儿童颅后窝肿瘤的磁共振成像

目的：探讨磁共振成像（MRI）对儿童颅后窝肿瘤的诊断价值。材料和方法：回顾性分析23例经手术病理证实的儿童颅后窝肿瘤的MRI和临床资料，其中髓母细胞瘤13例、室管膜瘤6例、星形细胞瘤2例、血管母细胞瘤2例。结果：肿瘤位于小脑半球8例，小脑蚓部5例，第四脑室10例。所有病灶均引起梗阻性脑积水。MR扫描能显示肿瘤的大小、形态、信号、边缘情况，强化扫描对肿瘤的定性诊断有帮助，结论：儿童颅后窝肿瘤的MRI表现具有一定的特征性，MRI检查多方位、多序列成像，对其诊断有重要作用，是儿童颅后窝肿瘤检查的首选。     

不典型后颅窝肿瘤的MRI诊断价值

目的:总结分析6例不典型后颅窝肿瘤的MRI表现,旨在提高对后颅窝肿瘤的认识。方法:对手术和病理证实的6例后颅窝肿瘤进行回顾性分析。6例均行MRI平扫加增强检查。结果:手术病理证实室管膜瘤1例,T1WI低信号,T2WI高信号,信号均匀;髓母细胞瘤2例,其中1例位于四脑室内;星形细胞瘤2例,其中1例位于小脑蚓部,1例T1WI稍低信号,T2WI高信号;实性血管网织细胞瘤1例,T1WI稍低信号,T2WI高信号,无明显囊性改变,大部分肿瘤明显强化。结论:不同的后颅窝肿瘤有其好发部位,MRI可显示各种肿瘤的不同特征,具有较高的定位定性准确率,是诊断后颅窝肿瘤最重要的手段之一。增强扫描能提高定性准确率。     

后颅窝肿瘤的CT诊断与鉴别（附153例分析）

报道经手术及病理证实的后颅窝肿瘤１５３例，听神经瘤４９例（３２％），为第一位，其次为髓母细胞瘤２６例（１７％），血管母细胞瘤２０例（１３％），星形细胞瘤１９例（１２．４％），室管膜瘤１４例（９％），脑膜瘤及转移瘤均为７例（４％），胆脂瘤６例（４％），脉络丛乳头状瘤４例（２．６％），少支胶质瘤１例（０．６％），并对后颅窝肿瘤的ＣＴ特征和定性诊断、鉴别诊断进行了讨论，认为必须结合临床病史、年龄、肿瘤好发部位及相关的影像学资料，方可提高其正确诊断率。     

跨中后颅窝肿瘤的CT诊断

报告30例跨中后颅窝肿瘤的CT 表现。所有肿瘤都紧邻颅底骨结构。86.6%有颅底骨质破坏,发生的部位为岩尖,斜坡,中颅窝底,鞍旁和内听道。12例瘤周无水肿,18例有轻度水肿。29例肿瘤有清楚边界。肿瘤占位表现为相邻脑组织的受压移位,脑底池变形闭塞,三、四脑室移位及脑积水。本组资料表明,岩尖和相邻的斜坡是跨中后颅窝肿瘤易侵犯的部位,破坏多见。CT 能清楚显示跨中后窝肿瘤的大小、形态和累及范围,定位准确。跨中后颅窝肿瘤多属脑外肿瘤,常见的有脑膜瘤,三叉神经瘤,听神经瘤和胆脂瘤。作者讨论了它们的CT 定性诊断和鉴别。     

