单次激发EPI序列行颈髓磁共振功能成像的初步研究

目的　探讨颈髓磁共振功能成像的可行性和研究意义。方法　对 7例健康右利手进行握拳、屈腕及穴位按压试验 ,采用1.5TPhilipsGyroscan磁共振系统 ,运用单次激发EPI扫描序列进行颈髓功能成像并进行BOLD法功能分析。结果　 7例均不同程度激活相应脊髓兴奋区 ,握拳试验和屈腕试验主要激活C4 ～T1 支配区 ,信号增加强度一般在 10 %～ 2 0 %之间 ,穴位按压试验显示兴奋点分布较散在 ,信号增加强度略低。结论　 1.5T磁共振系统可以通过快速扫描序列进行颈髓功能磁共振成像的研究 ,有望对脊髓疾病的机理研究和治疗指导、疗效监测提供帮助     

颈髓扩散张量磁共振成像扫描参数的比较

目的 探索颈髓扩散张量磁共振成像(DTI)最佳扫描参数. 资料与方法 对40名成年健康志愿者行颈髓DTI,比较不同b值、扩散敏感梯度方向数、激励次数(NEX)、层厚对图像质量的影响.第1组,b值分别取400 mm2/s、700 mm2/s、1000 mm2/s;第2组,扩散敏感梯度方向数分别取6个、13个、25个;第3组,激励次数分别取2、4、8;第4组,层厚分别取2 mm、3 mm、4 mm. 结果 在四种不同扫描参数的比较中,b值为700 mm2/s的一级图像数较b值为400 mm2/s 和1000 mm2/s的多;方向为25时的一级图像数较方向为6和13的图像质量多;NEX为4的一级图像数较NEX为2和8的多;层厚为4 mm的一级图像质量较层厚2 mm和3 mm的多. 结论 b值为700 mm2/s、扩散敏感梯度方向数为25个、NEX为4和层厚为4 mm是颈髓DTI较好的扫描参数.     

MR弥散加权成像在颈髓中的应用

目的　探讨颈髓磁共振弥散加权成像技术方法及其临床应用价值。方法　对 5名健康志愿者的正常颈髓、10例水肿型颈髓外伤者、18例颈椎椎间盘突出者进行SEEPI多次激发弥散加权成像扫描。扫描中使用外周搏动门控减少脑脊液搏动伪影 ,同时使用自动匀场、抑脂技术和自动导航技术以减少各种伪影和增加图像的清晰度。结果　 3 3例均获得弥散加权图像和弥散系数图。 10例水肿型脊髓外伤表现表面弥散系数 (ADC)减低 ,ADC图低信号 ;18例椎间盘突出ADC增高 ,ADC图高信号。结论　合理应用扫描技术 ,可实现颈髓弥散加权成像 ,对颈髓病变的早期诊断具有较高的临床应用价值。     

3.0T MRI功能成像在急性创伤性颈髓损伤中的研究进展

急性颈髓损伤(ACSCI)是最常见的创伤性中枢神经损伤之一,致残、致死率较高,当T2WI发现颈髓异常信号时,提示颈髓损伤严重,因此选用一种有效、精确、无创的影像学技术早期发现ACSCI,尽早干预治疗对改善患者预后尤为关键。目前,无创性MRI功能成像不仅可观察颈髓的形态及信号改变,还可进行颈髓微观结构的研究。本文就SWI、DWI、DTI、扩散峰度成像(DKI)、MRS、BOLD-f MRI等无创性MRI技术在颈髓损伤方面的进展进行综述。     

颈髓损伤对颈髓细胞线粒体膜流动性与线粒体呼吸功能的影响

目的 探讨颈髓损伤后颈髓细胞线粒体膜流动性变化与线粒体呼吸功能的关系。方法 ３０只猫随机分成假手术组（对照组）和颈髓损伤后２,６,２４,７２ｈ组,每组６只。采用Ａｌｌｅｎ打击法造成猫颈髓损伤,观察颈髓损伤后线粒体膜流动性、磷脂酶Ａ２（ＰＬＡ２）活性、线粒体呼吸控制率（ＲＣＲ）、磷氧比值（Ｐ／Ｏ）、氧化磷酸化效率（ＯＰＲ）的变化。结果 颈髓损伤后２～７２ｈ线粒体膜ＰＬＡ２活性较假手术对照组明显增高（     

基于对比剂分段注射的颈髓双期CT血管成像

目的 探讨对比剂分段注射颈髓双期CT血管成像(CTA)检查在颈髓血管中的应用价值.方法 对30例临床怀疑脊髓型颈椎病拟行头颈部CTA检查的患者进行对比剂分段注射颈髓双期CTA检查(A组),先期团注流率为4 mL/s,后期以2 mL/s的低流率持续注射,先期团注和后期低流率持续注射对比剂剂量的比率为3∶1,采用常规峰值(...     

