bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction
Authors: Lin Jyh‐Miin , Tsai Shang‐Yueh , Liu Hua‐Shan , Chung Hsiao‐Wen , Mulkern Robert V. , Cheng Chou‐Min , Yeh Tzu‐Chen , Chen Nan‐Kuei 
Published: September 2009

AbstractIntrascan subject movement in clinical MR spectroscopic examinations may result in inconsistent water suppression that distorts the metabolite signals, frame‐to‐frame variations in spectral phase and frequency, and consequent reductions in the signal‐to‐noise ratio due to destructive averaging. Frame‐to‐frame phase/frequency corrections, although reported to be successful in achieving constructive averaging, rely on consistent water suppression, which may be difficult in the presence of intrascan motion. In this study, motion correction using non–water‐suppressed data acquisition is proposed to overcome the above difficulties. The time‐domain matrix‐pencil postprocessing method was used to extract water signals from the non–water‐suppressed spectroscopic data, followed by phase and frequency corrections of the metabolite signals based on information obtained from the water signals. From in vivo experiments on seven healthy subjects at 3.0 T, quantification of metabolites using the unsuppressed water signal as a reference showed improved correlation with water‐suppressed data acquired in the absence of motion (R2 = 0.9669; slope = 0.94). The metabolite concentrations derived using the proposed approach were in good agreement with literature values. Computer simulations under various degrees of frequency and phase variations further demonstrated robust performance of the time‐domain postprocessing approach. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Methods for metabolic evaluation of prostate cancer cells using proton and 13C HR‐MAS spectroscopy and [3‐13C] pyruvate as a metabolic substrate
Authors: Levin Yakir S. , Albers Mark J. , Butler Thomas N. , Spielman Daniel , Peehl Donna M. , Kurhanewicz John 
Published: September 2009

AbstractProstate cancer has been shown to undergo unique metabolic changes associated with neoplastic transformation, with associated changes in citrate, alanine, and lactate concentrations. 13C high resolution‐magic angle spinning (HR‐MAS) spectroscopy provides an opportunity to simultaneously investigate the metabolic pathways implicated in these changes by using 13C‐labeled substrates as metabolic probes. In this work, a method to reproducibly interrogate metabolism in prostate cancer cells in primary culture was developed using HR‐MAS spectroscopy. Optimization of cell culture protocols, labeling parameters, harvesting, storage, and transfer was performed. Using [3‐13C] pyruvate as a metabolic probe, 1H and 13C HR‐MAS spectroscopy was used to quantify the net amount and fractional enrichment of several labeled metabolites that evolved in multiple cell samples from each of five different prostate cancers. Average enrichment across all cancers was 32.4 ± 5.4% for [3‐13C] alanine, 24.5 ± 5.4% for [4‐13C] glutamate, 9.1 ± 2.5% for [3‐13C] glutamate, 25.2 ± 5.7% for [3‐13C] aspartate, and 4.2 ± 1.0% for [3‐13C] lactate. Cell samples from the same parent population demonstrated reproducible fractional enrichments of alanine, glutamate, and aspartate to within 12%, 10%, and 10%, respectively. Furthermore, the cells produced a significant amount of [4‐13C] glutamate, which supports the bioenergetic theory for prostate cancer. These methods will allow further characterization of metabolic properties of prostate cancer cells in the future. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Inverse reconstruction method for segmented multishot diffusion‐weighted MRI with multiple coils
Authors: Uecker Martin , Karaus Alexander , Frahm Jens 
Published: September 2009

