外部性脑积水与脑萎缩的CT鉴别诊断

本文对３０例外部性脑积水和１０例脑萎缩的ＣＴ表现作回顾性对照分析，ＥＨ的ＣＴ特征为：双侧额顶区蛛网膜下腔对称局限性增宽，不伴有脑质、脑沟异常和脑室扩大；其脑室颅腔横径率小于１５％。ＣＡ的特征为：脑周蛛网膜下腔普遍性增宽，且伴有脑皮质变薄，密度减低，脑沟普遍加深和脑室明显扩大，其ＶＴ／ＳＴ率大于１５％。文中介绍并讨论了ＶＴ／ＳＴ率的测算方法和鉴别诊断意义。     

浅谈外部性脑积水的CT诊断

外部性脑积水（External hydrpcepalus简称EH）是发生于婴儿期的一种良性自愈性疾病。大多数与新生儿缺血缺氧性脑病，早产儿、感染等因素有关。本文提供了对EH的认识标准，①短期内头围突然增大．②CT表现双侧额顶部对称性蛛网膜下腔增宽，大脑半球间裂前部开大，可伴有额顶部脑沟增宽硬脑室增大。本文报告的20例EH病的CT表现：①额区及额顶区对称性蛛网膜下腔增宽；②大脑半球间裂前部增宽，其中3例额顶区大脑半球间裂全部增宽；③基底池轻度扩大；④额顶区脑沟增深增宽；⑤脑室不大或有轻度扩大，额区及额顶区蛛网膜下腔增宽及大脑半球间裂前部或全部增宽，是诊断EH的依据。     

MRI单次激发FSE序列评价胎儿脑沟发育的可行性

目的:探讨MRI单次激发FSE序列评价宫内胎儿脑沟发育的可行性。方法:分析203例22～38孕周健康胎儿的脑部MRI图像,根据孕周分为17组,每一孕周为一组,评价胎儿半球间裂、外侧裂、顶枕沟、海马裂、胼胝体沟、距状裂、扣带沟、边缘沟、侧副沟、中央沟、额上沟、中央前沟、中央后沟、顶内沟、颞上沟、额下沟、颞下沟、枕颞沟、次级扣带沟、次级枕沟及岛沟是否可显示,并计算各孕周组中各个脑沟的可见率。结果:建立了22～38孕周胎儿大脑所有初级脑沟和部分次级脑沟的可见百分率的时间表。超过75%的胎儿在22孕周时可见半球间裂、外侧裂、顶枕沟、海马裂、胼胝体沟和距状裂;在24孕周可见扣带沟;在25孕周可见边缘沟、侧副沟、中央沟和额上沟;在26孕周可见中央前沟、中央后沟和顶内沟;在27孕周可见颞上沟和额下沟;在31孕周可见颞下沟、枕颞沟和次级扣带沟;在32孕周可见次级枕沟;在34孕周可见岛沟。结论:MRI单次激发FSE序列可用于评估胎儿脑沟的发育情况,可为评价胎儿脑部发育提供一定的参考标准,从而可辅助诊断脑发育滞后。     

CT鉴别脑外脑积水与脑萎缩

脑外脑积水是婴儿常见的良性自限性疾病。其主要ＣＴ表现为：１、两侧额顶部蛛网膜下腔增宽；２、大脑纵裂的前半部增宽；３、两侧额顶部脑皮质沟回增深、加宽；４、基底池扩大；５、脑室不扩张或仅有轻度扩张。脑萎缩的主要ＣＴ表现为脑皮质沟回增深、加宽，伴有脑室扩张。但脑萎缩的脑皮质沟回增深、加宽是整个大脑皮质，而不只局限于两侧额顶叶，并且脑萎缩没有两侧额顶部蛛网膜下腔增宽。依据上述ＣＴ表现可容易区别脑外脑积水与脑萎缩。     

胎儿主要器官的正常解剖及MR表现

目的了解胎儿主要器官的正常解剖及MR表现。方法对47例胎儿行快速MR成像检查，使用序列为单次激发快速自旋回波序列，观察主要正常器官的解剖和MR表现，包括脑、肺、心脏、肝、脾、胃肠道、肾脏、膀胱、骨骼、脊柱和皮下脂肪，并按不同的胎龄分组观察。结果47例胎儿MR检查结果表明：孕20周时，胎儿各主要器官均已发育。20周左右，大脑皮层光滑，无脑回、脑沟，之后脑回、脑沟逐渐缓慢形成；肺、气管、支气管均呈高信号，心脏、大血管及肝脾呈低信号，胃肠道、肾孟肾盏、膀胱呈高信号，肾实质为等信号，骨骼、肌肉呈低信号；脊柱20周已形成，皮下脂肪20周可见，随胎龄增长逐渐增多。结论快速MR成像能清楚显示胎儿各主要器官的正常解剖和发育变化，胎儿主要器官的解剖和MR表现与新生儿有较大的差别。     

婴幼儿脑外积液的MRI研究:脑外间隙发育性与病理性的扩大

目的 分析婴幼儿脑外积液的MRI特征，明确脑外积液的病因及与脑发育的关系。方法 选择经MRI确诊的46例年龄〈2岁的脑外积液患儿，分析其MRI特征。并按月龄分7组，在T2WI上测量脑外间隙宽度并与正常值对照。结果 引起婴幼儿脑外积液的主要原发病有感染性疾病、硬膜下或蛛网膜下出血、缺氧缺血性脑病（HIE）占67．4％（31／46例），原因不明占26．1％（12／46例）。脑外积液主要发生在大脑凸面的前部，以蛛网膜下腔积液多见，占80．4％（37／46例），硬膜下积液8．7％（4／46例），硬膜下和蛛网膜下积液并存10．9％（5／46例）。其中，化脓性脑膜炎可致硬脑膜或软脑膜的信号在T1WI或T2WI上增高，常引起硬膜下积液或与蛛网膜下腔积液并存。硬膜下和（或）蛛网膜下腔出血常为硬膜下和蛛网膜下腔积液并存，并常见大脑表面静脉（皮质静脉）增粗、淤滞和出血，在T1WI上信号增高。HIE所致脑外积液为蛛网膜下腔积液，可见HIE所致的特征性改变，常有髓鞘化落后占63．6％（7／11例）。原因不明者多为双侧对称性的蛛网膜下腔积液。脑室扩大主要见于HIE和硬膜下或蛛网膜下出血。结论 婴幼儿脑外积液多有明确病因，以出血、感染和HIE为多见，积液的部位与脑发育的特性有关，MRI对明确脑外积液的性质，判断病因有帮助。     

MR在妊娠中晚期正常胎儿及胎盘检查中的应用价值

目的了解正常胎儿主要器官及胎盘的MRI表现。资料与方法对36例孕20周以上正常胎儿行MRI检查,采用单次激发快速自旋回波序列(SSFSE),从胎儿头颅、躯干轴位、冠状位、矢状位等多体位观察胎儿各系统主要器官,包括脑、肺、心脏、肝、脾、胃肠道等和胎盘的解剖和MRI表现。结果 36例胎儿MRI检查结果表明:中枢神经系统:孕20周以后大脑三层结构在SSFSE上已经可以辨别,皮质与脑室周围的生发层呈稍低信号,中间白质为高信号。双侧侧脑室在25周前呈生理性扩大状态,枕角明显,25周后逐渐缩小;孕20周时,两侧大脑皮层光滑,无明显沟回形成;孕23周时,仅见双侧侧裂池初具形态;23～30周,两侧大脑皮质主要沟回逐渐形成;30～37周,两侧脑皮质脑沟、回形成明显增多。呼吸循环系统:两肺呈高信号,纵隔内心脏、大血管及两肺纹理呈低信号。消化系统:胃泡、胆囊呈高信号,肠管不扩张时呈等低信号,部分肠管内见低信号胎粪影。肝脏、脾脏呈等低信号位于上腹部两侧。泌尿系统:双侧肾脏呈卵圆形等低信号,膀胱呈囊性高信号位于盆腔内。骨骼、肌肉系统:脊柱、四肢呈低信号,肌肉呈等信号。胎盘信号从均匀、稍高信号向不均匀、稍低信号过渡,胎盘边缘也从平滑向分叶状过渡。结论快速MRI能清楚显示胎儿各主要器官正常解剖和发育变化,同时可以对胎盘成熟度进行准确判断。     

