bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of atherosclerosis with a 1.5‐T imaging system
Authors: Gold Garry E. , Pauly John M. , Glover Gary H. , Moretto John C. , Macovski Albert , Herfkens Robert J. 
Published: March 2007

AbstractIt is shown that a conventional 1.5‐T magnetic resonance (MR) imaging system can help characterize some of the key components of atherosclerotic plaque ex vivo. Fresh human aorta with atheromata was suspended in solutions of agarose and manganese chloride and heated to body temperature. The specimens were imaged with modified Dixon and projection‐reconstruction imaging sequences. The specimens were then examined histologically to obtain direct correlation between images, spectra, and histologic characteristics. The results show that vessel wall and plaque components can be identified by means of their MR characteristics and correlated with their histologic appearance. The authors were able to identify normal vessel wall components, such as adventitial lipids and smooth muscle. They were also able to identify and localize plaque components such as fibrous tissue, calcification, lipids, and possible areas of hemorrhage and hemosiderin deposition.
Multicenter trial of automated border detection in cardiac MR imaging
Authors: Fleagle Steven R. , Thedens Daniel R. , Stanford William , Pettigrew Roderic I. , Reichek Nathaniel , Skorton David J. 
Published: March 2007

AbstractThe purpose of the present study was to evaluate the robustness of a method of automated border detection in cardiac magnetic resonance (MR) imaging. Thirty‐seven short‐axis spin‐echo cardiac images were acquired from three medical centers, each with its own image‐acquisition protocol. Endo‐ and epicardial borders and areas were derived from these images with a graph‐searching‐based method of edge detection. Computer results were compared with observer‐traced borders. The method accurately defined myocardial borders in 36 of 37 images (97%), with excellent agreement between computer‐ and observer‐derived endocardial and epicardial areas (correlation coefficients,.94‐.99). The algorithm worked equally well for data from all three centers, despite differences in image‐acquisition protocols, MR systems, and field strengths. These data suggest that a method of computer‐assisted edge detection based on graphsearching principles yields endocardial and epicardial areas that correlate well with those derived by an independent observer.
On‐line monitoring of ultrasonic surgery with MR imaging
Authors: Darkazanli Ammar , Hynynen Kullervo , Unger Evan C. , Schenck John F. 
Published: March 2007

AbstractUltrasonic surgery was performed in rabbits and dogs under the guidance of magnetic resonance (MR) imaging. Two different MR techniques were used to guide the ultrasound beam. T2‐weighted images showed lesion formation within a few minutes after sonication. T1‐weighted GRASS (gradient‐recalled acquisition in the steady state) images were sensitive to temperature elevations, permitting monitoring of lesion creation with MR imaging. Short TR T1‐weighted GRASS images were not as helpful in detecting temperature elevation because of a reduction in signal‐to‐noise ratio. T2‐weighted fast spin‐echo images were compared with conventional T2‐weighted spin‐echo images. The former produced high‐quality images in a fraction of the imaging time. This study shows that it is possible to monitor and guide ultrasonic surgery with MR imaging.
Hemorrhagic lymphangioma mimicking hemoperitoneum: MR imaging diagnosis
Authors: Stoupis Christophoros , Ros Pablo R. , Williams Jonathan L. 
Published: March 2007

AbstractOmental cystic lymphangioma is an uncommon malformation that occurs in children. The authors report the magnetic resonance (MR) imaging findings in a case of hemorrhagic cystic abdominal lymphangioma, which clinically mimicked a recurrent hemoperitoneum. They demonstrate the superiority of MR imaging relative to computed tomography and ultrasound in diagnosing large hemorrhagic cystic masses and differentiating them from free intraperitoneal fluid with multi‐planar imaging and fluid characterization. This enables precise tumor localization and extension, aiding surgical resection.
Variation in MR signal intensity across normal human knee cartilage
Authors: Paul Pradip K. , Kris Jasani M. , Sebok David , Rakhit Ashok , Dunton Alan W. , Douglas Frank L. 
Published: March 2007

