bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology and Nanomechanics of Conducting Plastic Crystals
Authors: Volel Maritza , Alarco Pierre‐Jean , Abu‐Lebdeh Yaser , Armand Michel
Published: July 2004

We present a temperature‐controlled scanning probe microscopy characterisation of morphology and mechanical behaviour of conducting N,N′‐cyclized pyrazolium salts. These salts are plastic crystals belonging to the pyrazolium trifluoromethanesulfonimide family. Going from a five‐membered to a seven‐membered ring, and adding a methyl group in α to either the five‐membered or six‐membered rings, allows modulation of the temperature of the phase transitions. Before and after the transitions, the materials' Young moduli, hardnesses and surface roughnesses change. We attribute these macroscopic modifications to specific states: brittle, elastoplastic and viscoplastic, corresponding to variations in the extent of the dislocations present in the crystal lattice planes of the compounds.
2003 Nobel Prize in Physics for Theoretical Work on Superfluid 3He
Authors: Leggett Anthony J.
Published: July 2004

The element helium comes in two (stable) forms, 4He and 3He; at low temperatures and pressures both form liquids rather than solids. The liquid phase of the common isotope, 4He, was realized nearly a century ago, and since 1938 has been known to show, at temperatures below about 2 K, the property of superfluidity—the ability to flow through the narrowest capillaries without apparent friction. The light isotope, 3He, is believed to be of quite a different nature; however,because of its similarity to the electrons in metals, which at low temperatures sometimes form “Cooper pairs” and thereby become superconducting, theorists in the 1960s and early 1970s had speculated that something similar might happen in liquid 3He, which would then also show superfluidity though for reasons rather different than 4He. In 1972 nuclear magnetic resonance (NMR) experiments at Cornell University revealed the existence, below 3 millidegrees, if two new phases, one of which displayed extraordinary NMR properties. Anthony Leggett is one of the theorists who succeeded in fitting the experimental properties into the “Cooper‐pairing” scenario; in particular, he explained the NMR behavior and predicted further novel NMR phenomena which were subsequently found.
Type H Superconductors and the Vortex Lattice
Authors: Abrikosov Alexei A.
Published: July 2004

Superconducting material is used, for example, in magnetic resonance imaging for medical examinations and particle accelerators in physics. Knowledge about superfluid liquids can give us deeper insight into the ways in which matter behaves in its lowest and most ordered state. Work by the author on superconduction in liquid helium established the existence of type II superconductors and proved that vortex lattices exist in superfluid helium, in the presence of magnetic fields. He showed that the Ginzburg–Landau theory could be extended to include this “new” type of superconductors, which today are in common use. His work on phase transitions of these superconductors under the influence of magnetic fields was groundbreaking, although he has worked in many other areas since then. He was awarded the Nobel prize in 2003 “for pioneering contributions to the theory of superconductors and superfluids” with V. L. Ginzburg and A. J. Leggett.
Medical removal protection benefits: The special challenges of Beryllium
Authors: Abbotts John , Takaro Tim K.
Published: July 2004

During the 1990s, the Department of Energy (DOE) established a Chronic Beryllium Disease Prevention Program and revised regulations for beryllium exposure to DOE and contractor employees. DOE beryllium regulations include “medical surveillance” of potentially exposed workers, along with “medical removal protection benefits” for beryllium‐sensitized workers. Medical removal benefits were first introduced into individual standards of the Occupational Safety and Health Administration (OSHA), beginning with a standard for asbestos in 1972. DOE modeled its medical removal protection benefits for beryllium in part on OSHA standards for lead and cadmium. But DOE also recognized significant differences in the toxicology of beryllium compared to these other metals. We survey OSHA standards for medical removal protection, provide a comparison with beryllium, and identify potential limits in beryllium protection benefits. © 2004 Wiley Periodicals, Inc.
Evaluation of the Digital Opacity Compliance System at military and commercial industrial sites
Authors: McFarland Michael J. , Stone Daniel A. , Rasmussen Steven L. , Calidonna Michael J. , Kerch Paul E. , Gunter Josh A.
Published: July 2004

The U.S. Environmental Protection Agency (EPA) has established EPA Reference Method 9 (Method 9) as the preferred enforcement approach for verifying compliance with federal visible opacity standards. The costs associated with maintaining Method 9 certification, including tuition fees, attendee's travel, and the three days of missed work every six months, supports the claim that the Method 9 program is expensive. Beyond the economic burden associated with Method 9 certification, its reliance on human observers to quantify visible opacity is inherently subjective, a characteristic that exposes the results to claims of inaccuracy, bias, and/or outright fraud.

The Digital Opacity Compliance System (DOCS) has been proposed as a scientifically defensible alternative to Method 9. Field application of the DOCS at military and commercial industrial facilities has demonstrated that the accuracy of the DOCS in measuring plume opacity is not only comparable to Method 9–certified human observers but that the DOCS also provides a permanent digital image of the plume that can be easily referenced in challenging enforcement actions. © 2004 Wiley Periodicals, Inc.
Managing problem indoor environments by embracing subjective data: A case study for federal facilities
Authors: Thomas‐Mobley Linda , Oberle Rita
Published: July 2004

This article describes a new approach to embrace the multifaceted nature of “sick buildings” by analyzing industrial hygienist measurements, which are objective, along with occupant perception measurements, which are subjective, using a neural network–based model. Data, both objective and subjective, for this research were provided by the General Services Administration (GSA) on a wide variety of federal office buildings. Current literature on the subject suggests that the cause of poor indoor environments involves many variables interacting in an unlimited number of combinations. A blended definition of a narrowly defined “sick building” and a framework for a decision‐making support system is presented to help the building engineer better understand the complex nature of the indoor environment. The research and data analyses can be tailored to and applicable to any federal agency. © 2004 Wiley Periodicals, Inc.
Dynamical systems‐based optimal control of incompressible fluids
Authors: Hintermüller Michael , Kunisch Karl , Spasov Yulian , Volkwein Stefan
Published: July 2004

