bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of a dual echo in the steady state (DESS) free‐precession sequence for imaging cartilage
Authors: Hardy Peter A. , Recht Michael P. , Piraino David , Thomasson David 
Published: March 2007

AbstractThree‐dimensional (3D) MR imaging of the knee is useful to detect cartilage abnormalities, although the tissue contrast in 3D gradient‐recalled echo (GRE) sequences such as gradient‐recalled acquisition in the steady state (GRASS) or fast low‐angle shot (FLASH) is poor. T2 contrast can be added to a GRASS sequence by combining the signals from the first and second gradient echoes, which form immediately after and immediately before each radiofrequency (RF) pulse in a 3D GRE sequence. We have optimized a 3D dual echo in the steady state (DESS) sequence, which produces one averaged image from the two echoes, for use in the detection of articular cartilage abnormalities. In the optimization process, we examined the imaging parameters of flip angle (α), repetition time (TR), echo time (TE), and bandwidth to maximize the contrast between cartilage and joint fluid. A theoretical simulation of the sequence was confirmed with experiments conducted on phantoms with known T1 and T2. On the basis of theoretical predictions and experiments using healthy volunteers, we determined that an optimized sequence with a bandwidth of 98 Hz per pixel, a TR of 30 msec, a TE of 7.1 msec, and an α of 60° produced the highest contrast between cartilage and fluid within a defined acquisition time of 6 minutes. Additional contrast was obtained by filtering the second‐echo image to eliminate noise before adding it to the first‐echo image.
Theoretical and experimental evaluation of phase‐dispersion effects caused by brain motion in diffusion and perfusion MR imaging
Authors: Wirestam Ronnie , Greitz Dan , Thomsen Carsten , Brockstedt Sara , Olsson Magnus B. E. , Ståhlberg Freddy 
Published: March 2007

AbstractWe investigated intravoxel phase dispersion caused by pulsatile brain motion in diffusion spin‐echo pulse sequences. Mathematical models were used to describe the spatial and temporal velocity distributions of human brain motion. The spatial distribution of brain‐tissue velocity introduces a phase spread over one voxel, leading to signal loss. This signal loss was estimated theoretically, and effects on observed diffusion coefficient and perfused capillary fraction were assessed. When parameters from a diffusion pulse sequence without motion compensation were used, and ECG triggering with inappropriate delay times was assumed, the maximal signal loss caused by brain‐motion‐induced phase dispersion was predicted to be 21%. This corresponds to a 95% overestimation of the diffusion coefficient, and the perfusion‐fraction error was small. Corresponding calculations for motion‐compensated pulse sequences predicted a 1% to 1.5% signal loss due to undesired phase dispersion, whereas experimental results indicated a signal loss related to brain motion of 4%.
Hepatocellular carcinoma exhibiting a concentric structure of different histologic grades: Evaluation by chondroitin sulfate iron colloid‐enhanced MR imaging
Authors: Kamba Masayuki , Suto Yuji , Kodama Fumiko , Ohta Yoshio , Kobayashi Junko , Horie Yutaka , Kawasaki Hironaka 
Published: March 2007

AbstractA patient with hepatocellular carcinoma exhibiting a concentric structure of different histologic grades was examined with chondroitin sulfate iron colloid (CSIC)‐enhanced MR imaging. After CSIC injection, the advanced component was enhanced in comparison with the surrounding liver, and the well‐differentiated component was not enhanced. CSIC‐enhanced MR imaging was helpful in evaluating histologic grade on the basis of reticuloendothelial function.
Dynamic MRI of the gallbladder lesions: Differentiation of benign from malignant
Authors: Yoshimitsu Kengo , Honda Hiroshi , Kaneko Kuniyuki , Kuroiwa Toshiro , Irie Hiroyuki , Ueki Takashi , Chijiiwa Kazuo , Takenaka Kenji , Masuda Kouji 
Published: March 2007

AbstractForty‐nine pathologically proven gallbladder lesions were evaluated in 45 patients using dynamic MRI with a spoiled gradient pulse sequence (SPGR), to access the ability of this technique to differentiate benign from malignant gallbladder lesions. The studies were reviewed retrospectively. Signal intensity of the lesions were measured. Twenty‐one malignant and 28 benign lesions were classified into three categories: polypoid, diffuse wall thickening, and exophytic. Early and delayed enhancement patterns were evaluated. For the polypoid masses, malignant lesions (n = 9) demonstrated early and prolonged enhancements, whereas benign lesions (n = 14) had early enhancement with subsequent washout (P < .05). For diffuse gallbladder wall thickening, malignant lesions (n = 6) demonstrated early and prolonged enhancement and benign lesions (n = 14) showed relatively slow, prolonged enhancement (P < .05). The exophytic masses (n = 6) all were malignant and demonstrated early and prolonged enhancement. Dynamic MRI can help differentiate benign from malignant gallbladder lesions.
Analysis of magnetization transfer effects on T1‐weighted spin‐echo scans using a simple tissue phantom simulating gadolinium‐enhanced brain lesions
Authors: Finelli Daniel A. , Hurst Gregory C. , Frank Holly A. , Gullapali Rao P. , Apicella Anthony 
Published: March 2007

