bluuebunny/crossref_metadata_2025 huggingface dataset:
Average distance and maximum induced forest
Authors: Hansen Pierre , Hertz Alain , Kilani Rim , Marcotte Odile , Schindl David
Published: July 2008

With the help of the Graffiti system, Fajtlowicz conjectured around 1992 that the average distance between two vertices of a connected graph G is at most half the maximum order of an induced bipartite subgraph of G, denoted α2(G). We prove a strengthening of this conjecture by showing that the average distance between two vertices of a connected graph G is at most half the maximum order of an induced forest, denoted F(G). Moreover, we characterize the graphs maximizing the average distance among all graphs G having a fixed number of vertices and a fixed value of F(G) or α2(G). Finally, we conjecture that the average distance between two vertices of a connected graph is at most half the maximum order of an induced linear forest (where a linear forest is a union of paths). © 2008 Wiley Periodicals, Inc. J Graph Theory 60: 31–54, 2009
Piezoelectric biosensors assisted with electroacoustic impedance spectroscopy: a tool for accurate quantitative molecular recognition analysis
Authors: Encarnação João M. , Baltazar Raul , Stallinga Peter , Ferreira Guilherme N. M.
Published: August 2008

In this work, electroacoustic impedance analysis based on a modified Butterworth–Van Dyke (BVD) model is used to complement resonance frequency measurements of piezoelectric crystal sensors for the identification and removal of interfering signals. This approach enables the accurate use of the Sauerbrey correlation to establish a direct relationship between mass deposited at the sensor surface and measured frequency variations. Kinetic models can thus be evaluated and binding constants estimated directly from the measured data. We further demonstrate the usefulness of this approach by applying it to the study of the formation of 11‐hydroxy‐1‐undecanothiol self‐assembled monolayers (SAM) as well as to the binding of streptavidin to immobilized biotin. Kinetic and equilibrium parameters were estimated from transient analysis, adsorption isotherms, Scatchard and Hill plots obtained from the frequency data for both the alkanethiol and streptavidin films.

This strategy based on electroacoustic impedance assisted quartz‐crystal microbalance (QCM) biosensors is expected to be a major contribution for the use of these piezoelectric devices as a reliable and cheap detection system that can easily be integrated into analytical techniques. Copyright © 2008 John Wiley & Sons, Ltd.
Modified electrocardiograph‐triggered black‐blood turbo spin‐echo technique to improve T1‐weighting in contrast‐enhanced MRI of atherosclerotic carotid arteries
Authors: Boussel Loic , Herigault Gwenael , Sigovan Monica , Loffroy Romaric , Canet‐Soulas Emmanuelle , Douek Philippe Charles
Published: July 2008

Purpose

To assess the efficacy of a modified electrocardiograph (EKG)‐triggered black‐blood T1W (T1W) spin‐echo sequence in improving contrast on post‐gadolinium high‐resolution carotid plaque imaging by implementing heart‐rate–independent contrast preparation.

Materials and Methods

We used a standard EKG‐triggered double inversion‐recovery (DIR) turbo spin‐echo (TSE) sequence modified with the addition of an extra saturation (90°) radio frequency (RF) pulse placed immediately after the DIR module, shortening the repetition time to a fixed value of 400 msec. A total of 10 patients with atherosclerotic disease were included in the study. Postinjection intraplaque contrast measurements were performed on each patient for the standard and the modified sequence.

Results

Post‐gadolinium‐injection intraplaque contrast was 31.7 ± 12.8% with the standard T1W sequence (nT1‐TSE), and 45.3 ± 17.2% with the modified T1W sequence (mT1‐TSE), showing a significant contrast enhancement of 13.6% (P < 0.001) without significant image quality modification.

Conclusion

The addition of a RF pulse to the standard EKG‐triggered T1W TSE sequence increased intraplaque contrast without increasing sequence acquisition time. Furthermore, it appeared to be a robust technique, easy to implement on clinical scanners. J. Magn. Reson. Imaging 2008;28:533–537. © 2008 Wiley‐Liss, Inc.
Transit delay and flow quantification in muscle with continuous arterial spin labeling perfusion‐MRI
Authors: Wu Wen‐Chau , Wang Jiongjiong , Detre John A. , Ratcliffe Sarah J. , Floyd Thomas F.
Published: July 2008

Purpose

To test the hypothesis that flow measurements using continuous arterial spin labeling (CASL) magnetic resonance imaging (MRI) in muscle depend upon transit delay, and examine the repeatability of CASL measurements.

Materials and Methods

A total of 23 healthy subjects underwent CASL imaging of the calf, foot, and forearm with varying postlabeling delay (PLD = 1000, 1500, and 1900 msec). Experiments were conducted on a 3.0T system. An orthopedic tourniquet system was employed to create a five‐minute period of ischemia followed by a transient hyperemic flow. Imaging commenced two minutes prior to cuff inflation and ended three minutes after cuff release.

Results

CASL was found able to well resolve the time course of the hyperemic flow pattern with an effective TR of 16 seconds, although we were unable to establish that a plateau had been reached in the flow measurements even at a PLD as long as 1900 msec. Peak hyperemic flow measurements compared favorably with those obtained with contrast‐enhanced (CE) MRI following a similar period of ischemia. Region‐of‐interest (ROI)–based repeated measurements varied by approximately 20% over a period of one hour.

