bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen ultrathin phase‐encoded spectroscopy (HUPSPEC)
Authors: Listerud John , Lenkinski Robert E. , Axel Leon , Roberts Michael
Published: March 2007

This paper describes a new clinical spectroscopy pulse program, hydrogen ultrathin phase‐encoded spectroscopy. This sequence combines high spatial resolution with magnitude hydrogen spectroscopy. A linear volume is spatially frequency encoded with a conventional readout gradient and phase encoded spectrally by incrementing the timing of acquisition. The pulse sequence is implemented on a whole‐body MRI scanner and supports several standard scanner options, including autoprescanning, offset of the center of field of view in the frequency‐encoding direction, and oblique imaging. Some preliminary experimental experience is reported, demonstrating the possibility of observing the spectral line widths of fat and water in marrow, and of observing the spectral line widths of fat and water in marrow, and of observing multiline spectra. Combination of the technique with water suppression methods in a sequence called WASHUP is also discussed © 1990 Academic Press, Inc.
Enzyme kinetics and relaxation measurements with surface coils
Authors: Clarke Geoffrey D. , Rehr Roger B.
Published: March 2007

A pulse sequence which produces the inversion of magnetization at a selected chemical shift for in vivo surface coil spectroscopy is proposed. The sequence uses a shaped, complex sech inversion pulse and “depth pulse” phase alternation. The sequence can be used for both in vivo inversion transfer and inversion recovery experiments. © 1990 Academic Press, Inc.
Metabolic response to exercise in malignant hyperthermia‐sensitive patients measured by 31P magnetic resonance spectroscopy
Authors: Webster D. W. , Thompson T. , Gravelle D. R. , Laschuk M. J. , Driedger A. A.
Published: March 2007

The currently favored theory of pathogenesis of malignant hyperthermia (MH) implicates an abnormality in skeletal muscle calcium ion transport. During a MH crisis a profound lactic acidosis occurs and in MH‐sensitive individuals a delayed recovery of venous lactate has been previously noted postexercise. We have used 31P magnetic resonance spectroscopy to follow noninvasively in vivo changes in muscle of intracellular pH and high‐energy phosphate metabolites during rest, exercise, and recovery of MH‐sensitive subjects. Eleven biopsy‐positive MH‐sensitive patients have been studied and compared to 26 normal subjects. The MH‐sensitive subjects as a group prematurely dropped their intracellular pH during mild aerobic exercise and they demonstrated a marked delay before the recovery of pH after maximal exercise. PCr/(PCr + Pi) ratios also dropped early during exercise but recovered normally. The observed changes in pH and PCr/(PCr + Pi) are consistent with a myopathy in MH‐susceptible individuals. © 1990 Academic Press, Inc.
Two‐dimensional spectra of intact tissue: Homonuclear Hartmann‐Hahn spectroscopy provides increased sensitivity and information content as compared to COSY
Authors: Alonso Juli , Arüs Carles , Westler William M. , Markley John L.
Published: March 2007

Hartmann‐Hahn (HOH AHA) spectroscopy led to good definition of proton spin systems of metabolites such as lactate, (phospho) creatine, and carnosine from a 3‐g sample of excised frog gastrocnemius muscle in a 17‐min experiment. The sign of the HOHAHA cross‐peak intensity appears to provide additional information about interactions between metabolites and their protein binding sites. © 1990 Academic Press, Inc.
Optimization of magnetization transfer measurements: Statistical analysis by stochastic simulation. Application to creatine kinase kinetics
Authors: Rydzy Marek , Deslauriers Roxanne , Smithand Ian C. P. , Saunders John K.
Published: March 2007

A systematic study was performed to optimize the accuracy of kinetic parameters derived from magnetization transfer measurements. Three techniques were investigated: time‐dependent saturation transfer (TDST), saturation recovery (SRS), and inversion recovery (IRS). In the last two methods, one of the resonances undergoing exchange is saturated throughout the experiment. The three techniques were compared with respect to the accuracy of the kinetic parameters derived from experiments performed in a given, fixed, amount of time. Stochastic simulation of magnetization transfer experiments was performed to optimize experimental design. General formulas for the relative accuracies of the unidirectional rate constant (k) were derived for each of the three experimental methods. It was calculated that for k values between 0.1 and 1.0 s−1, T, values between 1 and 10 s, and relaxation delays appropriate for the creatine kinase reaction, the SRS method yields more accurate values of k than does the IRS method. The TDST method is more accurate than the SRS method for reactions where T1 is long and k is large, within the range of k and T1 values examined. Experimental verification of the method was carried out on a solution in which the forward (PCr → ATP) rate constant (k) of the creatine kinase reaction was measured. © 1990 Academic Press, Inc.
Improved quantification of in vivo1H NMR spectra by optimization of signal acquisition and processing and by incorporation of prior knowledge into the spectral fitting
Authors: De Graaf A. A. , Bovée W. M. M. J.
Published: March 2007

Quantification of localized in vivo brain 1H spectra is in general very difficult due to excessive spectral overlap. In addition, intensity distortions may result from the effects of the NMR pulse sequence on the spins. This paper describes an approach to solving these problems. It comprises optimization of the pulse sequence; correction of the experimental lineshape; determination of intensity distortions, of relative line positions, and of linewidths using model solutions; and incorporation of the thus obtained prior knowledge into a nonlinear least‐squares spectral fitting procedure. This approach resulted in greatly improved accuracy, precision, and reliability of the quantitation of our in vivo spectra of rat brain, and enabled us to estimate absolute metabolite concentrations. © 1990 Academic Press, Inc.
Localized 1H in vivo NMR spectroscopy of small‐volume elements in human brain at 1.5 T
Authors: Jung Wulf‐Ingo , Grodd Wolfgang , Lutz Otto , Petersen Dirk
Published: March 2007

