Diffusion Tensor Magnetic Resonance Imaging In Ring-enhancing Cerebral Lesions

Purpose To determine differential diagnostic value and clinical significance of diffusion tensor imaging(DTI)in high-grade astrocytomas,solitary metastasis and abscesses.Materials and Methods 53 patients with intracranial solitary lesions which showed ring enhancement sign on contrast-enhanced T1-weighted images were enrolled in this study.Brain tissues were examined pathologically from 50 patients to confirm the intracranial occupational diseases.Four patients have been diagnosed with primary cancer plus brain solitary metastasis. The DTI maps were calculated as well as measurements of mean diffusivity(MD)and FA values of the region of interest,including the central cavity,peri-edema,and cerebral parenchyma of the normal side.Fiber tractography was reconstructed that diaplay the encountered patterns of tumor-related alteration to cerebral white matter.Results On DTI,the cavity of high-grade astrocytoma and metastasis displayed as hypointense signal;most of the abscess cavities displayed high signal intensity except for one with an isodensity cavity.MD values and FA values aid the differentiation between tumors and abscesses.The abscess cavities showed restricted diffusion and anisotropy(MD=0.604±0.13×10^-3mm²/s,FA=0.185±0.03),whereas the central portion of high-grade astrocytoma (MD=2.76±0.26×10^-3mm²/s,FA=0.069±0.02)and solitary metastases(2.82±0.29×10^-3mm²/s, FA=0.064±0.02)showed unrestricted diffusion and isotropy.Abscesses could be differentiated by MD values and FA values in their cavities from brain tumors(P＜0.01).The peri-edemas were all depicted as hyperintense or isointense signals on DTI.The difference of FA values in the peri-edemas between high-grade astrocytoma and others was statistically significant(P＜0.01).Furthermore,Fiber tractography and FA map can gave a quick and intuitive overview of the displaced course of white matter tracts in three-dimensional space.Conclusion Our results suggested the potential role of the cavity MD values and cavity FA values in the differential diagnoses between brain tumors and brain abscesses;Meanwhile, high-grade astrocytomas could be distinguished from solitary metastases and abscesses by evaluating their corresponding FA values in the surrounding edema area in brain MRI.Fiber tractography can display the detailed relationship between tumors and nearby white matter tract,thus it is useful for plan before surgery.Combined with conventional MRI,DTI may help physician to facilitate the differential diagnosis of ring-enhancing intracranial lesions in clinical practice.