bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small bowel neoplastic disease: Demonstration by MRI
Authors: Semelka Richard C. , John Gesine , Kelekis Nikolaos L. , Burdeny Derek A. , Ascher Susan M. 
Published: March 2007

AbstractThis study demonstrates the appearance of small bowel tumors on MR images. Sixteen patients with tumors involving small bowel were studied by MRI. All tumors were proven with histopathology. Eleven patients had primary tumors of the small bowel, which included the following: four carcinoid tumors, three adenocarcinomas, two lymphomas, one leiomyosarcoma, and one leiomyoma. Five patients had recurrent or metastatic disease to small bowel: two patients had colon cancer, one patient had pancreatic cancer, one patient had uterine leiomyosarcoma, and one patient had chloroma (leukemia). MR examination included breath‐hold T1‐weighted spoiled gradient echo (all patients), immediate postgadolinium‐spoiled gradient echo (10 patients), and 2 to 4 minutes postgadolinium T1‐weighted, fat‐suppressed images (all patients). Tumor size, local extent, signal intensity, and enhancement features of tumor and adjacent tissue were determined. Tumor ranged in diameter from 1 to 9 cm (mean, 4.0 cm). Tumors had similar signal intensity to normal small bowel on precontrast images. Fourteen malignant tumors showed heterogeneous enhancement greater than adjacent bowel on gadolinium‐enhanced images. Tumor local extent was best shown on precontrast‐spoiled gradient‐echo images and postgadolinium T1‐weighted fat‐suppressed images. Image quality was most consistent on breath‐hold images. The results of this study show that small bowel tumors are demonstrable on MR images. Precontrast breath‐hold T1‐weighted spoiled gradient‐echo images and gadolinium‐enhanced fat suppressed images demonstrate tumor extent most reliably.
Assessing tumor angiogenesis using macromolecular MR imaging contrast media
Authors: Brasch Robert , Pham Christine , Shames David , Roberts Timothy , Van Dijke Kees , Van Bruggen Nick , Mann Jeffry , Ostrowitzki Susanne , Melnyk Ostap 
Published: March 2007

AbstractMRI enhanced with a macromolecular contrast medium (MMCM) has previously been shown to estimate tumor microvascular characteristics that correlate closely with histologic microvascular density, an established surrogate of tumor angiogenesis. A similar MMCM‐enhanced MRI technique has now been used to investigate the acute tumor microvascular effects of antibody‐mediated inhibition of vascular endothelial growth factor (VEGF), a well‐studied and potent angiogenesis stimulator. Athymic rats xenografted with a human breast carcinoma (MDA‐MB‐435) were imaged after administration of albumin‐gadolinium diethylenetri‐amine pentaacetic acid (Gd‐DTPA30) using a heavily TI‐weighted three dimensional‐spoiled gradient‐refocused acquisition in a steady‐state pulse sequence before and 24 hours after treatment with anti‐VEGF antibody (single dose of 1 mg). Changes in longitudinal relaxivity (ΔR1) were analyzed using a bidirectional two‐compartment kinetic model to estimate tumor fractional blood volume (fBV) and permeability surface area product (PS). Data showed a significant decrease (P < .05) of tumor PS with respect to macromolecular contrast medium at 24 hours after treatment with anti‐VEGF antibody. No significant change was observed in fBV. Suppression of tumor microvascular permeability induced by anti‐VEGF antibody can be detected and quantified by MMCM‐enhanced MRI. MRI grading of tumor angiogenesis and monitoring of anti‐angiogenesis interventions could find wide clinical application.
Water diffusion and exchange as they influence contrast enhancement
Authors: Donahue Kathleen M. , Weisskoff Robert M. , Burstein Deborah 
Published: March 2007