Localized in vivo proton NMR spectra of volume elements of minimal size (13 × 13 × 13 mm3) were obtained in human brain with a whole‐body imager working at 1.5‐T field strength. By use of an optimized version of the 90°‐180°‐180° volume selection method, well‐resolved proton spectra were acquired within 9 min and a comparison of spectra with different echo times (135 and 270 ms) was possible within 20 min. © 1990 Academic Press, Inc.
Velocity imaging of slow coherent flows using stimulated echoes
Authors: Caprihan A. , Griffey R. H. , Fukushima E.
Published: March 2007

We measure the velocity distribution of slow fluid flow in model systems using stimulated echoes and velocity phase encoding. We show velocity images of slow coherent flow with velocities of the order of 0.1 mm/s which is slower than can be obtained by the bolus‐tracking method. The eddy current errors were compensated by phase Correction. © 1990 Academic Press, Inc.
Aortoiliac and femoropopliteal phase‐based NMR angiography: A comparison between FLAG and RSE
Authors: Lanzer P. , Bohning D. , Groen J. , Gross G. , Nanda N. , Pohost G.
Published: March 2007

To assess the performance of FLAG and RSE NMR angiography 22 aortoiliac (A1) and 22 femoropopliteal (FP) angiograms in 11 healthy males, mean age 38 ± 7.6 years, were acquired. The image quality was graded in a blinded fashion by two independent readers. The readers grades were not statistically different (K = 0.5696). The representation of diagnostic images was 6/ 11 FLAG and 8/ 11 RSE A1 as well as 8/ 11 FLAG and 8/ 11 RSE FP. On back‐to‐back comparison six RSE A1 and seven RSE FP were graded bettcr than their FLAG counterparts. Although these differences did not achieve a statistical significance RSE NMR angiography provided consistently better images and appears preferable for imaging of the peripheral vascular system in normal subjects. © 1990 Academic Press, Inc.
Application of reverse‐DEPT polarization transfer pulse sequence to study the metabolism of carbon‐13‐labeled substrates in perfused organs by 1H NMR Spectroscopy
Authors: Desmoulin F. , Confort‐Gouny S. , Masson S. , Bernard M. , Doddrell D. M. , Cozzone P. J.
Published: March 2007

Metabolism of 13C‐enriched metabolites can be advantageously studied by reverse‐polarization transfer methods. In this work an improved reverse‐DEPT sequence has been applied for the first time on perfused organs in a 20‐mm probe. The metabolic fate of 99% enriched [ 2‐13C] acetate perfused in excised rat liver and heart has been documented. © 1990 Academic Press, Inc.
High‐speed line scan MR angiography
Authors: Brown Donna G. , Riederer Stephen J. , Wright Ronald C. , Liu Yu , Farzaneh Farhad
Published: March 2007

We describe a system which forms MR angiographic images at high speed. Multiple axial sections are imaged sequentially using a 2DFT GRASS sequence with TR/TE 50/15 ms, 64 phase encodings per image. Reconstruction and projection of each image are performed immediately (within 220 ms) after data for that image are acquired. The projection angiogram is constructed line by line as the scan progresses, thereby totally eliminating any additional time required for reconstruction and projection. © 1990 Academic Press, Inc.
Magnetic resonance imaging of blood vessels at high fields: In vivo and in vitro measurements and image simulation
Authors: Ogawa Seiji , Lee Tso‐Ming
Published: March 2007

Unusually high image contrast in vivo magnetic resonance imaging of the brain becomes observable at high magnetic fields when the blood oxygenation level is lowered. The cause of the contrast has been attributed to a magnetic susceptibility effect induced by paramagnetic deoxyhemoglobin in red cells. When the cylinder axis of a blood vessel is not parallel to the main magnetic field, the susceptibility difference produces varying local fields around the blood vessel. In gradient‐echo images, not in spin‐echo images, these local fields cause intravoxel dephasing of the water signal of the surrounding tissue. This description of the contrast enhancement has been confirmed by a series of in vitro blood sample experiments and image simulations. A predicted contrast change has been demonstrated in brain images of a mouse placed at two different orientations in the magnet. From the simulated images, the dependence of the contrast on the field strength has been estimated. © 1990 Academic Press, Inc.
Analysis of glycogen storage disease by in vivo13C NMR comparison of normal volunteers with a patient
Authors: Beckmann N. , Seelig J. , Wick H.
Published: March 2007

Broadband proton‐decoupled natural abundance 13C spectra of the human calf. liver, and head were obtained from normal volunteers and a patient with glycogen type IIIA storage disease. Two concentric and coplanar surface coils of diameters 8.0 cm and 13.0 cm were used for 13C (at 16.0 MHz) and 'H (at 63.6 MHz), respectively. A WALTZ‐8 sequence lead to homogeneous decoupling over a large volume. In addition to lipid resonances a variety of other metabolite resonances could be resolved. The glycogen concentration in the muscle and the liver of normal volunteers varied considerably depending on dietary preparation and physical exercise. The glycogen level in the liver and the calf of a patient with glycogen type IIIA storage disease was increased by a factor of 2–3 compared to normal. well‐trained volunteers. Proton‐decoupled 13C spectra of human head are reported for the first time. The spectra are dominated by lipid resonances but an additional resonance at 54.0 ppm is clearly visible. The proton‐decoupled 13C head spectrum of a patient with glycogen type IIIA storage disease revealed additional resonances between 71.0 and 85.0 ppm. © 1990 Academic Press, Inc.
Noise correlations in data simultaneously acquired from multiple surface coil arrays
Authors: Hayes Cecil E. , Roemer Peter B.
Published: March 2007

