bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion imaging with the MP‐rage sequence
Authors: Lee Haakil , Price Ronald R. 
Published: March 2007

AbstractDiffusion‐weighted magnetic resonance (MR) images obtained with conventional spin‐echo techniques are known to be sensitive to subject motion because of long image acquisition times. To reduce the acquisition time, use of a magnetization‐prepared rapid gradient‐echo (MP‐RAGE) sequence modified for diffusion sensitivity was studied. In this sequence, a preparation phase with a 90°–180°–90° pulse train is used to sensitize the magnetization to diffusion. Centric‐ordered phase encoding, short TRs (5.2–6.5 msec), and small flip angles (5°–8°) are necessary to minimize saturation effects from tissues with short relaxation times. Phantom studies with various concentrations of copper sulfate (T1 ranging from 2,459 to 90 msec) were performed to validate that the diffusion‐weighted signal obtained with the MP‐RAGE sequence was independent of relaxation time. Diffusion‐weighted images of water, isopropyl alcohol, and acetone were acquired to confirm the accuracy of measured diffusion coefficients. Brain images of healthy normal volunteers were obtained to demonstrate motion insensitivity and general image quality of the technique. The results indicate that accurate diffusion‐weighted images can be obtained with a diffusion‐weighted MP‐RAGE sequence, with imaging times of about 1 second.
Registration of images from sequential MR studies of the brain
Authors: Nelson Sarah J. , Nalbandian Allen B. , Proctor Evelyn , Vigneron Daniel B. 
Published: March 2007

AbstractFor sequential studies of patients with brain tumors, the authors have designed an automated registration procedure for intra‐ and interexamination alignment of magnetic resonance images. This was evaluated with artificially misregistered data and data from repeat studies of six healthy volunteers and six brain tumor patients. In a subset of cases, a manual procedure based on matching of neuroanatomic landmarks was also applied for comparison. The results showed that the technique is robust and reproducible, giving an accuracy in the range of 1–2 mm, which corresponded to the spatial resolution of the images. Subject motion between imaging sequences within the same study was negligible, although adjustments (one to two section thicknesses) were required in the z direction to correlate multisection and volume images and to allow accurate image segmentation. For alignment between sequential volunteer and patient examinations, translations of up to 22 mm and rotations in the x, y, and z axes of up to 9° were required. This alignment procedure may be valuable in numerous aspects of treatment planning and patient follow‐up.
MR angiography of the foot and ankle
Authors: Unger Evan C. , Schilling Jolyon D. , Awad A. Nicholas , McIntyre Kenneth E. , Yoshino Mark T. , Pond Gerald D. , Darkazanli Ammar , Hunter Glenn C. , Bernhard Victor M. 
Published: March 2007

AbstractTo better understand the use of magnetic resonance angiography (MRA) in evaluating peripheral vascular disease, the authors studied arteries in the foot and ankle. Twenty patients with arterial occlusive disease of the lower extremity were studied with two‐dimensional time‐of‐flight MRA, and the results were compared with those of 10 conventional x‐ray arteriograms, four digital subtraction arteriograms, and three intraoperative arteriograms. The studies were reviewed and rated by three radiologists blinded to the patients' clinical history. Also, the first 16 patients were examined with MRA before and after intravenous injection of gadopentetate dimeglumine. The mean confidence levels for the reviewers' interpretations of the MRA studies were significantly higher than those for the conventional arteriograms for the medial plantar, lateral plantar, and plantar arch arteries of the feet (P ≦ 0.005).Postcontrast MRA images were inferior to precontrast images because of overlapping of veins and arteries. Time‐of‐flight MRA without gadolinium can serve as a useful complementary study for evaluating patients with peripheral vascular disease in the foot and ankle.
Safety of gadoteridol injection: U.S. clinical trial experience
Authors: Olukotun Adeoye Y. , Parker John R. , Meeks Marion J. , Lucas Maria A. , Fowler Dennis R. , Lucas Thomas R. 
Published: March 2007

