bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical comparison of three‐dimensional MP‐RAGE and FLASH techniques for MR imaging of the head
Authors: Runge Val M. , Kirsch John E. , Thomas Gregory S. , Mugler John P.
Published: March 2007

Three‐dimensional (3D) MP‐RAGE (magnetization‐prepared rapid gradient‐echo) imaging was evaluated as a high‐resolution 3D T1‐weighted brain imaging technique for patients with suspected neurologic disease. Fourteen patients were studied. In five, 3D MP‐RAGE images were compared with 3D FLASH (fast low‐angle shot) images. Signal difference‐to‐noise ratios and T1 contrast were not statistically different for 3D MP‐RAGE images as opposed to 3D FLASH images. Advantages intrinsic to the application of 3D MP‐RAGE sequences include decreased imaging time and decreased motion artifact. With this technique, it is possible to perform a relatively motion‐insensitive, T1‐weighted screening brain study with voxel resolution of 1.0 × 1.4 × 2.0 mm or smaller, in an imaging time of 5.9 minutes or less‐permitting offline (poststudy) reconstruction of high‐resolution images in any desired plane.
Prostate and seminal vesicles after irradiation: MR appearance
Authors: Chan Teresa W. , Kressel Herbert Y.
Published: March 2007

Familiarity with the morphologic changes in the prostate and seminal vesicles (SV) after pelvic irradiation is important to the correct interpretation of follow‐up magnetic resonance (MR) studies. A retrospective study of 38 patients with prostatic or other pelvic tumors treated with radiation showed that 31.6% had a normal prostatic zonal pattern (peripheral zone hyper‐intense to central gland) on T2‐weighted images, and 7.9% showed reversal of the zonal pattern; among the rest, the entire gland was diffusely isointense to fat in 42.1%, hypointense to fat in 10.5%, and hyperintense to fat in 7.9%. Sixty‐three percent of the SV had a normal appearance, 21% had fewer tubules but normal signal intensity (SI), 8% had diffuse loss of SI (hypointense to fat), and 8% were hypointense to muscle. Quantitative measurements of SI of the prostate and SV demonstrated a statistically significant lower mean value for the irradiated patients relative to 10 control patients. A decrease in the size of both the prostate and SV was observed in 33% of patients with baseline studies. Use of additional treatment modalities in patients with prostatic carcinoma appeared to correlate with increased likelihood of developing abnormal changes. The authors conclude that in the irradiated patient, the prostate and SV can develop several patterns of SI abnormalities; in particular, diffuse low SI in the prostate and SV should establish radiation fibrosis as an important differential diagnosis to consider.
Diagnostic value of gadopentetate dimeglumine for 1.5‐T MR imaging of musculoskeletal masses: Comparison with unenhanced T1‐and T2‐weighted imaging
Authors: Rosenthal Richard E. , Wozney Paul
Published: March 2007

Three magnetic resonance (MR) imaging techniques (T1‐weighted, T2‐weighted, and T1‐weighted gadopentetate dimeglumine—enhanced) were compared in 32 consecutive MR imaging studies of 26 patients with suspected musculoskeletal masses. T2‐weighted images were superior to T1‐weighted enhanced images with respect to detection and definition of lesions in 12% of cases (n = 4) and were equal in 88% of cases (n = 28). T2‐weighted images were also superior to T1‐weighted images in 38% of cases (n = 12). In no cases were T1‐weighted enhanced images superior to T2‐weighted images. In two cases, T1‐weighted images were superior to both T1‐weighted enhanced and T2‐weighted images. The authors conclude that gadopentetate dimeglumine did not provide much value in lesion detection above that obtained with T2‐weighted images. They also conclude that T1‐weighted images were occasionally superior to T1‐weighted enhanced images and T2‐weighted images because of loss of definition between fat and lesion on the latter.
Rapid three‐dimensional T1‐weighted MR imaging with the MP‐RAGE sequence
Authors: Mugler John P. , Brookeman James R.
Published: March 2007

The authors investigated the application of three‐dimensional (3D) magnetization‐prepared rapid gradient‐echo (MP‐RAGE) imaging to the acquisition of small (32 × 128 × 256) T1‐weighted 3D data sets with imaging times of approximately 1 minute. A theoretical model was used to study the contrast behavior of brain tissue. On the basis of these theoretical results, 3D MP‐RAGE sequences were implemented on a 1.5‐T whole‐body imager. Thirty‐two‐section 3D data sets demonstrating good signal‐to‐noise ratios and resolution and strong T1‐weighted contrast were obtained in 1 minute. Compared with standard short TR/TE spin‐echo sequences with the same imaging times and comparable sequence parameters, the 3D MP‐RAGE sequence delivered increases of more than 50% in the white matter/gray matter signal difference‐to‐noise and white matter signal‐to‐noise ratios, and provided almost twice as many sections. These sequences may find a clinical role in 3D scout imaging and screening and in patients with claustrophobia or trauma.
T2‐weighted thin‐section imaging with the multislab three‐dimensional RARE technique
Authors: Oshio Koichi , Jolesz Ferenc A. , Melki Philippe S. , Mulkern Robert V.
Published: March 2007

