Pilot Study On Presurgical Grading Of Oligodendrogliomas With Diffusion-weighted And Contrast-enhanced MR Imaging

Pilot Study on Presurgical Grading of Oligodendrogliomas with Diffusion-weighted and Contrast-enhanced MR ImagingPartⅠMRI appearance of different grades and subtypes of oligodendroglial tumorsObjective:To explore the MRI appearance of oligodendroglial tumors and to compare the various MRI features of different grade and subtype of oligodendroglial tumors.Methods:Findings from 31 surgical pathologically proved oligodendroglial tumors in 30 patients were retrospectively analyzed and compared.The MRI features include lesion site,margin,extent,inner tumor signal,peritumor edema,and enhancement characteristics(degree of enhancement and enhancement pattern).Result:The 31 tumors include 24 pure oligodendrogliomas(9 gradeⅢtumors, 15 gradeⅡ) and 7 mixed oligoastrocytomas(4 gradeⅢtumors,3 gradeⅡ).29 lesions located at peripheral of the brain parenchyma,12 extended to deep region such as corpus callosum or basal ganglial region even to the contralateral hemisphere;2 arised in deep structures.Deep region involvement was more common in high grade tumors than in low grade tumors(69%9/13 Vs 28%5/18).The margin of the lesions could be well-demarcated(33%4/12 Vs 56%10/18),partially well demarcated(15% 2/13 Vs 11%2/18),or ill demarcated(54%7/13 Vs 33%6/18) when compared gradeⅢtumors with gradeⅡ;little perilesional edema was observed except 2 anaplastic oligoastrocytomaso Post contrast enhancement observed in 11 of 13 gradeⅢtumors Vs 8 of 18 gradeⅡ(85%Vs 44%),with strong enhancement observed in 10 of 13 gradeⅢtumors Vs 4of 18 gradeⅡtumors(77%Vs 22%);enhancement pattern(gradeⅢVs gradeⅡ,ring enhancement 69%9/13 Vs 11%2/18,nodular enhancement 15%2/13 Vs 33%6/18);necro-cystic change observed in 11 of 13 gradeⅢtumors Vs 6 of 18 gradeⅡtumors(85%Vs 33%),and 6 of 7 mixed tumors Vs 10 of 24 pure oligodendroglial tumors)(86%Vs 42%)。Conclusion No significant difference was found in tumor site,margin of oligodendroglial tumors on MRI.Tumor extension to deep region,inner tumor cystic-necrotic change,strong enhancement and ring enhancement pattern were more common in high grade tumors。PartⅡOligodendroglial tumors:Can relative apparent diffusion coefficient be used in prediction of tumor grade and subtypePurpose:To retrospectively assess whether the relative apparent diffusion coefficient(rADC) can be used in prediction of tumor grade or subtype of oligodendroglial tumors.Materials and methods:Findings from 24 patients(13 men, 11 women,mean age 45) with pathologically proved oligodendrogliomas that include 4 anaplastic oligoastrocytomas(OA gradeⅢ),6 anaplastic oligodendrogliomas(OD gradeⅢ),2 well-differentiated oligoastrocytomas(OA gradeⅡ) and 12 well-differentiated oligodendrogliomas(OD gradeⅡ).The minimum apparent diffusion coefficient(ADC_min) value in tumor solid part of each tumor were measured, relative ADC_min was calculated by divided the ADC value at the normal appearing contralateral site into it.Mean values of rADC_min of different grades and subgroups were analyzed.Results:Mean rADC_min of different subgroups were 0.95±0.05 for OA gradeⅢ,1.11±0.30 for OD gradeⅢ,1.69±0.59 for OA gradeⅡ,1.45±0.41 for OD gradeⅡrespectively.A significant negative correlation existed between rADC_min and different subgroups of oligodendroglial tumors(P=0.004).While A significant difference was observed of rADC_min in the two grades of thetumor(P=0.014),whereas significant difference was only found between OA gradeⅢand the two low grade tumors(P=0.027,P=0.029 respectively).A cutoff of rADC_min=1.03 gave the sensitivity 100%,specificity 100%for differentiation low grade tumors from anaplastic oligoastrocytomas,but specificity 100%,sensitivity only 60%for differentiating the two grades of oligodendroglial tumors.Conclusion:The rADC_min can provide additional information about tumor grades,rADC_min has the potential benefit in differentiation high grade oligoastrocytomas from low grade oligodendroglial tumors with a cut off of rADC_min=1.03,but overlapped with that of anaplastic oligodendrogliomas,rADC_min alone has limited value for differentiation the two grades of oligodendroglial tumors.However a rADC_min smaller than 1.03 might not lead to the diagnosis of low grade oligodendroglial tumors.PartⅢOligodendroglial tumors:The correlation between tumor grades and tumor MRI enhancementObjective:To evaluate the correlation between tumor grades and tumor enhancement in oligodendroglial tumors.Methods:Findings from 31 surgical pathologically proved oligodendroglial tumors in 30 patients were retrospectively analyzed and compared.Contrast enhanced ratios(CERs) were measured;Mean CERs were compared between both the grades and among the subtypes.Enhancement pattern were also observed.Result:The 31 tumors include 24 pure oligodendrogliomas(9 gradeⅢ,15 gradeⅡ) and 7 mixed oligoastrocytomas(4 gradeⅢ,3 gradeⅡ).Mean CER was 1.11±0.11 for OD gradeⅡ,1.37±0.31 for OA gradeⅡ,1.65±0.18 for OD gradeⅢ, 2.16±0.32 for OA gradeⅢ.Positive correlation was observed between CERs and tumor subtypes(P=0.000),statistic difference was noted between the two grades(p=0.002).The cutoff value of CER=1.30,gives the sensitivity of 85%, specificity of 78%for differentiation of the two grades.3 enhancement patterns were observed in 19 of the 31 tumors(gradeⅢVs gradeⅡ:11/13 Vs 8/18);dot and nodular like enhancement(gradeⅢVs gradeⅡ:7/13 Vs 7/18),ring enhancement (9/13 Vs 2/18),bulk enhancement(2/13 Vs 0).Conclusion Tumor enhancement was more common in high grade oligodendroglial tumors.An upward tendency was noted of mean CERs in order of OD gradeⅡ,OA gradeⅡ,OD gradeⅢ,OA gradeⅢ.Nodular-like enhancement was characteristic of oligodendroglial tumors.Ring enhancement may indicate high grade of the tumor.