For optimal control problems related to fluid flow the choice of an adequate cost functional for suppression of vortices is of significant importance. In this research we propose a cost functional based on a local dynamical systems characterization of vortices. The resulting functional is a non‐convex function of the velocity gradient tensor. The resulting optimality system describing first order necessary optimality conditions is derived, a possible strategy for numerical realization of the optimal control problem is provided and a numerical feasibility study is conducted. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of Cryptosporidium parvum oocyst transport in porous media
Authors: Kim Song‐Bae , Corapcioglu M. Yavuz
Published: July 2004

Cryptosporidium parvum is a protozoan parasite, transmitted through aqueous environments in the form of an oocyst. In this study, a transport model into which sorption, filtration and inactivation mechanisms are incorporated is applied to simulate laboratory column data, and the suitability of a kinetic model to describe the C. parvum oocyst transport and removal in porous media is compared with an equilibrium model. The kinetic model is applied to simulate previous column experimental data and successfully simulates the concentration peak; the late time tailing effect appeared in the breakthrough curves, indicating that the kinetic model is more suitable than the equilibrium one at simulating the fate and transport of the oocysts in porous media. Simulation illustrates that sorption causes retardation along with a tailing in the breakthrough curve. Additionally, filtration acts as a major mechanism of removing the oocysts from the aqueous phase, whereas the role of inactivation in reducing the viable oocyst concentration is minimal. Copyright © 2004 John Wiley & Sons, Ltd.
Active microwave remote sensing for soil moisture measurement: a field evaluation using ERS‐2
Authors: Walker Jeffrey P. , Houser Paul R. , Willgoose Garry R.
Published: July 2004

Active microwave remote sensing observations of backscattering, such as C‐band vertically polarized synthetic aperture radar (SAR) observations from the second European remote sensing (ERS‐2) satellite, have the potential to measure moisture content in a near‐surface layer of soil. However, SAR backscattering observations are highly dependent on topography, soil texture, surface roughness and soil moisture, meaning that soil moisture inversion from single frequency and polarization SAR observations is difficult. In this paper, the potential for measuring near‐surface soil moisture with the ERS‐2 satellite is explored by comparing model estimates of backscattering with ERS‐2 SAR observations. This comparison was made for two ERS‐2 overpasses coincident with near‐surface soil moisture measurements in a 6 ha catchment using 15‐cm time domain reflectometry probes on a 20 m grid. In addition, 1‐cm soil moisture data were obtained from a calibrated soil moisture model. Using state‐of‐the‐art theoretical, semi‐empirical and empirical backscattering models, it was found that using measured soil moisture and roughness data there were root mean square (RMS) errors from 3·5 to 8·5 dB andr2values from 0·00 to 0·25, depending on the backscattering model and degree of filtering. Using model soil moisture in place of measured soil moisture reduced RMS errors slightly (0·5 to 2 dB) but did not improver2values. Likewise, using the first day of ERS‐2 backscattering and soil moisture data to solve for RMS surface roughness reduced RMS errors in backscattering for the second day to between 0·9 and 2·8 dB, but did not improver2values. Moreover, RMS differences were as large as 3·7 dB andr2values as low as 0·53 between the various backscattering models, even when using the same data as input. These results suggest that more research is required to improve the agreement between backscattering models, and that ERS‐2 SAR data may be useful for estimating fields‐scale average soil moisture but not variations at the hillslope scale. Copyright © 2004 John Wiley & Sons, Ltd.
Infiltration and solute transport under a seasonal wetland: bromide tracer experiments in Saskatoon, Canada
Authors: Parsons David F. , Hayashi Masaki , van der Kamp Garth
Published: July 2004

In the northern glaciated plain of North America, the duration of surface water in seasonal wetlands is strongly influenced by the rate of infiltration and evaporation. Infiltration also plays important roles in nutrient exchange at the sediment–water interface and groundwater recharge under wetlands. A whole‐wetland bromide tracer experiment was conducted in Saskatchewan, Canada to evaluate infiltration and solute transport processes. Bromide concentrations of surface water, groundwater, sediment pore water and plant tissues were monitored as the pond water‐level gradually dropped until there was no surface water. Hydraulic head gradients showed strong lateral flow from under the wetland to the treed riparian zone during the growing season. The bromide mass balance analysis showed that in early spring, almost 50% of water loss from the wetland was by infiltration, and it increased to about 70% in summer as plants in and around the wetland started to transpire more actively. The infiltration contributed to recharging the shallow, local groundwater under the wetland, but much of it was taken up by trees without recharging the deeper groundwater system. Emergent plants growing in the wetlands incorporated some bromide, but overall uptake of bromide by vegetation was less than 10% of the amount initially released. After one summer, most of the subsurface bromide was found within 40–80 cm of the soil surface. However, some bromide penetrated as deep as 2–3 m, presumably owing to preferential flow pathways provided by root holes or fractures. Copyright © 2004 Crown in the Right of Canada. Published by John Wiley & Sons, Ltd.
Antigenicity and immunogenicity of collagen
Authors: Lynn A.K. , Yannas I.V. , Bonfield W.
Published: July 2004

