bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton overhauser enhancements in human cardiac phosphorus NMR spectroscopy at 1.5 T
Authors: Bottomley Paul A. , Hardy Christopher J. 
Published: March 2007

AbstractNarrowband irradiation of water protons with a surface coil yields significant nuclear Overhauser enhancement (nOe) of phosphocreatine (PCr) and some adenosine triphosphate (ATP) moieties in localized and unlocalized phosphorus (31P) NMR spectra from chest and heart muscle. In seven normal subjects at 1.5 T the nOe values were 0.6 ± 0.3, 0.6 ± 0.3, 0 ± 0.3, and 0.3 ± 0.2 for myocardial PCr, γ‐ATP, α‐ATP, and β‐ATP, respectively, not significantly different from those in chest muscle. Distortion of the measured PCr/ATP ratios due to differences in the nOe may require accurate correction to realize the full benefit of the effect in studies involving quantitative intergroup comparisons. © 1992 Academic Press, Inc.
Phosphorus‐31 magnetic resonance imaging of hydroxyapatite: A model for bone imaging
Authors: Ackerman Jerome L. , Raleigh Daniel P. , Glimcher Melvin J. 
Published: March 2007

AbstractOne‐dimensional 31P nuclear magnetic resonance images (projections) of syntheticcalcium hydroxyapatite, Ca10(OH)2(PO4)6, have been obtained for samples on the order of 0.5 to 1.0 cm in linear extent at 7.4 T magnetic field strength. Because of the solid state nature of these samples, short 31P spin‐spin relaxation times under 1 ms occur, necessitating echo times of 1 ms and phase‐encoding magnetic field gradient pukesshorter than 500 μs. Optimal projection quality and shortest acquisition times result from pulsedgradient phase‐encoding of the spatial dimension, using a compensating gradient pulse to cancel the distorting effects of gradient waveform transients. The exceedingly long 31P spin‐lattice relaxation times could lead to potentially intolerable image acquisition times; these have been reduced with a flipback pulse technique. In addition to holding great potential as a novel research tool in the study of biomineralization of those organisms containing calcium phosphate solid phases, these methods should be of general utility in the multinuclear imaging of a wide variety of solids of interest in biophysics and materials science.
Hadamard spectroscopic imaging technique as applied to study human calf muscles
Authors: Goelman Gadi , Walter Glenn , Leigh John S. 
Published: March 2007

AbstractIn vivo results obtained by the B1 insensitive Hadamard spectroscopic imaging multivolume technique used with a surface coil are shown. The functional behavior of different human calf muscles during exercise was determined and the Pi/PCr ratio in each calf muscle, during steady‐state conditions, was measured as a function of work level. Different levels of metabolic and physical activity were observed at the three calf muscles. © 1992 Academic Press, Inc.
Analysis of phospholipids in brain tissue by 31P NMR at different compositions of the solvent system chloroform‐methanol‐ water
Authors: Edzes Hommo T. , Teerlink Tom , Knaap Marjo S. Van Der , Valk Jaap 
Published: March 2007

AbstractBrain phospholipids can be quantitated by high‐resolution 31P NMR of crude brain tissue extracts in the solvent system chloroform‐methanol‐water (+EDTA) which was introduced recently (P. Meneses and T. Glonek, J. Lipid Res. 29, 679 (1988)). Phospholipid resonance positions depend on the type of tissue extract and on solvent composition. The effects of systematic variation of the solvent system on phospholipid NMR profiles are presented. Resolution can be optimized by adjustment of the solvent composition. Virtually all phospholipid classes can be resolved, and the major phospholipids in brain: sphingo‐myelin and phosphatidyl‐choline, ‐serine, ‐inositol, ‐ethanolamine, and ‐ethanolamine plasmalogen can be quantitated easily. Additional resonances have been assigned to phosphatidylcholine plasmalogen, alkylacyl‐phosphatidylcholine and phosphatidylinositolbis‐phosphate. NMR offers a rapid method for quantitative analysis of the phospholipid composition in brain tissue which requires minimum sample handling.
Analysis of hybrid imaging techniques
Authors: Ortendahl Douglas A. , Kaufman Leon , Kramer David M. 
Published: March 2007

