bluuebunny/crossref_metadata_2025 huggingface dataset:
23Na‐NMR detects hypoxic injury in intact kidney: Increases in sodium inhibited by DMSO and DMTU
Authors: Cross M. , Endre Z. H. , Stewart‐Richardson P. , Cowin G. J. , Westhuyzen J. , Duggleby R. G. , Fleming S. J.
Published: March 2007

Hypoxic injury in the isolated perfused rat kidney (IPRK) was monitored using 23Na‐NMR in the presence or absence of 1.5 and 15 mM dimethylthiourea (DMTU) or 15 mM dimethylsulphoxide (DMSO) before and after inducing hypoxia. Hypoxia induced a prompt exponential increase in total renal 23Na+, renal vascular resistance, and sodium excretion and decreased inulin clearance and adenine nucleotides and reduced glutathione concentrations. Lipid peroxide metabolites were unaltered. The increase in 23Na+ was significantly reduced (P < 0.001) by both DMTU and DMSO although hypoxic perturbations of function and biochemical parameters were not. Posthypoxic increases in renal 23Na+ include approximately 10% from the intratubular compartment, but principally reflect the intracellular and interstitial compartments. The results demonstrate that 23Na‐NMR is a sensitive indicator of hypoxic renal injury in intact kidney and suggest that DMTU and1 DMSO protect against hypoxic injury by a mechanism independent of free radical‐binding.
Complete elimination of the extracellular 23Na NMR signal in triple quantum filtered spectra of rat hearts in the presence of shift reagents
Authors: Navon Gil
Published: March 2007

A method is suggested whereby the shifted extracellular triple quantum filtered 23Na signal of an isolated organ is completely eliminated. The method is based on the long relaxation time of the triple quantum coherence and on its fast evolution rate. When the carrier frequency is set on top of the intracellular sodium signal and the time interval between the last two pullses to (12 Δv)‐l (Δv is the frequency difference between the intiracellular and the extracellular signals), a complete elimination of the extracellular 23Na signal is achieved. The method is demonstrated for isolated rat hearts and the quantification of intracellular sodium using triple quantum filtered spectroscopy is discussed.
MR angiography using velocity‐selective preparation pulses and segmented gradient‐echo acquisition
Authors: Korosec F. R. , Grist T. M. , Polzin J. A. , Weber D. M. , Mistretta C. A.
Published: March 2007

We describe a cardiac‐gated MR angiographic imaging method that employs velocity‐selective preparation (VSP) pulses in conjunction with segmented gradient‐echo acquisitioin and subtraction to produce images that, ideally, contain no signal from stationary tissues and display vessels with a signal intensity that is dependent on the velocity of the blood in the vessels. The novel features of this method are a) it acquires several phase‐encoding valueslapplication of a single VSP pulse, b) it uses subtraction to eliminate signal that is not sufficiently suppressed by the VSP pulses, and c) it uses VSP pulses that are synchronized with the cardiac cycle so it can be used to produce ghost‐free images of pulsatile blood. An advantage of this sequence is that it detects a signal that, after preparation, is relatively unaffected by changes in blood velocity. This leads to a large signal‐to‐noise ratio for all the phase‐encoding values, a reduction of ghosting artifacts, and the ability to visualize blood that is in motion for only a short time during the cardiac cycle. Because the signal is prepared during peak flow, venous signal can be suppressed by making the sequence sensitive to high velocities. An additional advantage of this sequence is that it permits sampling with a short TE because the velocity‐encoding gradient can be applied in a preparatory interval. Signal loss that results from dephasing during the longer TE preparation interval can be reduced or eliminated by allowing the dephased spins to flow out of the region of complex flow, and perhaps out of the field‐of‐view, by introducing a delay between the finish of the VSP pulse and the beginning of data acquisition.
Evaluation of radiation injury by 1H and 31P NMR of human urine
Authors: Yushmanov Victor E.
Published: March 2007

1H and 31P NMR techniques were applied to study the changes in metabolite profiles in human urine resulting from radiation exposure following the Chemobyl reactor accident. In cases of acute leukemia and different accumulated doses of external radiation (from 0.20 to 4.00 Sv), the proton spectra were classified on the basis of the peaks due to N‐trimethyl groups, creatinine, citrate, glycine, and hippurate. Unidentified resonances were observed between 15.9 and 21.4 ppm in six phosphorus spectra of patients with preleukemia and acute leukemia. Characteristic spectral changes were similar for external radiation and Incorporation‐induced internal irradiation. The spectral patterns described may serve as a criterion of radiation injury.
pH control in rat skeletal muscle during exercise, recovery from exercise, and acute respiratory acidosis
Authors: Kemp G. J. , Thompson C. H. , Sanderson A. L. , Radda G. K.
Published: March 2007