Multiple images acquired simultaneously from an array of surface coils can be combined to give a composite image with an improved signal‐to‐noise ratio (SNR) and a large field of view. The composite images' SNR can be optimized by taking advantage of noise correlations between coils and phase shifts induced by surface coil reception. Methods are derived for making optimal composite images with uniform noise or with uniform sensitivity. A simplified model is used to provide an intuitive understanding of the interaction of noise correlation and phase shift phenomena. © 1990 Academic Press, Inc.
The slotted crossover surface coil: A detector for in vivo NMR of skin
Authors: Nagel Timothy L. , Alderman Donald W. , Schoenborn Robin R. , Hendrickson Margo , Shelby Jane , Saffle Jeffrey , Schweizer Martin P.
Published: March 2007

An elongated, narrow, slotted crossover surface coil provides surface localization capable of resolving in vivo 31 P NMR spectra from skin tissues. The shallow B1 field penetration achieves localization objectives while the probe length maintains signal‐to‐noise requirements. Dielectric and inductive losses are minimized via the crossover design (see T. L. Nagel et al., Magn. Reson. Med. 13, xxx (1990). In vivo spectra with millimeter depth resolution were acquired in 5 min at 2 T without pulse localization sequences. Preliminary 31P NMR spectra of normal and thermally injured rat skin were completed using a 25 × 3‐mm slotted probe with a 3 × 2‐cm surface region of excitation. Normal rat skin tissue PCr/Pi ratios ranged from 3.8 to 4.7 for 5‐, 10‐, and 30‐γs pulse widths, while partial‐and full‐thickness scald injured tissues ranged from 0 to 2.8. Evaluation of a single minor partial thickness injury 1 to 5 h postburn shows evidence of a localized hypermetabolic response associated with hyperemia. Determination of bum depth and tissue viability appears feasible using: (1) PCr/Pi ratios and (2) observation of localized hypermetabolism. © 1990 Academic Press, Inc.
Hemodynamic and hepatic pH responses to sodium bicarbonate and carbicarb during systemic acidosis
Authors: Shapiro J. I. , Whalen M. , Chan L.
Published: March 2007

Rats subjected to ammonium chloride‐induced metabolic acidosis were given alkalinization therapy with either sodium bicarbonate or Carbicarb. Ammonium chloride‐induced Severe metabolic acidosis had minimal effect on mean arterial blood pressure and cardiac output. This acidosis resulted in a small but statistically significant fall in intracellular liver pH (pHi) as measured with 31P magnetic resonance spectroscopy (7.01 ± 0.05 vs 7.08 ± 0.04, p <0.05). Sodium bicarbonate treatment resulted in systemic alkalinization and increases in arterial pCO2 as well as transient but extreme decreases in cardiac output and mean arterial pressure. Alkalinization with sodium bicarbonate also resulted in a transient but significant decrease in intracellular liver pH (7.02 ± 0.06 at 5 min vs 7.09 f 0.06 at baseline, p <0.05). Carbicarb therapy resulted in systemic alkalinization without major changes in arterial pCO2, cardiac output, or mean arterial blood pressure. Moreover, Carbicarb effected a sustained intracellular alkalinization of the liver (pHi = 7.12 ± 0.07 at 5 min, p <0.05, pHi = 7.19 ± 0.07 at 10 min, p < 0.01, pHi = 7.16 ± 0.06 at 15 min, p <0.01, vs baseline pHi = 7.05 ± 0.06). These data suggest that Carbicarb may be a more effective buffer than sodium bicarbonate during conditions where ventilation is limited and hemodynamic instability is present. © 1990 Academic Press, Inc.
A high‐sensitivity, high‐B1 homogeneity probe for quantitation of metabolites
Authors: Hoult David I. , Deslauriers Roxanne
Published: March 2007

Accurate quantitation of metabolites in biological samples of irregular shape and in‐homogeneous composition is generally acknowledged to be difficult. The difficulties are less pronounced with a probe having excellent B1 field homogeneity, high sensitivity, and a resonant frequency independent of sample size and composition. A prototype probe that aims to fulfill these requirements in wide‐bore horizontal magnets is described. It comprises four separate tuned rings on a spherical surface which give a B1 field that is flat to ±1% over the design volume. Inter‐ring coupling, and to a fifth ring used for matching, is by induction, and the mathematics of the tuning of the system are derived. It is shown that resonant frequency variation with sample size is negligible, and that the sensitivity closely approaches the theoretical limit. © 1990 Academic Press, Inc.
Phosphorus metabolites and the distribution of cell cycle phase of RIF‐1 tumors in response to 14 Gy irradiation
Authors: Majors Anthony W. , Ng Thian C. , Karalis Ipatia M. , Edinger Mark G. , Tubbs Raymond R. , Higgins Patrick D. , Shin Kyo H.
Published: March 2007

Simultaneous measurements of DNA cell phase cycle distributions and in vivo 31P NMR spectroscopy were performed on 40 RIF‐1 murine tumors irradiated with 14 Gy of X‐radiation. Diploid and tetraploid tumor populations were observed. The cells blocked in G2/M phase were measured as a function of the ratios of tetraploid cell number in G2/ M phase versus total cell population measured. The G2/M population reached a maximum at 32 h post irradiation, dropping to control values by 72 h, while the ratio of inorganic phosphate to β‐nucleotide triphosphate dropped significantly at 32 h and remained significantly lower than control up to 72 h post irradiation. Measurements of PME, PDE, PCr, and pH showed no significant variations at any time point. No significant change in host cell population could be observed. Since the measured G2/M population never increased to more than 3% of the total cell population, the change observed in the 31P NMR spectra were not simply the result of possible differences in NMR profiles of the different cell phase populations but were more likely due to a change in the metabolic characteristics or environment of a majority of the Cells. © 1990 Academic Press, Inc.
The design of practical selective pulses for magnetic resonance imaging and spectroscopy using SPINCALC
Authors: Morris Peter G. , McIntyre Dominick J. O. , Rourke David E. , Ngo J. Thomas
Published: March 2007

