共查询到10条相似文献,搜索用时 187 毫秒
1.
Jose A. Goncalves Neto Ersan Altun Mohamed Elazzazi Georgeta D. Vaidean Matthew Chaney Richard C. Semelka 《Magnetic resonance imaging》2010
Purpose
To compare the extent of enhancement of abdominal organs as shown on subphases of hepatic arterial phase quantitatively between 1.5- and 3.0-T MRI among patients with various abdominal conditions.Materials and Methods
A total of 126 patients, of whom 68 were women (age range, 3–82 years; mean age, 48 years) and 58 were men (age range, 6–73 years; mean age, 50 years), were included in the study. Of 126 patients, 98 were scanned at 1.5 T and 28 were scanned at 3.0 T. The presence of one of three predefined subphases of hepatic arterial phase was determined on early post-gadolinium sequence in each patient by two reviewers in consensus. Extent of enhancement of the kidney, pancreas, spleen and liver on these subphases was determined quantitatively by measuring the signal intensities. Mann Whitney–Wilcoxon test was used to compare the contrast enhancement of organs on each subphase between 1.5- and 3.0-T MRI.Results
The kidney, spleen, pancreas and liver demonstrated 1.79- to 2.45-, 1.65- to 1.97-, 1.66- to 1.8- and 1.1- to 2.02-fold higher enhancement on the subphases of hepatic arterial phase at 3.0 T compared to 1.5 T, respectively. The differences in contrast enhancement were significant for the kidney, pancreas and spleen on all subphases between 1.5 and 3.0 T.Conclusion
The relative enhancement of the kidney, spleen and pancreas is consistently and significantly higher at 3.0 T than at 1.5 T in matched subphases of hepatic arterial enhancement. 相似文献2.
Pablo Bächler Natalia Pinochet Julio Sotelo Gérard Crelier Pablo Irarrazaval Cristián Tejos Sergio Uribe 《Magnetic resonance imaging》2013
Objective
The purpose of this study was to analyze flow patterns in the pulmonary circulation of healthy volunteers by using 4D flow magnetic resonance imaging.Materials and Methods
The study was approved by the local ethics committee and all subjects gave written informed consent. Eighteen volunteers underwent a 4D flow scan of the whole-heart. Two patients with congenital heart disease were also included to detect possible patterns of flow abnormalities (Patient 1: corrected transposition of great arteries (TGA); Patient 2: partial anomalous pulmonary venous return and atrial septal defect). To analyze flow patterns, 2D planes were placed on the main pulmonary artery (PA), left and right PA. Flow patterns were assessed manually by two independent viewers using vector fields, streamlines and particle traces, and semi-automatically by vorticity quantification.Results
Two counter-rotating helices were found in the main PA of volunteers. Right-handed helical flow was detected in the right PA of 15 volunteers. Analysis of the helical flow by particles traces revealed that both helices contributed mainly to the flow in the right PA. In the patient with corrected TGA helical flow was not detected. Abnormal vortical flow was visualized in the main PA of patient 2, suggesting elevated mean PA pressure.Conclusions
Helical flow is normally present in the main PA and right PA. 4D flow is an excellent tool to evaluate noninvasively complex blood flow patterns in the pulmonary circulation. Knowledge of normal and abnormal flow patterns might help to evaluate patients with congenital heart disease adding functional information undetectable with other imaging modalities. 相似文献3.
Jaime F. Mata Ugur BozlarJohn P. Mugler III Grady W. MillerStuart S. Berr Klaus D. Hagspiel 《Magnetic resonance imaging》2010
Purpose
Evaluate feasibility of using time-resolved and high-resolution, contrast-enhanced magnetic resonance angiography (MRA) at 7 T for characterization of an animal model of pulmonary embolism.Methods
MRAs were performed in five rabbits using a 7-T MR scanner. Preceding the MR studies, each rabbit underwent a pulmonary artery catheterization with balloon placement. Two doses of gadodiamide were injected: first during a time-resolved MRA, immediately followed by a high-resolution acquisition. Balloon was then deflated, permitting reperfusion for 5 min. A second dose was then injected and another high-resolution MRA acquired. Measurements of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel cross-sections down to fourth-order branches were made, among other parameters.Results
Occlusion was detected in all rabbits. Despite a TE of 0.58 ms for the time-resolved MRA, regions of nonuniform enhancement attributed to susceptibility effects at the 7-T field were observed in perfused lung. Mean SNR=7.5±3.3 and 134.2±46.5 for the lung and aorta, respectively, and mean CNR=126.7±46.4 for aorta versus lung were obtained. Diameters of vessels in lung that was never occluded were not statistically different from those in reperfused lung.Conclusion
Results show that time-resolved and high-resolution MRA of the lung are feasible at 7 T and provide high SNR, CNR and resolution, but TEs smaller than 0.58 ms are required to avoid susceptibility artifacts in time-resolved MRAs. 相似文献4.