Magnetic Resonance Imaging of the Normal Fetus and Placenta in Medium to Late Pregnancy

目的 了解正常胎儿主要器官及胎盘的MRI表现. 资料与方法 对36例孕20周以上正常胎儿行MRI检查,采用单次激发快速自旋回波序列(SSFSE),从胎儿头颅、躯干轴位、冠状位、矢状位等多体位观察胎儿各系统主要器官,包括脑、肺、心脏、肝、脾、胃肠道等和胎盘的解剖和MRI表现.结果 36例胎儿MRI检查结果表明:中枢神经系统:孕20周以后大脑三层结构在SSFSE上已经可以辨别,皮质与脑室周围的生发层呈稍低信号,中间白质为高信号.双侧侧脑室在25周前呈生理性扩大状态,枕角明显,25周后逐渐缩小;孕20周时,两侧大脑皮层光滑,无明显沟回形成;孕23周时,仅见双侧侧裂池初具形态;23～ 30周,两侧大脑皮质主要沟回逐渐形成;30～ 37周,两侧脑皮质脑沟、回形成明显增多.呼吸循环系统:两肺呈高信号,纵隔内心脏、大血管及两肺纹理呈低信号.消化系统:胃泡、胆囊呈高信号,肠管不扩张时呈等低信号,部分肠管内见低信号胎粪影.肝脏、脾脏呈等低信号位于上腹部两侧.泌尿系统:双侧肾脏呈卵圆形等低信号,膀胱呈囊性高信号位于盆腔内.骨骼、肌肉系统:脊柱、四肢呈低信号,肌肉呈等信号.胎盘信号从均匀、稍高信号向不均匀、稍低信号过渡,胎盘边缘也从平滑向分叶状过渡.结论 快速MRI能清楚显示胎儿各主要器官正常解剖和发育变化,同时可以对胎盘成熟度进行准确判断.     

正常胎脑髓鞘发育状况的MRI研究

目的：探讨胎脑髓鞘的生长发育状况。材料与方法：采用超导０．３５Ｔ磁共振成像仪，对４４例孕妇进行ＭＲ成像，分析其正常胎脑主要结构的信号变化。结果：胎儿的大脑（基底节除外）、小脑实质在Ｔ１加权像上为略低信号，在质子密度加权像上为等信号，在Ｔ２加权像上为高信号。孕２９周前脑干、基底节在Ｔ１加权像上呈略低信号，孕２９周后呈等信号；在质子密度加权像及Ｔ２加权像上其信号同大脑、小脑实质信号。结论：脑干、基底节的髓鞘在孕２９周后形成；其形成过程由脑干开始至基底节；而在胎儿期，大脑（基底节除外）、小脑实质内髓鞘尚未形成。南京军区总医院医学影像科（王中秋）；上海长征医院影像诊断科     

高场强MRI对不同孕龄胎儿标本脑组织的显示能力研究

目的 探讨高场强MRI对不同孕龄胎儿标本脑组织的显示能力.方法 108个14～40周胎儿标本进行3.0 T MR扫描,并从中选取扫描图像清晰的11个14～27周标本行7.0 T MR扫描.选取不同场强与方位的MR图像,分析MRI对发育中的皮质脑沟、层状结构及基底核团的显示情况.结果 在3.0 T MR胎儿标本T_1WI上,14周时皮质层状结构即可显示;16周后脑沟可以较准确辨认;20周后基底核团可以较清晰辨认,三者都随孕龄增大而逐渐清晰.相同胎龄的胎儿标本在7.0 T MR T_2WI上,脑沟、层状结构及基底核团的显示较3.0 T T_1WI图像更加清楚,尤其优于显示发育早期阶段的脑沟.结论 3.0 T MR胎儿标本T_1WI可以较好地显示发育中的胎脑结构;7.0 T MR T_2WI可以更加清晰地显示皮质脑沟、层状结构与基底核团的发育变化.     