表观扩散系数值鉴别儿童后颅窝肿瘤的价值

目的评价MRI表观扩散系数(ADC)值在儿童小脑常见后颅窝肿瘤的鉴别诊断价值。资料与方法 43例经临床治疗及手术病理证实的儿童后颅窝肿瘤患者中,髓母细胞瘤24例,毛细胞型星形细胞瘤10例,室管膜瘤9例。所有患者行常规MRI、扩散加权成像(DWI)及增强MRI检查,在重组的ADC图像上比较肿瘤实质与正常小脑实质的信号强度,定量测定肿瘤实质区的ADC值。三组肿瘤实质的ADC值比较采用Wilcoxon秩和检验。结果 ADC图像上24例髓母细胞瘤中,9例肿瘤呈低信号、12例呈略低信号、3例呈等信号;肿瘤实质的平均ADC值为(0.70±0.11)×10-3mm2/s。所有10例毛细胞型星形细胞瘤均呈高信号,肿瘤实质的平均ADC值为(1.80±0.30)×10-3mm2/s。9例室管膜瘤中,5例肿瘤呈略高信号、4例呈高信号;肿瘤实质的平均ADC值为(1.16±0.18)×10-3mm2/s。髓母细胞瘤较毛细胞型星形细胞瘤的ADC值减低,差异有统计学意义(Z=-4.54,P值(0.01)。髓母细胞瘤较室管膜瘤的ADC值减低,差异有统计学意义(Z=-4.29,P值(0.01)。毛细胞型星形细胞瘤较室管膜瘤的ADC值增高,差异...     

Time-Dependent Structural Changes of the Dentatothalamic Pathway in Children Treated for Posterior Fossa Tumor

BACKGROUND AND PURPOSE:Injury to the dentatothalamic pathway that originates in the cerebellum has been suggested as a mechanism for neurologic complications in children treated for posterior fossa tumors. We hypothesized that time-dependent changes occur in the dentatothalamic pathway.MATERIALS AND METHODS:Diffusion tensor evaluation was performed in 14 children (median age, 4.1 years; age range, 1–20 years) who underwent serial MR imaging at 3T as part of routine follow-up after posterior fossa tumor resection with or without adjuvant therapy. Tensor metrics were obtained in the acute (≤1 week), subacute (1 to <6 months), and chronic (≥6 months) periods after surgery. We evaluated the following dentatothalamic constituents: bilateral dentate nuclei, cerebellar white matter, and superior cerebellar peduncles. Serial dentate nuclei volumes were also obtained and compared with the patient''s baseline.RESULTS:The most significant tensor changes to the superior cerebellar peduncles and cerebellar white matter occurred in the subacute period, regardless of the tumor pathology or therapy regimen, with signs of recovery in the chronic period. However, chronic volume loss and reduced mean diffusivity were observed in the dentate nuclei and did not reverse. This atrophy was associated with radiation therapy and symptoms of ataxia.CONCLUSIONS:Longitudinal diffusion MR imaging in children treated for posterior fossa tumors showed time-dependent tensor changes in components of the dentatothalamic pathway that suggest evolution of structural damage with inflammation and recovery of tissue directionality. However, the dentate nuclei did not show tensor or volumetric recovery, suggesting that the injury may be chronic.

Posterior fossa (PF) tumors represent a significant number of pediatric brain tumors and largely comprise pilocytic astrocytoma, medulloblastoma, and ependymoma.¹ Despite an increase in survival from advances in therapy, many survivors of PF tumors have cognitive and various forms of cerebellar dysfunction thought to reflect brain injury incurred by a combination of tumor and treatment.^2–4 Given its important role not only in motor coordination but also in cognition, injuries to the cerebellum and, more specifically, the cerebrocerebellar pathway have been proposed as possible mechanisms.^5–7One such pathway, the dentatothalamic (DTT) tract, has been shown to display a role in linguistic and cognitive functions.^8–10 The DTT tract contains axons that originate in the dentate nucleus of the cerebellum, project through the ipsilateral superior cerebellar peduncle (SCP), decussate in the dorsal midbrain, and then terminate in the contralateral ventrolateral nucleus of the thalamus. From there, the axons project to the primary motor cortex as well as secondary and tertiary association areas within the frontal and parietal lobes.¹¹Studies have shown that injury to the DTT tract and associated degeneration may be implicated in cognitive and behavioral deficits as well as the development of posterior fossa syndrome (PFS), a unique constellation of symptoms including speech impairment, emotional lability, hypotonia, and ataxia.^12–15 Recent studies have used diffusion MR imaging to evaluate DTT pathways in patients treated for PF tumors but have reported variable DTI metric results.^12,13,16,17 A possible explanation might be that associated axonal degeneration, tissue inflammation, and repair that occur after injury are not static but evolve in a time-dependent manner.^18–20 A study that investigates temporally relevant tissue changes might provide insight into cerebellar injury and its evolution in children who undergo PF tumor therapy. We hypothesized that time-dependent changes occur in the DTT pathway as measured by DTI metrics and dentate nuclei volume in children treated for PF tumors.     