AbstractHybrid imaging techniques have been proposed as a means of decreasing imaging time without the cost and technical constraints of echo planar imaging. With this technique phase encoding measurements acquired at different echo times in more than one multiecho experiment are used to form a single image. This study analyzes the trade‐offs which occur in the selection of this technique over more conventional imaging in terms of signal/noise, contrast, resolution, imaging time, and efficiency. Hybrid imaging is shown to be advantageous when raw speed is essential such as in abdominal or pediatric imaging. When coverage rather than time becomes the important factor, hybrid imaging does not offer a significant advantage over conventional methods. T2 decay will also serve as a roll‐off filter which will reduce the spatial resolution, but not the noise, for short TE hybrid imaging.
Direct measurement of spin‐lattice relaxation times of Phosphorus Metabolites in Human Myocardium
Authors: Neubauer S. , Krahe T. , Schindler R. , Hillenbrand H. , Entzeroth C. , Horn M. , Bauer W. R. , Stephan T. , Lackner K. , Haase A. , Ertl G. 
Published: March 2007

AbstractT1 values of phosphorus metabolites visible in human cardiac 31P‐MR spectra were determined in 12 volunteers at 1.5 T. Consecutive spectra were acquired with varying pulse repetition time (TR) from 1.6 to 24 s; volume selection was achieved with ISIS. T 1's of creatine phosphate (CP), [γ‐P], [α‐P], and [β‐P] ATP, 2‐3 diphosphoglycerate, and phosphodiesters were 6.1 ± 0.5, 5.4 ± 4 0.5, 5.5 ± 0.5, 5.8 ± 1.0, 7.6 ± 1.0, and 5.0 ± 1.0 s, respectively. CP/ATP ratios showed little change with varying TR; linear regression of CP/ATP vs TR was of borderline significance (r = 0.28, P = 0.06). T1'S for CP and ATP were also determined in standard solution (20 mM CP, 10 mM ATP) yielding TIcp of 8.7 ± 0.2 and T1[γ‐P]‐atpof 9.9 ± 0.7 s. Thus, T1'S for CP and ATP were similar at 1.5 T in both human heart and standard solution. In human cardiac 31P‐MR spectra, CP/ATP ratios may need little correction for partial saturation.
Automatic in vivo nmr data processing based on an enhancement procedure and linear prediction method
Authors: Diop A. , Briguet A. , Graveron‐Demilly D. 
Published: March 2007

AbstractA new data processing method for in vivo NMR data quantitation is presented. This method (EPLPSVD) is based on the enhancement procedure (EP) proposed by J. A. Cadzow (IEEE Trans. Acoust. Speech Signal Process. 36, 49, 1988) followed by the usual linear prediction method using the singular value decomposition (LPSVD). The evaluation of this protocol is performed using synthesized 31P signals with different signal‐to‐noise ratios. A Monte‐Carlo simulation as a function of signal‐to‐noise ratio (SNR) has proved that EPLPSVD leads to unbiased estimated values of parameters. Then the Cramer‐Rao method yields reliable confidence intervals for the estimated parameters. The estimates of NMR parameters using EPLPSVD are reliable and accurate for SNR ≥ 1.2 while the LPSVD method failed for SNR ≤ 4. This protocol is applied to analyze automatically a series of 31P free induction decays obtained from the human gastrocnemius muscle during exercise. Spectral parameters with their confidence intervals, curves of relative intensity variations in phosphocreatine and inorganic phosphate, and pH curves are automatically provided.
T1 and t2 of ferritin at different field strengths: effect on mri
Authors: Vymazal Josef , Brooks Rodney A. , Zak Olga , Mcrill Connie , Shen Cynthia , Chiro Giovanni Di 
Published: March 2007

AbstractNuclear magnetic relaxation times T1 and T2 were measured in ferritin solutions at field strengths from 0.04 to 1.5 T.T1 was relatively constant, but 1/T2 increased linearly with field strength, in agreement with earlier MRI observations in the monkey brain. This finding supports the theory that ferritin is responsible for T2 shortening in brain nuclei containing iron. The linear dependence of 1/T2 on magnetic field is unique and not explained by present theories of the magnetic properties of ferritin.
An Investigation of Tumor 1H Nuclear Magnetic Resonance Spectra by the Application of Chemometric Techniques
Authors: Howells S. L. , Maxwell R. J. , Peet A. C. , Griffiths J.R. 
Published: March 2007

Abstract1H nuclear magnetic resonance (NMR) spectra of tumors and normal tissue include signals from all hydrogen‐containing metabolites and can therefore be considered multicomponent multivariate mixtures. We have obtained 1H spectra from perchloric acid extracts of three normal tissues (liver, kidney, and spleen) and five rat tumors (GH3 prolactinoma, Morris hepatomas 7777 and 9618a, LBDS1 fibrosarcoma, and Walker 256 carcinosarcoma). We have applied several different chemometric methods to analyze the data. First, we used principal component analysis, cluster analysis, and an optimized artificial neural network to develop a classification rule from a training set of samples of known origin or class. The classification rule was then assessed using a set of unknown samples. We were able to successfully determine the class of each unknown sample. Second, we used the chemometric techniques of factor analysis followed by target testing to investigate the underlying biochemical differences that are detected between the classes of samples.© 1992 Academic Press,Inc.
A new approach to study cardiac motion: The optical flow of cine MR images
Authors: Amartu Sundar C. , Vesselle Hubert J. 
Published: March 2007

