bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrast media for MR imaging of the heart
Authors: Saeed Maythem , Wendland Michael F. , Higgins Charles B. 
Published: March 2007

AbstractThe role of contrast media for quantitative characterization of ischemic myocardial events with magnetic resonance (MR) imaging has advanced considerably in the past few years. Contrast material‐enhanced MR imaging is useful for identifying and sizing myocardial infarcts and for distinguishing between occlusive and reperfused myocardial infarcts. Recent results suggest that contrast‐enhanced MR imaging can also be used to identify areas of cell death in regions of reperfused myocardial infarction. With the aid of MR contrast media, fast MR imaging techniques may be useful in estimating regional myocardial perfusion. Although no simple relationship between signal intensity and concentration exists, contrast‐enhanced MR perfusion imaging can demonstrate the presence and relative severity of hypoperfused myocardium. Combining myocardial perfusion imaging with the anatomic and functional information provided by other MR imaging techniques could make MR imaging a comprehensive noninvasive means of evaluating ischemic cardiac disease.
Intraluminal contrast agents for MR imaging of the abdomen and pelvis
Authors: Rijcken Tammo H. Pels , Davis Michael A. , Ros Pablo R. 
Published: March 2007

AbstractMagnetic resonance (MR) imaging of the abdomen and pelvis with use of gastrointestinal (GI) contrast agents is slowly emerging as a valuable diagnostic tool. In the past few years, considerable effort has been expended on developing an oral contrast agent to serve as a bowel marker during abdominal and pelvic imaging. Four major categories of agents have been studied: compounds with positive contrast‐enhancing characteristics (ie, which increase signal intensity), which may be either miscible or immiscible with bowel contents, and compounds with negative contrast‐enhancing characteristics (ie, which decrease signal intensity), which also may be miscible or immiscible. Compared with precontrast images, MR images acquired after administration of GI contrast agents have shown increased anatomic delineation of the bowel lumen, pancreas, and paraaortic nodes, allowing increased detection of pancreatic lesions, improved assessment of bowel wall lesions, and distinction between intrahepatic and extrahepatic lesions. This review focuses on the general physics and requirements for intraluminal GI contrast media for MR imaging, the currently used intraluminal agents and their regulatory status, current and near‐future availability, and cost considerations.
Malignant lesions of the liver identified on T1‐ but not T2‐weighted MR images at 1.5 T
Authors: Semelka Richard C. , Bagley Ann S. , Brown Elizabeth D. , Kroeker Mervyn A. 
Published: March 2007

AbstractThe authors reviewed their 21/2‐year experience with a magnetic resonance (MR) imaging protocol for a 1.5‐T MR imager that included T2‐weighted fat‐suppressed spin‐echo, T1‐weighted breath‐hold gradient‐echo, and serial dynamic gadolinium‐enhanced T1‐weighted gradient‐echo imaging to identify histologic types of malignant liver lesions more apparent on T1‐ than on T2‐weighted images. MR images of 212 consecutive patients with malignant liver lesions were reviewed. T2‐weighted, T1‐weighted, and dynamic contrast‐enhanced T1‐weighted images were examined separately in a blinded fashion. Seven patients demonstrated liver lesions (lymphoma [two patients] and carcinoid, hepatocellular carcinoma, colon adenocarcinoma, transitional cell carcinoma, and melanoma [one patient each]) on T1‐weighted images that were inconspicuous on T2‐weighted images. In all cases, the lesions were most conspicuous on T1‐weighted images obtained immediately after administration of contrast agent. Histologic confirmation was present for all seven patients. The consistent feature among these lesions was that they were hypovascular, due either to a fibrous stroma or to dense monoclonal cellularity. These results suggest that in some patients with hypovascular primary neoplasms, the lesions may be identified only on T1‐weighted images, and that immediate postcontrast T1‐weighted images are of particular value in demonstrating lesions.
Ischemic heart disease: Assessment with gadolinium‐enhanced ultrafast MR imaging and dipyridamole stress
Authors: Eichenberger André C. , Schuiki Ernst , Köhli Victor D. , Amann F. Wolfgang , McKinnon Graeme C. , von Schulthess Gustav K. 
Published: March 2007

