Image size magnification and power and dilation factors for optical instruments in general

Traditional treatments of spectacle magnification for distant objects consider only stigmatic spectacle lenses and they compare the retinal image size in a refractively fully compensated eye with the image size in the uncompensated eye. Spectacle magnification is expressed as a product of two factors, the power and shape factors of the lens. The power factor depends on the position of the entrance pupil of the eye. For an eye with an astigmatic cornea, however, the position of the entrance pupil is not well defined. Thus, the traditional approach to spectacle magnification does not generalize properly to allow for astigmatism. Within the constraints of linear optics and subject to the restriction that the eye's iris remains the aperture stop, this paper provides a complete, unified and exact treatment for optical instruments in general. It compares retinal image size in a generalized sense (including image shape and orientation) for any instrument in front of an eye with that of the eye alone irrespective of whether the instrument compensates or not. The approach does not make use of the concept of the entrance pupil at all and it allows for astigmatism and for non-alignment of refracting elements in the instrument and in the eye. The concept of spectacle magnification generalizes to the concept of instrument size magnification. Instrument size magnification can be expressed as the product of two matrix factors one of which can be interpreted as a power factor (as back-vertex power) and the other factor for which the name dilation factor is more appropriate in general. The general treatment is then applied to a number of special cases including afocal instruments, spectacle lenses (including obliquely crossing thick bitoric lenses), contact lenses, stigmatic systems and stigmatic eyes. In the case of spectacle lenses, the dilation factor reduces to the usual shape factor.     

磁共振扩散加权成像对超急性期、急性期脑缺血的应用价值

磁共振扩散加权成像(DWI)可以快速、无创地反映脑缺血区分子水平发生的微观变化,为临床提供信息,本文对其在超急性期、急性期脑缺血的应用价值和限度进行综述。     

采用扩散张量纤维束成像技术研究活体Broca语言功能区及其纤维环路的结构

目的 采用扩散张量成像技术揭示健康人Broea区与其他脑功能区间的纤维联系规律。方法 健康成人20名，采用Siemens Trio 3．0T MR仪及工作站行数据采集和后处理及Broea区（B45和44区）纤维追踪，分析由语言功能区发出的神经纤维分布和走行。结果 BroeaB45区纤维束平均值左侧为428束，右侧相应脑区为416束，两侧差异无统计学意义（t=0．216，P〉0．05）；B44区纤维束平均值左侧为432束，右侧相应脑区为344束，两侧差异有统计学意义（t=2．314，P〈0．05）。B45区部分各向异性左侧平均为0．336，右侧同区为0．317（t=-3．656，P〈0．05）；B44区左侧平均为0．342，右侧同脑区为0．342（t=0．093，P〉0．05）。弓状纤维束平均左侧为199束，右侧为205束（t=-0．465，P〉0．05）；平均部分各向异性左侧为0．385，右侧为0．375（t=1．912，P〈0．05）。Broea区发出纤维走行和分布，主要向前上到额叶前部内侧面皮层下，过胼胝体到对侧相应结构，向外下穿外囊向后经颞叶到枕叶，向内下穿苍白球和内囊后肢向下行。结论 Broea区及其相关的纤维结构形成重要的语言纤维环路结构，结构完整是完成语言功能的基础。     

Propriospinal myoclonus: utility of magnetic resonance diffusion tensor imaging and fiber tracking.

Propriospinal myoclonus (PSM) is a rare movement disorder characterized by involuntary spinal-generated muscular jerks that spread rostrally and caudally to other spinally innervated muscles. Most patients have no clear etiology, and conventional MRI of the spinal cord is generally normal. Here we report the use of magnetic resonance diffusion tensor imaging (DTI) and fiber tracking to detect tract-specific abnormalities in a patient with propriospinal myoclonus. As the patient had the fragile-X premutation and antithyroid antibodies, spinal cord DTI abnormalities may be related to these conditions. Tract-specific analysis may provide new insights into the pathophysiology of propriospinal myoclonus.     

