【作者】 王莉；

【导师】 乔中伟； 邵肖梅；

【作者基本信息】 复旦大学 ， 影像医学与核医学（专业学位）， 2014， 硕士

【摘要】 第一部分正常足月新生儿常规MRI、DWI表现及不同区域脑组织的ADC值目的：探讨正常足月新生儿常规磁共振成像(MRI)、弥散加权成像(DWI)的表现特点及不同部位脑组织的表观弥散系数(ADC)值的差异,建立正常参数,为后续研究提供正常对照。材料和方法：收集正常足月新生儿9例,平均胎龄为39.19周,平均出生体重3477 g,其母孕期间均无异常产科病史,无明显宫内窘迫史,出生时无窒息史,出生后1分钟和5分钟Apgar评分均≥8分。无明显神经系统症状和体征,颅脑常规MRI和DWI检查未见异常。9例均行头颅常规MRI (T1WI、T2WI)和DWI扫描。测量双侧丘脑腹外侧、豆状核、小脑皮质、枕叶皮质、额叶皮质、顶叶皮质、大脑脚、内囊后肢、胼胝体压部、枕叶白质、额叶白质及顶叶白质共24个感兴趣区(ROI)的ADC值,分析脑各部位的ADC值在左右半球的差异以及脑不同部位ADC值差异。结果：由于新生儿脑发育不成熟、含水量较高,其头颅MRI表现不同于成人。常规MRI、DWI图像上各有其特点及优势。各部位ADC值统计分析示左右半球对称部位的ADC值的差异无统计学意义(P>0.05)。足月新生儿不同部位脑组织的ADC值存在着差异(P<0.05)。在所测不同区域脑组织的ADC值中,以浅层白质结构为最高(枕叶、额叶和顶叶白质),明显高于深部白质纤维结构(大脑脚、内囊后肢和胼胝体压部,P<0.05)、深部灰质核团(丘脑腹外侧核和豆状核,P<0.05)和浅层灰质结构(小脑、枕叶、额叶和顶叶皮质,P<0.05)。而深部白质纤维结构、深部灰质核团、浅层灰质结构的ADC值,除大脑脚与额叶皮质、大脑脚与顶叶、丘脑腹外侧与顶叶皮质有统计学差异(P=0.001,0.000,0.044)外,其余之间均无统计学差异(P>0.05)。浅层白质纤维结构中枕叶白质ADC值低于额叶白质和顶叶白质(P<0.05),而额叶白质与顶叶白质ADC值无统计学差异(P>0.05)。皮质脊髓束行径区中内囊后肢、大脑脚的ADC值相近,均低于浅层白质结构(P<0.05)。结论：正常足月新生儿脑各部位的ADC值在左右半球间无明显差异,不同部位脑组织的ADC值有显著差异,反映了髓鞘化时间、髓鞘本身结构特点的差异。第二部分MRI在足月新生儿围产期动脉缺血性脑梗死的应用研究目的：探讨常规MRI、DWI及磁共振血管成像(MRA)在足月新生儿围产期动脉缺血性脑梗死(PA1S)的应用价值,通过ADC值定量分析梗死大脑各部位的ADC值与正常对照组的差异。材料和方法：收集足月PAIS新生儿21例,男12例,女9例,平均胎龄为39.62周,平均出生体重为3 383 g,5例紧急剖宫产,15例首发临床表现为惊厥,入院时间为生后3 h至5 d。所有患儿均于生后7天内行常规MRI、DWI扫描,其中9例还进行了磁共振血管成像(MRA)扫描。测量双侧丘脑腹外侧、豆状核、小脑皮质、额叶皮质、大脑脚、内囊后肢、胼胝体压部、额叶皮质和白质以及病灶区域和病灶对侧相应区域共18个ROI的ADC值,并与对照组相比较,分析病灶侧、病灶对侧和正常对照组不同部位脑组织的ADC值差异,定量分析脑内各部位水分子弥散运动情况。对MCA梗塞患者进行分型,比较不同梗塞类型其皮质脊髓束的受累情况。结果：21例患儿常规MRI中,18例T1WI呈现异常信号,7例表现为受累区域皮层及皮层下弥漫T1信号减低,11例T1WI信号稍减低,信号改变轻微；19例T2WI见异常信号,14例表现为受累区域皮层及皮层下弥漫T2WI信号增高,5例T2WI信号稍增高,且灰白质分界不清。21例患儿首次DWI检查中均出现异常高信号,病灶边缘的显示较常规MRI清晰,DWI还发现了常规MRI未显示的胼胝体膝部、压部、丘脑腹外侧、内囊后肢、大脑脚等部位的受累。19例累及大脑中动脉(MCA)供血区,2例累及大脑后动脉供血区(PCA)。21例中双侧梗塞2例,单侧梗塞19例。21例中9例行MRA检查,6例表现为梗塞侧MCA皮质分支较对侧增多现象,局部管径较对侧增粗。比较不同MCA梗塞类型特点,发现混合型梗塞较之于表浅型梗塞更易发生大脑脚、丘脑腹外侧核的受累,且混合型梗塞内囊后肢、大脑脚、胼胝体等脑深部白质纤维结构的受累发生率高于表浅型梗塞。病灶侧与病灶对侧各部位ADC值比较,病灶侧内囊后肢、大脑脚、丘脑腹外侧ADC值较对侧明显降低(P=0.0012,0.0038,0.0119),病灶区域ADC值降低程度最显著(P=0.0001)。而患儿MRI表现正常部位与对照组相比ADC值差异均不具有统计学意义(P>0.05)。混合型梗塞组病灶侧内囊后肢、豆状核、丘脑腹外侧核ADC值明显低于表浅型梗塞组(P=0.0246,0.0268,0.0153),病灶侧其他部位和病灶对侧各部位ADC值两组之间比较差异不具有统计学意义(P>0.05)。结论：常规MRI在急性期的诊断价值不如DWI,而在亚急性期对病变范围的显示优于DWI序列,两者结合运用可大致推测具体发病时间。DWI可早期诊断PAIS,可敏感探及大脑深部小病灶的受累情况,尤其是病灶同侧的内囊后肢、大脑脚、脑干前部(皮质脊髓束行径区)的信号异常,可一定程度预测远期预后。PAIS的MRA检查大多表现为病灶侧MCA皮质分支较对侧增多、管径增粗,可影响治疗决策。足月新生儿PAIS脑内不同部位ADC值统计分析结果显示病变侧内囊后肢、大脑脚、丘脑腹外侧ADC值明显降低,为易受累区域,病灶区域ADC值降低程度最显著。而颅内未受累区域ADC值与对照组相比差异不具有统计学意义,提示脑梗死病变呈局灶性,与HIE不同。更多还原