Conclusion

In all anatomic regions studied, flow measurements were found to increase with PLD, suggesting the prolonged transit delay in muscle. J. Magn. Reson. Imaging 2008;28:445–452. © 2008 Wiley‐Liss, Inc.
Real‐time catheter‐directed MRA with effective background suppression and persistent rendering
Authors: Guttman Michael A. , Raval Amish N. , Lederman Robert J. , McVeigh Elliot R.
Published: July 2008

Purpose

To develop an imaging and visualization technique for real‐time magnetic resonance angiography (rtMRA) fully integrated with a real‐time interactive imaging environment on a clinical MR scanner.

Materials and Methods

Intraarterial injections of contrast agent and imaging processing techniques were employed for rapid catheter‐directed assessment of vessel patency and regional tissue perfusion. Operators can image multiple thin slices to maximize anatomic detail or use thick slice or projection imaging to maximize vessel coverage. Techniques in both pulse sequence and image processing were employed to ensure background suppression. Accumulation of maximum pixel values allows persistent display of bolus signal as it passes through the vessels and into tissues. Automatic brightness adjustment was used to ensure visibility at all stages of bolus passage.

Results

Experimental intraarterial rtMRA of coronary, renal, and carotid arteries show that vessel trajectories and perfusion territories are well visualized in swine. Switching between standard real‐time imaging and rtMRA imaging after contrast injection was easy to perform during a procedure without stopping the scanner.

Conclusion

The proposed technique facilitates visualization of intraarterial contrast injections using real‐time MRI. Although designed for rapid deployment during rtMRI‐guided interventional procedures, the technique may also be useful to supplement the study of vessel anatomy, flow, or perfusion. J. Magn. Reson. Imaging 2008;28:538–542. © 2008 Wiley‐Liss, Inc.
Characterization of hepatocellular carcinoma and colorectal liver metastasis by means of perfusion MRI
Authors: Abdullah Siraj Saadaldin , Pialat Jean Baptiste , Wiart Marlene , Duboeuf François , Mabrut Jean‐Yves , Bancel Brigitte , Rode Agnès , Ducerf Christian , Baulieux Jacques , Berthezene Yves
Published: July 2008

Purpose

To characterize and compare hepatocellular carcinoma and liver metastases of colorectal metastatic cancer (CMC) by means of quantitative liver perfusion MRI.

Materials and Methods

Liver perfusion was assessed in 26 HCC and CMC patients (50 nodules) by means of contrast‐enhanced MRI. Six perfusion parameters—hepatic perfusion index (HPI), mean transit time (MTT), distribution volume (DV), total blood flow (FT), arterial blood flow (FA), and portal blood flow (FP)—were calculated in tumor nodules and the adjacent hepatic parenchyma.

Results

The values of FT, FA, FP, and DV were significantly higher in the HCC than in the CMC group, whereas MTT was significantly higher in the CMC group. There was no significant difference in HPI. Arterial blood flow was higher than portal blood flow in the CMC group, while portal blood flow was slightly higher than arterial blood flow in the HCC group.

Conclusion

The present work describes the use of dynamic MRI to quantitatively assess liver perfusion, which in the future may help studying liver cancers on the basis of their microvascular characteristics. J. Magn. Reson. Imaging 2008;28:390–395. © 2008 Wiley‐Liss, Inc.
Reduction of artifacts in susceptibility‐weighted MR venography of the brain
Authors: Jin Zhaoyang , Xia Ling , Du Yiping P.
Published: July 2008

Purpose

To reduce the off‐resonance artifact in susceptibility‐weighted imaging (SWI)‐based MR venography (MRV) in the brain regions with severe field inhomogeneity and to reduce the signal loss in the minimum‐intensity projection (mIP) display of the 3D MRV.

Materials and Methods

A novel postprocessing approach was presented to map the local field gradients (LFGs) using the 3D SWI data without phase‐unwrapping. LFG measurements were used to assess the severity of field inhomogeneity and suppress the residual phase in the phase mask induced by the off‐resonance effect. Volume segmentation of brain tissue was used to reduce the signal loss in the peripheral regions of the brain in the through‐plane mIP images and enable in‐plane mIP display of MRV.

Results

Off‐resonance artifact in the brain regions with severe field inhomogeneity was effectively reduced by the LFG‐based phase suppression approach. Signal loss was reduced in the through‐plane mIP of MRV using volume segmentation of brain tissue prior to projection. In‐plane mIP of MRV also became feasible with volume segmentation.

Conclusion

Off‐resonance artifacts and signal loss in mIP display of MRV can be effectively reduced through postprocessing. J. Magn. Reson. Imaging 2008;28:327–333. © 2008 Wiley‐Liss, Inc.
Automatic correction of intensity inhomogeneities improves unsupervised assessment of abdominal fat by MRI
Authors: Positano Vincenzo , Cusi Kenneth , Santarelli Maria Filomena , Sironi Annamaria , Petz Roberta , DeFronzo Ralph , Landini Luigi , Gastaldelli Amalia
Published: July 2008

Purpose

To demonstrate that unsupervised assessment of abdominal adipose tissue distribution by magnetic resonance imaging (MRI) can be improved by integrating automatic correction of signal inhomogeneities.

Materials and Methods

Twenty subjects (body mass index [BMI] 23.7–44.0 kg/m2) underwent abdominal (32 slices) MR imaging with a 1.9T Elscint Prestige scanner. Many images were affected by relevant intensity distortions. Unsupervised segmentation of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) was performed by a previously validated algorithm exploiting standard fuzzy clustering segmentation. Images were also processed by an improved version of the software, including automatic correction of intensity inhomogeneities. To assess the effectiveness of the two methods SAT and VAT volumes were compared with manual analysis performed by a trained operator.

