bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy evaluation of gadoteridol for MR angiography of intracranial vascular lesions
Authors: McLachlan Stuart J. , Francisco John C. , Pernicone Joseph R. , Hasso Anton N.
Published: March 2007

A phase III multicenter study was conducted in 89 patients with known intracranial vascular lesions to evaluate an extracellular gadolinium contrast agent, gadoteridol, for intracranial magnetic resonance (MR) angiography. The pre‐ and postcontrast MR angiograms of 82 patients were evaluated by the unblinded investigators and by two blinded readers (A and B) for visualization of lesions; arterial and venous anatomy; extent, size, and number of lesions; and disease classification. The unblinded readers indicated that lesions were visualized better on postcontrast images in the following categories: venous anatomy, 87 (81%) of 107 lesions; arterial anatomy, 43 lesions (40%); and extent or size of lesions, 38 lesions (36%). In 29 (35%) of 82 patients, the unblinded readers determined that enhanced MR angiography provided more diagnostic information than unenhanced MR angiography. The blinded readers determined that enhanced MR angiography provided more information for visualization of vascular anatomy in more than 60% of cases. The additional information provided with gadoteridol would have changed the diagnosis in nine (8%) of 107 lesions seen by the unblinded readers, 11 (12%) of 90 lesions seen by reader A, and three (3%) of 93 lesions seen by reader B. The results confirm that the use of gadoteridol improves the visualization of intracranial vascular lesions with MR angiography. The authors conclude that development of new postprocessing algorithms will improve the utility of contrast‐enhanced MR angiography.
Dynamic contrast‐enhanced MR imaging assessment of vascularized free fibular grafts
Authors: Lomasney Laurie M. , Madden John F. , Rizk Wagdy S. , Hedlund Lawrence W. , Martinez Salutorio , Coleman Robert E. , Richardson William J. , Sostman H. Dirk
Published: March 2007

Magnetic resonance (MR) imaging may be a noninvasive method for assessing perfusion of vascularized bone grafts placed for treatment of avascular necrosis. One proximal femur of seven beagles was devascularized, with insertion of a vascularized fibular graft. MR imaging at 1 week (seven dogs) and 6 weeks (five dogs) after surgery included pre‐ and postcontrast spin‐echo sequences, unenhanced twodimensional time‐of‐flight (TOF) vascular imaging, and dynamic gradient‐echo imaging during infusion of gadolinium. Relative signal intensity values of selected regions obtained from the dynamic gradientecho images were plotted as percent enhancement versus time. In the operated hip, MR imaging did not show enhancement in six of seven femoral heads and greater trochanters at 1 week after surgery, with similar results after 6 weeks. MR imaging of fibular grafts 6 weeks after surgery showed an initial rapid increase in enhancement and a subsequent slower increase in five of five dogs, although no enhancement was seen in six of seven dogs at 1 week. These findings contrasted with a rapid initial increase in enhancement followed by slow decline in non‐operated hips. Two‐dimensional TOP imaging did not show the vascular pedicle of the graft in any dog. Findings of radionuclide bone scanning performed 1 week after surgery were consistent with devascularization of the operated femur and fibular graft. However, tetracycline distribution and histologic findings confirmed the viability of five of five grafts within the devascularized femurs 6 weeks after surgery. Thus, dynamic contrast‐enhanced MR imaging at 6 weeks after surgery is valuable for assessing vascular bone graft perfusion, while similar imaging at 1 week may suggest otherwise.
MR imaging of soft‐tissue masses: Role of gadopentetate dimeglumine
Authors: Benedikt Richard A. , Jelinek James S. , Kransdorf Mark J. , Moser Richard P. , Berrey B. Hudson
Published: March 2007

To assess the effectiveness of gadopentetate dimeglumine in the magnetic resonance (MR) imaging evaluation of soft‐tissue masses without osseous involvement, 30 patients underwent MR imaging before and after administration of contrast material (0.1 mmol/ kg) of the 30 lesions, 22 were benign and eight were malignant; histologic confirmation was available in all lesions except one benign lesion. Overall, enhancement was detected in 26 (87%) of 30 lesions: 18 (82%) of the 22 benign lesions and eight (100%) of eight malignant lesions. Enhancement was characterized as homogeneous (two [11%] benign lesions, two [25%] malignant lesions), inhomogeneous (11 [61%] benign lesions, six [75%] malignant lesions), or peripheral (five [28%] benign lesions, no malignant lesions) of the 19 lesions assessed for a change in enhancement over time, seven (37%) showed an increase and two (11%) showed a decrease in signal intensity. The authors conclude that benign and malignant soft‐tissue lesions could not be differentiated solely on the basis of enhancement (pattern, degree, or time course).
Reduction of slab boundary artifact with multiple overlapping thin slab acquisition in MR angiography of the cervical carotid artery
Authors: Robison Ronald O. , Blatter Duane D. , Parker Dennis L. , Barney William W. , Perry David M. , Goodrich Kenneth C.
Published: March 2007