Pertinent issues of collagen antigenicity and immunogenicity are concisely reviewed as they relate to the design and application of biomedical devices. A brief discussion of the fundamental concepts of collagen immunochemistry is presented, with a subsequent review of documented clinical responses to devices containing reconstituted soluble or solubilized collagen. The significance of atelocollagen, concerns regarding collagen‐induced autoimmunity, and other relevant topics are also addressed in the context of current understanding of the human immune response to collagen. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 343–354, 2004
Simplified synthesis of 1,1′[14C]‐methylene‐di (2‐naphthol). A radiochemical and kinetic approach
Authors: Angelini Giancarlo , Ursini Ornella , Minetti Patrizia , Celona Diana , De Angelis Francesco
Published: July 2004

The synthesis of the 1,1′[14C]‐methylene‐di‐(2‐naphthol) 2, as the radiolabeled probe of a possible interaction between the β‐amyloid fibrils and the di‐naphthol mojety in the Alzheimer's disease, is reported. Very simple radiochemical procedure, starting from [14C]paraformaldehyde, produced 8.66 MBq of compound 2 at the specific radioactivity of 1.22 TBq/mol. A mechanistic and kinetic approach allowed the comprehension of the right experimental conditions. The stability of compound 2 in acetonitrile solution was investigated, denoting a significative decomposition process through the transient formation of the 1,2‐naphthyne intermediate. Copyright © 2004 John Wiley & Sons, Ltd.
A method for the synthesis of 2‐amino‐4‐fluoro‐bicyclo[3.1.0]hexane‐2,6‐dicarboxylic acid‐[3H2]
Authors: Kuo Fengjiun , Kulanthaivel Palaniappan , Rener Gregory A. , Yi Ping , Wheeler William J.
Published: July 2004

A process for double deuterium labeling of an alcohol was developed. The process was utilized in the subsequent tritium labeling of a secondary alcohol with high specific activity (24 Ci/mmol) by reduction of the corresponding ketone using sodium borotritide. The starting ketone was first brominated with pyridinium tribromide; the resulting alpha bromoketone was then reduced in THF/alcohol in the presence of Ni(OAc)2. The alcohol was then converted to 2‐amino‐4‐fluorobicyclo[3.1.0]hexane‐2,6‐dicarboxylic acid‐[3H2], an mGluR agonist. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of the carbon‐14 labeled isotopomers of (R)‐N‐methyl‐3‐[2‐methylphenoxyl]‐benzenepropanamine hydrochloride (atomoxetine hydrochloride, LY139603), and two of its metabolites
Authors: Kuo Fengjiun , Clodfelter Dean K. , Wheeler William J.
Published: July 2004

Carbon‐14 labeled StraterraTM (Atomoxetine HCl, LY139603, (‐)‐N‐methyl‐3‐(2‐methylphenoxy)‐benzenepropanamine hydrochloride), a potent inhibitor of the presynaptic norepinephrine transporter, and two of its major metabolites were synthesized. The key component, S‐(+)‐3‐chloro‐l‐phenyl‐l‐propanol‐[1‐14C] was synthesized by Stille coupling of benzoyl chloride‐[carbonyl‐14C] with vinyl tri‐n‐butylstannane, followed by HCl addition to the vinyl ketone, and asymmetric reduction of the ketone by Corey's CBS reagent. Mitsunobu reaction of this S‐(+)‐3‐chloro‐l‐phenyl‐l‐propanol‐[1‐14C] with various phenol derivatives, followed by converting the chloride to amines, gave desired products. Copyright © 2004 John Wiley & Sons, Ltd.
Request form history, clinical indication, and yield of brain magnetic resonance studies
Authors: Pack Jason R. , Yuh William T.C. , Sonnad J.R. , Maley Joan E. , Petropoulou Kalliopi , Wegner Kenneth F. , Loftus Christopher M. , Mayr Nina A. , Whitehead Donald P. , Maier Gerald J.
Published: July 2004

Purpose

To investigate whether improved clinical history allows the radiologist to better predict the pretest probability of obtaining a positive or negative result from a magnetic resonance (MR) examination.

Materials and Methods

Six neuroradiologists prospectively reviewed 100 consecutive requests for brain MR examinations and sequentially assessed 1) quality of written history, 2) degree of indication for requested study, and 3) any pertinent new information found during chart review that may have altered the degree of indication. MR yield was correlated with the degree of indication assessed before and after chart review.

Results

Most request form histories were judged as poor (63%), and chart review reduced the overall indications for MR examinations, as there was a tendency for high‐indication requests to migrate to the low‐indication category. Based on request form history alone, the yields for low‐ and high‐indication studies were 13% and 37%, respectively. Correlations between MR yield and indication after chart review improved significantly (P < 0.05) with 2% and 61% for low and high indications, respectively. Sensitivity and specificity for a positive MR yield were 71% and 62%, respectively, for the indication judged by the request history alone, and 96% and 80%, respectively, after chart review. Positive and negative prediction rates were 37% and 87%, respectively, for the indication judged by the request history alone, and 61% and 98%, respectively, for the indication judged after chart review.

Conclusion

Based on our limited data, most request form histories were inadequate, and essential information available in the chart before MR examinations was frequently missing from the request forms. When adequate information was provided, the indication for the studies as judged by the radiologists predicted the MR yield more accurately, particularly for those requests with low indication. Therefore, our study suggests that MR imaging (MRI) may be used more effectively when pertinent clinical history is available. However, our study is limited and further studies are needed to confirm our results. J. Magn. Reson. Imaging 2004;20:228–232. © 2004 Wiley‐Liss, Inc.
Development of brain infarct volume as assessed by magnetic resonance imaging (MRI): Follow‐up of diffusion‐weighted MRI lesions
Authors: Ritzl Afra , Meisel Stephanie , Wittsack Hans‐Jörg , Fink Gereon R. , Siebler Mario , Mödder Ulrich , Seitz Rüdiger J.
Published: July 2004

Purpose

To investigate the development of ischemic brain lesions, as present in the acute stroke phase, by diffusion‐weighted magnetic resonance imaging (DWI), and in the subacute and chronic phases until up to four months after stroke, in fluid‐attenuated inversion recovery (FLAIR)‐ and T2‐weighted (T2W) magnetic resonance (MR) images.