AbstractThe purpose of this study was to analyze the effect of several magnetization transfer (MT) pulse and T1‐weighted spin‐echo (SE) sequence parameters on lesion‐to‐background contrast, using a simple tissue phantom emulating the T1 relaxation and MT properties of gadolinium‐enhanced brain lesions. Eggbeaters (Nabisco Inc., East Hanover, NJ) liquid egg product was doped with gadolinium in six concentrations from .0 to 1.0 mmol and cooked. The gadolinium‐doped egg phantom and normal volunteer brains were studied using an SE sequence with TE = 20 msec and high power, pulsed, off‐resonance MT saturation. The effects of MT pulse frequency offset (1,000–6,000 Hz), sequence repetition time (TR = 500–1,000 msec, with MT power held constant), and slice‐select flip angle (60–120 degrees) on the magnetization transfer ratio (MTR) and the simulated lesion‐to‐background contrast were determined at the different “Intralesion” gadolinium concentrations. The MTR and lesion‐to‐background contrast of all materials were greatest at narrow MT pulse frequency offsets. There was an inverse relationship between gadolinium concentration and MTR and a positive correlation between the gadolinium concentration and lesion‐to‐background (L/B) contrast, a weak negative correlation between slice‐select flip angle and L/B, and a negative correlation between TR and L/B. The relaxation properties and MT behavior of the egg phantom are close to that expected for enhancing brain lesions, allowing a rigorous analysis of several variables affecting lesion‐to‐background contrast for high MT power, T1‐weighted SE sequences.
Progression of a focal ischemic lesion in rat brain during treatment with a novel glycine/nmda antagonist: An in vivo three‐dimensional diffusion‐weighted MR microscopy study
Authors: Qiu Hui , Hedlund Laurence W. , Gewalt Sally L. , Benveniste Helene , Bare Thomas M. , Johnson G. Allan 
Published: March 2007

AbstractStroke was induced in two groups of anesthetized rats by occlusion of the middle cerebral artery (MCA) and ipsilateral common carotid artery. Group 1 (control) received vehicle and group 2 received the glycine N‐methyl‐D‐aspartate (NMDA) antagonist ZD9379. Stroke volume was assessed by three‐dimensional diffusion‐weighted MR microscopy at 2.5 and 6 hours of MCA occlusion. At 2.5 hours, stroke volumes were identical in the two groups. At 6 hours, stroke volumes had increased by 15% in the control group; in contrast, the treated group showed a 40% reduced stroke volume. Conclusions from this in vivo study were as follows: (a) our technique allows more efficient and accurate measurement of stroke volume with an improvement in resolution over a previous method; (b) the ability to measure stroke volume at multiple time points shows volume change and assessment of time dependency of drug treatment; (c) at 6 hours, the glycine antagonist ZD9379 reduced stroke volume by 40%.
Paradoxic uptake of Gd‐EOB‐DTPA by hepatocellular carcinoma in mice: Quantitative image analysis
Authors: Fujita Makoto , Yamamoto Reiko , Takahashi Masaya , Tsuji Takashi , Yamanaka Tsuyoshi , Miyazawa Tomoaki , Fritz‐Zieroth Bernhard , Terada Nobuyuki , Kuroda Chikazumi 
Published: March 2007

AbstractTo determine whether paradoxic uptake of gadoliniumethoxybenzyl‐diethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA) occurs only with highly differentiated hepatocellular carcinomas, quantitative image analysis was performed in 37 mice with 133 hepatocellular carcinomas. The results of lesion/liver signal intensity measurement and relative enhancement calculation indicate that paradoxic positive enhancement occurs independently of cellular differentiation.
Adaptive correction of imaging plane position in segmented K‐space cine cardiac MRI
Authors: Chuang Michael L. , Chen Ming Hui , Khasgiwala Vaibhav C. , McConnell Michael V. , Edelman Robert R. , Manning Warren J. 
Published: March 2007