Multiple overlapping thin slab acquisition (MOTSA) is a magnetic resonance (MR) angiography technique combining advantages of two‐ and three‐dimensional time‐of‐flight techniques. The authors studied three image acquisition parameters (flip angle, TR, and the slab excitation fraction [SEF]) and a postprocessing algorithm, to evaluate their effect on MOTSA image quality, including contrast‐to‐noise ratio (C/N) and the severity of the slab boundary artifact. By increasing SEF from 0.75 to 1.10, the slab boundary artifact was reduced by 29%‐56% (P <.0001). The boundary artifact can be reduced an additional 46% by postprocessing of the overlapping section data. In the healthy volunteers studied, C/N of the cervical carotid artery could be increased sixfold (P <.0001) by increasing the flip angle from 10° to 50°, without significant worsening of the boundary artifact due to top‐of‐slab saturation. The effect of TR on image quality was not statistically significant for the range studied (52‐70 msec). We conclude that the slab boundary artifact seen with the MOTSA MR angiography technique can be reduced significantly by optimizing imaging acquisition parameters and using a postprocessing algorithm to combine overlapping section information.
MR imaging signal response to sustained stimulation in human visual cortex
Authors: Hathout Gasser M. , Kirlew Konrad A. T. , So George J. K. , Hamilton David R. , Zhang J. X. , Sinha Usha , Sinha Shantanu , Sayre James , Gozal David , Harper Ronald M. , Lufkin Robert B.
Published: March 2007

The response of signal intensity to transient (on‐off) motor and sensory stimulation has been well studied; however, the dependence of signal response on the duration of stimulus requires further characterization. The objective of this study was to determine the time course of signal response in the human visual cortex to prolonged, sustained stimulation and to examine possible contributory physiologic mechanisms. Nine healthy volunteers underwent magnetic resonance (MR) imaging during sustained visual stimulation with light‐proof binocular goggles. With photic stimulation, activation was observed in all subjects as an increase in signal intensity of the visual cortex. With sustained stimulation, a gradual decrease in signal intensity was subsequently observed, with progression toward an apparent steady state. Correlation with positron emission tomographic, MR spectroscopic, and visual evoked‐potential data suggests that the initial uncoupling of cerebral blood flow and oxidative metabolism with a neuronal activation burst may represent a transient phenomenon. This quick‐response phase may proceed to an equilibrium coupling of flow and oxidative metabolism, with a gradual normalization of venous deoxyhemoglobin levels and signal intensity.
Short TE hydrogen‐1 spectroscopic MR imaging of normal human brain: Reproducibility studies
Authors: Jackson Edward F. , Doyle Timothy J. , Wolinsky Jerry S. , Narayana Ponnada A.
Published: March 2007

Studies have been performed to evaluate the reproducibility of longitudinal acquisitions with short TE spectroscopic magnetic resonance (MR) imaging of human brain. In healthy volunteers, the ratios of N‐acetyl‐aspartate (NAA) and choline (Cho) with respect to total creatine (Cr) (creatine and phosphocreatine) have been examined in terms of voxel‐to‐voxel, acquisition‐to‐acquisition, and subject‐to‐subject variation. Overall coefficients of variation for NAA/Cr ratios and Cho/Cr ratios were 18% and 16%, respectively. The interacquisition variation was not statistically significant (P = .05) for either ratio. In terms of F ratios, the dominant source of variation in the NAA/Cr ratio was intersubject variability, whereas for the Cho/Cr ratio the dominant source of variation was intervoxel variability. Consequences of spectroscopic processing with spatial apodization and postacquisition water suppression and resolution enhancement were also examined. Such reproducibility studies are crucial if longitudinal spectroscopic evaluations are to be performed in a clinical setting to follow the natural course of disease states or the effects of therapy.
Nodular sarcoidosis of the liver and spleen: Appearance on MR images
Authors: Warshauer David M. , Semelka Richard C. , Ascher Susan M.
Published: March 2007

Small nodular lesions in the liver and spleen have been reported as an infrequent manifestation of sarcoidosis. Five patients with this appearance on either dynamic contrast material—enhanced computed tomographic (CT) or ultrasound scans underwent magnetic resonance (MR) imaging with and without dynamic gadolinium enhancement. The lesions were relatively uniform in size, ranging from 0.5 to 1.5 cm. On CT scans, they were hypoattenuating relative to surrounding parenchyma. On MR images, the lesions were hypointense relative to background parenchyma with all sequences. No substantial enhancement was observed in the lesions, although lesion conspicuity decreased over time on serial postcontrast images. Lesion conspicuity was greatest on either T2‐weighted fat‐suppressed (T2FS) images or early‐phase dynamic contrast‐enhanced images. Abdominal adenopathy was seen in three of the five patients and was hyperintense relative to liver on T2FS images in two and intermediate in intensity in one patient.
Stress MR imaging for evaluation of popliteal artery entrapment
Authors: Cesare Ernesto Di , Marsili Luca , Marino Giovanni , Masciocchi Carlo , Morettini Giuseppe , Spartera Carlo , Lupattelli Luciano , Passariello Roberto
Published: March 2007

