bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Increased Cerebral myo‐Inositol in the Dementia of Down Syndrome
Authors: Shonk Truda , Ross Brian D. 
Published: March 2007

AbstractThe purpose of this study was to determine cerebral myo‐inositol (ml) in adults with Down syndrome (DS), and to trace the chronobiology of DS to Alzheimer disease (AD). AD has characteristic neuropathology of neurofibrillary plaques and tangles; indirect evidence links this to earlier deposition of β‐amyloid. Elevated ml, which distinguishes AD from other common dementias, is also elevated in 23 young patients who have DS without dementia. In one patient who has DS with dementia, ml is elevated and N‐acetylaspartate (NAA) decreased. The similarity to AD is striking and may suggest a progressive neurochemical disorder in which elevation of ml precede loss of NAA in both AD and DS.
3D coronary MR angiography in multiple breath‐holds using a respiratory feedback monitor
Authors: Wang Yi , Grimm Roger C. , Rossman Phillip J. , Debbins Josef P. , Riederer Stephen J. , Ehman Richard L. 
Published: March 2007

AbstractTo reduce respiratory blur and ghosts in 3D coronary imaging, a data acquisition scheme using consistent multiple breath‐holds was implemented. A navigator echo was acquired and processed in real time to dynamically measure diaphragm position. This information was provided as a visual prompt to the patient to maintain consistency in breath‐hold levels such that the variation range of diastolic heart position was less than 2 mm. Preliminary results indicate that this multiple breath‐hold acquisition scheme, compared with acquisition under respiration, can significantly reduce blur and ghost artifacts in 3D coronary imaging.
3D Echo Planar Imaging: Application to the Human Head
Authors: Abduljalil Amir M. , Aletras Anthony H. , Robitaille Pierre‐Marie 
Published: March 2007

AbstractIn this work, the authors present 3D images acquired from the human head using echo planar encoding for two of the three dimensions of k‐space. The third dimension of k‐space is filled by selecting and phase encoding a slab of spins as in conventional 3D steady state (GRASS based) acquisition regimens. Using this approach, a 128 x 64 x 64 3D data matrix could be obtained in 3.4–4.7 sec using effective TE values of 24 and 34 ms, respectively. High quality 3D images could be acquired once phase ghosts present on 2D images were minimized through proper adjustments of scanner hardware.
Optimized gradient waveforms for spiral scanning
Authors: King Kevin F. , K. F. Foo Thomas , Crawford Carl R. 
Published: March 2007

AbstractSpiral scanning gradient waveforms can be optimized with respect to blurring from off‐resonance effects by minimizing the readout time. This is achieved by maximizing the gradient amplitude during the scan so that the edge of k‐space is reached as quickly as possible. Gradient hardware constraints are incorporated by considering a circuit model for the gradient coil and amplifier. The optimized gradient waveforms are determined by a set of coupled differential equations. The resulting solutions have shorter readout time than solutions that do not consider the circuit model.
Analytical resolution and noise characteristics of linearly reconstructed magnetic resonance data with arbitraryk‐space sampling
Authors: Pipe Mr James , , Duerk Jeffrey L. 
Published: March 2007

AbstractThe effects of time‐varying readout gradients and data sampling with variable dwell times in magnetic resonance imaging are examined. General reconstruction formulas are given for linear reconstruction with even k‐space weighting. Closed analytic expressions for estimator variance are given for data sampling during arbitrary gradient waveforms with both uniform kx step size and nonuniform kx step size. It is shown that estimator variance increases (the signal‐to‐noise ratio decreases) for nonconstant gradient waveforms. It is also shown that estimator variance is greater for constant k‐space sampling strategies than for constant time sampling at the Nyquist rate. Data collected during a triangular readout gradient waveform, with either constant time or constant k‐space sampling, versus conventional (constant gradient) collection confirms theoretical predictions for estimator variance. The benefits of collecting data while the readout gradient is ramping up from and down to zero are discussed.
Oximetry by dynamic nuclear polarization
Authors: Grucker Daniel , Guiberteau Thierry , Eclancher Bernard 
Published: March 2007