Results

Coefficient of variation between manual and unsupervised analysis was significantly improved by inhomogeneities correction in SAT evaluation. Systematic underestimation of SAT was also corrected. A less important performance improvement was found in VAT measurement.

Conclusion

The results of this study suggest that the compensation of signal inhomogeneities greatly improves the effectiveness of the unsupervised assessment of abdominal fat. Correction of intensity distortions is important in SAT evaluation and less significant in VAT measurement. J. Magn. Reson. Imaging 2008;28:403–410. © 2008 Wiley‐Liss, Inc.
3D TrueFISP imaging of mouse brain at 4.7T and 9.4T
Authors: Miraux Sylvain , Massot Philippe , Ribot Emeline J. , Franconi Jean‐Michel , Thiaudiere Eric
Published: July 2008

Purpose

To examine the ability of TrueFISP imaging for evaluating tumor size in mouse brain at high field.

Materials and Methods

Brains of healthy and glioma‐implanted nude mice were imaged at 4.7T and 9.4T. 3D imaging was performed with TrueFISP and T2w‐RARE. Radiofrequency pulses with alternating phase and the sum‐of‐squares reconstruction method were used in TrueFISP imaging. The contrast‐to‐noise ratio (CNR) was evaluated in healthy and in tumoral brain regions.

Results

Banding artifact was correctly suppressed in TrueFISP images thanks to the method used. The signal‐to‐noise ratio (SNR) and CNR were comparable in TrueFISP and T2w‐RARE images at 4.7T, but acquisition was around 4 times shorter with TrueFISP. Tumor was well detected at 4.7T with TrueFISP, but CNR between tumor and healthy tissue was low at 9.4T.

Conclusion

TrueFISP is efficient and fast to perform brain imaging at 4.7T. Multiple TrueFISP acquisitions with phase‐cycled radiofrequency (RF) pulses and sum‐of‐squares reconstruction allow suppression of banding artifact. Tumoral regions were well detected and the method allows longitudinal studies of tumor growth. J. Magn. Reson. Imaging 2008;28:497–503. © 2008 Wiley‐Liss, Inc.
Carcinosarcoma of the uterus: MR findings
Authors: Tanaka Yumiko O. , Tsunoda Hajime , Minami Rie , Yoshikawa Hiroyuki , Minami Manabu
Published: July 2008

Purpose

To clarify the imaging characteristics of carcinosarcomas, which are the most common malignant mixed epithelial and mesenchymal tumors (MEMTs) of the uterus.

Materials and Methods

We retrospectively reviewed MR findings of 17 histopathologically confirmed cases with carcinosarcomas, including the size, growth pattern, signal intensity, contrast enhancement, and extrauterine spread in each case.

Results

The maximum tumor diameter was 11–165 mm (mean 88 mm). Nine cases (53%) showed exophytic with a stalk and eight cases (47%) showed broad‐based exophytic growth. None of them showed invasive growth. Fourteen cases (82%) were isointense and three cases (18%) were hyperintense to myometrium on T1‐weighted images (T1WI). An extremely high intensity area suggesting intratumoral hemorrhage was seen in only two cases. In 15 cases (88%), more than half of the tumor showed higher signal intensity than the outer myometrium on T2WI. Eight of the 16 cases (50%) had an unenhanced area, whereas 13 cases (81%) had a strongly enhanced area. Extrauterine extension was observed in only two cases (12%) at initial presentation.

Conclusion

Uterine carcinosarcomas reveal a spectrum of imaging findings with a high signal on T2WI, with a prolonged intense enhancement being the most common imaging feature. J. Magn. Reson. Imaging 2008;28:434–439. © 2008 Wiley‐Liss, Inc.
Lateral parabrachial afferent areas and serotonin mechanisms activated by volume expansion
Authors: Margatho Lisandra Oliveira , Godino Andrea , Oliveira Fabíola Raquel Tenório , Vivas Laura , Antunes‐Rodrigues José
Published: August 2008

Recent evidence has shown that the serotonergic mechanism of the lateral parabrachial nucleus (LPBN) participates in the regulation of renal and hormonal responses to isotonic blood volume expansion (BVE). We investigated the BVE‐induced Fos activation along forebrain and hindbrain nuclei and particularly within the serotonergic clusters of the raphé system that directly project to the LPBN. We also examined whether there are changes in the concentration of serotonin (5HT) within the raphé nucleus in response to the same stimulus. With this purpose, we analyzed the cells doubly labeled for Fos and Fluorogold (FG) following BVE (NaCl 0.15 M, 2 ml/100 g b.w., 1 min) 7 days after FG injection into the LPBN. Compared with the control group, blood volume‐expanded rats showed a significant greater number of Fos‐FG double‐labeled cells along the nucleus of the solitary tract, locus coeruleus, hypothalamic paraventricular nucleus, central extended amygdala complex, and dorsal raphé nucleus (DRN) cells. Our study also showed an increase in the number of serotonergic DRN neurons activated in response to isotonic BVE. We also observed decreased levels of 5HT and its metabolite 5‐hydroxyindoleacetic acid (measured by high‐pressure liquid chromatography) within the raphé nucleus 15 min after BVE. Given our previous evidence on the role of the serotonergic system in the LPBN after BVE, the present morphofunctional findings suggest the existence of a key pathway (DRN‐LPBN) that may control BVE response through the modulation of 5HT release. © 2008 Wiley‐Liss, Inc.
Tumor spectrum of adult intussusception
Authors: Chiang Jy‐Ming , Lin Yann‐Sheng
Published: July 2008

Introduction

Adult intussusception is rare. Most general and colorectal surgeons are unfamiliar with its etiology and optimal management.

