bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of zonal renal ischemia with contrast‐enhanced MR imaging with a macromolecular blood pool contrast agent
Authors: Vexler Vladimir S. , Berthèzene Yves , Clément Olivier , Mühler Andreas , Rosenau Werner , Moseley Michael E. , Brasch Robert C. 
Published: March 2007

AbstractThe potential of magnetic resonance (MR) imaging enhanced with albumin‐(gadolinium diethylenetri‐aminepentaacetic acid [DTPA])35, a macromolecular blood pool marker, for detection of focal changes in renal perfusion was studied in a myoglobinuric acute renal failure (ARF) model in the rat. T1‐weighted spin‐echo postcontrast images of injured kidneys at 3 hours after glycerol injection showed three distinct zones: a strongly enhanced outer cortex, a low‐intensity inner cortex, and a strongly enhanced medulla. The distinct band of low intensity in the inner cortex indicated zonal decreased blood volume, corresponding to published microsphere data showing zonal low perfusion in the inner cortex. Contrast differences between parenchymal zones were significant for at least 30 minutes. No focal ischemic changes could be delineated on nonenhanced images. Enhanced and nonenhanced images of injured kidneys obtained at 24 hours after glycerol injection revealed no zonal differentiation. Contrast‐enhanced MR imaging data in this ARF model correlated well with pathologic data and microsphere perfusion results. Contrast‐enhanced characterization of the ischemic phase of renal injury with MR imaging may improve specificity for the diagnosis of ARF and may serve as a marker for therapeutic intervention.
Selective versus nonselective preparation pulses in two‐dimensional MP‐RAGE imaging of the liver
Authors: de Lange Eduard E. , Mugler John P. , Bertolina James A. , Brookeman James R. 
Published: March 2007

AbstractThe use of a section‐selective preparation pulse in two‐di‐mensional (2D) T1‐weighted magnetization‐prepared rapid gradient‐echo (MP‐RAGE) imaging of the liver was investigated. The images were compared with those obtained with a nonselective pulse. The performances of the sequences were evaluated in 11 patients with 12 focal liver lesions, and lesion‐liver and lesion‐vessel signal difference‐to‐noise ratios (SD/Ns) were calculated. With the section‐selective preparation pulse, small lesions were better differentiated from vessels, and multiple, consecutive images could be obtained at shorter intervals. The mean lesion‐liver SD/N was slightly but not signiticantly greater for images obtained with a selective pulse, while the lesion‐vessel SD/N was significantly greater (P < .01). It is concluded that a section‐selective preparation pulse can improve the clinical utility of the 2D MP‐RAGE sequence in the evaluation of focal liver disease.
Optimization of three‐dimensional T1‐weighted gradient‐echo imaging of the cervical spine
Authors: Ross Jeffrey S. , Tkach Jean A. , Dillinger John , Ruggieri Paul M. , Masaryk Thomas J. , Modic Michael T. 
Published: March 2007

AbstractVarious parameters of the three‐dimensional (3D) T1‐weighted magnetization‐prepared rapid acquisition gradient‐echo (MP‐RAGE) sequence were evaluated to improve spatial resolution while maintaining T1 contrast and a short examination time in imaging of the cervical spine in volunteers. The most dramatic improvements in image resolution occurred by decreasing section thickness to 1.2 mm and increasing the in‐plane matrix to 192 × 256, with a 230‐mm field of view. The increase in imaging time due to the increased matrix was offset by the elimination of the preparation pulse and wait time, without dramatic changes in contrast‐tonoise ratio or overall image quality. Optimum parameters included elimination of the preparation pulse and wait time, 12° flip angle, 192 × 256 matrix, 1.2‐mm section thickness, nonselective excitation (coronal acquisition), RF spoiling, and standard k‐space ordering, for an examination time of 5 minutes 21 seconds.
Cardiac masses: Signal intensity features on spin‐echo, gradient‐echo, gadolinium‐enhanced spin‐echo, and TurboFLASH images
Authors: Semelka Richard C. , Shoenut J. Patrick , Wilson Murray E. , Pellech Andrew E. , Patton J. Norman 
Published: March 2007