AbstractWe present a novel approach to study the intricate motion of the heart using the optical flow technique applied to cine MR images. The method uses image brightness variations between consecutive frames to compute in‐plane displacements or velocities of moving image features. The dense velocity field thereby obtained throughout the myocardial wall allows to not only characterize segmental left ventricular wall motion but also to resolve “fine” motion such as intramural differences in displacements and therefore in thickening. Other subtle features of systole like the descent of the base towards the apex or the counterclockwise rotation of the apex with respect to the base can also be detected by the algorithm. Contrary to other techniques proposed earlier, this noninvasive method presents the additional advantages of not requiring any special pulse sequence nor well defined endocardial and epicardial outlines.
Effect of glucose and confluency on phosphorus metabolites of perfused human prostatic adenocarcinoma cells as determined by31P MRS
Authors: Macdonald Jeffrey M. , Kurhanewicz John , Dahiya Rajvir , Espanol Maryceline T. , Chang Lee‐Hong , Goldberg Beth , James Thomas L. , Narayan Perinchery 
Published: March 2007

AbstractA series of perfused cell31P MRS studies were conducted using a well established human prostate adenocarcinoma cell line (DU 145) at different phases of growth, and exposed to varying glucose concentrations during growth. The spectral characteristics of perfused DU 145 cells were compared with the same cells grown in nude mice (xenografts). Perfused DU 145 cells had lower levels of inorganic phosphate and phos‐phocreative relative to in vivo nude mice xenografts. 31P MR spectra obtained from perfused cells at different phases of growth and exposed to varying glucose concentrations during grown suggest that increases in diphosphodiester levels are associated with high glucose concentrations and confluency. Perfused DU 145 cells grown in 5.5 mm glucose and harvested at log phase of growth best reflected the phosphorus MR spectra of the same cell line grown in nude mice.
Correction of translational motion artifacts in multi‐slice spin‐echo imaging using self‐calibration
Authors: Zang L.‐H. , Fielden J. , Wilbrink J. , Takane A. , Koizumi H. 
Published: March 2007

AbstractIn this paper, we describe a method for detecting and correcting in‐plane bulk translational motion in multislice spin‐echo imaging using self‐calibration and postprocessing. A constant phase encoding offset between slices is used to evenly spread out the low spatial frequency echoes to allow accurate motion detection by self‐calibration. Motion detection in both x and y directions is achieved by interchanging the readout and phase encoding directions for the alternate slices. Displacements are determined by cross correlating the modulus of each 1D transformed echo with a reference box car function whose width equals that of the imaged object. In addition, phase errors induced by the velocity in the readout direction are estimated and corrected using the displacement data. The results obtained from knee studies at 0.5 T and 1.5 T show that the artifacts due to translational motions are significantly suppressed upon correction. The method does not require any additional pulses or time, and the data processing can be easily implemented.
Changes in double quantum filtered sodium intensity during prolonged ischemia in the isolated perfused heart
Authors: Hutchison R. B. , Huntley J. J. A. , Zhou H. Z. , Ciesla D. J. , Shapiro J. I. 
Published: March 2007

AbstractIntracellular sodium (Nal) concentrations rose immediately and progressively during ischemia in the isolated heart. The intracellular double quantum filtered sodium coherence (DQ) intensity also increased during ischemia. However, when normalized for Nai, the DQ intensity began to fall after 40 min of ischemia, and remained depressed during reperfusion.
Noninvasive analysis of aldose reductase activities in rat testis: 3‐FDG NMR spectroscopy and imaging
Authors: Nakada Tsutomu , Kwee Ingrid L. 
Published: March 2007

AbstractNoninvasive investigation of aldose reductase activities in rat testis was performed using 3‐fluoro‐3‐deoxy‐D‐glucose (3‐FDG) and nuclear magnetic resonance (NMR) spectroscopy/imaging. Quantitative determination of testis aldose reductase activities, expressed as the sorbitol index, showed a value similar to that of brain. Sorbitol imaging demonstrated aldose reductase activities in testis to be confined primarily to the central region of this organ. The 3‐FDG 19F NMR method appears to have clinical potential in the evaluation of testicular function, especially that of spermatogenesis, noninvasively.
Development and characterization of an ergometer to study the bioenergetics of the human quadriceps muscle by 31P NMR spectroscopy inside a standard MR scanner
Authors: de Suso José M. Gonz Ález , Bernús Gema , Alonso Julio , Alay Albert , Capdevila Antoni , Gili Jaume , Prat Joan A. , Arús Carles 
Published: March 2007

