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1.
Efficient high-frequency body coil for high-field MRI. 总被引:1,自引:0,他引:1
J T Vaughan G Adriany C J Snyder J Tian T Thiel L Bolinger H Liu L DelaBarre K Ugurbil 《Magnetic resonance in medicine》2004,52(4):851-859
The use of body coils is favored for homogeneous excitation, and such coils are often paired with surface coils or arrays for sensitive reception in many MRI applications. While the body coil's physical size and resultant electrical length make this circuit difficult to design for any field strength, recent efforts to build efficient body coils for applications at 3T and above have been especially challenging. To meet this challenge, we developed an efficient new transverse electromagnetic (TEM) body coil and demonstrated its use in human studies at field strengths up to 4 T. Head, body, and breast images were acquired within peak power constraints of <8 kW. Bench studies indicate that these body coils are feasible to 8 T. RF shimming was used to remove a high-field-related cardiac imaging artifact in these preliminary studies. P41RR13230 相似文献
2.
J. R. Döhler S. P. F. Hughes 《Langenbeck's archives of surgery / Deutsche Gesellschaft fur Chirurgie》1997,382(3):164-166
In three groups of six mice each, the α- and β-receptors were blocked by phentolamine and propranolol. The mice in the three groups then received an intravenous bolus injection of saline solution, epinephrine, and insulin, respectively. Cortical bone capillaries from the tibia diaphysis were submitted to transmission electron microscopy (TEM). The lumen and endothelium were measured and the results compared. Significant changes were only noted in the endothelium after the administration of insulin. These findings suggest that there are also insulin receptors in bone. Furthermore, they support previous findings in similar studies with epinephrine. 相似文献
3.
MF1小鼠感染曼氏血吸虫六周后,经主动脉和门静脉灌注收虫.配对的成虫暴露在不含环孢素A及分别含有1微克/毫升、10微克/毫升、20微克/毫升的环孢素A的199型培养液中体外培养.药物导致的虫体损害分别作扫描电镜和透射电镜观察.药物作用后,雄虫外质膜损伤,外皮层基质出现水肿和空泡,分泌体减少.进行性表皮损害、肿胀以及皮(?)缺损最终导致皮质膜和合胞体的崩溃.本结果表明,环孢素A抗曼氏血吸虫的作用方式是直接的.而外皮质似乎是药物首先攻击的部位. 相似文献
4.
Eight-channel transmit/receive body MRI coil at 3T. 总被引:1,自引:0,他引:1
P. Vernickel P. Röschmann C. Findeklee K.‐M. Lüdeke Ch. Leussler J. Overweg U. Katscher I. Grässlin K. Schünemann 《Magnetic resonance in medicine》2007,58(2):381-389
Multichannel transmit magnetic resonance imaging (MR) systems have the potential to compensate for signal-intensity variations occurring at higher field strengths due to wave propagation effects in tissue. Methods such as RF shimming and local excitation in combination with parallel transmission can be applied to compensate for these effects. Moreover, parallel transmission can be applied to ease the excitation of arbitrarily shaped magnetization patterns. The implementation of these methods adds new requirements in terms of MRI hardware. This article describes the design of a decoupled eight-element transmit/receive body coil for 3T. The setup of the coil is explained, starting with standard single-channel resonators. Special focus is placed on the decoupling of the elements to obtain independent RF resonators. After a brief discussion of the underlying theory, the properties and limitations of the coil are outlined. Finally, the functionality and capabilities of the coil are demonstrated using RF measurements as well as MRI sequences. 相似文献
5.
6.
地塞米松对电光性眼炎防治作用的实验研究 总被引:3,自引:1,他引:2
本文对电光性眼炎家兔角膜上皮的超氧化物歧化酶(SOD)活性及脂质过氧化反应主要代谢产物丙二醛(MDA)含量进行测量。发现紫外线照射后3小时SOD活性降低,伴随上述改变,MDA含量增高。用地塞米松在照射前、后滴眼,3小时检测SOD和MDA,发现其可保护SOD,并降低MDA含量。透射电镜下显示,角膜上皮细胞的变化主要在其底部细胞,以水肿性改变为主。实验结果提示自由基损伤在急性电光性眼炎的发生、发展过程中起了重要作用,地塞米松可减轻这种变化。 相似文献
7.