AbstractFifteen patients with cardiac or paracardiac masses underwent magnetic resonance (MR) imaging with spin‐echo (n = 15), cine gradient‐echo (n = 15), gadopentetate dimeglumine‐enhanced spin‐echo (n = 15), and TurboFLASH (fast low‐angle shot) (n = 7) sequences. All masses had either histologic confirmation (n = 11) or confirmation with other imaging modalities (n = 4). Myxomas (n = 6) were characterized by an intermediate signal intensity (SI) on spin‐echo (n = 6) and low SI on cine gradient‐echo (n = 6) images and moderately high‐SI contrast enhancement (n = 5). Percent contrast enhancement for myxomas was 57% ± 11%. Thrombus (n = 4) had intermediate (n = 3) or high (n = 1) SI on spin‐echo images and low (n = 2) or intermediate (n = 2) SI on gradient‐echo images and did not show substantial contrast enhancement. Postcontrast first‐pass TurboFLASH images were useful by clearly demonstrating the nonen‐hancing mass lesion in a high‐SI blood pool. Other cardiac and paracardiac tumors (n = 5) showed variable pre‐and postcontrast spin‐echo SI; however, no other tumor showed low SI on cine gradient‐echo images.
MR angiography with adiabatic flow excitation
Authors: Lee James N. , Parker Dennis L. 
Published: March 2007

AbstractA new method of magnetic resonance (MR) angiog‐raphy is presented that produces signal from flowing spins and suppresses that from stationary spins by means of a flow excitation pulse sequence consisting of adiabatic 90° and 180° radio‐frequency (RF) pulses interleaved with flow‐dephasing gradient lobes. Stationary spins are refocused along the z axis, while flowing spins are dephased by the gradient lobes and generate a transverse component that can be measured directly to produce the angio‐gram. Adiabatic RF pulses and unipolar gradient lobes give the pulse sequence a high degree of immunity to RF and magnetic field inhomogeneity. The pulse sequence can be successfully applied with a transmit/receive surface coil. The disadvantage of adiabatic RF pulses is that their long duration makes it difficult to suppress the signal of stationary spins with short T2.
MR imaging of temporomandibular joint abnormalities associated with cervical hyperextension/hyperflexion (Whiplash) injuries
Authors: Pressman Barry D. , Shellock Frank G. , Schames Joseph , Schames Mayer 
Published: March 2007

AbstractPatients often have temporomandibular joint (TMJ) dysfunction‐related symptoms after cervical hyperextension/hyperflexion injuries (“whiplash”) caused by rear‐end motor‐vehicle collisions. To determine abnormalities of the TMJ associated with these injuries, 33 consecutive symptomatic patients (66 joints) with no direct trauma to the jaw, mouth, head, or face due to the accident and no prior history of TMJ dysfunction underwent magnetic resonance (MR) imaging, and the images were retrospectively analyzed. Overall, 29 (88%) patients had some type of TMJ abnormality related to whiplash injury. Displacement of the disk was seen in 37 (56%) of the TMJs as follows: 21 (32%) had anterior displacement with reduction, nine (14%) had anterior displacement without reduction, six (9%) had lateral or medial displacement, and one (2%) had posterior displacement. On T2‐weighted images, 43 (65%) TMJs had abnormal joint fluid or edema, predominantly affecting the joint capsule and/or lateral pterygoid muscles. The finding that many of the patients had joint fluid and/or soft‐tissue edema indicates that T2‐weighted images are especially useful for assessment of patients with a history of whiplash injury.
Computer‐controlled flow simulator for MR flow studies
Authors: Frayne Richard , Holdsworth David W. , Gowman Linda M. , Rickey Daniel W. , Drangova Maria , Fenster Aaron , Rutt Brian K. 
Published: March 2007

AbstractA novel computer‐controlled flow simulator for use in magnetic resonance (MR) flow experiments was evaluated. The accuracy in constant‐flow mode was better than 1%. The accuracy in pulsatile‐flow mode was found to be dependent on the interconnecting tubing. The short‐term and long‐term repro‐ducibilities of pulsatile waveforms were <0.4 mL/sec (1 standard deviation). Increased response times due to the lengths of tubing required in MR flow experiments were surmounted by using a modified tubing configuration and pre‐compensated waveforms. Piston reversal was found not to cause major difficulties in MR flow experiments.
Enhancement of tumor‐liver contrast‐to‐noise ratio with gadobenate dimeglumine in MR imaging of rats
Authors: Kreft Burkhard P. , Tanimoto Akihiro , Stark David D. , Baba Yuji , Zhao Longhai , Chen John T. , Compton Carolyn C. , Paul Finn J. , Cavagna Friedrich M. 
Published: March 2007