We used 31P magnetic resonance spectroscopy to compare the response of rat skeletal muscle to three kinds of proton load. During exercise (tetanic sciatic nerve stimulation), protons from lactic acid were buffered passively and consumed by net hydrolysis of phosphocreatine (PCr). During recovery from exercise, the pH‐dependent efflux of protons produced by PCr resynthesis could be partially inhibited by amiloride or 4,4′‐diisothiocyanostilbene‐2,2′‐disulphonate (DIDS), implicating both sodiudproton and bicarbonatelchloride exchange, but was not inhibited by simultaneous respiratory acidosis. In early recovery, up to 30% of proton efflux was mediated by lactatelproton cotransport. During acute respiratory acidosis at rest, the eventual change in muscle pH was consistent with passive buffering and was unaffected by amiloride or DIDS, implying no significant contribution of proton fluxes.
Magnetic characterization of iron oxides for magnetic resonance imaging
Authors: Sjøgren Carl E. , Briley‐Sæbø Karen , Hanson Maj , Johansson Christer
Published: March 2007

The OMP particle and four additional iron oxide samples were investigated in terms of zero field cooled magnetization (ZFCM) curves and hysteresis loops. The observation of superparamagnetic blocking and the absence of magnetic remanence demonstrated that the samples are superparamagnetic at room temperature. The magnitude of the ZFCM peak temperatures are in qualitative agreement with the iron oxide crystal size. One sample deviated from the remaining four in that it had a significantly lower magnetic moment and an irregular ZFCM curve showing the presence of various less magnetic phases. The similar results obtained with the OMP particles and the individual OMP crystallites without the polymer support show that the superparamagnetic properties of the individual OMP crystallites are retained on the OMP particle. Depending on the application, the ZFCM experiment may be viewed as an alternative or a supplement to Mössbauer spectroscopy in studies of the superaparamagnetic blocking of iron oxides.
Diffusion and relaxation mapping of cartilage‐bone plugs and excised disks using microscopic magnetic resonance imaging
Authors: Xia Yang , Farquhar Tony , Burton‐Wurster Nancy , Ray Edward , Jelinski Lynn W.
Published: March 2007

Spatially resolved maps of proton self‐diffusion coefficients (D) and relaxation times (T1andT2) were obtained on cartilage‐bone plug samples and on excised disks of canine cartilage at a transverse resolution of 30 μm, using microscopic magnetic resonance imaging (micro‐MRI). Results are compared for excised disks of cartilage and intact cartilage‐bone plugs. Correlations between the absolute water concentration, the self‐diffusion coefficient and theT1relaxation are reported. The diffusion coefficient is not a linear function of water concentration. The thickness of the disks is 600 μm, compared with the ca. 900 μm observed for the cartilage‐bone plugs, presumably due to the absence of the interfacial or tidemark layer of interdigitated cartilage and bone in the former samples. Our results suggest that excised disks of cartilage are excellent models for the articular surface and the first 500 or so microns of tissue. The molecular parameters of spin‐spin and spin‐lattice relaxation times, as well as the water self‐diffusion coefficient, are virtually identical in the two types of samples. However, the cartilage‐bone plugs have the additional feature of permitting the study of the tidemark region, a region that likely plays a major role in the transmission of mechanical force.
Experimental study of the effects of “Fractional” gating on flow measurements
Authors: Buonocore Michael H. , Gao Lisheng
Published: March 2007

Velocity encoded phase imaging is subject to errors from phase and amplitude variations of the k‐space data caused by beat‐to‐beat variations of the flow. Fractional cardiac gating is defined as asynchronous gating with each phase encode step occupying a fixed fraction of the RR interval. The gating fraction is the inverse of the number of phase encode steps taken per RR interval. Studies in normal subjects show that deviations and standard errors of ascending and descending aorta flow measurements are significantly greater with decreased gating fraction. Significant errors occur when gating does not separate systolic and diastolic data. The studies establish a graded trade‐off between flow measurement accuracy and precision with imaging time, and show that standard nongated phase contrast measurements of strongly pulsatile flow are unreliable.
adaptive fourier threshold filtering: A method to reduce noise and incoherent artifacts in high resolution cardiac images
Authors: Doyle M. , Chapman B. L. W. , Blackwell G. , Walsh E. G. , Pohost G. M.
Published: March 2007

We introduce an image processing method which reduces white noise and random artifacts in sets of high resolution, time resolved images. At each pixel, the processing consists of: (1) the isolation of a time intensity curve (TIC), (2) Fourier transformation of each TIC, (3) application of a threshold to remove low intensity coefficients, (4) inverse transformation to generate noise reduced TICS which are recombined to form images with improved signal‐to‐noise ratio (SNR). Noise filtering by Fourier thresholding is demonstrated on a set of cardiac images, resulting in a reduction of the noise energy by approximately 90%.
Cerebral blood oxygenation in rat brain during hypoxic hypoxia. Quantitative MRI of effective transverse relaxation rates
Authors: Prielmeier Franz , Nagatomo Yasushi , Frahm Jens
Published: March 2007

Oxygenation‐sensitive MRI of respiratory challenges in the brain of experimental animals will considerably benefit from a quantitative relationship between cerebral blood oxygenation and MRI parameters. Here, a multi‐echo gradient‐echo MRI technique was used to determine effective transverse relaxation rates R = 1/T of rat brain in vivo during short periods of hypoxia and interleaved normoxic phases. The differential contribution ΔR observed during hypoxia was found to increase linearly with arterial blood deoxygenation for mild to moderate conditions. Severe deoxygenation resulted in a plateau most likely due to enhanced cerebral blood flow.
Functional NMR imaging using fast spin echo at 1.5 T
Authors: Constable R. Todd , Kennan Richard P. , Puce Aina , McCarthy Gregory , Gore John C.
Published: March 2007

