bluuebunny/crossref_metadata_2025_split huggingface dataset:
High resolution MR imaging and localization of laser‐induced thermal injury in the vascular wall
Authors: Ahmad Asif , Roberts Cynthia , Herderick Edward E. 
Published: March 2007

AbstractWith the increasing use of lasers in surgical procedures, there is need for a noninvasive imaging modality to monitor laser–tissue interactions. MRI can be used readily for imaging human anatomy and holds the potential to map laser‐induced thermal injury. This study investigates high resolution T1‐weighted MR imaging of human aorta samples (in vitro) that have been damaged thermally using an argon ion laser and the corresponding histology. High resolution T1‐weighted MR images (voxel size, .156 × .156 × .700 mm) clearly detected residual thermal injury as areas of bright signal intensity. Effective localization of thermal injury was achieved by subtraction of preinjury and postinjury slices with pseudocoloring of positive and negative differences. The results may serve as a basis from which to guide future in vivo studies.
Application of keyhole imaging to interventional MRI: A simulation study to predict sequence requirements
Authors: Duerk Jeffrey L. , Lewin Jonathan S. , Wu Dee H. 
Published: March 2007

AbstractA wide variety of techniques have been proposed recently to improve the temporal resolution of MRI. These include echo‐planar imaging methods, wavelet encoding, singular value decomposition encoding, and k‐space sharing methods known as „keyhole”︁ imaging. In this work, we use a simulation study to investigate the phase‐encoding ordering and data‐sharing methods required for the application of keyhole imaging to interventional MRI (I‐MRI). The advantages of keyhole imaging over other methods are its simplicity and the use of conventional phase encoding and Fourier transform reconstruction found on virtually all modern MR imagers. Our analysis has predicted that conventional keyhole methods that repeatedly acquire only the center portion of k space, and those that sequentially progress from the center of k space outward, will not meet the combination of temporal and spatial resolution required for tip localization during I‐MRI needle insertion. Instead, acquisitions that acquire both high and low k‐space data, in ranked order, should provide acceptable tip position and needle width accuracy in both temporal and spatial domains for use in I‐MRI.
Cancellation of metal‐induced MRI artifacts with dual‐component paramagnetic and diamagnetic material: Mathematical modelization and experimental verification
Authors: Chauvel Brice , Cathelineau Guy , Balac Stéaphane , Lecerf Jean , De Certaines Jacques D. 
Published: March 2007

AbstractA mathematical model of dual‐component paramagnetic and diamagnetic material to cancel metal‐induced MRI artifacts was developed and verified experimentally. The magnetization produced by metallic material and then the gradient linearity distortion can be cancelled by using such materials with opposing paramagnetic and diamagnetic properties. This concept of dual‐component materials provides a novel solution to the problem of MRI artifacts.
Automatic removal of extrameningeal tissues from MR images of human brain
Authors: Bedell Barry J. , Narayana Ponnada A. 
Published: March 2007

AbstractAn automatic technique for removal of extrameningeal tissues from MR images of human brain is described. The algorithm is based on the segmentation of images acquired with a fast dual‐echo pulse sequence, which incorporates both fluid attenuation and magnetization transfer contrast for superior brain/extrameningeal tissue contrast compared to conventional MR sequences. Evaluation of this technique using MR images of six volunteers indicates rapid and consistent removal of extrameningeal tissues.
High resolution MR imaging of the bilateral hips with dual phased‐array coil
Authors: Niitsu Mamoru , Mishima Hajime , Miyakawa Shumpei , Itai Yuji 
Published: March 2007

AbstractWe applied dual‐flex coils in a phased‐array configuration to obtain high resolution MR images of the bilateral hips and compared the image quality with non‐phased‐array imaging. Multiple fast spin‐echo images of both hips were obtained in a single acquisition. Two consecutive acquisitions with and without phased‐array capability were performed in 22 hips and a fluid‐filled phantom. The signal‐to‐noise ratio (S/N) enhancement values were calculated. Subjective image analysis was also obtained from three independent reviewers. High quality MR images were obtained using dual‐array coils with a S/N enhancement value of 1.40 for a phantom and 1.83 to 2.22 for subject hips. On subjective analysis, the dual array enhanced delineation of the acetabular labrum, articular cartilage, and retained fluid. The dual array may be of diagnostic value with a higher S/N enhancement and subjective superiority of the images obtained.
MR imaging contrast agents — what's in a name?
Authors: Mitchell Donald G. 
Published: March 2007