Materials and Methods

Twelve consecutive patients with their first middle cerebral artery (MCA) infarction were included. Lesion volumes were assessed on T2W images recorded with a turbo spin echo (TSE) and on images recorded with the FLAIR sequence on average on day 8 and after about four months. They were compared with acute lesion volumes in perfusion and DWI images taken within 24 hours of stroke onset.

Results

On day 8, lesion volumes in images obtained with FLAIR exceeded the acute infarct volumes in DWI. The chronic lesion volumes were almost identical in T2W and FLAIR images but significantly reduced compared with the acute DWI lesions. The lesion volumes assessed on DWI images correlated highly with the lesions in the images obtained with TSE or FLAIR, as did the lesions in the images obtained with FLAIR and TSE. The secondary lesion shrinkage was accompanied by ventricular enlargement and perilesional sulcal widening, as most clearly visible in the images obtained with FLAIR.

Conclusion

Our results show that the acute DWI lesions are highly predictive for the infarct lesion in the chronic stage after stroke despite a dynamic lesion evolution most evident in MR images obtained with FLAIR. J. Magn. Reson. Imaging 2004;20:201–207. © 2004 Wiley‐Liss, Inc.
Improved three‐dimensional free‐breathing coronary magnetic resonance angiography using gadocoletic acid (B‐22956) for intravascular contrast enhancement
Authors: Paetsch Ingo , Huber Michael E. , Bornstedt Axel , Schnackenburg Bernhard , Boesiger Peter , Stuber Matthias , Fleck Eckart , Cavagna Friedrich , Nagel Eike
Published: July 2004

Purpose

To evaluate gadocoletic acid (B‐22956), a gadolinium‐based paramagnetic blood pool agent, for contrast‐enhanced coronary magnetic resonance angiography (MRA) in a Phase I clinical trial, and to compare the findings with those obtained using a standard noncontrast T2 preparation sequence.

Materials and Methods

The left coronary system was imaged in 12 healthy volunteers before B‐22956 application and 5 (N = 11) and 45 (N = 7) minutes after application of 0.075 mmol/kg of body weight (BW) of B‐22956. Additionally, imaging of the right coronary system was performed 23 minutes after B‐22956 application (N = 6). A three‐dimensional gradient echo sequence with T2 preparation (precontrast) or inversion recovery (IR) pulse (postcontrast) with real‐time navigator correction was used. Assessment of the left and right coronary systems was performed qualitatively (a 4‐point visual score for image quality) and quantitatively in terms of signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), vessel sharpness, visible vessel length, maximal luminal diameter, and the number of visible side branches.

Results

Significant (P < 0.01) increases in SNR (+42%) and CNR (+86%) were noted five minutes after B‐22956 application, compared to precontrast T2 preparation values. A significant increase in CNR (+40%, P < 0.05) was also noted 45 minutes postcontrast. Vessels (left anterior descending artery (LAD), left coronary circumflex (LCx), and right coronary artery (RCA)) were also significantly (P < 0.05) sharper on postcontrast images. Significant increases in vessel length were noted for the LAD (P < 0.05) and LCx and RCA (both P < 0.01), while significantly more side branches were noted for the LAD and RCA (both P < 0.05) when compared to precontrast T2 preparation values.

Conclusion

The use of the intravascular contrast agent B‐22956 substantially improves both objective and subjective parameters of image quality on high‐resolution three‐dimensional coronary MRA. The increase in SNR, CNR, and vessel sharpness minimizes current limitations of coronary artery visualization with high‐resolution coronary MRA. J. Magn. Reson. Imaging 2004;20:288–293. © 2004 Wiley‐Liss, Inc.
Nodule‐in‐nodule appearance of hepatocellular carcinomas: Comparison of gadolinium‐enhanced and ferumoxides‐enhanced magnetic resonance imaging
Authors: Goshima Satoshi , Kanematsu Masayuki , Matsuo Masayuki , Kondo Hiroshi , Kato Hiroki , Yokoyama Ryujiro , Hoshi Hiroaki , Moriyama Noriyuki
Published: July 2004

Purpose

To perform comparison of gadolinium‐enhanced and ferumoxides‐enhanced magnetic resonance imaging (MRI) in the detection of nodule‐in‐nodule appearance of hepatocellular carcinomas (HCCs).

Materials and Methods

During a recent 45‐month period, we had eight patients (five men and three women; age range, 63–84 years; mean, 71 years) with HCCs with nodule‐in‐nodule appearance who underwent gadolinium‐enhanced MRI, ferumoxides‐enhanced MRI, and computed tomography during arterial portography (CTAP) and computed tomography during hepatic arteriography (CTHA), combined and separately, within an interval of two weeks. Two blinded radiologists in consensus retrospectively evaluated three sets of sequences: unenhanced T1‐ and T2‐weighted MR, gadolinium‐enhanced MR, and ferumoxides‐enhanced MR images in random order of patients and imaging sequences. The depiction degree of nodule‐in‐nodule appearance of HCC was evaluated in a semiquantitative fashion. The sensitivities of unenhanced T1‐ and T2‐weighted, gadolinium‐enhanced, and ferumoxides‐enhanced MR images were compared with McNemar's test.

