bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of three‐dimensional segmented flash sequence with magnetization transfer contrast to improve gd‐dtpa‐enhanced intrahepatic MR portography
Authors: Suto Yuji , Kimura Toshihiko , Kamba Masayuki , Sugihara Shuji , Yoshida Kotaro , Takizawa Osamu 
Published: March 2007

AbstractTwenty healthy volunteers underwent gadopentetate dimeglumine (gadolinium diethylenetriaminepentaacetic acid (Gd‐DTPA))‐enhanced MR angiography (MRA) using three‐dimensional‐segmented fast low angle shot images (FLASH) with magnetization transfer contrast (MTC) pulses. MRA was obtained at 75 seconds (early phase) and 135 seconds (late phase) after bolus injection of Gd‐DTPA (MTC+ group) during one period of breath‐holding. Within 1 week, MRA without MTC was performed under the same scanning conditions. Visualization of intrahepatic portal branches with these methods was compared in both phases. Portal vein‐liver contrast‐to‐noise ratios were significantly higher in the MTC+ group in both phases. For third‐and fourth‐order portal branches, visualization was significantly better in the MTC+ group in both phases. Use of three‐dimensional‐segmented FLASH shortened acquisition time and facilitated imaging during breath‐holding and also reduced whole‐body average specific absorption rate values. Visualization of intrahepatic portal vein branches was improved by MTC pulses, and effective imaging time was prolonged.
Mycotic aneurysm of the aorta: MRI and MRA features
Authors: Walsh Daniel W. , Ho Vincent B. , Haggerty Michael F. 
Published: March 2007

AbstractMycotic aneurysms of the abdominal aorta are potentially fatal but uncommon. We report the MRI and MRA features of an abdominal aortic mycotic aneurysm in a patient who presented with nonspecific low back pain. By delineating the saccular nature of the aneurysm and identifying the coexistence of vertebral enhancement, MRI was crucial for the final diagnosis. A potential pitfall of contrast‐enhanced MRA is also demonstrated.
Comparison of albumin‐(Gd‐DTPA)30 and Gd‐DTPA‐24‐cascade‐polymer for measurements of normal and abnormal microvascular permeability
Authors: Roberts Heidi C. , Saeed Maythem , Roberts Timothy P. L. , Mühler Andreas , Shames David M. , Mann Jeffrey S. , Stiskal Michael , Demsar Franci , Brasch Robert C. 
Published: March 2007

AbstractThe purpose of this study was to compare a new MR macromolecular contrast medium (MMCM), gadolinium‐diethylenetriamine pentaacetic acid (Gd‐DTPA)‐24‐cascade‐polymer, to a well‐studied prototype MMCM, for the potential of distinguishing tissues of varying endothelial permeability. Three tissue models of varying capillary permeability were studied in a total of 46 rats: normal myocardium (normal capillaries), subcutaneously implanted adenocarcinoma (mild capillary leak), and reperfused infarcted myocardium (high capillary leak). T1‐weighted MRI was performed before and dynamically after injection of either albumin‐(Gd‐DTPA)30 or the cascade polymer (each .02 mmol gadolinium [Gd] per kg). Data analysis based on a two‐compartment kinetic model yielded estimates of fractional blood volume (BV) (percentage) and fractional leak rate (FLR) (1 per hour). Permeability to the cascade polymer as reflected in FLR was considerable in normal myocardium (8.24 per hour), of similar value in tumors (8.55 per hour), but significantly greater in infarcted myocardium (39.17 per hour, P < .01) versus normal myocardium. The larger albumin‐(Gd‐DTPA)30 demonstrated minimal extravasation in normal myocardium (FLR .33 per hour); FLR in tumors was 100% higher (.66 per hour, P < .002) and FLR in reperfused capillaries was significantly greater (7.94 per hour, P < .001). Based on capillary permeability measurements, the cascade polymer may have limited utility for detection of mildly increased microvascular permeabilities. For severe tissue injury, the cascade polymer can resolve abnormal microvascular integrity.
Flow velocity of the cortical vein and its effect on functional brain MRI at 1.5t: Preliminary results by Cine‐MR venography
Authors: Yamada Kei , Naruse Shoji , Nakajima Kazuhiro , Furuya Seiichi , Morishita Hiroyuki , Kizu Osamu , Maeda Tomoho , Takeo Kazuhiro , Shimizu Khoji 
Published: March 2007