Masaaki Hori Harushi Mori Shigeki Aoki Osamu Abe Tomohiko Masumoto Satoshi Kunimatsu Kuni Ohtomo Hiroyuki Kabasawa Nobuyuki Shiraga Tsutomu Araki 《Magnetic resonance imaging》2010
Object
Although three-dimensional (3D), high-spatial resolution susceptibility-weighted imaging (SWI) appears to be valuable in the evaluation of central nervous system gliomas, several evaluation methods are proposed in the literature. The purpose of this study was to evaluate the use of 3D SWI for grading intracranial gliomas with various analysis methods.Materials and Methods
Twenty-three patients suspected of having gliomas participated in this study. SWI was performed in addition to conventional MR sequences. In 15 cases, post-gadolinium enhanced SWI was also obtained. Imaging evaluation criteria were conventional grade, hypointensity ratio in the tumor-dominant structure of hypointensity on SWI (hemorrhage or vascular structure) and presence of abnormal enhancement surrounding the tumor.Results
Mean grading scores of conventional grade showed no statistically significant difference among WHO grades. Mean grading scores of hypointensity ratios in the tumor were higher for WHO Grades 3 and 4 than for lower grade tumors (P=.05, Mann–Whitney U test). Hemorrhagic foci were more frequently seen in the higher grade tumor. Post-contrast susceptibility-weighted images of five of 11 WHO Grade 3 and 4 cases showed bright enhancement surrounding the tumor, suggesting a breakdown of the blood–brain barrier.Conclusions
SWI at 3 T may be a useful method to analyze the structural characteristics of gliomas and to evaluate pathology in vivo. Assessment of hypointensity ratios in the glioma was the most preferable method in grading glioma. However, more studies, specifically concerning a suitable method for image analysis, are needed to establish SWI at 3 T as a useful tool in clinical routine. 相似文献5.
Jose A. Goncalves Neto Ersan Altun Georgeta Vaidean Mohamed Elazzazi Jeffrey Troy Sudha Ramachandran Richard C. Semelka 《Magnetic resonance imaging》2009
Purpose
The purpose of this study was to describe the subphases of early post-contrast enhancement of the liver, using vessel enhancement patterns, and correlate these findings with enhancement patterns of abdominal organs.Materials and Methods
A total of 114 patients who underwent gadolinium-enhanced abdominal magnetic resonance imaging examinations constituted the final study group, of which 56 were women (age range, 3–94 years; mean, 50 years) and 58 were men (age range, 6–85 years; mean, 54 years). Early post-contrast sequences in all patients were evaluated retrospectively by two reviewers for the determination of the presence of contrast enhancement in predetermined major vessels of the abdomen and qualitative and quantitative extent of enhancement of the renal cortex, spleen, pancreas and liver. Based on the overall findings, subphases of early contrast enhancement of the liver were described and quantitative extent of enhancement of organs was correlated with subphases of early contrast enhancement of the liver. Mann–Whitney U test and one-way unbalanced analysis of variance tests were used for the comparisons.Results
Early hepatic arterial phase was observed in 14/114 patients, mid-hepatic arterial phase in 23/114 patients, late hepatic arterial phase in 33/114 patients, splenic vein only hepatic arterial dominant phase in 20/114 patients and hepatic arterial dominant phase in 24/114 patients. There was an overall association between the subphases of enhancement and the quantitative extent of enhancement for all studied organs (P<.0001).Conclusion
The evaluation of vessel and organ enhancement patterns has allowed the characterization of five different subphases in early post-contrast enhancement of the liver. The quantitative extent of enhancement of abdominal organs also demonstrated significant correlation with these five subphases. 相似文献6.
Jason A. Pates Mustapha R. Hatab Donald D. McIntire F. Gary Cunningham Diane M. Twickler 《Magnetic resonance imaging》2010
Objective
The purpose of this study is to determine the feasibility of measuring total uterine blood flow in pregnancy using magnetic resonance imaging (MRI) technique.Methods
Uterine blood flow was determined in pregnant women in whom MRI was being carried out to assess a fetal anomaly. A two-dimensional time-of-flight magnetic resonance (MR) angiogram sequence was performed. Scout images and a peripherally gated phase contrast MR sequence were planned to study simultaneous blood flow in the uterine and ovarian arteries.Results
The MR pelvic angiogram sequence was completed in 13 women. The uterine arteries were visualized and their cross-sectional area determined. The complexity of the pelvic blood supply prevented the calculation of blood flow velocity and, thus, total uterine blood flow.Conclusion
The measurement of total uterine blood flow during pregnancy was not possible using our MR technique. The ovarian vessels were not consistently visualized. Doppler ultrasonography remains the best modality by which to estimate total uterine blood flow in pregnancy. 相似文献7.
