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With the emergence of ultrafast MR sequences,fetus MRI has been greatly improved.Because of its excellent detailed visualization and large view on soft tissue,MRI has more advantages in diagnosing fetal congenital brain malformation than ultrasound.Therefore,MRI has become an important examination method for prenatal screening and has a broad application prospect.This article reviews the safety,indications,scanning sequence, clinical application and precautions of fetal craniocerebral magnetic resonance.
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Objective To compare metabolite ratios in the basal ganglia regions between preterm and term neonates and analyze the correlation between metabolite ratio and postmenstrual age(PMA)using 2D magnetic resonance spectroscopy(MRS)at 3.0T,so as to explore the value of MRS in evaluating neonatal brain development.Methods Normal neonates who underwent 3.0T MRS exam ination were recruited.Axial 2D MRS was performed with the point-resolved spectroscopy sequence(PRESS)(echo time/repetition time,144 ms/1 000 ms) through the basal ganglia covering three regions of interest(ROI)(i.e.bilateral lenticular nucleus,thalamus and white matter beside the anterior horn of lateral ventricle).The peak areas ratios of Cho/Cr,NAA/Cho and NAA/Cr were calculated.Metabolite ratios were compared between preterm and term neonates,and between three ROIs. Correlation between metabolite ratio and PMA was further analyzed.Results Totally 54 neonates were included(preterm/term,27/27).In all the three ROIs,preterm neonates presented significantly higher Cho/Cr(P＜0.05) and significantly lower NAA/Cho ratios(P＜0.001)than those of term neonates;higher NAA/Cr ratio was only observed in the lenticular nucleus of preterm neonates(P＜0.001).Significant differences in metabolite ratios were detected among the three ROIs in preterm group(P＜0.05).For term group,metabolite ratios differed between lenticular nucleus and white matter beside the anterior horn of the lateral ventricle(P＜0.01),while no difference between lenticular nucleus and thalamus was found(P＞0.05).Significant correlation between metabolite ratio and PMA was found in all the three ROIs except NAA/Cr ratio in the white matter beside the anterior horn of the lateral ventricle.To be specific,we found linear negative correlation of Cho/Cr ratio(r= -0.325,-0.633,-0.438) and positive correlation of NAA/Cho ratio(r = 0.604,0.773,0.483)in all the three ROIs,but negative correlations of NAA/Cr ratio(r=0.487,0.367)in lenticular nucleus and thalamus with PMA.Conclusion Our findings suggest the tempo-spatial pattern of neonatal brain metabolite development in terms of anatomic location and PMA.Besides,the multi-voxel MRS presents potentials in establishing the normal topologic and age-matched reference in neonates and thus making brain maturation assessment and detection of early abnormal metabolism.
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Objective To investigate the reliability of MRI classification and clinical significance of deep gray matter injury(DGMI)in children with cerebral palsy(CP).Methods We made a retrospective assessment of 14 children with gross motor function classification system(GMFCS),manual ability classification system(MACS)and MRI classification system of deep gray matter injury.Based on T2WI,two radiologists worked independently and graded MRI pictures according to three-grading system and four-grading system.To evaluate the reliability of different grading systems,intra-observer and inter-observer agreements were tested by Kappa test.Spearman correlation analysis was performed to analyze the MRI classification system with GMFCS and MACS.Results The Kappa value of the intro-observer and inter-observe agreement of three-grading system was 0.873 and 0.873,respectively (P＜0.001).The Kappa value of the intro-observer and inter-observe agreement of four-grading system was 0.901 and 0.611(P＜0.001).Three-grading system had no significant correlation with GMFCS(r=0.053,P＞0.05)or MACS(r=0.128,P＞0.05).Four-grading system had a significant positive correlation with GMFCS(r=0.605, P＜0.05)and MACS(r=0.779,P＜0.05).Conclusion In the two grading systems,four-grading system is a more repeatable approach for detecting deep gray matter,gross motor function and manual function injuries in children with cerebral palsy.
