bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of perfusion on exercised muscle: MR imaging evaluation
Authors: Archer Branch T. , Fleckenstein James L. , Bertocci Loren A. , Haller Ronald G. , Barker Bruce , Parkey Robert W. , Peshock Ronald M. 
Published: March 2007

AbstractAn ischemic clamp model of exercise was used to evaluate the potential role of blood flow in mediating changes in the magnetic resonance imaging appearance of skeletal muscle. Proton relaxation times of muscle were serially estimated in 10 healthy subjects (a) before exercise, (b) after exercise in the presence of vascular occlusion (VO1), (c) during vascular reocclusion after 1 minute of reperfusion (VO2), and (d) after reinstitution of continuous flow. T1 and T2 of active muscles were increased during VO1. During VO2, there were additional increases in relaxation times of active muscles. Reinstitution of continuous flow was associated with a continuous decrease in the T2 of exercised muscle. Hence, blood flow was not required for increases in T1 and T2 with exercise. Additional relaxation time increases occurred after a brief period of reperfusion; however, continuous flow was associated with a decrease in T2.
MR imaging of blood vessels with an intravascular coil
Authors: Martin Alastair J. , Plewes Donald B. , Henkelman R. Mark 
Published: March 2007

AbstractA method for producing high‐resolution magnetic resonance (MR) images of blood vessel walls is described. The authors review a theoretical analysis of receiver‐coil design and present a coil well suited for intravascular MR imaging. The design is based on two coaxial solenoids separated by a gap region and with current driven in opposite directions. Placement of this receiver coil within the vascular space is shown to provide a substantial increase in sensitivity over that of external surface coils. Experimental verification of these predictions was obtained in a vessel phantom in which a 13‐cm surface coil was compared with a 3.5‐mm‐diameter opposed‐solenoid intravascular coil. This intravascular coil had a cylindric region of high sensitivity that offered a 10‐fold improvement in signal‐to‐noise ratio over that of an external coil near the vessel wall. The performance of this coil was also tested in the jugular vein of a swine.
Echo‐planar imaging of the central nervous system at 1.0 T
Authors: Schmitt Franz , Stehling Michael K. , Ladebeck Ralf , Fang Ming , Quaiyumi Ali , Bårschneider Erwin , Huk Walter J. 
Published: March 2007

AbstractEcho‐planar imaging (EPI) on the authors' 1‐T prototype im‐ager provides high‐quality 100‐msec images of the central nervous system. Contrast parameters can be chosen freely. Three‐dimensional EPI sequences provide isotropically resolved data sets with 1‐mm resolution. Brain perfusion and blood‐brain barrier disruption can be assessed in time‐course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.
Incremental hydraulic jaw opener for MR imaging of the temporomandibular joint
Authors: Vogl Thomas J. , Eberhard Dieter , Bergman Clifford , Lissner Josef 
Published: March 2007

AbstractMagnetic resonance (MR) imaging in the open‐and closed‐mouth positions is the method of choice for visualizing the temporomandibular joint (TMJ). To analyze the TMJ in response to various degrees of mouth opening, the authors constructed a hydraulic incremental jaw opener. This apparatus enables obtaining of reproducible and stable positions of TMJ articulation. With modified gradient pulse sequences, the technique yields good spatial resolution of joint anatomy, including that of the articular disk. The application of a cine program allows cinematographic display of TMJ motion, which in conjunction with static open‐and closed‐mouth views can be useful in the diagnosis of TMJ dysfunction. The authors used the incremental jaw opener to examine the disk‐condyie complex at each open‐mouth position, with particular attention to extreme open‐mouth positions.
Dynamic MR imaging of human brain oxygenation during rest and photic stimulation
Authors: Frahm Jens , Bruhn Harald , Merboldt Klaus‐Dietmar , Hänicke Wolfgang 
Published: March 2007

