bluuebunny/crossref_metadata_2025 huggingface dataset:
MR angiography of congenital heart disease: Value of segmented two‐dimensional inflow technique and maximum‐intensity‐projection display
Authors: Seelos Klaus C. , Smekal Alexander Von , Steinborn Marc , Gieseke Jürgen , Redel Dierk A. , Reiser Maximilian
Published: March 2007

Magnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two‐dimensional (2D) inflow technique based on a magnetization‐prepared gradient‐echo pulse sequence with segmented k‐space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40–50 overlapping sections. Both 2D angiograms and maximum‐intensity‐projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal‐to‐noise ratios were obtained with a flip angle of 65° and short prepulse delay times. Two‐dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in‐plane and hemodynamically induced signal intensity changes.
Carotid and vertebral artery blood flow in left‐ and right‐handed healthy subjects measured with MR velocity mapping
Authors: Bogren Hugo G. , Buonocore Michael H. , Gu Wei‐Zhong
Published: March 2007

The goal of the study was to establish normal carotid artery flow rates in left‐handed and right‐handed individuals as a standard against which patients with carotid artery disease could be compared. Antegrade and retrograde flow were measured in the ascending aorta, in the right and left common, internal, and external carotid arteries, and in the vertebral arteries of 12 healthy subjects. Five subjects were right‐handed, five left‐handed, and two ambidextrous. Measured flow rates were as follows: common carotid arteries, 360–557 mL/min (mean [± standard deviation], 465 mL/min ± 52); internal carotid arteries, 132–367 mL/min (mean, 265 mL/min ± 60); external carotid arteries, 113–309 mL/min (mean, 186 mL/min ± 51); vertebral arteries from 133–308 mL/min (mean, 244 mL/min ± 43); and cerebral circulation, 546–931 mL/min (mean, 774 mL/min ± 134). All right‐handed subjects had higher flow rates in the left internal carotid artery than in the right, and all left‐handed subjects had higher flow rates in the right internal carotid artery (P =.007). There were no significant differences in left and right common carotid artery flow rates between left‐ and right‐handed subjects. The standard deviation of a single measurement was 5%. The flow rates were similar to those obtained previously with other techniques and could be used as a normal standard.
Tissue temperature monitoring for thermal interventional therapy: Comparison of T1‐weighted MR sequences
Authors: Matsumoto Reiko , Mulkern Robert V. , Hushek Stephen G. , Jolesz Ferenc A.
Published: March 2007

For thermal interventional therapy, near real‐time monitoring of temperature changes in the treated area is desirable. In this study, various fast T1‐weighted magnetic resonance (MR) imaging protocols were compared to determine the sensitivity and resolution of signal intensity for temperatures within the range of 36°C–66°C in gel phantoms and in vitro porcine liver specimens. The results showed that a T1‐weighted fast spin‐echo sequence with a TR of 100 msec had better temperature sensitivity and resolution than other sequences with comparable temporal resolutions. The longer imaging times required for fast spin‐echo sequences with a TR of 300 msec did not improve temperature sensitivity. The methods introduced to evaluate temperature sensitivity and resolution should prove useful in selecting appropriate MR protocols for monitoring thermal treatment modalities such as interstitial laser therapy, focused ultrasound therapy, or radio‐frequency heating.
Hematopoietic reconstitution after bone marrow transplantation: Assessment with MR imaging and H‐1 localized spectroscopy
Authors: Schick Fritz , Einsele Hermann , Kost Renate , Duda Stephan , Jung Wulf‐Ingo , Lutz Otto , Claussen Claus D.
Published: March 2007

Magnetic resonance (MR) studies were performed in 14 patients as early as possible (21–110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1‐weighted spin‐echo imaging, water‐ and fatselective imaging with a frequency‐selective excitation technique, and point‐resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water‐ and fat‐selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.
MR Angiographic guidance for transjugular intrahepatic portosystemic shunt procedures
Authors: Müller Markus F. , Siewert Bettina , Stokes Kenneth R. , Lewis W. David , Jenkins Roger L. , Stehling Michael K. , Finn J. Paul
Published: March 2007