AbstractEach k‐space segment in multishot diffusion‐weighted MRI is affected by a different spatially varying phase which is caused by unavoidable motions and amplified by the diffusion‐encoding gradients. A proper image reconstruction therefore requires phase maps for each segment. Such maps are commonly derived from two‐dimensional navigators at relatively low resolution but do not offer robust solutions. For example, phase variations in diffusion‐weighted MRI of the brain are often characterized by high spatial frequencies. To overcome this problem, an inverse reconstruction method for segmented multishot diffusion‐weighted MRI is described that takes advantage of the full k‐space data acquired from multiple receiver coils. First, the individual coil sensitivities are determined from the non–diffusion‐weighted acquisitions by regularized nonlinear inversion. These coil sensitivities are then used to estimate accurate motion‐associated phase maps for each segment by iterative linear inversion. Finally, the coil sensitivities and phase maps serve to reconstruct artifact‐free images of the object by iterative linear inversion, taking advantage of the data of all segments. The efficiency of the new method is demonstrated for segmented diffusion‐weighted stimulated echo acquisition mode MRI of the human brain. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Enhanced positive‐contrast visualization of paramagnetic contrast agents using phase images
Authors: Mills Parker H. , Ahrens Eric T. 
Published: September 2009

AbstractIron oxide–based MRI contrast agents are increasingly being used to noninvasively track cells, target molecular epitopes, and monitor gene expression in vivo. Detecting regions of contrast agent accumulation can be challenging if resulting contrast is subtle relative to endogenous tissue hypointensities. A postprocessing method is presented that yields enhanced positive‐contrast images from the phase map associated with T2*‐weighted MRI data. As examples, the method was applied to an agarose gel phantom doped with superparamagnetic iron‐oxide nanoparticles and in vivo and ex vivo mouse brains inoculated with recombinant viruses delivering transgenes that induce overexpression of paramagnetic ferritin. Overall, this approach generates images that exhibit a 1‐ to 8‐fold improvement in contrast‐to‐noise ratio in regions where paramagnetic agents are present compared to conventional magnitude images. This approach can be used in conjunction with conventional T2* pulse sequences, requires no prescans or increased scan time, and can be applied retrospectively to previously acquired data. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Partial fourier reconstruction through data fitting and convolution in k‐space
Authors: Huang Feng , Lin Wei , Li Yu 
Published: September 2009

AbstractA partial Fourier acquisition scheme has been widely adopted for fast imaging. There are two problems associated with the existing techniques. First, the majority of the existing techniques demodulate the phase information and cannot provide improved phase information over zero‐padding. Second, serious artifacts can be observed in reconstruction when the phase changes rapidly because the low‐resolution phase estimate in the image space is prone to error. To tackle these two problems, a novel and robust method is introduced for partial Fourier reconstruction, using k‐space convolution. In this method, the phase information is implicitly estimated in k‐space through data fitting; the approximated phase information is applied to recover the unacquired k‐space data through Hermitian operation and convolution in k‐space. In both spin echo and gradient echo imaging experiments, the proposed method consistently produced images with the lowest error level when compared to Cuppen's algorithm, projection onto convex sets–based iterative algorithm, and Homodyne algorithm. Significant improvements are observed in images with rapid phase change. Besides the improvement on magnitude, the phase map of the images reconstructed by the proposed method also has significantly lower error level than conventional methods. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Motion correction of single‐voxel spectroscopy by independent component analysis applied to spectra from nonanesthetized pediatric subjects
Authors: de Nijs Robin , Miranda Maria J. , Hansen Lars Kai , Hanson Lars G. 
Published: September 2009

AbstractFor single‐voxel spectroscopy, the acquisition of the spectrum is typically repeatedntimes and then combined with a factor$\sqrt{n}$in order to improve the signal‐to‐noise ratio. In practice, the acquisitions are not only affected by random noise but also by physiologic motion and subject movements. Since the influence of physiologic motion such as cardiac and respiratory motion on the data is limited, it can be compensated for without data loss. Individual acquisitions hampered by subject movements, on the other hand, need to be rejected if no correction or compensation is possible. If the individual acquisitions are stored, it is possible to identify and reject the motion‐disturbed acquisitions before averaging. Several automatic algorithms were investigated using a dataset of spectra from nonanesthetized infants with a gestational age of 40 weeks. Median filtering removed most subject movement artifacts, but at the cost of increased sensitivity to random noise. Neither independent component analysis nor outlier identification with multiple comparisons has this problem. These two algorithms are novel in this context. The peak height values of the metabolites were increased compared to the mean of all acquisitions for both methods, although primarily for the ICA method. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Optimized MRI contrast for on‐resonance proton exchange processes of PARACEST agents in biological systems
Authors: Li Alex X. , Suchy Mojmir , Jones Craig K. , Hudson Robert H. E. , Menon Ravi S. , Bartha Robert 
Published: September 2009

