title: Intracranial stereotactic radiosurgery with an adapted linear accelerator vs. robotic radiosurgery: Comparison of dosimetric treatment plan quality.
abstract: OBJECTIVE
  Stereotactic radiosurgery with an adapted linear accelerator (linac-SRS) is an established therapy option for brain metastases, benign brain tumors, and arteriovenous malformations. We intended to investigate whether the dosimetric quality of treatment plans achieved with a CyberKnife (CK) is at least equivalent to that for linac-SRS with circular or micromultileaf collimators (microMLC).
  
  
  METHODS
  A random sample of 16 patients with 23 target volumes, previously treated with linac-SRS, was replanned with CK. Planning constraints were identical dose prescription and clinical applicability. In all cases uniform optimization scripts and inverse planning objectives were used. Plans were compared with respect to coverage, minimal dose within target volume, conformity index, and volume of brain tissue irradiated with ≥ 10 Gy.
  
  
  RESULTS
  Generating the CK plan was unproblematic with simple optimization scripts in all cases. With the CK plans, coverage, minimal target volume dosage, and conformity index were significantly better, while no significant improvement could be shown regarding the 10 Gy volume. Multiobjective comparison for the irradiated target volumes was superior in the CK plan in 20 out of 23 cases and equivalent in 3 out of 23 cases. Multiobjective comparison for the treated patients was superior in the CK plan in all 16 cases.
  
  
  CONCLUSIONS
  The results clearly demonstrate the superiority of the irradiation plan for CK compared to classical linac-SRS with circular collimators and microMLC. In particular, the average minimal target volume dose per patient, increased by 1.9 Gy, and at the same time a 14% better conformation index seems to be an improvement with clinical relevance.
authors.affiliation: Department of Stereotaxy and Functional Neurosurgery, University Hospital Cologne, Cologne, Germany, harald.treuer@uk-koeln.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Treuer
authors.forename: Moritz
authors.initials: M
authors.lastname: Hoevels
authors.forename: Klaus
authors.initials: K
authors.lastname: Luyken
authors.forename: Veerle
authors.initials: V
authors.lastname: Visser-Vandewalle
authors.forename: Jochen
authors.initials: J
authors.lastname: Wirths
authors.forename: Martin
authors.initials: M
authors.lastname: Kocher
authors.forename: Maximilian
authors.initials: M
authors.lastname: Ruge
mesh_terms: D001932:Brain Neoplasms / Q000601:surgery*; D016371:Cranial Irradiation; D006801:Humans; D010315:Particle Accelerators / Q000295:instrumentation*; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D012371:Robotics / Q000295:instrumentation* / Q000379:methods; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome