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After introduction of the first human 7 tesla (7T) system in 1999, 7T MR systems have been employed as one of the most advanced platforms for human MR research for more than 20 years. Currently, two 7T MR models are approved for clinical use in the U.S.A. The approval facilitated introduction of the 7T system, summing up to around 100 worldwide. The approval in Japan is much awaited. As a clinical MR scanner, the 7T MR system is drawing attention in terms of safety.Several large-sized studies on bioeffects have been reported for vertigo, dizziness, motion disturbances, nausea, and others. Such effects might also be found in MR workers and researchers. Frequency and severity of reported bioeffects will be presented and discussed, including their variances. The high resonance frequency and shorter RF wavelength of 7T increase the concern about the safety. Homogeneous RF pulse excitation is difficult even for the brain, and a multi-channel parallel transmit (pTx) system is considered mandatory. However, pTx may create a hot spot, which makes the estimation of specific absorption rate (SAR) to be difficult. The stronger magnetic field of 7T causes a large force of displacement and heating on metallic implants or devices, and the scan of patients with them should not be conducted at 7T. However, there are some opinions that such patients might be scanned even at 7T, if certain criteria are met. This article provides a brief review on the effect of the static magnetic field on humans (MR subjects, workers, and researchers) and neurons, in addition to scan sound, SAR, and metal implants and devices. Understanding and avoiding adverse effects will contribute to the reduction in safety risks and the prevention of incidents.  相似文献   
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Interleukin-5 is at 5q31 and is deleted in the 5q- syndrome   总被引:3,自引:0,他引:3  
Human interleukin-5 (IL-5) is a selective eosinophilopoietic and eosinophil-activating growth hormone. By in situ hybridization this gene is mapped to chromosome 5q23.3 to 5q32. It is shown to be deleted in two patients with the 5q-syndrome and in one patient previously diagnosed with myelodysplasia whose condition had progressed to acute myeloblastic leukemia. The clustering of other genes involved in hematopoiesis (IL-3, granulocyte-macrophage colony-stimulating factor, feline sarcoma viral oncogene homolog, colony-stimulating factor 1) to the same region as IL-5 suggests a nonrandom localization and raises interesting questions concerning the evolution and regulation of these genes.  相似文献   
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Purpose This study assesses the clinical performance of 92 resin-bonded fixed partial dentures (FPDs) placed at four private practices in Karachi, Pakistan, between 1982 and 1991. Materials and Methods The distribution of the FPDs was 9 perforated, 45 electrolytically etched, and 38 silicoated. Twenty-five FPDs replaced anterior teeth and 67 replaced posterior teeth. There were 66 FPDs with single pontics and 26 with multiple pontics. The perforated designs used a restorative composite for cementation, whereas the electrolytically etched and silicoated designs used a composite luting cement. The observation periods for the perforated, electrolytically etched, and silicoated FPDs were 114,99, and 30 months respectively. Results During the evaluation period, 27 FPDs (29%) failed; of these, 4 were perforated, 18 were electrolytically etched, and 5 were silicoated. The mean (±SD) duration of the successful clinical service for all FPDs was 41 ± 26 months. The mean time to failure for the FPDs that did not survive was 35 ± 23 months. The silicoated FPDs tended to have early failure, as did the FPDs with multiple pontics and those in the mandibular arch. Anterior and posterior FPDs performed equally well. Conclusions These findings, in conjunction with those from Europe and North American, show that resin-bonded FPD technology is as successful in a developing country as in industrialized areas of the world.  相似文献   
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Little is known about the efficacy and the factors affecting the outcome of fine needle aspiration biopsy of the testis for sperm retrieval in azoospermic men with defective spermatogenesis. A prospective study was designed to compare the efficacy of needle and open (window) testicular biopsies for testicular epididymal sperm extraction (TESE) in 35 consecutive men with azoospermia due to defective spermatogenesis undergoing testicular biopsy for intracytoplasmic injection of oocytes. Each of the consecutive 35 patients underwent TESE using a 19 gauge butterfly needle followed by a window (1-1.5 cm-sized incision) testicular biopsy in the same procedure. The extraction of spermatozoa into culture medium was compared with the assessment of testicular biopsies by histology, the mode of biopsy (needle or open biopsy) and the amount of tissue retrieved by either method. Testicular spermatozoa were retrieved in 22 (63%) who had an open testicular biopsy compared with five (14%) patients who had multiple needle biopsies, respectively; the difference was statistically significant. Open testicular biopsy retrieves more testicular tissue than needle biopsy. Needle testicular biopsy retrieved testicular spermatozoa in 50% of those with hypospermatogenesis, 10% with focal spermatogenesis and in no patients with maturation arrest or Sertoli cell-only pattern. In contrast, sperm retrieval was successful in 100%, 90% and 66% of those with respective histologies using open testicular biopsy. Other than bruising, for which they required no analgesia, none of the patients suffered any obvious complications associated with traditional testicular biopsy. We conclude that open testicular biopsy is more effective than needle biopsy for the retrieval of testicular spermatozoa in azoospermic men with defective spermatogenesis. The difference observed may be related to the amount of testicular tissue retrieved and to the influence of testicular histology.   相似文献   
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Catheters are generally known to be the last resort for blood access in dialysis. Because of the many problems related to catheter use, catheters are banned from vascular access courses organized by professional societies and the development of catheters and catheter related equipment relies on a few interested medical doctors with limited knowledge of hydraulics and material science. Rather than accepting the need for catheters and the need for improving catheters and catheter related procedures, vascular access meetings typically begin and end with statements saying that the use of fistulas must be increased and catheters must be banned. Several small companies have developed new catheters and catheter related equipment, which potentially overcome many of the problems related to the use of catheters. The authors had the privilege of participating in one of these developments and report about basic features and clinical experience of the DIALOCK® blood access port and an antimicrobial catheter locking solution (CLS) which is used with conventional catheters as well as with the DIALOCK®.  相似文献   
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陈旧性跟骨骨折截骨治疗40例   总被引:1,自引:0,他引:1  
张坤  沙浩渡  靳卫章 《医学争鸣》2000,21(12):1532-1532
0 引言 陈旧性跟骨骨折晚期出现患足疼痛及跛行 ,功能障碍的病理变化十分复杂 ,治疗也较困难 .近年来我们应用跟骨截骨 ,距后关节融合 ,外踝管扩大术治疗该病 40例共 41足 ,获得满意效果 .1 对象和方法1.1 对象 陈旧性跟骨骨折患者 40例 41足 ;随访 37足 ;男36例 ,女 4例 ;年龄 2 0~ 5 7(平均 36 )岁 .左足 2 6例 ,右足 13例 ,双足 1例 .早期经保守治疗无效 34例 ,跟骨撬拔治疗术后过早负重 ,骨折部再次移位而出现症状 6例 7足 .41足均出现负重时距下关节周围弥漫性疼痛 ,跛行 ,患足跟部增宽 ,外翻畸形 6 9% ,内翻畸形 7% ,纵弓塌陷、…  相似文献   
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