Volume effects in radiosurgical spinal cord dose tolerance: how small is too small?

  • Ting Martin Ma
  • Bahman Emami
  • Jimm Grimm
  • Jinyu Xue
  • Sucha O. Asbell
  • Gregory J. Kubicek
  • Rachelle Lanciano
  • James Welsh
  • Luke Peng
  • Chengcheng Gui
  • Indra J. Das
  • Howard Warren Goldman
  • Luther W. Brady
  • Kristin J. Redmond
  • Lawrence R. KleinbergEmail author
Original Research



Spinal cord dose constraints are a critical feature for stereotactic body radiation therapy (SBRT). Spinal cord maximum point dose (Dmax) by Monte Carlo (MC) calculations is used as a critical cord tolerance limit for SBRT, but information is lacking about its reproducibility. This study examines uncertainty of MC dose calculations for small volumes in spine SBRT.


Seven consecutive spine radiosurgery cases were randomly selected to measure precision of the Dmax calculation in comparison to other volumes. Each plan was calculated five times using MC with a 2% uncertainty objective, and variabilities in dose-volume histogram (DVH) parameters across recalculations were evaluated with coefficient of variation (standard deviation divided by mean). The average ratio of D0.03 cc/Dmax was calculated across a larger series of 130 cases.


The variability of Dmax was twice as high for D0.03 cc and five times as high for D1 cc across recalculations for the seven cases. For larger volumes, the variability was lower. The standard deviation of Dmax was 0.1959 Gy, compared to 0.0931 Gy, 0.0569 Gy, and 0.0364 Gy for D0.03 cc, D0.1 cc, and D1 cc, respectively. The average D0.03 cc/Dmax among 130 cases was 0.93.


Dmax has greater variability compared to D0.03 cc, D0.1 cc, and D1 cc, potentially creating risks when used for guidance for spinal cord. D0.03 cc may be an attractive alternative with higher reliability while its limits could be obtained by scaling the reported Dmax limit by a factor of 0.93. This may help guide treatment planning and aid in discovering true dose constraints for spine SBRT.


Stereotactic body radiation therapy (SBRT) Spine Monte Carlo Dmax D0.03 cc Uncertainty 


Compliance with ethical standards



Conflict of interest

Jimm Grimm designed and holds intellectual property rights to the DVH Evaluator software tool which is an FDA-cleared product in commercial use and which has been used for this analysis. Lawrence Kleinberg has received research grants from Novacure, Arbor, and Accuray. He also serves on the advisory board for Novacure. Ting Martin Ma, Bahman Emami, Jinyu Xue, Sucha O. Asbell, Gregory J. Kubicek, Rachelle Lanciano, James Welsh, Luke Peng, Chengcheng Gui, Indra J. Das, Howard Warren Goldman, Luther W. Brady, and Kristin J. Redmond declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Ting Martin Ma
    • 1
    • 2
  • Bahman Emami
    • 3
  • Jimm Grimm
    • 1
  • Jinyu Xue
    • 4
  • Sucha O. Asbell
    • 5
  • Gregory J. Kubicek
    • 5
  • Rachelle Lanciano
    • 6
  • James Welsh
    • 3
  • Luke Peng
    • 1
  • Chengcheng Gui
    • 1
  • Indra J. Das
    • 4
  • Howard Warren Goldman
    • 7
  • Luther W. Brady
    • 6
  • Kristin J. Redmond
    • 1
  • Lawrence R. Kleinberg
    • 1
    Email author
  1. 1.Department of Radiation Oncology and Molecular Radiation SciencesJohns Hopkins University HospitalBaltimoreUSA
  2. 2.Department of MedicineUniversity of Washington School of MedicineSeattleUSA
  3. 3.Department of Radiation OncologyLoyola University Medical CenterMaywoodUSA
  4. 4.Department of Radiation OncologyNYU Langone Medical CenterNew YorkUSA
  5. 5.Department of Radiation OncologyMD Anderson Cancer Center at Cooper University HospitalCamdenUSA
  6. 6.Philadelphia CyberKnifeCrozer-Keystone Health SystemHavertownUSA
  7. 7.Department of Neurological SurgeryMD Anderson Cancer Center at Cooper University HospitalCamdenUSA

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