bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of regional lung function in rats using hyperpolarized 3helium dynamic MRI
Authors: Chen Ben T. , Brau Anja C.S. , Johnson G. Allan 
Published: January 2003

AbstractDynamic regional lung function was investigated in rats using a radial acquisition cine (RA‐CINE) pulse sequence together with hyperpolarized (HP) 3He gas delivered by a constant flow ventilator. Based on regional differences in the behavior of inspired air, the lung was conceptually divided into two regions (the major airways and the peripheral airspace) for purposes of functional analysis. To measure regional function in the major airways, a large RF flip angle (24°) was applied to reduce 3He magnetization in the peripheral airspace, and signal intensity (SI) was normalized with the projected airway diameter to estimate local airflow. Higher normalized signal intensity was observed in the left branch airway as compared to the right branch airway. To determine regional function in the peripheral airspace, a small RF flip angle (6°) was used. Incremental increases of peripheral SI in successive lung images were consistent with the increase in lung volume. A new “skipping” scanning strategy using dummy frames allows a trade‐off between the number of frames acquired for dynamic information, the RF flip angle, and the penetration depth of 3He magnetization into the lung. This work provides a novel approach to simultaneously assess dynamic regional function and morphology. Magn Reson Med 49:78–88, 2003. © 2003 Wiley‐Liss, Inc.
Imaging of ischemia and infarction in blood‐perfused pig hearts using 87Rb MRI
Authors: Kupriyanov V.V. , Xiang B. , Sun J. , Jilkina O. , Kuzio B. 
Published: January 2003

Abstract87Rb‐MRI was used to measure Rb+ uptake in blood‐perfused pig hearts during complete occlusion (120 and 70 min) of the left anterior descending artery (LAD) and subsequent reperfusion (120 and 170 min). The Rb+ uptake rate and maximal Rb image intensity during 120‐min occlusion were significantly lower in the ischemic anterior left ventricular (LV) wall (0.35 ± 0.14%/min and 26 ± 4.7%) relative to those in the remote posterior LV wall (2.43 ± 0.33%/min and 98 ± 10%). Reperfusion after 120 and 70 min of occlusion resulted in formation of damaged areas, which had 40 ± 4 and 73 ± 10% of the 87Rb image intensity observed in the remote posterior wall. The infarct sizes determined histologically by triphenyltetrazolium chloride staining were 9.6 ± 3.4 and 5.6 ± 4.6% of the total ventricular mass (LV + RV) in the 120‐ and 70‐min occlusion groups, respectively. The sizes determined by MRI were 13.1 ± 2 and 2.8 ± 4.3% of the total number of pixels, respectively. The Rb+ uptake in the anterior wall during 120‐min occlusion was somewhat lower than that previously observed in crystalloid‐perfused hearts. It is concluded that blood does not interfere with the ability of 87Rb MRI to detect ischemic and infarct areas. Magn Reson Med 49:99–107, 2003. © 2003 Wiley‐Liss, Inc.
Triggered real‐time MRI and cardiac applications
Authors: Nayak Krishna S. , Hu Bob S. 
Published: January 2003

AbstractReal‐time interactive MRI is becoming the method of choice for many cardiac applications. One current limitation of real‐time techniques is inaccurate slice registration during free‐breathing. A simple “triggered real‐time” imaging approach is proposed which enables the acquisition of synchronized and accurately registered real‐time movie loops during short breathholds. Initial in vivo results demonstrate application to complete 4D ventricular function assessment and fully resolved flow imaging. Magn Reson Med 49:188–192, 2003. © 2003 Wiley‐Liss, Inc.
Detection of [1,6‐13C2]‐glucose metabolism in rat brain by in vivo 1H‐[13C]‐NMR spectroscopy
Authors: de Graaf Robin A. , Brown Peter B. , Mason Graeme F. , Rothman Douglas L. , Behar Kevin L. 
Published: January 2003