AbstractVariability among breath‐holds frequently produces registration errors, a situation that may contribute to reproducibility error in anatomic indices. A navigator‐echo‐based method for real‐time prospective correction of imaging slice level was applied to breath‐hold cine cardiac imaging of 13 subjects. Repeat acquisitions with correction in the cardiac short‐axis orientation showed significantly improved reproducibility in fractional area change and endocardial centroid location as compared with conventional noncorrected methods.
Segmental hyperintensity on T1‐weighted MRI of the liver: Indication of segmental cholestasis
Authors: Gabata Toshifumi , Matsui Osamu , Kadoya Masumi , Yoshikawa Jun , Ueda Kazuhiko , Kawamori Yasuhiro , Takashima Tsutomu 
Published: March 2007

AbstractThe purpose of this study was to determine the relationship between segmental hyperintensity of the liver on T1‐weighted images and segmental cholestasis in patients with obstructive jaundice. T1‐weighted and T2‐weighted MR images were obtained of 73 patients with obstructive jaundice caused by various diseases. Fat‐suppressed T1‐weighted images were also obtained of 10 patients. Eleven patients with segmental intra‐hepatic bile duct dilatation (cholestasis) showed segmental hyperintensity on T1‐weighted images and/or fat‐suppressed T1‐weighted images and no signal intensity difference on T2‐weighted images. Sixty‐two patients with widespread intrahepatic bile duct dilatation showed no intensity difference on T1‐weighted and T2‐weighted images (P < .01). Segmental hyperintensity on T1‐weighted images was correlated with intrahepatic cholestasis.
Improvement of spiral MRI with the measured k‐space trajectory
Authors: Ding Xiaoping , Tkach Jean , Ruggieri Paul , Perl John , Masaryk Thomas 
Published: March 2007

AbstractThe k‐space trajectory of a spiral imaging sequence was measured with a self‐encoding technique. The image quality improved dramatically when reconstructed with the measured k‐space trajectory. There were substantial artifacts in images reconstructed with the derived k‐space trajectory under the assumption of gradient system linearity. The results indicated the non‐linearity of the gradient system and the effectiveness of the correction technique.
Multiresolution, model‐based segmentation of MR angiograms
Authors: Summers Paul E. , Bhalerao Abhir H. , Hawkes David J. 
Published: March 2007

AbstractDuring the last decade, the quality of MR angiograms has risen substantially and their clinical utility has been demonstrated progressively. This acceptance has created a need for tools with which to summarize and display the information available. We have used a model‐based segmentation technique to extract vascular morphology and local flow parameters from phase contrast MR angiograms. A multiresolution data structure is used as the basis of recursive decision‐making to identify regions of blood flow. The resulting data representation allows more efficient data handling in subsequent processing and visualization and is directly applicable to the creation of a connected graph model of vascular regions. We describe this flow feature extraction algorithm and demonstrate the utility of the results.
Ultrasmall superparamagnetic iron oxide particles (AMI 227) as a blood pool contrast agent for MR angiography: Experimental study in rabbits
Authors: Loubeyre Pierre , Zhao Shihua , Canet Emmanuelle , Abidi Hassane , Benderbous Soraya , Revel Didier 
Published: March 2007

AbstractThe purpose of this study was to evaluate the contribution of an ultrasmall superparamagnetic iron oxide particles (USPIOs) based contrast agent (AMI 227), in a transverse three‐dimensional time‐of‐flight TONE MR angiography sequence of abdominal aorta in rabbits. The main goal was to assess improvement in the visualization of small arteries such as renal arteries, when using such a sequence. Imaging experiments were performed on a 1.5 T magnet, using a transverse 3D time‐of‐flight (TOF) tilted optimized nonsaturating excitation (TONE) sequence with magnetization transfer suppression. The contrast media used were composed of a USPIO core surrounded by a dextransurfactant (AMI 227). Different concentrations of AMI 227 were evaluated in 12 rabbits. Concentrations varied within the range 8.5–34 μmol Fe/kg‐bw: 8.5 μmol Fe/kg (three rabbits); 17 μmol Fe/kg (three rabbits); 25.5 μmol Fe/kg (three rabbits); 34 μmol Fe/kg (three rabbits). A visual analysis based on the improvement of visualization of small arteries (renal arteries) on MIP images and a quantitative analysis based on the percentage of contrast enhancement of the aorta plotted against distance in the slab from the top edge of the acquisition volume were obtained. A signal‐to‐noise ratio enhancement of the distal part of the aorta and only improvement in the delineation of the renal arteries were noted when using low concentrations of the contrast media. A loss of signal‐to‐noise ratio of the aorta and a decrease in arterial visualization were respectively noted with higher concentration of contrast media. In this experimental study, using a transverse three‐dimensional TOF TONE MR angiography sequence of renal arteries, in which sequence the saturation effect is minimized, the use of AMI 227 allows only improvement in the delineation.
MRI of pelvic masses: Efficacy of the rectal superparamagnetic contrast agent ferumoxsil
Authors: Scheidler Juergen , Heuck Andreas F. , Meier Werner , Reiser Maximilian F. 
Published: March 2007