A novel three‐dimensional (3D) RARE (rapid acquisition with relaxation enhancement) sequence was implemented on a clinical imager. In this technique, multiple slabs are excited in the same way as in the multisection spin‐echo sequence, and each slab is further phase encoded into eight sections along the section‐slab direction. With a 16‐echo RARE sequence, 128 excitations cover the 256 × 256 × 8 3D k space. With a TR of 2.500 msec, 10 slabs can be excited sequentially at each TR, yielding 80 sections in 5 minutes. Slabs were overlapped to give contiguous sections after discarding of the aliased sections at slab edges. This relatively fast sequence makes contiguous thin‐section T2‐weighted imaging possible, an impractical achievement with the much longer spin‐echo method. Compared with 3D Fourier transform gradient‐echo imaging, the sensitivity of 3D RARE sequences to magnetic susceptibility is reduced. The clinical potential of T2‐weighted 3D imaging is illustrated with high‐resolution brain, spine, and temporomandibular joint images.
In vivo F‐19 chemical shift imaging with FTPA and antibody‐coupled FMIQ
Authors: Mishima Hideyuki , Kobayashi Tetsurou , Shimizu Masahiro , Tamaki Yasuhiro , Baba Masashi , Shimano Takashi , Itoh Soichi , Yamazaki Masaru , Iriguchi Norio , Takahashi Mutsumasa , Mori Takesada
Published: March 2007

A mixture of perfluoromethyldecahydroisoquinoline (FMIQ) emulsion coupled with anti‐CEA (carcinoembryonic antigen) antibody and perfluorotripropylamine (FTPA) was injected into a nude mouse inoculated with human colon carcinoma LS174T. Three days after the injection, in vivo fluorine‐19 chemical shift images of the spectral signals of the two perfluorocarbons (PFCs) were obtained simultaneously. The signal intensities and distributions of FMIQ and FTPA were similar in the liver and spleen but different in the tumor. FMIQ was detected in almost the entire tumor, with scattered areas of high uptake. FTPA, however, was detected only in the center of the tumor. The results suggest that F‐19 chemical shift imaging of two PFCs, one coupled to antibody and the other not, has potential application in tumor diagnosis.
Extrusion of Eye socket magnetic implant after MR imaging: Potential hazard to patient with eye prosthesis
Authors: Yuh William T. C. , Hanigan Michael T. , Nerad Jeffrey A. , Ehrhardt James C. , Carter Keith D. , Kardon Randy H. , Shellock Frank G.
Published: March 2007

Metallic implants or prostheses can be potentially hazardous during magnetic resonance (MR) imaging because of movement or dislodgment of the foreign object. Magnetic eye implants have been reported to exhibit strong movement when placed in water and exposed to a field of 1.5 T. The authors report a case of orbital implant extrusion possibly caused by the movement of a magnetic orbital implant during MR imaging at 0.5 T.
Color flow‐encoded MR imaging
Authors: Tasciyan Talin A. , Mitchell Donald G. , Spritzer Charles E.
Published: March 2007

Magnetic resonance phase images can enable identification of any type of motion, including the velocity and direction of flow, and thus provide valuable supplements to magnitude images, which depict stationary tissue most effectively. A method is described for the simultaneous display of phase and magnitude by color encoding the phase data and superimposing it on the magnitude image to facilitate clinical interpretation. Colorencoded data not only depict the location and direction of flow along specific axes but can also provide relative velocity information through shades of color. Implementation of the technique is described, and the factors to be considered during interpretation of color flow‐encoded images are discussed.
Boron‐11 imaging with a three‐dimensional reconstruction method
Authors: Glover Gary H. , Pauly John M. , Bradshaw Kenneth M.
Published: March 2007

A three‐dimensional projection reconstruction technique is described for imaging boron‐11 distributions, with potential application to boron neutron capture therapy. The method samples a spherical volume of k space uniformly to obtain a 32 × 32 × 32 matrix with voxel size of 0.42 cm3. A signal‐to‐noise ratio (S/N) of 3 was obtained in 8.5 minutes in a phantom containing 75 ug/mL of boron in borocaptate sodium (BSH). Images were obtained in a dog after cessation of an intravenous infusion of BSH and again 30 minutes later, with a maximum boron S/N of about 12. Boron levels in the brain dropped about 6%‐8% and were more diffusely distributed on the images obtained 30 minutes after BSH infusion.
MR‐guided aspiration cytology in the head and neck at high field strength
Authors: Hathout Gasser , Lufkin Robert B. , Jabour Bradley , Andrews James , Castro Dan
Published: March 2007

Published reports of magnetic resonance (MR)‐guided needle biopsy have involved low‐and mid‐field‐strength systems because of the concern of needle artifact and risk of increased needle torque at higher field strengths. To the authors' knowledge, this is the first report of a high‐field‐strength (1.5‐T) system used to guide aspiration cytology in the head and neck in a patient. The procedure was successfully accomplished without additional needle torque or substantial increase in image artifact relative to lower‐field‐strength imaging.
Cardiac ejection fraction: Phantom study comparing cine MR imaging, radionuclide blood pool imaging, and ventriculography
Authors: Debatin Jörg F. , Nadel Scott N. , Paolini John F. , Sostman H. Dirk , Edward Coleman R. , Evans Avery J. , Beam Craig , Spritzer Charles E. , Bashore Thomas M.
Published: March 2007

