Significant temporal evolution of diffusion anisotropy for evaluating early response to radiosurgery in patients with vestibular schwannoma: findings from functional diffusion maps.
OBJECTIVE
Outcome evaluation in clinical oncology is conventionally based on long-term volumetric changes in the tumor size. The purpose of this study was to prospectively investigate the usefulness of fDMs in incorporating anisotropic diffusion in the evaluation of early response after radiosurgery in patients with vestibular schwannoma.


METHODS
The MD, FA, and IVDC were calculated by using simple averaging methods and fDMs. Six patients with vestibular schwannoma treated with stereotactic radiosurgery underwent longitudinal DTI studies on a 3T MR imaging scanner (maximum follow-up, 6 months). Posttreatment DTI data were spatially coregistered with pretreatment scans.


RESULTS
Tumors did not change significantly in size until 6 months after treatment. Diffusion indices changed significantly during the study period. There was a transient decrease in averaged MD followed by a significant increase. IVDC showed an opposite behavior compared with MD. FA decreased continuously throughout the study period. Functional diffusion maps showed a heterogeneous response of tumors to treatment, thereby providing complementary information to simple averaged values.


CONCLUSIONS
DTI allows early detection of therapeutic-induced changes in patients with vestibular schwannoma. Functional diffusion maps incorporating anisotropic diffusion may aid in assessing the heterogeneity of the therapeutic response in this patient group.
Department of Diagnostic Radiology, Chang Gung Memorial Hospital, Department of Electrical Engineering, Chang Gung University, Taiwan, Republic of China.
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YC
Lin
C-C
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Wang
Y Y
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Wai
Y-L
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Wan
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SH
Ng
Y-L
YL
Chen
H-L
HL
Liu
J-J
JJ
Wang
D000328:Adult; D056324:Diffusion Tensor Imaging / Q000379:methods*; D018450:Disease Progression; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D010865:Pilot Projects; D011446:Prospective Studies; D016634:Radiosurgery; D016896:Treatment Outcome