bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of regional left ventricular long‐axis motion with MR velocity mapping in healthy subjects
Authors: Karwatowski Stefan P. , Mohiaddin Raad , Yang Guang Z. , Firmin David N. , Sutton Martin St John , Underwood S. Richard , Longmore Donald B. 
Published: March 2007

AbstractThe pattern of left ventricular long‐axis motion during early diastole was assessed with magnetic resonance (MR) velocity mapping in 31 healthy volunteers. Regional long‐axis velocity varied with time and position around the ventricle. During systole, the base descended toward the apex. The greatest magnitude of long‐axis velocity occurred during early diastole. The lateral wall had the highest velocity (140 mm/sec ± 40 [mean ± standard deviation]); the anterior and inferior walls had lower velocities (96 mm/sec ± 27 and 92 mm/sec ± 34, respectively). The inferoseptal area consistently had the lowest velocities (87 mm/sec ± 40). Absolute values of peak early‐diastolic velocity declined with age (r = −.64, P <.001). Peak early‐diastolic velocity was not dependent on heart rate (r =.014, P =.94). Regional variations in left ventricular wall motion were seen. MR velocity mapping is a useful technique for assessing regional left ventricular long‐axis heart function.
Pulsatile flow artifacts in fast magnetization‐prepared sequences
Authors: Tasciyan Talin A. , Mitchell Donald G. 
Published: March 2007

AbstractFast magnetization‐prepared magnetic resonance imaging sequences allow clinical acquisitions in about 1 second, with the preparation phase providing the desired contrast. Pulsatile flow artifacts, although reduced by rapid acquisition, can degrade image quality. The authors explore the causes of aortic pulsatile flow artifacts in inversion‐recovery‐prepared acquisitions of the abdomen, taking into consideration various parameters. The flow signal within an 8‐mm‐thick section was simulated and subsequently Fourier transformed to determine the location and extent of flow artifacts. Results of simulations were validated with abdominal images of human subjects. Recording all encodings within one cardiac cycle reduced pulsatile flow artifacts in nonsegmented acquisitions with sequential phase‐encoding order, regardless of the location of magnetization preparation within the cardiac cycle. In segmented acquisitions, however, the sequential order always increased flow artifacts. To reduce the artifacts in short TI acquisitions, the magnetization should be prepared during diastole. In clinical acquisitions, flow artifacts were further reduced by modifying the phase‐encoding scheme.
Axonal transport and MR imaging: Prospects for contrast agent development
Authors: Filler Aaron G. 
Published: March 2007

AbstractAxonal transport plays a critical role in the physiology and pathology of neurons, yet there have been virtually no clinical tools for its evaluation in human subjects. A wide variety of molecules that can act as axonal transport facilitators have been discovered and, in many cases, used to deliver labels detectable with histologic methods. Recently a number of investigators have reported preliminary success in developing intraneural contrast agents based on various versions of dextran‐coated magnetite that may render magnetic resonance imaging capable of depicting axonal transport. It is not yet clear whether any clinically useful agents will eventually be developed, but there has been considerable progress in identifying design factors for such a pharmaceutical agent.
Superparamagnetic iron oxide: Detection of focal liver lesions at high‐field‐strength MR imaging
Authors: Duda Stephan H. , Laniado Michael , Kopp Andreas F. , Grönewäller Eckart , Aicher Klaus P. , Pavone Paolo , Jehle Ekkehard , Claussen Claus D. 
Published: March 2007

AbstractAMI‐25 was evaluated at 1.5 T as a superparamagnetic iron oxide contrast agent for the liver. Sixteen patients with up to five suspected focal liver lesions were examined with T1‐, proton‐density—, and T2‐weighted spin‐echo sequences before and after intravenous administration of AMI‐25 (15 μmol/kg iron). The contrast‐to‐noise ratio (C/N) increased from 1.8 to 3.5 on 600/15 (TR msec/TE msec) images and from 1.7 to 7.9 on 2,500/15 images after AMI‐25 administration (P <.01). C/N did not change significantly on 2,500/90 images. Two blinded readers counted the number of lesions visible on unenhanced and contrast‐enhanced images, with the 32 sets of images of the 16 patients presented in random order. Both readers identified more lesions on AMI‐25–enhanced images, but the difference was not statistically significant (P >.05). Two patients reported minor side effects (flushing, sensation of heat, lower back pain). On the basis of the results obtained in a limited number of patients, the authors conclude that at 1.5 T, AMI‐25 does not significantly improve the detection of focal liver lesions on conventional spin‐echo images.
Contrast‐enhanced MR imaging of diffuse and focal splenic disease with use of magnetic starch microspheres
Authors: Kreft Burkhard P. , Tanimoto Akihiro , Leffler Susan , Finn J. Paul , Øksendal Audun N. , Stark David D. 
Published: March 2007