儿童后颅凹肿瘤的CT, MRI诊断

目的：分析儿童后颅凹常见肿瘤的ＣＴ和ＭＲＩ影像学表现,提高诊断该病的准确性。材料和方法：收集儿童后颅凹常见肿瘤４０例,其中髓母细胞瘤１８例,星形细胞瘤１３例,室管膜瘤９例。行ＣＴ和ＭＲＩ检查。ＣＴ平扫４０例,增强扫描３２例;ＭＲＩ平扫２８例,增强扫描１６例。将其结果与手术病理对照。结果：４０例儿童后颅凹常见肿瘤ＣＴ显示率为９７５％,ＭＲＩ显示率为１００％。术前ＣＴ定性误诊１１例,准确率为７２５％。术前ＭＲＩ定性误诊４例,准确率为８５７％。ＣＴ和ＭＲＩ联合检查,能对后颅凹多数常见肿瘤作出定位及定性诊断。ＭＲＩ能多方位成像,去除后颅凹颅骨伪影的干扰,对该病的定位定性诊断明显优于ＣＴ。结论：ＣＴ和ＭＲＩ检查相结合,能提高诊断儿童后颅凹常见肿瘤的准确率,为临床提供更准确的诊疗信息。     

Metrics and Textural Features of MRI Diffusion to Improve Classification of Pediatric Posterior Fossa Tumors

BACKGROUND AND PURPOSE:Qualitative radiologic MR imaging review affords limited differentiation among types of pediatric posterior fossa brain tumors and cannot detect histologic or molecular subtypes, which could help to stratify treatment. This study aimed to improve current posterior fossa discrimination of histologic tumor type by using support vector machine classifiers on quantitative MR imaging features.MATERIALS AND METHODS:This retrospective study included preoperative MRI in 40 children with posterior fossa tumors (17 medulloblastomas, 16 pilocytic astrocytomas, and 7 ependymomas). Shape, histogram, and textural features were computed from contrast-enhanced T2WI and T1WI and diffusivity (ADC) maps. Combinations of features were used to train tumor-type-specific classifiers for medulloblastoma, pilocytic astrocytoma, and ependymoma types in separation and as a joint posterior fossa classifier. A tumor-subtype classifier was also produced for classic medulloblastoma. The performance of different classifiers was assessed and compared by using randomly selected subsets of training and test data.RESULTS:ADC histogram features (25th and 75th percentiles and skewness) yielded the best classification of tumor type (on average >95.8% of medulloblastomas, >96.9% of pilocytic astrocytomas, and >94.3% of ependymomas by using 8 training samples). The resulting joint posterior fossa classifier correctly assigned >91.4% of the posterior fossa tumors. For subtype classification, 89.4% of classic medulloblastomas were correctly classified on the basis of ADC texture features extracted from the Gray-Level Co-Occurence Matrix.CONCLUSIONS:Support vector machine–based classifiers using ADC histogram features yielded very good discrimination among pediatric posterior fossa tumor types, and ADC textural features show promise for further subtype discrimination. These findings suggest an added diagnostic value of quantitative feature analysis of diffusion MR imaging in pediatric neuro-oncology.