Results

The eight HCCs with nodule‐in‐nodule appearance ranged in size from 16–26 mm (mean, 20.0 ± 4.0 mm), and there existed nine internal HCC foci ranging in size from 5–14 mm (mean, 7.9 ± 3.5 mm). On gadolinium‐enhanced MR images, the nodule‐in‐nodule appearance of HCC was typically seen as hypervascular foci in an iso‐ or hypovascular area: the depiction degree of nodule‐in‐nodule appearance was distinct in two lesions, equivocal in three, and absent in three. On ferumoxides‐enhanced MR images, it was typically seen as hyperintense foci in a hypointense area: the depiction degree was distinct in four, moderate in one, and absent in three. The sensitivities for detection of nodule‐in‐nodule appearance were 25%, 25%, and 63% on T1‐ and T2‐weighted, gadolinium‐enhanced, and ferumoxides‐enhanced MR images, respectively, but there was no significant difference in sensitivity.

Conclusion

Nodule‐in‐nodule appearance of HCCs can be seen on ferumoxides‐enhanced MR images, in some cases more clearly than on gadolinium‐enhanced MR images, particularly when the background nodule shows hyperintensity on precontrast T1‐weighted images. Ferumoxides‐enhanced MRI may be considered when development of malignant foci is suspected during routine examinations. J. Magn. Reson. Imaging 2004;20:250–255. © 2004 Wiley‐Liss, Inc.
Diffusion anisotropy in subcortical white matter and cortical gray matter: Changes with aging and the role of CSF‐suppression
Authors: Bhagat Yusuf A. , Beaulieu Christian
Published: July 2004

Purpose

To determine the relevance of cerebrospinal fluid (CSF)‐suppression for the measurement of diffusion anisotropy in well‐localized areas of the brain, particularly the subcortical white matter (WM) within the gyri and cortical gray matter (GM), in young and elderly subjects, and to assess the changes of water diffusivity in the brain with normal aging.

Materials and Methods

Quantitative measures of anisotropy in 26 regions, including subcortical WM (i.e., in the gyri), cortical GM, major deep WM, and deep GM regions of young (21–25 years, N = 8) and elderly (61–74 years, N = 10) normal volunteers, were assessed with CSF‐suppressed diffusion tensor imaging (DTI) relative to standard DTI.

Results

CSF‐suppressed DTI demonstrated significant increases in fractional anisotropy (FA) of 3–12% in the young and 2–14% in the elderly groups with the largest changes being in the subcortical WM of the gyri. Furthermore, FA decreased by 10–19% in the subcortical WM of the gyri of the elderly subjects relative to the young, primarily due to increases in the perpendicular diffusivity, λ3, with age.

Conclusion

CSF‐suppressed DTI yields more accurate measures of quantitative anisotropy in cortical and subcortical brain regions. Reductions of anisotropy with aging were predominantly observed in subcortical WM of the gyri. J. Magn. Reson. Imaging 2004;20:216–227. © 2004 Wiley‐Liss, Inc.
Evaluation of specific absorption rate as a dosimeter of MRI‐related implant heating
Authors: Baker Kenneth B. , Tkach Jean A. , Nyenhuis John A. , Phillips Michael , Shellock Frank G. , Gonzalez‐Martinez Jorge , Rezai Ali R.
Published: July 2004

Purpose

To compare the magnetic resonance imaging (MRI)‐related heating per unit of whole body averaged specific absorption rate (SAR) of a conductive implant exposed to two different 1.5‐Tesla/64 MHz MR systems.

Materials and Methods

Temperature changes at the electrode contacts of a deep brain stimulation lead were measured using fluoroptic thermometry. The leads were placed in a typical surgical implant configuration within a gel‐filled phantom of the human head and torso. MRI was performed using two different transmit/receive body coils on two different generation 1.5‐Tesla MR systems from the same manufacturer. Temperature changes were normalized to whole body averaged SAR values and compared between the two scanners.

Results

Depending on the landmark location, the normalized temperature change for the implant was significantly higher on one MR system compared to the other (P < 0.001).

Conclusion

The findings revealed marked differences across two MR systems in the level of radiofrequency (RF)‐induced temperature changes per unit of whole body SAR for a conductive implant. Thus, these data suggest that using SAR to guide MR safety recommendations for neurostimulation systems or other similar implants across different MR systems is unreliable and, therefore, potentially dangerous. Better, more universal, measures are required in order to ensure patient safety. J. Magn. Reson. Imaging 2004;20:315–320. © 2004 Wiley‐Liss, Inc.
MRI of helium‐3 gas in healthy lungs: Posture related variations of alveolar size
Authors: Fichele Stanislao , Woodhouse Neil , Swift Andrew J. , Said Zead , Paley Martyn N.J. , Kasuboski Larry , Mills Gary H. , van Beek Edwin J.R. , Wild Jim M.
Published: July 2004

Purpose

To probe the variation of alveolar size in healthy lung tissue as a function of posture using diffusion‐weighted helium‐3 hyperpolarized gas imaging.

Materials and Methods

Measurements of the helium‐3 apparent diffusion coefficient (ADC) were made on six healthy subjects. These were used to show the variation of alveolar size between the lowermost dependent regions of the lung compared to the uppermost regions of the lung in four postures: supine, prone, left‐lateral decubitus, and right‐lateral decubitus.

Results

The distribution of acinar size in the lungs was found to be heterogeneous, and influenced by lung orientation. In nearly all postures, the ADC was significantly higher in the non‐dependent uppermost regions of the lung compared to the dependent lowermost regions of the lung; the greatest variation was found in the left‐lateral decubitus position. The difference in ADC between uppermost and lowermost regions was on average 0.012 cm2second−1, which represents 20% of the average ADC value for the whole lung. A systematic decrease in ADC from the apex of the lung to the base was also found, which corresponds to an inherent gradient in alveolar size.