The accuracy and reproducibility of cardiac ejection fraction (EF) measurements based on cine magnetic resonance (MR) imaging, radionuclide multigated acquisition (MUGA) blood pool imaging, and angiographic ventriculography were evaluated by comparing them with a volumetrically determined standard. A biventricular, compliant, fluid‐filled heart phantom was developed to mimic normal cardiac anatomy and physiology. Ventricular EFs were measured with cine MR imaging by summation of nine contiguous 10‐mm‐thick sections in short and long axis, with single‐plane ventriculography, and with MUGA. Three measurements were performed with each modality for each of three EFs. Ventriculography was least accurate, with average relative errors ranging from 7.9% for the largest EF to 60.1% for the smallest. Cine MR was most accurate, with average relative errors ranging from 4.4% to 8.5%. MUGA EF measurements showed good correlation, with average relative errors ranging from 7.1% to 22.4%. Comparison of the error variances for the three modalities with the F test revealed that MR and MUGA EF measurements were significantly more accurate than those based on ventriculography (P <.01). No significant difference was demonstrated between the accuracy of short‐ and long‐axis cine MR acquisitions.
Tracking motion with tagged rapid gradient‐echo magnetization‐prepared MR imaging
Authors: Niitsu Mamoru , Campeau Norbert G. , Holsinger‐Bampton Anna E. , Riederer Stephen J. , Ehman Richard L.
Published: March 2007

A technique for rapid assessment of tissue motion was developed by combining spatially selective radio‐frequency tagging pulses with centric phase‐encoding view ordering in a T1‐weighted, magnetization‐prepared gradient‐echo acquisition sequence. This sequence allowed labeling and tracking of tissue motion with single‐image acquisition times of less than 3 seconds. Multiple tagged bands 3 mm thick were superimposed orthogonal to the imaging plane. Motion in the interval between tagging and the start of image acquisition could then be precisely determined. The technique was evaluated with phantom studies and then applied to human volunteers for assessment of skeletal muscle motion, phonation, and pelvic floor motion.
MR imaging and metallic implants for anterior cruciate ligament reconstruction: Assessment of ferromagnetism and artifact
Authors: Shellock Frank G. , Mink Jerrold H. , Curtin Sharon , Friedman Marc J.
Published: March 2007

Magnetic resonance (MR) imaging is contraindicated for patients with certain ferromagnetic implants, primarily because of potential risks related to movement or dislodgment of the devices. An additional problem with metallic implants is the potential image distortion that may affect the interpretation of the MR study. Since MR imaging is frequently useful for the evaluation of postoperative anterior cruciate ligament (ACL) reconstruction, the ferromagnetic qualities and artifacts associated with MR imaging were determined for five metallic orthopedic implants commonly used for this surgery. Only the Perfix interference screw displayed a substantial deflection force and caused extensive signal loss. Images of the knee of one patient with two Perfix screws in place were not interpretable because of the image distortion caused by these implants. Therefore, alternative nonferromagnetic implants should be considered for reconstruction of the ACL.
An overview of digital spectrometers for MR imaging
Authors: Holland G. Neil , Macfall James R. ,   Instrumentation Subcommittee of the SMRI Basic Science Council
Published: March 2007

Most magnetic resonance (MR) imaging systems were originally designed with analog spectrometers, since that was the “state of the art” in the late 1970s, when they were developed. Advances in technology have allowed the design of radio‐frequency electronics with a much larger percentage of digital components while the cost of such components has decreased. This has given manufacturers the incentive to develop new spectrometers that incorporate these electronics for cost reduction and potentially better performance. Upgrades and new models of MR units have become available with these so‐called “digital spectrometers.” Because of the interest in the new systems, the Instrumentation Subcommittee of the Basic Science Council of the Society for Magnetic Resonance Imaging has produced this report to review the basic features of analog and digital spectrometers to help the MR imaging community better understand the similarities and differences of these systems. Some details of actual commercial implementations were left out to focus on the basic features. Regardless, the authors hope they have provided a readable introduction to this important topic.
Lipid‐suppressed single‐and multisection proton spectroscopic imaging of the human brain
Authors: Spielman Daniel M. , Pauly John M. , Macovski Albert , Glover Gary H. , Enzmann Dieter R.
Published: March 2007

Spectroscopic images of the brain have great potential in disease diagnosis and treatment monitoring. Unfortunately, interfering lipid signals from subcutaneous fat and poor water suppression due to magnetic field inhomogeneities can make such images difficult to obtain. A pulse sequence that uses inversion recovery for lipid suppression and a spectral‐spatial refocusing pulse for water suppression is introduced. In contrast to methods that eliminate fat signal by restricting the excited volume to lie completely within the brain, inversion‐recovery techniques allow imaging of an entire section without such restrictions. In addition, the spectral‐spatial pulse was designed to provide water suppression insensitive to a reasonable range of B0 and B1 inhomogeneities. Several data processing algorithms have also been developed and used in conjunction with the new pulse sequence to produce metabolite maps covering large volumes of the human brain. Images from single‐ and multisection studies demonstrate the performance of these techniques.
Proton MR spectroscopy of gadolinium‐enhanced multiple sclerosis plaques
Authors: Narayana Ponnada A. , Wolinsky Jerry S. , Jackson Edward F. , McCarthy Micheline
Published: March 2007

Magnetic resonance (MR) imaging and proton MR spectroscopy were performed in 14 patients with clinically definite multiple sclerosis (MS). Prominent resonances in the 0.5‐2.0‐ppm region were seen in the spectra of six of nine gadopentetate dimeglumine‐enhanced plaques in seven patients. These resonances were presumed to originate in lipids and other myelin breakdown products. Similar resonances were detected in only seven of 21 unenhancing plaques. The more frequent presence of such signals in the gadolinium‐enhanced regions indicates that myelin breakdown is often associated with the inflammation that occurs in early stages of MS plaque evolution. It remains uncertain, however, whether active inflammation as indicated by gadolinium enhancement is a necessary precursor of myelin breakdown as detected at MR spectroscopy. Quantitative spectral analysis did not indicate statistically significant differences in N‐acetyl aspartate and choline levels relative to creatine plus phosphocreatine between healthy volunteers and MS patients.
Ultrafast MR imaging of water mobility: Animal models of altered cerebral perfusion
Authors: McKinstry Robert C. , Weiskoff Robert M. , Belliveau John W. , Vevea James M. , Moore John B. , Kwong Kenneth W. , Halpern Elkan F. , Rosen Bruce R.
Published: March 2007