The authors used magnetic resonance (MR) angiography to guide catheter placement in transjugular intrahepatic portosystemic shunt (TIPS) procedures in nine of 18 patients and compared the results with those of the nine patients for whom prior planning based on MR angiography was not done. Two‐dimensional time‐of‐flight MR venography was performed during breath hold, and projection venograms were formatted in sagittal, coronal, and axial planes. MR angiography defined venous anatomy sufficiently to shorten the procedure and help minimize invasiveness. With MR angiographic guidance, intrahepatic needle punctures were significantly fewer (without MR guidance: mean, 12.1; with MR guidance: mean, 3.6; P < 0.001) and associated complications were absent (without MR guidance: failed placement, n = 1; bleeding requiring blood transfusions, n = 1; death due to intraperitoneal hemorrhage with hemobilia, n = 1; and death due to hepatic capsular perforation, n = 1). The average time for the procedure was 2.9 hours without MR angiographic guidance and 1.8 hours with MR angiographic guidance (P < 0.001). The authors conclude that MR angiography is a useful technique for defining portal and hepatic venous anatomy before the TIPS procedure and that planning based on MR angiography may decrease the difficulty and length of the procedure.
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

The 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

Fast 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

Axonal 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

AMI‐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

The 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

This 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

Gadolinium‐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

The 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

The 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

The 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

Oxygen‐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

The 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

Previously 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

The 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

The 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

The 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

Magnetic 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.
Diffusion imaging with the MP‐rage sequence
Authors: Lee Haakil , Price Ronald R.
Published: March 2007

Diffusion‐weighted magnetic resonance (MR) images obtained with conventional spin‐echo techniques are known to be sensitive to subject motion because of long image acquisition times. To reduce the acquisition time, use of a magnetization‐prepared rapid gradient‐echo (MP‐RAGE) sequence modified for diffusion sensitivity was studied. In this sequence, a preparation phase with a 90°–180°–90° pulse train is used to sensitize the magnetization to diffusion. Centric‐ordered phase encoding, short TRs (5.2–6.5 msec), and small flip angles (5°–8°) are necessary to minimize saturation effects from tissues with short relaxation times. Phantom studies with various concentrations of copper sulfate (T1 ranging from 2,459 to 90 msec) were performed to validate that the diffusion‐weighted signal obtained with the MP‐RAGE sequence was independent of relaxation time. Diffusion‐weighted images of water, isopropyl alcohol, and acetone were acquired to confirm the accuracy of measured diffusion coefficients. Brain images of healthy normal volunteers were obtained to demonstrate motion insensitivity and general image quality of the technique. The results indicate that accurate diffusion‐weighted images can be obtained with a diffusion‐weighted MP‐RAGE sequence, with imaging times of about 1 second.
Registration of images from sequential MR studies of the brain
Authors: Nelson Sarah J. , Nalbandian Allen B. , Proctor Evelyn , Vigneron Daniel B.
Published: March 2007

For sequential studies of patients with brain tumors, the authors have designed an automated registration procedure for intra‐ and interexamination alignment of magnetic resonance images. This was evaluated with artificially misregistered data and data from repeat studies of six healthy volunteers and six brain tumor patients. In a subset of cases, a manual procedure based on matching of neuroanatomic landmarks was also applied for comparison. The results showed that the technique is robust and reproducible, giving an accuracy in the range of 1–2 mm, which corresponded to the spatial resolution of the images. Subject motion between imaging sequences within the same study was negligible, although adjustments (one to two section thicknesses) were required in the z direction to correlate multisection and volume images and to allow accurate image segmentation. For alignment between sequential volunteer and patient examinations, translations of up to 22 mm and rotations in the x, y, and z axes of up to 9° were required. This alignment procedure may be valuable in numerous aspects of treatment planning and patient follow‐up.
MR angiography of the foot and ankle
Authors: Unger Evan C. , Schilling Jolyon D. , Awad A. Nicholas , McIntyre Kenneth E. , Yoshino Mark T. , Pond Gerald D. , Darkazanli Ammar , Hunter Glenn C. , Bernhard Victor M.
Published: March 2007

To better understand the use of magnetic resonance angiography (MRA) in evaluating peripheral vascular disease, the authors studied arteries in the foot and ankle. Twenty patients with arterial occlusive disease of the lower extremity were studied with two‐dimensional time‐of‐flight MRA, and the results were compared with those of 10 conventional x‐ray arteriograms, four digital subtraction arteriograms, and three intraoperative arteriograms. The studies were reviewed and rated by three radiologists blinded to the patients' clinical history. Also, the first 16 patients were examined with MRA before and after intravenous injection of gadopentetate dimeglumine. The mean confidence levels for the reviewers' interpretations of the MRA studies were significantly higher than those for the conventional arteriograms for the medial plantar, lateral plantar, and plantar arch arteries of the feet (P ≦ 0.005).