AbstractThe purpose of this brief review is to reduce the confusion surrounding the nomenclature of MRI contrast agents. There are several different categories of contrast agents for potential use in human diagnosis and several alternative names for each contrast agent, an array of choices that actually changes over time. This review describes the general process by which these various agents are named, presents one general categorization by which these agents can be considered, and provides a concise table to which readers can refer to identify the proper name to use for each of the agents that has thus far been administered to humans.
Application of contrast agents in the evaluation of stroke: Conventional MR and echo‐planar MR imaging
Authors: Maeda Masayuki , Maley Joan E. , Crosby Daniel L. , Quets Jerome P. , Zhu Ming‐Wang , Lee Ghi Jai , Lawler Gregory J. , Ueda Toshihiro , Bendixen Birgitte H. , Yuh William T. C. 
Published: March 2007

AbstractThe availability of new therapeutic interventions, including neuroprotective agents and endovascular thrombolysis, has given new hope to patients suffering an acute stroke. Early intervention remains a key factor in the effectiveness of these new and traditional treatments. More importantly, the capability to assess the viability and reversibility of the ischemic tissue became essential for better delineation and differentiation of infarcted versus ischemic tissue and patient management. Abnormal MR imaging (MRI) findings during acute stroke usually reflect the underlying pathophysiologic changes, which can be classified into three sequential stages: (a) hypoperfusion, (b) cellular dysfunction and (c) breakdown of the blood‐brain barrier. The first stage is a kinetic phenomenon (not biologic) and, therefore, can be detected immediately. Contrast agents accentuate the abnormal flow kinetics and facilitate the early diagnosis of ischemia using either conventional MRI or newly developed echo‐planar perfusion imaging (EPPI). The demonstration of abnormal arterial or parenchymal enhancement on conventional MRI during acute stroke provides the earliest sign of vascular occlusion/stenosis. EPPI, in contrast, provides information related to microcirculation (< 100 microns) and tissue reserve (cerebral blood volume) that cannot be obtained by conventional angiography and is directly related to the target end‐organ. Further information obtained from both contrast MRI and EPPI may have a predictive value in the clinical outcome of acute stroke patients.
Contrast‐enhanced MR imaging in the evaluation of treatment response and prediction of outcome in multiple sclerosis
Authors: Simon Jack H. 
Published: March 2007

AbstractMR imaging is becoming increasingly important in the evaluation of multiple sclerosis based on its sensitivity to acute, often subclinical events in the brain and because it provides a basis for measuring the accumulation of disease over time. Contrast‐enhanced MR imaging in particular evaluates disease at the fundamental level of events affecting the blood‐brain barrier. This review emphasizes (a) recent developments in the use of contrast‐enhanced MR imaging as a measure of disease in patient groups and individuals and (b) its emerging role in evaluating new therapies.
Contrast agents in functional MR imaging
Authors: Sorensen A. Gregory , Tievsky Andrew L. , Ostergaard Leif , Weisskoff Robert M. , Rosen Bruce R. 
Published: March 2007

AbstractContrast agents have greatly expanded the role of MR imaging (MRI) to allow assessment of physiologic, or “functional,” parameters. Although activation mapping generally does not require contrast agents, other forms of functional MRI, including mapping of cerebral hemodynamics (eg, perfusion imaging), are best done with the use of contrast agents. Serial echo planar images are obtained after bolus injection of lanthanide chelates. Application of susceptibility contrast physics and standard tracer kinetic principles permits generation of relative cerebral blood volume maps. Deconvolution of cerebral blood flow and mean transit time parameters is also possible within technical limitations. By using diffusion and perfusion pulse sequences, an imaging correlate to the ischemic penumbra can be identified. Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality. Clinical applications include biopsy site selection and postirradiation follow‐up. Further improvements in data analysis and map generation techniques may improve diagnostic accuracy and utility.
Physiologic measurements by contrast‐enhanced MR imaging: Expectations and limitations
Authors: Roberts Timothy P. L. 
Published: March 2007

