title: Partial volume tolerance of the spinal cord and complications of single-dose radiosurgery.
abstract: BACKGROUND
  Spine radiosurgery causes a rapid dose fall-off within the spinal cord. The tolerance of partial volume of the spinal cord may determine the extent of clinical application. The study analyzed the partial volume tolerance of the human spinal cord to single fraction radiosurgery.
  
  
  METHODS
  A total of 230 lesions with spine metastases in 177 patients were treated with radiosurgery with single fraction of 8 to 18 Gy, prescribed to the 90% isodose line that encompassed the target volume. Spinal cord volume was defined as 6 mm above and below the radiosurgery target volume. Spinal cord dose was calculated from the radiation dose/spinal cord volume histogram and correlated with clinical/neurological status and radiographic studies. Median follow-up was 6.4 months (range, 0.5-49 months). The 1-year survival rate was 49%.
  
  
  RESULTS
  The average spinal cord volume defined at the treated spinal segment was 5.9 +/- 2.2 mL. The average dose to the 10% spinal cord volume was 9.8 +/- 1.5 Gy, calculated from the dose-volume histogram in the group of 18 Gy prescribed dose. The spinal cord volume that received higher than 80% of the prescribed dose was 0.07 +/- 0.10 mL, which represented 1.3 +/- 1.8% of the cord volume. Among the 86 patients who survived longer than 1 year there was 1 case of radiation-induced cord injury after 13 months of radiosurgery. There were no other cases of spinal cord sequelae.
  
  
  CONCLUSIONS
  Whereas the maximum spinal cord tolerance to single-dose radiation is not known, partial volume tolerance of the human spinal cord is at least 10 Gy to 10% of the spinal cord volume defined as 6 mm above and below the radiosurgery target.
authors.affiliation: Department of Radiation Oncology, Henry Ford Hospital, Detroit, Michigan 48202, USA. sryu1@hfhs.org
authors.forename: Samuel
authors.initials: S
authors.lastname: Ryu
authors.forename: Jian-Yue
authors.initials: JY
authors.lastname: Jin
authors.forename: Ryan
authors.initials: R
authors.lastname: Jin
authors.forename: Jack
authors.initials: J
authors.lastname: Rock
authors.forename: Munther
authors.initials: M
authors.lastname: Ajlouni
authors.forename: Benjamin
authors.initials: B
authors.lastname: Movsas
authors.forename: Mark
authors.initials: M
authors.lastname: Rosenblum
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000379:methods*; D013116:Spinal Cord / Q000528:radiation effects*; D013125:Spinal Neoplasms / Q000401:mortality / Q000556:secondary / Q000601:surgery*; D015996:Survival Rate; D016896:Treatment Outcome