Functional NMR imaging of the brains response to a simple visual task has been performed using a fast spin echo (FSE) imaging sequence at 1.5 T. The FSE method refocuses dephasing effects induced by large‐scale susceptibility variations, and permits imaging in regions where macroscopic field gradients produce artifacts in gradient echo sequences. At 1.5 T, gradient echo (GRE) sequences are sensitive to the effects of brain activation, but relatively large effects may arise from large vessels and veins, and these may dominate the effects produced by smaller capillaries. Spin echo (SE) sequences with short echo times are relatively immune to large vessel effects and emphasize the susceptibility induced losses from small capillaries, but the imaging time for these sequences is prohibitive for most functional brain studies. We demonstrate that multislice functional brain imaging may be performed in reasonable imaging times at 1.5 T using an FSE imaging sequence. The FSE sequence with short echo spacing but long effective TE is sensitive to susceptibility induced effects at the capillary level. It is not sensitive to larger scale in homogeneities such as those found in veins and can be used in regions near tissuelair boundaries. Results are shown comparing conventional GRE and FSE images in activation of the visual cortex and these are supported by theoretical calculations and phantom experiments.
Construction of a 28‐mm 1H/13C probe and actively shielded Z‐gradient set for operation in a 9.4 T/89 mm magnet
Authors: Pruski Jan , Ahmad Asif , Sun Ling , Robitaille Pierre‐Marie L.
Published: March 2007

In this work, we present a new RF and gradient assembly for operation in a 9.4 Tesla 189 mm magnet. This assembly was designed in order to enable 1H‐NMR perfusion studies that are based on proton‐observed carbon‐edited approaches or gradient selected double quantum coherence. The RF portion of this probe assembly is comprised of a modified Alderman‐Grant coil and a saddle coil operating at 400 and 100 MHz, respectively. These coils are surrounded by an actively shielded Z gradient, which also allows for the use of gradient‐based water suppression without the need for carbon selection. We demonstrate that this probe can be used to implement gradient selected double quantum coherence experiments resulting in a high degree of water suppression.
MRI scanner transport system
Authors: Phillips Jason R. , Falconer James C. , Botzer Shabtai , Narayana Ponnada A.
Published: March 2007

A computer‐controlled transport system has been designed and tested for small bore magnetic resonance scanners for animal research. The transport system allows remote animal positioning based on scout images using a graphic interface. The design utilized commercially available components suitable for use in the scanner's strong magnetic field. Tests indicate positioning accuracy of the transport system to be within 0.13 mm.
Estimation of total coronary artery flow using measurements of flow in the ascending aorta
Authors: Buonocore Michael H.
Published: March 2007

This paper describes a technique for estimation of total (right + left) coronary artery flow using MRI flow measurements in the ascending aorta. The technique is based on the principle that the flow in a vessel branch is equal to the difference of the net flow measured above and below the branch ostia. Aortic net flow is measured at four or more axial oblique slices from below the aortic valve to above the highest location of the coronary vessel ostia in late diastole. A flow model properly interprets the flow measurements in slices that contain the coronary ostia. Results in five normal subjects show that total coronary artery flow can be measured with a standard error of about 90 cc/min, 30% of total coronary artery flow. Potential clinical uses include noninvasive measurement of coronary flow reserve. Pulse sequence improvements are necessary to reduce examination time and improve accuracy and precision.
A dynamically adaptive imaging algorithm for wavelet‐encoded MRI
Authors: Panych Lawrence P. , Jolesz Ferenc A.
Published: March 2007

A new adaptive algorithm based on wavelet‐encoded MRI is presented for application in dynamic imaging. This algorithm is adaptive because the strategy for updating image data in the dynamic series of images is determined by the processing of the most recently acquired data. The spatially selective multi‐resolution properties of the wavelet transform are exploited to selectively update only those regions of the field of view where change is actually occurring. A theoretical imaging model is presented to motivate use of the adaptive algorithm, and simulation results using both artificial and experimental wavelet‐encoded data are presented.
Minimization of dead‐periods in MRI pulse sequences for imaging oblique planes
Authors: Atalar Ergin , McVeigh Elliot R.
Published: March 2007

With the advent of breath‐hold MR cardiac imaging techniques, the minimization of TR and TE for oblique planes has become a critical issue. The slew rates and maximum currents of gradient amplifiers limit the minimum possible TR and TE by adding dead‐periods to the pulse sequences. We propose a method of designing gradient waveforms that will be applied to the amplifiers instead of the slice, readout, and phase encoding waveforms. Because this method ensures that the gradient amplifiers will always switch at their maximum slew rate, it results in the minimum possible dead‐period for given imaging parameters and scan plane position. A GRASS pulse sequence has been designed and ultra‐short TR and TE values have been obtained with standard gradient amplifiers and coils. For some oblique slices, we have achieved shorter TR and TE values than those for nonoblique slices.
The theory of shielded loop resonators
Authors: Harpen Michael D.
Published: March 2007

