T2?值在健康成年人脑铁含量与年龄的相关性分析

目的：采用3.0T ESWAN 定量测量健康成年人额叶白质区及灰质核团的 T2?值,探讨额叶白质区及灰质核团与年龄的相关性。方法收集年龄20~85岁的157例健康成年人进行 MRI 常规及 ESWAN 扫描,按其年龄段分为6组。A 组：20~29岁;B 组：30~39岁;C 组：40~49岁;D 组：50~59岁;E 组：60~69岁;F 组：≥70岁。经后处理在 T2?图像上分别测量左右侧额叶白质区、红核、黑质网状带、黑质致密带、尾状核头、壳核、苍白球和丘脑的 T2?值,分析 T2?值与年龄的相关性。结果健康成年人在黑质网状带、苍白球的T2?值最低,额叶白质区的T2?值最高。红核、壳核、苍白球、尾状核头和丘脑的T2?值在部分年龄段间有统计学意义(P <0.05),有一定规律性。而黑质网状带、黑质致密带、额叶白质区的 T2?值在不同年龄段间差异无统计学意义(P >0.05)。红核、黑质网状部、黑质致密部、壳核、苍白球、尾状核头的 T2?值与年龄呈明显负相关(r 值=-0.258、-0.229、-0.231、-0.584、-0.320、-0.437, P 值均<0.001),而丘脑、额叶白质区的 T2?值与年龄呈正相关(r 值=0.319、0.161,P <0.001及0.05)。结论ESWAN 能清晰显示脑内核团的结构,准确评估脑内的铁含量和随年龄变化的规律。     

三维增强T2*加权血管成像量化多发性硬化脑铁沉积的研究

目的 探讨三维增强T2*加权血管成像(ESWAN)相位值(phase)及有效横向弛豫率值(R2*)对多发性硬化(MS)患者深部灰质核团铁沉积的诊断价值,并分析测量值与扩展型残疾状态评分(EDSS)、病程相关性.方法 22例临床确诊MS患者及与之性别、年龄及教育程度相匹配的22名健康对照组行常规MRI和ESWAN扫描.测量患者及对照组深部灰质核团(双侧丘脑、尾状核头、壳核、苍白球、红核、黑质)phase值及R2*值.详细记录每例患者病程时间及EDSS评分.结果 (1)MS患者双侧深部灰质核团phase值均低于对照组,其中双侧尾状核头、壳核、红核及黑质与对照组比较差异具有统计学意义(P＜0.05).(2)MS患者双侧各个灰质核团R2*均高于对照组,差异均具有统计学意义(P＜0.05).(3)MS患者各深部灰质核团phase值、R2*值与EDSS评分、临床病程均无明显相关性(P＞0.05).结论 ESWAN序列多种测量值均能定量显示MS患者脑深部灰质核团明显铁质含量增多,有助于了解MS病理机制、研究颅内铁沉积与患者临床表现的相关性.     

肝硬化患者大脑基底节和白质弛豫时间测量研究

目的探讨肝硬化患者大脑基底节和白质的弛豫时间与肝硬化严重程度及血氨值的关系,评价MRI弛豫时间测量对肝硬化累及脑组织的诊断价值.方法应用MR SE脉冲序列对22例肝硬化患者[其中男20例,女2例,平均年龄(46.4±8.1)岁] 和18位成人健康志愿者[男16例,女2例,平均年龄(42.4±8.4)岁]行MR检查,应用经典SE脉冲序列2点法测量和计算苍白球、壳核、尾状核头、丘脑和大脑白质的T1和T2值.在MR扫描后1周内,对其中8例患者行血氨水平测定.结果 15例肝硬化患者T1WI可见基底节区信号增高,7例无明显异常改变.7例T2WI基底节区信号明显减低,15例无明显异常改变.肝硬化患者苍白球、壳核、尾状核头、丘脑与皮层下白质的T1值均与正常对照组差异有非常显著性意义(P<0.01),Child C级苍白球、壳核、尾状核头和丘脑的T1值与Child B级间差异有非常显著性意义(P<0.01),苍白球T1值与血氨值呈显著负相关(r= -0.790);除尾状核头外,苍白球、壳核、丘脑与皮层下白质的T2值患者与对照组差异均无显著性意义(P>0.05).结论 MRI大脑基底节T1值测量可用于评价肝硬化及其所致脑组织变性的严重程度.     