AbstractThe contrast‐enhanced magnetic resonance imaging (MRI) signal is rarely a direct measure of contrast concentration; rather it depends on the effect that the contrast agent has on the tissue water magnetization. To correctly interpret such studies, an understanding of the effects of water movement on the magnetic resonance (MR) signal is critical. In this review, we discuss how water diffusion within biological compartments and water exchange between these compartments affect MR signal enhancement and therefore our ability to extract physiologic information. The two primary ways by which contrast agents affect water magnetization are discussed: (1) direct relaxivity and (2) indirect susceptibility effects. For relaxivity agents, for which T1 effects usually dominate, the theory of relaxation enhancement is presented, along with a review of the relevant physiologic time constants for water movement affecting this relaxation enhancement. Experimental issues that impact accurate measurement of the relaxation enhancement are discussed. Finally, the impact of these effects on extracting physiologic information is presented. Susceptibility effects depend on the size and shape of the contrast agent, the size and shape of the compartment in which it resides, as well as the characteristics of the water movement through the resulting magnetic field inhomogeneity. Therefore, modeling of this effect is complex and is the subject of active study. However, since susceptibility effects can be much stronger than relaxivity effects in certain situations, they may be useful even without full quantitation.
MR assessment of iodinated contrast‐medium‐induced nephropathy in rats using ultrasmall particles of iron oxide
Authors: Laissy Jean Pierre , Benderbous Soraya , Idée Jean Marc , Chillon Sylvie , Beaufils Hélène , Schouman‐Claeys Elisabeth 
Published: March 2007

AbstractThe purpose of this study was to determine the diagnostic value of ultrasmall particles of iron oxide (USPIO)‐enhanced MR imaging at different concentrations to evaluate experimental nephropathy. This study was conducted in 23 uninephrectomized rats using a model of iodinated contrast media‐induced renal failure. Eleven rats received selective intra‐arterial renal administration of diatrizoate (370 mg I/m1) and were compared to two control groups, including five animals injected with isotonic saline and seven noninjected animals. MR imaging was performed 28 hours after the procedure, including T1‐ and T2‐weighted images before and after intravenous administration of successively 5 μmol Fe/kg and 60 μmol/kg of USPIO. Results were interpreted qualitatively and quantitatively with respect to pathologic data, and differences were studied statistically. The maximal signal intensity decrease was noted in normal kidneys in cortex (−65 ± 4%) and medulla (−84 ± 5%) on T2‐weighted images after injection of 60 μmol/kg of USPIO. At this dose, diseased kidneys displayed less signal intensity decrease than normal kidneys on T2‐weighted images (p = .05). Moreover, qualitative analysis showed that the highest sensitivity and specificity to diagnose kidney involvement were obtained with T2‐weighted MR images (75% and 91%, respectively) when 60 μmol/kg of USPIO were used (p < .01). USPIO should be useful for in vivo evaluation of the severity of experimentally induced iodinated contrast media renal impairment in animals.
Evaluation of portal MR angiography using superparamagnetic iron oxide
Authors: Knollmann F. D. , Böck J. C. , Teltenkötter S. , Wlodarczyk W. , Mühler A. , Vogl Th. J. , Felix R. 
Published: March 2007

AbstractThe purpose of our research was to determine the effects of superparamagnetic iron oxide on MR imaging of the portal venous system. Eight piglets were examined in deep anaesthesia and respiratory arrest using a time‐of‐flight magnetic resonance fast low angle shot, two‐dimensional angiography sequence at 1.5T. MR angiograms were acquired precontrast and after intravenous administration of a cumulative dose of 10, 20 and 40 μmol/kg SHU 555A, a superparamagnetic iron oxide contrast agent for MR imaging with a particle size of 60 nm. For each dose, two subsequent sets of scans were obtained and reconstructed by a maximum‐intensity‐projection algorithm. Hepatic parenchymal and portal venous signal intensities were measured, and portal vein contrast calculated for each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver operating characteristics of both observers were analyzed. The contrast agent reduced hepatic parenchymal signal in a dose‐dependent way. After a cumulative dose of 10 μmol iron oxide, hepatic parenchymal signal intensity decreased to 63 ± 6% (average of measurements at 4 and 14 minutes, mean ± standard error of the mean), after 20 μmol to 24 ± 3%, and after 40 μmol to 12 ± 1% of control. Intra‐vascular signal in the left main portal vein branch increased to 117 ± 6%, 127 ± 10%, and 133 ± 9% of control, respectively. The contrast‐to‐noise ratio of the portal vein improved (521 ± 90%, 891 ± 178%, and 995 ± 201% of control in the left portal vein main branch). Intravascular signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose‐dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visual rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous pathology.
MR‐Guided percutaneous ethanol ablation of liver tissue in a .2‐T open MR system: Preliminary study in porcine model
Authors: Lu David S. K. , Sinha Shantanu , Lucas John , Farahani Keyvan , Lufkin Robert , Lewin Klaus 
Published: March 2007