AbstractThe potential of magnetic resonance (MR) imaging for the detection of myocardial perfusion abnormalities in patients with coronary artery disease has not been fully explored. A feasibility study was conducted in 10 patients with a novel approach to determine whether myocardial ischemia can be assessed with MR imaging and dynamic first‐pass bolus tracking enhanced with gadolinium tetraazacyclododecanetetraacetic acid (DOTA). Three tomographic planes were acquired before and after pharmacologic stress with dipyridamole, with use of the bolus‐tracking series at rest as a reference. The change in myocardial rate of enhancement was compared with the results obtained by means of the established methods, exercise thallium scintigraphy and coronary angiography. Detection of ischemic regions with MR imaging showed a sensitivity, specificity, and diagnostic accuracy of 65%, 76%, and 74%, respectively. Ultrafast MR imaging can be used to detect regions of myocardial ischemia.
Comparative signal intensity measurements in dynamic gadolinium‐enhanced MR mammography
Authors: Gribbestad Ingrid S. , Nilsen Gunnar , Fjøsne Hans E. , Kvinnsland Stener , Haugen Olav A. , Rinck Peter A. 
Published: March 2007

AbstractIncreases in signal intensity enhancement were measured in defined regions of interest (ROIs) to allow distinction between malignant and benign tumors with dynamic gadolinium‐enhanced magnetic resonance (MR) mammography. Twenty patients with palpable breast lesions (15 malignant, five benign) underwent MR mammography. The dynamic gradient‐echo sequence was performed with intravenous bolus injection of gadopentetate dimeglumine and consisted of 25 images with a time resolution of 30 seconds. Contrast enhancement was calculated by comparing user‐defined ROIs on pre‐ and postcontrast images. An increase in signal intensity of 70% or more on the 1‐minute postcontrast image was used as the criterion of malignancy. MR mammographic results correlated with histopathologic findings in all patients when the defined ROI was in the most enhancing part of the tumor. For the ROI in areas of submaximal enhancement or when the ROI surrounded the whole lesion, only five and nine tumors, respectively, fulfilled the malignancy criterion. All malignant tumors showed large variations in signal intensity enhancement that depended on the position of the ROI in the tumor. Dynamic, gadolinium‐enhanced MR mammography allows distinction of benign from malignant breast tumors when the selected ROI is in the most enhancing part of the lesion.
Magnetoferritin: Characterization of a novel superparamagnetic MR contrast agent
Authors: Bulte Jeff W. M. , Douglas Trevor , Mann Stephen , Frankel Richard B. , Moskowitz Bruce M. , Brooks Rodney A. , Baumgarner Charles D. , Vymazal Josef , Strub Marie‐Paule , Frank Joseph A. 
Published: March 2007

AbstractA protein‐encaged superparamagnetic iron oxide has been developed and characterized by using horse spleen apoferritin as a novel bioreactive environment. The roughly spherical magnetoferritin molecules, 120 Å in diameter, are composed of a monocrystalline maghemite or magnetite core 73 Å ± 14 in diameter. Except for the additional presence of iron‐rich molecules of higher molecular weight, the appearance and molecular weight (450 kd) of magnetoferritin are identical to that of natural ferritin; the molecules are externally indistinguishable from their precursor, with a pI (isoelectric point) in the range 4.3–4.6. The measured magnetic moment of the superparamagnetic cores is 13,200 Bohr magnetons per molecule, with T1 and T2 relaxivities (r1 and r2) of 8 and 175 L‐mmol−1 (Fe)‐sec−1, respectively, at body temperature and clinical field strengths. The unusually high r2/r1 ratio of 22 is thought to arise from ideal core composition, with no evidence of crystalline paramagnetic inclusions. T2 relaxation enhancement can be well correlated to the field‐dependent molecular magnetization, as given by the Langevin magnetization function, raised to a power in the range 1.4–1.6. With its nanodimensional biomimetic protein cage as a rigid, convenient matrix for complexing a plethora of bioactive substances, magnetoferritin may provide a novel template for specific targeting of selected cellular sites.
Sclerosed liver hemangioma mimicking malignant tumor at MR imaging: Pathologic correlation
Authors: Mathieu Didier , Rahmouni Alain , Vasile Norbert , Jazaerli Nedal , Duvoux Christophe , Tran Van Nhieu Jeanne , Zafrani Elie Serge 
Published: March 2007