Patients and Methods

Patients older than 16 years and diagnosed with intestinal intussusception between January 1990 and June 2006 were retrospectively reviewed. Data related to presentation, diagnosis, treatment, and pathology were analyzed.

Results

Seventy‐two patients underwent surgery for intestinal intussusception. Neoplasm was identified as the cause of intussusception in 66 (92%) cases, and 6 (8%) were idiopathic. The incidence of malignant colonic intussusception (63%) was significantly higher than that of enteric intussusception (20%), P = 0.001. Primary colon adenocarcinoma (8 of 10 patients, 80%) and malignant lymphoma (2 of 10 patients, 20%) were the two most common underlying malignant lesions in the colon. Lipoma (15 of 40 patients, 38%) and Peutz–Jegher adenoma (10 of 40 patients, 25%) were the two most common lesions of benign small bowel neoplasms while 27% (3 of 11) of malignant enteric intussusception cases were malignant lymphoma and metastatic respectively.

Conclusion

Lipoma is the most common benign tumor in both small and large bowel intussusception. Whereas 80% of tumors associated with small bowel intussusception were benign, two‐thirds of colonic intussusceptions had resulted from primary adenocarcinoma. J. Surg. Oncol. © 2008 Wiley‐Liss, Inc.
Lymphatic fistulae after neck dissection: The fibrin sealant treatment
Authors: Vaiman Michael , Eviatar Efraim
Published: July 2008

Objective

to investigate possibility of treatment of lymphatic fistulae after neck dissection with the fibrin sealant.

Methods

During the period of 2001–2007, two cases of lymphatic fistulae after neck dissection were treated with human blood based fibrin sealant (Quixil fibrin glue). The sealant components were sprayed into the fistulae with the help of a dual‐syringe delivery system.

Results

Sixty patients were operated, 84 neck dissections were performed from 2001 till 2008. Lymphatic fistulae occurred in two cases (2.4% of operations). Fibrin sealant treatment resulted in immediate stop of a leak and complete healing of the fistulae in both cases after 3 days of treatment. One year follow‐up revealed no complications.

Conclusion

Fibrin sealant application might be an effective and time‐saving treatment of lymphatic fistulae after neck dissection. J. Surg. Oncol. © 2008 Wiley‐Liss, Inc.
Methylation‐Related silencing of p14ARF gene correlates with telomerase activity and mRNA expression of human telomerase reverse transcriptase in hepatocellular carcinoma
Authors: Zhang Changsong , Guo Xianling , Zhang Li , Lu Zhenghua , Ma Nannan , Cheng Yue , Shen Feng , Zhang Baihe , Wu Mengchao , Wei Lixin
Published: August 2008

Background and Objectives

The p14ARF gene encodes a critical negative regulator of cell cycle progression. And upregulation of telomerase activity has been considered a critical step to tumors. We investigated promoter methylation of p14ARF and expression as well as their effect on hTERT expression and telomerase activity in HCC.

Methods

We studied p14ARF methylation and mRNA in 30 hepatocellular carcinomas and corresponding non‐tumor liver tissues using methylation‐specific PCR. Reverse transcription‐PCR was performed for expression of p14ARF and hTERT. Telomerase activity was performed by TRAP assay.

Results

p14ARF hypermethylation was detected in 16 (53.3%) of HCC and 10 (33.3%) of non‐tumor tissues, and 12 of 16 with methylation were tumor tissues around large size (≥5 cm). p14ARF mRNA was observed in 25%, 80.0%, or 50.0% of tumors with hypermethylated, partially methylated or unmethylated p14ARF promoter, respectively. Among the 16 tumors with p14ARF hypermethylation, all 12 tumors lacking p14ARF mRNA were positive for hTERT expression, while only one of 4 tumors expressing p14ARF mRNA was positive for hTERT expression.

Conclusions

p14ARF hypermethylation may contribute to silencing of p14ARF mRNA expression in HCC. Telomerase activity is association with inactivation of the p14ARF–p53 pathway induced by methylation in HCC. J. Surg. Oncol. © 2008 Wiley‐Liss, Inc.
Mixed‐mode hydrophilic interaction/cation‐exchange chromatography (HILIC/CEX) of peptides and proteins
Authors: Mant Colin T. , Hodges Robert S.
Published: July 2008

This review represents a summary of the development and application of a novel mixed‐mode HPLC approach to the separation and analysis of peptides and proteins termed hydrophilic interaction/cation‐exchange chromatography (HILIC/CEX). This approach combines the most advantageous aspects of two widely different separation mechanisms, i.e. a separation based on hydrophilicity/hydrophobicity differences between polypeptides overlaid on a separation based on net charge. Applications described include HILIC/CEX separations of cyclic peptides, α‐helical peptides, random coil peptides and modified or deletion products of synthetic peptides. In addition, the excellent resolving ability of HILIC/CEX for modified histone proteins is described. This approach is shown to represent an excellent complement to RP chromatography (RPC), as well as being a potent analytical tool in its own right.
Synthesis and Association Behaviour of Linear Block Copolymers with Different Microstructures but the Same Composition
Authors: Schmitz Christof , Mourran Ahmed , Keul Helmut , Möller Martin
Published: August 2008

