tissue eosinophilia, and mucus metaplasia. Analysis of the bronchoalveolar fluids revealed a substantial reduction of IL‐13, eotaxin and cysteinyl‐leukotrienes. The lack of these cardinal features of asthma in MIF–/– mice occurs regardless of high concentrations of IL‐4 in the lung and OVA‐specific IgE in the serum. Antigen‐specific lymphocyte proliferation and IL‐13 production were similarly increased in the draining lymph nodes of OVA‐immunized and challenged MIF–/– mice compared to WT, but were reduced in the spleen of MIF–/–, thus indicating differential roles of MIF in these compartments. Stimulation of naive CD4+ cells with anti‐CD3 antibody demonstrated that MIF–/– cells produced increased amounts of IFN‐γ and IL‐4 compared to WT CD4+ cells. Finally, treatment of sensitized BALB/c mice with neutralizing anti‐MIF antibody abrogated the development of ARH and airway inflammation without affecting the production of Th2 cytokines or IgE. The present study demonstrates that MIF is required for allergic inflammation, adding important elements to our knowledge of asthma pathogenesis and suggesting that neutralization of MIF might be of therapeutic value in asthma.
On‐line coupling of solid‐phase microextraction to commercial CE‐MS equipment
Authors: Santos Bricio , Simonet Bartolomé M. , Ríos Ángel , Valcárcel Miguel
Published: March 2007

We developed a new interface for the on‐line coupling of a fiber for solid‐phase microextraction (SPME) with a CE system with an electrospray interface for MS detection. The on‐line interface was a modification of a split‐flow interface typically used for coupling flow systems to CE. The modification consists of an additional channel closed with a septum that permits the introduction of the fiber in the interface, right at the inlet region of the separation capillary. The interface was designed to be used with commercial fibers. Although commercial fibers can be used directly, we recommend cutting the stationary phase and using fibers with a 2‐mm stationary phase. The system was tested for the analysis of tetracycline antibiotic residues, viz., tetracycline, oxytetracycline and doxycycline in soils. The overall accuracy was assessed by regression analysis of spiked samples, showing successful results at a 95% confidence level. The reproducibility, expressed as RSD, was 5.3% and the LOD of tetracycline antibiotics in soil ranged from 2.9 to 3.2 μg/kg.
Study of recombinant cytochrome P450 2C9 activity with diclofenac by MEKC
Authors: Konečný Jiři , Juřica Jan , Tomandl Josef , Glatz Zdeněk
Published: March 2007

Cytochrome P450 2C9 (CYP2C9) is one of the most important isoforms in human liver involved in the metabolism of a large number of therapeutic agents. The aim of this paper is to demonstrate the applicability of CE for the determination of the enzymatic activity of CYP2C9 with diclofenac as a probe substrate. MEKC with SDS as a pseudostationary phase was used for this purpose. Compared to other assays, the MEKC‐based method is rapid, can be automated and requires only a small quantity of enzymes and substrate. Moreover, the enzymatic reaction can be monitored with high sensitivity and repeatability even when the reaction mixture is used for the analysis without any pretreatment. The kinetic study on the given enzymatic reaction was also performed since the basic characterization of drug biotransformation generally begins with the enzyme kinetic analysis of metabolite formation. As a result, the Michaelis constant and maximum reaction velocity were evaluated, the values 3.44 ± 0.45 μM and 19.78 ± 0.76 nmol⋅min−1nmol−1, respectively, were in agreement with the literature data. On the other hand, a slight deviation from typical Michaelis–Menten kinetics with a weak positive cooperativity was found at diclofenac concentrations below 2 μM. The same atypical kinetic behavior of CYP2C9 was also observed by other authors.
Manganese speciation in human cerebrospinal fluid using CZE coupled to inductively coupled plasma MS
Authors: Michalke Bernhard , Berthele Achim , Mistriotis Panos , Ochsenkühn‐Petropoulou Maria , Halbach Stefan
Published: March 2007

The neurotoxic effects of manganese (Mn) at elevated concentrations are well known. This raises the question, which of the Mn species can cross neural barriers and appear in cerebrospinal fluid (CSF). CSF is the last matrix in a living human organism available for analysis before a compound reaches the brain cells and therefore it is assumed to reflect best the internal exposure of brain tissue to Mn species. A previously developed CE method was modified for separation of albumin, histidine, tyrosine, cystine, fumarate, malate, inorganic Mn, oxalacetate, α‐keto‐glutarate, nicotinamide‐dinucleotide (NAD), citrate, adenosine, glutathione, and glutamine. These compounds are supposed in the literature to act as potential Mn carriers. In a first attempt, these compounds were analyzed by CZE‐UV to check whether they are present in CSF. The CZE‐UV method was simpler than the coupled CZE‐inductively coupled plasma (ICP)‐dynamic reaction cell (DRC)‐MS method and it was therefore chosen to obtain a first overview information. In a second step, the coupled method (CZE‐ICP‐DRC‐MS) was used to analyze, in detail, which of the compounds found in CSF by CZE‐UV were actually bound to Mn. Finally, 13 Mn species were monitored in CSF samples, most of them being identified: Mn‐histidine, Mn‐fumarate, Mn‐malate, inorganic Mn, Mn‐oxalacetate, Mn‐α‐keto glutarate, Mn‐carrying NAD, Mn‐citrate and Mn‐adenosine. By far the most abundant Mn species was Mn‐citrate showing a concentration of 0.7 ± 0.13 µg Mn/L. Interestingly, several other Mn species can be related to the citric acid cycle.
Dynamic response by large step integration
Authors: Argyris J. H. , Dunne P. C. , Angelopoulos T.
Published: March 2007

