bluuebunny/crossref_metadata_2025_split huggingface dataset:
A left atrial pseudomass: Potential pitfall at thoracic MR imaging
Authors: King Mark A. , Vrachliotis Thomas G. , Bergin Colleen J. 
Published: March 2007

AbstractWe frequently observed a nodular soft‐tissue structure in the region of the left atrium anterior to the orifice of the left inferior pulmonary vein on MR scans of the chest. To assess its morphologic characteristics and appearance, chest MR scans obtained in 49 patients were reviewed. ECG‐gated conventional spin‐echo T1‐weighted and fast spin‐echo (FSE) T2‐weighted sequences were used. The location, morphology, and appearance of this soft‐tissue structure was evaluated by two radiologists during one consensus reading. The psendomass in the region of the left atrium was identified on the T1‐weighted images in 25 of 49 patients. The structure was also identified on FSE T2‐weighted images in 6 of these patients. On the T1‐weighted images, its appearance was either linear (54%) or nodular (46%). In conclusion, a nodular soft‐tissue mass anterior to the orifice of the left inferior pulmonary vein into the left atrium is a frequent finding on chest MR scans and should not be confused with an intra‐atrial mass. Careful evaluation of the regional anatomy identifies this structure as extraluminal and helps to avoid misinterpretation of an intracardiac mass.
Experimental validation of an automated edge‐detection method for a simultaneous determination of the endocardial and epicardial borders in short‐axis cardiac MR images: Application in normal volunteers
Authors: Furber Alain , Balzer Philippe , Cavaro‐Ménard Christine , Croué Anne , Da Costa Eric , Lethimonnier Franck , Geslin Philippe , Tadéi André , Jallet Pierre , Le Jeune Jean‐Jacques 
Published: March 2007

AbstractThe goal of this study was to put together several techniques of image segmentation to provide a reliable assessment of the left ventricular mass with short‐axis cardiac MR images. No initial manual input was required for this process based on region growing, gradient detection, and adaptive thresholding. A comparison between actual mass and automatic assessment was implemented with 9 minipigs that underwent spin‐echo MR imaging. Fifteen normal volunteers were studied with a fast‐gradient‐echo sequence. The automatic segmentation was then controlled by three trained observers. Actual mass and automatic segmentation were strongly correlated (r = .97 with P < .01). For normal volunteers, the standard error of estimation of the automatic assessment (12 g) compared well with the average myocardial mass (120 ± 30 g) and the interobserver reproducibility of the manual assessment (9 g). These results allow the application of this method to the quantification of the left ventricular function and mass in clinical practice.
Frequency‐domain simulation of MR tagging
Authors: Crum William R. , Berry Elizabeth , Ridgway John P. , Sivananthan U. Mohan , Tan Lip‐Bun , Smith Michael A. 
Published: March 2007

AbstractSimulation of MR images is a useful tool for offline sequence development and as an aid to understanding image formation. One particular application of simulation is MR tagging, which is used for tracking myocardial motion. Simple spatial‐domain methods cannot adequately represent effects common in these images, such as motion artifact and signal wrap. An existing frequency‐domain model is shown to be inappropriate for tagged images, and an extension based on the Bloch equations and Fourier shift theorem is described to correct this. Software incorporating the new model is used to generate ideal tag intensity profiles and to accurately simulate tagged images. The shifted k‐space patterns associated with tagged images, and their dependence on the order of the binomial tagging sequence, are explained. An application of the Fourier shift theorem is suggested that allows more rapid simulation of static tagged images.
Black blood magnetic resonance angiography with Dy‐DTPA polymer: Effect on arterial intraluminal signal intensity, lumen diameter, and wall thickness
Authors: Eubank William B. , Schmiedl Udo P. , Yuan Chun , Black Christopher D. V. , Kellar Kenneth E. , Ladd David L. , Nelson James A. 
Published: March 2007