The popliteal artery entrapment (PAE) syndrome has been recognized as a cause of arterial occlusion in young people. It is the result of an anomaly of the relationship between the popliteal artery and the gastrocnemius muscle. Eight young healthy volunteers (16 legs) and six patients (10 legs) with suspected PAE underwent magnetic resonance (MR) imaging. Gradient‐echo images were obtained in axial planes with the leg at rest and during active plantar flexion against resistance. Imaging at rest allowed identification of PAE signs in only one leg, which had an anomalous medial course of the popliteal artery. In the other cases, only the stress technique was able to show signal loss in the popliteal artery due to muscular compression (two legs) or the presence of accessory muscle slip around the vessel (two legs), as confirmed at surgery. MR imaging is therefore a useful technique for the diagnosis of PAE because of its capability of combining information obtainable with other modalities.
Fragrance administration to reduce anxiety during MR imaging
Authors: Redd William H. , Manne Sharon L. , Peters Bruce , Jacobsen Paul B. , Schmidt Hilary
Published: March 2007

Fifty‐seven outpatients received either heliotropin (a vanillalike scent) with humidified air (n = 20) or humidified air alone (n = 37) via a nasal cannula during magnetic resonance imaging in the diagnostic workup for cancer. Delivery of heliotropin and air was determined by a computer‐controlled schedule. Fragrance administration resulted in a statistically significant reduction in average overall patientrated anxiety (on a visual analog scale) during imaging in patients who found the fragrance moderately to extremely pleasant. Administration of fragrance was associated with 63% less anxiety than administration of humidified air alone. Physiologic measures (pulse and heart rate) did not show a statistically significant effect with fragrance administration.
Reproducibility of nonparametric feature map segmentation for determination of normal human intracranial volumes with MR imaging data
Authors: Jackson Edward F. , Narayana Ponnada A. , Falconer James C.
Published: March 2007

Semiautomated segmentation of dual‐contrast magnetic resonance images was used to determine volumes of total brain, gray matter, white matter, and cerebrospinal fluid (CSF) in healthy volunteers. Reproducibility of the technique was evaluated in terms of intraobserver, interobserver, and study‐to‐study variations. Intraobserver coefficients of variation ranged from 0.4% to 6.0%, while interobserver values ranged from 0.8% to 9.9%. In both cases, the maximum variations were obtained in volume measurements of tissues with maximum complexity (ie, CSF), and the minimum variation was obtained in determining total brain volume. This was also true in the case of study‐to‐study variations in volume measurements, for which the coefficients of variation ranged from 0.5% to 8.7%. The use of appropriate preprocessing techniques, which are crucial to the accuracy and reproducibility of the segmentation technique, are described in detail.
In vivo comparison of two through‐plane MR velocity mapping methods: Fast fourier encoding and phase mapping
Authors: Mousseaux Elie , Idy‐Peretti Iiana , Bittoun Jacques , Jolivet Odile , Bourroul Eric , Tardivon Anne , Péronneau Pierre , Gaux Jean‐Claude
Published: March 2007

Magnetic resonance imaging maps of velocity were acquired with a 1.5‐T system in 10 subjects in a plane perpendicular to the main pulmonary artery. Velocity images were successively acquired with a method developed from Fourier‐encoding velocity imaging (FEVI) principles with eight gradient steps and one excitation, and with two‐point phase‐subtraction mapping. Reconstruction in FEVI was implemented by zero‐filling interpolation around the eight gradient steps and then around the four central steps. The methods were compared by using estimates of noise in velocity measurements based on the difference between the experimental map and a smooth fitted map. For the same acquisition time, FEVI with four encoding steps was more precise in velocity measurements than phase mapping. Precision was further increased by the use of eight encoding steps, but acquisition time was doubled.
Reduction of partial‐volume artifacts with zero‐filled interpolation in three‐dimensional MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L. , Cao Guang
Published: March 2007

Partial‐volume artifacts reduce vessel contrast and continuity (especially in small vessels) in magnetic resonance (MR angiography. The authors applied zero‐filled (band‐limited) interpolation to three‐dimensional (3D) MR angiograms to reduce partial‐volume artifacts. They demonstrated that zero‐filled interpolation can also be implemented by means of voxel shifting in real space. Voxel‐shifted interpolation is much less computer memory intensive than conventional zero‐filled interpolation. They numerically simulated the contrast loss due to partial‐volume artifacts and contrast recovery obtained with zero‐filled interpolation. Zero‐filled interpolation in all three orthogonal directions was applied to 3D MR angiography data sets from 29 human studies. These studies were obtained with the three commonly used 3D MR angiography techniques: 3D time of flight, multislab 3D time of flight, and 3D phase contrast. A substantial improvement in vessel contrast and vessel continuity was observed in all cases.
Guidelines and recommendations for MR imaging safety and patient management III. Questionnaire for screening patients before MR procedures
Authors: Shellock Frank G. , Kanal Emanuel ,   SMRI Safety Committee
Published: March 2007

The authors present the third installment of the guidelines and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (now the Society of Magnetic Resonance) concerning various issues related to the safety and management of patients undergoing magnetic resonance (MR) procedures. This document was developed to provide standardized and consistent information for use by health practitioners involved in screening patients or other individuals for MR procedures.
Effect on fetal mouse development of exposure to MR imaging and gadopentetate dimeglumine
Authors: Rofsky Neil M. , Pizzarello Donald J. , Weinreb Jeffrey C. , Ambrosino Michael M. , Rosenberg Carl
Published: March 2007