注射过线性钆对比剂病人的定量MRI全脑及局部脑评估

正摘要目的评估注射过线性钆对比剂(GBCA)病人全脑和局部脑组织弛豫时间的关系。材料与方法机构伦理委员会批准了这一横向研究。35例病人(9例注射过GBCA钆喷酸葡胺1~8次,26例没有注射过)行快速混合自旋回波脉冲序列的MRI检查。采用双聚类算法依据灰质白质结构对全脑进行分割。此外,在苍白球、齿状核、丘脑和脑桥选择兴趣区进行测量。Mann-Whitney U检验用于评估组间的差异。多重回归分析评估T1和T2与先前注射GBCA暴露的关联。结果注射过GBCA病人的灰质T1值明显低于未注射过GBCA     

正常胎儿脑形态和髓鞘形成的MRI以及弛豫时间测量

目的 :评价胎脑形态学和髓鞘形成过程的MR成像 ,对胎脑弛豫时间进行测量。材料和方法 :正常胎脑标本 3 2例 ,胎龄 16～ 3 9周。对胎脑形态以及 8个解剖区的信号强度进行了评价 ;对脑灰、白质的T1和T2弛豫时间进行了测量并对数据进行统计学分析。结果 :MR成像能很好地显示某些脑裂、脑沟及脑回按时间依次出现的过程 ;髓鞘形成过程发生较早 ,呈现为向头端有序的变化方式 ;胎儿脑白质的T1和T2弛豫时间明显长于灰质的T1和T2弛豫时间。结论 :MR成像可用于评价胎脑形态及髓鞘形成 ;胎脑含水量持续高于成人脑含水量 ,水在胎脑灰、白质中的分布与成人不同。     

7.0T磁敏感加权成像对脑铁含量测定的初步研究

目的:对比7.0T与3.0T磁敏感加权成像铁含量测量的差异,并积累超高场磁共振神经成像经验。方法:50例老年志愿者(年龄52～68岁,男36例,女14例)分别在7.0T和3.0T磁共振成像系统上行常规颅脑磁共振成像及磁敏感加权成像(SWI)。对比不同场强下的图像质量,测量受试者双侧苍白球、壳核、尾状核头、黑质、红核以及丘脑的大小及相位值,同时测量受试者各核团铁含量。结果:①幅度图上,7.0T影像能提供更多细节,并可区分核团亚分区(P<0.05);②7.0T下可辨识的ROI范围较3.0T下的略大,不同场强的各核团ROI范围差异有统计学意义(P<0.05);③除苍白球外,壳核、尾状核头、黑质、红核及丘脑3.0T和7.0T比较,铁含量测量值差异均有统计学意义(P<0.05)。结论:7.0T磁共振磁敏感成像可提供更多解剖细节,SWI脑铁含量测量值与3.0T可能存在差异。     

MRI T1ρ成像对脑胶质瘤术前病理分级的应用价值

目的 :初步探讨MRI T1ρ成像对脑胶质瘤术前病理分级的应用价值。方法 :回顾性分析经手术病理证实的37例脑胶质瘤,按照WHO 2007年标准分成2组:低级别胶质瘤(Ⅰ～Ⅱ级)21例,高级别胶质瘤(Ⅲ～Ⅳ级)16例。测量肿瘤实质部分的T1ρ值和对侧半球、白质、灰质的T1ρ值,并分别计算出肿瘤实质部分T1ρ值与对侧半球、白质、灰质T1ρ值的比值,分析不同级别胶质瘤T1ρ值及各项比值。结果:37例胶质瘤实质区的T1ρ值较对侧正常区均不同程度升高,肿瘤实质区的T1ρ值与对侧半球、白质和灰质T1ρ值的比值在高低级别2组胶质瘤间差异均有统计学意义(均P0.05)。肿瘤实质区T1ρ值和对侧半球、白质、灰质T1ρ值的比值与肿瘤级别均呈负相关(r=-0.77,P=0.037;r=-0.81,P=0.031;r=-0.72,P=0.027)。结论:T1ρ成像在脑肿瘤的临床应用是可行的,对胶质瘤的术前分级有重要的参考价值。     