A family of unconditionally stable algorithms for the economical computation of large linear dynamic systems is described and applied. Possible application to divergent systems is considered and some of the difficulties of extending the use of the algorithms to non‐linear systems are discussed. In the Appendix a previously developed conditionally stable algorithm is applied to the non‐linear gust response of a prestressed cable roof structure over the Munich Olympic Stadium. The idealization involves 1,164 degrees of freedom.
Accuracy of finite difference representations for the transient response analysis of shells
Authors: Underwood Philip
Published: March 2007

The frequency versus wave number characteristics of four O(ΔS2) finite difference formulations for one‐dimensional linear shell (ring and axisymmetric) equations are investigated and compared with the exact continuum characteristics. It is found that three of the formulations give virtually identical results. These are half‐spacing techniques with equilibrium in terms of displacements or resultants and whole‐spacing with equilibrium in terms of displacements. The formulation based on whole‐spacing with equilibrium in terms of resultants produces some dramatically different results. These discrepancies partially explain some late time instability problems and critical time step behaviour that have been reported by other investigators.
The seismic response of a reinforced concrete bridge pier designed to step
Authors: Beck J. L. , Skinner R. I.
Published: March 2007

A new technique to enhance the earthquake resistance of tall reinforced‐concrete bridges is introduced whereby the tall piers are allowed to ‘step’ during a severe seismic attack. This means that each pier is free to rock from side to side with vertical separation of parts of the pier from the supporting foundations. This stepping action limits stresses in the reinforced‐concrete piers to values below the yield levels and this should lead to a substantial reduction in the cost of providing earthquake resistance

As part of a feasibility study, a 200 feet‐high stepping pier is defined and its displacements are calculated for the ground accelerations of the 1940 El Centre earthquake, N‐S component. With no damping present the computations give many ‘stepping’ separations of rather large extent. When the effects of internal structural damping are included in the analysis, there is little reduction in the stepping motions at the level of damping expected in the pier. However, when the computations include the effects of some energy‐absorbing devices of a recently‐developed type, installed between the pier and its foundations, the amplitude and number of the stepping cycles are considerably reduced.
Factors influencing the choice of methods in federal evaluation practice
Authors: Chelimsky Eleanor
Published: March 2007

A critical historical review of the tensions in American governance places the method choice debate in a broader perspective. This chapter reviews the factors that influence the evaluation questions posed to evaluators and, in turn, the methods choices that stem from it. Political and professional pressures on the evaluators also influence methods choice. Flexibility in methods is considered essential for the evaluator to design a study that considers both the context and the specifics of the question.
Adding new dimensions to case study evaluations: The case of evaluating comprehensive reforms
Authors: Yin Robert K. , Davis Darnella
Published: March 2007

This chapter describes the adaptation of the case study method to assessing increasingly complex, comprehensive reform initiatives that highlight the blurring of the boundaries between phenomenon and context and the concurrence of multiple interventions. Completed studies of two education reform programs illustrate the ongoing challenges of identifying, measuring, and analyzing large‐scale reforms at multiple levels and across sites.
Methods for evidence‐based practice: Quantitative synthesis of single‐subject designs
Authors: Shadish William R. , Rindskopf David M.
Published: March 2007

Good quantitative evidence does not require large, aggregate group designs. The authors describe ground‐breaking work in managing the conceptual and practical demands in developing meta‐analytic strategies for single subject designs in an effort to add to evidence‐based practice.
Stabilized edge‐based finite element simulation of free‐surface flows
Authors: Elias Renato N. , Coutinho Alvaro L. G. A.
Published: March 2007