AbstractThis case report illustrates atypical magnetic resonance (MR) imaging findings in a liver hemangioma mimicking a malignant lesion—lower signal intensity than cerebrospinal fluid on T2‐weighted spin‐echo images and lack of early enhancement on dynamic contrast material—enhanced gradient‐echo images. Pathologic analysis demonstrated nearly total replacement of the vascular cavities by dense fibrous tissue. In this rare, sclerosed form, this lesion could not be defined as a hemangioma with MR imaging.
Thymopharyngeal duct cyst: MR imaging of a third branchial arch anomaly in a neonate
Authors: Vade Aruna , Griffiths Allison , Hotaling Andrew , Eisenbeis John F. , Husain Aliya N. 
Published: March 2007

AbstractThird branchial arch anomalies are rare. The authors present a case report of a neonate with a rapidly growing neck mass due to cystic dilation of a persistent thymopharyngeal duct, which is a derivative of the third branchial arch. The presence of thyroid and thymic tissue in the cyst wall, the communication of the cyst with the piriform sinus, and the relationship of the cyst to carotid vessels and the sternomastoid muscle were consistent with the features of a thymopharyngeal duct cyst embedded in the thyroid gland.
Tuning and matching networks for MR imaging and spectroscopy
Authors: Viohl Ingmar , Gullberg Grant T. 
Published: March 2007

AbstractThe authors briefly discuss four tuning and matching networks and their application range in magnetic resonance (MR) imaging and MR spectroscopy. Analytic expressions for the network elements needed to tune and match an MR imaging or spectroscopy probe for a given coil impedance are given, and the connection to the “standard” two‐element capacitive matching networks is shown. The power loss factor and the phase shift between the input current and the load current are explicitly calculated for each of the four networks. The merits of the different matching networks are then discussed in the context of a general‐purpose license plate coil commonly used in MR imaging.
Effects of spatial distribution on proton relaxation enhancement by particulate iron oxide
Authors: Tanimoto Akihiro , Pouliquen Daniel , Kreft Burkhard P. , Stark David D. 
Published: March 2007

AbstractThe proton relaxation effect of superparamagnetic iron oxide (SPIO) particles under varying conditions of spatial distribution was investigated with use of phantoms. Agar phantoms containing various concentrations of SPIO or gadopentetate dimeglumine, with and without Sephadex beads, were studied. Phantoms with Sephadex had a heterogeneous spatial distribution of iron oxide, comparable to liver tissue in vivo. Relaxometry at 0.47 T showed decreased T2 relaxivity of SPIO in Sephadex phantoms compared with that in agar phantoms without Sephadex. On T2‐weighted images obtained at 1.5 T, the signal intensity of Sephadex phantoms showed less SPIO relaxation effect than that of plain agar phantoms. Unlike SPIO, gadopentetate dimeglumine showed the same relaxivities and signal intensity in plain agar and Sephadex phantoms. The results show that the T2 relaxation effect of iron oxide depends on its spatial distribution. A heterogeneous spatial distribution, as in intact liver tissue, diminishes the T2 relaxivity of iron oxide particles.
Metabolite concentrations in the developing brain estimated with proton MR spectroscopy
Authors: Toft Peter B. , Leth Helle , Lou Hans C. , Pryds Ole , Henriksen Ole 
Published: March 2007

AbstractThe purpose of the present study was to estimate absolute concentrations and relaxation time constants of metabolites that were detectable with proton magnetic resonance (MR) spectroscopy in the healthy preterm, term, and infant brain. Five MR spectra were recorded for each infant by using STEAM (stimulated‐echo acquisition mode) sequences with different TEs and TRs. Water was used as an internal standard. The T1 of choline‐containing compounds (Cho) and the T1 of phosphocreatine plus creatine (PCr+Cr) decreased. The T2 of the N‐acetyl‐L‐aspartate (NAA) resonance increased, probably because of a relatively larger signal overlap with glutamate in the most immature brains. The concentration of NAA almost doubled, whereas the Cho concentration showed only a nonsignificant tendency to decrease; therefore, the well‐known increase in the ratio of NAA to Cho appears to be due mostly to an increase in NAA concentration. The concentration of PCr+Cr increased rapidly and reached adolescent values at approximately 4 months of age.
A novel fast T1‐mapping method
Authors: Tong Chun Y. , Prato Frank S. 
Published: March 2007

