bluuebunny/crossref_metadata_2025_split huggingface dataset:
Keyhole Dixon method for faster, perceptually equivalent fat suppression
Authors: Flask Chris A. , Salem Kyle A. , Moriguchi Hisamoto , Lewin Jonathan S. , Wilson David L. , Duerk Jeffrey L. 
Published: June 2003

AbstractPurposeTo reduce the acquisition time associated with the two‐point Dixon fat suppression technique by combining a keyhole in‐phase (Water + Fat) k‐space data set with a full out‐of‐phase (Water – Fat) k‐space data set and optimizing the keyhole size with a perceptual difference model.Materials and MethodsA set of keyhole Dixon images was created by varying the number of lines in the keyhole data set. Off‐resonance correction was incorporated into the image reconstruction process to improve the homogeneity of the fat suppression. A perceptual difference model (PDM) was validated with human observer experiments and used to compare the keyhole images to images from a full two‐point Dixon acquisition. The PDM was used to determine the smallest keyhole width required to obtain perceptual equivalence to images obtained from the full two‐point Dixon method.ResultsIn experimental phantom studies, the keyhole Dixon image reconstructed from 96 of 192 Water + Fat k‐space lines and 192 Water – Fat k‐space lines was perceptually equivalent to the full (192 + 192) two‐point Dixon images, resulting in a 25% reduction in scan time. Clinical images of a volunteer's knee, orbits, and abdomen created from the smallest, perceptually equivalent keyhole width resulted in a 27%–38% reduction in total scan time.ConclusionThis method improves the temporal efficiency of the conventional two‐point Dixon technique and may prove especially useful for high‐field systems where specific absorption rate (SAR) limits will constrain radiofrequency (RF)‐based fat suppression techniques. J. Magn. Reson. Imaging 2003;18:103–112. © 2003 Wiley‐Liss, Inc.
Three‐dimensional method for comparing in vivo interventional MR images of thermally ablated tissue with tissue response
Authors: Breen Michael S. , Lancaster Tanya L. , Lazebnik Roee S. , Nour Sherif G. , Lewin Jonathan S. , Wilson David L. 
Published: June 2003

AbstractPurposeTo investigate the ability of magnetic resonance (MR) to monitor radio‐frequency (RF) ablation treatments by comparing MR images of thermal lesions to histologically assayed cellular damage. We developed a new methodology using three‐dimensional registration for making spatial correlations.Materials and MethodsA low‐field, open MRI system was used to guide an ablation probe into rabbit thigh muscle and acquire MR volumes after ablation. After fixation, we sliced and photographed the tissue at 3‐mm intervals, using a specially designed apparatus, to obtain a volume of tissue images. Histologic samples were digitized using a video microscopy system. For our three‐dimensional registration method, we used the tissue images as the reference, and registered histology and MR images to them using two different computer alignment steps. First, the MR volume was aligned to the volume of tissue images by registering needle fiducials placed near the tissue of interest. Second, we registered the histology images with the tissue images using a two‐dimensional warping technique that aligned internal features and the outside boundary of histology and tissue images.ResultsThe MR and histology images were very well aligned, and registration accuracy, determined from displacement of needle fiducials, was 1.32 ± 0.39 mm (mean ± SD), which compared favorably to the MR voxel dimensions (0.70 mm in‐plane and 3.0 mm thick). A preliminary comparison of MR and tissue response showed that the region inside the elliptical hyperintense rim in MR closely corresponds to the region of necrosis as established by histology, with a mean absolute distance between MR and histology boundaries of 1.17 mm, slightly smaller than the mean registration error. The MR region slightly overestimated the region of necrosis, with a mean signed distance between boundaries of 0.85 mm.ConclusionOur results suggest that our methodology can be used to achieve three‐dimensional registration of histology and in vivo MR images. In MR lesion images, the inner border of the hyperintense region corresponds to the border of irreversible cell damage. This is good evidence that during RF ablation treatments, iMRI lesion images can be used for real‐time feedback. J. Magn. Reson. Imaging 2003;18:90–102. © 2003 Wiley‐Liss, Inc.
Methodological considerations for measuring rates of brain atrophy
Authors: Gunter Jeffrey L. , Shiung Maria M. , Manduca Armando , Jack Clifford R. 
Published: June 2003

