The Department of Diagnostic Radiology, Faculty of Medicine, Ain Shams University
Abstract Background: Intracranial cystic lesions are unnatural cavities in which the continuity of the brain parenchyma is disrupted because of different pathologies such as infections and tumors containing proteinaceous fluid and/or cellu-lar/necrotic materials. Aim of Study: The purpose of this study is to investigate the value of DWI in differentiation of the common intracranial intra-axial cystic/necrotic lesions. Patients and Methods: This is a descriptive study, con-ducted from July 2019 till February 2021. It is included twenty-four adult patients of either sex with a cystic/necrotic intra-axial brain lesion with variable perifocal edema and rim enhancement on post-contrast study at MRI unit, radiology department, Ain Shams University (ASU) Hospital. All exam-inations carried out after signing the informed consent by the patient himself or his guardian if the patient is incapacitated by any means. Results: The inflammatory lesions, the wall ADC values were not uniform. We found the lowest ADC value in contrast enhanced part of the pyogenic abscess 0.922x10-3 mm2/s and the highest ADC wall value 1.529x10-3 mm2/s found in toxoplasmosis abscess. There was a significant difference in the wall ADC values of metastatic lesions mean ADC of contrast enhanced part was 1.32±0.18x10-3 mm2/s and 0.80 ±0.13x10-3 mm2/s found in PCNSL, with a cut off value, sensitivity, specificity, positive predictive value (PPV) negative predictive value (NPV) and p-value of: 1.035, 100%, 100%, 100%, 100% and 0.007 respectively. The mean ADC value of the surrounding edema in our study were measured 1.40 ±0.11x10-3 mm2/s for abscess group and 1.59±0.31x10-3 mm2/s for malignant group with insignificant p-value of 0.201. Conclusion: Further more MR techniques may be used for discrimination brain abscess from cystic or necrotic tumors, as diffusion tensor imaging (DTI), MR spectroscopy and perfusion weighted imaging as well as positron emission tomography computed tomography (PET-CT) may be helpful. The use of these additional techniques will help to improve the accuracy of MR in differentiating brain abscess from cystic or necrotic tumors.