We present a mathematical model for shielded loop resonators. The model implies equivalent circuits for coaxial as well as flat Faraday shielded resonators under both balanced and unbalanced termination conditions. Expressions for impedance derived from the model are shown to agree well with observation using two test experimental resonators in a variety of experimental conditions.
1H NMR Detection of Lactate and Alanine in Perfused Rat Hearts during Global and Low Pressure Ischemia
Authors: Zhao Piyu , Storey Charles J. , Babcock Evelyn E. , Malloy Craig R. , Dean Sherry A.
Published: March 2007

A spin‐echo method is presented for obtaining high resolution, 13C coupled, proton spectra of lactate and alanine in intact, beating rat hearts. All hearts were depleted of glycogen prior to prolonged perfusion with either 10 mM unenriched glucose or [1−13C]glucose to restore glycogen. These two groups of hearts were then examined by 1H NMR during prolonged global (zero flow) or low pressure (low flow) ischemia. During global ischemia, lactate was derived from both glucose and glycogen, with endogenous glycogen contributing twice as much lactate as exogenous glucose. During low perfusion pressure ischemia, however, lactate was derived exclusively from exogenous glucose. The entire pool of lactate (both 12C and 13C) was visible by NMR in intact, glucose perfused hearts while alanine was not detected. However, upon adding 10 mM pyruvate to the perfusate, the entire alanine pool became NMR visible while some of the lactate became NMR invisible. These observations indicate that the NMR visibility of small, usually highly mobile metabolites such as alanine and lactate is not always 100% in intact hearts and that the NMR visibility of these molecules may depend upon which exogenous substrate is presented to the heart.
Breath‐Hold 3D STAR MR Angiography of the Renal Arteries Using Segmented Echo Planar Imaging
Authors: Wielopolski Piotr A. , Adamis Mary , Prasad Pottumarthi , Gaa Jochen , Edelman Robert
Published: March 2007

Three‐dimensional (3D), cardiac triggered renal MR angiograms were acquired with excellent background suppression within a single breath‐hold of 18 to 30 s using signal targeting with alternating radiofrequency (STAR), a subtraction time‐of‐flight MR angiography technique, and a 3D scheme combining echo planar imaging (EPI) readouts and k‐space segmentation. The 3D STAR sequence was evaluated on 17 healthy individuals, 3 potential renal donors, and 2 patients with suspected renovascular hypertension. An inversion tag through the aorta was applied to produce the vascular contrast. After a suitable inflow time, 16 to 64 sections were encoded. An additional presaturation pulse applied over the imaging volume prior to tagging permitted improved background suppression by reducing signal variations from involuntary motion and changes in the cardiac period during breath‐holding. Intrarenal branches were observed consistently in all healthy individuals. Longer inflow times provided better depiction of the intrarenal vessels while shorter delays delineated the proximal renal branches with better signal‐to‐noise ratio. Breath‐hold and diastolic data collection reduced both blurring and flow related dephasing. Our results demonstrate excellent visualization of the renal arteries to the level of intrarenal branch vessels using the proposed technique.
Intracellular Volume Measurement and Detection of Edema: Multinuclear NMR Studies of Intact Rat Hearts during Normothermic Ischemia
Authors: Askenasy Nadir , Tassini Maria , Vivi Antonio , Navon Gil
Published: March 2007

The present study describes the cell volume dynamics in intact rat hearts, during ischemia and after reperfusion. Cell volumes were measured in isolated hearts by either 13C or 59Co NMR of mannitol or cobalticyanide, respectively, as extracellular markers and 1H NMR of water as the aqueous space marker. A constant volume chamber was built inside a 15‐mm NMR tube; the contents of the chamber were measured with and without a heart. The intracellular volume of isolated rat hearts was estimated to be 2.45 ± 0.13 ml/g dry weight. In the perfused heart, adenosine triphosphate (ATP) and phosphocreatine (PCr) concentrations were calculated to be 12.2 ± 0.7 and 16.1 ± 1.0 mM, respectively. Consecutive volume measurements showed cell swelling of 16% during 30 min of ischemia, which was reduced at reperfusion to 7%. After 30 min of reperfusion, ATP and PCr concentrations were 4.5 ± 0.8 and 8.1 ± 0.9 mM. It is concluded that: (1) cell swelling is an ischemic event, which is partially reversed by reperfusion; and (2) continuous measurement of cell volumes provides intracellular molar concentrations of metabolites, which are the physiologically significant parameters.
Quantitative Mapping of Ocular Oxygenation Using Magnetic Resonance Imaging
Authors: Berkowitz Bruce A. , Wilson Charles A.
Published: March 2007

Retinal hypoxia is hypothesized to initiate angiogenesis, a leading cause of blindness in developed countries. Attempts to test this hypothesis suffer from the need to use highly invasive oxygen electrodes. In this communication, noninvasive and quantitative mapping of ocular oxygenation using magnetic resonance imaging is demonstrated for the first time.
Relative Concentrations of Proton MR Visible Neurochemicals in Gray and White Matter in Human Brain
Authors: Doyle Timothy J. , Bedell Barry J. , Narayana Ponnada A.
Published: March 2007