AbstractThe efficacy for tumor detection of the hepatocyte‐specific contrast agent gadobenate dimeglumine (gadolinium‐BOPTA/Dimeg) was evaluated in four different experimental tumor models in rats. Histo‐logic findings were correlated with quantitative data derived from ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Noninfiltrating tumors showed maximal enhancement of liver parenchyma 5–10 minutes after contrast agent administration, with a plateau over the next 30 minutes. In contrast, infiltrating tumors, which caused hepatocellular injury and inflammatory changes, delayed maximal enhancement of tumor‐free parenchyma by 15–20 minutes. Nonspecific tumor enhancement depended on tumor vascularity and occurred in the early phase after contrast agent administration. Despite differences in specific enhancement of tumor‐free parenchyma and nonspecific tumor enhancement, tumor‐liver contrast‐to‐noise ratios increased 96%–248% in all tumor models 30 minutes after intravenous administration of 75 mmol/kg Gd‐BOPTA/Dimeg. Gd‐BOPTA/Dimeg enhanced tumor conspicuity independently of the histologic characteristics of the tumor.
Tetra‐p‐aminophenylporphyrin conjugated with Gd‐DTPA: Tumor‐specific contrast agent for MR imaging
Authors: Hindré Francois , Plouzennec Maryvonne Le , de Certaines Jacques D. , Foultier Marie Thérèse , Patrice Thierry , Simonneaux Gérard 
Published: March 2007

AbstractTetra‐P‐aminophenylporphyrin (TPP) was conjugated with gadolinium diethylenetriaminepen‐taacetic acid (DTPA) and used as a contrast agent in magnetic resonance (MR) imaging to achieve tumor selectivity in nude mice. A substantial decrease in T1 was measured in excised tissues (kidneys, tumor, and liver) from mice that received the porphy‐rin derivative Gd2(DTPA)4 TPP. Toxicity and photo‐toxicity were less than those obtained with hematoporphyrin derivative in both L1210 lym‐phoblastic leukemia cells and HT 29 human co‐lonic cancer cells, as determined with in vitro assays. MR images showed an enhancement of contrast between the tumor and adjacent tissue after injection of this agent. The results indicate that Gd2(DTPA)4TPP could be a useful prototype paramagnetic porphyrin MR imaging contrast agent with an affinity for tumors.
Preliminary evaluation of iron phytate (inositol hexaphosphate) as a gastrointestinal MR contrast agent
Authors: Unger Evan C. , Fritz Thomas A. , Palestrant David , Meakem Thomas J. , Granstrom Per , Gatenby Robert A. 
Published: March 2007

AbstractA simple, effective, safe, and well‐tolerated contrast agent is needed as a bowel marker for magnetic resonance (MR) imaging. The authors tested a variety of foodstuffs admixed with ferric iron as potential gastrointestinal MR contrast agents. Phytate (inosi‐tol hexaphosphate) more than doubled the relaxiv‐ity of solutions of ferric iron. Because of the improved relaxivity of iron phytate, the concentration of iron could be reduced substantially relative to free ferric iron (eg, ferric chloride or ferric ammonium citrate). Imaging studies were performed in five volunteers to determine the optimal dose of iron phytate and in five additional volunteers to test its effectiveness. A 200 mg/L concentration of ferric iron with phytate functions as an effective gastrointestinal MR contrast agent for T1‐weighted abdominal MR imaging, significantly improving bowel contrast (P <.01). Blood studies after contrast agent administration showed no appreciable increase in serum iron. Compared with standard chelate complexcs that decrease the relaxivity of a given paramagnetic ion, phytate not only decreases the absorption of the iron but increases its relaxivity.
Safety aspects and pharmacokinetics of inhaled aerosolized gadolinium
Authors: Berthezëne Yves , Mühler Andreas , Lang Philipp , Shames David M. , Clëment Olivier , Rosenau Werner , Kuwatsuru Ryohei , Brasch Robert C. 
Published: March 2007

AbstractThis study evaluated the pharmacokinetics and potential toxicity of inhaled aerosolized gadopen‐tetate dimeglumine. The pharmacokinetics were evaluated with in vitro relaxometry of the lungs, blood, urine, and liver before and for up to 36 hours after a 5‐minute inhalation of aerosolized gadopen‐tetate dimeglumine (0.25 mol/L). For assessment of potential toxicity, hemodynamic variables were monitored during and for 10 minutes after inhalation. Extravascular lung water was measured before and after exposure. Finally, the potential for tissue damage was evaluated histologically. Pulmonary clearance of aerosolized gadopentetate dimeglumine was monoexponential with a half‐time of 2.16 hours. Aerosolized gadopentetate dimeglumine was excreted through the kidneys, as shown by the decrease in urinary T1. Renal elimination was completed by 30 hours. No acute hemodynamic effect, histologic change, or induction of edema was demonstrated. This study shows that inhalation of aerosolized gadopentetate dimeglumine is well tolerated in rats and favors the further evaluation of this administration route, including clinical trials.
MR imaging of the breast
Authors: Harms Steven E. , Flamig Duane P. 
Published: March 2007