AbstractAs part of the clinical evaluation of gadoteridol injection, intravenous doses ranging from 0.05 to 0.3 mmol/kg were administered to 1,709 patients and volunteers. Safety monitoring included pre‐ and postdose physical examinations, vital signs, and clinical laboratory values. Adverse event recording included occurrence, duration, severity, relationship to injection, and clinical importance. No clinically important changes in physical examination results, electrocardiograms, or vital signs were attributed to gadoteridol injection except for one case of hypotension. Four clinically important changes in laboratory values possibly or definitely related to the contrast agent were noted in two patients (0.1%). Adverse events were recorded in 118 subjects (6.9%), including nausea in 24 subjects (1.4%) and taste perversion in 22 subjects (1.3%). All other adverse events occurred with a frequency of less than 1%. Adverse events related to contrast agent administration occurred in 79 subjects (4.6%). Gadoteridol injection demonstrated excellent clinical safety and patient tolerance at various doses and injection rates.
High‐resolution MR imaging of human arteries
Authors: Martin Alastair J. , Gotlieb Avrum I. , Henkelman R. Mark 
Published: March 2007

AbstractThe authors studied the magnetic resonance (MR) imaging appearance of excised human arteries and correlated these findings with those from histologic sections obtained in corresponding planes. Imaging was performed with a 1.5‐T clinical imager modified with an additional gradient insert capable of a 30 mT/m gradient. High‐resolution images of arteries obtained at autopsy indicated that the medial and adventitial layers could be distinguished and that T2‐weighted sequences offered superior contrast. Intimal thickening could be detected at a relatively early stage as a long T2 rim on the luminal surface of the artery. Atherosclerotic plaque was found to have MR properties similar to those of intimal thickening. although necrotic regions within plaque had low signal intensity. Fat suppression sequences did not significantly alter the appearance of atherosclerotic plaque. Calcified plaque produced effects ranging from slight signal loss to signal void. MR imaging findings correlated reliably with the tissue types indicated by histologic analysis.
Single‐shot versus interleaved echo‐planar MR ‐imaging: Application to visualization of cardiac valve leaflets
Authors: Davis Clarence P. , McKinnon Graerne C. , Debatin Jorg F. , Duewell Stefan , Von Schulthess Gustav K. 
Published: March 2007

AbstractVisualization of the cardiac valves with standard magnetic resonance (MR) imaging is not adequate because of long acquisition times. Echo‐planar imaging (PI) can, however, be performed with a temporal resolution (30–50 msec) comparable to that of echocardiography. The authors evaluated the feasibility of real‐time imaging of cardiac valve motion with ultrafast MR techniques. Eight healthy volunteers and three patients with mitral stenosis and re‐ gurgitation were studied with a 1.5‐T whole‐body im‐ ager. Two different EPI sequences were assessed: a standard single‐shot gradient‐echo EPI (GEPI) SCquence and a fast imaging technique based on multiple‐shot EPI with interleaved k‐space acquisition (IGEPI). Fat‐suppressed images with an in‐plane resolution of 3.7 × 3.7 mm were obtained equally spaced through the cardiac cycle. Half‐k‐space acquisition was used. Morphologic evaluation was superior with IGEPI, owing to the better intracavitary signal homogeneity (P ≤ 0.01). and the mitral valve leaflets were easier to identify on systolic images. IGEPI provided adequate valve visibility in all three patients.
Exercise‐related changes in aortic flow measured with spiral echo‐planar MR velocity mapping
Authors: Mohiaddin Raad H. , Gatehouse Peter D. , Firmin David N. 
Published: March 2007

AbstractSpiral echo‐planar magnetic resonance (MR) velocity mapping was used to measure exercise‐related changes in flow in the descending thoracic aorta in 10 healthy volunteers. Flow was measured at rest and Immediately after dynamic exercise, with a 0.5‐T imager with a surface receiving coil and electrocardiographic triggering. Supine exercise was performed with a home‐built pedaling apparatus. Spiral velocity mapping was performed in a transverse plane through the descending thoracic aorta with the subject at rest. The subject was then asked to perform maximum exercise, stop, and hold his breath during a four‐heartbeat acquisition time. Eight cine frames with a temporal resolution of 50 msec were acquired through systole. Each image was acquired in 40 msec during spiral acquisition of k‐space data, starting at the center, 6 msec after the excitation pulse. Reproduclbility of the technique was established by repeating the flow measurement in four consecutive heartbeats. At rest, the heart rate (mean ± standard deviation), mean aortic flow, peak aortic flow, and time to peak flow were 68 beats per minute ± 6, 41 mllliliters per beat ±8, 107 mL/sec ± 20, and 175 msec ± 25, respectively. After exercise, the heart rate and mean and peak aortic flow were significantly increased (P < 0.001), measuring 101 beats per minute ±12, 57 milliliters per beat ± 11, and 158 mL/sec ±29, respectively, while the time to peak flow (115 msec ±32) was significantly reduced (P < 0.001). The four sets of values obtained for the first four consecutive heartbeats measured at rest were similar, as were those obtained for the first four heartbeats after exercise.
Regional myocardial blood volume and flow: First‐pass MR imaging with polylysine‐Gd‐DTPA
Authors: Wilke Norbert , Kroll Keith , Merkle Hellmut , Wang Ying , Ishibashi Yukata , Xu Ya , Zhang Jiani , Jerosch‐Herold Michael , Muhler Andreas , Stillman Arthur E. , Bassingthwaighte James B. , Bache Robert , Ugurbil Kamil 
Published: March 2007