The relative distributions of N‐acetylaspartate (NAA) + N‐acetylaspartylglutamate (NAAG), creatine + phosphocreatine (Cr/PCr), and choline (Cho) in the gray and white matter of human brain were determined by utilizing proton magnetic resonance spectroscopic imaging (SI). The SI data was processed using an automated spectroscopic image processing algorithm, and image segmentation was performed using a supervised technique. Linear regression analysis indicated that the NAA + NAAG (2.01 ppm) and Cr/PCr (3.02 ppm) peaks are greater in gray matter compared with white matter. The large intersubject variation observed in the Cho (3.20 ppm) resonance prevented the assessment of its regional distribution with confidence.
RF Electric Field Mapping in MR Coils with a Quartz Crystal
Authors: Wang Dah‐Jyuu , Leigh John S.
Published: March 2007

The electric field strength and distribution in MRI/MRS probes was assessed with a quartz crystal whose resonance frequency coincided with the probe frequency. A quartz crystal was used as the sensor because: (i) it was capable of producing a resonance signal when it was excited with a pulsed RF electric field; and (ii) the resonance signal was proportional to the square of the electric field strength (or RF excitation power). The sensor was placed in the vicinity of the MR coil under evaluation and was excited with a short RF pulse applied to the coil and, immediately after the pulse, the resonance signal induced was picked up by the same coil acting as a receiver coil. Intensities of the signals were used to assess the distribution of RF electric fields in the coil. This device is useful for probe design, particularly in the minimization of dielectric losses, which have been attributed to the presence of electric fields in MR coils.
Multislice first‐pass myocardial perfusion imaging on a conventional clinical scanner
Authors: Walsh Edward G. , Doyle Mark , Lawson Mark A. , Blackwell Gerald G. , Pohost Gerald M.
Published: March 2007

A technique is demonstrated for the acquisition and processing of multislice, first‐pass contrast‐enhanced pelfusion images in the myocardium. The acquisition is a modification of “keyhole” imaging in which time series images are acquired by sampling a limited segment of k‐space, corresponding to the low spatial frequencies. In the modification demonstrated here, keyhole samples are divided into two groups that are sampled on alternate cardiac cycles. The alternate “missing” k‐space portions are synthesized by Fourier interpolation. Visualization of contrast agent accumulation by image subtraction is demonstrated. A motion artifact reduction process using time domain Fourier filtering is used to reduce artifacts from respiration. Studies were performed on 46 patients at 1.5 T using gadoteridol (0.05–0.1 mmol/kg) injected into the right antecubital vein in conjunction with radionuclide imaging. Fully concordant studies were noted in 27 of these patients. Remaining studies were either partially or completely discordant for reasons relating to the differing natures of radionuclide versus MR contrast agent characteristics.
Theory of 1/T1 and 1/T2 NMRD profiles of solutions of magnetic nanoparticles
Authors: Koenig Seymour H. , Kellar Kenneth E.
Published: March 2007

Organically coated iron oxide crystallites with diameters of 5–50 nm (“nanoparticles”) are potential magnetic resonance imaging contrast agents. 1/T1 and 1/T2 of solvent water protons are increased dramatically by magnetic interactions in the “outer sphere” environment of the nanoparticles; subsequent diffusive mixing distributes this relaxation throughout the solvent. Published theory, valid for the solute magnetic energy small compared with thermal energy, is applicable to small magnetic solutes (e.g., gadolinium and manganese diethylenetriaminopentaacetic acid, and nitroxide free radicals) at generally accessible fields (≤ 50 T). It fails for nanoparticles at fields above ˜0.05 T, i.e., at most imaging fields. The authors have reformulated outer sphere relaxation theory to incorporate progressive magnetic saturation of solute nanoparticles and, in addition, indicate how to use empirical magnetization data for realistic particles when their magnetic properties are not ideal. It is important to handle the effects of rapid thermally induced reorientation of the magnetization of the nanoparticles (their “superparamagnetism”) effectively, including their sensitivity to particle size. The theoretical results are presented as the magnetic field dependence (NMRD profiles) of 1/T1 and 1/T2, normalized to Fe content, for three sizes of particles, and then compared with the limited data extant for well‐characterized material.
In Vivo proton MR spectroscopy of human gliomas: definition of metabolic coordinates for multi‐dimensional classification
Authors: Hagberg Gisela , Burlina Alessandro P. , Mader Irina , Roser Werner , Radue Ernst W. , Seelig Joachim
Published: March 2007

Several multi‐dimensional statistical evaluation methods were applied to single‐voxel proton MR spectra of glial brain tumors and of healthy volunteers. Metabolic coordinates with histological relevance for future diagnosis were found by which spectra from controls, low‐grade tumors, and highgrade tumors were completely separated. Significant differences between low‐grade and high‐grade glioma patients and controls were found for several metabolic ratios by variance analysis. Cluster analysis both with and without principal component analysis was applied. The outcome of these two approaches depended mainly on the lipid‐to‐creatine ratio. Two other approaches, discriminant factor analysis and the orthonormal discriminant vector method were then used to find discriminatory metabolic coordinates. It turned out that a linear combination of all evaluable metabolic ratios made it possible to separate the three groups completely. On the basis of these results, a classification method that uses the entire proton MRS spectrum is proposed.
Noninvasive MRI thermometry with the proton resonance frequency method: Study of susceptibility effects
Authors: Poorter John De
Published: March 2007