Pregnant mice were exposed to one of five regimens at 9.5 days of gestation: no treatment (group 1), intraperitoneal injection of normal saline (group 2), intraperitoneal injection of gadopentetate dimeglumine (group 3), intraperitoneal injection of gadopentetate dimeglumine and magnetic resonance (MR) exposure (group 4), and MR exposure alone (group 5). At 18 days of gestation, the mice were sacrifice and fetuses were removed and examined for the following end points: litter size, number alive or dead, fetal weight, extremity morphology, eye and ear development, and appearance of the head. A total of 739 fetuses were analyzed: group 1 (n = 161), group 2 (n = 149), group 3 (n = 142), group 4 (n = 136), and group 5 (n = 151). The only statistically significant difference was a lower mean fetal weight in the saline‐injection group compared with the control group. The results show that MR exposure with and without gadopentetate dimeglumine had no adverse effect on the end points analyzed.
Eddy current correction in volume‐localized MR spectroscopy
Authors: Lin Chen , Wendt Richard E. , Evans Harlan J. , Rowe Roger M. , Hedrick Thomas D. , LeBlanc Adrian D.
Published: March 2007

The quality of volume‐localized magnetic resonance spectroscopy is affected by eddy currents caused by gradient switching. Eddy currents can be reduced with improved gradient systems; however, it has been suggested that the distortion due to eddy currents can be compensated for during postprocessing with a single‐frequency reference signal. The authors propose modifying current techniques for acquiring the single‐frequency reference signal by using relaxation weighting to reduce interference from components that cannot be eliminated by digital filtering alone. Additional sequences with T1 or T2 weighting for reference signal acquisition are shown to have the same eddy current characteristics as the original signal without relaxation weighting. The authors also studied a new eddy current correction method that does not require a single‐frequency reference signal. This method uses two free induction decays (FIDs) collected from the same volume with two sequences with opposite gradients. Phase errors caused by eddy currents are opposite in these two FIDs and can be canceled completely by combining the FIDs. These methods were tested in a phantom. Eddy current distortions were corrected, allowing quantitative measurement of structures such as the –CHCH– component, which is otherwise undetectable.
Safety and optimum concentration of a manganese chloride–based oral MR contrast agent
Authors: Bernardino Michael E. , Weinreb Jeffrey C. , Mitchell Donald G. , Small William C. , Morris Marie
Published: March 2007

To determine the safety of a manganese chloride‐based oral magnetic resonance (MR) contrast agent and the ideal concentration of the agent for marking in three different anatomic sites (stomach, middle of the small bowel, and ileocecal region), six healthy volunteers were evaluated before and after administration of 900 mL of three different concentrations of the contrast agent. Images were evaluated subjectively and objectively. No adverse events were noted. There was a minimal rise in manganese blood levels at 6 hours after administration, with a return to baseline at 24 hours. The imaging data demonstrated good‐to‐excellent bowel marking on T1‐weighted images at all three concentrations. However, on T2‐weighted images, the 40 mg Mn+2/L concentration provided improved hypointense bowel marking relative to the 20 mg/L concentration. Little difference was seen between the 40 and 60 mg/L concentrations. Fast T1‐and T2‐weighted sequences provided superior image quality to that of conventional spin‐echo sequences.
MR imaging assessment of experimental hepatic dysfunction with mn‐DPDP
Authors: Coley Brian D. , Mattrey Robert F. , Baker Kristine G. , Peterson Thomas , Burgan Anthony R.
Published: March 2007

Manganese (II) N, N'‐dipyridoxylethylenediamine‐N, N'‐diacetate 5,5′‐bis(phosphate) (DPDP) is a paramagnetic magnetic resonance (MR) contrast agent that enhances the liver and is predominantly excreted through the biliary tree. The authors evaluated its utility in diffuse liver disease by assessing liver and gallbladder enhancement in 24 rabbits. Total (n = 6) or segmental (n = 6) biliary occlusion or galactosamine‐induced hepatitis (n = 6) was induced 3 days before imaging. Six rabbits served as normal controls. T1‐ and T2‐weighted axial MR images were acquired at baseline, followed by T1‐weighted images every 10 minutes for 1 hour after the intravenous administration of 20 μmol/kg Mn‐DPDP. Except for the segmental occlusion group, the baseline study did not allow distinction between normal and abnormal livers. The temporal hepatic enhancement pattern was statistically different for each group. The normal, segmental occlusion, and hepatitis groups showed patterns similar to one another but markedly higher signal intensity than the total‐occlusion group throughout the observation period. In contrast, the gallbladder showed a greater difference in both degree of enhancement and time to peak enhancement among the four groups. Mn‐DPDP produces a temporal hepatic enhancement pattern that allows recognition of markedly impaired livers, and gallbladder enhancement patterns that allow distinction of more subtly impaired livers.
Nonsusceptibility artifacts due to metallic objects in MR imaging
Authors: Camacho Christopher R. , Plewes Donald B. , Henkelman R. Mark
Published: March 2007

The authors investigated eddy current artifacts due to metallic objects within the magnetic resonance imaging field. The problem was simplified by using a circular copper loop as a model for the more complex eddy current pathways present in a metallic implant. With this simple geometry, the authors show that radio‐frequency (RF)‐induced eddy currents in the metal produce a significant local artifact. However, no appreciable artifacts due to the switching magnetic field gradients were observed. A detailed quantitative analysis of the mechanism of RF‐induced eddy current artifact due to the the copper loop was performed. The artifact was demonstrated experimentally to result from perturbations of the transmit and receive sensitivities of the RF coil. Theoretical calculations of these perturbations showed excellent agreement with experimental results. With an understanding of the artifact mechanism, methods for correcting the RF‐induced eddy current artifact were applied.
Mr angiography artifact due to metal joint of ventriculoperitoneal shunt mimicking severe carotid stenosis
Authors: Kuta A. John , Smoker Wendy R. K. , Cole Timothy J. , Beskin Robert R.
Published: March 2007