Normal fetal brain development: MR imaging with a half-Fourier rapid acquisition with relaxation enhancement sequence

PURPOSE: To analyze normal maturation of the fetal brain with half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: The normal brains of 25 fetuses of 12-38 weeks gestational age were examined in utero with half-Fourier RARE imaging. Gyrus maturation, gray and white matter differentiation, ventricle-to-brain diameter ratio, and subarachnoid space size were evaluated with respect to gestational age. RESULTS: At 12-23 weeks, the brain had a smooth surface, and two or three layers were differentiated in the cerebral cortex. At 24-26 weeks, only a few shallow grooves were seen in the central sulcus, and three layers, including the immature cortex, intermediate zone, and germinal matrix, were differentiated in all fetuses. At 27-29 weeks, sulcus formation was observed in various regions of the brain parenchyma, and the germinal matrix became invisible. Sulcation was seen in the whole cerebral cortex from 30 weeks on. However, the cortex did not undergo infolding, and opercular formation was not seen before 33 weeks. At 23 weeks and earlier, the cerebral ventricles were large; thereafter, they gradually became smaller. The subarachnoid space overlying the cortical convexities was slightly dilated at all gestational ages, most markedly at 21-26 weeks. CONCLUSION: Changes in brain maturation proceed through stages in an orderly and predictable fashion and can be evaluated reliably with half-Fourier RARE MR imaging.     

Evaluation of normal brain development by prenatal MR imaging

PURPOSE: The aim of this study was to describe the normal pattern of development and maturation of the foetal brain with respect to gestational age as assessed with magnetic resonance imaging (MRI) and to provide an overview of the possibilities of the technique. MATERIALS AND METHODS: Foetal cerebral MRI was performed on 56 pregnant women between 19 and 37 weeks of gestation. Half-Fourier single-shot turbo spin-echo (HASTE), true fast imaging with steady precession (FISP), T1-weighted fast low angle shot (FLASH) two-dimensional (2D) and diffusion-weighted (DW) sequences with apparent diffusion coefficient (ADC) were obtained. Biometric parameters and developmental areas of the cerebral cortex were correlated to gestational age by using the Spearman rank correlation test. RESULT: We found a negative correlation between the germinal matrix/biparietal diameter ratio and gestational age and a positive correlation between the germinal and cortical matrix when expressed as external intraocular diameter ratio (R=0.452, p=0.02). The cortical mantle was correlated with biometric parameters, such as the biparietal diameter and the frontooccipital diameter, and with gestational age. The interhemispheric fissure, the parietooccipital fissure and the sylvian fissure were detectable by the 22nd week. In the grey matter, the mean ADC values varied from 1.76 x 10(-3) mm(2)/s (at week 19) to 0.89 x 10(-3) mm(2)/s (at week 37), whereas in the white matter, the values varied from 2.03 x 10(-3) mm(2)/s (at week 19) to 1.25 x 10(-3) mm(2)/s (at week 37). CONCLUSIONS: MRI provides a reliable valuation of brain maturation during pregnancy.     

Clinical evaluation of further-developed MRCP sequences in comparison with standard MRCP sequences

The purpose of this study was the comparison of technically improved single-shot magnetic resonance cholangiopancreatography (MRCP) sequences with standard single-shot rapid acquisition with relaxation enhancement (RARE) and half-Fourier acquired single-shot turbo spin-echo (HASTE) sequences in evaluating the normal and abnormal biliary duct system. The bile duct system of 45 patients was prospectively investigated on a 1.5-T MRI system. The investigation was performed with RARE and HASTE MR cholangiography sequences with standard and high spatial resolutions, and with a delayed-echo half-Fourier RARE (HASTE) sequence. Findings of the improved MRCP sequences were compared with the standard MRCP sequences. The level of confidence in assessing the diagnosis was divided into five groups. The Wilcoxon signed-rank test at a level of p<0.05 was applied. In 15 patients no pathology was found. The MRCP showed stenoses of the bile duct system in 10 patients and choledocholithiasis and cholecystolithiasis in 16 patients. In 12 patients a dilatation of the bile duct system was found. Comparison of the low- and high spatial resolution sequences and the short and long TE times of the half-Fourier RARE (HASTE) sequence revealed no statistically significant differences regarding accuracy of the examination. The diagnostic confidence level in assessing normal or pathological findings for the high-resolution RARE and half-Fourier RARE (HASTE) was significantly better than for the standard sequences. For the delayed-echo half-Fourier RARE (HASTE) sequence no statistically significant difference was seen. The high-resolution RARE and half-Fourier RARE (HASTE) sequences had a higher confidence level, but there was no significant difference in diagnosis in terms of detection and assessment of pathological changes in the biliary duct system compared with standard sequences.     