AbstractThe diagnostic value of magnetic starch microspheres (MSM), a new superparamagnetic contrast agent, was studied in experimental models of diffuse and focal splenic disease in rats by means of ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Owing to small differences in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor‐bearing animals from control animals by signal‐to‐noise ratios (SNRs) obtained with T1‐ and T2‐weighted spin‐echo sequences. One hour after injection of 20 μmol/kg MSM, lymphomatous spleen showed significantly (P <.001) reduced enhancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 ± 1.7) could be easily differentiated from control animals (SNR: 5.5 ± 0.6) on T2‐weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enhancement of nontumorous splenic tissue, whereas relaxation times of tumors were not different before and after contrast agent injection. On T2‐weighted images (2,000/45), the tumor‐spleen contrast‐to‐noise ratio increased from (4.8 ± 1.6 to 21.8 ± 1.9 +354%), improving conspicuity of splenic tumors. The results show that MSM‐enhanced MR imaging improves the detection of diffuse and focal splenic disease.
Comparison of the safety of the standard dose and a higher dose of gadodiamide injection for MR imaging of the central nervous system
Authors: Svaland Marit G. , Lundby Bjørg , Kristoffersen Doris T. 
Published: March 2007

AbstractThis study compared the safety and tolerability of gadodiamide injection at the standard dose (0.1 mmol/kg) and at a higher dose (0.3 mmol/kg) in 289 patients participating in a parallel group multiple independent trial program. All patients had a known or suspected central nervous system lesion necessitating investigation with contrast mediumenhanced magnetic resonance imaging. Safety assessments were made before and after injection of the contrast medium, and 1 day later. No adverse events were judged to be related to gadodiamide injection, and only 3.5% of the patients in each dose group reported adverse events that had an uncertain relationship to the contrast medium; both doses were therefore well tolerated. Headache was the most frequently reported event (2%). There were no significant injection‐related changes in neurologic status, laboratory test results, or vital signs. The data obtained indicate that the higher dose of gadodiamide injection is as safe and well tolerated as the standard dose.
Gd‐DTPA‐cascade‐polymer: Potential blood pool contrast agent for MR imaging
Authors: Adam Gerhard , Neuerburg Jörg , Spüntrup Elmar , Mühler Andreas , Surg Kira Scherer Vet , Günther Rolf W. 
Published: March 2007

AbstractGadolinium‐DTPA (diethylenetriaminepentaacetic acid)‐cascade‐polymer, a potential new blood pool contrast agent for magnetic resonance (MR) imaging, was compared with a known blood pool agent, Gd‐DTPA‐polylysine, in an animal model. The relative signal intensities of liver, renal cortex, pancreas, and trunk muscle were assessed in 12 pigs between 4 seconds and 120 minutes after injection of a 20 μmol/kg dose of each contrast agent, by using a FLASH (fast low‐angle shot) sequence. Except for muscle, all tissues showed visible enhancement after injection of either contrast agent. After injection of Gd‐DTPA‐polymer, enhancement patterns in the liver, renal cortex, and pancreas were similar to those seen after injection of Gd‐DTPA‐polylysine. No statistically significant differences in enhancement between the two contrast agents were found at any time point. The authors conclude that the contrast kinetics of Gd‐DTPA‐cascade‐polymer are similar to those of Gd‐DTPA‐polylysine and that this agent may also be used as a blood pool contrast agent for MR imaging.
Gd‐DTPA‐polylysine—enhanced pulmonary time‐of‐flight MR angiography
Authors: Böck Johannes C. , Pison Ulrich , Kaufmann Frank , Felix Roland 
Published: March 2007

