A wavelet-based approximation of surface coil sensitivity profiles for correction of image intensity inhomogeneity and parallel imaging reconstruction

We evaluate a wavelet-based algorithm to estimate the coil sensitivity modulation from surface coils. This information is used to improve the image homogeneity of magnetic resonance imaging when a surface coil is used for reception, and to increase image encoding speed by reconstructing images from under-sampled (aliased) acquisitions using parallel magnetic resonance imaging (MRI) methods for higher spatiotemporal image resolutions. The proposed algorithm estimates the spatial sensitivity profile of surface coils from the original anatomical images directly without using the body coil for additional reference scans or using coil position markers for electromagnetic model-based calculations. No prior knowledge about the anatomy is required for the application of the algorithm. The estimation of the coil sensitivity profile based on the wavelet transform of the original image data was found to provide a robust method for removing the slowly varying spatial sensitivity pattern of the surface coil image and recovering full FOV images from two-fold acceleration in 8-channel parallel MRI. The results, using bi-orthogonal Daubechies 97 wavelets and other members in this family, are evaluated for T1-weighted and T2-weighted brain imaging.     

ROCKⅡ与子痫前期发病的关系

为了解ROCKⅡ与子痫前期发病的关系,查阅国内外文献并对文献进行整理,发现ROCKⅡ在子痫前期发病过程中起一定作用,现就Rho/ROCK信号传导通路与妊娠的关系做一综述。     

螺旋弹簧和橡皮链拉尖牙向远中的临床效果研究

目的研究Ni-Ti螺旋弹簧和橡皮链施力后,尖牙远中移动速率、龈沟液(gingival crevicular fluid,GCF)中碱性磷酸酶(alkaline phosphatase,ALP)活性,探讨不同持续张力的正畸效果和生物学效应。方法用OPAK直丝弓矫治技术托槽,排齐整平后,采用0.018×0.025″SS的Ni-Ti方丝进行尖牙远中移动。然后,用初始力150g的Ni-Ti螺旋弹簧和橡皮链牵引尖牙向远中,21d后,采用游标卡尺测定牙齿移动距离,Beckman全自动生化分析仪检测龈沟液中碱性磷酸酶(GCF-ALP)的活性。结果螺旋弹簧和橡皮链施力21d后,尖牙向远中移动距离差异有显著性(P<0.05)。在螺旋弹簧和橡皮链持续牵引力作用下,GCF-ALP活性随时间推移逐渐增加,6个月时达到最高水平,与加力前比较,差异有显著性(P<0.05);6个月后,GCF-ALP开始下降,12个月时,橡皮链加力侧GCF-ALP活性基本恢复到加力前的水平。但在6和12个月时,GCF-ALP活性在螺旋弹簧施力侧显著高于橡皮链施力侧,差异有显著性(P<0.01)。结论螺旋弹簧拉尖牙向远中移动速率较快,产生的生物学效应较强而持久。     

Transceive surface coil array for MRI of the human prostate at 4T.

A novel torso transceive surface coil array for prostate magnetic resonance imaging (MRI) and spectroscopy (MRS) at 4T is presented. It is shown that with the use of a conformal transceive surface coil array with 50 Omega transmitter amplifiers and receiver preamplifiers, one can perform whole-volume torso imaging while maintaining the high signal-to-noise ratio (SNR) inherent to surface coil designs. Recent theoretical considerations have shown that by focusing the infringing radiofrequency (RF) electromagnetic field, one can achieve increased penetration and signal homogeneity compared to a conventional circularly polarized driving scheme. A variation of this driving scheme particular to the proposed coil design resulted in a twofold increase in SNR in the prostate compared to that achieved with a conventional circularly polarized driving scheme. The novel transceive surface coil array presented is capable of full-volume imaging of the human torso at 4T while maintaining signal penetration in the deep region of the prostate gland.     

颅内动脉瘤介入治疗20例疗效分析

目的: 观察血管内弹簧圈栓塞治疗颅内动脉瘤的临床疗效,并探讨术中操作注意事项。方法: 对20例颅内动脉瘤患者施行血管内弹簧圈栓塞治疗,其中2例宽瘤颈动脉瘤采用支架辅助弹簧圈栓塞治疗。20例术前均经数字减影血管造影(DSA)检查明确诊断。结果: 19例术中栓塞满意,其中1例术中动脉瘤破裂,4天后死亡;1例术后3天并发右侧大脑后动脉梗塞,2天后死亡。15例患者术后6~8个月随访行DSA复查,瘤体栓塞完全,载瘤动脉通畅。结论: 弹簧圈栓塞治疗颅内动脉瘤是一种安全、有效的治疗方法,根据动脉瘤具体形态联合运用多种栓塞技术可提高动脉瘤栓塞的治愈率。     