AbstractFour rabbits in which atherosclerotic disease was induced by diet and balloon angioplasty underwent conventional angiography and MR angiography (MRA) using a black blood pulse sequence before and 10 minutes after the iv injection of a macromolecular contrast agent, NC 100283 (1.0 mmol/kg), a dysprosium diethylenetriaminepentaacetic acid hexamethylenediamine copolymer (Dy‐DTPA polymer). Intraluminal signal intensity, apparent wall thickness, and lumen size measurements of the aorta and proximal common iliac arteries on precontract MRA images were compared with postcontrast images. Aortic lumen diameter measurements on the precontrast and postcontrast MRA studies were compared with lumen diameters from conventional angiograms. Intraluminal signal intensity decreased on postcontrast MRA images compared with precontrast images, with an average loss of signal equal to 29% (P < .05). Apparent wall thickness decreased by 24% (P < .05). Lumen diameter and area were generally larger (average of 15% and 33%, respectively) on postcontrast MRA images than on precontrast images. Aortic lumen diameter measurements from postcontrast MRA agreed closely (95% confidence interval of the mean difference was −.2 to .3 mm), and precontrast MRA images tended to underestimate aortic lumen diameter (95% confidence interval of the mean difference was .3 to .8 mm) compared with conventional angiography. Postcontrast MRA with NC 100283, a macromolecular Dy‐DTPA contrast agent, provides more accurate assessment of aortic lumen diameter than precontrast MRA, using conventional angiography as the standard reference.
Prospective evaluation of peripheral arterial occlusive disease by 2D MR subtraction angiography
Authors: Laissy Jean Pierre , Debray Marie‐Pierre , Menegazzo David , Rangheard Anne‐Sophie , Benamer Hakim , Charlier Patrick , Schouman‐Claeys Elisabeth 
Published: March 2007

AbstractThe purpose of this study was to assess the diagnostic value of two‐dimensional (2D) MR subtraction angiography of lower extremities in patients with symptomatic peripheral arterial occlusive disease with conventional angiography as the standard of reference. Twenty patients were prospectively included. 2D subtraction MR angiography (MRA) consisted of multisection gradient‐recalled echo (GRE) acquisitions with the shortest TE available on our machine (4 msec), obtained in the coronal plane before and after intravenous bolus administration of gadolinium chelate. MR images were reconstructed after subtraction with a maximum‐pixel‐intensity‐projection (MIP) algorithm. MRA was performed in all cases 1–4 days before diagnostic angiography. In a prospective blinded analysis, the number and location of significant (ie, >50%) stenoses and occlusions were evaluated for each vascular segment. Sensitivity and specificity were used to evaluate MRA data. Significant stenoses (38 of 46, 83%) and occlusions (66 of 67, 99%) seen at conventional angiography were identified with MRA. The sensitivity and specificity of MRA for determination of stenoses >50% or occlusions was 100% and 97%, respectively. The location and extent of stenoses and/or occlusions on MRA and angiograms were well correlated (kappa values, r = .73, P < .05). Contrast 2D MR subtraction angiography, by providing comparable information to that of conventional angiography, is well suited to evaluate the presence and severity of atherosclerotic lesions of the lower limbs.
Intraoperative dynamic MRI: Localization of sites of brain tumor recurrence after high‐dose radiotherapy
Authors: Schwartz Richard B. , Hsu Liangge , Kacher Daniel F. , Wong Terence Z. , Alexander Eben , Okon Stephen , Guttmann Charles R. G. , Black Peter McL. , Kelley Raymond A. , Moriarty Thomas , Martin Claudia , Isbister Holly G. , Cahill Cheryl D. , Spaulding Sharon A. , Jolesz Ferenc A. 
Published: March 2007

AbstractIn patients with malignant astrocytomas or metastatic brain disease treated with high‐dose radiotherapy, conventional imaging methods may not adequately distinguish recurrent tumor from radiation change. We used a fast spoiled gradient refocusing technique in the open‐configuration intraoperative MR system to assess the rate of regional enhancement of the treated tumor bed and to localize specific sites for pathologic sampling to determine whether gadolinium uptake correlated with histologic data. Twenty‐four patients were studied. Fourteen of 15 patients with areas of early enhancement had recurrent tumor present in histologic samples, and 8 of the remaining 9 patients had only reactive changes. Dynamic MRI was predictive of recurrent tumor (P < .0005, Fisher exact test and P < .002, Student t test). We conclude that dynamic MRI in the open‐bore magnet is a promising method for localizing potential sites of active tumor growth in patients treated for malignant astrocytomas and metastatic brain lesions.
Proton T1ρ‐dispersion imaging of rodent brain at 1.9 T
Authors: Rizi Rahim R. , Charagundla Sridhar R. , Song Hee Kwon , Reddy Ravinder , Stolpen Alan H. , Schnall Mitchell D. , Leigh John S. 
Published: March 2007