The temperature dependence of proton resonance frequency (PRF) is related to the temperature dependence of the screening constant and of the volume susceptibility constant. To evaluate the relative importance, an experimental setup was designed allowing quantification of both effects in different tissues, notably pure water in a gel structure, and porcine muscle and fat tissue. The temperature varied from 28 to 44°C, a range significant for hyperthermia applications. Good agreement with results from the literature was obtained for water. Porcine muscle tissue behaves like water. Its screening constant varies linearly at a rate of 0.97 10‐8 (oC)‐1 and the effects of temperature‐induced changes of the susceptibility constant are negligible for muscle thermometry applications. The PRF‐temperature relation in fat tissue, however, is almost completely determined by susceptibility effects.
1H mrs of human brain abscesses in vivo and in vitro
Authors: Rémy Chantal , Grand Sylvie , Laï Ernest Sam , Belle ValéRie , Hoffmann Dominique , Berger FrançOis , Estève FrançOis , Ziegler Anne , Bas Jean‐FrsançOis Le , Benabid Alim L. , Décorps Michel , Segebarth Christoph M.
Published: March 2007

Five patients, each with a brain abscess, were examined by means of 1H MR spectroscopic imaging in vivo. The aspirated pus was analyzed in vitro by means of 1D and 2D COSY 1H MRS. In addition to resonance lines from compounds (lactate, alanine and lipids) often found in the spectra from intracranial tumors, resonance lines were detected from a number of markers of infectious involvement (acetate, succinate, and various amino acids). These results suggest that 1H MRS in vivo might contribute in establishing noninvasively a differential diagnosis between brain abscess and tumor.
Ultra‐fast imaging using low flip angles and fids
Authors: Madio David P. , Lowe Irving J.
Published: March 2007

A new ultra‐fast imaging technique that does not place extreme demands on the speed of the gradient system is described. When used with comparable MRI systems, the rotating ultra‐fast imaging sequence (RUFIS) can acquire images 4 to 5 times faster than gradient‐moment nulled EPI and more than twice as fast as DUFIS, OUFIS, or BURST techniques. Because the technique uses free induction decays instead of echoes, it can be made particularly insensitive to effects of motion, flow, and diffusion. Preliminary images of turbulent flow are presented to demonstrate this insensitivity. However, with appropriate encoding, flow effects may be imaged.
In vivo31p spectroscopy study of treated and untreated recovery of rat partial brain ischemia
Authors: Macri Maria Antonietta , Campanella Renzo , Luca Francesco De , Montalbano Antonio , Taggi Franco , Maraviglia Bruno
Published: March 2007

Quantitative 31P NMR was used to follow the time variation of the hypometabolic response to hypoxic partial ischemia in an animal model. The purpose of the study was to establish the value of this repeated spectroscopy operating by means of a surface coil. It aimed at determining whether a therapeutic intervention could influence the transient changes occurring during the insult or early recovery. A pharmacological substance was thus used during a reversible forebrain ischemia, induced by a combination of vascular occlusion and mild hypoxia in two groups of rats. As an available and convenient example, L‐carnitine was chosen. Statistical analysis of the experimental results revealed a significant difference of the P1 and PCr levels between treated and untreated animals.
Simultaneous calculation of flow and diffusion sensitivity in steady‐state free precession imaging
Authors: Gudbjartsson HÁKon , Patz Samuel
Published: March 2007

In this paper the authors quantitatively evaluate the combined effect of both flow and diffusion in steady‐state free precession (SSFP) imaging. A partition analysis (PA) is used to derive a fourth order approximation (in E2) of the signal in an echo SSFP sequence. The authors also introduce a novel very fast simulation technique, based on a circular convolution, which accurately accounts for both flow and diffusion. A 2D SSFP‐echo sequence was implemented to obtain experimental data from a phantom containing three different solutions. Excellent agreement between the theory and the experimental data was found. Then by using the simulation algorithm and experimental measurements of in vivo brain motion, the authors estimated the artifacts to be expected in SSFP diffusion imaging of the brain and found them to be comparable with those of pulsed gradient spin echo. Finally, the authors point out the equivalence between the flow sensitivity of SSFP and RF spoiling commonly used in fast imaging.
High resolution renal diffusion imaging using a modified steady‐state free precession sequence
Authors: Ding Shujun , Trillaud Herve , Yongbi Martin , Rolett Ellis L. , Weaver John B. , Dunn Jeff F.
Published: March 2007