AbstractThe authors present a novel fast T1‐mapping technique that allows a T1 map to be reconstructed from data acquired in less than 3 seconds. Data were acquired by using two modified TurboFLASH (fast low‐angle shot) sequences and were processed with a combination of one‐dimensional Fourier transforms and a parameter‐fitting routine, instead of a standard two‐dimensional Fourier transform. Apparent T1 (T1*) maps were obtained, from which T1 maps were calculated. Comparisons of T1 values obtained in phantoms and the human brain by using this technique with those obtained with multipoint inversion‐recovery T1 mapping showed that the new method yielded accurate T1 values. Optimization of the method will further improve speed and accuracy. The general approach of this T1‐mapping technique is believed to be also applicable to other problems, such as T2 and T2* mapping.
MR imaging evaluation of knee collateral ligaments and related injuries: Comparison of T1‐weighted, T2‐weighted, and fat‐saturated T2‐weighted sequences—correlation with clinical findings
Authors: Mirowitz Scott A. , Shu Hui Hua 
Published: March 2007

AbstractThe objectives of this study were to compare the ability of T1‐weighted (T1W), proton density/T2‐weighted (PD/T2W), and fat saturation (FS) PD/T2W magnetic resonance (MR) sequences for depiction of the knee collateral ligaments and related injuries, and to compare MR findings with clinical findings. Ten subjects with normal knee ligaments and 64 patients with suspected collateral ligament injuries underwent coronal T1W, PD/T2W, and FS PD/T2W imaging. Abnormalities ranged from edema surrounding the collateral ligaments (grade I) to complete disruption of ligamentous fibers (grade III). FS PD/T2W images improved definition of the medial collateral ligament (MCL) and lateral collateral ligament (LCL) compared with other sequences in 78% and 81% of patients, respectively. While the apparent grade of collateral ligament injury was similar with all pulse sequences in most patients, depiction of such injury was usually most conspicuous on FS PD/T2W images (MCL, 92% of patients; LCL, 38% of patients). In no patients were clinically diagnosed collateral ligament injuries undetected or understaged with MR imaging. MR findings indicated higher‐grade MCL and LCL injuries than did clinical examination in 24 and 15 patients, respectively.
Effects of MR exposure at 1.5 T on early embryonic development of the chick
Authors: Yip Yee Ping , Capriotti Christine , Talagala S. Lalith , Yip Joseph W. 
Published: March 2007

AbstractThe potential teratogenicity of magnetic resonance (MR) field exposure on the early development of the chick embryo was examined. Eggs at four developmental stages within the first 42 hours of incubation were exposed to a static magnetic field of 1.5 T for 6 hours and to 64‐MHz radio‐frequency field pulses and a switched magnetic field gradient with an amplitude of 0.6 G/cm for 4 h. When the embryos were sacrificed shortly thereafter (at ±53 hours of incubation), the abnormality and mortality rates of exposed and unexposed (control) embryos in each of the developmental groups did not show a consistent pattern. When embryos were sacrificed on the 6th day of incubation, exposed embryos from all developmental groups showed a trend toward higher abnormality and mortality rates than their controls. More extensive studies are needed to confirm these findings.
Tracking the motion of skeletal muscle with velocity‐encoded MR imaging
Authors: Drace John E. , Pelc Norbert J. 
Published: March 2007

AbstractPhase‐contrast magnetic resonance velocity‐encoding techniques were used to track two‐dimensional movement of skeletal muscle tissue. Axial and longitudinal planes in the forearms of five healthy volunteers were imaged during cyclic flexion and extension of the fingers, and the resulting data were used to plot the trajectories of the motion of pieces of muscle tissue. A phantom that produced complex two‐dimensional trajectories validated the accuracy of the imaging and analysis techniques; after adjustments for phase errors, two‐dimensional trajectories were tracked with an root‐mean‐square error of 0.1 cm. Preliminary results indicate that velocity‐encoded image data can characterize motion trajectories and that refinements in data acquisition and analysis techniques may make it possible to correlate the movements of different regions within a muscle, characterize muscle contraction, and quantify longitudinal strain. This ability to track velocity vectors may provide a foundation for quantitative analysis of muscle motion.
MR evaluation of cervical cancer in hysterectomy specimens: Correlation of quantitative T2 measurement and histology
Authors: Martin Alastair J. , Poon Colin S. , Thomas Gillian M. , Kapusta Linda R. , Shaw Patricia A. , Henkelman R. Mark 
Published: March 2007