An artifact due to the metal joint of a ventriculoperitoneal shunt resulted in a diagnosis of severe internal carotid artery stenosis at magnetic resonance angiography. Conventional x‐ray angiography showed the presence of the metal joint and revealed that the artery was not stenotic.
Surface coil MR imaging of the human brain with an analytic reception profile correction
Authors: Moyher Susan E. , Vigneron Daniel B. , Nelson Sarah J.
Published: March 2007

An analytic correction method was developed and applied to correct the signal intensity nonuniformity caused by the inhomogeneous reception profile of surface coils used—because of their higher sensitivity—for magnetic resonance imaging of the brain at 1.5 T. The reception profile was analytically modeled by using the Blot–Savart law. The correction considerably improved visual interpretation of the images by modeling and removing the dependence of signal intensity on distance from the coil. The method can be used for single or multiple coils of any planar geometry and in any orientation. Application of this technique allows imaging of the brain with surface coils, yielding increased resolution and signal‐to‐noise ratio, without the penalty of image nonuniformity.
Unsuppressed fat in the right anterior diaphragmatic region on fat‐suppressed T2‐weighted fast spin‐echo MR images
Authors: Yoshimitsu Kengo , Varma Datla G. K. , Jackson Edward F.
Published: March 2007

The authors retrospectively evaluated magnetic resonance Images of the abdomen obtained In 52 consecutive patients. All cases included fast spinecho (FSE) T2‐weighted images acquired with a frequency‐selective fat saturation technique. All imaging was performed with a 1.5‐T unit. In 42 patients (81%), fat was not suppressed in the right anterior diaphragmatic region on the T2‐welghted FSE images with fat suppression. In 11 (26%) of these 42 patients, subcutaneous fat adjacent to the unsuppressed anterior diaphragmatic fat was well suppressed. Hence, the fat In the diaphragmatic region mimicked fluid or peritoneal implants. The cause of the artifact appears to be the juxtaposition of liver, fat, and lung parenchymal air within a small anatomic space, creating a localized inhomogeneity of the magnetic field and susceptibility effects. Radiologists should be aware of this phenomenon to prevent confusion of an artifact with fluid or neoplasms.
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‐flight 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.
Delineation of pancreas with MR imaging: Multiobserver comparison of five pulse sequences
Authors: Mitchell Donald G. , Winston Corrine B. , Outwater Eric K. , Ehrlich Saundra M.
Published: March 2007

The authors compared five magnetic resonance (MR) imaging pulse sequences for their ability to depict the pancreas in 59 patients, each evaluated with at least two of the five sequences. Focal pancreatic carcinomas were present in eight patients. The five sequences were T1‐weighted spin echo (T1‐SE), fat‐suppressed T1‐SE (T1‐FS). T1‐weighted gradient echo (T1‐GRE). T2‐weighted SE (T2‐SE), and T2‐weighted fast spin echo (T2‐FSE). Using repeated‐measures analysis, three blinded observers independently reviewed 198 separate MR imaging series and rated them on a 5‐point scale with regard to image quality and depiction of pancreatic borders and the number of sections containing pancreatic and common bile ducts. The most superior and most inferior sections containing pancreas were recorded for each sequence in each patient. The results were compared with analysis of variance, and interobserver agreement was measured with the intraclass correlation coefficient (ICC). For image quality, all sequences were rated good to excellent, with the T1‐SE sequence having the highest rating. For clarity of pancreatic borders, however, the T1‐FS sequence was rated significantly higher (P<.006) than the other sequences; the T2‐SE sequence was least satisfactory. Common bile and pancreatic ducts were seen in the most sections with the T2‐FSE sequence. There were no significant differences regarding identification of the most superior and inferior sections containing pancreas, and the ICC was high (.91–.97) for all sequences. For detecting focal carcinomas, no single pulse sequence was sufficient.
Multiparametric display of spin‐echo data from MR studies of brain
Authors: Alfano Bruno , Brunetti Arturo , Arpaia Margherita , Ciarmiello Andrea , Covelli Eugenic M. , Salvatore Marco
Published: March 2007

A magnetic resonance (MR) image processing technique that uses a single color image for simultaneous presentation of spin‐echo information and its application to MR studies of the brain is described. Relaxation rate and proton‐density maps were calculated from 160 brain MR studies performed at 1.5 and 1.0 T with standard spin‐echo sequences. Maps were fused into single color images, with R1, R2. and proton density coded, respectively, by red, green, and blue. The possibility of standardizing the technique was evaluated. Comparative analysis of color and conventional MR images of white matter disease and brain tumors was performed to assess intra‐ and interob‐server variability. Unequivocal and reproducible chromatic characterization of normal brain structures and a variety of lesions was obtained. Intra‐and interobserver analysis showed that color images can be used as a diagnostic tool. The technique may provide a simplified and timesaving approach for interpretation and presentation of brain MR studies.
MR imaging of viscoelastic properties
Authors: Lewa Czeslaw J. , de Certaines Jacques D.
Published: March 2007

