MRI Findings In Intracranial Embryonal Tumors Of Children

PartⅠ Distinctive MRI features of medulloblastoma subtypes in childrenObjective:To analyze the diagnostic value of MRI,diffusion-weighted imaging and ~1H-MR spectroscopy in pediatric medulloblastoma histologic subtypes.Methods:Between 2010 and 2016,the preoperative MRI(136),DWI(136)and~1H-MRS(50)of 136 children with pathologically confirmed medulloblastomas were retrospectively analyzed.There were 87 boys and 49 girls.The mean age of these patients was 4.8±2.9 months,ranging from 1 year to 14 years.The mean ADC values(ADCmean),minimum ADC values(ADCmin),tumor/normal brain ADC ratios(r ADC)and metabolites were compared among the subtypes of medulloblastoma.Results:The histologic subtypes included 83 classic medulloblastomas(CMB),28desmoplastic medulloblastomas(DMB),11 medulloblastomas with extensive nodularity(MB-EN),and 14 large cell or anaplastic medulloblastomas(LC/A).Conventional MRI manifestations including T1 and T2 signal intensities,contrast enhancement,cyst,peritumoral edema,dissemination,and hemorrhage were not significantly different among all histologic subtypes(P>0.05).The ADCmean,ADCmin and r ADC of DMB was lower than that of LC/A or CMB whereas the ADCmean,ADCmin and r ADC of LC/A was highest among all histologic Subtypes(P<0.05).The ADCmean,ADCmin and r ADC were not significantly different between MB-EN and CMB or DMB(P>0.05).The ADCmean,ADCmin and r ADC of LC/A medulloblastoma histologic subtype were greater than that of CMB whereas the ADCmean,ADCmin and r ADC of DMB were smaller than that of both LC/A and CMB.The ADCmean,ADCmin and r ADC were not significantly different between MB-EN and CMB or DMB.On ~1H-MRS,the ratios of N-acetylaspartate(NAA)/Cr,the ratios of choline(Cho)/creatine(Cr),NAA/Cho, myo-inositol(m I)/Cr and the presence of lipid were not significantly different among all histologic subtypes(all P>0.05)whereas lactate was significantly(P<0.05)more common in LC/A than MB-EN followed by CMB and least common in DMB subtypes.Conclusion:Conventional MRI manifestations,metabolite ratios and presence of lipid are not significantly different among medulloblastoma subtypes.The ADCmean,ADCmin,r ADC and presence of lactate varied significantly and are helpful in differential diagnosis of medulloblastoma subtypes.Part ⅡComparative study between infratentorial Atypical Teratoid Tumor/Rhabdoid Tumor and medulloblastoma of Children on MRIObjective: To investigate the value of MRI and apparent diffusion coefficient(ADC)of diffusion-weighted imaging(DWI)in differential diagnosis of infratentorial atypical teratoid tumor /rhabdoid tumor(AT/RT)and medulloblastoma.Material and methods: 71 cases of medulloblastoma and 21 cases of infratentorial AT/RT,confirmed with surgically and pathologically,were retrospectively analyzed on preoperative MRI,DWI.The differences of the mean ADC values(ADCmean),minimum ADC values(ADCmin),tumor/normal brain ADC ratios(r ADC)were compared between AT/RT and medulloblastoma.Results: In the 71 patients with medulloblastoma and the 21 patients with infratentorial AT/RT,Regular MRI manifestations,including T1-weighted MRI,T2-weighted MRI,peritumoral edema,hemorrhage and disseminate were no significant differences(all P>0.05).While contrast enhancement degree and cyst were significantly different(all P<0.05).The pattern of band-like enhancement zones surrounding cystic or necrotic areas was typical in AT/RT.The ADCmean,ADCmin and r ADC of AT/RT was lower than medulloblastoma(all P<0.05).The ROC analysis showed that the area under the curve(AUC)of ADCmin for identifying the two kinds of tumors was 0.929,which was greater than that of ADCmean(0.820)as well as that of r ADC(0.916).The cutoff point of ADCmean for identifying the two kinds of tumors was set at 0.613×10-3 mm2/s with 78.9% sensitivity and 81.0% specifity.The cutoff point of ADCmin for identifying the two kinds of tumors was set at 0.507×10-3 mm2/s with 81.7% sensitivity and 90.5% specifity.The cutoff point of r ADC for identifying the two kinds of tumors was set at 0.790 with 90.1% sensitivity and 85.7% specifity.Conclusion: The results of this study indicate that combination analysis of Regular MRI manifestations and DWI parameter(ADCmin、r ADC)were a reliable method for differential diagnosis of infratentorial AT/RT and medulloblastoma,and ADCmin and r ADC has higher sensitivity and specificity in diagnosis of the two kinds of tumors,which is very helpful in making clinical treatment plan and in judging the prognosis.