Diffusion MR imaging discriminates different types of adult brain tumors.^1–3 In the pediatric literature, the diffusion restriction has also been suggested to differentiate primitive neuroectodermal tumor/medulloblastoma (MB) and other supra- and infratentorial tumors.⁴ Several studies demonstrated that pilocytic astrocytomas (PAs) are characterized by significantly higher average ADC values than ependymomas (EPs) and medulloblastomas, but no clear difference was shown between EPs and MBs (3,5–7 However, by using the 75th percentile from the ADC histogram, instead of an average ADC, a promising discrimination of 90% was achieved,⁷ suggesting that individual tumor components allow better classification or grading than averaged metrics. This concept is well in line with the known heterogeneity of underlying tumor biology and the current practice of histologic diagnosis based on the most characteristic tumor parts.Table 1:Average tumor ADC values in pediatric posterior fossa tumors (×10⁻³mm²/s)

扩散加权成像在小儿脑肿瘤诊断中的价值

目的:探讨磁共振扩散加权成像在d,JL脑肿瘤诊断中的应用价值.方法:回顾性分析60例经病理证实不同类型的小儿脑肿瘤扩散加权成像及ADC图像,其中包括神经胶质瘤36例,室管膜瘤11例,髓母细胞瘤13例.结果:正常脑白质ADC值在三组间无统计学差别,均值为(0.76±0.06)×10-3mm2/s.三组肿瘤实质的ADC值及rADC(肿瘤实质/正常白质)值如下:胶质瘤为(1.18±0.33)×10-3mm>2/s、1.54±0.44;室管膜瘤为(0.97±0.19)× 10-3mm2/B、1.26±0.26;髓母细胞瘤为(0.62±0.09)×10-3mm2/s、0.84±0.16.三组肿瘤的ADC及rADC值存在显著性差异,胶质瘤高于室管膜瘤,髓母细胞瘤最低.Ⅰ-Ⅱ级胶质瘤为(1.32±0.32)×10-3mm2/s、1.71±0.43;Ⅲ-Ⅳ级胶质瘤为(1.02±0.28)×10-3mm2/s、1.35±0.37,两者之间也有显著性差异,前者高于后者.结论:DWI对于小儿上述三类脑肿瘤的鉴别诊断有一定的帮助.ADC及rADC值能较为可靠地鉴别小儿常见颅内肿瘤以及区分Ⅰ-Ⅱ与Ⅲ-Ⅳ级胶质瘤.     

后颅凹肿瘤的磁共振灌注成像

目的　评价磁共振灌注成像 (PWI)在后颅凹肿瘤的诊断和鉴别诊断中的价值。方法　本组 3 7例后颅凹肿瘤病人行双倍剂量PWI,求出肿瘤和脑白质的相对脑血流容积 (rCBV)和平均通过时间 (MTT) ,计算肿瘤与脑白质的rCBV之比QrCBV、肿瘤的MTT较白质的延长值rMTT。结果　血管母细胞瘤的血流灌注最高 ,明显高于其它肿瘤。转移瘤的QrCBV和rMTT变化范围较大 ,与其它肿瘤不易区别。髓母细胞瘤的QrCBV高于毛细胞型星形细胞瘤和室管膜瘤 ,但后两者间无显著统计学差异。脑膜瘤和神经源性肿瘤较脑内原发性肿瘤的rMTT明显延长。结论　PWI在后颅凹肿瘤的诊断和鉴别诊断中具有重要价值 ,可作为常规MRI检查的补充     

颅后窝及松果体区占位性病变对小脑扁桃体位置影响的MRI研究

目的:探讨颅后窝及松果体区占位性病变对小脑扁桃体位置的影响。方法:搜集129例经临床、影像和手术 病理证实的颅后窝及松果体区占位性病变(病例组)和525例健康志愿者(正常对照组),对比研究颅后窝及松果体区不同 部位和不同大小的占位性病变与小脑扁桃体位置之间的关系。结果:正常人小脑扁桃体下缘至枕大孔前后唇连线的平均 距离为(0.6±1.8)mm,颅后窝及松果体区占位性病变组的平均距离为(-4.2±3.8)mm,两者间差异有极显著性意义 (χ2=13.82,P<0.01)。四脑室、小脑及桥小脑角区占位性病变对小脑扁桃体位置的影响有极显著性意义(P<0.01),且 占位性病变的大小与小脑扁桃体的位置有明显相关性;而位于松果体区和脑干的占位性病变对小脑扁桃体位置影响较小 (P>0.01)。结论:颅后窝占位性病变的部位和大小与小脑扁桃体的位置有明显相关性,根据占位性病变的大小可以预测 小脑扁桃体疝的发生。     