“Single shot” magnetic resonance (MR) diffusion imaging was used to study the details of signal decay curves in experimental perturbations of cerebral perfusion induced by hypercapnia or death. Despite large perfusion increases observed with dynamic susceptibility‐contrast MR imaging, no correlation with these changes was seen in either the diffusion coefficient or any other intravoxel incoherent motion (IVIM) model parameters in dog gray matter as arterial carbon dioxide pressure increased. Non‐monoexponential signal decay in cat gray matter was seen both before and after death. In addition, cat gray matter demonstrated a steady decrease in the diffusion coefficient after death. These data are strong evidence that the fast component of the non‐monoexponential diffusion‐related signal decay is not due solely to perfusion. The authors believe that a second compartment of nonex‐changing spins, most likely cerebrospinal fluid, accounts for the non‐monoexponential decay.
Effect of perfusion on exercised muscle: MR imaging evaluation
Authors: Archer Branch T. , Fleckenstein James L. , Bertocci Loren A. , Haller Ronald G. , Barker Bruce , Parkey Robert W. , Peshock Ronald M.
Published: March 2007

An ischemic clamp model of exercise was used to evaluate the potential role of blood flow in mediating changes in the magnetic resonance imaging appearance of skeletal muscle. Proton relaxation times of muscle were serially estimated in 10 healthy subjects (a) before exercise, (b) after exercise in the presence of vascular occlusion (VO1), (c) during vascular reocclusion after 1 minute of reperfusion (VO2), and (d) after reinstitution of continuous flow. T1 and T2 of active muscles were increased during VO1. During VO2, there were additional increases in relaxation times of active muscles. Reinstitution of continuous flow was associated with a continuous decrease in the T2 of exercised muscle. Hence, blood flow was not required for increases in T1 and T2 with exercise. Additional relaxation time increases occurred after a brief period of reperfusion; however, continuous flow was associated with a decrease in T2.
MR imaging of blood vessels with an intravascular coil
Authors: Martin Alastair J. , Plewes Donald B. , Henkelman R. Mark
Published: March 2007

A method for producing high‐resolution magnetic resonance (MR) images of blood vessel walls is described. The authors review a theoretical analysis of receiver‐coil design and present a coil well suited for intravascular MR imaging. The design is based on two coaxial solenoids separated by a gap region and with current driven in opposite directions. Placement of this receiver coil within the vascular space is shown to provide a substantial increase in sensitivity over that of external surface coils. Experimental verification of these predictions was obtained in a vessel phantom in which a 13‐cm surface coil was compared with a 3.5‐mm‐diameter opposed‐solenoid intravascular coil. This intravascular coil had a cylindric region of high sensitivity that offered a 10‐fold improvement in signal‐to‐noise ratio over that of an external coil near the vessel wall. The performance of this coil was also tested in the jugular vein of a swine.
Echo‐planar imaging of the central nervous system at 1.0 T
Authors: Schmitt Franz , Stehling Michael K. , Ladebeck Ralf , Fang Ming , Quaiyumi Ali , Bårschneider Erwin , Huk Walter J.
Published: March 2007

Echo‐planar imaging (EPI) on the authors' 1‐T prototype im‐ager provides high‐quality 100‐msec images of the central nervous system. Contrast parameters can be chosen freely. Three‐dimensional EPI sequences provide isotropically resolved data sets with 1‐mm resolution. Brain perfusion and blood‐brain barrier disruption can be assessed in time‐course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.
Incremental hydraulic jaw opener for MR imaging of the temporomandibular joint
Authors: Vogl Thomas J. , Eberhard Dieter , Bergman Clifford , Lissner Josef
Published: March 2007

Magnetic resonance (MR) imaging in the open‐and closed‐mouth positions is the method of choice for visualizing the temporomandibular joint (TMJ). To analyze the TMJ in response to various degrees of mouth opening, the authors constructed a hydraulic incremental jaw opener. This apparatus enables obtaining of reproducible and stable positions of TMJ articulation. With modified gradient pulse sequences, the technique yields good spatial resolution of joint anatomy, including that of the articular disk. The application of a cine program allows cinematographic display of TMJ motion, which in conjunction with static open‐and closed‐mouth views can be useful in the diagnosis of TMJ dysfunction. The authors used the incremental jaw opener to examine the disk‐condyie complex at each open‐mouth position, with particular attention to extreme open‐mouth positions.
Dynamic MR imaging of human brain oxygenation during rest and photic stimulation
Authors: Frahm Jens , Bruhn Harald , Merboldt Klaus‐Dietmar , Hänicke Wolfgang
Published: March 2007