Conclusion

The posture dependent variations in ADC were attributed to compression of the parenchyma under its own weight and the mass of the heart. J. Magn. Reson. Imaging 2004;20:331–335. © 2004 Wiley‐Liss, Inc.
Correlative MR imaging and histopathology in porcine neurocysticercosis
Authors: Chawla Sanjeev , Husain Nuzhat , Kumar Sunil , Pal Lily , Tripathi Mukesh , Gupta Rakesh K.
Published: July 2004

Purpose

To examine whether all the histopathologically seen features of cysticercus cysts excised from brain of swine naturally infected with neurocysticercosis during its evolution are actually visible on magnetic resonance imaging (MRI).

Materials and Methods

Five swine naturally infected with cerebral cysticercosis were subjected to fast spin‐echo (SE) T2, SE T1, fluid attenuated inversion recovery imaging, T1‐weighted magnetization transfer (MT), and postcontrast T1‐weighted MT sequences on MRI. These animals were sacrificed after imaging and ex vivo imaging of the intact excised brain using the same imaging protocol was also performed. Grossing of these brains was done similar to the ex vivo imaging planes. Numeral density and external appearance of each cyst and scolex were evaluated on each pulse sequence. Amount of pericystic edema, if present, was also assessed. On histopathology, cellular characteristics, inflammatory response, and the extent of edema, if present, in the brain parenchyma around the cysts were graded. Cysts were categorized into viable, early, and late degenerated on histopathology. The MRI features of each cyst were correlated with their histopathologic findings.

Results

Out of 31 cysts, eight were found to be viable, 13 early degenerated, and 10 late degenerated on histopathology. T2‐weighted imaging demonstrated all the cysts while T1‐weighted imaging showed 97% of the cysts. Scolex was seen in 90.3% and 93.5% of the cysts on T2‐ and T1‐weighted images, respectively. Minimal edema (grade I) and inflammation in degenerating cysts present on histopathology was not visible on MRI. All but one of eight degenerated cysts, which showed enhancement on postcontrast MRI, had edema on imaging as well as on histopathology.

Conclusion

T2‐weighted MRI demonstrated all the cysts that were visible on histopathology. Non‐enhancement of some of the degenerated cysts along with absence of edema on MRI is likely to underestimate the staging of neurocysticercosis evolution, and these early degenerating cysts may be misdiagnosed as in viable stage. J. Magn. Reson. Imaging 2004;20:208–215. © 2004 Wiley‐Liss, Inc.
Single‐shot half‐fourier RARE sequence with ultra‐short inter‐echo spacing for lung imaging
Authors: Ohno Yoshiharu , Oshio Koichi , Uematsu Hidemasa , Nakatsu Masashi , Gefter Warren B. , Hatabu Hiroto
Published: July 2004

Purpose

To improve the image quality of pulmonary magnetic resonance (MR) imaging using an ultra‐short inter‐echo spacing half‐Fourier single shot rapid acquisition with relaxation enhancement (USHA‐RARE) sequence.

Materials and Methods

Pulmonary MR images were acquired by USHA‐RARE sequence with various inter‐echo spacings. The sequence parameters were as follows: repetition time (TR)/effective TE: infinite/39–41 msec; section thickness: 10 mm; acquisition matrix: 128 × 128; field of view: 450 × 450 mm. Inter‐echo spacing varied (2.5 msec, 3.0 msec, 3.5 msec, 4.0 msec, 4.5 msec, 5.0 msec), and the respective phase‐encoding steps were 80, 77, 75, 74, 73, and 72. Signal‐to‐noise ratios (SNRs), the signal ratios between lung and fat (lung‐to‐fat ratio: LFRs), and the signal ratios between the lung and the serratus anterior muscle (lung‐to‐muscle ratio: LMRs) of each inter‐echo spacing were calculated, and statistically evaluated.

Results

The SNRs at inter‐echo spacings of ≤ 3.0 msec were significantly higher than those ≥ 4.0 msec (P < 0.05). The LFRs and LMRs at inter‐echo spacing ≤ 3.0 msec were significantly higher than those ≥ 4.0 msec (P < 0.05).

Conclusion

USHA‐RARE sequence does improve signal intensity from the lung. J. Magn. Reson. Imaging 2004;20:336–339. © 2004 Wiley‐Liss, Inc.
Statistics‐based approach for aneurysm volume measurements
Authors: Vemuri Prashanthi , Kholmovski Eugene G. , Goodrich K. Craig , Zhang Ling , Tsuruda Jay S. , Parker Dennis L.
Published: July 2004

Purpose

To evaluate the ability of high‐resolution MRA to monitor changes in intracranial aneurysm volume, and devise a highly reliable technique for obtaining these measurements.

Materials and Methods

To obtain a baseline estimate of the repeatability of MRA scans and validate the statistics‐based technique for aneurysm volume measurement, multiple scans were obtained on individual subjects over a period of up to 1 year. These 3D MRA data sets were coregistered and then analyzed using the volumetric analysis of segmented data and the proposed statistical method.

Results

It was shown that high‐resolution MRA provides highly repeatable data sets. Both methods used for the aneurysm volume measurements showed consistent results. However, the proposed statistical method had lower error and was much less sensitive to the choice of segmentation parameter than the volumetric analysis of segmented data. A change of 1 mm in the average radius of the aneurysm was detectable with the statistics‐based technique.

Conclusions

This study demonstrates that the statistical method of aneurysm volume measurement in high‐resolution MRA allows reliable and accurate assessments of aneurysm volume changes. J. Magn. Reson. Imaging 2004;20:340–346. © 2004 Wiley‐Liss, Inc.
Relationship of apparent myocardial T2 and oxygenation: Towards quantification of myocardial oxygen extraction fraction
Authors: Zheng Jie , Wang Jinghua , Rowold Faith E. , Gropler Robert J. , Woodard Pamela K.
Published: July 2004

Purpose

To explore the relationship of myocardial T2 and oxygenation for the quantification of myocardial oxygen extraction fraction (OEF).