后颅窝皮样囊肿合并黑色素瘤1例报告

男 ,48岁 ,因右面部麻木 ,走路不稳 3个月 ,视物模糊 1月余于 2 0 0 3 -0 4-2 8以“右侧桥小脑角占位性病变”收入院。体检 :神志清楚 ,无定向障碍。右眼外展轻度受限 ,双眼水平眼球震颤、复视 ,右面部感觉减退 ,右眼角膜反射消失 ,右耳听力下降 ,四肢肌力Ⅴ级 ,双下肢肌张力稍     

多层面CT和单层面CT对颅后窝结构显示的对比评价

对多层面CT和单层面CT在颅后窝产生的伪影情况进行分析。材料和方法;用2例头颅标本分别行平行于眶耳线平面的多层面CT 和单层面CT扫描,扫描范围包括从枕骨大孔到颞骨岩部上缘的整个颅后窝区。单层面CT分别采用120kV和135kV两种电压,多层面CT采用120kV ,其他扫描参数均相同。所有图像质量均由三位有经验的放射医师采用盲法进行独立评分,并按图像质量予以记分3、2、1分（3分为伪影很少,2分为有部分伪影,1分伪影较重）。统计结果采用SPSS软件分析。结果：将三位放射医师的评分结果进行统计学处理并分析。结果显示：在相同的扫描条件下,多层面CT图像的质量明显优于单层面CT（p＜0．01）。多层面CT中,3分43．3％,2分50％,1分6．7％,单层面CT的120kV中3分26．7％,2分43．3％,1分30％;135kV中3分30％,2分46．7％,1分23．3％。在单层面螺旋CT120KV和135KV之间图像质量无明显差异（P＞0．05）。结论：多层面CT能明显减少颅后窝伪影,提供优质的CT图像。     

Clinical Feasibility of Synthetic MRI in Multiple Sclerosis: A Diagnostic and Volumetric Validation Study

BACKGROUND AND PURPOSE:Quantitative MR imaging techniques are gaining interest as methods of reducing acquisition times while additionally providing robust measurements. This study aimed to implement a synthetic MR imaging method on a new scanner type and to compare its diagnostic accuracy and volumetry with conventional MR imaging in patients with MS and controls.MATERIALS AND METHODS:Twenty patients with MS and 20 healthy controls were enrolled after ethics approval and written informed consent. Synthetic MR imaging was implemented on a Siemens 3T scanner. Comparable conventional and synthetic proton-density–, T1-, and T2-weighted, and FLAIR images were acquired. Diagnostic accuracy, lesion detection, and artifacts were assessed by blinded neuroradiologic evaluation, and contrast-to-noise ratios, by manual tracing. Volumetry was performed with synthetic MR imaging, FreeSurfer, FMRIB Software Library, and Statistical Parametric Mapping. Repeatability was quantified by using the coefficient of variance.RESULTS:Synthetic proton-density–, T1-, and T2-weighted images were of sufficient or good quality and were acquired in 7% less time than with conventional MR imaging. Synthetic FLAIR images were degraded by artifacts. Lesion counts and volumes were higher in synthetic MR imaging due to differences in the contrast of dirty-appearing WM but did not affect the radiologic diagnostic classification or lesion topography (P = .50–.77). Synthetic MR imaging provided segmentations with the shortest processing time (16 seconds) and the lowest repeatability error for brain volume (0.14%), intracranial volume (0.12%), brain parenchymal fraction (0.14%), and GM fraction (0.56%).CONCLUSIONS:Synthetic MR imaging can be an alternative to conventional MR imaging for generating diagnostic proton-density–, T1-, and T2-weighted images in patients with MS and controls while additionally delivering fast and robust volumetric measurements suitable for MS studies.