Dynamic FLASH (fast low‐angle shot) magnetic resonance (MR) imaging was used to monitor changes in brain oxygenation in the human visual cortex during photic stimulation. The approach exploits the sensitivity of the gradient‐echo signal to susceptibility changes induced by varying concentrations of paramagnetic deoxyhemoglobin in the cerebral blood pool. After the onset of binocular photic stimulation (10 Hz, red light, checkerboard), there was a distinct increase in the MR signal in the calcarine cortex within 6–9 seconds, indicating a decrease in the total deoxyhemoglobin concentration. After the stimulation was switched off, the MR signal returned to a basal value within a similar period of time. Assuming enhanced blood flow and only a minor increase in oxygen consumption (production of deoxyhemoglobin) during physiologic activation, the results reflect an enhanced supply of diamagnetic oxyhemoglobin and an increase in the partial oxygen pressure in the capillary and venous blood pools. In addition, a decrease in the basal MR signal in the calcarine cortex was observed during the first 60–90 seconds of persistent activation, which may be understood as an autoregulatory adaptation to increased overall brain activity associated with information processing due to continuous perception of visual stimuli.
Identification of aberrant right subclavian artery on MR images of the cervical spine
Authors: Easterbrook James S.
Published: March 2007

Nine cases of aberrant right subclavian artery were identified after review of 674 magnetic resonance (MR) studies of the cervical spine. This common aortic arch anomaly is readily identified on sagittal MR images. All vessels were found in the typical retroesophageal location, abutting the esophagus from the vertebral C‐7 to T‐3 levels. Arterial flow created signal voids on T1‐weighted images and confirmatory increased signal intensity due to flowrelated enhancement on gradient‐echo images. This anomaly should be recognized and distinguished from pathologic processes in the prevertebral space. The diagnosis may allay patient concern regarding their dysphagia and also have important ramifications in certain clinical settings.
Minimizing TE in moment‐nulled or flow‐encoded two‐and three‐dimensional gradient‐echo imaging
Authors: Bernstein Matt A. , Shimakawa Ann , Pelc Norbert J.
Published: March 2007

A method for minimizing field‐echo delay in moment‐nulled gradient‐echo imaging is presented. Even though ramps are accounted for, the analysis yields simple closed‐form solutions. The method is then generalized to the section‐select waveform for three‐dimensional volume imaging and to flow encoding for phase‐contrast imaging. Three strategies for first‐moment selection in phase‐contrast imaging are discussed, including a new strategy that always yields the minimum echo delay. Trapezoidal and triangular gradient lobe shapes are analyzed.
MR imaging of the pericardial cyst
Authors: Vinee Philippe , Stover Brigitte , Sigmund Gunther , Laubenberger Jorg , Hauenstein Karl Heinz , Weyrich Georges , Hennig Jurgen
Published: March 2007

Findings obtained with magnetic resonance (MR) imaging in four patients with pericardial cyst are reported. MR imaging allowed not only localization and diagnosis in all four cases but characterization of cystic content. MR imaging, including RARE (rapid acquisition with relaxation enhancement) MR hydrography, which shows only liquids with T2s greater than 500 msec, proved to be useful in characterizing the fluid content of a mediastinal lesion and monitoring follow‐up. In one case, MR imaging allowed differentiation of a pericardial cyst from a suspected necrotic lymph node in a patient with colic carcinoma, with subsequent correction of staging and therapy. The authors conclude that MR imaging is the method of choice for diagnosis (especially in unusual locations) and monitoring of pericardial cysts and for differential diagnosis of malignant mediastinal cystic tumors that show a solid part.
Phase‐contrast MR angiography of vascular malformations of the spinal cord at 0.5 T
Authors: Gelbert Françoise , Guichard Jean‐Pierre , Reizine Daniel , Aymard Armand , Gobin Pierre , Merland Jean‐Jacques , Mourier Klaus L. , George Bernard , Cophignon Jean
Published: March 2007

Preliminary experience with phase‐contrast magnetic resonance (MR) angiography at 0.5 T applied in 12 cases of vascular malformations of the spinal cord is reported. There were six intramedullary arteriovenous malformations (AVMs), four perimedullary fistulas, and two dural arteriovenous fistulas with perimedullary drainage, all proved with x‐ray angiography. The small size of the vessels and their location within a bony structure presented a technical challenge. Serpentine vascular signal patterns were identified within the spinal canal in all cases, showing good correlation with the x‐ray angiographic pattern. Relative to spin‐echo images, MR angiograms allowed better visualization of the venous drainage. The nidus of intramedullary AVMs was more difficult to recognize. The ability to manipulate the velocity‐encoding value allows better characterization of flow speed. The results underline the two dimensions of the phase‐contrast technique, which provides both anatomic images and dynamic information about vascular malformations. MR angiography does not replace selective x‐ray angiography, which is indispensable for therapeutic strategy (endovascular procedure or surgery), but it can be considered a valuable alternative to x‐ray angiography during follow‐up.
Correlation of MR imaging and histologic findings in mouse melanoma
Authors: DeJordy John O. , Bendel Peter , Salomon Yoram , Degani Hadassa , Horowitz Ada
Published: March 2007

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 μm thick, with an in‐plane resolution of 195 μm. The distribution of melanin within the histologic slices correlated well with the high‐signal‐intensity regions on the T1‐weighted images (T1W1s), while these regions had low signal intensity on the T2‐weighted images (T2WIs), providing evidence that melanin or melanin‐associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton‐density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton‐density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin‐rich, viable‐melanoma, and necrotic regions on MR images.
Cardiac metabolism in patients with dilated and hypertrophic cardio‐myopathy: Assessment with proton‐decoupled P‐31 MR spectroscopy
Authors: De Roos Albert , Doornbos Joost , Luyten Peter R. , Oosterwaal Lambère J. M. P. , den Hollander Jan A. , van der Wall Ernst E.
Published: March 2007

