MR image segmentation using vector decomposition and probability techniques: A general model and its application to dual-echo images

A general model is developed for segmenting magnetic resonance images using vector decomposition and probabilfty techniques. Each voxel is assigned fractional volumes of q tissues from p differently weighted images (q ≤ p + 1) in the presence of partial-volume mixing, random noise, and other tissues. Compared wtth the eigenimage method, fewer differently weighted images are needed for segmenting the q tissues, and the contrast-to-noise ratio in the calculated fractional volumes is improved. The model can produce com-posrte tissue-type images similar to that of the probability methods, by comparing the fractional volumes assigned to different tissues on each voxel. A three-tissue (p = 2, q = 3) model is illustrated for segmenting three tissues from dual-echo images. M provides statistical analysis to the algebraic method. A three-compartment phantom is segmented for validation. Two clinical examples are presented.     

Congenital defects of lower limbs and associated malformations: A population based study

As part of a detailed study of limb defects and associated patterns of congenital malformations, cases with lower limb deficiencies were analysed separately. We identified a total of 130 cases with deficiencies of the lower limbs without defects of the upper limbs. This gives an incidence of 1.07/10,000 livebirths, or 1/9,337 for this group of limb defects. Most common were femur deficiencies and deficiencies of the foot. A preponderance of males was found in the group of transverse defects of the leg (fibula/tibia deficiencies) and central axis deficiencies, while females had significantly more often longitudinal tibia defects and preaxial ray defects. © 1993 Wiley-Liss, Inc.     

下尿路梗阻性肾积水患者逼尿肌功能变化

目的：探讨下尿路梗阻性肾积水患者逼尿肌功能变化。方法：对20例（3．5－73岁）下尿路梗阻导致的肾积水组和10例（13－67岁）无肾积水的对照组进行膀胱压力容积测定与压力－流率测定，并记录不同膀胱灌注量的逼尿肌基础压力。结果：下尿路梗阻性肾积水组逼尿肌－括约肌协同失调（DSD）11例（55％），逼尿肌功能过度活跃5例；而对照组仅发现1例（10％）DSD，未发现有逼尿肌功能过度活跃。下尿路梗阻性肾积水组平均膀胱顺应性显著低于对照组（P＜0．05），而下尿路梗阻性肾积水组平均逼尿肌基础压力，平均逼尿肌最大收缩压和残余尿量均显著高于对照组（P＜0．05），且下尿路梗阻性肾积水组在灌注量逐渐增加时高逼尿肌基础压力发生率逐渐增加。结论：下尿路梗阻性肾积水多伴有逼尿肌功能异常，提示膀胱逼尿肌功能改变与下尿路梗阻性肾积水的形成及发展有一定的相关性。     

Contrast agents in functional MR imaging

Contrast agents have greatly expanded the role of MR imaging (MRI) to allow assessment of physiologic, or “functional,” parameters. Although activation mapping generally does not require contrast agents, other forms of functional MRI, including mapping of cerebral hemodynamics (eg, perfusion imaging), are best done with the use of contrast agents. Serial echo planar images are obtained after bolus injection of lanthanide chelates. Application of susceptibility contrast physics and standard tracer kinetic principles permits generation of relative cerebral blood volume maps. Deconvolution of cerebral blood flow and mean transit time parameters is also possible within technical limitations. By using diffusion and perfusion pulse sequences, an imaging correlate to the ischemic penumbra can be identified. Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality. Clinical applications include biopsy site selection and postirradiation follow-up. Further improvements in data analysis and map generation techniques may improve diagnostic accuracy and utility.     

Localized echo-volume imaging methods for functional MRI

To perform true three-dimensional activation experiments in the human brain, dedicated localized echo-volume imaging (L-EVI) methods were developed. Three-dimensional acquisition allows generation of activation maps with minimal vascular enhancement related to inflow effects. The rapid acquisition of the L-EVI (～100 msec) reduces signal instabilities caused by motion, facilitating the detection of the small intensity changes expected with brain activation. Single-shot L-EVI was performed on normal volunteers at 1.5 T, imaging a three-dimensional predefined volume (240 × 45 × 45 mm³) in the superior portion of the brain with a spatial resolution of 3.75 × 5 × 5 mm³. Increased brain coverage was achieved with a multi-volume imaging (three-shot) version, which simultaneously achieved effective suppression of signals from cerebrospinal fluid. In addition, both asymmetric spin-echo (ASE) and spin-echo (SE) versions of the technique were used to detect blood oxygenation level dependent (BOLD) signal changes in the motor cortex with a finger-tapping paradigm. Images obtained by the L-EVI sequence were qualitatively comparable to standard multislice two-dimensional echo-planar images. Both ASE and SE functional MRI (fMRI) experiments showed consistent activation in the contralateral primary sensorimotor cortex. Furthermore, significant differences in location and magnitude of activation was observed between the two methods, confirming theoretical predictions.     