Objective
The objective was to determine imaging features that distinguish small (≤3cm) solid pancreatic adenocarcinoma, neuroendocrine tumor (NET) and solid pseudopapillary tumor (SPT) on gadoxetic-acid-enhanced magnetic resonance imaging (MRI) and diffusion-weighed imaging (DWI).Materials and methods
Twenty-four adenocarcinomas, 10 NETs and 8 SPTs were retrospectively included. Two radiologists analyzed morphologic features, signal intensity of the tumors on MR images including DWI (b=800) and dynamic enhancement pattern with consensus. Tumor-to-parenchyma ratio and tumor apparent diffusion coefficients (ADCs) were quantitatively assessed.Results
All adenocarcinomas had an ill-defined margin and irregular shape, and more frequently had pancreatic duct dilatation compared with other tumors (P<.05). All SPTs and all but one of the adenocarcinomas (95.8%) had no arterial enhancement with progressively increased enhancement, whereas seven NETs (70%) had arterial enhancement with progressively decreased enhancement (P<.01). The mean value of tumor-to-parenchyma ratio on arterial and portal phases was significantly higher for NETs, and the mean value of tumor ADCs was significantly lower for SPTs than for other tumors (P<.05).Conclusions
Gadoxetic-acid-enhanced MRI may aid in differentiation between small adenocarcinomas, NETs and SPTs based on morphologic features with dynamic enhancement pattern in adenocarcinomas, dynamic enhancement pattern with tumor-to-parenchyma ration on arterial and portal phases in NETs, and dynamic enhancement pattern with lower ADC value in SPTs. 相似文献8.
Purpose
To compare peak enhancement (PE), determined from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and the magnetic resonance (MR) directionally-averaged apparent diffusion coefficient (Materials and Methods
MRI, MR spectroscopic imaging, DCE MRI and MR diffusion were evaluated in 17 untreated subjects with suspected or proven prostate cancer. PE andResults
The glandular-ductal tissues had lower PE [125±6.4 (% baseline)] and higherConclusions
The very different MR results in the glandular-ductal versus stromal-low ductal tissues suggest that these tissues have different underlying structure. These results support the hypothesis that Gd-DTPA does not enter healthy prostatic glands or ducts. This may explain the higher PE and lower9.
Chuen Y. Poon Julie M. Edwards C. John Evans Ashley D. Harris Beverly Tsai-Goodman Charlotte E. Bolton John R. Cockcroft Richard G. Wise Sailesh Kotecha 《Magnetic resonance imaging》2013
Purpose
To assess the feasibility of measuring pulmonary artery (PA) pulse wave velocity (PWV) in children breathing ambient air and 12% oxygen.Methods
Velocity-encoded phase-contrast MR images of the PA were acquired in 15 children, aged 9–12 years, without evidence of cardiac or pulmonary diseases. PWV was derived as the ratio of flow to area changes during early systole. Each child was scanned twice, in air and after at least 20 minutes into inspiratory hypoxic challenge. Intra-observer and inter-observer variability and repeatability were also compared.Results
PA PWV, which was successfully measured in all subjects, increased from 1.31 ± 0.32 m/s in air to 1.61 ± 0.58 m/s under hypoxic challenge (p = 0.03). Intra- and inter-observer coefficients of variations were 9.0% and 15.6% respectively. Good correlation within and between observers of r = 0.92 and r = 0.72 respectively was noted for PA PWV measurements. Mean (95% limit of agreement) intra- and inter-observer agreement on Bland–Altman analysis were − 0.02 m/s (− 0.41–0.38 m/s) and -0.28 m/s (− 1.06–0.49 m/s).Conclusion
PA PWV measurement in children using velocity-encoded MRI is feasible, reproducible and sufficiently sensitive to detect differences in PA compliance between normoxia and hypoxia. This technique can be used to detect early changes of PA compliance and monitor PAH in children. 相似文献10.
Linda Knutsson Danielle van Westen Esben T. Petersen Karin Markenroth Bloch Stig Holtås Freddy Ståhlberg Ronnie Wirestam 《Magnetic resonance imaging》2010