多层面螺旋CT血管成像应用参数优化

目的 探讨多层面螺旋CT血管成像(MSCTA)中扫描参数和重建方法的影响。资料与方法 60例共120次MSCT扫描，Marconi Mx8000型4层CT扫描仪，分别将准直层厚5．0mm、2．5mm、1．0mm与PitchO．875、1．25、1．75相匹配，各组数据分别以0％、50％、70％重叠重建率，对容积再现(VR)重建血管图像的图像质量和血管分支级数显示评分，不同层厚、重叠重建率和Pitch分组比较，将准直层厚2．5mm、1．0mm组，重叠50％重建68次血管成像行最大密度投影(MIP)重建，与对应VR图像行配对t检验。结果准直层厚1．0mm组O％和50％重叠重建及准直层厚2．5mm组重叠重建率50％、70％图像得分无显著性差异，但与准直层厚2．5mm组重叠重建率0％及准直层厚5．0mm组图像得分有显著性差异；准直层厚2．5mm时3种Pitch图像得分无显著性差异；准直层厚2．5mm和1．0mm时VR重建和MIP重建的得分无显著性差异。结论MSCTA时选择适当的扫描重建参数，可以显示较多血管分支级数，获得较好的图像质量，其优化的条件为：准直层厚2．5mm，Pitch1．75，50％重叠重建，两种重建方法VR和MIP在显示血管方面无明显差别。     

正常人颈髓弥散张量成像的初步研究

目的 探讨弥散张量成像(DTI)在正常人颈髓中的应用.方法 使用单次激发自旋回波平面成像(SS-SE-EPI)序列对30例MR检查的正常人行颈髓DTI成像,在C2～3、C4～5、C6～7节段测量颈髓平均扩散系数值(Dcavg)及各向异性分数(FA).结果 (1) 正常人颈髓在Dcavg图及FA图上为较均匀的等信号及高信号,在彩色Dcavg图及FA图上为深蓝色及红色信号. (2) C2～3、C4～5、C6～7节段Dcavg值(1×10-3mm/s)分别为0.882±0.034、0.811±0.042 、0.717±0.068,FA值分别为 0.719±0.038、0.618±0.051、0.537±0.034.(3)C2～3、C4～5、C6～7节段的Dcavg值及FA值均有统计学意义(P<0.05).结论 SS-SE-EPI序列能够获得满意的颈髓DTI图像.颈髓的平均Dcavg值为(0.803±0.082)×10-3mm/s,FA值为0.624±0.091.     

多发性硬化颈髓病变磁化传递成像的临床应用

目的探讨3.0T磁共振扫描仪(Siemens Trio Tim)磁化传递成像(MTI)在多发性硬化(MS)颈髓病变中的应用价值及其与临床的关系。资料与方法对11例伴颈髓病变的MS患者和20名健康自愿者行颈髓常规MRI和MTI。测量健康自愿者C2～7水平、MS患者MS斑块及正常表观颈髓(NACC)的磁化传递率(MTR),对其进行对照研究,并分析MTR与扩展病残状态评分(EDSS)之间的相关性。结果健康自愿者颈髓平均MTR值为(27.12±0.27)%,C2～7水平间颈髓MTR值差异无统计学意义(P>0.05)。MS斑块组、NACC组及对照组间的MTR值差异均具有统计学意义(P<0.05)。MS斑块组的MTR值与EDSS值存在高度负相关(r=-0.754,P=0.007)。结论颈髓MTI能发现MS患者T2WI病灶以外的隐匿性损伤,为判断损害程度提供信息。     

Functional magnetic resonance imaging of the human brain based on signal enhancement by extravascular protons (SEEP fMRI).

Functional magnetic resonance imaging (fMRI) studies of the human brain were carried out at 3 Tesla to investigate an fMRI contrast mechanism that does not arise from the blood oxygen-level dependent (BOLD) effect. This contrast mechanism, signal enhancement by extravascular protons (SEEP), involves only proton-density changes and was recently demonstrated to contribute to fMRI signal changes in the spinal cord. In the present study it is hypothesized that SEEP fMRI can be used to identify areas of neuronal activity in the brain with as much sensitivity and precision as can be achieved with BOLD fMRI. A detailed analysis of the areas of activity, signal intensity time courses, and the contrast-to-noise ratio (CNR), is also presented and compared with the BOLD fMRI results. Experiments were carried out with subjects performing a simple finger-touching task, or observing an alternating checkerboard pattern. Data were acquired using a conventional BOLD fMRI method (gradient-echo (GE) EPI, TE = 30 ms), a conventional method with reduced BOLD sensitivity (GE-EPI, TE = 12 ms), and SEEP fMRI (spin-echo (SE) EPI, TE = 22 ms). The results of this study demonstrate that SEEP fMRI may provide better spatial localization of areas of neuronal activity, and a higher CNR than conventional BOLD fMRI, and has the added benefit of lower sensitivity to field inhomogeneities.     