Recently, we introduced a new numerical approach to the design and optimization of NMR selective pulses, which we have christened “SPINCALC” (J. T. Ngo and P. G. Morris, Biochem. Soc. Trans. 14, 1271 (1986); J. T. Ngo and P. G. Morris, Magn. Reson. Med. 5, 217(1987)). The first practical application of pulses generated by SPINCALC is demonstrated on a standard 0.5‐T clinical MRI system. Results are shown for single phase π pulses suitable both for selective inversion and for selective refocusing. The extension of SPINCALC to multidimensional pulses is illustrated by the design of a two‐dimensional π pulse. © 1991 Academic Press, Inc.
Assignment of resonances in the 1H spectrum of rat brain by two‐dimensional shift correlated and j‐resolved NMR spectroscopy
Authors: Behar Kevin L. , Ogino Takashi
Published: March 2007

Two‐dimensional shift‐correlated (COSY) and J‐resolved NMR spectroscopy was used to identify and assign resonances in the aliphatic region (0.8 to 4.5 ppm) of the 1H spectrum of acid extracts and tissue of rat brain. The chemical shift and spin‐spin coupling constants of several resonances, which could not be resolved in one‐dimensional spectra of tissue, were determined. These properties, together with the appropriate multiplet structure and scalar coupling patterns observed in 2D J‐resolved and COSY spectra, were used to assign the resonances of lactate, threonine, alanine, γ‐amino butyrate, N‐acetyl aspartate, aspartate, glutamate, glutamine, taurine, and myo‐inositol. The single peak observed at 1.33 ppm in the ID 1H spectrum of excised brain tissue, which is generally assigned to lactate, was shown instead to consist of two overlapping peaks in 2D COSY contour plots. The intensity of both resonances increased considerably after death. The second resonance was assigned to threonine and the assignment was confirmed by ion‐exchange chromatography. Several cross peaks were identified in 2D COSY spectra of intact brain tissue that were not present in similar spectra of the acid extract. These nonmetabolite resonances were assigned to macromolecules. Analysis of 2D COSY contour plots in conjunction with 1D spectra revealed that the total creatine (creatine + phosphocreatine) resonance at 3.0 ppm was overlapped by both GABA and macromolecules. This macromolecule resonance was present in a 2D COSY spectrum of the rat brain obtained in situ with a surface coil following cardiac arrest, indicating that its presence in the 2D spectrum of excised brain tissue did not arise from tissue disruption. © 1991 Academic Press, Inc.
Yb‐DTPA, a novel contrast agent in magnetic resonance imaging: Application to rat kidney
Authors: Sarkar Susanta K. , Rycyna Robert E. , Lenkinski Robert E. , Solleveld Henk A. , Kinter Lewis B.
Published: March 2007

We have developed a novel contrast agent, ytterbium‐diethylenetriamine pentaacetic acid (Yb‐DTPA), for magnetic resonance imaging (MRI) and its mechanism of action is predominantly by the susceptibility mechanism. We have applied this contrast agent for renal MRI studies. We also demonstrate that Yb‐DTPA has a renal clearance similar to that of inulin in rats and may therefore be useful for the estimation of glomerular filtration rate. © 1991 Academic Press, Inc.
Application of Single‐Shot Spiral Scanning for Volume Localization
Authors: Ra J. B. , Rim C. Y. , Cho Z. H.
Published: March 2007

A new technique using a spiral scan single‐shot RF pulse for localized volume selection has been developed and its experimental results are presented. This technique employs an additional radial‐gradient coil in conjunction with the oscillating gradients for the spiral scan to localize the 3D volume. The short selection time in this technique minimizes both signal contamination from unwanted regions and signal attenuation due to T2 decay. We provide both the theoretical background of the technique and the experimental results obtained from a phantom as well as a human volunteer. The proposed method appears simple and accurate in localizing a volume which would be used as either fast imaging or localized Spectroscopy. © 1991 Academic Press, Inc.
Analysis of 23Na NMR spectra from isolated perfused hearts
Authors: Kohler Susan J. , Perry Stanton B. , Stewart Laura C. , Atkinson David E. , Clarke Kieran , Ingwall Joanne S.
Published: March 2007

The 23Na NMR spectra obtained from isolated hearts perfused with buffer containing the paramagnetic shift reagent dysprosium triethylenetetraminehexaacetic acid, Dy(TTHA)3−, are complex and contain a number of overlapping peaks of different intensities. Spectra from rat, rabbit, guinea pig, and ferret hearts obtained during periods of control perfusion are similar and undergo similar changes when the hearts are subjected to periods of ischemia and reflow. The contributions from the intracellular, interstitial, vascular, and bath compartments to the multiple peaks in the spectra of rat hearts have been assigned. The significant contributions to these spectra of bulk magnetic susceptibility effects and incomplete mixing have been demonstrated through a series of modeling experiments. Since the spectra from hearts of different species are so similar, the peak assignments made for the rat are applicable to spectra from rabbit, guinea pig, and ferret hearts as well. This work provides a framework for quantitative analysis of the spectral changes which occur during conditions such as ischemia and reflow. © 1991 Academic Press. Inc.
Lipoproteins in heart transplantation: Proton magnetic resonance spectroscopy of plasma
Authors: Eugene Michel , Le Moyec Laurence , De Certaines Jacques , Desruennes Michèle , Le Rumeur Elisabeth , Fraysse Jean B. , Cabrol Christian
Published: March 2007