The di‐ and triblock copolymers, P(MAA)‐b‐P(MMA), P(MAA)‐b‐P(BMA), P(MAA)‐b‐P(MAA‐co‐MMA)‐b‐P(MMA) and P(MAA)‐b‐P(MAA‐co‐BMA)‐b‐P(BMA), were synthesised via ATRP in order to study the association behaviour in water via polyelectrolyte titration, fluorescence spectroscopy, dynamic light scattering and scanning force microscopy. P(BMA) block copolymers spontaneously self‐associate into micelles whereas for P(MMA) block copolymers addition of salt is necessary to induce aggregation. Principally, the hydrodynamic radius of the micelles decreases from di‐ to triblock copolymer which was attributed to a different conformation of the random middle block at the core/corona interface.

magnified image
Evaluation of MR angiography at 7.0 Tesla MRI using birdcage radio frequency coils with end caps
Authors: Kang Chang‐Ki , Hong Suk‐Min , Han Jae‐Yong , Kim Kyoung‐Nam , Kim Sang‐Hoon , Kim Young‐Bo , Cho Zang‐Hee
Published: July 2008

The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16‐rung high‐pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine whether the end cap configuration was effective, the signal intensity profiles along the superior–inferior (S–I) direction were analyzed in phantom and in vivo human experiments. The effects were also investigated in two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight (TOF) MRA experiments. The signal intensity profiles showed that B1 homogeneity at the service end, that is, the end cap side, was improved as the diameter of the end caps increased and the end cap became closer to the coil end ring. The results of 2D and 3D TOF experiments showed the best improvement of vessel visibility at the BC coil with an 80% end cap, when compared with BC coils with other end cap sizes or without an end cap. In conclusion, the BC coil with an end cap was effective for improving S–I directional homogeneity and suitable for MRA applications, especially at ultrahigh field MRI, such as 7.0T. Magn Reson Med 60:330–338, 2008. © 2008 Wiley‐Liss, Inc.
Myocardial T measurement in iron‐overloaded thalassemia: An ex vivo study to investigate optimal methods of quantification
Authors: He Taigang , Gatehouse Peter D. , Kirk Paul , Mohiaddin Raad H. , Pennell Dudley J. , Firmin David N.
Published: July 2008

Myocardial T measurement has been increasingly used for iron quantification to assess the risk of cardiac complications in thalassemia patients. In this study the noise effects were evaluated along with different curve‐fitting models on an iron overloaded ex vivo heart in order to determine the optimal method of T measurement and to help understand issues affecting reproducibility and accuracy. Gradient multiecho short axis images were acquired with differing numbers of excitations to generate varying signal‐to‐noise ratio (SNR) images. A noise correction method was implemented; linear and nonlinear curve‐fitting algorithms were compared and different curve‐fitting models (monoexponential, truncation, baseline subtraction, and offset) were evaluated. This study suggests that the T decay curve in an ex vivo heart can be fitted by a monoexponential model and accurate T measurements can be obtained with proper noise correction. With MRI noise, T is generally overestimated by including late low SNR data points, but underestimated by the offset or baseline subtraction models, which are in fact equivalent. In this situation the truncation model proves to be reproducible and more accurate than the other models. The study also shows that the nonlinear algorithm is preferred in T curve fitting. Magn Reson Med 60:350–356, 2008. © 2008 Wiley‐Liss, Inc.
Effect of feature extraction for brain tumor classification based on short echo time 1H MR spectra
Authors: Luts Jan , Poullet Jean‐Baptiste , Garcia‐Gomez Juan M. , Heerschap Arend , Robles Montserrat , Suykens Johan A. K. , Huffel Sabine Van
Published: July 2008

This study examines the effect of feature extraction methods prior to automated pattern recognition based on magnetic resonance spectroscopy (MRS) for brain tumor diagnosis. Since individual inspection of spectra is time‐consuming and requires specific spectroscopic expertise, the introduction of clinical decision support systems (DSSs) is expected to strongly promote the clinical use of MRS. This study focuses on the feature extraction step in the preprocessing protocol of MRS when using a DSS. On two independent data sets, encompassing single‐voxel and multi‐voxel data, it is observed that the use of the full spectra together with a kernel‐based technique, handling high dimensional data, or using an automated pattern recognition method based on independent component analysis or Relief‐F achieves accurate performances. In addition, these approaches have low cost and are easy to automate. When sophisticated quantification methods are used in a DSS, user interaction should be minimized. The computationally intensive quantification techniques do not tend to increase the performance in these circumstances. The results suggest to simplify the feature reduction step in the preprocessing protocol when using a DSS purely for classification purposes. This can greatly speed up the execution of classifiers and DSSs and may accelerate their introduction into clinical practice. Magn Reson Med 60:288–298, 2008. © 2008 Wiley‐Liss, Inc.
Imaging pH using the chemical exchange saturation transfer (CEST) MRI: Correction of concomitant RF irradiation effects to quantify CEST MRI for chemical exchange rate and pH
Authors: Sun Phillip Zhe , Sorensen A. Gregory
Published: July 2008