AbstractContrast‐enhanced magnetic resonance imaging (MRI) offers the opportunity to quantitatively assess physiologic properties of tissue, such as perfusion, blood volume, and capillary permeability. Use of such quantitation potentially allows tissues to be characterized in terms of pathophysiology and to be monitored over time, during the course of therapeutic intervention. The degree to which such quantitation is applicable relies heavily on simplified model descriptions of the tissue space and assumptions relating the signal intensity observed to the contrast agent concentration. This article presents a perspective on the use of quantitative contrast‐enhanced MRI, analysis of the accuracy of derived physiologic parameters, and recommendations for pulse sequence choice.
Assessment of tumor microcirculation: A new role of dynamic contrast MR imaging
Authors: Griebel Jürgen , Mayr Nina A. , De Vries Alexander , Knopp Michael V. , Gneiting Thomas , Kremser Christian , Essig Marco , Hawighorst Hans , Lukas Peter H. , Yuh William T. C. 
Published: March 2007

AbstractWith the advances in MR techniques, information related to tumor microcirculation now can be obtained in the clinical setting. This information can be valuable in the assessment of tumor blood supply/oxygenation status and tumor response to therapy. In this article, we review the tracer‐kinetic modeling for tumor microcirculatory parameters derived from dynamic contrast MR imaging and report several preliminary results from both an animal model and early experience with human tumors. Despite the application of different MR protocols and tracer‐kinetic models, the initial results of these pioneer studies consistently support the role of MR‐derived microcirculatory tumor parameters, in providing prognostic information to assess and predict the response of cancers to cytotoxic therapy.
Ferumoxides and Tc‐99m sulfur colloid: Comparison of the tumor‐to‐liver uptake in focal nodular hyperplasia
Authors: Grandin Cécile B. , Van Beers Bernard E. , Pauwels Stanislas , Demeure Roger , Jamart Jacques , Pringot Jacques 
Published: March 2007

AbstractThe tumor‐to‐liver uptake of two reticuloendothelial agents, namely ferumoxides and technetium‐99m (Tc‐99m) sulfur colloid, was compared in focal nodular hyperplasia (FNH). Twelve patients with FNH who had undergone ferumoxides‐enhanced MR imaging and planar Tc‐99m sulfur colloid scintigraphy within 1 year were included from the study. Fourteen patients with FNH with a diameter larger than 3 cm were selected for the comparison. The tumor‐to‐liver ferumoxides uptake was calculated and the Tc‐99m sulfur colloid uptake was assessed visually. Ferumoxides uptake was observed in all but one patient with FNH (mean tumor‐to‐liver ratio = .36). The six tumors showing normal (n = 5) or increased (n = 1) radiocolloid uptake when compared to the liver accumulated more ferumoxides than the eight tumors showing decreased radiocolloid uptake (P < .01). However, in some tumors, no direct relation was observed between ferumoxides and Tc‐99m sulfur colloid uptake. Our observations suggest that ferumoxides uptake might not exactly mimic Tc‐99m sulfur colloid uptake in FNH.
Contrast‐enhanced MR imaging of the liver: Comparison between Gd‐BOPTA and mangafodipir
Authors: Schima Wolfgang , Petersein Jan , Hahn Peter F. , Harisinghani Mukesh , Halpern Elkan , Saini Sanjay 
Published: March 2007

AbstractThe purpose of the study was to evaluate the MR contrast agents gadolinium benzyloxypropionictetro‐acetate (Gd‐BOPTA) and Mangafodipir for liver enhancement and the lesion‐liver contrast on T1W spin‐echo (SE) and gradient‐recalled‐echo (GRE) images. Fifty‐one patients (three groups of 17 patients each) with known or suspected liver lesions were evaluated with T1W SE (300/12) and GRE (77‐80/2.3‐2.5/80°) images before and after intravenous (IV) Gd‐BOPTA (0.1 or 0.05 mmol/kg) or Mangafodipir (5 μmol/kg) in phase II to III clinical trials. Quantitative analysis by calculating liver signal‐to‐noise ratio (SNR), lesion‐liver contrast‐to‐noise ratio (CNR), and spleen‐liver CNR was performed. Liver SNR and spleen‐liver CNR were always significantly increased postcontrast. SNR was highest after application of 0.1 mmol/kg Gd‐BOPTA (51.3 ± 3.6, P < .05). CNR was highest after Mangafodipir (−22.6 ± 2.7), but this was not significantly different from others (P = .07). Overall, GRE images were superior to SE images for SNR and CNR. Mangafodipir and Gd‐BOPTA (0.1 mmol/kg) provide equal liver enhancement and lesion conspicuity postcontrast. By all criteria, contrast‐enhanced T1‐weighted GRE were comparable to SE images.
MR imaging of the liver: Effect of portal hypertension on hepatic parenchymal enhancement using a gadolinium chelate
Authors: Soyer Philippe , Dufresne Anne‐Charlotte , Somveille Edith , Scherrer Antoine 
Published: March 2007