In conventional MR imaging, multiple sequences with different contrast weightings are obtained. This process is time-consuming with redundant data acquisition. Techniques such as MR fingerprinting and synthetic MR imaging can reduce acquisition times and thereby increase MR imaging availability for both clinical applications and research.^1–3 SyMRI is a synthetic MR imaging method based on a quantitative approach in which a single saturation recovery TSE sequence is used to estimate absolute physical properties, the proton density (PD), longitudinal relaxation rate, and transverse relaxation rate, including correction for B₁-inhomogeneities. Rather than predetermining acquisition parameters such as TE, TI, and TR to maximize tissue contrast,³ synthetic MR imaging produces a free range of synthetic weightings based on a single sequence through mathematic inference.^4,5 The quantitative nature of the method and its ability to probe multiple physical properties in a single sequence make it suitable for volumetric analysis.^6–10 Synthetic MR imaging has shown promising initial results for use in MS and patients with an ischemic event.^11,12 The technique is consequently gaining interest as a potentially time-efficient alternative to conventional MR imaging to visualize and quantify brain tissue properties.MS is a chronic neuroinflammatory disorder affecting 2.5 million people globally.¹³ MS has a heterogeneous clinical expression, which complicates the choice of disease-modifying therapy.¹⁴ MR imaging is a cornerstone for the diagnosis and monitoring of MS, but qualitative MR imaging measurements are poorly correlated with the clinical outcome. Volumetric MR imaging measurements have an independent predictive value in MS but require laborious image postprocessing, limiting its clinical potential.^15,16 Robust and fully automatic volumetry approved for clinical use would thus be important for clinical care and research purposes. The synthetic MR imaging technique has initially been developed for use on Philips (Best, the Netherlands) and GE Healthcare (Milwaukee, Wisconsin) MR imaging systems, but it is not available for other systems and independent evaluations of the method are scarce.^5,6The purpose of this study was to implement the synthetic MR imaging technique for use on Siemens (Erlangen, Germany) MR imaging scanners and to compare the diagnostic accuracy of synthetic and conventional images in MS. A secondary aim was to test the repeatability of the volumetric synthetic MR imaging measurements and compare the volumetric results and practicality with other commonly used brain volumetric methods.     

Occlusion of Posterior Fossa Dural Sinuses in Vein of Galen Malformation

BACKGROUND AND PURPOSE:Spontaneous or progressive occlusion of the posterior fossa dural sinuses is often observed in patients with vein of Galen malformation, which can affect the clinical course. The aim of this study was to examine the patency of the posterior fossa dural sinuses in patients with vein of Galen malformation and to analyze the clinical and angiographic course of this condition.MATERIALS AND METHODS:We retrospectively reviewed 61 consecutive children with vein of Galen malformations. Clinical presentation, management, outcome, and angiographic change were analyzed for the patients with attention paid to all dural sinus occlusions.RESULTS:Twenty patients (32.8%) demonstrated spontaneous sinus occlusion, mostly in the sigmoid sinus. This condition was not observed in neonates and was first discovered during infancy or childhood. Progression of sinus occlusion was seen in 10 patients, and the conditions of 6 of them deteriorated in accordance with the progression of sinus occlusion. After total or subtotal obliteration of the malformation by transarterial glue embolization, 13 patients recovered to healthy, 3 patients had only mild developmental delay, and 4 patients remained neurologically disabled.CONCLUSIONS:Spontaneous sinus occlusion is not a rare condition and can result in neurologic deterioration in the natural history of untreated vein of Galen malformation. If signs of progressive sinus occlusion are noticed, early arteriovenous shunt reduction or elimination by transarterial glue embolization is expected to prevent permanent brain damage.

