Advanced multiparametric magnetic resonance imaging of intra-axial posterior fossa tumors

Abstract

Background: For early treatment planning, it is required that accurate diagnosis of intra-axial posterior fossa tumors can be done. However, imaging diagnosis can be challenging due to analogous magnetic resonance imaging (MRI) features. Aims and Objectives: The aim of the study was to determine the accuracy of advanced MRI sequences such as diffusion-weighted imaging and magnetic resonance spectroscopy (MRS) in diagnosis of intra-axial posterior fossa masses in a tertiary care center. Materials and Methods: This was a retrospective observational study including 43 patients with posterior fossa intra-axial space-occupying tumors. Mean of minimum apparent diffusion coefficient (ADC) values (mean ADCmin) was derived in tumor, and normal white matter regions and ADC ratio was estimated. On MRS, choline/creatinine (Cho/Cr) and Cho/N-acetyl aspartate (NAA) ratios were noted. Receiver operating characteristic (ROC) curve was used to determine cut-off values for mean tumor ADCmin, ADC ratio, Cho/Cr ratio, and Cho/NAA ratio. Results: The most common tumor was medulloblastoma (MB) (30.23%), followed by metastasis (25.58%), pilocytic astrocytoma (16.28%), brainstem glioma (9.3%), hemangioblastoma (6.98%), glioneuronal tumor (6.98%), and ependymoma (4.65%). MBs showed lowest mean tumor ADCmin (0.57±0.12×10-3 mm2/s) and ADC ratio (0.92±0.18) and highest Cho/Cr ratio (8.26±3.9) and Cho/NAA ratio (6.4±1.83) with significant difference from the group of remaining tumors. ROC curve analysis revealed cutoff values of ≤0.71×10-3mm2/s for ADCmin; ≤ 1.02 for ADC ratio; >3.76 for Cho/Cr ratio, and >3.2 for Cho/NAA ratio for the differentiation of MBs from other tumors. Conclusion: The combined use of ADCmin values, ADC ratio, Cho/Cr ratio, and Cho/NAA ratio can help in better non-invasive analysis of similarly appearing intra-axial posterior fossa tumors.