AbstractThe purpose of this study is to demonstrate the effect of altering flow velocity of cerebral cortical veins as the source of the signal change observed in functional magnetic resonance imaging (fMRI) of the brain. 10 healthy volunteers were examined after instructions in self‐paced hand grasping. Experiments were performed using a 1.5‐Tesla whole body MR scanner with a conventional two‐dimensional gradient echo sequence (TR/TE/flip angle 400/60/40, first order flow rephased, reduced band width 8 Hz/pixel). Flow velocity measurements were performed for the cortical veins which corresponded to the activated areas depicted on fMRI. Velocity was estimated from the cine‐MR venography (cine‐MRV) with a tagging technique. Flow phantom studies were performed to delineate the effect of flow velocity differences upon the subtraction images of fMRI. The cine‐MRV revealed increased flow velocity of the cortical veins during activation in seven volunteers, with a mean velocity difference of 15 mm/sec. Flow phantom studies suggested that the increased flow velocity may result in changes of the flow signal profile due to oblique flow displacement. Subtraction of the two images with different flow profiles produces flow signal enhancement. Increased flow velocity of the cortical veins during the activation is an important factor which contributes to the signal of fMRI.
Segmentation analysis in functional MRI: Activation sensitivity and gray‐matter specificity of RARE and FLASH
Authors: Hutchinson M. , Rusinek H. , Nenov V. I. , Feinberg D. A. , Johnson G. 
Published: March 2007

AbstractBrain activation is accompanied by local decreases in vascular deoxyhemoglobin. Theoretically, gradient‐echo and spin‐echo sequences show similar sensitivity to capillary deoxyhemoglobin, but spin‐echo sequences should be less sensitive to venous deoxyhemoglobin. This is an important distinction in the context of cortical localization. We report herein a direct experimental comparison of a gradient‐echo sequence (fast low‐angle shot [FLASH]) with a spin‐echo sequence (rapid acquisition with relaxation enhancement [RARE]) for functional MRI (fMRI) in seven subjects undergoing visual stimulation. A Student t test analysis was used to locate areas of significant activation, and then computerized image segmentation was performed to determine the type of activated tissue. Contrary to previous reports, both sequences proved equally sensitive to overall activation. RARE activation, however, was more specific for gray matter, as suggested by prior theoretical models.
Field strength and angle dependence of trabecular bone marrow transverse relaxation in the calcaneus
Authors: Song H. K. , Wehrli F. W. , Ma J. 
Published: March 2007

AbstractThe contribution from reversible dephasing, R2, to the effective transverse relaxation rate, R2*, in trabecular bone marrow, is governed by the magnetic field inhomogeneity induced by the difference in diamagnetic susceptibility between bone and bone marrow and should, therefore, scale linearly with field strength. Measurement of R2′ in the calcaneus at 1.5 and 4 T by means of the GESFIDE (gradient‐echo sampling of free induction decay and echo) pulse sequence showed R2′ to increase by a factor of 2.73 at the higher field, which is close to the ratio of the field strengths (2.67). At both field strengths, R2′ dominates R2*, contributing more than 90% to the total relaxation rate at 4 T. The data further indicate large regional variations within the calcaneus and a notable dependence of R2′ on the angle of the foot relative to the direction of the static field. The findings have implications on the choice of the calcaneal site for assessment of trabecular density.
Useful internal standards for distinguishing infiltrative marrow pathology from hematopoietic marrow at MRI
Authors: Carroll Kevin W. , Feller John F. , Tirman Phillip F. J. 
Published: March 2007

AbstractThe objective of this study was to establish internal standards on MRI differentiating infiltrative marrow pathology from hematopoietic marrow. The T1‐weighted images of 74 patients (51 biopsy‐proven; 23 clinical follow‐up) were reviewed retrospectively. The relative signal intensity of bone marrow was compared to adjacent skeletal muscle (n = 65) and/or nondegenerated intervertebral disk (n = 53). Twenty foci were hyperintense compared to muscle, of which 17 (85%) cases represented normal red marrow (P < .0001); 45 were isointense or hypointense compared to muscle, of which 44 (98%) represented infiltrative marrow processes (P < .0001). Twelve were hyperintense compared to disk, of which 12 (100%) represented normal red marrow (P < .0001); 41 were isointense or hypointense compared to disk, of which 40 (98%) represented infiltrative marrow processes (P < .0001). On T1‐weighted spin‐echo MRI, skeletal muscle and intervertebral disk may serve as internal standards for differentiating infiltrative pathology from normal hematopoietic marrow. Marrow lesions that are relatively isointense or hypointense to muscle and/or disk should not be considered normal hematopoietic marrow.
Diffusion imaging with a multi‐echo MISSTEC sequence
Authors: Franconi F. , Lethimonnier F. , Sonier C. B. , Pourcelot L. , Akoka S. 
Published: March 2007