Vein of Galen malformations (VGMs) are direct arteriovenous shunts in the subarachnoid space of the velum interpositum cistern and quadrigeminal cistern, supplied by the choroidal and quadrigeminal arteries and drained by the dilated median prosencephalic vein of Markowski, the embryonic precursor of the vein of Galen.^1,2 This malformation is considered to form between 6 and 11 weeks of gestational age when this transient embryonic vein exists.The clinical presentation of VGM varies depending on the age of the patient. Neonates typically present with high-output congestive heart failure due to high-flow shunt producing cardiac overload, whereas infants and children usually present with hydrovenous disorders, such as macrocrania, prominent facial and scalp veins, and hydrocephalus.^2,3 Hydrovenous disorders result from diminished absorption of CSF due to cerebral venous hypertension.⁴ Development of outflow restriction in the posterior fossa dural sinuses will improve the cardiac overload but will lead to further intracranial venous hypertension, which will not only interfere with absorption of CSF but will also create congestion within cerebral veins. Venous hypertension consequently results in brain tissue loss and hence developmental delay.^2,3Thus, posterior fossa dural sinus occlusion is thought to aggravate the clinical course of VGM. However, its incidence, pathogenic mechanism, and the effect of endovascular embolization are unknown. The aim of this study was to analyze the clinical and angiographic course of patients with VGM with sinus occlusion and to determine whether embolization can prevent clinical deterioration in these patients.     

Normal Fetal Posterior Fossa in MR Imaging: New Biometric Data and Possible Clinical Significance

BACKGROUND AND PURPOSE:Posterior fossa malformations are a common finding in prenatal diagnosis. The objectives of this study are to re-evaluate existing normal MR imaging biometric data of the fetal posterior fossa, suggest and evaluate new parameters, and demonstrate the possible clinical applications of these data.MATERIALS AND METHODS:This was a retrospective review of 215 fetal MR imaging examinations with normal findings and 5 examinations of fetuses with a suspected pathologic posterior fossa. Six previously reported parameters and 8 new parameters were measured. Three new parameter ratios were calculated. Interobserver agreement was calculated by using the intraclass correlation coefficient.RESULTS:For measuring each structure, 151–211 MR imaging examinations were selected, resulting in a normal biometry curve according to gestational age for each parameter. Analysis of the ratio parameters showed that vermian lobe ratio and cerebellar hemisphere ratio remain constant with gestational age and that the vermis-to-cisterna magna ratio varies with gestational age. Measurements of the 5 pathologic fetuses are presented on the normal curves. Interobserver agreement was excellent, with the intraclass correlation coefficients of most parameters above 0.9 and only 2 parameters below 0.8.CONCLUSIONS:The biometry curves derived from new and existing biometric data and presented in this study may expand and deepen the biometry we use today, while keeping it simple and repeatable. By applying these extensive biometric data on suspected abnormal cases, diagnoses may be confirmed, better classified, or completely altered.

The posterior cranial fossa is located between the foramen magnum, which forms its caudal boundary, and the tentorium cerebelli, which form its cephalad boundary. It includes the 3 parts of the brain stem: medulla oblongata, pons, and midbrain; the cerebellum with its vermis; and the fluid-filled spaces: the fourth ventricle and cisterna magna. The structures of the posterior fossa (PF) develop from the mesencephalon of the neural tube (midbrain and vermis), the metencephalon part of the rhombencephalon (pons and cerebellar hemispheres), and the myelencephalon part of the rhombencephalon (medulla oblongata), starting at the fourth gestational week. Normally, by the 18th gestational week, the PF consists of a developed vermis and cerebellum, a developed pons, and a fourth ventricle fully covered by the caudal part of the vermis, and the fluid-filled spaces are connected by the foramina of Luschka and Magendie.^1,2During the development of the structures and fluid-filled spaces of the PF, a wide spectrum of malformations of these structures is often observed. The variety of these malformations, isolated or part of a syndrome, and of their outcomes makes it difficult to classify the different pathologies.^3,4 During the past decade, attempts to classify the PF malformations have been made, to help physicians and radiologists diagnose and give an accurate prognosis for fetuses with a pathologic PF.^5–7The different classifications and the possible diagnoses are mainly on the basis of the morphology of the fetal PF and its biometric data. Formerly, normal biometric data were taken mainly from studies of PF biometry in ultrasonographic imaging.^8–12 However, MR imaging has advantages over sonography when assessing fetal PF, such as better accuracy when evaluating the vermis and better contrast resolution, which enable evaluation of the brain stem.^13,14 Therefore, during the past 2 decades, MR imaging has become an important tool to prenatally evaluate the morphology of the PF, and many studies have been published to supply valid MR imaging biometric data.^15–17 However, because using MR imaging prenatally is still not a common procedure and is usually performed on suspected abnormal fetuses, re-evaluation is still needed. In addition, the high resolution of MR images makes it possible to measure structures that could not be measured before.In this study, we re-evaluated existing normal MR imaging biometric data of PF structures in a large cohort. In addition, we suggest new biometric data, that, to our knowledge, were not measured in previous studies, to help correctly diagnose suspected pathologic fetuses. We demonstrate the potential clinical use of these data by retrospectively evaluating 5 different suspected pathologic cases.     

