Preliminary Study Of Differential Diagnosis Value In Peritumoral Edema With DTI And MRS

Object:To discuss whether diffusion tensor imaging and proton spectroscopic MR imaging can be used to help differentiate brain tumors on the basis of differences in vascularity and metabolite levels in the peritumoral edema.Material and Methods: Thirty-seven brain tumors (18 gliomas, 13 metastases, 6 meningiomas) were performed by conventional MRI, diffusion tensor imaging, and/or MRS. The ADC,FA value and the ratio of Cho/Cr,NAA/Cr were measured in parenchymatous part, peritumoral edema region and contralateral normal brain. And all the relatively FA values were calculated in parenchymatous and peritumoral edema. The peritumoral signal abnormality was divided into immediate and distant peritumoral edema with the distance from the enhancing portion of the tumor. The distance less than 2cm was defined to be immediate peritumoral edema, otherwise was defined distant peritumoral edma. To calculate the correlation and the significant difference between the ADC and FA value, Cho/Cr of peritumoral edema. Statistic analysis was performed with SPSS 13.0 software for windows. If homogeneity of variance, we use independent samples t-test for statistical analysis in two sample. Parameters of different groups were performed with one-way ANOVA, least significant difference method was used for multiple comparison. Correlation analysis was performed with Pearson. P<0.05 indicated statistical significance.Results: 1. ADC maps can show the peritumoral edema more clearly. Compared with the brain parenchyma, tumor solid part demonstrated iso/slightly hyperintense signal, and the peritumoral edema showed hyperintense signal in the ADC maps. The maps of FA can demonstrate the white matter more clearly than conventional MRI, but they can not show the definite boundary of tumor and peritumoral edema.2. The ADC values of tumor solid part among high-grade gliomas, metastases and meningiomas were (1027±96)×10^-6mm²/s, (1103±114)×10^-6mm²/s and (1110±208)×10^-6mm²/s,the differences were not significant between them. The ADC value of immediate peritumoral edema in high-grade glioma was lower than distant peritumal edema, there was significant difference(P<0.05). But the result was contrary in metastases and meningiomas. In immediate peritumoral edema gliomas was lower than metastases and meningiomas, it was found significant differences between gliomas and metastases(P<0.05). The ADC values of distant peritumoral edema were not significant differences among them.3. The FA values in tumor solid, immediate and distant peritumoral edema were lower than the normal brain parenchyma, the ratio of FA value less than 0.5, there were not significant differences among them.4. The ADC value of immediate peritumoral edema in glioma was (1565±112)×10^-6mm²/s, which was certain degree negative correlation with FA value, but it was no significant difference between them(r=-0.276,p>0.05). However, in metastases a strong negative correlation was found between ADC and FA value(r=-0.737,p<0.05).5. There were not significant differences for Cho/Cr in parenchymatous, but in peritumoral edema of high-grade gliomas the ratio of Cho/Cr increased, NAA/Cr decreased. Between metastases and meningiomas, the ratio of Cho/Cr was normal, but the ratio of NAA/Cr decreased. The ratio of Cho/Cr in peritumoral edema among three groups tumors were 1.61±0.15,1.08±0.15,1.10±0.145, gliomas was higher than metastases and meningiomas(P<0.001). And the ratio of NAA/Cr among them were 0.87±0.20,1.22±0.27,1.18±0.18, gliomas was lower than metastases and meningiomas(P<0.05). 6. A strong negative correlation was found between the ADC values and Cho/Cr in the peritumoral edema of high-grade glioma(r=-0.699,p<0.05), but no significant differences in metastases(r=-0.126,p>0.05).Conclusion: The ADC value measurement in peritumoral edema can help the differential diagnosis of high-grade gliomas, metastases and meningiomas. Peritumoral FA value showed no such discrepancy, it stay at the further research.MR spectroscopy can enable distinction to brian tumors on the basis of differences in metabolite levels in the peritumoral edema. It can deduce that there were tumor cells in peritumoral edema of high-grade glioma.A negative correlation was found between the ADC and Cho/Cr in the peritumoral edema of high-grade gliomas, Which provided molecular imageology basis for its pathology foundation. MRI in combination of DTI and MR spectroscopy can be of potential value in characterizing peritumal edema histopathologic state, guiding surgery and stereotactic biopsy.