AbstractAn imaging method is presented to measure the water‐diffusion coefficient. The sequence (MISSTEC) uses the simultaneous acquisition of a spin echo and several stimulated echoes with the same intensity except for diffusion weighting. The optimal number of stimulated echoes was calculated to minimize the diffusion coefficient error (D). D values obtained in vitro and in vivo were in good agreement with those from the spin‐echo sequence (Intra Voxel Incoherent Motion [IVIM] method). The total acquisition time is half that of the classic IVIM method.
Correspondence of closest gradient Voxels—A robust registration algorithm
Authors: Ostuni John L. , Levin Ronald L. , Frank Joseph A. , DeCarli Charles 
Published: March 2007

AbstractA robust, automatic volume registration algorithm based on intensity gradients is presented. This algorithm can successfully perform registrations under conditions of unrelated intervolume voxel intensities, significant object displacements, and/or significant amounts of missing data. It also allows the user to visualize the registration convergence, clearly illustrating any source of registration errors. This algorithm consists of a matching algorithm based on iteratively finding the correspondence of the closest voxels containing a high three‐dimensional intensity gradient magnitude. This algorithm was tested by registering T2‐weighted MR volumes that had undergone varying displacement transformations to simultaneously acquired proton‐density volumes. These transformations involved rotations of up to 25° followed by translations of up to 25 mm along the axis of rotation. For all registrations, the mean registration error was less than one‐fifth of a voxel and the mean registration time was less than 30 minutes. In conclusion, this algorithm is shown to be a powerful method of sequence‐independent MR volume registration that is simple to both use and understand.
Simulation of two‐dimensional tagged MRI
Authors: Crum William R. , Berry Elizabeth , Ridgway John P. , Sivananthan U. Mohan , Tan Lip‐Bun , Smith Michael A. 
Published: March 2007

AbstractMR tagging is a recent imaging development that, in cardiac applications, makes possible the tracking of points in the myocardium during the cardiac cycle. Researchers have developed semiautomated, computer‐based methods for analyzing tagged images, but the images are complex and present a challenge to automated tracking systems. Simulation can provide an inexhaustible supply of images for testing and validation of tag tracking software and preview the effect of parameter changes in acquisition. SIMTAG is an interactive computer program that simulates two‐dimensional tagged‐MR experiments. The mathematic model used in the simulation and algorithms for simulating image noise and object deformation are described. Examples of the use of simulated images in SPAMM parameter selection, a comparison of tag contrast in signal‐averaged SPAMM and CSPAMM, and simulated images as test sets for tag‐tracking software are presented.
Database prescan: A time‐efficient alternative to brain MRI autoprescan
Authors: Medina L. Santiago , Mulkern Robert V. , Strife Katherine R. , Zurakowski David , Barnes Patrick D. 
Published: March 2007

AbstractThe purpose of this study was to determine the feasibility of database prescan as an alternative to conventional auto‐prescan in pediatric brain MRI. Autoprescan parameters [receiver levels and transmit gain (TG)] were analyzed prospectively in 236 pediatric brain MRI studies. Paired t test and linear regression analysis were performed to determine predictability of autoprescan parameters by database‐generated parameters. Signal‐to‐noise ratio, image quality, and potential time efficiency of database‐generated parameters were assessed. No statistical difference (P = .13) and a high correlation between the TG of the axial fast spin echo (FSE) proton density (PD) and axial FSE T2‐weighted sequences (r = .92) was seen. Strong correlations were noted between the TG of the sagittal T1‐weighted and the TG of the axial FSE PD (r = .79), axial FSE T2‐weighted (r = .81), and contrast‐enhanced T1‐weighted (r = .78) sequences. The receiver levels did not change significantly between sequences. Quantitative and qualitative analyses revealed no differences in the signal‐to‐noise ratios of the autoprescan and the database‐predicted prescan parameters. Implementation of database prescan could improve time efficiency by 28 to 33%. Autoprescan parameters can be predicted by using database‐generated information while preserving the diagnostic image quality of the study. Incorporation of database prescan into commercial MRI systems could improve MRI time efficiency and patient throughput.
Microvessel density in invasive breast cancer assessed by dynamic gd‐dtpa enhanced MRI
Authors: Buckley David L. , Drew Philip J. , Mussurakis Stavros , Monson John R. T. , Horsman Anthony 
Published: March 2007