Despite the major improvement in immunosuppressive therapy, noninvasive detection of heart graft rejection remains a challenge. As lipoproteins are involved in several immunomodulation mechanisms, we studied their proton NMR spectra in plasma from patients after heart transplantation. NMR data were compared to clinical and functional evaluation of rejection process. The total linewidths (TLW) of methyl and methylene peaks, mainly arising from lipoproteins, were significantly lower for patients without a rejection process than for patients before surgery and patients with evidences of a rejection process. When TLW values are referred to TLW on the 8th day for each patient, the sensitivity and the specificity of the test are increased, with resulting positive and negative predictive values of 90 and 9195, respectively. The results obtained on more than 400 samples from 46 patients justify the use of proton NMR spectroscopy as a clinical tool. © 1991 Academic Press. Inc.
Three‐dimensional MR microscopy with large arrays
Authors: Suddarth S. A. , Johnson G. A.
Published: March 2007

MR microscopy of fixed specimens is described using large (2563) arrays. Images are acquired at 7.0 T with voxels as small as 70 × 70 × 70 μm (3.4 × 10−4 mm3), more than 25,000 times smaller than routine clinical body imaging. Separation of the acquisition, reconstruction, archival, and analysis onto networked workstations provides flexibility and efficiency in handling the large data sets. The isotropic data can be interactively displayed through any plane without loss of in‐plane resolution. The potential for applications of MR microscopy in clinical pathology is addressed. © 1991 Academic Press. Inc.
1H spectroscopic imaging using a spectral‐spatial excitation pulse
Authors: Spielman Daniel , Meyer Craig , Macovski Albert , Enzmann Dieter
Published: March 2007

Excellent water suppression is required to perform in vivo 1H spectroscopic experiments. However water suppression is difficult due to both B0 and RF inhomogeneities. These inhomogeneities are particularly troublesome in spectroscopic imaging experiments where water suppression is required throughout some large region of interest. In this paper, we propose the use of spectral‐spatial excitation pulses for such experiments. These two‐dimensional pulses are shown to provide water suppression that is insensitive to a range of B0 and RF variations while simultaneously providing spatial localization. Experimental results including images (with voxel volumes ranging from 3.4 to 1.5 cc) of various brain metabolites from both a normal volunteer and a patient with a metastatic lung carcinoma are presented. © 1991 Academic Press. Inc.
Effect of differential saturation on the spatial localization performance of depth pulses
Authors: Michael David , Schleich Thomas
Published: March 2007

Computer simulations of Depth pulse B (Θ(2Θ[±x, ±y])2; acquire) and other Depth pulses, verified by experimental surface coil NMR studies utilizing phantom samples, reveal that the spatial localization performance of Depth pulses degrades when the repetition time is short relative to T1 because of differential saturation, i.e., T1, discrimination effects. Simulations of Depth pulse A (Θ(2Θ[±x, ±y]); acquire) and Depth pulse B indicate that there is no phase‐cycled pulse sequence delivery order which negates the untoward effect of T1 discrimination on spatial localization performance. The results of this study demonstrate the importance of consistent magnetization preparation prior to the delivery of each phase‐cycled multiple pulse sequence in a Depth pulse cycle for obtaining optimal spatial localization performance. The untoward effects of inconsistent magnetization preparation, resulting from T1 discrimination, may be ameliorated by the application of many Depth pulse cycles. © 1991 Academic Press. Inc.
Spectroscopic imaging with multidimensional pulses for excitation: SIMPLE
Authors: Spielman Daniel , Pauly John , Macovski Albert , Enzmann Dieter
Published: March 2007

Proton spectroscopy and spectroscopic imaging in the human brain require the elimination of both water and lipid signals. Strong lipid signals from subcutaneous fat are usually eliminated by confining the excited volume to lie wholly within the skull. Water suppression, however, can be difficult due to both B0 and RF inhomogeneities, which are particularly troublesome in imaging experiments where a relatively large region‐of‐interest (ROI) is typical. In this paper, we discuss the use of multidimensional selective‐excitation pulses (e.g., pulses that are simultaneously selective along two axes) to both define the ROI and provide the necessary water suppression. Pulse sequences providing three‐dimensional localization along with water suppression that is insensitive to a range of B0 and RF inhomogeneities are described. Spectra and spectroscopic images (voxel volume = 3.4 cc, acquisition time = 38 min) of various 1H metabolites from a patient with an astrocytoma show clear differences between normal and cancerous tissues and demonstrate the ability of these techniques to be used in vivo.
In vivo measurements of bone marrow cellularity using volume‐localized proton NMR spectroscopy
Authors: Ballon D. , Jakubowski A. , Gabrilove J. , Graham M. C. , Zakowski M. , Sheridan C. , Koutcher J. A.
Published: March 2007

Volume‐localized proton NMR spectroscopy was used to estimate bone marrow cellularity in the posterior iliac crests of patients undergoing treatment with hematopoietic growth factors for a variety of hematologic and neoplastic disorders. Twelve patients were accrued, six of whom were studied more than once, yielding a total of 25 measurements. These data were compared to cellularity assessments derived from conventional bone marrow core biopsies obtained within a 24‐h period before or after the NMR exam. The results obtained by the two methods are well correlated (R = 0.94, P < 0.001), suggesting that this noninvasive technique may preclude the need for biopsies in some cases. © 1991 Academic Press, Inc.
ACE: A single‐shot method for water‐suppressed localization and editing of spectra, images, and spectroscopic images
Authors: van Vaals J. J. , Bergman A. H. , den Boef J. H. , van den Boogert H. J. , van Gerwen P. H. J.
Published: March 2007