AbstractThis study describes quantitatively the effect of O2 on the dynamic nuclear polarization (DNP) of water protons. It is shown theoretically how DNP enhancement is altered by the paramagnetism of O2. The nonlinear effect of oxygen on the enhancement factor has been approximated by a first order expression that provides accurate predictions of the experimental results obtained with phosphate‐buffered solutions of 2,2,6,6 tetramethyl‐4‐oxo‐piperidine‐N‐oxyl. The proton relaxation rates and DNP line width were measured for nitroxide concentrations ranging from 0.5 to 10 mM and for oxygen partial pressures ranging from 0 to 760 mmHg. A method is suggested for the calculation of the nitroxide and oxygen concentrations of a sample, based on two measurements, one with on‐resonance EPR irradiation, the other with slightly off‐resonance irradiation. Although the correlation between the values for the actual and calculated oxygen concentrations is good, the accuracy of the calculated oxygen concentration values remains poor, because of the large number of parameters involved in this calculation.
Mapping the biodistribution and catabolism of 5‐fluorouracil in tumor‐bearing rats by chemical‐shift selective 19F MR imaging
Authors: Brix Gunnar , Bellemann Matthias E. , Haberkorn Uwe , Gerlach Ludwig , Bachert Peter , Lorenz Walter J. 
Published: March 2007

AbstractA chemical‐shift selective (CHESS) 19F MR imaging technique was used to map selectively the antineoplastic drug 5‐fluorouracil (5‐FU) and its major catabolite α‐fluoro‐β‐alanine (FBAL) in tumor‐bearing rats. The pulse sequence employed a CHESS RF saturation pulse to suppress either the 5‐FU or the FBAL resonance before the other component in the two‐line 19F MR spectra was measured. Selective 5‐FU and FBAL images with a spatial resolution of 10 x 10 x 15 mm3 (1.5 ml) were obtained in 40 min from six ACI rats with implanted Morris hepatoma. Because the transmitter frequency could always be set to the Larmor frequency of the 19F resonance employed for imaging, the images were free of chemical‐shift artifacts in readout and slice‐selection direction. Whereas FBAL appeared only in the liver, the kidneys, and the bladder, 5‐FU could also be detected in all major organs and in the muscular system. In the Morris hepatomas, a small 5‐FU uptake and no FBAL accumulation were measured. The CHESS 19F MRI technique provides useful physiological and biochemical data on the biodistribution of the antineoplastic drug 5‐FU and on the different catabolic activities of the tissues.
Dynamic Gd‐DTPA enhanced MRI measurement of tissue cell volume fraction
Authors: Donahue Kathleen M. , Weisskoff Robert M. , Parmelee David J. , Callahan Ronald J. , Wilkinson Robert A. , Mandeville Joseph B. , Rosen Bruce R. 
Published: March 2007

AbstractA new technique for measuring tissue cellular volume fraction, based on an improved modeling of the dynamic distribution of Gd‐DTPA and the effect of proton exchange, is described. This technique uses peak T1 enhancement and blood Gd‐DTPA concentration to compute tissue cellular volume fraction. The feasibility of this technique is demonstrated with computer simulations that explore the limits of the simplifying assumptions (small vascular space, slow vascular‐extravascular proton exchange), and by direct comparison of MR and radionuclide cell fraction measurements made in muscle, liver, and tumor tissue in a rat model. The computer simulations demonstrate that with slow to intermediate vascular proton exchange and vascular fractions less than 10% the error in our cell fraction measurements typically remains less than 10%. Consistent with this prediction, a direct comparison between MR and radionuclide measurements of cell fraction demonstrates mean percent differences of less than 10%: 1.9% in muscle (n = 4); 9% in liver (n = 1) and 9.5% in tumor (n = 4). Similarly, for all rats studied, the MR‐measured cell fractions (muscle (0.92 ± 0.04, n = 20); liver (0.76 ± 0.11, n = 9); whole tumor (0.69 ± 0.15, n = 22)) agree with the cell fraction values reported in the literature. In general, the authors' results demonstrate the feasibility of a simple method for measuring tissue cell fraction that is robust across a broad range of vascular volume, flow, and exchange conditions. Consequently, this method may prove to be an important means for evaluating the response of tumors to therapy.
Correction of motional artifacts in diffusion‐weighted images using a reference phase map
Authors: Uluǧ Aziz MÜFit , Barker Peter B. , Zijl Peter C. M. Van 
Published: March 2007