AbstractIt has been postulated that the rapid enhancement demonstrated by breast carcinomas after administration of contrast media is a direct result of tumor angiogenesis. However, to date, little quantitative data have been published to support this view. A retrospective study has been undertaken to compare dynamic contrast‐enhanced data obtained from 40 patients with microvessel density (MVD) evaluated in specimens immunohistochemically stained with a factor VIII related antigen. The dynamic data were analyzed quantitatively using both simple indices of enhancement and a two‐compartment kinetic model. A moderate but significant correlation was demonstrated between initial enhancement and MVD, and this correlation strengthened when node‐positive tumors were considered in isolation (r = .77, P < .0005). However, the data showed considerable variability. The enhancement characteristics of the tumors could not be explained solely by their MVD; therefore, MRI cannot be used to predict MVD in vivo. Further work is required to address the exact relationship between contrast‐enhanced MRI and tumor angiogenesis.
Assessment of reperfusion injury by means of MR contrast agents in rat liver
Authors: Reimer Peter , Allkemper Thomas , Bremer Christoph , Rummeny Ernst J. , Spiegel Hans U. , Balzer Thomas , Peters Peter E. 
Published: March 2007

AbstractThe purpose of this study was to investigate whether extracellular MR contrast agents or intracellular liver‐specific MR contrast agents may enable the assessment of liver reperfusion injury. Ischemia‐related reperfusion was induced in 32 rats using Pringle's maneuver. Pringle's maneuver consisted of cross‐clamping of the complete hepatoduodenal ligament for 45 minutes followed by 90 minutes of reperfusion. Two extracellular (gadopentetate dimeglumine and gadobutrol) and two intracellular (gadoxetic acid and SH U 555 A) MR contrast agents were evaluated as model agents. Control animals and animals with liver ischemia were used to calculate changes in liver signal enhancement after Pringle's maneuver. Significant changes in liver signal after reperfusion injury were observed only with reticuloendothelial system (RES)‐specific SH U 555 A. Liver signal enhancement after Pringle's maneuver with RES‐specific SH U 555 A was decreased by 25.4% as compared with the control group. RES‐specific contrast agents such as SH U 555 A seem to be more sensitive to ischemia‐related dysfunction of the liver than hepatobiliary contrast agents such as gadoxetic acid or extracellular gadolinium chelates at different concentrations because Kupffer cells are more sensitive to liver ischemia than hepatocytes.
Oral administration of a low‐cost negative contrast agent: A three‐year experience in routine practice
Authors: Ernst Olivier , Sergent Geraldine , L'Hermine Claude 
Published: March 2007

AbstractA low cost, well tolerated, and effective gastrointestinal contrast agent is needed for abdominal MRI. The authors tested, in vitro and in routine practice, a mixture of 192 g of barium sulfate (Micropaque HD oral, Guerbet, France) diluted in 500 ml of gastric antacid (Maalox, Rohrer, Fort Washington, PA). Its T1 and T2 relaxation times were 324 and 14 msec, respectively (.2 T). This contrast agent was used in routine practice in 789 patients (.5 T). It had a low signal intensity in 86% and 82% of the cases on T1‐ and T2‐weighted sequences, respectively. No side effect due to magnetic susceptibility was seen, even with gradient‐echo sequences. The dilution of barium sulfate in gastric ant‐acid, instead of water, causes a low signal intensity on all sequences for a low barium sulfate concentration (38% w/v). This product is an effective and low cost contrast agent in routine practice.
High resolution T2‐weighted imaging of the human brain using surface coils and an analytical reception profile correction
Authors: Moyher Susan E. , Wald Lawrence L. , Nelson Sarah J , Hallam Danial , Dillon William P. , Norman David , Vigneron Daniel B. 
Published: March 2007

AbstractHigh spatial resolution T2‐weighted MR images of the human brain were obtained at 1.5 T. An optimized fast spin‐echo (FSE) sequence and 1.5 g/cm gradients were used to obtain T2‐weighted images in 4 to 9 minutes with an in‐plane resolution of .27 mm and slice thicknesses from 1.5 to 3 mm. Phased arrays of surface coils were used as receivers, providing increased sensitivity but image intensities dependent on the reception profile of the coils. This image nonuniformity was removed by analyzing the data with a theoretical intensity correction algorithm developed in this laboratory. The FSE sequences, the specialized phased arrays of surface coils, and the intensity correction algorithm allowed improved visualization of nerves within the inner auditory canals and surface anatomy of the cerebral cortex. It is expected that this technique will be useful for clinical applications that require high resolution imaging of small, superficial structures of the brain.
Evaluation of peri‐infarcted hypoperfusion with T2*‐weighted dynamic MRI
Authors: Tsuchida Chika , Yamada Hiroki , Maeda Masayuki , Sadato Norihiro , Matsuda Tsuyoshi , Kawamura Yasutaka , Hayashi Nobushige , Yamamoto Kazutaka , Yonekura Yoshiharu , Ishii Yasushi 
Published: March 2007