AbstractDynamic FLASH (fast low‐angle shot) magnetic resonance (MR) imaging was used to monitor changes in brain oxygenation in the human visual cortex during photic stimulation. The approach exploits the sensitivity of the gradient‐echo signal to susceptibility changes induced by varying concentrations of paramagnetic deoxyhemoglobin in the cerebral blood pool. After the onset of binocular photic stimulation (10 Hz, red light, checkerboard), there was a distinct increase in the MR signal in the calcarine cortex within 6–9 seconds, indicating a decrease in the total deoxyhemoglobin concentration. After the stimulation was switched off, the MR signal returned to a basal value within a similar period of time. Assuming enhanced blood flow and only a minor increase in oxygen consumption (production of deoxyhemoglobin) during physiologic activation, the results reflect an enhanced supply of diamagnetic oxyhemoglobin and an increase in the partial oxygen pressure in the capillary and venous blood pools. In addition, a decrease in the basal MR signal in the calcarine cortex was observed during the first 60–90 seconds of persistent activation, which may be understood as an autoregulatory adaptation to increased overall brain activity associated with information processing due to continuous perception of visual stimuli.
Identification of aberrant right subclavian artery on MR images of the cervical spine
Authors: Easterbrook James S. 
Published: March 2007

AbstractNine cases of aberrant right subclavian artery were identified after review of 674 magnetic resonance (MR) studies of the cervical spine. This common aortic arch anomaly is readily identified on sagittal MR images. All vessels were found in the typical retroesophageal location, abutting the esophagus from the vertebral C‐7 to T‐3 levels. Arterial flow created signal voids on T1‐weighted images and confirmatory increased signal intensity due to flowrelated enhancement on gradient‐echo images. This anomaly should be recognized and distinguished from pathologic processes in the prevertebral space. The diagnosis may allay patient concern regarding their dysphagia and also have important ramifications in certain clinical settings.
Minimizing TE in moment‐nulled or flow‐encoded two‐and three‐dimensional gradient‐echo imaging
Authors: Bernstein Matt A. , Shimakawa Ann , Pelc Norbert J. 
Published: March 2007

AbstractA method for minimizing field‐echo delay in moment‐nulled gradient‐echo imaging is presented. Even though ramps are accounted for, the analysis yields simple closed‐form solutions. The method is then generalized to the section‐select waveform for three‐dimensional volume imaging and to flow encoding for phase‐contrast imaging. Three strategies for first‐moment selection in phase‐contrast imaging are discussed, including a new strategy that always yields the minimum echo delay. Trapezoidal and triangular gradient lobe shapes are analyzed.
MR imaging of the pericardial cyst
Authors: Vinee Philippe , Stover Brigitte , Sigmund Gunther , Laubenberger Jorg , Hauenstein Karl Heinz , Weyrich Georges , Hennig Jurgen 
Published: March 2007

AbstractFindings obtained with magnetic resonance (MR) imaging in four patients with pericardial cyst are reported. MR imaging allowed not only localization and diagnosis in all four cases but characterization of cystic content. MR imaging, including RARE (rapid acquisition with relaxation enhancement) MR hydrography, which shows only liquids with T2s greater than 500 msec, proved to be useful in characterizing the fluid content of a mediastinal lesion and monitoring follow‐up. In one case, MR imaging allowed differentiation of a pericardial cyst from a suspected necrotic lymph node in a patient with colic carcinoma, with subsequent correction of staging and therapy. The authors conclude that MR imaging is the method of choice for diagnosis (especially in unusual locations) and monitoring of pericardial cysts and for differential diagnosis of malignant mediastinal cystic tumors that show a solid part.
Phase‐contrast MR angiography of vascular malformations of the spinal cord at 0.5 T
Authors: Gelbert Françoise , Guichard Jean‐Pierre , Reizine Daniel , Aymard Armand , Gobin Pierre , Merland Jean‐Jacques , Mourier Klaus L. , George Bernard , Cophignon Jean 
Published: March 2007

AbstractPreliminary experience with phase‐contrast magnetic resonance (MR) angiography at 0.5 T applied in 12 cases of vascular malformations of the spinal cord is reported. There were six intramedullary arteriovenous malformations (AVMs), four perimedullary fistulas, and two dural arteriovenous fistulas with perimedullary drainage, all proved with x‐ray angiography. The small size of the vessels and their location within a bony structure presented a technical challenge. Serpentine vascular signal patterns were identified within the spinal canal in all cases, showing good correlation with the x‐ray angiographic pattern. Relative to spin‐echo images, MR angiograms allowed better visualization of the venous drainage. The nidus of intramedullary AVMs was more difficult to recognize. The ability to manipulate the velocity‐encoding value allows better characterization of flow speed. The results underline the two dimensions of the phase‐contrast technique, which provides both anatomic images and dynamic information about vascular malformations. MR angiography does not replace selective x‐ray angiography, which is indispensable for therapeutic strategy (endovascular procedure or surgery), but it can be considered a valuable alternative to x‐ray angiography during follow‐up.
Correlation of MR imaging and histologic findings in mouse melanoma
Authors: DeJordy John O. , Bendel Peter , Salomon Yoram , Degani Hadassa , Horowitz Ada 
Published: March 2007