AbstractThe current strategy for breast cancer treatment involves early detection of the neoplasm before it has metasta‐sized outside the breast, and surgical treatment of the lesion that minimizes deformity. Conventional methods of diagnostic imaging of the breast, including mammogra‐phy, sonography, and galactography, do not adequately address clinical needs with regard to lesion characterization and staging. Magnetic resonance (MR) imaging has been proposed as a modality that may address these needs. The potential clinical uses of MR imaging are defined in terms of clinical needs and technologic requirements. Applications of MR imaging in detection of breast lesions can be divided into two major approaches based on the clinical questions to be answered: (a) improved specificity and (b) improved sensitivity. These approaches are defined by specific sets of clinical needs and have substantially different technologic requirements. The specificity approach is used to reduce the number of biopsies performed to confirm false‐positive mammo‐graphic findings. The MR imaging device that is used to improve specificity must visualize only the lesions that are seen mammographically. The sensitivity approach requires the visualization of lesions not identified at mammography, so that breast disease can be more effectively staged for treatment. The technologic requirements for the sensitivity approach are considerably more rigorous, because all lesions must be identified. The advantages and disadvantages of each of these approaches and the potential clinical ramifications are described.
Preoperative local staging of rectal carcinoma with MR imaging and a rectal balloon
Authors: Okizuka Hiromi , Sugimura Kazuro , Ishida Tetsuya 
Published: March 2007

AbstractMagnetic resonance (MR) imaging for the preoperative assessment of rectal carcinoma was evaluated. Thirty‐three patients underwent MR imaging with a 1.5‐T unit. On the basis of results of barium enema studies and/or digital examination, a balloon catheter was inserted to the level of the lesion before MR imaging. Both T1‐and T2‐weighted axial spin‐echo images were obtained in all patients. With the balloon catheter, the three layers of the normal bowel wall could be seen on T2‐weighted images. Muscular invasion was detected with a sensitivity of 90%, a specificity of 84%, a positive predictive value of 90%, a negative predictive value of 84%, and an overall accuracy of 88%. False‐positive results were related to chemical shift artifact and intramural lymph node metastases. Perirectal fat invasion was detected with a sensitivity of 64%, a specificity of 89%, a positive predictive value of 82%, a negative predictive value of 77%, and an overall accuracy of 79%. One of the false‐positive results was related to intramural lymph node metastases and the other to perirectal vessels. Evaluation of adjacent organ invasion was accurate in all patients. Lymph node metastasis was correctly detected in six of nine patients. Absence of lymph node metastasis was correctly predicted in 23 of 24 patients. Thus, MR imaging with a balloon catheter was useful for detection of tumor invasion into muscularis propria and adjacent organs; however, its demonstration of perirectal fat and lymph node involvement was less accurate.
Three‐dimensional MR reconstruction images of skull base tumors
Authors: Vogl Thomas J. , Assal Josef , Bergman Clifford , Grevers Gerd , Wustrow Thomas , Hamburger Christian , McMahon Christine , Lissner Josef 
Published: March 2007

AbstractForty‐eight patients with skull base tumors were evaluated prospectively with T1‐weighted spin‐echo two‐dimensional (2D) magnetic resonance (MR) sequences, a three‐dimensional (3D) MR TurboFLASH (fast low‐angle shot) sequence, and a 3D reconstruction window technique. All patients underwent surgery with histopathologic correlation, and the three MR imaging techniques were compared to assess representation of tumor margins and the topographic relationship of tumor to surrounding tissue and adjacent vasculature. The best results were obtained with standard 2D spin‐echo sequences after administration of the paramagnetic contrast agent gadopentetate dimeglumine. The 2D MR sequences gave the highest contrast‐to‐noise ratios, with decreasing values for 3D sequences and 3D reconstructions, respectively. Nevertheless, 3D MR imaging, by virtue of its good representation of adjacent structures, aided surgeons in planning surgical intervention. This study presents the technical features of 3D imaging of the skull base, the choices involved in its implementation, and its potential clinical applications.
Analysis of MR phase‐contrast measurements of pulsatile velocity waveforms
Authors: Hangiandreou Nicholas J. , Rossman Phillip J. , Riederer Stephen J. 
Published: March 2007