Chemical exchange saturation transfer (CEST) MRI has been shown capable of detecting dilute labile protons and abnormal tissue glucose/oxygen metabolism, and thus, may serve as a complementary imaging technique to the conventional MRI methods. CEST imaging, however, is also dependent on experimental parameters such as the power, duration, and waveform of the irradiation RF pulse. As a result, its sensitivity and specificity for microenvironment properties such as pH is not optimal. In this study, the dependence of CEST contrast on experimental parameters was solved and an iterative compensation algorithm was proposed that corrects the experimentally measured CEST contrast from the concomitant RF irradiation effects. The proposed algorithm was verified with both numerical simulation and experimental measurements from a tissue‐like pH phantom, and showed that pH derived from the compensated CEST imaging agrees reasonably well with pH‐electrode measurements within 0.1 pH unit. In sum, our study validates the use of a correction algorithm to compensate CEST imaging from concomitant RF irradiation effects for accurate calibration of the chemical exchange rate, and demonstrates the feasibility of pH imaging with CEST MRI. Magn Reson Med 60:390–397, 2008. © 2008 Wiley‐Liss, Inc.
Evaluation of MRI models in the measurement of CMRO2 and its relationship with CBF
Authors: Lin Ai‐Ling , Fox Peter T. , Yang Yihong , Lu Hanzhang , Tan Li‐Hai , Gao Jia‐Hong
Published: July 2008

The aim of this study was to investigate the various MRI biophysical models in the measurements of local cerebral metabolic rate of oxygen (CMRO2) and the corresponding relationship with cerebral blood flow (CBF) during brain activation. This aim was addressed by simultaneously measuring the relative changes in CBF, cerebral blood volume (CBV), and blood oxygen level dependent (BOLD) MRI signals in the human visual cortex during visual stimulation. A radial checkerboard delivered flash stimulation at five different frequencies. Two MRI models, the single‐compartment model (SCM) and the multicompartment model (MCM), were used to determine the relative changes in CMRO2 using three methods: [1] SCM with parameters identical to those used in a prior MRI study (M = 0.22; α = 0.38); [2] SCM with directly measured parameters (M from hypercapnia and α from measured δCBV and δCBF); and [3] MCM. The magnitude of relative changes in CMRO2 and the nonlinear relationship between CBF and CMRO2 obtained with Methods [2] and [3] were not in agreement with those obtained using Method [1]. However, the results of Methods [2] and [3] were aligned with positron emission tomography findings from the literature. Our results indicate that if appropriate parameters are used, the SCM and MCM models are equivalent for quantifying the values of CMRO2 and determining the flow‐metabolism relationship. Magn Reson Med 60:380–389, 2008. © 2008 Wiley‐Liss, Inc.
Alias‐free image reconstruction using Fresnel transform in the phase‐scrambling Fourier imaging technique
Authors: Ito Satoshi , Yamada Yoshifumi
Published: July 2008

An image reconstruction technique that reduces aliasing artifacts by scalable image reconstruction in magnetic resonance imaging (MRI) is proposed. The signal obtained by the phase‐scrambling Fourier transform (PSFT) imaging technique can be transformed to the signal described in the Fresnel transform equation of the objects. Therefore, image reconstruction can be performed not only by inverse FT but also by inverse Fresnel transform. When a phase‐scrambling coefficient is given in a certain range, image reconstruction by inverse Fresnel transform allows shrinking of images over rather wide scales. Thus, reduced aliasing images can be reconstructed even from signals that produce serious aliasing artifacts by standard inverse FT reconstruction. Simulation and experimental studies reveal that the proposed method can be used to produce reduced aliasing images. Magn Reson Med 60:422–430, 2008. © 2008 Wiley‐Liss, Inc.
Fat‐water separation with alternating repetition time balanced SSFP
Authors: Çukur Tolga , Nishimura Dwight G.
Published: July 2008

Balanced SSFP achieves high SNR efficiency, but suffers from bright fat signal. In this work, a multiple‐acquisition fat‐water separation technique using alternating repetition time (ATR) balanced SSFP is proposed. The SSFP profile can be modified using alternating repetition times and appropriate phase cycling to yield two spectra where fat and water are in‐phase and out‐of‐phase, respectively. The signal homogeneity and the broad width of the created in‐phase and out‐of‐phase profiles lead to signal cancellation over a broad stop‐band. The stop‐band suppression is achieved for a wide range of flip angles and tissue parameters. This property, coupled with the inherent flexibility of ATR SSFP in repetition time selection, makes the method a good candidate for fat‐suppressed SSFP imaging. The proposed method can be tailored to achieve a smaller residual stop‐band signal or a decreased sensitivity to field inhomogeneity depending on application‐specific needs. Magn Reson Med 60:479–484, 2008. © 2008 Wiley‐Liss, Inc.
Numerical solution of Helmholtz equation by the modified Hopfield finite difference techniques
Authors: Dehghan Mehdi , Nourian Mojtaba , Menhaj Mohammad B.
Published: July 2008

One property of the Hopfield neural networks is the monotone minimization of energy as time proceeds. In this article, this property is applied to minimize the energy functions obtained by finite difference techniques of the Helmholtz‐equation. The mathematical representation and correlation between finite difference techniques and modified Hopfield neural networks of the Helmholtz equation are presented. Significant advantages of the above method are its parallel, robust, easy programming nature, and ability of direct hardware implementation. Results of numerical simulations are described and analyzed to demonstrate the method. The results obtained using the proposed method show a very good agreement with theoretical and numerical solutions. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
A priori and a posteriori error estimations for the dual mixed finite element method of the Navier‐Stokes problem
Authors: Farhloul M. , Nicaise S. , Paquet L.
Published: July 2008