AbstractPurposeTo systematically compare two techniques for measuring brain atrophy rates from serial magnetic resonance imaging (MRI) studies.Materials and MethodsUsing the separation in atrophy rate between cohorts of cognitively normal elderly subjects and patients with Alzheimer's disease (AD) as the gold standard, we evaluated 1) different methods of computing volume change; 2) different methods for steps in image preprocessing—intensity normalization, alignment mask used, and bias field correction; 3) the effect of MRI acquisition hardware changes; and 4) the sensitivity of the method to variations in initial manual volume editing. For each of the preceding evaluations, measurements of whole‐brain and ventricular atrophy rates were calculated.ResultsIn general, greater separation between the clinical groups was seen with ventricular rather than whole‐brain measures. Surprisingly, neither the use of bias field correction nor a major hardware change between the scan pairs affected group separation.ConclusionAtrophy rate measurements from serial MRI are candidates for use as surrogate markers of disease progression in AD and other dementing neurodegenerative disorders. The final method has excellent precision and accurately captures the expected biology of AD—arguably the two most important features if this technique is to be used as a biomarker of disease progression. J. Magn. Reson. Imaging 2003;18:16–24. © 2003 Wiley‐Liss, Inc.
Echo planar imaging at 4 tesla with minimum acoustic noise
Authors: Tomasi Dardo G. , Ernst Thomas 
Published: June 2003

AbstractPurposeTo minimize the acoustic sound pressure levels of single‐shot echo planar imaging (EPI) acquisitions on high magnetic field MRI scanners.Materials and MethodsThe resonance frequencies of gradient coil vibrations, which depend on the coil length and the elastic properties of the materials in the coil assembly, were measured using piezoelectric transducers. The frequency of the EPI‐readout train was adjusted to avoid the frequency ranges of mechanical resonances.ResultsOur MRI system exhibited two sharp mechanical resonances (at 720 and 1220 Hz) that can increase vibrational amplitudes up to six‐fold. A small adjustment of the EPI‐readout frequency made it possible to reduce the sound pressure level of EPI‐based perfusion and functional MRI scans by 12 dB.ConclusionNormal vibrational modes of MRI gradient coils can dramatically increase the sound pressure levels during echo planar imaging (EPI) scans. To minimize acoustic noise, the frequency of EPI‐readout trains and the resonance frequencies of gradient coil vibrations need to be different. J. Magn. Reson. Imaging 2003;18:128–130. © 2003 Wiley‐Liss, Inc.
Acromiohumeral distance in a seated position in persons with impingement syndrome
Authors: Hébert Luc J. , Moffet Hélène , Dufour Marie , Moisan Christian 
Published: June 2003

AbstractPurposeTo compare the acromiohumeral distance (AHD) of both shoulders in subjects with a unilateral shoulder impingement syndrome (SIS) and healthy subjects in a seated position during free shoulder movements of large amplitude.Materials and MethodsUsing a 0.5‐Tesla SIGNA‐SP/i™ open‐configuration magnetic resonance imaging (MRI) system, the AHD was measured at several arm positions, in a standardized seated position.ResultsIn flexion (rest to 130°), the mean AHD of SIS varied from 8.3 to 2.8 mm, as compared to from 8.7 to 4.1 mm for asymptomatic contralateral shoulders. In abduction (rest to 110°), the AHD varied from 8.1 to 3.4 mm and from 8.8 to 4.6 mm for SIS and asymptomatic shoulders, respectively. The smallest AHD (P < .01) was observed at 110°. From 80° of arm elevation, the AHD was significantly smaller in impingement than in asymptomatic shoulders (P < .05). The AHD of asymptomatic shoulders did not differ from that of healthy subjects. In SIS, the AHD at rest was correlated with its reduction at all shoulder positions (rp = 0.62–0.88), but was a poor predictor of the smallest AHD observed at 110° (flexion, R2 = 0.09; abduction, R2 = 0.08).ConclusionIn the critical arm elevation positions for impingement, AHD is discriminative for SIS, compared to asymptomatic shoulders and healthy ones. AHD at rest is a good indicator of the magnitude of its reduction in elevation, but not of the smallest AHD in arm elevation. J. Magn. Reson. Imaging 2003;18:72–79. © 2003 Wiley‐Liss, Inc.
Perilesional hyperintense rim of malignant hepatic tumors on ferumoxide‐enhanced T1‐weighted gradient‐echo MR images: Correlation between MR imaging and histopathologic findings
Authors: Kanematsu Masayuki , Matsuo Masayuki , Yamada Yasuhiro , Semelka Richard C. , Kondo Hiroshi , Goshima Satoshi , Hoshi Hiroaki , Moriyama Noriyuki 
Published: June 2003