AbstractThe enhancing effect of gadolinium diethylenetriam‐inepentaacetic acid (DTPA) polylysine (a macromolecular paramagnetic contrast agent) in time‐of‐flight magnetic resonance (MR) angiography of isolated perfused sheep lungs was studied. Unilateral lung damage was induced with hydrochloric acid in eight sheep. The heart and lungs were removed from the thoracic cavity, and after cannulation of the trachea and both ventricles, pulsatile perfusion and ventilation were initiated. The heart‐lung preparations were placed in the head coil of a 1.5‐T imager. Time‐of‐flight pulmonary MR angiography was performed during respiratory arrest, before and after administration of 0.02 mmol/kg Gd‐DTPA‐polylysine. On the postcontrast angiograms, the signal intensity increased by 120% in pulmonary arteries (P <.01). The contrast‐to‐noise ratio between pulmonary arteries and parenchyma increased significantly (P <.01). The number of visualized generations of pulmonary artery branches increased from four to six in normal lungs and from three to five in edematous lungs. Low‐dose Gd‐DTPA‐polylysine significantly improves the conspicuity of the pulmonary vascular tree in time‐of‐flight pulmonary MR angiography.
Bone marrow characterization in the lumbar spine with inner volume spectroscopic CPMG imaging studies
Authors: Mulkern Robert V. , Meng Jiqun , Oshio Koichi , Guttmann Charles R. G. , Jaramillo Diego 
Published: March 2007

AbstractThe authors describe new magnetic resonance (MR) spectroscopic and postprocessing methods for characterizing major proton peaks and their spectral T2 values in many small voxels throughout extensive regions of bone marrow within the adult lumbar spine. The techniques are based on spectroscopic interrogation of 128 voxels along columns oriented through the spine at eight TE values. Mean fat content measurements, based on quantification of the proton peaks of water and saturated fat (‐CH2‐)n, corrected for T2 decay, ranged from 40% to 60%. The mean T2 value of the lipid peak, 113 msec ±21, was significantly longer (P <.001) than that of water (71 msec ± 14). The techniques combine features of MR spectroscopy and imaging most suited for spatially efficient coverage of bone marrow at spectral resolutions sufficient for intravoxel fat or water content measurements. The methods introduced provide a practical, quantitative means for characterizing vertebral marrow in diseases affecting marrow cellularity.
In vivo fluorine‐19 MR imaging: Relaxation enhancement with Gd‐DTPA
Authors: Lee Haakil , Price Ronald R. , Holburn George E. , Partain C. Leon , Adams Max D. , Cacheris William P. 
Published: March 2007

AbstractThe lack of a naturally occurring background signal from fluorine in magnetic resonance (MR) imaging makes fluorinated compounds potentially attractive candidates for tissue‐specific MR contrast agents. Problems associated with the in vivo use of fluorinated compounds are toxicity, which limits the amount of agent that can be used; multiple resonance lines; and an excessively long T1, which leads to long sequence TRs and consequently long imaging times. Many fluorinated agents also possess complex MR spectra that result in chemical shift artifacts if not corrected. The authors demonstrate the use of an extracellular fluorinated agent with a single MR peak for selective imaging of a brain abscess in an animal model and show that the image signal per unit of acquisition time can be enhanced through the use of a T1 relaxation agent, gadolinium diethylenetriamine‐pentaacetic acid (DTPA). Trifluoromethylsulfonate was administered at a fluorine‐19 dose of 4 mmol/kg, and fluorine images of the induced abscess were acquired before and after the injection of a standard dose of Gd‐DTPA (0.1 mmol/kg); non—section‐selected projection images were used. Typical imaging times were less than 5 minutes. The signal enhancement factor achieved was approximately four (4.0 ± 0.8) with use of a 500/12 (TR msec/TE msec) spinecho sequence.
Evaluation of the influence of the aqueous phase bioconstituent environment on the F‐19 T1 of perfluorocarbon blood substitute emulsions
Authors: Thomas Stephen R. , Pratt Ronald G. , Millard Ronald W. , Samaratunga R. C. , Shiferaw Yoseph , Clark Leland C. , Hoffmann Richard E. 
Published: March 2007

AbstractOxygen‐sensitive F‐19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F‐19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC‐43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd‐DTPA. For a constant Po2, the F‐19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC‐43 and perflubron, F‐19 T1 was independent of the Gd‐DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO‐10 (smallest emulsion particle size) showed a slight decrease in F‐19 T1 with increasing Gd‐DTPA concentration at 0.66 T.
Fast spin‐echo MR imaging of the abdomen: Contrast optimization and artifact reduction
Authors: Low Russell N. , Hinks R. Scott , Alzate Gregg D. , Shimakawa Ann 
Published: March 2007