Sonographic cerebral sulcal pattern in normal fetuses

PURPOSE: Define normal sulcation patterns and their chronological order of appearance on transabdominal ultrasound by comparing them with brain maturation references available in fetopathological studies and MRI findings. PATIENTS AND METHODS: By means of a prospective study, 158 normal fetal brains aged 21 to 34 gestational weeks have been analyzed with standardized data by transabdominal ultrasound in eleven different views using axial, coronal and sagittal orientation. RESULTS: The sequential development of cerebral sulci has been described according to the gestational age. This chronology was consistent with anatomo-pathologic references presenting a mean late period of one week and with MRI but without any late period. This study is available on the following website: CONCLUSION: This ultrasound study provides accurate landmarks and imaging features of normal fetal brain sulcation. The analysis and the knowledge of this sulcation provide better understanding of the brain cortex maturation and may be helpful in diagnosing brain diseases.     

Fetal hyaloid artery: timing of regression with US

Large-aperture, dynamically focused ultrasonic imaging permits noninvasive, anatomic study of the eye at the millimeter level in the second and third trimesters of pregnancy. The authors report their observations of the hyaloid artery in 210 of 219 fetuses examined with this technique. This vessel is seen in fetuses of 20 weeks gestational age or less and regresses spontaneously at the start of the third trimester. The 210 subjects included 100 who were examined at gestational ages of 16-32 weeks or more and 85 healthy fetuses and 25 with pathologic findings at birth who were examined at 34 weeks gestational age to term. The presence of the hyaloid artery in the mid third trimester was uncommon in healthy subjects (less than 1%) and was not seen in any beyond 29.9 weeks gestational age. However, in nine of the 25 fetuses with abnormalities (five with trisomy syndromes), the vessel was seen at 30.8-36.8 weeks gestational age. The temporarily delayed regression of the hyaloid artery may occur with trisomy 21 syndrome and other forms of retarded brain development.     

Maturation of the human fetal brain as observed by 1H MR spectroscopy.

Proton MRS was used to monitor cerebral metabolite tissue levels in 35 normal fetuses during development in the gestational age range of 30-41 weeks. First, MRI in three orthogonal orientations was performed. A volume of interest (VOI) (15-43 cc) of fetal brain tissue was then selected for (1)H MRS. For localization, two pulse sequences (stimulated echo acquisition mode (STEAM) at TE = 20 ms, and point-resolved spectroscopy (PRESS) at TE = 135 ms) were applied. The MR spectra of the brain showed signals for inositol (Ino), choline (Cho), creatine (Cr), and N-acetyl (NA) compounds. From 30 to 41 weeks the absolute tissue level of NA, and the ratios of NA/Cr and NA/Cho increased, whereas the ratio of Cho/Cr decreased. These changes reflect maturation of the brain. Considering the diagnostic value of proton MRS in pediatric neurology, this new approach may also be useful for characterizing pathological conditions in the fetal brain.     

Fetal cerebral cortex: normal gestational landmarks identified using prenatal MR imaging

BACKGROUND AND PURPOSE: Few investigators have analyzed the MR imaging patterns of fetal gyration. Our purpose was to establish, with a large prospective series, the normal sulcation landmarks according to gestational age by using in utero MR imaging and to correlate our findings with established neuroanatomic timetables. METHODS: A standardized fetal cerebral MR examination was performed in 173 normal fetuses at 22 to 38 weeks' gestation. Eight T1- and T2-weighted coronal, axial, and sagittal slices were obtained for each fetus and systematically analyzed. The sequential development of the different fissures and sulci of the cerebral cortex with respect to gestational age were tabulated. RESULTS: Sulcation of the medial, lateral, and inferior surfaces of the brain was depicted, and a timetable for the MR depiction of the primary and secondary sulci was established for the 22- to 38-week gestational period. This timetable was in good agreement with the neuroanatomic standards of reference, with a mean lag time of 1 week. CONCLUSION: This analysis of fetal brain sulcation in a large series of fetuses contributes to a better understanding of the maturation of the fetal cortex on MR imaging studies. It furthermore provides a standard of reference that can be used to assess the normality of fetal sulcation and to diagnose gyrational abnormalities with prenatal MR imaging.     