Free‐surface flows occur in several problems in hydrodynamics, such as fuel or water sloshing in tanks, waves breaking in ships, offshore platforms, harbours and coastal areas. The computation of such highly nonlinear flows is challenging since free‐surfaces commonly present merging, fragmentation and breaking parts, leading to the use of interface‐capturing Eulerian approaches. In such methods the surface between two fluids is captured by the use of a marking function which is transported in a flow field. In this work we present a three‐dimensional parallel edge‐based incompressible SUPG/PSPG finite element method to cope with free‐surface problems with volume‐of‐fluid (VOF) extensions to track the evolving free surface. The pure advection equation for the scalar marking function was solved by a fully implicit parallel edge‐based SUPG finite element formulation. We studied variants of this formulation, considering the effects of discontinuity capturing and a particular tangent transformation designed to increase interface sharpness. Global mass conservation is enforced adding or removing mass proportionally to the absolute value of the normal velocity of the interface. We introduce a parallel dynamic deactivation algorithm to solve the marking function equation only in a small region around the interface. The implementation is targeted to distributed memory systems with cache‐based processors. The performance and accuracy of the proposed solution method were tested with several validation problems. Copyright © 2007 John Wiley & Sons, Ltd.
Congenital lung malformations in the second trimester: Prenatal ultrasound diagnosis and pathologic findings
Authors: Harmath Ágnes , Csaba Ákos , Hauzman Erik , Hajdú Júlia , Pete Barbara , Papp Zoltán
Published: March 2007

Purpose.

To correlate prenatal sonographic diagnosis of cystic lung malformations with fetopathologic findings after termination of pregnancy.

Methods.

We retrospectively analyzed the data of 16 terminated cases in which a cystic lung lesion was diagnosed pre‐ or postnatally.

Results.

On average, prenatal diagnosis was established on the 21st gestational week (range, 19–26 weeks). The cause of termination was severe polyhydramnios in 4 cases, nonimmune fetal hydrops in 4 cases, other congenital malformation in 5 cases (renal malformation, 2 cases; congenital diaphragmatic hernia, 3 cases), and obstetrical conditions (intrauterine death, placental abruption, spontaneous abortion) in 3 cases. In 11 cases, congenital cystic adenomatoid malformation (CCAM) was the presumptive prenatal diagnosis. Autopsy confirmed the prenatal diagnosis in 6 of them, while in the other 5 cases, an enteric cyst, a laryngeal atresia, an unidentified tumor, a pulmonary hypoplasia, and an extralobar pulmonary sequestration were found on histologic examination. On the other hand, the autopsy revealed CCAM in those 5 cases in which other malformations were suggested prenatally.

Conclusion.

The prenatal sonographic diagnosis of CCAM is difficult. Our cases emphasize the important role of fetopathology even today in the verification of prenatal diagnosis based on sonographic examinations. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Left ventricular non‐Hodgkin lymphoma visualized on contrast echocardiography
Authors: Mendiolaza Jesús , Baltasar Jonnah Fatima T. , Anis Ather , Harrison Jonathan , Chen Fan , Klapholz Marc , Saric Muhamed
Published: March 2007

We present a case of AIDS‐related Burkitt's type cardiac lymphoma in a middle‐aged woman with Epstein‐Barr virus infection and profound immunodeficiency. The original features of our case include left ventricular location, female sex, and the use of contrast echocardiography to help establish the diagnosis. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Experimental test of the effects of fluctuating incubation temperatures on hatchling phenotype
Authors: Les Heather L. , Paitz Ryan T. , Bowden Rachel M.
Published: March 2007

In the painted turtle (Chrysemys picta) and red‐eared slider turtle (Trachemys scripta), the temperature that eggs are exposed to during incubation determines the sex of the developing embryo. Constant temperature incubation experiments have shown that for each of these species there is a pivotal temperature that produces a 1:1 sex ratio; higher temperatures bias sex ratios toward females, and lower temperatures toward males. Few studies have examined how fluctuating temperatures, as would be experienced in natural nests, affect hatchling phenotype. Models predict that under fluctuating temperatures sex determination depends on the proportion of development that occurs above or below the pivotal temperature. We tested the effect of fluctuating versus constant temperature incubation regimes on sex ratios and other hatchling traits for both painted and red‐eared slider turtles. Eggs were divided into two treatments with half of the eggs from each species incubated at a constant intermediate temperature, 28.5°C, and half incubated under temperatures that fluctuated 3°C above and below 28.5°C. We converted the fluctuating temperature data into a constant temperature equivalent (CTE) so that we could directly compare constant and fluctuating incubation regimes. The CTE for the fluctuating regime for both species was higher than the constant temperature, which would predict an increase in the production of females. The fluctuating regime did produce a higher proportion of females, but also resulted in increased developmental time and increased hatchling mass, indicating that fluctuating temperatures produce complex effects on hatchling phenotype. J. Exp. Zool. 307A:274–280, 2007. © 2007 Wiley‐Liss, Inc.
Myofibrillar gene expression in differentiating lobster claw muscles
Authors: Medler Scott , Lilley Travis R. , Riehl Jocelyn H. , Mulder Eva P. , Chang Ernest S. , Mykles Donald L.
Published: March 2007