Day-Night Variation of Urine Volume in Parkinson's Disease

Abstract: Studies on the circadian rhythm of urine excretion in healthy men have demonstrated that the maximal urine flow occurs in the early afternoon and the minimal around midnight. In this study, an abnormality in the variation of urine volume was found in parkinsonian patients. Urine samples were collected during daytime (9:00–21:00) and nighttime (21:00–9:00). Fifteen healthy control subjects were examined and found to excrete 60% during the daytime and 40% during the nighttime of the total urine volume. Sixteen parkinsonian patients excreted 43% during the daytime and 57% during the nighttime. In contrast to the control subjects, the parkinsonian patients excreted a smaller volume of their urine during the daytime than during the nighttime. This finding might be related to the degeneration of dopaminergic and/or nondopaminergic neurons in the brain which control urinary excretion.     

低位直肠癌根治性切除保肛术式53例临床应用研究

本文介绍一种经腹低位直肠癌根治性切除，保留肛门，乙状结肠拖下固定术式。６年来共施行此手术５３例，占同期低位直肠癌（肿瘤下缘距齿状线２～８ｃｍ）手术部数的９６％（５３／５５）。术后２年和５年肿瘤复发率分别７．７％和１４．３％。术后４周、８周和６个月内完全肛门排便功能者分别占４．９１％、９８％和１００％。肛门功能恢复程度均属均属优良。作者对此术式的特点，并根据手术疗效对保留肛门功能的合理性及其根治性进     

Application of a 3D volume 19FMR imaging protocol for mapping oxygen tension (pO2) in perfluorocarbons at low field

A limited flip angle gradient-echo 3D volume acquisition imaging protocol for mapping partial pressure of oxygen (pO₂) in perfluorocarbon compounds (PFCs) at low field (0.14 T) is presented. The pO₂ measurement method is based on the paramagnetic effect of dissolved molecular oxygen (O₂) which reduces the PFC ¹⁹F T_1? Specific objectives related to imaging of PFCs through use of the protocol include improved image signal-to-noise characteristics and elimination of ¹⁹F chemical shift artifacts. A parametric Wiener deconvolution filtering algorithm is used for suppression of ¹⁹F chemical shift artifacts. Application of the protocol is illustrated in a series of calculated pO₂ maps of a gas equilibrated, multi-chamber phantom containing perfluorotributylamine (FC-43). The utility of the protocol is demonstrated in vivo through images of a commercially available perfluorocarbon based blood substitute emulsion containing FC-43 sequestered in the liver and spleen of a rat.     

微创刨吸术治疗下肢静脉曲张初步研究

目的探讨微创刨吸术治疗下肢静脉曲张的初步疗效.方法对2003年6～9月40例(53条肢体)下肢静脉曲张病人进行手术治疗.53条患肢均存在浅静脉曲张,16条患肢同时伴交通支静脉功能不全,10条患肢同时伴慢性静脉性溃疡,5条患肢同时伴重度深静脉返流.根据病情需要分别或同时行内镜深筋膜下交通支静脉结扎、大隐静脉高位结扎和剥脱飞股浅静脉瓣膜外修复成形术和下肢曲张浅静脉微创刨吸术.结果术后53条患肢肢体症状和浅静脉曲张消失,10条患慢性静脉性溃疡肢体短期内愈合.术后短期随访,无新生的渍疡,无静脉曲张复发,小腿外观无明显手术疤痕.结论微创刨吸术治疗下肢静脉曲张安全有效,损伤少,并发症少,达到了微创和显效的目的,可能是治疗下肢慢性静脉功能不全的重要组成部分.     

下腰椎后路手术并发脑脊液漏的处理

目的探讨下腰椎后路手术并发脑脊液漏的预防措施及处理。方法收集1999年1月-2004年6月259例下腰椎后路手术病例,腰间盘突出症174例,腰椎管狭窄症36例,腰椎滑脱症18例,腰椎间盘突出症失败再手术31例。术中发生硬脊膜损伤依次为8、5、2、6例,共计21例。术中采用硬脊膜破损口缝合术和明胶海绵封堵填塞法处理,术后采用侧俯卧头低腰高体位,引流管拔除时管口皮肤全层缝合,或经引流管口填塞明胶海绵 管口皮肤全层缝合及对症处理。结果21例中12例经术中及术后处理,切口1期愈合,未发生术后脑脊液漏(CSFL),9例术后发生CSFL,轻型2例、中型4例、重型3例。其中重型1例发生感染,其余8例术后9￣24d治愈。感染病例予以再次手术,再手术后第35d治愈。术后随访9￣31个月(平均16个月),全部病例未发生脑脊液囊肿形成,术后神经功能恢复良好。结论下腰椎后路手术发生CSFL,术中尽可能修复硬脊膜破损口并以明胶海绵填塞,术后采用头低腰高体位,适时拔除引流管并全层缝合管口皮肤等措施,可获得满意疗效。