AbstractA method of correcting motional artifacts in diffusion‐weighted images is described. Motion causes changes in the phase of the k‐space NMR signal and thereby introduces positional shifts (or ghosts) in the spatial domain. By correcting the phase of the NMR signal before Fourier transformation, the image sharpness is greatly enhanced. The new method measures the phases of the NMR signal once and stores this phase information in a phase map. Subsequent images with motional artifacts are corrected during postprocessing using this reference phase map.
Calculation of signal intensities in hybrid sequences for fast NMR imaging
Authors: Deichmann Ralf , Adolf Holger , Nöth Ulrike , Kuchenbrod Erwin , Schwarzbauer Christian , Haase Axel 
Published: March 2007

AbstractA number of techniques that recently have been used for fast NMR‐imaging are based on a hybrid sequence of echo planar imaging (EPI) and FLASH imaging: after each NMR excitation several k‐space lines are measured. The complete k‐space is covered by performance of several excitations. It has been observed that there is usually an optimal hybrid sequence that maximizes the signal‐to‐noise ratio. In this work, a method is presented that allows a determination of the optimal sequence as a function of the relaxation times T1 and T2*.
The apparent diffusion constant measured by mri correlates with po2 in a rif‐1 tumor
Authors: Dunn Jeff F. , Ding Shujun , O'Hara Julia A. , Liu Ke J. , Rhodes Erik , Weaver John B. , Swartz Harold M. 
Published: March 2007

AbstractAs tissue oxygen tension (pO2 is an important variable in cancer therapy, it would be of major clinical benefit to be able to measure pO2 noninvasively. Current methods for determining pO2 in clinical settings are limited to superficial tumors. The authors measured the apparent diffusion constant (ADC) in an implanted murine fibrosarcoma (RIF‐1) using magnetic resonance imaging and correlated the ADC with tissue pO2 measured by electron paramagnetic resonance oximetry. The ADC correlates significantly with tissue pO2 in this tumor (r = 0.89; n = 14) and so may provide a noninvasive index of pO2 in tumors.
MR pulsatility measurements in peripheral arteries: Preliminary results
Authors: Krug Barbara , Kugel Harald , Harnischmacher Urs , Heindel Walter , Schmidt Rainer , Krings Friedrich 
Published: March 2007

AbstractPhase contrast flow velocity measurements were performed in six healthy volunteers and 30 patients with arteriosclerotic disease. The iliac arteries were investigated in 8 cases and the femoral arteries in 28 cases. In the first 24 patients, 16 evenly distributed data sets were acquired during one cardiac cycle. In the last 12 patients, a trigger pulse followed by the acquisition of 30 evenly distributed data sets was applied every second heart beat. This procedure allowed data to be acquired over a full heart cycle without any acquisition gap. The measured flow velocities were displayed as function of time. Systolic acceleration, postsystolic deceleration and pulsatility of flow velocity were calculated and compared with stenosis grades determined from DSA angiograms. Flattening of the flow velocity patterns was found to correlate with the local severity of arteriosclerotic disease.
Utilization of carbon from dietary polyunsaturates for brain cholesterol synthesis during early postnatal development in the rat: a 13c nmr study
Authors: Likhodii Sergei S. , Cunnane Stephen C. 
Published: March 2007

AbstractIncorporation of 13C from a dietary precursor into cholesterol was studied in neonatal rats. Rats were given uniformly 13C‐enriched polyunsaturated fatty acids intragastrically and total lipid extracts of liver and brain were analyzed by 13C‐NMR 1,4, 8, and 15 days later. 13C‐enrichment was detected in brain but not in liver cholesterol. Maximal 13C‐labeling was observed 4 days after injection of the label. Spectra revealed that 70% of newly incorporated 13C had 13C as an adjacent neighbor, the other 30% had 12C as the neighbor. Double quantum NMR revealed the arrangement in the cholesterol skeleton of the 13C‐13C pairs transferred from precursors to cholesterol. Desmosterol, an intermediate of cholesterol synthesis, was identified in the spectra of brain lipids. Comparison of 13C‐13C unit arrangements in both cholesterol and desmosterol allowed carbons 26 and 27 of desmosterol to be unambiguously assigned.
Changes of relaxation times (T1, T2) and apparent diffusion coefficient after permanent middle cerebral artery occlusion in the rat: temporal evolution, regional extent, and comparison with histology
Authors: Hoehn‐berlar Mathias , Eis Manfred , Back Tobias , Kohno Kanehisa , Yamashita Katsuhiro 
Published: March 2007

