bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apigenin suppresses insulin‐like growth factor I receptor signaling in human prostate cancer: An in vitro and in vivo study
Authors: Shukla Sanjeev , Gupta Sanjay 
Published: August 2008

AbstractDeregulation of insulin‐like growth factor (IGF)‐I/IGF‐IR signaling has been implicated in the development and progression of prostate cancer. Agents that can suppress the mitogenic activity of the IGF/IGF‐IR growth axis may be of preventive or therapeutic value. We have previously demonstrated that apigenin, a plant flavone, modulates IGF signaling through upregulation of IGFBP‐3. In this study, we investigated the mechanism(s) of apigenin action on the IGF/IGF‐IR signaling pathway. Exposure of human prostate cancer DU145 cells to apigenin markedly reduced IGF‐I‐stimulated cell proliferation and induced apoptosis. Apigenin inhibited IGF‐I‐induced activation of IGF‐IR and Akt in DU145 cells. Similar growth inhibitory and apoptotic responses were observed in PC‐3 cells, which constitutively overexpress this pathway. This effect of apigenin appears to be due partially to reduced autophosphorylation of IGF‐IR. Inhibition of p‐Akt by apigenin resulted in decreased phosphorylation of GSK‐3β along with decreased expression of cyclin D1 and increased expression of p27/kip1. In vivo administration of apigenin to PC‐3 tumor xenografts inhibited tumor growth, resulted in IGF‐IR inactivation and dephosphorylation of Akt and its downstream signaling. These results suggest that inhibition of cell proliferation and induction of apoptosis by apigenin are mediated, at least in part, by its ability to inhibit IGF/IGF‐IR signaling and the PI3K/Akt pathway. © 2008 Wiley‐Liss, Inc.
High spectral and spatial resolution MRI of age‐related changes in murine prostate
Authors: Foxley Sean , Fan Xiaobing , Jansen Sanaz A. , Zamora Marta , Markiewicz Erica , Al‐Ahmadie Hikmat , Karczmar Gregory S. 
Published: August 2008

AbstractThe purpose of this work was to evaluate high‐resolution echo‐planar spectroscopic MRI of normal and precancerous prostatic changes in a transgenic mouse line. Simian virus large T‐antigen transgenic male mice (N = 7, age = 34 ± 3.7 weeks) with prostatic hyperplasia and intraepithelial neoplasia (PIN) were studied. High spectral and spatial resolution (HiSS) MRI of the water proton signal was compared to the free induction decay (FID) integral image and conventional gradient‐echo and spin‐echo imaging. Water peak‐height images of the prostate produced from HiSS datasets showed improved contrast‐to‐noise ratio (CNR) (P < 0.03), and greater morphological detail (P < 0.004) based on texture analysis. Despite the high spectral resolution of the HiSS datasets, signal‐to‐noise ratio (SNR) compared favorably with that of the FID integral and conventional images. Lobular features in HiSS images of older mice were consistent with hyperplasia seen on histology. A partially deuterated water‐filled catheter was inserted in the mouse rectum for susceptibility matching between the colon interior and exterior to minimize image artifacts. These preliminary results suggest that HiSS MRI provides detailed morphology of the murine prostate and can detect early changes associated with the development of cancer. HiSS MRI of patients may have similar advantages. Magn Reson Med 60:575–581, 2008. © 2008 Wiley‐Liss, Inc.
Tracking the effects of crusher gradients on gradient‐echo BOLD signal in space and time during rat sensory stimulation
Authors: Goelman Gadi , Pelled Galit , Dodd Steve , Koretsky Alan 
Published: August 2008

AbstractA unique method to map the effect of crusher gradients in space and time on the gradient echo blood oxygen level dependent (BOLD) signal is introduced. Using the Radial Correlation Contrast (RCC) analysis method, amplitude‐RCC maps at different time segments and different gradient strengths were obtained. The ratio of amplitude‐RCC cluster volumes, with and without crusher gradients, showed a temporal dependency with stronger volume reduction for stimulation‐onset versus stimulation‐decline. Aside from signal‐to‐noise ratio reduction in diffusion weighted images, the average temporal patterns were equal. Comparison of the data with and without crushers showed a stronger reduction in local coherence for stimulation‐onset times. We hypothesize that the stimulation decline was weighted by extravascular effects originating in expanded veins due to their larger volume and long range susceptibility which couples neighboring voxels. The ratio of amplitude‐RCC with and without crushers calculated for each voxel at each time segment yielded a spatial–temporal mapping of the crusher effect. These maps suggest that early stimulation‐onset (∼9 s) is weighted by flow; later a dynamic steady‐state between intra‐ and extravascular effects is obtained. Stimulation‐decline was dominated by extravascular effects, and at late stimulation decline as well as at early stimulation onset, clusters were small and localized to expected site of neuronal activity. Magn Reson Med 60:548–554, 2008. © 2008 Wiley‐Liss, Inc.
Balanced left ventricular myocardial SSFP‐tagging at 1.5T and 3T
Authors: Markl M. , Scherer S. , Frydrychowicz A. , Burger D. , Geibel A. , Hennig J. 
Published: August 2008