A modified steady‐state free precession (SSFP) diffusion sequence is proposed for high resolution renal imaging. A pair of bipolar diffusion gradients was used to minimize the errors in measured apparent diffusion coefficient (ADC) caused by variations in T1, T2, and RF flip angle that have been observed with previously employed SSFP diffusion sequences. Motion sensitivity was reduced by the use of compensated gradients, frame‐by‐frame averaging, and a repetition time of 22 ms, which for a single‐acquisition 128 × 128 image requires only 3 s. High resolution was achieved by signal averaging. The modified sequence was applied to in vivo diffusion measurements. In six normal rat kidneys the ADCs (mean±SD; × 10−3 mm2/s) of the cortex, outer medulla, and inner medulla were 2.28 ± 0.05, 2.38 ± 0.10, and 2.95 ± 0.05, respectively. The technique requires relatively large gradients to achieve adequate diffusion weighting.
MRS imaging using anatomically based K‐space sampling and extrapolation
Authors: Plevritis Sylvia K. , Macovski Albert
Published: March 2007

A comprehensive strategy for the acquisition, reconstruction, and postprocessing of MR spectroscopic images is presented. The reconstruction algorithm is the most critical component of this strategy. It is assumes that the desired image is spatially bounded, meaning that the desired image contains an object that is surrounded by a background of zeros. The reconstruction algorithm relies on prior knowledge of the background zeros fork‐space extrapolation. This algorithm is a good candidate for proton MR spectroscopic image reconstruction because these images are often spatially bounded and prior knowledge of the zeros is easily obtained from a rapidly acquired high resolution conventional MRI. Although the reconstruction algorithm can be used with the standard 3DFTk‐space distribution, a distribution that relies on anatomical features that are likely to occur in the spectroscopic image can produce better results. Prior knowledge of these anatomical features is also obtained from a conventional MRI. Finally, the postprocessing component of this strategy is valuable for reducing subcutaneous lipid contamination. Overall, the comprehensive approach presented here produces images that are better resolved than standard approaches without increasing acquisition time or reducing SNR. Examples using NAA data are provided.
Coronary artery imaging at 0.5 t using segmented 3d echo planar imaging
Authors: Börnert Peter , Jensen Dye
Published: March 2007

The application of segmented 3D gradient echo EPI at 0.5 T for coronary artery imaging is described. Experiments were performed using fat suppression, ECG triggering, and a patient‐controlled breath‐holding scheme. This approach provides a sufficient signal‐to‐noise ratio for thin contiguous slices in conjunction with a phased array cardiac receive coil. Wide 3D volumes, covering the proximal branches of the coronary tree, were measured with a high spatial resolution. Such data sets can be used for subsequent vessel segmentation. Furthermore, data out of narrow 3D volumes were obtained containing fewer slices angulated in the direction of a selected coronary artery. This provides a good visualization of the selected vessel over several centimeters without the need for segmentation.
An in vivo automated shimming method taking into account shim current constraints
Authors: Wen Han , Jaffer Farouc A.
Published: March 2007

Many in vivo imaging techniques require magnetic field homogeneity in the volume of interest. Shim coils of the second and third order spherical harmonics have been used successfully to compensate for complicated field variations caused by the human anatomy itself. The available currents of these coils are invariably limited. In this note we demonstrate that these limits significantly affect the optimal shim condition. We propose an automated in vivo shimming method for arbitrary volumes of interest using 3‐dimensional (3D) field maps. This method is a modification of previous works using least‐squares criteria. The main difference is that a constrained optimization is performed in vivo under the current limits of the shim coils, which improved the field homogeneity significantly over simple truncations of the least‐squares solutions. This shimming method was used with head scans of five normal volunteers on a 4.0 tesla scanner. A fast double‐echo sequence was used to obtain field maps, and a new field uniformity measure was derived for this method. The field mapping sequence was tested against a standard single‐echo Dixon sequence used by previous investigators, and the stability of the shimming method was tested by repeated studies on the same subject.
Analysis of practical policies for a single link distribution system
Authors: Bertazzi Luca , Chan Lap Mui Ann , Speranza Maria Grazia
Published: March 2007

In this paper we consider a transportation problem where several products have to be shipped from an origin to a destination by means of vehicles with given capacity. Each product is made available at the origin and consumed at the destination at the same constant rate. The time between consecutive shipments must be greater than a given minimum time. All demand needs to be satisfied on time and backlogging is not allowed. The problem is to decide when to make the shipments and how to load the vehicles with the objective of minimizing the long run average of the transportation and the inventory costs at the origin and at the destination over an infinite horizon. We consider two classes of practical shipping policies, the zero inventory ordering (ZIO) policies and the frequency‐based periodic shipping (FBPS) policies. We show that, in the worst‐case, the Best ZIO policy has a performance ratio of
$\sqrt{2}$. A better performance guarantee of ${16\sqrt{3045}\over 255} - {37\over 17} \approx 1.286$
is shown for the best possible FBPS policy. The performance guarantees are tight. Finally, combining the Best ZIO and the Best FBPS policies, a policy that guarantees a $5\over 4$
performance is obtained. Computational results show that this policy gives an average percent optimality gap on all the tested instances of <1%. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007
Home blood glucose monitoring in children with insulin‐dependent diabetes mellitus
Authors: Tomalin Deborah , Moyer Alwyn
Published: March 2007