Postcontrast MRA images were inferior to precontrast images because of overlapping of veins and arteries. Time‐of‐flight MRA without gadolinium can serve as a useful complementary study for evaluating patients with peripheral vascular disease in the foot and ankle.
Safety of gadoteridol injection: U.S. clinical trial experience
Authors: Olukotun Adeoye Y. , Parker John R. , Meeks Marion J. , Lucas Maria A. , Fowler Dennis R. , Lucas Thomas R.
Published: March 2007

As part of the clinical evaluation of gadoteridol injection, intravenous doses ranging from 0.05 to 0.3 mmol/kg were administered to 1,709 patients and volunteers. Safety monitoring included pre‐ and postdose physical examinations, vital signs, and clinical laboratory values. Adverse event recording included occurrence, duration, severity, relationship to injection, and clinical importance. No clinically important changes in physical examination results, electrocardiograms, or vital signs were attributed to gadoteridol injection except for one case of hypotension. Four clinically important changes in laboratory values possibly or definitely related to the contrast agent were noted in two patients (0.1%). Adverse events were recorded in 118 subjects (6.9%), including nausea in 24 subjects (1.4%) and taste perversion in 22 subjects (1.3%). All other adverse events occurred with a frequency of less than 1%. Adverse events related to contrast agent administration occurred in 79 subjects (4.6%). Gadoteridol injection demonstrated excellent clinical safety and patient tolerance at various doses and injection rates.
High‐resolution MR imaging of human arteries
Authors: Martin Alastair J. , Gotlieb Avrum I. , Henkelman R. Mark
Published: March 2007

The authors studied the magnetic resonance (MR) imaging appearance of excised human arteries and correlated these findings with those from histologic sections obtained in corresponding planes. Imaging was performed with a 1.5‐T clinical imager modified with an additional gradient insert capable of a 30 mT/m gradient. High‐resolution images of arteries obtained at autopsy indicated that the medial and adventitial layers could be distinguished and that T2‐weighted sequences offered superior contrast. Intimal thickening could be detected at a relatively early stage as a long T2 rim on the luminal surface of the artery. Atherosclerotic plaque was found to have MR properties similar to those of intimal thickening. although necrotic regions within plaque had low signal intensity. Fat suppression sequences did not significantly alter the appearance of atherosclerotic plaque. Calcified plaque produced effects ranging from slight signal loss to signal void. MR imaging findings correlated reliably with the tissue types indicated by histologic analysis.
Single‐shot versus interleaved echo‐planar MR ‐imaging: Application to visualization of cardiac valve leaflets
Authors: Davis Clarence P. , McKinnon Graerne C. , Debatin Jorg F. , Duewell Stefan , Von Schulthess Gustav K.
Published: March 2007

Visualization of the cardiac valves with standard magnetic resonance (MR) imaging is not adequate because of long acquisition times. Echo‐planar imaging (PI) can, however, be performed with a temporal resolution (30–50 msec) comparable to that of echocardiography. The authors evaluated the feasibility of real‐time imaging of cardiac valve motion with ultrafast MR techniques. Eight healthy volunteers and three patients with mitral stenosis and re‐ gurgitation were studied with a 1.5‐T whole‐body im‐ ager. Two different EPI sequences were assessed: a standard single‐shot gradient‐echo EPI (GEPI) SCquence and a fast imaging technique based on multiple‐shot EPI with interleaved k‐space acquisition (IGEPI). Fat‐suppressed images with an in‐plane resolution of 3.7 × 3.7 mm were obtained equally spaced through the cardiac cycle. Half‐k‐space acquisition was used. Morphologic evaluation was superior with IGEPI, owing to the better intracavitary signal homogeneity (P ≤ 0.01). and the mitral valve leaflets were easier to identify on systolic images. IGEPI provided adequate valve visibility in all three patients.
Exercise‐related changes in aortic flow measured with spiral echo‐planar MR velocity mapping
Authors: Mohiaddin Raad H. , Gatehouse Peter D. , Firmin David N.
Published: March 2007