AbstractThe authors investigated the utility of an intra‐vascular magnetic resonance (MR) contrast agent, poly‐L‐lysine‐gadolinium diethylenetriaminepentaacetic acid (DTPA), for differentiating acutely ischemic from normally perfused myocardium with first‐pass MR imaging. Hypoperfused regions, identified with microspheres, on the first‐pass images displayed significantly decreased signal intensities compared with normally perfused myocardium (P < 0.0007). Estimates of regional myocardial blood content, obtained by measuring the ratio of areas under the signal intensity‐versus‐time curves in tissue regions and the left ventricular chamber, averaged 0.12 mL/g ± 0.04 (n = 35), compared with a value of 0.11 mL/g ±0.05 measured with radiolabeled albumin in the same tissue regions. To obtain MR estimates of regional myocardial blood flow, in situ calibration curves were used to transform first‐pass intensity‐time curves into content‐time curves for analysis with a multiple‐pathway, axially distributed model. Flow estimates, obtained by automated parameter optimization, averaged 1.2 mL/min/g ±0.5 (n =29), compared with 1.3 mL/min/g ±0.3 obtained with tracer microspheres in the same tissue specimens at the same time. The results represent a combination of T1‐weighted first‐pass imaging, intravascular relaxation agents, and a spatially distributed perfusion model to obtain absolute regional myocardial blood flow and volume.
MP‐RAGE subtraction venography: A new technique
Authors: Stevenson Jeffrey , Knopp Edmond A. , Litt Andrew W. 
Published: March 2007

AbstractPreliminary evaluation of a new magnetic resonance (MR) venography technique was performed with data sets from five patients undergoing BAR imaging of the brain before and after intravenous administration of gadopentetate dimeglumine. Before contrast agent injection, the patients were imaged with MP‐RAGE (magnetization‐prepared rapid gradient‐echo) and axial turbo T2‐weighted sequences. After contrast agent injection, the MP‐RAGE sequence was repeated. Images were post‐processed with an algorithm that calculates, on a pizel‐by‐pixel basis, the absolute value of signal intensity of each postcontrast MP‐RAGE partition minus that of each precontract MP‐RAGE partition. These subtracted partitions were then subjected to a standard maximum‐intensity‐projection algorithm to obtain the venogram. In all cases, the new method afforded a high‐resolution venogram with clear depiction of venous sinus anatomy. Cortical venous anatomy was also clearly depicted.
Endometriosis: Appearance and detection with conventional and contrast‐enhanced fat‐suppressed spin‐echo techniques
Authors: Ascher Susan M. , Agrawal Rajneesh , Bis Kostaki G. , Brown Elizabeth D. , Maximovich Alexander , Markham Sanford M. , Patt Richard H. , Semelka Richard C. 
Published: March 2007

AbstractSuspected pelvic endometrlosis was prospectively evaluated in 31 women with T1‐ and T2‐weighted conventional spin‐echo (CSE) magnetic resonance imaging alone and in combination with Tl‐weighted fat‐suppressed (TIPS) and gadolinium‐enhanced TIPS (Gd‐TlFS) spin‐echo techniques. Images were grouped for interpretation and comparison as follows: (a) CSE alone, (b) CSE/T1FS. and (c) CSE/T1FS/ Gd‐TlFS. All patients underwent surgery within 3 months of imaging, and 21 patients were found to have endometrlosis: 59 endometriomas (26 large and 33 small) and 51 sites of implants were seen. With CSE images, 23 large and six small endometriomas were detected. With CSE/T1FS images, 25 large and 14 small endometriomas were identified. With CSE/ TIFS/Gd‐TlFS Images, 24 large and 14 small endometriomas were detected and ill‐defined areas of enhancement were noted in 22 sites throughout the pelvis. These corresponded to endometriotic implants seen at surgery in 14 sites. The sensitivity, specificity, and accuracy, respectively, for the detection of endometriosis were 76%, 60%, and 71% for CSE, 86%, 50%, and 74% for CSE/T1FS, and 81%, 50%, and 71% for CSE/TlFS/Gd‐TlFS images. No significant differences (P > 0.1) between image combinations for correctly identifying patients with and without endometriosis were seen. The difference in sensitivity between CSE and CSE/T1FS and between CSE and CSE/TlFS/Gd‐TlFS images for detecting small endometriomas was significant (P=.03).
Multislab three‐dimensional T2‐weighted fast spin‐echo imaging of the hippocampus: Sequence optimization
Authors: Murakami James W. , Weinberger Ed , Tsuruda Jay S. , Mitchell James D. , Yuan Chun 
Published: March 2007