Lobster claw muscles undergo a process of fiber switching during development, where isomorphic muscles containing a mixture of both fast and slow fibers, become specialized into predominantly fast, or exclusively slow, muscles. Although this process has been described using histochemical methods, we lack an understanding of the shifts in gene expression that take place. In this study, we used several complementary techniques to follow changes in the expression of a number of myofibrillar genes in differentiating juvenile lobster claw muscles. RNA probes complementary to fast and slow myosin heavy chain (MHC) mRNA were used to label sections of 7th stage (∼3 months old) juvenile claw muscles from different stages of the molt cycle. Recently molted animals (1–5 days postmolt) had muscles with distinct regions of fast and slow gene expression, whereas muscles from later in the molt cycle (7–37 days postmolt) had regions of fast and slow MHC expression that were co‐mingled and indistinct. Real‐time PCR was used to quantify several myofibrillar genes in 9th and 10th stages (∼6 months old) juvenile claws and showed that these genes were expressed at significantly higher levels in the postmolt claws, as compared with the intermolt and premolt claws. Finally, Western blot analyses of muscle fibers from juvenile lobsters ∼3 to 30 months in age showed a shift in troponin‐I (TnI) isoform expression as the fibers differentiated into the adult phenotypes, with expression of the adult fast fiber TnI pattern lagging behind the adult slow fiber TnI pattern. Collectively, these data show that juvenile and adult fibers differ both qualitatively and quantitative in the expression of myofibrillar proteins and it may take as much as 2 years for juvenile fibers to achieve the adult phenotype. J. Exp. Zool. 307A:281–295, 2007. © 2007 Wiley‐Liss, Inc.
Thermal variation reveals natural variation between isolates of Caenorhabditis elegans
Authors: Harvey S.C. , Viney M.E.
Published: March 2007

The free‐living nematode Caenorhabditis elegans is distributed globally and found in many varied habitats. However, in comparison to our understanding of the genetics of the species, little is known about natural variation and many major life history traits appear to show only limited differences between isolates. Here we show that temperature affects the lifetime fecundity and the reproductive timing of C. elegans and that there is a genotype by environment interaction, with isolates varying in how lifetime fecundity changes with temperature. We show that the lower lifetime fecundity observed at higher temperatures is primarily due to a reduction in the number of functional sperm. Further, isolates vary in their lifetime fecundity because of inter‐isolate differences in this effect of temperature on the number of functional sperm. J. Exp. Zool. (Mol. Dev. Evol.) 308B:409–416, 2007. © 2007 Wiley‐Liss, Inc.
Adaptation to long sperm in Drosophila: correlated development of the sperm roller and sperm packaging
Authors: Joly Dominique , Luck Nathalie , Dejonghe Béatrice
Published: March 2007

Sperm are generally small and produced in huge numbers, but some species combine exaggerated sperm length with extremely limited numbers of sperm, an evolutionary trend that deviates from the theory of anisogamy. Sperm gigantism has arisen recurrently in various species, but insects exhibit the longest sperm, with some species of the Drosophilidae family producing sperm up to 6 cm in length. The anatomical, cytological, and physiological requirements for males to cope with these giant sperm were hitherto poorly understood. In this paper, we investigate the internal morphology of the male reproductive tract, and highlight specific features that may be linked to this increase in sperm size. We focus on species in the repleta group, within which sperm length varies by a factor of 35. An associated development of the sperm roller, a special twisting device inserted between the testis and the seminal vesicle, is demonstrated. Its length and the number of coils involved increase with sperm size, and it allows individual sperm to swell and roll into a spermatic pellet before reaching the seminal vesicle. This process occurs independently of and in addition to the sperm bundle coiling that takes place at the base of the testis. It is suggested that the emergence and development of the sperm roller may be a male adaptation to sperm gigantism. J. Exp. Zool. (Mol. Dev. Evol.) 310B:167–178, 2008. © 2007 Wiley‐Liss, Inc.
Gadobenate dimeglumine (BOPTA) enhanced MR imaging: Patterns of enhancement in normal liver and cirrhosis
Authors: Manfredi Riccardo , Maresca Giulia , Baron Richard L. , De Franco Antonio , De Gaetano Anna Maria , Cotroneo Antonio R. , Pirovano Giampaolo , Spinazzi Alberto , Marano Pasquale
Published: March 2007

