bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accuracy of sonography for detecting renal stone: Comparison with CT
Authors: Ulusan Serife , Koc Zafer , Tokmak Naime 
Published: March 2007

AbstractPurpose.To determine the diagnostic accuracy values of sonography in the detection of renal stones using noncontrast CT as the gold standard. In addition, we correlated the accuracy of sonography with stone size, the kidney affected (right versus left), and body mass index (BMI).Methods.Fifty patients underwent 2 separate sonographic examinations performed by 2 radiologists. CT scans were evaluated by another 2 radiologists, and the diagnosis was made by consensus. We compared the sonograms and CT scans and the sonographic detection of stones in the left and right kidneys. All sonographic findings were correlated with the BMI groups.Results.The sensitivity of sonography for any stone in a patient was 52–57% for the right kidney (radiologist 1 and 2) and 32–39% for the left kidney (radiologist 1 and 2). The overall accuracy of sonography in detecting a stone in the right kidney by radiologists 1 and 2 was 67% and 77%, respectively. The corresponding accuracy values for the left kidney were 53% and 54%, respectively.Conclusion.Sonography is of limited value for detecting renal stones. The sonographic detection of a renal stone is dependent on the side of the kidney involved but is independent of BMI. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Juvenile hormone mediates sexual dimorphism in horned beetles
Authors: Shelby J. Andrew , Madewell Richard , Moczek Armin P. 
Published: March 2007

AbstractThe causes and consequences of sexual dimorphism are major themes in biology. Here we explore the endocrine regulation of sexual dimorphism in horned beetles. Specifically, we explore the role of juvenile hormone (JH) in regulating horn expression in females of two species with regular sexual dimorphism for pronotal horns (females have much shorter horns than males) and a third species with a rare reversed sexual dimorphism for both pronotal and head horns (females have much larger horns in both body regions compared with males). Applications of the JH analog methoprene caused females of the two more typical species to grow significantly shorter pronotal horns than control females, whereas no consistent effect on pronotal horn development was detected in the third, sex‐reversed species. Instead, females in this species showed an unexpected and significant increase in head horn expression in response to methoprene treatment. Lastly, horn shape was also affected in females of one of the regularly sexually dimorphic species, but in the opposite direction than horn lenght. Although methoprene exerted a feminizing effect on female horn length in this species, it significantly masculinized horn shape by inducing a peculiar shape change observed naturally only in males. Our results suggest that JH influences both overall size and shape of female horns, but does so flexibly and as a function of species, sex and horn location. We use our results to review current models on the role of endocrine mechanisms in development and evolution of horned beetle diversity. J. Exp. Zool. (Mol. Dev. Evol.) 308B:417–427, 2007. © 2007 Wiley‐Liss, Inc.
Analysis of myocardial motion based on velocity measurements with a black blood prepared segmented gradient‐echo sequence: Methodology and applications to normal volunteers and patients
Authors: Hennig Juergen , Schneider Britta , Peschl Simone , Markl Michael , Laubenberger Thomas Krause Jörg 
Published: March 2007

AbstractThe paper describes a strategy for measuring and characterizing myocardial motion in terms of velocity parameters derived from measurements with a segmented black blood prepared phase contrast gradient echo sequence. The characteristic parameters are calculated by transforming the velocities measured on a pixel‐by‐pixel basis across the left ventricle from the laboratory frame of reference into a cylindrical coordinate system, in which the motion velocities within the short axis plane are represented in polar coordinates and which is located at the center of the myocardium and moving with it over the ECG cycle. First results in a study with 12 healthy volunteers gave highly consistent values for the radial (expansion/ compression) as well as the rotational velocities. Except for one volunteer, motion at the R wave of the ECG starts with clockwise rotation, followed by contraction and expansion accompanied by counterclockwise rotation. First examinations of patients with global and focal disease demonstrate the potential to detect disturbances in the local as well as the overall motion patterns.
Accuracy of arterial pulse‐wave velocity measurement using MR
Authors: Bolster Bradley D. , Atalar Ergin , Hardy Christopher J. , McVeigh Elliot R. 
Published: March 2007