AbstractDetection of H217O with proton T1ρ‐dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1ρ dispersion of tissue. To investigate these properties, we implemented a T1ρ imaging sequence on a 1.9‐T Signa GE scanner. A series of T1ρ images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5 % (wt/vol) gelatin phantoms containing different concentrations of 17O ranging from .037 % (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1ρ‐dispersion in phantoms doped with H217O, the T1ρ of rat brain undergoes minimal dispersion for spin‐locking frequencies between .2 and 1.5 kHz. A small degree of T1ρ dispersion is present below .2 kHz, which we postulate arises from natural‐abundance H217O. Moreover, the signal‐to‐noise ratios of T1ρ‐weighted images are significantly better than comparable T2‐weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1ρ‐dispersion imaging for detecting intravenous H217O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.
Evaluation of the stability of the proton chemical shifts of some metabolites other than water during thermal cycling of normal human muscle tissue
Authors: Young Ian R. , Bell Jimmy D. , Hajnal Joseph V. , Jenkinson Gabriele , Ling Junxiao 
Published: March 2007

AbstractMR temperature measurements made by the chemical‐shift‐of‐water technique in peripheral muscle of volunteers have produced larger‐than‐expected coefficients of change and shown significant hysteresis effects as the temperature was cycled, although these effects were not reproduced in the present study. Previous work has suggested that susceptibility effects could be a contributor to the behavior of the chemical shift data. Here, we use proton spectroscopy of muscle in conjunction with temperature cycling to evaluate the relative shifts of the water peak and those of creatine, choline, and lipids. These latter are considered not to have significant temperature coefficients of chemical shift. The results show that these lines remain very stable as the temperature is cycled, suggesting that susceptibility effects are not present in this study. The method offers the possibility that the lines can be used as frequency references if there are any questions about the stability of other moieties.
Carpal tunnel syndrome: Staging of median nerve compression by MR imaging
Authors: Kleindienst Andrea , Hamm Bernd , Lanksch Wolfgang R. 
Published: March 2007

AbstractThe purpose of this prospective study was to determine the potential of MR imaging to depict morphologic alterations of the median nerve correlating with the stage of carpal tunnel syndrome (CTS). Eighteen wrists of normal subjects and 81 wrists of patients with CTS were examined. MR imaging was performed with proton‐density‐ and T2‐weighted spin‐echo sequences. Staging of CTS was done on the basis of clinical and electrophysiological testing, including evaluation of the number of previous steroid infiltrations in conservative treatment. Median nerve flattening, cross‐sectional area, and signal intensity were measured from the distal radius to the end of the carpal tunnel. Delineation and structure of the median nerve were recorded qualitatively by two experienced radiologists in consensus. Three major MR imaging criteria of early CTS were (a) isolated prestenotic and intracarpal swelling of the median nerve (P < .01), (b) the absence of significant flattening, and (c) a generalized increase in signal intensity retrograde to the distal radius (P < .01). The nerve showed sharply delineated contours and a homogeneous signal pattern. Advanced CTS was characterized by retrograde swelling of the median nerve to the distal radius (P < .01) and decreased signal intensity (P < .05). Demarcation of the nerve became poorer, and its signal pattern appeared fasciculated. After steroid infiltration, the median nerve was difficult to delineate, showed an inhomogeneous structure, and swelling was less pronounced than without steroid infiltration (P < .05). MR imaging yields typical morphologic findings that correlate with the duration and severity of median nerve compression. Hence, MR imaging allows staging of median nerve compression in CTS and thus may contribute to therapeutic decision‐making.
Digital wavelet‐encoded MRI: A new wavelet‐encoding methodology
Authors: Panych Lawrence P. , Zientara Gary P. , Saiviroonporn Pairash , Yoo Seung‐Schik , Jolesz Ferenc A. 
Published: March 2007