This article is concerned with a dual mixed formulation of the Navier‐Stokes system in a polygonal domain of the plane with Dirichlet boundary conditions and its numerical approximation. The gradient tensor, a quantity of practical interest, is introduced as a new unknown. The problem is then approximated by a mixed finite element method. Quasi‐optimal a priori error estimates are obtained. These a priori error estimates, an abstract nonlinear theory (similar to (Verfürth, RAIRO Model Math Anal Numer 32 (1998), 817–842)) and a posteriori estimates for the Stokes system from (Farhloul et al., Numer Funct Anal Optim 27 (2006), 831–846) lead to an a posteriori error estimate for the Navier‐Stokes system. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Interests and lobbying in Lithuania: a spectrum of development
Authors: Hrebenar Ronald J. , McBeth Courtney H. , Morgan Bryson B.
Published: July 2008

By focusing on the case of Lithuania, this paper develops a framework for understanding the development and characteristics of interest groups and the broader category of interest systems in the former Communist countries of Eastern Europe.

Nearly two decades have passed since the transition to democracy in the former Baltic Soviet republics and Eastern Europe. These nations have established democratic elections, modern judicial systems, institutions of representative government and guarantees of civil rights and civil liberties. Successful democratization, however, also requires the construction of a civil society characterized by open channels of communication between citizens and interests and their governments. Recent studies of the democratization of the former Soviet republics and satellite states in Eastern Europe have rarely addressed the development and role of interest groups and lobbying in these nations. This paper fills this void by presenting the findings of the first major study of interest group politics and lobbying in Lithuania. The major findings are based upon interviews of nearly 50 Lithuanian political, academic, bureaucratic and media elites conducted in the July of 2005.

Overall, the lobbying community in Lithuania is underdeveloped, often corrupt, and is negatively perceived by many Lithuanians elites. Much of this is due to the legacy of communism which heavily influences the perception and efficacy of interest groups and lobbying resulting in a suspicion among the public and government officials that has impeded the development of an effective lobbying community. Lithuanian interest groups do not use sophisticated practices or tactics of lobbying; access is largely based on personal connections and corrupt practices. The business community is the most effective lobby due to its contacts and extensive resources; in contrast, the labour lobby is weak due to a hangover from communist times. Looking to the future development of the Lithuanian lobbying community, it is unclear what effect the entry of Lithuania into the European Union (May 2004) will have on the development of interest group activities and lobbying.

Copyright © 2008 John Wiley & Sons, Ltd.
Economic interest groups and the consolidation of democracy in the Czech Republic
Authors: Evanson Robert K.
Published: July 2008

This paper discusses organized economic interest groups in the Czech Republic placed in the context of the development of interest group activity in the post communist era and how this bodes for the consolidation of Czech democracy. After a brief overview of Czech political and economic developments since the end of communist rule, the origins, evolution and present state of interest groups are outlined. There has been a proliferation of economic interest groups, particularly in the business arena. However, there are some concerns about interest groups activity, which are examined next. The paper then moves to its main focus—the examination of economic interests. It does this by explaining the interaction among business, labour and government in the policy‐making arena and explaining apparent contradictions in the perceived influence of business. This is followed by a similar look at Czech agriculture. The paper concludes with some speculation about the likely future development of interest groups and what this might mean for the nature of Czech democracy. Copyright © 2008 John Wiley & Sons, Ltd.

Copyright © 2008 John Wiley & Sons, Ltd.
Business lobbies and policymaking in developing countries: the contrasting cases of India and China
Authors: Yadav Vineeta
Published: July 2008

Among the key decisions lobbies make are which political players to lobby, at what stage or stages to intervene in the policy process and which strategies and tactics to use. This paper addresses the lack of sources of knowledge beyond the United States for understanding these key decisions. It argues that the manner in which the design of legislative institutions establishes the balance of power between political parties and individual politicians has a significant influence on all three choices of the target of lobbying, the stage of the policymaking process in which to lobby and the strategies and tactics used by lobbies. Data to support the arguments are presented from a survey of groups in India and China.

Copyright © 2008 John Wiley & Sons, Ltd.
Simultaneous occurrence of right adrenocortical tumor and left adrenal neuroblastoma in an infant with Beckwith–Wiedemann syndrome
Authors: Alsultan Abdulrahman , Lovell Mark A. , Hayes Kari L. , Allshouse Michael J. , Garrington Timothy P.
Published: July 2008

Children with Beckwith–Wiedemann syndrome (BWS) have increased risk for development of embryonal tumors. We present the case of an infant with BWS who has hypomethylation of LIT1 gene in the 11p15.5 chromosomal region and at 6 months of age presented with simultaneous occurrence of neuroblastoma arising from the left adrenal gland and a right adrenocortical tumor. She underwent surgical resection of both tumors and remains tumor free 18 months after surgery. Pediatr Blood Cancer 2008;51:695–698. © 2008 Wiley‐Liss, Inc.
Structure–properties of electron beam irradiated and dicumyl peroxide cured low density polyethylene blends
Authors: Ali Zakaria , Youssef Hussein , Afify Tamer
Published: July 2008

Low density polyethylene (LDPE) and its blends with styrene butadiene rubber and ethylene propylene diene monomer were cured, using electron beam irradiation as well as dicumyl peroxide (DCP). The effect of blending was found to change the melt viscosity when compared with the virgin LDPE. Also, the influence of curing system on the various properties was investigated. It was found that either irradiation or DCP curing enhanced the gel content and crosslink density as well as the mechanical and hot set properties. The obtained data showed that the curing greatly influence the stress strain and hot set properties, in which there is a variation in such properties for both curing methods in spite of the gel contents were comparable. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Compatibilization of low‐density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation
Authors: Senna Magdy M. , Hossam Fatma M. , El‐Naggar Abdel Wahab M.
Published: July 2008