关于引进双源CT的可行性分析

本文就双源CT的市场需求、特点和用途进行了详细分析,为医院引进双源CT提供参考。     

DTI在急性缺血性脑卒中所致皮质脊髓束损伤中的应用研究

目的:利用DTI探讨急性缺血性脑卒中病人大脑白质纤维束各向异性特征和皮质脊髓束受损与肌力的关系。方法:对9例正常被试和9例急性期缺血性脑卒中病人进行常规MR T1WI、T2WI和DTI检查,对数据进行离线后处理,采用dTV.II软件处理,获得FA图及方向编码彩色(DEC)图,并重建双侧皮质脊髓束3D纤维束图。结果:在正常组双侧白质纤维束FA值无明显差异,重建FA值图与方向编码彩色图可显示大部分主要的白质纤维束。在脑卒中病人组梗死区FA值显著低于健侧,两侧相比差异有显著性意义(t=4.570,P<0.001)。病变侧皮质脊髓束受压、变形、移位、部分断裂,皮质脊髓束受累情况与肌力有相关性(rs=0.888,P<0.05)。结论:DTI可显示脑内白质纤维束的走行及分布,为大脑白质纤维束的研究开辟了新的广阔领域。DTI FA值图及DEC图可以显示卒中病人梗死区白质纤维的方向与各向异性程度。3D纤维束图可以更立体直观的显示锥体束状况,有利于探讨皮质脊髓束损伤程度与肌力的关系,对临床及判断预后有重要价值。     

感染日本血吸虫的家兔治疗前后肝纤维化动态观察

感染日本血吸虫的家兔治疗前后肝纤维化Ｂ超声像图模型、血清ＭＡＯ水平及病理学结果表明，血吸虫引起的肝纤维化变化过程与血清ＭＡＯ水平升降趋势趋向一致，均在１８周达到高峰。解剖与病理学检查结果基本相符，血吸虫性肝纤维化形成后，只要及时给予杀虫治疗，肝纤维化部分可发生逆转。     

Assessment of tardive dyskinesia by means of digital image processing

A wireless device for the assessment of tardive dyskinesia by means of digital image processing is presented. Four skin-cream dots placed around the subjects' mouth are recorded by a video camera. The image is passed to a framegrabber with a signal processor, where it is converted from analogue to digital. A fast spot-detecting algorithm implemented on the signal processor tracks the dots and passes the information to a personal computer, where a Fourier transformation is performed to calculate the frequency spectrum of the movements. The device provided detailed information on the magnitude and on the frequencies of the movements. Data from a longitudinal investigation suggest a higher sensitivity and reliability than conventional rating scales to detect and evaluate abnormal perioral movements. The device might be useful for the early detection, for the longitudinal assessment (p.e. clinical trials) and in some cases for the differential diagnosis of tardive dyskinesia, thus providing a tool for both research and clinical purposes.     

Distribution and spatial geometry of dopamine interplexiform cells in the retina. II. External arborizations in the adult rat and monkey

The morphology and distribution of dopaminergic interplexiform cells in adult rat and monkey retinas were analyzed to determine any correlation with the function of dopamine in the outer retinal layers. The retinas were processed as whole mounts for tyrosine hydroxylase immunohistochemistry. There was a network formed by the sclerally directed processes of interplexiform cells in the inner nuclear, outer plexiform, and outer nuclear layers running throughout the retina. Their density was higher in the superior retina than in the inferior retina of the rat and was especially high in the superior temporal quadrant. The external network in this quadrant was significantly less dense in the monkey than in the rat, as are the interplexiform cells. The somata of interplexiform and other dopaminergic cells were about the same size in both rats and monkeys. Computer-assisted reconstruction of external arborizations of individual cells showed that external processes lay very close to horizontal and photoreceptor cells and also to blood capillaries. Because they were long, thin, and highly varicose; branched at right angles; and often arose from an axon hillock, the external processes were identified as axons. Therefore, we define the dopaminergic interplexiform cells as multiaxonal neurons, with at least one outwardly directed axon that reaches the outer plexiform layer. The function of the network of external processes from the interplexiform dopaminergic cells is discussed in terms of modulating the release of dopamine to external layers.     

核医学影像设备的发展与临床应用

γ相机和SPECT只能进行常规单光子显像，PET和双探头SPECT符合显像系统既能进行单光子显像，又能进行正电子符合显像，PET／CT系统的出现不仅提供高质量的衰减校正图像，保证了正电子显像校正数据的可靠性，而且能进行同机图像融合，提高了影像定位诊断的准确性。本文简要介绍了核医学影像设备发展历程，PET和PET／CT的原理以及在临床的应用。