AbstractA new digital wavelet‐encoding method for MRI is described. The method differs from previously described wavelet‐encoding approaches, because the pointspread function is made independent of the wavelet basis used. This has a significant practical advantage, because wavelet bases can now be considered that would otherwise be excluded due to the difficulty of precisely exciting wavelet‐shaped RF profiles. The method has been implemented on a clinical MRI system, and human images are presented.
MR versus fluoroscopic guidance of a catheter/guidewire system: In vitro comparison of steerability
Authors: Zimmermann‐Paul Gesine G. , Ladd Mark E. , Pfammatter Thomas , Hilfiker Paul R. , Quick Harald H. , Debatin Jörg F. 
Published: March 2007

AbstractOur purpose in this study was to evaluate the steerability of a combined catheter guide‐wire system with MR tracking in an open‐configuration .5T MR system and compare it with fluoroscopic guidance. Experiments were performed with an aorta‐shaped glass phantom with different‐size branches connected to a roller flow pump to simulate pulsatile flow. A .035″ guidewire was used in conjunction with a 5F Cobra 2‐shaped catheter. For active MR guidance, a small RF coil was incorporated into the tips of all devices. In addition to fluoroscopic guidance, we used MR tracking devices to selectively catheterize all branches in the .5T open magnet (Signa SP, GEMS). Time requirements for the latter were compared with those needed under conventional angiographic conditions using standard catheters and guidewires. Active MR tracking permitted the simultaneous real time (4 updates/sec) guidance of both guide‐wire and catheter. Under MR guidance, all branch vessels were successfully catheterized. We found no significant differences in time requirements between guidance with the MR tracking device and fluoroscopic guidance. However, cannulation under fluoroscopic guidance with standard angiography devices required significantly less time (P < .05). Selective catheterization of small branch vessels is possible with active MR tracking of a combined cath‐eter/guidewire system. Limitations of MR tracking device material and design result in a considerable lengthening of the cannulation procedures.
Cystic adenomyosis of the uterus: MRI
Authors: Troiano Robert N. , Flynn Stuart D. , McCarthy Shirley 
Published: March 2007

AbstractAdenomyosis of the uterus is most often seen as focal or diffuse thickening of the myometrial junctional zone on MRI. We describe the morphologic features and signal characteristics of the rarer cystic form of the disease, as revealed by MRI. We conclude that cystic adenomyosis of the uterus is characterized by a well‐circumscribed cystic lesion within the myometrium that demonstrates hemorrhage in differential stages of organization on MR images.
Comparison of ultrafast half‐Fourier single‐shot turbo spin‐echo sequence with turbo spin‐echo sequences for T2‐weighted imaging of the female pelvis
Authors: Yamashita Yasuyuki , Tang Yi , Abe Yasuko , Mitsuzaki Katsuhiko , Takahashi Matsumasa 
Published: March 2007

AbstractSo that we might evaluate the ultrafast half‐Fourier single‐shot turbo spin‐echo (HASTE) sequence in T2‐weighted MRI of the female pelvis and compare it with the turbo spin‐echo (TSE) sequence, we prospectively studied 60 consecutive females with suspected abnormalities of the pelvis. For all MR examinations, we used a 1.5‐T superconductive magnet with a phased array coil. The HASTE sequence was applied with TR/effective TE/echo train = ∞/90/64 and a 128 × 256 matri× (acquisition time: .3 sec/slice), conventional TSE imaging with 3,400 to 5,000/132/15 and a 128 × 256 matri× (mean acquisition time: 2 min 4 sec), and high‐resolution TSE imaging with 3,400 to 5,000/132/15 and a 300 × 512 matri× (6 min 4 sec). Although the lesion conspicuity for the HASTE sequence was less than that for the high‐resolution TSE sequences, artifacts (including ghosting, bowel motion, susceptibility difference, and chemical shift) were negligible on HASTE images of all patients. The lesion conspicuity for the HASTE sequence was significantly better than for the conventional TSE sequence. In spite of the very short acquisition time, the subjective scoring of the overall image quality for the HASTE sequence was significantly higher than for the conventional TSE sequence (P < .01) and were slightly lower than for the high‐resolution TSE sequence. Compared with high‐resolution TSE, HASTE provided clearer visualization of large leiomyomas and ovarian tumors but slightly poorer visualization of uterine cancer. In occlusion, HASTE sequence generates higher contrast and is free from motion and chemical shift artifact with much higher time efficacy. Because of limited image resolution, the HASTE sequence should be used when the high‐resolution TSE imaging is suboptimal.
Fast and ultrafast magnetic resonance imaging in renal lesions
Authors: Walter Christof , Jockenhöfer Anke , Heindel Walter , Phd Harald Kugel , Jung Gregor , Krahe Thomas , Krug Barbara , Lackner Klaus 
Published: March 2007