AbstractErrors in the measurement of the mean velocity of pulsatile velocity waveforms with ungated phasecontrast techniques were studied theoretically and experimentally. Waveforms consisting of a constant and two sinusoidal components were analyzed. Variations in magnitude and phase of the vascular magnetic resonance (MR) signal resulted in errors, the severity of which increased when either factor increased. Magnitude variations always resulted in overestimation. The general shape of the waveform greatly influenced the error, with certain waveforms producing greater inherent error than others. Experimental measurements were performed, validating the predicted sensitivity of these errors to changes in imaging parameters, including TR and flow‐encoding sensitivity. Errors generally became more severe with increased flow‐encoding sensitivity. The theoretical and experimental results suggest that accurate mean velocity measurements in many vessels of the body‐with acquisition times of less than 15 seconds‐should be attainable with ungated imaging techniques and with careful selection of relevant imaging parameters.
Accuracy and precision of MR velocity mapping in measurement of stenotic cross‐sectional area, flow rate, and pressure gradient
Authors: Søndergaard Lars , Ståhlberg Freddy , Thomsen Carsten , Stensgaard Anders , Lindvig Knud , Henriksen Ole 
Published: March 2007

AbstractReliability of magnetic resonance (MR) velocity mapping to assess severity of stenosis was assessed in vitro. Steady flow at different flow rates through five stenoses with a central orifice area ranging from 17 to 176 mm2 was measured with velocity mapping performed perpendicular to the stenotic jet. Besides determination of the stenotic cross‐sectional area and flow rate, the pressure gradient was calculated with the modified Bernoulli equation and compared with manometer measurements. Cross‐sectional areas were measured with an accuracy of ⩾76%, a precision of ⩾91%, and an error of ⩽19 mm2. Flow rates had an accuracy of ⩾72%, a precision of ⩽94%, and an error of ⩽1.4 L/min. The modification of the Bernoulli equation limited its reliability to stenoses with areas of 35‐113 mm2. Pressure gradients were calculated with an accuracy of ⩾80%, a precision of ⩾88%, and an error of ⩽15 mm Hg. The method was applied in a single patient with aortic stenosis and gave estimates that agreed with those obtained by heart catheterization.
Three‐dimensional MR imaging of the coronary arteries: Preliminary clinical experience
Authors: Paschal Cynthia B. , Mark Haacke E. , Adler Lee P. 
Published: March 2007

AbstractA three‐dimensional (3D) magnetization‐prepared (MP) rapid gradient‐echo (RAGE) and 3D RAGE technique was used to image the coronary arteries in healthy volunteers and patients with known disease. Each sequence produced images of volumes partitioned into 16 thin sections with differing blood‐fat‐myocardium contrast. The two types of images were subtracted to null fat signal, thus producing a third image set that showed flowing blood. Total imaging time was about 17 minutes. In the volunteers, the 3D MP‐RAGE and subtraction images consistently showed the morphology of the right coronary artery. The left main and left anterior descending arteries were also well seen. The circumflex artery was less consistently identified. Of the 17 diseased coronary artery segments identified at catheterization, 16 had altered signal intensity (narrowing, occlusion, reduced contrast‐to‐noise ratio, irregularity) on the subtraction images, while 13 had altered signal intensity on the 3D MP‐RAGE images. The results indicate that this 3D MP‐RAGE and 3D RAGE technique has potential utility as a screening method for coronary heart disease.
Sedation, anesthesia, and physiologic monitoring during MR imaging: Evaluation of procedures and equipment
Authors: Holshouser Barbara A. , Hinshaw David B. , Shellock Frank G. 
Published: March 2007

AbstractThe authors developed safe standard sedation and general anesthesia procedures for adults and children, including adequate physiologic monitoring, during magnetic resonance (MR) imaging. Six‐year results are reported from one institution; 75% of the 600 patients per year who require sedation or anesthesia are children who require sedation only. Testing was done to determine MR compatibility of various types of equipment essential for monitoring and supporting sedated or anesthetized patients in 1.0‐and 1.5‐T MR imagers. Use of sedation procedures that include oral chloral hydrate after sleep deprivation resulted in a failure rate of 3.8% in sedating outpatient children. Every physiologic parameter that can be monitored under normal circumstances in the critical care unit or operating room can be monitored during MR imaging. Our experience indicates that with careful consideration of the unique MR environment and with rigorous testing of monitoring equipment, MR imaging can be performed safely in sedated or anesthetized patients.