AbstractThe quantitative NMR parameters T1, T2, p, and apparent diffusion coefficient (ADC) were determined during the 7 h after middle cerebral artery occlusion in rats. In the normal caudate‐putamen (CP), 869 ± 145 ms and 72 ± 2ms for T1 and for T2, respectively, were found; the corresponding values for cortex were 928 ± 117 ms and 73 ± 2 ms. The ADC showed significant dependence on gradient direction: diffusion along x resulted in 534 ± 53 μm2/s (CP) and 554 ± 62 μm2/s (cortex), and along y in 697 ± 58 μm2/s (CP) and 675 ± 53 μm2/s (cortex). In the ischemic territory, a continuous increase over time of both relaxation times was observed in the CP, leading to an increase of 29 ± 20% (T1) and 51 ± 41% (T2 above control level. ADC dropped to 63 ± 15% of control in the CP and to 74 ± 4% of control in the temporal cortex. No significant change was noted in proton density during the observation period. Strongest ADC reduction was in the center of the ischemic territory (≤ 60% of control) surrounded by a region of lesser reduction (≤ 80% of control). During the early part of the study, the area of reduced ADC was larger than that of elevated relaxation times. Toward the end of the experiment, the area of increased relaxation times approached that of decreased ADC at ≤ 80% of control. Good agreement of histological presentation of infarct with the total area of decreased ADC (≤ 80%) was demonstrated.
Contrast optimization of fluid‐attenuated inversion recovery (flair) imaging
Authors: Rydberg John N. , Riederer Stephen J. , Rydberg Charlotte H. , Jack Clifford R. 
Published: March 2007

AbstractThe optimization of contrast is considered for the fluid‐attenuated inversion recovery (FLAIR) MRI pulse sequence, specifically the contrast of multiple sclerosis (MS) to white matter (WM). A performance bound is identified at 1.5 Tesla as that provided using an inversion time (TI) of 2900 ms. It is shown that TR/TI times exceeding 11000/2600 ms provide about 90% of the MS‐WM contrast possible theoretically. The commonly reported TR/TI combination of 6000/2000 provides only about 60%. For TR times exceeding 8000 ms, an echo time (TE) of 140 ms is at or near optimum. Use of TR/TI times less than 9000/2400 lacks efficiency in multisection imaging. Predicted relative contrast performance of TR/TI 11000/2600 versus 6000/2000 was evaluated in seven patients with known MS lesions, and measurements closely matched theoretical predictions. It is strongly recommended that for near optimum contrast and high multisection efficiency, FLAIR should be performed with TR/TI times exceeding 10000/2500 ms.
Sleep disruption frequency in rheumatoid arthritis: Perceived stress predicts poor outcome over one year
Authors: Treharne G. J. , Lyons A. C. , Hale E. D. , Douglas K. M. J. , Goodchild C. E. , Booth D. A. , Kitas G. D. 
Published: March 2007

AbstractBackground: Sleep is an important daily process that can be disrupted by chronic illnesses including rheumatoid arthritis (RA).Aims: We tested whether demographic, medical and psychological factors act as predictors of change in frequency of sleep disruption associated with RA.Methods: A cohort of 129 White British people with RA (mean duration of RA 7.19 years; mean age 55.40 years; 75% women) was followed for one year. Self‐report questionnaires were employed to record demographic information and assess participants' sleep disruption (on a 4‐point frequency scale), morning stiffness (duration), pain and fatigue (visual analogue scales), impact of disability, anxiety, depression, stress, coping, illness perceptions and self‐efficacy. Hospital notes were reviewed for duration of RA, antidepressant use and comorbidity.Results:  Participants were split into those with sleep disruption that was consistently infrequent or decreasing in frequency (n = 56; 43%) and those with sleep disruption that was consistently frequent or increasing in frequency (n = 73; 57%). Results of a logistic regression demonstrated that greater perceived stress at baseline predicted sleep disruption that was consistently frequent or increasing in frequency over the year. Change in sleep disruption frequency was not predicted by any other assessed variable. Perceived stress at the end of the year was not predicted by change in frequency of sleep disruption.Conclusions: Self‐reported frequency of sleep disruption among people with RA relates to perceived stress. Psychoeducational programmes that help people with RA manage their stress may be a non‐pharmacological method of improving sleep quality and therefore merits testing in specific interventional studies. Copyright: © 2007 John Wiley & Sons, Ltd.
Rendez‐vous search on a rectangular lattice
Authors: Ruckle William H. 
Published: March 2007