AbstractThe performance of a one‐dimensional MR technique for the estimation of pulse‐wave velocity in the aorta was evaluated. An expression for the error in this estimate was formulated and verified both by simulation and by experiment. On the basis of this formulation, guidelines for increasing the efficiency of the acquisition were established. The technique was further validated by comparison with pulse‐wave velocity measurements made with a pressure catheter. All data were acquired from a latex tube driven by a pulsatile flow system. MR measurements of pulse‐wave velocity in the tube were found to be very reproducible in the presence of white noise. Measurements by other techniques were in good agreement, falling within 2 SD of the mean. Because of its sensitivity and spatial resolution, this technique shows promise for making spatially resolved estimates of vessel distensibility. This would allow assessment of diseases, such as atherosclerosis, that cause local changes in the material properties of the vasculature.
Systematic assessment and evaluation of sliding interleaved ky (SLINKY) acquisition for 3D MRA
Authors: Liu Kecheng , Lee Donald H. , Rutt Brian K. 
Published: March 2007

AbstractIn comparison with the conventional three‐dimensional multiple overlapped thin slab acquisition (MOTSA) for magnetic resonance angiography (MRA), we have developed a novel sliding interleaved ky (SLINKY) acquisition technique, which can eliminate the slab boundary artifact (SBA) or venetian blind artifact without any a priori knowledge of blood flow. This work addresses the systematic assessment and evaluation of the SLINKY technique and verifies the advantages of SLINKY in the following several aspects: (a) scan time efficiency; (b) signal‐to‐noise ratio (SNR), and signal‐difference‐to‐noise ratio (SDNR); (c) sensitivity to flow velocity range; (d) sensitivity to flow direction; (e) signal loss in slow/reversal flow regions; and (f) reconstruction efficiency and feasibility. Both phantom and in vivo experiments verify the clinical significance of the technique. The new MRA images acquired with this imaging technique in 31 volunteer/patient examinations show highly reliable mapping of vascular morphology without the SBA and reduction of signal voids in complex/slow flow regions.
Improved clinical echo‐planar MRI using spatial‐spectral excitation
Authors: Schick Fritz , Forster Jürgen , Machann Jürgen , Kuntz Reinhard , Claussen Claus D. 
Published: March 2007

AbstractEcho‐planar imaging (EPI) is markedly susceptible to B0 field distortions and to frequency differences caused by chemical shift, because the phase of the signals is accumulating during the acquisition train. Thus, only water proton signals are usually recorded after frequency‐selective suppression of the fat portions of magnetization. Otherwise, a shifted signal frequency from fat results in ghosting artifacts. In this article, a technique is presented working with spatial‐spectral excitation for highly selective water or fat EPI. The proposed method allows recording in multislice operation on EPI scanners without irregular gradient or RF pulse shapes. Examples of gradient‐echo and spin‐echo EPI using spatial‐spectral excitation by series of two to eight single slice‐selective RF pulses are demonstrated. The method is not sensitive to misadjustments or inhomogeneities of the B1 field, but sufficient homogeneity of the static magnetic field B0 is required. Especially the quality of diffusion‐weighted echo‐planar images can be markedly improved by the new technique compared to conventional EPI, because artifacts from undesired chemical shift components are completely avoided.
Hybrid ordered phase encoding (HOPE): An improved approach for respiratory artifact reduction
Authors: Jhooti Permi , Wiesmann Frank , Taylor Andrew M. , Gatehouse Peter D. , Yang Guang Z. , Keegan Jennifer , Pennell Dudley J. , Firmin David N. 
Published: March 2007

AbstractRespiration causes continuous change in cardiac position, which leads to image degradation. Phase‐encode reordering methods are often used to reduce these artifacts. An improved method for suppressing motion artifacts by reordering the acquisition of k space has been developed that is less sensitive to change of breathing patterns and bulk movement. We describe the theory behind the new approach and compare its results with those of existing methods by use of a phantom with simulated and actual acquired breathing patterns. The comparison was also made in vivo; cardiac scans were performed in 15 subjects with image planes that are known to be particularly susceptible to respiratory artifact. A significant improvement in image quality was achieved compared with conventional nonreordered and existing reordering methods.
Reduction of field of view in MRI using a surface‐spoiling local gradient insert
Authors: Wiesler David G. , Wen Han , Wolff Steven D. , Balaban Robert S. 
Published: March 2007