AbstractOur purpose was to analyze and compare the image quality and contrast‐to‐noise ratio (CNR) of different fast T1‐ and T2‐weighted sequences with conventional spin‐echo sequences in renal MRI. Twenty‐three patients with focal renal lesions were examined with a T2‐weighted ultrafast turbo spin‐echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient‐and‐spin‐echo sequence (GraSE), and a conventional spin‐echo sequence (SE). In addition, T1‐weighted images were obtained pre‐and postcontrast, using a fast spin‐echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2‐weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat‐suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1‐weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2‐weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1‐weighted fast sequences provided no alternative to the gradient‐echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2‐weighted fast techniques for improved diagnostic accuracy of renal MRI.
Vital sign changes during infant magnetic resonance examinations
Authors: Taber Katherine H. , Hayman L. Anne , Northrup S. Robert , Maturi Luxmi 
Published: March 2007

AbstractHeart rate (HR) and blood oxygen saturation (SaO2) were monitored before and during clinically indicated MR examinations of newborns to (a) identify any temporal relationship between MR scanning and vital sign fluctuations and (b) assess the reliability of SaO2 monitoring of dynamic changes. Fluctuations in HR (but not in SaO2) that are temporally linked to the MR image acquisition occur in most neonates during routine clinical MR examinations.
Magnetic resonance imaging of shear wave propagation in excised tissue
Authors: Bishop Jonathan , Poole Greg , Leitch Michael , Plewes Donald B. 
Published: March 2007

AbstractThe propagation of shear waves in ex vivo tissue samples, agar/gel phantoms, and human volunteers was investigated. A moving coil apparatus was constructed to generate low acoustic frequency shear perturbations of 50 to 400 Hz. Oscillating gradients phase‐locked with the shear stimulus were used to generate a series of phase contrast images of the shear waves at different time‐points throughout the wave cycle. Quantitative measurements of wave velocity and attenuation were obtained to evaluate the effects of temperature, frequency, and tissue anisotropy. Results of these experiments demonstrate significant variation in shear wave behavior with tissue type, whereas frequency and anisotropic behavior was mixed. Temperature‐dependent behavior related mainly to the presence of fat. Propagation velocities ranged from 1 to 5 m/sec, and attenuation coefficients of from 1 to 3 nepers/unit wavelength, depending on tissue type. These results confirm the potential of elastic imaging attributable to the intrinsic variability of elastic properties observed in normal tissue, although some difficulty may be experienced in clinical implementation because of viscous attenuation in fat.
Determination of focal ischemic lesion volume in the rat brain using multispectral analysis
Authors: Carano Richard A. D. , Takano Kentaro , Helmer Karl G. , Tatlisumak Turgut , Irie Katsumi , Petruccelli Joseph D. , Fisher Marc , Sotak Christopher H. 
Published: March 2007

AbstractMultispectral (MS) analysis was used to determine the ischemic lesion volume in the rat brain after permanent middle cerebral arterial occlusion. MS analysis used a four‐dimensional MS model consisting of an estimate of the average apparent diffusion coefficient of water (ADCay), T2, proton density, and perfusion. Four classification methods were investigated: (a) multivariate gaussian (MVG); (b) k‐nearest neighbor (k‐NN); (c) k‐means (KM); and (d) fuzzy c‐means (FCM). MVG and k‐NN classifiers are supervised methods requiring labeled training data to characterize the stroke lesion. Unsupervised classifiers (KM, FCM) do not require previous statistics or labeled training data, resulting in potentially greater clinical usefulness. All MS methods provided significant correlation with postmortem findings beyond the use of ADCav alone (partial correlation given the ADCav estimate: MVG, .66; k‐NN, .75; KM, .68; FCM, .70). This study demonstrates that MS analysis provides an improved estimate of ischemic lesion volume over that obtained from ADC alone.