AbstractSignal intensity(SI) of individual pixels on sagittal magnetic resonance (MR)images of normal human knee cartilage was quantified to investigate whether it was related to cartilage proteoglycan content. In five subjects, images were acquired with spin‐echo sequences with a TR msec/TE msec ofl,OOO or 7OO/2O and a three‐dimensional gradient‐echo(GRE)sequence (60/15). In a sixth subject, the GRE sequence alone was used with 15°,30°,and 50° flip angles. In all subjects, SI was maximal in pixel layers of the medial zone and minimal at both cartilage edges, resulting in the presence of a bell‐shaped curve of interpixel(zonal) SI variation across the cartilage thickness. The magnitude of SI was dependent on the pulse sequence and flip angle, but the bell shape of the SI variation curve was independent of them. For example, in the medial tibial cartilage, the peak SI was highest with the 1,000/20 spin‐echo sequence, intermediate with the 7OO/2O sequence, and lowest with the GRE sequence. The differences were statistically significant. The bell‐shaped SI variation curve resembled the curve for zonal variation in cartilage proteoglycan content but not the curves for collagen or free water content. The physiologic basis for this resemblance and the potential usefulness of the findings for early diagnosis of diseases such as osteoarthritis are discussed.
Fatty replacement of bone marrow after radiation therapy for Hodgkin disease: Quantification with chemical shift imaging
Authors: Kauczor Hans‐Ulrich , Dietl Barbara , Brix Gunnar , Jarosch Klaus , Knopp Michael V. , Van Kaick Gerhard 
Published: March 2007

AbstractThe authors studied the long‐term fatty replacement of bone marrow in 23 patients who had received radiation therapy for Hodgkin disease, with T1‐weighted magnetic resonance imaging and quantitative chemical shift imaging. T1‐weighted images revealed a mostly homogeneous high‐signal‐intensity pattern, in contrast to the hypointense pattern of nonirradiated marrow. The degree of fatty replacement was objectively assessed with chemical shift imaging, comparing patients to age‐matched healthy volunteers. The authors found an increase in relative fat signal of 37% in the thoracic spine and 34% in the lumbar spine. The relative fat signal of nonirradiated pelvic and femoral marrow was decreased by 8%, indicating marrow reconversion. No radiation dose dependence was found in the range from 25 to 50 Gy. No signs of marrow regeneration were observed 15‐126 months after radiation therapy. With chemical shift imaging, the degree of long‐term radiogenic fatty replacement of the bone marrow can be quantified, confirming the lack of regeneration after radiation therapy for Hodgkin disease.
Flow pattern analysis in the abdominal aorta with velocity‐encoded cine MR imaging
Authors: Mostbeck Gerhard H. , Dulce Matthias C. , Caputo Gary R. , Proctor Evelyn , Higgins Charles B. 
Published: March 2007

AbstractThe sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity‐encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% ± 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.
Pulsatile flow artifacts in two‐dimensional time‐of‐flight MR angiography: Initial studies in elastic models of human carotid arteries
Authors: Buxton Richard B. , Kerber Charles W. , Frank Lawrence R. 
Published: March 2007

AbstractInitial experimental and numerical analysis of artifacts due to pulsatile flow in two‐dimensional time‐of‐flight (2D‐TOF) magnetic resonance (MR) angiography are presented. The experimental studies used elastic models of the carotid artery bifurcation cast from fresh cadavers and accurately reproducing the twisting and tapering of the human blood vessels, allowing direct comparison of images with and without flow. Prominent image artifacts, including periodic ghosts and signal loss, were produced by pulsatile flow even though flow‐compensated gradient waveforms were used. The dependence of artifacts due to partial saturation on pulse sequence parameters (TR and flip angle) was investigated theoretically for a simple pulsatile velocity profile and compared with experimental results from a model of a normal carotid artery. Signal reduction was observed proximal and distal to the stenosis in a model with a 70% internal carotid artery (ICA) stenosis and a model with 90% stenoses in both the ICA and the external carotid artery. Although this study deals exclusively with 2D‐TOF imaging, the methods can also be applied to evaluate other MR angiography techniques.
Mn‐DPDP–enhanced MR imaging of malignant liver lesions: Efficacy and safety in 20 patients
Authors: Aicher Klaus P. , Laniado Michael , Kopp Andreas F. , Grönewäller Eckart , Duda Stephan H. , Claussen Claus D. 
Published: March 2007