AbstractM2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 μm thick, with an in‐plane resolution of 195 μm. The distribution of melanin within the histologic slices correlated well with the high‐signal‐intensity regions on the T1‐weighted images (T1W1s), while these regions had low signal intensity on the T2‐weighted images (T2WIs), providing evidence that melanin or melanin‐associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton‐density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton‐density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin‐rich, viable‐melanoma, and necrotic regions on MR images.
Cardiac metabolism in patients with dilated and hypertrophic cardio‐myopathy: Assessment with proton‐decoupled P‐31 MR spectroscopy
Authors: De Roos Albert , Doornbos Joost , Luyten Peter R. , Oosterwaal Lambère J. M. P. , den Hollander Jan A. , van der Wall Ernst E. 
Published: March 2007

AbstractProton‐decoupled phosphorus‐31 heart spectros‐copy was performed in healthy subjects (n = 9) and patients with dilated cardiomyopathy (DCM, n = 9) or hypertrophic cardiomyopathy (HCM, n = 8). The phosphocreatine (PCr)‐to–adenosine triphosphate ratio (± one standard deviation) after correction for blood contribution and partial saturation was significantly lower in HCM patients relative to the control subjects (1.32 ± 0.29 vs 1.65 ± 0.26, P < .05) but not in DCM patients (1.52 ± 0.58 vs 1.65 ± 0.26). The inorganic phosphate (Pi) peak was resolved only in patients with the highest spectral quality. Myocardial pH was lower in HCM patients (n = 6) relative to control subjects (n = 4) (7.07 ± 0.07 vs 7.15 ± 0.03, P < .05). The Pi/PCr ratio was higher in DCM (n = 3) and HCM (n = 6) patients relative to control subjects (n = 4) (0.29 ± 0.06 and 0.20 ± 0.04, respectively, vs 0.14 ± 0.06; P < .05). Elevated phosphodiester signal in DCM patients correlated with 2,3‐diphosphoglycerate signal (r = .94), reflecting blood pool contamination. P‐31 spectroscopy enabled detection of abnormalities in cardiac metabolism and determination of pH in patients with HCM and DCM.
Laryngospasm after administration of gadopentetate dimeglumine
Authors: Omohundro James E. , Elderbrook Marcia K. , Ringer Thomas V. 
Published: March 2007

AbstractFew serious adverse reactions associated with the use of gadopentetate dimeglumine in magnetic resonance imaging have been reported. The present case involves an 8‐year‐old girl who developed laryngospasm after administration of gado‐pentetate dimeglumine.
Mn‐DPDP enhancement patterns of hepatocellular lesions on MR images
Authors: Vogl Thomas J. , Hamm Bernd , Schnell Birgit , McMahon Christine , Branding Gordian , Lissner Josef , Wolf Karl‐Jürgen 
Published: March 2007

AbstractThe recently developed paramagnetic hepatobiliary contrast agent manganese dipyridoxyl diphosphate (DPDP) was evaluated in eight patients. Pathologic diagnoses included five hepatocellular carcinomas, two cirrhoses, and one focal nodular hyperplasia. T1‐weighted spin‐echo and gradient‐echo images were obtained after intravenous injection of 5 or 10 μmol/kg Mn‐DPDP; these were compared with un‐enhanced T1‐weighted spin‐echo and gradient‐echo images and T2‐weighted spin‐echo images. In all patients with lesions of hepatocellular origin, focal areas of increased enhancement were seen in the lesions after administration of Mn‐DPDP. In the cir‐rhotic livers, these areas corresponded to foci of hepatic regeneration. In all patients, the signal‐to‐noise ratio in normal liver tissue increased significantly after injection of Mn‐DPDP. Signal intensity in the six primary liver tumors was further increased, so that they appeared hyperintense relative to surrounding liver tissue on all T1‐weighted images. Conspicuity and demarcation of all lesions were improved on Mn‐DPDP‐enhanced images.
Quantitative analysis of gadopentetate dimeglumine excreted in breast milk
Authors: Rofsky Neil M. , Weinreb Jeffrey C. , Litt Andrew W. 
Published: March 2007