A versatile method for localized (1H) NMR spectroscopy is presented. The method intrinsically combines B0‐based spatial localization with the possibility of water suppression and spectral editing. With this sequence it is feasible to localize not only single spectra but also phase‐encoded images and spectroscopic images. The technique essentially integrates the “Hahn spin‐echo” with the “stimulated echo” sequence and is therefore called ACE (acquiring combined echoes). It realizes water‐suppressed three‐dimensional localization in a single shot and can be used for localized shimming. Studies in which the new method is applied to phantoms with metabolites diluted at low concentrations are presented. Discrimination between lactate and alanine, employing an adapted spectral editing method with complete inversion, combined with simultaneous water suppression and localization of a 0.06‐cc volume is shown. The suppression of signals from outside the selected volume is a ⩾ 24,000. Also, the method is demonstrated by in vivo experiments at 6.3 T. Localized water‐suppressed 1H spectra are obtained completely noninvasively, leaving scalp and fur intact, from well‐defined volumes of 0.15 cc in the brain of a living rat. Water‐suppressed spectroscopic imaging over a localized volume with “body” coil excitation and noninvasive surface coil detection yielded spectra from voxels as small as 25 μl in the in vivo rat brain.
Diffusion and perfusion in high resolution NMR imaging and microscopy
Authors: Ahn C. B. , Chos Z. H.
Published: March 2007

Diffusion and perfusion phenomena under strong gradient fields (∼100 G/cm) are examined in high resolution nuclear magnetic resonance (NMR) imaging and microscopy, where diffusion‐associated signal attenuation predominates over T1 and T2 relaxation decays. Image contrast based on the diffusion and microcirculation is discussed with experimental results obtained with a 7.0‐T microscopy system. Ultimate resolution limit due to diffusion is investigated in high resolution NMR imaging and microscopy. © 1991 Academic Press, Inc.
Dynamic imaging of contrast enhancement in brain tumors
Authors: Bullock P. R. , Mansfield P. , Gowland P. , Worthington B. S. , Firth J. L.
Published: March 2007

Gadolinium‐DTPA has been shown to be a good probe for demonstrating defects in the blood‐brain barrier, but it has a rapid rate of elimination so that peak circulating levels are short‐lived. In this study ultrafast echo‐planar imaging has been used in combination with a bolus injection of gadolinium‐DTPA to evaluate perfusion within brain tumors and to assess the degree of disruption of the blood‐brain barrier. The temporal profile of enhancement may allow discrimination between different tumor types. © 1991 Academic Press, Inc.
Fast Fourier projection for MR angiography
Authors: Napel Sandy , Dunne Shane , Rutt Brian K.
Published: March 2007

We have developed a technique called fast Fourier projection which rapidly produces projections through images and is particularly useful for generating MR angiograms. Based on the projection‐slice theorem of Fourier transform theory, this method extracts planes from three‐dimensional spatial frequency space and computes projections at arbitrary viewing angles by two‐dimensional inverse Fourier transformation. Typical computation times are on the order of 1 s per projection. This performance makes possible interactive selection of optimal projection directions for visualizing the desired vasculature in single or stereo‐pair angiographic images and drastically reduces the time required to generate sequences of projections for display in movie loops compared to the conventional ray‐casting approach. The method is easily implemented on off‐line workstations or directly on MRI computer systems. © 1991 Academic Press, Inc.
The water resonance as an alternative pH reference: Relevance to in Vivo31P NMR localized spectroscopy studies
Authors: Madden Anthoula , Leach Martin O. , Collins David J. , Payne Geoffrey S.
Published: March 2007

pH measurements require a suitable pH reference within the 31P NMR spectrum with respect to which the chemical shift of P1 and hence pH, may be calculated. In muscle spectra PCr is prominent and provides a reference frequency. However, recent localized tumor studies have reported the absence of PCr, for example, in breast tumors. The use of the α, β, and γ‐ATP peaks as suitable references has been suggested, but the position of the β‐ and γ‐ATP peaks is dependent upon the intracellular Mg2+ concentration. The α‐ATP is not affected by ionic concentrations; however, it contains UDPG and NAD+, the presence of which can lead to peak‐shape distortion. This paper considers the use of the H2O resonance from the proton spectrum used for shimming as a suitable pH reference, provided this is also localized to the same region of interest, using a sequence giving rise to eddy current effects comparable to those of the 31P NMR sequence. Localized in vivo measurements in the muscle and brain of volunteers indicate good agreement between the proton and phosphorus chemical shifts, allowing the PCr position to be predicted to within 0.01 ppm in all cases. © 1991 Academic Press, Inc.
On the use of a slice‐selective 270° self‐refocusing Gaussian pulse for magnetic resonance imaging
Authors: Doddrell David M. , Galloway Graham J. , Rose Stephen E. , Moulds Peter J. , Brereton Ian M.
Published: March 2007

Theoretical and experimental results are presented demonstrating that the slice intensity resulting from a self‐refocusing 270° Gaussian pulse (L. Elmsley and G. Bodenhausen, Magn. Reson. in Med. 10, 273, 1989) is approximately 60% of that following an appropriately refocused 90° Gaussian pulse.
A magnetization transfer preparation scheme for snapshot FLASH imaging
Authors: Jones Richard A. , Southon Timothy E.
Published: March 2007

