MR Imaging Findings And ADC Values In Differential Diagnosis Of Intracranial Hemangiopericytoma And Atypical Meningioma

ObjectiveTo analyze the differences of MRI features between intracranial hemangiopericytoma(HPC)and atypical meningioma(AM).And to explore the clinical value of DWI and ADC value in differential diagnosis of them.Materials and methodsWe retrospectively analyzed the patients with intracranial HPC and AM who were surgically proved in Shandong Provincial Hospital from 2013 to 2016,including their clinical,pathological and imaging information.All the pathological information were confirmed by a professional pathologist that they all met the standards of the 2016 World Health Organization Classification of Tumors of the Central Nervous System.There were 12 patients with intracranial HPC,8 males and 4 females,aging from 8 to 66 years old and the average age was 40.Clinical manifestation:headache(n=9),disorder of limb movement(n=7),dizziness(n=7),vomiting(n=4),blurred vision(n=1).There were 36 patients with atypical meningioma,17 males and 19 females,aging from 28 to 74 years old and the average age was 52.4.Clinical manifestation:headache(n=30),dizziness(n=28),vomiting(n=18),mental disorder(n=12),epilepsy(n=7),disorder of limb movement(n=7),blurred vision(n=3).All the MR images were obtained by using 3.0T MR system(Signa HDxt,GE,USA)and a standard eight-channel quadrature head coil.Slice thickness was 5mm,spacing 1.5mm,field of view 24×24 cm,matrix 256X256.MR scan protocol included the following sequences:T1-weighted images(TR 1750ms,TE 24ms,TI 860ms),T2-weighted images(TR 3280ms,TE 110ms,ETL 8)and FLAIR images(TR 9000ms,TE 150ms,TI 2250ms).DW MR images was acquired in the axial plane by using b=0,1000 s/mm,slice thickness was 5mm,spacing 1.5mm,field of view 24 X 24 cm,matrix 256 X 256,TR 5300ms,TE 74.5ms.We also obtained axial,coronal and sagittal T1-weighted images after administration of O.1mmol/Kg of body weight of Gd-DTPA.All the images were analyzed by 2 radiologists who were blinded to the diagnosis.The MRI features analyzed in the study included：tumor size,tumor shape,T1-weighted signal intensity,T2-weighted signal intensity,peritumoral edema size,vessel voids sign,tumor necrosis and hemorrhage,dural attachment,dural tail sign,adjacent bone erosion,uniformity and degree of tumor enhancement,and so on.ADC maps were calculated from DWI by using Functool software on GE-workstation.All ADC values were measured on the ADC maps on the same workstation by using the regions of interests(ROIs).Selecting 3 slices that included the solid portion of the tumors according to the conventional MR images and placed the round ROIs on the 3 slices,avoiding cystic,necrotic or hemorrhage regions inside the tumors.The average value of the 3 ROIs was defined as the ADC value of the tumor.The clinical information included the sex and age of the patients.SPSS 20.0 was used for statistically analyzing the clinical and imaging features of the patients with intracranial HPC and AM.Mean,standard deviation,median and range for continuous variables,frequency for discrete data were calculated for patient demographics.Student t test,Rank sum test and chi-square test were conducted to examine the association of radiological and clinical features between the two independent groups.For all analysis,p<0.05 were considered statistically significant.Receiver operating curve(ROC)were used to assess the diagnostic ability of ADC value and the best cut-off value which allowed the best sensitivity and specificity between intracranial HPC and AM.ResultsThe mean age of intracranial HPCs was younger than that of AMs(40.0 ± 17.6<52.4± 11.6,p=0.038).The vessels void sign was more likely to be observed in the intracranial HPCs(x2 =18.000,p<0.001).The differences of dural attachment types between the two tumors were statistically significant(x2=10.890,p=0.001),which means the intracranial HPCs were more likely to have a narrow-based attachment,the AMs,however,had a wide-based one.The dural tail sign more often favored the diagnosis of AM(x2=12.690,p<0.001).The intracranial HPCs had higher signal intensity than the AMs on T1-weighted gadolinium enhanced MRI(x2=4.211,P=0.040).Difference in tumor size,tumor shape,T1-weighted signal intensity,T2-weighted signal intensity,peritumoral edema size,tumor necrosis and hemorrhage,adjacent bone erosion and uniformity of tumor enhancement were not statistically significant(P>0.05).The ADC value of intracranial HPCs was[1.14(1.00,1.21)]×1 0-3 mm2/s,which was significantly higher than that of AMs[0.79(0.74,0.85)]× 1 0-3 mm2/s,(p<0.01).The ADC cut-off value of 0.93×10-3 mm2/s provided the best combination of sensitivity(100%)and specificity(91.7%)for the differentiation between intracranial HPCs and AMs.ConclusionThe differences in age of on-set,vessels void sign,dural attachment types,dural tail sign and enhancement degree of tumors between intracranial HPC and AM are significant,and these MR features may be useful in differentiating the two kinds of tumors.However,when the two imaging findings are similar and difficult to diagnose,ADC values for the differential diagnosis is of great value,and can increase the diagnositic accuracy.