Spiral echo‐planar magnetic resonance (MR) velocity mapping was used to measure exercise‐related changes in flow in the descending thoracic aorta in 10 healthy volunteers. Flow was measured at rest and Immediately after dynamic exercise, with a 0.5‐T imager with a surface receiving coil and electrocardiographic triggering. Supine exercise was performed with a home‐built pedaling apparatus. Spiral velocity mapping was performed in a transverse plane through the descending thoracic aorta with the subject at rest. The subject was then asked to perform maximum exercise, stop, and hold his breath during a four‐heartbeat acquisition time. Eight cine frames with a temporal resolution of 50 msec were acquired through systole. Each image was acquired in 40 msec during spiral acquisition of k‐space data, starting at the center, 6 msec after the excitation pulse. Reproduclbility of the technique was established by repeating the flow measurement in four consecutive heartbeats. At rest, the heart rate (mean ± standard deviation), mean aortic flow, peak aortic flow, and time to peak flow were 68 beats per minute ± 6, 41 mllliliters per beat ±8, 107 mL/sec ± 20, and 175 msec ± 25, respectively. After exercise, the heart rate and mean and peak aortic flow were significantly increased (P < 0.001), measuring 101 beats per minute ±12, 57 milliliters per beat ± 11, and 158 mL/sec ±29, respectively, while the time to peak flow (115 msec ±32) was significantly reduced (P < 0.001). The four sets of values obtained for the first four consecutive heartbeats measured at rest were similar, as were those obtained for the first four heartbeats after exercise.
Regional myocardial blood volume and flow: First‐pass MR imaging with polylysine‐Gd‐DTPA
Authors: Wilke Norbert , Kroll Keith , Merkle Hellmut , Wang Ying , Ishibashi Yukata , Xu Ya , Zhang Jiani , Jerosch‐Herold Michael , Muhler Andreas , Stillman Arthur E. , Bassingthwaighte James B. , Bache Robert , Ugurbil Kamil
Published: March 2007

The authors investigated the utility of an intra‐vascular magnetic resonance (MR) contrast agent, poly‐L‐lysine‐gadolinium diethylenetriaminepentaacetic acid (DTPA), for differentiating acutely ischemic from normally perfused myocardium with first‐pass MR imaging. Hypoperfused regions, identified with microspheres, on the first‐pass images displayed significantly decreased signal intensities compared with normally perfused myocardium (P < 0.0007). Estimates of regional myocardial blood content, obtained by measuring the ratio of areas under the signal intensity‐versus‐time curves in tissue regions and the left ventricular chamber, averaged 0.12 mL/g ± 0.04 (n = 35), compared with a value of 0.11 mL/g ±0.05 measured with radiolabeled albumin in the same tissue regions. To obtain MR estimates of regional myocardial blood flow, in situ calibration curves were used to transform first‐pass intensity‐time curves into content‐time curves for analysis with a multiple‐pathway, axially distributed model. Flow estimates, obtained by automated parameter optimization, averaged 1.2 mL/min/g ±0.5 (n =29), compared with 1.3 mL/min/g ±0.3 obtained with tracer microspheres in the same tissue specimens at the same time. The results represent a combination of T1‐weighted first‐pass imaging, intravascular relaxation agents, and a spatially distributed perfusion model to obtain absolute regional myocardial blood flow and volume.
MP‐RAGE subtraction venography: A new technique
Authors: Stevenson Jeffrey , Knopp Edmond A. , Litt Andrew W.
Published: March 2007

Preliminary evaluation of a new magnetic resonance (MR) venography technique was performed with data sets from five patients undergoing BAR imaging of the brain before and after intravenous administration of gadopentetate dimeglumine. Before contrast agent injection, the patients were imaged with MP‐RAGE (magnetization‐prepared rapid gradient‐echo) and axial turbo T2‐weighted sequences. After contrast agent injection, the MP‐RAGE sequence was repeated. Images were post‐processed with an algorithm that calculates, on a pizel‐by‐pixel basis, the absolute value of signal intensity of each postcontrast MP‐RAGE partition minus that of each precontract MP‐RAGE partition. These subtracted partitions were then subjected to a standard maximum‐intensity‐projection algorithm to obtain the venogram. In all cases, the new method afforded a high‐resolution venogram with clear depiction of venous sinus anatomy. Cortical venous anatomy was also clearly depicted.
Endometriosis: Appearance and detection with conventional and contrast‐enhanced fat‐suppressed spin‐echo techniques
Authors: Ascher Susan M. , Agrawal Rajneesh , Bis Kostaki G. , Brown Elizabeth D. , Maximovich Alexander , Markham Sanford M. , Patt Richard H. , Semelka Richard C.
Published: March 2007

