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排序方式: 共有1051条查询结果,搜索用时 15 毫秒
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Fa-Hsuan Lin Shang-Yueh Tsai Ricardo Otazo Arvind Caprihan Lawrence L Wald John W Belliveau Stefan Posse 《Magnetic resonance in medicine》2007,57(2):249-257
Magnetic resonance spectroscopic imaging (MRSI) provides spatially resolved metabolite information that is invaluable for both neuroscience studies and clinical applications. However, lengthy data acquisition times, which are a result of time-consuming phase encoding, represent a major challenge for MRSI. Fast MRSI pulse sequences that use echo-planar readout gradients, such as proton echo-planar spectroscopic imaging (PEPSI), are capable of fast spectral-spatial encoding and thus enable acceleration of image acquisition times. Combining PEPSI with recent advances in parallel MRI utilizing RF coil arrays can further accelerate MRSI data acquisition. Here we investigate the feasibility of ultrafast spectroscopic imaging at high field (3T and 4T) by combining PEPSI with sensitivity-encoded (SENSE) MRI using eight-channel head coil arrays. We show that the acquisition of single-average SENSE-PEPSI data at a short TE (15 ms) can be accelerated to 32 s or less, depending on the field strength, to obtain metabolic images of choline (Cho), creatine (Cre), N-acetyl-aspartate (NAA), and J-coupled metabolites (e.g., glutamate (Glu) and inositol (Ino)) with acceptable spectral quality and localization. The experimentally measured reductions in signal-to-noise ratio (SNR) and Cramer-Rao lower bounds (CRLBs) of metabolite resonances were well explained by both the g-factor and reduced measurement times. Thus, this technology is a promising means of reducing the scan times of 3D acquisitions and time-resolved 2D measurements. 相似文献
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Dynamic imaging with lanthanide chelates in normal brain: contrast due to magnetic susceptibility effects 总被引:22,自引:0,他引:22
A Villringer B R Rosen J W Belliveau J L Ackerman R B Lauffer R B Buxton Y S Chao V J Wedeen T J Brady 《Magnetic resonance in medicine》1988,6(2):164-174
Using a one-dimensional rapid imaging technique, we have found that injection of lanthanide chelates such as Gd(DTPA)2- leads to a significant decrease (50%) in rat brain signal intensity at 1.45 T using T2-weighted pulse sequences; however, no effect of comparable size is observed with T1-weighted pulse sequences. The transient effect and its kinetics were followed with a temporal resolution of between 1 and 8 s. Experiments with different lanthanide chelates show that the observed decrease in signal intensity correlates with the magnetic moment of each agent but not with their longitudinal relaxivity. Three-dimensional chemical-shift resolved experiments demonstrate significant line broadening in brain during infusion with Dy(DTPA)2-. Our results show that the cause of this effect is the difference in susceptibility between the capillaries, containing the contrast agent, and the surrounding tissue. As a result of these susceptibility differences, field gradients are produced in the tissue and diffusion of water through these gradients leads to a loss of spin phase coherence and thus a decrease in signal intensity. We propose this as a new type of contrast agent mechanism in NMR. The effect and its kinetics are likely to be related to important physiological parameters such as cerebral blood volume and cerebral blood flow, and do not depend on a breakdown of the blood-brain barrier as do conventional contrast agent techniques. 相似文献
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Gabriela A Ghitulescu Nancy Morin Prasad Jetty Paul Belliveau 《Canadian journal of surgery》2003,46(2):92-98
INTRODUCTION: The use of the biofragmentable anastomotic ring (BAR) has been reported in the literature with good results. Our purpose in this review was to document the clinical outcomes after gastrointestinal anastomoses performed with use of the BAR. METHODS: Data were gathered systematically through chart review with the help of data collection forms from 159 patients who underwent 173 intestinal anastomoses performed with use of the BAR between 1992 and 1999. Of the 165 patients who had anastomoses (6 had 2 anastomoses constructed on separate occasions and were considered separately), 23 (13.9%) had surgery with anastomosis under emergency conditions, and 44 (26.7%) were steroid-dependent patients. The indications for surgery were malignant disease in 63 (38.2%) patients, inflammatory bowel disease in 54 (32.7%) patients, diverticular disease in 13 (7.9%) patients and other conditions in 35 (21.2%) patients. RESULTS: A clinical anastomotic leak developed in the first 2 weeks after surgery in 7 (4.2%) patients, 6 of whom required reoperation. All recovered well, withno deaths related to use of the BAR. Early small-bowel obstruction developed in 13 patients (7.9%), none of whom required reoperation. The average postoperative length of hospital stay was 9.0 days, the average time to pass the first flatus was 3.2 days, and the average time to begin oral fluid intake was 3.3 days. The rate of leakage at the anastomosis in our series was comparable to that found in randomized trials with the BAR (2.0%-4.4%) and as reported with hand-sewn and stapled anastomoses (1.9%-8.2%). CONCLUSIONS: Our data indicate that use of the BAR is safe and effective in both elective and emergent surgery. The rate of leakage is comparable to that reported in the literature when a BAR is used. 相似文献
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Identification of the multiple endocrine neoplasia type 1 (MEN1) gene. The European Consortium on MEN1 总被引:10,自引:0,他引:10
Lemmens I; Van de Ven WJ; Kas K; Zhang CX; Giraud S; Wautot V; Buisson N; De Witte K; Salandre J; Lenoir G; Pugeat M; Calender A; Parente F; Quincey D; Gaudray P; De Wit MJ; Lips CJ; Hoppener JW; Khodaei S; Grant AL; Weber G; Kytola S; Teh BT; Farnebo F; Thakker RV 《Human molecular genetics》1997,6(7):1177-1183