Diagnostic Performance of Arterial Spin Labeling for Grading Nonenhancing Astrocytic Tumors

PURPOSE: We evaluated the utility of arterial spin labeling (ASL) imaging of tumor blood flow (TBF) for grading non-enhancing astrocytic tumors. MATERIALS AND METHODS: Thirteen non-enhancing astrocytomas were divided into high-grade (n = 7) and low-grade (n = 6) groups. Both ASL and conventional sequences were acquired using the same magnetic resonance machine. Intratumoral absolute maximum TBF (TBF(max)), absolute mean TBF (TBF(mean)), and corresponding values normalized to cerebral blood flow (TBF(max) and TBF(mean) ratios) were measured. The Mann-Whitney U test and receiver operating characteristic (ROC) curve analysis were used to assess the accuracy of TBF variables for tumor grading. RESULTS: Compared with low-grade astrocytoma, high-grade astrocytoma exhibited significantly greater absolute TBF(max) (90.93 ± 24.96 vs 46.94 ± 20.97 ml/100 g/min, P < 0.001), TBF(mean) (58.75 ± 19.89 vs 31.16 ± 17.63 ml/100 g/min, P < 0.001), TBF(max) ratio (3.34 ± 1.22 vs 1.35 ± 0.5, P < 0.001), and TBF(mean) ratio (2.15 ± 0.94 vs 0.88 ± 0.41, P < 0.001). The TBF(max) ratio yielded the highest diagnostic accuracy (sensitivity 100%, specificity 86.3%), while absolute TBF(mean) yielded the lowest accuracy (sensitivity 85.7%, specificity 70.1%) by ROC analysis. CONCLUSION: Parameters from ASL perfusion imaging, particularly TBF(max) ratio, may be useful for distinguishing high-grade from low-grade astrocytoma in cases with equivocal conventional MRI findings.