A rapid method of generating images whose contrast is dependent on the exchange of magnetization between the free and restricted proton pools is presented. The contrast obtained is similar to that obtained from T2‐weighted spin‐echo images. The rapid nature of the sequence means that the RF power deposition problems encountered when using magnetization transfer in conjunction with conventional imaging sequences are avoided. © 1991 Academic Press, Inc.
In Vivo13C NMR spectroscopy of glucose metabolism of RIF‐1 tumors
Authors: Constantinidis Ioannis , Chatham John C. , Wehrle Janna P. , Glickson Jerry D.
Published: March 2007

An efficient method for measuring in vivo 13C NMR spectra of tumors has been developed and employed to monitor glucose metabolism in radiation‐induced fibrosarcomas (RIF‐1) subcutaneously implanted in C3H/HeN mice. [1‐13C]Glucose was injected directly into the tumors at a dose of 1 g/kg body wt. Spectra were obtained with a Bruker AM 360‐WB spectrometer (8.4 T/8.9 cm bore) employing a homebuilt probe equipped with a four‐turn solenoidal coil (1.5 cm outer diameter) for detection of 13C signals and a Helmholtz coil (two 3‐cm turns separated by a 3‐cm gap, oriented orthogonally to the 13C coil) for 1H decoupling. In addition to the natural abundance 13C resonances of the tumors, signals were detected from the α‐and β‐anomers of labeled glucose. Within 15 min following injection of labeled glucose [3‐13C]lactate and [3‐13C]alanine were detected. Lactate labeling approached steady state levels within about 50 min after glucose injection; in contrast, alanine labeling increased continuously over the duration of the experiment (70 min). Sixty minutes after glucose injection, the ratio of the intensity of [3‐ 13C]lactate to the principal lipid methylene resonance (30 ppm from external tetramethylsilane), which served as an internal intensity reference, was correlated with tumor size, whereas the corresponding ratio of the [3‐ 13C] alanine resonance was not. Labeling of glutamate was below the level of detection in the in vivo spectra; however, labeling of C4‐glutamate at a level approximately 50‐fold lower than the level of [3‐ 13C]lactate was detected in perchloric acid extracts. Incorporation of 13C label into C2‐and C3‐glutamate and C2‐lactate was also observed. © 1991 Academic Press, Inc.
Noise correlation
Authors: Jesmanowicz A. , Hyde James S. , Froncisz W. , Kneeland J. Bruce
Published: March 2007

Calculations and experiments that provide support for our previously stated theorem are presented: If two coils simultaneously receiving magnetic resonance signals from the same anatomic region exhibit zero mutual inductance, there can be no correlation of the noise. It is shown that correlation does not exist even in the presence of mutual inductance unless the two signal paths have amplifiers prior to signal combination. It is further found that in the presence of mutual inductance with ideal amplifiers (0 dB noise figure) in the two signal paths, there is no correlation of noise. In order to satisfy the condition of zero mutual inductance, it may be necessary to employ a decoupling circuit external to the body. A novel coil assembly, which was used in the experiments, places a single‐turn surface coil in the median plane between the two loops of a counter rotating current coil. The signal‐to‐noise ratio can be improved by combining signals. This is in analogy to quadrature receiving coils, where the mutual inductance is zero because vector reception fields are perpendicular. In the present geometry, vector reception fields are collinear, but are parallel and antiparallel on the two sides of the coil assembly, resulting in zero mutual inductance. © 1991 Academic Press, Inc.
NMR angiography of coronary vessels with 2‐D planar image scanning
Authors: Cho Z. H. , Mun C. W. , Friedenberg R. M.
Published: March 2007

On the basis of the principles of the time‐of‐flight method and the 3‐D angiogram obtained by the 2‐D planar image scanning technique using 90° RF pulses with short repetition time, we have obtained a coronary angiogram around the heart including the coronary arteries and veins. The cine NMR imaging technique is also incorporated in synchronizing ECG R waves to reduce the motion artifact and at the same time to induce the saturation effect on the static samples. Images of the large bulk blood flow corresponding to the heart chamber and descending aorta are further removed by postprocessing. The final 3‐D angiogram is then formed by stacking the 2‐D images and contrast is further enhanced by the maximum ray tracing algorithm. © 1991 Academic Press, Inc.
Delayed‐focus pulses for magnetic resonance imaging: An evolutionary approach
Authors: Wu Xi‐Li , Xu Ping , Freeman Ray
Published: March 2007

An evolutionary algorithm has been used to design a family of shaped radiofrequency pulses giving uniform absorption‐mode excitation across a predetermined frequency band. By allowing a free precession interval before signal acquisition, time is left for field gradients to be switched and for undesirable transients to decay. © 1991 Academic Press, Inc.
Cholesterol of myelin is the determinant of gray‐white contrast in MRI of brain
Authors: Koenig Seymour H.
Published: March 2007

The relative brightness of adult white matter in T1‐weighted MRI arises from myelin, but the mechanisms responsible remain to be clarified. Koenig et al. [Magn. Reson. Med. 14, 482 (1990)] conjectured that the cholesterol of myelin (∼ 30% of its lipid) was responsible. We present 1/T1 and magnetization transfer contrast imaging data [Wolff and Balaban, Magn. Reson. Med. 10, 135 (1989)] on a model system— 50% lipid—50% water by weight, with the lipid one‐half phosphatidyl cholinc (PC) and one‐half cholesterol—and a control in which the lipid is all PC. The differences between the model and control samples mimic the myelin contribution to white matter in both experiments. © 1991 Academic Press, Inc.
Proton spectroscopic imaging: A tool for studying intracerebral tumor models in rat
Authors: Bourgeois D. , Remy C. , Lefur Y. , Devoulon P. , Benabid A. L. , Decorps M.
Published: March 2007

