title: Iridium-Knife: Another knife in radiation oncology.
abstract: OBJECTIVE
  Intratarget dose escalation with superior conformity is a defining feature of three-dimensional (3D) iridium-192 (192Ir) high-dose-rate (HDR) brachytherapy (BRT). In this study, we analyzed the dosimetric characteristics of interstitial192Ir HDR BRT for intrathoracic and cerebral malignancies. We examined the dose gradient sharpness of HDR BRT compared with that of linear accelerator-based stereotactic radiosurgery and stereotactic body radiation therapy, usually called X-Knife, to demonstrate that it may as well be called a Knife.
  
  
  METHODS
  Treatment plans for 10 patients with recurrent glioblastoma multiforme or intrathoracic malignancies, five of each entity, treated with X-Knife (stereotactic radiosurgery for glioblastoma multiforme and stereotactic body radiation therapy for intrathoracic malignancies) were replanned for simulated HDR BRT. For 3D BRT planning, we used identical structure sets and dose prescription as for the X-Knife planning. The indices for qualitative treatment plan analysis encompassed planning target volume coverage, conformity, dose falloff gradient, and the maximum dose-volume limits to different organs at risk.
  
  
  RESULTS
  Volume coverage in HDR plans was comparable to that calculated for X-Knife plans with no statistically significant difference in terms of conformity. The dose falloff gradient-sharpness-of the HDR plans was considerably steeper compared with the X-Knife plans.
  
  
  CONCLUSIONS
  Both 3D192Ir HDR BRT and X-Knife are effective means for intratarget dose escalation with HDR BRT achieving at least equal conformity and a steeper dose falloff at the target volume margin. In this sense, it can reasonably be argued that 3D192Ir HDR BRT deserves also to be called a Knife, namely Iridium-Knife.
authors.affiliation: Department of Medical Physics and Engineering, Sana Klinikum Offenbach, Offenbach, Germany. Electronic address: natasa.milickovic@sana.de.
authors.forename: Natasa
authors.initials: N
authors.lastname: Milickovic
authors.affiliation: Department of Radiation Oncology, Sana Klinikum Offenbach, Offenbach, Germany; Department of Radiotherapy and Oncology, J. W. Goethe University, Frankfurt am Main, Germany.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Tselis
authors.affiliation: Department of Radiation Oncology, Sana Klinikum Offenbach, Offenbach, Germany.
authors.forename: Efstratios
authors.initials: E
authors.lastname: Karagiannis
authors.affiliation: Department of Radiation Oncology, Sana Klinikum Offenbach, Offenbach, Germany.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Ferentinos
authors.affiliation: Department of Radiation Oncology, Sana Klinikum Offenbach, Offenbach, Germany.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Zamboglou
keywords: Brachytherapy; High-dose-rate; Iridium-Knife; Stereotactic body radiation therapy; Stereotactic radiosurgery; X-Knife