AbstractThe purpose of this study was to evaluate cerebral perfusion with T2*‐weighted dynamic MRI in the area around the infarcted core. We examined seven patients with subacute cerebral infarction. After bolus injection of gadopentetate dimeglumine, a series of gradient‐echo images were recorded in a selected slice. From these images, concentration‐time curves were created on a region‐of‐interest (ROI) basis around infarction for calculating relative regional cerebral blood volume (rrCBV). Brain perfusion single photon emission computed tomography (SPECT) study also was performed with intravenous injection of 123I‐labeled N‐isopropyl‐p‐iodoamphetamine (123I‐IMP). All patients showed prolonged signal decrease in the area around the infarcted core. ROI analysis showed significantly increased rrCBV compared to the normal side (P < .01, paired t test). The 123I‐IMP SPECT study showed that these areas had decreased cerebral blood flow. These findings suggest compensatory vascular dilatation due to decreased perfusion pressure. T2*‐weighted dynamic MRI is a useful method for detecting compensatory vasodilatation of ischemic insult in the peri‐infarcted area.
Contrast‐to‐noise ratio in functional MRI of relative cerebral blood volume with sprodiamide injection
Authors: Lev Michael H. , Kulke Sarah F. , Sorensen A. Gregory , Boxerman Jerry L. , Brady Thomas J. , Rosen Bruce R. , Buchbinder Brad R. , Weisskoff Robert M. 
Published: March 2007

AbstractThe purpose of this study was to investigate the dependence of contrast‐to‐noise ratio (CNR) on the dose and rate of sprodiamide injection in magnetic resonance relative cerebral blood volume (rCBV) imaging. rCBV maps for 35 normal volunteers were constructed from dynamic MR image sets acquired with echo‐planar spin‐echo imaging after intravenous injection of sprodiamide. Doses of .1, .2, and .3 mmol/kg, at rates of 2 ml/second and 5 ml/second, were tested. CNRs and blood/volume ratios of gray to white matter were computed. CNR depended on dose (P < .0001) but was independent of injection rate (P < .69). rCBV ratios of gray to white matter were dose independent (P < .38) and rate independent (P < .97). The dependence of CNR on dose, but not injection rate, has practical implications in optimal protocol design. The independence of gray/white ratios supports the theory underlying the generation of rCBV maps.
Imaging of the lungs using 3he MRI: Preliminary clinical experience in 18 patients with and without lung disease
Authors: Kauczor Hans‐Ulrich , Ebert Michael , Kreitner Karl‐Friedrich , Nilgens Helge , Surkau Reinhard , Heil Werner , Hofmann Dirk , Otten Ernst W. , Thelen Manfred 
Published: March 2007

AbstractThe purpose of this study was to describe the 3He MRI findings of normal pulmonary ventilation in healthy volunteers and to evaluate abnormalities in patients with different lung diseases. Hyperpolarized 3He gas (300 ml, 3 × 105 Pa, polarized to 35–45% by optical pumping, provided in special glass cells) was inhaled by 8 healthy volunteers and 10 patients with different lung diseases. Imaging was performed with a three‐dimensional fast low‐angle shot (FLASH) sequence (TR = 11.8 msec; TE = 5 msec; transmitter amplitude, 5–8 V; corresponding flip angle, <5°) in a single breath‐hold (22–42 seconds). Clinical and radiologic examinations were available for correlation. The studies were performed successfully in eight of eight volunteers and in 8 of 10 patients. The lung parenchyma of volunteers with normal ventilatory function exhibited rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease or bronchiectasis presented with severe signal inhomogeneities with patchy or wedge‐shaped defects. The mass effect of bronchogenic carcinoma, chronic empyema, lymphadenopathy, or pleural effusion caused large signal defects, representing the lesion and adjacent hypoventilation, the extent of which had not been presumed from chest x‐ray or CT. 3He MRI is a promising new modality for the assessment of pulmonary ventilation and its abnormalities. Additional studies are needed to determine its potential clinical role.