AbstractThe purpose of this study was to determine the potential value of rectally administered Ferumoxsil for pelvic MRI. Twenty patients with suspected rectosigmoid and ovarian tumors were prospectively examined before and after rectal administration of 300 to 600 ml of the superparamagnetic contrast agent Ferumoxsil. Imaging parameters (1.5‐T system, phased‐array coil, transverse T1‐weighted spin echo (SE) and T2‐weighted turbo‐SE sequences, 6‐mm slice thickness, 350‐mm field of view [FOV], 512 × 512 matrix) were kept constant. Images were evaluated for tumor presence, lymphadenopathy, bowel involvement, and peritoneal implants. Precontrast and postcontrast studies were rated for bowel delineation, lesion/organ‐to‐bowel differentiation, presence of artifacts, and confidence of diagnosis. Delineation of rectum and sigmoid colon (P < .001) as well as separation of bowel and vagina, uterus/adnexa, dome of the urinary bladder, lymph nodes, and vessels improved significantly (P < .01) on both T1‐weighted and T2‐weighted postcontrast sequences. The rectal contrast agent did not increase the level of artifacts. Changes in diagnosis in 7 of 20 patients were mainly due to identification of colorectal tumors or bowel involvement on postcontrast images. The readers' diagnostic confidence was significantly higher on contrast‐enhanced than on unenhanced studies (93 ± 6.4% vs 68 ± 25.2%). Rectal application of Ferumoxsil improves lesion/organ‐to‐bowel delineation and overall diagnostic confidence in pelvic MRI.
Rapidly enhancing hepatic hemangiomas at MRI: Distinction from malignancies with T2‐weighted images
Authors: Outwater Eric K. , Ito Katsuyoshi , Siegelman Evan , Martin C. Edwin , Bhatia Manoj , Mitchell Donald G. 
Published: March 2007

AbstractThe purpose of this study is to describe a subset of atypical hepatic hemangiomas that enhance rapidly and diffusely and to determine whether heavily T2‐weighted images could distinguish between atypically enhancing liver hemangiomas and hypervascular malignancies. A retrospective search of MR records identified seven patients with liver hemangiomas that demonstrated diffuse early enhancement and 23 patients with biopsy‐proven malignant liver lesions that were hypervascular on dynamic gadolinium‐enhanced MR images. Quantitative analysis of signal intensity measurements was performed on the T2‐weighted images, heavily T2‐weighted (TE < 140), and dynamic gadolinium‐enhanced images. Blinded reader comparison of the T2‐weighted images and gadolinium‐enhanced images was performed. Hypervascular hemangiomas enhanced to a greater degree than hypervascular malignant liver lesions on the early phase gadolinium‐enhanced images. Perilesional parenchymal enhancement was demonstrated in five cases of rapidly enhancing hemangiomas. Signal intensity and contrast‐to‐noise ratios on the heavily T2‐weighted images of the hemangiomas were significantly greater than that of the hypervascular malignant lesions (P < .05). Hemangiomas were differentiated from the hypervascular malignant liver lesions with high accuracy (97–100%) by three blinded readers based on the T2‐weighted images. A subset of hemangiomas have atypical rapid diffuse enhancement on dynamic gadolinium‐enhanced images. These atypical hemangiomas can be distinguished from hypervascular malignant liver lesions on T2‐weighted MR images.
Liver lesion detection, characterization, and effect on patient management: Comparison of single‐phase spiral CT and current MR techniques
Authors: Semelka Richard C. , Worawattanakul Suvipapun , Kelekis Nikolaos L. , John Gesine , Woosley John T. , Graham Mark , Cance William G. 
Published: March 2007