Abstract – This study describes the early microbial colomization of teeth by the use of light-and transmission electron microscopy. Six dental students carried a total of 60 test pieces of unerupted enamel and root surface in intraoral acrylic appliances for 4, 8, 12, 24 and 48 h, during which periods oral hygiene was abandoned. Pronounced variations were recorded in structure and thickness of the pellicle across the individual surfaces of both dental tissues. Bacterial single-cell colonization increased the electron density of the adjoining pellicle. Micro-colonies of bacteria were observed in relation to enamel surface irregularities such as perikymata, while the distribution on root surfaces appeared incidental. Root surfaces were generally colonized by thicker deposits than homologous enamel surfaces although the structural composition of the microbiota was similar. Gram-positive bacteria with thick cell walls appeared in coccoid or rod-shaped configurations depending on the age of the bacterial deposit. These bacteria were further characterized by selective invasion between collagen fibers. After 48 h the complexity of the microbiota was increased by the establishment of new bacterial species in the superficial layer. It is concluded that the pattern and composition of the early microbiota on teeth is more complex and variable than hitherto assumed. 相似文献
8.
Baccetti B Collodel G Estenoz M Manca D Moretti E Piomboni P 《Human reproduction (Oxford, England)》2005,20(10):2790-2794
BACKGROUND: Asthenozoospermia may sometimes be related to geneticstructural defects of the sperm tail detectable by transmissionelectron microscopy. Dysplasia of the fibrous sheath (DFS) isa genetic sperm defect, characterized by dysplastic developmentof the axonemal and periaxonemal cytoskeleton. We report thecase of an infertile man with normal sperm count and total spermimmotility in which dysplasia of the fibrous sheath, Akap3,Akap4 gene deletions, meiotic segregation of chromosomes 18,X and Y and Y microdeletions were investigated. METHODS: A 32-year-oldman with a 3-year history of primary infertility presented atour Regional Referral Center for Male Infertility. Family medicalhistory, lymphocyte karyotype, PCR analysis, physical examination,hormone assays and semen analysis were performed. RESULTS: Ultrastructuralsperm evaluation showed dysplasia of the fibrous sheath. Immunostainingof AKAP4 protein was negative in sperm tails. PCR analysis revealedintragenic deletions of the Akap3 and Akap4 genes. Fluorescencein situ hybridization on sperm showed a high frequency of XYdisomy. CONCLUSION: In this infertile patient, our results suggesta possible relationship between dysplasia of the fibrous sheath,partial deletions in the Akap3 and Akap4 genes and absence ofAKAP4 protein in the fibrous sheath. These findings, however,were not detected in another four patients with dysplasia ofthe fibrous sheath. Our results require future confirmatorymolecular analyses. 相似文献
9.
10.
Baccetti B Collodel G Marzella R Moretti E Piomboni P Scapigliati G Serafini F 《Human reproduction (Oxford, England)》2005,20(8):2295-2300
BACKGROUND: In order to clarify the relationship between chromosomal rearrangements, sperm morphology and interchromosomal effects (ICE), we studied the spermatogenetic defects in seven infertile Robertsonian translocation carriers. METHODS: Lymphocyte karyotypes were evaluated using Giemsa-Trypsin-Giemsa banding and fluorescence in-situ hybridization (FISH). Semen analysis was performed by light and transmission electron microscopy. FISH of sperm nuclei was carried out to detect possible ICE. RESULTS: Lymphocyte karyotype analysis revealed five t(13;14), one t(13;21) and one t(14;22) carriers. Sperm ultrastructural examination highlighted a higher percentage of immaturity, apoptosis and necrosis than in controls. Aneuploidies of gonosomes were detected in sperm from five out of six carriers of Robertsonian translocation, whereas aneuploidy of chromosome 18 was evident in three out of six carriers. The frequencies of diploidy were altered in all cases. CONCLUSIONS: Since these infertile patients showed severe spermatogenetic impairment from the morphological and meiotic points of view, we recommend detailed sperm ultrastructural and chromosomal analysis before undertaking ICSI cycles in Robertsonian translocation carriers. 相似文献