AbstractSpecimens of breast milk were obtained from each breast in a lactating patient for a 24‐hour period after a gadolinium‐enhanced MR imaging examination was performed. A quantitative analysis of gadolinium content in specimens obtained at 2, 11, 17, and 24 hours after the intravenous administration of gadopentetate dimeglumine demonstrated that gadolinium is excreted in small amounts (total of 1.60 μmol during a 24‐hour period) and in similar amounts from each breast. These results suggest that a waiting period of 24 hours, with active expression of breast milk from each breast, should provide a reasonable safety margin for allowing resumption of breast‐feeding. Additional data will be required before establishing definitive recommendations.
T2‐weighted MR imaging of focal hepatic lesions: Comparison of various RARE and fat‐suppressed spin‐echo sequences
Authors: Semelka Richard C. , Patrick Shoenut J. , Kroeker Randall M. 
Published: March 2007

AbstractThe authors prospectively compared four T2‐weighted magnetic resonance (MR) sequences, including high‐resolution 512 × 512 (matrix size) RARE (rapid acquisition with relaxation enhancement), 256 × 256 RARE, 128 × 256 breath‐hold RARE, and 192 × 256 fat‐suppressed spin‐echo (T2FS) sequences, in the evaluation of 16 patients with focal hepatic masses. MR images were evaluated by quantitative lesion‐liver signal difference‐to‐noise ratios (SDNRs) and subjective evaluation of image artifact and image quality. No significant differences were observed between RARE sequences in SDNR values. The T2FS sequence had a significantly higher SDNR than the 512 × 512 RARE sequence (24.6 ± 15.0 vs 14.5 ± 9.7) (P =.008). Image quality was rated highest for the 512 × 512 RARE and T2FS sequences (P =.006). The inherent advantage of high spatial resolution suggests that the 512 × 512 RARE sequence may be of value in detecting hepatic lesions.
Boronated Metalloporphyrins: A novel approach to the diagnosis and treatment of cancer using contrast‐enhanced MR imaging and neutron capture therapy
Authors: Huang Leryang R. , Straubinger Robert M. , Kahl Stephen B. , Koo Myoung‐Seo , Alletto James J. , Mazurchuk Richard , Chau Robert I. , Thamer Sandra L. , Fiel Robert J. 
Published: March 2007

AbstractPorphyrins are a unique class of metal chelating agents that have shown specific affinity for neoplasms. The water‐soluble free‐base derivative, tetrakiscarborane carboxylate ester of 2,4‐(α,β‐dihydroxyethyl) deuteroporphyrin IX (BOPP), an agent designed for neutron capture therapy, has previously demonstrated selective localization and retention in a C6 murine glioma. In the present work, the authors demonstrate that the manganese chelate of BOPP also selectively localizes in a rat 9L gliosarcoma and preferentially enhances the tumor‐normal brain contrast of T1‐weighted images for at least 92 hours. The data indicate a maximal enhancement of contrast between tumor and normal brain at 24 hours after injection, compared with 5 minutes for manganese (III) tetraphenylporphine sulfonate (TPPS4). The results also indicate that Mn‐BOPP may have a slower uptake in the 9L glioma than Mn‐TPPS4 but a longer retention in the tumor. Mn‐BOPP is unique in that it represents, to the authors' knowledge, the first example of a single agent that can enhance contrast between tumor and normal tissue and be potentially effective as an agent for boron neutron capture therapy.
Three‐dimensional time‐of‐flight MR angiography with a specialized gradient head coil
Authors: Tkach Jean A. , Ruggieri Paul M. , Dillinger John J. , Ross Jeffrey S. , Modic Michael T. , Masaryk Thomas J. 
Published: March 2007

AbstractA gradient head coil has been developed, incorporating two independent gradients within the conventional body coil of the magnetic resonance (MR) system, with reduced rise times (200 μsec) and maximum amplitudes of 37 and 18 mT/m in the z and y directions, respectively. This gradient coil was systematically evaluated by testing two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight (TOF) MR angiography sequences applied to a pulsatile flow phantom simulating a carotid stenosis and the intracranial vasculature. When standard 2D and 3D TOF MR angiography techniques were used to image the carotid stenosis model, dramatic signal loss in the stenotic segment and a large flow void distal to the stenosis were seen. The shorter (3.8 msec) absolute echo times (TEs) achievable with the gradient coil in 3D sequences substantially reduced the phase dispersion and associated signal loss in the region of stenosis. Shorter TEs alone (3.2 msec) did not minimize signal loss, and firstorder flow compensation in the read and section‐select directions provided further improvements (despite slightly longer TEs). Reduction of TEs in 2D sequences yielded relatively poor results regardless of the refocusing scheme or TE. This study confirms the predicted benefits of a dedicated coil with improved gradient capabilities for 3D MR angiography. The study suggests the limitations of 2D TOF MR angiography in the evaluation of severe stenoses.
Accuracy of phase‐contrast flow measurements in the presence of partial‐volume effects
Authors: Tang Chao , Blatter Duane D. , Parker Dennis L. 
Published: March 2007

