title: Dosimetric comparisons of helical tomotherapy treatment plans and step-and-shoot intensity-modulated radiosurgery treatment plans in intracranial stereotactic radiosurgery.
abstract: OBJECTIVE
  To evaluate dose conformity, dose homogeneity, and dose gradient in helical tomotherapy treatment plans for stereotactic radiosurgery, and compare results with step-and-shoot intensity-modulated radiosurgery (IMRS) treatment plans.
  
  
  METHODS
  Sixteen patients were selected with a mean tumor size of 14.65 +/- 11.2 cm3. Original step-and-shoot IMRS treatment plans used coplanar fields because of the constraint of the beam stopper. Retrospective step-and-shoot IMRS plans were generated using noncoplanar fields. Helical tomotherapy treatment plans were generated using the tomotherapy planning station. Dose conformity index, dose gradient score index, and homogeneity index were used in plan intercomparisons.
  
  
  RESULTS
  Noncoplanar IMRS plans increased dose conformity and dose gradient, but not dose homogeneity, compared with coplanar IMRS plans. Tomotherapy plans increased dose conformity and dose gradient, yet increased dose heterogeneity compared with noncoplanar IMRS plans. The average dose conformity index values were 1.53 +/- 0.38, 1.35 +/- 0.15, and 1.26 +/- 0.10 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The average dose homogeneity index values were 1.15 +/- 0.05, 1.13 +/- 0.04, and 1.18 +/- 0.09 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean dose gradient score index values were 1.37 +/- 19.08, 22.32 +/- 19.20, and 43.28 +/- 13.78 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean treatment time in tomotherapy was 42 +/- 16 min.
  
  
  CONCLUSIONS
  We were able to achieve better dose conformity and dose gradient in tomotherapy plans compared with step-and-shoot IMRS plans for intracranial stereotactic radiosurgery. However, tomotherapy treatment time was significantly larger than that in step-and-shoot IMRS.
authors.affiliation: Department of Radiation Physics, City of Hope National Medical Center, Duarte, CA 91010, USA. chan@coh.org
authors.forename: Chunhui
authors.initials: C
authors.lastname: Han
authors.forename: An
authors.initials: A
authors.lastname: Liu
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Schultheiss
authors.forename: Richard D
authors.initials: RD
authors.lastname: Pezner
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Chen
authors.forename: Jeffrey Y C
authors.initials: JY
authors.lastname: Wong
mesh_terms: D000465:Algorithms; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D016371:Cranial Irradiation / Q000379:methods* / Q000592:standards; D006801:Humans; D011879:Radiotherapy Dosage / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013679:Technology, Radiologic / Q000379:methods / Q000592:standards; D036542:Tomography, Spiral Computed