AbstractHerein is presented a method for suppressing the magnetic resonance signal to a controlled depth by applying a spatially heterogeneous spoiler field between the slice‐select and readout pulses. Eliminating the signal from near‐surface regions allows one to shrink the field of view without introducing aliasing artifacts, thereby decreasing imaging time over a smaller defined volume. A unique planar magnetic gradient coil was constructed to generate the spoiler field. Phantom and human subject studies showed that the signal can be suppressed to controlled distances of up to 90 mm from the coil, with modest requirements on power supplies, pulse sequences, and materials, and with no increase in imaging time.
A simple method for the correction of endorectal surface coil inhomogeneity in prostate imaging
Authors: Liney Gary P. , Turnbull Lindsay W. , Knowles Adrian J. 
Published: March 2007

AbstractA simple method is described that corrects for the intensity inhomogeneity experienced when using endorectal surface coils in prostate imaging. The method uses a series of proton‐density‐weighted images, which are acquired to demonstrate the sensitivity profile of the coil and used to correct T2‐weighted images acquired in the same plane. The results demonstrate improved image uniformity and visualization of prostatic anatomy.
MRI evaluation of right ventricular pressure overload in chronic obstructive pulmonary disease
Authors: Marcus J. Tim , Noordegraaf Anton Vonk , De Vries Peter M. J. M. , Van Rossum Albert C. , Roseboom Bea , Heethaar Robert M. , Postmus Pieter E. 
Published: March 2007

AbstractIn chronic obstructive pulmonary disease (COPD), the development of pulmonary hypertension is common. This study was performed to assess the signs of right ventricular (RV) pressure overload and RV failure in COPD. In 8 COPD patients without primary cardiac disease, RV wall thickness, mass, and end‐diastolic volume were measured by cardiac‐triggered cine MRI. MR phase‐contrast velocity quantification was used to measure stroke volume and the patterns of flow into and out of the RV. Data of patients were tested versus those of a control group matched for age (n = 8). Results showed that the RV wall thickness was increased (.6 ± 0.1 vs 0.4 ± 0.1 cm, P < .001). RV mass was increased (67 ± 11 vs 57 ± 5 g, P < .005). RV stroke volume was decreased (57 ± 13 vs 71 ± 13 ml, P < .01), but RV ejection fraction was not different. In the main pulmonary artery flow, the quotient of acceleration time divided by ejection time was decreased (33 ± 5% vs 38 ± 4%, P < .05), which is indicative of pulmonary hypertension. In conclusion, this MRI protocol provides a tool to assess the effects of RV pressure overload in COPD before heart failure has become manifest.
Comparison of fast spiral, echo planar, and fast low‐angle shot MRI for cardiac volumetry at .5T
Authors: Wiesmann Frank , Gatehouse Peter D. , Panting Jonathan R. , Taylor Andrew M. , Firmin David N. , Pennell Dudley J. 
Published: March 2007

AbstractThe application of fast imaging is necessary to reduce the scanning time for cardiac volumetric MRI. Fast spiral, echo planar imaging (EPI), and fast low‐angle shot (FLASH) imaging are rapid MRI techniques that allow image acquisition within a fraction of a second. Performed as a multi‐shot technique, breath‐hold imaging with high temporal and spatial resolution is feasible. This study evaluated the accuracy of interleaved spiral, EPI, and FLASH imaging for measuring ventricular volume and mass at .5T. Breath‐hold short‐axis cines in parallel planes covering both ventricles were acquired in 16 volunteers with all three fast methods, as well as with conventional gradient‐echo imaging for comparison. All fast techniques showed good agreement with conventional imaging. Despite its lower temporal resolution, FLASH imaging yielded higher image quality than EPI and spiral, making FLASH more reliable and suggesting that at .5T, it is the method of choice for rapid cardiac volumetric imaging.
MRI in focal liver disease: A comparison of small and ultra‐small superparamagnetic iron oxide as hepatic contrast agents
Authors: Mergo Patricia J. , Engelken John D. , Helmberger T. , Ros Pablo R. 
Published: March 2007