Blends based on various compositions of low‐density polyethylene (LDPE) and plasticized starch (PLST) were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and temperature against mixing time. The structural properties of LDPE/PLST blends before and after electron beam irradiation was characterized by IR spectroscopy, tensile mechanical testing, and scanning electron microscopy (SEM). The torque‐time curves during the mixing process showed that the values of torque in the first region of mixing for pure LDPE or LDPE/PLST blends are higher in the presence of the compatibilizer PEMA than that in the presence of EVA. In addition, the stability of mixing was attained after a short time in the presence of PEMA. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress–strain curves of pure LDPE and its blends with PLST showed the behavior of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and the effect of electron beam irradiation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Preparation, characterization, and electrocatalytic activity of Prussian blue/poly(N‐acetylaniline) composite film
Authors: Wu Shouguo , Wang Chuanqin , Wang Changqin , Zhang Xian , Wang Taoling
Published: July 2008

Electrochemical preparation of the Prussian blue (PB)/poly (N‐acetylaniline) (PNAANI) composite film was carried out by cyclic voltammetry (CV). Its surface morphology, which was evaluated by Atom Force Microscope (AFM), revealed that PNAANI film provides lots of redox centers for PB growth so that the electrodeposition of PB showed high current densities, and the composite film is much denser than pure PB film. The surface microstructure of the composite film was also characterized by X‐ray photoelectron spectrum (XPS). Due to the existence of electrostatic interaction between the PNAANI (polycation) film and the PB (polyanion) film, the composite film cannot be considered as a simple adherent bilayer of PB film and PNAANI film. The electroactivity and stability of the PB/PNAANI composite film in acidic electrolytes containing potassium ions were comparatively higher than that of the pure PB film. The functional composite film is expected for use in the system capable of effective accumulation of charge, and for the analytical applications towards the reduction of hydrogen peroxide due to its high electrocatalytic activity. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Calcium polyphosphate fibers/unsaturated poly(ester‐amide) composites for bone‐fixation materials
Authors: Ai Yong‐Ping , Shi Zong‐Li , Guo Wen‐Xun
Published: July 2008

A new type of unsaturated poly(ester‐amide) viz maleic anhydride‐phthalic anhydride‐propylene glycol‐neopentylene glycol‐glycin copolymer was prepared by melt polycondensation and characterized after sealed end with cyclohexanol. Mechanical strength of the crosslinked unsaturated poly(ester‐amide) with different heat‐treatment conditions was measured. Calcium polyphosphate fibers (CPPF) were used to boost up the new unsaturated poly(ester‐amide), mechanical strength, degradation, and hydrolysis behavior of CPPF/unsaturated poly(ester‐amide) composites with different CPPF content were measured. All the preliminary results suggested that the CPPF/unsaturated poly(ester‐amide) composites might be potentially used as a new type of bone‐fixation material. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Rheological behavior of LDPE/CaCO3 blends containing EAA
Authors: Dong Aiqin , Yin Qin , Xie Jie , Li Dan , Yin Yeping
Published: July 2008

Calcium carbonate (CaCO3) filler particles were surface treated with organic titanate (TTS), a coupling agent. The composites were prepared by blending low‐density polyethylene (LDPE) with the surface‐modified fillers at various weight ratios. Ethylene‐acrylic acid copolymer (EAA) was added to improve the adhesion of LDPE to fillers. A capillary rheometer was used to evaluate rheological properties of the LDPE/CaCO3/EAA blends. The blends were shown to be pseudoplastic with shear thinning behavior. When CaCO3 was modified by TTS (<2 wt%), the viscosity of the blends decreased quickly, and, addition of a small amount of EAA (<6 wt%) could also decrease the viscosity of the blends. The thermal behavior of these materials is evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The addition of a small amount of EAA and TTS enhances the stabilization of the blends, which could be explained by the “ball belling” action. The effects of temperature, TTS content, CaCO3 granule size, and content on the rheological property were also studied. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Preparation and characteristics of pH‐sensitive derivated dextran hydrogel nanoparticles
Authors: Zhang Hui , Wu Hong , Fan Li , Li Fei , Gu Chun‐hu , Jia Min
Published: July 2008

An optimized procedure was used to prepare erythromycin (EM)‐loaded pH‐sensitive glycidyl methacrylate derivatized dextran (dex‐GMA)/acrylic acid (AAc) nanoparticles. The size distribution and drug release profile at different pH demonstrated that poly(dex‐GMA/AAc) nanoparticles possessed pH‐sensitivity. At pH 1.2, the mean diameter of nanoparticles was about 60 nm. While at pH 7.4 it increased approximately to 250 nm. The release of EM was about 7% of initial loading after 2 h at pH 1.2. However, at pH 7.4 it reached to 17.8%, 30.9% after 2 and 6 h, respectively. The results demonstrated that poly(dex‐GMA/AAc) nanoparticles could release EM slightly while passing through acerbic stomach, whereas in the alkaline intestine the drug is released considerably. The prepared nanoparticles were partially degradable and also had satisfactory biocompatibility. This study suggests that the poly(dex‐GMA/AAc) nanoparticles are potential colon‐specific targeting carriers, which can keep promising pharmaceutical dosage form of EM. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers