bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of mitral regurgitation with MR phase‐velocity mapping using a control volume method
Authors: Chatzimavroudis George P. , Oshinski John N. , Pettigrew Roderic I. , Walker Peter G. , Franch Robert H. , Yoganathan Ajit P. 
Published: March 2007

AbstractReliable diagnosis and quantification of mitral regurgitation are important for patient management and for optimizing the time for surgery. Previous methods have often provided suboptimal results. The aim of this in vitro study was to evaluate MR phase‐velocity mapping in quantifying the mitral regurgitant volume (MRV) using a control volume (CV) method. A number of contiguous slices were acquired with all three velocity components measured. A CV was then selected, encompassing the regurgitant orifice. Mass conservation dictates that the net inflow into the CV should be equal to the regurgitant flow. Results showed that a CV, the boundary voxels of which excluded the region of flow acceleration and aliasing at the orifice, provided accurate measurements of the regurgitant flow. A smaller CV provided erroneous results because of flow acceleration and velocity aliasing close to the orifice. A large CV generally provided inaccurate results because of reduced velocity sensitivity far from the orifice. Aortic outflow, orifice shape, and valve geometry did not affect the accuracy of the CV measurements. The CV method is a promising approach to the problem of quantification of the MRV.
Slice‐selective fat saturation in MR angiography using spatial‐spectral selective prepulses
Authors: Forster Jürgen , Schick Fritz , Breuer Johannes , Sieverding Ludger , Lutz Otto 
Published: March 2007

AbstractPresaturation of fat signals by frequency‐selective radiofrequency (RF) pulses is often applied in MR angiography to improve the visualization of the blood vessels. Unfortunately, standard fat saturation methods might cause a considerable reduction of the blood signal in the measured slices. This effect is caused by an attenuation of blood magnetization in remote tissue regions with water protons showing a similar Larmor frequency as the fat protons in the recorded slice. The affected blood water protons subsequently flow into the recorded slice and provide low signal intensity. Suitable spatial‐spectral selective methods for slice‐selective fat saturation were developed to avoid this unwanted effect. A spatial‐spectral fat saturation technique was compared with a corresponding only spectrally selective approach. Both saturation techniques were included in a standard two‐dimensional (2D) cine sequence and applied in angiographic examinations of the thighs. The results indicate that spatial‐spectral saturation (acting slice selectively) leads to a clearly higher blood signal intensity in fat‐suppressed MR angiography compared with standard techniques, especially in measurements performed during the systolic phase of the cardiac cycle.
Variations in blood flow waveforms in stenotic renal arteries by 2D phase‐contrast cine MRI
Authors: Westenberg Jos J. M. , Wasser Martin N. J. M. , van der Geest Rob J. , Pattynama Peter M. T. , de Roos Albert , Vanderschoot Jan , Reiber Johan H. C. 
Published: March 2007

AbstractWaveform variations in blood flow measurements through stenotic renal arteries have been reported already with echo Doppler studies. We studied these variations with MRI in 14 patients (mean age, 60 years) with suspected renal arterial stenosis (24 patent arteries, four occluded). Flow measurements were successful in 15 arteries and unsuccessful in nine, due to practical limitations. Seven healthy younger volunteers (mean age, 28 years) and five healthy older volunteers (mean age, 58 years) were recruited for comparison purposes. In patients, the severity of stenoses was also assessed by digital subtraction angiography and intraarterially measured transstenotic pressure drops. We found flow patterns to be statistically significantly (P< 0.01) age‐related. Younger healthy subjects showed shorter wave duration, higher diastolic flow, and total blood flow per minute. Also, with increasing stenosis severity, the systolic wave became more damped and the systolic wave duration became statistically significantly (P> = .03) longer.
Contrast‐enhanced 3D MRA with centric ordering in k space: A preliminary clinical experience in imaging the abdominal aorta and renal and peripheral arterial vasculature
Authors: Shetty Anil N. , Bis Kostaki G. , Vrachliotis Thomas G. , Kirsch Matthias , Shirkhoda Ali , Ellwood Robert 
Published: March 2007

AbstractThe objective of this study was to determine the clinical utility of a contrast‐enhanced, centric reordered, three‐dimensional (3D) MR angiography (MRA) pulse sequence in imaging the abdominal aorta and renal and peripheral lower extremity arteries. Twenty‐eight MRA studies were performed on 23 patients and four volunteers at 1.5 T using a 3D contrast‐enhanced, centric reordered pulse sequence. In 20 patients, the abdominal aorta and renal arteries were imaged, and in seven patients, the lower extremity arteries were imaged. In 19 patients, a total of 51 renal vessels were evaluated (33 renal arteries using .1 mmol/kg of gadopentetate dimeglumine and 18 renal arteries using .2 mmol/kg of gadoteridol). A total of 70 peripheral arterial segments were assessed using .2 mmol/kg of gadoteridol. Correlation with conventional angiography was made for the following 14 cases: renal artery stenosis (four cases), abdominal aortic stenosis (one case), arteriovenous fistula in a transplant kidney (one case), renal arteriovenous malformation (one case), common iliac artery aneurysms (one case), and peripheral lower extremity (six cases). Of the 70 peripheral arterial segments evaluated, in 35, there was correlation with x‐ray angiography. The mean percent of aortic signal enhancement was significantly higher in the .2 mmol/kg dose group (370.8 ± 190.3) than in the .1 mmol/kg dose group (184.5 ± 128.9) (P = .02). However, there was no apparent difference between the two doses for visualization of the renal and accessory renal arteries. There was concordance between the contrast‐enhanced 3D MRA studies and conventional angiography in all cases of renal artery and peripheral arterial stenoses and occlusions, including visualization of reconstituted peripheral arterial segments. There was no evidence of spin dephasing effects at sites of stenoses on the 3D contrast‐enhanced MRA studies. Contrast‐enhanced, centric reordered, 3D MRA can rapidly image the abdominal aorta and renal and accessory renal arteries, as well as peripheral lower extremity arteries, with high resolution. Accurate depiction of the vascular lumen at sites of stenosis is made because of the lack of spin dephasing effects, even with hemody‐namically significant stenoses. Additional larger clinical trials are required with this promising technique.
Characterization of atherosclerotic plaque components by high resolution quantitative MR and US imaging
Authors: Raynaud Jean‐Sébastien , Bridal S. Lori , Toussaint Jean‐François , Fornès Paul , Lebon Vincent , Berger Geneviève , Leroy‐Willig Anne 
Published: March 2007

AbstractHigh resolution MRI at 3 T and US imaging at 50 MHz were used for atherosclerotic plaque characterization. For 14 excised segments of human arteries, conventional MR and US images, quantitative MR T2 maps, US integrated attenuation (IA) maps, and histologic sections were produced and compared. The MR T2 and US attenuation mean values estimated in selected regions of interest were related with tissue type as identified on histologic sections. Significant distinction between media or collagen and lipid or collagen lipidic plaque was achieved with both techniques (MR: P < .001; US: P < .01). Significant distinction was obtained between media and collagen (P < .0001) and between iliac and aortic media (P < .05) with MR T2 but not with IA. MR and US native and parametric images, with different sensitivities to tissue type, provide complementary information useful for quantitative plaque characterization.
High resolution MRI of MCF7 human breast tumors: Complemented use of iron oxide microspheres and Gd‐DTPA
Authors: Furman‐Haran Edna , Margalit Raanan , Grobgeld Dov , Degani Hadassa 
Published: March 2007

AbstractThe differential capacity of iron oxide microspheres and of gadolinium‐diethylenetriamine pentaacetic acid (Gd‐DTPA) to serve as contrast agents that can map the microcirculation of MCF7 human breast cancer implanted in nude mice has been examined by high resolution MRI. Modulation of signal intensity in T2*‐weighted, gradient‐echo images after iron oxide administration and the temporal signal enhancement after Gd‐DTPA administration were monitored and analyzed at a spatial resolution of 98 × 98 × 500 μm and 195 × 390 × 1,000 μm, respectively. The pathophysiologic features revealed in the contrast‐enhanced images were analyzed in reference to those obtained from the corresponding high resolution T2‐weighted, spin‐echo images and from histologic sections stained with hematoxylin and eosin and with an endothelial cell marker. The results showed that iron oxide microspheres can aid in the characterization of gross histopathologic features and in the assessment of the distribution of the microvasculature, whereas Gd‐DTPA estimates the permeability of the microvessels to this agent and determines the cellularity (cell volume fraction) in the vicinity of the vessels.
The value of respiratory triggered T2‐weighted turbo spin‐echo imaging of the liver using a phased array coil
Authors: Namimoto Tomohiro , Yamashita Yasuyuki , Mitsuzaki Katsuhiko , Takahashi Mutsumasa 
Published: March 2007

AbstractThe purpose of this study was to evaluate the value of the respiratory triggered turbo spin‐echo (TSE) technique for T2‐weighted MRI of liver lesions. Fifty‐nine patients (32 men, 27 women; mean age, 63.3 years) with focal hepatic lesions were prospectively studied with MRI at 1.5 T with use of a body phased array coil. In the first 15 patients, breath‐hold TSE, respiratory triggered TSE, and conventional nonrespiratory triggered TSE T2‐weighted imaging were compared. Because nonrespiratory triggered TSE imaging was significantly inferior (P < .01) to breath‐hold or respiratory triggered images, breath‐hold and respiratory triggered TSE T2‐weighted images were compared in the remaining 44 patients. Images were analyzed quantitatively by measuring the liver signal‐to‐noise ratio and the lesion‐liver and spleen‐liver contrast‐to‐noise ratios and qualitatively by evaluating the lesion conspicuity, liver parenchymal homogeneity, and sharpness of intrahepatic vessels. The imaging time was 26 seconds for breath‐hold TSE imaging, 49 to 219 seconds (mean, 149 seconds) for the respiratory triggered TSE imaging, and 79 to 379 seconds (mean, 239 seconds) for the nonrespiratory triggered TSE imaging. Quantitatively, the signal‐to‐noise ratio of the liver for breath‐hold imaging was comparable to that for respiratory triggered imaging. The lesion‐liver and liver‐spleen contrast‐to‐noise ratios for the respiratory triggered images were greater by 37% and 39%, respectively, than for the breath‐hold T2‐weighted TSE images. Qualitatively, the respiratory triggered images showed lower frequency of image artifact, better lesion conspicuity, and greatly superior depiction of intrahepatic structures compared with the breath‐hold T2‐weighted TSE images. The respiratory triggered T2‐weighted TSE technique provides better quality liver images than the breath‐hold TSE technique or nonrespiratory triggered technique within a reasonable acquisition time.
Dynamic evaluation of the hepatic uptake and clearance of manganese‐based MRI contrast agents: A 31P NMR study on the isolated and perfused rat liver
Authors: Colet Jean‐Marie , Elst Luce Vander , Muller Robert N. 
Published: March 2007

AbstractThis spectroscopic study compares the mechanisms of the hepatic uptake of manganese chloride (MnCl2) and manganese dipyridoxyl diphosphate (MnDPDP). Alterations of the phosphorus‐31 (31P)‐NMR spectrum of the intracellular adenosine 5′‐triphosphate (ATP) are used to monitor the internalization of manganese by the isolated and perfused rat liver. Mn2+ delivered as MnCl2 in the perfusate rapidly enters the hepatocytes, where it strongly interacts with ATP, inducing a broadening of the 31P lines. The inhibition of the process by nifedipine confirms that manganese ions cross the cellular membrane at least partly through Ca2+ channels. MnDPDP induces weaker but still significant changes of the ATP spectrum. The inability of pyridoxine to compete for the uptake of manganese confirms that the vitamin B6 carrier is not involved in the internalization process of the paramagnetic complex. Finally, preincubation of MnDPDP with blood does not increase the extent of the dissociation. The alterations of the 31P spectrum of the liver subsequent to the administration of MnDPDP are attributable to a fraction of free Mn2+ released by the chelate and delivered to the hepatocytes.
Sequential use of ferumoxide particles and gadolinium chelate for the evaluation of focal liver lesions on MRI
Authors: Semelka Richard C. , Lee Joseph K. T. , Worawattanakul Suvipapun , Noone Tara C. , Patt Richard H. , Ascher Susan M. 
Published: March 2007

AbstractThis study describes the sequential use of ferumoxide (superparamagnetic iron oxide) particles and nonspecific extracellular gadolinium chelate (Gd) for evaluation of focal liver lesions on MRI to evaluate order of contrast administration and imaging effect of the first contrast agent on sequences acquired after the second contrast agent. Thirteen patients underwent MR examinations that included ferumoxide and Gd. The order and timing of administration were as follows: separate sessions (three patients; Gd study 4‐19 days before ferumoxide study), same session, Gd first (seven patients; Gd study 1‐2 hours before ferumoxide study), and same session, ferumoxide first (three patients; ferumoxide administered less than 1 hour before Gd study). Postcontrast sequences were reviewed in a randomized, blinded fashion by two separate investigators. Determination was made regarding whether (a) the presence of the first agent administered could be detected on sequences obtained after the second agent and (b) the presence of the first agent interfered with the image quality of those sequences. No evidence for the presence of Gd was appreciated by either observer on postferumoxide sequences acquired in separate session studies. In same session, Gd first studies, the presence of Gd was observed in six of seven patients on T1‐weighted spoiled gradient‐echo (SGE) images obtained after ferumoxide administration. The presence of Gd was not apparent in seven of seven patients on T2‐weighted fat‐suppressed images obtained after ferumoxide. In same session, ferumoxide first studies, the presence of ferumoxide was appreciated on post‐Gd sequences in two of three patients. The presence of ferumoxide did not appreciably diminish image quality on those sequences. Exact agreement was achieved by the independent investigators. Our results suggest that Gd and ferumoxide can be administered sequentially within one study session without substantial loss of diagnostic information obtained on sequences performed after administration of the second contrast agent. Administrating Gd first resulted in less of an effect of the visualization of the first agent on sequences acquired after the second agent.
Uptake of mangafodipir trisodium in liver metastases from endocrine tumors
Authors: Wang Chen , Ahlström Håkan , Eriksson Barbro , Lönnemark Maria , McGill Steven , Hemmingsson Anders 
Published: March 2007

AbstractThe purpose of the study was to investigate retrospectively whether mangafodipir trisodium (MnDPDP) can enhance the liver metastases from endocrine tumors. Thirteen patients with endocrine tumors and liver metastases underwent T1‐weighted spin‐echo (SE) and turbo gradient‐echo (GRE) MRI conducted before and 20 to 60 minutes after iv infusion of MnDPDP. Additional 24‐hour‐delay scans were performed in 8 of 13 patients. MR signal intensity (SI) was measured in liver parenchyma and metastases, which was then related to that of paraspinal muscle. A total of 30 lesions on precontrast and postcontrast images and 18 lesions on 24‐hour‐delay images were measured. An enhancement by 49% in SE and 40% in GRE images (P = .0001) was observed in tumor tissues after MnDPDP infusion. In 24‐hour‐delay images, the SI of the lesions remained relatively high, but in liver parenchyma, it decreased significantly, and the tumor‐liver tissue contrast was reduced.
A three‐point dixon method for water and fat separation using 2D and 3D gradient‐echo techniques
Authors: Wang Yi , Li Debiao , Haacke E. Mark , Brown Jeffrey J. 
Published: March 2007

AbstractA water and fat separation technique based on a three‐point Dixon method using two‐dimensional (2D) and three‐dimensional (3D) gradient‐echo sequences and a new phase‐unwrapping approach is presented. Using velocity‐compensated sequences, three images, with water and fat protons in phase, opposed phase, and in phase, were acquired in an interleaved fashion for each phase‐encoding line of the image. A fast 2D scan permitted acquisition of images within a single breathhold, eliminating respiratory motion artifacts. The 3D sequence allowed coverage of a large region of interest with thin, contiguous slices. To correct field inhomogeneity effects, phase unwrapping was required. This was accomplished by comparing the corresponding pixels in the two water and fat in‐phase images on a pixel‐by‐pixel basis. This phase‐unwrapping approach is faster, more reliable, and requires less user interfacing than other methods. The water and fat separation method performed well in various parts of the body.
MRI of the foot and ankle: Diagnostic performance and patient acceptance of a dedicated low field MR scanner
Authors: Verhoek Guido , Zanetti Marco , Duewell Stefan , Zollinger Hans , Hodler Juerg 
Published: March 2007

AbstractThe objective of this study was to compare image quality and patient acceptance of a dedicated .2‐T MR system and a 1.0‐T whole body system. Forty‐one consecutive patients referred for MRI of the foot or ankle were prospectively examined with a dedicated .2‐T low field system and a 1.0‐T whole body system. Images were evaluated qualitatively by two observers and quantitatively using signal‐difference‐to‐noise ratios. The patients were interviewed with respect to positioning, examination time, noise, claustrophobia, confidence in the diagnosis, and willingness to repeat the examination, using a questionnaire. The qualitative score was significantly higher for the 1.0‐T system (2.6 vs 2.2 for reader 1 [P = .008] and 2.6 vs 1.7 for reader 2 [P < .0001]), respectively. The signal‐difference‐to‐noise ratios were also superior for the 1.0‐T MR system (2.96 vs .88, P < .0001). However, 96% of the lesions visualized at 1.0 T were also detected with the low field system. Patient acceptance was significantly better for the 1.0‐T MR scanner (48.6 vs 43.9, P = .007). Image quality of the dedicated low field system was inferior to the 1.0‐T system using objective parameters, and patients did not prefer the low field system. Although only 4% of lesions were missed in this series, the low field MR system can only be recommended when funding is limited and the available space is limited.
Chronic lymphocytic leukemia: Changes in bone marrow composition and distribution assessed with quantitative MRI
Authors: Lecouvet Frederic E. , Berg Bruno C. Vande , Michaux Lucienne , Scheiff Jean‐Marie , Malghem Jacques , Jamart Jacques , Maldague Baudouin E. , Michaux Jean Louis , Ferrant Augustin 
Published: March 2007

AbstractThe purposes of this study were (α) to determine the prevalence of bone marrow abnormalities in patients with chronic lymphocytic leukemia (CLL) using quantitative MR assessment of axial marrow composition and peripheral marrow distribution; (b) to assess the agreement between both quantitative MR methods and compare their sensitivities to detect marrow alterations; and (c) to correlate MR findings with clinical and laboratory parameters. Twenty‐nine consecutive patients with biopsy‐proven CLL were investigated on a .5‐T MR imager to determine bulk T1 relaxation times of the vertebral bone marrow and proportion of proximal femur surface area occupied by nonfatty marrow on coronal T1‐weighted MR images of one hip. Of the 29 patients, 12 (41%) had abnormal increase in lumbar marrow T1 values (>600 msec) and 16 (55%) had increased proportion of surface area occupied by non‐fatty marrow in the proximal femur (>+1 SD compared to normal values determined in sex‐ and age‐matched healthy subjects). The results of both quantitative MR methods were normal in 12 patients and abnormal in 11 patients (agreement, 79%). Patients with alterations in peripheral marrow distribution had significantly higher T1 relaxation times (P = .001) than those with normal peripheral marrow. Patients with abnormal marrow composition or distribution at MRI had significantly higher blood and marrow lymphocytosis than patients without these features. In conclusion, the agreement between both quantitative MR methods suggests a parallelism between changes in axial marrow composition and in peripheral marrow distribution in patients with CLL. The limits of quantitative MRI in CLL must be kept in mind, because quantitative MR methods failed to detect leukemic marrow infiltration in 41% of patients.
An automated measurement system for characterization of RF and gradient coil parameters
Authors: Boyer Jeffrey S. , Wright Steven M. , Porter Jay R. 
Published: March 2007

AbstractA fully automated laboratory‐based measurement system for characterization of coil system parameters is presented. This method uses an inexpensive personal computer (PC)‐controlled stepper motor positioning system in conjunction with a network/spectrum analyzer and an analog‐to‐digital converter (A/D) board that allows high resolution data acquisition in an unattended manner. A graphical interface was created for complete control of stepper motor movement, measurement, and data acquisition. The system is capable of performing a wide range of measurements that can, either individually or combined, characterize radiofre‐quency (RF) and gradient coils used in MRI. Measurement methods, theory, and results for conductor and shield current distributions, mutual impedance, and magnetic fields are given. Comparisons with theoretical calculations are included to validate the accuracy and utility of the system.
Placenta Accreta: MRI antenatal diagnosis and surgical correlation
Authors: Ha Taryn P. T. , Li King C. P. 
Published: March 2007

AbstractWe describe a case of a placenta previa accreta that was diagnosed antenatally by MRI with subsequent surgical confirmation. We show the advantages of ultrafast MRI single shot (SS) fast spin echo (FSE) techniques for accurate diagnosis with minimal scan time and fetal motion artifacts.