Mechanical waves in magnetic resonance imaging, which have been suggested for possible clinical applications, were analyzed with regard to imaging of the viscoelastic properties of large objects. The method is based on the Larmor frequency modulation caused by the application of mechanical waves. Possible clinical applications include all diseases that result in a change in the mechanical properties of biologic tissues (eg, atherosclerosis).
Pancreatic signal intensity on Tl‐ weighted fat saturation MR images: Clinical correlation
Authors: Winston Corrine B. , Mitchell Donald G. , Cutwater Eric K. , Ehrlich Saundra M.
Published: March 2007

To determine whether signal intensity (SI) of the pancreas that was less than that of liver on Tl‐ weighted fat‐suppressed (T1FS) magnetic resonance (MR) images could be used to help predict the presence of pancreatic disease, three blinded independent observers graded pancreatic SI relative to liver and/or renal cortex in 89 patients on T1PS images. Results were correlated with patient age and diagnosis. Among the 47 patients with a clinically normal pancreas, pancreatic SI was higher than that of liver in 42 and equal to that of liver in the rest, none of whom had evidence of fatty pancreas. These five patients had a mean age of 71 years, compared with 55 years for patients whose pancreas was more intense than liver (P=.02). Of the 42 patients with a clinically abnormal pancreas, only eight had pancreatic SI higher than that of liver. The positive predictive value for normal pancreas of an SI higher than that of liver was 84% and the positive predictive value for abnormal pancreas of an SI less than or equal to that of liver was 88%, with an overall accuracy of 86%. If normal pancreatic SI is defined as higher than that of liver for patients younger than 60 years and as equal to or higher than that of liver for patients older than 60 years, the positive predictive value of normal SI becomes 76%, the positive predictive value of decreased SI becomes 100%, and the overall accuracy becomes 83%. Pancreatic SI less than that of liver correlates highly with pancreatic disease, especially in younger patients. Mildly decreased pancreatic SI, equal to that of nondiseased liver, is common in older persons without clinically apparent pancreatic disease.
MR imaging of myositis ossificans: Variable patterns at different stages
Authors: Shirkhoda Ali , Armin Ali‐Reza , Bis Kostaki G. , Makris John , Irwin Ronald B. , Shetty Anil N.
Published: March 2007

Five patients with a palpable mass at presentation underwent magnetic resonance (MR) imaging. The final diagnosis was myositis ossificans (MO). MR imaging features, particularly after injection of gadopentetate dimeglumine, mimicked those of an inflammatory mass or neoplasm. The lesions were excised in three patients, and the Images were correlated with histologic findings. Three different appearances were noted on MR images, corresponding to the stages of maturation of MO. Two cases Involved early‐stage lesions, and Tl‐weighted MR images showed a mass with homogeneous intermediate signal intensity. Both lesions showed rim enhancement after contrast agent injection and high signal intensity on T2‐weighted images. Pathologic specimens demonstrated stroma with masses of spindle cells in which osteoid production was interspersed. The enhanced rim of the lesion mimicked the expected MR appearance of an abscess or necrotic tumor. Areas of enhancement in adjacent muscle were also seen on postcontrast T1‐weighted images. Intermediate‐stage MO was present in one case; there was evidence of a thin rim of calcification on plain radiographs and fatty changes in the lesion on T1‐weighted Images, corresponding with histologic findings. One case of a mature lesion showed a considerable degree of peripheral calcification both on MR images and at histology. MR imaging is nonspecific in the diagnosis of early‐stage MO.
Validation of cine phase‐contrast MR imaging for motion analysis
Authors: Lingamneni Anila , Hardy Peter A. , Powell Kimerly A. , Pelc Norbert J. , White Richard D.
Published: March 2007

The accuracy of cine phase‐contrast magnetic resonance (MR) imaging for motion analysis was evaluated. By using a rotating phantom and postprocessing algorithm for phase tracking, errors arising during data acquisition were identified and compensation methods were developed. A spatially varying background phase offset in the velocity images was found to be due to eddy current‐induced fields. The magnitude of the offset was in the range of 0–20 cm/sec, which is of the same order of magnitude as cardiac contractile velocities. Background offset is thus an important source of error in tracking cardiac motion. Study of different tracking algorithms revealed the need for an integration scheme using motion terms higher than velocity. Also, considerable improvement in the accuracy and stability of the predicted trajectories was obtained by averaging the trajectories proceeding both forward and backward in time from the starting point. With the algorithm developed, the motion of the phantom was tracked through a complete rotation of the phantom to an accuracy of 2 pixels.
Accuracy of MR phase contrast velocity measurements for unsteady flow
Authors: Frayne Richard , Steinman David A. , Rutt Brian K. , Ethier C. Ross
Published: March 2007