减轻后颅窝伪影的后处理方案优化的探讨

目的 评价多种后处理方式在减轻后颅窝伪影方面的应用价值.方法 临床需行头颅CT平扫并且后颅窝有伪影的成人患者40例,分别采用不同后处理方式减轻后颅窝伪影.A组卷积核D30,B组卷积核D24,C组卷积核D34,D组为A组行SAFIRE 3级重建后图像Q3,E组为A组行单能谱软件处理后的16组图像,F组为D组行单能谱软件处理后的16组图像.分别评价A～D组及E、F组中16个亚组图像的后颅窝伪影,并对各感兴趣区域进行图像质量客观评价及后颅窝伪影分析.结果 六组三个部位的平均CT值差异均无统计学意义(P＞0.05),SD值的差异有统计学意义(P＜0.05),且F组80keV时最小,SNR有统计学差异(P＜0.05),且F组80keV时最大.结论 单纯卷积核D24图像最佳;D30经SAFIRE 3级重建后的图像,减轻伪影效果较好;D30图像经SAFIRE 3级和单能谱软件再处理后的图像,减轻伪影效果更佳.推荐临床使用D30经SAFIRE 3级重建后的图像,因其简单、方便操作效果亦较好.     

妊娠期X线骨盆测量对胎儿影响的远期观察

本文报道1963～1977年在本院做x线骨盆测量者所生子女498例进行远期随访、观察了身高、体中、检查外周血像、询问学习成绩及女青年月经初潮年龄。用自制人体腹部模型,按原来骨盆像酡:互照条件,模拟测得妊37周的子宫,左枕前位睁儿,照x线骨盆测量像时,宫内胎儿吸收剂量为0.01～0.03Gy。在随访493例青少年生长发育,外用血像等方面来见到明显影响。若改善投照条件可使剂量减少至小于0.01Gy。结果表明x线骨盐'捌量对胎儿可能是无害的。     

后颅窝原发性中枢神经系统淋巴瘤的磁共振多模态诊断

目的 探讨磁共振多模态成像在后颅窝原发性中枢神经系统淋巴瘤(PCNSL)中的诊断价值.方法 回顾性分析经病理证实的16例后颅窝PCNSL患者的MR平扫、扩散加权成像(DWI)、动态增强及氢质子磁共振波谱(1H-MRS)影像资料.结果 16例患者共有26个病灶,6例为多发病灶.所有病灶在T1WI呈低或稍低信号;T2WI上21个病灶呈稍高信号,3个呈等信号,2个呈混杂稍高信号;DWI上2例扩散受限呈高信号,13例扩散稍受限呈稍高信号,1例扩散不受限呈等信号.表观扩散系数(ADC)图上测得肿瘤实质与对照侧平均ADC值分别为(0.610 ±0.092)×10-3mm2/s和(0.700 ±0.044)×10-3mm2/s,两者差异有统计学意义(P=0.02,＜0.05,Z=-2.269),rADC为0.884±0.125.增强扫描26个病灶呈明显强化,其中12个病灶可见“尖角征”、“脐凹征”,时间一信号强度(TIC)曲线为Ⅰ型(缓升型).瘤周轻、中度水肿12例.MRS表现为病灶实质区出现高大的Lip峰.结论 多模态磁共振成像有助于后颅窝PCNSL的明确诊断.