Electrodynamics and ultimate SNR in parallel MR imaging.

The purpose of this article is to elucidate inherent limitations to the performance of parallel MRI. The study focuses on the ultimate signal-to-noise ratio (SNR), which refers to the maximum SNR permitted by the electrodynamics of the signal detection process. Using a spherical model object, it is shown that the behavior of the ultimate SNR imposes distinct limits on the acceleration rate in parallel imaging. For low and moderate acceleration, the ultimate SNR performance is nearly optimal, with geometry factors close to 1. However, for high reduction factors beyond a critical value, the ultimate performance deteriorates rapidly, corresponding to exponential growth of the geometry factor. The transition from optimal to deteriorating performance depends on the electrodynamic characteristics of the detected RF fields. In the near-field regime, i.e., for low B0 and small object size, the critical reduction factor is constant and approximately equal to four for 1D acceleration in the sphere. In the far-field wave regime the critical reduction factor is larger and increases both with B0 and object size. Therefore, it is concluded that parallel techniques hold particular promise for human MR imaging at very high field.     

On information field of clinical diagnosis

“Field” is a universal phenomenon existing in both nature and society, and determines the existence and significance of all materials or information. The man being has always been generating and carrying a large quantity of life information in his whole life. Each piece of life information has an independent information field. The life information field includes such three subfields as bioinformation field, psychoinformation field and psycho-bioinformation field.The clinical diagnosis information field which is a specific information field within the information field of human activities consists of all information concerning man‘s health. Only after we have cognized and ascertained the clinic diagnosis information field, can we accurately utilize its function to serve the human being.     

SOD降低辐射诱发染色体畸变的实验研究

目的　观察加入外源性SOD对辐射诱发人血淋巴细胞染色单体型畸变和染色体型畸变的影响。方法　 (1)人血 37℃培养 70h后加入不同浓度SOD ,接受 1Gy60 Co -γ射线照射 ,再培养 3h ,按常规方法制片 ,每组镜检 30 0个细胞 ,观察SOD对辐射诱发染色单体型畸变的影响 ;(2 )人血先加入不同浓度SOD ,再按上述条件照射 1Gy ,37℃培养 5 4h ,按常规方法制片 ,每组镜检 30 0个细胞 ,观察SOD对辐射诱发染色体型畸变的影响。 结果　(1)各个浓度SOD(5× 10 -3 ～ 5× 10 -1mg/ml )对辐射诱发的染色单体型互换和断裂均有非常明显的降低作用 ;(2 )只有中浓度SOD对染色体性畸变包括染色体互换与断片 ,以及高浓度SOD对染色体互换才产生降低作用。结论　在上述实验条件下 ,不同浓度SOD对辐射诱发的染色单体型畸变和染色体型畸变均有不同程度降低作用。     

WR-2721对γ线照射小鼠胃排空的防护作用

小鼠经γ线1200rad照射后胃排空受到明显抑制,如照前15min腹腔注射WR-2721 5mg或10mg对照后3天胃排空的抑制有明显改善。虽然WR-2721药物本身对胃排空具有一定的抑制作用,但经过24～48h后则可表现出对胃排空有一定程度的改善效应,这可能与该药减轻急性放射损伤的过程有关。     

Positive autoradiographic findings in brains of four MS patients

Autoradiography of brain slices from 4 multiple sclerosis (MS) and 9 control patients was performed. After 6 weeks of exposure the exact picture of the white matter appeared on the X-ray films in all cases with MS, but only in one of the controls. The high level of autoradiographic signal from MS white matter suggests that an abnormal accumulation of radioactive trace elements takes place within the brains of MS victims.     

放射性脑损伤和脑肿瘤复发的鉴别诊断

放射性脑损伤是放射治疗的严重的并发症,其与脑肿瘤复发的鉴别诊断非常困难,目前主要依靠影像学诊断,核磁共振弥散加权像、磁共振波谱、正电子发射型计算机体层显像、单光子发射计算机体层显像等被认为对于鉴别诊断有一定的帮助,但其敏感性和特异性还有待于进一步研究。最终确诊依赖标本的组织学检查。     

Severe hemorrhagic radiation proctitis advancing to gradual cessation with hyperbaric oxygen

Summary We report a case of a male patient suffering from a severe hemorrhagic radiation proctitis which gradually ceased with hyperbaric oxygen. We discuss the mechanisms of chronic radiation injury and the effect of the hyperbaric oxygen. This therapy is proposed as an alternative to surgical intervention for this abnormality.     

改进微波幅射器探头治疗宫颈糜烂疗效观察

目的：探讨改进的微波辐射器探头治疗宫颈糜烂的疗效。方法：将微波辐射器探头由双直线形、双针形、单针形等点线状改进成为“单舌形”和“双舌形”两种弧形平面探头，用于治疗宫颈糜烂。分析1999-2002年450例宫颈糜烂治疗资料，其中300例经微波治疗(A组)，150例经C02—激光治疗(B组)，随访1—3个月。结果：两组治疗后3个月内A组治愈率明显高于B组(P＜0．005)，总有效率A组明显高于B组(P＜0．025)。两组术中、术后不良反应比较：术中宫颈创面出血A组明显低于B组(P＜0．005)，术中腹痛、脱痂期出血量、术后局部感染率方面两组相似。结论：所改进的微波辐射器探头治疗宫颈糜烂治愈率高，操作安全，术后并发症少，医患乐于接受。     

视场角设置对虚拟环境中目标判断的影响

目的探讨不同视场角参数对虚拟环境中目标判断的影响规律 ,找出最佳视场角参数。方法利用自行研制基于PC平台的虚拟现实 (VR)实验系统 ,选定 45名年龄在 2 3～ 5 8岁被试者并完成大小与角度判断的实验设计。首先进行 30 0人次的预实验 ,确定引起虚拟环境中目标判断差错的视场角及相应观察任务的差别等级 ,然后开始单因素、4水平的完全随机正式实验。结果方差分析表明 ,不同的虚拟环境视场角对目标判断的真实性有显著性影响 ,当视场角为 60°时 ,目标判断的正确率最大。结论利用VR技术进行载人航天器工效设计、操作训练或其它任务的研究时 ,应考虑视场角的作用 ,适合目标大小判断的视场角参数值宜取 60°,以便获得最大的工效     

青光眼病人视野改变与行走速度的相关性研究

目的探讨青光眼病人的视野改变是否影响其行走速度。方法测量 71例青光眼病人的视野和走完一段规定路程所需时间 ,并与相同视力、年龄和性别的正常人进行对比。结果青光眼病人走完规定路程所需时间比正常人多 15 % ;早期青光眼组视野较正常组下降 (P <0 .0 5 ) ,而在行走时间上差异无显著性意义 (P >0 .0 5 ) ;中晚期青光眼组视野较正常组显著下降、行走时间明显增加 (均P <0 .0 1) ,且视野下降程度与所需时间呈显著正相关 (r =0 .78,P <0 .0 1)。结论中晚期青光眼病人的视野缺损可导致行走速度减慢 ,提示对该类病人就诊时要耐心、细致地加以引导 ,在日常生活中给予理解、关怀