VBM-DARTEL法对青少年肥胖针灸治疗的中枢机制研究

目的应用VBM-DARTEL分析法探讨针灸疗法对肥胖青少年大脑皮层重建的影响。方法 10名单纯性肥胖青少年〔男7例,女3例,14～18岁,右利手,体重指数:(29.03±4.81)kg/m2〕行阶段性针灸减肥治疗,在治疗前、后分别行颅脑高分辨三维T1加权成像,同时招募10名年龄性别相匹配的健康自愿者〔右利手,体重指数:(25.05±5.02)kg/m2〕作为对照组。数据分析使用软件平台为SPM8MATLAB R2009a。结果①右侧额上回,小脑后叶椎体灰质体积减小,右侧中央前回灰质体积增大;左侧海马旁区梭状回,桥脑及中央前回区白质体积减小;右侧楔前叶白质体积增大(P<0.05);②治疗前肥胖受试者与体重正常对照组比较,小脑及外侧苍白球灰质体积增大,桥脑及小脑白质体积减小;治疗后肥胖受试者与体重正常对照组比较,外侧苍白球灰质体积增大更显著,桥脑白质增大,原先位于小脑的灰质及白质差异区未显现。结论①针灸疗法对大脑发育及皮层重建可能存在影响;②正常体重者与肥胖者间可能存在大脑细微结构的差异。     

SWI 测量脑铁在帕金森病病情评估中的应用价值

目的：探讨磁敏感加权成像(SWI)测量脑铁在帕金森病(PD)的诊断以及病情评估中的应用价值。方法30例经临床诊断为PD 的患者行颅脑磁共振常规序列和 SWI 序列扫描,PD 患者病情评估采用统一帕金森病评定量表(UPDRS)。在 SWI 序列相位图上手动测量患者黑质、红核、尾状核、苍白球和壳核的相位值,分析以上感兴趣区(ROI)核团的相位值与 UPDRS 评分的相关性。结果ROI 核团病重侧与病轻侧的相位值比较无差异(黑质,P =0.120;红核,P =0.402;尾状核,P =0.196;苍白球,P =0.616;壳核, P =0.985);PD 患者 UPDRS Ⅲ评分分别与黑质、尾状核和苍白球的相位值呈负相关(黑质-UPDRS Ⅲ：r =-0.407,P =0.026;尾状核-UPDRS Ⅲ：r=-0.424,P=0.02;苍白球-UPDRS Ⅲ：r=-0.363,P=0.048);黑质相位值与 UPDRS Ⅴ的分期呈负相关(r=-0.373, P =0.043);尾状核相位值与 UPDRSⅠ的评分呈负相关(r=-0.367,P =0.046);苍白球相位值与 UPDRS Ⅲ中的步态障碍评分呈负相关(r=-0.411,P =0.024),而其余核团的相位值与 UPDRS 评分不相关。结论SWI 可以定量评估 PD 患者脑部核团的异常铁沉积,为 PD 的临床诊断和病情评估提供参考。     