AbstractTwenty patients with malignant liver lesions underwent magnetic resonance (MR) imaging with manganese (II) DPDP [N,N′‐dipyridoxylethylenediamine‐N,N′‐diacetate 5,5′‐bis(phosphate)] to evaluate the safety and efficacy of the contrast agent. In two groups of 10 patients each, 5 μmol/kg Mn‐DPDP was administered intravenously (3 mL/min) at a concentration of either 50 or 10 μmol/mL. T1‐ and T2‐weighted images were obtained with a 1.5‐T imager. Six patients reported a total of eight instances of side effects (flush, feeling of warmth, metallic taste) of which seven occured at the 50 μmol/mL concentration. A significant decrease in alkaline phosphatase levels 2 hours after injection was recorded. On T1‐weighted images, the 10 μmol/mL formulation yielded significantly greater increases in contrast‐to‐noise ratio (79.8%–137.5%) than the 50 μmol/mL formulation (46.2%–86.6%). In a blinded reader study of 10 patients with one to five lesions each, no lesion was missed on Mn‐DPDP–enhanced T1‐weighted images; however, four false‐positive foci were identified. The authors conclude that slow administration of 5 μmol/kg Mn‐DPDP at a concentration of 10 μmol/mL is safe and efficient enough to proceed to further clinical trials.
Adrenal tissue characterization with 0.5‐T MR imaging: Value of T2*‐weighted images
Authors: Ichikawa Tomoaki , Fujimoto Hajime , Murakami Koji , Tauchi Mikio , Mochizuki Shigeru , Ohtomo Kuni , Uchiyama Guio 
Published: March 2007

AbstractThe authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor–liver signal intensity ratios on T1‐, T2‐, and T2*‐weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*‐weighted images (21 of 23, 91%) than on T2‐weighted images (15 of 23, 65%). T1‐weighted images were not useful for this distinction. In conclusion, T2*‐weighted images were better than routine T2‐weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*‐weighted images because of an out‐of‐phase effect.
Perfusion and diffusion MR imaging of thromboembolic stroke
Authors: de Crespigny Alexander J. , Tsuura Mitsuharu , Moseley Michael E. , Kucharczyk John 
Published: March 2007

AbstractA carotid embolic stroke model in rats was studied with a combination of diffusion‐ and perfusion‐sensitive magnetic resonance (MR) imaging at 4.7 T. Capillary blood deoxygenation changes were monitored during formation of focal ischemia by acquiring multisection magnetic susceptibility‐weighted echo‐planar images. A signal intensity decrease of 7% ± 3 in ischemic brain (1% ± 2 in normal brain) was attributable to a T2* decrease due to increased blood deoxygenation, which correlated well with subsequently measured decreases in the apparent diffusion coefficient. The same multisection methods were used to track the first‐pass transit of a bolus of dysprosium‐DTPA‐BMA [diethylenetriaminepentaacetic acid‐bis(methylam‐ide)] to assess relative tissue perfusion before and after stroke and after treatment with a thrombolytic agent. Analysis of contrast agent transit profiles suggested a total perfusion deficit in ischemic tissue and essentially unchanged perfusion in normal brain tissue after stroke.
Theoretical analysis of gadopentetate dimeglumine enhancement in T1‐weighted imaging of the brain: Comparison of two‐dimensional spin‐echo and three‐dimensional gradient‐echo sequences
Authors: Mugler John P. , Brookeman James R. 
Published: March 2007