AbstractThree‐dimensional (3D) fast spin‐echo (FSE) imaging can produce contiguous thin sections for high‐quality multiplanar reconstructions. Such reformatted images may be useful in the evaluation of three‐dimensionally complex, curvilinear anatomic structures such as the hippocampus. The authors describe a 3D FSE protocol for T2‐weighted Imaging of the hippocampus. The protocol uses an overlapplng‐multiple‐slab imaging strategy to decrease Imaging times and a modified refocusing radio‐frequency pulse train to improve the reformatted images. The authors describe their parameter optimization, discuss the benefits and limitations of the new sequence, and present representative images of healthy volunteers.
Vessel enhancement filtering in three‐dimensional MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L. 
Published: March 2007

AbstractFor a variety of reasons, small vessels have low signal intensity in magnetic resonance angiography. When the vessel signal Intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum‐intensity‐projection images. The authors developed a nonlinear second‐difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second‐difference filters are presented and compared with the linear Laplacian second‐difference filter. To evaluate the performance of these filters, they were applied to intracranial three‐dimensional time‐of‐night MR angiographic data and the results compared with the vessel enhancement obtained with a simple second‐difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar improvement in small‐vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast‐to‐noise ratio is much greater with the nonlinear filters than the Laplacian filter.
Intracavitary birdcage resonator: Applications to the human prostate
Authors: Merchant Thomas E. , Schwartz Lawrence H. , Ballon Douglas , Koutcher Jason A. , Scher Howard I. , Minsky Bruce D. 
Published: March 2007

AbstractTwenty‐five patients with prostatic cancer were pro‐ spectively examined with a prototype endorectal surface coil featuring a birdcage resonator circuit design. The purpose was to determine the safety of an intracavitary probe for magnetic resonance (MR) imaging of the pelvis that incorporates the “inside‐out” characteristics of a volume coil design and allows high‐resolution MR imaging of the prostate and potentially serves as an alternative to single‐loop intracavitary surface coils. Clinically useful images supplementing images obtained with the body or external surface coils were obtained with the prototype probe. It was tolerated by all patients enrolled in the study, and none experienced side effects. The cylindrically symmetric sensitivity profile of the probe allowed identification of prostate tumors and pelvic lymph node and bone me‐tastases. Volume‐type coils may improve endopelvic MR imaging when used alone or in combination with external coil systems.
Nonlinear excitation profiles for three‐dimensional inflow MR angiography
Authors: Nägele Thomas , Klose Uwe , Grodd Wolfgang , Voigt Karsten , Nüsslin Fridtjof 
Published: March 2007

AbstractAn RF excitation pulse for three‐dimensional (3D) time‐of‐flight (TOP) MR angiography (MRA) with a nonlinear excitation profile was numerically calculated under the condition of uniform vessel signal across the excitation volume (slab), and the superiority of the optform pulse as compared with conventional RF pulses and TONE pulses was demonstrated. For this purpose we acquired MRA of the lower leg and of the carotid and vertebral arteries in a 30‐year‐old healthy volunteer. Although the flow velocity ranges in these two anatomic locations are different by about a factor of 10, in both cases the corresponding optform pulse provided the best signal homogeneity at the highest level.
Mr imaging of ventriculomegaly—a qualitative and quantitative comparison of communicating hydrocephalus, central atrophy, and normal studies
Authors: Kurihara Yoshiko , Simonson Tereasa M. , Nguyen Hoang D. , Fisher David J. , Sato Chin‐Shoou Lin Yutaka , Yuh William T. C. 
Published: March 2007