AbstractSpecimens from modified radical hysterectomies performed for invasive carcinoma of the cervix were analyzed with quantitative T2 magnetic resonance (MR) imaging and histologic study to determine to what degree there was a correlation between the findings of the two modalities. The mean T2 of cervical stroma was 48 msec, while the outer zone of the cervix had a mean T2 of 62 msec and the central canal region typically had T2 values of 115 msec ± 20 (standard deviation). A total of nine cervical cancers were analyzed, and their mean T2 value was 79 msec. Separation between cervical stroma and tumor was good, with stromal T2 values ranging from 30 to 66 msec, while tumor T2s ranged from 60 to 97 msec. Statistical analysis indicated that these data were associated with a sensitivity of 89% and a specificity of 95%, with 95% confidence intervals of [50%,99.4%] and [74%,99.7%], respectively, for separating tumor from stroma on the basis of T2 value. Quantitative T2 imaging was found to provide an effective, nonsubjective means of classifying cervical anatomy and neo‐plastic disease.
MR susceptometry: an external‐phantom method for measuring bulk susceptibility from field‐echo phase reconstruction maps
Authors: Holt Randall W. , Diaz Pedro J. , Duerk Jeffrey L. , Bellon Errol M. 
Published: March 2007

AbstractA novel method for estimating the susceptibility of an object by using the magnetic resonance (MR) imaging field distortions in an external‐reference water bath next to the object is described. The field measurement was obtained with a phase reconstruction from a gradient‐echo acquisition. A field model of an arbitrary object in a static magnetic field was discretely calculated from geometry determined from the magnitude reconstruction. Least‐squares estimation yields the susceptibility of the object. Required (and proven) assumptions include validity of superposition, object homogeneity, negligible higher‐order field terms, field‐model accuracy, geometric‐model accuracy, and correlation of gradient‐echo phase to field distortion. MR susceptometry estimation of phantoms yielded susceptibility estimates that correlated well with known values (r >.9975). This MR susceptometry method is a first step toward quantitation of iron levels through MR imaging phase information in patients with iron overload.
Dynamic spin‐echo imaging: Theoretical assessment and implementation
Authors: Bishop Jonathan , Henkelman R. Mark , Plewes Donald B. 
Published: March 2007

AbstractA spin‐echo method for obtaining dynamic magnetic resonance (MR) images is described. The method combines the RARE (rapid acquisition with relaxation enhancement) pulse sequence with a data acquisition scheme in which only a centric fraction of the raw data is sampled to increase the time resolution of the dynamic images. The missing high‐resolution data are supplied from reference images. By these means, an effective time resolution of about 10 seconds per image is achieved, which is suitable for diagnostic assessment of contrast enhancement procedures. A promising clinical application is contrast‐enhanced MR imaging of the pituitary. Although the resolution of small objects in this size range is potentially degraded, this shortcoming is compensated for with use of variable refocusing flip angles. In the context of pituitary imaging, the centric 30%–40% of the raw data is shown to be the optimal fraction to acquire for the low‐resolution dynamic images. Ten patients with previous history of pituitary disease have been imaged with dynamic and conventional spin‐echo techniques. In six of these patients, an equivalent diagnosis was reached with dynamic and conventional images, while in two, only the dynamic images showed the lesion; in the final two patients, only the conventional images showed the lesion.
Planar‐motion correction with use of k‐space data acquired in fourier MR imaging
Authors: Wood Michael L. , Shivji Mansur J. , Stanchev Peter L. 
Published: March 2007

AbstractThe authors have developed a method for reducing magnetic resonance (MR) image artifacts caused by planar motion. Segments of k‐space acquired with the subject stationary are detected automatically. Each k‐space segment is Fourier transformed into an image in which rotational and translational displacements are measured manually. Before correction, k‐space is made as Hermitian as allowed by the largest symmetric range of low spatial frequencies acquired with the subject stationary. Segments of k‐space acquired with the subject in different positions are corrected separately. Although translation corrections can be applied effectively to both k‐space and the spatial domain, rotation corrections are applied in the spatial domain to avoid image artifacts. To complement the correction, data corrupted by rotation are replaced by the complex conjugate of data of the opposite kx, and ky, provided that these data have not been corrupted by rotation. The method reduced ghosts and blurring substantially on sagittal head images acquired with a standard spin‐echo pulse sequence while a volunteer subject nodded his head.