AbstractThe accuracy of volume flow rate measurements obtained with phase‐contrast methods was assessed by means of computer simulation and in vitro experiments. Factors studied include (a) the partial‐volume effect due to voxel dimensions relative to vessel dimensions and orientation and (b) intravoxel phase dispersion. It is shown that limited resolution (partial‐volume effect) is the major obstacle to accurate flow measurement for both laminar and plug flow. The results show that at least 16 voxels must cover the cross section of the vessel lumen to obtain a measurement accuracy to within 10%. Measurement accuracy also greatly depends on the relative signal intensity of stationary tissue and is better for laminar flow than plug flow.
MR detection of quantitative and structural changes in human aortic aneurysms
Authors: Vinée Philippe , Meurer Bernard , Constantinesco André , Kohlberger Bernd , Hauenstein Karl Heinz , Stöver Brigitte , Laubenberger Jörg , Petkov Simeon , Oursin Caroline , Eisenmann Bernard 
Published: March 2007

AbstractCollagen is a major component of the extracellular matrix and a determinant of the elastic behavior of the human aorta. To investigate the changes found in aneurysmal degeneration, the authors studied the solid‐state hydrogen‐1 nuclear magnetic resonance line shape of collagen in aneurysms and normal human aortas. A three‐component decomposition of the free induction decay was performed, with collagen characterized by a T2 of about 18 μsec. The second moment of the collagen line shape was found to be increased in aneurysms (5.3 vs 4.8 G2), while, correspondingly, the T2 of collagen was lower in aneurysms (16.3 vs 17.7μsec). This corresponds to a modification of collagen structure and molecular motion. Collagen concentration was lower in nondiseased aortic walls (9.4% vs 7.3%). These results are discussed in reference to the contradictory conclusions in the current literature. The increase in collagen and the modification of its structure and molecular motion are explained by the need to resist an increasing tangential tension due to increased aortic diameter and diminished wall thickness in aneurysms and by intercalation or site binding in the helices or electric dipolar interactions in the less mobile side groups.
MR characterization of blood flow in native and grafted internal mammary arteries
Authors: Debatin Jörg F. , Strong John A. , Dirk Sostman H. , Negro‐Vilar Rosa , Paine Susan S. , Douglas James M. , Pelc Norbert J. 
Published: March 2007

AbstractIn the postoperative patient with anginal symptoms, differentiation between bypass graft compromise and nonischemic causes has until now been accomplished only by means of x‐ray angiography. A noninvasive test is clearly desirable. The authors used a cine phase‐contrast (PC) magnetic resonance (MR) imaging technique to characterize blood flow in native and grafted internal mammary arteries (IMAs). Ten volunteers and 15 patients who had recently undergone IMA coronary artery bypass grafting were imaged. Cine PC MR imaging was performed in the transaxial plane at the level of the pulmonary artery bifurcation. Flow in both IMAs was quantified and expressed as a percentage of cardiac output measured in the ascending aorta. In the 15 patients, flow analysis was performed in both the native and grafted IMAs. In the volunteers, IMA blood flow ranged from 2.1% to 4.3% of cardiac output on the left (mean, 3.5%) and 2.1% to 5.1% (mean, 3.5%) on the right. There was considerable intersubject variability, with coefficients of variation of 10.7% for the left and 12.3% for the right IMA. Intrasubject variability was limited, with estimated common standard deviations of 0.45% of cardiac output (range, 0.2%–1.1%) for the left and 0.39% (range, 0.1%–0.6%) for the right IMA. Flow in grafted IMAs was identified in 13 of 15 patients. In one of two patients without demonstrable IMA graft flow, cardiac catheterization confirmed lack of flow. IMA graft flow varied from 28 to 164 mL/min (mean, 80.3 mL/min). This study shows the feasibility of using cine PC MR imaging as a quantitative method of evaluating blood flow in IMA coronary artery bypass grafts.