Proton‐decoupled phosphorus‐31 heart spectros‐copy was performed in healthy subjects (n = 9) and patients with dilated cardiomyopathy (DCM, n = 9) or hypertrophic cardiomyopathy (HCM, n = 8). The phosphocreatine (PCr)‐to–adenosine triphosphate ratio (± one standard deviation) after correction for blood contribution and partial saturation was significantly lower in HCM patients relative to the control subjects (1.32 ± 0.29 vs 1.65 ± 0.26, P < .05) but not in DCM patients (1.52 ± 0.58 vs 1.65 ± 0.26). The inorganic phosphate (Pi) peak was resolved only in patients with the highest spectral quality. Myocardial pH was lower in HCM patients (n = 6) relative to control subjects (n = 4) (7.07 ± 0.07 vs 7.15 ± 0.03, P < .05). The Pi/PCr ratio was higher in DCM (n = 3) and HCM (n = 6) patients relative to control subjects (n = 4) (0.29 ± 0.06 and 0.20 ± 0.04, respectively, vs 0.14 ± 0.06; P < .05). Elevated phosphodiester signal in DCM patients correlated with 2,3‐diphosphoglycerate signal (r = .94), reflecting blood pool contamination. P‐31 spectroscopy enabled detection of abnormalities in cardiac metabolism and determination of pH in patients with HCM and DCM.
Laryngospasm after administration of gadopentetate dimeglumine
Authors: Omohundro James E. , Elderbrook Marcia K. , Ringer Thomas V.
Published: March 2007

Few serious adverse reactions associated with the use of gadopentetate dimeglumine in magnetic resonance imaging have been reported. The present case involves an 8‐year‐old girl who developed laryngospasm after administration of gado‐pentetate dimeglumine.
Mn‐DPDP enhancement patterns of hepatocellular lesions on MR images
Authors: Vogl Thomas J. , Hamm Bernd , Schnell Birgit , McMahon Christine , Branding Gordian , Lissner Josef , Wolf Karl‐Jürgen
Published: March 2007

The recently developed paramagnetic hepatobiliary contrast agent manganese dipyridoxyl diphosphate (DPDP) was evaluated in eight patients. Pathologic diagnoses included five hepatocellular carcinomas, two cirrhoses, and one focal nodular hyperplasia. T1‐weighted spin‐echo and gradient‐echo images were obtained after intravenous injection of 5 or 10 μmol/kg Mn‐DPDP; these were compared with un‐enhanced T1‐weighted spin‐echo and gradient‐echo images and T2‐weighted spin‐echo images. In all patients with lesions of hepatocellular origin, focal areas of increased enhancement were seen in the lesions after administration of Mn‐DPDP. In the cir‐rhotic livers, these areas corresponded to foci of hepatic regeneration. In all patients, the signal‐to‐noise ratio in normal liver tissue increased significantly after injection of Mn‐DPDP. Signal intensity in the six primary liver tumors was further increased, so that they appeared hyperintense relative to surrounding liver tissue on all T1‐weighted images. Conspicuity and demarcation of all lesions were improved on Mn‐DPDP‐enhanced images.
Quantitative analysis of gadopentetate dimeglumine excreted in breast milk
Authors: Rofsky Neil M. , Weinreb Jeffrey C. , Litt Andrew W.
Published: March 2007

Specimens of breast milk were obtained from each breast in a lactating patient for a 24‐hour period after a gadolinium‐enhanced MR imaging examination was performed. A quantitative analysis of gadolinium content in specimens obtained at 2, 11, 17, and 24 hours after the intravenous administration of gadopentetate dimeglumine demonstrated that gadolinium is excreted in small amounts (total of 1.60 μmol during a 24‐hour period) and in similar amounts from each breast. These results suggest that a waiting period of 24 hours, with active expression of breast milk from each breast, should provide a reasonable safety margin for allowing resumption of breast‐feeding. Additional data will be required before establishing definitive recommendations.
T2‐weighted MR imaging of focal hepatic lesions: Comparison of various RARE and fat‐suppressed spin‐echo sequences
Authors: Semelka Richard C. , Patrick Shoenut J. , Kroeker Randall M.
Published: March 2007

The authors prospectively compared four T2‐weighted magnetic resonance (MR) sequences, including high‐resolution 512 × 512 (matrix size) RARE (rapid acquisition with relaxation enhancement), 256 × 256 RARE, 128 × 256 breath‐hold RARE, and 192 × 256 fat‐suppressed spin‐echo (T2FS) sequences, in the evaluation of 16 patients with focal hepatic masses. MR images were evaluated by quantitative lesion‐liver signal difference‐to‐noise ratios (SDNRs) and subjective evaluation of image artifact and image quality. No significant differences were observed between RARE sequences in SDNR values. The T2FS sequence had a significantly higher SDNR than the 512 × 512 RARE sequence (24.6 ± 15.0 vs 14.5 ± 9.7) (P =.008). Image quality was rated highest for the 512 × 512 RARE and T2FS sequences (P =.006). The inherent advantage of high spatial resolution suggests that the 512 × 512 RARE sequence may be of value in detecting hepatic lesions.
Boronated Metalloporphyrins: A novel approach to the diagnosis and treatment of cancer using contrast‐enhanced MR imaging and neutron capture therapy
Authors: Huang Leryang R. , Straubinger Robert M. , Kahl Stephen B. , Koo Myoung‐Seo , Alletto James J. , Mazurchuk Richard , Chau Robert I. , Thamer Sandra L. , Fiel Robert J.
Published: March 2007