AbstractImage contrast associated with paramagnetic chemical exchange saturation transfer agents can be generated by off‐resonance irradiation of agent‐bound water or amide protons or on‐resonance irradiation of bulk water. Previously, a four‐pool model was developed to describe an in vivo system. The model incorporated the magnetization transfer effect from macromolecules when using off‐resonance irradiation. In the current study, this four‐pool model is modified to describe the in vivo system when using on‐resonance irradiation. The influences of pulse power, pulse duration, the chemical shift of bound water, the proton exchange rate between bulk water and bound water, and agent concentration on the on‐resonance paramagnetic agent chemical exchange effects were simulated using a WALTZ‐16 pulse train in the absence and presence of the macromolecule pool. The results demonstrated that while contrast increases with pulse duration in aqueous solution, there is an optimal pulse duration that maximizes on‐resonance paramagnetic agent chemical exchange effects contrast in vivo. This predication was verified by experimental spectroscopic and imaging results from aqueous solution, bovine serum albumin phantoms, and a tissue phantom containing thulium‐DOTAM (1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetamide)‐glycine‐lysine. This model can be used to optimize sequence parameters to maximize in vivo on‐resonance paramagnetic agent chemical exchange effects contrast. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Proton MRS detects metabolic changes in hormone sensitive and resistant human prostate cancer models CWR22 and CWR22r
Authors: Le H. Carl , Lupu Mihaela , Kotedia Khushali , Rosen Neal , Solit David , Koutcher Jason A. 
Published: September 2009

Abstract17‐Allylamino, 17‐demethoxygeldanamycin (17‐AAG), an effective inhibitor of the heat shock protein hsp90, preferentially inhibiting tumor hsp90 compared to hsp90 from normal cells, has shown promising results against several cancers, including hormone‐resistant prostate cancer. Levels of several oncogenic proteins critical to tumor growth and progression, such as androgen receptor and HER2/neu, were reduced 4 h post 17‐allylamino, 17‐demethoxygeldanamycin treatment. Posttreatment metabolic changes have also been observed in several tumor cell lines. In this study, total choline distributions in hormone sensitive CWR22 and hormone resistant CWR22r prostate cancer xenograft tumors in mice were measured before and at 4 h and 48 h after a single‐bolus 17‐allylamino, 17‐demethoxygeldanamycin treatment at 100 mg/kg, using proton MR spectroscopy. Our results show that tumor total choline levels declined 4 h after the treatment for CWR22 (P = 0.001) and 48 h post treatment for CWR22r (P = 0.003). Metabolic changes, in particular of total choline intensity detected by proton magnetic resonance spectroscopic imaging (MRSI), are consistent with the observed immunohistochemistry changes, tumor growth inhibition for CWR22r (P = 0.01 at 14 days post treatment), and a constant prostate specific antigen level versus increasing prostate specific antigen for control CWR22 (P = 0.01). Metabolic changes in total choline by proton MRSI can be used as an early biomarker of response for advanced‐stage prostate cancer in targeted therapy such as 17‐allylamino, 17‐demethoxygeldanamycin. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
4D retrospective black blood trueFISP imaging of mouse heart
Authors: Miraux Sylvain , Calmettes Guillaume , Massot Philippe , Lefrançois William , Parzy Elodie , Muller Bernard , Arsac Laurent M. , Deschodt‐Arsac Véronique , Franconi Jean‐Michel , Diolez Philippe , Thiaudière Eric 
Published: September 2009