AbstractLocalized, water‐suppressed 1H‐[13C]‐NMR spectroscopy was used to detect 13C‐label accumulation in cerebral metabolites following the intravenous infusion of [1,6‐13C2]‐glucose (Glc). The 1H‐[13C]‐NMR method, based on adiabatic RF pulses, 3D image‐selected in vivo spectroscopy (ISIS) localization, and optimal shimming, yielded high‐quality 1H‐[13C]‐NMR spectra with optimal NMR sensitivity. As a result, the 13C labeling of [4‐13C]‐glutamate (Glu) and [4‐13C]‐glutamine (Gln) could be detected from relatively small volumes (100 μL) with a high temporal resolution. The formation of [n‐13C]‐Glu, [n‐13C]‐Gln (n = 2 or 3), [2‐13C]‐aspartate (Asp), [3‐13C]‐Asp, [3‐13C]‐alanine (Ala), and [3‐13C]‐lactate (Lac) was also observed to be reproducible. The 13C‐label incorporation curves of [4‐13C]‐Glu and [4‐13C]‐Gln provided direct information on metabolic pathways. Using a two‐compartment metabolic model, the tricarboxylic acid (TCA) cycle flux was determined as 0.52 ± 0.04 μmol/min/g, while the glutamatergic neurotransmitter flux equaled 0.25 ± 0.05 μmol/min/g, in good correspondence with previously determined values. Magn Reson Med 49:37–46, 2003. © 2003 Wiley‐Liss, Inc.
Performance of a new gadolinium‐based intravascular contrast agent in free‐breathing inversion‐recovery 3D coronary MRA
Authors: Huber Michael E. , Paetsch Ingo , Schnackenburg Bernhard , Bornstedt Axel , Nagel Eike , Fleck Eckart , Boesiger Peter , Maggioni Fabio , Cavagna Friedrich M. , Stuber Matthias 
Published: January 2003

AbstractIn three‐dimensional (3D) coronary magnetic resonance angiography (MRA), the in‐flow contrast between the coronary blood and the surrounding myocardium is attenuated as compared to thin‐slab two‐dimensional (2D) techniques. The application of a gadolinium (Gd)‐based intravascular contrast agent may provide an additional source of signal and contrast by reducing T1blood and supporting the visualization of more distal or branching segments of the coronary arterial tree. In six healthy adults, the left coronary artery (LCA) system was imaged pre‐ and postcontrast with a 0.075‐mmol/kg bodyweight dose of the intravascular contrast agent B‐22956. For imaging, an optimized free‐breathing, navigator‐gated and ‐corrected 3D inversion recovery (IR) sequence was used. For comparison, state‐of‐the‐art baseline 3D coronary MRA with T2 preparation for non‐exogenous contrast enhancement was acquired. The combination of IR 3D coronary MRA, sophisticated navigator technology, and B‐22956 allowed for an extensive visualization of the LCA system. Postcontrast, a significant increase in both the signal‐to‐noise ratio (SNR; 46%, P < 0.05) and contrast‐to‐noise ratio (CNR; 160%, P < 0.01) was observed, while vessel sharpness of the left anterior descending (LAD) artery and the left coronary circumflex (LCX) were improved by 20% (P < 0.05) and 18% (P < 0.05), respectively. Magn Reson Med 49:115–121, 2003. © 2003 Wiley‐Liss, Inc.
Transmit SENSE
Authors: Katscher Ulrich , Börnert Peter , Leussler Christoph , van den Brink Johan S. 
Published: January 2003