Porphyrins are a unique class of metal chelating agents that have shown specific affinity for neoplasms. The water‐soluble free‐base derivative, tetrakiscarborane carboxylate ester of 2,4‐(α,β‐dihydroxyethyl) deuteroporphyrin IX (BOPP), an agent designed for neutron capture therapy, has previously demonstrated selective localization and retention in a C6 murine glioma. In the present work, the authors demonstrate that the manganese chelate of BOPP also selectively localizes in a rat 9L gliosarcoma and preferentially enhances the tumor‐normal brain contrast of T1‐weighted images for at least 92 hours. The data indicate a maximal enhancement of contrast between tumor and normal brain at 24 hours after injection, compared with 5 minutes for manganese (III) tetraphenylporphine sulfonate (TPPS4). The results also indicate that Mn‐BOPP may have a slower uptake in the 9L glioma than Mn‐TPPS4 but a longer retention in the tumor. Mn‐BOPP is unique in that it represents, to the authors' knowledge, the first example of a single agent that can enhance contrast between tumor and normal tissue and be potentially effective as an agent for boron neutron capture therapy.
Three‐dimensional time‐of‐flight MR angiography with a specialized gradient head coil
Authors: Tkach Jean A. , Ruggieri Paul M. , Dillinger John J. , Ross Jeffrey S. , Modic Michael T. , Masaryk Thomas J.
Published: March 2007

A gradient head coil has been developed, incorporating two independent gradients within the conventional body coil of the magnetic resonance (MR) system, with reduced rise times (200 μsec) and maximum amplitudes of 37 and 18 mT/m in the z and y directions, respectively. This gradient coil was systematically evaluated by testing two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight (TOF) MR angiography sequences applied to a pulsatile flow phantom simulating a carotid stenosis and the intracranial vasculature. When standard 2D and 3D TOF MR angiography techniques were used to image the carotid stenosis model, dramatic signal loss in the stenotic segment and a large flow void distal to the stenosis were seen. The shorter (3.8 msec) absolute echo times (TEs) achievable with the gradient coil in 3D sequences substantially reduced the phase dispersion and associated signal loss in the region of stenosis. Shorter TEs alone (3.2 msec) did not minimize signal loss, and firstorder flow compensation in the read and section‐select directions provided further improvements (despite slightly longer TEs). Reduction of TEs in 2D sequences yielded relatively poor results regardless of the refocusing scheme or TE. This study confirms the predicted benefits of a dedicated coil with improved gradient capabilities for 3D MR angiography. The study suggests the limitations of 2D TOF MR angiography in the evaluation of severe stenoses.
Accuracy of phase‐contrast flow measurements in the presence of partial‐volume effects
Authors: Tang Chao , Blatter Duane D. , Parker Dennis L.
Published: March 2007

The accuracy of volume flow rate measurements obtained with phase‐contrast methods was assessed by means of computer simulation and in vitro experiments. Factors studied include (a) the partial‐volume effect due to voxel dimensions relative to vessel dimensions and orientation and (b) intravoxel phase dispersion. It is shown that limited resolution (partial‐volume effect) is the major obstacle to accurate flow measurement for both laminar and plug flow. The results show that at least 16 voxels must cover the cross section of the vessel lumen to obtain a measurement accuracy to within 10%. Measurement accuracy also greatly depends on the relative signal intensity of stationary tissue and is better for laminar flow than plug flow.
MR detection of quantitative and structural changes in human aortic aneurysms
Authors: Vinée Philippe , Meurer Bernard , Constantinesco André , Kohlberger Bernd , Hauenstein Karl Heinz , Stöver Brigitte , Laubenberger Jörg , Petkov Simeon , Oursin Caroline , Eisenmann Bernard
Published: March 2007

Collagen is a major component of the extracellular matrix and a determinant of the elastic behavior of the human aorta. To investigate the changes found in aneurysmal degeneration, the authors studied the solid‐state hydrogen‐1 nuclear magnetic resonance line shape of collagen in aneurysms and normal human aortas. A three‐component decomposition of the free induction decay was performed, with collagen characterized by a T2 of about 18 μsec. The second moment of the collagen line shape was found to be increased in aneurysms (5.3 vs 4.8 G2), while, correspondingly, the T2 of collagen was lower in aneurysms (16.3 vs 17.7μsec). This corresponds to a modification of collagen structure and molecular motion. Collagen concentration was lower in nondiseased aortic walls (9.4% vs 7.3%). These results are discussed in reference to the contradictory conclusions in the current literature. The increase in collagen and the modification of its structure and molecular motion are explained by the need to resist an increasing tangential tension due to increased aortic diameter and diminished wall thickness in aneurysms and by intercalation or site binding in the helices or electric dipolar interactions in the less mobile side groups.
MR characterization of blood flow in native and grafted internal mammary arteries
Authors: Debatin Jörg F. , Strong John A. , Dirk Sostman H. , Negro‐Vilar Rosa , Paine Susan S. , Douglas James M. , Pelc Norbert J.
Published: March 2007