To determine whether gadobenate dimeglumine (BOPTA) will adequately enhance cirrhotic liver parenchyma, and to document the enhancement patterns in cirrhosis, 14 cirrhotic and 20 non‐cirrhotic patients were evaluated before and 60–120 minutes after gadolinium‐BOPTA. Proof of liver cirrhosis was biopsy (6), surgical resection (3), and clinical follow‐up (5). Enhancement effects were compared quantitatively by determining the liver signal‐to‐noise ratio (SNR) and signal enhancement in both populations. Qualitatively assessment of the liver enhancement was performed and classified as homogeneous or heterogeneous. Quantitative analysis: cirrhotic liver parenchyma presented a higher increase in SNR values, relative to noncirrhotic liver parenchyma, on postcontrast images. Likewise the signal enhancement of cirrhotic liver parenchyma was superior to non‐cirrhotic liver on T1‐weighted SE images (P = .02) and in‐phase GRE images (P < .001). There was no statistical difference on out‐of‐phase GRE images. Qualitative analysis: on T1‐weighted SE postcontrast images, cirrhotic liver parenchyma showed a homogeneous enhancement in 7 patients and heterogeneous in 7. Whereas on GRE images, cirrhotic parenchyma showed heterogeneous enhancement in 9 patients and homogeneous in 5 patients. The heterogeneous enhancement was due to the presence of hypointense nodules in 7 patients and hyperintense nodules in 2 patients. In conclusion, our study has shown that the hepatobiliary contrast agent Gd‐BOPTA is effective in the cirrhotic liver, demonstrating an increased liver enhancement compared with non‐cirrhotic patients.
Sliding interleaved KY (SLINKY) acquisition: A novel 3D MRA technique with suppressed slab boundary artifact
Authors: Liu Kecheng , Rutt Brian K.
Published: March 2007

This work addresses the elimination of the slab boundary artifact (SBA) or venetian blind artifact in three‐dimensional multiple overlapped thin slab acquisition (3D MOTSA) for magnetic resonance angiography (MRA). Our method uses a sliding‐slab, interleaved kY (SLINKY) data acquisition strategy, equalizing flow‐related signal intensity weighting across the entire slab dimension. This technique demodulates signal intensity changes along the slab direction and can essentially eliminate the SBA while retaining the same or better imaging time efficiency than that of conventional MOTSA, providing robustness to complicated flow patterns and thereby resulting in more accurate depiction of vascular morphology. In addition, this technique does not need specialized reconstruction and extra computation. The unique penalty of this technique is the sensitivity to phase inconsistency in the data. Both phantom and in vivo experiments verify the clinical significance of the technique. The new MRA images acquired with this imaging technique show highly reliable mapping of vascular morphology without the SBA and reduction of signal voids in complex/slow flow regions.
Dynamic scan‐plane tracking using MR position monitoring
Authors: Derbyshire J. Andrew , Wright Graham A. , Henkelman R. Mark , Hinks R. Scott
Published: March 2007

An MR‐based method for tracking subject motion is presented. The technique identifies subject motion from the three‐dimensional positions of three small samples attached to the subject in a fixed, triangular configuration. The updated positions of these samples relative to their initial positions determine a rigid body transformation. Applied to the MRI scan prescription via adaptive feedback controls, this transformation yields an updated MRI scan plane that tracks the prescribed imaging section as the subject moves. The scan‐plane tracking procedure is demonstrated experimentally for two‐dimensional imaging of a standard imaging phantom and the head of a human subject. Sets of images were acquired sequentially, with motion (translations and/or rotations) introduced between image frames. The scan‐plane tracking system provides well registered image slices of the same section, adaptively compensating for the subject motion.
Monitoring and visualization techniques for MR‐guided laser ablations in an open MR system
Authors: Kettenbach Joachim , Silverman Stuart G. , Hata Nobuhiko , Kuroda Kagayaki , Saiviroonporn Pairash , Zientara Gary P. , Morrison Paul R. , Hushek Stephen G. , Black Peter McL. , Kikinis Ron , Jolesz Ferenc A.
Published: March 2007

Our purpose was to develop temperature‐sensitive MR sequences and image‐processing techniques to assess their potential of monitoring interstitial laser therapy (ILT) in brain tumors (n = 3) and liver tumors (n = 7). ILT lasted 2 to 26 minutes, whereas images from T1‐weighted fast‐spin‐echo (FSE) or spoiled gradient‐recalled (SPGR) sequences were acquired within 5 to 13 seconds. Pixel subtraction and visualization of T1‐weighted images or optical flow computation was done within less than 110 msec. Alternating phase‐mapping of real and imaginary components of SPGR sequences was performed within 220 msec. Pixel subtraction of T1‐weighted images identified thermal changes in liver and brain tumors but could not evaluate the temperature values as chemical shift‐based imaging, which was, however, more affected by susceptibility effects and motion. Optical flow computation displayed the predicted course of thermal changes and revealed that the rate of heat deposition can be anisotropic, which may be related to heterogeneous tumor structure and/or vascularization.
MRI evaluation of acute renal trauma
Authors: Marcos Hani B. , Noone Tara C. , Semelka Richard C.
Published: March 2007

We describe the MR findings in a patient with acute renal injury after blunt abdominal trauma associated with perinephric hematoma and urinoma. Both CT and MR findings are described. Active urine extravasation into a perinephric urinoma is demonstrated by serial post‐contrast imaging with CT and MRI showing progressively increased attenuation/signal intensity fluid in communication with the collecting system, commencing 2 minutes after contrast administration.
A left atrial pseudomass: Potential pitfall at thoracic MR imaging
Authors: King Mark A. , Vrachliotis Thomas G. , Bergin Colleen J.
Published: March 2007