AbstractBy using a theoretical model, the signal difference‐to noise ratios between simulated lesions and normal white matter and gray matter were calculated as a function of lesion concentration of gadopentetate dimeglumine (GD) for two‐dimensional (2D) T1‐weighted spin‐echo (SE), three‐dimensional (3D) steady‐state spoiled gradient‐echo (GRE) (FLASH [fast low‐angle shot]), and 3D magnetization‐prepared rapid gradient echo (MP‐RAGE) pulse sequences. The 3D GRE sequences provided greater contrast enhancement at relatively high [GD], and the 2D SE sequence demonstrated greater enhancement and a higher rate of enhancement at low [GD]. The results predict that at low [GD], certain lesions could probably be detected with the 2D SE sequence but possibly not with one or both of the 3D GRE sequences. At high [GD], certain lesions could probably be detected with one or both of the 3D GRE sequences but possibly not with the 2D SE sequence. This provides a potential explanation for the clinical observation that certain contrast agent enhanced lesions appear less conspicuous on 3D GRE images than on 2D SE images and vice versa. Modified parameter values were derived for the 3D FLASH and 3D MP‐RAGE sequences that are predicted to produce contrast enhancement behavior equivalent or superior to that of a conventional 2D SE sequence.
Ghost phase cancellation with phase‐encoding gradient modulation
Authors: Hinks R. Scott , Xiang Qing‐San , Henkelman R. Mark 
Published: March 2007

AbstractMotion artifacts are a dominant cause of magnetic resonance image quality degradation. Periodic or nearly periodic motion results in image replicates of the moving structures in spin‐warp Fourier imaging. The replicates, or ghosts, propagate in the image in the phase encoding, or y, direction. These ghosted images can be considered to consist of the time‐averaged spin density I0and a ghost mask g. A set of J ghosted images Ij may be acquired in which the ghost mask is intentionally phase shifted by varying amounts relative to I0 with interleaved acquisitions that have shifted phaseencoding orders or by acquiring multiple images during a single readout period in the presence of an oscillating phase‐encoding gradient. The resulting complex images Ij have the same time‐averaged spin density I0 but have ghost contributions gj that, on a pixel‐by‐pixel basis, trace part of a circle around I0. The source images Ij can then be used to estimate I0. Simulations and experiments with the phase‐encoding gradient modulation method show good general ghost suppression for a variety of quasi‐periodic motion sources including both respiratory‐type artifacts and flow artifacts. The primary limitation of the method is the need for rapid gradient switching.
Evaluation of hepatocyte‐specific paramagnetic contrast media for MR imaging of hepatitis
Authors: Tanimoto Akihiro , Kreft Burkhard P. , Baba Yuji , Zhao Longhai , Finn J. Paul , Compton Carolyn C. , Stark David D. 
Published: March 2007

AbstractThe hepatocyte‐specific paramagnetic magnetic resonance (MR) contrast agents manganese‐DPDP [N,N′‐dipyridoxylethylenediamine‐N,N′‐diacetate 5,5′ bis‐(phosphate)] and gadobenate dimeglumine were used for diagnosing chemically induced hepatitis in rats. Ex vivo liver tissue relaxation times and in vivo MR image signal‐to‐noise ratios were compared before and after contrast agent administration. Ex vivo relaxometry and in vivo MR imaging showed that Mn‐DPDP enhanced normal and diseased livers to the same degree at all time points from 5 to 120 minutes. Gadobenate dimeglumine showed reduced T1 and T2 enhancements in hepatitis relative to those of normal liver, in the early phase (5–30 minutes). However, these effects are offsetting, and as a result, MR imaging failed to allow distinction of diseased from normal livers. This surprising result observed in vivo was in fact predicted by applying the Bloch equation to our ex vivo data. Our results show that detection and quantitation of hepatitis with MR imaging enhanced with paramagnetic cellspecific contrast agents will be more difficult than anticipated.
Pulse sequence strategies for vascular contrast in time‐of‐flight carotid MR angiography
Authors: Tkach Jean A. , Ruggieri Paul M. , Ross Jeffrey S. , Modic Michael T. , Dillinger John J. , Masaryk Thomas J. 
Published: March 2007

