Prediction of malignancy grading using computed tomography perfusion imaging in nonenhancing supratentorial gliomas

Tumor grade differentiation is often difficult using routine neuroimaging alone. Computed tomography perfusion imaging (CTP) provides quantitative information on tumor vasculature that closely parallels the degree of tumor malignancy. This study examined whether CTP is useful for preoperatively predicting the grade of malignancy in glioma showing no enhancement on contrast-enhanced magnetic resonance imaging (MRI). Subjects comprised 17 patients with supratentorial glioma without enhancement on MRI. CTP was performed preoperatively, and absolute values and normalized ratios of parameters were calculated. Postoperatively, subjects were classified into two groups according to histological diagnosis of grade 3 (G3) glioma or grade 2 (G2) glioma. Absolute values and normalized ratios for each parameter were compared between G3 and G2. Accuracies of normalized ratios for cerebral blood flow (nCBF) and cerebral blood volume (nCBV) in predicting a diagnosis of G3 were assessed. In addition, nCBV was compared between diffuse astrocytoma, G2 oligodendroglial tumor (OT), and G3 OT. Values for nCBF and nCBV differed significantly between G3 and G2. Using nCBV of 1.6 as a cutoff, specificity and sensitivity for distinguishing G3 were 83.3% and 90.9%, respectively. No significant difference in nCBV was seen between diffuse astrocytoma and G2 OT, whereas differences were noted between G2 and G3 OTs, and between diffuse astrocytoma and G3 OT. CTP offers a useful method for differentiating between G3 and G2 in nonenhancing gliomas.