Tolerance of Pyramidal Tract to Gamma Knife Radiosurgery Based on Diffusion-Tensor Tractography

Keisuke Maruyama, Kyousuke Kamada, Takahiro Ota, Tomoyuki Koga, Daisuke Itoh, Kenji Ino, Shigeki Aoki, Masao Tago, Yoshitaka Masutani, Masahiro Shin, Nobuhito Saito

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29 Scopus citations


Purpose: To minimize the morbidity of radiosurgery for critically located lesions, we integrated diffusion-tensor tractography into treatment planning for gamma-knife radiosurgery. We calculated the refined tolerance of the pyramidal tract (PT) after prospective application of the technique to additional patients. Methods and Materials: The relationship between the dosimetry during treatment planning and the development of subsequent motor complications was investigated in 24 patients, 9 studied retrospectively and 15 studied prospectively. The maximal dose to the PT and the volumes of the PT that received ≥20 Gy (20-Gy volume) and ≥25 Gy (25-Gy volume) were calculated. Univariate logistic regression analyses were used to produce dose-response curves. Differences in the tolerable dose according to the PT location were calculated. Results: Univariate logistic regression analysis of the motor complications revealed a significant independent correlation with the maximal dose to the PT and the 20- and 25-Gy volumes. The maximal dose to the PT with a 5% risk of motor complications was 23 Gy compared with 15 Gy in our previous report. The risk of motor complications was significantly greater in the internal capsule than in the corona radiata for the 20- and 25-Gy volumes in generalized Wilcoxon tests (p = 0.031), although no significant difference was observed for the maximal dose. Conclusion: The tolerable dose of the PT was greater than that previously reported. The internal capsule was more sensitive to high-dose irradiation over a wide area of the PT, probably owing to the dense concentration of motor fibers.

Original languageEnglish (US)
Pages (from-to)1330-1335
Number of pages6
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number5
StatePublished - Apr 1 2008
Externally publishedYes

Bibliographical note

Funding Information:
Supported, in part, by the Takeda Science Foundation and by a Grant-in-Aid for Scientific Research awarded to K. Maruyama by the Ministry of Education, Science, and Culture of Japan (Grant 18791013).


  • Diffusion-tensor tractography
  • Gamma-knife radiosurgery
  • Internal capsule
  • Pyramidal tract
  • Tolerance


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