AbstractBoth communicating hydrocephalus and central atrophy cause ventricular dilatation. However, patients with hydrocephalus may require treatment. The aim of this study was to asscss qualitatively and quantitatively the cffcacy of MR imaging in the differentiation of communicating hydrocephalus from central atrophy. The midsagittal T1‐weighted MR images of 33 patients with communicating hydrocephalus, 31 patients with central atrophy, and 23 normal objects were evaluated qualitatively and quantitativly. This included configuration of the aqueduct; area of the sep‐tum pellucidum, third ventricle, and fourth ventricle; and morphology of the corpus callosum. Distal dilatation of the aqueduct was detected in 33.3% of patients with communicating hydroccphalus and in none of those with central atrophy. The corpus callosum was elevated in patients with communicating hydrocephalus when compared with that in patients with central atrophy. In conclusion, an analysis of midsagittal T1‐ weighted images has identified useful qualitative and quantitative criteris in the differentiation of communicating hydrocephalus from central atrophy. The configuration of the aqueduct with funneling at the fourth ventricular end strongly suggests the presence of communicating hydrocephalus rather than central atrophy alone.
Effects of MR exposure on akonal outgrowth in the sympathetic nervous system of the chick
Authors: Yip Yee Ping , Capriotti Christine , W. Y Joseph 
Published: March 2007

AbstractThe effects of MR exposure on the rate and specificlty of sympathetic preganglionic axonal outgrowth were examined in the chick embryo. Embryos were exposed to a static magnetic field of 1.5 T for 6 hours, 64 MHt RF field pulses, and a Switched magnetic field gradient of amplitude 0.6 G/cm for 4 hours. No significant difference in axonal outgrowth wm observed between MR‐exposed and control embryos. In addition. the distributionr of several major extracellular matrix (ECM) molecules, lpmlnln, fibronectin, and collagen N, were examined. Immunoetaining patterns of these ECM molecules duxing axonal outgrowth showed no difference between MR‐expored and control embryos. Our results suggert that the MR erporure conditions used in this study do not affect axonal outgrowth in the sympathetic nervous system of the chick.
Mr assessment of posttraumatic flexion contracture of the elbow
Authors: Fortier Marielle V. , Forster Bruce B. , Pinney Stephen , Regan William 
Published: March 2007

AbstractReoperative assessment of posttraumatic flexion contracture of the elbow includes plain radiographs and tomograms, which are dif0cult to obtain in the coronal plane due to the contracture. We conducted this study to determine the uaefulness of MR haghg in the work‐up of these patients. Twelve patients with flexion contracture of the elbow were studied. In addition to standard spin‐echo sequences, a sagittally acquired spoiled gradient‐recalled echo 3D data set of the flexed elbow was obtained and reformatted coronally using a curved plane of reconstruction. The MR hdings were compared to the plain filmrr. tomograms and surgical results. MRI allowed identification of loose bodies that were sometimes poorly visualized, or not seen. on plain films, and demonstrated degenerative changes eqdy as well M tomograms. MR showed soft tissue abnormalities including capsular and collateral ligament thickening. Cwillnear reconstructions were helpful in the assessment of collateral ligaments in patients with severe contractures. We conclude that MR is useful in the evaluation of elbow flexion contractures. particularly in assessing soft tissue causes.
Hr imaging and vascular access ports: Ex vivo evaluation of ferromagnetism, heating, and artifacts at 1.5 t
Authors: Shellock Frank G. , Nogueira Marcia , Morisoli Stacy 
Published: March 2007

AbstractThe purpose of our study was to asacsa Futomagneh. hating. ad artifactr, associated with vabcular access ports exposed to a 1.5‐T MR system. Tweaty‐cight different vabcular access port. were evaluated in thb investlgation. Fmmagnetism was determined by using two previouely de techniques. Temperature changes were measured immediately before and after performing a pulse sequence on the vascular access port6 for 80 min at a speciflc absorption rate of 3.1 W/kg. Artifacts were assessed h aesoclation with the use of a fht CRASS pulse sequence. None of the vascular access ports displayed ferromnlpletim. Heating was 0.2°or less. The prerence of adhcts varied. depending on the component materials. The Lack of fcrromagnetiam and negligible heating indicates that MR imaging performed at 1.6 T or lees may be conducted dely in patients with any of the vascular access port. tested. None of the associated artifacts produced by the vascdar access port. is comddercd to paw a rubsttantial problem for MR imaging.