AbstractThe idea of using parallel imaging to shorten the acquisition time by the simultaneous use of multiple receive coils can be adapted for the parallel transmission of a spatially‐selective multidimensional RF pulse. As in data acquisition, a multidimensional RF pulse follows a certain k‐space trajectory. Shortening this trajectory shortens the pulse duration. The use of multiple transmit coils, each with its own time‐dependent waveform and spatial sensitivity, can compensate for the missing parts of the excitation k‐space. This results in a maintained spatial definition of the pulse profile, while its duration is reduced. This work introduces the concept of parallel transmission with arbitrarily shaped transmit coils (termed “Transmit SENSE”). Results of numerical studies demonstrate the theoretical feasibility of the approach. The experimental proof of principle is provided on a commercial MR scanner. The lack of multiple independent transmit channels was addressed by combining the excitation patterns from two separate subexperiments with different transmit setups. Shortening multidimensional RF pulses could be an interesting means of making 3D RF pulses feasible even for fast T relaxing species or strong main field inhomogeneities. Other applications might benefit from the ability of Transmit SENSE to improve the spatial resolution of the pulse profile while maintaining the transmit duration. Magn Reson Med 49:144–150, 2003. © 2003 Wiley‐Liss, Inc.
Fast, automated, N‐dimensional phase‐unwrapping algorithm
Authors: Jenkinson Mark 
Published: January 2003

AbstractThis work investigates the general problem of phase unwrapping for arbitrary N‐dimensional phase maps. A cost function‐based approach is outlined that leads to an integer programming problem. To solve this problem, a best‐pair‐first region merging approach is adopted as the optimization method. The algorithm was implemented and tested with 3D MRI medical data for venogram studies, as well as for fMRI applications in EPI unwarping and rapid, automated shimming. Magn Reson Med 49:193–197, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of the dependence of blood R2 and R on oxygen saturation at 1.5 and 4.7 Tesla
Authors: Silvennoinen M.J. , Clingman C.S. , Golay X. , Kauppinen R.A. , van Zijl P.C.M. 
Published: January 2003

AbstractGradient‐echo (GRE) blood oxygen level‐dependent (BOLD) effects have both intra‐ and extravascular contributions. To better understand the intravascular contribution in quantitative terms, the spin‐echo (SE) and GRE transverse relaxation rates, R2 and R, of isolated blood were measured as a function of oxygenation in a perfusion system. Over the normal oxygenation saturation range of blood between veins, capillaries, and arteries, the difference between these rates, R′2 = R − R2, ranged from 1.5 to 2.1 Hz at 1.5 T and from 26 to 36 Hz at 4.7 T. The blood data were used to calculate the expected intravascular BOLD effects for physiological oxygenation changes that are typical during visual activation. This modeling showed that intravascular ΔR is caused mainly by R2 relaxation changes, namely 85% and 78% at 1.5T and 4.7T, respectively. The simulations also show that at longer TEs (>70 ms), the intravascular contribution to the percentual BOLD change is smaller at high field than at low field, especially for GRE experiments. At shorter TE values, the opposite is the case. For pure parenchyma, the intravascular BOLD signal changes originate predominantly from venules for all TEs at low field and for short TEs at high field. At longer TEs at high field, the capillary contribution dominates. The possible influence of partial volume contributions with large vessels was also simulated, showing large (two‐ to threefold) increases in the total intravascular BOLD effect for both GRE and SE. Magn Reson Med 49:47–60, 2003. © 2003 Wiley‐Liss, Inc.
On‐ and off‐resonance T1ρ MRI in acute cerebral ischemia of the rat
Authors: Gröhn Olli H.J. , Mäkelä Heidi I. , Lukkarinen Jouko A. , DelaBarre Lance , Lin Joseph , Garwood Michael , Kauppinen Risto A. 
Published: January 2003

