title: Evaluation of the peripheral dose in stereotactic radiotherapy and radiosurgery treatments.
abstract: OBJECTIVE
  The main purpose of this work was to compare peripheral doses absorbed during stereotactic treatment of a brain lesion delivered using different devices. These data were used to estimate the risk of stochastic effects.
  
  
  METHODS
  Treatment plans were created for an anthropomorphic phantom and delivered using a LINAC with stereotactic cones and a multileaf collimator, a CyberKnife system (before and after a supplemental shielding was applied), a TomoTherapy system, and a Gamma Knife unit. For each treatment, 5 Gy were prescribed to the target. Measurements were performed with thermoluminescent dosimeters inserted roughly in the position of the thyroid, sternum, upper lung, lower lung, and gonads.
  
  
  RESULTS
  Mean doses ranged from of 4.1 (Gamma Knife) to 62.8 mGy (LINAC with cones) in the thyroid, from 2.3 (TomoTherapy) to 30 mGy (preshielding CyberKnife) in the sternum, from 1.7 (TomoTherapy) to 20 mGy (preshielding CyberKnife) in the upper part of the lungs, from 0.98 (Gamma Knife) to 15 mGy (preshielding CyberKnife) in the lower part of the lungs, and between 0.3 (Gamma Knife) and 10 mGy (preshielding CyberKnife) in the gonads.
  
  
  CONCLUSIONS
  The peripheral dose absorbed in the sites of interest with a 5 Gy fraction is low. Although the risk of adverse side effects calculated for 20 Gy delivered in 5 Gy fractions is negligible, in the interest of optimum patient radioprotection, further studies are needed to determine the weight of each contributor to the peripheral dose.
authors.affiliation: Department of Neurosurgery, Division of Medical Physics, Fondazione IRCCS, Istituto Neurologico C. Besta, 20133 Milano, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Di Betta
authors.forename: Laura
authors.initials: L
authors.lastname: Fariselli
authors.forename: Achille
authors.initials: A
authors.lastname: Bergantin
authors.forename: Federica
authors.initials: F
authors.lastname: Locatelli
authors.forename: Antonella
authors.initials: A
authors.lastname: Del Vecchio
authors.forename: Sara
authors.initials: S
authors.lastname: Broggi
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Fumagalli
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy / Q000601:surgery; D006801:Humans; D008297:Male; D009900:Optic Nerve / Q000528:radiation effects; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D013269:Stochastic Processes