胎儿磁共振成像-胎儿头颅MRI检查

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MRI检查技术
• 1.5T及以下MR机 • 体部相共振线圈 • 序列：单次激发FSE(0.5NEX）
FIASTA序列 • 常规轴、冠、矢扫描
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胎儿头颅MRI检查
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• 胎儿头颅MR检查主要观察
--脑室扩大 --可疑后颅窝异常 --胼胝体发育不良
Normal
Abnormal
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22－week fetus
A. axial sonography showed a large cystic posterior fossa with small cerebellar
hemispheres.
B. the tegmento-vermian angle is increased with the fourth ventricle uncovered .
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孕28＋3周，B超提示胎儿脑室扩张
9.8mm
12.3mm
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14.9mm
18
上下蚓比
• 小脑蚓部胚胎期呈线性协调发育 • 以顶点为分界上下蚓比例为47％和53％，不随
生长发育变化
ቤተ መጻሕፍቲ ባይዱ2021/3/27
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23-week fetus
The craniocaudal diameter of vermis measures 10.9mm (equivalent of 22 weeks). The expected measurement is 14.8mm.
The transcerebellar diameter is also small.
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大枕大池
36-week fetus
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枕大池蛛网膜囊肿
29-week fetus
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5-month
22
孕32周，外院超声提示左脑室扩张、枕大池积水
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孕31周，超声提示：可疑侧脑室增宽
resulting in large temporal horns
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22－week fetus
Sonography and MRI findings are similar to the previous case except that the cerebellar hemispheres seems larger and vermian tisse can be seen in the midline.
23 (59%)
Disagreement
16 (41%)
Excluded fetal MRI
6 (15%)
Revealed additional
abnormalities
10 (26%)
Limperopoulos C, et al. AJR Am J Roentgenol 2008; 190:1637–1643.
The vermis is very small; there is no primary fissure or fastigial point.
C. Diagrammatic representation of DWC.
D. the cerebellar hemispheres are small.The ventricular system is dilated,
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• 枕大池(cisterna magna)正常值2－11mm • 侧脑室体部<10mm
• 异常表现：Dandy-Walker 畸形，小脑蚓部发
育不良，大枕大池，蛛网膜囊肿
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小脑蚓部的发育
• 11－12W，小脑及原始蚓部从第四脑室嘴侧发生 • 13－14W，原始顶点可见（第四脑室顶部裂缝） • 14－16W，小脑蚓部原裂出现 • 16W，小脑蚓部向尾侧发育，于顶点处“折叠”
• 小脑原裂 primary fissure • 顶点 fastigial point • 顶－蚓角tengmento-vermian angle，TVA • 颅尾径 craniocaudal diameter，CCD
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Tengmento-vermian angle
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知识回顾 Knowledge Review
完
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Total fetuses 90
MRI abnormal 60 (67%)
Comparison of antenatal and postnatal MR findings in 39 of 42 live born infants
Complete agreement
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Craniocaudal diameter
Craniocaudal diameter (perpendicular to fastigial point-declive line)
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28-week fetus
胎儿磁共振成像
MR Imaging of the Fetus
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• 超声－Ultrasound --母体肥胖
--羊水过少 --妊娠中晚期胎头增大 --胎儿颅骨骨化
• MRI－Ultrafast MRI
--单次激发快速序列 --大FOV
--安全性？
MRI仅适用于当产前超声不足以解决临床问题时
覆盖四脑室顶，第四脑室“闭合”
• 16－17W，锥前裂、顶前裂等可见 • 18－19W，蚓部颅尾方向长度与小脑半球相等
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11－12W
13－14W
16W
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18W
9
17.5w
21w
22w
24w
27w
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Assessment of Vermian Maturity