AbstractThe purpose of this study was to test the feasibility of MR‐guided percutaneous ethanol ablation of liver tissue on a .2‐T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low‐angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol‐infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol‐induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR‐guided hepatic tumor ablation.
Magnetic Resonance Urography by Breath‐Hold Contrast‐Enhanced Three‐Dimensional FISP
Authors: Li Wei , Chavez David , Edelman Robert R. , Prasad Pottumarthi V. 
Published: March 2007

AbstractThe purpose of this study was to present our initial experience with contrast‐enhanced MR urography with a breath‐hold three‐dimensional imaging technique. We performed MR urographic studies in two pigs (four studies) and five human subjects using gadopentetate dimeglumine. The FISP sequence we used was the same as the one used for contrast‐enhanced three‐dimensional breath‐hold angiography. MR three‐dimensional urograms were obtained 7–24 minutes after the contrast injection with a dose as low as .03 mmol/kg. The calyces, renal pelves, and ureters were very well visualized. Three‐dimensional MR urography can be acquired within a single breath‐hold after administration of gadolinium chelates. This technique could become part of a protocol that could potentially lead to a single comprehensive diagnostic workup for suspected ureteral obstruction and gross hematuria.
Combined analysis of spatial and velocity displacement artifacts in phase contrast measurements of complex flows
Authors: Steinman David A. , Ethier C. Ross , Rutt Brian K. 
Published: March 2007

AbstractMR phase contrast (PC) velocity imaging is a promising tool for quantifying blood flow velocity in vivo. PC velocity imaging is, however, susceptible to artifacts that result from the displacement of spins during the finite duration pulse sequences. Such displacement artifacts can lead to errors in velocity measurements, especially in the presence of oblique and accelerating flows, which are common throughout the cardiovascular system. By tracking particles (representing spins) through a computed velocity field, and assuming that spatial and velocity encodings occur at discrete times during the pulse sequence, we simulate the separate and combined effects of oblique and acceleration artifacts on PC velocity images. We demonstrate, both by simulation and MR measurement, the errors associated with such artifacts in PC velocity measurements in a representative flow geometry. Using example particle trajectories, we provide a fluid dynamic basis for characteristic phase‐velocity image distortions that can arise when imaging complex, physiologically relevant flows.
Intracranial contour extraction with active contour models
Authors: Matsumoto Sumiaki , Asato Reinin , Okada Tomohisa , Konishi Junji 
Published: March 2007

AbstractA novel image processing scheme for extracting the intracranial contours in axial magnetic resonance data sets is proposed. The scheme incorporates the method of active contour models, a recently introduced paradigm for contour extraction. Its performance is nearly ideal for T2‐weighted images. Although the performances for proton‐density‐weighted images and T1‐weighted images drop slightly, qualitatively satisfactory extraction still can be obtained for T1‐weighted images. Due to high degree of automation, the scheme should help speed up some image processing applications that require the presegmentation of the intracranial cavity.
A reproducible repositioning method for serial magnetic resonance imaging studies of the brain in treatment trials for multiple sclerosis
Authors: Gallagher H. L. , Macmanus D. G. , Webb S. L. , Miller D. H. 
Published: March 2007

AbstractSerial MRI is an important measure of disease progression in evaluating the treatment of multiple sclerosis (MS). Accurate comparisons of scans for lesion activity and lesion volume require precise repositioning of patients. A simple, reproducible repositioning method is described. In a multicenter treatment trial of MS using β‐interferon‐1b, this method has been successful, with only 1.1% of scans being rejected because of poor repositioning.
Vessel enhancement filtering in three‐dimensional MR angiograms using long‐range signal correlation
Authors: Du Yiping P. , Parker Dennis L. 
Published: March 2007

AbstractSmall vessels in three‐dimensional MR angiograms have low visibility in maximum‐intensity projection images because of their low contrast. In a previous study, we had two nonlinear filters that appeared to give significant improvement in small vessel detail. In this paper, we report on a generalization of this filter that allows a more general modeling of the vessels and a more complete suppression of background. One implementation of the general filter gave a vessel mean contrast‐to‐noise ratio that is 2.52 and 3.51 times higher than the vessel mean contrast‐to‐noise ratio obtained using our previously reported maximum‐minimum (max‐min) filter and cross‐ section filter, respectively.
Peroneal tendons: Use of kinematic MR imaging of the ankle to determine subluxation
Authors: Shellock Frank G. , Feske William , Frey Carol , Terk Michael 
Published: March 2007

