Comparison of the values of MRI diffusion kurtosis imaging and diffusion tensor imaging in cerebral astrocytoma grading and their association with aquaporin-4.

OBJECTIVE: To compare the value of MRI diffusion kurtosis imaging (DKI) and diffusion tensor imaging (DTI) in grading cerebral astrocytomas and to analyze the correlation of respective parameters with aquaporin-4 (AQP4) expression.
METHODS: Sixty patients with cerebral astrocytoma, including low-grade astrocytomas (LGA, n = 25) and high-grade astrocytomas (HGA, n = 35), were studied. The values of DKI parameters (mean kurtosis [MK], radial kurtosis [Kr], and axial kurtosis [Ka]) and DTI parameters (fractional anisotropy, mean diffusivity [MD]) corrected by contralateral normal-appearing white matter in the solid parts of the tumors and peritumoral edema were compared. Receiver operating characteristic curves were used to identify the best parameters. Spearman correlation analysis was conducted to assess the correlation of AQP4 expression with each parameter value.
RESULTS: MK, Ka, and Krvalues were significantly higher whereas MD values were significantly lower in the solid parts of HGA, as compared to those of LGA. MK value in peritumoral edematous tissue was significantly higher in HGA as compared to that in LGA. Ka (0.889) had the largest area under the curve (AUC), followed by MK (0.840), Kr (0.750), and MD (0.764). The AUC of Kaand MK was significantly higher than that of MD. Optimal thresholds for MK, Ka, Kr, and MD for differentiating the two groups were 0.490, 0.525, 0.432, and 1.493, respectively. The AQP4 expression in the solid parts of the tumors was significantly higher in HGAs. MK, Kr, Kavalues positively correlated with the AQP4 expression, whereas MD showed a slight negative correlation with AQP4.
CONCLUSION: Use of DKI improved grading of cerebral astrocytomas when compared with DTI. DKI parameters appeared to reflect the level of AQP4 expression in astrocytomas.