AbstractA description is given of an ergometer made of nonmagnetic materials which fits into a standard whole body MR magnet. T2‐weighted images show that exercise is highly specific for quadriceps muscles. The ergometer permits the noninvasive study of T2‐related changes in the proton images of the leg as well as changes occurring in muscle bioenergetics during exercise and recovery.
Nontriggered magnetic resonance velocity measurement of the time‐average of pulsatile velocity
Authors: Hofman Mark B. M. , Kouwenhoven Marc , Sprenger Michiel , van Rossum Albert C. , Valk Jaap , Westerhof Nico 
Published: March 2007

AbstractThe feasibility of the determination of the time‐average of pulsatile velocity obtained via a nontriggered magnetic resonance (MR) acquisition is studied. The advantage of this method, in comparison with a triggered acquisition, is a considerable reduction (≈15×) in acquisition time. However, pul‐satility causes image artifacts, known as ghosts, and the Fourier transform technique required for the imaging procedure accomplishes time‐averaging of the complex MR signal. Both effects can result in errors in the velocity determined. Calculations show that these errors depend on the velocity time function and the acquisition parameters. In vivo comparison of triggered and nontriggered MR velocity measurements in the femoral artery of volunteers (n = 7) shows larger statistical and systematic errors in the latter, which depend on the excitation angle. Therefore, this nontriggered average velocity measurement is only useful as a fast and rough estimation of the time‐averaged velocity.
In vivo1H chemical shift imaging of silicone implants
Authors: Pfleidere Bettina , Ackerman Jerome L. , Garrido Leoncio 
Published: March 2007

AbstractIn order to study the aging process (i.e., silicone migration, fat infiltration) of silicone (polydimethylsiloxane, PDMS) based biomaterials in living subjects by NMR imaging a hybrid 1H selective excitation and saturation chemical shift imaging technique (IR/CHESS‐CSSE) has been developed. This sequence allows selective mapping of the distribution of silicone protons in vivo, while suppressing the contributions of fat and water. Our results indicate that a combined inversion recovery and CHESS pulse, followed by a spoiler gradient, must be applied to suppress all contributions of fat protons to the NMR signal. The sensitivity of our experiments allows the detection of a chemically unchanged silicone concentration of 5% in a voxel of 0.9 mm3 at a signal/noise ratio of 2.
High‐Field MR microscopy using fast spin‐echoes
Authors: Zhou Xiaohong , Cofer Gary P. , Suddarth Steve A. , Allan Johnson G. 
Published: March 2007

AbstractFast spin‐echo imaging has been investigated with attention to the requirements and opportunities for high‐field MR microscopy. Two‐and three‐dimensional versions were implemented at 2.0 T, 7.1 T, and 9.4 T. At these fields, at least eight echoes were collectable with a 10 ms TE from fixed tissue specimens and living animals, giving an eightfold improvement in imaging efficiency. To reduce the phase‐encoding gradient amplitude and its duty cycle, a modified pulse sequence with phase accumulation was developed. Images obtained using this pulse sequence exhibited comparable signal‐to‐noise (SNR) to those obtained from the conventional fast spin‐echo pulse sequences. Signal losses due to imperfections in RF pulses and lack of phase rewinders were offset in this sequence by reduced diffusion losses incurred with the gradients required for MR microscopy. Image SNR, contrast, edge effects and spatial resolution for three k‐space sampling schemes were studied experimentally and theoretically. One method of sampling k‐space, 4‐GROUP FSE, was found particularly useful in producing varied T2 contrast at high field. Two‐dimensional images of tissue specimens were obtained in a total acquisition time of 1 to 2 min with in‐plane resolution between 30 to 70 μm, and 3D images with 2563 arrays were acquired from fixed rat brain tissue (isotropic voxel = 70 μm) and a living rat (isotropic voxel = 117 μm) in∼4.5 h.
In Vivo localized proton NMR spectroscopy of silicone
Authors: Pfleiderer Bettina , Ackerman Jerome L. , Garrido Leoncio 
Published: March 2007

