Diffusion Kurtosis Imaging in the Assessment of Peritumoral Brain Edema in Glioblastomas and Brain Metastases
Authors: Turkin A. M. , Pogosbekyan E. L. , Tonoyan A. C. , Shults E. I. , Maximov I. I. , Dolgushin M. B. , Khachanova N. V. , Fadeeva L. M. , Melnikova-Pitskhelauri T. V. , Pitskhelauri D. I. , Pronin I. N. , Kornienko V. N. 
Published: February 2019

Aim: to explore the opportunities of application of diffusionkurtosis imaging (DKI) for assessment and estimation of diffusion scalar metrics in different locations of peritumoral edema for extra- and intracerebral tumors and in contralateral normal tissue.Materials and methods. 38 patients with supratentorial brain tumors were investigated: 24 (63%) patients with primarily revealed glioblastomas (GB) and 14 (37%) patients with solitary cancer brain metastasis (MTS). MRI was performed on 3.0 T MR-scanner (Signa HDxt, General Electric, USA) with the standard protocols for brain tumor and additional protocol for DKI. The standard protocol for brain tumor included: T1-, T2-weighted images, T2-FLAIR, DWI, T1 with contrast enhancement. Diffusion kurtosis MRI based on SE EPI with TR = 10000 ms, TE = 102 ms, FOV = 240 mm, isotropic voxel size 3 × 3 × 3 mm3, 60 noncoplanar diffusion directions. We used three b-values: 0, 1000 and 2500 s/mm2. Аcquisition time was 22 min. Total acquisition time was near 40 min. This study was approved by Ethical committee of Burdenko National Scientific and Practical Center for Neurosurgery. Parametric maps were constructed for the following diffusion coefficients: mean (MK), transverse / radial (RK), longitudinal / axial (AK) kurtozis; medium (MD), transverse / radial (RD) and longitudinal / axial (AD) diffusion; fractional anisotropy (FA) and a bi-exponential diffusion model coefficients: axonal water fractions (AWF), axial (AxEAD) and radial (RadEAD) extra-axonal water diffusion and the water molecules trajectory tortuosity index (TORT). Normative quantitative indicators were obtained for the six regions of the peritumoral zone as they moved away from the tumor (region 2) to the edema periphery (regions 4–5), as well as in the normal brain on the contralateral hemisphere (C/L) (zone 7). A comparative analysis of these indicators was conducted for cases with GB and MTS. DKI scalar metrics were estimated using Explore DTI (http://www.exploredti.com/).Results. Anatomic MRI (T1 without/with contrast enhancement) for all cases with GB and MTS visualized a contrast enhancement tumor. The peritumoral edema, spreading mainly over the brain white matter, was well visualized on T2-FLAIR. Diffusion kurtosis coefficients decreased in the near peritumoral edema (regions 2–3) and a gradually increased to the edema periphery (regions 5–6). In Region 2, MK in both GB and MTS groups were MKGB(2) = 0.637 ± 0.140 and MKMTS(2) = 0.550 ± 0.046; RK in this region were RKGB(2) = 0.690 ± 0.154 and RKMTS (2) = 0.584 ± 0.051. Differences both MK and RK coefficients in patients with GB and MTS of region 2 were significant (p < 0.001). There were no differences in AK values for GB and MTS in region 2 (p > 0.05), but in regions 3 and 4 differences were observed (p < 0.01). The minimum value of AK in the central edema (regions 3–4) was AKMTS(3–4) = 0.433 ± 0.063 in patients with MTS. The values of MK and RK on the contralateral side in patients with MTS were significantly higher than in the GB group (p < 0.02); MKC/LMTC = 0.954 ± 0.140, RKC/LMTC = 1.257 ± 0.308 and MKC/LGB = 0.829 ± 0.146, RKc/LGB = 0.989 ± 0.282. There was no significant difference for contralateral AK between the groups.Conclusions. We found that DKI scalar metrics are the sensitive tumor biomarkers. It allows us to perform a robust differentiation between the infiltrating GB tumor and purely vasogenic edema of МТS. The obtained results will allow further differential diagnosis of extra- and intracerebral tumors and can be used to plan surgical / radiosurgical treatment for brain tumors.