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Evaluating Radiation-Induced White Matter Changes in Patients with Recurrent Malignant Gliomas Under Treatment of Stereotactic Radiosurgery Using Diffusion Tensor Imaging

Z Chang*, J Kirkpatrick, J Cai, Z Wang, F Yin, Duke University Medical Center, Durham, NC

WE-A-217A-9 Wednesday 8:00:00 AM - 9:55:00 AM Room: 217A

Purpose:
Stereotactic radiosurgery (SRS) has been an effective treatment for brain tumors; however, few data are available regarding radiation-induced white matter (WM) damage by SRS. WM is generally vulnerable to radiation, which may compromise sensory and neurocognitive functions. In this work, diffusion tensor imaging (DTI) was used to assess WM changes following SRS.

Methods:
In this study, 15 patients with recurrent, unifocal malignant gliomas were enrolled. The prescription dose ranged from 16Gy to 26Gy. Patients were scanned with MRI 1-4 days before and 7-day and two-month after SRS treatment. All MR scans including DTI were acquired on a 1.5T clinical scanner. DTI scans were acquired axially using a spin-echo echo-planar imaging sequence (TR = 9,100ms, TE = 98ms, field-of-view = 30x30cm², matrix size = 128x128, slice thickness = 5mm, b = 1,000s/mm²).
Diffusion tensors were calculated and fiber tracking was performed. Tract seeding is performed within a defined volume of interest (VOI). In the study, the volumes of WM receiving dose > 5Gy were contoured as VOIs. Diffusion coefficient , fractional anisotropy (FA), number of fibers (NF) were statistically calculated. Wilcoxon signed-rank test was used to assess the differences, with statistical significance at p < 0.05.

Results:
After 7 days of SRS, increased by approximately 1% (p= 0.53), and FA decreased by 1.8% (p = 0.17) with 24% decline of NF (p = 0.12). After two months of SRS, increased by 2.3% (p= 0.36), and FA decreased significantly by 6.8% (p <0.01) with nearly 40% decline of NF (p = 0.02).

Conclusions:
DTI data indicated compromise of WM fiber integrity after SRS, which shall not be ignored. These preliminary results suggest that dose sparing to white matter should be considered in SRS, particularly when the target is close to white matter fiber bundles such as genu and splenium.

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