AbstractThe effects of various fast spin‐echo (FSE) magnetic resonance (MR) imaging parameters and artifact reduction techniques on FSE image contrast and quality were studied. The authors performed 139 abdominal MR examinations, comparing standard FSE images (echo train length [ETL] = 8, echo space [E‐space] = 17 msec, bandwidth = ±16‐kHz) with FSE images with an ETL of 16 (n = 22) or FSE images with a ±32‐kHz bandwidth and an E‐space of 11‐14 msec (n = 22). FSE artifact reduction techniques were evaluated with spectral fat saturation (n = 40) or with a new flow compensation FSE sequence (n = 55). Images of liver lesions were reviewed qualitatively and with contrast‐to‐noise ratio (C/N) measurements. Decreasing the time of echo train sampling produced superior image quality, with increased anatomic sharpness, less image artifact, and improved liver‐lesion C/N. Images obtained with an ETL of 16 showed more image blurring and a 23% decrease in relative contrast and 28% decrease in relative C/N for liver tumors. Increasing the bandwidth reduced E‐space, producing a 12% decrease in background noise. Artifact reduction with fat saturation or flow compensation produced images with less ghosting artifact and superior overall image quality, with 39% and 20% increases in liver‐tumor C/N, respectively. FSE image quality and contrast in the depiction of hepatic disease can be optimized with careful selection of imaging parameters and the use of artifact reduction techniques.
Time after excision and temperature alter ex vivo tissue relaxation time measurements
Authors: Baba Yuji , Lerch Markus M. , Stark David D. , Tanimoto Akihiro , Kreft Burkhard P. , Zhao Longhai , Saluja Ashok K. , Takahashi Mutsumasa 
Published: March 2007

AbstractPreviously unreported effects of tissue storage were recently observed in the authors' experimental magnetic resonance (MR) studies. To evaluate the effect of elapsed time after excision and storage temperature on tissue relaxation time measurements, tissue samples from the liver, pancreas, kidney, testis, spleen, and brain were obtained in rats. T1 and T2 were first measured within 5 minutes of excision, and between subsequent measurements, tubes were kept in a water bath at 40°C, at room temperature (28°C), or in an ice bath (4°C). Cellular and organellar integrity was assessed with electron microscopy and correlated with the MR findings. At 40°C (20‐MHz spectrometer), the T1 of liver decreased from 280 msec ± 8 to 212 msec ± 10 during the first 60 minutes; the T1 of pancreas decreased from 276 msec ± 3 to 208 msec ± 2. Other tissues showed less than a 5% decrease in T1. T2 changes were smaller than T1 changes in all tissues. Electron microscopy of pancreatic acinar cells showed postmortem changes in mitochondria evolving over the first 60 minutes after death. Manganese loading experiments implicated mitochondrial manganese stores in the observed enhanced postmortem decrease in T1. This study calls into question reported relaxation time data for liver and pancreas. MR studies of excised tissues must account for time and temperature to prevent systematic experimental errors.
Contrast‐enhanced MR imaging of liver and spleen: First experience in humans with a new superparamagnetic iron oxide
Authors: Hamm Bernd , Staks Thomas , Taupitz Matthias , Maibauer Renate , Speidel Andrea , Huppertz Alexander , Frenzel Thomas , Lawaczeck Rüdiger , Wolf Karl J. , Lange Lothar 
Published: March 2007

AbstractThe aim of this prospective study was to obtain the first human safety and magnetic resonance (MR) imaging results with a new formulation of superparamagnetic iron oxide (SPIO) (SHU 555 A). The SPIO was tested at four iron doses, from 5 to 40 μmol/kg. Laboratory tests and clinical measurements were done in 32 healthy volunteers for up to 3 weeks after administration. MR imaging at 1.5 T was performed before and 8 hours to 14 days after fast intravenous injection (500 μmol Fe/min) of the SPIO (six subjects per dose). Results of this phase I study demonstrate that SHU 555 A at a concentration of 0.5 mol Fe/L was well tolerated. A dose‐dependent minor increase in activated partial thromboplastin time, which remained within the normal range, was seen. All doses of SPIO caused a signal loss in both liver and spleen (P <.05) with a spin‐echo sequence (TR = 2,300 msec, TE = 45 msec). The signal losses in the liver 8 hours after contrast agent injection were 58%, 79%, 82%, and 87% for the 5, 10, 20, and 40 μmol Fe/kg doses, respectively. The corresponding signal losses in the spleen were 23%, 45%, 65%, and 78%, respectively. The doses that reduced signal intensity by half were 3.1 μmol Fe/kg for the liver and 12.8 μmol Fe/kg for the spleen. The results suggest that the new SPIO formulation is a safe and efficient MR contrast agent.
MR Imaging detection of cerebral metastases with a single injection of high‐dose gadoteridol
Authors: Runge Val M. , Wells John W. , Nelson Kevin L. , Linville Pam M. 
Published: March 2007