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Objective To explore developmental states on the preterm and term neonatal brain white matter based on the co-variation of metrics derived from diffusion tensor imaging(DTI).Methods This work enrolled 66 neonates,consisting of 33 preterm(21 males and 12 females;gestational age:30.143-36.286 weeks)and 33 full-term neonates(22 males and 11 females;gestational age:37.000 -41.429 weeks).DTI derived metrics included axial diffusivity(AD),radial diffusivity(RD),and fractional anisotropy(FA).Spearman's rank correlation between metrics and postmenstrual age was analyzed in the preterm and term neonates.Developmental states were evaluated according to the method proposed by Dubois:fiber organization was associated with increased AD, decreased RD and increased FA;pre-myelination was related to decreased AD,decreased RD and unchanged/increased FA;myelination was revealed by unchanged AD,decreased RD and increased FA.Mann-Whitney U test was used to compare DTI metrics between the preterm and term neonates.Results According to the method proposed by Dubois,posterior limb of internal capsule and corpus callosum underwent myelination in the preterm-neonate period.Cerebral peduncle started myelination in the term-neonate period.Superior corona radiate,inferior fronto-occipital fasciculus and external capsule underwent pre-myelination on preterm and term neonates.FA values were higher in term neonates than those in preterm neonates in all the selected regions(P＜0.05).AD and RD values were lower in term neonates than those in preterm neonates in the selected regions except for cerebral peduncle(P＜0.05).Conclusion Changes in DTI metrics and the method of Dubois can be used to quantitatively evaluate developmental states of the neonatal brain white matter.The changes coincided with DTI variations associated with pre-myelination and myelination.White matter development is delayed in preterm neonates compared with term neonates.
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Objective To explore the significance of signal classification by multimodal magnetic resonance imaging(MRI)(including conventional MRI,diffusion imaging,and susceptibility-weighted imaging)on neonatal punctate white matter lesions(PWML).Methods Between March 2011 and February 2013,neonates with PWML who underwent 3.0T MRI examination were recruited.The routine protocols included T1 weighted imaging (T1WI),T2 weighted imaging(T2WI),diffusion tensor imaging(DTI),and 3D-enhanced susceptibility-weighted angiography(ESWAN).Apparent diffusion coefficient(ADC)map,magnitude image,and phase image were obtained from DTI and ESWAN,respectively.The signal of PWML was one-to-one observed on T1WI,T2WI, ADC map and magnitude image.The combined signals were classified and the number of cases of each type was counted.Results Totally 84 neonates with PWML were included(preterm/term,47/37).Seven signal types were found and classified into three groups: ① Type Ⅰ was the most,59 cases,accounting for 70.24%,with the performance of high-signal intensity on T1WI,low-signal intensity on T2WI,low-signal intensity on ADC map,and high-signal intensity on magnitude image. ② Type Ⅱ,7 cases,accounting for 8.33%,high-signal intensity on T1WI,low-signal intensity on T2WI,low-signal intensity on ADC map,and low-signal intensity on magnitude image.③ Type Ⅲ - Ⅶ,26 cases,accounting for 30.95%,high-signal intensity on T1WI,low/iso-signal intensity on T2WI,low/iso-signal intensity on ADC map,high/iso-signal intensity on magnitude image.There was no significant difference in the incidence of different signal types between preterm and full-term PWML neonates. Conclusion Magnetic resonance signal may reflect the characteristics of PWML lesions.Signal classification of PWML by multimodal magnetic resonance imaging is helpful in determining injury type and has certain significance in guiding clinical treatment.
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<p><b>BACKGROUND</b>Mild hypoxic-ischemic encephalopathy (HIE) injury is becoming the major type in neonatal brain diseases. The aim of this study was to assess brain maturation in mild HIE neonatal brains using total maturation score (TMS) based on conventional magnetic resonance imaging (MRI).</p><p><b>METHODS</b>Totally, 45 neonates with clinically mild HIE and 45 matched control neonates were enrolled. Gestated age, birth weight, age after birth and postmenstrual age at magnetic resonance (MR) scan were homogenous in the two groups. According to MR findings, mild HIE neonates were divided into three subgroups: Pattern I, neonates with normal MR appearance; Pattern II, preterm neonates with abnormal MR appearance; Pattern III, full-term neonates with abnormal MR appearance. TMS and its parameters, progressive myelination (M), cortical infolding (C), involution of germinal matrix tissue (G), and glial cell migration bands (B), were employed to assess brain maturation and compare difference between HIE and control groups.</p><p><b>RESULTS</b>The mean of TMS was significantly lower in mild HIE group than it in the control group (mean ± standard deviation [SD] 11.62 ± 1.53 vs. 12.36 ± 1.26, P < 0.001). In four parameters of TMS scores, the M and C scores were significantly lower in mild HIE group. Of the three patterns of mild HIE, Pattern I (10 cases) showed no significant difference of TMS compared with control neonates, while Pattern II (22 cases), III (13 cases) all had significantly decreased TMS than control neonates (mean ± SD 10.56 ± 0.93 vs. 11.48 ± 0.55, P < 0.05; 12.59 ± 1.28 vs. 13.25 ± 1.29, P < 0.05). It was M, C, and GM scores that significantly decreased in Pattern II, while for Pattern III, only C score significantly decreased.</p><p><b>CONCLUSIONS</b>The TMS system, based on conventional MRI, is an effective method to detect delayed brain maturation in clinically mild HIE. The conventional MRI can reveal the different retardations in subtle structures and development processes among the different patterns of mild HIE.</p>