title: Peripheral doses in patients undergoing Cyberknife treatment for intracranial lesions. A single centre experience.
abstract: BACKGROUND
  Stereotactic radiosurgery/radiotherapy procedures are known to deliver a very high dose per fraction, and thus, the corresponding peripheral dose could be a limiting factor for the long term surviving patients. The aim of this clinical study was to measure the peripheral dose delivered to patients undergoing intracranial Cyberknife treatment, using the MOSFET dosimeters. The influence of the supplemental shielding, the number of monitor units and the collimator size to the peripheral dose were investigated.
  
  
  METHODS
  MOSFET dosimeters were placed in preselected anatomical regions of the patient undergoing Cyberknife treatment, namely the thyroid gland, the nipple, the umbilicus and the pubic symphysis.
  
  
  RESULTS
  The mean peripheral doses before the supplemental shielding was added to the Cyberknife unit were 51.79 cGy, 13.31 cGy and 10.07 cGy while after the shielding upgrade they were 38.40 cGy, 10.94 cGy, and 8.69 cGy, in the thyroid gland, the umbilicus and the pubic symphysis, respectively. The increase of the collimator size corresponds to an increase of the PD and becomes less significant at larger distances, indicating that at these distances the PD is predominate due to the head leakage and collimator scatter.
  
  
  CONCLUSIONS
  Weighting the effect of the number of monitor units and the collimator size can be effectively used during the optimization procedure in order to choose the most suitable treatment plan that will deliver the maximum dose to the tumor, while being compatible with the dose constraints for the surrounding organs at risk. Attention is required in defining the thyroid gland as a structure of avoidance in the treatment plan especially in patients with benign diseases.
authors.affiliation: Department of Medical Physics, School of Medicine, University of Patras, Achaia, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Vlachopoulou
authors.forename: Christos
authors.initials: C
authors.lastname: Antypas
authors.forename: Harry
authors.initials: H
authors.lastname: Delis
authors.forename: Argyrios
authors.initials: A
authors.lastname: Tzouras
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Salvaras
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kardamakis
authors.forename: George
authors.initials: G
authors.lastname: Panayiotakis
mesh_terms: D001932:Brain Neoplasms / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D011835:Radiation Protection / Q000295:instrumentation / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted
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