The accuracy of MR phase contrast (PC) velocity measurements for unsteady flow has been quantitatively assessed. Spatially resolved velocity fields were measured in a long straight tube using a gated PC technique. and the resulting MR PC velocity data were compared with velocities derived from the analytic Womeraley solution to the Navier‐Stokes equations governing fluid flow. The overall root‐meansquare (rms) difference between the measured and analytic velocities was 1.6 cm s−1 for nominally sinusoidal flow waveforms with peak velocities ranging from 51.6 cm s−1 to 59.8 cm s−1 This rms difference corresponded to 7.5% of the mean fluid velocity, which is similar to the cited accuracy of approximately 5% for MR PC velocimetry for steady flows. Linear regression between the PC velocity measurements and the velocities obtained using the analytic expression was highly significant (r2 = 0.997) and yielded a slope of 0.998, close to the expected value of 1. We conclude that the gated MR PC velocity measurements in unsteady flow are accurate.
Unusual MR features in a case of completely thrornbosed giant aneurysm of the posterior cerebral artery
Authors: Rastogi H. , Gupta R. K. , Gujral R. B. , Jain V. K. , Pandey R.
Published: March 2007

An unusual case of completely thmmbosed giant aneurysm of the left posterior arebrsl artery, ohowing much morc lors of signal on T2‐wdghtcd imagca compared with T2*‐wdghtcd imagea in the periphuy d the thrombus ie pnmted. pocuible mcchadam of this preferential dgml loss on T2‐ weighted images is discussed.
Imaging of ovarian cancer
Authors: Forstner Rosemarie , Chen Min , Hricak Hedvig
Published: March 2007

Cross sectional imaging continues to play an increasingly important role in ovarian cancer diagnosis, staging, and treatment follow‐up. Screening for ovarian cancer remains a controversial subject. The combined use of clinical examination, CA‐125, and endovaginal ultrasound (US) are being advocated for high risk patients but consensus recommendation for screening awaits further studies. in characterization of an ovarian neoplasm US is indisputedly the primary imaging approach. Only when US is inconclusive are further studies warranted. Magnetic resonance imaging (MRI) is generally preferred to computer tomography (CT). A prospective MRI‐CT clinical trial has not been performed as yet. Preoperative staging by imaging is slowly gaining its acceptance. This is mostly due to the awareness of the difficulties and inaccuracy in surgical staging when unsuspected extensive disease is present. Furthermore, in known resectable ovarian cancer, primary chemotherapeutic cytoreduction may be a better treatment option. Accuracy of CT and MRI in staging ovarian cancer is similar. CT, however, is faster, more widely available, and less expensive; these are important attributes that are decisive in this time of health reimbursement constraints.
Ex Vivo Evaluation of Ferromagnetism, Heating, and Artifacts of Breast Tissue Expanders Exposed to a 1.5‐T MR System
Authors: Pagan Linda‐Lynn , Shellock Frank G. , Brenner R. James , Rothman Barry
Published: March 2007

Three breast tissue expanders were evaluated for compatibility with MR imaging (1.5 Tesla). The metallic components of the breast tissue expanders were shown to be nonferromagnetic, heating .2°C and the artifacts varied. These results indicate that MR procedures may be performed safely in patients with these implants; however, artifacts may obscure Implant leaks or breast lesions if located near and metal portion of the breast tissue expanders.
Hyperparathyroidism: A comparison of sestamibi scintigraphy, mri, and ultrasonography
Authors: Numerow Leonard M. , Morita Eugene T. , Clark Orlo H. , Higgins Charles B
Published: March 2007

For patients with persistent or recurrent hyperpara‐thyroldism, parathyroid imaging is indicated to confirm the presence of abnormal parathyroid gland(s) and identify their location. These imaging techniques are being modified constantly and newer methods have been developed. Sestamibi scintigraphy, MRI and sonography were compared in 23 patients with persistent or recurrent hyperparathyroidism. Preoperative 99m‐Technetium Sestamibi (MIBI), MRI and ultraaono‐graphic (US) studies of 23 patients with 25 histopatho‐logically confirmed abnormal parathyroid glands were compared, using independent prospective interpretations. All patients had been operated upon previously for hyperparthytroidism. Accuracy of various combinations of MRI. MIBI, and US also were calculated. The results are shown for all abnormal glands (n = 25): sensitivities and accuracies were 88 and 84% for MRI. 80 and 80% for MIBI. and 58 and 44% for US. For only parathyroid adenomas (n = 18). sensitivities and accuracies were 89 and 89% for MRI, 94 and 94% for MIBI. and 58 and 39% for US. Finally, for parathyroid hyperplasla (n = 7 glands in five patients), sensitivities and accuracies were 83 and 71% for MRI. 43 and 43% for MIBI, and 57 and 57% for US. Either MIBI or MRI results were significantly better for detecting abnormal parathyroid glands than US (P <0.01), but MRI and MIBI were not statistically different. Combining MRI and MIBI produced a combined accuracy of 92%, whereas combining either of these tests with US did not improve on the accuracy of either test alone. In conclusion, for patients with persistent or recurrent hyperparathyroidism, MRI and MIBI are equally accurate for detecting abnormal parathyroid glands, and the combination of both tests may be more accurate than either test alone.
Paramagnetic polymerized liposomes as new recirculating MR contrast agents
Authors: Storrs Richard W. , Tropper FrançOis D. , Li Henry Y. , Song Curtis K. , Sipkins Dorothy A. , Kuniyoshi Jeremy K. , Bednarski Mark D. , Strauss H. William , Li King C. P.
Published: March 2007