We frequently observed a nodular soft‐tissue structure in the region of the left atrium anterior to the orifice of the left inferior pulmonary vein on MR scans of the chest. To assess its morphologic characteristics and appearance, chest MR scans obtained in 49 patients were reviewed. ECG‐gated conventional spin‐echo T1‐weighted and fast spin‐echo (FSE) T2‐weighted sequences were used. The location, morphology, and appearance of this soft‐tissue structure was evaluated by two radiologists during one consensus reading. The psendomass in the region of the left atrium was identified on the T1‐weighted images in 25 of 49 patients. The structure was also identified on FSE T2‐weighted images in 6 of these patients. On the T1‐weighted images, its appearance was either linear (54%) or nodular (46%). In conclusion, a nodular soft‐tissue mass anterior to the orifice of the left inferior pulmonary vein into the left atrium is a frequent finding on chest MR scans and should not be confused with an intra‐atrial mass. Careful evaluation of the regional anatomy identifies this structure as extraluminal and helps to avoid misinterpretation of an intracardiac mass.
Experimental validation of an automated edge‐detection method for a simultaneous determination of the endocardial and epicardial borders in short‐axis cardiac MR images: Application in normal volunteers
Authors: Furber Alain , Balzer Philippe , Cavaro‐Ménard Christine , Croué Anne , Da Costa Eric , Lethimonnier Franck , Geslin Philippe , Tadéi André , Jallet Pierre , Le Jeune Jean‐Jacques
Published: March 2007

The goal of this study was to put together several techniques of image segmentation to provide a reliable assessment of the left ventricular mass with short‐axis cardiac MR images. No initial manual input was required for this process based on region growing, gradient detection, and adaptive thresholding. A comparison between actual mass and automatic assessment was implemented with 9 minipigs that underwent spin‐echo MR imaging. Fifteen normal volunteers were studied with a fast‐gradient‐echo sequence. The automatic segmentation was then controlled by three trained observers. Actual mass and automatic segmentation were strongly correlated (r = .97 with P < .01). For normal volunteers, the standard error of estimation of the automatic assessment (12 g) compared well with the average myocardial mass (120 ± 30 g) and the interobserver reproducibility of the manual assessment (9 g). These results allow the application of this method to the quantification of the left ventricular function and mass in clinical practice.
Frequency‐domain simulation of MR tagging
Authors: Crum William R. , Berry Elizabeth , Ridgway John P. , Sivananthan U. Mohan , Tan Lip‐Bun , Smith Michael A.
Published: March 2007

Simulation of MR images is a useful tool for offline sequence development and as an aid to understanding image formation. One particular application of simulation is MR tagging, which is used for tracking myocardial motion. Simple spatial‐domain methods cannot adequately represent effects common in these images, such as motion artifact and signal wrap. An existing frequency‐domain model is shown to be inappropriate for tagged images, and an extension based on the Bloch equations and Fourier shift theorem is described to correct this. Software incorporating the new model is used to generate ideal tag intensity profiles and to accurately simulate tagged images. The shifted k‐space patterns associated with tagged images, and their dependence on the order of the binomial tagging sequence, are explained. An application of the Fourier shift theorem is suggested that allows more rapid simulation of static tagged images.
Black blood magnetic resonance angiography with Dy‐DTPA polymer: Effect on arterial intraluminal signal intensity, lumen diameter, and wall thickness
Authors: Eubank William B. , Schmiedl Udo P. , Yuan Chun , Black Christopher D. V. , Kellar Kenneth E. , Ladd David L. , Nelson James A.
Published: March 2007

Four rabbits in which atherosclerotic disease was induced by diet and balloon angioplasty underwent conventional angiography and MR angiography (MRA) using a black blood pulse sequence before and 10 minutes after the iv injection of a macromolecular contrast agent, NC 100283 (1.0 mmol/kg), a dysprosium diethylenetriaminepentaacetic acid hexamethylenediamine copolymer (Dy‐DTPA polymer). Intraluminal signal intensity, apparent wall thickness, and lumen size measurements of the aorta and proximal common iliac arteries on precontract MRA images were compared with postcontrast images. Aortic lumen diameter measurements on the precontrast and postcontrast MRA studies were compared with lumen diameters from conventional angiograms. Intraluminal signal intensity decreased on postcontrast MRA images compared with precontrast images, with an average loss of signal equal to 29% (P < .05). Apparent wall thickness decreased by 24% (P < .05). Lumen diameter and area were generally larger (average of 15% and 33%, respectively) on postcontrast MRA images than on precontrast images. Aortic lumen diameter measurements from postcontrast MRA agreed closely (95% confidence interval of the mean difference was −.2 to .3 mm), and precontrast MRA images tended to underestimate aortic lumen diameter (95% confidence interval of the mean difference was .3 to .8 mm) compared with conventional angiography. Postcontrast MRA with NC 100283, a macromolecular Dy‐DTPA contrast agent, provides more accurate assessment of aortic lumen diameter than precontrast MRA, using conventional angiography as the standard reference.
Prospective evaluation of peripheral arterial occlusive disease by 2D MR subtraction angiography
Authors: Laissy Jean Pierre , Debray Marie‐Pierre , Menegazzo David , Rangheard Anne‐Sophie , Benamer Hakim , Charlier Patrick , Schouman‐Claeys Elisabeth
Published: March 2007