Agenesis of the corpus callosum in fetuses with mild ventriculomegaly: role of MR imaging

Purpose

We evaluated the role of magnetic resonance (MR) imaging in the diagnosis of corpus callosum agenesis — isolated or associated with other anomalies — in fetuses with mild cerebral ventriculomegaly, as depicted at prenatal sonography.

Material and methods

Between January 2005 and March 2007, 33 fetuses with a mean gestational age of 28.9 weeks (range 17–37) and mild ventriculomegaly diagnosed at prenatal sonography were included in this prospective study. All fetuses underwent MR imaging according to the following protocol: half-Fourier T2-weighted images along the three orthogonal plane according to the longitudinal axis of the mother, and subsequently three orthogonal planes were acquired according to the fetal brain. Quantitative image analysis included the size of the transverse diameter of the lateral ventricles, in the axial plane, and the thickness of the adjacent cerebral cortex. Qualitative image analysis included morphology of the lateral ventricles (normal, parallel pattern colpocephaly), signal intensity changes of the fetal brain, interruption of the germinative matrix, agenesis of the corpus callosum (complete/partial) and associated malformations. Postnatal physical examination and diagnostic imaging, as well as surgery, were the standard of diagnosis.

Results

Mean axial diameter of the lateral ventricle was 11.6 mm (range 10–15 mm), and mean thickness of the adjacent cerebral cortex was 2.1 mm (range 1.8–3 mm); 23/33 fetuses (70%) showed normal morphology of the lateral ventricles, and 8/33 (24%) showed abnormal morphology (parallel pattern, colpocephaly). The entire corpus callosum was visualised in 20/33 fetuses (60%). In 8/33 fetuses (25%), partial agenesis was diagnosed, whereas in 5/33 (15%), there was hypogenesis. In 6/13 fetuses (46%), isolated corpus callosum agenesis was detected, and two cases of hypogenesis of the corpus callosum were misinterpreted — overestimated in one case and underestimated in another.

Conclusions

MR imaging may prove to be a useful second-line imaging modality in the prenatal diagnosis of corpus callosum agenesis in fetuses with mild ventriculomegaly.     

Comparison of conventional fast spin echo, single-shot two-dimensional and three-dimensional half-fourier RARE for T2-weighted female pelvic imaging

PURPOSE: To evaluate the usefulness of the three-dimensional half-Fourier RARE sequence in comparison with single-shot two-dimensional half-Fourier RARE and conventional fast spin echo (FSE) for female pelvic imaging. MATERIALS AND METHODS: Imaging with all sequences was performed in 146 patients with 166 focal lesions on a 1.5-T system. The images were compared on the basis of quality, lesion conspicuity, and lesion to the uterus contrast-to-noise ratio (CNR). RESULTS: The sharpness of intrapelvic organs on the three-dimensional half-Fourier RARE sequence was better than that on two-dimensional half-Fourier RARE and worse than that on FSE. Motion-related artifacts for three-dimensional half-Fourier RARE were more frequent than those for two-dimensional half-Fourier RARE. There was no statistical difference between the three-dimensional half-Fourier RARE sequence and FSE in regard to lesion conspicuity and overall image quality. The CNR of leiomyoma to myometrium and cervical cancer to cervical stroma was the highest with three-dimensional half-Fourier RARE (P< 0.05). CONCLUSION: The three-dimensional half-Fourier RARE sequence generates images with higher contrast and better image resolution than two-dimensional-RARE. The three-dimensional data set provided images that can be observed in any orientation without acquiring an additional scan by using the multiplanar reconstruction (MPR) method.