AbstractThe ability of on‐resonance T1ρ (T1ρ) and off‐resonance T1ρ (T) measurements to indicate acute cerebral ischemia in a rat model of transient middle cerebral artery (MCA) occlusion was investigated at 4.7 T. T1ρ was determined with B1 fields of 0.4, 0.8, and 1.6 G, and T with five offset frequencies (Δω) ranging from 0–7.5 kHz at B1 of 0.4 G, yielding effective B1 (Beff) from 0.4 to 1.8 G. Diffusion, T1, and T2 were also quantified. Both T1ρ and T acquired with Δo < 2.5 kHz showed positive contrast during the first hours of MCA occlusion in the ischemic tissue delineated by low diffusion. Interestingly, T contrast acquired with Δω > 2.5 kHz was clearly less sensitive to ischemic alterations, and developed with a delayed time course. This discrepancy is thought to be a consequence of the frequency dependency of cross‐relaxation during irradiation with spin‐lock pulses. Magn Reson Med 49:172–176, 2003. © 2003 Wiley‐Liss, Inc.
Co‐registration of acquired MR ventilation and perfusion images—Validation in a porcine model
Authors: Rizi Rahim R. , Saha Punam K. , Wang Binquan , Ferrante Margaret A. , Lipson David , Baumgardner James , Roberts David A. 
Published: January 2003

AbstractUnder controlled imaging conditions, functional, co‐registered ventilation and perfusion images were obtained for quantitative MRI assessment of pulmonary function. Experiments were conducted on 25–35 kg Yorkshire pigs (N = 5) under ketamine/isoflurane anesthesia. Ventilation and perfusion MR images were obtained using laser polarized gas and gadolinium (Gd), respectively. The mutual information‐based technique was used to quantify the initial misregistration between the acquired ventilation and perfusion images, to cope with different intensity characteristics. Means and standard deviations (SDs) of misregistrations for the five subjects, in terms of absolute translation and absolute rotations around each of the three coordinate axes, were computed to evaluate the hypothesis. For qualitative illustrations, plots of mutual information values under absolute translations and rotations around each of the three coordinate axes are presented. This preliminary study shows the feasibility of acquiring functional image data that are spatially co‐registered. This method has potential applications in the quantitative assessment of regional alveolar ventilation and pulmonary perfusion ratio, in both normal and diseased lung. Magn Reson Med 49:13–18, 2003. © 2003 Wiley‐Liss, Inc.
High‐resolution assessment of blood flow in murine RIF‐1 tumors by monitoring uptake of H217O with proton T1ρ‐weighted imaging
Authors: Tailor Dharmesh R. , Poptani Harish , Glickson Jerry D. , Leigh John S. , Reddy Ravinder 
Published: January 2003

AbstractPerfusion parameters, such as blood flow, are critical properties of tumors related to angiogenesis, drug delivery, radiosensitivity, bioenergetic status, and steady state levels of metabolites, such as lactate, that have been proposed as indices of tumor response to therapy. The existing MR methods for measuring tumor blood flow (TBF) have limitations related to sensitivity, spatial resolution, or dependence on other physiological properties such as vascular permeability. To address many of these difficulties, this study introduces the use of an 17O‐enriched tracer in conjunction with high‐resolution, indirect MRI to measure TBF. To demonstrate the advantages of this technique, relative TBF was measured in subcutaneous RIF‐1 tumors in C3H mice by monitoring the uptake of H217O with a resolution of 0.16 × 0.31 × 3 mm in 13 sec. At this resolution, tumor heterogeneity with respect to blood flow is clearly visible. Measurement of the tracer arterial input function, which is necessary for determination of absolute blood flow, may be facilitated with improved temporal resolution. Magn Reson Med 49:1–6, 2003. © 2003 Wiley‐Liss, Inc.
Viral RNA in nerve tissues of patients with hepatitis C infection and peripheral neuropathy
Authors: De Martino Luisa , Sampaolo Simone , Tucci Celeste , Ambrosone Lucia , Budillon Alberta , Migliaresi Sergio , Di Iorio Giuseppe 
Published: January 2003