AbstractPurposeTo correlate the perilesional hyperintense rim of malignant hepatic tumors seen on ferumoxide‐enhanced T1‐weighted gradient‐echo (GE) MR images with histopathologic findings.Materials and MethodsIn 13 tumors in 12 patients, T1‐weighted GE images (TE of 1.4 msec, flip angle of 90 degrees) obtained after IV administration of ferumoxide were evaluated. MR imaging was initiated within one hour of the completion of ferumoxide administration. Surgical resection for tumors was performed within an interval of two weeks of the MR imaging. Resected specimens were histopathologically examined for peritumoral sinusoidal congestion, desmoplastic reaction, compressed hepatic parenchyma, lymphocytic infiltration, and vascular proliferation.ResultsIn twelve tumors (92%), prominently (N = 2), moderately (N = 5), and mildly to minimally (N = 5), a perilesional hyperintense rim was observed. Among histopathologic findings, the degree of peritumoral sinusoidal congestion correlated (R = .75, P < .04) with the degree of perilesional hyperintense rim. The thickness of the perilesional hyperintense rim showed a moderate positive correlation (R = .65, P < .02) with the thickness of peritumoral area with sinusoidal congestion.ConclusionPerilesional hyperintense rim of malignant hepatic tumors on ferumoxide‐enhanced T1‐weighted GE images may correlate with sinusoidal congestion surrounding malignant hepatic tumors. J. Magn. Reson. Imaging 2003;18:40–48. © 2003 Wiley‐Liss, Inc.
Comparison of right ventricular volume measurements between axial and short axis orientation using steady‐state free precession magnetic resonance imaging
Authors: Alfakih Khaled , Plein Sven , Bloomer Tim , Jones Tim , Ridgway John , Sivananthan Mohan 
Published: June 2003

AbstractPurposeTo compare right ventricular (RV) volume measurements and their reproducibility between axial and short axis orientation acquisition techniques.Materials and MethodsMeasurements of RV volumes from data sets acquired in axial and short axis orientations were compared in 20 normal subjects. The observer variabilities were assessed and the left ventricle (LV) and RV stroke volumes (SV) were compared.ResultsThere was a significant and systematic difference in the EDV and ESV volumes between the axial and short axis methods. The latter method resulted in larger volumes (mean bias EDV 7.5 ± 13.2, 4.7% difference; ESV 7.2 ± 8.6, 10.7% difference). The axial method had lower intra‐ and interobserver variability than the short axis method. The standard deviation of the difference (SDD) and the limits of agreement were consistently lower for the axial method. The mean differences between LV and RV stroke volumes expressed as mean ± 1 SD (r2 =correlation coefficient) were: axial 7.6 ± 9.1 (r2 = 0.93); and short axis 7.4 ± 10.8 (r2 = 0.90).ConclusionThere is a significant systematic difference between volumes measured using the two different orientations. The axial orientation resulted in better inter‐ and intraobserver reproducibility. J. Magn. Reson. Imaging 2003;18:25–32. © 2003 Wiley‐Liss, Inc.
Functional magnetic resonance imaging: A review of methodological aspects and clinical applications
Authors: Hennig Jürgen , Speck Oliver , Koch Martin A. , Weiller Cornelius 
Published: June 2003

AbstractThis paper gives an overview of the recent literature on methodological developments of functional magnetic resonance imaging (fMRI) and recent trends in clinical applications. With the recent introduction of high‐field systems and methodological developments leading to more robust signal behavior, fMRI is in a transition state from a research modality for use by experts to a standard procedure with useful applications in patient management. Compared to the use in neuroscientific research, which is often based on BOLD techniques alone, the application in patients is distinguished by a multiparametric characterization of the brain using a combination of several techniques. Neuronal fiber tracking based on diffusion anisotropy measurements, in particular, has already turned out to provide relevant supplementary information to the BOLD‐based cortical activation maps. J. Magn. Reson. Imaging 2003;18:1–15. © 2003 Wiley‐Liss, Inc.
Dynamic T1 estimation of brain tumors using double‐echo dynamic MR imaging
Authors: Ishimori Yoshiyuki , Kimura Hirohiko , Uematsu Hidemasa , Matsuda Tsuyoshi , Itoh Harumi 
Published: June 2003