Somatotopic arrangement of thermal sensory regions in the healthy human spinal cord determined by means of spinal cord functional MRI

Previous functional MRI studies of normal sensory function in the human spinal cord, including right-to-left symmetry of activity, have been influenced by order effects between repeated studies. In this study, we apply thermal sensory stimulation to four dermatomes within each functional MRI time-series acquisition. Each of the four dermatomes receives a unique stimulation paradigm, such that the four paradigms form a linearly independent set, enabling detection of each individual stimulus response. Functional MRI data are shown spanning the cervical spinal cord and brainstem in 10 healthy volunteers. Results of general linear model analysis demonstrate consistent patterns of activity within the spinal cord segments corresponding to each dermatome, and a high degree of symmetry between right-side and left-side stimulation. Connectivity analyses also demonstrate consistent areas of activity and connectivity between spinal cord and brainstem regions corresponding to known anatomy. However, right-side and left-side responses are not at precisely the same rostral-caudal positions, but are offset by several millimeters, with left-side responses consistently more caudal than right-side responses. The results confirm that distinct responses to multiple interleaved sensory stimuli can be distinguished, enabling studies of sensory responses within the spinal cord without the confounding effects of comparing sequential studies.     

SSFSE sequence functional MRI of the human cervical spinal cord with complex finger tapping

Purpose

Functional MR imaging of the human cervical spinal cord was carried out on volunteers during alternated rest and a complex finger tapping task, in order to detect image intensity changes arising from neuronal activity.

Methods

Functional MR imaging data using single-shot fast spin-echo sequence (SSFSE) with echo time 42.4 ms on a 1.5 T GE Clinical System were acquired in eight subjects performing a complex finger tapping task. Cervical spinal cord activation was measured both in the sagittal and transverse imaging planes. Postprocessing was performed by AFNI (Analysis of Functional Neuroimages) software system.

Results

Intensity changes (5.5–7.6%) were correlated with the time course of stimulation and were consistently detected in both sagittal and transverse imaging planes of the cervical spinal cord. The activated regions localized to the ipsilateral side of the spinal cord in agreement with the neural anatomy.

Conclusion

Functional MR imaging signals can be reliably detected with finger tapping activity in the human cervical spinal cord using a SSFSE sequence with 42.4 ms echo time. The anatomic location of neural activity correlates with the muscles used in the finger tapping task.     

Investigation of human cervical and upper thoracic spinal cord motion: implications for imaging spinal cord structure and function.

Spinal cord (SC) motion is thought to be the dominant source of error in current diffusion and spinal functional MRI (fMRI) methods. However, until now, such motion has not been well characterized in three dimensions. While previous studies have predominantly examined motion in the superior/inferior (S/I) direction, the foci of the present study were the anterior/posterior (A/P) and right/left (R/L) components of human cervical and upper thoracic SC motion. Cardiac-gated, turbofast low-angle shot (turbo-FLASH) cinematic MRI was employed at 3T to acquire images of the cord at 24 phases throughout the cardiac cycle. Time-dependent signal fluctuations within voxels adjacent to the cord/cerebrospinal fluid (CSF) interface were then used to measure SC motion, which was found to occur predictably as a function of cardiac activity. Cord movement was largest in the A/P direction, for which principal components of motion were calculated, thereby indicating consistent patterns of SC oscillation that can potentially be used to improve SC imaging.     

Spatially filtering functional magnetic resonance imaging data

When constructing MR images from acquired spatial frequency data, it can be beneficial to apply a low-pass filter to remove high frequency noise from the resulting images. This amounts to attenuating high spatial frequency fluctuations that can affect detected MR signal. A study is presented of spatially filtering MR data and possible ramifications on detecting regionally specific activation signal. It is shown that absolute activation levels are strongly dependent on the parameters of the filter used in image construction and that significance of an activation signal can be enhanced through appropriate filter selection. A comparison is made between spatially filtering MR image data and applying a Gaussian convolution kernel to statistical parametric maps.     