AbstractThe purpose of the study was to evaluate the performance of steady‐state free precession (SSFP)‐tagging at 1.5T and 3T and to define the ideal settings with respect to optimized tag contrast throughout the cardiac cycle for both field strengths. To identify optimal imaging parameters data acquisition was repeated for different flip angles. Left ventricular tag‐tissue contrast, tag fading times, tag persistence, and myocardial signal‐to‐noise ratio (SNR) were quantified in basal, mid‐ventricular, and apical slice locations. To assess the effect of field strength on image quality and artifact level, additional semiquantitative image grading was performed by two experienced readers. SSFP‐tagging at 3T proved superior to 1.5T and provided significantly enhanced tag persistence and myocardial SNR while maintaining overall image quality and artifact level. The definition of a tag quality index demonstrated optimal SSFP‐tagging performance for a flip angle of 20°. Diastolic tag visibility was improved at 3T and resulted in enhanced average tag persistence of 789 ± 128 ms compared to 523 ± 40 ms at 1.5T. For SSFP‐tagging at 3T the combination of T1 lengthening and superior myocardial SNR is highly promising and has the potential to improve the depiction of tagged myocardial function throughout the entire cardiac cycle. Magn Reson Med 60:631–639, 2008. © 2008 Wiley‐Liss, Inc.
3D high temporal and spatial resolution contrast‐enhanced MR angiography of the whole brain
Authors: Haider Clifton R. , Hu Houchun Harry , Campeau Norbert G. , Huston John , Riederer Stephen J. 
Published: August 2008

AbstractSensitivity encoding (SENSE) and partial Fourier techniques have been shown to reduce the acquisition time and provide high diagnostic quality images. However, for time‐resolved acquisitions there is a need for both high temporal and spatial resolution. View sharing can be used to provide an increased frame rate but at the cost of acquiring spatial frequencies over a duration longer than a frame time. In this work we hypothesize that a CArtesian Projection Reconstruction‐like (CAPR) technique in combination with 2D SENSE, partial Fourier, and view sharing can provide 1–2 mm isotropic resolution with sufficient temporal resolution to distinguish intracranial arterial and venous phases of contrast passage in whole‐brain angiography. In doing so, the parameter of “temporal footprint” is introduced as a descriptor for characterizing and comparing time‐resolved view‐shared pulse sequences. It is further hypothesized that short temporal footprint sequences have higher temporal fidelity than similar sequences with longer temporal footprints. The tradeoff of temporal footprint and temporal acceleration is presented and characterized in numerical simulations. Results from 11 whole‐brain contrast‐enhanced MR angiography studies with the new method with SENSE acceleration factors R = 4 and 5.3 are shown to provide images of comparable or higher diagnostic quality than the unaccelerated reference. Magn Reson Med 60:749–760, 2008. © 2008 Wiley‐Liss, Inc.
Novel MRI method to detect altered left ventricular ejection and filling patterns in rodent models of disease
Authors: Stuckey Daniel J. , Carr Carolyn A. , Tyler Damian J. , Aasum Ellen , Clarke Kieran 
Published: August 2008