AbstractPurposeTo assess the clinical utility of a new method for real‐time estimation of T1 during the first pass of contrast agent by using this method to examine brain tumors.Materials and MethodsThe multi‐phase spoiled gradient‐echo pulse sequence using the double‐echo magnetic resonance (MR) technique was modified. In the first half of the pulse sequence, the flip angle was varied systematically. Then, static T1 values were calculated using differences in MR signal intensities between different flip angles. In the latter half of this sequence, changes in absolute T1 were calculated using differences in signal intensities before and after injection of contrast agent. The double‐echo MR data were used to minimize the T2* effect. Five cases of neurinoma and seven cases of meningioma were examined. Changes in T1 during the first pass of contrast agent were compared between neurinoma and meningioma.ResultsChanges in absolute T1 were clearly demonstrated on the parametric map. Although the changes in absolute T1 during the first pass of contrast agent did not allow differentiation between the two types of tumors, the mean gradient after the first pass was statistically higher for neurinoma than for meningioma (P < 0.05; meningioma, 0.011 ± 0.012 second−1/second; neurinoma, 0.034 ± 0.020 second−1/second).ConclusionThe present method appears to be useful for estimation of dynamic T1 changes in brain tumors in clinical settings. J. Magn. Reson. Imaging 2003;18:113–120. © 2003 Wiley‐Liss, Inc.
A single breath‐hold multiecho T2* cardiovascular magnetic resonance technique for diagnosis of myocardial iron overload
Authors: Westwood Mark , Anderson Lisa J. , Firmin David N. , Gatehouse Peter D. , Charrier Clare C. , Wonke Beatrix , Pennell Dudley J. 
Published: June 2003

AbstractPurposeTo assess tissue iron concentrations by the use of a gradient echo T2* multiecho technique.Materials and MethodsWe compared the results of measurements of heart T2* from 32 patients using the established multiple breath‐hold variable TR technique with a new multiecho sequence that acquires all images within a single breath‐hold with constant TR.ResultsThere was good agreement of myocardial T2* values between both methods in the abnormal range of T2* < 20 msec (mean difference 0.2msec, 95% CI −1.3 to 0.9 msec, r = 0.97, P < 0.0001). The coefficient of variability between the methods was 3.5%. The interstudy reproducibility using the multiecho sequence had a variability coefficient of 2.3% in the abnormal T2* range and 5.8% over all T2* values. There was good agreement between the techniques for the liver T2* values.ConclusionsThe use of the single breath‐hold, multiecho acquisition allowed reliable quantification of myocardial T2*. The good reproducibility, speed, and T1 independence of this technique allows greater accuracy, faster patient throughput, and, therefore, reduced costs (which is important in developing countries where thalassemia is most prevalent). J. Magn. Reson. Imaging 2003;18:33–39. © 2003 Wiley‐Liss, Inc.
High signal peripancreatic fat on fat‐suppressed spoiled gradient echo imaging in acute pancreatitis: Preliminary evaluation of the prognostic significance
Authors: Martin Diego R. , Karabulut Nevzat , Yang Ming , McFadden David W. 
Published: June 2003

AbstractPurposeTo evaluate peripancreatic signal changes on fat‐suppressed T1‐weighted spoiled gradient echo images associated with acute pancreatitis and investigate potential utility in regards to relationship to clinical outcome.Materials and MethodsThe abdominal MR images in 31 patients with acute pancreatitis were reviewed, and evaluated for the presence of elevated signal intensity within the peripancreatic fat on fat‐suppressed T1‐weighted spoiled gradient echo images; the degree of signal changes was graded as mild, moderate, or severe.ResultsTen of 31 patients demonstrated abnormal high signal intensity in the peripancreatic fat on fat‐suppressed T1‐weighted images. The degree of signal change was mild in three patients, moderate in one, and severe in six patients. All six patients with severe elevated peripancreatic soft tissue signal died within seven to 68 days (mean, 47 days) of their admission. All 21 patients without elevated peripancreatic fat signal survived without any complications. The correlation between the presence and severity of elevated peripancreatic MR signal and patient outcome was significant (P < 0.05).ConclusionElevated peripancreatic signal on fat‐suppressed T1‐weighted images is associated progressively with poor outcome in patients with acute pancreatitis, and may represent a simplified method for prognostic cross‐sectional imaging. J. Magn. Reson. Imaging 2003;18:49–58. © 2003 Wiley‐Liss, Inc.
Spatial excitation using variable‐density spiral trajectories
Authors: Schröder Christoph , Börnert Peter , Aldefeld Bernd 
Published: June 2003