采用磁敏感加权成像技术研究年龄相关的脑铁沉积现象

目的 采用磁敏感加权成像技术,探讨正常人大脑不同区域的铁含量随年龄变化的规律.方法 78名成年健康志愿者按照年龄分为青年组(≤35岁)27名、中年组(36～55岁)35名和老年组(≥56岁)16名,所有受试者均进行磁敏感加权成像,在校正相位图上分别测量苍白球、壳核、尾状核、黑质、红核、丘脑和额叶白质的相位值.30岁以上受试者各脑区的平均相位值和文献报道的脑铁实际含量进行Pearson相关分析,采用单因素方差分析比较各脑区不同年龄组之间的校正相位值差异.用线性回归分析法进一步研究由方差分析法所揭示的年龄相关的铁含量变化,并计算其变化率.结果 各脑区的平均相位值和文献报道的脑铁实际含量问存在负相关性(r=-0.796,P=0.032),铁含量多的脑区相位值的负值大.青年组、中年组和老年组壳核相位值的中位数分别是-0.0185、-0.0362和-0.0566,额叶白质相位值中位数分别是0.0034、-0.0031和-0.0021,各年龄组间的差异具有统计学意义(F值分别为20.115、3.536,P值分别＜0.01、＜0.05).线性回归分析表明,壳核、红核和额叶白质的铁含量随着年龄的增加而增加(回归系数分别为-0.001、-0.001、＜-0.001,P值均＜0.05),苍白球、尾状核、黑质和丘脑的铁含量不随年龄而变化.结论 研究结果证明并拓展了对年龄相关的脑铁沉积现象的认识,为全面、准确认识疾病相关的脑铁异常沉积现象提供了必要的基础.     

Relationship between brain R2 and liver and serum Iron concentrations in elderly men

Studies of iron overload in humans and animals suggest that brain iron concentrations may be related in a regionally specific way to body iron status. However, few quantitative studies have investigated the associations between peripheral and regional brain iron in a normal elderly cohort. To examine these relationships, we used MRI to measure the proton transverse relaxation rate (R₂) in 13 gray and white matter brain regions in 18 elderly men (average age, 75.5 years) with normal cognition. Brain R₂ values were compared with liver iron concentrations measured using the FerriScan® MRI technique and serum iron indices. R₂ values in high‐iron gray matter regions were significantly correlated (positively) with liver iron concentrations (globus pallidus, ventral pallidum) and serum transferrin saturation (caudate nucleus, globus pallidus, putamen) measured concurrently with brain R₂, and with serum iron concentrations (caudate nucleus, globus pallidus) measured three years before the current study. Our results suggest that iron levels in specific gray matter brain regions are influenced by systemic iron status in elderly men. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

MRI of brain iron

A prominently decreased signal intensity in the globus pallidum, reticular substantia nigra, red nucleus, and dentate nucleus was routinely noted in 150 consecutive individuals on T2-weighted images (SE 2000/100) using a high field strength (1.5 T)MR system. This MR finding correlated closely with the decreased estimated T2 relaxation times and the sites of preferential accumulation of ferric iron using the Perls staining method on normal postmortem brains. The decreased signal intensity on T2-weighted images thus provides an accurate in vivo map of the normal distribution of brain iron. Perls stain and MR studies in normal brain also confirm an intermediate level of iron distribution in the striatum, and still lower levels in the cerebral gray and white matter. In the white matter, iron concentration is (a) absent in the most posterior portion of the internal capsule and optic radiations, (b) higher in the frontal than occipital regions, and (c) prominent in the subcortical "U" fibers, particularly in the temporal lobe. There is no iron in the brain at birth; it increases progressively with aging. Knowledge of the distribution of brain iron should assist in elucidating normal anatomic structures and in understanding neurodegenerative, demyelinating, and cerebrovascular disorders.     

Human brain atlas‐based volumetry and relaxometry: Application to healthy development and natural aging

This work investigated the feasibility and utility of using T2‐weighted or dual spin‐echo data to provide volume and T2 relaxation time for regional and global gray and white matter using standardized brain templates and anatomically labeled atlases. A total of 130 healthy males and females (age range 15–59 years) were included. Dual echo magnetic resonance imaging data were acquired and analyzed using standardized International Consortium for Human Brain Mapping atlas‐based tissue segmentation procedures implemented in the statistical parametric mapping toolbox to obtain the age trajectories of volume and corresponding T2 relaxation time in whole brain white and gray matter, in the caudate nucleus and in the anterior limb of internal capsule. Whole brain gray matter and caudate nucleus volumes linearly decreased with age while whole brain white matter and anterior limb internal capsule volume increased slowly with age bilaterally in males and females. The relation between T2 relaxation time and age of whole brain gray and white matter, and caudate nucleus and anterior limb internal capsule followed a quadratic U‐curve. The T2 relaxation times of the human brain followed a U curve both globally and regionally in both white and gray matter. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