AbstractTo assess the presence of viral ribonucleic acid (RNA) in nerve tissues of 15 patients with hepatitis C virus (HCV) infection and peripheral neuropathy with (11) or without (4) mixed cryoglobulinemia, nested reverse transcription–polymerase chain reaction (RT‐PCR) was performed. Amplification of HCV‐RNA was successful in 7 patients with and 3 without mixed cryoglobulinemia. This study demonstrates that the nested RT‐PCR technique is a sensitive method to detect viral RNA in nerve tissue, and offers further evidence that in patients with HCV infection peripheral neuropathy can occur in the absence of mixed cryoglobulinemia. Muscle Nerve 27:102–104, 2003
Two novel mutations in the myophosphorylase gene in a patient with McArdle disease
Authors: Deschauer Marcus , Hertel Kathrin , Zierz Stephan 
Published: January 2003

AbstractWe identified two novel mutations in exon 2 of the myophosphorylase gene in a 33‐year‐old German women with McArdle disease. The patient was compound heterozygous for a novel nonsense mutation at codon 84 changing tyrosine to stop codon (Y84X) and for a novel missense mutation at codon 93 changing arginine to tryptophan (R93W). These mutations are the first to be described in exon 2 and expand the genetic heterogeneity in patients with McArdle disease. Muscle Nerve 27: 105–107, 2003
Predictability of maximum voluntary isometric knee extension force from submaximal contractions in older adults
Authors: Stackhouse Scott K. , Stevens Jennifer E. , Johnson Christopher D. , Snyder‐Mackler Lynn , Binder‐Macleod Stuart A. 
Published: January 2003

AbstractThe purposes of this study were to develop and test a model describing the relationship between the central activation ratio (CAR; a measure of voluntary muscle activation) and percent maximum voluntary contraction (%MVC) force for old adults and to provide a method for more accurate determination of voluntary muscle activation failure. Twenty‐one adults (ages 64–81) performed isometric testing of the quadriceps at 25%, 50%, 75%, and 100% MVC. During each contraction, a 100‐HZ, 120‐ms train of electrical pulses was delivered to the quadriceps muscle to quantify voluntary muscle activation. Similar to a young, healthy population (ages 20–35), a curvilinear relationship existed between the CAR and %MVC force for older adults. Predictions of subjects' MVCs using the linear model of CAR–%MVC force relationship generally demonstrated poor agreement with actual MVCs. Predictions of MVC from submaximal contractions (25%, 50%, and 75%) using a previously identified curvilinear young adult CAR–%MVC relationship were good [ICC (2,1): 0.81, 0.96, and 0.82, respectively]. Similar agreement was obtained from the curvilinear older adult CAR–%MVC relationship. These data suggest that the CAR–%MVC relationship is similar in young and older adult subjects and that curvilinear models of this relationship can predict MVC forces in older adults more accurately. Reexamination of the relationship between the CAR and %MVC force may allow a more accurate determination of how failure of voluntary muscle activation contributes to weakness in old adults. Muscle Nerve 27: 40–45, 2003
Attenuation of stretch‐induced histopathologic changes of skeletal muscles by quinacrine
Authors: Willems Mark E. T. , Stauber William T. 
Published: January 2003

AbstractQuinacrine is an inhibitor of phospholipase A2, an enzyme thought to be involved in activity‐related injury of skeletal muscles. Histopathologic changes after injury by stretches of activated plantar‐flexor muscles were measured in untreated and quinacrine‐treated rats. On day 4 of treatment (50 mg·kg−1 intraperitoneally for 5 days), 30 stretches were induced by ankle rotation after muscles reached a maximal isometric force. During the stretch protocol, peak stretch forces and isometric force deficits after each stretch [total deficits 56.7 ± 2.8% (untreated rats) and 59.6 ± 1.7% (quinacrine‐treated rats)] were similar for both groups (n = 6 each). Two days after the stretch protocol, histopathologic changes were evaluated using antibody staining on cross‐sections of gastrocnemius medialis muscles. Swollen myofibers devoid of desmin were identified. Similar cells, but not all swollen myofibers, in adjacent sections stained for albumin. Quinacrine reduced the number of desmin‐negative and albumin‐positive cells by 88% (P < 0.05) and 84% (P < 0.05), indicating that it attenuated histopathologic changes that follow stretch injury of activated skeletal muscles. Histopathologic changes following muscle injury or myopathic disease may thus be reduced or even prevented by selective drug intervention, thereby reducing the risk of muscle fibrosis. Muscle Nerve 27: 65–71, 2003
Leukocytoclastic‐vasculitic neuropathy associated with chronic Epstein–Barr virus infection
Authors: Kanai Kazuaki , Kuwabara Satoshi , Mori Masahiro , Arai Kimihito , Yamamoto Takako , Hattori Takamichi 
Published: January 2003