AbstractIn a rendez‐vous search two or more teams called seekers try to minimize the time needed to find each other. In this paper, we consider s seekers in a rectangular lattice of locations where each knows the configuration of the lattice, the distribution of the seekers at time 0, and its own location, but not the location of any other. We measure time discretely, in turns. A meeting takes place when the two seekers reach the same point or adjacent points. The main result is that for any dimension of lattice, any initial distribution of seekers there are optimal strategies for the seekers that converge (in a way we shall make clear) to a center. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007
A modified operator splitting (OS) method for collaborative structural analysis (CSA)
Authors: Tada Motohide , Pan Peng 
Published: March 2007

AbstractThe collaborative structural analysis (CSA) system is capable of performing highly sophisticated structural analyses utilizing the beneficial features of existing individual structural analysis programmes. It requires a time consuming static condensation procedure if adopting an implicit integration scheme. The operator splitting (OS) method, which does not require the tangential stiffness, can be used to improve the system efficiency. Furthermore, the conventional OS method is not able to provide enough numerical stability, particularly for the analyses considering geometrical non‐linearity. Thus, improvement is needed. To this end, a modified OS method is proposed, which treats unbalanced forces in the current step as pseudo‐external forces in the immediate following step. In this paper, first, the conventional OS method is reformulated in an incremental form, and a CSA scheme based on it is proposed. Second, a modified OS method is developed to improve the numerical stability. Third, a fixed‐base steel column with a lumped mass assigned at its top is analysed using the CSA system as a numerical example. It is found that the OS methods are effective for CSA, and the modified OS method exhibits better numerical stability than the conventional one for the analysis considering geometrical non‐linearity. Copyright © 2007 John Wiley & Sons, Ltd.
Oscillotonometry: A simple non‐invasive method of differentiating proximal arterial obstruction from distal microangiopathy in the vascular assessment of diabetics
Authors: Tovey F I , Karanjia N , Plant G R , Rees M 
Published: March 2007

AbstractIn diabetic patients with ischaemic feet a frequent clinical problem is the differentiation between those with distal microangiopathy alone and those with proximal arterial inflow obstruction.Doppler pressure measurement is of assistance but there is a significant subgroup who have proximal obstruction despite the findings of a high ankle systolic pressure. These patients have stiff arterial walls and the Doppler cuff does not compress them normally.If oscillotonometry is performed, a low range of swing suggests an inflow obstruction whereas a high range suggests a good inflow. This differentiation enables suitable patients to be selected for angiography and possible angioplasty or bypass surgery.
Diabetes education and schools
Authors: Burden Mary L , Burden A C , Butterworth S 
Published: March 2007

AbstractA questionnaire was sent to schools, prisons and industries in the Trent region using addresses supplied by diabetes health visitors or specialist nurses to discover the level of diabetes education and whether it was thought to be adequate. Forty four (59%) of the 75 responded. Twenty four schools had received literature and all found it useful or adequate. However only 50% felt there was a need for educational facilities for children with diabetes within their school, but 56% thought there was a need for educational facilities for staff who deal with children with diabetes.
A combination of once daily insulin and glibenclamide therapy in patients with type 2 diabetes and secondary drug failure
Authors: Fonseca V A , D'Souza V. , Bell J L , Dandona P 
Published: March 2007

AbstractTwenty eight patients with non‐insulin‐dependent diabetes mellitus (NIDDM) who were not adequately controlled with maximum doses of sulphonylureas and metformin (Group I; n=13) or with insulin injections (Group II; n=15) were treated with a combination of insulin injections in the morning and glibenclamide, a sulphonylurea, in the evening. Patients in Group I had significantly lower glycosylated haemoglobin (HbA1) and post‐breakfast blood glucose concentrations after treatment with the combination. Similarly, HbA1 and post‐breakfast blood glucose concentrations improved in Group II patients. Nocturnal hypoglycaemia resolved. The removal of glibenclamide from treatment in both groups resulted in a significant increase in glycosuria and abnormal fasting blood glucose concentrations.We conclude that in patients with non‐insulin‐dependent diabetes and drug failure, the institution of treatment with a combination of insulin in the morning and sulphonylurea in the evening produces adequate control of diabetes, and that the removal of the evening dose of sulphonylurea results in marked hyperglycaemia in the fasting state.