电解可脱卸弹簧圈栓塞治疗颅内破裂动脉瘤的疗效及影响因素

目的：探讨电解可脱卸弹簧圈（Guglielmi detachable coil,GDC）栓塞治疗颅内破裂动脉瘤的近期疗效及相关影响因素。方法：应用GDC栓塞治疗123例157枚动脉瘤,分析动脉瘤几何形态学、病情严重程度对栓塞效果及临床治疗的影响。结果：Hunt-Hess分级Ⅰ-Ⅱ级患中,预后良好（GOS＞3分）为100％,Ⅲ、Ⅳ-Ⅴ级患中分别为95．0％、76．0％;窄颈动脉瘤完全栓塞率、大部栓塞率及部分栓塞率分别为92．4％、5．7％、1．9％,宽颈动脉瘤中分别为80．8％、13．5％、5．8％,大动脉瘤的疗效明显低于小动脉瘤。结论：动脉瘤的栓塞程度不仅与瘤颈大小有关,还受瘤体大小的影响。而临床预后与Hunt-Hess分级呈负相关。     

经数字减影血管造影行颅内动脉瘤栓塞术的麻醉体会

目的探讨经数字减影血管造影(DSA)行颅内动脉瘤电解可脱性弹簧圈(GDC)栓塞术的麻醉效果。方法22例经DSA行颅内动脉瘤GDC栓塞术的患者全部采用静脉快速诱导气管内插管,术中以微量泵持续泵注丙泊酚、瑞芬太尼,间断静脉注射维库溴铵维持肌松,持续泵注尼莫地平,以防血管痉挛,控制性降压等方法处理。结果22例经DSA行颅内动脉瘤GDC栓塞术的患者麻醉诱导、术中维持,术后苏醒平稳,控制性降压效果满意,无动脉瘤破裂。结论经DSA行颅内动脉瘤栓塞术麻醉处理的关键是:选择合适的麻醉药物,采取有效措施防止脑血管痉挛和动脉瘤再破裂,控制血压降低颅内压,以提高手术成功率。     

Designed polyanionic coiled-coil proteins: acceleration of heparin cofactor II inhibition of thrombin

Novel polyanionic proteins were designed to increase the rate of heparin cofactor II (HC) inhibition of α-thrombin, an essential protease in the coagulation cascade. Two α-helical coiled-coil proteins, a 62-residue dimer containing 8 Glu residues (E8C) and a 104-residue dimer containing 14 Glu residues (E14C), plus two 31-residue control peptides containing 8 Glu residues each (E8A and E8B), were chemically synthesized, structurally characterized and enzymatically assayed. Circular dichroic spectrophotometry indicated that both E8C and E14C formed stable two-chain α-helical coiled coils at pH 7 and 25 °C. The control peptides were only partially α-helical. E14C remained folded at 90 °C but E8C was half unfolded at 49 °C. Coiled-coil proteins E8C and E14C maximally accelerated by 35- and 33-fold, respectively, the rate of HC inhibition of α-thrombin. None of these compounds accelerated antithrombin inhibition of α-thrombin, and neither control peptide accelerated HC inhibition of α-thrombin. Acceleration of the HC inhibition of α-thrombin showed bimodal dependence on the concentration of the polyanionic protein, which is consistent with formation of a HC-coiled-coil-thrombin ternary complex. The results suggest that antithrombotic polyanionic α-helical coiled-coil proteins can be designed and synthesized and that the occurrence of secondary structure can be correlated with biologcal activity. © Munksgaard 1995.     

ERC测定枸橼酸盐在前列腺疾病中的鉴别诊断作用

目的：探讨磁共振直肠内线圈（ERC）测定前列腺组织中枸橼酸盐（cit）在前列腺疾病中的鉴别诊断价值。方法：本组共69例,对腔内线圈和腹部线圈成像效果比较。均于术前测定枸橼酸盐（Cit）,术后经尿道前列腺切除术、经直肠前列腺穿刺活检术或耻骨上前列腺切除术获得病理结果。前列腺增生组（BPH）34例,腺体增生型17例、混合增生型12例、基质增生型5例。前列腺癌组（Pca）35例。分别测量各组（Cho＋Cr）/Cit即CC/C比值。结果：相控阵腹部线圈和ERC扫描的T2像对前列腺癌检出的敏感性分别为60%和80%,特异性分别为76.5%和85.2%。前列腺腺体增生型CC/C值为0.73±0.29;基质增生型CC/C值为1.13±0.38;混合增生型CC/C值为0.94±0.27;正常前列腺外周带、PCa区、外周带良性结节和BPH中央带的CC/C平均比值分别为0.94±0.53,2.23±1.67,1.19±0.64和0.93±0.49。PCa与前列腺外周带良性结节及BPH之间的差异均有统计学意义（t值分别为2.78、4.4,P值分别为0.01,0.00）。结论：腔内线圈显示靠近线圈的外周带及精囊腺解剖结构及病灶比腔内线圈具有一定优势,可得到较腹部线圈信噪比更好的MRS信息。前列腺正常组织MRS谱线特点以Cit为主峰,前列腺癌中MILS是Cho为主峰。Cit与Cho峰的负向变化,是前列腺疾病鉴别诊断的重要依据。