MRI of the neonatal brain: optimization of spin-echo parameters

OBJECTIVE: Our aim was to measure the relaxation times of the neonatal brain and to use these to derive pulse sequence parameters that enhance the signal-to-noise ratio (SNR) and contrast of MRI scans of the neonatal brain. SUBJECTS AND METHODS: The transverse (T2) and longitudinal (T1) relaxation times were measured for 10 healthy neonates, and the average relaxation times were calculated for both gray and white matter. Simulations using these values were then performed to estimate the optimal pulse sequence parameters. Images were obtained in three neonates using both the optimized and conventional sequence parameters. RESULTS: The measured (mean +/- SD) relaxation times of the neonatal brain at 1.5 T were T1 equals 1712 +/- 235 msec and T2 equals 394 +/- 52 msec in white matter and T1 equals 1144 +/- 245 msec and T2 equals 206 +/- 26 msec in gray matter. The optimized T1-weighted imaging used a turbo spin-echo sequence with an echo-train length of 3 and TR/TE of 850/11 msec and showed increases in both the contrast and the SNR. The optimized T2-weighted sequence used a TE of 270 msec and markedly increased the contrast but at the expense of a reduction in the SNR. CONCLUSION: Parameters of MRI turbo spin-echo sequences for scanning neonates are different from those required for adult studies, and appropriate protocols should be used.     

T2 values in the human brain: comparison with quantitative assays of iron and ferritin

Magnetic resonance (MR) imaging with a whole-body imager was performed in 10 fresh, unfixed whole human brains selected randomly from cadavers. All subjects were neurologically intact before death. T2 time constants were measured within the caudate nucleus, putamen, globus pallidus, cortical gray matter, subcortical white matter, and optic radiation. These regions were then excised, and T2 values were measured again with a 1.5-T MR spectrometer. Quantitative assays of iron, ferritin, and protein from these areas were then performed. Iron concentration varied significantly among brain regions, whereas ferritin and protein concentrations were constant among brain regions and among individuals. Neither iron nor ferritin concentration showed any consistent correlation with T2 values. Histologic examination of brain micro-sections with iron- and ferritin-specific stains of demonstrated poor correlation with biochemical assays of ferritin and iron concentrations. Results indicate that T2 values correlate poorly with iron and ferritin concentrations found in neurologically intact brains.     

Correlation of R2 with total iron concentration in the brains of rhesus monkeys

PURPOSE: To estimate the relationship between R2 = 1/T2 as measured with a double echo spin echo sequence and total iron concentration in gray matter structures in the brains of aging rhesus monkeys. MATERIALS AND METHODS: Using a 1.5-T magnetic resonance (MR) imager, we collected double echo spin echo images of the brains of 12 female rhesus monkeys aged between 9 and 23 years. From the double echo images, the transverse relaxation rate R2 = 1/T2 was calculated in selected gray matter regions. After the animals were euthanized, their brains were excised and tissue punches were taken of the substantia nigra, globus pallidus, and gray matter regions of the cerebellum. Some of the tissue punches were assayed for total iron using atomic absorption spectroscopy. RESULTS: The range of tissue iron concentration spanned from 15 to 450 microg/g wet weight, with the highest levels in the globus pallidus and the lowest levels in the cerebellum. The results show that R2 was highly correlated with the total iron concentration and that the relationship between R2 and tissue iron concentration appeared to depend upon the iron concentration. For concentrations above approximately 150 microg/g wet weight, R2 increased with a sensitivity of 0.0484 +/- 0.0023 second(-1)(microg/g)(-1). In contrast, where the iron concentration was below 150 microg/g, R2 increased at 0.0013 +/- 0.0073 second(-1)(microg/g)(-1). The bilinear behavior may reflect changes with age in the relative amounts of iron distributed diffusely and in granular form in the globus pallidus and substantia nigra. Histological sections of the tissues stained for iron and ferritin support this hypothesis and indicate that the distribution of ferritin is similar to the distribution of iron. CONCLUSION: This study reaffirms the value of measuring the MR relaxation rate R2 for a noninvasive estimate of iron content in the brain and identified limitations in the relationship at low tissue iron concentrations.     