AbstractThis study compares liver lesion detection, characterization, and effect on patient management between single‐phase spiral CT and MRI using spoiled gradient echo (SGE), T2‐weighted fat‐suppressed spin echo, and serial post gadolinium SGE. All patients with suspected liver lesions who underwent spiral CT and MRI within a 1‐month period between January 1993 and September 1996 were included in the study. Spiral CT and MRI were interpreted prospectively in a blinded fashion by separate individual experienced investigators, and lesion detection and characterization were determined. Confirmation was obtained by surgery (6 patients), biopsy (18 patients), imaging follow‐up (36 patients), or combined reading of all imaging studies and clinical follow‐up (29 patients). Effect on patient management was determined by combined chart review and interview of the patients' physicians and by retrospective clinical assessment performed by a surgical oncologist and medical oncologist separately. Eighty‐nine patients were included in the study. Regarding true positive lesion detection, 295 and 519 lesions were detected on spiral CT and MR images, respectively, which was significantly different on a patient‐by‐patient basis (P < .001). More lesions were detected on MR than on spiral CT in 44 of 89 patients (49.4%), and 11 of these 44 patients had lesions shown on MRI in whom no lesions were apparent on CT images. No patients had true positive lesions shown on spiral CT that were not shown on MRI. Regarding lesion characterization, 129 and 466 lesions were characterized on spiral CT and MRI images, respectively, which was significantly different on a patient‐by‐patient basis (P < .001). More lesions were characterized on MR than CT images in 67 patients (75.3%). Regarding effect on patient management, chart review with physician interview demonstrated that findings on MRI provided information that altered patient management as compared with findings on spiral CT in 57 patients. Retrospective clinical evaluation by the surgical and medical oncologist showed that MRI was considered to have a greater effect on patient management than spiral CT in 58 and 55 patients, respectively. Comparing current MRI technique to single‐phase spiral CT, MRI detected more lesions in 49.4% and characterized more lesions in 75.3% of patients investigated for focal liver disease. MRI had a greater effect on patient management in each of the three methods than singlephase spiral CT in more than 61% of patients.
The effects of incomplete breath‐holding on 3D MR Image Quality
Authors: Maki Jeffrey H. , Chenevert Thomas L. , Prince Martin R. 
Published: March 2007

AbstractThe purpose of this study was to investigate how fast three‐dimensional (3D) MR image quality is affected by breath‐holding and to develop an optimal breath‐holding strategy that minimizes artifact in the event of an incomplete breath‐hold. A computer model was developed to study variable‐duration breath‐holds during fast 3D imaging. Modeling was validated by 3D gradient‐echo imaging performed on 10 volunteers. Signal‐to‐noise ratio (SNR) and image blur were measured for both simulated and clinical images. Insights gained were applied to clinical 3D gadolinium‐enhanced MR angiography. Breath‐holding significantly improved abdominal 3D MR image quality. Most of this benefit could be achieved with a breath‐hold fraction of 50% if it occurred during acquisition of central k space. Breath‐holding during peripheral k‐space acquisition, however, had no significant benefit. Respiratory motion artifact on fast 3D MRI occurring when a patient fails to suspend respiration for the entire scan duration can be minimized by collecting central k space first (centric acquisition) so that premature breathing affects only the acquisition of peripheral k space.
Uptake of dextran‐coated monocrystalline iron oxides in tumor cells and macrophages
Authors: Moore Anna , Weissleder Ralph , Bogdanov Alexei 
Published: March 2007

AbstractAlthough several dextran‐coated iron oxide preparations are in preclinical and clinical use, little is known about the mechanism of uptake into cells. As these particles have been shown to accumulate in macrophages and tumor cells, we performed cellular uptake and inhibition studies with a prototypical monocrystalline iron oxide nanoparticle (MION). MION particles were labeled with fluorescein isothiocyanate or radioiodinated and purified by gel permeation chromatography. Two preparations of MION particles were used in cell experiments: nontreated MION and plasma‐opsonized MION purified by gradient density purification. As determined by immunoblotting, opsonization resulted in C3, vitro‐nectin, and fibronectin association with MION. Incubation of cells with fluorescent MION showed active uptake of particles in macrophages both before and after opsonization. In C6 tumor cells, however, intracellular MION was only detectable in dividing cells. Quantitatively, 125I‐labeled MION was internalized into cells with uptake values ranging from 17 ng (in 9L gliosarcoma) to 970 ng iron per million cells for peritoneal macrophages. Opsonization increased MION uptake into macrophages sixfold, whereas it increased the uptake in C6 tumor cells only twofold. Results from uptake inhibition assay suggest that cellular uptake of nonopsonized (dextran‐coated) MION particles is mediated by fluid‐phase endocytosis, whereas receptor‐mediated endocytosis is presumably responsible for the uptake of opsonized (protein‐coated) particles.