AbstractThe purpose of this study was to compare small and ultrasmall superparamagnetic iron oxide particles (SPIO and USPIO, respectively) as MR contrast agents for the evaluation of focal hepatic disease. In two different patient groups (SPIO [n = 53], USPIO [n = 27]), with focal liver disease (metastases, hepatocellular carcinoma [HCC], hepatocellular adenoma [HCA], and focal nodular hyperplasia [FNH]), spin‐echo T1‐ and T2‐weighted images (T1WI, T2WI) were obtained at 1.0T, before and after intravenous contrast administration. The percentage signal‐to‐noise ratio (SNR) change and lesion‐to‐liver contrast (LLC) were measured and statistically compared. The liver decreased in signal intensity (SI) after SPIO administration (−28%) and increased after USPIO administration (+16%) on T1WI. On T2WI, the liver decreased in SI on postcontrast images with both agents (−78% SPIO, −73% USPIO). This difference was not statistically significantly different (P ⩽ .07). Both SPIO and USPIO provided >500% improvement in LLC on T2WI. On T1WI, LLC was increased in metastases (120%) and HCC (325%) with SPIO. Post‐USPIO, LLC was increased on T1WI only in metastases (>500%). Both SPIO and USPIO show excellent hepatic uptake, presumed secondary to reticuloendothelial activity, based on the degree of %SI change seen in the liver after administration of contrast on T2WI. However, USPIO preparations exhibit blood pool activity that may aid in further characterization of focal liver lesions, as is evidenced by their greater T1 effect in the liver and in some focal liver lesions.
Comparison of multishot turbo spin echo and HASTE sequences for T2‐weighted MRI of liver lesions
Authors: Yu Jeong‐Sik , Kim Ki Whang , Kim Young Hwan , Jeong Eun‐Kee , Chien Daisy 
Published: March 2007

AbstractThe purpose of this study was to compare the relative usefulness of multishot turbo spin echo (TSE) and half‐Fourier single‐shot turbo spin echo (HASTE) for determination of optimal breath‐hold fast T2‐weighted technique in terms of lesion detection, lesion‐to‐liver contrast‐to‐noise ratio (CNR), and image quality. The images of TSE with and without fat suppression (FS) and of HASTE with and without FS were retrospectively reviewed for 49 patients with 128 lesions. Without FS, TSE and HASTE images allowed depiction of focal hepatic masses (112 of 128, sensitivity = 87.5%) at the same rate. TSE with FS depicted more focal lesions (115 of 128, 89.8%) than HASTE with FS (109 of 128, 85.2%), but the difference was not statistically significant (P > .05). The CNR of each lesion on HASTE sequences was greater (P < .01) than that on TSE sequences. The CNR of hemangioma was distinct from that of solid tumors and cystic lesions in all sequences, and the range of CNR in each group of pathologies overlapped less and were well separated in the HASTE sequences. HASTE sequences produced better image quality with fewer artifacts (P < .0001). The results of this study suggest that HASTE sequences allow differentiation between solid tumors, hemangiomas, and cystic lesions in terms of CNR, producing fewer image artifacts, with acceptable sensitivity in lesion detection.
Quantification of white matter and gray matter volumes from three‐dimensional magnetic resonance volume studies using fuzzy classifiers
Authors: Herndon R. Craig , Lancaster Jack L. , Giedd Jay N. , Fox Peter T. 
Published: March 2007