【Abstract】 Part I Conventional MRI, Diffusion weighted imaging and ADC value in normal term neonatal brainObjective:To investigate the appearance of normal neonatal brain on conventional MRI and diffusion weighted imaging and the diversity of ADC values in various brain regions, establish normal parameters for the follow-up study. Materials and Methods: 9 term neonates without abnormal obstetric history during pregnancy were examined with a 1.5T MR imaging system(Avanto; Siemens, Erlangen, Germany). Their perinatal medical records and nervous system examinations were nothing remarkable. All of 9 neonates were performed with conventional MRI and DWI, and there was no abnormal signal-intensity on conventional MRI and diffusion weighted imaging. The routine MR imaging protocol include transverse T1-weighted, transverse T2-weighted, transverse diffusion-weighted imaging. ADC values in bilateral cerebellar cortex(CC), posterior limb of internal capsule(PLIC), cerebral peduncle(CP), splenium of corpus callosum(Splenium), lentiform nucleus (LN), ventrolateral nuclei of the thalamus(VLN), occipital cortex(OC), occipital white matter(OWM), parietal cortex(PC), parietal white matter(PWM), frontal cortex(FC) and frontal white matter(FWM) were analyzed. Results:All of 9 neonates were successfully performed with conventional MRI sequences and DWI. The appearance of neonatal brain on MRI is different from adults, since the immaturity of neonatal brain with high content of moisture. ADC values in the same region of interest(ROI) had no statistic difference between left and right hemisphere(P>0.05). ADC values of superficial white matter were significantly higher than deep white matter, deep nuclear, and superficial grey matter (P<0.05). In deep white matter, deep nuclear, and cortex, ADC value of different regions was with no difference between each other except for CP and FC, CP and PC, and VLN and PC(P<0.05). In superficial white matter, ADC value of OWM was lower than FWM and PWM(P<0.05). Conclusion:ADC values in the same brain regions of normal term newborns have no statistic difference between left and right hemisphere. ADC values in various brain regions is different, it reflects the myelination time and the features of myelin sheath.Part Ⅱ The application of MRI in term newborns with perinatal arterial ischemic strokeObjective:To discuss the role of conventional MRI, diffusion weighted imaging and magnetic resonance angiography in term newborns with perinatal arterial ischemic stroke. To investgate the difference of ADC values in various regions between stroke brain and control group by quantitative analysing of ADC values. Materials andMethods:21 term neonates diagnosed with PAIS, including 12 males and 9 females, birth weight 3 383±422 g.5 cases of emergency cesarean delivery,15 cases presented with seizure, admission time was 3 h to 5 d after birth. All MRI examinations were performed within 7 days after birth including routine MRI and DWI. And 9 cases performed magnetic resonance angiography (MRA) scan. ADC values of different regions of affected side and the other side including VLN, LN, CC, FC, CP, PLIC, Splenium, PC, PWM, lesions, symmetrical region on the other hemisphere, a total of 18 ROIs were analyzed with the control group. Different MCA infarction types were analyzed. Results:In the first series of conventional MRI images, there were hypointensity in T1WI in the affected areas (7 cases), subtle hypointensity (11 cases); there were hyperintensity in T2WI in the affected areas (14 cases), subtle hyperintensity (5 cases) and with poor differentiation between grey and white matter. First series of DWI images showed distinct hyperintensity in 21 cases in affected areas, the edge of the lesions were clearer than routine MRI. In addition, DWI found more lesions than routine MRI including the genu and splenium of corpus callosum, thalamus, posterior limb of internal capsule and cerebral peduncle.19 patients’MCA territory was involved.9 patients had MRA examination.6 patients presented with cortical branches increased in the affected areas. Compared with superficial type, mixed infarction had a strong relationship with the involving of CP, VLN, and with a higher incidence of PLIC, CP corpus callosum(CC) involved. ADC values of PLIC, CP, VLN in affected side were significantly lower than the other side(P<0.05), and the affected areas was the most significantly decreased region(P< 0.01). There was no statistic difference between regions of health side and control group(P>0.05). Compared with superficial group, ADC values of PLIC, LN and VLN in the affected hemisphere of mixed group were lower (P=0.0246,0.0268, 0.0153), and the rest were with no difference(P>0.05). Conclusion:Compared with conventional MRI, DWI can diagnosis PAIS earlier and find small lesions in the deep brain. The combined use of conventional MRI and DWI can detect the occurring time of the disease. The early MRA mostly show the cortical branches increased in the affected areas, which is different from arteriostenosis or occlusion in adults. ADC values of PLIC, CP, VLN in affected side were significantly lower than health side(vulnerable to affcet), and the affected areas was the most significantly decreased region. ADC values of other areas were similar to that of control group.更多还原