AbstractThe purpose of this study was to develop a technique for kinematic MRI of the ankle to evaluate subluxation of the peroneal tendons. A special device was used to perform incremental, passive positioning of the ankle from dorsiflexed to plantarflexed positions for the kinematic MRI examination. A fast spoiled gradient‐recalled acquisition in the steady state pulse sequence was used to obtain axial images to assess the peroneal tendons during different positions of the ankle. Seven asymptomatic volunteers and five patients with suspected peroneal tendon subluxation were studied. There was no transverse displacement of the peroneal tendons observed in the asymptomatic subjects nor in two of the patients. Two patients had peroneal tendon subluxation observed on the kinematic MRI studies, and one patient had the peroneal tendons maintained in a displaced position in all ankle positions. The preliminary results suggest that kinematic MRI of the ankle is a potentially useful technique to facilitate evaluation of patients with suspected subluxation of the peroneal tendons, particularly in instances in which subluxation is position‐dependent, and spontaneous reduction of the tendons may occur.
Contrast enhancement pattern and frequency of previously unoperated lumbar discs on MRI
Authors: Hwang Geum‐Ju , Suh Jin‐Suck , Na Jae‐Bum , Lee Hwan‐Mo. , Kim Nam‐Hyun 
Published: March 2007

AbstractEnhancement frequency and patterns (linear intradiscal, nodular intradiscal, and peridiscal) of the 210 previously unoperated lumbar discs were evaluated using contrast‐enhanced lumbar MRI. They also were compared with morphologic abnormalities (normal, bulging, protruded, and extruded) and signal alteration (high signal on T2‐weighted images) of the disc. Image interpretation was decided by the consensus of two musculoskeletal radiologists. Enhancement was observed in 69 (32.6%) discs. The enhancement patterns were either intradiscal, linear of (79.7%) or nodular (10.2%), peridiscal (7.2%), or combined (2.9%). Thirty‐five (77.8%) of the 45 herniated discs, 35 (77.8%) were enhanced, whereas 34 (20.6%) of 165 normal‐appearing discs were enhanced. Enhancement was observed more frequently in discs with high signal intensity zones (P < 0.05). In the six patients with enhanced discs, surgery revealed granulation tissue in three extruded discs, two protruded discs, and one bulging disc. The authors believe that contrast enhancements are frequent in herniated discs and are not infrequent in normal‐appearing discs. The understanding of various enhancement patterns may help in the interpretation of lumbar spine MRI.
Relaxivity of Gd‐EOB‐DTPA in the normal and biliary obstructed guinea pig
Authors: Shuter B. , Wang S.‐C. , Roche J. , Briggs G. , Pope J. M. 
Published: March 2007

AbstractAfter injection of Gd‐EOB‐DTPA, T1 and T2 were determined on a clinical MR scanner (1.5 T) in the liver and kidneys of sacrificed but intact guinea pigs with normal and obstructed biliary systems and in bile, urine, and blood collected postmortem. Tissue [Gd] was determined by radioassay of 153Gd and relaxivities (R1 and R2; units of s−1·mmol−1·kg) of Gd‐EOB‐DTPA calculated. Compared with R1 in 2% agarose gel (4.49 ± 0.03), in normal animals R1 was increased in liver (9.3 ± 0.5), similar in kidney cortex (4.1 ± 0.5), but reduced in kidney medulla (2.5 ± 0.4) and papilla (2.7 ± 0.4). Chronic biliary obstruction did not change R1 in liver (9.7 ± 4.3) but reduced R1 further in kidney tissues (1.0–0.4). In normal animals, R2 values of all tissues (9.5–18.4) were greater than R2 in gel (5.72 ± 0.12). Biliary obstruction possibly elevated R2 in liver (40.1 ± 63.5), severely depressed R2 in kidney cortex (−4.2 ± 6.2) and medulla (−2.3 ± 5.4), and reduced R2 in papilla (5.4 ± 4.6). Obstruction had little effect on R1 and R2 in bile and urine. Water content, macromolecular binding, microviscosity, compartmentalization, and susceptibility effects can readily account for the R1 and R2 observed in liver and kidney. Negative R2 could be a result of several factors, including reduced endogenous magnetic field gradients due to “susceptibility matching” as [Gd] increased, changes in tissue T2 with period of ligation, or a physiological effect of EOB‐DTPA. These results show that disease can alter both R1 and R2 from their values in normal tissues.
Tropospheric biennial oscillation of the Indian summer monsoon with and without the El Nino‐Southern Oscillation
Authors: Pillai Prasanth A. , Mohankumar K. 
Published: March 2007