Materials and Methods

A proposed myocardial T2‐OEF relationship was evaluated by computer simulation and in nine normal dogs in vivo. The relationship was based on a simplified two‐compartment T2 model. In the dogs, dipyridamole was infused intravenously to increase blood flow and change in myocardial oxygen content. The accuracy of the measurement in myocardial OEF in vivo by magnetic resonance imaging (MRI) was determined by arterial and coronary sinus blood sampling.

Results

Global myocardial T2 increased 16.1% from rest to the peak of dipyridamole‐induced vasodilation (44.6 ± 2.1 msec vs. 51.4 ± 2.1 msec, P < 0.001). Corresponding OEF measured by arterial and venous (AV) sampling decreased from 0.64 ± 0.15 at rest to 0.18 ± 0.08 during the dipyridamole vasodilation, whereas OEF calculated by MRI at the peak effect of dipyridamole was 20 ± 4%. Global myocardial OEF measured dynamically by MRI showed a strong correlation with OEF measured by blood sampling (correlation coefficient (CC) = 0.83) during pharmacologic vasodilation.

Conclusion

When combined with vasodilator stress, assessment of OEF may provide a putative measure of myocardial flow reserve, allowing consecutive monitoring of myocardial dose‐responses to a variety of interventions and offering a new tool for the detection of coronary artery disease. J. Magn. Reson. Imaging 2004;20:233–241. © 2004 Wiley‐Liss, Inc.
Tumor enhancement using Mn‐metalloporphyrin in mice: Magnetic resonance imaging and histopathologic correlation
Authors: Nasu Hatsuko , Takehara Yasuo , Isogai Satoshi , Kodaira Nami , Takeda Hiroyasu , Saga Tsuneo , Nakajima Susumu , Sakata Isao , Sakahara Harumi
Published: July 2004

Purpose

To determine the signal enhancement characteristics of tumors after administration of a metalloporphyrin derivative, HOP‐9P (13, 17‐bis (1‐carboxypropionyl) carbamoylethyl‐3, 8‐bis (1‐phenylpropyloxyethyl)‐2, 7, 12, 18‐tetramethyl‐porphyrinato manganese (III)) and to determine whether HOP‐9P is tumor‐necrosis specific.

Materials and Methods

Ten C3H/He mice bearing a SCC VII tumor in the right flank were examined using T1‐weighted conventional spin echo magnetic resonance (MR) imaging before contrast injection, and five minutes, one hour, and 24 hours after intravenous administration of 0.1 mmol/kg of HOP‐9P. Following the imaging schedule, the mice were sacrificed, and sectioned in the same axial planes as the MR images. Based on an MR imaging‐histopathologic correlation, mean signal intensities were measured, and signal‐to‐noise ratios (SNR) were calculated for both pure viable component and admixture of necrotic and viable component of the tumor.

Results

Mean SNR of the pure viable component peaked at one hour (35.0 ± 3.8) and maintained that level until 24 hours (34.6 ± 3.6). Mean SNR of the admixture of necrotic and viable component peaked at 24 hours (44.3 ± 12.1).

Conclusion

Although different enhancement patterns were seen between the pure viable component and the admixture of necrotic and viable component, HOP‐9P enhanced both of the two components. J. Magn. Reson. Imaging 2004;20:294–299. © 2004 Wiley‐Liss, Inc.
Contrast‐enhanced magnetic resonance cholangiography using mangafodipir compared with standard T2W MRC sequences: A pictorial essay
Authors: Sheppard Declan , Allan Lynsay , Martin Pat , McLeay Trudy , Milne Wendy , Houston J. Graeme
Published: July 2004

Mangafodipir, a manganese‐containing hepatobiliary contrast agent, is excreted in bile. We review the principles and practice of a contrast‐enhanced MRC technique using mangafodipir and compare it with standard T2‐weighted magnetic resonance cholangiography (MRC) sequences. Potential applications include the evaluation of leaks and strictures; the assessment of drainage in normal, surgically by‐passed, stented and obstructed biliary systems; the diagnosis of cholecystitis; and the evaluation of normal and variant biliary anatomy. J. Magn. Reson. Imaging 2004;20:256–263. © 2004 Wiley‐Liss, Inc.
Image construction methods for phased array magnetic resonance imaging
Authors: Erdogmus Deniz , Yan Rui , Larsson Erik G. , Principe Jose C. , Fitzsimmons Jeffrey R.
Published: July 2004

Purpose

To study image construction in phased array magnetic resonance imaging (MRI) systems from a statistical signal processing point of view.

Materials and Methods

Three new approaches for image combination with multiple coils are proposed: 1) one based on the singular value decomposition of the measurement matrix, which is asymptotically optimal in the signal‐to‐noise ratio sense; 2) one based on a maximum‐likelihood formulation, incorporating a priori information on the coil sensitivities in a Bayesian manner; and 3) one based on a least‐squares formulation, which incorporates a smoothness constraint on the coil sensitivities.

Results

Numerical examples using synthetic and real data are presented to illustrate the performance of these new approaches. Results on the synthetic data show improvement in signal‐to‐error ratio, while results on the real data (a 4.7 T four‐coil image of a cat spinal cord) show that the proposed methods can improve the SNR in the final image by up to 3 dB in the regions of interest compared to conventional sum‐of‐squares processing.