Home blood glucose monitoring (HBGM), if performed correctly, is potentially the most satisfactory way of monitoring diabetic control. This study describes the prevalence, pattern and performance of HBGM in 171 children, aged 10‐16 years, with insulin‐dependent diabetes mellitus (IDDM). All children had access to a diabetes specialist nurse (DSN) and all but two performed blood tests routinely, with 82% maintaining a record book. Blood tests were found to be adequate in number but failed to cover the ideal spectrum of test points over a one week period. The majority of children were responsible for their own HBGM and 79% altered their insulin without first consulting a doctor or nurse; 28% of those altering insulin did so without parental advice. Only 56% of children performed tests competently; skill was associated with age but not with duration of diabetes. Educational strategies are suggested.
Shared care for diabetes in Chester: Preliminary experience with a ‘clinic‐wide’ scheme
Authors: Worth R C , Nicholson Ann , Bradley Pam
Published: March 2007

In conjunction with local general practices a scheme for shared care of diabetes was set up with an initial pilot study in 1985. Subsequently this was expanded to include virtually all patients with insulin‐dependent diabetes and non‐insulin‐dependent diabetes attending the hospital clinic and incorporated over 1200 patients by the end of 1989. In the pilot study the improved ability to screen for complications was not offset by any deterioration in biochemical control resulting from the reduced frequency of hospital visits. Patients and general practitioners appeared enthusiastic in support of the ‘clinic‐wide’ Chester shared care scheme.
Practical advice for new diabetes specialist nurses
Authors: Wallymahmed Maureen
Published: March 2007

The number of nurses specialising in the care of people with diabetes is increasing rapidly. On Merseyside in 1984 only four hospitals employed diabetes specialist nurses. However, six years later there are at least 16 specialist nurses working in the ten health districts and each district employs at least one specialist nurse.

The British Diabetic Association (BDA) recommends that each district health authority should have, as an absolute minimum, one nurse whose full time work is with diabetic patients and their families. We are likely to see many more appointments made nationally in the next decade.

Several useful articles have been written on the role of the diabetes specialist nurse1–5 but these contain limited practical guidelines for the newly appointed person.

I have recorded my observations and experiences over my first two years as a diabetes specialist nurse and suggest guidelines for nurses joining this speciality.
Transplacental passage of insulin in pregnant women with insulin‐dependent diabetes mellitus. Menon R K, Cohen R M, Sperling M A, et al. New England Journal of Medicine, 1990; 323: 309–15
Authors: Shaw K M
Published: March 2007

Fifty one babies of insulindependent mothers had cord blood measured for levels of insulin and anti‐insulin antibody. of six mothers who only received human insulin during pregnancy, only human insulin was detected in cord blood, whereas 28 out of 45 of those whose mothers had received animal insulin, up to 27% of total insulin within cord blood proved to be of animal origin. significant correlation between maternal and cord blood levels of both insulin and anti‐insulin antibodies was found. suggesting that considerable amounts of anti‐body bound insulin could bc transferred across the placenta during pregnancy. Furthermore high concentrations of animal insulin in cord blood correlated with both increased birth weight and in particular macrosomia.
Prevalence of serological markers for hepatitis‐B in patients with insulin‐dependent diabetes
Authors: Pozzilli P , Pagani S , Buzzetti R , Cruciani L , Beales P E , Cucinotta D , Benzi L , Porta M , Biasio L , Zanetti A , Tanzi E , Andreani D
Published: March 2007

The prevalence of serological markers for hepatitis‐B infection was investigated in patients affected by insulin‐dependent diabetes (IDDM) living in different Italian regions and in the London area of the UK.

Thirty five percent of Italian and 13% of British patients showed positive markers for hepatitis‐B infection but none was found to be HBsAg carrier positive.

When these results are compared with data observed in control populations in both countries, these findings suggest a higher prevalence of hepatitis‐B infection in patients with IDDM. However, the negativity for HbsAg indicates that diabetic patients infected by the hepatitis‐B virus have an effective capacity for clearance of HBsAg.
Quality matters and standard setting
Authors: Craddock S , Girvin J
Published: March 2007

This article documented the problems of standard setting in a group of six ward nurses, a nurse teacher and the author, a senior nurse at the Royal Gwent Hospital, Newport.

The group's knowledge of standard setting was limited, and in order to increase knowledge, members read about current work being conducted in other authorities and attended study days and seminars. The need to incorporate the views and advice of ward nurses was agreed.

After a visit from Alison Kitson, the Royal College of Nursing's Standards of Care Project Director, the group devised, a strategy for setting standards in South Gwent based on the Dynamic Standard Setting System, which particularly points out the need for support at all levels of the organisation.

The first priority was to devise an education programme that would reach all nurses throughout the unit rapidly.

Half day seminars where small groups of nurses were given information on standards and practical experience of writing a standard for themselves were organised. About four half day seminars are run each month at the District General Hospital and the peripheral hospitals are served on an ad hoc basis.

Guidance support and explanation of standards are given. Some standards are now being audited, and methods include patient questionnaires, nurse questionnaires, chart audit and direct observation.

Provisional results show some significant changes are taking place, one ward has reduced the prevalence of pressure sores by 50 per cent, for example.

It took nearly two years to get standard setting off the ground, but South Gwent nurses are now writing and measuring their own standards, and taking responsibility for identifying any necessary changes in their working practice.