Role of iron and ferritin in MR imaging of the brain: a study in primates at different field strengths

The authors measured in vivo signal intensity on magnetic resonance (MR) images and postmortem iron concentrations in the brains of three young and two old rhesus monkeys. T2-weighted MR imaging was done at 0.5, 1.5, 2.0, and 4.7 T. Relative assessment of iron concentration was made from the optical density of brain sections stained with the Perls' method intensified with diaminobenzidine. MR imaging and optical density measurements were made in the centrum semiovale (white matter) and in four gray matter areas: the insular cortex, caudate nucleus, putamen, and globus pallidus, the latter three of which accumulate significant iron deposits with age. High optical density and decreased signal intensity were found in these areas, and the inverse correlation between gray matter/white matter signal ratio and optical density was in good agreement with the theory of T2 shortening caused by diffusion of water through magnetic inhomogeneities. However, the dependence of T2 shortening on field strength was not quadratic, as expected for paramagnetic iron, but instead showed a marked leveling off at higher field strengths. This magnetic "saturation" is explainable by antiferromagnetism and superparamagnetism of the ferritin core and has been observed in ferritin solutions at low temperatures. Similar observations at body temperature are needed before the iron-ferritin explanation for T2 shortening can be considered proved.     

T(2) relaxation rate of basal ganglia and cortex in patients with beta-thalassaemia major

In thalassaemic patients, neurophysiological disturbances have been associated with high serum ferritin levels and desferrioxamine therapy. In the presence of a magnetic field, ferritin, the main iron storage protein, induces a preferential decrease of the T(2) relaxation time. The purpose of this study was to evaluate thalassaemic patients for brain iron deposition by assessing the T(2) relaxation rate (1/T(2)) of the grey matter. 41 thalassaemic patients (age range 8.5-44 years, mean 24 years) and 58 age- and sex-matched controls were included in the study. Current serum ferritin levels were obtained. The 1/T(2) values of the cortex (motor and temporal) (mean 0.0122 ms(-1), SD 0.0004), putamen (mean 0.0137 ms(-1), SD 0.0004) and caudate nucleus (mean 0.0132 ms(-1), SD 0.0003) were higher in patients compared with the controls (mean 0.0110 ms(-1), SD 0.0004; mean 0.0120 ms(-1), SD 0.0005; mean 0.0117 ms(-1), SD 0.0003, respectively) (p<0.001 for all parameters). No statistically significant differences were found in the globus pallidus. No correlation was found between 1/T(2) and serum ferritin. The higher values of 1/T(2) in the cortex, putamen and caudate nucleus of thalassaemic patients probably reflect a higher iron deposition. The lack of differences in 1/T(2) of the globus pallidus might suggest that even in thalassaemic patients iron cannot exceed a saturation level.     

Normal deposition of brain iron in childhood and adolescence: MR imaging at 1.5 T

Magnetic resonance (MR) images of the brain in 285 patients between the ages of 2 and 25 years were retrospectively studied to determine the appearance of brain iron accumulation. The globus pallidus, red nucleus, substantia nigra, and dentate nucleus were evaluated with long TR/TE (repetition time/echo time) spin-echo sequences and staged. All four regions in most patients were initially hyperintense compared with white matter (stage I) before becoming isointense (stage II) and subsequently hypointense (stage III). The globus pallidus was the first to reach stage III, the red nucleus and substantia nigra were next, and the dentate nucleus was last. In general, decreased signal intensity (stage III) was not seen in these regions in patients less than 10 years old; in most patients it was seen by age 25 years. The dentate nucleus decreased in signal intensity more slowly and inconsistently; only one-third of patients had reached stage III by age 25 years. The temporal sequence of normal iron deposition as detected with MR imaging is helpful not only in the diagnosis of known iron-deposition diseases but also in the detection of iron-related pathologic changes.