AbstractThe purpose of this study was to demonstrate the feasibility of steady‐state True fast imaging with steady precession (TrueFISP) four‐dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three‐dimensional cine‐imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG‐triggering. The k‐space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time = 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three‐dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum‐of‐square reconstruction method. Black‐blood three‐dimensional images at around 200 μm resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 ± 2 vs 15.1 ± 2; P < 0.05, 24.9 ± 2 vs 20.4 ± 2; P < 0.05, respectively). In conclusion, four‐dimensional black‐blood TrueFISP imaging in living mice is a method of choice to investigate cardiac abnormalities in mouse models. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Split gradient coils for simultaneous PET‐MRI
Authors: Poole Michael , Bowtell Richard , Green Dan , Pittard Simon , Lucas Alun , Hawkes Rob , Carpenter Adrian 
Published: September 2009

AbstractCombining positron emission tomography (PET) and MRI necessarily involves an engineering tradeoff as the equipment needed for the two modalities vies for the space closest to the region where the signals originate. In one recently described scanner configuration for simultaneous positron emission tomography–MRI, the positron emission tomography detection scintillating crystals reside in an 80‐mm gap between the 2 halves of a 1‐T split‐magnet cryostat. A novel set of gradient and shim coils has been specially designed for this split MRI scanner to include an 110‐mm gap from which wires are excluded so as not to interfere with positron detection. An inverse boundary element method was necessarily employed to design the three orthogonal, shielded gradient coils and shielded Z0 shim coil. The coils have been constructed and tested in the hybrid positron emission tomography‐MRI system and successfully used in simultaneous positron emission tomography‐MRI experiments. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Inactive Wnt/β‐catenin pathway in conventional high‐grade osteosarcoma
Authors: Cai Yongping , Mohseny Alexander B , Karperien Marcel , Hogendoorn Pancras CW , Zhou Gengyin , Cleton‐Jansen Anne‐Marie 
Published: September 2009

AbstractOsteosarcoma is the most common malignant bone tumour, with a peak incidence in children and young adolescents, suggesting a role of rapid bone growth in its pathogenesis. The Wnt/β‐catenin pathway plays a crucial role in skeletal development and is indispensable for osteoblasts' lineage determination. Previous studies suggesting an oncogenic role for the Wnt/β‐catenin pathway in osteosarcoma were based on cytoplasmic staining of β‐catenin or the detection of one component of this pathway. However, those approaches are inappropriate to address whether the Wnt/β‐catenin pathway is functionally active. Therefore, in this study, we examined nuclear β‐catenin expression in 52 human osteosarcoma biopsies, 15 osteoblastomas (benign bone tumours), and four human osteosarcoma cell lines by immunohistochemistry. Furthermore, we modulated Wnt/β‐catenin pathway activity using a GIN (GSK3β inhibitor) and evaluated its effect on cell growth and osteogenic differentiation. Absence of nuclear β‐catenin staining was found in 90% of the biopsies and all osteosarcoma cell lines, whereas strong nuclear β‐catenin staining was observed in all osteoblastomas. Wnt‐luciferase activity was comparable to the negative control in all osteosarcoma cell lines. GIN stimulated the Wnt/β‐catenin pathway, as shown by translocation of β‐catenin into the nucleus and increased Wnt‐luciferase activity as well as mRNA expression of AXIN2, a specific downstream target gene. Stimulation of the Wnt/β‐catenin pathway by GIN significantly reduced cell proliferation in the cell lines MG‐63 and U‐2‐OS and enhanced differentiation in the cell lines HOS and SJSA‐1, as shown by an increase in alkaline phosphatase (ALP) activity and mineralization. In contrast with the oncogenic role of the Wnt/β‐catenin pathway in osteosarcoma as previous studies suggested, here we demonstrate that this pathway is inactivated in osteosarcoma. Moreover, activation of the Wnt/β‐catenin pathway inhibits cell proliferation or promotes osteogenic differentiation in osteosarcoma cell lines. Our data suggest that loss of Wnt/β‐catenin pathway activity, which is required for osteoblast differentiation, may contribute to osteosarcoma development. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Polymorphic and miscibility behavior in crystalline/crystalline blends of poly(pentamethylene terephthalate) with poly(heptamethylene terephthalate)
Authors: Yen Kai Cheng , Woo Eamor M 
Published: September 2009

