Role of MRI modalities in assessment of cystic brain Lesions: a prospective study

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 cellular/necrotic materials.
 Purpose – to investigate the value of some MRI modalities, mostly DWI and MR spectroscopy, in differentiation of the common intracranial intra-axial cystic brain lesions to help these patients benefit from the best medical management and treatment.
 Materials and Methods. This is a prospective study, conducted from April 2019 till April 2021. It involved forty adult patients of both sexes 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 examinations were carried out after signing of the informed consent by the patients themselves or their guardian if the patient was incapacitated by any means.
 Results. The ADC values in the center of lesions were not uniform. We found the lowest ADC value in the center of the lesion at the abscess 0.4x10–3 mm2 /s, and the highest ADC value 3.2x10–3 mm2 /s was in cystic neoplastic lesion. There was a significant difference in the ADC values in the center of neoplastic necrotic lesions; mean ADC value was (1.95±1.08) x10–3 mm2 /s and (1.15±0.65) x10–3 mm2 /s in abscess lesions, with a cut-off value, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy value of: 1.55%, 92.9%, 91.7%, 96.3%, 84.6% and 92.5% respectively. MRS was performed in 40 cases, and the Cho/Cr, Cho/NAA and NAA/Cr mean ratios were calculated. These ratios were compared between the different categories. Statistically significant differences were found in the Cho/Cr, Cho/NAA ratios between both groups (p values<0.001**), while no statistically significant difference was found in the NAA/Cr ratio.
 Conclusion. Diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) are useful as additional diagnostic modalities for differentiating brain abscesses from cystic or necrotic brain tumors. Furthermore, the following MR techniques may be helpful for discriminating brain abscess from cystic or necrotic tumors: diffusion tensor imaging (DTI), perfusion weighted imaging as well as positron emission tomography computed tomography (PET-CT). This will help to improve the accuracy of MR in differentiating brain abscess from cystic or necrotic tumors.