AbstractThe aim of this study was to determine whether high‐temporal‐resolution (HTR) cardiac cine‐MRI could be used to identify subtle alterations in contractility and diastolic function in rodent models of disease. Following standard 45‐min in vivo MRI measurements of left ventricular (LV) volumes, a single mid‐ventricular slice was selected for 3‐min HTR imaging. Cavity volume was measured every 2.4 ms, yielding approximately 60 images through the cardiac cycle. From these images, peak ejection and filling rates were calculated and two separate filling phases (comparable with the early (E) and late (A) phases of a Doppler echocardiogram) were identified during diastole. Repeated HTR imaging of the same animals on sequential days indicated reproducibility of E′/A′ ratios of 11%. In chronically infarcted rat hearts, HTR imaging revealed lower peak ejection rates (PERs), peak early filling rates (E′) and E′/A′ ratios, and higher peak late filling rates (A′) than in sham‐operated rats. Diabetic db/db mouse hearts had the same function as controls when using standard cine‐MRI, yet HTR imaging identified significantly lower PERs, early filling rates and E′/A′ ratios in diabetic mouse hearts. In conclusion, the HTR MRI technique revealed changes in function that were below the limits of detection of standard cine‐MRI. Magn Reson Med 60:582–587, 2008. © 2008 Wiley‐Liss, Inc.
Comparison of parallel MRI reconstruction methods for accelerated 3D fast spin‐echo imaging
Authors: Xiao Zhikui , Hoge W. Scott , Mulkern R.V. , Zhao Lei , Hu Guangshu , Kyriakos Walid E. 
Published: August 2008

AbstractParallel MRI (pMRI) achieves imaging acceleration by partially substituting gradient‐encoding steps with spatial information contained in the component coils of the acquisition array. Variable‐density subsampling in pMRI was previously shown to yield improved two‐dimensional (2D) imaging in comparison to uniform subsampling, but has yet to be used routinely in clinical practice. In an effort to reduce acquisition time for 3D fast spin‐echo (3D‐FSE) sequences, this work explores a specific nonuniform sampling scheme for 3D imaging, subsampling along two phase‐encoding (PE) directions on a rectilinear grid. We use two reconstruction methods—2D‐GRAPPA‐Operator and 2D‐SPACE RIP—and present a comparison between them. We show that high‐quality images can be reconstructed using both techniques. To evaluate the proposed sampling method and reconstruction schemes, results via simulation, phantom study, and in vivo 3D human data are shown. We find that fewer artifacts can be seen in the 2D‐SPACE RIP reconstructions than in 2D‐GRAPPA‐Operator reconstructions, with comparable reconstruction times. Magn Reson Med 60:650–660, 2008. © 2008 Wiley‐Liss, Inc.
Effects of refocusing flip angle modulation and view ordering in 3D fast spin echo
Authors: Busse Reed F. , Brau Anja C.S. , Vu Anthony , Michelich Charles R. , Bayram Ersin , Kijowski Richard , Reeder Scott B. , Rowley Howard A. 
Published: August 2008

AbstractRecent advances have reduced scan time in three‐dimensional fast spin echo (3D‐FSE) imaging, including very long echo trains through refocusing flip angle (FA) modulation and 2D‐accelerated parallel imaging. This work describes a method to modulate refocusing FAs that produces sharp point spread functions (PSFs) from very long echo trains while exercising direct control over minimum, center‐k‐space, and maximum FAs in order to accommodate the presence of flow and motion, SNR requirements, and RF power limits. Additionally, a new method for ordering views to map signal modulation from the echo train into ky‐kz space that enables nonrectangular k‐space grids and autocalibrating 2D‐accelerated parallel imaging is presented. With long echo trains and fewer echoes required to encode large matrices, large volumes with high in‐ and through‐plane resolution matrices may be acquired with scan times of 3–6 min, as demonstrated for volumetric brain, knee, and kidney imaging. Magn Reson Med 60:640–649, 2008. © 2008 Wiley‐Liss, Inc.
Sources of hepatic glucose production by 2H2O ingestion and Bayesian analysis of 2H glucuronide enrichment
Authors: Delgado T.C. , Barosa C. , Castro M.M.C.A. , Geraldes C.F.G.C. , Bastos M. , Baptista C. , Fagulha A. , Barros L. , Mota A. , Carvalheiro M. , Jones J.G. , Merritt Matthew 
Published: August 2008