AbstractBACKGROUND: The phase behavior of blends of semicrystalline aryl polyesters with long methylene segments ((CH2)nwith n = 5 or 7) in the repeat units has not been much studied. Thus, crystalline/crystalline blends comprising monomorphic poly(pentamethylene terephthalate) (PPT) and polymorphic poly(heptamethylene terephthalate) (PHepT) were prepared and the crystal growth kinetics, polymorphism behavior and miscibility in this blend system were probed using polarized‐light optical microscopy, differential scanning calorimetry and wide‐angle X‐ray diffraction.RESULTS: The PPT/PHepT blends of all compositions were first proven to be miscible in the melt state or quenched amorphous phase, whose interaction strength was determined (χ12 = − 0.35), showing favorable interactions and phase homogeneity. Although the spherulites of neat PPT and PHepT could exhibit ring bands at different crystallization temperature (Tc) ranges (100–110 and 50–65 °C, respectively), the spherulites of PPT/PHepT (50/50) blend became ringless in the range 50–110 °C. Growth analysis and polymorphic behavior in the crystalline phases of the blends provided extra evidence for the miscibility between these two crystalline polymers. Spherulitic growth rates of PPT in the PPT/PHepT blends were significantly reduced in comparison with those of neat PPT. In addition, miscible blending of a small fraction of monomorphic PPT (20 wt%) with polymorphic PHepT altered the crystal stability and led to the originally polymorphic PHepT exhibiting only the β‐crystal form when melt‐crystallized at all values of Tc.CONCLUSION: The highly intimate mixing in polymer chains of crystalline PPT and PHepT causes significant disruption in ring‐band patterns and reduction in crystallization rates of PPT as well as alteration in the polymorphic behavior of PHepT. Copyright © 2009 Society of Chemical Industry
Initiating events and independent protection layers
Authors: Murphy John F. , Chastain Wayne , Bridges William (Bill) 
Published: September 2009

AbstractLayer of protection analysis (LOPA) is a semiquantitative tool for analyzing and assessing process risk. The tool has grown greatly in popularity and usefulness since the publication of the first CCPS/AIChE guidebook on the subject, Layer of Protection Analysis, Simplified Process Risk Assessment (LOPA). This article is a summary of a new CCPS guideline book that includes the following:
Initiating events (IEs).
Independent protection layers (IPLs).
Criteria for identifying the value of each prospective IE and prospective IPL.
Example IE and IPL data.
This book is a necessary reference for those applying the LOPA methodology. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009
Re‐thinking environmental flows: from allocations and reserves to sustainability boundaries
Authors: Richter Brian D. 
Published: September 2009

AbstractAttempts to implement environmental flows have encountered many obstacles. Many water allocation systems include a system of prioritization among water uses that generally does not favor environmental flow protection, or do not allow for protection of high flow events for ecological purposes. It has proven very difficult to implement complicated environmental flow prescriptions that attempt to mimic natural flow variability within water allocation systems. Additionally, many water allocation systems do not adequately address interconnections between surface water and groundwater, or releases from dams. It is time to re‐think our approaches to protecting environmental flows. As with water quality protection, environmental flows should be viewed not as an “allocation” of water, but rather as a desirable outcome of integrated management of water and land resources for long‐term sustainability. In this sense, environmental flows should be managed in a manner similar to water quality protection, in which the influences of diverse land and water use activities are regulated to ensure that the ecological and social values of water are optimized. Both water quality and environmental flow management protect a vast array of important social benefits that are sustained by managing for healthy freshwater ecosystems. In this paper I offer a definition of sustainable water management that explicitly recognizes the fact that society derives substantial benefits both from out‐of‐stream extractions of water as well as by maintaining adequate flows of water within freshwater ecosystems. To help facilitate sustainable water management, a ”Sustainability Boundary Approach“ is described for use in setting quantitative water management goals. When the cumulative hydrologic impacts of water and land uses are managed within these sustainability boundaries, the full array of values associated with water can be more fully realized. Copyright © 2009 John Wiley & Sons, Ltd.