title: High precision radiosurgery and technical standards.
abstract: BACKGROUND
  A high degree of precision and accuracy in radiosurgery is a fundamental requirement for therapeutic success. Small radiation fields and steep dose gradients are clinically applied thus necessitating a dedicated quality assurance program in order to guarantee dosimetric and geometric accuracy.
  
  
  METHODS
  A detailed analysis of the course of treatment independent of the irradiation technique used results in the so-called chain of uncertainties in radiosurgery (immobilisation, imaging, treatment planning system, definition of regions of interest, mechanical accuracy, dose planning, dose verification). Each link in this chain is analysed for accuracy and the established quality assurance procedures are discussed. A "System Test" was used to check the whole chain of uncertainties simultaneously.
  
  
  RESULTS
  The tests described are compatible with published reports on quality assurance in radiosurgery. In terms of accuracy the weakest link in the chain of uncertainties is stereotactic MR imaging. Geometric overall accuracy measured in the "System Test" is less than 0.7 mm.
  
  
  CONCLUSIONS
  The established quality assurance routines have clinically been validated. MR imaging dominates geometric overall accuracy in radiosurgery, which can be limited to less than 1 mm by an adequate quality assurance protocol.
authors.affiliation: Department of Medical Radiation Physics, Klinik Im Park, Zurich, Switzerland. stefan.scheib@hirslanden.ch
authors.forename: S G
authors.initials: SG
authors.lastname: Scheib
authors.forename: S
authors.initials: S
authors.lastname: Gianolini
authors.forename: N J
authors.initials: NJ
authors.lastname: Lomax
authors.forename: A
authors.initials: A
authors.lastname: Mack
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000601:surgery; D015901:Angiography, Digital Subtraction / Q000295:instrumentation / Q000592:standards; D016477:Artifacts; D001932:Brain Neoplasms / Q000175:diagnosis / Q000601:surgery; D004867:Equipment Design; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000592:standards; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000592:standards; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000592:standards; D009442:Neurilemmoma / Q000175:diagnosis / Q000601:surgery; D038361:Neuronavigation / Q000295:instrumentation* / Q000592:standards; D019047:Phantoms, Imaging; D010911:Pituitary Neoplasms / Q000175:diagnosis / Q000601:surgery; D011785:Quality Assurance, Health Care / Q000592:standards*; D016634:Radiosurgery / Q000295:instrumentation* / Q000592:standards; D012680:Sensitivity and Specificity; D013238:Stereotaxic Techniques / Q000295:instrumentation; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000592:standards