Correlation of Perfusion MRI of Brain Tumors with their Histopathological Grade

Abstract

Introduction: Gliomas are the most common primary neoplasms of the central nervous system, histologically varying from low grade (benign) to high grade (malignant). Their grade can be underestimated even on histopathology because even a single lesion may be histologically heterogeneous. For planning the optimal treatment strategy and assessing prognosis, accurate histologic grading is essential because treatment options are different for high-grade and low-grade gliomas as high grades are usually treated with adjuvant and neoadjuvant radiation or chemotherapy, whereas low-grade gliomas are not. The study aims to differentiate glioma grades by using perfusion MRI and to correlate findings of brain tumors on perfusion MRI with histopathological grading. Materials and Methods: We investigated 50 consecutive patients with brain tumors who had undergone both conventional and perfusion MR imaging during a period of one and half year period. Dynamic contrast-enhanced T2*-weighted and conventional T1- and T2-weighted imaging. rCBV maps were obtained by fitting a gamma-variate function to the contrast material concentration versus time curve. rCBV ratios between tumor and normal white matter (maximum rCBV of tumor/rCBV of contralateral white matter) were calculated and compared between four grades of glioma. Results: Mean rCBV ratios were 1.00 ± 0.35 for grade 1 gliomas, 2.6 ± 1.17 for grade 2 gliomas, 4.98 ± 0.76 for grade 3 gliomas and 6.54 ± 1.47 for grade 4 gliomas, and were thus significantly different. Lymphomas have less vascularity than other tumors, with a mean rCBV of 1.85 ± 0.77. Metastasis is a relatively high vascular tumor with a mean rCBV of 4.57 ± 0.67, which is near to grade 3 gliomas. High-grade gliomas can be differentiated from low-grade gliomas with cut-off value of mean rCBV of 2.86 with a sensitivity of 93%. Conclusion: Perfusion MRI is a useful and dependable means of noninvasively preoperative diagnosis and assessing the histologic grade of brain tumors, especially gliomas and determining the appropriate treatment according to the vascularity of the tumor and respective grade of glioma