AbstractA systematic evaluation in healthy volunteers of the relative efficacy of various techniques for background suppression to improve two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight magnetic resonance angiography of the cervical carotid arteries was performed. Conventional 2D and 3D FISP (fast imaging with steady‐state precession) sequences with flow compensation were compared with modifications of these sequences, including a tracking saturation pulse (2D), prolonged absolute TEs for fat suppression based on T2* decay (2D and 3D), frequency‐selective saturation of fat (2D and 3D), in‐plane spatial saturation (2D), and magnetization transfer contrast (2D and 3D). The tracking saturation pulse and slight overlap of the excitation sections provided uniform background suppression without impairing depiction of the morphology of the cervical carotid arteries. Frequency‐selective fat saturation was the most effective background suppression scheme among the 2D and 3D techniques but was occasionally compromised by local field inhomo‐geneities. Magnetization transfer contrast provided little suppression of stationary tissues in the neck because of the intrinsic limitations of the coil. In‐plane spatial saturation yielded the highest background suppression but reduced apparent arterial diameters and could not be implemented in a 3D version. The T2* decay method not only reduced the apparent size of the vessels but also their signal intensity.
MR imaging of patellar retinacular ligament injuries
Authors: Quinn Stephen F. , Brown Thomas R. , Demlow Thomas A. 
Published: March 2007

AbstractSeventeen patients with patellar retinacular ligament injuries were evaluated with magnetic resonance (MR) imaging. MR findings were correlated with clinical, surgical, and arthroscopic findings. The injuries involved the medial retinacular ligament in 16 of 17 patients and the medial and lateral retinacular ligament in one patient. Nine of 17 patients showed MR evidence of a patellar dislocation. In these patients, a triad of findings that included focal impaction injuries involving the lateral femoral condyle, osteochondral injuries of the medial patellar facet, and injuries of the medial retinacular ligament were seen. Seven of the nine patients with patellar dislocation injuries had frank osteochondral injuries. The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. The patellar dislocations were clinically unsuspected in the initial evaluation of eight of these nine patients. In eight of 17 patients, the mechanism of injury was a patellar tendon tear (n = 1) or valgus hyperextension (n = 7). In the seven patients with hyperextension injuries, three had associated meniscal and cruciate ligament tears. MR imaging can help define patellar retinacular and associated osteochondral injuries, which may be clinically useful information.
Automated pixel‐by‐pixel mapping of dynamic contrast‐enhanced MR images for evaluation of osteosarcoma response to chemotherapy: Preliminary results
Authors: Hanna Soheil L. , Reddick Wilburn E. , Parham David M. , Gronemeyer Suzanne A. , Taylor June S. , Fletcher Barry D. 
Published: March 2007

AbstractAn automated technique for pixel‐by‐pixel computer mapping of tumor necrosis was developed to improve the accuracy and applicability of dynamic contrast agent–enhanced magnetic resonance (MR) imaging in assessing the response of osteosarcoma to preoperative chemotherapy. The technique was evaluated in nine osteosarcoma patients who underwent MR imaging at diagnosis (n = 7) and after preoperative chemotherapy (n = 9). Sequential FLASH (fast low‐angle shot) images of the tumor were obtained in one plane every 15 seconds before and for 3 minutes after gadopentetate dimeglumine injection. A region of interest was selected that included the entire tumor area. Slopes representing percent increase in signal intensity over baseline values per minute were calculated automatically for each pixel and displayed as grayscale maps of the tumor. Matching histologic maps of each tumor were obtained. Visual region‐by‐region comparison of the pixel and histologic maps showed a high degree of correlation and the ability of the MR imaging technique to help identify small foci of residual viable tumor.
Functional mapping of human motor cortical activation with conventional MR imaging at 1.5 T
Authors: Cao Yue , Towle Vernon L. , Levin David N. , Balter James M. 
Published: March 2007

AbstractA conventional 1.5‐T magnetic resonance (MR) imager was used to detect signal intensity changes on T2*‐weighted images of human motor and sensory cortices during performance of hand and tongue movements. Narrow receiver bandwidths were used to improve the signal‐to‐noise ratio. Protocols consisting of baseline, motor task, rest, and second motor task periods were performed by nine volunteers. Two‐dimensional cross correlation was applied to correct in‐plane translation and rotation of the head during the imaging session before the control images were subtracted from the task images. Measurements obtained during finger movement tasks indicated a 3%–8% increase in signal intensity near the contralateral central sulcus and smaller ipsilateral signal intensity increases. Bilateral signal intensity increases were also observed during tongue movement studies. A retrospective image registration technique was used to map the signal changes onto conventional anatomic images, which were used to create integrated three‐dimensional models of brain structure and function. These integrated images showed that the highest signal intensity due to hand movement was near the putative central sulcus.