Conclusion

It is demonstrated that phased array MRI reconstruction performance can be improved by the use of more elaborate statistical signal processing algorithms. J. Magn. Reson. Imaging 2004;20:306–314. © 2004 Wiley‐Liss, Inc.
A comparison of images generated from diffusion‐weighted and diffusion‐tensor imaging data in hyper‐acute stroke
Authors: Harris Ashley D. , Pereira Raoul S. , Mitchell J. Ross , Hill Michael D. , Sevick Robert J. , Frayne Richard
Published: July 2004

Purpose

To compare isotropic (combined diffusion‐weighted image [CMB], apparent diffusion coefficient [ADC], TRACE, exponential ADC [eADC], and isotropically‐weighted diffusion image [isoDWI]) and anisotropic (relative anisotropy [RA], fractional anisotropy [FA], and volume ratio [VR]) diffusion images collected with fast magnetic resonance (MR) diffusion‐weighted (DWI) and diffusion‐tensor (DTI) acquisition strategies (each less than one minute) in hyper‐acute stroke.

Materials and Methods

Twenty‐one patients suffering from ischemic stroke—imaged within six hours of symptom onset using both DWI and DTI—were analyzed. Regions of interest were placed in the ischemic lesion and in normal contralateral tissue and the percent difference in image intensity was calculated for all nine generated images.

Results

The average absolute percent changes for the isotropic strategies were all > 38%, with isoDWI found to have a difference of 50.7% ± 7.9% (mean ± standard error, P < 0.001). The ADC maps had the most significant difference (–42.4% ± 2.0%, P < 0.001, coefficient of variation = 0.22). No anisotropic images had significant differences.

Conclusion

Anisotropic maps do not consistently show changes in the first six hours of ischemic stroke; therefore, isotropic maps, such as those obtained using DWI, are more appropriate for detecting hyper‐acute stroke. Anisotropic images, however, may be useful to differentiate hyper‐acute stroke from acute and sub‐acute stroke. J. Magn. Reson. Imaging 2004;20:193–200. © 2004 Wiley‐Liss, Inc.
6‐hydroxydopamine induces dopaminergic cell degeneration via a caspase‐9‐mediated apoptotic pathway that is attenuated by caspase‐9dn expression
Authors: Liang Qinghua , Liou Anthony K.F. , Ding Yunmin , Cao Guodong , Xiao Xiao , Perez Ruth G. , Chen Jun
Published: July 2004

This study showed that primary dopaminergic neurons or the dopaminergic cell line MN9D, when exposed to 15 min of the parkinsonian toxin 6‐hydroxydopamine (6‐OHDA) in the range of 30–100 μM, underwent delayed degeneration and exhibited hallmarks of apoptosis. These results, along with the absence of any increase in lactate dehydrogenase (LDH) release from the degenerated cells, imply that apoptosis was the dominant mode of cell death. Moreover, a distinct elevation in the measured cellular activities of caspase‐9 and ‐3 but not of caspase‐8 points to the caspase‐9/caspase‐3 cascade as the predominant apoptotic pathway in the degeneration of dopaminergic neurons and MN9D cells. In addition, the presence of caspase‐9 or ‐3 peptide inhibitors but not of caspase‐8 inhibitor attenuated cell death significantly, supporting the notion that only the intrinsic apoptotic pathway is utilized to achieve cell death. Finally, overexpression of a mutant caspase‐9 with dominant negative phenotype (caspase‐9dn) in MN9D cells and primary dopaminergic neurons via the adenovirus and adenoassociated virus gene delivery system, respectively, conferred marked increases in tolerance to the toxicity of 6‐OHDA. These results point to the intrinsic caspase‐9/caspase‐3 cascade as the predominant signaling pathway underlying dopaminergic cell death induced by 6‐OHDA and suggest that gene delivery of caspase‐9dn can attenuate this pathway and its degenerative consequences. © 2004 Wiley‐Liss, Inc.
Lectin‐binding epitopes at the surface of Escherichia coli K‐12: examination by electron microscopy, with special reference to the presence of a colanic acid‐like polymer
Authors: Stoitsova Stoyanka , Ivanova Radka , Dimova Ivanka
Published: July 2004

The presence and distribution of lectin‐binding epitopes at the surface of Escherichia coli K‐12, strain W1655, was studied by electron microscopy after lectin‐gold labeling and negative staining. A comparison was made between the lectin‐binding capacity of cells cultivated at 20 °C and 37 °C (in broth or on agar). A variety of pre‐treatment protocols were applied prior to labeling. The gold‐conjugated lectins used were wheat germ agglutinin (WGA), soybean agglutinin (SBA) and Ulex europaeus lectin (UEA‐I). For all culture conditions, the bacteria had moderate exposure of WGA‐binding sites, and this was not changed after pre‐treatment. Cells cultivated at 37 °C had exposed SBA‐ and UEA‐I‐binding epitopes apparently associated with the cell surface. These significantly increased in number after boiling the cells for 10 min. With bacteria cultivated at 20 °C these two lectins recognized sites situated on exopolysaccharide filaments. Affino dot‐blot experiments with isolated polysaccharides of the strain identified the K‐12 lipooligosaccharide as the source of WGA‐binding epitopes, and the exopolysaccharide, colanic acid (CA) as the source of SBA‐ and UEA‐I‐binding sites. The interaction with these two lectins of bacteria cultivated at 37 °C could be due to altered translocation of CA from the cytoplasm to the environment. This suggestion was supported by the demonstration by electron microscopy of SBA and UEA‐I binding at the surface of hot phenol‐water extracted cell walls. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lignoren, a new sesquiterpenoid metabolite from Trichoderma lignorum HKI 0257
Authors: Berg Albrecht , Kemami Wangun Hilaire V. , Nkengfack Augusin E. , Schlegel Brigitte
Published: July 2004

The new compound lignoren (1) was isolated from Trichoderma lignorum HKI 0257 by chromatographic methods. This metabolite has a santalane‐like structure, which was elucidated by mass spectrometric and NMR spectroscopic investigations. Lignoren (1) shows a moderate narrow‐spectrum of antibacterial and antifungal activity. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)