SU‐F‐J‐92: Predictive Value of Diffusion Tensor Imaging Parameters for Gamma Knife Radiosurgery in Meningiomas

Purpose:Subtypes of WHO grade I meningiomas are difficult to distinguish with conventional magnetic resonance imaging. Control rates in meningiomas after Gamma Knife Stereotactic Radiosurgery (GKRS) are high; however, there are about 7.5 % of meningiomas which continue to grow [Santacroce et al, Neurosurgery 70:32–39, 2012]. A superior control rate may be achieved if there would be a possibility to predict the meningioma subtype without intervention and to adjust prescription dose accordingly. Diffusion Tensor Imaging (DTI) parameters are able to differentiate between meningioma subtypes, based on their fibrous tissue concentration [Tropine et al, J Magn Reson Imaging 25(4):703–8, 2007]. We tested the hypothesis that there is a correlation between different DTI parameters and the change of tumor volume after GKRS, expecting that fibrous‐rich tissue has lower radiosensitivity.Methods:DTI parameters were measured by Magnetic Resonance Imaging (3T Achieva Philips) before GKRS in 34 patients with meningiomas. After GKRS treatment with a prescription dose of 11 to 18 (mean: 13.9±1.7) Gy, the change rate of tumor size was followed over more than 12 month, up to 43 months (average: 27.9 months).Results:Only those meningiomas showing the highest Fractional Anisotropy (FA), the lowest Spherical Index (Cs) and the lowest Radial Diffusibility (RD) increased or remained stable in volume, whereas all others decreased. The correlation between DTI parameters (FA: −0.78, Cs: 0.71, RD: 0.66) and volume change rate was significant (p<0.001). Other factors, including original tumor size, prescription dose and patient's age, do not correlate significantly.Conclusion:Meningiomas showing high FA, as well as low Cs and low RD are less susceptible to GKRS. This finding might be due to their higher content of fibrous tissue. In order to improve the control rate of meningiomas showing high FA we propose to increase the prescription dose.