AbstractThe purpose of this study was to prospectively investigate the extent to which reduced portal blood flow in patients with hepatic cirrhosis and portal hypertension affects hepatic parenchymal enhancement during gadolinium‐chelate‐enhanced dynamic MR imaging. Breath‐hold three‐dimensional (3D) spoiled gradientrecalled echo (GRE) MR imaging technique obtained after intravenous administration of a gadolinium chelate was used to measure hepatic parenchymal enhancement and time to peak enhancement in 20 patients with hepatic cirrhosis and clinical evidence of portal hypertension (group 1) and in 20 control subjects without portal hypertension (group 2) who were matched for age, sex, and body weight. Mean peak hepatic enhancement values ± SD and times to peak enhancement ± SD were determined for both groups of patients. Mean peak enhancement value (±SD) was 78.7% ± 36.2 in group 1 and 91.6% ± 46.2 in group 2 (not significant). However, in the nine patients in group 1 with splenomegaly, mean peak enhancement value was 61.3% ± 14.4, whereas it was 93.0% ± 42.7 in the 11 patients without splenomegaly (P < .05). Mean time to peak enhancement was 84 seconds ± 23 in group 1 and 54.0 sec ± 25.0 in group 2 (P < .01). Our results show that mean peak enhancement value of hepatic parenchyma after intravenous administration of a gadolinium chelate is significantly altered for patients with portal hypertension and splenomegaly. In addition, the time to peak enhancement is delayed significantly when portal hypertension is present. Thus, it is possible that the optimal time for imaging the liver during the portal phase must be tailored to the status of the portal system of the patient.
Evaluation of the hepatocyte‐specific contrast agent gadobenate dimeglumine for MR imaging of acute hepatitis in a rat model
Authors: Marzola Pasquina , Maggioni Fabio , Vicinanza Eleonora , Daprà Massimo , Cavagna Friedrich M. 
Published: March 2007

AbstractThis work was conducted to test the hypothesis that contrast‐enhanced MRI with hepatocyte‐specific contrast agents facilitates quantitation and mapping of diffuse liver diseases such as hepatitis and cirrhosis. Gadobenate dimeglumine (Gd‐BOPTA/Dimeg, Bracco SpA, Milano, Italy) is a new paramagnetic hepatocytespecific contrast agent currently undergoing clinical trials. We have assessed the usefulness of gadobenate dimeglumine for the diagnosis of diffuse liver diseases in a rat model of chemically induced hepatitis. The study was based on the measurements of in vivo liver relaxation times as well as on the acquisition of standard SE images. Acute hepatitis considerably reduced the degree of T1 shortening of liver parenchyma caused by intravenous injection of .25 mmol/kg of gadobenate dimeglumine. Analogously, the enhancement of the MRI signal intensity of the liver of rats with hepatitis observed in T1‐weighted spin‐echo (SE) images was inferior, in terms of both strength and duration, to that recorded in control rats at doses of .25 mmol/kg and .075 mmol/kg of gadobenate dimeglumine. Our results show that gadobenate dimeglumine enhanced MR imaging has the potential for visualization of hepatitis and for assessment of liver function. Our conclusions differ from those previously published on this subject by other authors. The reasons that led to differing conclusions are discussed.
Renal cell cancer: Incidence of hemorrhage on MR images in patients with chronic renal insufficiency
Authors: John Gesine , Semelka Richard C. , Burdeny Derek A. , Kelekis Nikolaos L. , Woosley John T. , Kettritz Ute , Freeman John A. 
Published: March 2007