AbstractTropospheric biennial oscillation (TBO) is the tendency for a relatively strong monsoon to be followed by a weaker one, and vice versa, for the Asian–Australian monsoon system. According to this definition, TBO years include most of the El nino‐Southern Oscillation (ENSO)‐onset years and some other years also. It is believed that the TBO years, with and without ENSO‐onset years, have differences only in the magnitude of the signal. In the present paper, the process of coupled TBO involving the Indian monsoon and the Indian Ocean are studied through composites of relatively strong minus weak monsoon years, with and without the ENSO‐onset years, using National Centers for Environmental Prediction/National Centers for Atmospheric Research (NCEP/NCAR) data sets for the 1950–2004 time period. Different seasonal evolutions of anomalies for convection, Sea Surface Temperature (SST) and wind in a biennial cycle have been identified with and without the ENSO‐onset years. In both these cases, a perfect biennial cycle for convection has been noted. In the non‐ENSO biennial cycle, a perfect biennial cycle is obtained in the areas close to the Indian subcontinent for SST and wind. But for the ENSO‐only years, the seasonal evolutions are different. The Indian Ocean dipole, which is considered an inherent factor for TBO, is absent in the non‐ENSO years. The development and propagation of anomalies are also different in these two cases. It seems that factors other than ENSO are contributing to the biennial cycle in the non‐ENSO years. Copyright © 2007 Royal Meteorological Society
Benzoyl‐Peroxide‐Initiated Inverse Emulsion Copolymerization of Aniline and o‐Toluidine: Effect of Dodecylbenzenesulfonic Acid on the Physicochemical Properties of the Copolymers
Authors: Shreepathi Subrahmanya , Holze Rudolf 
Published: March 2007

AbstractHomo‐ and copolymers of aniline and o‐toluidine have been synthesized using an inverse emulsion pathway; the copolymerization was initiated by benzoyl peroxide. The resulting homo‐ and copolymers are soluble in common organic solvents such as chloroform. Fairly higher doping percentages and polymerization yields for POT suggests that DBSA (a bulky molecule) can efficiently dope the polymer backbone by overcoming the steric hindrances created by the methyl substituent. However, in contrast to the PATs reported so far, solubility of POT as well as copolymers is lower than that of PANI. The homo‐ and copolymers have been characterized with UV‐Vis and FT‐IR spectroscopy, CV, in situ conductivity measurements and SEM. When dissolved in a 2:1 mixture of toluene and 2‐propanol, POT, unlike PANI and the copolymers, does not undergo any conformational rearrangement. A copolymer containing equimolar feed fractions of the comonomers has been obtained in higher yield and its morphology is similar to that of polyaniline.magnified image
Propagation Kinetics of Binary Acrylate–Methacrylate Free‐Radical Bulk Copolymerizations
Authors: Buback Michael , Müller Elena 
Published: March 2007

AbstractRate coefficients of propagation, kp,copo, for MA–MMA, MA–DMA, DA–MMA, and DA–DMA bulk copolymerizations have been determined via PLP–SEC. The kp,copo values are analyzed in terms of the terminal and penultimate unit effect models. Alkyl acrylate and alkyl methacrylate reactivity ratios, as obtained from copolymer composition, are not significantly dependent on the size of the alkyl ester moiety, whereas kp,copo clearly depends on the size of the alkyl group. For MA–DMA, an almost perfect simultaneous fit of copolymer composition and kp,copo is obtained via the terminal model. For DA–MMA, even the penultimate unit effect model affords no adequate simultaneous fit. The observed effects are assigned to hindrance of internal rotational motion in the transition state due to intermolecular and intramolecular mobility terms.magnified image