AbstractThe contribution of gluconeogenesis to hepatic glucose production (GP) was quantified after 2H2O ingestion by Bayesian analysis of the position 2 and 5 2H‐NMR signals (H2 and H5) of monoacetone glucose (MAG) derived from urinary acetaminophen glucuronide. Six controls and 10 kidney transplant (KTx) patients with cyclosporine A (CsA) immunosuppressant therapy were studied. Seven KTx patients were lean and euglycemic (BMI = 24.3 ± 1.0 kg/m2; fasting glucose = 4.7 ± 0.1 mM) while three were obese and hyperglycemic (BMI = 30.5 ± 0.7 kg/m2; fasting glucose = 7.1 ± 0.5 mM). For the 16 spectra analyzed, the mean coefficient of variation for the gluconeogenesis contribution was 10% ± 5%. This uncertainty was associated with a mean signal‐to‐noise ratio (SNR) of 79:1 and 45:1 for the MAG H2 and H5 signals, respectively. For control subjects, gluconeogenesis contributed 54% ± 7% of GP as determined by the mean and standard deviation (SD) of individual Bayesian analyses. For the lean/normoglycemic KTx subjects, the gluconeogenic contribution to GP was 62% ± 7% (P = 0.06 vs. controls), while hyperglycemic/obese KTx patients had a gluconeogenic contribution of 68% ± 3% (P < 0.005 vs. controls). These data suggest that in KTx patients, an increased gluconeogenic contribution to GP is strongly associated with obesity and hyperglycemia. Magn Reson Med 60:517–523, 2008. © 2008 Wiley‐Liss, Inc.
Voxel‐shift and interpolation for hadamard‐encoded MR images
Authors: Fleysher Lazar , Fleysher Roman , Liu Songtao , Gonen Oded 
Published: August 2008

AbstractAlthough Fourier gradient phase‐encoding and Hadamard radio‐frequency encoding are two established spatial MR localization techniques, the absence of voxel‐shift and interpolation postprocessing algorithms for the latter has always placed it at a discouraging disadvantage. This article presents a method for voxel‐shift and interpolation of Hadamard‐encoded data and demonstrates both theoretically and experimentally the similarities of the respective operations between the two localization methods. Magn Reson Med 60:524–535, 2008. © 2008 Wiley‐Liss, Inc.
Modeling SSFP functional MRI contrast in the brain
Authors: Miller Karla L. , Jezzard Peter 
Published: August 2008

AbstractSteady‐state free precession (SSFP) has recently been proposed for function MRI because of the potential for reducing image distortion and signal dropout. Several different contrast mechanisms have been suggested to explain the reported observations, but there has been limited work comparing theory with experiment in the brain. Moreover, the detailed work that has considered oxygen‐dependent signal in SSFP outside the brain has focused on R2 effects in the pass band, and largely neglected the signal contrast that occurs due to off‐resonance effects. The article describes a model for SSFP functional contrast based on the convolution of the theoretical SSFP profile with the underlying frequency distribution. It is demonstrated that such a model must account for the effects of diffusion, which can alter the apparent R2 and linespread. Monte Carlo simulations are used to calibrate corrections for these terms. This new model has the computational efficiency of the convolution model while encapsulating information from more time‐consuming Monte Carlo simulations. This corrected convolution model is shown to agree well with experimental data, and model predictions and limitations are discussed. Magn Reson Med 60:661–673, 2008. © 2008 Wiley‐Liss, Inc.
Evaluation of lactate and alanine as metabolic biomarkers of prostate cancer using 1H HR‐MAS spectroscopy of biopsy tissues
Authors: Tessem May‐Britt , Swanson Mark G. , Keshari Kayvan R. , Albers Mark J. , Joun David , Tabatabai Z. Laura , Simko Jeffry P. , Shinohara Katsuto , Nelson Sarah J. , Vigneron Daniel B. , Gribbestad Ingrid S. , Kurhanewicz John 
Published: August 2008

AbstractThe goal of this study was to investigate the use of lactate and alanine as metabolic biomarkers of prostate cancer using 1H high‐resolution magic angle spinning (HR‐MAS) spectroscopy of snap‐frozen transrectal ultrasound (TRUS)‐guided prostate biopsy tissues. A long‐echo‐time rotor‐synchronized Carr‐Purcell‐Meiboom‐Gill (CPMG) sequence including an electronic reference to access in vivo concentrations (ERETIC) standard was used to determine the concentrations of lactate and alanine in 82 benign and 16 malignant biopsies (mean 26.5% ± 17.2% of core). Low concentrations of lactate (0.61 ± 0.28 mmol/kg) and alanine (0.14 ± 0.06 mmol/kg) were observed in benign prostate biopsies, and there was no significant difference between benign predominantly glandular (N = 54) and stromal (N = 28) biopsies between patients with (N = 38) and without (N = 44) a positive clinical biopsy. In biopsies containing prostate cancer there was a highly significant (P < 0.0001) increase in lactate (1.59 ± 0.61 mmol/kg) and alanine (0.26 ± 0.07 mmol/kg), and minimal overlap with lactate concentrations in benign biopsies. This study demonstrates for the first time very low concentrations of lactate and alanine in benign prostate biopsy tissues. The significant increase in the concentration of both lactate and alanine in biopsy tissue containing as little as 5% cancer could be exploited in hyperpolarized 13C spectroscopic imaging (SI) studies of prostate cancer patients. Magn Reson Med 60:510–516, 2008. © 2008 Wiley‐Liss, Inc.
Improved calibration technique for in vivo proton MRS thermometry for brain temperature measurement
Authors: Zhu M. , Bashir A. , Ackerman J.J. , Yablonskiy D.A. 
Published: August 2008