AbstractWe report a patient with leukocytoclastic‐vasculitic neuropathy associated with chronic Epstein–Barr virus (EBV) infection. A 55‐year‐old man had been suffering from chronic progressive axonal polyneuropathy and skin erythema for 3 years. A skin biopsy showed capillary vasculitis with clustered leukocyte fragments. Findings of serum assays, a polymerase chain reaction for EBV‐DNA, and in situ hybridization indicated chronic EBV infection. Immunosuppressive treatment resulted in the gradual lessening of his general and neurologic symptoms. Muscle Nerve 27:113–116, 2003
Depression of spinal motoneurons may underlie weakness associated with severe anemia
Authors: Leis A. Arturo , Stokic Dobrivoje S. , Shepherd Jinna M. 
Published: January 2003

AbstractA 37‐year‐old woman had a 2‐week history of progressive weakness, muscle hypotonia, and absent or hypoactive deep tendon reflexes. Nerve conduction studies showed diminished H‐reflexes and absent or decreased persistence of F‐waves in all limbs. The patient was admitted to the hospital with a diagnosis of Guillain–Barré syndrome. Laboratory studies revealed severe anemia with a hemoglobin level of 4.1 g/dl and hematocrit of 15.1%. Immediate blood transfusion resulted in a hemoglobin of 13.2 g/dl and hematocrit of 40.2%, associated with rapid neurological recovery (normal stretch reflexes and muscle strength) and normalization of F‐waves and H‐reflexes. This case demonstrates that severe anemia may be associated with signs and symptoms that mimic Guillain–Barré syndrome, both clinically and electrophysiologically. It also suggests that a relative depression of spinal motoneuron excitability may be a possible mechanism for the weakness that is commonly observed in severe anemia. Muscle Nerve 27:108–112, 2003
Effects of superimposed electrical stimulation on perceived discomfort and torque increment size and variability
Authors: Miller Michael , Downham David , Lexell Jan 
Published: January 2003

AbstractSuperimposed electrical stimulation techniques can be used to detect central activation failure (CAF), that is, incomplete central nervous system recruitment or suboptimal activation of motor units. The purpose of this study was to evaluate the effects of two stimulation parameters on perceived discomfort and torque increment size and variability. Discomfort was evaluated using a visual analog scale (0–100 mm) for pain. The rectus femoris muscle of the dominant leg of 24 young healthy men was stimulated during submaximal (80% maximal) voluntary contractions. The size and variability of torque increments and perceived discomfort were assessed following stimulation with: (1) pulse trains (100 HZ, 150 V, 0.2‐ms pulse duration) of different lengths (50 ms and 100 ms); and (2) pulse trains (100 HZ, 100 ms, 150 V) with different pulse durations (0.2 ms and 0.1 ms). Pulse trains of 100 ms generated larger torque increments and produced less variability, but caused more discomfort than pulse trains of 50 ms. Average discomfort ratings for pulse trains of 100 ms were 43.1 mm, and of 50 ms were 53.2 mm. There was no difference in torque increment size or in variability between pulse trains with pulse durations of 0.1 ms and 0.2 ms, whereas discomfort was less for the shorter pulse durations; average discomfort ratings were 53.1 mm and 58.1 mm for pulse durations of 0.1 ms and 0.2 ms, respectively. Thus, the appropriate selection of stimulation parameters can reduce discomfort but maintain the ability to detect CAF. Muscle Nerve 27: 90–98, 2003