Suspected pelvic endometrlosis was prospectively evaluated in 31 women with T1‐ and T2‐weighted conventional spin‐echo (CSE) magnetic resonance imaging alone and in combination with Tl‐weighted fat‐suppressed (TIPS) and gadolinium‐enhanced TIPS (Gd‐TlFS) spin‐echo techniques. Images were grouped for interpretation and comparison as follows: (a) CSE alone, (b) CSE/T1FS. and (c) CSE/T1FS/ Gd‐TlFS. All patients underwent surgery within 3 months of imaging, and 21 patients were found to have endometrlosis: 59 endometriomas (26 large and 33 small) and 51 sites of implants were seen. With CSE images, 23 large and six small endometriomas were detected. With CSE/T1FS images, 25 large and 14 small endometriomas were identified. With CSE/ TIFS/Gd‐TlFS Images, 24 large and 14 small endometriomas were detected and ill‐defined areas of enhancement were noted in 22 sites throughout the pelvis. These corresponded to endometriotic implants seen at surgery in 14 sites. The sensitivity, specificity, and accuracy, respectively, for the detection of endometriosis were 76%, 60%, and 71% for CSE, 86%, 50%, and 74% for CSE/T1FS, and 81%, 50%, and 71% for CSE/TlFS/Gd‐TlFS images. No significant differences (P > 0.1) between image combinations for correctly identifying patients with and without endometriosis were seen. The difference in sensitivity between CSE and CSE/T1FS and between CSE and CSE/TlFS/Gd‐TlFS images for detecting small endometriomas was significant (P=.03).
Multislab three‐dimensional T2‐weighted fast spin‐echo imaging of the hippocampus: Sequence optimization
Authors: Murakami James W. , Weinberger Ed , Tsuruda Jay S. , Mitchell James D. , Yuan Chun
Published: March 2007

Three‐dimensional (3D) fast spin‐echo (FSE) imaging can produce contiguous thin sections for high‐quality multiplanar reconstructions. Such reformatted images may be useful in the evaluation of three‐dimensionally complex, curvilinear anatomic structures such as the hippocampus. The authors describe a 3D FSE protocol for T2‐weighted Imaging of the hippocampus. The protocol uses an overlapplng‐multiple‐slab imaging strategy to decrease Imaging times and a modified refocusing radio‐frequency pulse train to improve the reformatted images. The authors describe their parameter optimization, discuss the benefits and limitations of the new sequence, and present representative images of healthy volunteers.
Vessel enhancement filtering in three‐dimensional MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L.
Published: March 2007

For a variety of reasons, small vessels have low signal intensity in magnetic resonance angiography. When the vessel signal Intensity is lower than the signal intensity of background tissues, these vessels tend not to be visible on maximum‐intensity‐projection images. The authors developed a nonlinear second‐difference spatial filtering technique that enhances the details of small vessels while suppressing both noise and uniform background tissue. Two similar nonlinear second‐difference filters are presented and compared with the linear Laplacian second‐difference filter. To evaluate the performance of these filters, they were applied to intracranial three‐dimensional time‐of‐night MR angiographic data and the results compared with the vessel enhancement obtained with a simple second‐difference Laplacian filter and with magnetization transfer contrast (MTC) techniques. The comparisons demonstrated that nonlinear filtering and MTC techniques result in similar improvement in small‐vessel visibility and apparent continuity. A quantitative comparison demonstrated that the improvement in the contrast‐to‐noise ratio is much greater with the nonlinear filters than the Laplacian filter.
Intracavitary birdcage resonator: Applications to the human prostate
Authors: Merchant Thomas E. , Schwartz Lawrence H. , Ballon Douglas , Koutcher Jason A. , Scher Howard I. , Minsky Bruce D.
Published: March 2007

Twenty‐five patients with prostatic cancer were pro‐ spectively examined with a prototype endorectal surface coil featuring a birdcage resonator circuit design. The purpose was to determine the safety of an intracavitary probe for magnetic resonance (MR) imaging of the pelvis that incorporates the “inside‐out” characteristics of a volume coil design and allows high‐resolution MR imaging of the prostate and potentially serves as an alternative to single‐loop intracavitary surface coils. Clinically useful images supplementing images obtained with the body or external surface coils were obtained with the prototype probe. It was tolerated by all patients enrolled in the study, and none experienced side effects. The cylindrically symmetric sensitivity profile of the probe allowed identification of prostate tumors and pelvic lymph node and bone me‐tastases. Volume‐type coils may improve endopelvic MR imaging when used alone or in combination with external coil systems.