We describe a well‐tolerated blood pool contrast agent with extended reclrculatory half‐life based on paramagnetic polymerized liposomes (PPLs). PPLs were constructed from a new type of polymerizable lipid molecule that has a derivative of gadopentetate dimeghimine as the hydrophilic head group and diacetylene groups in the hydrophobia acyl chains, which cross‐link when irradiated with ultraviolet (UV) light. Biodistributlon, blood pool half‐life, and MR image enhancement were determined for PPLs composed of 10% of the gadopentetate dimeglumine lipid and 90% of ditricosadiynoyl tricosadiynayl phospha‐tidylcholine (DAPC) at a dose of 0.015 mmnol Gd+3/kg in rats. In T1‐weighed MR images (TR/TE = 400/18 msec), an average signal enhancement of 34% in the kidneys and 20% in the liver was observed, which persisted for at least 90 minutes after administration of the PPLs. Biodistribution studies using radiolabe‐led PPLs confirmed that 80% of the injected dose remained in the blood pool after 2 hours. The half‐life of elimination from the blood pool was 19 hours. The preparation was well tolerated in rats and produced similar MR contrast enhancement of the blood pool as produced by other liposome contrast agents. However, the half‐life of PPL elimination from the blood pool was prolonged relative to other liposome systems.
Nuclear magnetic relaxation dispersion studies of water‐soluble gadolinium(iii)‐texaphyrin complexes
Authors: Geraldes C. F. G. C. , Sherry A. D. , Vallet P. , Maton F. , Muller R. N. , Mody T. D. , Hemmi G. , Sessler J. L.
Published: March 2007

Water proton 1/T1 nuclear magnetic relaxation dispersion (NMRD) profiles were measured for a water‐soluble gadolinium(III) texaphyrin (Gd‐tex) complex as a function of temperature and in the presence and absence of 5% human serum albumin (HSA). Upon dissolving the complex in water (0.259 mM), the water relaxivity values decreased with time but remained higher than those of free Gd3+(aq)at all fields. Concurrent measurements of free Gd3+ using metallochromic dyes indicated that demetallation of the texaphyrin did not occur over a period of several days at 37°C. The high relaxivity values and shape of the NMRD profile of this complex may be ascribed to a combination of large water coordination number (q estimated at 3.5) and long TR. Upon mixing an aqueous solution of the complex with 5% HSA, the low‐field water relaxivity slightly decreased whereas the high‐field relaxivity Increased relative to the free complex in water, and the relaxivities became nearly independent of temperature. These observations indicate that water exchange between the inner coordination sphere of Gd‐tex and bulk water becomes limiting in the presence of HSA.
Three‐dimensional triple quantum‐filtered 23na imaging of rabbit kidney with weighted signal averaging
Authors: Bansal Navin , Seshan Viswanathan
Published: March 2007

Low signal‐to‐noise ratio (SNR) has been the main obstacle to multiple quantum‐filtered 23Na imaging becoming an important technique for biologic and clinical applications. Through computer simulations and phantom experiments, we show that the SNR in 23Na imaging can be substantially improved by weighted signal averaging. Three‐dimensional single quantum and triple quantum (TQ)‐filtered 23Na images of an externalized rabbit kidney were collected with this technique. The TQ‐filtered image did not show any signal when the animal was alive. However, upon sacrificing the animal, the renal cortex became clearly visible without any significant increase in signal from the medullary region. This increase in TQ‐flltered signal in the renal cortex may be caused by an increased concentration of intracellular Na+ in the large intracellular space present herein, compared with the medulla. To our knowledge, this study represents the first example of three‐dimensional TQ‐filtered 23Na image of a biological sample.
Magnetization transfer on in vitro circulating blood: Implications for time‐of‐flight MR angiography
Authors: Dousset Vincent , Degrèze Philippe , Mièze Stéphane , Sesay Musa , Basse‐Cathalinat Bernard , Caillé Jean‐Marie
Published: March 2007

Effects of magnetization transfer were evaluated In vitro on circulating blood. Various velocities were tested from 0 to 72 cm/second. Decrease signal intensity caused by magnetization transfer effects was inversely proportional to inflow velocity. It reached 10% at very low velocities and disappeared at velocities higher than 30 cm/second.
Identification and characterization of TSAP, a novel gene specifically expressed in testis during spermatogenesis
Authors: Bin Li , Gang Wu , Hu Jiarui , Gong Wuming , Yue Mingjin , Song Ping
Published: March 2007

Through in silico screens, we have identified many previously uncharacterized genes that display similar expression patterns as the mouse Dazl gene, a germ line‐specific marker. Here, we report the identification and characterization of one of these novel genes. TSAP gene encodes a protein with 350 amino acids and contains five ankyrin repeats and a PEST sequence motif. Furthermore, we have generated an anti‐TSAP antibody and have used three different approaches (RT‐PCR, in situ hybridization, and immunohistochemistry) to investigate the expression profiles of TSAP mRNAs and proteins. TSAP is specifically expressed in testis, but not in other tissues such as ovary. Within the testis, TSAP is detected 10 days after birth and is mainly expressed in spermatocytes (ST) and later stage of germ cells, but not in spermatogonia (SG) or sertoli cells. Therefore, TSAP protein likely plays a role in spermatogenesis. Mol. Reprod. Dev. 74: 1141–1148, 2007. © 2007 Wiley‐Liss, Inc.