AbstractThe utility of a single high‐dose (0.3 mmol/kg) injection of gadoteridol, a gadolinium chelate, in the detection of brain metastases on magnetic resonance images was studied. Patients (n = 29) with a high suspicion for brain metastases at clinical examination and by history were imaged on two occasions–separated by more than 24 hours and less than 7 days–with a 0.1 mmol/kg contrast agent dose used for the first study and a 0.3 mmol/kg dose for the second. In patients (n = 15) with confirmed brain metastases by clinical, radiologic, and/or histologic criteria, 40 lesions were detected at the 0.3 mmol/kg dose by a single reader blinded to contrast agent dose, compared with 33 lesions at 0.1 mmol/kg, a 21% increase. Three of 15 patients (20%) demonstrated an increase in the number of lesions detected at the higher dose. Region‐of‐interest analysis of signal intensity measurements showed that lesion contrast (relative to normal brain) improved from 54% at 0.1 mmol/kg to 92% at 0.3 mmol/kg. A 0.3 mmol/kg dose of gadoteridol, administered in a single injection, permits identification of brain metastases not detected at 0.1 mmol/kg. Such information can influence the choice of therapy.
Effects of intravoxel velocity distributions on the accuracy of the phase‐mapping method in phase‐contrast MR angiography
Authors: Hamilton Craig A. , Moran Paul R. , Peter Santago, II  , Rajala Sarah A. 
Published: March 2007

AbstractThe phase‐mapping method of phase‐contrast magnetic resonance angiography is shown to be based on an implicit assumption that the intravoxel velocity distribution is symmetric about its mean velocity. The effect of asymmetric distributions on the accuracy of quantitative average velocity measurements is determined analytically and verified experimentally. An explicit formulation is developed for the estimated average velocity in a voxel as a function of the true average velocity and the asymmetry of the distribution about the true average velocity. Worst‐case distributions are determined for unidirectional and bidirectional flow, and the special case of laminar flow is also investigated. Computer simulations and phantom imaging experiments demonstrate the accuracy of the analysis. For voxels with unidirectional flow, the phase‐mapping method produces accurate estimates of average velocity, while results for bidirectional flow indicate possible large errors unless the aliasing velocity is increased. which decreases the signal‐to‐noise ratio in the resultant velocity map image.
MR portography: Preliminary comparison with CT portography and conventional MR imaging
Authors: Dravid Vikram S. , Shapiro Marcelle J. , Mitchell Donald G. , Outwater Eric K. , Piccoli Catherine W. , Feld Rick I. , Wechsler Richard J. , Rosato Francis E. 
Published: March 2007

AbstractMagnetic resonance (MR) imaging with arterial portography (MRAP) was compared with computed tomography with arterial portography (CTAP) and conventional MR imaging for preoperative evaluation of hepatic masses in eight patients (nine studies). Twenty contiguous, 10‐mm‐thick‐section CTAP images were obtained. MR imaging included T1‐ and T2‐weighted spin‐echo and fast multiplanar SPGR (spoiled gradient‐recalled acquisition in the steady state) techniques. For MRAP, 0.1 mmol/kg gadopentetate dimeglumine was injected into the superior mesenteric artery. Portographic‐phase, 8‐mm‐thick‐section, axial SPGR images were first obtained, followed by “systemic phase” SPGR images. Lesions were seen best on the portographic‐phase MRAP images and were less conspicuous on the systemic‐phase MRAP, CTAP and conventional MR images. Of 19 visualized lesions, 18 were seen with MRAP; however; five subcentimeter lesions seen with MRAP were not seen with conventional MR imaging or CTAP. Systemic recirculation of iodinated contrast material from the bolus and from previous angiography is a potential limitation of CTAP. For both CTAP and MRAP, optimal results are expected if all images are obtained during a single breath hold, within seconds of the onset of contrast agent administration.