AbstractThis study describes the occurrence of hemorrhage in renal cancer in patients with chronic renal insufficiency as shown on MR images. Thirteen consecutive patients with chronic renal insufficiency who had his tologically proven renal cancer and underwent MRI at 1.5 T were entered in the study. MR examinations included spoiled gradient echo (SGE) and T1‐weighted fat‐suppressed imaging pre‐ and postgadolinium administration. All renal cancers were well shown on MR images and were most clearly depicted on postgadolinium T1‐weighted fat‐suppressed images. Tumors in 12 of 13 patients had regions of high signal intensity on precontrast T1‐weighted images. Histology demonstrated intratumoral hemorrhage in all 12 of these patients. Four hemorrhagic tumors were largely cystic on imaging studies. One of these cancers altered in appearance from largely cystic with extensive hemorrhage to largely solid with substantial enhancement after a 2.5‐year interval. Renal cancers demonstrated minimal enhancement (11 patients) on early postgadolinium images and were minimally enhanced on delayed images in 10 of 13 tumors. Two renal cancers demonstrated intense enhancement. Renal cancers are well shown on MR images in patients with chronic renal insufficiency. Because of the common occurrence of hemorrhage into renal cancers in patients with renal insufficiency, caution should be exercised when evaluating hemorrhagic cystic lesions in these patients.
Contrast‐enhanced, ultrafast 3d pulmonary MR angiography in a single breath‐hold: Initial assessment of imaging performance
Authors: Steiner Paul , McKinnon Graeme C. , Romanowski Ben , Goehde Susanne C. , Hany Thomas , Debatin Jörg F. 
Published: March 2007

AbstractAn ultrafast three‐dimensional (3D) sequence was developed, enabling the acquisition of 44 contiguous 2.0‐to 2.2‐mm thin sections, during intravenous application of paramagnetic contrast, in a single breath‐hold. To estimate the potential clinical usefulness, images were assessed qualitatively and quantitatively with regard to visibility of main, lobar, segmental, and subsegmental pulmonary arteries. Five volunteers were examined using a 192 × 192 matrix with an imaging time of 23 seconds and five other volunteers with a 160 × 160 matrix (18 seconds). Each volunteer was imaged in apnea and during shallow respiration. The breath‐held 23‐second scans revealed excellent image quality and near complete visualization of central and segmental, as well as 81% of subsegmental, pulmonary arteries. Imaging time can be shortened to 18 seconds with only marginal loss in visualization performance (P < .05). Respiratory motion was found to cause significant worsening of image quality and vessel detectability. To maintain relevance in a clinical setting, imaging time can be minimized at the cost of a reduction in spatial resolution.
Evaluation of the iliac arteries: Comparison of two‐dimensional time of flight magnetic resonance angiography with cardiac compensated fast gradient recalled echo and contrast‐enhanced three‐dimensional time of flight magnetic resonance angiography
Authors: Quinn Stephen F. , Sheley Robert C. , Szumowski Jerzy , Shimakawa Ann 
Published: March 2007

AbstractWe compared dynamic contrast‐enhanced three‐dimensional time of flight (3DTOF) magnetic resonance angiography (MRA) with two‐dimensional time of flight (2DTOF) MRA with cardiac compensated fast gradient recalled echo (C‐MON) and conventional angiography (CA) when it was available. C‐MON re‐orders the normal data acquisition to minimize ghosting artifacts generated by pulsatile flow. The initial phase of the study involved optimization of parameters and comparison C‐MON with no C=MON in eight patients and volunteers. The final phase of the study involved 53 patients who were imaged with contrast‐enhanced 3DTOF MRA and 2DTOF MRA with C‐MON. Thirty of these patients also had CA. In the initial phase, 2DTOF MRA with C‐MON was found to be equal (n = 3) or superior (n = 5) to 2DTOF without C‐MON. In the final phase, the agreement among all imaging modalities varied from substantial to almost perfect (Cohen's K = .6‐.83). The lowest agreement was using 2DTOF to evaluate the external iliac segments. The among suggested treatments varied from substantial to almost perfect for all imaging modalities (Cohen's K = .73–93). The diagnostic efficacies of 2DTOF with C‐MON and contrast‐enhanced 3DTOF were high overall, with the lowest value being a specificity of 63% for one reader in the evaluation of an external iliac segment using 2DTOF. In summary, 2DTOF with C‐MON helped to eliminate artifacts due to pulsatility in the iliac arterial segments. In our experience, both dynamic constrast‐enhanced 3DTOF MRA and 2DTOF MRA with C‐MON performed well in the evaluation of the iliac arteries. Both studies have high interobserver agreement and high diagnostic efficacy. Contrast‐enhanced 3DTOF MRA should be reserved for situations in which the iliac vessels are extremely tortuous or occluded or the external iliac segments are poorly seen.