Diffusion tensor magnetic resonance imaging in ring-enhancing cerebral lesions: differential diagnosis and clinical significance

Abstract

Objective To determine differential diagnostic value and clinical significance of diffusion tensor imaging (DTI) in high-grade astrocytomas, solitary metastasis and abscesses. Method 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. Three patients have been diagnosed with primary cancer plus brain solitary metastasis. DTI measurements were obtained from regions of interest (ROI) placed on central cavity, peri-edema and cerebral parenchyma of the normal side. Fiber tractography was reconstructed that display the encountered patterns of tumor-related alteration to cerebral white matter. Results On DTI, the cavity of high-grade astrocytoma and metastases displayed as hypo-intense signal ;most of the absecess 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 =0.60±0.13×10-3 mm2/s, FA =0.18±0.03), whereas the central portion of high-grade astrocytoma (MD=2.76±0.26×10-3 mm2/s, FA=0.07±0.02) and solitary metastases (2.82±0.29×10-3mm2/s, FA=0.06±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 iso-intense signals on DTI. The difference of FA values in the peri-edemas between high-grade astrocytomas and others was statistically significant(P<0.01). Furthermore, Fiber tractography and FA map could give a quick and intuitive overview of the displaced course of white matter tracts in three-dimensional space. Conclusions Our results suggest 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 astroeytomas could be distinguished from solitary metastases and abscesses by evaluating their corresponding FA values in the surrounding edema area in brain MRI. DTT and FA maps 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. Key words: Magnetic resonance imaging; Brain neoplasms; Brain abscess