Functional magnetic resonance imaging of the human lumbar spinal cord

PURPOSE: To determine whether consistent regions of activity could be observed in the lumbar spinal cord of single subjects with spin-echo functional MRI (fMRI) if several repeated experiments were performed within a single imaging session. MATERIALS AND METHODS: Repeated fMRI experiments of the human lumbar spinal cord were performed at 1.5 T with a single-shot spin-echo technique (half-Fourier single-shot turbo spin-echo (HASTE)) as used by previous investigators, and a modified method (fluid-attenuated inversion recovery (FLAIR)-HASTE) that nulled the otherwise highly variable signal from the cerebrospinal fluid (CSF). RESULTS: FLAIR-HASTE reduced the variability of the signal in the CSF region to background levels, and presumably reduced associated artifacts in the spinal cord. Consistent areas of activation in the spinal cord in response to a thermal stimulus just below the knee were not observed across the fMRI experiments with either method. CONCLUSION: FLAIR-HASTE was useful for removing artifact in the spinal cord signal induced by variability in the CSF signal. However, with the techniques used in this study, we were not able to confirm the presence of a consistent fMRI response in the lumbar spinal cord because of the signal enhancement by extravascular protons (SEEP) effect during thermal stimulation of the hindlimb.     

Functional magnetic resonance imaging of the human spinal cord during vibration stimulation of different dermatomes

Introduction We investigated noninvasively areas of the healthy human spinal cord that become active in response to vibration stimulation of different dermatomes using functional magnetic resonance imaging (fMRI). The objectives of this study were to: (1) examine the patterns of consistent activity in the spinal cord during vibration stimulation of the skin, and (2) investigate the rostrocaudal distribution of active pixels when stimulation was applied to different dermatomes. Methods FMRI of the cervical and lumbar spinal cord of seven healthy human subjects was carried out during vibration stimulation of six different dermatomes. In separate experiments, vibratory stimulation (about 50 Hz) was applied to the right biceps, wrist, palm, patella, Achilles tendon and left palm. Results The segmental distribution of activity observed by fMRI corresponded well with known spinal cord neuroanatomy. The peak number of active pixels was observed at the expected level of the spinal cord with some activity in the adjacent segments. The rostrocaudal distribution of activity was observed to correspond to the dermatome being stimulated. Cross-sectional localization of activity was primarily in dorsal areas but also spread into ventral and intermediate areas of the gray matter and a distinct laterality ipsilateral to the stimulated limb was not observed. Conclusion We demonstrated that fMRI can detect a dermatome-dependent pattern of spinal cord activity during vibratory stimulation and can be used as a passive stimulus for the noninvasive assessment of the functional integrity of the human spinal cord. Demonstration of cross-sectional selectivity of the activation awaits further methodological and experimental refinements.     

Magnetic resonance imaging of the normal and chronically injured adult rat spinal cord in vivo

We assessed the capacity of MRI to show and characterise the spinal cord (SC) in vivo in normal and chronically injured adult rats. In the chronically injured animals the SC was studied by MRI and histological examination. MRI was performed at 1.5 T, using gradient-echo and spin-echo (SE) sequences, the latter with and without gadolinium-DTPA (Gd-DTPA). Several positions were tried for good alignment and to diminish interference by respiratory movements. Images of the SC were obtained in sagittal, coronal, and axial planes. Normal SC was observed as a continuous intensity in both sequences, although contrast resolution was better using SE; it was not possible to differentiate the grey and white matter. Low signal was seen in the damaged area in chronically injured rats, which corresponded to cysts, trabeculae, mononuclear infiltrate, and fibroglial wall on histological examination. Gd-DTPA failed to enhance the SC in normal or chronically injured rats. It did, however, cause enhancement of the lesion after acute SC injury.     

Manganese-enhanced magnetic resonance imaging for in vivo assessment of damage and functional improvement following spinal cord injury in mice.

In past decades, much effort has been invested in developing therapies for spinal injuries. Lack of standardization of clinical read-out measures, however, makes direct comparison of experimental therapies difficult. Damage and therapeutic effects in vivo are routinely evaluated using rather subjective behavioral tests. Here we show that manganese-enhanced magnetic resonance imaging (MEMRI) can be used to examine the extent of damage following spinal cord injury (SCI) in mice in vivo. Injection of MnCl2 solution into the cerebrospinal fluid leads to manganese uptake into the spinal cord. Furthermore, after injury MEMRI-derived quantitative measures correlate closely with clinical locomotor scores. Improved locomotion due to treating the detrimental effects of SCI with an established therapy (neutralization of CD95Ligand) is reflected in an increase of manganese uptake into the injured spinal cord. Therefore, we demonstrate that MEMRI is a sensitive and objective tool for in vivo visualization and quantification of damage and functional improvement after SCI. Thus, MEMRI can serve as a reproducible surrogate measure of the clinical status of the spinal cord in mice, potentially becoming a standard approach for evaluating experimental therapies.