The purpose of this study was to assess the diagnostic value of two‐dimensional (2D) MR subtraction angiography of lower extremities in patients with symptomatic peripheral arterial occlusive disease with conventional angiography as the standard of reference. Twenty patients were prospectively included. 2D subtraction MR angiography (MRA) consisted of multisection gradient‐recalled echo (GRE) acquisitions with the shortest TE available on our machine (4 msec), obtained in the coronal plane before and after intravenous bolus administration of gadolinium chelate. MR images were reconstructed after subtraction with a maximum‐pixel‐intensity‐projection (MIP) algorithm. MRA was performed in all cases 1–4 days before diagnostic angiography. In a prospective blinded analysis, the number and location of significant (ie, >50%) stenoses and occlusions were evaluated for each vascular segment. Sensitivity and specificity were used to evaluate MRA data. Significant stenoses (38 of 46, 83%) and occlusions (66 of 67, 99%) seen at conventional angiography were identified with MRA. The sensitivity and specificity of MRA for determination of stenoses >50% or occlusions was 100% and 97%, respectively. The location and extent of stenoses and/or occlusions on MRA and angiograms were well correlated (kappa values, r = .73, P < .05). Contrast 2D MR subtraction angiography, by providing comparable information to that of conventional angiography, is well suited to evaluate the presence and severity of atherosclerotic lesions of the lower limbs.
Intraoperative dynamic MRI: Localization of sites of brain tumor recurrence after high‐dose radiotherapy
Authors: Schwartz Richard B. , Hsu Liangge , Kacher Daniel F. , Wong Terence Z. , Alexander Eben , Okon Stephen , Guttmann Charles R. G. , Black Peter McL. , Kelley Raymond A. , Moriarty Thomas , Martin Claudia , Isbister Holly G. , Cahill Cheryl D. , Spaulding Sharon A. , Jolesz Ferenc A.
Published: March 2007

In patients with malignant astrocytomas or metastatic brain disease treated with high‐dose radiotherapy, conventional imaging methods may not adequately distinguish recurrent tumor from radiation change. We used a fast spoiled gradient refocusing technique in the open‐configuration intraoperative MR system to assess the rate of regional enhancement of the treated tumor bed and to localize specific sites for pathologic sampling to determine whether gadolinium uptake correlated with histologic data. Twenty‐four patients were studied. Fourteen of 15 patients with areas of early enhancement had recurrent tumor present in histologic samples, and 8 of the remaining 9 patients had only reactive changes. Dynamic MRI was predictive of recurrent tumor (P < .0005, Fisher exact test and P < .002, Student t test). We conclude that dynamic MRI in the open‐bore magnet is a promising method for localizing potential sites of active tumor growth in patients treated for malignant astrocytomas and metastatic brain lesions.
Proton T1ρ‐dispersion imaging of rodent brain at 1.9 T
Authors: Rizi Rahim R. , Charagundla Sridhar R. , Song Hee Kwon , Reddy Ravinder , Stolpen Alan H. , Schnall Mitchell D. , Leigh John S.
Published: March 2007

Detection of H217O with proton T1ρ‐dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1ρ dispersion of tissue. To investigate these properties, we implemented a T1ρ imaging sequence on a 1.9‐T Signa GE scanner. A series of T1ρ images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5 % (wt/vol) gelatin phantoms containing different concentrations of 17O ranging from .037 % (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1ρ‐dispersion in phantoms doped with H217O, the T1ρ of rat brain undergoes minimal dispersion for spin‐locking frequencies between .2 and 1.5 kHz. A small degree of T1ρ dispersion is present below .2 kHz, which we postulate arises from natural‐abundance H217O. Moreover, the signal‐to‐noise ratios of T1ρ‐weighted images are significantly better than comparable T2‐weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1ρ‐dispersion imaging for detecting intravenous H217O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.
Evaluation of the stability of the proton chemical shifts of some metabolites other than water during thermal cycling of normal human muscle tissue
Authors: Young Ian R. , Bell Jimmy D. , Hajnal Joseph V. , Jenkinson Gabriele , Ling Junxiao
Published: March 2007