AbstractWe accurately measured white matter (WM) and gray matter (GM) from three‐dimensional (3D) volume studies, using a fuzzy classification technique. The new segmentation method is a modification of a recently published method developed for T1 parametric images. 3D MR images were transformed into pseudo forms of T1 parametric images and segmented into WM and GM voxel fraction images with a set of standardized fuzzy classifiers. This segmentation method was validated with synthesized 3D MR images as phantoms. These phantoms were developed from cryosectioned human brain images located in the superior, middle, and inferior regions of the cerebrum. Phantom volume measurements revealed that, generally, the difference between measured and actual volumes was less than 3% for 1.5‐mm simulated brain slices. The average cerebral GM/WM ratio calculated from 3D MR studies in four subjects was 1.77, which compared favorably with the estimate of 1.67 derived from anatomical data. Results indicate that this is an accurate and rapid method for quantifying WM and GM from T1‐weighted 3D volume studies.
Simultaneous gradient‐echo/spin‐echo EPI of graded ischemia in human skeletal muscle
Authors: Donahue Kathleen M. , Van Kylen Joel , Guven Safak , El‐Bershawi Ahmed , Luh Wen‐Ming , Bandettini Peter A. , Cox Robert W. , Hyde James S. , Kissebah Ahmed H. 
Published: March 2007

AbstractThe goal of this study was to evaluate the usefulness of blood oxygenation level‐dependent (BOLD) methodologies to provide temporal and spatial information about skeletal muscle perfusion. A simultaneous gradient echo (GE) and spin‐echo (SE) imaging sequence (GE/SE) with alternating TE was used to acquire images of leg skeletal muscle throughout a stepped reactive hyperemia paradigm. The change in both the GE and SE relaxation rates (ΔR2*, ΔR2) measured during ischemia and reactive hyperemia scaled with the duration of cuff inflation (the ischemic period) plateaued for cuff inflations lasting longer than 120 seconds and were greater in soleus muscle than in gastrocnemius. The ratio ΔR2*/ΔR2 was found to be less during the reactive hyperemia period relative to ischemia. Considering that a greater proportion of capillary vessels are perfused during reactive hyperemia than during ischemia, this finding suggests that magnetic susceptibility methodologies, with their dependence on compartment size, may provide a measure of the relative distribution of small and large vessels in skeletal muscle.
Gradient coil design considerations for iron core interventional magnets
Authors: Ersahin Atila , Bronskill Michael J. , Henkelman R. Mark , Collick Bruce , Hinks R. Scott 
Published: March 2007

AbstractThe requirements for access and imaging performance compete in the design of open‐concept MR magnets and gradient coils. We conducted a theoretical and experimental investigation of gradient coil design using both solid and laminated pole piece construction to determine whether adequate eddy current control can be obtained without shielded gradient coils while maintaining good patient access and high gradient performance. Eddy currents, gradient characteristics, gradient efficiency, and magnet openness are compared and contrasted for various construction options based on a compact, .27 T iron yoke magnet. The resulting pole pieces and gradient coils have high efficiency for an interventional open‐configuration magnet while taking up minimal space between the poles for improved patient access.
Determination of gradient magnetic field‐induced acoustic noise associated with the use of echo planar and three‐dimensional, fast spin echo techniques
Authors: Shellock Frank G. , Ziarati Mokhtar , Atkinson Dennis , Chen Dar‐Yeong 
Published: March 2007

AbstractThe purpose of this study was to assess gradient magnetic‐field‐induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three‐dimensional fast spin echo (3D‐FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field‐strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D‐FSE pulse sequences. Parameters were selected to produce “worst case” acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A‐weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D‐FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.
Combined MRI and CFD analysis of fully developed steady and pulsatile laminar flow through a bend
Authors: Weston S. J. , Wood N. B. , Tabor G. , Gosman A. D. , Firmin D. N. 
Published: March 2007

AbstractA combined MR and computational fluid dynamics (CFD) study is made of flow in a simple phantom laboratory flow rig consisting of a 180° bend with straight entry and exit sections. The aim was to investigate the potential of the use of MRI‐linked CFD simulations for in vivo use. To this end, the experiment was set up for both steady and pulsatile laminar flow conditions, with Reynolds and Dean numbers and Womersley pulsatility parameter representative of resting flow in the human aorta. The geometrical images of the pipe and the velocity images at entry to the bend were used as boundary conditions for CFD simulations of the flow. The CFD results for both steady and pulsatile cases compared favorably with velocity images obtained at exit from the bend. Additional information such as pressure and wall shear stress, which either could not be measured adequately via MRI, or could not be measured at all, was also extracted from the simulation. Overall, the results were sufficiently promising to justify persuing subsequent in vivo studies.