AbstractPurposeTo examine the usefulness of variable‐density k‐space trajectories for the design of multi‐dimensional spatially selective RF pulses.Materials and MethodsExperimental phantom and in vivo studies were performed and confirmed by simulations. Two‐dimensional spatially selective magnetization patterns were excited using variable‐density spiral trajectories and analyzed with respect to the signal excitation outside the excitation field of view (FOX).ResultsBy using variable‐density trajectories, signal excitation outside the FOX was drastically reduced compared to trajectories with a uniform density, while maintaining fairly short pulse durations.ConclusionA main advantage of the method is that unwanted signal excitation outside the nominal FOX can be reduced without significantly increasing the duration of the RF excitation pulse. The variable‐density approach is useful for all applications that require a well‐defined spatial excitation profile, e.g., to perform imaging in a reduced field of view (FOV), for spatial saturation pulses, for curved slice imaging or in MR spectroscopy. J. Magn. Reson. Imaging 2003;18:136–141. © 2003 Wiley‐Liss, Inc.
Role and expression of thrombin receptor PAR‐1 in muscle cells and neuromuscular junctions during the synapse elimination period in the neonatal rat
Authors: Lanuza María A. , Garcia Neus , González Carmen M. , Santafé Manel M. , Nelson Phillip G. , Tomas Josep 
Published: June 2003

AbstractA role for thrombin and its receptor (ThR) during mammalian skeletal muscle cell differentiation and neuromuscular junction (NMJ) formation has been suggested. Previously, we found that the synapse elimination process in the neonatal rat muscle was accelerated by thrombin and blocked by hirudin, its specific inhibitor (Lanuza et al. [2001] J. Neurosci. Res. 63:330–340). To test whether this process resulted from a signal transduction cascade initiated by activation of ThR, in particular PAR‐1, we applied to the levator auris longus (LAL) muscle of newborn rats two synthetic peptides (SFLL and FSLL). SFLL is a potent specific agonist for activation of PAR‐1, whereas FSLL is an inactive peptide. We have demonstrated that the activation of PAR‐1 by SFLL produced acceleration of the presynaptic loss of connections and the postsynaptic maturation of NMJs. Moreover, Western blot analysis showed that PAR‐1 was present in the skeletal muscle, and by immunohistochemistry we detected PAR‐1 in muscle fibers concentrated in the synaptic area but also in satellite cells. Several lines of evidence suggested that PAR‐1 is localized in the postsynaptic membrane: PAR‐1 immunofluorescence was concentrated at denervated synaptic sites and was present in the myotube membrane in vitro in the absence of neurons and in dissociated single muscle fibers from which nerve terminals and Schwann cells had been removed. Taken together, these results indicate that thrombin mediates certain stages of activity‐dependent synapse elimination in the skeletal muscle and does so through its action on the thrombin receptor PAR‐1 localized, at least in part, on the postsynaptic membrane. © 2003 Wiley‐Liss, Inc.
Motor cortical control of cardiovascular bulbar neurones projecting to spinal autonomic areas
Authors: Viltart Odile , Mullier Olivia , Bernet François , Poulain Pierre , Ba‐M'Hamed Saadia , Sequeira Henrique 
Published: June 2003

AbstractThere is evidence that the motor cortex is involved in cardiovascular adjustments associated with somatic motor activity, as it has functional connections with the ventrolateral medulla, a brainstem region critically involved in the control of blood pressure and the regulation of plasma catecholamine levels. The ventrolateral medulla sends projections to the spinal intermediolateral nucleus, where preganglionic neurones controlling heart and blood vessels (T2 segment) and adrenal medulla (T8 segment) are found. The aim of the present study was to determine whether electrical stimulation of the rat motor cortex induces cardiovascular responses and Fos expression in ventrolateral medulla neurones projecting to the T2 and T8 segments. After a set of experiments designed to record cardiovascular parameters (blood pressure and plasma catecholamine levels), injections of retrograde tracer (Fluorogold) were performed in the intermediolateral nucleus of two groups of rats, at the T2 or at the T8 segmental levels. Five days later, the motor cortex was stimulated in order to induce Fos expression in the ventrolateral medulla. Stimulation of the motor cortex induced: (1) hypotension and a significant decrease in plasma noradrenaline levels, and (2) a significant increase in the number of the double‐labelled neurones in the rostral ventrolateral medulla projecting to T2. These data demonstrate that cardiovascular adjustments, preparatory to, or concomitant with, motor activity may be initiated in the motor cortex and transmitted to cardiac and vasomotor spinal preganglionic neurones, via the ventrolateral medulla. © 2003 Wiley‐Liss, Inc.