MR temperature measurements made by the chemical‐shift‐of‐water technique in peripheral muscle of volunteers have produced larger‐than‐expected coefficients of change and shown significant hysteresis effects as the temperature was cycled, although these effects were not reproduced in the present study. Previous work has suggested that susceptibility effects could be a contributor to the behavior of the chemical shift data. Here, we use proton spectroscopy of muscle in conjunction with temperature cycling to evaluate the relative shifts of the water peak and those of creatine, choline, and lipids. These latter are considered not to have significant temperature coefficients of chemical shift. The results show that these lines remain very stable as the temperature is cycled, suggesting that susceptibility effects are not present in this study. The method offers the possibility that the lines can be used as frequency references if there are any questions about the stability of other moieties.
Carpal tunnel syndrome: Staging of median nerve compression by MR imaging
Authors: Kleindienst Andrea , Hamm Bernd , Lanksch Wolfgang R.
Published: March 2007

The purpose of this prospective study was to determine the potential of MR imaging to depict morphologic alterations of the median nerve correlating with the stage of carpal tunnel syndrome (CTS). Eighteen wrists of normal subjects and 81 wrists of patients with CTS were examined. MR imaging was performed with proton‐density‐ and T2‐weighted spin‐echo sequences. Staging of CTS was done on the basis of clinical and electrophysiological testing, including evaluation of the number of previous steroid infiltrations in conservative treatment. Median nerve flattening, cross‐sectional area, and signal intensity were measured from the distal radius to the end of the carpal tunnel. Delineation and structure of the median nerve were recorded qualitatively by two experienced radiologists in consensus. Three major MR imaging criteria of early CTS were (a) isolated prestenotic and intracarpal swelling of the median nerve (P < .01), (b) the absence of significant flattening, and (c) a generalized increase in signal intensity retrograde to the distal radius (P < .01). The nerve showed sharply delineated contours and a homogeneous signal pattern. Advanced CTS was characterized by retrograde swelling of the median nerve to the distal radius (P < .01) and decreased signal intensity (P < .05). Demarcation of the nerve became poorer, and its signal pattern appeared fasciculated. After steroid infiltration, the median nerve was difficult to delineate, showed an inhomogeneous structure, and swelling was less pronounced than without steroid infiltration (P < .05). MR imaging yields typical morphologic findings that correlate with the duration and severity of median nerve compression. Hence, MR imaging allows staging of median nerve compression in CTS and thus may contribute to therapeutic decision‐making.
Digital wavelet‐encoded MRI: A new wavelet‐encoding methodology
Authors: Panych Lawrence P. , Zientara Gary P. , Saiviroonporn Pairash , Yoo Seung‐Schik , Jolesz Ferenc A.
Published: March 2007

A new digital wavelet‐encoding method for MRI is described. The method differs from previously described wavelet‐encoding approaches, because the pointspread function is made independent of the wavelet basis used. This has a significant practical advantage, because wavelet bases can now be considered that would otherwise be excluded due to the difficulty of precisely exciting wavelet‐shaped RF profiles. The method has been implemented on a clinical MRI system, and human images are presented.
MR versus fluoroscopic guidance of a catheter/guidewire system: In vitro comparison of steerability
Authors: Zimmermann‐Paul Gesine G. , Ladd Mark E. , Pfammatter Thomas , Hilfiker Paul R. , Quick Harald H. , Debatin Jörg F.
Published: March 2007

Our purpose in this study was to evaluate the steerability of a combined catheter guide‐wire system with MR tracking in an open‐configuration .5T MR system and compare it with fluoroscopic guidance. Experiments were performed with an aorta‐shaped glass phantom with different‐size branches connected to a roller flow pump to simulate pulsatile flow. A .035″ guidewire was used in conjunction with a 5F Cobra 2‐shaped catheter. For active MR guidance, a small RF coil was incorporated into the tips of all devices. In addition to fluoroscopic guidance, we used MR tracking devices to selectively catheterize all branches in the .5T open magnet (Signa SP, GEMS). Time requirements for the latter were compared with those needed under conventional angiographic conditions using standard catheters and guidewires. Active MR tracking permitted the simultaneous real time (4 updates/sec) guidance of both guide‐wire and catheter. Under MR guidance, all branch vessels were successfully catheterized. We found no significant differences in time requirements between guidance with the MR tracking device and fluoroscopic guidance. However, cannulation under fluoroscopic guidance with standard angiography devices required significantly less time (P < .05). Selective catheterization of small branch vessels is possible with active MR tracking of a combined cath‐eter/guidewire system. Limitations of MR tracking device material and design result in a considerable lengthening of the cannulation procedures.
Cystic adenomyosis of the uterus: MRI
Authors: Troiano Robert N. , Flynn Stuart D. , McCarthy Shirley
Published: March 2007

Adenomyosis of the uterus is most often seen as focal or diffuse thickening of the myometrial junctional zone on MRI. We describe the morphologic features and signal characteristics of the rarer cystic form of the disease, as revealed by MRI. We conclude that cystic adenomyosis of the uterus is characterized by a well‐circumscribed cystic lesion within the myometrium that demonstrates hemorrhage in differential stages of organization on MR images.