Water‐suppressed 2D 1H spectroscopic imaging was used with surface coils to study in vivo the cerebral metabolism changes in rat brain induced by a glial tumor growing in situ. To achieve slice selection without a chemical‐shift artifact, we exploited the depth pulse properties of a spin‐echo sequence. In order to give a spectral response which is independent of the position, the water suppression was achieved by using a spin‐locking excitation and a binomial refocusing pulse. Spectroscopic images were obtained with an in‐plane resolution of 1.1 × 1.1 mm and a slice thickness of roughly 3 mm. The growing of the tumor induced dramatic modifications in the proton spectra, including a nearly complete loss of N‐acetyl aspartate, an increase of the 1.3‐ppm peak, an increase in choline, and a decrease in creatine. The results demonstrate the potential of spectroscopic imaging in the study of intracranial tumor models in rats. © 1991 Academic Press, Inc.
Elevation in relative levels of brain membrane unsaturated fatty acids in Alzheimer's disease: High resolution proton spectroscopic studies of membrane lipid extracts
Authors: Kwee Ingrid L. , Nakada Tsutomu , Ellis William G.
Published: March 2007

Unsaturation indices of cerebral cortex membrane phospholipids in Alzheimer's disease were determined utilizing high resolution proton nuclear magnetic resonance (NMR) spectroscopy of lipid extracts. The unsaturation index of Alzheimer's brain was found to be significantly higher (P < 0.01) than that of age‐matched controls. The study provides further support for the hypothesis that alteration in phospholipid metabolism, especially an elevation in unsaturated fatty acids, may play a role in the pathogenesis of Alzheimer's disease. © 1991 Academic Press, Inc.
Real‐time magnetic resonance imaging of laser heat deposition in tissue
Authors: Bleier Alan R. , Jolesz Ferenc A. , Cohen Mark S. , Weisskoff Robert M. , Dalcanton Julianne J. , Higuchi Nobuya , Feinberg David A. , Rosen Bruce R. , McKinstry Robert C. , Hushek Stephen G.
Published: March 2007

We applied diffusion‐sensitive echo planar (Instascan) imaging to study thermal changes caused by a Nd:YAG laser. Images of phantom materials and normal rabbit brain tissue in vivo, acquired in 150 ms, every 2 s, clearly showed the dynamics of temperature‐related signal intensity changes in the regions irradiated by the laser. © 1991 Academic Press, Inc.
Hepatic D‐galactosamine toxicity studied with localized in Vivo31P magnetic resonance spectroscopy in intact rats
Authors: Weisdorf Sally , Hendrich Kristy , Buchthal Steven , Wike John , Bratt Gerald , Merkle Hellmut , Garwood Michael , Uǧurbil Kâmil
Published: March 2007

Spatially resolved 13P magnetic resonance spectroscopy (MRS) at 4.7 T was applied to noninvasively assess liver phosphorus metabolites in a biochemically well‐characterized model of hepatotoxicity induced by injection of a sublethal dose of D‐galactosamine (galN). A newly developed hybrid method based on spectral localization with B0 and B1 gradients was employed to obtain multivoxel spectra in intact anesthesized rats. Spatially localized in vivo spectra were recorded 0 to 26 h after galN injection of female rats. In response to galN exposure, diphosphodiester peaks ascribed to UDP‐hexosamines became detectable by 4 h and persisted up to 26 h. A metabolite coresonating with inorganic phosphate increased rapidly in intensity by 2 h after galN and returned to baseline by 18 h; this resonance was shown not to be Pi and was assigned to galN‐1‐phosphate by subsequent high resolution MRS experiments on extracts prepared from these livers. These results confirmed in vivo the metabolic perturbations described previously for this model of hepatotoxicity following biochemical studies based on classical extraction methods. Unlike the in vitro studies, however, these noninvasive experiments provided additional information on the time course of metabolic alterations on the same animal. © 1991 Academic Press, Inc.
Hexagonal surface gradient coil for localized MRS of the heart
Authors: Jasinski Andrzej , Kozlowski Piotr , Urbanski Andrzej , Saunders John K.
Published: March 2007

A surface gradient coil designed to obtain localized magnetic resonance spectroscopy of the heart in vivo is described. Images and 31P spectra from phantoms and both pig and dog hearts in vivo are shown. The coil was used in conjunction with a rf surface coil to obtain 31P spectra from transmural sections of the left ventricular wall of a dog heart in vivo to demonstrate differences between normal and ischemic tissue. © 1991 Academic Press, Inc.
Localized proton NMR observation of [3‐13C] lactate in stroke after [1‐13C] glucose infusion
Authors: Rothman D. L. , Howseman A. M. , Graham G. D. , Petroff O. A. C. , Lantos G. , Fayad P. B. , Brass L. M. , Shulman G. I. , Shulman R. G. , Prichard J. W.
Published: March 2007

To assess whether elevated lactate in stable stroke is being actively produced from blood glucose localized 1H NMR stimulated echo spectra were obtained from a patient in the region of a 32‐day‐old cortical infarct before and 60–100 min after infusion of [1‐13C]glucose. Prior to the infusion the spectrum from the region of the infarct contained an elevated resonance from C3 lactate and a greatly reduced resonance from N‐acetyl groups relative to an unaffected contralateral region. After the infusion two additional resonances were observed at 62 and −64 Hz relative to the unlabeled resonance of C3 lactate which were assigned on the basis of chemical shift and relative intensity to[3‐13C]lactate. The [3‐13C]lactate fractional enrichment in the infarct region was measured to be 32% which is within error one‐half the average [1‐13C]plasma glucose enrichment during the postinfusion NMR measurement. The result suggests that the stroke lactate pool was completely derived from infused glucose. © 1991 Academic Press, Inc.