Abstract1H NMR localized spectroscopy (STEAM) can assess unambiguously the presence of free chemically unchanged silicone in animal tissue after injection of silicone oil. Although the signal—to—noise ratio obtained in 1H imaging is sufficient to detect the distribution of relatively large amounts of silicone in vivo, the specificity of silicone detection can be improved by using 1H localized spectroscopy techniques. The sensitivity of the STEAM experiments is sufficient to detect silicone at a concentration of 0.5% in a voxel of 27 mm3. Preliminary results from rats with silicone gel—filled implants show no detectable amounts of silicone in sites such as lymph nodes, the liver or the spleen, 3 or 6 months after implantation.
Stabilization of echo amplitudes in FSE sequences
Authors: Roux Patrick Le , Hinks R. Scott 
Published: March 2007

AbstractThe classical CPMG sequence and its extension as an imaging sequence, fast spin echo (FSE, based on RARE), suffer from signal magnitude variations in the early echoes when the re‐focusing pulses are not set exactly to 180°. It has been suggested that by varying the value of the nutation angle of each refocusing pulse the signal magnitude could be made constant. This article describes an algorithm permitting the generation of sequences of nutation angles yielding series of echsoes with constant signal magnitudes. This result is then usesd to design selective pulses for the FSE imaging technique.
Measurement of the extraction efficiency and distribution volume for Gd‐DTPA in normal and diseased canine myocardium
Authors: Tong Chun Y. , Prato Frank S. , Wisenberg Gerald , Lee Ting Y. , Carroll Edwin , Sandler David , Wills Jane , Drost Dick 
Published: March 2007

AbstractWe have previously shown that the myocardial Gd‐DTPA concentration ([Gd‐DTPA]t(t)) after a bolus injection of Gd‐DTPA can be predicted by the Modified Kety Equation (MKE). If [Gd‐DTPA]t(t) can be determined by MRI and the data fit to the MICE, then the distribution volume (λ) of Gd‐DTPA and the myocardial flow (F) times the extraction efficiency (E), i.e., the FE product, can be determined. Therefore F can only be quantified if E is known. We measured the global E in vivo in normal canine myocardium, and measured E and λ, in vitro, locally in normal, acute ischemic (n = 5; coronary artery occlusion < 4 h), infarcted (n = 4; coronary artery occlusion, 6 days) and reperfused (n = 4; coronary artery occlusion 2 h, and reperfusion 2 h and 6 days) myocardium. Results indicate that E differs with F and with individuals and consequently, F cannot be quantified using the MKE unless the local E is also determined in vivo.
Predicting RF field penetration in heterogeneous bodies using a 3‐D finite element approach: Preliminary results
Authors: Petropoulos L. S. , Haacke E. M. , Brown R. W. , Boerner E. 
Published: March 2007

AbstractWe present preliminary results for a 3D finite element calculation to evaluate RF penetration in conducting dielectric materials at high field strengths. A tetrahedral mesh is used along with a Coulomb gauge constraint in a finite element method that yields excellent numerical stability at high frequencies. Accuracy is verified by comparisons with analytic solutions for single‐layer and multiple‐layer heterogeneous systems and for a 3D spherical model. We have also compared the finite element model with experimental results presented by Foo et al., Magn. Reson. Med. 23, (1992). Agreement is very good and argues for the usefulness of the method in the calculation of RF penetration and RF power deposition effects in heterogeneous objects.
Time of flight quantification of coronary flow with echo‐planar MRI
Authors: Poncelet Brigitte P. , Weisskoff Robert M. , Wedeen Van J. , Brady Thomas J. , Kantor Howard 
Published: March 2007

AbstractDetection and quantification of flow of the left anterior descending (LAD) coronary artery in healthy volunteers are demonstrated using echo‐planar imaging (EPI). A time‐of‐flight TOF) model was used to derive coronary flow velocities from wash‐in curves, free of cardiac wall motion contamination. Short‐axis cardiac studies were performed using a gated, gradient echo EPI technique to limit the effect of cardiac wall motion on coronary vessel imaging. A series of 10 to 20 single or multislice images were acquired within a single breath‐hold. Real‐time cine series showed the LAD coronary artery with a detectability of 91% (n = 23) and revealed beat‐to‐beat variability in vessel position of a magnitude equal to or greater than its diameter. Flow velocity was measured in the proximal portion of the artery at rest and during exercise. The data demonstrated the known phasic pattern of LAD flow:‐Vsystole ≤ 5 cm/s and peak Vdiastole = 14 ± 3 cm/s (n = 11, V = mean laminar flow velocity). During isometric exercise, a LAD flow velocity increase (52 ± 24%) was detected in eight of nine subjects. The capacity of the EPI TOF method to detect flow velocity changes should prove clinically useful for future assessment of coronary flow reserve.