In the postoperative patient with anginal symptoms, differentiation between bypass graft compromise and nonischemic causes has until now been accomplished only by means of x‐ray angiography. A noninvasive test is clearly desirable. The authors used a cine phase‐contrast (PC) magnetic resonance (MR) imaging technique to characterize blood flow in native and grafted internal mammary arteries (IMAs). Ten volunteers and 15 patients who had recently undergone IMA coronary artery bypass grafting were imaged. Cine PC MR imaging was performed in the transaxial plane at the level of the pulmonary artery bifurcation. Flow in both IMAs was quantified and expressed as a percentage of cardiac output measured in the ascending aorta. In the 15 patients, flow analysis was performed in both the native and grafted IMAs. In the volunteers, IMA blood flow ranged from 2.1% to 4.3% of cardiac output on the left (mean, 3.5%) and 2.1% to 5.1% (mean, 3.5%) on the right. There was considerable intersubject variability, with coefficients of variation of 10.7% for the left and 12.3% for the right IMA. Intrasubject variability was limited, with estimated common standard deviations of 0.45% of cardiac output (range, 0.2%–1.1%) for the left and 0.39% (range, 0.1%–0.6%) for the right IMA. Flow in grafted IMAs was identified in 13 of 15 patients. In one of two patients without demonstrable IMA graft flow, cardiac catheterization confirmed lack of flow. IMA graft flow varied from 28 to 164 mL/min (mean, 80.3 mL/min). This study shows the feasibility of using cine PC MR imaging as a quantitative method of evaluating blood flow in IMA coronary artery bypass grafts.
MR imaging of infradiaphragmatic lymphadenopathy in children and adolescents with Hodgkin disease: Comparison with lymphography and CT
Authors: Hanna Soheil L. , Fletcher Barry D. , Boulden Thomas F. , Hudson Melissa M. , Greenwald Carol A. , Kun Larry E.
Published: March 2007

The ability of short‐inversion‐time inversion recovery (STIR) magnetic resonance imaging to depict infradiaphragmatic lymphadenopathy was evaluated in 25 consecutive patients with newly diagnosed Hodgkin disease. All patients underwent computed tomography (CT) and multiplanar STIR imaging prior to lymphography (LAG). The STIR and CT images were evaluated for paraaortic and parailiac node enlargement. Findings were compared with LAG findings, which showed the architectural pattern of the opacified lymph nodes. In the upper paraaortic region, STIR imaging showed more abnormal nodes than did CT or LAG. In the lower paraaortic and parailiac regions, lymph node enlargement was shown equally well with STIR and LAG, whereas CT showed fewer enlarged lymph nodes. LAG showed paraaortic or parailiac focal tumor infiltration in three patients with normal‐size nodes, and hyperplasia in two patients with enlarged nodes. STIR imaging showed more abnormal infradiaphragmatic nodes than did CT because of improved lymph node conspicuity. STIR imaging may be a useful addition to CT for staging pediatric Hodgkin disease.
Echo‐planar MR imaging of human brain oxygenation changes
Authors: Stehling Michael K. , Schmitt Franz , Ladebeck Ralf
Published: March 2007

Echo‐planar magnetic resonance (MR) imaging was used to observe signal intensity changes in the human brain during hypoxia. Increasing arterial blood levels of deoxyhemoglobin (0%–42%) during prolonged apnea were monitored with a pulse oximeter and correlated with gray matter and white matter signal attenuation of 13% and 20%, respectively. The results suggest the possibility of using deoxyhemoglobin boluses as a physiologic, intravascular susceptibility contrast agent for assessment of local cerebral oxygen utilization.
Rapid MR imaging of a vascular challenge to focal ischemia in cat brain
Authors: De Crespigny Alexander J. , Wendland Michael F. , Derugin Nikita , Vexler Zinaida S. , Moseley Michael E.
Published: March 2007

Deoxygenated blood was effectively used as a magnetic resonance (MR) susceptibility contrast agent to distinguish perfused and nonperfused (ischemic) regions in a focal ischemia model in cat brain at 2 T. Modulation of cerebral blood oxygenation levels in response to apnea was followed in real time with T2*‐weighted (gradient‐recalled) echo‐planar MR imaging. Signal loss in the T2*‐weighted images occurred only in perfused tissues as blood became globally deoxygenated. These data complemented information from diffusion‐weighted and contrast agent bolus–‐tracking images. In addition, observation of the signal recovery behavior on reventilation in both normal and ischemic brain offered potentially useful information about the state of the cerebral autoregulatory mechanism.
Brodie Abscess: MR imaging appearance in 10 patients
Authors: Marti‐Bonmati Luis , Aparisi Francisco , Poyatos Cecilio , Vilar Jose
Published: March 2007

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1‐weighted images and high signal intensity on T2‐weighted and STIR (short‐inversion‐time inversion recovery) images, (b) an inner ring isointense to muscle on T1‐weighted images and with high signal intensity on T2‐weighted and STIR images, (c) an outer ring hypoin‐tense on all images, and (d) a peripheral halo hypointense on T1‐weighted images. In six of eight cases, a soft‐tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1‐weighted images and high signal intensity on T2‐weighted and STIR images. Only the peripheral halo was clearly identified in both cases.
Single‐breath‐hold venous or arterial flow‐suppressed pulmonary vascular MR imaging with phased‐array coils
Authors: Foo Thomas K. F. , Macfall James R. , Dirk Sostman H. , Hayes Cecil E.
Published: March 2007

A method for acquiring pulmonary vascular magnetic resonance (MR) images with either venous or arterial flow suppression is described. The proposed method only marginally increases the overall imaging time compared with conventional flow‐suppression techniques. This enables an acquisition to be completed within a single breath hold with some selectivity as to flow direction. Instead of applying a spatially selective presaturation pulse before each radio‐frequency (RF) excitation pulse, the flow presaturation pulse is applied once every 16‐20 RF excitation pulses. To avoid image artifacts and to maintain a steady state, each presaturation pulse interval is followed by a normal imaging segment but with data acquisition turned off. Overall imaging time is increased by two TR intervals for each presaturation segment. For a 256 × 128 matrix acquisition, venous flow presaturation increases overall imaging time by approximately 14 TR intervals, while arterial flow suppression increases imaging time by 10 TR intervals.