AbstractThe most common MR‐based approach to noninvasively measure brain temperature relies on the linear relationship between the 1H MR resonance frequency of tissue water and the tissue's temperature. Herein we provide the most accurate in vivo assessment existing thus far of such a relationship. It was derived by acquiring in vivo MR spectra from a rat brain using a high field (11.74 Tesla [T]) MRI scanner and a single‐voxel MR spectroscopy technique based on a LASER pulse sequence. Data were analyzed using three different methods to estimate the 1H resonance frequencies of water and the metabolites NAA, Cho, and Cr, which are used as temperature‐independent internal (frequency) references. Standard modeling of frequency‐domain data as composed of resonances characterized by Lorentzian line shapes gave the tightest resonance‐frequency versus temperature correlation. An analysis of the uncertainty in temperature estimation has shown that the major limiting factor is an error in estimating the metabolite frequency. For example, for a metabolite resonance linewidth of 8 Hz, signal sampling rate of 2 Hz and SNR of 5, an accuracy of approximately 0.5°C can be achieved at a magnetic field of 3T. For comparison, in the current study conducted at 11.74T, the temperature estimation error was approximately 0.1°C. Magn Reson Med 60:536–541, 2008. © 2008 Wiley‐Liss, Inc.
Strongly modulating pulses for counteracting RF inhomogeneity at high fields
Authors: Boulant N. , Bihan D. Le , Amadon A. 
Published: August 2008

AbstractA new pulse technique for counteracting RF inhomogeneity at high fields is reported. The pulses make use of the detailed knowledge of the voxels' B1 and B0 amplitude 2D histogram to generate, through an optimization procedure, gates where the flip angle is made uniform. Although most approaches to date require the use of parallel transmission, this method does not and therefore offers several advantages. The data necessary for the algorithm to determine an irradiation scheme requires only one transmit B1 along with a B0 inhomogeneity measurement. The use of a B1 and B0 amplitude 2D histogram instead of their spatial distribution also decreases substantially the complexity of the optimization problem, allowing the algorithm to find an RF solution in less than 30 s. Finally, the optimization procedure is based on an exact calculation and does not use any linear approximation. In this article, the theory behind the method in addition to spoiled gradient echo experimental data at 3T for 3D brain imaging are reported. The images obtained yield a reduction of the standard deviation of the sine of the flip angle by a factor of up to 15 around the desired value, compared to when a standard square pulse calibrated by the scanner is used. Magn Reson Med 60:701–708, 2008. © 2008 Wiley‐Liss, Inc.
Quantitative magnetization transfer imaging using balanced SSFP
Authors: Gloor M. , Scheffler K. , Bieri O. 
Published: August 2008

AbstractIt is generally accepted that signal formation in balanced steady‐state free precession (bSSFP) is a simple function of relaxation times and flip angle only. This can be confirmed for fluids, but for more complex substances, magnetization transfer (MT) can lead to a considerable loss of steady‐state signal. Thus, especially in tissues, the analytical description of bSSFP requires a revision to fully take observed effects into account. In the first part of this work, an extended bSSFP signal equation is derived based on a binary spin‐bath model. Based on this new model of bSSFP signal formation, quantitative MT parameters such as the fractional pool size, corresponding magnetization exchange rates, and relaxation times can be explored. In the second part of this work, model parameters are derived in normal appearing human brain. Factors that may influence the quality of the model, such as B1 field inhomogeneities or off‐resonances, are discussed. Overall, good correspondence between parameters derived from two‐pool bSSFP and common quantitative MT models is observed. Short repetition times in combination with high signal‐to‐noise ratios make bSSFP an ideal candidate for the acquisition of high resolution isotropic quantitative MT maps, as for the human brain, within clinically feasible acquisition times. Magn Reson Med 60:691–700, 2008. © 2008 Wiley‐Liss, Inc.